Novel parameter estimation methods for 11C-acetate dual-input liver model with dynamic PET.

The successful investigation of 11C-acetate in positron emission tomography (PET) imaging for marking hepatocellular carcinoma (HCC) has been validated by both clinical and quantitative modeling studies. In the previous quantitative studies, all the individual model parameters were estimated by the weighted nonlinear least squares (NLS) algorithm. However, five parameters need to be estimated simultaneously, therefore, the computational time-complexity is high and some estimates are not quite reliable, which limits its application in clinical environment. In addition, liver system modeling with dual-input function is very different from the widespread single-input system modeling. Therefore, most of the currently developed estimation techniques are not applicable. In this paper, two parameter estimation techniques: graphed NLS (GNLS) and graphed dual-input generalized linear least squares (GDGLLS) algorithms were presented for 11C-acetate dual-input liver model. Clinical and simulated data were utilized to test the proposed algorithms by a systematic statistical analysis. Compared to NLS fitting, these two novel methods achieve better estimation reliability and are computationally efficient, and they are extremely powerful for the estimation of the two potential HCC indicators: local hepatic metabolic rate-constant of acetate and relative portal venous contribution to the hepatic blood flow.     

Prevalence of antimicrobial-resistant pathogens in middle ear fluid: multinational study of 917 children with acute otitis media

The management of acute otitis media is complicated by the emergence of resistance to beta-lactam and other antibiotics among common pathogens. We conducted a large, international study of infants and children with acute otitis media to identify pathogens and susceptibility patterns. During the winter of 1994 to 1995, middle ear fluid samples were collected from 917 patients with acute otitis media in Bulgaria, the Czech Republic, Hungary, Romania, Slovakia, Israel, and the United States. A single reference laboratory performed in vitro susceptibility testing. Pathogens were isolated from 62% of the patients. For Streptococcus pneumoniae (30% of the patients), untypeable Haemophilus influenzae (17%), and Moraxella catarrhalis (4%), there was significant variation among geographic regions (P < 0.001). The composite susceptibilities of these three organisms to amoxicillin ranged from 62% in the United States to 89% in Eastern and Central Europe; the corresponding susceptibilities to amoxicillin-clavulanate ranged from 90% in Israel to 95% in Eastern and Central Europe. beta-Lactamase was produced by 31 and 100% of the isolates of H. influenzae and M. catarrhalis, respectively. More isolates of S. pneumoniae were susceptible to amoxicillin (90%) or amoxicillin-clavulanate (90%) than to penicillin (70%; P = 0.002). The prevalence of resistant S. pneumoniae was highest in patients less than 12 months of age. S. pneumoniae, H. influenzae, and M. catarrhalis remain the most important bacterial pathogens in patients with acute otitis media; however, their prevalence is variable and resistance patterns are changing.     

为集成电路选择合适的散热器

为发热的集成电路提供足够的散热，需要高效率、大功率的散热方案     

A new double modeling approach for dynamic cardiac PET studiesusing noise and spillover contaminated LV measurements

A new double modeling approach for dynamic cardiac studies with positron emission tomography (PET) to estimate physiological parameters is proposed. This approach is exemplified by tracer fluorodeoxyglucose (FDG) studies and estimation of myocardial metabolic rate of glucose (MMRGlc). A separate input function model characterising the tracer kinetics in plasma is used to account for the measurement noise and spillover problems of the input curve obtained from the left ventricular region on the PET images. Measured left ventricle (LV) plasma time-activity and tissue time-activity curves are fitted simultaneously with cross contaminations by this input function model and the FDG model. The results indicate that the MMRGlc can be estimated much more accurately and reliably by this new approach. Compared with the traditional method, an improvement of about 20% in the estimated MMRGlc was achieved when the bidirectional spillover fractions are 20% at different noise levels studied. This new double modeling approach using two models fitting both the input and the output functions simultaneously is expected to be generally applicable to a broad range of system modeling     

Geometric superresolution by code division multiplexing

In many highly resolved optical systems the resolution is limited not by the optics but by the CCD's nonzero pixel size. As a result, overall resolution is decreased. Here we propose a novel approach to enhancing resolution beyond the limit set by the CCD's pixels. This method does not involve additional mechanical elements, such as those used for microscans. In this scheme neither the CCD nor additional elements are moved. The geometric superresolving procedure is based on code-division multiplexing, with all its inherent benefits, such as relative noise immunity to single-tone interference. A setup is proposed for coherent and incoherent illumination, with slight modifications for the latter. A theoretical analysis of the setup is presented and compared with empirical results. This scheme is shown to enhance one-dimensional image resolution with the use of only a simple mask that doubles image resolution. This method can easily be expanded to two-dimensional images and to resolution-enhancement factors greater than 2.     

Ortho Effects. I. The Mechanisms of the H3O and CH3O2 Elimination from the Molecular Ion of N-Methyl Ortho-Nitro-Para-Toluidine

The molecular ion of the N-methyl ortho-nitro-para-toluidine (I) readily eliminates H₃O. The sources of the H atoms lost were proved by deuterium labeling to be an HNCH₃ group as well as, probably, the C-methyl group of the aromatic ring. The interaction between the N-methyl and nitro groups in I also leads to the expulsion of CH₃O₂ from the molecular ion.     

Nasopharyngeal colonization in southern Israel with antibiotic-resistant pneumococci during the first 2 years of life: relation to serotypes likely to be included in pneumococcal conjugate vaccines

Nasopharyngeal carriage of Streptococcus pneumoniae was studied in 162 healthy infants at ages 2, 4, 6, 7, 12, and 13 months and in an additional 352 healthy children at ages 12, 15, 18, 21, and 24 months. Carriage was 26%, 39%, and 62% at 2, 12, and 24 months, respectively, and the respective resistance to > or = 1 antibiotic was 11%, 19%, and 27%. The presence of an older sibling or antibiotic treatment during the month preceding the culture was associated with carriage of resistant pneumococci in infants, whereas attendance at large day care centers was associated with carriage during the second year of life. Antibiotic resistance was detected in all 7 serotypes included in the candidate pediatric conjugate vaccines and was significantly more prevalent among vaccine-type pneumococci than among non-vaccine-type pneumococci. The use of conjugate vaccines may reduce the spread of resistant pneumococci.     

Transport of testosterone and estrogen from dairy-farm waste lagoons to groundwater

Although concentrated animal feeding operations constantly generate physiologically active steroidal hormones, little is known of their environmental fate. Estrogen and testosterone concentrations in groundwater and their distribution in sediments below a dairy-farm wastewater lagoon were therefore determined and compared to a reference site located upgradient of the farm. Forward simulations of flow as well as estrogen and testosterone transport were conducted based on data from the sediment profile obtained during drilling of a monitoring well belowthe dairy-farm waste lagoon. Testosterone and estrogen were detected in sediments to depths of 45 and 32 m, respectively. Groundwater samples were directly impacted by the dairy farm, as evidenced by elevated concentrations of nitrate, chloride, testosterone, and estrogen as compared to the reference site. Modeling potential transport of hormones in the vadose zone via advection, dispersion, and sorption could not explain the depths at which estrogen and testosterone were found, suggesting that other transport mechanisms influence hormone transport under field conditions. These mechanisms may involve interactions between hormones and manure as well as preferential flow paths, leading to enhanced transport rates. These types of interactions should be further investigated to understand the processes regulating hormone transport in the subsurface environment and parametrized to forecast long-term fate and transport of steroidal hormones.