Добірка наукової літератури з теми "Left symmetry"

Presymmetry, the hidden symmetry underlying the charge and generational patterns of quarks and leptons, is utilized for repairing the left–right asymmetry of the standard model with Dirac neutrinos. It is shown that the restoration of parity is consequent with an indispensable left–right symmetric residual presymmetry. Thus, presymmetry substantiates left–right symmetry and the experimental search for the latter is the test of the former, with the nature of neutrinos as a crucial feature that can distinguish the left–right symmetry alone and its combination with presymmetry. This phenomenological implication is in accordance with the fact that Majorana neutrinos are usually demanded in the first case, but forbidden in the second.

AbstractThe left-right symmetric models extend the gauge group of the Standard Model enabling treatment of the left- and right-handed fermions in the same footing. The left-right symmetry requires the existence of right-handed neutrinos, leading naturally to non-zero masses for neutrinos. Here some aspects of a supersymmetric version of the left-right symmetric models are reviewed. Such models have many virtues, including possibility for dark matter without any new additional symmetry needed in order to have a stable lightest supersymmetric particle. In the model the lightest sneutrino or the lightest neutralino can form dark matter of the universe, at the same time fulfilling all the experimental constraints. The dark matter particle in the model can be very different from the dark matter typical in the minimal supersymmetric standard model. Specific signals for this kind of models at the LHC are also discussed.

Dissertação para obtenção do Grau de Mestre em Genética Molecular e Biomedicina
We tend to view the vertebrate body as bilaterally symmetric, but in fact, this only happens from the outside. Internally, most of the organs from heart to liver are asymmetrically positioned. Skeleton and its associated muscles, symmetric structures of the vertebrate body, have its origins in the transient symmetric blocks of mesoderm called somites whereas the asymmetric morphogenesis of the internal organs is due to asymmetric gene expression in the lateral plate mesoderm (LPM). Previous studies using Morpholino (MO) technology have shown that dmrt2a is involved in these two processes in zebrafish. When Dmrt2a levels are reduced, asymmetric gene expression in the LPM becomes randomized and symmetric gene expression in the presomitic mesoderm (PSM) is disrupted. The paralogous of dmrt2a, the fish specific dmrt2b has been shown to be involved in regulating asymmetric gene expression in the LPM as well. Here we used the recent Transcription activator-like effector nucleases (TALENs) technology to generate dmrt2a and dmrt2b mutant alleles that will allow us in the future to uncover the downstream effectors of these transcription factors using high-throughput experiments. In addition, we overexpressed dmrt2a at the one-cell stage to characterize asymmetry versus symmetry phenotypes. The results show clearly the ability of TALEN technology to generate mutant alleles in zebrafish. Nevertheless, dmrt2a and dmrt2b homozygous mutants developed so far fail to recapitulate their previously described MO phenotypes which raise the question on what molecular mechanism(s) allow(s) zebrafish to cope with frameshift mutations. The overexpression of dmrt2a shows that a time window of opportunity during which symmetric embryonic territories are able to respond to asymmetric signals does exist during embryonic development.

In ambito di ricerca (clinica e sportiva), la necessità di sviluppare un approccio ‘multilaterale’ (qualitativo e quantitativo) che caratterizzi matematicamente la traiettoria tri-dimensionale di una variabile fisica assolutamente importante ma spesso dimenticata, quale il centro di massa corporeo (CMC) (ovvero, il punto immaginario assimilabile al corpo umano in cui si suppone che tutte le masse corporee stiano concentrate), diviene oggi sempre più impellente e quanto mai urgente. Pertanto l’obiettivo di questo dottorato, perseguito tramite un differente utilizzo delle classiche metodologie biomeccaniche, è rappresentare le grandezze cinematiche che descrivono il movimento dei segmenti corporei e del suddetto CMC nel tempo e nello spazio. Per conseguire questo traguardo si sono pensati e realizzati due diversi progetti. Con il primo progetto si sono previsti: a) lo sviluppo di un metodo matematico quantitativo (Serie di Fourier) per descrivere e rappresentare graficamente la traiettoria tri-dimensionale del CMC durante la locomozione su treadmill (la cosiddetta Impronta Digitale Locomotoria, specifica per soggetto/popolazione); b) la caratterizzazione della simmetria nella traiettoria del CMC (il cosiddetto Indice di Simmetria); infine, c) la costituzione di un database di valori normali (coefficienti di equazioni) in un insieme piuttosto esteso di condizioni, al variare di sesso (maschi versus femmine), età (dai 6 ai 65 anni), tipologia di locomozione (marcia versus corsa), velocità e pendenza (piano, salita e discesa). Questo database iniziale rappresenta il parametro principale di riferimento per la locomozione sana. Attraverso questo studio è stato ampiamente dimostrato che la locomozione umana risulta genericamente asimmetrica. Nello specifico: 1) tra maschi e femmine non si sono riscontrate differenze significative; 2) indipendentemente da età e pendenza, le velocità più basse, meno naturali e comuni, sono caratterizzate da pattern di Impronte Digitali Locomotorie più variabili. Viceversa, un aumento di velocità è accoppiato con un progressivo e continuo innalzamento del CMC; 3) l’asimmetria destra e sinistra del passo è molto probabilmente correlata sia con l’anatomia (lunghezza della gamba) che con la predominanza dell’arto; in linea con l’ipotesi iniziale, 4) mediamente, la corsa è più asimmetrica della marcia; infine, 5) i bambini e gli anziani presentano maggiori asimmetrie (marcia e corsa): questo è dovuto alla progressiva maturazione del ciclo del cammino (nei bambini) ed alle caratteristiche muscolari e scheletriche dell’apparato locomotore (negli anziani). Pertanto, attraverso una caratterizzazione matematica della traiettoria tri-dimensionale del CMC, si è potuto: a) quantificare il suo spostamento nel tempo e nello spazio; b) individuare l’Impronta Digitale Locomotoria specifica di sesso, età, tipologia di locomozione, velocità e pendenza. Questo importante traguardo permetterà, in un immediato futuro, la comparazione con la situazione di normalità di condizioni di locomozione compromessa o impedita (ad esempio, bambini con paralisi cerebrale infantile, obesi e amputati). Infine, la stima della principali variabili biomeccaniche è risultata fondamentale sia nel descrivere la meccanica di marcia e corsa che nel caratterizzarne la corrispondente impronta locomotoria. Le nostre misure di tali variabili (semplici e complesse), ottenute con metodo discreto (ciclo per ciclo), con l’impiego di una funzione matematica continua (Serie di Fourier) e con l’applicazione di un’equazione predittiva (misura indiretta), soddisfano completamente ed addirittura ampliano la letteratura già esistente. Nel secondo progetto, partendo da uno studio sulla performance dei cavalli, si è cercato di verificare se esiste una correlazione tra simmetrie corporee (statiche e dinamiche) ed economia nella corsa anche in corridori umani variamente allenati (classificati in tre gruppi sulla base del loro miglior tempo nella maratona). Inoltre: a) si sono sviluppati metodi di analisi bi- e tri-dimensionale delle Risonanze Magnetiche per Immagini (regione pelvica ed arti inferiori), impiegate come riferimento per le simmetrie statiche; b) attraverso sia l’Impronta Digitale Locomotoria che l’Indice di Simmetria si sono caratterizzate le simmetrie dinamiche; infine c) l’economia della corsa è stata espressa attraverso il suo reciproco, ovvero il costo metabolico. L’analisi sia bi- che tri-dimensionale delle immagini ha evidenziato differenze davvero esigue in base al livello di allenamento. Positivamente ed indipendentemente dai corridori, si è dimostrato che ad una maggiore simmetria nella regione del ginocchio corrisponde una maggiore simmetria nella regione della caviglia. Inoltre l’analisi delle simmetrie dinamiche ha permesso di osservare che: 1) il CMC si solleva leggermente in funzione della velocità; 2) le asimmetrie destre e sinistre del passo sono principalmente marcate lungo la direzione di movimento e, contemporaneamente, ridotte lungo la direzione verticale. Esse sono strettamente dipendenti dall’anatomia e dall’arto dominante; 3) diversamente da quanto ci si aspettava, sono state comunque evidenziate solamente poche differenze tra i corridori. Negativamente, l’economia della corsa non mostra differenze significative tra i gruppi testati. Perciò, diversamente dall’ipotesi iniziale, non è stata evidenziata l’esistenza di alcuna relazione tra le simmetrie corporee e l’economia della corsa, quanto piuttosto solo la presenza di una discreta variabilità in simmetria statica e dinamica. Infine, l’analisi di bioenergetica (treadmill versus pista) e biomeccanica (variabili semplici/complesse e variabilità spazio/temporale del CMC) della corsa ha evidenziato la presenza solamente di poche differenze dovute al livello di allenamento dei soggetti studiati.
In both research laboratory and sport/clinical settings, it becomes very important to develop a ‘multilateral approach’ (qualitative and quantitative) to fully describe the individual behaviour of the centre of mass of the human body (BCOM) (i.e. the imaginary specific point at which the body behaves as if its masses were concentrated) over time and space. Consequently, the aim of this doctorate is to describe kinematic variables of the BCOM in varying locomotion conditions. This purpose, focusing on the BCOM as the investigation object fulfilling such a need, has been achieved through a different use of classic biomechanical procedures. In effect, two different studies were carried out. The first project sought: a) to develop a mathematical method (Fourier Series) which could describe and graphically represent each individual (subject or population) gait signature (i.e. Digital Locomotory Signature, a global index of the BCOM dynamics) during locomotion on a treadmill; b) to assess the symmetry (i.e. Symmetry Index) in each movement direction, along the BCOM trajectory, between the two stride phases; finally, c) to build up an initial comprehensive database of ‘healthy values’ (equation coefficients) in a set of different conditions considering gender (males versus females), age (from 6 to 65 years), gait (walking versus running), speed and gradient (level, uphill and downhill). Although only slight gender differences were found, human ‘healthy’ gait is rather asymmetrical. To be precise: 1) the lowest speeds have the most peculiar signature independently of age and gradient: indeed, these speeds are not so completely natural and common. However, if speed increases, the BCOM raises in such a way that its corresponding 3D contour becomes more regular; 2) right and left sides of the stride are quite asymmetrical (i.e. in the forward direction). Globally, this asymmetry is probably related both to anatomy (i.e. leg length) and which hand you use (i.e. right-handedness); 3) on average, the symmetry pattern is slightly lower in running gaits; and as expected, 4) young children and elderly adults are the most asymmetrical subjects, independently of testing conditions: while, during the early stages of life, this global asymmetry could be ascribed to the process of gait development, old age asymmetries are probably due to structural wearing down of the musculoskeletal system. Importantly, the mathematical methodology used here, by analysing even subtle changes in the 3D BCOM trajectory: a) characterizes its displacements over both time and space; b) quantitatively describes the individual gait signature; and c) represents the basis for the evaluation of gait anomaly/pathology (e.g. children with cerebral palsy, obese people and amputees). Finally, knowing the main biomechanical variables becomes fundamental both to fully describe the mechanics of walking and running and to extract and characterize the individual gait signature. In effect, our measurements (discrete method versus continuous mathematical function, and direct versus indirect measurement) of both simple and complex variables wholly confirm, complete and amplify previous literature data. Similarly to what previously demonstrated in horse performances, the second project tried: a) to verify both static anatomical and kinematic functional symmetries as important and relevant indicators of running economy (i.e. the reciprocal of metabolic cost) in humans featuring different running levels (i.e. occasional, skilled and top runners categorized primarily upon their best marathon time); b) to develop imaging based bi- and three-dimensional methods to analyse static symmetries recorded by Magnetic Resonance Imaging (lower limbs and pelvic area); c) to describe the kinematic symmetries defining both the Digital Locomotory Signature and the Symmetry Index; finally, d) to investigate running economy as a performance determinant. In effect, both the 2D/3D analysis of static symmetries highlight very few differences among runners; however, a strong relationship between ankle and knee areas has been underlined in all runners. Furthermore, independently of training ability: as expected, 1) the BCOM raises and lifts slightly as a function of running speed; 2) right and left steps are mostly asymmetrical in the forward direction and symmetrical in the vertical direction (i.e. combined action of gravity and ground reaction force); 3) differently to what was expected, slight differences have been found among runners. On the whole, the asymmetry is probably related both to anatomy and handedness. Other than that, no running economy differences were found. In conclusion, while a relationship between symmetries and running economy has not been found, significant results have however been underlined in each trial (static and dynamic symmetries). Finally, the deep investigation of both bioenergetics (treadmill versus over-ground) and biomechanics (simple/complex variables and spatial/temporal variability of the BCOM) of running has highlights only little (significant) differences among groups.

La coordination des membres est un élément essentiel pour la marche terrestre chez les mammifères. Les mécanismes neuronaux et biomécaniques s'ajustent pour assurer le maintien d'un équilibre dynamique dans un environnement changeant. Lorsque le système est confronté à une perturbation persistante, la coordination des membres s'adapte. L'adaptation est définie comme un recalibrage du mouvement en réponse à une perturbation persistante ainsi que la présence d'après-effets une fois la perturbation disparue, ce qui indique que le nouveau patron a été entreposé dans le système nerveux central. Chez l'homme, le patron locomoteur s'adapte à une marche prolongée sur un tapis roulant partitionné, où l’une des jambes marche à une vitesse supérieure à l'autre, en rétablissant progressivement la symétrie des variables inter-jambes: périodes de double support et des longueurs des pas, ainsi qu’en réduisant l'amplitude de l'activité musculaire (EMG, électromyographie). L’objectif de notre étude était de déterminer si des chats intacts et des chats ayant subis une lésion complète de la moelle épinière (chat spinalisé) s’adaptent à la marche partitionnée prolongée. Pour caractériser l’adaptation locomotrice chez le chat intact et spinalisé, une prise de données cinématiques et électromyographiques des membres postérieurs a été effectuée chats intacts et les chats spinalisés, les longueurs de pas et les périodes de doubles supports étaient, en moyenne, symétriques, pendant la locomotion sur tapis roulant non-partitionné, et sont devenus asymétriques lors de la locomotion sur tapis roulant partitionné. Ces mesures inter-jambes sont demeurées asymétriques tout au long de la période de marche sur tapis roulant partitionné. Au retour à la marche sur tapis roulant non-partitionné, la symétrie a été immédiatement restaurée sans la présence d’après-effets. Chez les chats intacts, l'amplitude EMG moyenne des extenseurs a augmenté pendant la locomotion sur tapis roulant partitionné et elle est restée augmentée tout au long de cette période, alors que chez les chats spinalisés, l'amplitude EMG des membres postérieurs n'a pas changé. Ces résultats indiquent qu’il n’y a pas d’adaptation locomotrice chez le chat intact et spinalisé, ce qui suggère une importante différence physiologique dans le contrôle de la locomotion entre les chats et les humains lors d’une marche asymétrique prolongée. Par conséquent, nous proposons que la symétrie gauchedroite ne s’avère pas importante pour maintenir un équilibre dynamique pendant la locomotion asymétrique prolongée chez le chat, un quadrupède, comparé à l’humain adulte, un bipède.
Abstract : Coordination of the limbs is an essential component of terrestrial locomotion in mammals. When the system is confronted with persistent perturbations from the environment, the interlimb pattern learns to adapt. Adaptation is defined as a recalibration of the movement in response to a persistent perturbation as well as the presence of after-effects upon removal of the perturbation, indicating storage of the new pattern within the central nervous system. In humans, the pattern adapts to prolonged locomotion on a split-belt treadmill, where one leg steps faster than the other, by gradually restoring the symmetry of interlimb variables (double support periods, step lengths) and by reducing the amplitude of muscle activity (EMG, electromyography). The adaptation is also characterized by a reversal of the asymmetry of interlimb kinematic variables initially observed during the early split-belt period when returning to tied-belt locomotion (i.e. an after-effect). To assess the presence of locomotor adaptation, we measured intralimb (stance durations) and interlimb (double support periods, step lengths) variables bilaterally as well as EMG in the hindlimbs of intact and spinal-transected cats before, during and after 10 mins of split-belt locomotion. In both intact and spinal cats, step lengths and double support periods were, on average, symmetric, during tied-belt locomotion, and became asymmetric during split-belt locomotion. These interlimb variables remained asymmetrical throughout the split-belt period and upon returning to the tied-belt condition, left-right symmetry was immediately restored. In intact cats, the mean EMG amplitude of extensors increased during split-belt locomotion and remained increased throughout the split-belt period, while in spinal cats, hindlimb EMG amplitude did not change. The results indicate a lack of adaptation during prolonged split-belt locomotion in intact and spinal cats, suggesting an important physiological difference in the control of locomotion between cats and humans during prolonged asymmetric stepping. We propose that restoring left-right symmetry is not important to maintain dynamic balance during prolonged asymmetrical locomotion in the cat, a quadruped, as opposed to the adult human, a biped.

Bien qu'ayant beaucoup de succès pour décrire la grande variété de phénomènes de la physique des particules, le Modèle Standard (MS) laisse certaines propriétés de la nature sans explication. Ici, nous allons mettre l'accent sur le traitement différent des chiralités de type gauche et droite dans le cadre du MS. Une façon naturelle d'expliquer cela est de plonger le MS dans un modèle plus fondamental, capable de traiter les chiralités d'une manière symétrique. Cette classe de modèles, connue sous le nom de "modèles à symétrie droite-gauche" (LR models, en anglais), introduit une nouvelle interaction qui couple préférentiellement aux champs "droitiers". Puis, à une haute échelle d'énergie, la symétrie reliant droite et gauche est brisée spontanément donnant naissance au MS et aux phénomènes de violation de symétrie de parité. La manière spécifique par laquelle le mécanisme Brout-Englert-Higgs (BEH) se produit dans les modèles LR peut être sondée par des observables électrofaibles de précision, ce qui sert de premier test de l'extension du MS dans le secteur électrofaible. Comme conséquence du mécanisme BEH dans les modèles LR, de nouveaux bosons de jauge sont présents. Ce sont W’ et Z’, censés être beaucoup plus lourds que les bosons de jauge W et Z afin d'expliquer pourquoi ils n'ont jamais été vus jusqu'à présent. Ces nouvelles particules sont accompagnées d'une riche phénoménologie, comme de nouvelles sources de violation de CP au-delà de celle du MS. En outre, un nouveau secteur scalaire neutre introduit des courants qui changent la saveur (FCNC, en anglais) au niveau des arbres, un processus fortement restreint dans le MS, où il arrive seulement à l'ordre des boucles. L'existence de FCNCs fournit des contraintes extrêmement puissantes sur les modèles LR, et mérite donc une attention spéciale, en particulier lors du calcul des corrections venant de la QCD. Nous calculons donc les corrections au Next-to-Leading Order des effets à de courtes distances venant de la QCD aux contributions du modèle LR aux observables liées au mélange de mésons neutres et sensibles donc aux FCNC.Ensuite, nous considérons l'étude phénoménologique des modèles LR afin de tester leur viabilité et leur structure. Plus particulièrement, nous considérons le cas où des doublets scalaires sont responsables de la brisure du groupe de jauge des modèles LR. A cet effet, nous menons une étude combinée des observables de précision électrofaible, des bornes directes sur la masse des nouveaux bosons de jauge et des observables qui dérivent de l'oscillation des mésons neutres, dans le cas plus simple où la matrice de mixing dans le secteur droit est égal à la matrice CKM. Ces observables sont combinées dans le cadre du paquet CKMfitter d'analyse statistique. La combinaison de différentes classes d'observables doit prendre en compte la particularité des incertitudes théoriques, qui ne sont pas de nature statistique comme d'autres sources d'incertitude. A ce propos, nous considérons aussi la comparaison de différentes modèles d'incertitude théorique, afin de trouver des méthodes bien adaptées à la situation actuelle de notre connaissance des incertitudes théoriques impliquées dans un fit global en physique de la saveur
Though very successful in explaining a wide variety of particle physics phenomena, the Standard Model (SM) leaves unexplained some properties of nature. Here we focus on the different behaviours of left- and right-handed chiralities, or in other words the violation of parity symmetry. A possible and somewhat natural avenue to explain this feature is to embed the SM into a more symmetric framework, which treats the chiralities on equal footing. This class of models, the Left-Right (LR) Models, introduces new gauge interactions that couple preferentially to right-handed fields. Then, at an energy scale high enough, LR symmetry is spontaneously broken through the Brout-Englert-Higgs (BEH) mechanism, thus giving origin to the SM and to parity violating phenomena. The specific way in which the BEH mechanism operates in LR Models can be probed by EW Precision Observables, consisting of quantities that have been very accurately measured, serving as a first test of consistency for extensions of the SM in the EW sector. We revisit a simple realization of LR Models containing doublet scalars, and consider the phenomenological study of this doublet scenario in order to test the viability and structure of the LR Models. In particular, there is a rich phenomenology associated to the new gauge bosons W’ et Z’ introduced by LR Models, such as new sources of CP violation beyond the one of the SM. Moreover, the extended neutral scalar sector introduces Flavour Changing Neutral Couplings (FCNC) at tree level, which are strongly suppressed in the SM where they arrive first at one loop. FCNCs typically lead to extremely powerful constraints since they contribute to meson-mixing processes, and therefore deserve close attention. For this reason, we consider the calculation of short-distance QCD effects correcting the LR Model contributions to meson-mixing observables up to the Next-to-Leading Order (NLO), a precision required to set solid lower bounds on the LR Model scales. Finally, we combine in a global fit electroweak precision observables, direct searches for the new gauge bosons and meson oscillation observables in the simple case where the right-handed analogous of the CKM mixing-matrix is equal to the CKM matrix itself (a scenario called CKMfitter symmetry). The full set of the observables is combined by using the CKMfitter statistical framework, based on a frequentist analysis and a particular scheme for modeling theoretical uncertainties. We also discuss other possible modelings of theoretical uncertainties in a prospective study for future global flavour fits made by the CKMfitter Collaboration

Although there is no obvious communication between the left and right limb buds they develop to form bilaterally symmetrical structures of equal size (Summerbell & Wolpert, 1973). The underlying mechanisms that ensure symmetrical limb formation are unknown. Holt-Oram Syndrome (HOS) [OMIM 142900] is a congenital syndrome associated with mutations in TBX5 that lead to heart and upper limb defects. Strikingly, over 70% of HOS patients have left-biased upper limb defects. Using two separate strategies, I show that hypomorphic levels of Tbx5 in both the left and right forelimb buds produces forelimb defects that are consistently more severe in the left limb than the right. Using the INV/INV mutant background, in which the left-right axis is reversed, I show that the laterality of these defects is reversed in Tbx5 hypomorphic mutants with situs inversus. Additionally, I also show that transgenic expression of equal levels of Fgf10 in the forelimb buds of these Tbx5 hypomorphs can partially rescue outgrowth defects but not the left-bias asymmetry of their presentation. Together, this data suggests that Tbx5 has a role in ensuring symmetrical forelimb formation and that this is independent of its transcriptional regulation of Fgf10. Tbx4, the paralogue of Tbx5, is expressed in the hindlimb. I have used a conditional deletion approach to delete Tbx4 expression from the hindlimb area thus avoiding early embryonic lethality. I show that deletion of Tbx4 leads to a loss of proximal hindlimb skeletal elements as well as mispatterning of the distal hindlimb. I also show that Pitx1 partially contributes towards the establishment of the FGF signalling positive feedback loop during initiation of hindlimb bud outgrowth.

AbstractIn rendez-vous protocols an arbitrarily large number of indistinguishable finite-state agents interact in pairs. The cut-off problem asks if there exists a number B such that all initial configurations of the protocol with at least B agents in a given initial state can reach a final configuration with all agents in a given final state. In a recent paper [17], Horn and Sangnier prove that the cut-off problem is equivalent to the Petri net reachability problem for protocols with a leader, and in "Image missing" for leaderless protocols. Further, for the special class of symmetric protocols they reduce these bounds to "Image missing" and "Image missing" , respectively. The problem of lowering these upper bounds or finding matching lower bounds is left open. We show that the cut-off problem is "Image missing" -complete for leaderless protocols, "Image missing" -complete for symmetric protocols with a leader, and in "Image missing" for leaderless symmetric protocols, thereby solving all the problems left open in [17].

An engineer presented with a design challenge often creates a symmetric solution. For instance, consider a table (front-back and left-right symmetry), a car (left and right symmetry), a bridge (front-back and left-right symmetry), or the space shuttle (left-right) symmetry. These examples may not be 100% symmetric, but their overriding features are remarkably similar. The reasons for the design of symmetric structures is not always clear. In some cases, like the table, symmetry may be a tradition. Similarly, the symmetry may be for aesthetic reasons. However in automated design algorithms, especially stochastic techniques, the output is often largely asymmetric, One reason for this is that fitness functions are not rewarded for symmetry. A possible resolution to this is to add a reward function for symmetry. Unfortunately, this approach is computationally intractable as well as arbitrary. In this paper a Genetic Algorithm based method is presented that rewards re-use of parts. The method is applied to a simple, idealized situation as well as to real design case. The results show that in some situations, symmetry naturally emerges from the synthesis, but that it does not provide clear performance advantages over asymmetric configurations.

Evidence from studies requiring the recognition and discrimination of facial and letter stimuli suggests that the right and left cerebral hemispheres are more sensitive to low and high spatial frequencies, respectively. More direct tests requiring the detection of simple sinusoidal gratings have yielded inconclusive findings with some supporting hemispheric asymmetries and others failing to do so. These studies using sinusoidal gratings have used small n terms of 2 or 3, have not controlled eye movements, and in some cases have confounded hemiretina with hemispheric stimulation. Therefore, in the present study we investigated hemispheric and hemiretinal sensitivity to a low (0.8-cycle/deg) and a high (8.7-cycles/deg) spatial frequency grating in 8 observers. To minimize eye movements, the gratings were randomly presented for 100 ms, 1.4 deg from a central fixation in the right, left, upper, or lower visual fields. The right and left eye of each observer was tested during each of two sessions using a criterion-free spatial forced choice procedure. No evidence for asymmetric sensitivity to either spatial frequency was found between the right and left visual fields or for the nasal and temporal hemiretina.

We study the properties of fractional differentiation with respect to the reflection symmetry in a finite interval. The representation and integration formulas are derived for the symmetric and anti-symmetric fractional derivatives, both of the Riemann -Liouville and Caputo type. The action dependent on the left -sided Caputo derivatives of orders in range (1.2) is considered and we derive the Euler-Lagrange equations for the symmetric and anti-symmetric part of the trajectory. The procedure is illustrated with an example of the action dependent linearly on fractional velocities. For the obtained Euler-Lagrange system we discuss its localization resulting from the subsequent sym-metrization of the action.

The Interaural Time Difference is one of the primary localiza- tion cues for 3D sound. However, due to differences in head and ear anthropometry across the population, ITDs related to a sound source at a given location around the head will differ from sub- ject to subject. Furthermore, most individuals do not possess sym- metrical traits between the left and right pinnae. This fact may cause an angle-dependent ITD asymmetry between locations mir- rored across the left and right hemispheres. This paper describes an exploratory analysis performed on publicly available databases of individually measured HRIRs. The analysis was first performed separately for each dataset in order to explore the impact of dif- ferent formats and measurement techniques, and then on pooled sets of repositories, in order to obtain statistical information closer to the population values. Asymmetry in ITDs was found to be consistently more prominent in the rear-lateral angles (approxi- mately between 90° and 130° azimuth) across all databases inves- tigated, suggesting the presence of a sensitive region. A signifi- cant difference between the peak asymmetry values and the aver- age asymmetry across all angles was found on three out of four examined datasets. These results were further explored by pooling the datasets together, which revealed an asymmetry peak at 110° that also showed significance. Moreover, it was found that within the region of sensitivity the difference between specular ITDs ex- ceeds the just noticeable difference values for perceptual discrim- ination at all frequency bands. These findings validate the sta- tistical presence of ITD asymmetry in public datasets of individ- ual HRIRs and identify a significant, perceptually-relevant, region of increased asymmetry. Details of these results are of interest for HRIR modeling and personalization techniques, which should consider implementing compensation for asymmetric ITDs when aiming for perceptually accurate binaural displays. This work is part of a larger study aimed at binaural-audio personalization and user-characterization through non-invasive techniques.

Abstract It can be seen that the studies on fuel assembly mixing performance in the reports are all focused on the influence factors of thermal parameters, and few on the structural parameters. In order to systematically investigate the influence of radial power distribution of rod bundles on the mixing characteristics of fuel assembly, the experimental study was carried out by a 14 ft 5 × 5 full-length rod bundle fuel assembly with both left-right symmetry and center-symmetric arrangement of cold and hot rod bundles. CFD numerical simulation method was used to calculate the same condition. The results show that the radial power ratio of the rod bundles has little effect on the mixing coefficient kT of the fuel assembly when the rod bundle is centrally symmetrical. When the rod bundle is left-right symmetrical, the temperature matrix of the sub-channel section presents an angular symmetry phenomenon near 45°. The experimental results and CFD simulation both show that the configuration of the mixing vanes forms a macroscopic diagonal circulation of the fluid in the sub-channel. FLLICA-IIIF subchannel software could not accurately simulate the diagonal circulation phenomenon of the fluid in the subchannel.