Characterization of Mott-insulating and superfluid phases in the one-dimensional Bose--Hubbard model

We use strong-coupling perturbation theory, the variational cluster approach (VCA), and the dynamical density-matrix renormalization group (DDMRG) method to investigate static and dynamical properties of the one-dimensional Bose--Hubbard model in both the Mott-insulating and superfluid phases. From the von Neumann entanglement entropy we determine the central charge and the transition points for the first two Mott lobes. Our DMRG results for the ground-state energy, momentum distribution function, boson correlation function decay, Mott gap, and single particle-spectral function are reproduced very well by the strong-coupling expansion to fifth order, and by VCA with clusters up to 12 sites as long as the ratio between the hopping amplitude and on-site repulsion, t/U, is smaller than 0.15 and 0.25, respectively. In addition, in the superfluid phase VCA captures well the ground-state energy and the sound velocity of the linear phonon modes. This comparison provides an authoritative estimate for the range of applicability of these methods. In strong-coupling theory for the Mott phase, the dynamical structure factor is obtained from the solution of an effective single-particle problem with an attractive potential. The resulting resonances show up as double-peak structure close to the Brillouin zone boundary. These high-energy features also appear in the superfluid phase which is characterized by a pronounced phonon mode at small momenta and energies, as predicted by Bogoliubov and field theory. In one dimension, there are no traces of an amplitude mode in the dynamical single-particle and two-particle correlation functions.Comment: 15 pages, 12 figure

Microstructure of Temporo-Parietal White Matter as a Basis for Reading Ability Evidence from Diffusion Tensor Magnetic Resonance Imaging

AbstractDiffusion tensor magnetic resonance imaging (MRI) was used to study the microstructural integrity of white matter in adults with poor or normal reading ability. Subjects with reading difficulty exhibited decreased diffusion anisotropy bilaterally in temporo-parietal white matter. Axons in these regions were predominantly anterior–posterior in direction. No differences in T1-weighted MRI signal were found between poor readers and control subjects, demonstrating specificity of the group difference to the microstructural characteristics measured by diffusion tensor imaging (DTI). White matter diffusion anisotropy in the temporo-parietal region of the left hemisphere was significantly correlated with reading scores within the reading-impaired adults and within the control group. The anisotropy reflects microstructure of white matter tracts, which may contribute to reading ability by determining the strength of communication between cortical areas involved in visual, auditory, and language processing

The effect of amblyopia treatment on stereoacuity

Purpose: To explore how stereoacuity changes in patients while they are being treated for amblyopia. Methods: The Monitored Occlusion Treatment for Amblyopia Study (MOTAS) comprised 3 distinct phases. In the first phase, baseline, assessments of visual function were made to confirm the initial visual and binocular visual deficit. The second phase, refractive adaptation, now commonly termed “optical treatment,” was an 18-week period of spectacle wear with measurements of logMAR visual acuity and stereoacuity with the Frisby test at weeks 0, 6, 12, and 18. In the third phase, occlusion, participants were prescribed 6 hours of patching per day. Results: A total of 85 children were enrolled (mean age, 5.1 ± 1.5 years). In 21 children amblyopia was associated with anisometropia; in 29, with strabismus; and in 35, with both. At study entry, poor stereoacuity was associated with poor visual acuity (P < 0.001) in the amblyopic eye and greater angle of strabismus (P < 0.001). Of 66 participants, 25 (38%) who received refractive adaptation and 19 (29%) who received occlusion improved by at least one octave in stereoacuity, exceeding test–retest variability. Overall, 38 (45%) improved one or more octaves across both treatment phases. Unmeasureable stereoacuity was observed in 56 participants (66%) at study entry and in 37 (43%) at study exit. Conclusions: Stereoacuity improved for almost one half of the study participants. Improvement was observed in both treatment phases. Factors associated with poor or nil stereoacuity at study entry and exit were poor visual acuity of the amblyopic eye and large-angle strabismus

Five-year efficacy and safety of asfotase alfa therapy for adults and adolescents with hypophosphatasia

Hypophosphatasia (HPP) features low tissue-nonspecific alkaline phosphatase (TNSALP) isoenzyme activity resulting in extracellular accumulation of its substrates including pyridoxal 5\u27-phosphate (PLP), the principal circulating form of vitamin B6, and inorganic pyrophosphate (PPi), a potent inhibitor of mineralization. Asfotase alfa is an enzyme replacement therapy developed to treat HPP. This multinational, randomized, open-label study (NCT01163149; EudraCT 2010-019850-42) evaluated the efficacy and safety of asfotase alfa in adults and adolescents 13-66 years of age with HPP. The study comprised a 6-month primary treatment period and a 4.5-year extension phase. In the primary treatment period, 19 patients were randomized to receive asfotase alfa 0.3 mg/kg/d subcutaneously (SC; n = 7), asfotase alfa 0.5 mg/kg/d SC (n = 6), or no treatment (control; n = 6) for 6 months. In the extension phase, patients received asfotase alfa (0.5 mg/kg/d for 6 mo-1 y, then 1 mg/kg/d 6 d/wk). During the primary treatment period, changes from Baseline to Month 6 in plasma PLP and PPi concentrations (coprimary efficacy measure) were greater in the combined asfotase alfa group compared with the control group, reaching statistical significance for PLP (P = 0.0285) but not for PPi (P = 0.0715). However, for the total cohort, the within subject changes in both PLP and PPi after 6 months and over 5 years of treatment with asfotase alfa were significant (P \u3c 0.05). Secondary efficacy measures included transiliac crest histomorphometry, dual-energy X-ray absorptiometry (DXA), and the 6-Minute Walk Test (6MWT). A significant decrease from Baseline in mineralization lag time was observed in the combined asfotase alfa group at Year 1. There were no significant differences between treated and control patients in DXA mean bone mineral density results at 6 months; Z-scores and T-scores were within the expected range for age at Baseline and remained so over 5 years of treatment. On the 6MWT, median (min, max) distance walked increased from 355 (10, 620; n = 19) meters before treatment to 450 (280, 707; n = 13) meters at 5 years (P \u3c 0.05). Results for the exploratory outcome measures suggested improvements in gross motor function, muscle strength, and patient-reported functional disability over 5 years of treatment. There were no deaths during this study. Asfotase alfa was generally well tolerated; the most common adverse events were mild to moderate injection site reactions. This study suggests that in adults and adolescents with pediatric-onset HPP, treatment with asfotase alfa is associated with normalization of circulating TNSALP substrate levels and improved functional abilities

Burning down the brewery: establishing and evacuating an ancient imperial colony at Cerro Baúl, Peru.

Abstract: Before the Inca reigned, two empires held sway over the central Andes from anno Domini 600 to 1000: the Wari empire to the north ruled much of Peru, and Tiwanaku to the south reigned in Bolivia. Face-to-face contact came when both colonized the Moquegua Valley sierra in southern Peru. The state-sponsored Wari incursion, described here, entailed large-scale agrarian reclamation to sustain the occupation of two hills and the adjacent high mesa of Cerro Baúl. Monumental buildings were erected atop the mesa to serve an embassy-like delegation of nobles and attendant personnel that endured for centuries. Final evacuation of the Baúl enclave was accompanied by elaborate ceremonies with brewing, drinking, feasting, vessel smashing, and building burning. andes | archaeology | empire | Inca | Per

Personalized versus standardized dosing strategies for the treatment of childhood amblyopia: study protocol for a randomized controlled trial

Background: Amblyopia is the commonest visual disorder of childhood in Western societies, affecting, predominantly, spatial visual function. Treatment typically requires a period of refractive correction (‘optical treatment’) followed by occlusion: covering the nonamblyopic eye with a fabric patch for varying daily durations. Recent studies have provided insight into the optimal amount of patching (‘dose’), leading to the adoption of standardized dosing strategies, which, though an advance on previous ad-hoc regimens, take little account of individual patient characteristics. This trial compares the effectiveness of a standardized dosing strategy (that is, a fixed daily occlusion dose based on disease severity) with a personalized dosing strategy (derived from known treatment dose-response functions), in which an initially prescribed occlusion dose is modulated, in a systematic manner, dependent on treatment compliance. Methods/design: A total of 120 children aged between 3 and 8 years of age diagnosed with amblyopia in association with either anisometropia or strabismus, or both, will be randomized to receive either a standardized or a personalized occlusion dose regimen. To avoid confounding by the known benefits of refractive correction, participants will not be randomized until they have completed an optical treatment phase. The primary study objective is to determine whether, at trial endpoint, participants receiving a personalized dosing strategy require fewer hours of occlusion than those in receipt of a standardized dosing strategy. Secondary objectives are to quantify the relationship between observed changes in visual acuity (logMAR, logarithm of the Minimum Angle of Resolution) with age, amblyopia type, and severity of amblyopic visual acuity deficit. Discussion: This is the first randomized controlled trial of occlusion therapy for amblyopia to compare a treatment arm representative of current best practice with an arm representative of an entirely novel treatment regimen based on statistical modelling of previous trial outcome data. Should the personalized dosing strategy demonstrate superiority over the standardized dosing strategy, then its adoption into routine practice could bring practical benefits in reducing the duration of treatment needed to achieve an optimal outcome