Al改性HP40合金力学性能的研究

在HP40合金中加入5%～20％的Al替代Ni，进行室温压缩和硬度力学性能试验。结果表明，铝的加入使合金的强度和硬度得到了显著提高。但随着Al含量的提高，由于树枝状（Ni，Fe）Al金属间化合物的析出及增加,使合金的脆性增加。     

Casein kinase 2 down-regulation and activation by polybasic peptides are mediated by acidic residues in the 55-64 region of the beta-subunit. A study with calmodulin as phosphorylatable substrate

The noncatalytic beta-subunit is responsible for the latency of casein kinase 2 (CK2) activity toward calmodulin. Twenty-one mutants of the beta-subunit bearing either deletions or Ala substitutions for charged residues in the 5-6, 55-70, and 171-178 sequences have been assayed for their ability to substitute for wild-type beta-subunit as a suppressor of activity toward calmodulin. The only mutations that reduced the ability of the beta-subunit to suppress calmodulin phosphorylation activity, though being compatible with normal reconstitution of CK2 holoenzyme, were those affecting Asp55, Glu57 and the whole triplet Glu59-Asp-Glu61. The activity of CK2 holoenzyme, either native or reconstituted, toward calmodulin can be elicited by a variety of polybasic effectors, including polylysine, polyarginine, salmine, and histones H4, H3, and, to a lesser extent, H2a and H2b. Histone H1 and polyamines are conversely ineffective. The latent "calmodulin kinase" activity of CK2 can also be specifically unmasked by a peptide (alpha[66-86]) reproducing a basic insert of the catalytic subunit. This effect is reversed by equimolar addition of a peptide (beta[55-71]) including the 55-64 acidic stretch of the beta-subunit. Comparable polylysine stimulation was observed with the holoenzymes reconstituted with either beta wt or the beta mutants capable of assembling with the alpha-subunit, with the notable exception of those bearing Ala substitutions for acidic residues at positions 55, 57, and 59-61. These were nearly insensitive to 42 nM polylysine, which conversely promotes a more than 10-fold increase of calmodulin phosphorylation with wild-type beta.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence that human cardiac allograft acceptance is associated with a decrease in donor-reactive helper T lymphocytes

We have reported that acute cardiac allograft rejection is associated with increased numbers of donor-reactive helper T lymphocytes (HTL) in the peripheral blood of patients. Further, increased frequencies of circulating donor-reactive HTL may predict allograft rejection episodes diagnosed by endomyocardial biopsy. The present study evaluates the relationship between donor-reactive HTL and allograft "acceptance" in cardiac transplant recipients bearing long-term allografts (> 1 year). Patients were categorized as either long-term acceptors or persistent rejecters based on the number of rejection episodes and the ability to withdraw steroid therapy. Limiting dilution analysis for IL-2-producing HTL was utilized, with cadaver donor splenocytes as a source of donor alloantigens. Donor-reactive HTL frequencies were determined from peripheral blood samples obtained before transplant, and at 1 month and 1 year after transplant. Individuals who accommodated their allografts and were withdrawn from steroid therapy had reduced numbers of donor-reactive HTL at 1 year after transplant as compared with earlier time points. Further, PBMC obtained from these individuals at 1 year after transplant responded weakly to donor alloantigens in a mixed lymphocyte response (MLR). This relationship between donor-reactive HTL and allograft accommodation was exemplified in a cardiac/liver transplant patient who was diagnosed with progressive multifocal leukoencephalopathy and removed from all immunosuppression. No subsequent rejection episodes were diagnosed. Donor-reactive HTL were not detectable and this individual failed to mount an MLR to donor alloantigens. However, a vigorous donor-reactive response was observed when MLR cultures were supplemented with exogenous IL-2. Therefore, nonresponsiveness to the allograft appeared to be due to a deficit in IL-2 production. In contrast, patients who experienced persistent rejection episodes and required continued steroid therapy maintained large numbers of donor-reactive HTL at 1 year after transplant. PBMC from these individuals responded vigorously to donor alloantigens in an MLR. Hence, monitoring donor-reactive HTL may identify individuals who have accommodated their graft and may tolerate a reduction in immunosuppression.     

Hownot to demarcate cognitive science and folk psychology: A response to Pickering and Chater

Pickering and Chater (P&C) maintain that folk psychology and cognitive science should neither compete nor cooperate. Each is an independent enterprise, with a distinct subject matter and characteristic modes of explanation. P&C's case depends upon their characterizations of cognitive science and folk psychology. We question the basis for their characterizations, challenge both the coherence and the individual adequacy of their contrasts between the two, and show that they waver in their views about the scope of each. We conclude that P&C do not so muchdiscover ascreate the gap they find between folk psychology and cognitive science. It is an artifact of their implausible and unmotivated attempt to demarcate the two areas, and of the excessively narrow accounts they give of each.     

Herding stochastic autonomous agents via local control rules and online target selection strategies

Autonomous Robots - We propose a simple yet effective set of local control rules to make a small group of “herder agents” collect and contain in a desired region a large ensemble of...     

Targeted Nanoparticle Thermometry: A Method to Measure Local Temperature at the Nanoscale Point Where Water Vapor Nucleation Occurs

An optical nanothermometer technique based on laser trapping, moving and targeted attaching an erbium oxide nanoparticle cluster is developed to measure the local temperature. The authors apply this new nanoscale temperature measuring technique (limited by the size of the nanoparticles) to measure the temperature of vapor nucleation in water. Vapor nucleation is observed after superheating water above the boiling point for degassed and nondegassed water. The average nucleation temperature for water without gas is 560 K but this temperature is lowered by 100 K when gas is introduced into the water. The authors are able to measure the temperature inside the bubble during bubble formation and find that the temperature inside the bubble spikes to over 1000 K because the heat source (optically‐heated nanorods) is no longer connected to liquid water and heat dissipation is greatly reduced.     

溶液燃烧法合成Co3O4纳米粉体及热处理研究

分别以氨基乙酸、柠檬酸、葡萄糖为燃料,Co(NO_3)_2·6H_2O为氧化剂,采用溶液燃烧法合成Co_3O_4粉体,并对氨基乙酸为燃料合成的Co_3O_4粉体在500℃、600℃和700℃热处理,研究其结构、微观形貌和磁学性能。研究表明各燃料配制的前驱体溶液在300℃均可发生燃烧反应合成Co_3O_4粉体,以氨基乙酸为燃料时,合成粉体的颗粒较大,中间有气孔,分散性好,残留少量的氨基乙酸。n(氨基乙酸)∶n(硝酸钴)=1.11∶1时合成的Co_3O_4粉体600℃热处理后得到了高纯度、分散性好、平均径向尺寸80nm的Co_3O_4纳米粉体。以氨基乙酸为燃料合成的Co_3O_4产物在600℃和700℃热处理后,其矫顽力和剩磁值都比500℃热处理后的要小。     

How evolution makes proteins fold quickly

Sequences of fast-folding model proteins (48 residues long on a cubic lattice) were generated by an evolution-like selection toward fast folding. We find that fast-folding proteins exhibit a specific folding mechanism in which all transition state conformations share a smaller subset of common contacts (folding nucleus). Acceleration of folding was accompanied by dramatic strengthening of interactions in the folding nucleus whereas average energy of nonnucleus interactions remained largely unchanged. Furthermore, the residues involved in the nucleus are the most conserved ones within families of evolved sequences. Our results imply that for each protein structure there is a small number of conserved positions that are key determinants of fast folding into that structure. This conjecture was tested on two protein superfamilies: the first having the classical monophosphate binding fold (CMBF; 98 families) and the second having type-III repeat fold (47 families). For each superfamily, we discovered a few positions that exhibit very strong and statistically significant "conservatism of conservatism"-amino acids in those positions are conserved within every family whereas the actual types of amino acids varied from family to family. Those amino acids are in spatial contact with each other. The experimental data of Serrano and coworkers [Lopez-Hernandez, E. & Serrano, L. (1996) Fold. Des. (London) 1, 43-55]. for one of the proteins of the CMBF superfamily (CheY) show that residues identified this way indeed belong to the folding nucleus. Further analysis revealed deep connections between nucleation in CMBF proteins and their function.     

Comparison of molecular changes in lung cancers in HIV-positive and HIV-indeterminate subjects

CONTEXT: Human immunodeficiency virus (HIV) infection has been associated with an increasing incidence of malignancy, and HIV-infected persons have an increased incidence of primary lung carcinoma compared with the general population. OBJECTIVE: To investigate the molecular changes present in HIV-associated lung tumors and compare them with those present in lung carcinomas arising in HIV-indeterminate subjects ("sporadic tumors"). DESIGN: Convenience sample. SUBJECTS: Archival tissues from 11 HIV-positive persons and from 35 persons of indeterminate HIV status. SETTING: University-based medical centers and affiliated hospitals. MAIN OUTCOME MEASURES: Analysis of frequency of loss of heterozygosity (LOH) and microsatellite alteration (MA) using polymerase chain reaction and 16 polymorphic microsatellite markers at 8 chromosomal regions frequently deleted in lung cancer. Presence of HIV and human papillomavirus (HPV) sequences. RESULTS: The overall frequency of LOH at all chromosomal regions tested and the frequencies at most of the individual regions were similar in the 2 groups. Frequency of MA present in the HIV-associated tumors (0.18) was 6-fold higher than in sporadic tumors (0.03) (P<.001). At least 1 MA was present in 10 (91%) of 11 HIV-associated tumors vs 17 (48%) of 35 sporadic tumors (P=.02). Molecular changes were independent of tumor stage and gender. HIV and HPV sequences were not detected in the HIV-associated lung carcinomas. CONCLUSIONS: Microsatellite alterations, which reflect widespread genomic instability, occur at greatly increased frequency in HIV-associated lung carcinomas. Although the mechanism underlying the development of increased MAs is unknown, it may play a crucial role in the development of many HIV-associated tumors.     

Longitudinal assessment of inpatient use and functioning of seriously mentally ill veterans with and without co-occurring substance use disorders

Within a fungal species, a subset of individuals may have more than the minimal complement of chromosomes. If the extra chromosomes are composed primarily of DNA not found in all representatives of the species, they are most appropriately referred to as supernumerary chromosomes. The patterns of repeated DNA sequences on certain supernumerary chromosomes suggest that they have a different evolutionary history from the essential chromosomes in the same genome. Supernumerary chromosomes can carry functional genes and, in at least two fungal species, genes on such chromosomes play important roles in host-pathogen interactions. Supernumerary chromosomes that confer an adaptive advantage in certain habitats, such as the ability to cause disease on a specific host, may be referred to as "conditionally dispensable" chromosomes in order to reflect their importance in some, but not all, growth conditions. In addition to describing the structural and functional characteristics of known supernumerary chromosomes in fungi, this review discusses the relative merits of the terms that have been used to describe them, and establishes experimental criteria for their identification.