14,336 research outputs found
Dynamic Radio-Frequency Transverse Susceptibility in Magnetic Nanoparticle Systems
A novel resonant method based on a tunnel-diode oscillator (TDO) is used to
study the dynamic transverse susceptibility in a Fe nanoparticle system. The
magnetic system consists of an aggregate of nanometer-size core (Au)-shell (Fe)
structure, synthesized by reverse micelle methods. Static and dynamic
magnetization measurements carried out in order to characterize the system
reveal a superparamagnetic behavior at high temperature. The field-dependent
transverse susceptibility at radio-frequencies (RF), for different temperatures
reveals distinct peak structure at characteristics fields (H_k, H_c) which
changes with temperature. It is proposed that relaxation processes could
explain the influence of the temperature on the field dependence of the
transverse susceptibility on the MI.Comment: 3 pages, 2-column, 3 figures, To be published in J. Appl. Phys. 2000
(44th Annual MMM proceedings
Inventory Investment, Internal-Finance Fluctuation, and the Business Cycle
macroeconomics, inventory investment, internal-finance fluctuation, business cycle
What is the influence on water quality in temperate eutrophic lakes of a reduction of planktivorous and benthivorous fish? A systematic review protocol
Background: In lakes that have become eutrophic due to sewage discharges or nutrient runoff from land, problems such as algal blooms and oxygen deficiency often persist even when nutrient supplies have been reduced. One reason is that phosphorus stored in the sediments can exchange with the water. There are indications that the high abundance of phytoplankton, turbid water and lack of submerged vegetation seen in many eutrophic lakes may represent a semi-stable state. For that reason, a shift back to more natural clear-water conditions could be difficult to achieve. In some cases, though, temporary mitigation of eutrophication-related problems has been accomplished through biomanipulation: stocks of zooplanktivorous fish have been reduced by intensive fishing, leading to increased populations of phytoplankton-feeding zooplankton. Moreover, reduction of benthivorous fish may result in lower phosphorus fluxes from the sediments. An alternative to reducing the dominance of planktivores and benthivores by fishing is to stock lakes with piscivorous fish. These two approaches have often been used in combination. The implementation of the EU Water Framework Directive has recently led to more stringent demands for measures against eutrophication, and a systematic review could clarify whether biomanipulation is efficient as a measure of that kind. Methods: The review will examine primary field studies of how large-scale biomanipulation has affected water quality and community structure in eutrophic lakes or reservoirs in temperate regions. Such studies can be based on comparison between conditions before and after manipulation, on comparison between treated and non-treated water bodies, or both. Relevant outcomes include Secchi depth, concentrations of oxygen, nutrients, suspended solids and chlorophyll, abundance and composition of phytoplankton, zooplankton and fish, and coverage of submerged macrophytes.A Systematic review to this article was published on 22 May 2015: ernes, C., Carpenter, S.R., Gårdmark, A. et al. What is the influence of a reduction of planktivorous and benthivorous fish on water quality in temperate eutrophic lakes? A systematic review. Environ Evid 4, 7 (2015). DOI: 10.1186/s13750-015-0032-9Mistr
Spin transition in GdN@C, detected by low-temperature on-chip SQUID technique
We present a magnetic study of the GdN@C molecule, consisting of a
Gd-trimer via a Nitrogen atom, encapsulated in a C cage. This molecular
system can be an efficient contrast agent for Magnetic Resonance Imaging (MRI)
applications. We used a low-temperature technique able to detect small magnetic
signals by placing the sample in the vicinity of an on-chip SQUID. The
technique implemented at NHMFL has the particularity to operate in high
magnetic fields of up to 7 T. The GdN@C shows a paramagnetic
behavior and we find a spin transition of the GdN structure at 1.2 K. We
perform quantum mechanical simulations, which indicate that one of the Gd ions
changes from a state () to a state (), likely due to a charge transfer between the C cage and the ion
Local adaptation drives the diversification of effectors in the fungal wheat pathogen Parastagonospora nodorum in the United States
Filamentous fungi rapidly evolve in response to environmental selection pressures in part due to their genomic plasticity. Parastagonospora nodorum, a fungal pathogen of wheat and causal agent of septoria nodorum blotch, responds to selection pressure exerted by its host, influencing the gain, loss, or functional diversification of virulence determinants, known as effector genes. Whole genome resequencing of 197 P. nodorum isolates collected from spring, durum, and winter wheat production regions of the United States enabled the examination of effector diversity and genomic regions under selection specific to geographically discrete populations. 1,026,859 SNPs/InDels were used to identify novel loci, as well as SnToxA and SnTox3 as factors in disease. Genes displaying presence/absence variation, predicted effector genes, and genes localized on an accessory chromosome had significantly higher pN/pS ratios, indicating a higher rate of sequence evolution. Population structure analyses indicated two P. nodorum populations corresponding to the Upper Midwest (Population 1) and Southern/Eastern United States (Population 2). Prevalence of SnToxA varied greatly between the two populations which correlated with presence of the host sensitivity gene Tsn1 in the most prevalent cultivars in the corresponding regions. Additionally, 12 and 5 candidate effector genes were observed to be under diversifying selection among isolates from Population 1 and 2, respectively, but under purifying selection or neutrally evolving in the opposite population. Selective sweep analysis revealed 10 and 19 regions that had recently undergone positive selection in Population 1 and 2, respectively, involving 92 genes in total. When comparing genes with and without presence/absence variation, those genes exhibiting this variation were significantly closer to transposable elements. Taken together, these results indicate that P. nodorum is rapidly adapting to distinct selection pressures unique to spring and winter wheat production regions by rapid adaptive evolution and various routes of genomic diversification, potentially facilitated through transposable element activity
Saving Saba Bank: Policy Implications of Biodiversity Studies
Saba Bank has always been an area of special importance to the neighboring island of Saba in the Netherlands Antilles. Sabans traditionally fished on the Bank as far back as 1907, but increasing foreign fishing pressures on the Bank in the 1970s and 1980s forced many Saban fishermen out. Concerns were compounded by the suspicion that shipping was also damaging the benthic habitat of the bank. Fishery legislation, enacted in 1996, brought an end to unlicensed fishing and established Coast Guard enforcement on the Bank, but also led to protests from neighboring countries that previously fished on the Bank.Research was necessary to support the need for protection. Review of available research of Saba Bank and rapid biological assessments and fisheries surveys since 1996 emphasized the richness of Saba Bank\u27s biodiversity and the need for protection of fisheries stocks. The national nature policy plan recognized this and encouraged further research to base conservation measures on.Recent biological surveys of corals, fishes, and algae presented in this collection of articles emphasized habitat heterogeneity and the relative richness of the marine flora and fauna. These assessments formed the basis for a management plan to protect Saba Bank\u27s biodiversity and a draft proposal to the International Maritime Organization (IMO) seeking Particularly Sensitive Sea Area (PSSA) status for the Bank. The intention of the PSSA proposal is to protect the benthic habitat on Saba Bank from anchor damage. This paper serves to provide the context for the results of the recent biodiversity surveys of Saba Bank. It is hoped that this collection will serve as a knowledge baseline and engender further research in the area
The role of the individual in the coming era of process-based therapy
For decades the development of evidence-based therapy has been based on experimental tests of protocols designed to impact psychiatric syndromes. As this paradigm weakens, a more process-based therapy approach is rising in its place, focused on how to best target and change core biopsychosocial processes in specific situations for given goals with given clients. This is an inherently more idiographic question than has normally been at issue in evidence-based therapy over the last few decades. In this article we explore methods of assessment and analysis that can integrate idiographic and nomothetic approaches in a process-based era.Accepted manuscrip
Brain neurons as quantum computers: {\it in vivo} support of background physics
The question: whether quantum coherent states can sustain decoherence,
heating and dissipation over time scales comparable to the dynamical timescales
of the brain neurons, is actively discussed in the last years. Positive answer
on this question is crucial, in particular, for consideration of brain neurons
as quantum computers. This discussion was mainly based on theoretical
arguments. In present paper nonlinear statistical properties of the Ventral
Tegmental Area (VTA) of genetically depressive limbic brain are studied {\it in
vivo} on the Flinders Sensitive Line of rats (FSL). VTA plays a key role in
generation of pleasure and in development of psychological drug addiction. We
found that the FSL VTA (dopaminergic) neuron signals exhibit multifractal
properties for interspike frequencies on the scales where healthy VTA
dopaminergic neurons exhibit bursting activity. For high moments the observed
multifractal (generalized dimensions) spectrum coincides with the generalized
dimensions spectrum calculated for a spectral measure of a {\it quantum} system
(so-called kicked Harper model, actively used as a model of quantum chaos).
This observation can be considered as a first experimental ({\it in vivo})
indication in the favour of the quantum (at least partially) nature of the
brain neurons activity
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