大体积泵送混凝土的裂缝控制措施

混凝土在施工和使用过程中出现不同程度和形式的裂缝是相当普遍的问题,对于泵送混凝土浇筑大体积结构混凝土更是常见。如何采取有效措施防治泵送混凝土裂缝,本文就台泥二期磨机基础工程实例浅谈一点体会。     

乌鲁木齐市外环路A1.17合同段道路裂缝的成因及防止措施

乌鲁木齐市快速路部分砼路面通过一段时间的使用,出现了不同程度的裂缝。通过对道路常见裂缝的现状和原因进行分析,提出处理裂缝的方法以及在道路施工中如何控制和防止裂缝。     

浅谈公路沥青路面裂缝的预防和处理

沥青路面具有表面平整、行车舒适、耐磨、噪音小、施工工期短、养护维修简便等优点,但由于受路面结构、气候、地形、地质条件、行车荷载等多种因素的影响,都会不同程度的产生裂缝,裂缝的存在不仅破坏了路面的连续性、整体性及美观,而且使自由水很容易进入沥青面层,使裂缝两侧的路面结构层和七路基的含水量增大,路基和路面强度降低,导致沥青路面产生各种病害,为了减少路面早期破坏,延长路面使用寿命,必须对沥青路面裂缝进行有效的维修.在当前公路建养资金尚不充裕的情况下,研究分析沥青路面裂缝产生的原因和防治措施具有十分重要的现实意义.     

对细石砼刚性防水屋面渗漏水的分析与防治

细石砼刚性防水屋面在我公司主要用于民用建筑平顶屋面上,这种防水屋面耐久性好,施工方便。与油毡屋面相比可改善劳动条件,加速施工进度,取材容易。但如果设计、施工不当,容易引起屋面裂缝渗漏水。通过对我公司现有细石砼防水屋面使用情况的调查发现,大约有50％的细石砼防水屋面有大小不同程度的渗漏水。其中约70％以上是由于细石砼屋面裂缝引起的。现将细石砼防水屋面的渗漏水原因与防治方法进行分析。     

混凝土现浇楼板裂缝分析

针对混凝土现浇楼板的裂缝问题，结合工程施工经验，就裂缝产生的原因进行了分析，并提出了避免产生裂缝应采取的防治措施。     

住宅楼温度裂缝产生的原因与防治措施

本文对建筑物温度裂缝产生的原因进行了分析和探讨 ,并从设计、施工方面对防治裂缝提出了措施。     

致密裂缝性储层水平井中阵列侧向测井正演响应研究

运用改进三维球状介质模型,利用有限元数值模拟技术,研究水平井中阵列侧向测井仪器在致密裂缝性储层中的正演响应规律。研究表明:在目标地层中的仪器响应与裂缝部分的孔隙度大小密切相关,同时在致密性地层中裂缝倾角也相关。在此基础上,模拟了不同裂缝孔隙度下储层厚度以及其他的相关因素对本仪器响应的影响。结果表明:不同裂缝孔隙度储层中各影响因素对仪器响应的影响程度也不同,明确储层裂缝孔隙度的大小对准确进行影响因素校正工作至关重要。裂缝孔隙度越小,阵列侧向测井响应随层厚变化越剧烈,当层厚达到10 m,层厚对仪器响应的影响基本可以忽略;井眼半径越小,不同裂缝孔隙度对应的视电阻率曲线分离度越大,当井眼半径大于0.5 m后,裂缝孔隙度的影响基本可以忽略;裂缝性储层中泥浆侵入深度的不同会导致仪器结果出现极性特征。     

建筑施工中楼面裂缝的成因及防治

文章针对高层住宅现浇楼板裂缝这一质量通病,结合大量施工实践的经验和教训,阐述了楼板产生裂缝的原因,并探讨了综合防治措施和处理方法,指导实际施工中对楼面裂缝进行有效控制。     

砖混结构墙顶温度裂缝控制

砌体结构由于气温变化,往往在墙体、屋面、挑檐等部位出现程度不同的温度裂缝,不仅破坏了结构的整体性,而且导致了房屋抗震能力的降低。本文主要通过对砌体结构墙顶温度裂缝的形状、特点和裂缝产生的原因进行分析,并结合砌体结构的型式、保温材料性能、砌体强度以及设计施工中一些问题,提出了温度裂缝预防措施。     

浅析住宅工程砌体结构裂缝的防治

本文针对住宅工程砌体结构常见裂缝的特征、产生原因进行了分析 ,并提出了防治措施 ,旨在控制砌体裂缝的产生 ,保证住宅结构安全及其使用功能。     

A comparison of in vivo and in vitro methods for determining availability of iron from meals

A comparison is made between in vitro and human and rat in vivo methods for estimating food iron availability. Complex meals formulated to replicate meals used by Cook and Monsen (Am J Clin Nutr 1976;29:859) in human iron availability trials were used in the comparison. The meals were prepared by substituting pork, fish, cheese, egg, liver, or chicken for beef in two basic test meals and were evaluated for iron availability using in vitro and rat in vivo methods. When the criterion for comparison was the ability to show statistically significant differences between iron availability in the various meals, there was substantial agreement between the in vitro and human in vivo methods. There was less agreement between the human in vivo and the rat in vivo and between the in vivo and the rat in vivo and between the in vitro and the rat in vivo methods. Correlation analysis indicated significant agreement between in vitro and human in vivo methods. Correlation between the rat in vivo and human in vivo methods were also significant but correlations between the in vitro and rat in vivo methods were less significant and, in some cases, not significant. The comparison supports the contention that the in vitro method allows a rapid, inexpensive, and accurate estimation of nonheme iron availability in complex meals.     

Morphological study of laryngeal ganglions and associated nerve cells in humans and five mammals

The arrangement and numbers of intralaryngeal ganglia and associated neurons in humans and four mammals (dogs, rabbits, guinea pigs and rats) were investigated morphologically and compared with the results obtained in the cat which have been reported previously. Intralaryngeal ganglia were mostly distributed in branches of the internal branch of superior laryngeal nerve in all species, dorsal and/or dorsolateral to the posterior cricoarytenoid muscle in humans, dogs and cats and around the inferior laryngeal nerve in humans, dogs, cats, guinea pigs and rats. The total number of laryngeal ganglionic neurons was 2,000 to 2,400 in humans, 300-450 in dogs, 600-800 in cats, 250-320 in rats, and 100-150 in rabbits and guinea pigs. More than 80 percent of ganglionic neurons were present in the supraglottis in all species, except the rat, in which about 60 percent were in the subglottis. Each ganglion in all species existed within the nerve bundle, and was chiefly encapsulated with fibrous tissue, many ganglionic cells, glial cells, Schwann cells, vessels and connective tissue. The present morphological study of intralaryngeal ganglia in humans and four mammals suggests that the laryngeal ganglionic neurons have the same arrangement as in cats.     

Cardiovascular responses to postural changes: differences with age for women and men

The cardiovascular responses to postural change, and how they are affected by aging, are inadequately described in women. Therefore, the authors examined the influence of age and sex on the responses of blood pressure, cardiac output, heart rate, and other variables to change in posture. Measurements were made after 10 minutes each in the supine, seated, and standing positions in 22 men and 25 women who ranged in age from 21 to 59 years. Several variables differed, both by sex and by age, when subjects were supine. On rising, subjects' diastolic and mean arterial pressures, heart rate, total peripheral resistance (TPR), and thoracic impedance increased; cardiac output, stroke volume, and mean stroke ejection rate decreased; and changes in all variables, except heart rate, were greater from supine to sitting than sitting to standing. The increase in heart rate was greater in the younger subjects, and increases in TPR and thoracic impedance were greater in the older subjects. Stroke volume decreased less, and TPR and thoracic impedance increased more, in the women than in the men. The increase in TPR was particularly pronounced in the older women. These studies show that the cardiovascular responses to standing differ, in some respects, between the sexes and with age. The authors suggest that the sex differences are, in part, related to greater decrease of thoracic blood volume with standing in women than in men, and that the age differences result, in part, from decreased responsiveness of the high-pressure baroreceptor system.     

Rapid detection cytomegalovirus pneumonia in recipients of bone marrow transplant: evaluation and comparison of five survey methods for bronchoalveolar lavage fluid

To detect cytomegalovirus-associated interstitial pneumonia (CMV-IP) in recipients of BMT in its earliest stage, five CMV methods were assessed for their usefulness using bronchoalveolar lavage fluid as the test specimen. Of the 43 cases enrolled in the study, PCR was positive in 12 cases, shell vial in eight, culture in eight and cytology in three. There were no positive cases in in situ hybridization. Based on this result, the 43 cases were classified into four groups: Group 1, three cases: positive in PCR, shell vial and cytology; Group 2, five cases: positive in PCR and shell vial; Group 3, four cases: positive only in PCR; and Group 4, 31 cases: negative in all CMV tests. Cases in Group 1 were judged as having the highest risk of overt CMV-IP. They were successfully treated with a combination of ganciclovir and immunoglobulin. Group 2 was diagnosed as having active CMV infection and ganciclovir monotherapy was effective for these patients. Groups 3 and 4 were not given anti-CMV therapy, but they were free from CMV-related manifestations throughout the study. The sensitivity and specificity of each survey method for the detection of Groups 1 and 2 were 1.0 and 0.89 in PCR, 1.0 and 1.0 in shell vial, 0.88 and 1.0 in culture, and 0.38 and 1.0 in cytology. Similarly, the positive and negative predictive values were 0.67 and 1.0 in PCR, 1.0 and 1.0 in shell vial, 1.0 and 0.97 in culture, and 1.0 and 0.88 in cytology. Thus, CMV survey on bronchoalveolar fluid was thought to be useful in detecting post BMT CMV-IP in its earliest stage.     

Distribution of six transplasma membrane NADH-dehydrogenases in rat brain tissue

Transplasma membrane redox plays a significant role in cellular activation and growth. Six isoenzymes could be prepared from purified rat brain synaptic plasma membrane. Polyclonal antibodies have been prepared against six transplasma membrane oxydoreductases (PMO-I to PMO-VI) and the tissue distribution of the various iso-enzymes have been investigated in adult rat brains by means of immunohistochemistry. PMO-I is densely observed in layers I, IV and V of the parietal cortex, in CA1 of the hippocampus (except for the molecular layer), in the caudate putamen, in the dorsal, granular and ventral parts of the auditory nuclei, in some loci of the vestibular nuclei as well as in the deep cerebellar nucleus and in the granular layer of the cerebellar cortex. PMO-II is mainly located in the polymorphic layer of the dentate gyrus and in the deep cerebellar nucleus and in the granular layer of the cerebellar cortex. PMO-III is abundant in the piriform cortex, in the pyramidal layers of both CA1 and CA2, in the diagonal band of the basal ganglia, in the supraoptic nucleus and in various loci of the magnetocellular paraventricular nucleus of the hippothalamus as well as in the vestibular nuclei from the brain stem. In addition PMO-III is also densely present in motor nuclei (oculomotor, facial, hypoglossal and ambiguus nuclei), in the reticular formation and in the deep cerebellar nucleus as well as in the Purkinje layer of the cerebellar cortex. PMO-IV has a similar location but is less abundant in the vestibular nuclei of the sensory brain stem and in the motor nucleus. PMO-V in contrast is poorly present in most brain areas compared to the other iso-enzymes, apart of the Purkinje layer of the cerebellar cortex. Finally PMO-VI is mainly present in the oriens layer and in the stratum radiatum of the hippocampus formation, in the supraoptic and lateral magnocellular nucleus of the hypothalamus, in the mesencephalic trigeminal nucleus, in the ventral auditory nucleus and in the facial nucleus of the brain stem as well as in red nucleus of the reticular formation and in the Purkinje layer of the cerebellar cortex. These data show that the iso-enzymes are located in specific brain nuclei. The significance of the results in respect to the yet very poorly defined function of PMO's is discussed.     

Developmental and ageing changes in aminopeptidase activities in selected tissues of the rat

Aminopeptidase activities, assayed as arylamidase activities, were investigated in selected tissues of 1, 6, 12 and 24-month-old rats. The enzyme activities were found to have a heterogeneous distribution and age-related changes were observed. The highest levels of soluble arginyl-aminopeptidase activity were detected in brain homogenate at all the studied ages, whereas membrane-bound activity presented the highest levels in brain and kidney in the four ages tested. Aspartyl-aminopeptidase activity was detected mainly in the particulate fraction of kidney at all four ages. In 1, 6 and 12-month-old animals, soluble aspartyl-aminopeptidase activity was also higher in the kidney than in the rest of the tissues, whereas in the group of 2-year-old rats, the highest levels were found in both kidney and liver. Age-related changes were observed in all the studied tissues and for all the assayed enzymatic activities. In general, the maximal levels were detected in both the youngest and the oldest animals, and the minimal ones in 6 and 12-month-old rats. However, in the adrenals, the soluble and membrane-bound arginyl-aminopeptidase activity was higher in 6-month and 2-year-old rats than in 1-month and 12-month-old rats. These changes may reflect the functional status of the susceptible endogenous substrates of aminopeptidases.     

Alterations of antioxidant enzymes and oxidative damage to macromolecules in different organs of rats during aging

Oxygen free radicals have been hypothesized to play an important role in the aging process. To investigate the correlation between the oxidative stress and aging, we have determined the levels of oxidative protein damage and lipid peroxidation in the brain and liver, and activities of antioxidant enzymes in the brain, liver, heart, kidney, and serum from the Fisher 344 rats at ages of 1, 6, 12, 18, and 24 months. The results showed that the level of oxidative protein damage (measured as carbonyl content) in the brain and liver was significantly higher in older animals than in young animals. No statistical difference was observed in the lipid peroxidation of the liver and brain between young and old animals. The activities of antioxidant enzymes in most tissues displayed an age-dependent decline. Superoxide dismutases in the heart, kidney, and serum, glutathione peroxidase activities in the serum and kidney, and catalase activities in the brain, liver, and kidney, significantly decreased during aging. Cytochrome c oxidase, an enzyme involved in electron transport in mitochondria, initially increased, but subsequently decreased in the aged brain, whereas no significant alteration was observed in the liver mitochondrial antioxidant enzymes. The present studies suggest that the accumulation of oxidized proteins during aging is most likely to be linked with an age-related decline of antioxidant enzyme activities, whereas lipid peroxidation is less sensitive to predict the aging process.     

Iron deposition at mineralization fronts and osteoid formation following chronic cadmium exposure in ovariectomized rats

Integrins are heterodimeric glycoproteins that have been found to undergo dynamic temporal and spatial changes in distribution in the endometrium during the menstrual cycle in women. Likewise the extracellular matrix (ECM) ligands for these receptors are likely to play a role in the establishment of a receptive endometrium. To develop primate models to study the role of these molecules in the cascade of molecular events leading to implantation, integrin expression and associated changes in ECM were investigated during the menstrual cycle and in early pregnancy in the baboon. Antibodies specific for the integrins (alpha(1-6) and alpha(v); beta1, beta3, and beta4) and ECM (laminin, collagen IV, fibronectin) were utilized. In addition, cytokeratin and alpha-smooth muscle actin were used as epithelial, stromal, and smooth muscle cell markers, respectively. Endometrium was obtained in duplicate or triplicate during the menstrual cycle and early pregnancy. Changes observed during the natural menstrual cycle were confirmed using ovariectomized, steroid-treated animals. Constitutively expressed integrins on the endometrial epithelium included the collagen/laminin receptors: alpha2, alpha3, alpha6, and beta4. The pattern of expression correlated well with the distribution of ECM in this tissue. Collagen IV was confined to the basement membrane of glandular epithelium and blood vessels. Laminin immunostaining was found in the basement membrane, mostly in the stroma of the basal region, in the glandular endometrium and vasculature. Fibronectin was present throughout the stroma but not in the basement membrane. The collagen receptor alpha1 beta1 and fibronectin receptor alpha4 beta1 appeared in the glandular epithelium in the luteal phase. As in the human, alpha1 and alpha4 disappeared from the glandular epithelium with the establishment of pregnancy. In contrast, the alpha4 beta3 vitronectin receptor appeared in the glandular epithelium only in pregnancy or following long-term steroid treatment with estrogen and progesterone but not during the time of uterine receptivity associated with the initial period of embryo attachment. Osteopontin, an ECM ligand for alpha(v) beta3, was coexpressed with this integrin in invading cytotrophoblasts, glandular epithelium, and decidualizing stromal cells. Decidualization in the baboon was associated with changes in integrin expression similar to those found in humans: there was an increase in alpha1, alpha3, alpha6, beta1, and alpha(v) beta3 in the decidualized stromal cells. Laminin and collagen IV expression also increased at the implantation site and throughout the endometrium. In contrast, fibronectin expression was most evident at the implantation site and corresponded to alpha5 expression on the invading cytotrophoblasts. In summary, marked similarities were found in the expression of ECM and the integrin receptors between the baboon and the human endometrium throughout the menstrual cycle and in pregnancy. Cycle-specific integrins, alpha1, and alpha4, were present on epithelial cells during the secretory phase. Delayed expression of alpha(v) beta3 in baboon endometrial glands correlated closely with the time of enhanced glandular secretory activity in this primate. The baboon appears to be an excellent model for the investigation of the role of integrins and ECM leading to successful implantation.     

Excretion and metabolism of tipredane, a novel glucocorticoid, in the rat, mouse, monkey, and human

The excretion and metabolism of [3H]tipredane, a novel glucocorticoid, has been studied in mice, rats, marmosets, rhesus and cynomolgus monkeys, and humans. After oral administration, [3H]tipredane was rapidly absorbed, metabolized, and excreted into urine and feces. In mice and male rats, radioactivity was excreted primarily into feces or bile, whereas in female rats, monkeys, and humans, excretion was mainly via the renal route. Some sex differences in the proportions excreted into urine and feces were noted in rodents, with females eliminating relatively more radioactivity in urine. Tipredane was shown to be extensively metabolized, but the routes were highly species-dependent and, in the rat, they were sex-dependent. Unchanged tipredane was not detected in any urine, bile, or blood extracts. Urinary and blood extract profiles indicated that there were between 10 and 30 metabolites in rats and mice, the majority of which constituted < 2% of the dose. In these species, the major pathways involved loss of the thioethyl moiety, S-oxidation of the thiomethyl group, and saturation of the adjacent saturated C16-17 bond. Hydroxylation of the steroid B-ring was seen in the 7 alpha-position in mice and female rats, and in the 6 beta-position in male rats. Metabolism of tipredane in rhesus and cynomolgus monkeys and humans was similar, but less extensive and different to that seen in rodents. The major products, the 6 beta-hydroxylated sulfoxide and sulfone metabolites of tipredane, accounted for 21-36% of the dose in human and monkey urine, and were also major components in blood. In contrast to mice and rats, S-oxidation and an unsaturated C16-17 bond were evident in primates. Metabolism of tipredane was rapid and complex, with significant species differences, although the disposition in rhesus and cynomolgus monkeys seemed to be similar to humans.