Response of Bose gases in time-dependent optical superlattices

The dynamic response of ultracold Bose gases in one-dimensional optical lattices and superlattices is investigated based on exact numerical time evolutions in the framework of the Bose-Hubbard model. The system is excited by a temporal amplitude modulation of the lattice potential, as it was done in recent experiments. For regular lattice potentials, the dynamic signatures of the superfluid to Mott-insulator transition are studied and the position and the fine-structure of the resonances is explained by a linear response analysis. Using direct simulations and the perturbative analysis it is shown that in the presence of a two-colour superlattice the excitation spectrum changes significantly when going from the homogeneous Mott-insulator the quasi Bose-glass phase. A characteristic and experimentally accessible signature for the quasi Bose-glass is the appearance of low-lying resonances and a suppression of the dominant resonance of the Mott-insulator phase.Comment: 20 pages, 9 figures; added references and corrected typo

Quantum phases of atomic boson-fermion mixtures in optical lattices

The zero-temperature phase diagram of a binary mixture of bosonic and fermionic atoms in an one-dimensional optical lattice is studied in the framework of the Bose-Fermi-Hubbard model. By exact numerical solution of the associated eigenvalue problems, ground state observables and the response to an external phase twist are evaluated. The stiffnesses under phase variations provide measures for the boson superfluid fraction and the fermionic Drude weight. Several distinct quantum phases are identified as function of the strength of the repulsive boson-boson and the boson-fermion interaction. Besides the bosonic Mott-insulator phase, two other insulating phases are found, where both the bosonic superfluid fraction and the fermionic Drude weight vanish simultaneously. One of these double-insulator phases exhibits a crystalline diagonal long-range order, while the other is characterized by spatial separation of the two species.Comment: 4 pages, 3 figures, using REVTEX

Ab initio many-body calculations of nucleon scattering on 4He, 7Li, 7Be, 12C and 16O

We combine a recently developed ab initio many-body approach capable of describing simultaneously both bound and scattering states, the ab initio NCSM/RGM, with an importance truncation scheme for the cluster eigenstate basis and demostrate its applicability to nuclei with mass numbers as high as 17. Using soft similarity renormalization group evolved chiral nucleon-nucleon interactions, we first calculate nucleon-4He phase shifts, cross sections and analyzing power. Next, we investigate nucleon scattering on 7Li, 7Be, 12C and 16O in coupled-channel NCSM/RGM calculations that include low-lying excited states of these nuclei. We check the convergence of phase shifts with the basis size and study A=8, 13, and 17 bound and unbound states. Our calculations predict low-lying resonances in 8Li and 8B that have not been experimentally clearly identified yet. We are able to reproduce reasonably well the structure of the A=13 low lying states. However, we find that A=17 states cannot be described without an improved treatment of 16O one-particle-one-hole excitations and alpha clustering.Comment: 18 pages, 20 figure

Executive functions in obsessive-compulsive disorder : a neuropsychological and event-related potential investigation

A number of authors have argued that obsessive-compulsive disorder (OCD) is associated with a significant disturbance of executive functions (e.g., response inhibition, mental flexibility). The present investigation employed both neuropsychological tests and event-related potentials (ERPs) to evaluate this hypothesis. In experiment one 23 outpatients with OCD and 23 normal control participants (matched for age, gender, education and handedness) completed a battery of neuropsychological tests assessing the domains of executive functions, verbal memory, nonverbal memory, language abilities, visuospatial and motor functioning. Data were evaluated for group differences on raw test scores, composite scores formed by averaging standardized tests scores grouped according to sensitivity to areas of neuropsychological functioning, and effect size. Results have revealed poorer language ability in the context of overall adequate functioning in the OCD group. This finding may have been due in part to subtle disturbances in other cognitive functions as statistical evidence of differential deficit was not observed. Results could not be accounted for by demographic or clinical characteristics of the participants. In experiment two 16 outpatients with OCD and 18 normal control participants completed a visual go/nogo task while ERPs were recorded. Results failed to support previous observation of nogo P300 topographic differences implicating impaired response inhibition in OCD. In contrast, controls demonstrated shorter posterior N100 latency, suggesting that OCD may be characterized by less efficient recruitment of posterior cortical pathways involved in the encoding of visual stimuli. In addition, the OCD group demonstrated shorter N200 and P300 latencies related to task parameters, consistent with previous investigations. The functional significance of the N200 and P300 findings is unclear but may reflect disturbances in the monitoring of self-generated actions and dysregulation of stimulus evaluation processes, respectively. Finally, unmedicated OCD patients demonstrated larger P300 amplitude to go than nogo stimuli suggesting that this group may have been composed largely of individuals who would show a positive response to treatment with selective serotonin reuptake inhibitors. Again, results could not be fully accounted for by demographic or clinical characteristics of the participants. The pattern of findings suggest that OCD may be related to a subtle disturbance of response monitoring. Further investigations addressing the potential influence of symptom subtypes, level of insight and comorbid diagnoses on executive functions in OCD are likely to prove fruitful

Neurophysiological evaluation of sensory gating and selective attention in schizotypal personality

Current debate centres around the question of whether schizotypal personality is part of a spectrum of schizophrenia-related disorders. Investigations of biological markers for schizophrenia in schizotypal subjects have tried to test this relationship. Given that there is considerable evidence for both sensory gating and binaural selective attention abnormalities in schizophrenia, as reflected by event-related potentials (ERP), these attention and preattention mechanisms were investigated in students scoring in the top (n = 11) and bottom (n = 12) 10% of scores on the Schizotypal Personality Questionnaire (Raine, 1991). Groups were matched for age, gender composition, handedness and education. Results failed to reveal group differences in suppression of the P50 in the sensory gating task, suggesting that preattentive gating is not disturbed. In contrast, on the selective attention task, predicted patterns of ERP differences were generally found. The schizotypal group was characterized by hyperarousal as indexed by shorter latencies of most ERP components, selective dishabituation of the orienting response to the rare salient stimuli, response-set deficits, intrusion effects, as well as large post-response cognitive processing of stimuli. Results were consistent with ERP abnormalities found in schizophrenics with florid and low formal thought disorders

Ab Initio Theory of Light-ion Reactions

The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent a theoretical and computational challenge for ab initio approaches. After a brief overview of the field, we present a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei. By combining the resonating-group method with the ab initio no-core shell model, we complement a microscopic cluster technique with the use of realistic interactions and a microscopic and consistent description of the clusters. We show results for neutron and proton scattering on light nuclei, including p-7Be and n-8He. We also highlight the first results of the d-3He and d-3H fusion calculations obtained within this approach.Comment: To appear in the proceedings of the International Nuclear Physics Conference INPC 2010, Vancouver, Canada, July 4 - 9, 2010, 10 pages, 5 figure

Spectroscopic Discovery of the Broad-Lined Type Ic Supernova 2010bh Associated with the Low-Redshift GRB 100316D

We present the spectroscopic discovery of a broad-lined Type Ic supernova (SN 2010bh) associated with the nearby long-duration gamma-ray burst (GRB) 100316D. At z = 0.0593, this is the third-nearest GRB-SN. Nightly optical spectra obtained with the Magellan telescopes during the first week after explosion reveal the gradual emergence of very broad spectral features superposed on a blue continuum. The supernova features are typical of broad-lined SNe Ic and are generally consistent with previous supernovae associated with low-redshift GRBs. However, the inferred velocities of SN 2010bh at 21 days after explosion are a factor of ~2 times larger than those of the prototypical SN 1998bw at similar epochs, with v ~ 26,000 km/s, indicating a larger explosion energy or a different ejecta structure. A near-infrared spectrum taken 13.8 days after explosion shows no strong evidence for He I at 1.083 microns, implying that the progenitor was largely stripped of its helium envelope. The host galaxy is of low luminosity (M_R ~ -18.5 mag) and low metallicity (Z < 0.4 Z_solar), similar to the hosts of other low-redshift GRB-SNe.Comment: 6 pages, 4 figures, 1 table, submitted to ApJ Letter

Vitamin D Status of Infants in Northeastern Rural Bangladesh: Preliminary Observations and a Review of Potential Determinants

Vitamin D deficiency is a global public-health concern, even in tropical regions where the risk of deficiency was previously assumed to be low due to cutaneous vitamin D synthesis stimulated by exposure to sun. Poor vitamin D status, indicated by low serum concentrations of 25-hydroxyvitamin D [25(OH)D], has been observed in South Asian populations. However, limited information is available on the vitamin D status of young infants in this region. Therefore, to gain preliminary insights into the vitamin D status of infants in rural Bangladesh, 25(OH)D was assessed in a group of community-sampled control participants in a pneumonia case-control study in rural Sylhet, Bangladesh (25°N) during the winter dry season (January-February). Among 29 infants aged 1-6 months, the mean 25(OH)D was 36.7 nmol/L [95% confidence interval (CI) 30.2-43.2]. The proportion of infants with vitamin D deficiency defined by 25(OH)D <25 nmol/L was 28% (95% CI 10-45), 59% (95% CI 40-78) had 25(OH)D<40 nmol/L, and all were below 80 nmol/L. From one to six months, there was a positive correlation between age and 25(OH)D (Spearman=0.65; p=0.0001). Within a larger group of 74 infants and toddlers aged 1-17 months (cases and controls recruited for the pneumonia study), young age was the only significant risk factor for vitamin D deficiency [25(OH)D <25 nmol/L]. Since conservative maternal clothing practices (i.e. veiling) and low frequency of intake of foods from animal source (other than fish) were common among the mothers of the participants, determinants of low maternal-infant 25(OH)D in Bangladesh deserve more detailed consideration in future studies. In conclusion, the vitamin D status in young infants in rural Sylhet, Bangladesh, was poorer than might be expected based on geographic considerations. The causes and consequences of low 25(OH)D in infancy and early childhood in this setting remain to be established

Familial Childhood Sleep Apnea

We report four siblings who had polysomnographically documented sleep apnea. Two presented with the typical clinical picture of sleep apnea syndrome including daytime somnolence and snoring, had repetitive obstructive apneic episodes during sleep, and were effectively treated with upper airway surgery. The other two were asymptomatic and showed infrequent apneic episodes during sleep. This family illustrates the distinction between the sleep apnea syndrome and infrequent apneic episodes during sleep. The sleep apnea syndrome is associated with daytime symptomatology and requires treatment. The presence of apneic episodes during sleep in all four siblings has implications regarding the predisposing factors (eg, upper airway anatomy and central nervous system dysfunction) versus precipitating factors (eg, obesity, upper airway infection, and central nervous system depressants) in sleep apnea