Leptin is a physiologically important regulator of food intake

OBJECTIVE: These studies were designed to test the hypothesis that endogenous leptin, acting within the brain plays a physiologically important role in the control of food intake in lean rats. DESIGN: Antibodies directed against mouse leptin were raised in rabbits. The purified IgG fractions prepared from pre-immune and immune sera were injected into the right lateral ventricle of lean Sprague-Dawley rats and obese Zucker fatty fa/fa rats. Changes in food intake were measured over the following 20 h period. RESULTS: The anti-leptin antibodies recognized a major epitope in the C-terminal region of the leptin molecule. The antibodies bound both mouse and rat leptin with high affinity, but did not bind human leptin, or a selected range of other hormones and neurotransmitters known to affect food intake. In competition studies, the binding of mouse, but not human leptin to the human Ob-Rb receptor was prevented by the antibodies. This indicates that the antibodies can block the action of leptin by preventing its binding to the ob-Rb receptor. Injection of the anti-leptin antibodies into the brain of lean rats led to an increase in food intake during the first hour after injection which was not compensated during the following 19 h period. Injection of the anti-leptin antibodies did not affect food intake in Zucker fatty fa/fa rats which express an abnormal ob-Rb receptor. CONCLUSION: Endogenous leptin acting within the brain plays a physiologically important role in the control of food intake in lean rats.     

Integration of high- and low-resolution satellite data to estimate pine forest productivity in a Mediterranean coastal area

The estimation of vegetation primary productivity is particularly important in fragile Mediterranean environments that are vulnerable to both natural and human-induced perturbations. The current work was aimed at using remotely sensed data taken by various sensors to infer information about a protected coastal pine forest in Tuscany (Central Italy), which could serve for driving a simplified model of carbon fluxes, C-Fix. Being based on the direct relationship between normalized difference vegetation index (NDVI) and fraction of absorbed photosynthetically active radiation (FAPAR), C-Fix uses satellite and standard meteorological data to simulate gross (GPP) and net (NPP) primary productivity of forest ecosystems. Due to the limited size of the study area, a major difficulty was in creating an NDVI dataset with suitable spatial and temporal resolutions, which was essential for the model functioning. To reach this objective, eight Thematic Mapper (TM)/Enhanced Thematic Mapper Plus (ETM+) images of two years (2000 and 2001) were merged to low-resolution NDVI estimates taken by both the Advanced Very High Resolution Radiometer (AVHRR) and VEGETATION (VGT) sensors. The C-Fix outputs for representative pine forest sites were evaluated by comparison to accurate estimates derived from a model of forest ecosystem processes previously calibrated in a similar environment (Forest-BGC). This analysis showed the potential of C-Fix for rapidly estimating GPP over wide forest areas when suitable NDVI inputs are provided. In particular, a slight superiority of VGT over AVHRR data was demonstrated, which could be reasonably attributed to the relevant higher radiometric and geometric properties. The estimation of NPP was instead quite inaccurate, due to the problematic simulation of forest respiration, which should necessarily rely on more complete modeling operations.     

Use of remotely sensed and ancillary data for estimating forest gross primary productivity in Italy

The current paper describes the development and testing of a procedure which can use widely available remotely sensed and ancillary data to assess large-scale patterns of forest productivity in Italy. To reach this objective a straightforward model (C-Fix) was applied which is based on the relationship between photosynthetically active radiation absorbed by plant canopies and relevant gross primary productivity (GPP). The original C-Fix methodology was improved by using more abundant ancillary information and more efficient techniques for NDVI data processing. In particular, two extraction methods were applied to NDVI data, derived from two sensors (NOAA-AVHRR and SPOT-VGT) to feed C-Fix. The accuracy of the model outputs was assessed through comparison with annual and monthly values of forest GPP derived from eight eddy covariance flux towers. The results obtained indicated the superiority of SPOT-VGT over NOAA-AVHRR data and a higher efficiency of the more advanced NDVI extraction method. Globally, the procedure was proved to be of easy and objective implementation and allowed the evaluation of mean productivity levels of existing forests on the national scale.     

Evaluation of statistical methods to estimate forest volume in a mediterranean region

The use of three estimation methods was investigated for mapping forest volume over a complex Mediterranean region (Tuscany, central Italy). The first two methods were based on the processing of satellite images, specifically a summer Landsat Thematic Mapper scene. From this scene, information about forest volume was extracted through a nonparametric approach [k-nearest neighbor (k-NN)] and by means of locally calibrated regressions. The last method considered, kriging, instead used only the spatial autocorrelation of tree volume relying on geostatistical principles. The experiments performed demonstrated that, at the original sampling density, the three methods produced nearly equivalent accuracies. This was no more the case when reducing the sampling density to various levels. Whereas, in fact, this reduction marginally affected the performances of the two remote-sensing-based methods, it dramatically degraded that of kriging. Additionally, the investigation showed how per-pixel estimates of error variance were obtainable also by k-NN and locally calibrated regression procedures, in analogy with the same property of kriging. Such estimated error variances were utilized to optimally integrate the outputs of the methods based on remotely sensed data and spatial autocorrelation. In all cases, the integrated estimation outperformed the single procedures. These results are relevant to develop an operational strategy for mapping forest attributes in complex Mediterranean areas.     

65 nm CMOS SSB mixer for UWB synthesiser

The present work addresses the design of a 65 nm CMOS wide-band single-sideband mixer for UWB synthesiser. The circuit has been designed inductorless and with few capacitors, in order to save silicon area and, at the same time, to get a mixer independent of the adopted frequency plan and synthesiser architecture. Particular attention has been paid to reducing the spurs as much as possible. In order to address a realistic investigation, the design has accounted also for the corner cases and the possible impairments in the input signals. A comparison with the state-of-the-art of the SSB mixers shows the low power consumption of the present work.     

Use of lidar data to simulate forest net primary production

A method has been recently presented to predict the net primary production (NPP) of Mediterranean forests by integrating conventional and remote-sensing data. This method was based on the use of two models, C-Fix and BIOME-BGC, whose outputs are combined with estimates of stem volume and tree age to predict the NPP of the examined ecosystems. This article investigates the possibility of deriving these two forest attributes from airborne high-resolution lidar data. The research was carried out in the San Rossore pine forest, a test site in Central Italy where several investigations have been conducted. First, estimates of stand stem volume and tree age were obtained from lidar data by application of a simplified method based on existing literature and a few ground measurements. The accuracy of these stand attributes was assessed by comparison with the independent ground data derived from a recent forest inventory. Next, the stem volume and tree age estimates were used to drive the NPP modelling strategy, whose outputs were evaluated against the inventory measurements of current annual increment (CAI). The simplified lidar data processing method produces stand stem volume and tree age estimates having moderate accuracy, which are useful to feed the modelling strategy and predict CAI at a stand level. This method's success raises the possibility of integrating ecosystem modelling techniques and lidar data for the simulation of net forest carbon fluxes.     

Cytomegalovirus retinitis in patients with AIDS in Europe. AIDS in Europe Study Group

The incidence of cytomegalovirus (CMV) retinitis and risk factors associated with the condition were studied in patients with the acquired immune deficiency syndrome (AIDS) in a multicenter retrospective cohort study of 6458 patients from 52 centers in 17 countries in Europe. Cytomegalovirus retinitis was diagnosed in 154 patients (2.4%) at the time of AIDS diagnosis, the probability of this diagnosis being significantly higher for those with CD4+ cell counts of < 100/mm3 (3.4%) than with counts of 100-200/mm3 (1.3%) or > 200/mm3 (0.8%). The rate of developing CMV retinitis after AIDS diagnosis was 9.4 per 100 patient years of follow-up. Multivariate analysis showed that risk behavior was significantly associated with the risk of developing CMV retinitis: lower for intravenous drug users [relative risk (RR) 0.47] and those engaged in "other risk behavior" (RR 0.58) than for homosexual men. The risk of developing CMV retinitis after AIDS diagnosis was significantly associated with CD4+ cell count at the time of AIDS diagnosis: for counts < 100/mm3 (RR 2.90) and from 100 to 200/mm3 (RR 2.13), there was a higher risk than for counts > 200/mm3. Patients with Pneumocystis carinii pneumonia, toxoplasmosis, or extraocular CMV infection at time of AIDS diagnosis exhibited an increased risk of developing CMV retinitis. Patients treated with zidovudine exhibited an increased rate of CMV retinitis: RR was 1.75 during and 2.87 after the second year of treatment as compared to those who had not received zidovudine. Median survival after CMV retinitis at time of AIDS diagnosis was eight months.     

High Load Ratio Fatigue Strength and Mean Stress Evolution of Quenched and Tempered 42CrMo4 Steel

The fatigue strength at a high number of cycles with initial elastic–plastic behavior was experimentally investigated on quenched and tempered 42CrMo4 steel. Fatigue tests on unnotched specimens were performed both under load and strain controls, by imposing various levels of amplitude and with several high load ratios. Different ratcheting and relaxation trends, with significant effects on fatigue, are observed and discussed, and then reported in the Haigh diagram, highlighting a clear correlation with the Smith–Watson–Topper model. High load ratio tests were also conducted on notched specimens with C (blunt) and V (sharp) geometries. A Chaboche model with three parameter couples was proposed by fitting plain specimen cyclic and relaxation tests, and then finite element analyses were performed to simulate the notched specimen test results. A significant stress relaxation at the notch root became clearly evident by reporting the numerical results in the Haigh diagram, thus explaining the low mean stress sensitivity of the notched specimens.     

Chopping of a weak magnetic field by a saturable magnetic shield

A method for measuring a weak magnetic field with a Hall sensor is described. This method consists of chopping the magnetic field to be measured with a magnetic shield surrounding the Hall sensor. The magnetic shield is periodically driven into saturation by means of an excitation coil. Thus, the Hall device is alternately exposed to/shielded from the d.c. or slowly varying external field to be measured. During the time intervals when the magnetic shield is saturated, the external field passes and is detected by the Hall sensor. When it is not saturated the Hall sensor is shielded from the external field. This chopping method yields a magnetic measurement unaffected by 1/ƒ noise and offset errors of the Hall sensor, therefore improving its detectivity.