591 research outputs found
Relaxation mechanisms of multi-quantum coherences in the Zeeman structure of atomic Cs trapped in solid He
This paper extends our previous work on near-degenerate magnetic resonance transitions in alkali ground states involving the simultaneous absorption of multiple radio-frequency quanta. New experimental results with an improved spectral resolution were obtained with cesium atoms trapped in the cubic phase of a helium crystal. The main objective of the paper is a theoretical study of the influence of stochastic perturbations of given multipole orders on the various multi-photon coherences. Algebraic and numerical results for perturbations of both dipolar and quadrupolar symmetry are presented. The present experimental resolution does not yet allow us to distinguish between these two most likely relaxation mechanisms. Nonetheless, the experimental spectra are very well described when allowing in the calculations for a magnetic field inhomogeneity of 2×10-
Discovery of dumbbell-shaped Cs*He_n exciplexes in solid He 4
We have observed several new spectral features in the fluorescence of cesium
atoms implanted in the hcp phase of solid helium following laser excitation to
the 6P states. Based on calculations of the emission spectra using
semiempirical Cs-He pair potentials the newly discovered lines can be assigned
to the decay of specific Cs*He exciplexes: an apple-shaped CsHe and a dumbbell-shaped CsHe exciplex with
a well defined number of bound helium atoms. While the former has been
observed in other enviroments, it was commonly believed that exciplexes with
might not exist. The calculations suggest CsHe to be
the most probable candidate for that exciplex, in which the helium atoms are
arranged on a ring around the waist of the dumbbell shaped electronic density
distribution of the cesium atom.Comment: 4 pages, 4 figure
Multi-photon processes in the Zeeman structure of atomic Cs trapped in solid helium
We report magnetic resonance experiments with optical detection performed on cesium atoms trapped in a crystalline Hematrix. Multi-photon transitions, i.e., processes in which several radio-frequency photons are absorbed simultaneously in a given hyperfine Zeeman multiplet of the ground state, were the central topic of these studies. The long relaxation times of spin coherences of Cs in solid He allow such transitions to be spectrally resolved in fields as low as 1mT. We observed all allowed multi-photon transitions up to the ΔM=8 transition in the F=4 state. We compare the experimental spectra with theoretical spectra obtained from numerical solutions of the Liouville equation that include optical pumping and the interaction with the static and oscillating fields. Multi-photon transitions may find applications in magnetometry, suppress systematic effects in EDM experiments, and allow the study of relaxation phenomena in doped He crystals. The demonstration of these features is still hindered by inhomogeneous line broadenin
A molecular dynamics study on the equilibrium magnetization properties and structure of ferrofluids
We investigate in detail the initial susceptibility, magnetization curves,
and microstructure of ferrofluids in various concentration and particle dipole
moment ranges by means of molecular dynamics simulations. We use the Ewald
summation for the long-range dipolar interactions, take explicitly into account
the translational and rotational degrees of freedom, coupled to a Langevin
thermostat. When the dipolar interaction energy is comparable with the thermal
energy, the simulation results on the magnetization properties agree with the
theoretical predictions very well. For stronger dipolar couplings, however, we
find systematic deviations from the theoretical curves. We analyze in detail
the observed microstructure of the fluids under different conditions. The
formation of clusters is found to enhance the magnetization at weak fields and
thus leads to a larger initial susceptibility. The influence of the particle
aggregation is isolated by studying ferro-solids, which consist of magnetic
dipoles frozen in at random locations but which are free to rotate. Due to the
artificial suppression of clusters in ferro-solids the observed susceptibility
is considerably lowered when compared to ferrofluids.Comment: 33 pages including 12 figures, requires RevTex
Entwicklung eines zeitlichen und räumlichen Entscheidungshilfesystems gegen den Erbsenwickler (Cydia nigricana, Fabricius)
Pea moths (Cydia nigricana) can cause severe damages in pea crops (Pisum sativum). Larvae feed on the seeds in the pods and contaminate them with feces. In the cultivation of organic green peas 0.5 % damaged seeds lead to the denial of
whole pea fields (Schulz & Saucke 2005). There can be a yield loss in forage peas and a loss of quality of seeds for propagation. Within the framework of the project to improve the spatial and temporal cultivation strategy of peas to get less damage due to pea moths, is the intention. For
a better spatial and temporal cultivation strategy, the DSS creates a map with areas with an infestation risk factor. The higher the risk factor, the earlier the new fields
should be cultivated. Therefore, the first part of the DSS works with georeferenced data, like distances between fields of the previous year and the currently planned fields and their infestation risk. The coincidence of the flowering of peas and the flight of pea moths is very important for the infestation. Hence, the second part of the DSS predicts the phenology of the pea and the development of the pea moth for a better precision of the pest control
Erbsenwickler (Cydia nigricana) in Gemüse- und Körnererbsen: Grundlagen zur Befallsprognose und Schadensprävention
Spatio-temporal distribution, combined with aspects of insect biology and ecology can influence the infestation risk of the key pea pest Cydia nigricana in vegetable- and
field peas. The proximity of pea fields of the previous cultivation period highly affects the infestation potential of the moth. The presented study aims to monitor the
infestation development in three different regions in Germany (North Hesse, Saxony, Saxony-Anhalt) in four consecutive years and to relate empirical pest incidences to
key factors as crop abundance, the distance to previous pea fields, the pea plant phenology and climatic conditions. In a next step, these data will form the basis for the
elaboration of a computer-aided decision support system, which assists farmers in implementing preventive strategies based on risk avoidance
Gene expression in acute Stanford type A dissection: a comparative microarray study
BACKGROUND: We compared gene expression profiles in acutely dissected aorta with those in normal control aorta. MATERIALS AND METHODS: Ascending aorta specimen from patients with an acute Stanford A-dissection were taken during surgery and compared with those from normal ascending aorta from multiorgan donors using the BD Atlas™ Human1.2 Array I, BD Atlas™ Human Cardiovascular Array and the Affymetrix HG-U133A GeneChip(®). For analysis only genes with strong signals of more than 70 percent of the mean signal of all spots on the array were accepted as being expressed. Quantitative real-time polymerase chain reaction (RT-PCR) was used to confirm regulation of expression of a subset of 24 genes known to be involved in aortic structure and function. RESULTS: According to our definition expression profiling of aorta tissue specimens revealed an expression of 19.1% to 23.5% of the genes listed on the arrays. Of those 15.7% to 28.9% were differently expressed in dissected and control aorta specimens. Several genes that encode for extracellular matrix components such as collagen IV α2 and -α5, collagen VI α3, collagen XIV α1, collagen XVIII α1 and elastin were down-regulated in aortic dissection, whereas levels of matrix metalloproteinases-11, -14 and -19 were increased. Some genes coding for cell to cell adhesion, cell to matrix signaling (e.g., polycystin1 and -2), cytoskeleton, as well as several myofibrillar genes (e.g., α-actinin, tropomyosin, gelsolin) were found to be down-regulated. Not surprisingly, some genes associated with chronic inflammation such as interleukin -2, -6 and -8, were up-regulated in dissection. CONCLUSION: Our results demonstrate the complexity of the dissecting process on a molecular level. Genes coding for the integrity and strength of the aortic wall were down-regulated whereas components of inflammatory response were up-regulated. Altered patterns of gene expression indicate a pre-existing structural failure, which is probably a consequence of insufficient remodeling of the aortic wall resulting in further aortic dissection
Impact of estrogen receptor alpha on the tamoxifen resistance in breast cancer patients
Genetic aberrations and changes in the activity of estrogen receptors alpha (ERa[lpha]) play an important role in the endocrine sensitivity. The aim of this study was to examine the relationship between the ESR1 expression level, its polymorphic variants, and the distribution pattern of ER[alpha] expression with the prognosis and efficacy of tamoxifen treatment in breast cancer patients. Our data suggest that the ESR1 expression level, SNPs in the ESR1 gene and the distribution pattern of ERα expression can be a potential molecular marker of tamoxifen resistance in breast cancer patients
Increase of the mean inner Coulomb potential in Au clusters induced by surface tension and its implication for electron scattering
Electron holography in a transmission electron microscope was applied to
measure the phase shift induced by Au clusters as a function of the cluster
size. Large phase shifts Df observed for small Au clusters cannot be described
by the well-known equation Df=C_E V_0 t (C_E: interaction constant, V_0: mean
inner Coulomb potential (MIP) of bulk gold, t: cluster thickness). The rapid
increase of the Au MIP with decreasing cluster size derived from Df, can be
explained by the compressive strain of surface atoms in the cluster
Web-Based Randomized Controlled Trial
Background: Patients often seek other patients’ experiences with the disease.
The Internet provides a wide range of opportunities to share and learn about
other people’s health and illness experiences via blogs or patient-initiated
online discussion groups. There also exists a range of medical information
devices that include experiential patient information. However, there are
serious concerns about the use of such experiential information because
narratives of others may be powerful and pervasive tools that may hinder
informed decision making. The international research network DIPEx (Database
of Individual Patients’ Experiences) aims to provide scientifically based
online information on people’s experiences with health and illness to fulfill
patients’ needs for experiential information, while ensuring that the
presented information includes a wide variety of possible experiences.
Objective: The aim is to evaluate the colorectal cancer module of the German
DIPEx website krankheitserfahrungen.de with regard to self-efficacy for coping
with cancer and patient competence. Methods: In 2015, a Web-based randomized
controlled trial was conducted using a two-group between-subjects design and
repeated measures. The study sample consisted of individuals who had been
diagnosed with colorectal cancer within the past 3 years or who had metastasis
or recurrent disease. Outcome measures included self-efficacy for coping with
cancer and patient competence. Participants were randomly assigned to either
an intervention group that had immediate access to the colorectal cancer
module for 2 weeks or to a waiting list control group. Outcome criteria were
measured at baseline before randomization and at 2 weeks and 6 weeks Results:
The study randomized 212 persons. On average, participants were 54 (SD 11.1)
years old, 58.8% (124/211) were female, and 73.6% (156/212) had read or heard
stories of other patients online before entering the study, thus excluding any
influence of the colorectal cancer module on krankheitserfahrungen.de. No
intervention effects were found at 2 and 6 weeks after baseline. Conclusions:
The results of this study do not support the hypothesis that the website
studied may increase self-efficacy for coping with cancer or patient
competencies such as self-regulation or managing emotional distress. Possible
explanations may involve characteristics of the website itself, its use by
participants, or methodological reasons. Future studies aimed at evaluating
potential effects of websites providing patient experiences on the basis of
methodological principles such as those of DIPEx might profit from extending
the range of outcome measures, from including additional measures of website
usage behavior and users’ motivation, and from expanding concepts, such as
patient competency to include items that more directly reflect patients’
perceived effects of using such a website. Trial Registration:
Clinicaltrials.gov NCT02157454;
https://clinicaltrials.gov/ct2/show/NCT02157454 (Archived by WebCite at
http://www.webcitation.org/6syrvwXxi
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