No description available.

No description available.

No description available.

No description available.

The preparation and physical properties of the estertin halides X 4-nSn[ (CH2)mCO2R]n, where n = 1 or 2, m = 1, 2 or 3 and R is a alkyl or aryl substituent are reported. During the course of this work the molecular structures of Cℓ3SnCH 2CH2CO2Pri and Cℓ3SnCH 2CH2CO2CO2Et were determined. The preparations of Ph3Sn(CH2)3R compounds, where R is a functional group, are reported. The reactions of these compounds with electrophiles were investigated as a route to organotin halides. Explanations on their reactivity are postulated. The preparation of Ph3Sn[CHRR'] compounds where R and R' are the same or different functional groups, from the reaction of (Ph3Sn) 2S with Hg[CHRR']2 is also reported along with the physical properties and evidence for their particular structures. Investigations into the Lewis acidity of estertin halides were undertaken. Chloride ion acceptor strengths, adduct formation with nitrogen bases and catalysis of allylic rearrangement were used as a basis for the evaluation of the Lewis acidity. Explanations are offered for the various observations made during these studies. Finally the preparations of estertin mercaptides, [Et02C(CH 2)]n Sn(SCH2CO2C8H 17)4-n, where n = 1 or 2 are reported. Comparisons of the P.V.C. stabilising ability of these estertin mercaptides were made with the commercially available octyltin tris-mercaptide. Explanations are offered for the apparent difference in stabilising ability of each of these compounds in thermally processed P.V.C. during oven testing.

Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / It is the purpose of this thesis to assemble and evaluate the art of cinephotomicrography as related to biology. Early investigators used photographic methods but did not describe them in a manner that could be used by others. The first recorded use of cinephotomicrography was made by Marey in 1894 in studying the flight of birds. Later camera-microscope combinations were employed to study fertilization and division of cells, and in observing capillary circulation. The motion picture camera is uniquely suited to automatically record microscopic phenomena, and to the slowing or accelerating of natural processes for detailed study. The Committee on Standards for Motion Pictures of Biological Material (Biological Photographers Association) has outlined the following criteria for successful cinephotomicrography: 1. The 16mm film size is preferable because of low cost and generally available projection facilities. 2. Color film is preferable to black and white when the color of the object photographed is essential to identification. 3. Sound films are valuable for historical purposes, and for recording auditory phenomena as speech, animal sounds and diagnostic sounds. Their use in teaching is limited because of the necessity of adapting films to specific classroom situations by the use of teacher commentary. 4. Excellence of a film depends on the quality of photographic teachique, presentation, adequacy of titles, and editing. 5. Subject matter must be carefully chosen. Cinephotomicrographic techniques appear to be especially valuable for use in the following circumstances: 1. Recording of life of organisms in their natural environment or showing their adaptability to unusual conditions. 2. Analysis of living processes. 3. Audience viewing of small-scale processes. 4. For demonstration of experiments. At Boston University a simple and practical method of cinephotomicrography applicable to research on the microcirculation was developed by the author during the period 1936-40. The basic instrumentation (including apochromatic objectives, compensating oculars, and a light splitting prism) has since been improved and is now widely used in research and in the preparation of teaching films. The cinephotomicrographic method has in some instances been found to be one of the best means of recording scientific data. Films can also be used to eliminate the necessity of repeating experiments, to demonstrate to a class experiments too elaborate or expensive to perform in a school laboratory, and to illustrate biological processes for the understanding of the layman. Recently several new instruments and techniques have been applied to scientific motion picture use. The stroboscopic light developed by H.E. Edgerton has made possible the analysis of extremely rapid motions. Television systems have been adapted for the study of such phenomena as transcapillary exchange in living organs. The use of television opens the possibility of sharing scientific experiments and data on a wider basis. The polar planimeter is an instrument used for the determination of the area of irregular plane surfaces. Used in conjunction with the camera and microscope this device is a reasonably accurate tool. Infra red photography is valuable in the study of disease symptoms To data this technique has been mainly applied to plants but is being adapted by the medical profession for use in animal tissues. In recent years teaching films have become an important part of most science curricula. The well known film "Hemo the Magnificent" was based on work by Fulton and Lutz at Boston University. Video tape recording and closed circuit television systems offer tremendous possibilities in the area of team teaching. Technical advances in cinephotomicroscopy are now reaching a level matching that of other areas of our technology. / 2031-01-01

Chinese is very different from alphabetical languages such as English, as there are no delimiters between Chinese words. So Chinese segmentation is an important step for most Chinese natural language processing (NLP) tasks. We propose a tightness continuum for Chinese semantic units. The construction of the continuum is based on statistical informations. Based on this continuum, sequences can be dynamically segmented, and then that information can be exploited in a number of information retrieval tasks. In order to show that our tightness continuum is useful for NLP tasks, we propose two methods to exploit the tightness continuum within IR systems. The first method refines the result of a general Chinese word segmenter. The second method embeds the tightness value into IR score functions. Experimental results show that our tightness measure is reasonable and does improve the performance of IR systems.

The withanolid compounds (Tubocapsanolide A, B, and C) were purify from Tubocapsium anomalum and shown with cell growth inhibitory property. However, the molecular mechanisms of withanolide type compounds on the cell have not been fully clarified. Tubocapsanolide A, B, and C (TA, TB, and TC) of antiproliferative activity on human colorectal adenocarcinoma cells, HT29 and HCT116, were tested and the inhibitory concentration of 50% cell viability (IC50) for these compounds was determined by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. We found that TA has the best inhibitory effect in these compounds. Therefore we utilized TA to study the mechanism of cell toxicity. The caspase 3 and PARP cleavage experiment results indicated that TA induced apoptosis was time and dose dependent. Cells with functional p53 (HCT116) are more sensitive to TA compared to the mutant p53 cells (HT29). With low dose TA treatment, HCT116 and HT29 are arrested at G1 and G2/M phase respectively. We also found that TA induced sub-G1 accumulation and reactive oxygen species (ROS) release with flow cytometry analysis. Pretreatment of N-Acetyl-L-cysteine (NAC), an antioxidant agent, can reverse the antiproliferation effect by TA. Our results indicated that TA can induce cell apoptosis and intracellular ROS generation. The ROS triggers cells damage and decreases the mitochondria membrane potential and thus induce cell apoptosis.

Abstract The effect of joint strength of PbSn and AuSn solder on temperature cycling tests in laser packages has been studied experimentally and numerically. It was found that the solder joint strength increased as temperature cycle number increased, and then became steady after 400 cycles. This is may be due to the redistribution of the residual stresses within the solder during temperature cycling test, and hence reducing the residual stresses and increasing the solder joint as the temperature cycle increased. Numerical calculations were in good agreement with the experimental measurement that the solder joint strength increased as the temperature cycle increased. In this work, we also study the intermetallic compound (IMC) growth of PbSn and AuSn solders under cycling test and aging test. The thickness of IMC growth do not significantly increase under cycling test, because the cycling test temperature was from ¡V40 to 85ºC. However, under the high temperature aging of 200ºC for 25 days, the IMC thickness was increased to 4.71£gm.

The 1:1 reaction between MgR2 and diphenylamine gave heteroleptic alkyl -magnesium amide monomeric compounds [RMgNPh2(THF)2] [R=Et (1) and iPr (2)]. Subsequently, addition of stronger donor solvent HMPA to compound 1 results in the disproportionation reaction to give a bisamidomagnesium crystal [Mg(NPh2)2(HMPA)2] (3). The different size secondary amine HNEt2 or HN(SiMe3)2 reacting with Grignard reagent EtMgBr produced diethylamino-bridging and bromo-bridging Hauser base [(Me3Si)2NMg(£g-Br)(OEt2)]2 (4) and [BrMg(£g-NEt2)(HMPA)]2(5) respectively. Unexpectedly, [(Me3Si)NMg (£g-OEt)(THF)]2 (6) was obtained from the reaction of MgEt2 and HN(SiMe3)2 in the refluxing THF solution. Additionally, iPrMgBr and MgY2 (Y = iPr, C