Physical characteristics of the ECAT 953B/31: a new high resolution brain positron tomograph

A high spatial resolution brain positron tomograph, the ECAT 953B/31, is presented. The machine consists of two 76.5 cm diameter rings (patient port diameter: 36 cm) made of 24 8x8 BGO detector blocks each, each block being coupled to four 1 in(2) Hammamatsu phototubes. The machine has 15 9 cmx1 mm motorized removable septa, which allows reconstruction of 31 slices 3.375 mm apart. The transaxial resolution (FWHM) in the reconstructed image (with wobbling) is 4.5 mm at center, 5.2 mm (tangential) and 5.6 mm at 10 cm from center. With septa out of the field of view (FOV), the axial resolution degrades to 5.5 mm a center and 6.3 mm at 10 cm from center. At 1 muCi/cc with a 250 keV threshold and a 12 ns coincidence window, the sensitivity is 146100 true events, the ratio of randoms to trues is 0.10, the scatter fraction is 17% and the dead-time losses are 30%. With septa out of the FOV, the sensitivity is increased by a factor 3.6, while the scatter fraction reaches 0.9. Images obtained with (18 )F-DG and H(2)(15)O in human brains and (18 )F-DOPA in a baboon brain demonstrate that the ECAT 953B/31 will be suitable for high resolution and for low count rate brain studies.     

Potent Inhibition of Acid Sphingomyelinase by Phosphoinositide Analogues

The different mammalian sphingomyelinases are involved in cell regulation, apoptosis and inflammatory events. Recent reports suggest pharmacological potential especially for inhibitors of the acid sphingomyelinase. Phosphatidyl inositol‐3,5bisphosphate (PtdIns3,5P₂) is the most potent selective acid sphingomyelinase inhibitor known to date. In the present study, we synthesized analogues of PtdIns3,5P₂ for initial structure–activity‐relationship (SAR) studies. We identified an inhibitor that is easy to synthesize, that has superior chemical and biophysical properties when compared to PtdIns3,5P₂ and that should be stable against virtually all phospholipases. Last but not least, the new inhibitor partially protected cells from dexamethasone‐induced cell death.     

Development of a predictive simulation method for thin flash generation in flashless precision forging processes of aluminum parts using FEA and experiments

In this paper, the investigation of thin flash generation in precision forging process of an aluminum long flat part is described. The aim was to derive a predictive simulation method for thin flash generation in order to increase both process and part quality in the future. The forging processes were varied by use of different preforms with equal volumes but different mass distributions while using the same final part geometry. The experimentally forged parts were analyzed concerning the amount and part area of the generated thin flash. The conducted FE simulations were analyzed concerning the hydrostatic pressure values p in the part areas near to the tool gap between upper and lower die immediately before form-filling. For a more detailed comparison, single p values were included to hydrostatic pressure functions P. The comparison between the P functions and the experimentally determined thin flash height shows, that high pressure values as well as high gradients of the P functions indicate less thin flash generation. The method therefore allows a qualitative prediction of thin flash generation. It can provide two kind of information. First: The prediction of the specific locations where thin flash is likely to occur in one final part by use of one single preform. Second: The qualitative prediction of the specific final part areas were thin flash is likely to occur depending on different preform geometries. This method will decreases the necessity of time-consuming forging trials and can shorten the preform designing process in the future.     

Early treatment can improve prognosis in diabetic nephropathy

Prognosis in diabetic nephropathy has changed dramatically during the past decade, and slowing of the disease process has been made possible by intervention against specific risk factors. Nonetheless, diabetic nephropathy has become the leading cause of end stage renal disease. Early detection and prevention, or at least delaying, of disease progression have become crucial aims, and several treatment strategies designed to prevent end stage renal disease have recently been published. The common denominator of these strategies is screening for microalbuminuria in diabetic patients rather than awaiting the appearance of overt symptoms.     

Lightness determination at curved surfaces with applications todynamic range compression and model-based coding of facial images

Lightness algorithms, which have been proposed as a model for human vision, are aimed at recovering surface reflectance in a close approximation. They attempt to separate reflectance data from illumination data by thresholding a spatial derivative of the image intensity. This, however, works only reliable in a world of plane Mondrians. An extension of the classical lightness approach of Land and McCann (1971) to curved surfaces is presented. Assuming smooth surfaces with Lambertian reflection properties and leaving aside occlusions and cast shadows, the separation of those components of the intensity gradient due to reflectance from those due to irradiance is posed as a constraint minimization problem. To do so, two classification operators were introduced which identify potential reflectance and irradiance data using a scale-space filtering approach. Two exemplary applications of the proposed extended lightness algorithm in the field of visual telecommunications are presented: (i) the simulation of more uniformly illuminated videophone portrait scenes to give dynamic range compressed images with a most realistic appearance and (ii) the synthesis of videophone portrait images from model-based coded data with a correct illumination effect. In both applications, the extended lightness algorithm is employed for estimating the reflectance functions at facial surfaces. Results obtained by applying the extended lightness algorithm are compared with results obtained by conventional methods known from literature.     

Calcium antagonists and mortality risk in men and women with hypertension in the Framingham Heart Study

BACKGROUND: Several recent studies have suggested that calcium antagonist drugs, which are widely used for the treatment of hypertension, are associated with increased risk of cardiovascular disease. These studies have cast doubts on the long-term safety of calcium antagonists. OBJECTIVE: To examine the association of calcium antagonist use with mortality in subjects with hypertension followed up in the Framingham Heart Study. SUBJECTS AND METHODS: We stratified 3539 subjects (mean+/-SD age, 64+/-13 years) from the Framingham Heart Study who had hypertension at routine clinic examinations, according to the use of calcium antagonists and presence of coronary heart disease at the baseline examination. At each follow-up examination (every 2-4 years), subjects were reclassified with regard to the use of calcium antagonists. The end point of the study was all-cause mortality. Hazard ratios and 95% confidence intervals associated with the use of calcium antagonists were obtained using Cox proportional hazards regression models. RESULTS: There were 970 deaths during follow-up. Hazard ratios for mortality associated with the use of calcium antagonists were 0.93 (95% confidence interval, 0.72-1.21; P=.59) for subjects with hypertension without coronary heart disease, and 0.92 (95% confidence interval, 0.69-1.24; P=.58) for those with coronary heart disease at baseline. All models were adjusted for age, sex, current smoking, systolic and diastolic blood pressure, use of beta-blockers, and use of other antihypertensive medications. CONCLUSIONS: In this cohort of 3539 subjects with hypertension there were no differences in mortality among subjects with hypertension using a calcium antagonist compared with those who were not. Results were similar among subjects with hypertension with and without coronary heart disease. The results of ongoing long-term, randomized clinical trials will provide more definitive data on the safety of calcium antagonists.     

Automated detection and quantitation of bacterial RNA by using electrical microarrays

Low-density electrical 16S rRNA specific oligonucleotide microarrays and an automated analysis system have been developed for the identification and quantitation of pathogens. The pathogens are Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus epidermidis, which are typically involved in urinary tract infections. Interdigitated gold array electrodes (IDA-electrodes), which have structures in the nanometer range, have been used for very sensitive analysis. Thiol-modified oligonucleotides are immobilized on the gold IDA as capture probes. They mediate the specific recognition of the target 16S rRNA by hybridization. Additionally three unlabeled oligonucleotides are hybridized in close proximity to the capturing site. They are supporting molecules, because they improve the RNA hybridization at the capturing site. A biotin labeled detector oligonucleotide is also allowed to hybridize to the captured RNA sequence. The biotin labels enable the binding of avidin alkaline phophatase conjugates. The phosphatase liberates the electrochemical mediator p-aminophenol from its electrically inactive phosphate derivative. The electrical signals were generated by amperometric redox cycling and detected by a unique multipotentiostat. The read out signals of the microarray are position specific current and change over time in proportion to the analyte concentration. If two additional biotins are introduced into the affinity binding complex via the supporting oligonucleotides, the sensitivity of the assays increase more than 60%. The limit of detection of Escherichia coli total RNA has been determined to be 0.5 ng/microL. The control of fluidics for variable assay formats as well as the multichannel electrical read out and data handling have all been fully automated. The fast and easy procedure does not require any amplification of the targeted nucleic acids by PCR.     

Visual impairment in Swedish children. III. Diagnoses

PURPOSE: To gain an overview of the spectrum of diagnoses among Swedish visually impaired children. METHODS: An epidemiological study of all known visually impaired children was made by review of medical records. RESULTS AND CONCLUSION: In all we found 2373 children, 0-19 years of age, with an age-specific prevalence of 10.9/10,000. The two largest diagnostic groups included neuro-ophthalmological and retinal diseases. The most frequent disorders were cerebral visual impairment, non-hereditary optic atrophy, retinal dystrophy (when regarded as a general entity), congenital hypoplasia of the optic nerve and congenital cataract. Nystagmus secondary to brain disorder, albinism, congenital nystagmus, retinopathy of prematurity and high myopia were also found in a considerable number of patients. The leading diagnoses in children with WHO-defined childhood blindness were non-hereditary optic atrophy, cerebral visual impairment and retinopathy of prematurity. A large proportion of the children, especially in the groups with neuro-ophthalmological disorders and malformations of the posterior segment had additional impairments, emphasizing the importance of a multi-disciplinary approach when assessing multi-handicapped children.     

Vacuum-processed polyethylene as a dielectric for low operating voltage organic field effect transistors

We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C₆₀ as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm²/Vs. Devices with pentacene showed a mobility of 0.16 cm²/Vs. Devices using tyrian Purple as semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ～0.3 cm²/Vs. These devices demonstrate low hysteresis and operational stability over at least several months. Grazing-angle infrared spectroscopy of evaporated thin films shows that the structure of the polyethylene is similar to solution-cast films. We report also on the morphological and dielectric properties of these films. Our experiments demonstrate that polyethylene is a stable dielectric supporting both hole and electron channels.