Explosive Detection by Microthermal Analysis

Differential scanning microcalorimetry at high heating rates of ～ 300°C/s was performed on 30- to 100-µm-size explosive particles using two MEMS-based thermal conductivity gauges in air and under N₂. The gauges consist of a thin-film Si₃N_x membrane with a centrally located Al thin-film heater, which is surrounded by six thin-film Si/Al junctions, creating a temperature-sensitive thermopile (～ 1.3 mV/K) with an effective sensitive area of ca. 200 × 200 µm. Heating was carried out by applying a linear voltage ramp during 1.6 s. The measurements were performed in a specially designed exposure chamber having a transparent glass lid that enabled optical observation of the thermal process.

Besides explosives (TNT, RDX, picric acid, urea nitrate, and TATP) we have studied nonexplosive materials, organic and inorganic, in order to see whether the explosives have a unique response. The materials we studied were oxygen-poor and -rich organic compounds (polyethylene and sugars, respectively), sea sand, and iron flakes.

Clear, well-resolved exotherms were obtained at moderated temperatures (～ 250°C) for all types of explosive materials tested by us. In addition, all explosives exhibited a melting endotherm preceding the exotherm. Sea sand and iron showed no peaks at the heating temperature range. Polyethylene showed an endotherm representing its melting. The sugars showed an endotherm but also an exotherm when heated to elevated temperatures (> 370°C). The thermogram of each material depends on its properties and is characterized by a unique pattern. This pattern may enable the detection and identification of explosive particles using this technology.     

Residual Stress Profile Assessment by Eddy Current for Shot Peened Nickel Superalloy

Eddy current (EC) measurements have shown promise toward becoming a nondestructive method of residual stress characterization, particularly for nickel-base superalloys. However, previous studies on shot-peened materials have shown apparent discrepancies between directly measured residual stress profiles and those determined from EC data. Here, we report a study of the inter-relationship among electrical conductivity deviation, residual stress and texture of shot peened materials, in order to improve understanding of the piezoresistivity effect that is essential to the on-going efforts to make EC measurements a viable technique for residual stress assessment. Specifically, we develop a macroscopic piezoresistivity theory for polycrystalline materials influenced by texture. The theory was applied to analyze the swept high frequency eddy current data obtained from a shot peened Inconel 718 sample, which was found to exhibit shot-induced texture in the near surface region using X-ray diffraction (XRD) and orientation imaging microscopy (OIM). The residual stress profile of the peened sample was inverted from EC data using a physics model-based approach, and was found to agree with the residual stress profiles measured independently using the standard layer removal XRD technique.     

Online dynamic graph drawing

This paper presents an algorithm for drawing a sequence of graphs online. The algorithm strives to maintain the global structure of the graph and thus the user's mental map, while allowing arbitrary modifications between consecutive layouts. The algorithm works online and uses various execution culling methods in order to reduce the layout time and handle large dynamic graphs. Techniques for representing graphs on the GPU allow a speedup by a factor of up to 17 compared to the CPU implementation. The scalability of the algorithm across GPU generations is demonstrated. Applications of the algorithm to the visualization of discussion threads in Internet sites and to the visualization of social networks are provided.     

Dispersion of an inertia mixture of varying size in a two-phase axisymmetrical stream

Experimental data on the dispersion of a powdered mixture of varying size in an axisymmetrical turbulent stream are described.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 18, No. 4, pp. 643–647, April, 1970.     

Atrial natriuretic peptide and its potential role in pharmacotherapy

Atrial natriuretic peptide (ANP) is a 28 amino-acid polypeptide secreted into the blood by atrial myocytes after atrial pressure and distension. Although its role in humans is not clear, it can produce a variety of physiologic effects including vasodilatation, natriuresis, and suppression of the renin-angiotensin-aldosterone axis. These actions are potentially useful in a variety of pathologic states such as hypertension and congestive heart failure, and diverse methods to augment the effects of ANP in these states have been devised. The results are exciting and, despite some problems, may lead to the pharmacologic use of enhancement of ANP actions in several clinical disorders.     

Variations of the C2H2 zinc finger motif in the yeast genome and classification of yeast zinc finger proteins

The PROSITE pattern Zinc_Finger_C2H2 was extended to permit the detection of all C2H2 zinc fingers and their parent proteins in the recently completed sequence of the yeast genome. Additionally, a new computer program was written that extracts other zinc binding motifs (non C2H2 'fingers'), overlapping with the classical zinc finger pattern, from the found set of yeast C2H2 fingers. The complete and correct detection of all fingers is a prerequisite for the classification of the yeast zinc finger proteins in functional terms. The detected 53 yeast C2H2 zinc finger proteins do not contain finger clusters with 10 or more repeats, as is frequently found in higher eukaryotes. Only three proteins contain four or more fingers in a cluster. Moreover, nearly all 27 yeast proteins with tandem arrays of two or three finger domains can be classified into nine subgroups with high sequence conservation in their finger clusters, in particular of their DNA recognition helices. These results and application of the recently elaborated finger/DNA recognition rules suggest that the yeast proteins belonging to the same subgroup may recognize identical or very similar DNA sites.     

Fenoldopam: a new dopamine agonist for the treatment of hypertensive urgencies and emergencies

Vascular nephropathies are a steadily increasing cause of end-stage renal failure. Arterionephrosclerosis and arteriolonephrosclerosis are common features in the hypertensive patient. This is especially true for blacks of African descent, in whom hypertension and nephrovasculopathies are a major cause of renal insufficiency. That primary hypertension leads to renal vascular lesions, glomerular obsolescence and interstitial fibrosis has long been established. It should not, however, obscure the fact that renal vascular lesions can be observed in animal models as well as in some humans, especially young blacks, in the absence of, or anticipating the onset of hypertension. This leads to considering the hypothesis that nephroangiosclerosis might stem from a genetic defect in the renal vascular bed and that this defect is strongly associated with the hypertensive trait. Atherosclerotic renal disease is a major, potentially treatable cause of chronic renal disease is a major, potentially treatable cause of chronic renal failure, especially in whites. It leads to renal atrophy, but the ischemic kidney retains a vigorous potential for tubular cell regeneration, which pleads for early recognition and treatment. Recent data suggest that renal ischemia, be it due to renal artery stenosis or to cholesterol crystal embolism, ranks among the multiple causes of secondary focal segmental glomerulosclerosis. Irrespective of its initial mechanism, ischemia induces renal fibrosis, the pathophysiology of which is centered on increased generation of angiotensin II. Finally, renal vascular lesions are commonly observed in the course of various nephropathies, even in the absence of hypertension, and the relationship between these lesions and the unfavorable prognosis of glomerulopathies, especially primary focal-segmental glomerulosclerosis, membranous glomerulopathy and IgA glomerulonephritis, remains to be elucidated. Expanding knowledge of the spectrum of nephrovasculopathies opens perspectives for investigating, understanding and treating a major mechanism of progressive renal insufficiency.     

The precision of velocity discrimination across spatial frequency

The precision of velocity coding for moving stimuli of different spatial frequencies was assessed by measuring velocity discrimination thresholds for a 1-c/deg grating paired with a grating whose spatial frequency ranged from 0.25 to 4 c/deg and for grating pairs of the same spatial frequency (0.25, 1, and 4 c/deg). The gratings always moved upward, with velocities ranging from 0.5 to 16 deg/sec. Velocity discrimination was as precise for stimuli that varied in spatial frequency by +/- 2 octaves (0.25 vs. 1 c/deg and 4 vs. 1 c/deg) as for stimuli of the same spatial frequency, for specific ranges of velocity that depended on the spatial and, therefore, the temporal frequencies of the stimuli. Compared with a 1-c/deg grating, the perceived velocity of 4-c/deg gratings was about 1.3 times faster and that of 0.25-c/deg gratings was about 1.3 times slower. Although these perceived velocity biases imply variation of velocity-signal processing among spatial frequency channels, the discrimination results indicate that the motion-sensing system can compare signals across different spatial frequency channels to make fine velocity discrimination within appropriate temporal frequency limits.