金属换热器传热过程的数学模型及应用

应用蒙特卡洛法仿真辐射式金属换热器内的辐射传热过程，建立了换热器综合传热的数学模型，利用概率论原理，把辐射能迁移过程仿真为一定累积概率分面下的随机过程，该模型能较好地反映换热器内传热过程的真实情况，可以计算出换热器内烟气、筒壁、空气的温度和壁面热流分布，以及研究烟气进口温度、换热器筒径和狭逢宽度对换热效果的影响。     

Neutrophil alkaline phosphatase activity increase in bacterial infections is not associated with a general increase in secretory vesicle membrane components.

The content of alkaline phosphatase (ALP) was determined in neutrophils isolated from patients with acute bacterial infections by a standard enzyme assay. Compared with control cells, patient cells exhibited about a fivefold increase in ALP activity. There was no difference between the ALP Km values of control and patient cells, which indicates that the elevated activity in patient cells was due to the presence of increased amounts of the enzyme. The ALP isozyme in both cell types was determined to be the tissue-unspecific ALP. The fact that much of the ALP activity was measurable only in the presence of detergent suggested that the enzyme was localized in the secretory vesicles, a putative reservoir of plasma membrane components. The amount and subcellular distribution of two other secretory vesicle membrane proteins, i.e., cytochrome b and complement receptor 3, were not altered; hence, we conclude that there was no general increase in amounts of secretory vesicle membrane constituents in the patient cells.     

Cytoskeletal requirements in Chlamydia trachomatis infection of host cells.

Infection of genital epithelial cells by the closely related sexually transmitted pathogens Chlamydia trachomatis serovars E and L2 results in different clinical disease manifestations. Following entry into target host cells, individual vesicles containing chlamydiae fuse with one another to form one large inclusion. At the cellular level, the only obvious difference between these serovars is the time until inclusion maturation, which is 48 h for the invasive serovar L2 and 72 h for serovar E. To begin to define the intracellular events of these pathogens, the effect of cytoskeletal disruption on early endosome fusion and inclusion development in epithelial (HEC-1B) and fibroblast (McCoy) cells was analyzed by fluorescence microscopy. Disruption of microfilaments with cytochalasin D markedly reduced serovar E, but not serovar L2, infection of both cell lines. Conversely, microfilament as well as microtubule disruption, with colchicine or nocodazole, had no effect on serovar E inclusion development but resulted in the formation of multiple serovar L2 inclusions per cell during early and mid-development. Later in serovar L2 inclusion development (> 36 h postinfection), vesicles containing chlamydiae fused to form one large inclusion in the absence of an intact cytoskeleton. These results imply that (i) C. trachomatis serovar E may utilize a different pathway for uptake and development from serovar L2; (ii) these differences are consistent in both epithelial cells and fibroblasts; and (iii) the cytoskeleton plays a unique role in the infection of host cells by these two genital pathogens.     

A Mycoplasma strain F38 growth-inhibiting monoclonal antibody (WM-25) identifies an epitope on a surface-exposed polysaccharide antigen.

Monoclonal antibody (MAb) WM-25 differentiates by in vitro growth inhibition Mycoplasma capricolum subsp. capripneumoniae (Mycoplasma strain F38), which causes contagious carpine pleuropneumonia, from other Mycoplasma spp. (F. R. Rurangirwa, T. C. McGuire, A. J. Musoke, and A. Kibor, Infect. Immun. 55:3219-3220, 1987). The antigen identified by MAb WM-25 was isolated from solubilized Mycoplasma strain F38 organisms by MAb WM-25 affinity chromatography and was stained with Schiff's reagent, but not with Coomassie blue, after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Treatment of purified F38 polysaccharide with periodate abolished binding with MAb WM-25, and MAb WM-25 binding was blocked with laminarin, a complex oligosaccharide with beta(1-->3) sugar linkages. Purified F38 polysaccharide blocked both growth inhibition and agglutination of live F38 organisms caused by MAb WM-25 and rabbit antiserum to F38 organisms. The results in this paper demonstrate that MAb WM-25 binds a periodate-sensitive epitope on the F38 polysaccharide which is also exposed on the surface of Mycoplasma strain F38. Because MAb WM-25 also causes in vitro growth inhibition of F38, the reactive polysaccharide epitope may induce protective immune responses.     

Changes to the ocular biota with time in extended- and daily-wear disposable contact lens use.

Gram-negative bacteria may play a role in the etiology of certain soft contact lens (SCL)-related diseases. Contact lens (CL) wear may modify the normal ocular biota, providing a more favorable environment for potential pathogens. This study reports temporal changes in ocular biota in daily-wear (DW) and extended-wear (EW) disposable SCL use in experienced and neophyte wearers. Lid margin and bulbar conjunctival biota were sampled prior to CL fitting in 26 previous DW SCL users, 18 previous EW SCL users, and 26 neophytes. Wearers were fitted with an etafilcon A CL in one eye and a polymacon CL in the fellow eye. Lenses were worn on a daily basis by the 26 previous DW SCL wearers and on an EW basis by the remaining 44 subjects. The ocular biota was further sampled after 1, 3, 6, 9, and 12 months of wear. The ocular biota consisted of coagulase-negative staphylococci, Corynebacterium spp., Micrococcus spp., and Propionibacterium spp. Potential pathogens were rarely isolated at baseline. No significant trend of increasing ocular colonization was shown for extended CL wear. Lid and conjunctival colonization increased with DW SCL use (P < 0.001), although this increase occurred for nonpathogenic species only. Fewer potential pathogens were isolated from DW SCL than from EW SCL users (P < 0.05). The lid margin consistently showed greater colonization than the conjunctiva and may be a source of potential pathogens during CL wear. Hydrogel CL wear appears to modify the ocular biota. An increased number of commensal organisms were present in DW SCL use. EW SCL use altered the spectrum of organisms isolated. These alterations may suppress the normal ocular defense mechanisms and may be relevant in the pathogenesis of CL-related disease.     

Borrelia burgdorferi shows specificity of binding to glycosphingolipids.

Live but not fixed or heat-killed Borrelia burgdorferi bound to galactocerebroside, lactosylceramide, and ceramide trihexoside. In addition, this organism bound to the disialoganglioside GD1a and the trisialoganglioside GT1b but not to gangliosides GM1, GD1b, GM2, and GM3 and not to asialo GM1. This adhesion pattern confirmed earlier findings of binding to galactocerebroside and places this organism within a prokaryotic group which binds to lactosylceramide. The binding to GD1a and GT1b, both of which carry terminal as well as multiple sialic acids, indicates that B. burgdorferi can show specificity of binding within a group of acidic gangliosides. Adhesion could not be inhibited by several concentrations of sugars and sialic acid, indicating more complex binding requirements than for terminal carbohydrates alone. Low-passage strains adhered to the four substrates in greater numbers than strains in culture for long periods of time. OspB mutants in general bound better or at least equally well to several of the glycosphingolipids, and preincubation of substrates with soluble recombinant and affinity-purified Osp did not inhibitor or weakly inhibited the binding of the organisms. These findings suggest that outer surface lipoproteins A and B are not directly involved in adhesion to glycosphingolipids.     

Attitudes and behaviors of African-American and Mexican-American women delivering newborns in inner-city Los Angeles.

To study some of the factors relating to the care of mothers and newborns in an inner-city hospital, three sources of information were reviewed: an obstetric database including information on prenatal care and perinatal mortality, a database of all admissions to the hospital neonatal intensive care unit over the past 5 years, and a detailed questionnaire concerning attitudes and behaviors of recently delivered women. While analyses from these hospital-based data are not conclusive, the results add evidence for the following propositions: 1) Optimal prenatal care is infrequently obtained by mothers delivering at inner-city hospitals. Lack of prenatal care is clearly associated with increased perinatal mortality. While the need for prenatal care is appreciated by 98% of the mothers in this sample, the most frequent reasons why prenatal care is not obtained earlier or more frequently involve knowledge about and access to prenatal care. 2) Inner-city mothers, in general, manifest attitudes and behaviors that promote the welfare of their pregnancies and newborns. These attitudes and behaviors are in stark contrast to those that are frequently attributed to inner-city women by the media. 3) Acute perinatal medical and nursing care are perceived by many postpartum women as suboptimal, particularly in terms of the lack of respect shown to patients by nurses and doctors. 4) Improved acute obstetric and neonatal care improves perinatal morbidity and mortality of infants delivered at inner-city hospitals.     

Purification of antigenically intact Ro ribonucleoproteins; biochemical and immunological evidence that the 52-kD protein is not a Ro protein.

Anti-Ro sera immunoprecipitate Ro ribonucleoproteins (RNPs) from human cell extracts. Ro RNPs are biochemically heterogeneous particles whose functions are unknown and whose exact composition remains controversial. In addition to 60-kD Ro and to La proteins, a 52-kD polypeptide (p52) has been proposed to be a stable component of the Ro RNPs. To confirm the immunological studies supporting this hypothesis, we have biochemically purified Ro RNPs from HeLa cells using non-denaturing conditions. Ro RNPs segregated into three distinct populations, one of which only contained hY5 RNA (RohY5 RNPs). No p52 co-purified with Ro RNPs. Despite the absence of p52, purified Ro RNPs had biochemical and immunological properties identical to those of unfractionated Ro RNPs. Many anti-Ro sera only recognize p52 in immunoblots, and are said to be monospecific anti-p52. Preincubation with purified RohY5 RNPs (free of p52) of all human anti-Ro (including so-called monospecific anti-p52) sera abolished their capacity to immunoprecipitate Ro RNPs from unfractionated HeLa cell extracts. Conversely, preincubation of anti-Ro sera with purified p52 protein specifically inhibited recognition of p52 in immunoblots, but did not interfere with immunoprecipitation of Ro RNPs. Our data demonstrate that anti-p52 antibodies do not target intact Ro RNPs, nor do they target the native 60-kD Ro protein. Contrary to previous reports, p52 protein is not a stable component of antigenically intact Ro RNPs.