Physico-mechanical properties and structure of diamond polycrystalline composite materials produced from variously dispersed powders

A nanostructural diamond composite material having grains of average size 0.08 μm and hardness corresponding to the hardness of diamond composite materials with grains of average size 30 μm has been produced using nanotechnologies of powder materials. Temperature dependences of hardness of nanostructural diamond composites of various dispersions have been compared. The thermostability of a diamond composite has been shown to depend not only on the composition of a sintering aid but on the size of diamond powders as well. Our findings have indicated that the material obtained holds promise in finishing products of nonferrous metals and alloys instead of natural diamonds.     

Ubiquitous human computing

Ubiquitous computing means network connectivity everywhere, linking devices and systems as small as a drawing pin and as large as a worldwide product distribution chain. What could happen when people are so readily networked? This paper explores issues arising from two possible emerging models of ubiquitous human computing: fungible networked brainpower and collective personal vital sign monitoring.     

The black hole symphony: probing new physics using gravitational waves

The next decade will very likely see the birth of a new field of astronomy as we become able to directly detect gravitational waves (GWs) for the first time. The existence of GWs is one of the key predictions of Einstein's theory of general relativity, but they have eluded direct detection for the last century. This will change thanks to a new generation of laser interferometers that are already in operation or which are planned for the near future. GW observations will allow us to probe some of the most exotic and energetic events in the Universe, the mergers of black holes. We will obtain information about the systems to a precision unprecedented in astronomy, and this will revolutionize our understanding of compact astrophysical systems. Moreover, if any of the assumptions of relativity theory are incorrect, this will lead to subtle, but potentially detectable, differences in the emitted GWs. Our observations will thus provide very precise verifications of the theory in an as yet untested regime. In this paper, I will discuss what GW observations could tell us about known and (potentially) unknown physics.     

The science of space weather

The basic physics underpinning space weather is reviewed, beginning with a brief overview of the main causes of variability in the near-Earth space environment. Although many plasma phenomena contribute to space weather, one of the most important is magnetic reconnection, and recent cutting edge research in this field is reviewed. We then place this research in context by discussing a number of specific types of space weather in more detail. As society inexorably increases its dependence on space, the necessity of predicting and mitigating space weather will become ever more acute. This requires a deep understanding of the complexities inherent in the plasmas that fill space and has prompted the development of a new generation of scientific space missions at the international level.     

Impermeable atomic membranes from graphene sheets

We demonstrate that a monolayer graphene membrane is impermeable to standard gases including helium. By applying a pressure difference across the membrane, we measure both the elastic constants and the mass of a single layer of graphene. This pressurized graphene membrane is the world's thinnest balloon and provides a unique separation barrier between 2 distinct regions that is only one atom thick.     

Silica surface modification reactions with aluminum and boron alkyls and (alkyl) chlorides: reactivities and surface nanostructures

The functionalization of nanoporous and nanoparticulate silica surfaces requires a molecular level understanding of the chemistry and structures which result from surface reactions. Various types of reactive groups on silica can participate, giving rise to different nanostructures. It is necessary to devise methods to alter the reactive nature of silica surfaces to control the nanoscale chemical structure. Various silica pretreatments are utilized to alter the silica surface prior to reaction with AlEt3, AlEtxCl(3-x), BEt3, BCl3, and TiCl4. Reactivities of these surface reactive reagents are compared. Aluminum compounds preferentially react with loss of alkane rather than HCl, in a thermodynamically controlled reaction as determined by ab initio computational methods. Consideration of the structures resulting from reaction of the boron and aluminum compounds above with silica surface diols has been taken into account. Particular attention has been paid to the possibility of forming a cyclic 4-membered ring structure. While this is unlikely to form from reactions with MCl3, such structures may be possible when reacting silicas with MMe3.     

Nanofibrous glass tailored with apatite-fibronectin interface for bone cell stimulation

Exploring a material with smart and biomimetic interface has great potential in the biomaterials and tissue engineering field. This paper reports a novel nanofibrous bone matrix that was developed to retain a cell-stimulating and bone-mimetic biointerface. The bone mineral, apatite, and the cell adhesive protein, fibronectin (FN), were hybridized on the interface of a bioactive glass nanofibrous mesh, through the dissolution-and-reprecipitation process. The hybridized nanofibrous mesh showed significant improvement in the initial responses of the bone-derived cells. It is believed that this biomimetic and cell-stimulating nanofibrous mesh can be used as a potential bone regeneration matrix.     

High-yield production of graphene by liquid-phase exfoliation of graphite

Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to approximately 0.01 mg ml(-1), produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of approximately 1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.     

Volumetric Strains of Clean Sands Subject to Cyclic Loads

We utilize simple shear testing to investigate the volume change of clean sands subject to cyclic loads. We examine the effects of a number of compositional and environmental factors on the vertical strain at 15 uniform shear strain cycles and on the cycle-to-cycle variation of vertical strain. The compositional factor found to principally affect seismic compression susceptibility is relative density. Compositional factors found to not significantly affect cyclic volume change include gradation parameters (mean grain size and uniformity coefficient), particle angularity, soil fabric, mineralogy, and void ratio “breadth” e-emin. An environmental factor found to affect seismic compression susceptibility is confining stress, with volumetric strains decreasing with increasing stress. Environmental factors that do not significantly affect seismic compression susceptibility for clean sands are saturation and age. Stress history can decrease vertical strains from seismic compression for certain conditions, but we find such effects to be insignificant for the levels of overburden stress where compacted fills are typically overconsolidated from compaction-induced stresses. An empirical model is developed to represent the major trends of the data for application in engineering practice, which improves upon an earlier model that is based on a much smaller database and does not account for the aforementioned environmental factors.     

Delay discrimination and reversal eyeblink classical conditioning in abstinent chronic alcoholics.

[Correction Notice: An erratum for this article was reported in Vol 23(2) of Neuropsychology (see record 2009-02621-003). The lifetime drinking data listed in Table 1 on p. 198 was not correctly calculated and underestimated lifetime exposure to alcohol. The corrected lifetime variables from that table are included.] Evidence has shown that alcoholism leads to volume reductions in brain regions critical for associative learning using the eyeblink classical conditioning paradigm (EBCC). Evidence indicates that cerebellar shrinkage causes impairment in simple forms of EBCC, whereas changes in forebrain structures result in impairment in more complex tasks. In this study, the ability of abstinent alcoholics and matched control participants to acquire learned responses during delay discrimination and discrimination reversal was examined and related to severity of drinking history and neuropsychological performance. During discrimination learning, one tone (CS+) predicted the occurrence of an airpuff (unconditioned stimulus), and another tone (CS-) served as a neutral stimulus; then the significance of the tones was reversed. Alcoholics who learned the initial discrimination were impaired in acquiring the new CS+ after the tones reversed; this is a function that has previously been linked to forebrain structures. It is suggested that a factor important to alcoholic addiction may be the presence of alcoholic-related associative responses that interfere with the ability to learn new more adaptive associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)