Growth characteristics of adenocarcinoma 755 recurrences in C57Bl/6 and (DBA/2 X C57Bl/6) F1 mouse strains

Peculiarities of growth and recurrences of the adenocarcinoma 755 are studied in C57Bl/6 mice and hybrids (DBA/2 X +C57Bl/6)F1 after chemotherapy with cyclophosphamide and 6-mercaptopurine (6-MP). The growth rate of tumours was practically identical in the both mice strains. Growth rate of recurrences was slower in examined lines than in corresponding tumours. The obtained results showed that the antitumour effect of the drugs, in particularly of 6-MP, and the growth rate of the first and that of the second recurrences clearly depended on the tumour host strain.     

Diffusivity and growth rate of silicon in solid-phase epitaxy with an aluminum medium

Using the classical diffusion equation for an amorphous (a)-Si---Al---Si sandwich structure, we have measured the diffusivity of a-Si in Al between 470–570°C and have derived the mass-transfer coefficient under the equilibrium solid-phase epitaxial growth condition. Our data can be used to explain recent results of junction formation by solid-phase epitaxy. The activation energy of this process is found to be 0.80 eV.     

肿瘤微环境中转化生长因子β的免疫抑制作用和靶向治疗

转化生长因子β是肿瘤细胞、微环境基质细胞和免疫调节细胞分泌的功能最强的免疫抑制因子,对T细胞、NK细胞、DC细胞均有显著抑制作用。TGF-β信号通路可分为Smad依赖途径和Smad非依赖途径,许多恶性肿瘤存在TGF-β信号通路的异常改变。反义RNA或RNA干扰策略、大分子单克隆抗体、小分子激酶抑制剂和缺陷型TGF-β受体等研究为肿瘤的靶向治疗提供了新的方法和机遇。     

松果体区肿瘤的超微结构诊断

对松果体区的4例生殖细胞瘤,1例松果体细胞瘤及1例松果母细胞瘤进行了光镜、电镜对比观察,并结合临床资料分析。提出生殖细胞瘤与松果体细胞瘤的超微结构鉴别要点为：①松果体细胞瘤有许多类似神经轴突的突起;②生殖细胞瘤细胞周围见淋巴细胞;③两者核不同。同时提出,是否有节细胞分经是松果体细胞瘤与松果体母细胞瘤的电镜鉴别诊断的要点。     

Kinetics of the growth of an amorphous layer at the surface of silicon bombarded with fast heavy ions at low temperatures

The accumulation of defects in the surface region of Si bombarded with 0.5-MeV Bi ions at a temperature of ?196°C is considered. It is shown that the buildup of disorder in the surface region as the ion dose increases manifests itself in the planar growth of an amorphous layer starting from the Si-SiO₂ interface, and this growth sets in after a threshold implantation dose is attained. The results obtained can be described adequately in the context of a model based on the migration of mobile point defects generated by fast ions to the surface, subsequent processes of segregation of these defects at the interphase boundary, and the presence of saturable sinks in the initial samples.     

Dependence of the growth rate of an AlN layer on nitrogen pressure in a reactor for sublimation growth of AlN crystals

The dependence of the layer growth rate on nitrogen pressure in a reactor has been examined in order to analyze the conditions of growth of AlN thick layers and bulk crystals by the sublimation sandwich method. It is shown that the layer growth rate steadily increases as the pressure in the reactor is lowered within the range 1–0.02 bar. This suggests that a key role in the layer growth kinetics is played by the source-to-substrate transfer of the components (Al, N), rather than by their adsorption (desorption) on the substrate surface.     

Experimental evaluation of tumor therapy with cytostatic agents deposited in the abdominal cavity in acetylcellulose

For the purpose of improving the effectiveness of the chemotherapy of gastrointestinal tract tumours, the experimental investigation of the possibility to deposit the various antitumour preparations in the abdominal cavity by including them into acetylcellulose microspheres was carried out. It was shown that the use of the polymeric drug complexes permits obtaining a significantly more pronounced antitumour effect than the introduction of the same preparation in a free form. A decrease of the toxic effect of the deposited preparations was established.     

The monoaminergic receptors of the internal organs in rats with a tumor and after partial hepatectomy

Sensitivity to phenylephrine, isoproterenol, serotonin, oxytocin, acetylcholine and barium chloride of vas deferens uterus und fundus strip was studied comparatively in hepatectomized and sarcoma-45, sarcoma-M1, Walker carcinosarcoma and Zajdela ascites hepatoma bearing rats. The contractile response to monoamines and oxytocin was considerably lower or absent at certain periods after hepatectomy or tumour grafting. Effects of biogenic amine antagonists were also substantially altered. The response to isoproterenol, acetylcholine and barium chloride remained unchanged. Apparently a selective alteration of a response of visceral smooth muscles mediated through alpha-adrenergic and D-serotonin receptors occurred not only during the tumour growth but also in the case of active (extensive) proliferation of the normal tissue.     

The content of tumor angiogenesis factor in the blood serum of C57Bl/6 mice during the growth and metastasis of transplanted tumors

The tumour growth and metastasis development after the primary tumour removal is accompanied by the appearance of the tumour angiogenesis factor (TAF) in blood. The TAF level directly correlates with the volume of tumour cell masses. These results confirm the present notions about the close correlation of the tumour growth and neovascularization and may be used to control the activity of neovascularization and malignant growth.     

Microwave properties of a proposed read-like device with variable current multiplication in the avalanche zone and an additional transverse field in the drift zone

A study of the high-frequency properties of a Read-like IMPATT device, which is arranged to have a variable current multiplication in the avalanche zone by means of controlled injection of minority carriers into the reverse biased junction, and also an additional transverse field in the intrinsic drift region, is presented. The additional field shifts the direction of space-charge waves emerging from the avalanche layer without altering the drift velocity which is already saturated. It is shown that the frequency of the maximum negative conductance, avalanche frequency, magnitude of the negative conductance, and susceptance of the device can be controlled over a wide range by varying the current multiplication in the avalanche zone. It is also shown that a fine variation of the negative conductance without altering the avalanche frequency or susceptance can be obtained by means of the additional transverse field.     

Changes in the growth characteristics of mouse and rat fibroblasts during tumor progression

Changes in growth characteristics (the growth in a mat of normal cells, contact inhibition of division, growth-substrate dependence, dependence on the serum growth factors) and tumourigenicity were compared in 6 cells lines of mice and rats during their in vitro and in vivo long passages. All these factors progressed independently of a tumourigenicity increase, i.e. they obeyed the Fould principle. The trait responsible for the cell capacity to proliferate on a layer of normal cells proved to be the most correct one relative to tumourigenicity prediction.     

Dependence of structural and optical properties of QD arrays in an InAs/GaAs system on surface temperature and growth rate

Properties of InAs QD arrays on a <100> GaAs surface in relation to the surface temperature and InAs growth rate are studied experimentally and theoretically. A kinetic model of QD formation in heteroepitaxial growth is developed, which allows the calculation of the mean lateral size and surface density of islands as functions of the growth conditions and duration. Experimental study of optical and structural properties is performed for QDs with an effective thickness of 2 ML, grown at different substrate temperatures and growth rates. The calculated results correlate well with the experimental data. The raising of the surface temperature and slowing of the growth rate result in a considerable increase in the QD mean lateral size and a decrease in their surface density.     

Effect of cooling rate on growth of the intermetallic compound and fracture mode of near-eutectic Sn-Ag-Cu/Cu pad: Before and after aging

Several near-eutectic solders of (1) Sn-3.5Ag, (2) Sn-3.0Ag-0.7Cu, (3) Sn-3.0Ag-1.5Cu, (4) Sn-3.7Ag-0.9Cu, and (5) Sn-6.0Ag-0.5Cu (in wt.% unless specified otherwise) were cooled at different rates after reflow soldering on the Cu pad above 250°C for 60 sec. Three different media of cooling were used to control cooling rates: fast water quenching, medium cooling on an aluminum block, and slow cooling in furnace. Both the solder composition and cooling rate after reflow have a significant effect on the intermetallic compound (IMC) thickness (mainly Cu₆Sn₅). Under fixed cooling condition, alloys (1), (3), and (5) revealed larger IMC thicknesses than that of alloys (2) and (4). Slow cooling produced an IMC buildup of thicker than 10 μm, while medium and fast cooling produced a thickness of thinner than 5 μm. The inverse relationship between IMC thickness and shear strength was confirmed. All the fast- and medium-cooled joints revealed a ductile mode (fracture surface was composed of the β-Sn phase), while the slow-cooled joints were fractured in a brittle mode (fracture surface was composed of Cu₆Sn₅ and Cu₃Sn phases). The effect of isothermal aging at 130°C on the growth of the IMC, shear strength, and fracture mode is also reported.     

光动力学疗法联合He-Ne激光照射脾区对荷瘤小鼠肿瘤生长的抑制作用

目的 :探讨光动力学疗法联合He -Ne激光照射脾区对荷瘤小鼠肿瘤生长的抑制作用。方法 :将 4 0只昆明种小鼠接种Louis肺癌细胞 ,做成动物模型。随机分为 4组 ,对照组、光动力学疗法组、He-Ne激光照射组、光动力学疗法与He-Ne激光照射脾区联合治疗组。观察各组小鼠肿瘤的体积、肿瘤抑制脾区率随照射天数的变化及肿瘤生长延迟期。结果 :光动力学疗法与He -Ne激光照射脾区联合治疗组 ,肿瘤抑制率和生长延迟期均优于其他组。结论 :动力学疗法结合He-Ne激光照射脾区可提高治疗肿瘤的疗效     

Kinetics of structural and phase transformations in thin SiO<Subscript>x</Subscript> films in the course of a rapid thermal annealing

Infrared spectroscopy and analysis of photoluminescence spectra have been used to study variations in the composition of the oxide phase in a SiO_x film and the precipitation of the Si phase in the course of a rapid thermal annealing for 1–40 s at temperatures of 500–1000°C. Kinetics of phase segregation has been observed for the first time at temperatures of 600–700°C: an increase in the amount of precipitated silicon as the annealing duration increases followed by an eventual leveling off. The phase separation is brought to completion in a time as short as 1 s at temperatures higher than 900°C. The diffusion coefficient is estimated in the context of a model of the diffusion-controlled formation of Si nanoparticles. The obtained values of the diffusion coefficient exceed, by five to ten orders of magnitude, those of the silicon diffusion coefficients in SiO₂ and Si and are comparable to the diffusion coefficients of the oxygen contained in these structures. It is assumed that oxygen mobility forms the basis for the mechanism of structural and phase transformations in the SiO_x layers and for the formation of Si nanoparticles in the course of annealing.     

Imitation, copying, and the use of models: report writing in an introductory physics course

The article focuses on the use and misuse of models-both appropriate and inappropriate-in the report-writing practices of first year physics students, especially those from non-English speaking backgrounds. It analyzes the students' propensity to use any available text on a given topic as a source of model sentences. Examples of "copying" are provided and analyzed. It is argued that many forms of copying are legitimate learning strategies of novice writers, for the production of certain kinds of texts, but that this can become a problem when inappropriate models are used or when appropriate models are used inappropriately. Copying is discussed in relation to imitative learning and modeling as well as plagiarism, and some suggestions to improve teaching practice are made.     

A linearly dependent service rate for the queue: M/M/1/N with general balk function, reflecting barrier, reneging and an additional server for longer queues

The objective of this paper is to derive the solution of the state-dependent queue: M/M/1/N with general balk function, reflecting barrier, reneging and an additional server for longer queues. The researchers deduce some measures of effectiveness and also, some special cases. In fact the service rate in this work is a linearly dependent and the general balk function is Abou El-Ata balk function and it is an interesting one.     

Anomalous oxidation rate in 6H-SiC depending on the partial pressure of O2 and H2O

On the thermal oxidation of silicon carbide, the partial pressure of H₂O affects the oxidation rate very differently from silicon. We have found that the oxide thickness shows the bell-shape as the function of the relative partial pressure of H₂O, called the p parameter. The main reason for this is that the diffusion limiting process diminishes according to the reduction of p while the linear rate constant does not depend on p strongly until p=0.15. The reduction of the oxide thickness below p=0.15 is explained by the abrupt reduction of the linear rate constant. In addition, the interface quality for oxides grown in the different p has been investigated. For the reduction of the surface states, the large p (over p=0.8) is favorable.