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Both case-ascertained household studies, in which households are recruited after an ‘index case’ is identified, and household cohort studies, where a household is enrolled before the start of the epidemic, may be used to test and estimate the protective effect of interventions used to prevent influenza transmission. A simulation approach parameterized with empirical data from household studies was used to evaluate and compare the statistical power of four study designs: a cohort study with routine virological testing of household contacts of infected index case, a cohort study where only household contacts with acute respiratory illness (ARI) are sampled for virological testing, a case-ascertained study with routine virological testing of household contacts, and a case-ascertained study where only household contacts with ARI are sampled for virological testing. We found that a case-ascertained study with ARI-triggered testing would be the most powerful design while a cohort design only testing household contacts with ARI was the least powerful. Sensitivity analysis demonstrated that these conclusions varied by model parameters including the serial interval and the risk of influenza virus infection from outside the household.
Confinement and loss properties of tangentially co-injected beam ions have been studied for a standard configuration of the Compact Helical System (Rax/Bt=0.921 m/1.9 T) by use of the global particle simulation code DELTA5D. Both ripple transport and collisions with a background plasma are taken into account. It has appeared that partially thermalized, pitch-angle scattered beam ions are dominantly lost at the small major radius side. It has also been shown that the negative potential can enhance beam ions losses.
This study investigated the infectiousness of smallpox relative to the onset of fever using a likelihood-based estimation procedure based on the observed transmission network (n=223) and on the distribution of the incubation period (n=379). Who-infected-whom information enabled us to back-calculate the infectiousness by disease age, employing a step function model for infectiousness. Frequency of secondary transmissions was highest between 3 and 6 days after onset of fever, yielding an expected daily frequency of 20·6% (95% CI 15·1–26·4) of the total number of secondary transmissions, which is consistent with previous observations. The estimated cumulative frequency suggests that 91·1% of secondary transmissions occurred up to 9 days after onset of fever. The proposed method appeared to be useful for diseases with an acute course of illness, where transmission was not hampered by depletion of susceptible contacts.
The dependence of phosphorus doping on crystal face and C/Si ratio in the epitaxial growth of 4H-SiC using phosphine were investigated. Phosphorus incorporation was highest on off-axis (000-1) and lowest on off-axis (0001). Phosphorus incorporation on (11-20) came between that on off-axis (0001) and (000-1). With increasing C/Si ratio from 0.5 to 2.5, phosphorus incorporation increased on (11-20) and off-axis (000-1). Phosphorus incorporation on off-axis (0001) showed unclear C/Si ratio dependence. On (000-1), the highest phosphorus concentration of 2 × 1018cm-3 was obtained by an increasing PH3 flow rate. The roughness, growth rate, and surface morphology of the high phosphorus doped epilayer were investigated.
In this study, we investigated surface features formed by molten KOH etching of (000-1) substrates and epilayers, using scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (TEM). We found the surface features formed on (000-1) are protrusions, in contrast to well-known dimples on (0001).
It is important to develop flexible transparent polymer films having high gas barrier properties and abrasion resistance because new applications involving transparent polymer films for flat panel displays require these properties. We report on organic-inorganic hybrid coatings of polyvinylalcohol (PVA)/polyacrylicacid (PAA)-silica, which have high gas barrier properties almost equivalent to those achieved by the dry coating process. The hybrid coatings were prepared by the sol-gel reaction of alkoxysilane in a PVA/PAA aqueous solution. In order to obtain transparent coating films, 3-aminopropyltrimethoxysilane (APTMOS) was used as a compatibilizer in the sol-gel reaction of tetramethoxysilane (TMOS). No structure could be seen in the TEM of the cross-sectional coating layer, indicating that polymers and silica were mixed homogeneously. PVA/PAA-silica hybrid coatings were shown to have excellent abrasion resistance based on the ΔHaze index. O2 permeability of PVA/PAA-silica hybrid coatings evaluated by MOCON under the conditions of 23°C, 90% RH was lower than that of PVA/PAA polymer coating, which suggests that silica affects the barrier property of the hybrid coating in humid conditions. Furthermore, O2 permeability decreased as silica content increased in the coatings. Unexpectedly, high gas barrier properties appeared when the silica content exceeded 50 wt%. From the result of element distribution analysis measured by EF-TEM, it was confirmed that phase separation occurred between PVA/PAA and silica on a nanometer scale and silica forms continuous structures, which are considered to suppress O2 permeability.
In order to study environmental effects on the nuclear activity in galaxies, we have been conducting a spectroscopic study of Hickson Compact Groups of galaxies (HCGs, Hickson 1982) which are the densest agglomeration of galaxies. We obtained nuclear spectra of 62 galaxies in 29 HCGs in the spectral range 6200–7000Å with the 188cm telescope at Okayama Astrophysical Observatory. These spectra were classified into the three types by using the emission line ratio [NII]λ6583/Hα; (1) AGN: [NII]λ6583/Hα >0.6, (2) HII nuclei: [NII]λ6583/Hα <0.6, and (3) Absorption: no emission line. We compared the nuclear activity of galaxies in HCGs with that of nearby galaxies (Ho 1996; Ho, Filippenko & Sargent 1997) which provides a representative sample of field galaxies. In early-type spirals (Sa-Sbc), the fraction of HII nuclei in HCGs is smaller than that in the field galaxies, while the fraction of absorption in HCGs is larger than that in field galaxies. On the other hand, in early-type galaxies (E-S0a) and late-type spirals (Sc-P), we found little difference in the nuclear activity between HCGs and field galaxies.
We prove the well-posedness for a one-dimensional free boundary problem arising from some reaction diffusion system. The interfacial point hits a boundary point in finite time or remains inside for all time. In the large diffusion limit, the system is reduced to ordinary differential equations of finite dimension.
Malignant tumor cells have an enhanced rate of cell division and of metabolic activities of cells. We studied IgG positive immunoblastic sarcoma cells by means of freeze-fracturing and found significant structural differences between these tumor cells and control B-cells.
Lymphnodes infiltrated with sarcoma cells were dissected from the cervical areas of two patients. The sarcoma cell suspension was obtained from these lymphnodes. Sarcoma cells had fine granules stained with PAS and mothyl green pyronin in cytoplasma. Most of sarcoma cells were positive fluorescent (SIgG bearing). Alpha-naphthyl-acetate-esterase test was negative or false positive. Single cell suspension of lymphnodes was obtained from patients of non-lymphatic diseases. EAC rosette forming cells and adherent cells to nylon column fiber were used as control B-cells. The pellet of sarcoma cells and control B-cells were fixed with 2. 5% glutaraldehyde solution. Freeze-fracture was done as described previously. Under the electron microscope, EAC rosette forming cells were selected as control B-cells.
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