576 research outputs found
Jet engine powers large, high-temperature wind tunnel
Wind tunnel for large component testing uses a jet engine with afterburner to provide high temperatures /1200 degrees to 2000 degrees F/ and controlled high velocity gas. This economical wind tunnel can accommodate parts ten feet by ten feet or larger, and is a useful technique for qualitative information
Minerals information GIS for regional development and inward investment in Northern Highlands of Scotland
The principal aim of this project, funded by the Department of Trade and Industry (DTI), is to stimulate exploration for metalliferous minerals in the Northern Highlands of Scotland, thereby promoting inward investment, job creation and the development of infrastructure in the region. The Northern Highlands study area occupies about 27,000 km2 located to the north and west of the Great Glen, including the Hebrides, Orkney and Shetland. The regional geology is highly varied, comprising mainly Archaean and Proterozoic metamorphic rocks and Palaeozoic sedimentary rocks. Intrusive igneous rocks are also widely developed. This geological diversity enhances the potential of the region for the occurrence of a wide range of mineral deposit types. The Northern Highlands are under-explored, relative to other parts of Scotland; nevertheless, this study has documented more than 350 recorded mineral occurrences
Conformations of closed DNA
We examine the conformations of a model for a short segment of closed DNA.
The molecule is represented as a cylindrically symmetric elastic rod with a
constraint corresponding to a specification of the linking number. We obtain
analytic expressions leading to the spatial configuration of a family of
solutions representing distortions that interpolate between the circular form
of DNA and a figure-eight form that represents the onset of interwinding. We
are also able to generate knotted loops. We suggest ways to use our approach to
produce other configurations relevant to studies of DNA structure. The
stability of the distorted configurations is assessed, along with the effects
of fluctuations on the free energy of the various configurations.Comment: 39 pages in REVTEX with 14 eps figures. Submitted to Phys. Rev. E.
This manuscript updates, expands and revises, to a considerable extent, a
previously posted manuscript, entitled "Conformations of Circular DNA," which
appeared as cond-mat/970104
A stitch in time: Efficient computation of genomic DNA melting bubbles
Background: It is of biological interest to make genome-wide predictions of
the locations of DNA melting bubbles using statistical mechanics models.
Computationally, this poses the challenge that a generic search through all
combinations of bubble starts and ends is quadratic.
Results: An efficient algorithm is described, which shows that the time
complexity of the task is O(NlogN) rather than quadratic. The algorithm
exploits that bubble lengths may be limited, but without a prior assumption of
a maximal bubble length. No approximations, such as windowing, have been
introduced to reduce the time complexity. More than just finding the bubbles,
the algorithm produces a stitch profile, which is a probabilistic graphical
model of bubbles and helical regions. The algorithm applies a probability peak
finding method based on a hierarchical analysis of the energy barriers in the
Poland-Scheraga model.
Conclusions: Exact and fast computation of genomic stitch profiles is thus
feasible. Sequences of several megabases have been computed, only limited by
computer memory. Possible applications are the genome-wide comparisons of
bubbles with promotors, TSS, viral integration sites, and other melting-related
regions.Comment: 16 pages, 10 figure
Superhelical Duplex Destabilization and the Recombination Position Effect
The susceptibility to recombination of a plasmid inserted into a chromosome
varies with its genomic position. This recombination position effect is known to
correlate with the average G+C content of the flanking sequences. Here we
propose that this effect could be mediated by changes in the susceptibility to
superhelical duplex destabilization that would occur. We use standard
nonparametric statistical tests, regression analysis and principal component
analysis to identify statistically significant differences in the
destabilization profiles calculated for the plasmid in different contexts, and
correlate the results with their measured recombination rates. We show that the
flanking sequences significantly affect the free energy of denaturation at
specific sites interior to the plasmid. These changes correlate well with
experimentally measured variations of the recombination rates within the
plasmid. This correlation of recombination rate with superhelical
destabilization properties of the inserted plasmid DNA is stronger than that
with average G+C content of the flanking sequences. This model suggests a
possible mechanism by which flanking sequence base composition, which is not
itself a context-dependent attribute, can affect recombination rates at
positions within the plasmid
GeneWiz browser: An Interactive Tool for Visualizing Sequenced Chromosomes
We present an interactive web application for visualizing genomic data of prokaryotic chromosomes. The tool (GeneWiz browser) allows users to carry out various analyses such as mapping alignments of homologous genes to other genomes, mapping of short sequencing reads to a reference chromosome, and calculating DNA properties such as curvature or stacking energy along the chromosome. The GeneWiz browser produces an interactive graphic that enables zooming from a global scale down to single nucleotides, without changing the size of the plot. Its ability to disproportionally zoom provides optimal readability and increased functionality compared to other browsers. The tool allows the user to select the display of various genomic features, color setting and data ranges. Custom numerical data can be added to the plot allowing, for example, visualization of gene expression and regulation data. Further, standard atlases are pre-generated for all prokaryotic genomes available in GenBank, providing a fast overview of all available genomes, including recently deposited genome sequences. The tool is available online from http://www.cbs.dtu.dk/services/gwBrowser. Supplemental material including interactive atlases is available online at http://www.cbs.dtu.dk/services/gwBrowser/suppl/
Experiences of help-seeking from professional services for a child or young person’s mental health concerns during the pandemic: A qualitative study
This is the final version. Available from Public Library of Science via the DOI in this record. Introduction
The immediate response to the Covid-19 pandemic saw school closures and a shift in provision to online health services for children and young people experiencing mental health concerns. This study provides mental health and referral services with an insight into difficulties experienced as well as recommendations on potential improvements.
Methods
Semi-structured interviews with 11 parents and six young people. Reflexive thematic analysis was used to analyse the data.
Results
Parents and young people reported mixed experiences on accessing mental health support. Priorities and pressures on health services impacted the likelihood of choosing to seek and being able to obtain help. Parents and young people had varying expectations and experiences in help-seeking during the pandemic which were also impacted by others’ experiences and views. For many, the relationship with the professional they were in contact with impacted their mental health treatment. Provision was sometimes accessed via private services due to long waiting lists or problems that did not “meet threshold”.
Conclusion
Understanding the experiences of seeking mental healthcare during the pandemic can inform improvements to access to services at a time when people are most vulnerable. Accessible provision other than private services needs to be made for those on waiting lists. For those who do not meet service threshold, intermediary support needs to be secured to prevent unnecessary exacerbation of symptoms and prolonged problems. If schools are to remain the hub for children and young people’s mental health services, they should be considered essential services at all times.UK Research and InnovationNational Institute for Health Researc
Conformations of Linear DNA
We examine the conformations of a model for under- and overwound DNA. The
molecule is represented as a cylindrically symmetric elastic string subjected
to a stretching force and to constraints corresponding to a specification of
the link number. We derive a fundamental relation between the Euler angles that
describe the curve and the topological linking number. Analytical expressions
for the spatial configurations of the molecule in the infinite- length limit
were obtained. A unique configuraion minimizes the energy for a given set of
physical conditions. An elastic model incorporating thermal fluctuations
provides excellent agreement with experimental results on the plectonemic
transition.Comment: 5 pages, RevTeX; 6 postscript figure
Dynamics of liquid 4He in Vycor
We have measured the dynamic structure factor of liquid 4He in Vycor using
neutron inelastic scattering. Well-defined phonon-roton (p-r) excitations are
observed in the superfluid phase for all wave vectors 0.3 < Q < 2.15. The p-r
energies and lifetimes at low temperature (T = 0.5 K) and their temperature
dependence are the same as in bulk liquid 4He. However, the weight of the
single p-r component does not scale with the superfluid fraction (SF) as it
does in the bulk. In particular, we observe a p-r excitation between T_c =
1.952 K, where SF = 0, and T_(lambda)=2.172 K of the bulk. This suggests, if
the p-r excitation intensity scales with the Bose condensate, that there is a
separation of the Bose-Einstein condensation temperature and the superfluid
transition temperature T_c of 4He in Vycor. We also observe a two-dimensional
layer mode near the roton wave vector. Its dispersion is consistent with
specific heat and SF measurements and with layer modes observed on graphite
surfaces.Comment: 3 pages, 4 figure
Mesoscopic models for DNA stretching under force: new results and comparison to experiments
Single molecule experiments on B-DNA stretching have revealed one or two
structural transitions, when increasing the external force. They are
characterized by a sudden increase of DNA contour length and a decrease of the
bending rigidity. It has been proposed that the first transition, at forces of
60--80 pN, is a transition from B to S-DNA, viewed as a stretched duplex DNA,
while the second one, at stronger forces, is a strand peeling resulting in
single stranded DNAs (ssDNA), similar to thermal denaturation. But due to
experimental conditions these two transitions can overlap, for instance for
poly(dA-dT). We derive analytical formula using a coupled discrete worm like
chain-Ising model. Our model takes into account bending rigidity, discreteness
of the chain, linear and non-linear (for ssDNA) bond stretching. In the limit
of zero force, this model simplifies into a coupled model already developed by
us for studying thermal DNA melting, establishing a connexion with previous
fitting parameter values for denaturation profiles. We find that: (i) ssDNA is
fitted, using an analytical formula, over a nanoNewton range with only three
free parameters, the contour length, the bending modulus and the monomer size;
(ii) a surprisingly good fit on this force range is possible only by choosing a
monomer size of 0.2 nm, almost 4 times smaller than the ssDNA nucleobase
length; (iii) mesoscopic models are not able to fit B to ssDNA (or S to ss)
transitions; (iv) an analytical formula for fitting B to S transitions is
derived in the strong force approximation and for long DNAs, which is in
excellent agreement with exact transfer matrix calculations; (v) this formula
fits perfectly well poly(dG-dC) and -DNA force-extension curves with
consistent parameter values; (vi) a coherent picture, where S to ssDNA
transitions are much more sensitive to base-pair sequence than the B to S one,
emerges.Comment: 14 pages, 9 figure
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