3,620 research outputs found
The bend stiffness of S-DNA
We formulate and solve a two-state model for the elasticity of nicked,
double-stranded DNA that borrows features from both the Worm Like Chain and the
Bragg--Zimm model. Our model is computationally simple, and gives an excellent
fit to recent experimental data through the entire overstretching transition.
The fit gives the first value for the bending stiffness of the overstretched
state as about 10 nm*kbt, a value quite different from either B-form or
single-stranded DNA.Comment: 7 pages, 1 figur
The Experiences of Mental Illness and Addiction among Men and Women with Co-occurring Disorders
The study presented used empirical phenomenological methods to gain insight into the experiences of chemical dependence and mental illness among men and women with co-occurring disorders. The literature review discussed issues concerning: gender with the self-construal, traditional gender norms, and gender as a factor in the co-occurring disorder population. The results of this study include the following themes: catalysts for change, positive and negative self-concept, substance use as a means of self-medication, and therapeutic factors. Implications for the counseling profession, and implications for further research were discussed
Off-lattice Monte Carlo Simulation of Supramolecular Polymer Architectures
We introduce an efficient, scalable Monte Carlo algorithm to simulate
cross-linked architectures of freely-jointed and discrete worm-like chains.
Bond movement is based on the discrete tractrix construction, which effects
conformational changes that exactly preserve fixed-length constraints of all
bonds. The algorithm reproduces known end-to-end distance distributions for
simple, analytically tractable systems of cross-linked stiff and freely jointed
polymers flawlessly, and is used to determine the effective persistence length
of short bundles of semi-flexible worm-like chains, cross-linked to each other.
It reveals a possible regulatory mechanism in bundled networks: the effective
persistence of bundles is controlled by the linker density.Comment: 4 pages, 4 figure
Evaluation of SIR-A space radar for geologic interpretation: United States, Panama, Colombia, and New Guinea
Comparisons between LANDSAT MSS imagery, and aircraft and space radar imagery from different geologic environments in the United States, Panama, Colombia, and New Guinea demonstrate the interdependence of radar system geometry and terrain configuration for optimum retrieval of geologic information. Illustrations suggest that in the case of space radars (SIR-A in particular), the ability to acquire multiple look-angle/look-direction radar images of a given area is more valuable for landform mapping than further improvements in spatial resolution. Radar look-angle is concluded to be one of the most important system parameters of a space radar designed to be used for geologic reconnaissance mapping. The optimum set of system parameters must be determined for imaging different classes of landform features and tailoring the look-angle to local topography
Infrared Surface Brightness Distances to Cepheids: a comparison of Bayesian and linear-bisector calculations
We have compared the results of Bayesian statistical calculations and
linear-bisector calculations for obtaining Cepheid distances and radii by the
infrared surface brightness method. We analyzed a set of 38 Cepheids using a
Bayesian Markov Chain Monte Carlo method that had been recently studied with a
linear-bisector method. The distances obtained by the two techniques agree to
1.5 \pm 0.6% with the Bayesian distances being larger. The radii agree to 1.1%
\pm 0.7% with the Bayesian determinations again being larger. We interpret this
result as demonstrating that the two methods yield the same distances and
radii. This implies that the short distance to the LMC found in recent
linear-bisector studies of Cepheids is not caused by deficiencies in the
mathematical treatment. However, the computed uncertainties in distance and
radius for our dataset are larger in the Bayesian calculation by factors of
1.4-6.7. We give reasons to favor the Bayesian computations of the
uncertainties. The larger uncertainties can have a significant impact upon
interpretation of Cepheid distances and radii obtained from the infrared
surface brightness method.Comment: 27 pages with 9 figure
Social Circuits: Peptidergic Regulation of Mammalian Social Behavior
Mammals have developed patterns of social relationships that enhance the survival of individuals and maximize the reproductive success of species. Although social stimuli and social responses are highly complex, recent studies are providing substantial insights into their neural substrates. Neural pathways employing the nonapeptides vasopressin and oxytocin play a particularly prominent role both in social recognition and the expression of appropriate social responses. New insights into social neuroscience are discussed, along with the relevance of this rapidly developing field to human relationships and disease processes
Glomerulonephritis and malignancy: A population-based analysis
Glomerulonephritis and malignancy: A population-based analysis.BackgroundAn association between glomerulonephritis and malignant tumors has previously both been found and discarded in clinical series, but to our knowledge never has been tested in a population-based setting.MethodsThe Danish Kidney Biopsy Registry includes all kidney biopsies performed from 1985. Using a unique personal identification number, each person in the registry to the National Population Registry and the Danish Cancer Registry were linked. Cancer occurrence after the biopsy was compared in patients with morphological, glomerular diseases with that of the general Danish population, taking into account sex, age, calendar period and time since biopsy, and the 95% confidence interval (95% CI) for the observed-to-expected rates was calculated, assuming a Poisson distribution. Cancer occurrence was stratified to <1 year, 1 to 4, and ≥5 years after a biopsy.ResultsA total of 102 de novo cancers were found in 1958 patients. These cancers represent a two- to threefold excess of the expected number at <1 and 1 to 4, but not ≥5 years after a biopsy. Non-Hodgkin's lymphomas were observed six to eight times more than expected. Cancer excess was seen in glomerulonephritides with a known or suspected virus etiology.ConclusionsThe excess cancer rate could be the result of underlying undiagnosed tumors whose antigens have initiated glomerulonephritis, or the immunosuppressive therapy that initiated or energized tumor cells. Based on the findings in our study, there is some support for an association to persistent viruses causing first the glomerulonephritides and then the malignancies, perhaps through a common pathogenesis. This calls for other studies to be done that are specifically designed to investigate this issue, with more data on patient characteristics and confounders
Automated myocardial perfusion from coronary X-ray angiography
The purpose of our study is the evaluation of an algorithm to determine the physiological relevance of a coronary\ud
lesion as seen in a coronary angiogram. The aim is to extract as much as possible information from a standard\ud
coronary angiogram to decide if an abnormality, percentage of stenosis, as seen in the angiogram, results in\ud
physiological impairment of the blood supply of the region nourished by the coronary artery. Coronary angiography,\ud
still the golden standard, is used to determine the cause of angina pectoris based on the demonstration\ud
of an important stenose in a coronary artery. Dimensions of a lesion such as length and percentage of narrowing\ud
can at present easily be calculated by using an automatic computer algorithm such as Quantitative Coronary\ud
Angiography (QCA) techniques resulting in just anatomical information ignoring the physiological relevance of\ud
the lesion. In our study we analyze myocardial perfusion images in standard coronary angiograms in rest and\ud
in artificial hyperemic phases, using a drug e.g. papaverine intracoronary. Setting a Region of Interest (ROI) in\ud
the angiogram without overlying major vessels makes it possible to calculate contrast differences as a function of\ud
time, so called time-density curves, in the basal and hyperemic phases. In minimizing motion artifacts, end diastolic\ud
images are selected ECG based in basal and hyperemic phase in an identical ROI in the same angiographic\ud
projection. The development of new algorithms for calculating differences in blood supply in the region as set\ud
are presented together with the results of a small clinical case study using the standard angiographic procedur
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