Memory effects on the statistics of fragmentation

We investigate through extensive molecular dynamics simulations the fragmentation process of two-dimensional Lennard-Jones systems. After thermalization, the fragmentation is initiated by a sudden increment to the radial component of the particles' velocities. We study the effect of temperature of the thermalized system as well as the influence of the impact energy of the ``explosion'' event on the statistics of mass fragments. Our results indicate that the cumulative distribution of fragments follows the scaling ansatz $F(m)\propto m^{-\alpha}\exp{[-(m/m_0)^\gamma]}$, where $m$ is the mass, $m_0$ and $\gamma$ are cutoff parameters, and $\alpha$ is a scaling exponent that is dependent on the temperature. More precisely, we show clear evidence that there is a characteristic scaling exponent $\alpha$ for each macroscopic phase of the thermalized system, i.e., that the non-universal behavior of the fragmentation process is dictated by the state of the system before it breaks down.Comment: 5 pages, 8 figure

Scanning Tunneling Microscopy of Proteins on Graphite Surfaces

We applied scanning tunneling microscopy (STM) to the observation of amino acids and proteins deposited and/or adsorbed on highly oriented pyrolytic graphite (HOPG). Although many questions remain, it is demonstrated that relatively high resolution images of uncoated proteins can often be obtained in air. We present images of five amino acids (glycine, leucine, lysine, methionine and tryptophan) and three proteins (lysozyme, albumin and fibrinogen) under various conditions of deposition and adsorption. We discuss the role of affinity of the amino acids and proteins to the substrate, their adsorbed states and distribution, and STM tip-induced deformation and/or destruction. STM studies of adsorbed proteins are expected to provide useful and even unique information on the conformation and packing of the proteins

Imaging the postoperative patient: long-term complications of gastrointestinal surgery

The objectives of this review are (1) to become acquainted with the long-term complications of surgery of the gastrointestinal tract, and (2) to appreciate the appropriate use of imaging in the assessment of long-term complications

Espaçamento de plantio de maracujá sob dois sistemas de irrigação localizada.

bitstream/item/72656/1/CPAMN-PESQ.-AND.-13-91.pd

PUMPCOM: a simulation model for operating characteristics of pumping stations through combination of individual pumps.

The computer model PUMPCOM has been developed to combine pump curves series and in parallel for a variety of pumping stations using a WINDOWS environment. The model determines the performance of a pump station and of individual pumps within the station via construction of head-discharge curves, efficiency curves and curves indicating net positive suction head requeriments, graphical interface allows the user to draw the pump station layout on sreen, to view discrete data entered, and to view the fit of polynomial equations. An icon "tool box" allows the user to select an appropriate pipe fixture and place it in the layout between pumps. This allowns the pump station drawing to resemble as closely as possible the real pump station. Data tables, plots of the curves and equation coefficients, and station layout can be printed. Polynomial equations as fitted to individual pump curves and to the combined pump station curves. Cubic spline interpolations is employed to combine curves of pumps having different sizes. Performance indicators of the station and of each pump within the station are calculated over flow rate range for the entire station

Avaliação da cobertura vegetal para a bacia do Rio Ji-Paraná (RO).

Este estudo tem por objetivo a descrição e o uso do método de classificação de imagens de satélite denominado híbrido, visando a análise de coberturas vegetais. O local escolhido para tal foi a bacia hidrográfica do rio Ji-Paraná, localizada na parte leste do estado de Rondônia. Foram utilizadas imagens do satélite Landsat 5 do ano 2009; sendo a bacia recoberta por oito cenas. A acurácia da classificação obtida foi baseada no índice estatístico kappa e atingiu o valor de 0,7990. O mapa classificado criado referente ao ano de 2009, foi comparado a outro preexistente de 2001 e, após a análise da área de cobertura vegetal nativa (floresta) de cada um deles, pode-se inferir a variação desta no período referido. Foi constatada uma redução de 4102 ha da floresta local

Trajectories in a space with a spherically symmetric dislocation

We consider a new type of defect in the scope of linear elasticity theory, using geometrical methods. This defect is produced by a spherically symmetric dislocation, or ball dislocation. We derive the induced metric as well as the affine connections and curvature tensors. Since the induced metric is discontinuous, one can expect ambiguity coming from these quantities, due to products between delta functions or its derivatives, plaguing a description of ball dislocations based on the Geometric Theory of Defects. However, exactly as in the previous case of cylindric defect, one can obtain some well-defined physical predictions of the induced geometry. In particular, we explore some properties of test particle trajectories around the defect and show that these trajectories are curved but can not be circular orbits.Comment: 11 pages, 3 figure

Gravitational Energy-Momentum Density in Teleparallel Gravity

In the context of a gauge theory for the translation group, a conserved energy-momentum gauge current for the gravitational field is obtained. It is a true spacetime and gauge tensor, and transforms covariantly under global Lorentz transformations. By rewriting the gauge gravitational field equation in a purely spacetime form, it becomes the teleparallel equivalent of Einstein's equation, and the gauge current reduces to the M{\o}ller's canonical energy-momentum density of the gravitational field.Comment: RevTeX, 4 pages, no figures, to appear in Phys. Rev. Let