On the Distributed Compression of Quantum Information

The problem of distributed compression for correlated quantum sources is considered. The classical version of this problem was solved by Slepian and Wolf, who showed that distributed compression could take full advantage of redundancy in the local sources created by the presence of correlations. Here it is shown that, in general, this is not the case for quantum sources, by proving a lower bound on the rate sum for irreducible sources of product states which is stronger than the one given by a naive application of Slepian–Wolf. Nonetheless, strategies taking advantage of correlation do exist for some special classes of quantum sources. For example, Devetak and Winter demonstrated the existence of such a strategy when one of the sources is classical. Optimal nontrivial strategies for a different extreme, sources of Bell states, are presented here. In addition, it is explained how distributed compression is connected to other problems in quantum information theory, including information-disturbance questions, entanglement distillation and quantum error correction

Selective Effects of D- and L-Govadine in Preclinical Tests of Positive, Negative, and Cognitive Symptoms of Schizophrenia

There is a critical need to develop novel pharmacotherapeutics capable of addressing the positive, negative, and cognitive symptoms of schizophrenia. Building on recent studies with a racemic mixture of the synthetic tetrahydroprotoberberine, D,L-Govadine, we isolated the D- and L-stereoisomers and employed a battery of behavioral, neurochemical, and electrophysiological procedures to assess their individual therapeutic potential. Rodent models predictive of antipsychotic efficacy and those that model positive symptoms were employed and we found that L-Govadine, but not D-Govadine, improved these measures. Pretreatment with either stereoisomer during CS pre-exposure prevented the disruption of latent inhibition by amphetamine. Moreover, pretreatment with either stereoisomer also improved deficits in social interaction in the neonatal ventral hippocampal lesioned rat. Improved cognitive performance in two different prefrontal cortex-dependent tasks was observed with D-, but not L-Govadine, which strongly suggests that the D-steroisomer may be an effective cognitive enhancer. Alterations in dopamine efflux were also assessed and L-Govadine increased dopamine efflux in both the prefrontal cortex and nucleus accumbens. However, D-Govadine only increased dopamine efflux in the prefrontal cortex and not in the nucleus accumbens. Electrophysiological studies confirmed that L-Govadine is a DA-D2 antagonist, whereas D-Govadine shows no appreciable physiological effects at this receptor. Collectively these data show that L-Govadine performs well on measures predictive of antipsychotic efficacy and rodent models of positive symptoms through antagonism of DA-D2 receptors, whereas D-Govadine improves impairments in compromised memory function in delayed response tasks possibly through selective increases in DA efflux in the frontal cortex

The Limits of Reductionism in Medicine: Could Systems Biology Offer an Alternative?

In the first of a two part series, Ahn and colleagues discuss the reductionist approach pervading medicine and explain how a systems approach (as advocated by systems biology) may complement reductionism

Subcutaneous Fascial Bands—A Qualitative and Morphometric Analysis

BACKGROUND: Although fascial bands within the subcutaneous (SQ) layer are commonly seen in ultrasound images, little is known about their functional role, much less their structural characteristics. This study's objective is to describe the morphological features of SQ fascial bands and to systematically evaluate the bands using image analyses tools and morphometric measures. METHODS: In 28 healthy volunteers, ultrasound images were obtained at three body locations: the lateral aspect of the upper arm, medial aspect of the thigh and posterior aspect of lower leg. Using image analytical techniques, the total SQ band area, fascial band number, fascial band thickness, and SQ zone (layer) thickness were determined. In addition, the SQ spatial coherence was calculated based on the eigenvalues associated with the largest and smallest eigenvectors of the images. RESULTS: Fascial bands at these sites were contiguous with the dermis and the epimysium forming an interconnected network within the subcutaneous tissue. Subcutaneous blood vessels were also frequently encased by these fascial bands. The total SQ fascial band area was greater at the thigh and calf compared to the arm and was unrelated to SQ layer (zone) thickness. The thigh was associated with highest average number of fascial bands while calf was associated with the greatest average fascial band thickness. Across body regions, greater SQ zone thickness was associated with thinner fascial bands. SQ coherence was significantly associated with SQ zone thickness and body location (calf with statistically greater coherence compared to arm). CONCLUSION: Fascial bands are structural bridges that mechanically link the skin, subcutaneous layer, and deeper muscle layers. This cohesive network also encases subcutaneous vessels and may indirectly mediate blood flow. The quantity and morphological characteristics of the SQ fascial band may reflect the composite mechanical forces experienced by the body part

CO(2) Diffusion in Polar Ice: Observations from Naturally Formed CO(2) Spikes in the Siple Dome (Antarctica) Ice Core

One common assumption in interpreting ice-core CO(2) records is that diffusion in the ice does not affect the concentration profile. However, this assumption remains untested because the extremely small CO(2) diffusion coefficient in ice has not been accurately determined in the laboratory. In this study we take advantage of high levels of CO(2) associated with refrozen layers in an ice core from Siple Dome, Antarctica, to study CO(2) diffusion rates. We use noble gases (Xe/Ar and Kr/Ar), electrical conductivity and Ca(2+) ion concentrations to show that substantial CO(2) diffusion may occur in ice on timescales of thousands of years. We estimate the permeation coefficient for CO(2) in ice is similar to 4 x 10(-21) mol m(-1) s(-1) Pa(-1) at -23 degrees C in the top 287 m (corresponding to 2.74 kyr). Smoothing of the CO(2) record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the firn. However, simulations for depths of similar to 930-950m (similar to 60-70 kyr) indicate that smoothing of the CO(2) record by diffusion in deep ice is comparable to smoothing in the firn. Other types of diffusion (e.g. via liquid in ice grain boundaries or veins) may also be important but their influence has not been quantified

Jumbo Bacteriophages Are Represented Within an Increasing Diversity of Environmental Viruses Infecting the Emerging Phytopathogen, Dickeya solani

Dickeya species are economically important phytopathogens widespread in mainland Europe that can reduce crop yields by 25%. There are no effective environmentally-acceptable chemical systems available for diseases caused by Dickeya. Bacteriophages have been suggested for use in biocontrol of these pathogens in the field, and limited field trials have been conducted. To date the majority of bacteriophages capable of infecting Dickeya solani, one of the more aggressive species, are from the same family, the Ackermannviridae, many representatives of which have been shown to be unsuitable for use in the field due to their capacity for generalized transduction. Members of this family are also only capable of forming individual plaques on D. solani. Here we describe novel bacteriophages from environmental sources isolated on D. solani, including members of two other viral families; Myoviridae and Podoviridae, most of which are capable of forming plaques on multiple Dickeya species. Full genomic sequencing revealed that the Myoviridae family members form two novel clusters of jumbo bacteriophages with genomes over 250 kbp, with one cluster containing phages of another phytopathogen Erwinia amylovora. Transduction experiments showed that the majority of the new environmental bacteriophages are also capable of facilitating efficient horizontal gene transfer, however the single Podoviridae family member is not. This particular phage therefore has potential for use as a biocontrol agent against multiple species of Dickeya

Zeolite-Templated Carbon Materials for High-Pressure Hydrogen Storage

Zeolite-templated carbon (ZTC) materials were synthesized, characterized, and evaluated as potential hydrogen storage materials between 77 and 298 K up to 30 MPa. Successful synthesis of high template fidelity ZTCs was confirmed by X-ray diffraction and nitrogen adsorption at 77 K; BET surface areas up to ~3600 mT2 g^(–1) were achieved. Equilibrium hydrogen adsorption capacity in ZTCs is higher than all other materials studied, including superactivated carbon MSC-30. The ZTCs showed a maximum in Gibbs surface excess uptake of 28.6 mmol g–1 (5.5 wt %) at 77 K, with hydrogen uptake capacity at 300 K linearly proportional to BET surface area: 2.3 mmol g^(–1) (0.46 wt %) uptake per 1000 m^2 g^(–1) at 30 MPa. This is the same trend as for other carbonaceous materials, implying that the nature of high-pressure adsorption in ZTCs is not unique despite their narrow microporosity and significantly lower skeletal densities. Isoexcess enthalpies of adsorption are calculated between 77 and 298 K and found to be 6.5–6.6 kJ mol^(–1) in the Henry’s law limit

Continuous quantum error correction via quantum feedback control

We describe a protocol for continuously protecting unknown quantum states from decoherence that incorporates design principles from both quantum error correction and quantum feedback control. Our protocol uses continuous measurements and Hamiltonian operations, which are weaker control tools than are typically assumed for quantum error correction. We develop a cost function appropriate for unknown quantum states and use it to optimize our state-estimate feedback. Using Monte Carlo simulations, we study our protocol for the three-qubit bit-flip code in detail and demonstrate that it can improve the fidelity of quantum states beyond what is achievable using quantum error correction when the time between quantum error correction cycles is limited.Comment: 12 pages, 6 figures, REVTeX; references fixe

A Record of Atmospheric Co2 During the Last 40,000 Years from the Siple Dome, Antarctica Ice Core

We have measured the CO2 concentration of air occluded during the last 40,000 years in the deep Siple Dome A ( hereafter Siple Dome) ice core, Antarctica. The general trend of CO2 concentration from Siple Dome ice follows the temperature inferred from the isotopic composition of the ice and is mostly in agreement with other Antarctic ice core CO2 records. CO2 rose initially at similar to 17.5 kyr B. P. ( thousand years before 1950), decreased slowly during the Antarctic Cold Reversal, rose during the Younger Dryas, fell to a local minimum at around 8 kyr B. P., and rose continuously since then. The CO2 concentration never reached steady state during the Holocene, as also found in the Taylor Dome and EPICA Dome C ( hereafter Dome C) records. During the last glacial termination, a lag of CO2 versus Siple Dome isotopic temperature is probable. The Siple Dome CO2 concentrations during the last glacial termination and in the Holocene are at certain times greater than in other Antarctic ice cores by up to 20 ppm (mumol CO2/mol air). While in situ production of CO2 is one possible cause of the sporadic elevated levels, the mechanism leading to the enrichment is not yet clear

Assessment of differential gene expression in human peripheral nerve injury

BACKGROUND: Microarray technology is a powerful methodology for identifying differentially expressed genes. However, when thousands of genes in a microarray data set are evaluated simultaneously by fold changes and significance tests, the probability of detecting false positives rises sharply. In this first microarray study of brachial plexus injury, we applied and compared the performance of two recently proposed algorithms for tackling this multiple testing problem, Significance Analysis of Microarrays (SAM) and Westfall and Young step down adjusted p values, as well as t-statistics and Welch statistics, in specifying differential gene expression under different biological states. RESULTS: Using SAM based on t statistics, we identified 73 significant genes, which fall into different functional categories, such as cytokines / neurotrophin, myelin function and signal transduction. Interestingly, all but one gene were down-regulated in the patients. Using Welch statistics in conjunction with SAM, we identified an additional set of up-regulated genes, several of which are engaged in transcription and translation regulation. In contrast, the Westfall and Young algorithm identified only one gene using a conventional significance level of 0.05. CONCLUSION: In coping with multiple testing problems, Family-wise type I error rate (FWER) and false discovery rate (FDR) are different expressions of Type I error rates. The Westfall and Young algorithm controls FWER. In the context of this microarray study, it is, seemingly, too conservative. In contrast, SAM, by controlling FDR, provides a promising alternative. In this instance, genes selected by SAM were shown to be biologically meaningful