Exact duality and dual Monte-Carlo simulation for the Bosonic Hubbard model

We derive the exact dual to the Bosonic Hubbard model. The dual variables take the form of conserved current loops (local and global). Previously this has been done only for the very soft core model at very high density. No such approximations are made here. In particular, the dual of the hard core model is shown to have a very simple form which is then used to construct an efficient Monte Carlo algorithm which is quite similar to the World Line algorithm but with some important differences. For example, with this algorithm we can measure easily the correlation function of the order parameter (Green function), a quantity which is extremely difficult to measure with the standard World Line algorithm. We demonstrate the algorithm for the one and two dimensional hardcore Bosonic Hubbard models. We present new results especially for the Green function and zero mode filling fraction in the two dimensional hardcore model.Comment: 14 pages, 15 figures include

Algebraic and Computer-based Methods in the Undirected Degree/diameter Problem - a Brief Survey

This paper discusses the most popular algebraic techniques and computational methods that have been used to construct large graphs with given degree and diameter

Electronic Correlations in CoO2, the Parent Compound of Triangular Cobaltates

A 59Co NMR study of CoO2, the x=0 end member of AxCoO2 (A = Na, Li...) cobaltates, reveals a metallic ground state, though with clear signs of strong electron correlations: low-energy spin fluctuations develop at wave vectors q different from 0 and a crossover to a Fermi-liquid regime occurs below a characteristic temperature T*~7 K. Despite some uncertainty over the exact cobalt oxidation state n this material, the results show that electronic correlations are revealed as x is reduced below 0.3. The data are consistent with NaxCoO2 being close to the Mott transition in the x -> 0 limit.Comment: 4 pages, submitte

Coaxial prime focus feeds for paraboloidal reflectors

A TE11 - TM11 dual mode coaxial feed for use in prime focus paraboloidal antenna systems is investigated. The scattering matrix parameters of the internal bifurcation junction was determined by the residue calculus technique. The scattering parameters and radiation fields of the aperture were found from the Weinstein solution. The optimum modeing ratio for minimum cross-polarization was determined along with the corresponding optimum feed dimensions. A peak cross-polarization level of -58 dB is predicted. The frequency characteristics were also investigated and a bandwidth of 5% is predicted over which the cross-polarization remains below -30 dB, the input VSWR is below 1.15, and the phase error is less than 10 deg. Theoretical radiation patterns and efficiency curves for a paraboloidal reflector illuminated by this feed were computed. The predicted sidelobe level is below -30 dB and aperture efficiencies greater than 70% are possible. Experimental results are also presented that substantiates the theoretical results. In addition, experimental results for a 'short-cup' coaxial feed are given. The report includes extensive design data for the dual-mode feed along with performance curves showing cross-polarization as a function of feed parameters. The feed is useful for low-cost ground based receiving antennas for use in direct television satellite broadcasting service

A perception and manipulation system for collecting rock samples

An important part of a planetary exploration mission is to collect and analyze surface samples. As part of the Carnegie Mellon University Ambler Project, researchers are investigating techniques for collecting samples using a robot arm and a range sensor. The aim of this work is to make the sample collection operation fully autonomous. Described here are the components of the experimental system, including a perception module that extracts objects of interest from range images and produces models of their shapes, and a manipulation module that enables the system to pick up the objects identified by the perception module. The system was tested on a small testbed using natural terrain

Injection of hydrogen and vacancy-type defects during dissolution of aluminum

Formation of interfacial nanoscale voids in Al during room-temperature caustic corrosion was characterized by positron annihilation spectroscopy (PAS) and compared with measurements of deuterium absorption using secondary ion mass spectrometry (SIMS). The hypothesis was investigated that voids are created from vacancy-hydrogen (Vac-H) defects introduced during corrosion. Evidence for both mobile and immobile forms of absorbed hydrogen was obtained, the latter present within distances of 50 nm from the metal-oxide interface, where voids were also found. During corrosion, the immobile hydrogen was found only during discrete 1-2 min intervals of time separated by periods of 1-2 min when it was not present. Model calculations suggested that this transient behavior is consistent with repeated nucleation and dissolution of clusters of Vac-H defects. Only some aspects of the time-dependence of the void concentration from PAS corresponded with that of absorbed hydrogen; the former is believed to be influenced by metallic impurities

Bilingualism Is Associated with a Delayed Onset of Dementia but Not with a Lower Risk of Developing it: a Systematic Review with Meta-Analyses.

Some studies have linked bilingualism with a later onset of dementia, Alzheimer's disease (AD), and mild cognitive impairment (MCI). Not all studies have observed such relationships, however. Differences in study outcomes may be due to methodological limitations and the presence of confounding factors within studies such as immigration status and level of education. We conducted the first systematic review with meta-analysis combining cross-sectional studies to explore if bilingualism might delay symptom onset and diagnosis of dementia, AD, and MCI. Primary outcomes included the age of symptom onset, the age at diagnosis of MCI or dementia, and the risk of developing MCI or dementia. A secondary outcome included the degree of disease severity at dementia diagnosis. There was no difference in the age of MCI diagnosis between monolinguals and bilinguals [mean difference: 3.2; 95% confidence intervals (CI): -3.4, 9.7]. Bilinguals vs. monolinguals reported experiencing AD symptoms 4.7 years (95% CI: 3.3, 6.1) later. Bilinguals vs. monolinguals were diagnosed with dementia 3.3 years (95% CI: 1.7, 4.9) later. Here, 95% prediction intervals showed a large dispersion of effect sizes (-1.9 to 8.5). We investigated this dispersion with a subgroup meta-analysis comparing studies that had recruited participants with dementia to studies that had recruited participants with AD on the age of dementia and AD diagnosis between mono- and bilinguals. Results showed that bilinguals vs. monolinguals were 1.9 years (95% CI: -0.9, 4.7) and 4.2 (95% CI: 2.0, 6.4) older than monolinguals at the time of dementia and AD diagnosis, respectively. The mean difference between the two subgroups was not significant. There was no significant risk reduction (odds ratio: 0.89; 95% CI: 0.68-1.16) in developing dementia among bilinguals vs. monolinguals. Also, there was no significant difference (Hedges' g = 0.05; 95% CI: -0.13, 0.24) in disease severity at dementia diagnosis between bilinguals and monolinguals, despite bilinguals being significantly older. The majority of studies had adjusted for level of education suggesting that education might not have played a role in the observed delay in dementia among bilinguals vs. monolinguals. Although findings indicated that bilingualism was on average related to a delayed onset of dementia, the magnitude of this relationship varied across different settings. This variation may be due to unexplained heterogeneity and different sources of bias in the included studies. Registration: PROSPERO CRD42015019100

Efektivitas Ekstrak Daun Jeruk Purut (Citrus Hystrix), Jeruk Limau (Citrus Amblycarpa), Dan Jeruk Bali (Citrus Maxima) Terhadap Larva Aedes Aegypti

The used of chemicals as larvicidal may causing resistance, health problem, and environment problem. Leaf extracts of Citrus as biolarvicidal against Aedes aegypti larvae can be used as an alternative larvicidal. The aims of this study is to find out the species of Citrus in the study sample, which is the most effective as biolarvicidal. This study was conducted using nested experiment design, with six treatments and five replicates. Larvae mortality was observed after 24 and 48 hours. Then, data were analyzed by probit. The results of this study show that (1) the LC95 value after 24 hours of exposure of leaf extracts of Citrus hystrix, Citrus amblycarpa, and Citrus maxima, were each 3,176 ppm; 4,174 ppm; and 6,369 ppm. (2) the LC95 value after 48 hours of exposure of leaf extracts of Citrus hystrix, Citrus amblycarpa, and Citrus maxima, were each 2,499 ppm; 3,256 ppm; and 4,886 ppm. (3) leaf extract of Citrus hystrix is the most effective among others as biolarvicidal against Aedes aegypti larvae. Leaf extract of Citrus hystrix can be used as alternative biolarvicidal