A role of cadmium exposure in prostate cancer etiology has been suggested by epidemiologic and laboratory studies, but conclusive evidence on this topic is still lacking. We investigated the relation between cadmium exposure, estimated by determining toenails cadmium levels, and prostate cancer risk in forty patients newly diagnosed with prostate cancer and fifty-eight hospital controls recruited in two provinces from southern and northern Italy. We found an excess cancer risk in subjects in the third and fourth (highest) quartiles of toenail cadmium concentration (odds ratio 1.3 and 4.7, respectively) compared with subjects in the bottom quartile. Results were basically unchanged when limiting the analysis to each province or entering toenail cadmium concentrations as continuous values in the regression model (P=0.004). Despite the limited statistical stability of the point estimates, these findings appear to support the hypothesis that cadmium exposure increases prostate cancer risk. 相似文献
This paper presents an automated algorithm to determine DNA fragment size from atomic force microscope images and to extract the molecular profiles. The sizing of DNA fragments is a widely used procedure for investigating the physical properties of individual or protein-bound DNA molecules. Several atomic force microscope (AFM) real and computer-generated images were tested for different pixel and fragment sizes and for different background noises. The automated approach minimizes processing time with respect to manual and semi-automated DNA sizing. Moreover, the DNA molecule profile recognition can be used to perform further structural analysis. For computer-generated images, the root mean square error incurred by the automated algorithm in the length estimation is 0.6% for a 7.8 nm image pixel size and 0.34% for a 3.9 nm image pixel size. For AFM real images we obtain a distribution of lengths with a standard deviation of 2.3% of mean and a measured average length very close to the real one, with an error around 0.33%. 相似文献
The colossal magnetoresistance (CMR) manganese oxides, have been the subject of intense studies. To elucidate the mechanisms at work in the ferromagnetic metallic state is essential for the comprehension of the M–I transition and the associated CMR effect. We present here comparison among resistivities behavior in Ca and Sr-doped manganite films (x = 0.3) grown by different techniques and on several substrates allowing to analyze samples with different amounts of disorder. At low temperatures, a dominant T2 term in the resistivity has generally been observed. Our analysis shows that for residual resistivity values larger than a critical one, there is a substantial deviation from the T2-like behavior and that an unusual T2.5 one is robust. This behavior supports the theoretical proposal of single magnon scattering in the presence of minority spin states localized by the disorder. In the high temperature insulating paramagnetic phase the resistivity shows the activated behavior characteristic of polaronic carriers. Finally in the whole range of temperatures the experimental data are found to be consistent with a phase separation scenario. 相似文献
Many group-living animals construct transportation networks of trails, galleries and burrows by modifying the environment to facilitate faster, safer or more efficient movement. Animal transportation networks can have direct influences on the fitness of individuals, whereas the shape and structure of transportation networks can influence community dynamics by facilitating contacts between different individuals and species. In this review, we discuss three key areas in the study of animal transportation networks: the topological properties of networks, network morphogenesis and growth, and the behaviour of network users. We present a brief primer on elements of network theory, and then discuss the different ways in which animal groups deal with the fundamental trade-off between the competing network properties of travel efficiency, robustness and infrastructure cost. We consider how the behaviour of network users can impact network efficiency, and call for studies that integrate both network topology and user behaviour. We finish with a prospectus for future research. 相似文献
The analysis of the SCGT (Semi-Closed Gas Turbine cycle) is extended to the treatment of acid condensation (sulphur compounds) at the exit of the separator (SEP), with reference to different possible configurations already studied from the thermodynamic and environmental points of view. This detailed analysis was considered necessary because the natural gas fuel can contain a small amount of H2S which, reacting with air, can form SO2 and finally sulphuric acid. This can represent a problem (mainly from the economic point of view) because of the possibility of sulphuric acid condensation at the exit of the separator, where the temperature can reach values below the acid dew point of the mixture.
The data obtained from ENI publications were used for the natural gas composition, and a 0.005% H2S molar fraction was additionally hypothesized. With these assumptions, about 0.1% SO2 can be found in the exhaust gases at the separator inlet.
Aspen Plus was used in order to evaluate the chemical effects of the acidity of the condensate produced in the separator. An evaluation about costs of the devices to be used for condensation of the recirculated flue gas humidity has been performed, considering use of the special materials necessary for reducing the aggressive effects of acid water condensation.
A final evaluation of the overall conversion system plant is also produced, showing the economic balance in terms of resulting cost of the unit of electrical energy produced and of inlet power in terms of fuel.
The results are also evaluated in terms of CO2 emissions, considering the ratio between the global cost of the power generation plant and the global carbon dioxide emissions, compared to other types of energy conversion open cycle solutions. 相似文献
We investigated the predictors of the rate of glomerular filtration rate decline (delta GFR) and progression to end-stage renal failure (ESRF) in the 352 patients with proteinuric non-diabetic chronic nephropathies [urinary protein excretion rate (UProt) > or = 1 g/24 hr, creatinine clearance 20 to 70 ml/min/1.73 m2] enrolled in the Ramipril Efficacy In Nephropathy (REIN) study. Overall the GFR declined linearly by 0.46 +/- 0.05 ml/min/1.73 m2/month (mean rate +/- SEM) over a median follow-up of 23 months (range 3 to 64 months), and progression to ESRF was 17.3%. Using multivariate analysis, higher UProt and mean arterial pressure (MAP) independently correlated with a faster delta GFR (P = 0.0001 and P = 0.0002, respectively) and progression to ESRF (P = 0.0001 and P = 0.003, respectively). Mean UProt and systolic blood pressure during follow-up were the only time-dependent covariates that significantly correlated with delta GFR (P = 0.005 and P = 0.003, respectively) and ESRF (P = 0.006 and P = 0.0001, respectively). After stratification for baseline UProt, patients in the lowest tertile (UProt < 1.9 g/24 hr) had the slowest delta GFR (0.16 +/- 0.07 ml/min/1.73 m2/month) and progression to ESRF (4.3%) as compared with patients in the middle tertile (UProt 2.0 to 3.8 g/24hr; delta GFR, 0.55 +/- 0.09 ml/min/1.73 m2/month, P = 0.0002; ESRF, 15.3%, P = 0.0001) and in the highest tertile (UProt 3.9 to 18.8 g/24 hr; delta GFR, 0.70 +/- 0.11 ml/min/1.73 m2/month, P = 0.0001; ESRF, 32.5%, P = 0.0001). Both delta GFR (P = 0.01) and progression to ESRF (P = 0.01) significantly differed even between the middle and the highest tertiles. On the contrary, stratification in tertiles of baseline MAP failed to segregate subgroups of patients into different risk levels. Patients with the highest proteinuria and blood pressure were those with the fastest progression (delta GFR, 0.91 +/- 0.23; ESRF 34.7%). Of interest, at each level of baseline MAP, a higher proteinuria was associated with a faster delta GFR and progression to ESRF. On the other hand, at each level of proteinuria, a faster delta GFR was associated with MAP only in the highest tertile (> 112 mm Hg) and the risk of ESRF was independent of the MAP. Thus, in chronic nephropathies proteinuria is the best independent predictor of both disease progression and ESRF. Arterial hypertension may contribute to the acceleration of renal injury associated with enhanced traffic of plasma proteins. Antihypertensive drugs that most effectively limit protein traffic at comparable levels of blood pressure are those that most effectively slow disease progression and delay or prevent ESRF in proteinuric chronic nephropathies. 相似文献
Nickel alloy matrix/dispersed carbide (VC, NbC, WC) composites were prepared by either flame-spray, liquid phase sintering, or solid state sintering. A commercial Ni-B-Si alloy was mixed with 15% vol. of carbide particles and used to prepare composite coatings by flame-spray, bulk composite materials by solid state sintering (below 1045°C) or liquid phase sintering (above 1050°C). Phase characterization was performed by X-ray diffraction, optical microscopy, scanning electron microscopy and X-ray fluorescence in energy and wavelength dispersive spectroscopy modes. Similar microstructural features were produced by thermal spray and liquid phase sintering: a Ni-rich matrix and a boron-rich intergranular phase. Sintered samples showed higher wear resistance than the coatings obtained by flame spraying. In both cases the wear mechanism is dominated by the plastic flow of the Ni-rich ductile matrix and the fracture of a boron-rich intergranular phase, the latter serving as a retainer. Carbide removal was observed for solid state sintered samples. 相似文献