Infrared optical properties of the spin-1/2 quantum magnet TiOClTiOCl

We report results on the electrodynamic response of $TiOCl$, a low-dimensional spin-1/2 quantum magnet that shows a spin gap formation for T$<T_{c1}$= 67 $K$. The Fano-like shape of a few selected infrared active phonons suggests an interaction between lattice vibrations and a continuum of low frequency (spin) excitations. The temperature dependence of the phonon mode parameters extends over a broad temperature range well above $T_{c1}$, indicating the presence of an extended fluctuation regime. In the temperature interval between 200 $K$ and $T_{c1}$ there is a progressive dimensionality crossover (from two to one), as well as a spectral weight shift from low towards high frequencies. This allows us to identify a characteristic energy scale of about 430 $K$, ascribed to a pseudo spin-gap

Thermal Hydraulic Analyses for Coupling High Temperature Gas-Cooled Reactor to Hydrogen Plant

The US Department of Energy is investigating the use of high-temperature nuclear reactors to produce hydrogen using either thermochemical cycles or high-temperature electrolysis. Although the hydrogen production processes are in an early stage of development, coupling either of these processes to the high-temperature reactor requires both efficient heat transfer and adequate separation of the facilities to assure that off-normal events in the production facility do not impact the nuclear power plant. An intermediate heat transport loop will be required to separate the operations and safety functions of the nuclear and hydrogen plants. A next generation high-temperature reactor could be envisioned as a single-purpose facility that produces hydrogen or a dual-purpose facility that produces hydrogen and electricity. Early plants, such as the proposed Next Generation Nuclear Plant (NGNP), may be dual-purpose facilities that demonstrate both hydrogen and efficient electrical generation. Later plants could be single-purpose facilities. At this stage of development, both single- and dual-purpose facilities need to be understood. A number of possible configurations for a system that transfers heat between the nuclear reactor and the hydrogen and/or electrical generation plants were identified. These configurations included both direct and indirect cycles for the production of electricity. Both helium and liquid salts were considered as the working fluid in the intermediate heat transport loop. Methods were developed to perform thermal-hydraulic and cycle-efficiency evaluations of the different configurations and coolants. The thermal-hydraulic evaluations estimated the sizes of various components in the intermediate heat transport loop for the different configurations. The relative sizes of components provide a relative indication of the capital cost associated with the various configurations. Estimates of the overall cycle efficiency of the various configurations were also determined. The evaluations determined which configurations and coolants are the most promising from thermalhydraulic and efficiency points of view

Spinning Q-Balls

We present numerical evidence for the existence of spinning generalizations for non-topological Q-ball solitons in the theory of a complex scalar field with a non-renormalizable self-interaction. To the best of our knowledge, this provides the first explicit example of spinning solitons in 3+1 dimensional Minkowski space. In addition, we find an infinite discrete family of radial excitations of non-rotating Q-balls, and construct also spinning Q-balls in 2+1 dimensions.Comment: To appear in Phys.Rev.

Lepton Flavour Violation in a Class of Lopsided SO(10) Models

A class of predictive SO(10) grand unified theories with highly asymmetric mass matrices, known as lopsided textures, has been developed to accommodate the observed mixing in the neutrino sector. The model class effectively determines the rate for charged lepton flavour violation, and in particular the branching ratio for $\mu -> e \gamma$, assuming that the supersymmetric GUT breaks directly to the constrained minimal supersymmetric standard model (CMSSM). We find that in light of the combined constraints on the CMSSM parameters from direct searches and from the WMAP satellite observations, the resulting predicted rate for $\mu -> e \gamma$ in this model class can be within the current experimental bounds for low $\tan \beta$, but that the next generation of $\mu -> e \gamma$ experiments would effectively rule out this model class if LFV is not detected.Comment: 23 page

Number--conserving model for boson pairing

An independent pair ansatz is developed for the many body wavefunction of dilute Bose systems. The pair correlation is optimized by minimizing the expectation value of the full hamiltonian (rather than the truncated Bogoliubov one) providing a rigorous energy upper bound. In contrast with the Jastrow model, hypernetted chain theory provides closed-form exactly solvable equations for the optimized pair correlation. The model involves both condensate and coherent pairing with number conservation and kinetic energy sum rules satisfied exactly and the compressibility sum rule obeyed at low density. We compute, for bulk boson matter at a given density and zero temperature, (i) the two--body distribution function, (ii) the energy per particle, (iii) the sound velocity, (iv) the chemical potential, (v) the momentum distribution and its condensate fraction and (vi) the pairing function, which quantifies the ODLRO resulting from the structural properties of the two--particle density matrix. The connections with the low--density expansion and Bogoliubov theory are analyzed at different density values, including the density and scattering length regime of interest of trapped-atoms Bose--Einstein condensates. Comparison with the available Diffusion Monte Carlo results is also made.Comment: 21 pages, 12 figure

Exposure to prenatal maternal distress and infant white matter neurodevelopment

The prenatal period represents a critical time for brain growth and development. These rapid neurological advances render the fetus susceptible to various influences with life-long implications for mental health. Maternal distress signals are a dominant early life influence, contributing to birth outcomes and risk for offspring psychopathology. This prospective longitudinal study evaluated the association between prenatal maternal distress and infant white matter microstructure. Participants included a racially and socioeconomically diverse sample of 85 mother-infant dyads. Prenatal distress was assessed at 17 and 29 weeks' gestational age (GA). Infant structural data were collected via diffusion tensor imaging (DTI) at 42-45 weeks' postconceptional age. Findings demonstrated that higher prenatal maternal distress at 29 weeks' GA was associated with increased fractional anisotropy, b =.283, t(64) = 2.319, p =.024, and with increased axial diffusivity, b =.254, t(64) = 2.067, p =.043, within the right anterior cingulate white matter tract. No other significant associations were found with prenatal distress exposure and tract fractional anisotropy or axial diffusivity at 29 weeks' GA, or earlier in gestation

Maternal adverse childhood experiences and infant subcortical brain volume

Background: A large body of research supports the deleterious effects of adverse childhood experiences (ACEs) on disease susceptibility and health for both the exposed individual and the next generation. It is likely that there is an intergenerational transmission of risk from mother to child; however, the mechanisms through which such risk is conferred remain unknown. The current study evaluated the association between maternal ACEs, neonatal brain development of the amygdala and hippocampus, and later infant negative emotionality at six months of age. Methods: The sample included 85 mother-infant dyads (44 female infants) from a longitudinal study. Maternal ACEs were assessed with the Adverse Childhood Experiences Questionnaire (ACE-Q) and neonatal hippocampal and amygdala volume was assessed using structural magnetic resonance imaging (MRI). Infant negative emotionality was assessed at 6 months using the Infant Behavior Questionnaire (IBQ). Results: Multivariate analyses demonstrated that maternal ACEs were associated with bilateral amygdala volume (F(2,78) = 3.697,p =.029). Specifically, higher maternal ACEs were associated with smaller left (β = -0.220, t(79) = -2.661, p =.009, R2= 0.494, and right (β = −0.167, t(79) = -2.043, p =.044, R2= 0.501) amygdala volume. No significant association between maternal ACEs and bilateral hippocampal volume (F(2,78) = 0.215,p =.0807) was found. Follow-up regression analyses demonstrated that both high maternal ACEs and smaller left amygdala volume were associated with higher infant negative emotionality at six months of age (β =.232, p =.040, R2= 0.094, and β = −0.337, p =.022, R2= 0.16, respectively) although statistically significant mediation of this effect was not observed (Indirect effect = 0.0187, 95% CI [-0.0016-0.0557]). Conclusions: Maternal ACEs are associated with both newborn amygdala volume and subsequent infant negative emotionality. These findings linking maternal adverse childhood experiences and infant brain development and temperament provide evidence to support the intergenerational transmission of adversity from mother to child

Cosmology With Non-Minimally Coupled K-Field

We consider non-minimally coupled (with gravity) scalar field with non-canonical kinetic energy. The form of the kinetic term is of Dirac-Born-Infeld (DBI) form.We study the early evolution of the universe when it is sourced only by the k-field, as well as late time evolution when both the matter and k-field are present. For the k-field, we have considered constant potential as well as potential inspired from Boundary String Field Theory (B-SFT). We show that it is possible to have inflationary solution in early time as well as late time accelerating phase. The solutions also exhibit attractor property in a sense that it does not depend on the initial conditions for a certain values of the parameters.Comment: 10 pages, Revtex style, 14 eps figures, to appear in General Relativity and Gravitatio

Longitudinal and prospective assessment of prenatal maternal sleep quality and associations with newborn hippocampal and amygdala volume

Background: The rapid maturation of the fetal brain renders the fetus susceptible to prenatal environmental signals. Prenatal maternal sleep quality is known to have important health implications for newborns including risk for preterm birth, however, the effect on the fetal brain is poorly understood. Method: Participants included 94 pregnant participants and their newborns (53% female). Pregnant participants (Mage = 30; SDage= 5.29) reported on sleep quality three times throughout pregnancy. Newborn hippocampal and amygdala volumes were assessed using structural magnetic resonance imaging. Multilevel modeling was used to test the associations between trajectories of prenatal maternal sleep quality and newborn hippocampal and amygdala volume. Results: The overall trajectory of prenatal maternal sleep quality was associated with hippocampal volume (left: b = 0.00003, p = 0.013; right: b = 0.00003, p =.008). Follow up analyses assessing timing of exposure indicate that poor sleep quality early in pregnancy was associated with larger hippocampal volume bilaterally (e.g., late gestation left: b = 0.002, p = 0.24; right: b = 0.004, p =.11). Prenatal sleep quality was not associated with amygdala volume. Conclusion: These findings highlight the implications of poor prenatal maternal sleep quality and its role in contributing to newborn hippocampal development