343 research outputs found
The dynamical transition in proteins and non-Gaussian behavior of low frequency modes in Self Consistent Normal Mode Analysis
Self Consistent Normal Mode Analysis (SCNMA) is applied to heme c type
cytochrome f to study temperature dependent protein motion. Classical Normal
Mode Analysis (NMA) assumes harmonic behavior and the protein Mean Square
Displacement (MSD) has a linear dependence on temperature. This is only
consistent with low temperature experimental results. To connect the protein
vibrational motions between low temperature and physiological temperature, we
have incorporated a fitted set of anharmonic potentials into SCNMA. In
addition, Quantum Harmonic Oscillator (QHO) theory has been used to calculate
the displacement distribution for individual vibrational modes. We find that
the modes involving soft bonds exhibit significant non-Gaussian dynamics at
physiological temperature, which suggests it may be the cause of the
non-Gaussian behavior of the protein motions probed by Elastic Incoherent
Neutron Scattering (EINS). The combined theory displays a dynamical transition
caused by the softening of few "torsional" modes in the low frequency regime (<
50cm-1or 0.6ps). These modes change from Gaussian to a classical
distribution upon heating. Our theory provides an alternative way to understand
the microscopic origin of the protein dynamical transition.Comment: 17 pages, 6 figures, 1 tabl
Cerebral Abscess and \u3ci\u3eCephenemyia phobifer\u3c/i\u3e in a Mule Deer in Central Nebraska
A wild yearling male mule deer (Odocoileus hemionus) from south central Nebraska was submitted to the University of Nebraska North Platte Station Diagnostic Laboratory with the history of severe depression, slight incoordination, and visual impairment. Gross examination revealed a large abcess involving approximately 65-75% of the cebral hemispheres of the brain and approximately bots in the retropharyngeal pouches
Cerebral Abscess and \u3ci\u3eCephenemyia phobifer\u3c/i\u3e in a Mule Deer in Central Nebraska
A wild yearling male mule deer (Odocoileus hemionus) from south central Nebraska was submitted to the University of Nebraska North Platte Station Diagnostic Laboratory with the history of severe depression, slight incoordination, and visual impairment. Gross examination revealed a large abcess involving approximately 65-75% of the cebral hemispheres of the brain and approximately bots in the retropharyngeal pouches
Influence of the Environment Fluctuations on Incoherent Neutron Scattering Functions
In extending the conventional dynamic models, we consider a simple model to
account for the environment fluctuations of particle atoms in a protein system
and derive the elastic incoherent structure factor (EISF) and the incoherent
scattering correlation function C(Q,t) for both the jump dynamics between sites
with fluctuating site interspacing and for the diffusion inside a fluctuating
sphere. We find that the EISF of the system (or the normalized elastic
intensity) is equal to that in the absence of fluctuations averaged over the
distribution of site interspacing or sphere radius a. The scattering
correlation function is ,
where the average is taken over the Q-dependent effective distribution of
relaxation rates \lambda_n(a) and \psi(t) is the correlation function of the
length a. When \psi(t)=1, the relaxation of C(Q,t) is exponential for the jump
dynamics between sites (since \lambda_n(a) is independent of a) while it is
nonexponential for diffusion inside a sphere.Comment: 7 pages, 7 eps figure
Multiple-scattering effects on incoherent neutron scattering in glasses and viscous liquids
Incoherent neutron scattering experiments are simulated for simple dynamic
models: a glass (with a smooth distribution of harmonic vibrations) and a
viscous liquid (described by schematic mode-coupling equations). In most
situations multiple scattering has little influence upon spectral
distributions, but it completely distorts the wavenumber-dependent amplitudes.
This explains an anomaly observed in recent experiments
Assessment of 24-hour physical behaviour in children and adolescents via wearables: a systematic review of free-living validation studies.
Objectives
Studies that assess all three dimensions of the integrative 24-hour physical behaviour (PB) construct, namely, intensity, posture/activity type and biological state, are on the rise. However, reviews on validation studies that cover intensity, posture/activity type and biological state assessed via wearables are missing.
Design
Systematic review. The risk of bias was evaluated by using the QUADAS-2 tool with nine signalling questions separated into four domains (ie, patient selection/study design, index measure, criterion measure, flow and time).
Data sources
Peer-reviewed validation studies from electronic databases as well as backward and forward citation searches (1970-July 2021).
Eligibility criteria for selecting studies
Wearable validation studies with children and adolescents (age <18 years). Required indicators: (1) study protocol must include real-life conditions; (2) validated device outcome must belong to one dimension of the 24-hour PB construct; (3) the study protocol must include a criterion measure; (4) study results must be published in peer-reviewed English language journals.
Results
Out of 13â285 unique search results, 76 articles with 51 different wearables were included and reviewed. Most studies (68.4%) validated an intensity measure outcome such as energy expenditure, but only 15.9% of studies validated biological state outcomes, while 15.8% of studies validated posture/activity type outcomes. We identified six wearables that had been used to validate outcomes from two different dimensions and only two wearables (ie, ActiGraph GT1M and ActiGraph GT3X+) that validated outcomes from all three dimensions. The percentage of studies meeting a given quality criterion ranged from 44.7% to 92.1%. Only 18 studies were classified as 'low risk' or 'some concerns'.
Summary
Validation studies on biological state and posture/activity outcomes are rare in children and adolescents. Most studies did not meet published quality principles. Standardised protocols embedded in a validation framework are needed.
PROSPERO registration number
CRD42021230894
Assessment of 24-hour physical behaviour in children and adolescents via wearables: a systematic review of free-living validation studies
Objectives: Studies that assess all three dimensions of the integrative 24-hour physical behaviour (PB) construct, namely, intensity, posture/activity type and biological state, are on the rise. However, reviews on validation studies that cover intensity, posture/activity type and biological state assessed via wearables are missing.
Design: Systematic review. The risk of bias was evaluated by using the QUADAS-2 tool with nine signalling questions separated into four domains (ie, patient selection/study design, index measure, criterion measure, flow and time).
Data sources: Peer-reviewed validation studies from electronic databases as well as backward and forward citation searches (1970âJuly 2021).
Eligibility criteria for selecting studies: Wearable validation studies with children and adolescents (age <18 years). Required indicators: (1) study protocol must include real-life conditions; (2) validated device outcome must belong to one dimension of the 24-hour PB construct; (3) the study protocol must include a criterion measure; (4) study results must be published in peer-reviewed English language journals.
Results: Out of 13â285 unique search results, 76 articles with 51 different wearables were included and reviewed. Most studies (68.4%) validated an intensity measure outcome such as energy expenditure, but only 15.9% of studies validated biological state outcomes, while 15.8% of studies validated posture/activity type outcomes. We identified six wearables that had been used to validate outcomes from two different dimensions and only two wearables (ie, ActiGraph GT1M and ActiGraph GT3X+) that validated outcomes from all three dimensions. The percentage of studies meeting a given quality criterion ranged from 44.7% to 92.1%. Only 18 studies were classified as âlow riskâ or âsome concernsâ.
Summary: Validation studies on biological state and posture/activity outcomes are rare in children and adolescents. Most studies did not meet published quality principles. Standardised protocols embedded in a validation framework are needed
Metastable Dynamics of the Hard-Sphere System
The reformulation of the mode-coupling theory (MCT) of the liquid-glass
transition which incorporates the element of metastability is applied to the
hard-sphere system. It is shown that the glass transition in this system is not
a sharp one at the special value of the density or the packing fraction, which
is in contrast to the prediction by the conventional MCT. Instead we find that
the slowing down of the dynamics occurs over a range of values of the packing
fraction. Consequently, the exponents governing the sequence of time
relaxations in the intermediate time regime are given as functions of packing
fraction with one additional parameter which describes the overall scale of the
metastable potential energy for defects in the hard-sphere system. Implications
of the present model on the recent experiments on colloidal systems are also
discussed.Comment: 21 pages, 5 figures (available upon request), RevTEX3.0, JFI
Preprint
Metastable Dynamics above the Glass Transition
The element of metastability is incorporated in the fluctuating nonlinear
hydrodynamic description of the mode coupling theory (MCT) of the liquid-glass
transition. This is achieved through the introduction of the defect density
variable into the set of slow variables with the mass density and
the momentum density . As a first approximation, we consider the case
where motions associated with are much slower than those associated with
. Self-consistently, assuming one is near a critical surface in the MCT
sense, we find that the observed slowing down of the dynamics corresponds to a
certain limit of a very shallow metastable well and a weak coupling between
and . The metastability parameters as well as the exponents
describing the observed sequence of time relaxations are given as smooth
functions of the temperature without any evidence for a special temperature. We
then investigate the case where the defect dynamics is included. We find that
the slowing down of the dynamics corresponds to the system arranging itself
such that the kinetic coefficient governing the diffusion of the
defects approaches from above a small temperature-dependent value .Comment: 38 pages, 14 figures (6 figs. are included as a uuencoded tar-
compressed file. The rest is available upon request.), RevTEX3.0+eps
Low-Temperature Polymorphic Phase Transition in a Crystalline Tripeptide L-Ala-L-Pro-Gly·H2O Revealed by Adiabatic Calorimetry
We demonstrate application of precise adiabatic vacuum calorimetry to observation of phase transition in the tripeptide l-alanyl-l-prolyl-glycine monohydrate (APG) from 6 to 320 K and report the standard thermodynamic properties of the tripeptide in the entire range. Thus, the heat capacity of APG was measured by adiabatic vacuum calorimetry in the above temperature range. The tripeptide exhibits a reversible first-order solid-to-solid phase transition characterized by strong thermal hysteresis. We report the standard thermodynamic characteristics of this transition and show that differential scanning calorimetry can reliably characterize the observed phase transition with <5 mg of the sample. Additionally, the standard entropy of formation from the elemental substances and the standard entropy of hypothetical reaction of synthesis from the amino acids at 298.15 K were calculated for the studied tripeptide.National Institute of Biomedical Imaging and Bioengineering (U.S.) (EB-003151)National Institute of Biomedical Imaging and Bioengineering (U.S.) (EB-001960)National Institute of Biomedical Imaging and Bioengineering (U.S.) (EB-002026
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