Water-assisted sub-critical crack growth along an interface between polyimide passivation and epoxy underfill

Direct chip attach (DCA) microelectronic packaging technology is gaining prominence due to its numerous advantages. Delamination (debonding) of the underfill epoxy/ polyimide passivation interface of a DCA during hydro-thermal reliability testing has always been one of the salient problems. We have studied the water-assisted sub-critical crack growth along this interface and our measurement offers important clues as to the origins of the poor hydro-thermal testing results for these interfaces. A modified asymmetric double cantilever beam (ADCB) testing technique has been used to measure the sub-critical crack growth velocity v at various relative humidities and temperatures as a function of the crack driving force (strain energy release rate) G ^*. The presence of a significant partial pressure of water p _H2O produces a marked decrease (by up to a factor of 12) in the threshold G ^* for crack growth at measurable velocities. Above the threshold log v rises linearly with but then enters a regime where the crack velocity (v=v ^*) is almost independent of . Finally, at the values of G ^* corresponding to rapid crack propagation in the absence of water, log v increases very rapidly with G ^*. By analogy to the classic work on water-assisted sub-critical crack growth in silica-based glasses, where very similar features are observed, we believe that the sub-critical crack growth along the polyimide-epoxy interface results from stress-assisted hydrolysis of primary covalent bonds, in our case ester bonds across the interface. The regime of just above the threshold corresponds to a physicochemical situation where the water activity (p _{H 2O} ) at the crack tip is the same as that of the gaseous environment. In the regime where v=v ^* constant, the water activity at the crack tip is below that in the environment and the crack growth velocity is limited by the transport of water vapor to the bonds ahead of the crack tip. We develop a model of this crack growth following Wiederhorn 1967 that allows us to predict the sub-critical crack growth as a function of G ^* for arbitrary relative humidity and temperature conditions.     

Tumor-Localized Administration of α-GalCer to Recruit Invariant Natural Killer T Cells and Enhance Their Antitumor Activity against Solid Tumors

Invariant natural killer T (iNKT) cells have the capacity to mount potent anti-tumor reactivity and have therefore become a focus in the development of cell-based immunotherapy. iNKT cells attack tumor cells using multiple mechanisms with a high efficacy; however, their clinical application has been limited because of their low numbers in cancer patients and difficulties in infiltrating solid tumors. In this study, we aimed to overcome these critical limitations by using α-GalCer, a synthetic glycolipid ligand specifically activating iNKT cells, to recruit iNKT to solid tumors. By adoptively transferring human iNKT cells into tumor-bearing humanized NSG mice and administering a single dose of tumor-localized α-GalCer, we demonstrated the rapid recruitment of human iNKT cells into solid tumors in as little as one day and a significantly enhanced tumor killing ability. Using firefly luciferase-labeled iNKT cells, we monitored the tissue biodistribution and pharmacokinetics/pharmacodynamics (PK/PD) of human iNKT cells in tumor-bearing NSG mice. Collectively, these preclinical studies demonstrate the promise of an αGC-driven iNKT cell-based immunotherapy to target solid tumors with higher efficacy and precision.     

SUPERCRITICAL EXTRACTION OF ISRAELI MISHOR ROTEM OIL SHALE 1. BATCH EXTRACTION WITH TOLUENE

ABSTRACT

Recovery of organic material from Israeli Mishor Rotem oil shale with toluene under supercritical conditions was investigated. The rate of solubilization, change of structural aspects and molecular weights of solubilized products with time were investigated. Experiments to recover organic material from shale were performed in a stainless steel high pressure autoclave. Shale Sample was charged in a sintered glass crucible suspended from the cap of the autoclave; toluene was the solvent in all experiments. Solvent/shale ratio was 20; experimental temperature was 34O^°C. The gaseous products were analyzed by gas chromatography. Molecular weights of the organic material recovered was measured by gel permeation chromatography technique. FTIR spectra of the organic material recovered and fractions isolated by extractive and chromatographical methods were measured. The amount of kerogen remaining in the spent shale was determined by oxidative derivative thermal gravimetry. A steady state in the production of solubles was reached within 60 minutes at 340^°C with a yield of 60 percent. After this time no further amounts of organic material was recovered. The molecular weights of the recovered organic material decreased at extended times after the steady state was reached. It appeared that the structure of the organic material recovered remained unchanged until the steady state condition is reached whereupon some structural changes occurred. At extended times the organic material was converted into more aromatic and less hydroxyl containing structures of lower molecular weight. The organic material recovered upon reaching steady state was fractionated into 63 percent oils (pentane solubles) and 32 percent asphaltenes (toluene solubles). The oile contained aliphatics and monoaromatic structures and the asphaltenes contained polyaromatic polar structures. Gases which constituted 4 percent of the initial kerogen were produced during the heating period to 340^°C. The amount of carbon monoxide produced remained constant and amounts of hydrogen, carbon dioxide and methane decreased after supercritical conditions were attained.     

A finite element formulation to model the flow of flotation foams

In this paper, a numerical model for the flow of foams in flotation cells in up to three dimensions is described. By using finite elements to solve Laplace's equation for a potential scalar, the flow pattern and velocity of the foam can be obtained. This has allowed, for the first time, the carrying out of numerical investigations of foam flow patterns regardless of the symmetry of the system. The numerical model has been implemented in Fluidity, a general purpose finite element method code that allows simulations to be carried out on anisotropic unstructured meshes. Such a model is of particular interest since other phenomena occurring in flotation depend on the foam velocity. Convergence tests that verify the numerical model are presented, and simulation results that showcase important features of the present implementation are discussed.     

钻进了野区的路西法

大家在筛选录像的时候会发现，每一场DOTA2比赛都有自己的等级，分为普通、高、非常高三种。比赛的等级是由每个人的Matchmarkingranking数值所决定的，我们简称其为MMR值，与天梯积分有点像。