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Various Phases (various + phase)
Selected AbstractsGlutathione depletion and cardiomyocyte apoptosis in viral myocarditisEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 3 2004V. Kytö Abstract Background, The course of viral myocarditis is highly variable. Oxidative stress and Bcl-2 family genes may play a role in its pathogenesis by regulating the amount of cardiomyocyte apoptosis. Apoptosis is difficult to detect and quantify in vivo. Therefore, we set to look for indicators of this potentially preventable form of cell death during various phases of experimental murine coxsackievirus B3 myocarditis. Methods, BALB/c mice were infected with the cardiotropic coxsackievirus B3 variant. Glutathione (HPLC), cardiomyocyte apoptosis (TUNEL and caspase-3 cleavage), Bax and Bcl-XL mRNA expression (real time RT-PCR), histopathology and viral replication (plaque assay and real time RT-PCR) were measured from day 3 to day 20 after infection. Results, Infection caused severe myocarditis and led to progressive decrease of plasma glutathione levels. Myocardial mRNA levels of pro-apoptotic Bax and antiapoptotic Bcl-XL were significantly increased from day 3 onwards. Bax mRNA and ratio of Bax to Bcl-XL correlated with cardiomyocyte apoptosis (r = 0·77, P = < 0·001 and r 0·51, P < 0·01, respectively). Cardiomyocyte apoptosis was highest on day 5, coinciding with a rapid decline in plasma glutathione (r = ,0·52, P = 0·003). Conclusions, Systemic oxidative stress as indicated by decreased plasma glutathione levels coincides with cardiomyocyte apoptosis in experimental coxsackievirus myocarditis. Decreased plasma glutathione levels and changes in cardiac Bax and Bcl-XL mRNA expression identify a phase of myocarditis in which the potentially preventable cardiomyocyte apoptosis is mostly observed. [source] Phase Diagrams and Glass Formation in Metallic Systems,ADVANCED ENGINEERING MATERIALS, Issue 6 2007M. Baricco Abstract The basic thermodynamic aspects of glass-formation in metallic systems are reviewed. In particular, the specific features of a phase diagram with respect to glass-formation are evidenced. On the basis of the regular solution model, the effect of various thermodynamic quantities on the free energy difference between undercooled liquid and crystal phases are outlined. In order to describe the amorphous phase, a specific heat difference between liquid and solid phases in the undercooling regime is introduced in the CALPHAD assessment of various binary systems. The glass-transition is described as a second order transition. Examples are given for different systems, including Fe-B and Cu-Mg. From the description of the free energy of various phases as a function of composition and temperature, the driving forces for nucleation of crystal phases and the T0 curves are estimated. [source] Cytosolic chaperonin-containing t-complex polypeptide 1 changes the content of a particular subunit species concomitant with substrate binding and folding activities during the cell cycleFEBS JOURNAL, Issue 17 2001Shin-ichi Yokota The chaperonin-containing t-complex polypeptide 1 (CCT) is a cytosolic molecular chaperone composed of eight subunits that assists in the folding of actin, tubulin and other cytosolic proteins. We show here that the content of particular subunits of CCT within mammalian cells decreases concomitantly with the reduction of chaperone activity during cell cycle arrest at M phase. CCT recovers chaperone activity upon resumption of these subunits after release from M phase arrest or during arrest at S phase. The levels of ,, , and ,-1 subunits decreased more rapidly than the other subunits during M phase arrest by colcemid treatment and recovered after release from the arrest. Gel filtration chromatography or native (nondenaturing) PAGE analysis followed by immunoblotting indicated that the , and , subunit content in the 700- to 900-kDa CCT complex was appreciably lower in the M phase cells than in asynchronous cells. In vivo, the CCT complex of M-phase-arrested cells was found to bind lower amounts of tubulin than that of asynchronous cells. In vitro, the CCT complex of M phase-arrested cells was less active in binding and folding denatured actin than that of asynchronous cells. On the other hand, the CCT complex of asynchronous cells (a mixture of various phases of cell cycle) exhibited lower , and , subunit content and lower chaperone activity than that of S-phase-arrested cells obtained by excess thymidine treatment. In addition, turnover (synthesis and degradation) rates of the , and , subunits in vivo were more rapid than those of most other subunits. These results suggest that the content of , and , subunits of CCT reduces from the complete active complex in S phase cells to incomplete inactive complex in M phase cells. [source] A practical grid-based method for tracking multiple refraction and reflection phases in three-dimensional heterogeneous mediaGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2006M. De Kool SUMMARY We present a practical grid-based method in 3-D spherical coordinates for computing multiple phases comprising any number of reflection and transmission branches in heterogeneous layered media. The new scheme is based on a multistage approach which treats each layer that the wave front enters as a separate computational domain. A finite-difference eikonal solver known as the fast-marching method (FMM) is reinitialized at each interface to track the evolving wave front as either a reflection back into the incident layer or a transmission through to the adjacent layer. Unlike the standard FMM, which only finds first arrivals, this multistage approach can track those later arriving phases explicitly caused by the presence of discontinuities. Notably, the method does not require an irregular mesh to be constructed in order to connect interface nodes to neighbouring velocity nodes which lie on a regular grid. To improve accuracy, local grid refinement is used in the neighbourhood of a source point where wave front curvature is high. The method also provides a way to trace reflections from an interface that are not the first arrival (e.g. the global PP phase). These are computed by initializing the multistage FMM from both the source and receiver, propagating the two wave fronts to the reflecting interface, and finding stationary points of the sum of the two traveltime fields on the reflecting interface. A series of examples are presented to test the efficiency, accuracy and robustness of the new scheme. As well as efficiently computing various global phases to an acceptable accuracy through the ak135 model, we also demonstrate the ability of the scheme to track complex crustal phases that may be encountered in coincident reflection, wide-angle reflection/refraction or local earthquake surveys. In one example, a variety of phases are computed in the presence of a realistic subduction zone, which includes several layer pinch-outs and a subducting slab. Our numerical tests show that the new scheme is a practical and robust alternative to conventional ray tracing for finding various phases in layered media at a variety of scales. [source] Multiple pathology and tails of disability: Space,time structure of disability in longevityGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 4 2003Satoru Matsushita Disability and the resulting lowered quality of life are serious issues accompanying increased longevity. Curiously, despite its potential contribution to aging theory, complete statistical and etiological structures of this common and unwelcome aging phenotype before death have not been well identified. Another neglected issue in aging and disability is the principles of phylogenesis and morphogenesis, which contemporary life science invariably starts with. In the present review these two related subjects are addressed, with an introduction of an analysis on patients and published data. Statistically rigorous log,normal and normal distributions distinguish disability for its duration and age-wise distribution, respectively. Multiple pathology and diverse effects of various endogenous diseases on disability are confirmed. The robust long-tailed log,normal distribution for various phases of disability validates the fact that patients in disability undergo series of stochastic subprocesses of many independent endogenous diseases until death. For 60% of patients, the log,normal distribution is mimicked by a random walk model. Diseases of core organs are major causes of the long tails. A declining force of natural selection after reproduction and trade-off of life history through pleiotropy of the genes are considered to be the roots of aging. The attenuated selection pressure and the resulting decrease of genetic constraints produce an increased opportunity for chance and stochastics. Elucidated stochastic behaviors of disability underscore the key role of chance in aging. Evolutionary modifications in the development of the structure tend to favor developmentally later stages first. Distal parts are developmentally last, therefore most subject to modification. The rate of molecular evolution of the genes is also found to be relatively slow at the core and rapid at the edge of cells and organs. Therefore, systems at the core must be relatively slow and inactive to comply with pleiotropy and trade-offs in comparison with systems at the edge. Hence, against flat and probabilistic aging, the core organs must be moulded to be more robust with a lower threshold for dysfunction, to age relatively slowly, and should have less of a disease quota in aging. The principle of core protective aging assures possibilities not only to reduce disability but also to accomplish the Third Age as well. Finally, it must also be acknowledged that the principle is a double-edged sword. Paradoxically, the developed biological and societal organization provides protection for the injured core, and so develops long tails of disability. The principle of core protective aging re-emphasizes the key role of prevention in order to reduce the amount of disability. [source] Developing theory-based risk-reduction interventions for HIV-positive young people with haemophiliaHAEMOPHILIA, Issue 1 2001J. R. Schultz Eleven haemophilia treatment centres in the United States collaborated in the Hemophilia Behavioural Intervention Evaluation Projects (HBIEP) to develop theory-based interventions to reduce the risk of HIV transmission from seropositive adolescents and young adults with haemophilia. While the Transtheoretical Model of Behaviour Change and the Theory of Reasoned Action provided the theoretical underpinnings, the exact form in which these theories would be applied depended on developmental research. This paper presents the various phases of the process to develop the theory based interventions: literature review, qualitative interviews, quantitative surveys, a provider survey, a materials review, and the actual planning. All or portions of this process could be applied to the development of interventions for many behaviour-change projects. A description of the HBIEP interventions is also provided. [source] Low-Dose Topiramate Versus Lamotrigine in Migraine Prophylaxis (The Lotolamp Study)HEADACHE, Issue 3 2007Praveen Gupta MD Objective.,To assess the efficacy and safety of topiramate and lamotrigine for prophylaxis in patients with frequent migraine as compared to each other and to placebo. Methods.,Sixty patients with frequent migraine (more than 4 attacks per month) from the headache clinic at a tertiary referral centre in India were randomized to receive 50 mg topiramate/lamotrigine or matching placebo for 1 month each in 2 divided doses in 4 phases in a crossover manner with a washout period of 7 days in between. Primary efficacy measure was responder rate (50% decrease in mean migraine frequency/intensity). Secondary efficacy measures included reduction in mean monthly frequency, intensity, duration, rescue medication use, migraine associated symptoms, and adverse events. Statistical analysis.,Analysis was on intention to treat basis. Data were analyzed as correlated data. Generalized estimation equation was used to compute overall mean standard deviation and 95% confidence intervals for each of the outcome variables. Bonferroni's correction done for multiple comparisons. P value of <.017 was taken as significant. Results.,Fifty-seven patients comprised the intent-to-treat population. Four patients withdrew from the study at various phases, none because of the side effects. Responder rate for frequency was significantly higher for topiramate versus placebo (63% vs 30%, P < .001), and versus lamotrigine (63% vs 46 %, P= .02). For intensity of headache also a responder rate of topiramate versus placebo (50% vs 10%, P < .001), and versus lamotrigine (50% vs 41%, P= .01) was observed. Topiramate showed statistically significant benefits (P < .017) in most of the secondary efficacy measures while lamotrigine was beneficial for reduction in headache frequency, and migraine associated symptoms. Adverse events were similar. Conclusion.,Low-dose topiramate is efficacious in migraine prophylaxis as compared to both placebo and lamotrigine. Lamotrigine in low doses might be beneficial for headache frequency; however, longer trials are required to establish its efficacy on the intensity and frequency of migraine. [source] Novel gel-entrapped base catalysts for the Claisen,Schmidt reactionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004Sachin S Chaphekar Abstract Novel gel-entrapped base catalysts (GEBCs) were prepared by entrapping aqueous solutions of bases in a gel matrix of agar agar. The bases used were NaOH, KOH, morpholine and piperidine. Ternary phase diagrams were constructed for the water,base,agar agar system to identify the various phases and especially the solid phase, useful as a solid base catalyst. The 10% NaOH solid gel was used to effect the Claisen,Schmidt reaction between benzaldehydes and acetophenones in ethanol under heterogeneous conditions to obtain 70,100% yield of the products. The solid GEBCs obtained using other bases were also used for the same reaction; however, the yields were lower. The catalyst needed no activation prior to use and could be recycled. Copyright © 2004 Society of Chemical Industry [source] Evaluating effectiveness of preoperative testing procedure: some notes on modelling strategies in multi-centre surveysJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 1 2008Dario Gregori PhD Abstract Rationale, In technology assessment in health-related fields the construction of a model for interpreting the economic implications of the introduction of a technology is only a part of the problem. The most important part is often the formulation of a model that can be used for selecting patients to submit to the new cost-saving procedure or medical strategy. The model is usually complicated by the fact that data are often non-homogeneous with respect to some uncontrolled variables and are correlated. The most typical example is the so-called hospital effect in multi-centre studies. Aims and objectives, We show the implications derived by different choices in modelling strategies when evaluating the usefulness of preoperative chest radiography, an exam performed before surgery, usually with the aim to detect unsuspected abnormalities that could influence the anaesthetic management and/or surgical plan. Method, We analyze the data from a multi-centre study including more than 7000 patients. We use about 6000 patients to fit regression models using both a population averaged and a subject-specific approach. We explore the limitations of these models when used for predictive purposes using a validation set of more than 1000 patients. Results, We show the importance of taking into account the heterogeneity among observations and the correlation structure of the data and propose an approach for integrating a population-averaged and subject specific approach into a single modeling strategy. We find that the hospital represents an important variable causing heterogeneity that influences the probability of a useful POCR. Conclusions, We find that starting with a marginal model, evaluating the shrinkage effect and eventually move to a more detailed model for the heterogeneity is preferable. This kind of flexible approach seems to be more informative at various phases of the model-building strategy. [source] Measuring diagnostic and predictive accuracy in disease management: an introduction to receiver operating characteristic (ROC) analysisJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 2 2006Ariel Linden DrPH MS Abstract Diagnostic or predictive accuracy concerns are common in all phases of a disease management (DM) programme, and ultimately play an influential role in the assessment of programme effectiveness. Areas, such as the identification of diseased patients, predictive modelling of future health status and costs and risk stratification, are just a few of the domains in which assessment of accuracy is beneficial, if not critical. The most commonly used analytical model for this purpose is the standard 2 × 2 table method in which sensitivity and specificity are calculated. However, there are several limitations to this approach, including the reliance on a single defined criterion or cut-off for determining a true-positive result, use of non-standardized measurement instruments and sensitivity to outcome prevalence. This paper introduces the receiver operator characteristic (ROC) analysis as a more appropriate and useful technique for assessing diagnostic and predictive accuracy in DM. Its advantages include; testing accuracy across the entire range of scores and thereby not requiring a predetermined cut-off point, easily examined visual and statistical comparisons across tests or scores, and independence from outcome prevalence. Therefore the implementation of ROC as an evaluation tool should be strongly considered in the various phases of a DM programme. [source] Nurses , psychiatrists' main collaborators when treating women with postpartum psychosisJOURNAL OF PSYCHIATRIC & MENTAL HEALTH NURSING, Issue 6 2010I. ENGQVIST rn ms Accessible summary ,The paper describes Swedish psychiatrists' experiences of collaboration with healthcare professionals when treating women with postpartum psychosis (PPP). ,,A qualitative design was used, and semi-structured interviews were performed with nine psychiatrists working in psychiatric hospitals in Sweden. ,,This result was identified: collaboration related to admission, collaboration during inpatient care and collaboration related to discharge. Collaboration with midwives and obstetricians was important in diagnosing the illness, as this often occurred on postnatal wards. Decisions about the form of care for the woman with PPP and for her baby demanded collaboration with various healthcare professionals. Collaboration with nurses was based on expectations and confidence in nurses' competence, and was very important during inpatient care. When the woman was to be discharged, collaboration with healthcare teams as outpatient clinic, child health clinic and community services, was required. ,,The conclusion was that psychiatrists collaborate with different professionals in the different parts of the caring process. When caring for women with PPP, they considered nurses to be their most important collaborators and relied on their competence. Abstract The focus was to describe Swedish psychiatrists' experiences of collaboration with healthcare professionals when treating women with postpartum psychosis (PPP). A qualitative design was used, and semi-structured interviews were performed with nine psychiatrists working in psychiatric hospitals in Sweden. Data were analysed using manifest and latent content analysis. The results of these experiences were categorized in this study as: collaboration related to admission, collaboration during inpatient care and collaboration related to discharge. Collaboration with midwives and obstetricians was important in diagnosing the illness, as this often occurred on postnatal wards; and decisions about the form of care for the woman with PPP and for her baby demanded collaboration with various healthcare professionals. Collaboration with nurses was based on expectations and confidence in nurses' competence, and was exceedingly important during inpatient care. When the woman was to be discharged, collaboration with healthcare teams, e.g. outpatient clinic, child health clinic and community services, was required. The conclusions were that psychiatrists collaborate with different professionals in the various phases of the caring process. They rely extensively on nurses' competence when caring for women with PPP, and consider nurses to be their most important collaborators. [source] Effect of Oxygen Partial Pressure on the Formation of Metastable Phases from an Undercooled YbFeO3 Melt Using an Aerodynamic LevitatorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009Malahalli S. Vijaya Kumar The Yb2O3,Fe2O3 system was studied to investigate the effect of oxygen partial pressure on the formation of metastable phases over a wide range of oxygen partial pressures from 105 to 10,1 Pa. Two kinds of metastable phases, with space groups of P63cm and P63/mmc, were found through rapid solidification of an undercooled YbFeO3 melt in an atmosphere with reduced Po2. The crystal structure of the as-solidified samples changed from orthorhombic Pbnm to hexagonal P63cm and P63/mmc with decreasing Po2. X-ray diffractometric and scanning electron microscopic results confirmed the existence of various phases in the as-solidified samples. The stabilities of each phase were studied by annealing the bulk sample in the thermogravimetric,differential thermal analysis (TG-DTA) furnace up to 1673 K, and the equilibrium phase diagram was constructed for the Yb,Fe,O system at 1473 K. TG analysis showed an increase of the sample mass during annealing and revealed that the existence of Fe2+, which has an ionic radius larger than that of Fe3+, decreases the tolerance factor and therefore destabilizes the perovskite structure. [source] Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid-state 17O NMR spectroscopy and ab initio MO calculationsMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2005Hideaki Kimura Abstract The structure of poly(diethylsiloxane) (PDES) has been characterized using solid-state NMR of 17O. The sample studied had a weight-average molecular weight of 2.45 × 105. The sample was prepared by utilizing the cationic ring-opening polymerization of 17O-enriched hexacyclotrisiloxane. Solid-state NMR of 17O-enriched PDES was measured on the low-temperature ,1 phase, the high-temperature ,2 phase, the two-phase system consisting of the liquid crystal and isotropic liquid phase and the isotropic phase. From these data, the molecular structure and dynamics of PDES in the various phases were characterized via the chemical shifts of 17O, and electric field gradient parameters were determined from NMR and ab initio molecular orbital (MO) calculations. In addition to the solid-state NMR of 1H, 13C and 29Si previously reported on these samples, knowledge of the dynamic behavior of PDES as inferred from the NMR of 17O in the present study was enhanced significantly. Further, the potential of combining the experimental NMR of 17O with ab initio MO calculations to characterize the dynamics of polymers containing oxygen is demonstrated. Copyright © 2004 John Wiley & Sons, Ltd. [source] The Urge to Merge: A Multiple-Case StudyNONPROFIT MANAGEMENT & LEADERSHIP, Issue 2 2002Martha Golensky The authors undertook a comparative study of three recent mergers of nonprofit organizations in a Midwestern urban center, within the context of political-economy theory. The research explored the impact of the same environmental factor, managed care, on the initial decisions by organizational leaders and the effects of these early decisions on subsequent actions taken to implement the merger. The study tested the authors' model of the motivations for merging, which proposes that the relationship between the decision-making style of the leadership and the internal and external resources of the prospective partners determines whether the merger is driven primarily by mission, practicality, stability, or fear. Although the findings provide initial support for the hypotheses derived from the model, a demonstration of the differences in the approach to the merger by each organization indicated that other factors emerged as important driving forces during the various phases of the process. [source] DISPOSITIONAL INFLUENCES ON TRANSFER OF LEARNING IN MULTISTAGE TRAINING PROGRAMSPERSONNEL PSYCHOLOGY, Issue 4 2002DAVID M. HEROLD The training effectiveness literature has paid little attention to the potentially dynamic interaction of individual differences with various phases of training in determining ultimate training success. This study investigates the role of individual differences in explaining the transfer of learning from 1 phase of training to another among pilot trainees in a multistage, aviation training program. Using 3 of the Big Five factors (Conscientiousness, Emotional Stability, Openness to Experience), the results showed these measures to contribute to the prediction of the number of hours it took for trainees to attain their private pilot's license. Significant interactions between some of these measures and success on an earlier, simulator phase of the training program were also found. The results are discussed in terms of both the role of individual differences in training research as well as the broader issue of transfer of learning between phases of training. [source] Magnetic-field-driven quantum criticality and thermodynamics in trimerized spin-1/2 isotropic XY chain with three-spin interactionsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2010L. J. Ding Abstract The quantum criticality and thermodynamics for the trimerized spin-1/2 isotropic XY chain with three-spin interactions in an external magnetic field are investigated by means of the Green's function theory combined with Jordan,Wigner transformation. The ground-state phase diagrams are explored, in which various phases are identified and described by typical M,h curves. Therein, two cusps emerge for strong three-spin interactions in two gapless phases at low and high fields, respectively. Moreover, the spin correlations and two-site entanglement entropy are calculated for a further understanding of quantum phase transition (QPT). It is also found that the magnetic-field-driven quantum criticality is closely related to the energy spectrum, in which an energy gap responsible for the appearance of 1/3 magnetization plateau can be opened up by three-spin interactions. The critical behavior disappears when the temperature becomes nonzero, yielding only a crossover behavior. In addition, the gapped low-lying excitations are responsible for the observed thermodynamic behaviors, wherein a structure with three peaks in the temperature dependence of specific heat is unveiled. [source] The effect of drought and heat stress on reproductive processes in cerealsPLANT CELL & ENVIRONMENT, Issue 1 2008BEÁTA BARNABÁS ABSTRACT As the result of intensive research and breeding efforts over the last 20 years, the yield potential and yield quality of cereals have been greatly improved. Nowadays, yield safety has gained more importance because of the forecasted climatic changes. Drought and high temperature are especially considered as key stress factors with high potential impact on crop yield. Yield safety can only be improved if future breeding attempts will be based on the valuable new knowledge acquired on the processes determining plant development and its responses to stress. Plant stress responses are very complex. Interactions between plant structure, function and the environment need to be investigated at various phases of plant development at the organismal, cellular as well as molecular levels in order to obtain a full picture. The results achieved so far in this field indicate that various plant organs, in a definite hierarchy and in interaction with each other, are involved in determining crop yield under stress. Here we attempt to summarize the currently available information on cereal reproduction under drought and heat stress and to give an outlook towards potential strategies to improve yield safety in cereals. [source] The efficacy of a test and ESS programQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 2 2002Asaf Katz Abstract Statistical results of all the 1621 failure analyses, which cover a four-year effort, are presented. The failure analyses were part of an elaborate test and ESS process of a high-reliability system. Of the failure analyses, 97.5% identified the root cause. The classification of the failures by 11 root cause classes, including the test and ESS process itself is provided. The distribution of failure root causes detected during the various phases of the process is shown. Each test phase was analyzed according to the share of failures found and the fraction of failures that occurred during that phase. Applying a linear formula that summarizes the relative efficacy of each test phase compares the performances of the various phases. The term efficacy is used to describe the ability of a test phase to reveal failures without generating new problems. Copyright © 2002 John Wiley & Sons, Ltd. [source] Neuroendocrine regulation of prolactin secretion in adult female rhesus monkeys during different phases of the menstrual cycle: role of neuroexcitatory amino acid (NMA)AMERICAN JOURNAL OF PRIMATOLOGY, Issue 4 2007S. Jahan Abstract The present study attempts to examine the role of N-methyl-D, L-aspartate (NMDA) receptors in the central regulation of prolactin (PRL) secretion, which may be involved in ovarian function and its alteration by glutamate in various phases of the menstrual cycle of female rhesus monkeys (Macaca mulatta). The results suggest that the glutaminergic component of the control system, which governs PRL secretion by utilizing NMDA receptors, may have an important role in regulating changes in PRL secretion. The response of PRL during the luteal phase of the cycle was different from that observed in follicular and menstrual phases. Steroids may influence the NMDA-dependent drive to release PRL. N-methyl-D-aspartic acid (NMA) involvement in the regulation of PRL secretion may occur through activation of the PRL-stimulating system depending on the physiological state or steroidal milieu. It is possible, therefore, that the NMA-induced release of PRL-releasing factors (PRF) and PRL are enhanced in the presence of ovarian feedback. Am. J. Primatol. 69:1,12, 2007. © 2006 Wiley-Liss, Inc. [source] Phase-dependent and task-dependent modulation of stretch reflexes during rhythmical hand tasks in humansTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Ruiping Xia Phase-dependent and task-dependent modulation of reflexes has been extensively demonstrated in leg muscles during locomotory activity. In contrast, the modulation of reflex responses of hand muscles during rhythmic movement is poorly documented. The objective of this study was to determine whether comparable reflex modulation occurs in muscles controlling finger motions during rhythmic, fine-motor tasks akin to handwriting. Twelve healthy subjects performed two rhythmic tasks while reflexes were evoked by mechanical perturbations applied at various phases of each task. Electromyograms (EMGs) were recorded from four hand muscles, and reflexes were averaged during each task relative to the movement phase. Stretch reflexes in all four muscles were found to be modulated in amplitude with respect to the phase of the rhythmic tasks, and also to vary distinctly with the tasks being conducted. The extent and pattern of reflex modulation differed between muscles in the same task, and between tasks for the same muscle. Muscles with a primary role in each task showed a higher correlation between reflex response and background EMG than other muscles. The results suggest that the modulation patterns observed may reflect optimal strategies of central,peripheral interactions in controlling the performance of fine-motor tasks. As with comparable studies on locomotion, the phase-dependency of the stretch reflexes implies a dynamically fluctuating role of proprioceptive feedback in the control of the hand muscles. The clear task-dependency is also consistent with a dynamic interaction of sensory feedback and central programming, presumably adapted to facilitate the successful performance of the different fine-motor tasks. [source] Investigation of the structure and phase transitions in the novel A-site substituted distorted perovskite compound Na0.5Bi0.5TiO3ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2002G. O. Jones Rietveld neutron powder profile analysis of the compound Na0.5Bi0.5TiO3 (NBT) is reported over the temperature range 5,873,K. The sequence of phase transitions from the high-temperature prototypic cubic structure (above 813,K), to one of tetragonal (673,773,K) and then rhombohedral structures (5,528,K) has been established. Coexisting tetragonal/cubic (773,813,K) and rhombohedral/tetragonal (with an upper temperature limit of 145,K between 528 and 673,K) phases have also been observed. Refinements have revealed that the rhombohedral phase, space group R3c, with aH = 5.4887,(2), cH = 13.5048,(8),Å, V = 352.33,(3),Å3, Z = 6 and Dx = 5.99,Mg,m,3, exhibits an antiphase, a,a,a, oxygen tilt system, , = 8.24,(4)°, with parallel cation displacements at room temperature. The tetragonal phase, space group P4bm, with aT = 5.5179,(2), cT = 3.9073,(2),Å, V = 118.96,(1),Å3, Z = 2 and Dx = 5.91,Mg,m,3, possesses an unusual combination of in-phase, a0a0c+ oxygen octahedra tilts, , = 3.06,(2)°, and antiparallel cation displacements along the polar axis. General trends of cation displacements and the various deviations of the octahedral network from the prototypic cubic perovskite structure have been established and their systematic behaviour with temperature is reported. An investigation of phase transition behaviour using second harmonic generation (SHG) to establish the centrosymmetric or non-centrosymmetric nature of the various phases is also reported. 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