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The high velocity impact of a drop on a surface causes the formation and, afterward, the breakup of a jet. The understanding of the jet breakup requires at first a detailed description of the processes preceding its formation and the determination of its initial characteristics. In this paper, we first describe the initial impact processes, revisiting the corresponding 2D shock theory; the resulting model is general and independent of the choice of the equation of state. In particular, we define in a simple way the criteria for the existence of a shock or a jet solution. The theoretical predictions are then compared with a numerical simulation using liquid tin as the material for the drop and a rigid material for the target. The theoretical shock solution fits very well the results obtained with an Eulerian hydrocode. Molecular dynamics simulations were used to simulate the growth and breakup of the jet. The theoretical jet orientation and velocity are consistent with the simulation. Finally, the rather complex velocity profile of the jet is associated with the specific phenomena related to the history of the drop. [ABSTRACT FROM AUTHOR]

We perform very large scale molecular dynamics (MD) simulations to investigate the ejection process from shock-loaded tin surfaces in regimes where the metal first undergoes solid to solid phase transitions and then melts on release. In these conditions, a classical two-wave structure propagates within the metal. When it interacts with the surface, our MD simulations reveal very different behaviors. If the surface geometry is perfectly flat or contains almost flat perturbations (sinusoidal type), a solid cap made of crystallites forms at the free surface, over a thickness of a few tens of nanometers. This surface cap melts more slowly than the bulk, and as a result, the ejection process is greatly slowed down. If the surface geometry contains V-shape geometrical perturbations, the oblique interaction of the incident shock wave with the planar interface of the defect leads to a sharp increase of temperature at the defect's bottom. At this place, the metal undergoes a solid to liquid phase change over the entire length of the groove, and this promotes the ejection of matter in the form of sheets of liquid metal. However, this phase change is not spatially uniform, and the sheets keep in memory this process by exhibiting a non-uniform leading edge and large ripples. These ripples grow over time, which ends up causing the fragmentation of the sheets as they develop. In this case, the fragmentation is non-uniform, and it differs from the rather uniform fragmentation process observed when the metal directly melts upon receiving the shock. [ABSTRACT FROM AUTHOR]

Introduction. In recent years different neuropsychological batteries have been developed to assess cognitive performance in schizophrenia. However, no test has been validated in Spanish for this purpose. The Barcelona Test has been one of the tests used. This present article has aimed to present a specific neurocognitive battery for schizophrenia by selecting specific subtests from the Barcelona Test. Normative data for patients with schizophrenia are presented and the influence of a number of variables is taken into account. Methods. The sample included 209 patients. The relationship between cognitive performance and gender, age, educational level, age of onset, duration of illness and symptomatology were assessed. Symptomatology was collected with the Positive and Negative Syndrome Scale for Schizophrenia. Results. More of the 50% of the sample had cognitive impairment when compared with standardized percentile scores of the Barcelona Test. No significant relationships between cognitive performance and variables assessed were found, except for in the educational level. Thus, percentile scores for the total sample and for the sample in terms of educational level were obtained. Conclusions. The high percentage of patients with cognitive impairment when standardized percentile scores were used reinforces the need to use normative data appropriate for the schizophrenia group. The lack of relationship between cognitive performance and the variables assessed supports the hypothesis that cognitive impairment is a core feature in schizophrenia. [ABSTRACT FROM AUTHOR]