8,118 research outputs found
Thermodynamics of beta-amyloid fibril formation
Amyloid fibers are aggregates of proteins. They are built out of a peptide
called --amyloid (A) containing between 41 and 43 residues,
produced by the action of an enzyme which cleaves a much larger protein known
as the Amyloid Precursor Protein (APP). X-ray diffraction experiments have
shown that these fibrils are rich in --structures, whereas the shape of
the peptide displays an --helix structure within the APP in its
biologically active conformation. A realistic model of fibril formation is
developed based on the seventeen residues A12--28 amyloid peptide, which
has been shown to form fibrils structurally similar to those of the whole
A peptide. With the help of physical arguments and in keeping with
experimental findings, the A12--28 monomer is assumed to be in four
possible states (i.e., native helix conformation, --hairpin, globular
low--energy state and unfolded state). Making use of these monomeric states,
oligomers (dimers, tertramers and octamers) were constructed. With the help of
short, detailed Molecular Dynamics (MD) calculations of the three monomers and
of a variety of oligomers, energies for these structures were obtained. Making
use of these results within the framework of a simple yet realistic model to
describe the entropic terms associated with the variety of amyloid
conformations, a phase diagram can be calculated of the whole many--body
system, leading to a thermodynamical picture in overall agreement with the
experimental findings. In particular, the existence of micellar metastable
states seem to be a key issue to determine the thermodynamical properties of
the system
Hybrid Focal Stereo Networks for Pattern Analysis in Homogeneous Scenes
In this paper we address the problem of multiple camera calibration in the
presence of a homogeneous scene, and without the possibility of employing
calibration object based methods. The proposed solution exploits salient
features present in a larger field of view, but instead of employing active
vision we replace the cameras with stereo rigs featuring a long focal analysis
camera, as well as a short focal registration camera. Thus, we are able to
propose an accurate solution which does not require intrinsic variation models
as in the case of zooming cameras. Moreover, the availability of the two views
simultaneously in each rig allows for pose re-estimation between rigs as often
as necessary. The algorithm has been successfully validated in an indoor
setting, as well as on a difficult scene featuring a highly dense pilgrim crowd
in Makkah.Comment: 13 pages, 6 figures, submitted to Machine Vision and Application
Intensive care in labour: a preliminary appraisal
This is a preliminary investigation into the value, function and practicability of an intensive care labour unit for highrisk cases. All the equipment necessary can be mounted on two standard theatre trolleys which can be moved to the patient's bedside, but there is no place at present for this equipment outside a teaching unit. The investigation reports on continuous foetal heart monitoring of 36 patients and simultaneous foetal scalp pH estimations on 16 of them. A high proportion of babies with low Apgar scores showed one of two (or both) characteristic foetal heart patterns during labour: (a) the well-known type 2 dip, (b) a steppe pattern not previously described as such. The latter is of importance because it is impossible to detect using only clinical methods.There was poor correlation between foetal pH values and Apgar rating, and between foetal pH values and monitor patterns. Moreover, the pH values of foetal scalp blood and foetal umbilical arterial and venous blood samples bore varying relations to one another. However, for practical purposes, a foetal scalp blood of pH less than 7·20 when associated with a maternofoetal pH difference of 0·250 or more should be regarded with anxiety. The place and value of intensive care are discussed
Rapid Integration Of WiFi Hotspots With A Cloud-based AAA Service
Public WiFi is typically provided by a network of smaller (local-area), independent service providers internetworked by a larger (wide-area) service provider. Currently, integration between the local-area and the wide-area service providers is a tedious process. This disclosure describes a set of vendor-agnostic application program interfaces (APIs) that enable a WiFi hotspot provider to integrate its control plane with a cloud-based authentication, authorization, and accounting (AAA) service in a self-service manner, without the direct involvement of personnel from the cloud service. This set of APIs enable a WiFi provider to self-register and self-configure its WiFi devices, such as controllers, with the cloud-based AAA service. Once registered and configured, the WiFi device can send requests to the cloud-based AAA service for creating WiFi sessions to control and account for users’ network access
Intensive care in labour: A preliminary appraisal
This is a preliminary investigation into the value, function and practicability of an intensive care labour unit for highrisk cases. All the equipment necessary can be mounted on two standard theatre trolleys which can be moved to the patient's bedside, but there is no place at present for this equipment outside a teaching unit. The investigation reports on continuous foetal heart monitoring of 36 patients and simultaneous foetal scalp pH estimations on 16 of them. A high proportion of babies with low Apgar scores showed one of two (or both) characteristic foetal heart patterns during labour: (a) the well-known type 2 dip, (b) a steppe pattern not previously described as such. The latter is of importance because it is impossible to detect using only clinical methods. There was poor correlation between foetal pH values and Apgar rating, and between foetal pH values and monitor patterns. Moreover, the pH values of foetal scalp blood and foetal umbilical arterial and venous blood samples bore varying relations to one another. However, for practical purposes, a foetal scalp blood of pH less than 7·20 when associated with a maternofoetal pH difference of 0·250 or more should be regarded with anxiety. The place and value of intensive care are discussed
Gate-to-Gate Life-Cycle Inventory of Softwood Lumber Production
To perform a life-cycle analysis, a life-cycle inventory is needed. Data from surveys of manufacturers are presented for the energy and materials required to produce 1.623 m3 (1 mbf) of planed, dry, dimension lumber from logs in the western and southern U.S. In the West and South, 53 and 41% of the log volume (3.05 and 3.92 m3) leaves the mill as planed, dry dimension lumber, respectively. A much greater portion of the energy used for production in the South is produced on site from wood fuels. CO2 emissions were greater in the South because of the wood fuel, 574 kg versus 419 kg per 1.623 m3 produced
Making Deep Heatmaps Robust to Partial Occlusions for 3D Object Pose Estimation
We introduce a novel method for robust and accurate 3D object pose estimation
from a single color image under large occlusions. Following recent approaches,
we first predict the 2D projections of 3D points related to the target object
and then compute the 3D pose from these correspondences using a geometric
method. Unfortunately, as the results of our experiments show, predicting these
2D projections using a regular CNN or a Convolutional Pose Machine is highly
sensitive to partial occlusions, even when these methods are trained with
partially occluded examples. Our solution is to predict heatmaps from multiple
small patches independently and to accumulate the results to obtain accurate
and robust predictions. Training subsequently becomes challenging because
patches with similar appearances but different positions on the object
correspond to different heatmaps. However, we provide a simple yet effective
solution to deal with such ambiguities. We show that our approach outperforms
existing methods on two challenging datasets: The Occluded LineMOD dataset and
the YCB-Video dataset, both exhibiting cluttered scenes with highly occluded
objects. Project website:
https://www.tugraz.at/institute/icg/research/team-lepetit/research-projects/robust-object-pose-estimation
Self-Calibration of Cameras with Euclidean Image Plane in Case of Two Views and Known Relative Rotation Angle
The internal calibration of a pinhole camera is given by five parameters that
are combined into an upper-triangular calibration matrix. If the
skew parameter is zero and the aspect ratio is equal to one, then the camera is
said to have Euclidean image plane. In this paper, we propose a non-iterative
self-calibration algorithm for a camera with Euclidean image plane in case the
remaining three internal parameters --- the focal length and the principal
point coordinates --- are fixed but unknown. The algorithm requires a set of point correspondences in two views and also the measured relative
rotation angle between the views. We show that the problem generically has six
solutions (including complex ones).
The algorithm has been implemented and tested both on synthetic data and on
publicly available real dataset. The experiments demonstrate that the method is
correct, numerically stable and robust.Comment: 13 pages, 7 eps-figure
Autocalibration with the Minimum Number of Cameras with Known Pixel Shape
In 3D reconstruction, the recovery of the calibration parameters of the
cameras is paramount since it provides metric information about the observed
scene, e.g., measures of angles and ratios of distances. Autocalibration
enables the estimation of the camera parameters without using a calibration
device, but by enforcing simple constraints on the camera parameters. In the
absence of information about the internal camera parameters such as the focal
length and the principal point, the knowledge of the camera pixel shape is
usually the only available constraint. Given a projective reconstruction of a
rigid scene, we address the problem of the autocalibration of a minimal set of
cameras with known pixel shape and otherwise arbitrarily varying intrinsic and
extrinsic parameters. We propose an algorithm that only requires 5 cameras (the
theoretical minimum), thus halving the number of cameras required by previous
algorithms based on the same constraint. To this purpose, we introduce as our
basic geometric tool the six-line conic variety (SLCV), consisting in the set
of planes intersecting six given lines of 3D space in points of a conic. We
show that the set of solutions of the Euclidean upgrading problem for three
cameras with known pixel shape can be parameterized in a computationally
efficient way. This parameterization is then used to solve autocalibration from
five or more cameras, reducing the three-dimensional search space to a
two-dimensional one. We provide experiments with real images showing the good
performance of the technique.Comment: 19 pages, 14 figures, 7 tables, J. Math. Imaging Vi
Differential protection of neuromuscular sensory and motor axons and their endings in Wld(S) mutant mice
Orthograde Wallerian degeneration normally brings about fragmentation of peripheral nerve axons and their sensory or motor endings within 24-48 h in mice. However, neuronal expression of the chimaeric, Wld(S) gene mutation extends survival of functioning axons and their distal endings for up to 3 weeks after nerve section. Here we studied the pattern and rate of degeneration of sensory axons and their annulospiral endings in deep lumbrical muscles of Wld(S) mice, and compared these with motor axons and their terminals, using neurone-specific transgenic expression of the fluorescent proteins yellow fluorescent protein (YFP) or cyan fluorescent protein (CFP) as morphological reporters. Surprisingly, sensory endings were preserved for up to 20 days, at least twice as long as the most resilient motor nerve terminals. Protection of sensory endings and axons was also much less sensitive to Wld(S) gene-copy number or age than motor axons and their endings. Protection of γ-motor axons and their terminals innervating the juxtaequatorial and polar regions of the spindles was less than sensory axons but greater than α-motor axons. The differences between sensory and motor axon protection persisted in electrically silent, organotypic nerve-explant cultures suggesting that residual axonal activity does not contribute to the sensory-motor axon differences in vivo. Quantitative, Wld(S)-specific immunostaining of dorsal root ganglion (DRG) neurones and motor neurones in homozygous Wld(S) mice suggested that the nuclei of large DRG neurones contain about 2.4 times as much Wld(S) protein as motor neurones. By contrast, nuclear fluorescence of DRG neurones in homozygotes was only 1.5 times brighter than in heterozygotes stained under identical conditions. Thus, differences in axonal or synaptic protection within the same Wld(S) mouse may most simply be explained by differences in expression level of Wld(S) protein between neurones. Mimicry of Wld(S)-induced protection may also have applications in treatment of neurotoxicity or peripheral neuropathies in which the integrity of sensory endings may be especially implicated
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