人口问题中具广义Ginzbur-Landau型方程解的渐近性和Blow-up

在文献[1][2][3]和[4]的基础上,研究人口问题中具广义Ginzbur-Landau型弥散方程（0.21）,（0.22）及更一般的非线性高阶抛物型方程（0.23）初边值问题,在古典解存在且唯一的条件下,利用文[7,8]的相应方法,深入探讨问题的广义解和古典解的渐近性及Blow-up现象,得到许多新结果。     

Large expansion segments in 18S rDNA support a new sponge clade (Class Demospongiae, Order Haplosclerida)

Newly emerging molecular phylogenetic hypotheses involving the sponge Order Haplosclerida (Class Demospongiae) are far removed from traditional views on their classification using morphology. In the new grouping of marine haplosclerid taxa by molecular data all members of one highly supported clade were found to have three large indels in the 18S rRNA gene. These indels were not found in this gene in other marine haplosclerids or in any other demosponges analysed. These indels were found in the variable V4 and V7 region of the gene, had high GC contents and formed stable double stranded helices in the 18S rRNA secondary structure. These indels are very important synapomorphies, provide high support for an alternative taxonomic scheme and could help resolve the phylogeny of this order in conjunction with other phylogenetically informative characters.     

Tests Against Qualitative Interaction: Exact Critical Values and Robust Tests

Consider a study to evaluate treatment A with a placebo in two or more groups of patients. If treatment A is beneficial to one group of patients and harmful to another, then we say that there is qualitative interaction or crossover interaction between patient groups and the treatments. Gail and Simon (1985, Biometrics 41, 361-372) developed a large-sample procedure for this testing problem. Their test has received favorable coverage in the literature. In this article, we obtain corresponding exact finite sample results for normal error distribution and provide a table of critical values. The test statistic is similar to the familiar F-ratio, and its p-value is equal to a weighted sum of tail areas of F-distributions. The computations to implement this are simple. A simulation study shows that the exact critical values provided here for normal error distribution are preferable to the asymptotic critical values for a wide range of error distributions. We also develop tests that are power robust against long-tailed error distributions. Our robust test uses M-estimators instead of the least squares estimators. We show that the efficiency robustness of the M-estimator translates to power robustness of the corresponding test. Therefore, our robust tests are better if outliers are expected. A simulation study illustrates the substantial power advantages of our robust tests.     

Bayesian Modeling of the Level and Duration of Fertility in the Menstrual Cycle

Time to pregnancy studies that identify ovulation days and collect daily intercourse data can be used to estimate the day-specific probabilities of conception given intercourse on a single day relative to ovulation. In this article, a Bayesian semiparametric model is described for flexibly characterizing covariate effects and heterogeneity among couples in daily fecundability. The proposed model is characterized by the timing of the most fertile day of the cycle relative to ovulation, by the probability of conception due to intercourse on the most fertile day, and by the ratios of the daily conception probabilities for other days of the cycle relative to this peak probability. The ratios are assumed to be increasing in time to the peak and decreasing thereafter. Generalized linear mixed models are used to incorporate covariate and couple-specific effects on the peak probability and on the day-specific ratios. A Markov chain Monte Carlo algorithm is described for posterior estimation, and the methods are illustrated through application to caffeine data from a North Carolina pregnancy study.     

Molecular Dynamics Investigation of Bond Ordering of Unsaturated Lipids in Monolayers

Molecular dynamics simulations of three model lipid monolayers of 2,3-diacyl-D-glycerolipids, that contained stearoyl (18:0) in the position 3 and oleoyl (18:9cis), linoleoyl (18:26cis), or linolenoyl (18:33cis) in the position 2, have been carried out. The simulation systems consisted of 24 lipid molecules arranged in a rectangular simulation cell, with periodic boundary conditions in the surface plane. 1 nanosecond simulations were performed at T = 295 K. C-C and C-H bond order parameter profiles and the bond orientation distributions about the monolayer normal have been calculated. The relation of the distributions to the order parameters was analyzed in terms of maxima and widths of the distributions. The cis double bond order parameter is found to be higher than those of adjacent single C-C bonds. The widths of the two distributions of C-H bonds of the cis double bond segment in di- and triunsaturated molecules are much smaller than that obtained for methylene group located between the double bonds. The bond orientation distribution function widths depend on both the segment location in the chain and the segment chemical structure.     

Backbone dynamics of bacteriorhodopsin as studied by <Superscript>13</Superscript>C solid-state NMR spectroscopy

The surface dynamics of bacteriorhodopsin was examined by measurements of site-specific ¹³C–¹H dipolar couplings in [3-¹³C]Ala-labeled bacteriorhodopsin. Motions of slow or intermediate frequency (correlation time <50 µs) scale down ¹³C–¹H dipolar couplings according to the motional amplitude. The two-dimensional dipolar and chemical shift (DIPSHIFT) correlation technique was utilized to obtain the dipolar coupling strength for each resolved peak in the ¹³C MAS solid-state NMR spectrum, providing the molecular order parameter of the respective site. In addition to the rotation of the Ala methyl group, which scales the dipolar coupling to 1/3 of the rigid limit value, fluctuations of the C–C vector result in additional motional averaging. Typical order parameters measured for mobile sites in bacteriorhodopsin are between 0.25 and 0.29. These can be assigned to Ala103 of the C–D loop and Ala235 at the C-terminal -helix protruded from the membrane surface, and Ala196 of the F–G loop, as well as to Ala228 and Ala233 of the C-terminal -helix and Ala51 from the transmembrane -helix. Such order parameters departing significantly from the value of 0.33 for rotating methyl groups are obviously direct evidence for the presence of fluctuation motions of the Ala C–C vectors of intact preparations of fully hydrated, wild-type bacteriorhodopsin at ambient temperature. The order parameter for Ala160 from the expectantly more flexible E–F loop, however, is unavailable under highest-field NMR conditions, probably because increased chemical shift anisotropy together with intrinsic fluctuation motions result in an unresolved ¹³C NMR signal.     

Non‐Parametric Selected Ranked Set Sampling

A nonparametric selected ranked set sampling is suggested. The estimator of population mean based on the new approach is compared with that using the simple random sampling (SRS), the ranked set sampling (RSS) and the median ranked set sampling (MRSS) methods. The estimator of population mean using the new approach is found to be more efficient than its counter‐parts for almost all the cases considered.     

Multiple Testing for Identifying Effective and Safe Treatments

In the literature various multiple test procedures to compare k treatments with a control have been investigated. They can be applied to establish either treatment efficacy or treatment safety. In this paper we propose procedures which control the multiple level α with respect to efficacy and safety simultaneously. On the one hand we consider a method with stagewise rejective adjustments of local levels applied to appropriately defined subfamilies of null hypotheses. When order restrictions are assumed to hold among the parameters of interest we can alternatively split the multiple level between the families of efficacy and safety null hypotheses. If either all treatments are declared to be safe or all are declared to be effective then the other family can be tested at the full multiple level α, respectively. The methods are compared in a simulation study.     

Folding of lipid monolayers containing lung surfactant proteins SP-B1-25 and SP-C studied via coarse-grained molecular dynamics simulations

To explore the role of lung surfactant proteins SP-B and SP-C in storing and redelivering lipid from lipid monolayers during the compression and re-expansion occurring in lungs during breathing, we simulate the folding of lipid monolayers with and without these proteins. We utilize the MARTINI coarse-grained force field to simulate monolayers containing pure dipalmitoylphosphatidylcholine (DPPC) and DPPC mixed with palmitoyloleoylphosphatidylglycerol (POPG), palmitic acid (PA), and/or peptides. The peptides considered include the 25-residue N-terminal fragment of SP-B (SP-B_1-25), SP-C, and several SP-B_1-25 mutants in which charged and hydrophilic residues are replaced by hydrophobic ones, or vice-versa. We observe two folding mechanisms: folding by the amplification of undulations and folding by nucleation about a defect. The first mechanism is observed in monolayers containing either POPG or peptides, while the second mechanism is observed only with peptides present, and involves the lipid-mediated aggregation of the peptides into a defect, from which the fold can nucleate. Fold nucleation from a defect displays a dependence on the hydrophobic character of the peptides; if the number of hydrophobic residues is decreased significantly, monolayer folding does not occur. The addition of POPG or peptides to the DPPC monolayer has a fluidizing effect, which assists monolayer folding. In contrast, the addition of PA has a charge-dependent condensing affect on DPPC monolayers containing SP-C. The peptides appear to play a significant role in the folding process, and provide a larger driving force for folding than POPG. In addition to promoting fold formation, the peptides also display fusogenic behavior, which can lead to surface refining.