Finite-temperature properties of frustrated classical spins coupled to the lattice

We present extensive Monte Carlo simulations for a classical antiferromagnetic Heisenberg model with both nearest ($J_1$) and next-nearest ($J_2$) exchange couplings on the square lattice coupled to the lattice degrees of freedom. The Ising-like phase transition, that appears for $J_2/J_1>1/2$ in the pure spin model, is strengthened by the spin-lattice coupling, and is accompanied by a lattice deformation from a tetragonal symmetry to an orthorhombic one. Evidences that the universality class of the transition does not change with the inclusion of the spin-lattice coupling are reported. Implications for ${\rm Li_2VOSiO_4}$, the prototype for a layered $J_1{-}J_2$ model in the collinear regime, are also discussed.Comment: 6 pages and 8 figure

Novel conantokins from Conus parius venom are specific antagonists of N-methyl-D-aspartate receptors

Journal ArticleWe report the discovery and characterization of three conantokin peptides from the venom of Conus parius. Each peptide (conantokin-Pr1, -Pr2, and -Pr3) contains 19 amino acids with three γ-carboxyglutamate (Gla) residues, a post-translationally modified amino acid characteristic of conantokins. The new peptides contain several amino acid residues that differ from previous conantokin consensus sequences

On the mechanism of the polynucleotide joining reaction

Journal ArticlePolynucleotide-joining enzymes (ligases) have been identified in uninfected and phage-infected Escherichia coli (Gellert, 1967; Olivera and Lehman, 1967a; Zimmerman et al., 1967; Gefter et al., 1967; Weiss and Richardson, 1967a; Cozzarelli et al., 1967). Both types of enzyme catalyze the synthesis of a phosphodiester bond between the 3' hydroxyl and 5' phosphoryl termini of DNA chains which have been properly aligned in a double-helical structure

Uniquely selective inhibitor of the mammalian fetal neuromuscular nicotinic acetylcholine receptor

Journal ArticleWe have purified and characterized a novel conotoxin from the venom of Conus obscurus, which has the unique property of selectively and potently inhibiting the fetal form of the mammalian neuromuscular nicotinic acetylcholine receptor (nAChR) (α1β1γδ-subunits). Although this conotoxin, αA-conotoxin OIVB (αA-OIVB), is a high-affinity antagonist (IC50 of 56 nM) of the fetal muscle nAChR, it has >1800-fold lower affinity for the adult muscle nAChR (α1β1εδ-subunits) and virtually no inhibitory activity at a high concentration on various neuronal nAChRs (IC50 > 100 μM in all cases)

Structural basis for tetrodotoxin-resistant sodium channel binding by μ-conotoxin SmIIIA

Journal ArticleSmIIIA is a new μ-conotoxin isolated recently from Conus stercusmuscarum. Although it shares several biochemical characteristics with other μ-conotoxins (the arrangement of cysteine residues and a conserved arginine believed to interact with residues near the channel pore), it has several distinctive features, including the absence of hydroxyproline, and is the first specific antagonist of tetrodotoxin-resistant voltage-gated sodium channels to be characterized

Pointing mechanisms for the Shuttle Radar Laboratory

The Shuttle Radar Laboratory (SRL) is scheduled for launch in December of 1993 on the first of its two missions. The SRL has three major radar instruments: two distributed phased-array antennas, which make up the Spaceborne Imaging Radar-C System (SIR-C) and are capable of being electronically steered, and one X-Band Synthetic Aperture Radar (X-SAR), which is pointed mechanically by a suite of mechanisms. This paper will describe these mechanisms and summarize the development difficulties that were encountered in bringing them from the design stage through prototype development and protoflight testing

Utilisation of Mucuna Beans (Mucuna pruriens (L.) DC ssp. deeringianum (Bart) Hanelt) to Feed Growing Broilers

Performance of broilers fed on diets containing mucuna beans (MB) (Mucuna pruriens (L.) DC ssp. deeringianum (Bart) Hanelt) with different treatments were studied in three experiments. First experiment: three sorghum diets using 0 and 280g/kg of MB raw or soaked were evaluated. Second experiment: three sorghum diets using 0 and 280g/kg of MB raw or boiled were evaluated. Third experiment: six maize diets: maize only, three diets containing 280g/kg of MB raw, soaked or boiled, one containing soybean and a balanced diet (control) were evaluated. Experiment one: the birds fed on the 0g MB/kg showed a higher live weight gain (LWG) and a lower feed:gain ratio (FG) (p 0.01) than birds fed on the MB diets. There were no differences for any of the variables studied between the birds fed on the MB diets. Experiment two: the birds fed on the 0g MB/kg performed better (p 0.01) than birds fed on the MB diets. However, birds fed on the boiled MB diet had a higher LWG and a lower FG (p 0.01) than birds fed on the raw and soaked MB diet. Experiment three: the birds fed on the control diet obtained a higher LWG (p 0.01) than birds fed on the remainder treatments. The birds fed on the raw MB diet had a lower FG (p 0.01) than birds on the remainder treatments. However, birds fed on the boiled MB had a higher LWG and feed intake than birds fed on raw and soaked MB diets and only maize diet (p 0.01), but, lower (p 0.01) in comparison to birds fed on the soybean diet. The birds on the raw and soaked MB diets performed worst (p 0.01), even in comparison to birds fed on only maize (p 0.01). The results from these experiments indicated that inclusion of 280g MB/kg in the diet affected adversely the poultry performance. However, utilisation of MB boiled improved the broilers performance compared to birds fed on the raw and soaked MB diets

Nonsingular and accelerated expanding universe from effective Yang-Mills theory

The energy-momentum tensor coming from one-parameter effective Yang- Mills theory is here used to describe the matter-energy content of the homogeneous and isotropic Friedmann cosmology in its early stages. The behavior of all solutions is examined. Particularly, it is shown that only solutions corresponding to an open model allow the universe to evolve into an accelerated expansion. This result appears as a possible mechanism for an inflationary phase produced by a vector field. Further, depending on the value of some parameters characterizing the system, the resulting models are classified as singular or nonsingular.Comment: 15 pages, 7 figures, some discussions were simplified and new remarks were introduce

Moisture activation and carbon use efficiency of soil microbial communities along an aridity gradient in the Atacama Desert

Due to their extreme aridity, high rate of UV irradiation and low soil carbon (C) content, the soils of the Atacama Desert represent one of the world's most hostile environments for microbial life and its survival. Although infrequent, climatic conditions may, however, prevail which temporarily remove these stresses and allow life to briefly flourish. In this study we investigated the response of soil microbial communities to water and C availability across an aridity gradient (semi-arid, arid, hyper-arid) within the Atacama Desert. We simulated the impact of hyper-dry spells, humid fogs and precipitation events on the activation of the microbial community and the subsequent mineralization of low (glucose) and high (plant residues) molecular weight C substrates. Our results showed that mineralization rate followed the trend: semi-arid > arid > hyper-arid. Some glucose mineralization was apparent under hyper-arid conditions (water activity, aw = 0.05), although this was 10-fold slower than under humid conditions and ca. 200-fold slower than under wet conditions. A lag phase in CO2 production after glucose-C addition in the hyper-arid soils suggested that mineralization was limited by the low microbial biomass in these soils. No lag phase was apparent in the corresponding semi-arid or arid soils. In contrast, the breakdown of the plant residues was initially much slower than for glucose and involved a much longer lag phase in all soils, suggesting that mineralization was limited by low exoenzyme activity, particularly in the humid and hyper-dry soils. Our results also showed that microbial C use efficiency followed the trend: hyper-arid > arid > semi-arid. In conclusion, we have shown that even under hyper-arid conditions, very low levels of microbial activity and C turnover do occur. Further, the microbial communities are capable of rapidly responding to available C once water becomes more abundant, however, this response is both biomass and metabolically limited in hyper-arid soils

Primate drum kit: A system for studying acoustic pattern production by non-human primates using acceleration and strain sensors

The possibility of achieving experimentally controlled, non-vocal acoustic production in non-human primates is a key step to enable the testing of a number of hypotheses on primate behavior and cognition. However, no device or solution is currently available, with the use of sensors in non-human animals being almost exclusively devoted to applications in food industry and animal surveillance. Specifically, no device exists which simultaneously allows: (i) spontaneous production of sound or music by non-human animals via object manipulation, (ii) systematical recording of data sensed from these movements, (iii) the possibility to alter the acoustic feedback properties of the object using remote control. We present two prototypes we developed for application with chimpanzees (Pan troglodytes) which, while fulfilling the aforementioned requirements, allow to arbitrarily associate sounds to physical object movements. The prototypes differ in sensing technology, costs, intended use and construction requirements. One prototype uses four piezoelectric elements embedded between layers of Plexiglas and foam. Strain data is sent to a computer running Python through an Arduino board. A second prototype consists in a modified Wii Remote contained in a gum toy. Acceleration data is sent via Bluetooth to a computer running Max/MSP. We successfully pilot tested the first device with a group of chimpanzees. We foresee using these devices for a range of cognitive experiments. © 2013 by the authors; licensee MDPI, Basel, Switzerland