Identification of extractable growth factors from small intestinal submucosa

When implanted as a biomaterial for tissue replacement, selected submucosal layers of porcine small intestine induce site-specific tissue remodeling. Small intestinal submucosa (SIS), as isolated, is primarily an acellular extracellular matrix material. In an attempt to discover the components of small intestinal submucosa which are able to induce this tissue remodeling, the material was extracted and extracts were tested for the ability to stimulate Swiss 3T3 fibroblasts to synthesize DNA and proliferate. Each of the four different extracts of small intestinal submucosa had measurable cell-stimulating activity when analyzed in both a whole cell proliferation assay (alamarBlue dye reduction) and a DNA synthesis assay ([3H]-thymidine incorporation). Proteins extracted from SIS with 2 M urea induced activity profiles in the two assays which were very similar to the activity profiles of basic fibroblast growth factor (FGF-2) in the assays. As well, the changes in cell morphology in response to the extracted proteins mimicked the changes induced by FGF-2. Neutralization experiments with specific antibodies to this growth factor confirmed the presence of FGF-2 and indicated that it was responsible for 60% of the fibroblast-stimulating activity of the urea extract of small intestinal submucosa. Western blot analysis with a monoclonal antibody specific for FGF-2 detected a reactive doublet at approximately 19 kDa and further confirmed the presence of FGF-2. Cell stimulating activity of proteins extracted from SIS with 4 M guanidine was neutralized by an antibody specific for transforming growth factor beta (TGF beta). Changes in the morphology of the fibroblasts exposed to this extract were nearly identical to changes induced by TGF beta. Although no reactive protein band was detected at 25 kDa in nonreduced western blot analysis, several bands were reactive at higher molecular weight. The identity of this TGF beta-related component of small intestinal submucosa is unknown. Identification of FGF-2 and TGF beta-related activities in SIS, two growth factors known to significantly affect critical processes of tissue development and differentiation, provides the opportunity to further elucidate the mechanisms by which this extracellular matrix biomaterial modulates wound healing and tissue remodeling.     

On the detection of motion and the computation of optical flow

A method for the detection of motion in image sequences is presented. In this method, the intensity history at each pixel is convolved with the second derivative in time of a temporal Gaussian smoothing function. The zero crossings in a single frame of the resulting function indicate the positions of moving edges. Intensity changes in time due to illumination effects do not produce zero crossings; thus, they are not interpreted as motion by the present method. It is also shown that the spatial and temporal derivatives of this function can be used to compute the component of the optical flow that is normal to the zero-crossing contours. This computation is also insensitive to nonconvective temporal and spatial variations in the image intensity that are caused by illumination effects     

Reliability assessment for solders with a stress buffer layer using ball shear strength test and board-level finite element analysis

The stress buffer layer (SBL) is a widely applied improvement in many advanced packages used to release the stress concentration at solder joints. However, it has been generally found that the metal line adjacent to the SBL may suffer larger deformation and its reliability should be addressed. In this study, the panel level package (PLP) technology with solder on polymer (SOP) structure is selected as the testing sample to investigate the effect of SBL. The ball shear strength test is conducted first to investigate the reliability of metal trace in PLP. In addition, finite element (FE) analysis is applied to understand the actual thermo-mechanical behavior of PLP after its assembly. The package-level and board-level reliability assessments are compared, and the suggested layout of the redistribution layer on the SBL is provided herein.     

The putative tumor suppressor gene on chromosome 5q for hepatocellular carcinoma is distinct from the MCC and APC genes

We have previously shown that the tumor suppressor gene for hepatocellular carcinoma (HCC) without cirrhosis may be located on chromosome 5q35-qter. In this study, we analyzed nine cases of primary HCC without cirrhosis using probes from the MCC and APC genes, which are in the region 5q21-22. None of the informative cases had allele loss detected by these probes, whereas the probe lambda MS8 for the region 5q35-qter showed allele loss in six out of six informative cases. The results confirm that the putative tumor suppressor gene for HCC without cirrhosis on chromosome 5q is distinct from the MCC and APC genes.     

Isolation and characterization of three Dictyostelium myosin-I isozymes

Using ion exchange chromatography and an ATP-dependent actin precipitation step, we have isolated three myosin-I isozymes that, together, account for most of the K+EDTA-ATPase activity recovered from extracts of Dictyostelium. The two major myosin-I isozymes, present in approximately equal amounts, had apparent molecular masses of 125 kDa on SDS gels and have been identified by amino acid sequence analysis as the products of the Dictyostelium myosin-IB (DMIB) and myosin-ID (DMID) genes. DMIB, with a specific K+EDTA-ATPase activity 10-fold higher than DMID, was responsible for most of the activity in cell extracts. The third isozyme, present in low amounts, had an apparent molecular mass of 137 kDa on SDS gels and is too large to be the product of any of the known myosin-I genes. DMIB eluted from DE53 cellulose columns as two distinct peaks (II and III). Addition of the phosphatase inhibitor okadaic acid to the extraction buffer increased the fraction of DMIB recovered from growth phase cells in peak III from 35 to 70%. DMIB isolated from peak III, but not from peak II, displayed a significant level of actin-activated MgATPase activity. These results indicate that peak III represents a phosphorylated, actin-activatable form of DMIB.     

Effects of hot carrier induced interface state generation insubmicron LDD MOSFET's

A two-dimensional numerical simulation including a new interface state generation model has been developed to study the performance variation of a LDD MOSFET after a dc voltage stress. The spatial distribution of hot carrier induced interface states is calculated with a breaking silicon-hydrogen bond model. Mobility degradation and reduction of conduction charge due to interface traps are considered. A 0.6 μm LDD MOSFET was fabricated. The drain current degradation and the substrate current variation after a stress were characterized to compare the simulation. A reduction of the substrate current at V_g ≃0.5 V_d in a stressed device was observed from both the measurement and the simulation. Our study reveals that the reduction is attributed to a distance between a maximum channel electric field and generated interface states     

Langmuir films from antibodies based on amphiphilic polyelectrolytes

A technique for forming Langmuir films from antibodies based on an amphiphilic polyelectrolyte was developed. The physicochemical and immunochemical properties of the Langmuir films obtained were studied. The interaction of HBsAg with the films was found to be described by a model with one binding site, whereas that of HBsAg with antibodies adsorbed on a polystyrene plate, by a model with a positive cooperativity. The use of the novel Langmuir films from antibodies increases the sensitivity of the immunoenzyme assay.     

基于媒体用户访问行为偏好模型的代理缓存算法

目前,代理缓存技术广泛应用于改善流媒体传输的服务质量.文章从实际用户日志文件的分析出发,利用发现的用户浏览流媒体对象时的行为分布模型,提出了一种新的视频流媒体缓存算法.仿真结果证明,该算法可以通过记录很少的用户访问信息获取较高的性能表现.     

Analysis of adaptive bandwidth allocation in wireless networks with multilevel degradable quality of service

A wireless/mobile network supporting multilevel quality of service (QoS) is considered. In such a network, users or applications can tolerate a certain degree of QoS degradation. Bandwidth allocation to users can, therefore, be adjusted dynamically according to the underlying network condition so as to increase bandwidth utilization and service provider's revenue. However, arbitrary QoS degradation may be unsatisfactory or unacceptable to the users, hence resulting in their subsequent defection. Instead of only focusing on bandwidth utilization or blocking/dropping probability, two new user-perceived QoS metrics, degradation ratio and upgrade/degrade frequency, are proposed. A Markov model is then provided to derive these QoS metrics. Using this model, we evaluate the effects of adaptive bandwidth allocation on user-perceived QoS and show the existence of trade offs between system performance and user-perceived QoS. We also show how to exploit adaptive bandwidth allocation to increase system utilization (for the system administrator) with controlled QoS degradation (for the users). By considering various mobility patterns, the simulation results are shown to match our analytical results, demonstrating the applicability of our analytical model to more general cases.