A Portable Device for the Measurement of Regional Cerebral Blood Flow in the Icu and or Using Cd Te Detectors and a Fourier Transform Based Data Analysis

A portable system for the measurement of cerebral blood flow in critical care environments such as the intensive care unit or operating room has been developed and tested in a limited series of patients. The flow measurements are based on the 133Xe inhalation or IV injection method. The system uses miniature solid state detectors, microprocessor technology and Fourier transform based data analysis to provide compactness and rapid on-line analysis of data. Preliminary patient studies comparing this system with a larger sodium iodide detector system show comparable results.     

cDNA cloning and expression of a novel family of enzymes with calcium-independent phospholipase A2 and lysophospholipase activities

Previous studies have suggested that activation of calcium-independent PLA2 (CaIPLA2) is an early event in cell death after hypoxic injury in proximal tubule cells. An approximately 28-kD CaIPLA2 with preferential activity toward plasmalogen phospholipids has been recently purified from rabbit kidney cortex (D. Portilla and G. Dai, J Biol Chem 271, 15,451-15,457, 1996). Their report describes the cloning of a full-length rat cDNA encoding CaIPLA2, using sequences derived from the purified rabbit kidney cortex enzyme. In addition, cDNA from rabbit kidney that encode the rabbit homologue of the enzyme and a closely related isoform were isolated. The rat cDNA is predicted to encode an approximately 24-kD protein, and each cDNA contains the sequence G-F-S-Q-G, which fits the active site consensus sequence G-X-S-X-G of carboxylesterases. Several lines of evidence (DNA sequence comparison, Southern blot analysis, and examination of the expressed sequence tag database) show that CaIPLA2 enzymes are encoded by a multigene family in rats, mice, rabbits, and humans. Northern analysis of various tissues from the rat indicated that the CaIPLA2 gene is ubiquitously expressed, with highest mRNA abundance observed in the kidney and small intestine. The rat CaIPLA2 cDNA, when expressed in a baculovirus expression system, and the purified rabbit kidney cortex protein exhibit both CaIPLA2 and lysophospholipase activities. The cloned CaIPLA2 cDNA are expected to aid in understanding the role of CaIPLA2 in cell death after hypoxic/ischemic cell injury.     

Shape reconstruction of 3D metallic objects via a physical optics distributional approach

The problem of determining the shape of 3D perfect electric conducting (PEC) objects starting from the scattered far field under the incidence of plane waves with a fixed angle of incidence, varying frequency and two orthogonal polarizations is dealt with.Two strategies of reconstruction are presented and compared. In particular, in the first solution strategy the data acquired at the two polarizations are singularly exploited to achieve two different reconstructions and the object surface is then obtained as their “union”. In the second one, all the data (i.e., for both the adopted polarizations) are simultaneously exploited to obtain the reconstruction.In all the cases, by adopting a distributional formulation for the unknown of the problem and thanks to the exploitation of the Kirchhoff approximation, the problem is cast as a linear inverse one and the solution is made stable by adopting a regularization scheme based on the truncated singular value decomposition (TSVD).The reliability of the inversion approach is tested with synthetic data against model error and noise on data.     

Exposure to welding particles in automotive plants

This work presents a monitoring study designed to evaluate workers' exposure to particles in several body shops within automotive plants. Concentrations in the proximity of welding activities were measured by a Fast Mobility Particle Sizer, several Condensation Particle Counters, a Nanoparticle Surface Area Monitor and a laser photometer, as well as by several gravimetric samplers. Average concentrations were found to be 1×10⁵ part cm^?3, 3×10³ μm² cm^?3 and 0.4 mg m^?3 for number, surface area and PM₁ concentration, respectively (worst case). Very high concentrations, particularly for surface area, were observed in locations with a high density of manual resistance welding activities or close to oxyacetylene welding activities. Welding emission factors in the automotive plants were also evaluated and in the most critical body shop, the overall welding activities led to emission factors of 2.8×10¹⁵ part min^?1, 7.0×10⁶ μm² min^?1 and 7.9 g min^?1 for number, surface area and PM₁ concentrations, respectively. Finally, particle concentration characterization, along with air exchange ratio measurements in the body shop, showed that the indoor concentrations and, hence, worker particle exposure can be reduced through the use of local exhaust ventilation.     

Time course of lesion development in patients with acute stroke: serial diffusion- and hemodynamic-weighted magnetic resonance imaging

BACKGROUND AND PURPOSE: We sought to characterize the evolution of acute ischemic stroke by MRI and its relationship to patients' neurological outcome. METHODS: Fourteen patients with acute ischemic stroke underwent MRI within 13 hours of symptom onset (mean, 7.4+/-3 hours) and underwent repeated imaging and concurrent neurological examination at 8, 24, 36, and 48 hours and 7 days and >42 days after first imaging. RESULTS: Diffusion-weighted imaging (DWI) lesion volumes increased between the first and second scans in 10 of 14 patients; scans with maximum DWI lesion volume occurred at a mean of 70.4 hours. Initial DWI lesion volume correlated with the largest T2 lesion volume (r=0.97; P<0.001). Final lesion volume was smaller than maximum lesion volume in 12 of 14 patients. There was positive correlation between the follow-up National Institutes of Health Stroke Scale score and the initial DWI lesion volume (r=0.67; P=0. 01) and maximum T2 lesion volume (r=0.77; P<0.01) and negative correlation with initial mean apparent diffusion coefficient ratio (ADCr) (r=-0.64; P<0.05). The ADCr was 0.73 at initial imaging and fell between the initial and second scans in 10 of 14 patients. Mean ADCr did not rise above normal until 42 days after stroke onset (P<0. 001). CONCLUSIONS: Serial MRI demonstrates the dynamic nature of progressive ischemic injury in acute stroke patients developing over hours to days, and it suggests that both primary and secondary pathophysiological processes can be valuable targets for neuroprotective interventions.     

Posterior leukoencephalopathy without severe hypertension: utility of diffusion-weighted MRI

OBJECTIVE: Standard MRI confirms the diagnosis of posterior leukoencephalopathy syndrome (PLES), recently associated with an increasing number of medical conditions. In PLES, T2-weighted MRI demonstrates hyperintensity spreading out from posterior brain regions; the pathophysiology remains mysterious. In the acute setting, diffusion-weighted imaging (DWI), but not standard MR imaging, can distinguish ischemic injury from those conditions known to cause vasogenic brain edema. DWI is potentially valuable in understanding the pathophysiology of PLES and in diagnosing patients who do not have previously known risk factors. METHODS: Serial CT and MRI studies (including DWI, apparent diffusion coefficient [ADC] maps, and, in one instance, perfusion-weighted imaging) were performed in three female patients with a neurologic syndrome consistent with PLES while hospitalized for treatment of other conditions. RESULTS: None of the patients had previously described risk factors for PLES; all had only mild elevations in blood pressure. MRI showed large, abnormal, T2 hyperintense regions in the posterior cerebrum with corresponding hyperintensity on ADC maps-signal characteristics predominantly consistent with vasogenic edema. There were also smaller patchy posterior cortical regions with decreased ADC and bright DWI consistent with infarction in one, and dramatic conversion of a large region to an ischemic pattern in another. CONCLUSIONS: ADC maps and DWI can successfully differentiate PLES from early cerebral ischemia, thus playing a pivotal role in treatment decisions. PLES is associated with a wider variety of conditions than has been previously reported and is not always reversible. Hyperintense DWI signal in patients with the syndrome likely marks a tissue stage of permanent brain injury.     

THE EFFECTIVE THERMAL CONDUCTIVITY OF PACKED BEDS OF SPHERES FOR A FINITE CONTACT AREA

The upper and lower bounds of the effective thermal conductivity range of packed beds of spheres is evaluated using the theoretical approach of the volume averaging method for a two-phase system. The solid mechanics and thermal problems are resolved by considering the effects of superficial roughness and pressure. The numerical solutions to the problem of thermal conduction through the periodic regular arrangement of stainless steel and aluminum spheres in the air are determined using the finite element method. As regards to the aluminum spheres, the influence of oxide stratum on the effective thermal conductivity is also considered. Finally, empirical equations are proposed for periodic regular arrangements of stainless steel and aluminum spheres.     

Large area, 38 nm half-pitch grating fabrication by using atomic spacer lithography from aluminum wire grids

We wrapped 150 nm period aluminum wire grid polarizer (WGP) with AlSiOx by using atomic layer deposition at 250 degrees C. The nanometer precision coating defined the spacer to double the spatial frequency of the 100 mm diameter grating fabricated by using a legacy immersion holography setup at 351 nm wavelength. Half-pitch grating of approximately 38 nm was demonstrated with good pattern uniformity, excellent repeatability, and a wide processing window. We believe 10 nm half-pitch grating over even larger areas are viable, overcoming one major hurdle to commercialize nanoimprint.