Super-resolution in PET imaging

This paper demonstrates a super-resolution method for improving the resolution in clinical positron emission tomography (PET) scanners. Super-resolution images were obtained by combining four data sets with spatial shifts between consecutive acquisitions and applying an iterative algorithm. Super-resolution attenuation corrected PET scans of a phantom were obtained using the two-dimensional and three-dimensional (3-D) acquisition modes of a clinical PET/computed tomography (CT) scanner (Discovery LS, GEMS). In a patient study, following a standard 18F-FDG PET/CT scan, a super-resolution scan around one small lesion was performed using axial shifts without increasing the patient radiation exposure. In the phantom study, smaller features (3 mm) could be resolved axially with the super-resolution method than without (6 mm). The super-resolution images had better resolution than the original images and provided higher contrast ratios in coronal images and in 3-D acquisition transaxial images. The coronal super-resolution images had superior resolution and contrast ratios compared to images reconstructed by merely interleaving the data to the proper axial location. In the patient study, super-resolution reconstructions displayed a more localized 18F-FDG uptake. A new approach for improving the resolution of PET images using a super-resolution method has been developed and experimentally confirmed, employing a clinical scanner. The improvement in axial resolution requires no changes in hardware.     

Effect of Fasting under Different Temperature Conditions on Nucleic Acid Ratios in the Opossum Shrimp Mysis relicta: a Calibration Approach

The opossum shrimp Mysis relicta is an important component of the diet of benthivorous and planktivorous fish in the Great Lakes. The invasion of the Great Lakes by exotic invertebrates (Bythotrephes longimanus, Cercopagis pengoi, Dreissena polymorpha, and D. bugensis) has altered the base and intermediate levels of the foodweb. Thus, information about the condition of M. relicta may reveal the extent of indirect effects of these changes on this trophically-important invertebrate. Biochemical indices based on nucleic acid ratios have been shown to be suitable proxies for the growth and condition of aquatic organisms. These indices are affected by multiple factors, such as; food level, temperature, body size, sex/life stage, maturation, and moult stage and need to be calibrated before field data can be interpreted on a quantitative basis. In this study, we investigated the effect of fasting under different temperature conditions on the nucleic acid ratios RNA/DNA, RNA/protein and protein/DNA in M. relicta. Juvenile M. relicta were exposed to fasting conditions for 11 and 21 d in two controlled laboratory experiments at 3°C and 8°C. Several effects of time and temperature on the condition indices of fasting M. relicta were observed; however, we concluded that, of the various metrics tested, only RNA/DNA ratios provide a suitable index of metabolism and condition in fasting animals. RNA concentrations declined in response to fasting on the order of 3–4 d at 8°C and between 4 and 11 d at 3°C. Juvenile M. relicta with RNA/DNA ratios < 1.5–1.8 were clearly identified as fasting animals. Field-caught animals having RNA/DNA ratios near these levels are demonstrating clear signs of metabolic stress.     

Characterization of a sex pheromone in the jird (Meriones tristrami)

The Israeli jird (Meriones tristrami) is a semidesert crecitid rodent found throughout the Mid-East. Jirds use a midventral sebaceous gland to scent-mark objects, the ground, and conspecifics. Volatile compounds from the male gland extract were found to containn-aliphatic acetates by thin-layer chromatography, gas chromatography, and mass spectroscopy. In a digital olfactometer, female jirds demonstrated preference for male glandular extract and many of then-aliphatic acetates. Other biologically important odors were also presented to the female jirds. Behavioral observations combined with olfactory bioassays implicate the involvement of the ventral sebaceous gland in jird sexual behavior.     

THE GENESIS OF THE ZOHAR GAS AS DEDUCED FROM ITS CHEMICAL AND CARBON ISOTOPE COMPOSITION

The hydrocarbon compositions (C₁/ΣC₁—C₄) = 0.96-0.98) and the carbon isotopes ratios of methane (—51.4 to—52.1%) studied in the Zohar Gas Field indicate that the generations of the gas was associated with an oil-generation process. Thus, gas and heavy oils found in the area could have formed simultaneously within one system.
The carbon isotope composition of the CO₂ is relatively heavy, with δ¹³ CO₂ value ofabout +7% which is probably the original value of the CO₂ generated by biodegradation of the cruded oil.
The dissimilarity in the organochemical characteristics of the Kidod shales, which cap the gas reservoirs and the oils found in the region, as well as the low degree of maturation of the Kidod, shales, negate the accepted hypothesis that these shales are the source rock of the heavy oils and the gas found in the Zohar area. The vitrinite reflectance of the reservoir rocks and of the underlying Jurassic sequences, which is only 0.5%, infers that the gas is not trapped near its site of generation.     

Effects of work overload and burnout on cholesterol and triglycerides levels: The moderating efffects of emotional reactivity among male and female employees.

The effects of objective and subjective overload, and of physical and emotional burnout, on cholesterol and triglycerides levels were studied in a quasiprospective design. The possible moderating effects of emotional reactivity on these relationships were also investigated. The study's hypotheses were tested separately for male and female employees. Time I (T1) data were collected from 665 healthy employees (30% women) while they were undergoing periodic health examinations in a health-screening center Time 2 (T2) measures of cholesterol and triglycerides were collected 2 to 3 years after T1. The hypotheses were tested by regressing each T2 criterion on its T1 level; the control variables of age, obesity, diet, alcohol consumption, and smoking; and the other predictors. For female employees, the T2-T1 changes in the serum lipids were positively predicted by emotional burnout, as expected, but negatively predicted by physical fatigue. For male employees, both types of T1 burnout were positive predictors of the T2-T1 change in total cholesterol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensitive measurement of NH4+ 15N/14N (delta 15NH4+) at natural abundance levels in fresh and saltwaters

We report a new method for determining the 15N/14N of NH4+ at natural abundance level in both freshwater and seawater. NH4+ is first quantitatively oxidized to NO2- by hypobromite (BrO-) at pH approximately 12. After the addition of sodium arsenite to consume excess BrO-, yield is verified by colorimetric NO2- determination. NO2- is further reduced to N2O using a 1:1 sodium azide and acetic acid buffer solution using previously established procedures. The product N2O is then analyzed for isotopic composition using a continuous flow purge and cryogenic trap system coupled to an isotope ratio mass spectrometer. Reliable delta 15N values (standard deviation is 0.3 per thousand or better) are obtained over an NH4+ concentration range of 0.5-10 microM using 20 mL volumes of either freshwater or seawater samples. Higher concentration samples are readily diluted to lower concentration. Preexisting NO2- is removed by treatment with sulfanilic acid. There is no interference from any of the nitrogen-containing compounds tested except short-chain aliphatic amino acids (i.e., glycine) which typically are present at very low environmental concentrations. As compared to published methods, our approach is more robust, readily applicable at low concentrations and small sample volumes, and requires less time for preparation and analysis.     

Effect of a barrier at the superconducting-normal metal interface

A superconducting-normal metal sandwich, in which there is a potential barrier at the interface, is considered. The Tomasch effect amplitude is shown to be reduced by a factor related to the barrier transmission coefficient. We then derive from first principles the boundary conditions obeyed by the kernel in the Gor'kov gap equation at the interface, within the diffusion approximation. This represents the first ab initio calculation of the second de Gennes boundary condition.Supported in part by the National Science Foundation and by the U.S. Office of Naval Research Contract No. N00014-75-C-0245.     

"Children of the dream" revisited: 70 years of collective early child care in Israeli kibbutzim.

This article focuses on kibbutz care for infants and young children. It reviews (1) past and present practices of collective education within the context of its historical background and guiding principles and (2) the results of developmental research regarding the impact of multiple caregiving and group care on children's socioemotional development within the framework of attachment theory. The research results indicate that, from a psychological point of view, collective sleeping is a problematic aspect of kibbutz child rearing. However, group care and multiple caregiving of high quality do not necessarily interfere with the formation of close relationships between parents and children or with the development of social skills. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Statistical analysis of the fluctuating counts of fecal bacteria in the water of Lake Kinneret

Counts of E. coli, Enteroccoci and fecal coliforms in four sites around Lake Kinneret (The Sea of Galilee), collected every 2-4 weeks for about 5 years during 1995-2002 showed irregular fluctuations punctuated by aperiodic outbursts of variable magnitude. Because of the haphazard nature of fecal contamination and large intervals between successive counts, these patterns were described by probabilistic models, based on the truncated Laplace or Extreme Value distribution. Their applicability was tested by comparing the predicted frequencies of counts exceeding different levels calculated from the first half of each record with those actually observed in its second half. Despite the records imperfections and minor violations of the underlying models' assumptions, there was a reasonable agreement between the estimated and actual frequencies. This demonstrated that it is possible to translate the irregular fluctuation pattern into a set of probabilities of future high counts. In principle, such probabilities can be used to quantify the water's fecal contamination pattern and as a tool to assess the efficacy of preventive measures to reduce it.