Presence of human immunodeficiency virus (HIV) type 1 subtype A infection in a New York community with high HIV prevalence: a sentinel site for monitoring HIV genetic diversity in North America. Centers for Disease Control and Prevention-Bronx Lebanon HIV Serosurvey Team

To determine whether US residents are infected with subtypes of human immunodeficiency virus (HIV) type 1 other than subtype B (Western), the predominant North American subtype with a unique GPGR genetic sequence in the V3 loop, viruses from 22 HIV-infected adults were serotyped and subtyped. Twenty patients had subtype B (Western), of whom 15 had serotype B (Western), 3 had serotype A/C, 1 had serotype B (Thai), and 1 had a nontypeable serotype. Two had subtype A, both serotype A/C. Both subtype A-infected patients, only 1 of whom had been outside the United States, reported sex with persons traveling abroad, suggesting possible acquisition in the United States. Because US residents are infected with non-subtype B (Western) strains, US surveillance for HIV-1 diversity is needed to elucidate subtype-specific transmission patterns and pathogenesis and to guide evaluation and development of HIV diagnostic tests and vaccines.     

Breakage Prediction of Laminated Glass Using the “Sacrificial Ply” Design Concept

Laminated architectural glass has proven to be well suited for use in glazing systems that must resist wind-borne debris impacts. When the inner glass ply in a laminated window unit remains unbroken after wind-borne debris impacts on the outer glass ply, the integrity of the building envelope is preserved. A mechanics-based analytical model is developed to predict the cumulative probability of inner glass ply breakage in laminated architectural glass subjected to simulated wind-borne debris impacts on the outer glass ply. A nonlinear dynamic finite-element analysis is employed to compute stresses in each layer of the laminate due to impact. Based on the cumulative damage theory, the two-parameter Weibull distribution is used to characterize the cumulative probability of inner glass ply breakage. The analytical predictive model is calibrated using available experimental data on material parameters. Cumulative probabilities of inner glass ply breakage predicted by the analytical model are in agreement with the corresponding experimental data.     

The gamma subunit of the Na,K-ATPase induces cation channel activity

The gamma subunit of the Na,K-ATPase is a hydrophobic protein of approximately 10 kDa. The gamma subunit was expressed in Sf-9 insect cells and Xenopus oocytes to ascertain its role in Na,K-ATPase function. Immunoblotting has shown that the gamma subunit is expressed in Sf-9 cells infected with recombinant baculovirus containing the cDNA for the human gamma subunit. Confocal microscopy demonstrates that the gamma subunit can be delivered to the plasma membrane of Sf-9 cells independently of the other Na,K-ATPase subunits and that gamma colocalizes with alpha1 when these proteins are coexpressed. When Sf-9 cells were coinfected with alpha1 and gamma, antibodies to the gamma subunit were able to coimmunoprecipitate the alpha1 subunit, suggesting that gamma is able to associate with alpha1. The gamma subunit is a member of a family of single-pass transmembrane proteins that induces ion fluxes in Xenopus oocytes. Evidence that the gamma subunit is a functional component was supported by experiments showing gamma-induced cation channel activity when expressed in oocytes and increases in Na+ and K+ uptake when expressed in Sf-9 cells.     

Developing soybean varieties with genetic resistance toPhomopsis spp.

Phomopsis longicolla Hobbs andP. sojae Lehman are the principal causal organisms ofPhomopsis seed decay. This disease can reduce germination and quality of soybean. Production of mycotoxins byPhomopsis spp. has been reported. No commercial cultivars are resistant toPhomopsis seed decay. However, the plant introduction Pl-417479 is a source of genetic resistance. When grown under field conditions favorable for infection byPhomopsis spp., Pl-417479 was free of seed infection in two tests and had 3% infection in another. In the same environments, the cultivar “Williams 82” had 25 to 59% infection. Inheritance of the trait was determined to provide information for efficient transfer of the resistance to improved cultivars. Crosses were made between Pl-417479 and two susceptible genotypes. Five generations were developed for each cross and tested at two locations. Plots were artificially inoculated to enhance infection. Seeds from plants that showed various degrees of infection in the first season were progeny-tested. Environment strongly influenced disease incidence, but results indicated that resistance toPhomopsis seed decay is controlled by two complementary dominant nuclear genes. Information developed in these studies will facilitate development of resistant cultivars.     

Achieving the ideal strength in annealed molybdenum nanopillars

The theoretical strength of a material is the stress required to deform an infinite, defect-free crystal. Achieving the theoretical strength of a material experimentally is hindered by the ability to create and mechanically test an absolutely defect-free material. Here we show that through annealing it is possible to employ the versatility of the focused ion beam (FIB) but recover a mechanically pristine limited volume. Starting with FIB-milled molybdenum pillars, we anneal them in situ in a transmission electron microscope (TEM) producing a molybdenum pillar with a spherical cap. This geometry allows for the maximum stress to occur in the interior of the spherical cap and is ideally suited for experimentally achieving the ideal strength. During in situ compression testing in the TEM the annealed pillars show initial elastic loading followed by catastrophic failure at, or very near, the calculated theoretical strength of molybdenum.     

The deformation of Gum Metal through in situ compression of nanopillars

The name “Gum Metal” has been given to a set of β-Ti alloys that achieve exceptional elastic elongation and, with appropriate preparation, appear to deform by a dislocation-free mechanism triggered by elastic instability at the limit of strength. We have studied the compressive deformation of these materials with in situ nanocompression in a quantitative stage in a transmission electron microscope. The samples studied are cylindrical nanopillars 80–250 nm in diameter. The deformation pattern is monitored in real time using bright-field microscopy, dark-field microscopy or electron diffraction. Interesting results include the following: (i) nanopillars approach, and in several examples appear to reach, ideal strength; (ii) in contrast to conventional crystalline materials, there is no substantial “size effect” in pillar strength; (iii) the deformation mode is fine-scale with respect to the sample dimension, even in pillars of 100 nm size; (iv) shear bands (“giant faults”) do form in some tests, but only after yield and plastic deformation; and (v) a martensitic transformation to the base-centered orthorhombic α′′ phase is sometimes observed, but is an incidental feature of the deformation rather than a significant cause of it.     

The nanostructured origin of deformation twinning

We have revealed the fundamental embryonic structure of deformation twins using in situ mechanical testing of magnesium single crystals in a transmission electron microscope. This structure consists of an array of twin-related laths on the scale of several nanometers. A computational model demonstrates that this structure should be a generic feature at the incipient stage of deformation twinning when there are correlated nucleation events. Our results shed light on the origin of twinning-induced plasticity and transformation toughening, critical to the development of advanced structural alloys with high strength, ductility, and toughness.