The effect of external vorticity on stagnation-point heat transfer at high prandtl number

The strong sensitivity of stagnation-point heat transfer to the presence of free-stream turbulence has been attributed to vorticity amplification by stretching of vortex filaments. A mathematical model proposed by Sutera, Maeder and Kestin is examined for the case of very high Prandtl number (Pr). Asymptotic solutions are obtained for the limit Pr → ∞. These show that the heat-transfer sensitivity continues to increase with Prandtl number. Approximately 95 per cent of the asymptotic value of the stagnation-point heat-transfer coefficient is attained at Pr = 100.     

Implementation of a third-generation 1.1-GHz 64-bit microprocessor

This third-generation 1.1-GHz 64-bit UltraSPARC microprocessor provides 1-MB on-chip level-2 cache, 4-Gb/s off chip memory bandwidth, and a new 200 MHz JBus interface that supports one to four processors. The 87.5-million transistor chip is implemented in a seven-layer-metal copper 0.13-/spl mu/m CMOS process and dissipates 53 W at 1.3 V and 1.1 GHz.     

Fifty Years of Precipitation: Some Spatially Remote Teleconnnections

In the present paper the authors analyse the drought occurrence over the European region by using the NCEP/NCAR reanalysis precipitation rates covering the period from 1948 to 2000. The drought assessment is based on the Standardized Precipitation Index (SPI), which has been proposed as an indicator of drought condition. At variance with other fields derived from precipitation, the SPI is, by construction, a Gaussian field. Thus, the understanding of its covariance structure exhausts the study of the associated density distribution. A method allowing a factorisation of a multivariate Gaussian distribution is the one known as Principal Component Analysis (PCA) or Kauman-Loeve decomposition. Therefore, a PCA is used to study the main spatial patterns and the time variability of drought first over Europe and then over the Northern Hemisphere. The analysis reveals a downward trend for the index over most of central Europe and the Mediterraneanbasin, implying an overall decrease of precipitation in the above mentioned regions. Moreover, the scores associated with the PCA covariance decomposition, besides the aforementioned trend, show few long-term periodicities.Similar drought analyses have been performed by considering the Palmer Drought Severity Index (PDSI).A preliminary comparison between the SPI and PDSI obtained by using the previously discussed data set is presented. It is shown that the indices compare favourably in assessing drought variability. Finally, when the SPI analysis is extended to the Northern Hemisphere some interesting spatially remote teleconnnections linking the Tropical Pacific with the European area are shown.     

Erythroid Induction of Chronic Myelogenous Leukemia K562 Cells Following Treatment with a Photoproduct Derived from the UV‐A Irradiation of 5‐Methoxypsoralen

Induction of terminal erythroid differentiation can be an efficient strategy to inhibit proliferation of chronic myelogenous leukemia cells. Psoralens, well‐known photo‐chemotherapeutic agents, were found to be efficient at inducing erythroid differentiation of K562 cells, an in vitro cell line isolated from the pleural effusion of a patient with chronic myelogenous leukemia in blast crisis. The effects of crude pre‐irradiated solutions of 5‐methoxypsoralen on erythroid differentiation of human leukemic K‐562 cells were evaluated. The major photoproduct was characterized and analyzed, and it was found to induce erythroid differentiation of K562 cells and inhibit NF‐κB/DNA interactions.     

Rheoscopic investigation of red cell deformability in sickle cell anemia

Adequate erythrocyte deformability is crucial to microvascular function. In sickle cell anemia, a significant fraction of the circulating red cells lose deformability and assume highly abnormal shapes when exposed to low plasma oxygen tension (PO2). The loss of deformability is believed to induce blockage of flow in capillaries with consequent painful crisis or organ infarcts. The deformability of sickle erythrocytes at graded levels of PO2 were investigated in the rheoscope, a viscometric device consisting of transparent counter-rotating cone and plate. Quantitative indices of deformability obtained from still photographs and videotape recordings of cells subjected to shear flow were: fraction of all suspended cells capable of deformation, steady-state elongation, and time course of transient shape recovery following abrupt flow cessation. Suspensions of unfractionated cells were first equilibrated against gas mixtures (O2, N2, CO2) with PO2 = 160, 40 or 20 mm Hg at room temperature and then sheared under the same atmosphere. Results obtained with blood samples from ten pediatric patients being treated at St. Louis Children's Hospital show strong donor-to-donor variations and significant impairment of deformability in the unsickled members of the cell populations relative to normal controls.     

Aloin delivery on buccal mucosa: ex vivo studies and design of a new locoregional dosing system

Context: Chemoprevention of potential malignant disorders or cancerous lesions that affect oral mucosae requires extended duration of treatment. Locoregional delivery of natural products could represent a promising strategy for this purpose.

Objective: To investigate the aptitude of aloin to permeate through, or accumulate in, the buccal mucosa and to develop a new prolonged oro-mucosal drug delivery system.

Materials and methods: Permeation/accumulation of aloin from Curacao Aloe (containing 50% barbaloin) was evaluated ex vivo, using porcine buccal mucosa as the most useful model to simulate human epithelium. Oro-mucosal matrix tablets were prepared by dispersing aloin (10% w/w) in Eudragit® RS 100 as, biocompatible, low permeable, pH-independent, and non-swelling polymer. The prepared tablets were evaluated for drug–polymer compatibility, weight variation, drug uniformity content, diameter, thickness, hardness, friability, swelling, mucoadhesive strength, and drug release.

Results: Aloin has low tendency to cross buccal mucosa, permeation is marginal, and high drug amounts remain entrapped into the epithelium. Matrix tablets characteristics were in agreement with pharmacopoeial requirements. Drug release showed highly reproducible Higuchian profile. Delivery through matrix tablets promoted drug accumulation in the mucosal tissue.

Discussion and conclusion: Following application of matrix tablets on porcine buccal mucosa, the amount of discharged drug recovered in the tissue should be sufficient to produce the desired effects, providing therapeutic drug levels directly at the site of action. Aloin-loaded tablets are valid candidates for prevention/treatment of potentially malignant disorders and oral cancer and could potentially lead to clinically relevant drug delivery system as coadjuvant of conventional chemotherapy/radiation therapy.     

Large-Scale Assessment of Drought Variability Based on NCEP/NCAR and ERA-40 Re-Analyses

The impacts of different spatial resolutions and different data assimilation schemes of the available re-analysis data sets (NCEP/NCAR and ERA-40) on the assessment of drought variability are analysed. Particular attention has been devoted to the analysis of the possible existence of a linear trend in the climatic signal. The long-term aspects of drought over the globe during the last forty years have been evaluated by computing the Standardized Precipitation Index (SPI) on 24-month time scale. The SPI, in fact, seems to be a useful tool for monitoring dry and wet periods on multiple time scales and comparing climatic conditions of areas governed by different hydrological regimes. To unveil possible discrepancies between the analyses carried out with the two data sets, we studied the leading space-time variability of drought by applying the principal component analysis (PCA) to the SPI time series. Results suggest that on the global scale, the two re-analyses agree in their first principal component score, but not in the associated loading: both re-analyses capture a linear trend, though the areas where this feature should be most likely observed are not uniquely identified by the two data sets. Moreover, while the ERA-40 unveils the presence of a weak net “global” trend towards wet conditions, the NCEP/NCAR re-analysis suggests that the areas in the world characterised by positive/negative trends balance to zero. At large regional scale, a good agreement of the results with those obtained from the observations are found for the United Stated, while for the European sector the two re-analyses show remarkable differences both in the first loading and in representing the timing of the wet and dry periods. Also for these areas a linear trend, superposed on other short-term fluctuations, is detectable in the first principal component of the SPI field.     

Spatial Variability of Drought: An Analysis of the SPI in Sicily

An analysis of drought in Sicily from 1926 to 1996 is presented.In identifying drought over the region, both the NCEP/NCARreanalysis precipitation data and those observed in 43 gauges,located quite uniformly over the territory of the Island, areused. Drought occurrence is estimated by means of theStandardized Precipitation Index (SPI). To study long-termdrought variability, a Principal Component Analysis was appliedto the SPI field.Results suggest that the entire Island is characterised by adrought variability with a multi-year fluctuations and atendency towards drier periods from the seventies onward. Apreliminary comparison between results obtained using themeteorological large-scale analysis and that derived from actualobservations on the ground shows a general good agreement,although further efforts are needed to get a better downscalingof the large-scale precipitation fields. Furthermore, byapplying orthogonal rotations to the principal componentpatterns, it has been found that three distinct areas havingcoherent climatic variability may be identified.Finally, the sensitivity of the SPI values on the calibrationperiod is also investigated.