Fragmentation Experiment and Model for Falling Mercury Drops

The experiment consists of counting and measuring the size of the many fragments observed after the fall of a mercury drop on the floor. The size distribution follows a power-law for large enough fragments. We address the question of a possible crossover to a second, different power-law for small enough fragments. Two series of experiments were performed. The first uses a traditional film photographic camera, and the picture is later treated on a computer in order to count the fragments and classify them according to their sizes. The second uses a modern digital camera. The first approach has the advantage of a better resolution for small fragment sizes. The second, although with a poorer size resolution, is more reliable concerning the counting of all fragments up to its resolution limit. Both together clearly indicate the real existence of the quoted crossover. The model treats the system microscopically during the tiny time interval when the initial drop collides with the floor. The drop is modelled by a connected cluster of Ising spins pointing up (mercury) surrounded by Ising spins pointing down (air). The Ising coupling which tends to keep the spins segregated represents the surface tension. Initially the cluster carries an extra energy equally shared among all its spins, corresponding to the coherent kinetic energy due to the fall. Each spin which touches the floor loses its extra energy transformed into a thermal, incoherent energy represented by a temperature used then to follow the dynamics through Monte Carlo simulations. Whenever a small piece becomes disconnected from the big cluster, it is considered a fragment, and counted. The results also indicate the existence of the quoted crossover in the fragment-size distribution.Comment: 6 pages, 3 figure

Periods Of Weed Interference In Maize Crops Cultivated In The First And Second Cycles

The interference of weeds in maize production may be reflected in grain yield losses that vary as a function of the density, stage and degree of aggressiveness of the species present. In the agricultural ecosystem, crops and weeds demand light, water, nutrients and space, which are frequently not available in sufficient quantities, leading to competition. The aim of this work was to determine the period of interference of weed plants, in particular of naked crabgrass (Digitaria nuda) on maize crop in the first and second harvest. The treatments were defined as increasing periods of coexistence and increasing control of weed community (7, 14, 21, 28, 35, 42, 49, and 56 days), two more controls, a control including one with weed control until the end of the culture cycle and another with coexistence until the harvest. For each period, were evaluated the stand of maize plants, length of ear, number of grains per row, number of rows per ear, cob, 100-grain weight, and grain productivity. The data obtained were subjected to analysis of variance using the F test, with average treatments compared using Tukey's test at 5% probability. Crop productivity was evaluated by means of regressions, the critical periods of interference were estimated. The critical timing of weed removal was 25 days for both harvests. The critical weed free period was 54 and 27 days for the first and second harvest respectively. For the conditions of the first and second harvest, the critical period of weed control was of 29 and 2 days respectively.3752867287

The effect of Nannochloropsis oceanica feed inclusion on rabbit muscle proteome

Nannochloropsis oceanica is a microalga, highly concentrated in protein and EPA (eicosapentaenoic acid). It has a recalcitrant cell wall that decreases nutrient digestibility. The objective of this study is to evaluate the effect of Nannochloropsis oceanica feed inclusion on the muscle proteome of fattening rabbits. Twenty rabbits were housed in individual cages for 5 weeks and were fed a control diet (n = 10) and one with 4.45% inclusion of microalga, replacing whole soybean meal (n = 10). After slaughter, samples of gastrocnemius muscle were taken for label-free proteomic analysis. A total of 1497 proteins were identified, 46 with differential abundance. Control rabbits had high abundance of proteins related to protein metabolism, suggesting higher muscle protein turnover. They also had higher abundance of structural proteins, suggesting a less tender meat by comparison with algae-fed rabbits. These had high abundance of proteins related to amino acid catabolism (Phe, Tyr) and synthesis (Gln). In addition, they had high abundance of proteins related to protein breakdown, overall suggesting that more tender meat may result from algae feedinginfo:eu-repo/semantics/acceptedVersio

Mineral profiling of muscle and hepatic tissues of Australian Merino, Damara and Dorper lambs: Effect of weight loss

Seasonal weight loss (SWL) is a major constraint to extensive animal production systems. The Australian sheep production is based on merino sheep, a European breed not tolerant to SWL. Tolerant alternative breeds such as the fat-tailed Damara and the Dorper have been increasingly used in Australia and elsewhere, due to their robustness. The aim of this study was to understand the mineral profile of muscle and liver tissues of Australian Merino, Damara and Dorper, when subjected to SWL in order to understand SWL-tolerance physiology. Twenty-four lambs were divided randomly between growing (control) and nutritionally restricted groups for each breed. The trial lasted 42 days. Animals were weighed bi-weekly and at the end of the trial, lambs were slaughtered. Liver and muscle samples were taken immediately after slaughter. Mineral assessment was carried out using inductively coupled plasma–optical emission spectrometry. Analysis of variance showed mineral concentrations were generally increased in the muscle of restricted animals, mainly because of fat tissue mobilization. An increase in Zn and Fe concentrations indicates an increase of enzymatic activity in the liver of restricted sheep as well as differential abundance of Fe-containing proteins. High concentrations of Cu in the liver of Dorper indicate higher ability to accumulate this element, even under SWLinfo:eu-repo/semantics/acceptedVersio

The interaction of La3+ complexes of DOTA/DTPA-glycoconjugates with the RCA120 lectin : a saturation transfer difference (STD) NMR spectroscopic study

The study of ligand-receptor interactions using high resolution NMR techniques, namely the Saturation Transfer Difference (STD), is presented for the recognition process between La(III) complexes of DOTA mono(amide) and DTPA bis(amide) glycoconjugates and the galactose specific lectin Ricinus Communis agglutinin (RCA120). This new class of Gd(III)-based potential targeted MRI contrast agents (CAs), bearing one or two terminal sugar (galactosyl or lactosyl) moieties, has been designed for in vivo binding to ASGPR (the asialoglycoprotein receptor), which is specifically expressed at the surface of liver hepatocytes, with the aim of leading to a new possible diagnosis of liver pathologies. The in vitro affinity constants of the divalent La(III)- glycoconjugate complexes to RCA120, used as a simple, water soluble receptor model, were higher than those of the monovalent analogues. The combination of the experimental data obtained from the STD NMR experiments with molecular modelling protocols (Autodock 4.1) allowed us to predict the binding mode of mono and divalent forms of these CAs to the galactose 1 binding sites of RCA120. The atomic details of the molecular interactions allowed corroborating and supporting the interaction of both the sugar moieties and the linkers with the surface of the protein and thus, their contribution to the observed interaction stabilities.Fundação para a Ciência e a Tecnologia (FCT

Cyclic carbonate synthesis from CO2and epoxides using zinc(II) complexes of arylhydrazones of β-diketones

Zinc(II) complexes of arylhydrazones of β-diketones (AHBD) were used for the first time as catalysts combined with tetrabutylammonium bromide (TBABr), in the coupling reaction between CO2 and epoxides. The influence of pressure and temperature on cyclic carbonate formation was investigated, as well as the catalytic activity toward different substrates (e.g. styrene oxide, propylene oxide and cyclohexene oxide). The molar ratio between metal complex and TBABr was determined for maximum catalytic activity

Cosmic ray knee and new physics at the TeV scale

We analyze the possibility that the cosmic ray knee appears at an energy threshold where the proton-dark matter cross section becomes large due to new TeV physics. It has been shown that such interactions could break the proton and produce a diffuse gamma ray flux consistent with MILAGRO observations. We argue that this hypothesis implies knees that scale with the atomic mass for the different nuclei, as KASKADE data seem to indicate. We find that to explain the change in the spectral index in the flux from E^{-2.7} to E^{-3.1} the cross section must grow like E^{0.4+\beta} above the knee, where \beta=0.3-0.6 parametrizes the energy dependence of the age (\tau \propto E^{-\beta}) of the cosmic rays reaching the Earth. The hypothesis also requires mbarn cross sections (that could be modelled with TeV gravity) and large densities of dark matter (that could be clumped around the sources of cosmic rays). We argue that neutrinos would also exhibit a threshold at E=(m_\chi/m_p)E_{knee}\approx 10^8 GeV where their interaction with a nucleon becomes strong. Therefore, the observation at ICECUBE or ANITA of standard neutrino events above this threshold would disprove the scenario.Comment: 10 pages, version to appear in JCA