Interval effect of beta-irradiation and subsequent 4-nitroquinoline 1-oxide painting on skin tumor induction in mice

Skin tumors were produced in female ICR mice by 90Sr-90Y beta-irradiation and subsequent 4-nitroquinoline 1-oxide painting. The doses were chosen so as to produce no tumors with a single agent alone; the interval between two treatments ranged from 11 to 408 days. The tumor induction rate was found to be at almost the same level (average, 12.4%) for each interval. The results indicate the persistence of the latent carcinogenic alterations in the beta-irradiated mouse skin.     

Use of skin electrogastrography for the gastrointestinal system evaluation

The major histocompatibility complex (MHC) in man, the HLA-complex, is for its marked significance in the regulation of immune system reactions and for its important role in clinical medicine the object of incessant interest for further studies. There is also a constant search for new methods of HLA typing. HLA antigens have been traditionally detected by serological and cellular methods. Recently HLA typing methods based on DNA typing utilising polymerase chain reaction (PCR) are being introduced. PCR-SSO (sequence-specific oligonucleotide) and PCR-SSP (sequence-specific primers) methods are most frequently used for routine typing of HLA class I alleles. We present technical details of the PCR-SSP method, recently introduced at our department and a short review of other techniques. (Fig. 1, Ref. 34.)     

固溶处理对Al-Cu-B合金组织的影响

铝铜合金中加入不同含量的B,在相同的熔炼工艺及固溶处理条件下,获得不同的组织。XRD、SEM、金相显微镜对显微组织以及布氏硬度分析,结果表明:显微组织主要为α固溶体和θ相(Al_2Cu)以及AlB_2。硼含量增加,硬度增大,θ相(Al_2Cu)逐渐由网状变为半网状,AlB_2等硼化物的弥散数目增多,当硼含量超过0.42%时,出现硼化物的偏聚,导致硬度降低。合金在540℃固溶后,布氏硬度逐渐变大,15 h时含硼铝铜合金硬度达到峰值120HBS,在24 h时达到另一峰值129HBS。     

The effect of cooling rate on the microstructures formed during solidification of ferritic steel

This article describes in detail the effect of cooling rate on the microstructure of a low-carbon Fe-12 pct Cr alloy. The alloy was prepared using a relatively simple technique, i.e., rapid cooling of the melt in a copper wedge mold. The dependence of microstructure on the cooling rate (∼40 to 10⁵ K/s) has been determined by X-ray diffraction (XRD), microhardness measurement, optical microscopy (OM), and transmission electron microscopy (TEM). It has been found that the matrix structure over a large cooling rate range is composed of columnar ferrite grains, the size of which decreases with increasing cooling rate. Precipitation of second phases has been observed at either the ferrite grain boundaries or within the ferrite grains. The former takes place along the entire wedge sample, whereas the latter characterizes a region 12 mm away from the tip of the wedge sample. The essential structure of the grain boundary precipitates was identified as martensite, which is a transformation product of austenite precipitated at high temperatures. Retained austenite was identified at the tip region as isolated particles (<4 μm). The precipitates within the ferrite grains appeared as planar colonies consisting of two sets of needles. The density of these precipitates increases with increasing the cooling rate while their size decreases. Characteristic precipitate-free zones (PFZs) at the ferrite grain boundaries were observed and are discussed.     

The effect of ranitidine on the tuberculin skin test

The previously unreported occurrence of dysbaric osteonecrosis in an amateur sport scuba diver who had no other identified cause of avascular bone necrosis is described.     

氮含量对螺纹钢夹杂物、组织及性能的影响

运用扫描电子显微镜、高温共聚焦显微镜等检测手段,研究了不同氮含量的螺纹钢样品中的夹杂物、钢组织及性能,并通过理论计算提出螺纹钢氮控制的方法.研究结果表明,一定含量的氮会在钢中以复合状夹杂物的形式出现,夹杂物尺寸为5～10μm,主要成分为Fe、N、C、O,其中氮含量可以高达30％～40％,含氮夹杂物会引发部分应力集中并使得裂纹扩展.氮含量过高,碳氮化合物固溶的区域会形成过饱和的固溶先析铁素体,与周围的珠光体共同形成魏氏组织,对钢的质量造成不良影响.在实际生产中,应尽量避免钢液与氮接触,减少钢液增氮,控制氮含量在0.01％以内.     

Comparative analysis of the cellular and Johnson-Mehl microstructures through computer simulation

The geometric properties of polygranular microstructures of the Johnson-Mehl cellular types have been studied through computer simulation. These prototypic microstructures arise naturally from the classical model of a phase transformation in a one-component solid through growth from a random distribution of nucleation sites. The Johnson-Mehl microstructure results in the kinetic limit of a constant nucleation rate over an essentially constant density of available nucleation sites; the cellular microstructure is produced in the kinetic limit of simultaneous activation of the available nucleation sites. Members of each of these microstructure types are similar to one another in all aspects of their geometrical statistics; they differ only through a homogeneous expansion or contraction. Their geometric features have been characterized through a combination of analytic and computer simulation studies. Comparison with available experimental results shows that the Johnson-Mehl microstructure compares well with such metallurgically diverse experimental structures as the crystallization structure of silicon iron and the intermediate structures established during the ordering of lithium ferrite. These correspondences suggest that the idealized microstructures studied here may be physically relevant as well as being pedagogically useful.     

Overview of non-destructive evaluation of steel microstructures using multifrequency electromagnetic sensors

Abstract

The characterisation of steel microstructures is an important tool for metallurgists as mechanical properties are controlled by microstructural parameters such as grain size, phase balance and precipitates. The majority of microstructural characterisation tools are indirect (inference from measurement of temperature), destructive (optical metallography, SEM and X-ray) or require small samples and laboratory equipment (dilatometry and DSC). This paper describes a multifrequency electromagnetic sensor that has been designed to detect changes in the relative permeability and resistivity of steel, which can be related directly to changes in microstructure. COMSOL multiphysics modelling software, considering the sensor design, sample geometry and sample microstructure, has been used to relate the measured sensor signal to changes in the steel microstructure. Examples presented in this paper are where the sensor has been used to monitor phase transformation (austenite to ferrite) below the Curie temperature (～770°C) during online processing of steel; detection of decarburisation, both online and offline; and evaluation of the effect of long term thermal exposure on alloyed steels (changes in martensitic/bainitic microstructures).     

Current viewpoints on the evaluation of testicular biopsy]

The aim of this study was to analize clinical diagnoses and histopathological reports in 185 cases of male infertility, investigated by testicular biopsies in the period 1993-1997. The classical objective of such investigations has been to clarify either obstructive, or so-called secretory lesions resulting in azoospermia. Histologically normal spermatogenesis was reported in 8 patients (4.3%). Hypospermatogenesis proved to be the most frequent pathologic lesion (69 cases, 37.3%), followed by maturation arrest (61 cases, 33%). Germ cell aplasia (Sertoli-cell-only syndrome) was found in 28 cases (15.1%). Tubular atrophy was the dominant lesion in 5 cases (2.7%). Inflammatory change without other histologic abnormalities was seen only in 1 biopsy (0.5%). Further 13 specimens (7%) showed miscellaneous lesions, including one intratubular germ cell neoplasia. Retrospective histopathologic analysis revealed the coexistence of different basic lesions in 43 of our cases (21.7%). According to the novel requirements, pathologists should always report the presence of germ cell forms in the specimen, which are potentially suitable for fertilization. This is essencial because the new methods of testicular spermium extraction and intracytoplasmatic spermium injection offer the chance of assisted fertilization, even for some patients with smaller testicles and slightly elevated FSH levels.     

Computer analysis of nystagmus

An algorithm for the computer analysis of nystagmus is described in this paper. This algorhythms was based on digital differentiator, which monitors the eye position. The computed eye velocity is next used as an input to the fast phase detector. Several procedures, including minimum velocity test, slope sense test, SPV and FPV relationship test are invoked to extract the fast phases from the recorded signal. Based on three-years experience (approx. 3000 examinations) using the ENG-PC System in clinical practice we can conclude, that application of the nystagmus detector was useful in most cases. In our opinion, despite from system imperfection which is observed during the analysis of recording disturbed by artifacts, this system has unquestionable advantage over the traditional technique.     

Characterisation of Al–B4C composite microstructures and their effect on fluidity

Abstract

Microstructural variables such as particle volume fraction, distribution and agglomeration significantly affect the properties of Al–B₄C metal matrix composites. The aim of the investigation was to study the quantitative characterisation of the microstructural variables and their effects on the fluidity of the composites. The results showed that the particle volume fraction, homogeneity of particle distribution, and volume fraction of agglomerates could be quantitatively analysed by the imaging analysis technique. It was found that the amounts of the particle clusters and networks, as well as the effective volume fraction of total particles augmented with the increase in the holding time. In addition, the longer holding time was, the less homogeneous the particle distribution became. Moreover, the particle agglomerates have a tendency to migrate to the flow end which results in an accelerated stopping of the flow. The increase in the effective particle volume fraction corresponded well with the fluidity deterioration of the composites during the melt holding.

Les paramètres microstructuraux, tels que la fraction volumique, la distribution et l’agglomération des particules affectent de manière significative les propriétés du composite à matrice métallique Al–B₄C. Ce travail porte sur la caractérisation quantitative des propriétés microstructurales ainsi que leurs effets sur la fluidité des matériaux composites. La fraction volumique des particules, l’homogénéité de leur distribution et la fraction volumique des agrégats ont été analysées quantitativement à l’aide de la technique d’analyse d’images. Les résultats montrent une augmentation de la quantité d’agrégats et de la fraction volumique effective des particules avec l’augmentation du temps de maintien. De plus, plus le temps de maintien est long, moins grande est l’homogénéité de la distribution des particules. Par ailleurs, les agglomérats ont tendance à migrer vers l’aval de l’écoulement, ce qui accélère l’arrêt de l’écoulement. L’augmentation de la fraction volumique effective des particules correspond parfaitement à la dégradation de la fluidité des matériaux composites.     

轧后穿水对20CrMnTiH组织和硬度影响的热模拟试验

 降低热轧棒材的硬度有利于下游用户的加工。试验利用热模拟试验机研究终轧温度、轧后穿水以及冷床冷速对小规格20CrMnTiH钢棒材的组织比例和硬度的影响。在轧后不穿水的情况下,终轧温度越低或者冷速越慢,轧材的铁素体体积分数越高,贝氏体体积分数越低,轧材的硬度也越低。轧后穿水能明显提高轧材的铁素体比例,降低贝氏体比例,从而大幅降低轧材的硬度。穿水轧材硬度小于217HBW,满足退火或高温回火材的硬度要求。     

Development of a computer-assisted thermoelectric Peltier cold test procedure with integrated photoplethysmography unit for noninvasive evaluation of acral skin circulation]

Local cold provocation tests are an important, non-invasive diagnostic tool for collecting information about skin perfusion during exposure to cold. In patients suffering from vasospastic circulatory disorders such as Raynaud's phenomenon, it is of particular importance to be able to collect data about acral circulation during the cooling test in the asymptomatic intervals between naturally occurring attacks. By carrying out a series of cold provocation tests, for example, patient response to a newly initiated therapy can be assessed. Here we present a recently developed, computer-aided thermoelectric Peltier device with an integrated finger holder for carrying out local cold provocation tests. The electronic control unit of the Peltier element make it possible to cool or heat to predefined temperatures. At the same time, the temperature of both the finger holder and the skin can be measured. A photoplethysmographic sensor is also integrated within the device, enabling the response of the pulse waves to the controlled temperature changes to be monitored accurately. It is also possible to measure simultaneously laser Doppler flux and capillary pressure in the nailfold and to perform nailfold capillaroscopy to determine red blood cell velocity. The new device provides us with the technical means to study the interrelationship between acral skin perfusion and the thermal regulation of the skin.