Three-Particle Coincidence of the Long Range Pseudorapidity Correlation in High Energy Nucleus-Nucleus Collisions

We report the first three-particle coincidence measurement in pseudorapidity (Delta eta) between a high transverse momentum (p(perpendicular to)) trigger particle and two lower p(perpendicular to) associated particles within azimuth |Delta phi| < 0.7 in root s(NN) = 200 GeV d + Au and Au + Au collisions. Charge ordering properties are exploited to separate the jetlike component and the ridge (long range Delta eta correlation). The results indicate that the correlation of ridge particles are uniform not only with respect to the trigger particle but also between themselves event by event in our measured Delta eta. In addition, the production of the ridge appears to be uncorrelated to the presence of the narrow jetlike component.

Identified particle production, azimuthal anisotropy, and interferometry measurements in Au plus Au collisions at root s(NN)=9.2 GeV

We present the first measurements of identified hadron production, azimuthal anisotropy, and pion interferometry from Au + Au collisions below the nominal injection energy at the BNL Relativistic Heavy-Ion Collider (RHIC) facility. The data were collected using the large acceptance solenoidal tracker at RHIC (STAR) detector at root s(NN) = 9.2 GeV from a test run of the collider in the year 2008. Midrapidity results on multiplicity density dN/dy in rapidity y, average transverse momentum < p(T)>, particle ratios, elliptic flow, and Hanbury-Brown-Twiss (HBT) radii are consistent with the corresponding results at similar root s(NN) from fixed-target experiments. Directed flow measurements are presented for both midrapidity and forward-rapidity regions. Furthermore the collision centrality dependence of identified particle dN/dy, < p(T)>, and particle ratios are discussed. These results also demonstrate that the capabilities of the STAR detector, although optimized for root s(NN) = 200 GeV, are suitable for the proposed QCD critical-point search and exploration of the QCD phase diagram at RHIC.

Gauge invariance and classical dynamics of noncommutative particle theory

We consider a model of classical noncommutative particle in an external electromagnetic field. For this model, we prove the existence of generalized gauge transformations. Classical dynamics in Hamiltonian and Lagrangian form is discussed; in particular, the motion in the constant magnetic field is studied in detail. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3299296]

Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation

Parity-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three-particle azimuthal correlator which is a P even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at s(NN)=200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.

Growth of Long Range Forward-Backward Multiplicity Correlations with Centrality in Au plus Au Collisions at root s(NN)=200 GeV

Forward-backward multiplicity correlation strengths have been measured with the STAR detector for Au + Au and p + p collisions at root s(NN) = 200 GeV. Strong short- and long-range correlations (LRC) are seen in central Au + Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short-range correlations are observed in peripheral Au + Au collisions. Both the dual parton model (DPM) and the color glass condensate (CGC) predict the existence of the long-range correlations. In the DPM, the fluctuation in the number of elementary (parton) inelastic collisions produces the LRC. In the CGC, longitudinal color flux tubes generate the LRC. The data are in qualitative agreement with the predictions of the DPM and indicate the presence of multiple parton interactions.

Semiconducting Sn(3)O(4) nanobelts: Growth and electronic structure

The study of structures based on nonstoichiometric SnO(2-x) compounds, besides experimentally observed, is a challenging task taking into account their instabilities. In this paper, we report on single crystal Sn(3)O(4) nanobelts, which were successfully grown by a carbothermal evaporation process of SnO(2) powder in association with the well known vapor-solid mechanism. By combining the structural data and transport properties, the samples were investigated. The results showed a triclinic semiconductor structure with a fundamental gap of 2.9 eV. The semiconductor behavior was confirmed by the electron transport data, which pointed to the variable range hopping process as the main conduction mechanism, thus giving consistent support to the mechanisms underlying the observed semiconducting character.

Microwave dielectric permittivity and photoluminescence of Eu(2)O(3) doped laser heated pedestal growth Ta(2)O(5) fibers

We report the microwave dielectric properties and photoluminescence of undoped and europium oxide doped Ta(2)O(5) fibers, grown by laser heated pedestal growth technique. The effects of Eu(2)O(3) doping (1-3 mol %) on the structural, optical, and dielectric properties were investigated. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for Eu(2)O(3) doped Ta(2)O(5) samples it increases, reaching up to 36 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value. For this wide band gap oxide, Eu(3+) optical activation was achieved and the emission is observed up to room temperature. Thus, the transparency and high permittivity make this material promising for electronic devices and microwave applications. (c) 2008 American Institute of Physics.

Awaking the Vacuum in Relativistic Stars

Void of any inherent structure in classical physics, the vacuum has revealed to be incredibly crowded with all sorts of processes in relativistic quantum physics. Yet, its direct effects are usually so subtle that its structure remains almost as evasive as in classical physics. Here, in contrast, we report on the discovery of a novel effect according to which the vacuum is compelled to play an unexpected central role in an astrophysical context. We show that the formation of relativistic stars may lead the vacuum energy density of a quantum field to an exponential growth. The vacuum-driven evolution which would then follow may lead to unexpected implications for astrophysics, while the observation of stable neutron-star configurations may teach us much on the field content of our Universe.

Reverse engineering in many-body quantum physics: Correspondence between many-body systems and effective single-particle equations

The mapping, exact or approximate, of a many-body problem onto an effective single-body problem is one of the most widely used conceptual and computational tools of physics. Here, we propose and investigate the inverse map of effective approximate single-particle equations onto the corresponding many-particle system. This approach allows us to understand which interacting system a given single-particle approximation is actually describing, and how far this is from the original physical many-body system. We illustrate the resulting reverse engineering process by means of the Kohn-Sham equations of density-functional theory. In this application, our procedure sheds light on the nonlocality of the density-potential mapping of density-functional theory, and on the self-interaction error inherent in approximate density functionals.

A PHASE TRANSITION FOR COMPETITION INTERFACES

We study the competition interface between two growing clusters in a growth model associated to last-passage percolation. When the initial unoccupied set is approximately a cone, we show that this interface has an asymptotic direction with probability 1. The behavior of this direction depends on the angle theta of the cone: for theta >= 180 degrees, the direction is deterministic, while for theta < 180 degrees, it is random, and its distribution can be given explicitly in certain cases. We also obtain partial results on the fluctuations of the interface around its asymptotic direction. The evolution of the competition interface in the growth model can be mapped onto the path of a second-class particle in the totally asymmetric simple exclusion process; from the existence of the limiting direction for the interface, we obtain a new and rather natural proof of the strong law of large numbers (with perhaps a random limit) for the position of the second-class particle at large times.

Simulation of sugarcane residue decomposition and aboveground growth

Due to the worldwide increase in demand for biofuels, the area cultivated with sugarcane is expected to increase. For environmental and economic reasons, an increasing proportion of the areas are being harvested without burning, leaving the residues on the soil surface. This periodical input of residues affects soil physical, chemical and biological properties, as well as plant growth and nutrition. Modeling can be a useful tool in the study of the complex interactions between the climate, residue quality, and the biological factors controlling plant growth and residue decomposition. The approach taken in this work was to parameterize the CENTURY model for the sugarcane crop, to simulate the temporal dynamics of aboveground phytomass and litter decomposition, and to validate the model through field experiment data. When studying aboveground growth, burned and unburned harvest systems were compared, as well as the effect of mineral fertilizer and organic residue applications. The simulations were performed with data from experiments with different durations, from 12 months to 60 years, in Goiana, TimbaA(0)ba and Pradpolis, Brazil; Harwood, Mackay and Tully, Australia; and Mount Edgecombe, South Africa. The differentiation of two pools in the litter, with different decomposition rates, was found to be a relevant factor in the simulations made. Originally, the model had a basically unlimited layer of mulch directly available for decomposition, 5,000 g m(-2). Through a parameter optimization process, the thickness of the mulch layer closer to the soil, more vulnerable to decomposition, was set as 110 g m(-2). By changing the layer of mulch at any given time available for decomposition, the sugarcane residues decomposition simulations where close to measured values (R (2) = 0.93), contributing to making the CENTURY model a tool for the study of sugarcane litter decomposition patterns. The CENTURY model accurately simulated aboveground carbon stalk values (R (2) = 0.76), considering burned and unburned harvest systems, plots with and without nitrogen fertilizer and organic amendment applications, in different climates and soil conditions.

Effects of Molybdenum, Nickel, and Nitrogen Sources on the Mineral Nutrition and Growth of Rice Plants

Upland rice plants, cultivar `IAC 202,` were grown in nutrient solution until full tillering. Treatments consisted of ammonium nitrate (AN) or urea (UR) as nitrogen (N) source plus molybdenum (Mo) and/or nickel (Ni): AN + Mo + Ni, AN + Mo - Ni, AN - Mo + Ni, UR + Mo + Ni, UR + Mo - Ni, and UR - Mo + Ni. The experiment was carried out to better understand the effect of these treatments on dry-matter yield, chlorophyll, net photosynthesis rate, nitrate (NO3 --N), total N, in vitro activities of urease and nitrate reductase (NR), and Mo and Ni concentrations. In UR-grown plants, Mo and Ni addition increased yield of dry matter. Regardless of the N source, chlorophyll concentration and net photosynthesis rate were reduced when Mo or Ni were omitted, although not always significantly. The omission of either Mo or Ni led to a decrease in urease activity, independent of N source. Nitrate reductase activity increased in nutrient solutions without Mo, although NO3 --N increased. There was not a consistent variation in total N concentration. Molybdenum and Ni concentration in roots and shoots were influenced by their supply in the nutrient solution. Molybdenum concentration was not influenced by N sources, whereas Ni content in both root and shoots was greater in ammonium nitrate-grown plants. In conclusion, it can be hypothesized that there is a relationship between Mo and Ni acting on photosynthesis, although is an indirect one. This is the first evidence for a beneficial effect of Mo and Ni interaction on plant growth.

Contribuition of nitrogen from biological nitrogen fixation, nitrogen fertilizer and soil nitrogen on the growth of the common bean and cowpea

Biological nitrogen fixation (BNF) constitutes a valuable source of this nutrient for the common bean Phaseolus vulgaris L and cowpea Vigna unguiculata (L.) Walp., being its avaibility affected by mineral N in the soil solution. The objectives of this work were to evaluate the effects of nitrogen rate, as urea, on symbiotic fixation of N(2) in common bean and cowpea plants, using the isotopic technique, and quantifying the relative contributions of N sources symbiotic N(2) fixation, soil native nitrogen and urea N on the growth of the common bean and cowpea. Non nodulating soybean plants were used as standard. The research was carried out in greenhouse, using pots with 5 kg of soil from a Typic Haplustox (Dystrophic Red Yellow Latosol). The experimental design was completely randomized blocks, with 30 treatments and three replications, arranged in 5x3x2 factorial outline. The treatments consisted of five N rates: 2, 15, 30, 45 and 60 mg N kg(-1) soil; three sampling times: 23, 40 and 76 days after sowing (DAS) and two crops: common bean and cowpea. The BNF decreased with increase N rates, varying from 81.5% to 55.6% for cowpea, and from 71.9% to 55.1% for common bean. The symbiotic N(2) fixation in cowpea can substitute totally the nitrogen fertilization. The nitrogen absorption from soil is not affected by nitrogen fertilizer rate. The N recovery from fertilizer at 76 DAS was of 60.7% by common bean, and 57.1% by cowpea. The symbiotic association in common bean needs the application of a starting dose (40 kg N ha(-1)) for economically acceptable yields.

EXPRESSION OF GENES RELATED TO MYOSTATIN SIGNALING DURING RAT SKELETAL MUSCLE LONGITUDINAL GROWTH

In this study we investigated the gene expression of proteins related to myostatin (MSTN) signaling during skeletal muscle longitudinal growth. To promote muscle growth, Wistar male rats were submitted to a stretching protocol for different durations (12, 24, 48, and 96 hours). Following this protocol, soleus weight and length and sarcomere number were determined. In addition, expression levels of the genes that encode MSTN, follistatin isoforms 288 and 315 (FLST288 and FLST315), follistatin-like 3 protein (FLST-L3), growth and differentiation factor-associated protein-1 (GASP-1), activin IIB receptor (ActIIB), and SMAD-7 were determined by real-time polymerase chain reaction. Prolonged stretching increased soleus weight, length, and sarcomere number. In addition, MSTN gene expression was increased at 12-24 hours, followed by a decrease at 96 hours when compared with baseline values. FLST isoforms, FLST-L3, and GASP-1 mRNA levels increased significantly over all time-points. ActIIB gene expression decreased quickly at 12-24 hours. SMAD-7 mRNA levels showed a late increase at 48 hours, which peaked at 96 hours. The gene expression pattern of inhibitory proteins related to MSTN signaling suggests a strong downregulation of this pathway in response to prolonged stretching. Muscle Nerve 40: 992-999, 2009

Effects of different levels of protein intake and physical training on growth and nutritional status of young rats

This study aimed to investigate the effects of physical training, and different levels of protein intake in the diet, on the growth and nutritional status of growing rats. Newly-weaned Wistar rats (n=48) were distributed into six experimental groups: three of them were subjected to physical swim training (1 h per day. 5 d per week, for 4 wk, after 2 wk of familiarization) and the other three were considered as controls (non-trained). Each pair of groups, trained and non-trained, received diets with a different level of protein in their composition: 14%. 21% or 28%. The animals were euthanized at the end of the training period and the following analyses were performed: proteoglycan synthesis as a biomarker of bone and cartilage growth, IGF-I (insulin-like growth factor-I) assay as a biomarker of growth and nutritional status. total RNA and protein concentration and protein synthesis measured in vivo using a large-dose phenylalanine method. As a main finding, increased dietary protein, combined with physical training, was able to improve neither tissue protein synthesis nor muscle growth. In addition, cartilage and bone growth seem to be deteriorated by the lower and the higher levels of protein intake. Our data allow us to conclude that protein enhancement in the diet, combined with physical exercise, does not stimulate tissue protein synthesis or muscle mass growth. Furthermore, physical training, combined with low protein intake, was not favorable to bone development in growing animals.