Spin excitations in the nematic phase and the metallic stripe spin-density wave phase of iron pnictides

We present a general study of the magnetic excitations within a weak-coupling five-orbital model relevant to itinerant iron pnictides. As a function of enhanced electronic correlations, the spin excitations in the symmetry broken spin-density wave phase evolve from broad low-energy modes in the limit of weak interactions to sharply dispersing spin wave prevailing to higher energies at larger interaction strengths. We show how the resulting spin response at high energies depends qualitatively on the magnitude of the interactions. We also calculate the magnetic excitations in the nematic phase by including an orbital splitting, and find a pronounced C_2 symmetric excitation spectrum right above the transition to long-range magnetic order. Finally, we discuss the C_2 versus C_4 symmetry of the spin excitations as a function of energy for both the nematic and the spin-density wave phase.Comment: 10 pages, 10 figure

Urban AI in China: social control or hyper-capitalist development in the post-smart city?

Research and wider societal debates has explored the potentially transformative role of AI in extended social control and hyper-capitalist development in China. In this paper, we use those debates to reflect on experiments with Urban AI in China. The key issue is whether AI offers something distinctive or different compared with the logics and imaginaries of ideas of the smart city. Analysis of emblematic sites of urban AI management in the cities of Shanghai and Hangzhou demonstrates: the resonances and dissonances between urban AI and smart. But they also demonstrate distinctive and complex landscape of urban AI experiments that is not neatly captured in social control and free market applications perspectives on AI. Moreover, the urban experimental contexts in which AI is being rolled, reveal aspirations for creating new “digital empires,” exploring new limits on data power and potential social resistance. The paper makes a distinctive contribution by providing a new framework for comparing logics of computational urban management in the context of emerging AI applications. As such the paper provides a distinctive framework for situating future applications of urban AI management in China and identifies the future urban research priorities

de Sitter spacetime: effects of metric perturbations on geodesic motion

Gravitational perturbations of the de Sitter spacetime are investigated using the Regge--Wheeler formalism. The set of perturbation equations is reduced to a single second order differential equation of the Heun-type for both electric and magnetic multipoles. The solution so obtained is used to study the deviation from an initially radial geodesic due to the perturbation. The spectral properties of the perturbed metric are also analyzed. Finally, gauge- and tetrad-invariant first-order massless perturbations of any spin are explored following the approach of Teukolsky. The existence of closed-form, i.e. Liouvillian, solutions to the radial part of the Teukolsky master equation is discussed.Comment: IOP macros, 10 figure

A novel isolator-based system promotes viability of human embryos during laboratory processing

In vitro fertilisation (IVF) and related technologies are arguably the most challenging of all cell culture applications. The starting material is a single cell from which one aims to produce an embryo capable of establishing a pregnancy eventually leading to a live birth. Laboratory processing during IVF treatment requires open manipulations of gametes and embryos, which typically involves exposure to ambient conditions. To reduce the risk of cellular stress, we have developed a totally enclosed system of interlinked isolator-based workstations designed to maintain oocytes and embryos in a physiological environment throughout the IVF process. Comparison of clinical and laboratory data before and after the introduction of the new system revealed that significantly more embryos developed to the blastocyst stage in the enclosed isolator-based system compared with conventional open-fronted laminar flow hoods. Moreover, blastocysts produced in the isolator-based system contained significantly more cells and their development was accelerated. Consistent with this, the introduction of the enclosed system was accompanied by a significant increase in the clinical pregnancy rate and in the proportion of embryos implanting following transfer to the uterus. The data indicate that protection from ambient conditions promotes improved development of human embryos. Importantly, we found that it was entirely feasible to conduct all IVF-related procedures in the isolator-based workstations

Differential expression of microRNAs and other small RNAs in muscle tissue of patients with ALS and healthy age-matched controls

Amyotrophic lateral sclerosis is a late-onset disorder primarily affecting motor neurons and leading to progressive and lethal skeletal muscle atrophy. Small RNAs, including microRNAs (miRNAs), can serve as important regulators of gene expression and can act both globally and in a tissue-/cell-type-specific manner. In muscle, miRNAs called myomiRs govern important processes and are deregulated in various disorders. Several myomiRs have shown promise for therapeutic use in cellular and animal models of ALS; however, the exact miRNA species differentially expressed in muscle tissue of ALS patients remain unknown. Following small RNA-Seq, we compared the expression of small RNAs in muscle tissue of ALS patients and healthy age-matched controls. The identified snoRNAs, mtRNAs and other small RNAs provide possible molecular links between insulin signaling and ALS. Furthermore, the identified miRNAs are predicted to target proteins that are involved in both normal processes and various muscle disorders and indicate muscle tissue is undergoing active reinnervation/compensatory attempts thus providing targets for further research and therapy development in ALS

Tuning Nonlinear Mechanical Mode Coupling in GaAs Nanowires Using Cross-Section Morphology Control.

We investigate the nonlinear mechanical properties of GaAs nanowires with anisotropic cross-section. Fundamental and second order flexural modes are studied using laser interferometry with good agreement found between experiment and theory describing the nonlinear response under mechanical excitation. In particular, we demonstrate that the sign of the nonlinear coupling between orthogonal modes is dependent on the cross-section aspect ratio. The findings are of interest for applications such as amplitude to frequency conversion and vectorial force sensing

VIOLIN: vaccine investigation and online information network

Vaccines are among the most efficacious and cost-effective tools for reducing morbidity and mortality caused by infectious diseases. The vaccine investigation and online information network (VIOLIN) is a web-based central resource, allowing easy curation, comparison and analysis of vaccine-related research data across various human pathogens (e.g. Haemophilus influenzae, human immunodeficiency virus (HIV) and Plasmodium falciparum) of medical importance and across humans, other natural hosts and laboratory animals. Vaccine-related peer-reviewed literature data have been downloaded into the database from PubMed and are searchable through various literature search programs. Vaccine data are also annotated, edited and submitted to the database through a web-based interactive system that integrates efficient computational literature mining and accurate manual curation. Curated information includes general microbial pathogenesis and host protective immunity, vaccine preparation and characteristics, stimulated host responses after vaccination and protection efficacy after challenge. Vaccine-related pathogen and host genes are also annotated and available for searching through customized BLAST programs. All VIOLIN data are available for download in an eXtensible Markup Language (XML)-based data exchange format. VIOLIN is expected to become a centralized source of vaccine information and to provide investigators in basic and clinical sciences with curated data and bioinformatics tools for vaccine research and development. VIOLIN is publicly available at http://www.violinet.or

First dose behavioral tolerance to phencyclidine on food-rewarded bar pressing behavior in the rat

The behavioral effects of single doses of phencyclidine (PCP) were examined in drug-naive adult male Holtzman rats trained to press a bar on a fixed ratio (4) schedule (FR 4 ), i.e., a reward of sugarsweetened milk was earned on every fourth bar press. Groups of rats (four to eight rats per group) received specific doses of PCP which were held constant for each group throughout the study. Dose-response curves for PCP given in doses of 1.0, 1.8, 2.4, and 3.2 mg/kg IP were first determined and then redetermined at weekly intervals. A drug-free interval of 7–8 days was maintained between injections given weekly over a period of 4 weeks. The final dose of PCP was administered after a 4-week drug-free period. Evidence was obtained for first dose behavioral tolerance as shown by the significantly shortened duration of suppression of bar pressing on subsequent injections. Although subsequent weekly effects of equal doses of PCP showed no significant differences, they all differed significantly from the first injection. The reduced response to PCP was shown to be due to learned behavioral tolerance as demonstrated when PCP (3.2 mg/kg IP) was given to drug-naive animals in their home cages and 1 week later given the second dose in the operant behavioral situation. Under these circumstances, the second dose of PCP showed a similarly protracted depression of FR 4 responding as other animals given the drug for the first time in the operant situation. Subsequent weekly injections in the operant situation produced similar behavioral tolerance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46412/1/213_2004_Article_BF00426513.pd