Spectral Function in Mott Insulating Surfaces

We show theoretically the fingerprints of short-range spiral magnetic correlations in the photoemission spectra of the Mott insulating ground states realized in the triangular silicon surfaces K/Si(111)-B and SiC(0001). The calculated spectra present low energy features of magnetic origin with a reduced dispersion ~10-40 meV compared with the center-of-mass spectra bandwidth ~0.2-0:3 eV. Remarkably, we find that the quasiparticle signal survives only around the magnetic Goldstone modes. Our findings would position these silicon surfaces as new candidates to investigate non-conventional quasiparticle excitations.Comment: 5 pages, 4 figures. To be published in Journal of Physics: Condensed Matte

Action of serotonin (5-hydroxytryptamine) on cyclic nucleotides in glomeruli of rat renal cortex

Action of serotonin (5-hydroxytryptamine) on cyclic nucleotides in glomeruli of rat renal cortex. Serotonin (5-hydroxytryptamine) is known to influence glomerular function and may have an important role in the pathogenesis of glomerulopathies. Because serotonin acts in nonrenal tissues through mediation of cyclic nucleotides, we investigated in vitro its effect on cAMP and cyclic guanosine monophosphate (cGMP) in tissue slices and isolated glomeruli from rat kidney. Serotonin increased cAMP 161 ± 35% but not cGMP in renal cortex; it had no effect on cyclic nucleotides in medulla and papilla. In isolated glomeruli, serotonin elicited a dose-dependent (in the range of 10−7 to 10−4M) increase in cAMP; the maximum increase over basal values was 376 ± 45%. Serotonin increased cAMP either in the presence or in the absence of a cAMP phosphodiesterase inhibitor. In tubular fraction, serotonin elevated cAMP to a much lesser degree (82 ± 15%). Neither in glomeruli nor in tubules did cGMP concentrations change in response to serotonin, but carbamylcholine, a known cGMP agonist, significantly increased cGMP concentrations. The increase in cAMP in response to serotonin was blocked (>85% inhibition) by equimolar concentrations of serotonin antagonists methysergide and cinanserine. Results of this study demonstrate that interaction of serotonin with receptors in the kidney, particularly in the glomeruli, cause a striking increase in cAMP concentrations without detectable changes in cGMP concentrations. These findings suggest that serotonin, either synthesized in the kidney or released locally from platelets aggregated in glomeruli (for example, in association with immu-nopathologic injury) may exert or modulate its physiologic or pathologic effects via mediation of cAMP.Action de la sérotonine (5-hydroxytryptamine) sur les nucléotides cycliques des glomérules du cortex rénal du rat. Il est connu que la sérotonine (5-hydroxytryptamine) influence la fonction glomérulaire et peut avoir un rôle important dans la pathogénie des glomérulopathies. Puisque la sérotonine agit sur d'autres tissus que le rein par l'intermédiaire des nucléotides cycliques, nous avons étudié son effet in vitro sur le contenu en cAMP et cGMP des tranches de rein et des glomérules isolés du rein de rat. La sérotonine augmente cAMP 161 ± 35%, mais pas cGMP du cortex rénal. Elle n'a pas d'effet sur les nucléotides cycliques de la médullaire et de la papille. Dans les glomérules isolés la sérontonine détermine une augmentation de cAMP dose dépendante (de 10−7 à 10−4M), l'augmentation maximale est de 376 ± 45% par rapport à la valeur basale. La sérotonine augmente cAMP aussi bien en présence qu'en l'absence d'inhibiteur de la cAMP phosphodiestérase. Dans les fractions tabulaires la sérotonine n'augmente cAMP qu'à un moindre degré (82 ± 15%). La sérotonine n'augmente cGMP ni dans les glomérules ni dans les tubules mais la carbamylcholine, un agoniste connu de cGMP augmente celui-ci significativement. L'augmentation de cAMP en réponse à la sérotonine est bloquée (inhibition supérieure à 85%) par des concentrations équimolaires des antagonistes méthysergide et cinansérine. Les résultats de ce travail démontrent que l'interaction de la sérotonine avec les récepteurs rénaux, particulièrement glomérulaires, détermine une augmentation importante de cAMP sans modification détéctable de cGMP. Ces constatations suggèrent que la sérotonine, qu'elle soit synthétisée dans le rein ou libérée localement par des aggrégats plaquettaires formés dans les glomérules (c'est à dire en association avec une lésion immunopathologique), peut exercer ou moduler ses effets physiologiques ou pathologiques par l'intermédiaire de cAMP

Why is the bandwidth of sodium observed to be narrower in photoemission experiments?

The experimentally predicted narrowing in the bandwidth of sodium is interpreted in terms of the non-local self-energy effect on quasi-particle energies of the electron liquid. The calculated self-energy correction is a monotonically increasing function of the wavenumber variable. The usual analysis of photo-emission experiments assumes the final state energies on the nearly-free-electron-like model and hence it incorrectly ascribes the non-local self-energy correction to the final state energies to the occupied state energies, thus leading to a seeming narrowing in the bandwidth.Comment: 9 page

Early Gesture and Vocabulary Development in Infant Siblings of Children with Autism Spectrum Disorder

This study examined longitudinal growth in gestures and words in infants at heightened (HR) vs. low risk (LR) for ASD. The MacArthur-Bates Communicative Development Inventory was administered monthly from 8 to 14 months and at 18 and 24 months to caregivers of 14 HR infants diagnosed with ASD (HR-ASD), 27 HR infants with language delay (HR-LD), 51 HR infants with no diagnosis (HR-ND), and 28 LR infants. Few differences were obtained between LR and HR-ND infants, but HR-LD and HR-ASD groups differed in initial skill levels and growth patterns. While HR-LD infants grew at rates comparable to LR and HR-ND infants, growth was attenuated in the HR-ASD group, with trajectories progressively diverging from all other groups

Theoretical investigations of a highly mismatched interface: the case of SiC/Si(001)

Using first principles, classical potentials, and elasticity theory, we investigated the structure of a semiconductor/semiconductor interface with a high lattice mismatch, SiC/Si(001). Among several tested possible configurations, a heterostructure with (i) a misfit dislocation network pinned at the interface and (ii) reconstructed dislocation cores with a carbon substoichiometry is found to be the most stable one. The importance of the slab approximation in first-principles calculations is discussed and estimated by combining classical potential techniques and elasticity theory. For the most stable configuration, an estimate of the interface energy is given. Finally, the electronic structure is investigated and discussed in relation with the dislocation array structure. Interface states, localized in the heterostructure gap and located on dislocation cores, are identified

Caregiver perspectives on the continued impact of the COVID-19 pandemic on children with intellectual/developmental disabilities

The COVID-19 pandemic has significantly impacted caregivers, especially those raising a child with an intellectual/developmental disability (IDD). While research has shown substantial disruption to the family, school, and occupational lives of the IDD community, little is known about the long-term impacts of COVID-19. To address this question, 249 caregivers were surveyed via an online questionnaire, between April and August of 2022 (more than 2 years into the pandemic) about potential impacts of the COVID-19 pandemic on their child\u27s access to health- and school-based therapeutic services, caregiver mental health, and family life. The majority of caregivers reported disruptions in access to and quality of school-based therapeutic services for their child as well as a reduction in educational accommodations in the 2021-2022 academic year. Nearly half of caregivers reported feeling anxious and almost a quarter reported feeling depressed for the majority of their days. More than half of respondents reported decreased social support, and one-fifth reported employment disruptions and decreased access to food. These findings suggest that families of children with IDD are still experiencing ongoing negative impacts of the pandemic, emphasizing the critical need for continued support in the wake of the initial and more obvious disruptions caused by the COVID-19 outbreak

Electronic structure of the MO oxides (M=Mg, Ca, Ti, V) in the GW approximation

The quasiparticle band structures of nonmagnetic monoxides, MO (M=Mg, Ca, Ti, and V), are calculated by the GW approximation. The band gap and the width of occupied oxygen 2p states in insulating MgO and CaO agree with experimental observation. In metallic TiO and VO, conduction bands originated from metal 3d states become narrower. Then the partial densities of transition metal e_g and t_2g states show an enhanced dip between the two. The effects of static screening and dynamical correlation are discussed in detail in comparison with the results of the Hartree-Fock approximation and the static Coulomb hole plus screened exchange approximation. The d-d Coulomb interaction is shown to be very much reduced by on-site and off-site d-electron screening in TiO and VO. The dielectric function and the energy loss spectrum are also presented and discussed in detail.Comment: 10 pages, 5 figure

Macroscopic polarization and band offsets at nitride heterojunctions

Ab initio electronic structure studies of prototypical polar interfaces of wurtzite III-V nitrides show that large uniform electric fields exist in epitaxial nitride overlayers, due to the discontinuity across the interface of the macroscopic polarization of the constituent materials. Polarization fields forbid a standard evaluation of band offsets and formation energies: using new techniques, we find a large forward-backward asymmetry of the offset (0.2 eV for AlN/GaN (0001), 0.85 eV for GaN/AlN (0001)), and tiny interface formation energies.Comment: RevTeX 4 pages, 2 figure

Natural ventilation reduces high TB transmission risk in traditional homes in rural KwaZulu-Natal, South Africa

Background: Transmission of drug susceptible and drug resistant TB occurs in health care facilities, and community and households settings, particularly in highly prevalent TB and HIV areas. There is a paucity of data regarding factors that may affect TB transmission risk in household settings. We evaluated air exchange and the impact of natural ventilation on estimated TB transmission risk in traditional Zulu homes in rural South Africa. Methods: We utilized a carbon dioxide decay technique to measure ventilation in air changes per hour (ACH). We evaluated predominant home types to determine factors affecting ACH and used the Wells-Riley equation to estimate TB transmission risk. Results: Two hundred eighteen ventilation measurements were taken in 24 traditional homes. All had low ventilation at baseline when windows were closed (mean ACH = 3, SD = 3.0), with estimated TB transmission risk of 55.4% over a ten hour period of exposure to an infectious TB patient. There was significant improvement with opening windows and door, reaching a mean ACH of 20 (SD = 13.1, p < 0.0001) resulting in significant decrease in estimated TB transmission risk to 9.6% (p < 0.0001). Multivariate analysis identified factors predicting ACH, including ventilation conditions (windows/doors open) and window to volume ratio. Expanding ventilation increased the odds of achieving ≥12 ACH by 60-fold. Conclusions: There is high estimated risk of TB transmission in traditional homes of infectious TB patients in rural South Africa. Improving natural ventilation may decrease household TB transmission risk and, combined with other strategies, may enhance TB control efforts

Atomic structure of dislocation kinks in silicon

We investigate the physics of the core reconstruction and associated structural excitations (reconstruction defects and kinks) of dislocations in silicon, using a linear-scaling density-matrix technique. The two predominant dislocations (the 90-degree and 30-degree partials) are examined, focusing for the 90-degree case on the single-period core reconstruction. In both cases, we observe strongly reconstructed bonds at the dislocation cores, as suggested in previous studies. As a consequence, relatively low formation energies and high migration barriers are generally associated with reconstructed (dangling-bond-free) kinks. Complexes formed of a kink plus a reconstruction defect are found to be strongly bound in the 30-degree partial, while the opposite is true in the case of 90-degree partial, where such complexes are found to be only marginally stable at zero temperature with very low dissociation barriers. For the 30-degree partial, our calculated formation energies and migration barriers of kinks are seen to compare favorably with experiment. Our results for the kink energies on the 90-degree partial are consistent with a recently proposed alternative double-period structure for the core of this dislocation.Comment: 12 pages, two-column style with 8 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/index.html#rn_di