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Articles de revues sur le sujet "White matter structure"
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Tian, Yin, Shanshan Liang, Zhen Yuan, Sifan Chen, Peng Xu et Dezhong Yao. « White matter structure in loneliness ». NeuroReport 25, no 11 (août 2014) : 843–47. http://dx.doi.org/10.1097/wnr.0000000000000197.
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Mizobe, Taro, Keisuke Ikari, Hirofumi Tomiyama, Keitaro Murayama, Kenta Kato, Suguru Hasuzawa, Osamu Togao, Akio Hiwatashi et Tomohiro Nakao. « Abnormal white matter structure in hoarding disorder ». Journal of Psychiatric Research 148 (avril 2022) : 1–8. http://dx.doi.org/10.1016/j.jpsychires.2022.01.031.
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Nowicki, Kamil W., et Raymond F. Sekula. « Pericytes Protect White-Matter Structure and Function ». Neurosurgery 83, no 3 (17 août 2018) : E103—E104. http://dx.doi.org/10.1093/neuros/nyy300.
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Yushkevich, Paul A., Hui Zhang, Tony J. Simon et James C. Gee. « Structure-specific statistical mapping of white matter tracts ». NeuroImage 41, no 2 (juin 2008) : 448–61. http://dx.doi.org/10.1016/j.neuroimage.2008.01.013.
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Darki, Fahimeh, Satu Massinen, Elina Salmela, Hans Matsson, Myriam Peyrard-Janvid, Torkel Klingberg et Juha Kere. « Human ROBO1 regulates white matter structure in corpus callosum ». Brain Structure and Function 222, no 2 (30 mai 2016) : 707–16. http://dx.doi.org/10.1007/s00429-016-1240-y.
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Yund, Brianna, Kyle Rudser, Victor Kovac, Alia Ahmed, Igor Nestrasil, Kathleen Delaney, Chester Whitley et Elsa Shapiro. « White matter structure and function in attenuated MPS II ». Molecular Genetics and Metabolism 111, no 2 (février 2014) : S116—S117. http://dx.doi.org/10.1016/j.ymgme.2013.12.292.
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Guitart-Masip, Marc, Zeb Kurth-Nelson, Jan Axelsson, Katrine Riklund, Lars Nyberg, Lars Bäckman et Benjamin Garzon. « Microscopic Structure of Frontal White Matter Predict Delay Discounting ». Biological Psychiatry 87, no 9 (mai 2020) : S197. http://dx.doi.org/10.1016/j.biopsych.2020.02.513.
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Schlegel, Alexander A., Justin J. Rudelson et Peter U. Tse. « White Matter Structure Changes as Adults Learn a Second Language ». Journal of Cognitive Neuroscience 24, no 8 (août 2012) : 1664–70. http://dx.doi.org/10.1162/jocn_a_00240.
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Traditional models hold that the plastic reorganization of brain structures occurs mainly during childhood and adolescence, leaving adults with limited means to learn new knowledge and skills. Research within the last decade has begun to overturn this belief, documenting changes in the brain's gray and white matter as healthy adults learn simple motor and cognitive skills [Lövdén, M., Bodammer, N. C., Kühn, S., Kaufmann, J., Schütze, H., Tempelmann, C., et al. Experience-dependent plasticity of white-matter microstructure extends into old age. Neuropsychologia, 48, 3878–3883, 2010; Taubert, M., Draganski, B., Anwander, A., Müller, K., Horstmann, A., Villringer, A., et al. Dynamic properties of human brain structure: Learning-related changes in cortical areas and associated fiber connections. The Journal of Neuroscience, 30, 11670–11677, 2010; Scholz, J., Klein, M. C., Behrens, T. E. J., & Johansen-Berg, H. Training induces changes in white-matter architecture. Nature Neuroscience, 12, 1370–1371, 2009; Draganski, B., Gaser, C., Busch, V., Schuirer, G., Bogdahn, U., & May, A. Changes in grey matter induced by training. Nature, 427, 311–312, 2004]. Although the significance of these changes is not fully understood, they reveal a brain that remains plastic well beyond early developmental periods. Here we investigate the role of adult structural plasticity in the complex, long-term learning process of foreign language acquisition. We collected monthly diffusion tensor imaging scans of 11 English speakers who took a 9-month intensive course in written and spoken Modern Standard Chinese as well as from 16 control participants who did not study a language. We show that white matter reorganizes progressively across multiple sites as adults study a new language. Language learners exhibited progressive changes in white matter tracts associated with traditional left hemisphere language areas and their right hemisphere analogs. Surprisingly, the most significant changes occurred in frontal lobe tracts crossing the genu of the corpus callosum—a region not generally included in current neural models of language processing. These results indicate that plasticity of white matter plays an important role in adult language learning and additionally demonstrate the potential of longitudinal diffusion tensor imaging as a new tool to yield insights into cognitive processes.
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Suzuki, Mitsuru, Keiko Obara, Yuka Sasaki, Koichi Matoh, Akihiro Kitabatake, Katsuya Sasaki et Fumiaki Nunosawa. « Comparison of perivascular astrocytic structure between white matter and gray matter of rats ». Brain Research 992, no 2 (décembre 2003) : 294–97. http://dx.doi.org/10.1016/j.brainres.2003.08.052.
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RIDLER, K., E. T. BULLMORE, P. J. DE VRIES, J. SUCKLING, G. J. BARKER, S. J. P. MEARA, S. C. R. WILLIAMS et P. F. BOLTON. « Widespread anatomical abnormalities of grey and white matter structure in tuberous sclerosis ». Psychological Medicine 31, no 8 (novembre 2001) : 1437–46. http://dx.doi.org/10.1017/s0033291701004561.
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Background. Neuroimaging studies of tuberous sclerosis complex (TSC) have previously focused mainly on tubers or subependymal nodules. Subtle pathological changes in the structure of the brain have not been studied in detail. Computationally intensive techniques for reliable morphometry of brain structure are useful in disorders like TSC, where there is little prior data to guide selection of regions of interest.Methods. Dual-echo, fast spin-echo MRI data were acquired from 10 TSC patients of normal intelligence and eight age-matched controls. Between-group differences in grey matter, white matter and cerebrospinal fluid were estimated at each intracerebral voxel after registration of these images in standard space; a permutation test based on spatial statistics was used for inference. CSF-attenuated FLAIR images were acquired for neuroradiological rating of tuber number.Results. Significant deficits were found in patients, relative to comparison subjects, of grey matter volume bilaterally in the medial temporal lobes, posterior cingulate gyrus, thalamus and basal ganglia, and unilaterally in right fronto-parietal cortex (patients −20%). We also found significant and approximately symmetrical deficits of central white matter involving the longitudinal fasciculi and other major intrahemispheric tracts (patients −21%); and a bilateral cerebellar region of relative white matter excess (patients +28%). Within the patient group, grey matter volume in limbic and subcortical regions of deficit was negatively correlated with tuber count.Conclusions. Neuropathological changes associated with TSC may be more extensive than hitherto suspected, involving radiologically normal parenchymal structures as well as tubers, although these two aspects of the disorder may be correlated.
Thèses sur le sujet "White matter structure"
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Liu, Zao. « Measurement of White Matter Structure Changes in Amyotrohpic Lateral Sclerosis Using Fractal Analysis ». Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1315930636.
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Clavenstam, Isabell. « The Effect of Methamphetamine Abuse on Brain Structure and Function ». Thesis, University of Skövde, School of Humanities and Informatics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-3106.
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The great amount of METH abuse all over the world causes enormous social and criminal justice problems. In the human brain the abuse of METH causes implications on both structures and functions given rise to acute as well as long term symptoms. In this essay the effects of METH abuse is described in the manner of the drug mechanism such as the impact on neurotransmitters, structural deficits with decreased and increased volumes and the implication on attention, memory, decision making and emotions. Results from studies showing brain structural and cognitive impairments in METH abusers and in prenatal METH exposed children.
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McQueen, Jamie. « Vulnerability of white matter structure and function to chronic cerebral hypoperfusion and the effects of pharmacological modulation ». Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9544.
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The structural integrity of the white matter is required for neuronal communication within the brain which is essential for normal cognitive function. Post-mortem and clinical imaging studies of elderly individuals have demonstrated that white matter integrity is weakened with increasing age which is proposed to underlie age-related cognitive decline. Whilst the exact mechanisms are unknown it is thought that modest age-related reductions in cerebral blood flow, termed chronic cerebral hypoperfusion, may contribute to white matter disruption and impaired cognition with ageing. Investigating the effects of white matter integrity in humans is limited as it is difficult to definitively ascertain a cause and effect relationship. Indeed, elderly individuals with cerebral hypoperfusion often have co-existing disease such as hypertension thus the effects of hypoperfusion in isolation cannot be determined. This has led to the development of a mouse model of chronic cerebral hypoperfusion which provides the opportunity to directly assess whether cerebral hypoperfusion results in disruption to white matter and cognitive impairment. This is achieved by applying small wire coils around both common carotid arteries of the mouse resulting in a global reduction in cerebral blood flow. Importantly the extent of blood flow reduction is dependent on the internal diameter of the coils meaning that differing severities of hypoperfusion can be studied. Previous studies using this model have demonstrated diffuse white matter pathology in white matter tracts including the corpus callosum, internal capsule and optic tract following 1 month of hypoperfusion which is accompanied by impaired spatial working memory. This thesis sought to test the hypothesis that chronic cerebral hypoperfusion would influence the structural integrity of nodal and paranodal domains of myelinated axons of the white matter and result in decreased numbers of oligodendroglial cells. It was additionally hypothesised that treatment with the anti-inflammatory and antioxidant drug dimethyl fumarate (DMF) would ameliorate structural and functional alterations to white matter following hypoperfusion. Aim 1 – To determine the impact of chronic cerebral hypoperfusion on the structural integrity of nodal and paranodal domains of myelinated axons The first aim of this thesis was to investigate the effects of chronic cerebral hypoperfusion on the structural integrity of nodal and paranodal domains of myelinated axons. This was addressed by examining key myelin and axonal proteins found at nodal, paranodal and internodal domains. This revealed significant alterations to the distribution of voltage-gated sodium (Nav1.6) channels at nodes of Ranvier which were differentially altered in response to increasing durations of chronic cerebral hypoperfusion. Specifically an increase in the Nav1.6+ domain length was observed in the corpus callosum following 3 days (p < 0.0001) and 1 month (p < 0.001) of chronic cerebral hypoperfusion but was not significantly different from sham controls following 6 weeks of hypoperfusion (p = 0.066). A significant decrease in Nav1.6 domain length was observed following 3 months of hypoperfusion (p = 0.003). Assessment of paranodal integrity was carried out by measuring nodal gap length and by ultrastructural analysis of paranodal domains. This revealed pronounced alterations to nodal gap length, loss of paranodal septate-like junctions and abnormal morphology of paranodal loops. Furthermore this study revealed a significant loss of myelin associated glycoprotein, a key protein involved in the maintenance of axon-glial integrity, as early as 3 days following the onset of hypoperfusion. A further aim of this study was to examine potential mechanisms underlying the observed alterations to nodal and paranodal domains following cerebral hypoperfusion. It was hypothesised that increased inflammation and accumulation of mitochondria at nodes of Ranvier would be observed following hypoperfusion. The extent of inflammation was assessed by counting numbers of microglia which revealed no significant difference between groups following 3 days of hypoperfusion (p = 0.425) but a significant increase in microglial number was observed following 1 month of hypoperfusion (p = 0.001). In addition, assessment of mitochondrial distribution along myelinated axons revealed decreased numbers of nodes containing mitochondria following 6 weeks of hypoperfusion (p = 0.03) with no difference between groups observed following 3 months (p = 0.742). Taken together the results from this study provide evidence that chronic cerebral hypoperfusion results in dynamic alterations in the localisation of Nav1.6 channels which are accompanied by disruption to paranodal domains and impaired axon-glial integrity. Furthermore microglial number does not appear to mediate nodal and paranodal disruption following 3 days but may contribute to ongoing pathology following 1 month of chronic cerebral hypoperfusion. Aim 2 – To determine the effects of chronic cerebral hypoperfusion on oligodendroglial populations. The second aim of this thesis was to determine the effect of chronic cerebral hypoperfusion on numbers of mature oligodendrocytes and oligodendrocyte precursor cells (OPCs). This revealed a significant decrease in numbers of both populations following 3 days of cerebral hypoperfusion however following 1 month numbers of OPCs were restored and a significant increase in mature oligodendrocyte number was observed. Assessment of OPC proliferation demonstrated low numbers of proliferating cells but revealed that a proportion of newly generated cells had differentiated into mature oligodendrocytes. To determine a potential mechanism involved in OPC differentiation following cerebral hypoperfusion the expression of the GPR17 receptor was examined which has recently been reported to mediate OPC differentiation in response to injury. The results demonstrated decreased expression of GPR17 following 3 days of hypoperfusion (p = 0.007) with no difference between groups observed following 1 month (p = 0.362) indicating that this receptor is not involved in differentiation of OPCs following hypoperfusion. Taken together the results from this study show that mature oligodendrocytes and OPCs are lost early in response to hypoperfusion but that these cells recover over time, highlighting the regenerative capacity of the white matter following cerebral hypoperfusion.Aim 3 – To investigate whether modulation of inflammation and oxidative stress could ameliorate alterations to white matter structure and function following severe chronic cerebral hypoperfusion The third and final aim of this thesis was to determine whether treatment with the anti-inflammatory and antioxidant drug DMF could ameliorate structural and functional alterations to white matter following severe chronic cerebral hypoperfusion. This was achieved by examining myelin and axonal integrity in addition to numbers of oligodendrocytes and OPCs following 7 days of severe chronic cerebral hypoperfusion. This revealed that myelin integrity was significantly decreased in vehicle-treated hypoperfused animals as compared to shams (p = 0.005). However no differences in myelin integrity were observed between sham and hypoperfused mice treated with DMF (p = 0.312). In contrast to the previous study, numbers of oligodendrocytes and OPCs were not altered following severe hypoperfusion however DMF treatment led to significantly increased numbers of oligodendrocytes in sham animals (p = 0.003). Assessment of white matter function using electrophysiology revealed that the conduction velocity of myelinated axons was significantly increased in DMF-treated hypoperfused animals as compared to those treated with vehicle (p = 0.04). Taken together the results of this study demonstrate that modulation of inflammation and oxidative stress may improve structural and functional white matter alterations following chronic cerebral hypoperfusion. Conclusions: The results presented in this thesis demonstrate that chronic cerebral hypoperfusion results in structural alterations to myelinated axons and to oligodendroglial populations within the white matter which are accompanied by impaired spatial working memory. Whilst previous studies using the model have reported that cerebral hypoperfusion results in diffuse white matter pathology, this study has highlighted the vulnerability of nodal and paranodal domains of myelinated axons as regions which are altered early in response to hypoperfusion. Furthermore, characterisation of oligodendroglial populations has revealed that these cells are replaced over time despite ongoing hypoperfusion which demonstrates the regenerative capacity of the white matter following cerebral hypoperfusion. Critically the results presented in this thesis demonstrate that treatment with DMF improved the function of myelinated axons in response to severe reductions in cerebral blood flow and thus may represent an appropriate therapeutic strategy for chronic cerebral hypoperfusion.
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Fenoll, Sanguino Raquel. « The influence of selected genetic and environmental factors on white matter pathway structure measured with diffusion tensor imaging ». Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/565943.
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The present doctoral thesis is focused on describing the effects that different environmental and genetic modulators have on white matter pathways and its consequences measured with diffusion tensor imaging. We chose to focus on two examples of each type of modulators. Firstly, we selected as environment modulating factors: pollutants and video games. On one side, pollution as an external factor that enters passively the brain and may influence developmental trajectories. And on the other hand, we used video games as a good example of active behavior that can modify white matter tracts through practice. Secondly, Down syndrome and Prader-Willi syndrome were selected as representative genetic syndromes that may interfere on white matter growth because, although Down syndrome has higher incidence rate than Prader- Willi syndrome, both show behavioral and cognitive alterations, indicating an abnormal brain development. The results of this doctoral thesis lead to the conclusion that white matter pathways development is not an immutable process and it can be modified by diverse modulators. In the same way, diffusion tensor imaging is a good-quality technique to capture and identify those white matter changes through life.La presente tesis doctoral se centra en describir los efectos que diferentes moduladores ambientales y genéticos tienen sobre las vías de la sustancia blanca y sus consecuencias a través de imágenes de tensor de difusión. Decidimos centrarnos dos ejemplos de cada tipo de moduladores. En primer lugar, se seleccionó como factores de modulación ambiental: contaminantes y videojuegos. Por un lado, la contaminación es un factor externo que penetra pasivamente el cerebro y puede influir en las trayectorias del desarrollo. Y por otro lado, los videojuegos son un buen ejemplo de comportamiento activo que puede modificar los tractos de la materia blanca a través de la práctica. En segundo lugar, se seleccionaron el síndrome de Down y síndrome de Prader-Willi como síndromes genéticos representativos que pueden interferir en el crecimiento de la materia blanca ya que, aunque el síndrome de Down tiene una tasa de incidencia superior al síndrome de Prader-Willi, ambos muestran alteraciones cognitivas y conductuales fruto de un subdesarrollo de las vías de sustancia blanca. Los resultados de esta tesis doctoral nos llevan a la conclusión de que el desarrollo de vías de sustancia blanca no es un proceso inmutable y puede ser modificado por diversos moduladores. De la misma manera, el tensor de difusión es una técnica adecuada para capturar e identificar los cambios en la sustancia blanca que acontecen a lo largo de la vida.
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Brubaker, Christopher John. « A Multimodal Magnetic Resonance Study of the Effects of Childhood Lead Exposure on Adult Brain Structure ». University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1248964743.
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Whitford, Thomas James. « A longitudinal study of brain structure in the early stages of schizophrenia ». Thesis, The University of Sydney, 2007. http://hdl.handle.net/2123/1895.
Texte intégralRésumé :
Schizophrenia is a severe mental illness that affects approximately 1% of the population worldwide, and which typically has a devastating effect on the lives of its sufferers. The characteristic symptoms of the disease include hallucinations, delusions, disorganized thought and reduced emotional expression. While many of the early theories of schizophrenia focused on its psychosocial foundations, more recent theories have focused on the neurobiological underpinnings of the disease. This thesis has four primary aims: 1) to use magnetic resonance imaging (MRI) to identify the structural brain abnormalities present in patients suffering from their first episode of schizophrenia (FES), 2) to elucidate whether these abnormalities were static or progressive over the first 2-3 years of patients’ illness, 3) to identify the relationship between these neuroanatomical abnormalities and patients’ clinical profile, and 4) to identify the normative relationship between longitudinal changes in neuroanatomy and electrophysiology in healthy participants, and to compare this to the relationship observed between these two indices in patients with FES. The aim of Chapter 2 was to use MRI to identify the neuroanatomical changes that occur over adolescence in healthy participants, and to identify the normative relationship between the neuroanatomical changes and electrophysiological changes associated with healthy periadolescent brain maturation. MRI and electroencephalographic (EEG) scans were acquired from 138 healthy participants between the ages of 10 and 30 years. The MRI scans were segmented into grey matter (GM) and white matter (WM) images, before being parcellated into the frontal, temporal, parietal and occipital lobes. Absolute EEG power was calculated for the slow-wave, alpha and beta frequency bands, for the corresponding cortical regions. The age-related changes in regional tissue volumes and regional EEG power were inferred with a regression model. The results indicated that the healthy participants experienced accelerated GM loss, EEG power loss and WM gain in the frontal and parietal lobes between the ages of 10 and 20 years, which decelerated between the ages of 20 and 30 years. A linear relationship was also observed between the maturational changes in regional GM volumes and EEG power in the frontal and parietal lobes. These results indicate that the periadolescent period is a time of great structural and electrophysiological change in the healthy human brain. The aim of Chapter 3 was to identify the GM abnormalities present in patients with FES, both at the time of their first presentation to mental health services (baseline), and over the first 2-3 years of their illness (follow-up). MRI scans were acquired from 41 patients with FES at baseline, and 47 matched healthy control subjects. Of these participants, 25 FES patients and 26 controls returned 2-3 years later for a follow-up scan. The analysis technique of voxel-based morphometry (VBM) was used in conjunction with the Statistical Parametric Mapping (SPM) software package in order to identify the regions of GM difference between the groups at baseline. The related analysis technique of tensor-based morphometry (TBM) was used to identify subjects’ longitudinal GM change over the follow-up interval. Relative to the healthy controls, the FES patients were observed to exhibit widespread GM reductions in the frontal, parietal and temporal cortices and cerebellum at baseline, as well as more circumscribed regions of GM increase, particularly in the occipital lobe. Furthermore, the FES patients lost considerably more GM over the follow-up interval than the controls, particularly in the parietal and temporal cortices. These results indicate that patients with FES exhibit significant structural brain abnormalities very early in the course of their illness, and that these abnormalities progress over the first few years of their illness. Chapter 4 employed the same methodology to investigate the white matter abnormalities exhibited by the FES subjects relative to the controls, both at baseline and over the follow-up interval. Compared to controls, the FES patients exhibited volumetric WM deficits in the frontal and temporal lobes at baseline, as well as volumetric increases at the fronto-parietal junction bilaterally. Furthermore, the FES patients lost considerably more WM over the follow-up interval than did the controls in the middle and inferior temporal cortex bilaterally. While there is substantial evidence indicating that abnormalities in the maturational processes of myelination play a significant role in the development of WM abnormalities in FES, the observed longitudinal reductions in WM were consistent with the death of a select population of temporal lobe neurons over the follow-up interval. The aim of Chapter 5 was to investigate the clinical correlates of the GM abnormalities exhibited by the FES patients at baseline. The volumes of four distinct cerebral regions where 31 patients with FES exhibited reduced GM volumes relative to 30 matched controls were calculated and correlated with patients’ scores on three primary symptom dimensions: Disorganization, Reality Distortion and Psychomotor Poverty. The results indicated that the greater the degree of atrophy exhibited by the FES patients in three of these four ‘regions-of-reduction’, the less severe their degree of Reality Distortion. These results suggest that an excessive amount of GM atrophy may in fact preclude the formation of hallucinations or highly systematized delusions in patients with FES. The aim of Chapter 6 was to identify the relationship between the longitudinal changes in brain structure and brain electrophysiology exhibited by 19 FES patients over the first 2-3 years of their illness, and to compare it to the normative relationship between the two indices reported in Chapter 2. The methodology employed for the parcellation of the MRI and EEG data was identical to Chapter 2. The results indicated that, in contrast to the healthy controls, the longitudinal reduction in GM volume exhibited by the FES patients was not associated with a corresponding reduction in EEG power in any brain lobe. In contrast, EEG power was observed to be maintained or even to increase over the follow-up interval in these patients. These results were consistent with the FES patients experiencing an abnormal elevation of neural synchrony. Such an abnormality in neural synchrony could potentially form the basis of the dysfunctional neural connectivity that has been widely proposed to underlie the functional deficits present in patients with schizophrenia. The primary aim of Chapter 7 was to assimilate the findings from the preceding empirical chapters with the theoretical framework provided in the literature, into an integrated and testable model of schizophrenia. The model emphasized dysfunctions in brain maturation, specifically in the normative processes of synaptic ‘pruning’ and axonal myelination, as playing a key role in the development of disintegrated neural activity and the subsequent onset of schizophrenic symptoms. The model concluded with the novel proposal that disintegrated neural activity arises from abnormal elevations in the synchrony of synaptic activity in patients with first-episode schizophrenia.
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Whitford, Thomas James. « A longitudinal study of brain structure in the early stages of schizophrenia ». University of Sydney, 2007. http://hdl.handle.net/2123/1895.
Texte intégralRésumé :
Doctor of Philosophy (PhD)Schizophrenia is a severe mental illness that affects approximately 1% of the population worldwide, and which typically has a devastating effect on the lives of its sufferers. The characteristic symptoms of the disease include hallucinations, delusions, disorganized thought and reduced emotional expression. While many of the early theories of schizophrenia focused on its psychosocial foundations, more recent theories have focused on the neurobiological underpinnings of the disease. This thesis has four primary aims: 1) to use magnetic resonance imaging (MRI) to identify the structural brain abnormalities present in patients suffering from their first episode of schizophrenia (FES), 2) to elucidate whether these abnormalities were static or progressive over the first 2-3 years of patients’ illness, 3) to identify the relationship between these neuroanatomical abnormalities and patients’ clinical profile, and 4) to identify the normative relationship between longitudinal changes in neuroanatomy and electrophysiology in healthy participants, and to compare this to the relationship observed between these two indices in patients with FES. The aim of Chapter 2 was to use MRI to identify the neuroanatomical changes that occur over adolescence in healthy participants, and to identify the normative relationship between the neuroanatomical changes and electrophysiological changes associated with healthy periadolescent brain maturation. MRI and electroencephalographic (EEG) scans were acquired from 138 healthy participants between the ages of 10 and 30 years. The MRI scans were segmented into grey matter (GM) and white matter (WM) images, before being parcellated into the frontal, temporal, parietal and occipital lobes. Absolute EEG power was calculated for the slow-wave, alpha and beta frequency bands, for the corresponding cortical regions. The age-related changes in regional tissue volumes and regional EEG power were inferred with a regression model. The results indicated that the healthy participants experienced accelerated GM loss, EEG power loss and WM gain in the frontal and parietal lobes between the ages of 10 and 20 years, which decelerated between the ages of 20 and 30 years. A linear relationship was also observed between the maturational changes in regional GM volumes and EEG power in the frontal and parietal lobes. These results indicate that the periadolescent period is a time of great structural and electrophysiological change in the healthy human brain. The aim of Chapter 3 was to identify the GM abnormalities present in patients with FES, both at the time of their first presentation to mental health services (baseline), and over the first 2-3 years of their illness (follow-up). MRI scans were acquired from 41 patients with FES at baseline, and 47 matched healthy control subjects. Of these participants, 25 FES patients and 26 controls returned 2-3 years later for a follow-up scan. The analysis technique of voxel-based morphometry (VBM) was used in conjunction with the Statistical Parametric Mapping (SPM) software package in order to identify the regions of GM difference between the groups at baseline. The related analysis technique of tensor-based morphometry (TBM) was used to identify subjects’ longitudinal GM change over the follow-up interval. Relative to the healthy controls, the FES patients were observed to exhibit widespread GM reductions in the frontal, parietal and temporal cortices and cerebellum at baseline, as well as more circumscribed regions of GM increase, particularly in the occipital lobe. Furthermore, the FES patients lost considerably more GM over the follow-up interval than the controls, particularly in the parietal and temporal cortices. These results indicate that patients with FES exhibit significant structural brain abnormalities very early in the course of their illness, and that these abnormalities progress over the first few years of their illness. Chapter 4 employed the same methodology to investigate the white matter abnormalities exhibited by the FES subjects relative to the controls, both at baseline and over the follow-up interval. Compared to controls, the FES patients exhibited volumetric WM deficits in the frontal and temporal lobes at baseline, as well as volumetric increases at the fronto-parietal junction bilaterally. Furthermore, the FES patients lost considerably more WM over the follow-up interval than did the controls in the middle and inferior temporal cortex bilaterally. While there is substantial evidence indicating that abnormalities in the maturational processes of myelination play a significant role in the development of WM abnormalities in FES, the observed longitudinal reductions in WM were consistent with the death of a select population of temporal lobe neurons over the follow-up interval. The aim of Chapter 5 was to investigate the clinical correlates of the GM abnormalities exhibited by the FES patients at baseline. The volumes of four distinct cerebral regions where 31 patients with FES exhibited reduced GM volumes relative to 30 matched controls were calculated and correlated with patients’ scores on three primary symptom dimensions: Disorganization, Reality Distortion and Psychomotor Poverty. The results indicated that the greater the degree of atrophy exhibited by the FES patients in three of these four ‘regions-of-reduction’, the less severe their degree of Reality Distortion. These results suggest that an excessive amount of GM atrophy may in fact preclude the formation of hallucinations or highly systematized delusions in patients with FES. The aim of Chapter 6 was to identify the relationship between the longitudinal changes in brain structure and brain electrophysiology exhibited by 19 FES patients over the first 2-3 years of their illness, and to compare it to the normative relationship between the two indices reported in Chapter 2. The methodology employed for the parcellation of the MRI and EEG data was identical to Chapter 2. The results indicated that, in contrast to the healthy controls, the longitudinal reduction in GM volume exhibited by the FES patients was not associated with a corresponding reduction in EEG power in any brain lobe. In contrast, EEG power was observed to be maintained or even to increase over the follow-up interval in these patients. These results were consistent with the FES patients experiencing an abnormal elevation of neural synchrony. Such an abnormality in neural synchrony could potentially form the basis of the dysfunctional neural connectivity that has been widely proposed to underlie the functional deficits present in patients with schizophrenia. The primary aim of Chapter 7 was to assimilate the findings from the preceding empirical chapters with the theoretical framework provided in the literature, into an integrated and testable model of schizophrenia. The model emphasized dysfunctions in brain maturation, specifically in the normative processes of synaptic ‘pruning’ and axonal myelination, as playing a key role in the development of disintegrated neural activity and the subsequent onset of schizophrenic symptoms. The model concluded with the novel proposal that disintegrated neural activity arises from abnormal elevations in the synchrony of synaptic activity in patients with first-episode schizophrenia.
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Koivukangas, J. (Jenni). « Brain white matter structure, body mass index and physical activity in individuals at risk for psychosis:the Northern Finland Birth Cohort 1986 Study ». Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526212869.
Texte intégralRésumé :
Abstract Recognition of individuals at highest risk for psychosis is challenging and no definitive biomarkers are yet available. Physical illnesses associated with a sedentary lifestyle are common in patients with severe mental illness. Both, bodyweight and risk for psychosis are associated with brain white matter (WM) abnormalities. There are several dysregulated pathways which are common in psychiatric illnesses and weight-related processes, but it is not known how weight and vulnerability for psychosis interact in the brain. The present study examines brain WM microstructure and its association to body mass index (BMI) in young adults with a familial risk for psychosis (FR). In addition, the level of physical activity and cardiorespiratory fitness in individuals vulnerable to psychosis was examined. Participants of the present study are members of the Northern Finland Birth Cohort 1986. Two separate clinical substudies were conducted. The first having been done when the participants were at age 15–16. At that time, physical activity was defined by postal questionnaire (n=6,987) and cardiorespiratory fitness was measured by a submaximal cycle ergometer test (n=4,803). Risk for psychosis was viewed from three perspectives, with possible overlap between groups: having familial risk for psychosis, existing prodromal symptoms at age 15–16, and development of hospital treated psychosis between the ages of 16 and 20 years. The latter substudy was conducted when the participants were aged between 20 and 25 years. Diffusion tensor imaging was performed on 108 participants. Our study showed that there was no difference in WM microstructure between FR and control groups suggesting that WM abnormalities are not a genetic feature for risk of psychosis in all populations. However, the association between BMI and WM microstructure differed significantly between the FR and control groups. We also demonstrated that the level of physical activity was lower before the onset of psychotic illness. Therefore, these results imply that it would be of great importance to consider weight and physical activity levels in subjects at risk for psychosis, in order to avoid the detrimental effects of a sedentary lifestyle on overall healthTiivistelmä Korkeimmassa psykoosiriskissä olevien tunnistaminen on haastavaa, eikä kunnollisia biomarkkereita ole käytettävissä. Vähäiseen liikunta-aktiivisuuteen liitetyt fyysiset sairaudet ovat yleisiä vakavaa mielenterveyshäiriötä sairastavilla. Sekä kehonpaino että psykoosialttius on yhdistetty aivojen valkean aineen rakenteen poikkeavuuksiin. Useat kehon säätelymekanismien poikkeavuudet liittyvät sekä psykiatrisiin sairauksiin että painoon liittyviin prosesseihin, mutta ei ole olemassa tutkimustietoa siitä, miten paino ja psykoosialttius vaikuttavat yhdessä aivojen rakenteeseen. Tässä osajulkaisuväitöskirjassa tutkitaan aivojen valkean aineen mikrorakennetta nuorilla aikuisilla, jotka ovat sukuriskissä sairastua psykoosiin, sekä painon vaikutusta valkean aineen rakenteeseen psykoosiriskissä. Lisäksi tutkitaan psykoosialttiiden nuorten liikunta-aktiivisuutta ja kuntoa. Tutkittavat kuuluvat Pohjois-Suomen vuoden 1986 syntymäkohorttiin. Kaksi osatutkimusta toteutettiin, joista aikaisempi kliininen tutkimus tutkittavien ollessa 15–16-vuotiaita. Tuolloin selvitettiin liikunta-aktiivisuus postikyselyn avulla (n=6,987) ja aerobinen kunto mittaamalla hapenottokyky polkupyöräergometrilla (n=4,803). Psykoosialttiutta tarkasteltiin kolmella tavalla, ja ryhmien välillä esiintyi osittaista päällekkäisyyttä: sukurasitus, 15–16 v. iässä raportoidut psykoosinkaltaiset oireet ja sairaalahoitoon johtanut psykoosi 16–20 v. iässä. Toinen kliininen osatutkimus toteutettiin tutkittavien ollessa 20–25-vuotiaita. Tutkimuksen yhteydessä tehtiin aivojen diffuusiotensorikuvaus 108 osallistuneelle. Aivojen valkean aineen mikrorakenteessa ei havaittu eroa sukuriskissä olevien ja kontrollien välillä viitaten siihen, että poikkeavuudet valkean aineen rakenteessa eivät olisi psykoosiriskin geneettinen piirre kaikissa populaatioissa. Havaitsimme kuitenkin, että assosiaatio painoindeksin ja valkean aineen rakenteen välillä oli erilainen sukuriski- ja kontrolliryhmissä. Tutkimus osoitti myös, että liikunta-aktiivisuus on alentunut jo ennen psykoosisairauden puhkeamista. Psykoosiriskissä olevien liikuntatottumuksiin ja painoon tulisi kiinnittää erityistä huomiota jo varhaisessa vaiheessa elimellisten sairauksien ehkäisemiseksi
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DuBose, Lyndsey Elisabeth. « Role of aging and aerobic fitness on large elastic artery stiffness, brain structure and cognitive performance in humans ». Thesis, University of Iowa, 2015. https://ir.uiowa.edu/etd/1590.
Texte intégralRésumé :
Older age is a primary risk factor for the development of cardiovascular disease in part through the stiffening of the large cardiothoracic elastic arteries (e.g., aorta, carotid arteries). Aging is also associated with reduced cognitive function, cerebrovascular reactivity and brain white matter integrity, but whether these changes in brain structure and function are associated with age-related large artery stiffness remains unclear. In contrast, older adults who have high aerobic fitness demonstrate attenuated large artery stiffness and better cognitive performance compared to their sedentary counterparts, but the effects of aerobic fitness on white matter integrity and cerebrovascular reactivity with aging are conflicting and limited. Moreover, whether high aerobic fitness-associated lower large artery stiffness in older adults is associated with, and perhaps mediates, the beneficial changes in cognitive function and white matter structure remains unknown. The purpose of this study was to investigate the extent to which high aerobic fitness is associated with preserved white matter structure, cerebrovascular reactivity, and cognitive performance in aged individuals, and if these changes in brain structure and function are associated with attenuated large artery stiffness. In young (n=19, 23.6 ± 2.5 years) and old (n=22, 64.4 ± 4.2 years) healthy adults, large elastic artery stiffness was measured by carotid-femoral pulse wave velocity (cfPWV, aortic stiffness) via non-invasive applanation tonometry of carotid and femoral pulse waveforms and carotid artery beta-stiffness index (β-stiffness index) and compliance using high-resolution ultrasound and carotid blood pressure via applanation tonometry. Aerobic fitness was measured as maximal exercise oxygen uptake (VO2max) using respiratory gas analysis on an upright cycle ergometer. Older subjects were stratified as high or low fit based on gender and age VO2max classification. Letter, pattern and N-Back cognitive tests were used to assess processing speed and working memory respectively. Fractional anisotropy (FA) from diffusion tensor images and Blood Oxygenation Level Dependent (BOLD) imaging was used to assess cerebrovascular reactivity (CVR) response to a breath hold and brain activation during a working memory task. The association between large artery stiffness and FA was then assessed using a voxel-wise general linear model approach and a region-of-interest analysis.
Our results confirmed age-related increases in cfPWV, carotid β-stiffness index and central (carotid) but not brachial systolic blood pressure, and expected reductions in carotid compliance, VO2max, working memory and processing speed, and in white matter integrity in select brain regions (bilateral cingulate, frontal, occipital, temporal). In contrast, we found no age-associated differences in CVR to breath hold stimulus or change in BOLD response to the N-Back. In our cohort of health adults, we found that the age-related changes in large artery stiffness were not attenuated by high compared with low VO2max. Among older adults, large elastic artery stiffness was not associated with regional white matter integrity or cerebrovascular reactivity in any regions-of-interest. Greater carotid artery compliance and lower β-stiffness index was associated with higher processing speed, while compliance was related to higher d'Prime scores and lower reaction time on the 2-Back task among the older adults. CVR to a breath hold stimulus was not related to any measure of cognitive performance. VO2max was not associated with any measures of vascular function, brain structure, function or cognition, indicating relations between large artery stiffness and cognition were independent of aerobic fitness capacity. Taken together, these data suggest that select measures of cognitive performance, but not white matter structure or CVR, may be susceptible to age-related changes in carotid stiffness/compliance and that are unaffected by aerobic fitness. More work is needed to understand the mechanisms by which age-related declines in carotid artery compliance and increased carotid stiffness are associated with reductions in cognitive function in older adults.
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Engelbrecht, Kara. « Intraindividual variability and micro-structural white matter changes in Alzheimer’s disease ». Master's thesis, Faculty of Humanities, 2019. http://hdl.handle.net/11427/31087.
Texte intégralRésumé :
The costs associated with diagnosis, treatment and care of Alzheimer’s disease (AD) patients places a significant financial and social strain on healthcare systems, patients and caregivers, especially in low-and middle-income countries (LAMICs). Traditional methods for diagnosing AD are time consuming and expensive, and treatments are often only effective in the early stages. These factors call for the development of alternative diagnostic methods. One such method that has gained attention due to its neural overlaps with AD is the measurement of intraindividual variability (IIV; the within-person variation in performance over multiple trials of a single task). IIV researchers have highlighted the role of white matter in increased IIV, and micro-structural white matter changes have been implicated in the early stages of AD. The current study examined the relationship between IIV on simple and choice reaction time tasks and micro-structural white matter changes, as indexed by fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (DA) and radial diffusivity (DR) in a sample of 16 AD patients and 20 healthy older adults. Across the entire sample, increased IIV on both the simple and choice reaction time tasks was significantly correlated with lower FA in an area of the right hemisphere inferior longitudinal fasciculus (R-ILF). Increased IIV on the choice reaction time task was significantly correlated with lower DA in the same area. Finally, IIV on the choice reaction time task contributed significantly and uniquely to variance in DA in the same area. These results suggest that further longitudinal studies into the diagnostic utility of IIV for neurological disorders might be of value for clinicians, patients and caregivers.
Livres sur le sujet "White matter structure"
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B, Westland Timothy, et Calton Robert N, dir. Handbook on white matter : Structure, function, and changes. Hauppauge, NY : Nova Science, 2009.
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Boedhoe, Premika S. W., et Odile A. van den Heuvel. The Structure of the OCD Brain. Sous la direction de Christopher Pittenger. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190228163.003.0023.
Texte intégralRésumé :
This chapter summarizes the most consistent findings of structural neuroimaging studies of obsessive-compulsive disorder (OCD), and discusses their relationship within the implicated brain networks. The techniques used in these studies are diverse, and include manual tracing of specific regions of interest, whole-brain voxel-based morphometry (VBM) for both gray matter and white matter volume comparisons, FreeSurfer to investigate differences in cortical thickness and subcortical volumes, and other methods such as covariance analyses. Findings on white matter integrity with tract-based spatial statistics (TBSS) and in diffusion tensor imaging (DTI) studies are discussed as well.The literature shows that the pathophysiology of OCD cannot be explained by alterations in function and structure of the classical cortico-striato-thalamo-cortical (CSTC) regions exclusively, but that fronto-limbic and fronto-parietal connections are important as well, and the role of the cerebellum needs more attention in future research.
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Carson, Matter. A Matter of Moral Justice. University of Illinois Press, 2021. http://dx.doi.org/10.5622/illinois/9780252043901.001.0001.
Texte intégralRésumé :
A Matter of Moral Justice explores the little-studied power laundry industry and its workers, beginning with the birth of the industry at the turn of the twentieth century and concluding with an epilogue on the state of the industry in the early twenty-first century. While providing a broad overview of working conditions, the book focuses on the activism of Black women, who by 1930 comprised a significant proportion of the power laundry workforce. In the urban industrial North, where the industry flourished, Black women eager to escape domestic service actively sought jobs in power laundries, taking their place, albeit on the lowest rungs, on the industrial ladder. This book examines the working conditions and occupational structure in the laundry industry and then narrows the focus to New York City, a leading center of the industry and one of the few places where the workers won union representation. The workers’ campaign spanned many decades and elicited the intervention of some of New York’s most prominent laborites, including New York Women’s Trade Union League president Rose Schneiderman; Amalgamated Clothing Workers of America president Sidney Hillman and his partner and fellow labor leader, Bessie Hillman; Negro Labor Committee president Frank Crosswaith; and a cadre of committed communist and African American organizers. The campaign took place during a period of cataclysmic change for American workers, one that saw the birth and growth of industrial feminism; the Great Migration of more than six million Black southerners to the urban industrial centers of the North and West; the rise of the “New Negro,” inspired by mass migration, Marcus Garvey’s Black nationalist movement, and the explosion of Black trade unionism; the emergence of the CIO and New Deal Order; the heyday of Communist Party organizing; two world wars; and the burgeoning civil rights and women’s movements. This book locates the women’s activism within the context of these movements, which inspired and shaped their organizing and to which they contributed. The book explores the multitude of factors that led to unionization in 1937, including the Wagner Act, the emergence of the CIO, communist organizing, and, most importantly, the militant and interracial organizing of the workers themselves. The final third of the book explores what happened to the workers once they organized under the ACWA-affiliated Laundry Workers Joint Board and thus provides an opportunity to assess the relationship between the industrial union movement and women and people of color employed in the traditionally low-wage industrial service sector. Following LWJB as it transitioned from its radical, grassroots, community-based origins into a bureaucratic organization led by white men illuminates some of the limitations of the industrial union movement for women and people of color but also demonstrates how Black working-class women overcame seemingly insurmountable odds and used the openings provided to mobilize in pursuit of equal treatment and dignity at work. Their stories challenge assumptions about worker passivity and about the inability of the most exploited to organize. Resurrecting these moments of resistance complicates the history of the industrial union movement and provides insights on organizing in the twenty-first century, when women and people of color in the postindustrial service and care sectors have been leading some of the most militant battles for economic and social justice. This story then contributes to our understanding of how race and gender shape working conditions, the formulation of union tactics, and the struggle for union control and union power in modern America.
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Ward, Gregory, Betty J. Birner et Elsi Kaiser. Pragmatics and Information Structure. Sous la direction de Yan Huang. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199697960.013.10.
Texte intégralRésumé :
Information structure deals with the question of how—and specifically, in what order—we choose to present the informational content of a proposition. In English and many other languages, this content is structured in such a way that given, or familiar, information precedes new, or unfamiliar, information. Because givenness and newness are largely matters of what has come previously in the discourse, information structuring is inextricably tied to matters of context—in particular, the prior linguistic context—and this is what makes information structure quintessentially pragmatic in nature. While it has long been recognized that various non-canonical word orders function to preserve a given-before-new ordering in an utterance, a great deal of research has focused on how to determine the specific categories of givenness and newness that matter for information structuring. A growing body of psycholinguistic work explores the role that these categories play in language comprehension.
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Jones, Janine. To Be Black, Excess, and Nonrecyclable. Sous la direction de Naomi Zack. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780190236953.013.1.
Texte intégralRésumé :
One way of understanding the white man’s burden is as a waste management problem. The White West abjected Africans and people of African descent, thereby enacting and enabling their perception and treatment as a form of waste. The value of black waste to white Western economies is discernable in the metaphysics of a white imaginary of black abjection. It is necessary to elucidate that metaphysics, which reveals the structure of a humanist discourse that imagines black bodies as alienated from language, and the degradation entailed by such alienation. For example, when Africana people today chant “Black lives matter,” they do so against the historical perception and treatment of black people as waste.
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Levy, David. Some practical matters. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780198766452.003.0012.
Texte intégralRésumé :
Type 1 diabetes in older people can be challenging; food and insulin are taken less reliably, and some have cognitive impairment. Simplify insulin regimens where appropriate; ‘low’ A1C measurements may signify recurrent hypoglycaemia. The regulatory framework for drivers in Europe is less tolerant of serious hypoglycaemia. Intensive education is required and precautions while driving need reinforcing. Severe hypoglycaemia in the young is associated with impaired school performance, especially in verbal IQ and spelling. Educational attainment is not affected by Type 1 diabetes, but there is some evidence for poor progression in employment, especially in women. Though popular, the evidence supporting structured education in Type 1 diabetes is weak. Peer support using social media is increasing; evidence for benefit is lacking. Serious bacterial infections are probably more common. Ensure all Type 1 patients are up to date with immunizations. Periodontal infections, common and sometimes severe, are reciprocally related to glycaemic control.
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Anderson, Michael, et Corinne Roughley. Changing Age and Sex Structures and Their Consequences. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198805830.003.0010.
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Scotland’s age and sex profiles have changed markedly over time, reflecting changing numbers of births, and the age and sex profiles of mortality and migration. For much of the period, large gender-differentials in emigration gave Scotland the most skewed sex ratios in north-western Europe. The impact on sex ratios in the most marrying age groups of Scottish First World War deaths (whose numbers have often been much exaggerated) was much less than in England. There were major differences in both sex ratios and age profiles between different parts of the country. Its impact on local cultures and the position of women is explored. Crude birth and death rates, while important for some policy purposes where numbers matter, are misleading as guides to the relative impacts on people and families in any area.
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Wilde, Elisabeth A., Kareem W. Ayoub et Asim F. Choudhri. Diffusion Tensor Imaging. Sous la direction de Andrew C. Papanicolaou. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199764228.013.10.
Texte intégralRésumé :
Diffusion tensor imaging (DTI) is a method of specifying and visualizing the functional integrity of white matter tracts that contribute to the functional and structural connectivity among different brain regions through the examination of water diffusion through tissue. It has gained rapid popularity in the past two decades, particularly for elucidating the process of normal white matter development and the effects of aging on it, as well as providing some insights into the possible neuroanatomical correlates of numerous psychiatric and neurologic disorders. This chapter outlines the instrumentation and the procedures employed in deriving estimates of the functional integrity of anatomical connections in the brain, and issues regarding the reliability and validity of the different DTI procedures are systematically addressed.
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van Schaaik, Gerjan. The Oxford Turkish Grammar. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198851509.001.0001.
Texte intégralRésumé :
The point of departure of this book is the fundamental observation that actual conversations tend to consist of loosely connected, compact, and meaningful chunks built on a noun phrase, rather than fully fledged sentences. Therefore, after the treatment of elementary matters such as the Turkish alphabet and pronunciation in part I, the main points of part II are the structure of noun phrases and their function in nominal, existential, and verbal sentences, while part III presents their adjuncts and modifiers. The verbal system is extensively discussed in part IV, and in part V on sentence structure the grammatical phenomena presented so far are wrapped up. The first five parts of the book, taken together, provide for all-round operational knowledge of Turkish on a basic level. Part VI deals with the ways in which complex words are constructed, and constitutes a bridge to the advanced matter treated in parts VII and VIII. These latter parts deal with advanced topics such as relative clauses, subordination, embedded clauses, clausal complements, and the finer points of the verbal system. An important advantage of this book is its revealing new content: the section on syllable structure explains how loanwords adapt to Turkish; other topics include: the use of pronouns in invectives; verbal objects classified in terms of case marking; extensive treatment of the optative (highly relevant in day-to-day conversation); recursion and lexicalization in compounds; stacking of passives; the Başı-Bozuk and Focus-Locus constructions; relativization on possessive, dative, locative, and ablative objects, instrumentals and adverbial adjuncts; pseudo-relative clauses; typology of clausal complements; periphrastic constructions and double negation.
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Woodly, Deva R. Reckoning. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197603949.001.0001.
Texte intégralRésumé :
Reckoning: Black Lives Matter and the Democratic Necessity of Social Movements is an analysis of the emergence of the Movement for Black Lives (M4BL), its organizational structure and culture, and its strategies and tactics, while also laying out and contextualizing the social movement’s unique political philosophy, radical Black feminist pragmatism (RBFM), along with documenting measurable political effects in terms of changing public meanings, public opinion, and policy. Throughout the text, the author interweaves theoretical and empirical observations, rendering both an illustration of this movement and an analysis of the work social movements do in democracy.
Chapitres de livres sur le sujet "White matter structure"
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van Duin, Esther D. A., Janneke Zinkstok, Grainne McAlonan et Therese van Amelsvoort. « White Matter Brain Structure in Asperger’s Syndrome ». Dans Comprehensive Guide to Autism, 1905–27. New York, NY : Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-4788-7_115.
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Yushkevich, Paul A., Hui Zhang, Tony J. Simon et James C. Gee. « Structure-Specific Statistical Mapping of White Matter Tracts ». Dans Mathematics and Visualization, 83–112. Berlin, Heidelberg : Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-88378-4_5.
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y Cajal, Santiago Ramón. « Structure of the White Matter of the Spinal Cord ». Dans Texture of the Nervous System of Man and the Vertebrates, 263–305. Vienna : Springer Vienna, 1999. http://dx.doi.org/10.1007/978-3-7091-6435-8_11.
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Kindlmann, Gordon, Xavier Tricoche et Carl-Fredrik Westin. « Anisotropy Creases Delineate White Matter Structure in Diffusion Tensor MRI ». Dans Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006, 126–33. Berlin, Heidelberg : Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/11866565_16.
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Sedlar, Sara, Abib Alimi, Théodore Papadopoulo, Rachid Deriche et Samuel Deslauriers-Gauthier. « A Spherical Convolutional Neural Network for White Matter Structure Imaging via dMRI ». Dans Medical Image Computing and Computer Assisted Intervention – MICCAI 2021, 529–39. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-87199-4_50.
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Cheng, Jian, et Peter J. Basser. « Director Field Analysis to Explore Local White Matter Geometric Structure in Diffusion MRI ». Dans Lecture Notes in Computer Science, 427–39. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-59050-9_34.
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Goebel, Rainer. « Revealing Brain Activity and White Matter Structure Using Functional and Diffusion-Weighted Magnetic Resonance Imaging ». Dans Clinical Functional MRI, 13–60. Berlin, Heidelberg : Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-662-45123-6_2.
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Goebel, Rainer. « Revealing Brain Activity and White Matter Structure Using Functional and Diffusion-Weighted Magnetic Resonance Imaging ». Dans Clinical Functional MRI, 21–83. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-83343-5_2.
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Anna, Tokola, Brandstack Nina, Hakkarainen Antti, Salli Eero, Åberg Laura et Autti Taina. « White Matter Microstructure and Subcortical Gray Matter Structure Volumes in Aspartylglucosaminuria ; a 5-Year Follow-up Brain MRI Study of an Adolescent with Aspartylglucosaminuria and His Healthy Twin Brother ». Dans JIMD Reports, 105–15. Berlin, Heidelberg : Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/8904_2016_36.
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Tokola, Anna, Nina Brandstack, Antti Hakkarainen, Eero Salli, Laura Åberg et Taina Autti. « Erratum to : White Matter Microstructure and Subcortical Gray Matter Structure Volumes in Aspartylglucosaminuria ; a 5-Year Follow-up Brain MRI Study of an Adolescent with Aspartylglucosaminuria and His Healthy Twin Brother ». Dans JIMD Reports, 117. Berlin, Heidelberg : Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/8904_2017_18.
Texte intégralActes de conférences sur le sujet "White matter structure"
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Gomez, Cristina Hilario, Luca Dodero, Alessandro Gozzi, Vittorio Murino et Diego Sona. « Atlas-free connectivity analysis driven by white matter structure ». Dans 2017 IEEE 14th International Symposium on Biomedical Imaging (ISBI 2017). IEEE, 2017. http://dx.doi.org/10.1109/isbi.2017.7950475.
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Aranda, Ramon, Mariano Rivera et Alonso Ramirez-Manzanares. « Self-oriented Diffusion Basis Functions for white matter structure estimation ». Dans 2013 IEEE 10th International Symposium on Biomedical Imaging (ISBI 2013). IEEE, 2013. http://dx.doi.org/10.1109/isbi.2013.6556680.
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Everts, M. H., H. Bekker et J. B. T. M. Roerdink. « Visualizing white matter structure of the brain using Dijkstra's algorithm ». Dans 2009 6th International Symposium on Image and Signal Processing and Analysis. IEEE, 2009. http://dx.doi.org/10.1109/ispa.2009.5297652.
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Yushkevich, Paul A., Hui Zhang, Tony J. Simon et James C. Gee. « Structure-Specific Statistical Mapping of White Matter Tracts using the Continuous Medial Representation ». Dans 2007 IEEE 11th International Conference on Computer Vision. IEEE, 2007. http://dx.doi.org/10.1109/iccv.2007.4409169.
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Ramzanpour, Mohammadreza, Mohammad Hosseini-Farid, Mariusz Ziejewski et Ghodrat Karami. « Microstructural Hyperelastic Characterization of Brain White Matter in Tension ». Dans ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11549.
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Abstract Axons as microstructural constituent elements of brain white matter are highly oriented in extracellular matrix (ECM) in one direction. Therefore, it is possible to model the human brain white matter as a unidirectional fibrous composite material. A micromechanical finite element model of the brain white matter is developed to indirectly measure the brain white matter constituents’ properties including axon and ECM under tensile loading. Experimental tension test on corona radiata conducted by Budday et al. 2017 [1] is used in this study and one-term Ogden hyperelastic constitutive model is applied to characterize its behavior. By the application of genetic algorithm (GA) as a black box optimization method, the Ogden hyperelastic parameters of axon and ECM minimizing the error between numerical finite element simulation and experimental results are measured. Inverse analysis is conducted on the resultant optimized parameters shows high correlation of coefficient (>99%) between the numerical and experimental data which verifies the accuracy of the optimization procedure. The volume fraction of axons in porcine brain white matter is taken to be 52.7% and the stiffness ratio of axon to ECM is perceived to be 3.0. As these values are not accurately known for human brain white matter, we study the material properties of axon and ECM for different stiffness ratio and axon volume fraction values. The results of this study helps to better understand the micromechanical structure of the brain and micro-level injuries such as diffuse axonal injury.
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Wu, Xuehai, John G. Georgiadis et Assimina A. Pelegri. « Brain White Matter Model of Orthotropic Viscoelastic Properties in Frequency Domain ». Dans ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-12182.
Texte intégralRésumé :
Abstract Finite element analysis is used to study brain axonal injury and develop Brain White Matter (BWM) models while accounting for both the strain magnitude and the strain rate. These models are becoming more sophisticated and complicated due to the complex nature of the BMW composite structure with different material properties for each constituent phase. State-of-the-art studies, focus on employing techniques that combine information about the local axonal directionality in different areas of the brain with diagnostic tools such as Diffusion-Weighted Magnetic Resonance Imaging (Diffusion-MRI). The diffusion-MRI data offers localization and orientation information of axonal tracks which are analyzed in finite element models to simulate virtual loading scenarios. Here, a BMW biphasic material model comprised of axons and neuroglia is considered. The model’s architectural anisotropy represented by a multitude of axonal orientations, that depend on specific brain regions, adds to its complexity. During this effort, we develop a finite element method to merge micro-scale Representative Volume Elements (RVEs) with orthotropic frequency domain viscoelasticity to an integrated macro-scale BWM finite element model, which incorporates local axonal orientation. Previous studies of this group focused on building RVEs that combined different volume fractions of axons and neuroglia and simulating their anisotropic viscoelastic properties. Via the proposed model, we can assign material properties and local architecture on each element based on the information from the orientation of the axonal traces. Consecutively, a BWM finite element model is derived with fully defined both material properties and material orientation. The frequency-domain dynamic response of the BMW model is analyzed to simulate larger scale diagnostic modalities such as MRI and MRE.
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Okamoto, Ruth J., Yuan Feng, Guy M. Genin et Philip V. Bayly. « Anisotropic Behavior of White Matter in Shear and Implications for Transversely Isotropic Models ». Dans ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14039.
Texte intégralRésumé :
Experimental studies [1] have shown that white matter (WM) in the brain is mechanically anisotropic. Based on its fibrous structure, transversely isotropic (TI) material models have been suggested to capture WM behavior. TI hyperelastic material models involve strain energy density functions that depend on the I4 and I5 pseudo-invariants of the Cauchy-Green strain tensor to account for the effects of stiff fibers. The pseudo-invariant I4 is the square of the stretch ratio in the fiber direction; I5 contains contributions of shear strain in planes parallel to the fiber axis. Most, if not all, published models of WM depend on I4 but not on I5.
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Begonia, Mark G. T., Jun Liao, Mark F. Horstemeyer et Lakiesha N. Williams. « Strain Rate Dependence in the Structure Property Relationship of Porcine Brain ». Dans ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206371.
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The brain is the control center for the central nervous system (CNS), and it is composed of specialized divisions that are attributed to a vast assortment of structural, homeostatic, and cognitive functions. These distinct regions are surrounded by supportive tissue and comprised of a complex arrangement of neurons that can be further categorized as either gray or white matter. The cerebrum constitutes the larger surrounding portion of the forebrain and includes sinuous ridges called gyri that are separated by grooves or fissures called sulci. The intermediate layer of the cerebrum primarily consists of white matter tracts that are responsible for integrating various regions throughout the cerebrum. The innermost and outermost layers of tissue mainly contain gray matter and are collectively known as the subcortical nuclei and cerebral cortex, respectively, which are crucial integrating components of the CNS [1]. An investigation into the mechanical properties of this vital organ coupled with microstructural characterization of its constituents under varying deformation levels is therefore crucial for implementing more accurate prediction and prevention of traumatic brain injury (TBI).
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Zhang, Biaobiao, W. Steve Shepard et Candace L. Floyd. « Investigation of Stress Wave Propagation in Brain Tissues Through the Use of Finite Element Method ». Dans ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39994.
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Because axons serve as the conduit for signal transmission within the brain, research related to axon damage during brain injury has received much attention in recent years. Although myelinated axons appear as a uniform white matter, the complex structure of axons has not been thoroughly considered in the study of fundamental structural injury mechanisms. Most axons are surrounded by an insulating sheath of myelin. Furthermore, hollow tube-like microtubules provide a form of structural support as well as a means for transport within the axon. In this work, the effects of microtubule and its surrounding protein mediums inside the axon structure are considered in order to obtain a better understanding of wave propagation within the axon in an attempt to make progress in this area of brain injury modeling. By examining axial wave propagation using a simplified finite element model to represent microtubule and its surrounding proteins assembly, the impact caused by stress wave loads within the brain axon structure can be better understood. Through conducting a transient analysis as the wave propagates, some important characteristics relative to brain tissue injuries are studied.
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Feng, Yuan, Ruth J. Okamoto, Ravi Namani, Guy M. Genin et Philip V. Bayly. « Identification of a Transversely Isotropic Material Model for White Matter in the Brain ». Dans ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88610.
Texte intégralRésumé :
Axonal fiber tracts in white matter of the brain form anisotropic structures. It is assumed that this structural anisotropy causes mechanical anisotropy, making white matter tissue stiffer along the axonal fiber direction. This, in turn, will affect the mechanical loading of axonal tracts during traumatic brain injury (TBI). The goal of this study is to use a combination of in-vitro tests to characterize the mechanical anisotropy of white matter and compare it to gray matter, which is thought to be structurally and mechanically isotropic. A more complete understanding of the mechanical anisotropy of brain tissue will provide more accurate information for computational simulations of brain injury.
Rapports d'organisations sur le sujet "White matter structure"
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Tsybekmitova, G. Ts, L. D. Radnaeva, N. A. Tashlykova, V. G. Shiretorova, A. K. Tulokhonov, B. B. Bazarova et M. O. Matveeva. THE EFFECT OF CLIMATIC SHIFTS ON BIODIVERSITY OF PHYTOCENOSIS : LAKE ARAKHLEY (EASTERN SIBERIA, RUSSIA). DOICODE, 2020. http://dx.doi.org/10.18411/0973-7308-2020-35-3-77-90.
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Lake Arakhley is located within the Lake Baikal basin in Eastern Siberia, Russia. The area is characterized by continental subarctic climate with considerate diurnal temperature range, long cold dry winters and short hot summers with more precipitation occurring during the latter half of the summer. Climatic shifts in high water years and low water years result in morphometric changes in the lake and in the chemical and physical parameters of the ecosystem. During low water years, concentrations of ammonium nitrogen and nitrite nitrogen are decreased, whereas nitrate concentration increases. High water years feature average concentrations of ammonium ions 1.5–2 times higher than the values of recent dry years. Redundancy analysis (RDA) of abiotic factors and biotic community indicated that the community structure shows the greatest correlation with physical and chemical parameters of water and biogenic elements (nitrites, ammonium, phosphates) along the first axis, and with the lake depth and transparency along the second axis. Changes in abiotic factors induce functioning and formation of characteristic communities of the primary producers in the trophic structure of the ecosystem. During low water years, with increased level of autochthonous organic matter, Lindavia comta dominance is observed, while during high water years, with increased allochthonous organic matter Asterionella formosa appeared as dominant. Currently, during low water years, the hydrophytes community is monodominant and composed of Ceratophyllum demersum. Meanwhile, such species indicating eutrophic conditions as Myriophyllum sibiricum, Potamogeton pectinatus are found in the lake vegetation.
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Downard, Alicia, Stephen Semmens et Bryant Robbins. Automated characterization of ridge-swale patterns along the Mississippi River. Engineer Research and Development Center (U.S.), avril 2021. http://dx.doi.org/10.21079/11681/40439.
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The orientation of constructed levee embankments relative to alluvial swales is a useful measure for identifying regions susceptible to backward erosion piping (BEP). This research was conducted to create an automated, efficient process to classify patterns and orientations of swales within the Lower Mississippi Valley (LMV) to support levee risk assessments. Two machine learning algorithms are used to train the classification models: a convolutional neural network and a U-net. The resulting workflow can identify linear topographic features but is unable to reliably differentiate swales from other features, such as the levee structure and riverbanks. Further tuning of training data or manual identification of regions of interest could yield significantly better results. The workflow also provides an orientation to each linear feature to support subsequent analyses of position relative to levee alignments. While the individual models fall short of immediate applicability, the procedure provides a feasible, automated scheme to assist in swale classification and characterization within mature alluvial valley systems similar to LMV.
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Qi, Yan, Ryan Fries, Shambhu Saran Baral et Pranesh Biswas. Evaluating the Costs and Benefits of Snow Fences in Illinois : Phase 2. Illinois Center for Transportation, novembre 2020. http://dx.doi.org/10.36501/0197-9191/20-020.
Texte intégralRésumé :
Serving as a windbreak, properly sited and designed snow fences have been proven effective in mitigating the negative impacts of blowing snow. To achieve the best snow-control effects, the ideal locations for snow fences are usually outside the roadway right-of-way. Few efforts have been made to examine the economic efficiency of snow fences and explore ways to reward private landowners. The objective of this project was to develop methodologies for evaluation of the costs and benefits of snow fences in Illinois and identify ways to encourage private landowners’ participation in the snow fence program while keeping it cost-effective. The researchers conducted a literature review as well as agency and landowner surveys. They also acquired crash data, snow fence and blowing snow segment inventory data, and blowing snow removal expenditure data as well as performed benefit-cost analyses of three types of snow fences following Federal Highway Administration guides. The survey results suggested that standing corn rows (SCRs) and structural snow fences (SSFs) were the least intrusive options for landowners and living snow fences (LSFs) with trees were the most intrusive. Some concerns related to LSFs could be reduced by allowing landowners to play a role in the design and plant-selection process. The crash data indicated that no fatal and severe crashes occurred at snow fence segments, while several fatal and severe crashes occurred at blowing snow segments during 2012–2016. The results of the benefit-cost analyses showed that the benefit-cost ratios for LSFs and SSFs are comparable. However, LSFs are favorable over SSFs because little maintenance is needed after the plants are mature. Although SCRs have the highest benefit-cost ratio, the need to renew the agency-landowner agreement annually and the alternating of crops planted may limit their snow-control effectiveness and large-scale implementation. A tool was developed using MS Excel to facilitate the benefit-cost analysis of snow fences.
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Litaor, Iggy, James Ippolito, Iris Zohar et Michael Massey. Phosphorus capture recycling and utilization for sustainable agriculture using Al/organic composite water treatment residuals. United States Department of Agriculture, janvier 2015. http://dx.doi.org/10.32747/2015.7600037.bard.
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Objectives: 1) develop a thorough understanding of the sorption mechanisms of Pi and Po onto the Al/O- WTR; 2) determine the breakthrough range of the composite Al/O-WTR during P capturing from agro- wastewaters; and 3) critically evaluate the performance of the composite Al/O-WTR as a fertilizer using selected plants grown in lysimeters and test-field studies. Instead of lysimeters we used pots (Israel) and one- liter cone-tainers (USA). We conducted one field study but in spite of major pretreatments the soils still exhibited high enough P from previous experiments so no differences between control and P additions were noticeable. Due to time constrains the field study was discontinued. Background: Phosphorous, a non-renewable resource, has been applied extensively in fields to increase crop yield, yet consequently has increased the potential of waterway eutrophication. Our proposal impetus is the need to develop an innovative method of P capturing, recycling and reuse that will sustain agricultural productivity while concurrently reducing the level of P discharge from and to agricultural settings. Major Conclusions & Achievements: An innovative approach was developed for P removal from soil leachate, dairy wastewater (Israel), and swine effluents (USA) using Al-based water treatment residuals (Al- WTR) to create an organic-Al-WTR composite (Al/O-WTR), potentially capable of serving as a P fertilizer source. The Al-WTR removed 95% inorganic-P, 80% to 99.9% organic P, and over 60% dissolved organic carbon from the agro-industrial waste streams. Organic C accumulation on particles surfaces possibly enhanced weak P bonding and facilitated P desorption. Analysis by scanning electron microscope (SEM- EDS), indicated that P was sparsely sorbed on both calcic and Al (hydr)oxide surfaces. Sorption of P onto WW-Al/O-WTR was reversible due to weak Ca-P and Al-P bonds induced by the slight alkaline nature and in the presence of organic moieties. Synchrotron-based microfocused X-ray fluorescence (micro-XRF) spectrometry, bulk P K-edge X-ray absorption near edge structure spectroscopy (XANES), and P K-edge micro-XANES spectroscopy indicated that adsorption was the primary P retention mechanism in the Al- WTR materials. However, distinct apatite- or octocalciumphosphatelike P grains were also observed. Synchrotron micro-XRF mapping further suggested that exposure of the aggregate exteriors to wastewater caused P to diffuse into the porous Al-WTR aggregates. Organic P species were not explicitly identified via P K-edge XANES despite high organic matter content, suggesting that organic P may have been predominantly associated with mineral surfaces. In screen houses experiments (Israel) we showed that the highest additions of Al/O-WTR (5 and 7 g kg⁻¹) produced the highest lettuce (Lactuca sativa L. var. longifolial) yield. Lettuce yield and P concentration were similar across treatments, indicating that Al/O- WTR can provide sufficient P to perform similarly to common fertilizers. A greenhouse study (USA) was utilized to compare increasing rates of swine wastewater derived Al/O-WTR and inorganic P fertilizer (both applied at 33.6, 67.3, and 134.5 kg P₂O₅ ha⁻¹) to supply plant-available P to spring wheat (TriticumaestivumL.) in either sandy loam or sandy clay loam soil. Spring wheat straw and grain P uptake were comparable across all treatments in the sandy loam, while Al/O-WTR application to the sandy clay loam reduced straw and grain P uptake. The Al/O-WTR did not affect soil organic P concentrations, but did increase phosphatase activity in both soils; this suggests that Al/O-WTR application stimulated microorganisms and enhance the extent to which microbial communities can mineralize Al/O-WTR-bound organic P. Implications: Overall, results suggest that creating a new P fertilizer from Al-WTR and agro-industrial waste sources may be a feasible alternative to mining inorganic P fertilizer sources, while protecting the environment from unnecessary waste disposal.
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Lacerda Silva, P., G. R. Chalmers, A. M. M. Bustin et R. M. Bustin. Gas geochemistry and the origins of H2S in the Montney Formation. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329794.
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The geology of the Montney Formation and the geochemistry of its produced fluids, including nonhydrocarbon gases such as hydrogen sulfide were investigated for both Alberta and BC play areas. Key parameters for understanding a complex petroleum system like the Montney play include changes in thickness, depth of burial, mass balance calculations, timing and magnitudes of paleotemperature exposure, as well as kerogen concentration and types to determine the distribution of hydrocarbon composition, H2S concentrations and CO2 concentrations. Results show that there is first-, second- and third- order variations in the maturation patterns that impact the hydrocarbon composition. Isomer ratio calculations for butane and propane, in combination with excess methane estimation from produced fluids, are powerful tools to highlight effects of migration in the hydrocarbon distribution. The present-day distribution of hydrocarbons is a result of fluid mixing between hydrocarbons generated in-situ with shorter-chained hydrocarbons (i.e., methane) migrated from deeper, more mature areas proximal to the deformation front, along structural elements like the Fort St. John Graben, as well as through areas of lithology with higher permeability. The BC Montney play appears to have hydrocarbon composition that reflects a larger contribution from in-situ generation, while the Montney play in Alberta has a higher proportion of its hydrocarbon volumes from migrated hydrocarbons. Hydrogen sulphide is observed to be laterally discontinuous and found in discrete zones or pockets. The locations of higher concentrations of hydrogen sulphide do not align with the sulphate-rich facies of the Charlie Lake Formation but can be seen to underlie areas of higher sulphate ion concentrations in the formation water. There is some alignment between CO2 and H2S, particularly south of Dawson Creek; however, the cross-plot of CO2 and H2S illustrates some deviation away from any correlation and there must be other processes at play (i.e., decomposition of kerogen or carbonate dissolution). The sources of sulphur in the produced H2S were investigated through isotopic analyses coupled with scanning electron microscopy, energy dispersive spectroscopy, and mineralogy by X-ray diffraction. The Montney Formation in BC can contain small discrete amounts of sulphur in the form of anhydrite as shown by XRD and SEM-EDX results. Sulphur isotopic analyses indicate that the most likely source of sulphur is from Triassic rocks, in particular, the Charlie Lake Formation, due to its close proximity, its high concentration of anhydrite (18-42%), and the evidence that dissolved sulphate ions migrated within the groundwater in fractures and transported anhydrite into the Halfway Formation and into the Montney Formation. The isotopic signature shows the sulphur isotopic ratio of the anhydrite in the Montney Formation is in the same range as the sulphur within the H2S gas and is a lighter ratio than what is found in Devonian anhydrite and H2S gas. This integrated study contributes to a better understanding of the hydrocarbon system for enhancing the efficiency of and optimizing the planning of drilling and production operations. Operators in BC should include mapping of the Charlie Lake evaporites and structural elements, three-dimensional seismic and sulphate ion concentrations in the connate water, when planning wells, in order to reduce the risk of encountering unexpected souring.
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Ossoff, Will, Naz Modirzadeh et Dustin Lewis. Preparing for a Twenty-Four-Month Sprint : A Primer for Prospective and New Elected Members of the United Nations Security Council. Harvard Law School Program on International Law and Armed Conflict, décembre 2020. http://dx.doi.org/10.54813/tzle1195.
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Under the United Nations Charter, the U.N. Security Council has several important functions and powers, not least with regard to taking binding actions to maintain international peace and security. The ten elected members have the opportunity to influence this area and others during their two-year terms on the Council. In this paper, we aim to illustrate some of these opportunities, identify potential guidance from prior elected members’ experiences, and outline the key procedures that incoming elected members should be aware of as they prepare to join the Council. In doing so, we seek in part to summarize the current state of scholarship and policy analysis in an effort to make this material more accessible to States and, particularly, to States’ legal advisers. We drafted this paper with a view towards States that have been elected and are preparing to join the Council, as well as for those States that are considering bidding for a seat on the Council. As a starting point, it may be warranted to dedicate resources for personnel at home in the capital and at the Mission in New York to become deeply familiar with the language, structure, and content of the relevant provisions of the U.N. Charter. That is because it is through those provisions that Council members engage in the diverse forms of political contestation and cooperation at the center of the Council’s work. In both the Charter itself and the Council’s practices and procedures, there are structural impediments that may hinder the influence of elected members on the Security Council. These include the permanent members’ veto power over decisions on matters not characterized as procedural and the short preparation time for newly elected members. Nevertheless, elected members have found creative ways to have an impact. Many of the Council’s “procedures” — such as the “penholder” system for drafting resolutions — are informal practices that can be navigated by resourceful and well-prepared elected members. Mechanisms through which elected members can exert influence include the following: Drafting resolutions; Drafting Presidential Statements, which might serve as a prelude to future resolutions; Drafting Notes by the President, which can be used, among other things, to change Council working methods; Chairing subsidiary bodies, such as sanctions committees; Chairing the Presidency; Introducing new substantive topics onto the Council’s agenda; and Undertaking “Arria-formula” meetings, which allow for broader participation from outside the Council. Case studies help illustrate the types and degrees of impact that elected members can have through their own initiative. Examples include the following undertakings: Canada’s emphasis in 1999–2000 on civilian protection, which led to numerous resolutions and the establishment of civilian protection as a topic on which the Council remains “seized” and continues to have regular debates; Belgium’s effort in 2007 to clarify the Council’s strategy around addressing natural resources and armed conflict, which resulted in a Presidential Statement; Australia’s efforts in 2014 resulting in the placing of the North Korean human rights situation on the Council’s agenda for the first time; and Brazil’s “Responsibility while Protecting” 2011 concept note, which helped shape debate around the Responsibility to Protect concept. Elected members have also influenced Council processes by working together in diverse coalitions. Examples include the following instances: Egypt, Japan, New Zealand, Spain, and Uruguay drafted a resolution that was adopted in 2016 on the protection of health-care workers in armed conflict; Cote d’Ivoire, Kuwait, the Netherlands, and Sweden drafted a resolution that was adopted in 2018 condemning the use of famine as an instrument of warfare; Malaysia, New Zealand, Senegal, and Venezuela tabled a 2016 resolution, which was ultimately adopted, condemning Israeli settlements in Palestinian territory; and A group of successive elected members helped reform the process around the imposition of sanctions against al-Qaeda and associated entities (later including the Islamic State of Iraq and the Levant), including by establishing an Ombudsperson. Past elected members’ experiences may offer some specific pieces of guidance for new members preparing to take their seats on the Council. For example, prospective, new, and current members might seek to take the following measures: Increase the size of and support for the staff of the Mission to the U.N., both in New York and in home capitals; Deploy high-level officials to help gain support for initiatives; Partner with members of the P5 who are the informal “penholder” on certain topics, as this may offer more opportunities to draft resolutions; Build support for initiatives from U.N. Member States that do not currently sit on the Council; and Leave enough time to see initiatives through to completion and continue to follow up after leaving the Council.