609 research outputs found
Organoaluminium complexes of ortho-, meta-, para-anisidines: synthesis, structural studies and ROP of Īµ-caprolactone (and rac-lactide)
Reaction of MeāAl (two equivalents) with ortho-, meta- or para-anisidine, (OMe)(NHā)CāHā, affords the complexes {[1,2-(OMe),NCāHā(Ī¼-MeāAl)](Ī¼-MeāAl)}ā (1), [1,3-(MeāAlOMe),NHCāHā(Ī¼-MeāAl)]2 (2) or [1,4-(MeāAlOMe),NHCāHā(Ī¼-MeāAl)]ā (3), respectively. The molecular structures of 1ā3 have been determined and all three complexes were found to be highly active for the ring opening polymerization (ROP) of Īµ-caprolactone. 1 was found highly active either with or without benzyl alcohol present; at various temperatures, the activity order 1 > 2 ā 3 was observed. For the ROP of rac-lactide results for 1ā3 were poor
Association between Post-Hospital Clinic and Telephone Follow-up Provider Visits with 30-Day Readmission Risk in an Integrated Health System
BACKGROUND: Follow-up visits with clinic providers after hospital discharge may not be feasible for some patients due to functional limitations, transportation challenges, need for physical distancing, or fear of exposure especially during the current COVID-19 pandemic.
METHODS: The aim of the study was to determine the effects of post-hospital clinic (POSH) and telephone (TPOSH) follow-up provider visits versus no visit on 30-day readmission. We used a retrospective cohort design based on data from 1/1/2017 to 12/31/2019 on adult patients (nā=ā213,513) discharged home from 15 Kaiser Permanente Southern California hospitals. Completion of POSH or TPOSH provider visits within 7 days of discharge was the exposure and all-cause 30-day inpatient and observation stay readmission was the primary outcome. We used matching weights to balance the groups and Fine-Gray subdistribution hazard model to assess for readmission risk.
RESULTS: Unweighted all-cause 30-day readmission rate was highest for patients who completed a TPOSH (17.3%) followed by no visit (14.2%), non-POSH (evaluation and management visits that were not focused on the hospitalization: 13.6%) and POSH (12.6%) visits. The matching weighted models showed that the effects of POSH and TPOSH visits varied across patient subgroups. For high risk (LACE 11+) medicine patients, both POSH (HR: 0.77, 95% CI: 0.71, 0.85, Pā\u3cā.001) and TPOSH (HR: 0.91, 95% CI: 0.83, 0.99, Pā=ā.03) were associated with 23 and 9% lower risk of 30-day readmission, respectively, compared to no visit. For medium to low risk medicine patients (LACE\u3cā11) and all surgical patients regardless of LACE score or age, there were no significant associations for either visit type with risk of 30-day readmission.
CONCLUSIONS: Post-hospital telephone follow-up provider visits had only modest effects on 30-day readmission in high-risk medicine patients compared to clinic visits. It remains to be determined if greater use and comfort with virtual visits by providers and patients as a result of the pandemic might improve the effectiveness of these encounters
MRI of Perfusion-Diffusion Mismatch in Non-Human Primate (Baboon) Stroke: A Preliminary Report
The goal of this study was to develop a clinically relevant non-human primate (baboon) stroke model and multi-parametric MRI protocols on a clinical scanner with long-term goals to better model human stroke and facilitate clinical translations of novel therapeutic strategies. Baboons were chosen because of their relatively large brain volume and that they are evolutionarily close to humans. Middle cerebral artery occlusion (MCAO) was induced using a minimally invasive endovascular approach to guide an inflatable balloon catheter into the MCA and followed by permanently or transiently inflate the balloon. Using multimodal MRI, including perfusion and diffusion imaging, the spatiotemporal dynamic evolution of the ischemic lesions in permanent and transient occlusion experiments in baboons were investigated. Perfusion-diffusion mismatch, which approximates the ischemic penumbra, was detected. In the permanent MCAO group (n = 2), the mean infarct volume was 29 ml (17% of total brain volume) whereas in the transient MCAO group (n = 2, 60 or 90 min of occlusion), the mean infarct volume was 15 ml (9% of total brain volume). Substantial perfusion-diffusion mismatch tissue (~50%) was salvaged by reperfusion compared to permanent MCAO. This baboon stroke model has the potential to become a translational platform to better design clinical studies, guide clinical diagnosis and improve treatment time windows in patients
Detecting bacteria and determining their susceptibility to antibiotics by stochastic confinement in nanoliter droplets using plug-based microfluidics
This article describes plug-based microļ¬uidic technology that enables rapid detection and drug
susceptibility screening of bacteria in samples, including complex biological matrices, without preincubation. Unlike conventional bacterial culture and detection methods, which rely on incubation
of a sample to increase the concentration of bacteria to detectable levels, this method conļ¬nes individual bacteria into droplets nanoliters in volume. When single cells are conļ¬ned into plugs of small
volume such that the loading is less than one bacterium per plug, the detection time is proportional
to plug volume. Conļ¬nement increases cell density and allows released molecules to accumulate
around the cell, eliminating the pre-incubation step and reducing the time required to detect
the bacteria. We refer to this approach as āstochastic conļ¬nementā. Using the microļ¬uidic hybrid
method, this technology was used to determine the antibiogram ā or chart of antibiotic sensitivity
ā of methicillin-resistant Staphylococcus aureus (MRSA) to many antibiotics in a single experiment
and to measure the minimal inhibitory concentration (MIC) of the drug cefoxitin (CFX) against
this strain. In addition, this technology was used to distinguish between sensitive and resistant
strains of S. aureus in samples of human blood plasma. High-throughput microļ¬uidic techniques
combined with single-cell measurements also enable multiple tests to be performed simultaneously
on a single sample containing bacteria. This technology may provide a method of rapid
and effective patient-speciļ¬c treatment of bacterial infections and could be extended to a variety
of applications that require multiple functional tests of bacterial samples on reduced timescales
CHANG-ES XI: Circular Polarization in the Cores of Nearby Galaxies
We detect 5 galaxies in the CHANG-ES (Continuum Halos in Nearby Galaxies --
an EVLA Survey) sample that show circular polarization (CP) at L-band in our
high resolution data sets. Two of the galaxies (NGC~4388 and NGC~4845) show
strong Stokes \%, two (NGC~660 and NGC~3628) have
values of \%, and NGC~3079 is a marginal detection at \%. The two strongest galaxies also have the most luminous X-ray
cores and the strongest internal absorption in X-rays. We have expanded on our
previous Faraday conversion interpretation and analysis and provide analytical
expressions for the expected signal for a general case in which the cosmic
ray electron energy spectral index can take on any value. We provide examples
as to how such expressions could be used to estimate magnetic field strengths
and the lower energy cutoff for CR electrons. Four out of our detections are
{\it resolved}, showing unique structures, including a {\it jet} in NGC~4388
and a CP `conversion disk' in NGC~4845. The conversion disk is inclined to the
galactic disk but is perpendicular to a possible outflow direction. Such CP
structures have never before been seen in any galaxy to our knowledge. None of
the galaxy cores show linear polarization at L-band. Thus CP may provide a
unique probe of physical conditions deep into radio AGNs.Comment: 30 pages, 4 figures, accepted to MNRA
Ethyleneglycol tungsten complexes of calix[6 and 8]arenes: Synthesis, characterization and ROP of Īµ-caprolactone
By varying the reaction conditions, the reaction of [W(eg)ā] (eg = 1,2-ethanediolato) with p-tert-butylcalix[n]areneHn (n = 6 or 8) in refluxing toluene affords, following work-up, a number of products which have been fully characterized. From the reaction of p-tert-butylcalix[6]areneHā with one or two equivalents of [W(eg)ā], only the oxo-bridged complex {[W(eg)]ā(Ī¼-O)p-tert-butylcalix[6]arene} (1) could be isolated, whereas the use of four equivalents of [W(eg)ā], in the presence of molecular sieves, afforded {[W(eg)ā]āp-tert-butylcalix[6]areneHā}Ā·2MeCN (2); molecules of 2 pack in bi-layers. Under similar conditions, use of one or two equivalents of [W(eg)ā] and p-tert-butylcalix[8]areneHā afforded {[W(eg)]āp-tert-butylcalix[8]arene}Ā·MeCN (3) in which each tungsten centre was bound by four calixarene oxygens. By contrast, the small orange prisms resulting from the use of four equivalents of [W(eg)ā] and p-tert-butylcalix[8]areneHā were shown by synchrotron radiation to be a mixture of two isomers (4a/4bĀ·3.5MeCN). In the major isomer {1,2-[W(eg)ā]āp-tert-butylcalix[8]areneHā} (4a), two tungsten centres bind to neighbouring sets of phenolate oxygens, whereas in the minor isomer {1,3-[W(eg)ā]āp-tert-butylcalix[8]areneHā} (4b), there is a protonated phenolic group between the two pairs of phenolate oxygens bound to tungsten; the major:minor ratio is about 83:17. Use of p-tert-butyltetrahomodioxacalix[6]areneHā with two equivalents of [W(eg)ā] resulted in the isolation of {[WO(eg)]āp-tert-butyltetrahomodioxacalix[6]areneHā} (5Ā·0.83tolueneĀ·MeCN), in which each dimethyleneoxa bridge is bound to an oxotungsten(VI) centre. Complexes 1ā5, together with the known complex [W(eg)p-tert-butylcalix[4]arene] (6), have been screened for their ability to ring open polymerize (ROP) Īµ-caprolactone; for 1, 2 and 5, 6 conversion rates were good (>88%) at 110 Ā°C over 12 or 24 h, whereas the calix[8]arene complexes 3 and 4 under the same conditions were inactive
HST Observations of Chromospheres in Metal Deficient Field Giants
HST high resolution spectra of metal-deficient field giants more than double
the stars in previous studies, span about 3 magnitudes on the red giant branch,
and sample an abundance range [Fe/H]= -1 to -3. These stars, in spite of their
age and low metallicity, possess chromospheric fluxes of Mg II (2800 Angstrom)
that are within a factor of 4 of Population I stars, and give signs of a
dependence on the metal abundance at the lowest metallicities. The Mg II k-line
widths depend on luminosity and correlate with metallicity. Line profile
asymmetries reveal outflows that occur at lower luminosities (M_V = -0.8) than
detected in Ca K and H-alpha lines in metal-poor giants, suggesting mass
outflow occurs over a larger span of the red giant branch than previously
thought, and confirming that the Mg II lines are good wind diagnostics. These
results do not support a magnetically dominated chromosphere, but appear more
consistent with some sort of hydrodynamic, or acoustic heating of the outer
atmospheres.Comment: 36 pages, 12 figures, 7 tables, and accepted for publication in The
Astronomical Journa
Calculating Unknown Eigenvalues with a Quantum Algorithm
Quantum algorithms are able to solve particular problems exponentially faster
than conventional algorithms, when implemented on a quantum computer. However,
all demonstrations to date have required already knowing the answer to
construct the algorithm. We have implemented the complete quantum phase
estimation algorithm for a single qubit unitary in which the answer is
calculated by the algorithm. We use a new approach to implementing the
controlled-unitary operations that lie at the heart of the majority of quantum
algorithms that is more efficient and does not require the eigenvalues of the
unitary to be known. These results point the way to efficient quantum
simulations and quantum metrology applications in the near term, and to
factoring large numbers in the longer term. This approach is architecture
independent and thus can be used in other physical implementations
Kinetic Characterisation of a Single Chain Antibody against the Hormone Abscisic Acid: Comparison with Its Parental Monoclonal
A single-chain Fv fragment antibody (scFv) specific for the plant hormone abscisic acid (ABA) has been expressed in the bacterium Escherichia coli as a fusion protein. The kinetics of ABA binding have been measured using surface plasmon resonance spectrometry (BIAcore 2000) using surface and solution assays. Care was taken to calculate the concentration of active protein in each sample using initial rate measurements under conditions of partial mass transport limitation. The fusion product, parental monoclonal antibody and the free scFv all have low nanomolar affinity constants, but there is a lower dissociation rate constant for the parental monoclonal resulting in a three-fold greater affinity. Analogue specificity was tested and structure-activity binding preferences measured. The biologically-active (+)-ABA enantiomer is recognised with an affinity three orders of magnitude higher than the inactive (-)-ABA. Metabolites of ABA including phaseic acid, dihydrophaseic acid and deoxy-ABA have affinities over 100-fold lower than that for (+)-ABA. These properties of the scFv make it suitable as a sensor domain in bioreporters specific for the naturally occurring form of ABA
High-Resolution 3D MR Microangiography of the Rat Ocular Circulation
To develop high-spatial-resolution magnetic resonance (MR) microangiography techniques to image the rat ocular circulation
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