Synthesis and photoluminescence of bright water-soluble CdSe/ZnS quantum dots overcoated by hybrid organic shell

Photoluminescence properties from water soluble CdSe/ZnS QDs encapsulated with hybrid trioctylphosphine-poly(acrylamide-co-acrylic acid)-ethanolamine (TOPO-PSMA-EA) shell have been investigated. It was found that PL efficiency of CdSe/ZnS QDs in water was increased 5–30% after introducing PSMA-EA polymers to encapsulate CdSe/ZnS-TOPO QDs. Higher PSMA concentrations were found to enhance the PL efficiency of QDs up to 1.8 folds, which is ascribed to a better packing and passivation of the TOPO-PSMA-EA shell over the QDs. Time-resolved photoluminescence suggested that the mean lifetime of photoexcited carriers in the water-soluble CdSe/ZnS-TOPO-PSMA-EA QDs elongated 2–17 ns compared with that of uncoated samples, indicating that PL quenching defects were effectively removed for CdSe/ZnS QDs with hybrid TOPO-PSMA-EA shell.     

Detection of surface antigens on living cells through incorporation of immunorecognition into the distinct positioning of cells with positive and negative dielectrophoresis

Rapid determination of surface antigens on cells is possible by immobilization of cells accumulated by positive dielectrophoresis (p-DEP) via effective surface immunoreactions and removal of unbound cells by negative DEP (n-DEP). The DEP device for cell manipulation comprises a microfluidic channel with an upper indium tin oxide (ITO) electrode and a lower ITO microband array electrode (band electrode) modified with an antibody. Cells with the surface antigen introduced into the channel immediately accumulated on the surface of the band electrode during p-DEP generated by the application of ac voltage between the ITO electrode and the band electrode to immobilize by the specific antibody. The removal of accumulated cells to the gap region during n-DEP was used for rapid estimation of the residual cells with a specific surface antigen. We demonstrate here that human promyelocytic leukemia cells with the surface antigen CD33 can be captured on a band electrode modified with anti-CD33 antibody. The time required for the determination of the surface antigen using this compelled accumulation of cells by p-DEP and the separation of unbound cells by n-DEP is decreased to 60 s compared to that required by a cell binding assay using microtiter plates (30 min). Furthermore, the present method for a novel cell binding assay does not require pretreatment such as target labeling or washing of unbound cells and thereby enhancing throughput in the clinic and in cytobiology studies.     

Primary spinal leptomeningeal gliomatosis presenting visual disturbance as the initial symptom: case report

We report a case of diffuse leptomeningeal gliomatosis which spread from the cervical to the sacral spine. A 60-year-old man was admitted with visual disturbance due to papilledema. Magnetic resonance imaging revealed holocord leptomeningeal gliomatosis without a definite intraparenchymal lesion, and the patient's neurological examination was unremarkable except for papilledema. Intracranial hypertension secondary to spinal tumor is well known but unusual, and the mechanism is still unclear. In our case, an elevated protein concentration of cerebrospinal fluid is suggested as the cause of intracranial hypertension.     

Digitalized Cross-Polarization Interference Canceller for Multilevel Digital Radio

This paper proposes a newly developed, highly precise cross-polarization interference canceller (XPIC), utilizing digitalized transversal filters. Performance of the digitalized XPIC is solely determined by quantization and tap numbers and is not affected by any circuit imperfection. Moreover, it can be universally applied to different bit rates and various modulation schemes. Performance of the XPIC is analytically estimated for various modulation schemes and various interference conditions. Then, the digitalized XPIC is realized and applied to a 12.5 MB 256 QAM digital radio system. Experimental results have closely conformed with theoretical estimations and it is confirmed that the XPIC is a powerful countermeasure against multipath fading for a future digital radio.     

Crystalline products and their formation mechanism in thermal hydrolysis of ZrOSO4 solution

Solid products were prepared from mixtures of zirconyl carbonate and sulphuric acid solution under thermal hydrolysis at 240°C. These crystalline products and their formation mechanism were investigated by evaluating the amount of products, and by X-ray diffraction analysis and TEM observation. The solid products precipitated were zirconium oxide sulphates (ZOS, PZOS, ZrOSO₄·H₂O) and m-ZrO₂. The area and thickness of the fine plate-like crystals of ZOS increased with increasing concentration of the solution and hydrothermal treatment time. For thin starting solutions, the precipitation velocity and the amount of PZOS increased. For thick starting solutions, those of ZOS increased. For 0.5 mol/l^–1 ZrOSO₄ solution (ZS0.5) from the thin solution, PZOS crystallized early and m-ZrO₂ crystallized by releasing sulphuric acid ions in PZOS with treatment time. For ZS2.5 from the thick solution, ZrOSO₄·H₂O was crystallized by increasing the proportion of sulphuric acid ions to zirconium ions in the solution, which was caused by ZOS precipitation.     

A call admission control scheme for ATM networks using a simplequality estimate

The authors propose a call admission control scheme based on a method of estimating cell loss quality for individual bursty traffic sources. The estimate is expressed in terms of virtual cell loss probability, which may be defined by two traffic characteristic parameters alone: peak and mean rate. The approach is suitable for the estimation of real cell loss probability in heterogeneous and homogeneous traffic models when burst length is larger than buffer capacity. The concept of virtual cell loss probability is extended to the individual call level so as to be able to estimate the quality of service (QOS) provided to individual calls. A virtual bandwidth method is used to develop a practical call admission control system. Quality is ensured by combining a traffic clustering scheme, with a scheme for assigning individual clusters to subcapacities of a link. Priority levels are presented in terms of the class of QOS required, i.e., deterministic or statistical, and the allocation of virtual bandwidth is discussed in terms of both QOS class and traffic characteristics     

Transport properties of porous media from the microgeometry of a three-dimensional voronoi network

In this work a way of calculating effective transport coefficients from the microgeometry of a porous medium is presented. The model material consists of a random packing of uniform spheres, and by applying the Voronoi—Delaunay tessellation technique the void between the spheres is simulated as a network of cylindrical pores. The tessellation yields all the necessary information for the structural characterization, such as the pore diameter, pore angle and pore length distribution functions and the topological interconnection. The effective transport coefficients of ordinary diffusion, Knudsen flow and viscous flow are calculated numerically by mass balancing at each network node and over all nodes of the system. The results obtained agree very well with the experimental ones, especially for ordinary diffusion. For Knudsen and viscous flow, inaccuracies in the estimation of the pore overlapping volume cause a relative error between the numerical and experimental results of the order of 16%–33%.     

Dynamic cardiac compression improves contractile efficiency of the heart

The effect of dynamic cardiac compression on left ventricular contractile efficiency was assessed in terms of the pressure-volume relationship and myocardial oxygen consumption. In 11 excised cross-circulated dog hearts, the ventricle was directly compressed during systole (dynamic cardiac compression). Measurements for pressure-volume area (a measure of total mechanical energy), external work, and myocardial oxygen consumption were done before and during dynamic cardiac compression. Dynamic cardiac compression increased pressure-volume area by 28% +/- 17% (mean plus or minus the standard deviation) and external work by 24% +/- 20% (p = 0.0000185 and 0.0000212, respectively) at given end-diastolic and stroke volumes without affecting myocardial oxygen consumption. As a result, the oxygen cost of pressure-volume area, that is, the slope of the myocardial oxygen consumption-pressure-volume area relationship, significantly decreased by 16% +/- 13% (p = 0.0000135) whereas the pressure-volume area-independent myocardial oxygen consumption was unchanged. Then, contractile efficiency, that is, the reciprocal of the slope of the myocardial oxygen consumption-pressure-volume area relationship in joules significantly improved from 45% +/- 8% to 53% +/- 13% (p = 0.0000437). When the native myocardial oxygen consumption-pressure-volume area relationship was assessed by subtracting the dynamic cardiac compression pressure applied to the heart, the slope of the myocardial oxygen comsumption-pressure-volume area relationship returned to the control level. This indicates that the contractile efficiency of the native heart was not affected by dynamic cardiac compression. We conclude that dynamic cardiac compression enhances left ventricular pump function by improving the contractile efficiency of the overall heart leaving the energetics of the native heart unchanged.     

Wide variations of plasma triglyceride concentrations in guinea pigs

Guinea pigs have varying plasma triglyceride concentrations ranging from 28 to 1392 mg/dl, with relatively uniform plasma cholesterol and phospholipid levels. To understand why the animals exhibit such wide variations of plasma triglyceride concentrations, we have explored the triglyceride hydrolyzing system by measuring tissue lipoprotein lipase activities and plasma activator for the enzyme. Lipoprotein lipase activities of epididymal adipose tissue of these animals were 759±117 (mean±SE) n moles FFA·min⁻¹·g wet tissue⁻¹, markedly low compared with those of rats. There were no relationships between plasma triglyceride concentrations and tissue lipase activities. Plasma activator for lipoprotein lipase was lacking in this animal. Guinea pigs with ascorbic acid deficiency for 2 weeks also showed marked variations of plasma triglyceride concentrations, without any changes in tissue lipoprotein lipase activities. Low adipose tissue lipoprotein lipase activities with deficient plasma activator for the enzyme suggest that the lipoprotein lipase-mediated triglyceride degradation could be impaired in this animal, and this may account for the marked variation of plasma triglyceride concentrations.