669 research outputs found
Interdiffusion in dilute polymer mixtures. A subtle concentration effect
Dynamic light scattering has been used to investigate the diffusional dynamics in very dilute polystyrene/poly(propylene oxide), PS/PPO, polymer blends. Compared to previous investigations in the field, this system is more suitable for this type of investigation due to the significant refractive index difference between the two components and the fact that the matrix (PPO) dynamics do not interfere with the measurements. The tracer diffusion coefficient of PS thus obtained in the limit of infinite dilution scales as Nâ0.8±0.04PS with the PS degree of polymerization, i.e., behavior intermediate between the limits of nondraining Zimm and freeâdraining Rouse behavior. The effect of the addition of a third component even at tracer concentrations on the diffusion dynamics was investigated both experimentally and theoretically in the framework of the dynamic random phase approximation. Similarities and differences between theory and experiment were found that are rather due to a modification of hydrodynamic interactions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70731/2/JCPSA6-101-4-3222-1.pd
Expected spectral characteristics of (101955) Bennu and (162173) Ryugu, targets of the OSIRIS-REx and Hayabusa2 missions
NASA's OSIRIS-REx and JAXA's Hayabusa2 sample-return missions are currently
on their way to encounter primitive near-Earth asteroids (101955) Bennu and
(162173) Ryugu, respectively. Spectral and dynamical evidence indicates that
these near-Earth asteroids originated in the inner part of the main belt. There
are several primitive collisional families in this region, and both these
asteroids are most likely to have originated in the Polana-Eulalia family
complex. We present the expected spectral characteristics of both targets based
on our studies of our primitive collisional families in the inner belt:
Polana-Eulalia, Erigone, Sulamitis, and Clarissa. Observations were obtained in
the framework of our PRIMitive Asteroids Spectroscopic Survey (PRIMASS). Our
results are especially relevant to the planning and interpretation of in-situ
images and spectra to be obtained by the two spacecraft during the encounters
with their targets.Comment: 22 pages, 11 figures. Accepted for publication in Icarus on May 11,
201
Suppressing dimension-5 operators in general SU(5) models
We discuss dimension-5 operators in supersymmetric models containing extra
hypercharge 1/3 color-triplets. We derive a general formula relating
dimension-5 operator to the color-triplet mass matrix. We show that certain
zeros in the triplet mass-matrix together with some triplet coupling selection
rules can lead to elimination of dimension-5 operators. In particular we focus
on SU(5) models and show that (a) Dimension-5 operators can be eliminated in
the standard SU(5) model by the introduction of an extra pair of 5+5b Higgses
with specific couplings (b) Flipped SU(5) models with extra 10+10b Higgses are
free of dimension-5 operators (c) Flipped SU(5) models with extra 5+5b and/or
extra 10+10b Higgses can be made free of dimension-5 operators for a textured
form of the triplet mass-matrix accompanied by constraints on the 5-plet
couplings to matter. Our analysis is motivated by the recently put forward
M-theory phenomenological framework that requires a strong string coupling and
reintroduces the problem of eliminating dimension-5 operators.Comment: 10 pages, Latex2e, minor changes, references adde
Point of care coagulometry in prehospital emergency care: an observational study
Background: Haemostatic impairment can have a crucial impact on the outcome of emergency patients, especially in cases of concomitant antithrombotic drug treatment. In this prospective observational study we used a point of care (POC) coagulometer in a prehospital physician-based emergency medical system in order to test its validity and potential value in the treatment of emergency patients. Methods: During a study period of 12Â months, patients could be included if venous access was mandatory for further treatment. The POC device CoaguChekÂź was used to assess international normalized ratio (INR) after ambulance arrival at the scene. Results were compared with in-hospital central laboratory assessment of INR. The gain of time was analysed as well as the potential value of POC testing through a questionnaire completed by the responsible prehospital emergency physician. Results: A total of 103 patients were included in this study. POC INR results were highly correlated with results of conventional assessment of INR (Bland-Altman-bias: 0.014). Using a cutoff value of INR >1.3, the deviceâs sensitivity to detect coagulopathy was 100Â % with a specificity of 98.7Â %. The median gain of time was 69Â min. Treating emergency physicians considered the value of prehospital POC INR testing âhighâ in 9Â % and âmediumâ in 21Â % of all patients. In patients with tracer diagnosis âneurologyâ, the value of prehospital INR assessment was considered âhighâ or âmediumâ (63Â %) significantly more often than in patients with non-neurological tracer diagnoses (24Â %). Conclusions: Assessment of INR through a POC coagulometer is feasible in prehospital emergency care and provides valuable information on haemostatic parameters in patients. Questionnaire results suggest that POC INR testing may present a valuable technique in selected patients. Whether this information translates into an improved management of respective patients has to be evaluated in further studies
Conserved cosmological structures in the one-loop superstring effective action
A generic form of low-energy effective action of superstring theories with
one-loop quantum correction is well known. Based on this action we derive the
complete perturbation equations and general analytic solutions in the
cosmological spacetime. Using the solutions we identify conserved quantities
characterizing the perturbations: the amplitude of gravitational wave and the
perturbed three-space curvature in the uniform-field gauge both in the
large-scale limit, and the angular-momentum of rotational perturbation are
conserved independently of changing gravity sector. Implications for
calculating perturbation spectra generated in the inflation era based on the
string action are presented.Comment: 5 pages, no figure, To appear in Phys. Rev.
Darboux transformations, finite reduction groups and related Yang-Baxter maps
In this paper we construct Yang-Baxter (YB) maps using Darboux matrices which
are invariant under the action of finite reduction groups. We present
6-dimensional YB maps corresponding to Darboux transformations for the
Nonlinear Schr\"odinger (NLS) equation and the derivative Nonlinear
Schr\"odinger (DNLS) equation. These YB maps can be restricted to
dimensional YB maps on invariant leaves. The former are completely
integrable and they also have applications to a recent theory of maps
preserving functions with symmetries \cite{Allan-Pavlos}. We give a
dimensional YB-map corresponding to the Darboux transformation for a
deformation of the DNLS equation. We also consider vector generalisations of
the YB maps corresponding to the NLS and DNLS equation.Comment: 18 pages, revised version. The format of the paper has changed, we
added one sectio
Evaluation of two high-throughput proteomic technologies for plasma biomarker discovery in immunotherapy-treated melanoma patients
Background: Selective kinase and immune checkpoint inhibitors, and their combinations, have significantly improved the survival of patients with advanced metastatic melanoma. Not all patients will respond to treatment however, and some patients will present with significant toxicities. Hence, the identification of biomarkers is critical for the selection and management of patients receiving treatment. Biomarker discovery often involves proteomic techniques that simultaneously profile multiple proteins but few studies have compared these platforms. Methods: In this study, we used the multiplex bead-based Eve Technologies Discovery assay and the aptamer-based SomaLogic SOMAscan assay to identify circulating proteins predictive of response to immunotherapy in melanoma patients treated with combination immune checkpoint inhibitors. Expression of four plasma proteins were further validated using the bead-based Millipore Milliplex assay. Results: Both the Discovery and the SOMAscan assays detected circulating plasma proteins in immunotherapy-treated melanoma patients. However, these widely used assays showed limited correlation in relative protein quantification, due to differences in specificity and the dynamic range of protein detection. Protein data derived from the Discovery and Milliplex bead-based assays were highly correlated. Conclusions: Our study highlights significant limitations imposed by inconsistent sensitivity and specificity due to differences in the detection antibodies or aptamers of these widespread biomarker discovery approaches. Our findings emphasize the need to improve these technologies for the accurate identification of biomarkers
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