533 research outputs found
What happens to patients with COPD with long-term oxygen treatment who receive mechanical ventilation for COPD exacerbation? A 1-year retrospective follow-up study
We performed a retrospective cohort study of patients with chronic obstructive lung disease (COPD) on long-term oxygen treatment (LTOT) who received invasive mechanical ventilation for COPD exacerbation. Of the 4791 patients, 23% died in the hospital, and 45% died in the subsequent 12 months. 67% of patients were readmitted at least once in the subsequent 12 months, and 26.8% were discharged to a nursing home or skilled nursing facility within 30 days. We conclude that these patients have high mortality rates, both in-hospital and in the 12 months postdischarge. If patients survive, many will be readmitted to the hospital and discharged to nursing home. These potential outcomes may support informed critical care decision making and more preference congruent care
Disordered, stretched, and semiflexible biopolymers in two dimensions
We study the effects of intrinsic sequence-dependent curvature for a two
dimensional semiflexible biopolymer with short-range correlation in intrinsic
curvatures. We show exactly that when not subjected to any external force, such
a system is equivalent to a system with a well-defined intrinsic curvature and
a proper renormalized persistence length. We find the exact expression for the
distribution function of the equivalent system. However, we show that such an
equivalent system does not always exist for the polymer subjected to an
external force. We find that under an external force, the effect of
sequence-disorder depends upon the averaging order, the degree of disorder, and
the experimental conditions, such as the boundary conditions. Furthermore, a
short to moderate length biopolymer may be much softer or has a smaller
apparent persistent length than what would be expected from the "equivalent
system". Moreover, under a strong stretching force and for a long biopolymer,
the sequence-disorder is immaterial for elasticity. Finally, the effect of
sequence-disorder may depend upon the quantity considered
Post-Prior discrepancies in CDW-EIS calculations for ion impact ionization fully differential cross sections
In this work we present fully differential cross sections (FDCSs)
calculations using post and prior version of CDW--EIS theory for helium single
ionization by 100 MeV C amu and 3.6 MeV amu Au and
Au ions. We performed our calculations for different momentum transfer
and ejected electron energies. The influence of internuclear potential on the
ejected electron spectra is taken into account in all cases. We compare our
calculations with absolute experimental measurements. It is shown that prior
version calculations give better agreement with experiments in almost all
studied cases.Comment: 9 pages, 7 figure
Adiabatic following criterion, estimation of the nonadiabatic excitation fraction and quantum jumps
An accurate theory describing adiabatic following of the dark, nonabsorbing
state in the three-level system is developed. An analytical solution for the
wave function of the particle experiencing Raman excitation is found as an
expansion in terms of the time varying nonadiabatic perturbation parameter. The
solution can be presented as a sum of adiabatic and nonadiabatic parts. Both
are estimated quantitatively. It is shown that the limiting value to which the
amplitude of the nonadiabatic part tends is equal to the Fourier component of
the nonadiabatic perturbation parameter taken at the Rabi frequency of the
Raman excitation. The time scale of the variation of both parts is found. While
the adiabatic part of the solution varies slowly and follows the change of the
nonadiabatic perturbation parameter, the nonadiabatic part appears almost
instantly, revealing a jumpwise transition between the dark and bright states.
This jump happens when the nonadiabatic perturbation parameter takes its
maximum value.Comment: 33 pages, 8 figures, submitted to PRA on 28 Oct. 200
Statistical Mechanics for Unstable States in Gel'fand Triplets and Investigations of Parabolic Potential Barriers
Free energies and other thermodynamical quantities are investigated in
canonical and grand canonical ensembles of statistical mechanics involving
unstable states which are described by the generalized eigenstates with complex
energy eigenvalues in the conjugate space of Gel'fand triplet. The theory is
applied to the systems containing parabolic potential barriers (PPB's). The
entropy and energy productions from PPB systems are studied. An equilibrium for
a chemical process described by reactions is also
discussed.Comment: 14 pages, AmS-LaTeX, no figur
A synoptic view of solar transient evolution in the inner heliosphere using the Heliospheric Imagers on STEREO
By exploiting data from the STEREO/heliospheric imagers (HI) we extend a well-established technique developed for coronal analysis by producing time-elongation plots that reveal the nature of solar transient activity over a far more extensive region of the heliosphere than previously possible from coronagraph images. Despite the simplicity of these plots, their power in demonstrating how the plethora of ascending coronal features observed near the Sun evolve as they move antisunward is obvious. The time-elongation profile of a transient tracked by HI can, moreover, be used to establish its angle out of the plane-of-the-sky; an illustration of such analysis reveals coronal mass ejection material that can be clearly observed propagating out to distances beyond 1AU. This work confirms the value of the time-elongation format in identifying/characterising transient activity in the inner heliosphere, whilst also validating the ability of HI to continuously monitor solar ejecta out to and beyond 1A
Landau-Zener transitions in a linear chain
We present an exact asymptotic solution for electron transition amplitudes in
an infinite linear chain driven by an external homogeneous time-dependent
electric field. This solution extends the Landau-Zener theory for the case of
infinite number of states in discrete spectrum. In addition to transition
amplitudes we calculate an effective diffusion constant.Comment: 3 figure
Bound-bound pair production in relativistic collisions
Electron-positron pair production is considered in the relativistic collision
of a nucleus and an anti-nucleus, in which both leptons are created in bound
states of the corresponding nucleus-lepton system. Compared to free and
bound-free pair production this process is shown to display a qualitatively
different dependency both on the impact energy and charged of the colliding
particles. Interestingly, at high impact energies the cross section for this
process is found to be larger than that for the analogous atomic process of
non-radiative electron capture although the latter does not involve the
creation of new particles.Comment: 4 pages, 3 figure
Single-molecule derivation of salt dependent base-pair free energies in DNA
Accurate knowledge of the thermodynamic properties of nucleic acids is
crucial to predicting their structure and stability. To date most measurements
of base-pair free energies in DNA are obtained in thermal denaturation
experiments, which depend on several assumptions. Here we report measurements
of the DNA base-pair free energies based on a simplified system, the mechanical
unzipping of single DNA molecules. By combining experimental data with a
physical model and an optimization algorithm for analysis, we measure the 10
unique nearest-neighbor base-pair free energies with 0.1 kcal mol-1 precision
over two orders of magnitude of monovalent salt concentration. We find an
improved set of standard energy values compared with Unified Oligonucleotide
energies and a unique set of 10 base-pair-specific salt-correction values. The
latter are found to be strongest for AA/TT and weakest for CC/GG. Our new
energy values and salt corrections improve predictions of DNA unzipping forces
and are fully compatible with melting temperatures for oligos. The method
should make it possible to obtain free energies, enthalpies and entropies in
conditions not accessible by bulk methodologies.Comment: Main text: 27 pages, 4 figures, 2 tables. Supporting Information: 51
pages, 19 figures, 4 table
UK-Wide Multicenter Evaluation of Second-line Therapies in Primary Biliary Cholangitis
Background & Aims: Thirty-to-forty percent of patients with primary biliary cholangitis inadequately respond to ursodeoxycholic acid. Our aim was to assemble national, real-world data on the effectiveness of obeticholic acid (OCA) as a second-line treatment, alongside non-licensed therapy with fibric acid derivatives (bezafibrate or fenofibrate). Methods: This was a nationwide observational cohort study conducted from August 2017 until June 2021. Results: We accrued data from 457 patients; 349 treated with OCA and 108 with fibric acid derivatives. At baseline/pre-treatment, individuals in the OCA group manifest higher risk features compared with those taking fibric acid derivatives, evidenced by more elevated alkaline phosphatase values, and a larger proportion of individuals with cirrhosis, abnormal bilirubin, prior non-response to ursodeoxycholic acid, and elastography readings >9.6kPa (P <.05 for all). Overall, 259 patients (OCA) and 80 patients (fibric acid derivatives) completed 12 months of second-line therapy, yielding a dropout rate of 25.7% and 25.9%, respectively. At 12 months, the magnitude of alkaline phosphatase reduction was 29.5% and 56.7% in OCA and fibric acid groups (P <.001). Conversely, 55.9% and 36.4% of patients normalized serum alanine transaminase and bilirubin in the OCA group (P <.001). The proportion with normal alanine transaminase or bilirubin values in the fibric acid group was no different at 12 months compared with baseline. Twelve-month biochemical response rates were 70.6% with OCA and 80% under fibric acid treatment (P =.121). Response rates between treatment groups were no different on propensity-score matching or on sub-analysis of high-risk groups defined at baseline. Conclusion: Across the population of patients with primary biliary cholangitis in the United Kingdom, rates of biochemical response and drug discontinuation appear similar under fibric acid and OCA treatment
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