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1
Ucar, Egemen. "Ternary Nanocomposites Of High Density, Linear Low Density And Low Density Polyethylenes." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608446/index.pdf.
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In this study, the effects of organoclay loading, compatibilizer loading and polyethylene type on the morphology, rheology, thermal properties and mechanical properties of polyethylene/compatibilizer/organoclay nanocomposites were investigated. As compatibilizer, terpolymer of ethylene-methacrylate-glycidyl methacrylate (Lotader®AX8900), as organoclay Cloisite®
15A were used. All samples were prepared by a co-rotating twin screw extruder, followed by injection molding. Considering ternary nanocomposites, highest impact strength results were obtained with 10% compatibilizer plus 2% organoclay
highest yield stress, elastic modulus, flexural strength, flexural modulus were obtained with 5% compatibilizer plus 4-6% organoclay. DSC data indicated that addition of organoclay and compatibilizer did not change the melting point remarkably
on the other hand it affected the crystallinity. The organoclay used had no nucleation effect on polyethylene, and the compatibilizer decreased the crystallinity of the matrix. X-ray diffraction showed that in all ternary nanocomposites and in binary nanocomposite of high density polyethylene with organoclay, layer separation associated with intercalation of the clay structure occurred,. The highest increase of interlayer gallery spacing was obtained with 10% compatibilizer plus 2% organoclay, which were 25%, 28% and 27% for HDPE, LLDPE and LDPE matrices respectively.
2
Cappello, Christian. "Ozoniertes Low Density-Lipoprotien (OzLDL)." kostenfrei, 2009. http://mediatum2.ub.tum.de/node?id=679935.
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Guo, Feng. "Low density parity check coding." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419159.
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Oliver, Matthew. "Density, temperature and magnetic field measurements in low density plasmas." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:df217453-1e10-4684-beb7-83c1bcecf285.
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Low density plasmas are found throughout the known universe. Therefore, accurate diagnostic methods have implications for our understanding of a variety of topics, ranging from star formation to the semi conductor industry. Low density plasmas are ubiquitous in the material processing industry. However, measurements of the electron temperature and density, two of the most fundamental plasma properties, are not straightforward. In the laboratory, we create a low density, radio frequency, helium plasma with a bi-Maxwellian electron distribution, similar to those found in the semiconductor processing industry. We use optical emission spectroscopy to perform a non invasive measurement of the plasma conditions. We compare this to measurements obtained using a Langmuir probe, a commonly used invasive diagnostic. The optical emission spectroscopy is found to be insensitive to electron density but good agreement is found between the two techniques for values of the temperature of the hot electron component of the bi-Maxwellian. Plasmas created with high-intensity lasers are able to recreate conditions similar to those found during astrophysical events. This development has led to these condi- tions being explored in laboratories around the world. An experiment was performed at the Rutherford Appleton Laboratory in Didcot, UK, investigating the properties of supersonic turbulent jets. For the first time a magneto-optic probe was used to measure the magnetic field in a low-density supersonic turbulent plasma. The results were compared to measurements taken using a magnetic-induction probe. Good agreement was found between measurements of the magnetic field strength within the plasma; however, the magnetic power spectra differ. We attribute this to the dif- ference in integration length between the two measurements. Statistical properties of the velocity field are inferred from the magnetic field measurements, which compare favourably to astrophysical observations and hydrodynamic simulations.
5
Isik, Coskunses Fatma. "Ternary Nanocomposites Of Low Density,high Density And Linear Low Density Polyethylenes With The Compatibilizers E-ma_gma And E-ba-mah." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613294/index.pdf.
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The effects of polyethylene, (PE), type, compatibilizer type and organoclay type
on the morphology, rheological, thermal, and mechanical properties of ternary
low density polyethylene (LDPE), high density polyethylene (HDPE), and linear
low density polyethylene (LLDPE), matrix nanocomposites were investigated in
this study. Ethylene &ndashMethyl acrylate &ndash
Glycidyl methacrylate terpolymer (E-MAGMA) and Ethylene &ndash
Butyl acrylate- Maleic anhydrate terpolymer (E-BA-MAH) were used as the compatibilizers. The organoclays selected for the study were Cloisite 30B and Nanofil 8. Nanocomposites were prepared by means of melt blending via co-rotating twin screw extrusion process. Extruded samples were injection molded to be used for material characterization tests. Optimum amounts of ingredients of ternary nanocomposites were determined based on to the mechanical test results of binary blends of PE/Compatibilizer and binary nanocomposites of PE/Organoclay. Based on the tensile test results, the optimum contents of compatibilizer and organoclay were determined as 5 wt % and 2 wt %, respectively. XRD and TEM analysis results indicated that intercalated and partially exfoliated structures were obtained in the ternary nanocomposites. In these nanocomposites E-MA-GMA compatibilizer produced higher d-spacing in comparison to E-BA-MAH, owing to its higher reactivity. HDPE exhibited the highest basal spacing among all the nanocomposite types with E-MA-GMA/30B system. Considering the polymer type, better dispersion was achieved in the order of LDPE<
LLDPE<
HDPE, owing to the linearity of HDPE, and short branches of LLDPE. MFI values were decreased by the addition of compatibilizer and organoclay to the matrix polymers. Compatibilizers imparted the effect of sticking the polymer blends on the walls of test apparatus, and addition of organoclay showed the filler effect and increased the viscosity. DSC analysis showed that addition of compatibilizer or organoclay did not significantly affect the melting behavior of the nanocomposites. Degree of crystallinity of polyethylene matrices decreased with organoclay addition. Nanoscale organoclays prevented the alignment of polyethylene chains and reduced the degree of crystallinity. Ternary nanocomposites had improved tensile properties. Effect of compatibilizer on property enhancement was observed in mechanical results. Tensile strength and Young&rsquo
s modulus of nanocomposites increased significantly in the presence of compatibilizers.
6
Pirou, Florent. "Low-density Parity-Check decoding Algorithms." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2160.
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Recently, low-density parity-check (LDPC) codes have attracted much attention because of their excellent error correcting performance and highly parallelizable decoding scheme. However, the effective VLSI implementation of and LDPC decoder remains a big challenge and is a crucial issue in determining how well we can exploit the benefits of the LDPC codes in the real applications. In this master thesis report, following a error coding background, we describe Low-Density Parity-Check codes and their decoding algorithm, and also requirements and architectures of LPDC decoder implementations.
7
Warburton, Keith. "Control jets in low density flow." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312454.
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Hogg, Neil. "Oxidative modification of low density lipoprotein." Thesis, University of Essex, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316228.
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Ahmad, Feroz. "Lysosomal oxidation of Low Density Lipoproteins." Thesis, University of Reading, 2017. http://centaur.reading.ac.uk/72957/.
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Oxidation of LDL is widely believed to be a key process in the pathogenesis of atherosclerosis. However, LDL oxidation has been shown to be inhibited by interstitial fluid and also large clinical trials have shown no protection by antioxidant. Recent work has shown that LDL can be oxidised by iron within the lysosomes of macrophages. Here, we have explored the possible mechanism by which iron is able to oxidise LDL under lysosomal conditions, and also how lysosomotropic antioxidant, cysteamine is able to prevent it. More recently, it has been shown that human macrophages are able to rapidly phagocytose LDL aggregated by enzymes, such as sphingomyelinase (SMaseLDL) and oxidised it by iron inside lysosomes, which have a pH of about 4.5. Here, the chemical characteristics (lipid hydroperoxides and oxysterols) of SMase-LDL oxidised by inorganic iron at lysosomal pH (4.5) have been determined in vitro and compared to the native LDL. In the lysosomes of macrophages, SMase-LDL increased the intralysosomal lipid peroxidation and ceroid formation which was greatly inhibited by cysteamine. There is good evidence which suggests that lysosomal dysfunction plays an important role in the atherosclerotic plaque development. Here, it is shown that lysosomal oxidation of SMase-LDL in human macrophages can cause lysosomal dysfunction, induce ceroid associated cellular senescence, and increase the expression of inflammatory cytokine like TNF-α. The work here also demonstrates that preventing the lysosomal LDL oxidation, with antioxidants like cysteamine, offers protection against the SMase-LDL induced lysosomal dysfunction.
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Verdugo, Salgado Celia Anahi. "Star formation in low gas density and low metallicity environments." Observatoire de Paris, 2015. https://hal.science/tel-02095302.
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Dans les galaxies proches, la relation empirique de Kennicutt-Schmidt (KS) a été établie entre la densité surfacique de formation d’étoiles et la densité surfacique de gaz. Elle est forte et presque linéaire quand on considère le gaz moléculaire (H2) mais devient moins valable lorsque l’hydrogène n’est qu’atomique (HI). Ces régions de densité de gaz faible sont d’une importance cruciale dans le domaine de la formation d’étoiles, car elles possèdent les mêmes conditions que dans les galaxies de l’univers jeune, de faible métallicité. Cette thèse compile les données observationnelles obtenues au télescope de 30 m. De l’IRAM sur deux types de régions distinctes : les galaxies à disque ayant une émission ultra-violet étendue (XUV), et le milieu interstellaire déplacé dans le milieu intra-amas (ICM) chaud sous l’effet du balayage de la pression dynamique dans l’amas de la Vierge. Pour déterminer la présence des molécules H2 et afin d’étudier la relation KS dans ces régions, des observations de CO ont été faites dans les parties externes des galaxies XUV, et nous avons à la fois des détections et des limites supérieures. Les relations KS ont montré une loi de puissance discontinue pour des densités de gaz faibles, en dessous du seuil de la transition de phase HI-H2. Dans l’amas de la Vierge, des observations similaires de Co ont été faites le long des bras marée qui relient NGC4388 et M86, où aucune présence de H2 n’est attendue. Nous avons effectué des détections, montrant une efficacité de formation d’étoiles très faible, et montrant de nouveau une discontinuité de la relation KS pour des densités de gaz faibles, prouvant que les processus bien connus de consommation du gaz à forte densité ne peuvent être généralisés aux densités plus faibles. D’autre part, nos résultats montrent que le gaz H2 peut survivre un temps long que prévu dans l’ICM hostileIn nearby galaxies, an empirical relation has been established between star formation and gas surface densities, the Kennicutt-Schmidt (KS). The relation is nearly linear when molecular gas (H2) is considered, while is less tight with atomic hydrogen (HI). These low gas density regions are of a key importance in the field of star formation, since the are also low metallicity environments, resembling the conditions of a younger universe. This thesis summarizes the observational work done with the IRAM 30MT telescope in two kinds of such regions : disk galaxies with extended ultra-violet emission (XUV), and the interstellar medium going into the hot intra-cluster medium (ICM) under ram-pressure stripping in the Virgo cluster. The galex telescope has unveiled in far ultra-violet (FUV) star formation in the outer parts of some disk galaxies that was not traced by HA. To determine the presence of H2 and analyse the K-S relation in these regions, CO observations where done in the outskirts of several XUV disk galaxies, finding both detections and upper limits. These K-S relations showed a broken power law at low gas densities, below the HI-H2 threshold. In the Virgo cluster, similar CO observations were done along the HI tidal arm connecting NGC4388 and M86, where no H2 is expected. Two detections were found, showing very low star formation efficiencies (depleting less than 0,1 % of the gas reservoir per 10 [exposant] 8 yr), and showing again a disconuity of the K-S relation at low gas densities, probing that the process of a gas consumption into stars well known at high densities cannot be extrapolated to lower densities, and that H2 can survive a certain time in the hostile ICM
11
Mizutani, T., H. Semi, and K. Kaneko. "Space charge behavior in low-density polyethylene." IEEE, 2000. http://hdl.handle.net/2237/6796.
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Behravesh, Amir Hossein. "Extrusion processing of low-density microcellular foams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/NQ35110.pdf.
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Gopalraj, Rangaraj K. "LOW DENSITY LIPOPROTEIN RECEPTOR AND ALZHEIMERS DISEASE." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/697.
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Since apoE allele status is the predominant Alzheimers disease (AD) genetic risk factor, functional single nucleotide polymorphisms (SNPs) in brain apoE receptors represent excellent candidates for association with AD. Therefore, three low density lipoprotein receptor (LDLR) SNPs were evaluated by TaqMan allelic discrimination assays for association with AD and I found that certain haplotypes alter the odds of AD. A SNP within LDLR exon 12, rs688, was identified in silico as neutralizing a putative exon splicing enhancer (ESE). Since LDLR is a major apoE receptor in the brain, I hypothesized that rs688 modulates LDLR splicing in neural tissues and associates with AD. To evaluate this hypothesis, I analyzed splicing patterns in human hippocampus samples and established that this SNP was associated with significantly decreased LDLR exon 12 splicing efficiency when the minor allele T is present in vivo. Lastly, I evaluated whether rs688 associates with AD by genotyping DNA from the Religious Orders Study (ROS) series. The rs688T/T genotype was associated with increased AD odds in males, but not in females, in a dataset consisting of 1,457 men and 2,055 women drawn from three case-control series. The rs688T/T genotype was associated with increased AD odds in males (recessive model, odds ratio (OR) of 1.49, 95% confidence interval (CI) of 1.13- 1.97, uncorrected p=0.005), but not in females. In summary, these studies identify a functional apoE receptor SNP that is associated with AD in a sex-dependent fashion.
14
McDowell, Andrew. "Modifications of low density lipoprotein and atherosclerosis." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314171.
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Martin, P. J. "Heat transfer through low density fibrous assemblies." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235418.
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Yiangou, Savvakis Chrysostomou. "Fatigue crack propagation in low density polyethylene." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47317.
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Ozlutas, Kezban. "Behaviour of ultra-low density foamed concrete." Thesis, University of Dundee, 2015. https://discovery.dundee.ac.uk/en/studentTheses/ece1c184-2dee-428b-8742-7515c09f230f.
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Kratzert, Daniel. "Charge Density Distribution in Low-Valent Tetrels." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://hdl.handle.net/11858/00-1735-0000-001C-63A3-B.
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Niepötter, Benedikt. "Charge Density Analysis of Low-Valent Tetrels." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-86C1-8.
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Planjery, Shiva Kumar. "Low-Complexity Finite Precision Decoders for Low-Density Parity-Check Codes." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605947.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaWe present a new class of finite-precision decoders for low-density parity-check (LDPC) codes. These decoders are much lower in complexity compared to conventional floating-point decoders such as the belief propagation (BP) decoder, but they have the potential to outperform BP. The messages utilized by the decoders assume values (or levels) from a finite discrete set. We discuss the implementation aspects as well as describe the underlying philosophy in designing these decoders. We also provide results to show that in some cases, only 3 bits are required in the proposed decoders to outperform floating-point BP.
21
Selvarathinam, Anand Manivannan. "High throughput low power decoder architectures for low density parity check codes." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2529.
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A high throughput scalable decoder architecture, a tiling approach to reduce the
complexity of the scalable architecture, and two low power decoding schemes have been
proposed in this research. The proposed scalable design is generated from a serial
architecture by scaling the combinational logic; memory partitioning and constructing a
novel H matrix to make parallelization possible. The scalable architecture achieves a high
throughput for higher values of the parallelization factor M. The switch logic used to
route the bit nodes to the appropriate checks is an important constituent of the scalable
architecture and its complexity is high with higher M. The proposed tiling approach is
applied to the scalable architecture to simplify the switch logic and reduce gate
complexity.
The tiling approach generates patterns that are used to construct the H matrix by
repeating a fixed number of those generated patterns. The advantages of the proposed
approach are two-fold. First, the information stored about the H matrix is reduced by onethird.
Second, the switch logic of the scalable architecture is simplified. The H matrix information is also embedded in the switch and no external memory is needed to store the
H matrix.
Scalable architecture and tiling approach are proposed at the architectural level of the
LDPC decoder. We propose two low power decoding schemes that take advantage of the
distribution of errors in the received packets. Both schemes use a hard iteration after a
fixed number of soft iterations. The dynamic scheme performs X soft iterations, then a
parity checker cHT that computes the number of parity checks in error. Based on cHT
value, the decoder decides on performing either soft iterations or a hard iteration. The
advantage of the hard iteration is so significant that the second low power scheme
performs a fixed number of iterations followed by a hard iteration. To compensate the bit
error rate performance, the number of soft iterations in this case is higher than that of
those performed before cHT in the first scheme.
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Persons, Jane Elizabeth. "Characterizing the relationship between low serum low-density lipoprotein and depressive symptoms." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/5600.
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The purpose of this study was to resolve a critical gap in depression literature through assessment of the temporal relationship between depression and low LDL.
A systematic review and meta-analysis was conducted to investigate the overall cross-sectional association between serum LDL and depression. Inconsistent findings suggest that more work must be done to clarify the link between LDL and depression.
Next, Cox regression was used to explore the association between LDL and the subsequent onset of depressive symptoms within a subset of the Women’s Health Initiative cohort and evaluate the potential for effect modification by lipid-lowering medication use. This study provides evidence toward an association between low LDL and the subsequent onset of depressive symptoms, with increased risk confined to LDL below 100 mg/dL. Elevated risk was not associated with lipid-lowering medication use.
The final study examined the differences in the magnitude and direction of change in serum LDL levels among individuals experiencing new-onset depression, and examines the potential for physical activity, energy intake, and total body weight to mediate the depression-LDL relationship. This study provides no evidence of an association between depression and subsequent serum LDL changes.
Altogether, this data suggests that LDL that is below 100 mg/dL without the use of lipid-lowering medication may predispose individuals to a greater risk of depression, and also suggests that low LDL is not likely a state brought about by physiological or behavioral changes following the onset of depression.
23
Chandler, Gary James. "Sensitivity analysis of low-density jets and flames." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/246531.
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This work represents the initial steps in a wider project that aims to map out the sensitive areas in fuel injectors and combustion chambers. Direct numerical simulation (DNS) using a Low-Mach-number formulation of the Navier–Stokes equations is used to calculate direct-linear and adjoint global modes for axisymmetric low-density jets and lifted jet diffusion flames. The adjoint global modes provide a map of the most sensitive locations to open-loop external forcing and heating. For the jet flows considered here, the most sensitive region is at the inlet of the domain. The sensitivity of the global-mode eigenvalues to force feedback and to heat and drag from a hot-wire is found using a general structural sensitivity framework. Force feedback can occur from a sensor-actuator in the flow or as a mechanism that drives global instability. For the lifted flames, the most sensitive areas lie between the inlet and flame base. In this region the jet is absolutely unstable, but the close proximity of the flame suppresses the global instability seen in the non-reacting case. The lifted flame is therefore particularly sensitive to outside disturbances in the non-reacting zone. The DNS results are compared to a local analysis. The most absolutely unstable region for all the flows considered is at the inlet, with the wavemaker slightly downstream of the inlet. For lifted flames, the region of largest sensitivity to force feedback is near to the location of the wavemaker, but for the non-reacting jet this region is downstream of the wavemaker and outside of the pocket of absolute instability near the inlet. Analysing the sensitivity of reacting and non-reacting variable-density shear flows using the low-Mach-number approximation has up until now not been done. By including reaction, a large forward step has been taken in applying these techniques to real fuel injectors.
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Karl, Michelle Marie. "Modelling the viscoelastic properties of low density polyethylene." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0013/MQ52585.pdf.
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Meidan, Amir. "Linear-time encodable low-density parity-check codes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/MQ40942.pdf.
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Sharifi, Tehrani Saeed. "Stochastic decoding of low-density parity-check codes." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97010.
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Low-Density Parity-Check (LDPC) codes are one of the most powerful classes of error-control codes known to date. These codes have been considered for many recent digital communication applications. In this dissertation, we propose stochastic decoding of state-of-the-art LDPC codes and demonstrate it as a competitive approach to practical LDPC decoding algorithms.In stochastic decoding, probabilities are represented as streams of random bits using Bernoulli sequences in which the information is contained in the statistics of the bit stream. This representation results in low hardware-complexity processing nodes that perform computationally-intensive operations. However, stochastic decoding is prone to the acute problem of latching. This problem is caused by correlated bit streams within cycles in the code's factor graph, and significantly deteriorates the performance of stochastic LDPC decoders.We propose edge memories, tracking forecast memories, and majority-based tracking forecast memories to address the latching problem. These units efficiently extract the evolving statistics of stochastic bit streams and rerandomize them to disrupt latching. To the best of our knowledge, these methods are the first successful methods for stochastic decoding of state-of-the-art LDPC codes.We present novel decoder architectures and report on several hardware implementations. The most advanced reported implementation is a stochastic decoder that decodes the (2048,1723) LDPC code from the IEEE 802.3an standard. To the best of our knowledge, this decoder is the most silicon area-efficient and, with a maximum core throughput of 61.3 Gb/s, is one of the fastest fully parallel soft-decision LDPC decoders reported in the literature. We demonstrate the performance of this decoder in low bit-error-rate regimes.In addition to stochastic LDPC decoding, we propose the novel application of the stochastic approach for joint decoding of LDPC codes and partial-response channels that are considered in practical magnetic recording applications. Finally, we investigate the application of the stochastic approach for decoding linear block codes with high-density parity-check matrices on factor graphs. We consider Reed-Solomon, Bose-Chaudhuri-Hocquenghem, and block turbo codes.À ce jour, les codes Low-Density Parity-Check (LDPC) font partie des codes correcteurs d'erreurs les plus performants. Ces codes sont inclus dans différents standards de communications numériques. Dans ce manuscrit, nous proposons d'utiliser le décodage stochastique pour les codes LDPC. D'autre part, nous démontrons que pour les codes LDPC, le décodage stochastique représente une alternative réaliste aux algorithmes de décodage existants.Dans le processus de décodage stochastique, les probabilités sont représentées sous forme de séquences de Bernoulli. L'information est contenue dans la statistique de ces flux binaires aléatoires. Cette représentation particulière permet d'exécuter des calculs intensifs avec une faible complexité matérielle. Cependant le décodage stochastique est enclin au problème du verrouillage ("latching"). La corrélation entre les bits des différents flux au sein des cycles du graphe biparti dégrade les performances du décodage stochastique des codes LDPC. Pour résoudre le problème du verrouillage, nous proposons trois solutions: les mémoires de branche, les mémoires de suivi, et les mémoires de suivi à majorité. Ces différents composants permettent de suivre l'évolution de la statistique des flux binaires et de réintroduire des éléments aléatoires au sein des séquences observées, minimisant ainsi le phénomène de verrouillage. À notre connaissance, il s'agit là des premiers résultats probants permettant un décodage stochastique efficace des codes LDPC. Nous proposons de nouvelles architectures de décodeurs associées à leurs implantations matérielles respectives. La plus perfectionnée des architectures présentée ici est celle d'un décodeur stochastique pour le code LDPC (2048,1723) associé au standard IEEE 802.3an. À notre connaissance, en comparaison avec l'état de l'art actuel, ce décodeur dispose du meilleur rapport vitesse/complexité. Le débit maximum (au niveau du coeur), est de 61.3 Gb/s, il s'agit là du plus rapide des décodeurs de codes LDPC à décisions souples connu à ce jour. Nous présentons par ailleurs les performances de ce décodeur à très faible taux d'erreurs binaire. De plus, nous proposons d'appliquer le calcul stochastique au décodage conjoint des codes LDPC et des canaux à réponse partielle qui est utilisé dans les applications d'enregistrement magnétique. Enfin, nous étudions l'extension du décodage stochastique au décodage des codes en blocs ayant une matrice de parité à forte densité. Nous appliquons le décodage stochastique sur des graphes biparti aux codes Reed-Solomon, Bose-Chaudhuri-Hocquenghem, et aux turbocodes en blocs.
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Brooks, David Graham. "Aspects of low density lipoprotein receptor gene regulation." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360598.
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Davey, M. C. "Error-correction using low-density parity-check codes." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598305.
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Gallager's low-density parity-check codes are defined by sparse parity-check matrices, usually with a random contruction. Such codes have near Shannon limit performance when decoded using an iterative probabilistic decoding algorithm. We report two advances that improve the error-correction performance of these codes. First, defining the codes over non-binary fields we can obtain a 0.6 dB improvement in signal to noise ratio for a given bit error rate. Second, using irregular parity-check matrices with non-uniform row and column weights we obtain gains of up to 0.5 dB. The empirical error-correction performance of irregular low-density parity-check codes is unbeaten for the additive white Gaussian noise channel. Low-density parity-check codes are also shown to be useful for communicating over channels which make insertions and deletions as well as additive (substitution) errors. Error-correction for such channels has not been widely studied, but is of importance whenever synchronisation of sender and receiver is imperfect. We introduce concatenated codes using novel non-linear inner codes which we call 'watermark' codes, and low-density parity-check codes over non-binary fields as outer codes. The inner code allows resynchronisation using a probabilistic decoder, providing soft outputs for the outer low-density parity-check decoder. Error-correction performance using watermark codes is several orders of magnitude better than any comparable results in the literature.
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Ling, I.-Fang. "REGULATION OF LOW DENSITY LIPOPROTEIN RECEPTOR SPLICING EFFICIENCY." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/794.
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Low density lipoprotein receptor (LDLR) is an apolipoprotein E (apoE) receptor and may play a role in Alzheimer’s disease (AD) development. A single nucleotide polymorphism (SNP), rs688, that has been identified to modulate the splicing efficiency of LDLR exon 12 and is associated with higher cholesterol and AD in some case-control populations. The exon 12 deleted mRNA is predicted to produce a soluble form of LDLR that fails to mediate apoE uptake. To gain additional insights, in this study, I seek to understand the regulation of LDLR splicing efficiency. To identify functional cis-elements within LDLR exon 12, I mutated several conserved putative exonic splicing enhancers (ESEs) to neutralize their affinity to serine/arginine-rich (SR) proteins. Transfection of wild type (WT) or mutant LDLR minigenes in HepG2 cells was performed, and splicing efficiency evaluated by quantitative RT-PCR. The results showed that two functional ESEs within exon 12, near rs688, are critical to LDLR splicing. To identify splicing factors that modulate exon 12 splicing, I co-transfected an LDLR minigene and vectors encoding different SR proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs). After quantifying the splicing efficiency, I found that SRp20 and SRp38 increased exon 11- skipping. Moreover, ectopic expression of SRp38-2 and hnRNP G increased exon 11&12-skipping. Interestingly, the actions of hnRNP G did not require its RNA recognition motif (RRM). To further investigate the role of theses splicing factors on LDLR splicing, I quantified the expression level of these splicing factors as well as LDLR splicing efficiency in human brain and liver. I found that SRp38 mRNA expression is associated with LDLR splicing efficiency. In conclusion, this study discovered that rs688 is located close to the two functional ESEs within LDLR exon 12, and revealed a role of SRp38 in LDLR splicing efficiency.
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Paolini, Enrico <1977>. "Iterative decoding methods based on low-density graphs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/406/.
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Patterson, Rebecca Anne. "Antioxidants, pro-oxidants and low density lipoprotein oxidation." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285960.
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Anderson, Simon Hamish Charles. "Silicon: a treatment for low bone mineral density." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414415.
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Pannala, Venkata Ananth Sekher. "Peroxynitrite induced oxidative modification of low density lipoprotein." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301124.
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Othman, Mohd Izani. "Low density lipoprotein induction of intracellular oxidants production." Thesis, University of Canterbury. School of Biological Sciences, 2015. http://hdl.handle.net/10092/11300.
Full textAbstract:
Atherosclerosis is a complex cardiovascular disease characterized by chronic progressive inflammation of the arteries. The progression of atherosclerosis from fatty streak to advance atherosclerotic plaque involves the development of a necrotic core region consists of cholesterol, lipids, calcium (Ca²⁺), dead cells and other cellular debris. Macrophage infiltrations occurred in all stages of atherosclerotic progression and they are abundantly found in atherosclerotic plaques. Oxidised low density lipoprotein (oxLDL) plays a vital role in the initiation and development of atherosclerosis. OxLDL is present within atherosclerotic plaque and has been shown to be cytotoxic to various types of cells including macrophages.
This research initially examined the cytotoxic effects of copper oxidised LDL on U937, human monocytes and HMDM cells. As expected oxLDL was cytotoxic; causing rapid, concentration and time dependent cell viability loss in all types of cells examined. Examination of the cell morphology showed that oxLDL caused a necrotic like cell death characterised by cell swelling and lysis. Flow cytometric assay coupled with propidium iodide (PI) staining of necrotic cells was compared to MTT reduction assays of cell viability. The flow cytometric technique had the advantage over the MTT reduction assay of being rapid and showing both the live and dead cell levels at an individual cell level.
The progression of oxLDL-induced cell death correlated with the rapid increased in intracellular ROS production in the cytosol and the mitochondria. Immunoblotting results showed that oxLDL induced NADPH oxidase (NOX) activation and increased p47phox expression. This suggests NOX as the generator of reactive oxygen species (ROS) induced by oxLDL in these cells. However, apocynin and VAS2870, the two NOX inhibitors used in this study, were unable to inhibit the ROS generation caused by the oxLDL. This suggests that either these inhibitors are unable to inhibit the targeted NOX or other sources of ROS might exist and contributed to the overall increase in oxidative flux.
OxLDL caused a rapid increase in cytosolic Ca²⁺ level. This was contributed by the extracellular Ca²⁺ source as well as Ca²⁺ mobilisation from the intracellular stores such as endoplasmic reticulum (ER). OxLDL-induced intracellular Ca²⁺ increase also correlated with the increase in intracellular ROS. Nevertheless, blocking of oxLDL-induced intracellular Ca²⁺ elevation by Ca²⁺ chelator, EGTA, did not reduce intracellular ROS generation. Accordingly, this suggests that oxLDL-induced intracellular Ca²⁺ increase is not the cause for oxLDL-induced cell death. Additionally, oxLDL may also initiate a Ca²⁺-independent cell death pathway.
The excess cytosolic Ca²⁺ taken up by the mitochondria may be detrimental and could result in mitochondrial Ca²⁺ overload. This will increase mitochondrial ROS production and initiate mitochondrial permeability transition (MPT) pores opening. Consequently, this could collapse the mitochondrial membrane potential ( m) due to the rupture of outer mitochondrial membrane (OMM) and resulted in cell death. Blocking of Ca²⁺ uptake into the mitochondria by ruthenium red protected cells from oxLDL-mediated cell death, possibly by reducing ROS production and preventing MPT activation.
This study also demonstrated the protective effect of 7,8-dihydroneopterin (7,8-NP) on oxLDL-induced oxidative stress. 7,8-NP protected cells from oxLDL-induced intracellular ROS generation and cell viability loss. Intracellular Ca²⁺ increase was also reduced by 7,8-NP in particular after 3 hours incubation with oxLDL. The action of 7,8-NP was better than that of apocynin in protecting U937 cells from oxLDL suggests its potential ability to scavenge ROS from various sources.
Studies have implicated the involvement of H₂S in various biological processes including atherosclerosis. Thus, the disruption of H₂S homeostasis may contribute to the progression of atherosclerosis. Slow releasing H₂S molecules (H₂S donors) have been developed for a controlled and stable delivery of H₂S to cells. In this study, specific H₂S donors, including one which targets the mitochondria, were found to be protective against oxLDL-induced cell death in U937, human monocytes and HMDM cells. Although the exact mechanism is yet to be elucidated, these H₂S donors were shown to block the elevation of intracellular Ca²⁺ and ROS production mediated by oxLDL. Therefore, these H₂S donors could be the potential candidates for future development of therapeutics in treating atherosclerosis.
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Berchuk, Vitaliy, Ed Grozalis, Jennifer Yin, and Chris Dehmelt. "A Low Cost, High Density Reconfigurable Recording Subsystem." International Foundation for Telemetering, 2012. http://hdl.handle.net/10150/581620.
Full textAbstract:
ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, CaliforniaModern test programs require an increase in sensor and bus data while at the same time seeking a decrease in the size and price of data acquisition components. Data archiving, which has been traditionally supplied via dedicated standalone hardware, is not exempt to this demand, but in many ways has not kept up with other instrumentation components in terms of flexibility, size, density and price. The archiving capabilities of a data acquisition system must be able to meet the changing needs of the customer. This paper presents a Solid State Drive (SSD) based data recorder implementation that can be easily reconfigured to address the requirements of different applications, including traditional PCM based systems and contemporary network based systems. The paper identifies the requirements, design challenges, trade-offs and risks in creating a low-cost, flexible data archiving subsystem that can be used in a standalone configuration or be directly integrated with a host data acquisition system.
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Rabie, Allan John. "Blends with low-density polyethylene (LDPE) and plastomers." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49870.
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Thesis (MSc)--Stellenbosch University, 2004.ENGLISH ABSTRACT: This study describes the design, building and optimization of a fully functional preparative TREF (Prep-TREF) apparatus. This apparatus allows for the fractionation of semicrystalline polyolefins according to the crystallizability of the molecules. Various factors, such as the sample cooling rate and the effect of on-support and off-support crystallization, are investigated. The preparative TREF is used to fractionate a commercial low-density polyethylene (LOPE), two commercially available plastomers (polyethylene-l-octene copolymers), as well as blends of the LOPE and the respective plastomers. It is shown that in each case the samples fractionated by crystallizability. The fractions recovered from the Prep-TREF were characterized by CRYSTAF, OSC and NMR analysis. It is shown how the results of this preparative fractionation allow for a better understanding of the molecular heterogeneity in the LOPE and plastomers. New ways of presenting the data from the preparative fractionation, in terms of 3- dimensional plots, are also investigated. These plots offer a novel way of presenting the molecular heterogeneity in the samples in terms of the molecular crystallizability. These plots highlight features that are difficult to detect in the conventional two-dimensional plots. In conclusion, the influences of various blending ratios of LOPE and plastomer on the morphological and physical properties of the blends, such as haze, clarity, and tear-and impact strength are determined.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was die ontwikkeling en optimisering van 'n ten volle funksionerende TREF. Hierdie tegniek word gebruik om polimeermengsels te fraksioneer deur gebruik te maak van die kristaliseerbaarheid van polimere. Verskeie faktore soos die afkoel spoed en die effect van met en sonder 'n ondersteuning(seesand) vir kristaliseering was ondersoek. Hierna is navorsing gedoen om 'n beter begrip ten opsigte van die meganiese, fisiese en optiese eienskappe van lae-digtheid poliëtileen (LDPE) te ontwikkel. Hierdie LDPE is met die affiniteitsreeks plastomere van die maatskappy, Dow Chemicals, gemeng om tendense in die gefraksioneerde polimere te indentifiseer. Een van Sasol se kommersiële LDPE produkte en twee van Dow Chemicals se plastomere is individueel gefraksioneer. Die mengsel van die twee ongefraksioneerde LDPE en plastomere is nog nooit voorheen op 'n molekulêre basis ondersoek nie. Dit is in hierdie studie gedoen deur van TREF gebruik te maak. Nuwe maniere is ontwikkel om data op 'n nuwe manier voor te stel deur middel van 3 Dimensionele grafieke te skep om resultate voor te stel wat andersins baie moelilik was om voor te stel in een dimensie agv die hoeveelheid data wat geinterpreteer word. Ten slotte is die invloed van die verskillende mengverhoudings van LDPE en plastomere op die morfologiese en fisiese eienskappe soos deursigtigheid, helderheid, skeur- en impaksterkte, ook ondersoek.
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Hayes, Bob. "LOW DENSITY PARITY CHECK CODES FOR TELEMETRY APPLICATIONS." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604497.
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ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, NevadaNext generation satellite communication systems require efficient coding schemes that enable high data rates, require low overhead, and have excellent bit error rate performance. A newly rediscovered class of block codes called Low Density Parity Check (LDPC) codes has the potential to revolutionize forward error correction (FEC) because of the very high coding rates. This paper presents a brief overview of LDPC coding and decoding. An LDPC algorithm developed by Goddard Space Flight Center is discussed, and an overview of an accompanying VHDL development by L-3 Communications Cincinnati Electronics is presented.
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Moon, Todd K., and Jacob H. Gunther. "AN INTRODUCTION TO LOW-DENSITY PARITY-CHECK CODES." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/607470.
Full textAbstract:
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, NevadaLow-Density Parity-Check (LDPC) codes are powerful codes capable of nearly achieving the Shannon channel capacity. This paper presents a tutorial introduction to LDPC codes, with a detailed description of the decoding algorithm. The algorithm propagates information about bit and check probabilities through a tree obtained from the Tanner graph for the code. This paper may be useful as a supplement in a course on error-control coding or digital communication.
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Tcheslavskaia, Ksenia Sergeyevna. "Mating Success in Low-Density Gypsy Moth Populations." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27859.
Full textAbstract:
Field studies were conducted to evaluate the effect of mating disruption on the mating
success of the gypsy moth, Lymantria dispar (L), in low-density populations. The gypsy moth is
an insect pest of hardwood forests in many regions of the world. The discovery of the sex
pheromone disparlure (cis-7,8-epoxy-2-methyloctadecane) produced by females marked the start
of a new era in the control and management of gypsy moth populations. Sex pheromones, like
disparlure, have been used for detecting new populations, monitoring the spread of populations
and for population control based on the disruption of mating communication. Although mating
disruption has been used against populations of insect pests in agricultural and forest systems,
considerable information about the use of this method for managing gypsy moths is still lacking.
Studies, therefore, were designed and carried out specifically to improve current understanding
of the mechanism of mating success, to evaluate existing techniques for mating disruption, and to
develop methods that would improve the application of pheromone used for mating disruption so
as to reduce the costs associated with the use of this management tactic.
The first study was conducted to compare the mating success and mortality of gypsy
moth females in low-density populations in Virginia and Wisconsin because of differences,
which have been observed in the population dynamics and the impact of management strategies
between these two states. The results suggested that the higher rate of population spread in
Wisconsin might be due to the increased mating success of females compared with Virginia,
which may be due in part to increased long-distance dispersal of males and increased longevity
of females.
The effect of artificial pheromone applied at various doses and formulations on mating
success in low-density gypsy moth populations also was studied. Dose-response relationships
were obtained for pheromone doses ranging from 0.15 to 75 g a.i./ha. The doses of 37.5 and 15 g
a.i./ha of pheromone were shown to effectively disrupt mating and, therefore, have been
recommended for operational use. The results also showed that the disruption of mating and
attraction of males to pheromone-baited traps as a result of application of pheromone formulated
in plastic flakes (Disrupt® II, Hercon Environmental, Emigsville, PA) was stronger and lasted
longer than for the pheromone formulated as microcapsule (3M Canada Co., London, Ontario,
Canada) and in liquid (Shin-Etsu Chemical Co. Ltd, Tokyo, Japan).
Another study was carried out to improve the use and efficacy of the pheromone for
mating disruption by reducing the amount of pheromone that was sprayed and the flight distance
during aerial application. This study showed that in mountainous landscapes the effect of
disparlure along the valley between mountains could be observed at a larger distance (633 ± 63
m) from the treated area than across the valley (104 ± 22m). In a relatively flat area, the effective
distance for mating disruption was similar to the effective distance across the valley in a
mountainous area (67 ± 17m). These dispersal characteristics of the pheromone provided further
evidence that it could be used effectively in mating disruption treatments.
Finally, a portable Electroantennogram (EAG) device was evaluated for its ability to
detect disparlure sprayed for mating disruption in gypsy moth populations. The study found no
relationship between the dose of artificial airborne pheromone and response of gypsy moth
antenna as measured by the voltage ratio. The inability to detect differences between airborne
pheromone concentrations in the plots treated for mating disruption might have been due to high
variability among antennae and also by the inability of the EAG device to detect the low
concentration of airborne pheromone used operationally for mating disruption. Further studies
are required to improve the sensitivity of the portable EAG device before it can be recommended
for use in the field.Ph. D.
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Anitei, Irina. "Circular Trellis based Low Density Parity Check Codes." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1226513009.
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Wheatley, Vincent. "Modelling low-density flow in hypersonic impulse facilities /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16173.pdf.
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Omidy, Ali D. "Multiphase Interaction in Low Density Volumetric Charring Ablators." UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/128.
Full textAbstract:
The present thesis provides a description of historical and current modeling methods with recent discoveries within the ablation community. Several historical assumptions are challenged, namely the presence of water in Thermal Protection System (TPS) materials, presence of coking in TPS materials, non-uniform elemental production during pyrolysis reactions, and boundary layer gases, more specifically oxygen, interactions with the charred carbon interface.
The first topic assess the potential effect that water has when present within the ablator by examining the temperature prole histories of the recent flight case Mars Science Laboratory. The next topic uses experimental data to consider the instantaneous gas species produced as the ablator pyrolyzes. In this study, key gas species are identified and assumed to be unstable within the gas phase; thus, equilibrating to the solid phase. This topic investigates the potential effects due to the these process. The finial topic uses a simplified configuration to study the role of carbon oxidation, from diatomic oxygen, on the ablation modes of a TPS, surface versus volumetric ablation.
Although each of these topics differ in their own right, a common theme is found by understanding the role that common pyrolysis and boundary layer gases species have as they interacts with the porous TPS structure. The main objective of the present thesis is to investigate these questions.
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Nouri, Nima. "Radiative Conductivity Analysis Of Low-Density Fibrous Materials." UKnowledge, 2015. https://uknowledge.uky.edu/me_etds/66.
Full textAbstract:
The effective radiative conductivity of fibrous material is an important part of the evaluation of the thermal performance of fibrous insulators. To better evaluate this material property, a three-dimensional direct simulation model which calculates the effective radiative conductivity of fibrous material is proposed. Two different geometries are used in this analysis.
The simplified model assumes that the fibers are in a cylindrical shape and does not require identically-sized fibers or a symmetric configuration. Using a geometry with properties resembling those of a fibrous insulator, a numerical calculation of the geometric configuration factor is carried out. The results show the dependency of thermal conductivity on temperature as well as the orientation of the fibers. The calculated conductivity values are also used in the continuum heat equation, and the results are compared to the ones obtained using the direct simulation approach, showing a good agreement.
In continue, the simulated model is replaced by a realistic geometry obtained from X-ray micro-tomography. To study the radiative heat transfer mechanism of fibrous carbon, three-dimensional direct simulation modeling is performed. A polygonal mesh computed from tomography is used to study the effect of pore geometry on the overall radiative heat transfer performance of fibrous insulators. An robust procedure is presented for numerical calculation of the geometric configuration factor to study energy-exchange processes among small surface areas of the polygonal mesh.
The methodology presented here can be applied to obtain accurate values of the effective conductivity, thereby increasing the fidelity in heat transfer analysis.
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Price, Aiden K. "Improved constructions of low-density parity-check codes." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/128373/1/Aiden_Price_Thesis.pdf.
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There is an ongoing need to improve the efficiency and error-correcting performance of error correcting codes, which are widely used to enhance accuracy when retrieving or communicating information. This research investigates several potential improvements to a high-performing class of error correcting codes known as low-density parity-check (LDPC) codes. The results presented here further the known literature surrounding a specific class of functions (Alltop functions). Additionally, this work demonstrates ways of manipulating existing LDPC code constructions using relaxed difference sets to provide constructions with far more flexible code parameters. These constructions have competitive performance when compared to relevant modern codes.
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Altintas, Bekir. "Electrical And Mechanical Properties Of Carbon Black Reinforced High Density Polyethylene/low Density Polyethylene Composites." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604976/index.pdf.
Full textAbstract:
In this study, the High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) blends prepared by Plasticorder Brabender were strengthened by adding Carbon Black (CB).
Blends were prepared at 190 °C. Amounts of LDPE were changed to 30, 40, 50 and 60 percent by the volume and the percent amounts of CB were changed to 5, 10,15, 20 and 30 according to the total volume. Thermal and morphological properties were investigated by using Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM). Mechanical properties were investigated by tensile test and hardness measurements. Melt flow properties were studied by Melt Flow Index (MFI) measurements. Electrical conductivities were measured by four probe and two probe techniques. Temperature dependence of electrical conductivity was also studied. In general, it is observed that stress at break and MFI values decrease by the addition of CB
however, modulus and hardness increase. DSC results indicated that the crystallization of the polymer blend was decreased by the addition of CB. SEM results showed that the components were mixed homogenously. Increasing CB content increased electrical conductivity. Furthermore, by increasing the temperature, positive temperature coefficient behavior was observed which increases when CB content decreased.
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Sànchez, Riera Lídia. "The Global Burden Attributable to Low Bone Mineral Density." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/305365.
Full textAbstract:
INTRODUCTION: Osteoporosis and osteoporotic fractures represent an enormous health burden and economic cost for most societies in the world, and future projections forecast their steady increase over the next few decades. Strategies to detect and treat those individuals with high risk of fracture have proved to be cost-effective, but still an important lack of awareness exists among health professionals and institutions. Low bone mineral density (BMD) is one of the factors better correlated with fracture risk. The Global Burden of Disease Study 2010 estimated the worldwide health burden of 291 diseases and injuries and 67 risk factors. The main metrics for the burden measurements were the Disability-Adjusted Life Years (DALYs), the Years lived with disability (YLDs), the Years of Life Lost due to premature mortality (YLLs) and Deaths. For the first time, BMD was analysed as a risk factor for fractures, which formed part of the health burden due to falls. Risk analysis followed the Comparative Risk Assessment (CRA) methodology to determine which proportion of the falls burden was attributable to low BMD.
OBJECTIVES: To calculate the global distribution of BMD, its population attributable fraction (PAF) for falls, and the number of DALYs, YLDs, YLLs and deaths due to low BMD, with estimates for each region, age group, sex and time period (1990 and 2010).
METHODS: Systematic review was performed seeking population-based studies with BMD measured by Dual-X-Ray-Absorptiometry at femoral neck in people 50 years and over. Age- and sex- specific levels of mean BMD+/-SD (g/cm2) were extracted from eligible studies. For the CRA methodology to calculate PAFs of BMD for fractures, the theoretical minimum risk factor exposure distribution was estimated as the age and sex-specific 90th percentile from NHANES III. Relative risks for fractures were obtained from a previous meta-analysis. Hospital data with double coding (cause and nature of injury) was used to calculate the fraction of the health burden of falls due to fractures.
RESULTS: Global deaths and DALYs attributable to low BMD increased from 103,000 and 3,125,000 in 1990 to 188,000 and 5,216,000 in 2010 respectively. The contribution to the total DALYs was slightly superior for YLLs compared to YLDs. The percentage of low BMD in the total global burden almost doubled from 1990 (0.12%) to 2010 (0.21%). In population 70 years old and over these percentages increased from 0.64% in 1990 to 0.79% in 2010. Around one third of all falls-related deaths were attributable to low BMD, with slight increase between 1990 and 2010. Low BMD was responsible for 12.1% and 14.8% of all global DALYs due to falls in 1990 and 2010, respectively. Males showed more contribution to the global deaths and DALYs, with a higher increase over time, compared to females. Asia South and Asia East were the world regions contributing the most in the increase of the global burden attributable to low BMD over time. The greatest proportion of DALYs within the regional burden was found in Europe Western, Europe Central and Asia Pacific-High Income. Low BMD was the eight risk factor with the highest number of global YLDs in population 80 years and over.
CONCLUSION: Results showed an increase of the burden attributable to low BMD worldwide from 1990 to 2010, greatly influenced by the ageing of the population. A significant fraction of all falls-related deaths and health burden in the world was attributable to low BMD and, therefore, preventable. Data systems should improve in the detection of injuries potentially related to low BMD and osteoporosis in general. This information can be used by health institutions and authorities to identify priorities and allocate resources.INTRODUCCIÓN: En la iniciativa The Global Burden of Disease Study 2010, la densidad mineral ósea (DMO) ha sido analizada como un factor de riesgo de fracturas, las cuales son analizadas como parte de la carga en salud atribuida a las caídas. Las medidas métricas principales para determinar la carga en salud de dicha iniciativa son los Disability-Adjusted Life Years (DALYs), los Years lived with disability (YLDs), los Years of Life Lost due to premature mortality (YLLs), y las Muertes. OBJETIVOS: Calcular la distribución mundial de los valores de DMO; calcular el número de DALYs, YLDs, YLLs y muertes debidos a la baja DMO. MÉTODOS: Se realizó una revisión sistémica de estudios poblacionales con valores de DMO medidos con Dual-X-Ray-Absorptiometry en cuello femoral en población a partir de 50 años. Se utilizó análisis de riesgo comparativo para determinar la fracción poblacional atribuible de la DMO para caídas. El percentil 90 por grupo de edad y género del estudio americano NHANESIII se adquirió como la distribución de mínimo riesgo posible del factor de exposición. Los riesgos relativos DMO-fractura se obtuvieron de una meta-análisis previa. Datos hospitalarios con doble codificación (causa y tipo de lesión) se utilizaron para calcular la fracción de la carga en salud de las caídas debido a las fracturas. RESULTADOS: Las muertes y los DALYs mundiales atribuibles a la baja DMO incrementaron de 103.000 y 3.125.000 en 1990 a 188.000 y 5.216.000 en 2010, respectivamente. Un tercio de todas las muertes relacionadas con caídas fueron atribuibles a la baja DMO. La DMO fue responsable de un 12.1% y un 14.8% de todos los DALYs por caídas en 1990 y 2010, respectivamente. El Asia Sur y Asia Este fueron las regiones del mundo que más contribuyeron al aumento de la carga mundial en salud atribuible a la baja DMO. CONCLUSIÓN: Los resultados muestran un aumento de la carga en salud mundial debido a la bajo DMO entre 1990 y 2010. Una séptima parte de los DALYs y un tercio de las muertes en el mundo debido a caídas fueron atribuibles a la baja DMO, y por lo tanto, prevenibles.
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Blad, Anton. "Efficient Decoding Algorithms for Low-Density Parity-Check Codes." Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2794.
Full textAbstract:
Low-density parity-check codes have recently received much attention because of their excellent performance and the availability of a simple iterative decoder. The decoder, however, requires large amounts of memory, which causes problems with memory consumption.
We investigate a new decoding scheme for low density parity check codes to address this problem. The basic idea is to define a reliability measure and a threshold, and stop updating the messages for a bit whenever its reliability is higher than the threshold. We also consider some modifications to this scheme, including a dynamic threshold more suitable for codes with cycles, and a scheme with soft thresholds which allow the possibility of removing a decision which have proved wrong.
By exploiting the bits different rates of convergence we are able to achieve an efficiency of up to 50% at a bit error rate of less than 10^-5. The efficiency should roughly correspond to the power consumption of a hardware implementation of the algorithm.
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Ha, Jeongseok Ha. "Low-Density Parity-Check Codes with Erasures and Puncturing." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5296.
Full textAbstract:
In this thesis, we extend applications of Low-Density Parity-Check (LDPC) codes to a combination of constituent sub-channels, which is a mixture of Gaussian channels with erasures. This model, for example, represents a common channel in magnetic recordings where thermal asperities in the system are detected and represented at the decoder as erasures. Although this channel is practically useful, we cannot find any previous work that evaluates performance of LDPC codes over this channel. We are also interested in practical issues such as designing robust LDPC codes for the mixture channel and predicting performance variations due to erasure patterns (random and burst), and finite block lengths.
On time varying channels, a common error control strategy is to adapt the coding rate according to available channel state information (CSI). An effective way to realize this coding strategy is to use a single code and puncture it in a rate-compatible fashion, a so-called rate-compatible punctured code (RCPC). We are interested in the existence of good puncturing patterns for rate-changes that minimize performance loss. We show the existence of good puncturing patterns with analysis and verify the results with simulations.
Universality of a channel code across a broad range of coding rates is a theoretically interesting topic. We are interested in the possibility of using the puncturing technique proposed in this thesis for designing universal LDPC codes. We also consider how to design high rate LDPC codes by puncturing low rate LDPC codes. The new design method can take advantage of longer effect block lengths, sparser parity-check matrices, and larger minimum distances of low rate LDPC codes.
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Schmauß, Daniel. "Modulation von dendritischen Zellen durch oxidiertes Low Density Lipoprotein." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-113040.
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Mizutani, T., H. Semi, K. Kaneko, T. Mori, and M. Ishioka. "Space Charge and Field Distributions in Low-Density Polyethylene." IEEE, 2000. http://hdl.handle.net/2237/7178.
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