1,059 research outputs found
Ball LightningâAerosol Electrochemical Power Source or A Cloud of Batteries
Despite numerous attempts, an adequate theoretical and experimental simulation of ball lightning still remains incomplete. According to the model proposed here, the processes of electrochemical oxidation within separate aerosol particles are the basis for this phenomenon, and ball lightning is a cloud of composite nano or submicron particles, where each particle is a spontaneously formed nanobattery which is short-circuited by the surface discharge because it is of such a small size. As free discharge-shorted current loops, aerosol nanobatteries are exposed to a powerful mutual magnetic dipoleâdipole attraction. The gaseous products and thermal energy produced by each nanobattery as a result of the intra-particle self-sustaining electrochemical reactions, cause a mutual repulsion of these particles over short distances and prevent their aggregation, while a collectivization of the current loops of separate particles, due to the electric arc overlapping between adjacent particles, weakens their mutual magnetic attraction over short distances. Discharge currents in the range of several amperes to several thousand amperes as well as the pre-explosive mega ampere currents, generated in the reductionâoxidation reactions and distributed between all the aerosol particles, explain both the magnetic attraction between the elements of the ball lightning substance and the impressive electromagnetic effects of ball lightning
Organizational perceptions of e-commerce: Re-assessing the benefits
This paper reports on preliminary findings from a wider and more in-depth study of six traditional organizations from different sectors that have successfully introduced e-commerce initiatives. The research adopted a case study approach, within which a questionnaire, identifying 16 generic benefits synthesized from the literature, was administered. The organizations were also asked to characterize whether e-commerce was strategic for them or not. The findings suggest that those organizations that perceived e-commerce to be strategic tended to consider intangible benefits as more important than tangible benefits, indicating perhaps a move away from the traditional view of e-commerce as a marketing driver to increase or create sales. Those organizations perceiving e-commerce as non-strategic rated the tangible benefits in much the same way as the strategic organizations, but rated the intangibles lower. Also it was found that e-commerce was important as a communication tool, not only with customers, as might be expected, but also with staff within the organization. The value of intra-organizational e-commerce was also found to be important, perhaps more than previously thought, as was its use in communicating and disseminating knowledge. The findings also reflect the importance of the sector and environment of the organization in determining their perceptions of e-commerce
The time-dependent rearrangement of the epithelial basement membrane in human skin wounds
In 62 human skin wounds (surgical wounds, stab wounds and lacerations after surgical treatment) we analyzed the immunohistochemical localization of collagen IV in the epithelial basement membrane. In 27 of these wounds the distribution of collagen VII, which represents a specific component of the basement membrane of stratified epithelia, was also analyzed. We were able to demonstrate a virtually identical co-distribution of both collagen IV and VII in the wound area with no significant time-dependent differences in the appearance of both collagen types. Fragments of the epithelial basement membrane could be detected in the wound area from as early as 4 days after wounding and after 8 days a complete restitution of the epithelial basement membrane was observed. In all cases with a wound age of more than 21 days the basement membrane was completely reformed over the former lesional area. The period between 8 and 21 days after wounding was characterized by a wide variability ranging from complete restitution to deposition of basement membrane fragments or total lack of the epidermal basement membrane
Use of Self-Care and Practitioner-Based Forms of Complementary and Alternative Medicine before and after a Diagnosis of Breast Cancer
Purpose. We examine factors associated with self-care, use of practitioner-based complementary and alternative medicine (CAM), and their timing in a cohort of women with breast cancer. Methods. Study participants were women with breast cancer who participated in the Long Island Breast Cancer Study Project. Self-care is defined as the use of multivitamins, single vitamins, botanicals, other dietary supplements, mind-body practices, special diets, support groups, and prayer. Within each modality, study participants were categorized as continuous users (before and after diagnosis), starters (only after diagnosis), quitters (only before diagnosis), or never users. Multivariable logistic regression was used for the main analyses. Results. Of 764 women who provided complete data, 513 (67.2%) initiated a new form of self-care following breast cancer diagnosis. The most popular modalities were those that are ingestible, and they were commonly used in combination. The strongest predictor of continuous use of one type of self-care was continuous use of other types of self-care. Healthy behaviors, including high fruit/vegetable intake and exercise, were more strongly associated with continuously using self-care than starting self-care after diagnosis. Conclusions. Breast cancer diagnosis was associated with subsequent behavioral changes, and the majority of women undertook new forms of self-care after diagnosis. Few women discontinued use of modalities they used prior to diagnosis
Latent class analysis suggests four distinct classes of complementary medicine users among women with breast cancer
Background:
Breast cancer patients commonly report using >1 form of complementary and alternative medicine (CAM). However, few studies have attempted to analyze predictors and outcomes of multiple CAM modalities. We sought to group breast cancer patients by clusters of type and intensity of complementary and alternative medicine (CAM) use following diagnosis.
Methods:
Detailed CAM use following breast cancer diagnosis was assessed in 2002â2003 among 764 female residents of Long Island, New York diagnosed with breast cancer in 1996â1997. Latent class analysis (LCA) was applied to CAM modalities while taking into account frequency and intensities.
Results:
Four distinct latent classes of CAM use emerged: 1) âLow-dose supplement usersâ (40 %), who used only common nutritional supplements; 2) âVitamin/mineral supplement usersâ (39 %), using an abundance of supplements in addition to other practices; 3) âMind-body medicine usersâ (12 %), with near-universal use of supplements, mind-body medicine techniques, and massage; and 4) âMulti-modality high-dose usersâ (9 %), who were highly likely to use nearly all types of CAM. Predictors of membership in classes with substantial CAM use included younger age, more education, higher income, Jewish religion, ideal body mass index, higher fruit and vegetable intake, higher levels of physical activity, receipt of adjuvant chemotherapy, and prior use of oral contraceptives.
Conclusions:
LCA identified important subgroups of breast cancer patients characterized by varying degrees of complementary therapy use. Further research should explore the reproducibility of these classes and investigate the association between latent class membership and breast cancer outcomes
Atomistic modelling of large-scale metal film growth fronts
We present simulations of metallization morphologies under ionized sputter
deposition conditions, obtained by a new theoretical approach. By means of
molecular dynamics simulations using a carefully designed interaction
potential, we analyze the surface adsorption, reflection, and etching reactions
taking place during Al physical vapor deposition, and calculate their relative
probability. These probabilities are then employed in a feature-scale
cellular-automaton simulator, which produces calculated film morphologies in
excellent agreement with scanning-electron-microscopy data on ionized sputter
deposition.Comment: RevTeX 4 pages, 2 figure
Numerical and Experimental Investigation of Circulation in Short Cylinders
In preparation for an experimental study of magnetorotational instability
(MRI) in liquid metal, we explore Couette flows having height comparable to the
gap between cylinders, centrifugally stable rotation, and high Reynolds number.
Experiments in water are compared with numerical simulations. Simulations show
that endcaps corotating with the outer cylinder drive a strong poloidal
circulation that redistributes angular momentum. Predicted azimuthal flow
profiles agree well with experimental measurements. Spin-down times scale with
Reynolds number as expected for laminar Ekman circulation; extrapolation from
two-dimensional simulations at agrees remarkably well with
experiment at . This suggests that turbulence does not dominate
the effective viscosity. Further detailed numerical studies reveal a strong
radially inward flow near both endcaps. After turning vertically along the
inner cylinder, these flows converge at the midplane and depart the boundary in
a radial jet. To minimize this circulation in the MRI experiment, endcaps
consisting of multiple, differentially rotating rings are proposed. Simulations
predict that an adequate approximation to the ideal Couette profile can be
obtained with a few rings
Narrow genetic base in forest restoration with holm oak (Quercus ilex L.) in Sicily
In order to empirically assess the effect of actual seed sampling strategy on
genetic diversity of holm oak (Quercus ilex) forestations in Sicily, we have
analysed the genetic composition of two seedling lots (nursery stock and
plantation) and their known natural seed origin stand by means of six nuclear
microsatellite loci. Significant reduction in genetic diversity and significant
difference in genetic composition of the seedling lots compared to the seed
origin stand were detected. The female and the total effective number of
parents were quantified by means of maternity assignment of seedlings and
temporal changes in allele frequencies. Extremely low effective maternity
numbers were estimated (Nfe 2-4) and estimates accounting for both
seed and pollen donors gave also low values (Ne 35-50). These values
can be explained by an inappropriate forestry seed harvest strategy limited to
a small number of spatially close trees
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