1,326 research outputs found
Multi-cycle recovery of lactoferrin and lactoperoxidase from crude whey using fimbriated high-capacity magnetic cation exchangers and a novel "rotor-stator" high-gradient magnetic separator
Cerium (IV) initiated "graft-from" polymerization reactions were employed to convert M-PVA magnetic particles into polyacrylic acid-fimbriated magnetic cation exchange supports displaying ultra-high binding capacity for basic target proteins. The modifications, which were performed at 25mg and 2.5g scales, delivered maximum binding capacities (Q) for hen egg white lysozyme in excess of 320mgg, combined with sub-micromolar dissociation constants (0.45-0.69μm) and "tightness of binding" values greater than 49Lg. Two batches of polyacrylic acid-fimbriated magnetic cation exchangers were combined to form a 5g pooled batch exhibiting Q values for lysozyme, lactoferrin, and lactoperoxidase of 404, 585, and 685mgg, respectively. These magnetic cation exchangers were subsequently employed together with a newly designed "rotor-stator" type HGMF rig, in five sequential cycles of recovery of lactoferrin and lactoperoxidase from 2L batches of a crude sweet bovine whey feedstock. Lactoferrin purification performance was observed to remain relatively constant from one HGMF cycle to the next over the five operating cycles, with yields between 40% and 49% combined with purification and concentration factors of 37- to 46-fold and 1.3- to 1.6-fold, respectively. The far superior multi-cycle HGMF performance seen here compared to that observed in our earlier studies can be directly attributed to the combined use of improved high capacity adsorbents and superior particle resuspension afforded by the new "rotor-stator" HGMS design. © 2013 Wiley Periodicals, Inc
An Error-Control System Based on Majority-Logic Decoding
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DAAB07-72-C-0259Rome Air Development Center / F30602-72-C-003
A QCD Analysis of the Mass Structure of the Nucleon
{}From the deep-inelastic momentum sum rule and the trace anomaly of the
energy-momentum tensor, I derive a separation of the nucleon mass into the
contributions of the quark and gluon kinetic and potential energies, the quark
masses, and the trace anomaly.Comment: 9 pages, MIT-CTP #2368, revtex with 1 tabl
Experimental Unit for (31,16) Binary Code Using Majority-Logic Decoding
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DAAB-07-72-C-0259Rome Air Development Center / F30602-72-C-003
Infrared Investigation of the Charge Ordering Pattern in the Organic Spin Ladder Candidate (DTTTF)2Cu(mnt)2
We measured the variable temperature infrared response of the spin ladder
candidate (DTTTF)2Cu(mnt)2 in order to distinguish between two competing ladder
models, rectangular versus zigzag, proposed for this family of materials. The
distortion along the stack direction below 235 K is consistent with a doubling
along b through the metal-insulator transition. While this would agree with
either of the ladder models, the concomitant transverse distortion rules out
the rectangular ladder model and supports the zigzag scenario. Intramolecular
distortions within the DTTTF building block molecule also give rise to on-site
charge asymmetry.Comment: 4 pages, 4 figures, submitted to Solid State Science
Effective action for scalar fields and generalised zeta-function regularisation
Motivated by the study of quantum fields in a Friedman-Robertson-Walker (FRW)
spacetime, the one-loop effective action for a scalar field defined in the
ultrastatic manifold , being the finite
volume, non-compact, hyperbolic spatial section, is investigated by a
generalisation of zeta-function regularisation. It is shown that additional
divergences may appear at one-loop level. The one-loop renormalisability of the
model is discussed and making use of a generalisation of zeta-function
regularisation, the one-loop renormalisation group equations are derived.Comment: Latex, 16 pages, no figures; Latex mistakes corrected; accepted for
publication in Physical Review
Comparison of exact and approximate cross-sections in relativistic Coulomb excitation
We present a new method of obtaining time-dependent matrix elements of the
electromagnetic pulse produced by a highly-relativistic projectile. These
matrix elements are used in a coupled-channel calculation to predict the
cross-sections for population of 1- and 2-phonon states of the giant dipole
resonance. Comparisons are made with the predictions of the long-wavelength and
Born approximations.Comment: 26 pages, LaTex2
Extragalactic neutrino background from very young pulsars surrounded by supernova envelopes
We estimate the extragalactic muon neutrino background which is produced by
hadrons injected by very young pulsars at an early phase after supernova
explosion. It is assumed that hadrons are accelerated in the pulsar wind zone
which is filled with thermal photons captured below the expanding supernova
envelope. In collisions with those thermal photons hadrons produce pions which
decay into muon neutrinos. At a later time, muon neutrinos are also produced by
the hadrons in collisions with matter of the expanding envelope. We show that
extragalactic neutrino background predicted by such a model should be
detectable by the planned 1 km neutrino detector if a significant part of
pulsars is born with periods shorter than ms. Since such population
of pulsars is postulated by the recent models of production of extremely high
energy cosmic rays, detection of neutrinos with predicted fluxes can be used as
their observational test.Comment: 4 pages, 2 figures, A&A style, accepted to A&A Let
Exact results for hydrogen recombination on dust grain surfaces
The recombination of hydrogen in the interstellar medium, taking place on
surfaces of microscopic dust grains, is an essential process in the evolution
of chemical complexity in interstellar clouds. The H_2 formation process has
been studied theoretically, and in recent years also by laboratory experiments.
The experimental results were analyzed using a rate equation model. The
parameters of the surface, that are relevant to H_2 formation, were obtained
and used in order to calculate the recombination rate under interstellar
conditions. However, it turned out that due to the microscopic size of the dust
grains and the low density of H atoms, the rate equations may not always apply.
A master equation approach that provides a good description of the H_2
formation process was proposed. It takes into account both the discrete nature
of the H atoms and the fluctuations in the number of atoms on a grain. In this
paper we present a comprehensive analysis of the H_2 formation process, under
steady state conditions, using an exact solution of the master equation. This
solution provides an exact result for the hydrogen recombination rate and its
dependence on the flux, the surface temperature and the grain size. The results
are compared with those obtained from the rate equations. The relevant length
scales in the problem are identified and the parameter space is divided into
two domains. One domain, characterized by first order kinetics, exhibits high
efficiency of H_2 formation. In the other domain, characterized by second order
kinetics, the efficiency of H_2 formation is low. In each of these domains we
identify the range of parameters in which, the rate equations do not account
correctly for the recombination rate. and the master equation is needed.Comment: 23 pages + 8 figure
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