On a family of numerical models for couple stress based flexoelectricity for continua and beams

A family of numerical models for the phenomenological linear flexoelectric theory for continua and their particularisation to the case of three-dimensional beams based on a skew-symmetric couple stress theory is presented. In contrast to the standard strain gradient flexoelectric models which assume coupling between electric polarisation and strain gradients, we postulate an electric enthalpy in terms of linear invariants of curvature and electric field. This is achieved by introducing the axial (mean) curvature vector as a strain gradient measure. The physical implication of this assumption is many-fold. Firstly, analogous to the standard strain gradient models, for isotropic (non-piezoelectric) materials it allows constructing flexoelectric energies without breaking material’s centrosymmetry. Secondly, unlike the standard strain gradient models, nonuniform distribution of volumetric part of strains (volumetric strain gradients) do not generate electric polarisation, as also confirmed by experimental evidence to be the case for some important classes of flexoelectric materials. Thirdly, a state of plane strain generates out of plane deformation through strain gradient effects. Finally, under this theory, extension and shear coupling modes cannot be characterised individually as they contribute to the generation of electric polarisation as a whole. As a first step, a detailed comparison of the developed couple stress based flexoelectric model with the standard strain gradient flexoelectric models is performed for the case of Barium Titanate where a myriad of simple analytical solutions are assumed in order to quantitatively describe the similarities and dissimilarities in effective electromechanical coupling under these two theories. From a physical point of view, the most notable insight gained is that, if the same experimental flexoelectric constants are fitted in to both theories, the presented theory in general, reports up to 200% stronger electromechanical conversion efficiency. From the formulation point of a view, the presented flexoelectric model is also competitively simpler as it eliminates the need for high order strain gradient and coupling tensors and can be characterised by a single flexoelectric coefficient. In addition, three distinct mixed flexoelectric variational principles are presented for both continuum and beam models that facilitate incorporation of strain gradient measures in to a standard finite element scheme while maintaining the C0 continuity. Consequently, a series of low and high order mixed finite element schemes for couple stress based flexoelectricity are presented and thoroughly benchmarked against available closed form solutions in regards to electromechanical coupling efficiency. Finally, nanocompression of a complex flexoelectric conical pyramid for which analytical solution cannot be established is numerically studied where curvature induced necking of the specimen and vorticity around the frustum generate moderate electric polarisation

Measuring Coverage in MNCH:A Validation Study Linking Population Survey Derived Coverage to Maternal, Newborn, and Child Health Care Records in Rural China

Accurate data on coverage of key maternal, newborn, and child health (MNCH) interventions are crucial for monitoring progress toward the Millennium Development Goals 4 and 5. Coverage estimates are primarily obtained from routine population surveys through self-reporting, the validity of which is not well understood. We aimed to examine the validity of the coverage of selected MNCH interventions in Gongcheng County, China.We conducted a validation study by comparing women's self-reported coverage of MNCH interventions relating to antenatal and postnatal care, mode of delivery, and child vaccinations in a community survey with their paper- and electronic-based health care records, treating the health care records as the reference standard. Of 936 women recruited, 914 (97.6%) completed the survey. Results show that self-reported coverage of these interventions had moderate to high sensitivity (0.57 [95% confidence interval (CI): 0.50-0.63] to 0.99 [95% CI: 0.98-1.00]) and low to high specificity (0 to 0.83 [95% CI: 0.80-0.86]). Despite varying overall validity, with the area under the receiver operating characteristic curve (AUC) ranging between 0.49 [95% CI: 0.39-0.57] and 0.90 [95% CI: 0.88-0.92], bias in the coverage estimates at the population level was small to moderate, with the test to actual positive (TAP) ratio ranging between 0.8 and 1.5 for 24 of the 28 indicators examined. Our ability to accurately estimate validity was affected by several caveats associated with the reference standard. Caution should be exercised when generalizing the results to other settings.The overall validity of self-reported coverage was moderate across selected MNCH indicators. However, at the population level, self-reported coverage appears to have small to moderate degree of bias. Accuracy of the coverage was particularly high for indicators with high recorded coverage or low recorded coverage but high specificity. The study provides insights into the accuracy of self-reports based on a population survey in low- and middle-income countries. Similar studies applying an improved reference standard are warranted in the future

Decadal changes of the Western Arabian sea ecosystem

Historical data from oceanographic expeditions and remotely sensed data on outgoing longwave radiation, temperature, wind speed and ocean color in the western Arabian Sea (1950–2010) were used to investigate decadal trends in the physical and biochemical properties of the upper 300 m. 72 % of the 29,043 vertical profiles retrieved originated from USA and UK expeditions. Increasing outgoing longwave radiation, surface air temperatures and sea surface temperature were identified on decadal timescales. These were well correlated with decreasing wind speeds associated with a reduced Siberian High atmospheric anomaly. Shoaling of the oxycline and nitracline was observed as well as acidification of the upper 300 m. These physical and chemical changes were accompanied by declining chlorophyll-a concentrations, vertical macrofaunal habitat compression, declining sardine landings and an increase of fish kill incidents along the Omani coast

Multifragmentation and the liquid-gas phase transition: an experimental overview

Two roads are presently being followed in order to establish the existence of a liquid-gas phase transition in finite nuclear systems from nuclear reactions at high energy. The clean experiment of observing the thermodynamic properties of a finite number of nucleons in a container is presently only possible with the computer. Performed with advanced nuclear transport models, it has revealed the first-order character of the transition and allowed the extraction of the pertinent thermodynamic parameters. The validity of the applied theory is being confirmed by comparing its predictions for heavy-ion reactions with exclusive experiments. The second approach is experimentally more direct. Signals of the transition are searched for by analysing reaction data within the framework of thermodynamics of small systems. A variety of potential signals has been investigated and found to be qualitatively consistent with the expectations for the phase transition. Many of them are well reproduced with percolation models which places the nuclear fragmentation into the more general context of partitioning phenomena in finite systems. A wealth of new data on this subject has been obtained in recent experiments, some of them with a new generation of multi-detector devices aiming at higher resolutions, isotopic identification of the fragments, and the coincident detection of neutrons. Isotopic effects in multifragmentation were addressed quite intensively, with particular attention being given to their relation to the symmetry energy and its dependence on density.Comment: 10 pages, 7 figures, Contribution to Proceedings of INPC2004, Goeteborg, Sweden, June 27 - July 2, 200

Enhanced self-renewal of hematopoietic stem/progenitor cells mediated by the stem cell gene Sall4

<p>Abstract</p> <p>Background</p> <p>Sall4 is a key factor for the maintenance of pluripotency and self-renewal of embryonic stem cells (ESCs). Our previous studies have shown that Sall4 is a robust stimulator for human hematopoietic stem and progenitor cell (HSC/HPC) expansion. The purpose of the current study is to further evaluate how Sall4 may affect HSC/HPC activities in a murine system.</p> <p>Methods</p> <p>Lentiviral vectors expressing Sall4A or Sall4B isoform were used to transduce mouse bone marrow Lin-/Sca1+/c-Kit+ (LSK) cells and HSC/HPC self-renewal and differentiation were evaluated.</p> <p>Results</p> <p>Forced expression of Sall4 isoforms led to sustained <it>ex vivo </it>proliferation of LSK cells. In addition, Sall4 expanded HSC/HPCs exhibited increased <it>in vivo </it>repopulating abilities after bone marrow transplantation. These activities were associated with dramatic upregulation of multiple HSC/HPC regulatory genes including HoxB4, Notch1, Bmi1, Runx1, Meis1 and Nf-ya. Consistently, downregulation of endogenous Sall4 expression led to reduced LSK cell proliferation and accelerated cell differentiation. Moreover, in myeloid progenitor cells (32D), overexpression of Sall4 isoforms inhibited granulocytic differentiation and permitted expansion of undifferentiated cells with defined cytokines, consistent with the known functions of Sall4 in the ES cell system.</p> <p>Conclusion</p> <p>Sall4 is a potent regulator for HSC/HPC self-renewal, likely by increasing self-renewal activity and inhibiting differentiation. Our work provides further support that Sall4 manipulation may be a new model for expanding clinically transplantable stem cells.</p

The moral technical imaginaries of internet convergence in an American television network

How emergent technologies are imagined, discussed, and implemented reveals social morality about how society, politics, and economics should be organized. For the television industry in the United States, for instance, the development of internet “convergence” provoked the rise of a new discourse about participatory democracy as well as the hopes for lucrative business opportunities. The simultaneity of technical, moral, and social ordering defines the “moral technical imaginary.” Populating this concept with ethnographic and historical detail, this article expands the theory of the moral technical imaginary with information from six years of participant observation, interviews, and employment with Current TV, an American-based television news network founded by Vice President Al Gore to democratize television production. This chapter explores the limits of political participation and morality when faced with neoliberal capitalism

The role of spalt proteins in development and disease

AbstractThe spalt proteins are encoded by a family of evolutionarily conserved genes found in species as diverse as Drosophila, C. elegans and vertebrates. In humans, mutations in some of these genes are associated with several congenital disorders which underscores the importance of spalt gene function in embryonic development. Recent studies have begun to cast light on the functions of this family of proteins with increasing understanding of the developmental processes regulated and the molecular mechanisms used. Here we review what is currently known about the role of spalt genes in vertebrate development and human disease

Hospital care for children and young adults in the last year of life: a population-based study

BACKGROUND: To help design population-based pediatric palliative care services, we sought to describe the hospital care received in the last year of life by children and young adults who died. We also determined the proportion with complex chronic conditions (CCCs) and tested whether the use of hospital services increased as the date of death drew nearer. METHODS: For all deaths occurring under 25 years of age from 1990 to 1996 in Washington State, USA, we linked death certificate information to hospital utilization records and analyzed the timing and duration of hospitalizations and the nature of hospital procedures during the year prior to death. RESULTS: Of the 8 893 deaths, 25 % had CCCs. Among infants with CCCs, 84 % were hospitalized at the time of death and 50 % had been mechanically ventilated during their terminal admission. Among the 458 CCC neonates dying under a week of age, 92% of all days of life were spent in the hospital; among the 172 CCC neonates dying during the second to fourth weeks of life, 85 % of all days of life were spent hospitalized; among the 286 CCC infants dying during the second to twelfth month of life, 41 % of all days of life were spent hospitalized. Among children and young adults with CCCs, 55 % were hospitalized at the time of death, and 19 % had been mechanically ventilated during their terminal admission. For these older patients, the median number of days spent in the hospital during the year preceding death was 18, yet less than a third of this group was hospitalized at any point in time until the last week of their lives. The rate of hospital use increased as death drew near. For subjects who had received hospital care, 44 % had governmental insurance as the source of primary payment. CONCLUSIONS: Infants who died spent a substantial proportion of their lives in hospitals, whereas children and adolescents who died from CCCs predominantly lived outside of the hospital during the last year of life. To serve these patients, pediatric palliative and end-of-life care will have to be provided in an integrated, coordinated manner both in hospitals and home communities

Humanized Rag1−/−γc−/− Mice Support Multilineage Hematopoiesis and Are Susceptible to HIV-1 Infection via Systemic and Vaginal Routes

Several new immunodeficient mouse models for human cell engraftment have recently been introduced that include the Rag2−/−γc−/−, NOD/SCID, NOD/SCIDγc−/− and NOD/SCIDβ2m−/− strains. Transplantation of these mice with CD34+ human hematopoietic stem cells leads to prolonged engraftment, multilineage hematopoiesis and the capacity to generate human immune responses against a variety of antigens. However, the various mouse strains used and different methods of engrafting human cells are beginning to illustrate strain specific variations in engraftment levels, duration and longevity of mouse life span. In these proof-of-concept studies we evaluated the Balb/c-Rag1−/−γ−/− strain for engraftment by human fetal liver derived CD34+ hematopoietic cells using the same protocol found to be effective for Balb/c-Rag2−/−γc−/− mice. We demonstrate that these mice can be efficiently engrafted and show multilineage human hematopoiesis with human cells populating different lymphoid organs. Generation of human cells continues beyond a year and production of human immunoglobulins is noted. Infection with HIV-1 leads to chronic viremia with a resultant CD4 T cell loss. To mimic the predominant sexual viral transmission, we challenged humanized Rag1−/−γc−/− mice with HIV-1 via vaginal route which also resulted in chronic viremia and helper T cell loss. Thus these mice can be further exploited for studying human pathogens that infect the human hematopoietic system in an in vivo setting