Scanning probe microscopy (SPM) studies of low-dimensional solids have yielded significant advances in the understanding of collective phenomena in these complex materials. In this article, SPM studies from the authors’ laboratory of charge density waves (CDWs) in metal dichalcogenide materials and of high-temperature copper–oxide superconductors (HTSCs) are reviewed. Temperature-dependent SPM studies of the structural properties of CDW phases in metal-doped tantalum disulfide (TaS2) and tantalum diselenide (TaSe2) have directly illuminated the problem of weak and strong CDW pinning. These studies have also led to the unexpected discovery of a hexatic CDW phase in niobium-doped TaS2. SPMs have also been used to probe the structural and electronic properties of HTSCs. SPM studies of metal-doped Bi2Sr2CaCu2O8 (BSCCO) superconductors have been used to elucidate the complex crystal chemistry of this system. Comparisons of these data with electron diffraction measurements also highlight the importance of local crystallography in these complex materials. In addition, SPM studies have been used to elucidate the interaction of magnetic flux lines with surface defects, thus enabling a quantitative assessment of pinning by surface roughness. Finally, etching has been studied by in situ SPM and shown to be a promising means for controlling the properties of HTSC surfaces.
I am not doing any superconductor work, but I have been looking into some of the historical aspects.I would like to show this transparency of the Tc temperatures of the oxide superconductors and the year in which each was "discov- ered," which I had brought with me to give to Praveen Chaudhari (Fig. 1).
The paper discusses issues pertinent to performance analysis of massively parallel systems. A model of parallel execution based on threads of control and events is then introduced. The key ingredient of this model is a measure of the communication complexity, which gives the number of events E as a function of the number of threads of control P and provides a signature of a parallel computation. Various consequences for speedup and load balancing are presented.
High intake of white rice has been associated with metabolic syndrome (MetS) and type 2 diabetes (T2D). Costa Ricans follow a staple dietary pattern that includes white rice and beans, yet the combined effect of these foods on cardio-metabolic risk factors has not been studied. We aimed to determine the association between intake of white rice and beans and MetS and its components in Costa Rican adults (n=1879) without T2D. Multivariate adjusted means were calculated for components of MetS by daily servings of white rice and beans (<1, 1, >1), and by the proportion of beans to white rice. Odds ratio for MetS was calculated by substituting one serving of beans for one of white rice. Results showed that increasing daily servings of white rice were associated positively with systolic blood pressure (BP), triglycerides (TG) and fasting glucose, and inversely with HDL-C (all P for trend <0.01). Increasing servings of beans were inversely associated with diastolic BP (P=0.049). Significant trends for higher HDL-C and lower BP and TG were observed for 1:3, 1:2, 1:1, and 2:1 proportions of beans to white rice. Substituting one serving of beans for white rice was associated with 36% (95% CI=13%–53%) lower odds of MetS. In conclusion, increasing the proportion of beans to white rice, or limiting the intake of white rice by substituting beans, may lower cardio-metabolic risk factors. Grant Funding Source: NIH grants HL 60692 and HL 49086
It is demonstrated that the removal of material or the creation or extension of cracks always reduces the total potential energy of any non-linear or linea
• This paper describes changes that have taken place, over a period of 10 years, in the way physicians and nursing staff in Finland give initial information and advice to the parents about their child's disability. It also discusses the association between quality of information given and parents' feelings of insecurity or helplessness. • In the study, we compared the experiences of parents of older (aged 12–17) disabled children with those of parents with younger (aged 7–9 years) disabled children. There were 85 children, whose disabilities were either learning or physical, or, in a few cases, both. • Parents completed a questionnaire and were interviewed by a social worker. • According to these reports, the initial information and advice received by the parents with younger children about their child's disability and its treatment, and on coping with the child at home, was better than that received by the parents of the older children. The parents of the younger children also reported feeling better prepared to take care of their child. • Those parents who reported having received little information and practical advice on coping with their child at home experienced feelings of insecurity and helplessness five times as often as those who were satisfied with the information and advice. • Feelings of being poorly prepared to take care of their child at home were reported four times more often by dissatisfied parents than by satisfied parents. • More attention should be paid to the manner in which information is given to parents, and doctors and nurses need to develop better ways to support parents and facilitate their adaptation.
The fracture of ductile solids has frequently been observed to result from the large growth and coalescence of microscopic voids, a process enhanced by the superposition of hydrostatic tensile stresses on a plastic deformation field. The ductile growth of voids is treated here as a problem in continuum plasticity. First, a variational principle is established to characterize the flow field in an elastically rigid and incompressible plastic material containing an internal void or voids, and subjected to a remotely uniform stress and strain rate field. Then an approximate Rayleigh-Ritz procedure is developed and applied to the enlargement of an isolated spherical void in a nonhardening material. Growth is studied in some detail for the case of a remote tensile extension field with superposed hydrostatic stresses. The volume changing contribution to void growth is found to overwhelm the shape changing part when the mean remote normal stress is large, so that growth is essentially spherical. Further, it is found that for any remote strain rate field, the void enlargement rate is amplified over the remote strain rate by a factor rising exponentially with the ratio of mean normal stress to yield stress. Some related results are discussed, including the long cylindrical void considered by F.A. McClintock (1968, J. appl. Mech. 35, 363), and an approximate relation is given to describe growth of a spherical void in a general remote field. The results suggest a rapidly decreasing fracture ductility with increasing hydrostatic tension.
