115 research outputs found
High Speed Isoelectric Focusing of Proteins Enabling Rapid Two-Dimensional Gel Electrophoresis
Two-Dimensional Gel Electrophoresis Reveals Differential Protein Expression Between Individual Daphnia
On the pion electroproduction amplitude
We analyze amplitudes for the pion electroproduction on proton derived from
Lagrangians based on the local chiral SU(2) x SU(2) symmetries. We show that
such amplitudes do contain information on the nucleon axial form factor F_A in
both soft and hard pion regimes. This result invalidates recent Haberzettl's
claim that the pion electroproduction at threshold cannot be used to extract
any information regarding F_A.Comment: 14 pages, 6 figures, revised version, accepted for publication in
Phys. Rev.
Comparing microfluidic performance of three-dimensional (3D) printing platforms
Three-dimensional (3D) printing has emerged as a potential revolutionary technology for the fabrication of microfluidic devices. A direct experimental comparison of the three 3D printing technologies dominating microfluidics was conducted using a Y-junction microfluidic device, the design of which was optimized for each printer: fused deposition molding (FDM), Polyjet, and digital light processing stereolithography (DLP-SLA). Printer performance was evaluated in terms of feature size, accuracy, and suitability for mass manufacturing; laminar flow was studied to assess their suitability for microfluidics. FDM was suitable for microfabrication with minimum features of 321 ± 5 μm, and rough surfaces of 10.97 μm. Microfluidic devices >500 μm, rapid mixing (71% ± 12% after 5 mm, 100 μL/min) was observed, indicating a strength in fabricating micromixers. Polyjet fabricated channels with a minimum size of 205 ± 13 μm, and a surface roughness of 0.99 μm. Compared with FDM, mixing decreased (27% ± 10%), but Polyjet printing is more suited for microfluidic applications where flow splitting is not required, such as cell culture or droplet generators. DLP-SLA fabricated a minimum channel size of 154 ± 10 μm, and 94 ± 7 μm for positive structures such as soft lithography templates, with a roughness of 0.35 μm. These results, in addition to low mixing (8% ± 1%), showed suitability for microfabrication, and microfluidic applications requiring precise control of flow. Through further discussion of the capabilities (and limitations) of these printers, we intend to provide guidance toward the selection of the 3D printing technology most suitable for specific microfluidic applications
Separable potential model for interactions at low energies
The effective separable meson-baryon potentials are constructed to match the
equivalent chiral amplitudes up to the second order in external meson momenta.
We fit the model parameters (low energy constants) to the threshold and low
energy data. In the process, the -proton bound state problem is
solved exactly in the momentum space and the 1s level characteristics of the
kaonic hydrogen are computed simultaneously with the available low energy
cross sections. The model is also used to describe the
mass spectrum and the energy dependence of the amplitude.Comment: 31 pages, v2 - added corrections to make it compatible with the
published versio
Weak axial nuclear heavy meson exchange currents and interactions of solar neutrinos with deuterons
Starting from the axial heavy meson exchange currents, constructed earlier in
conjunction with the Bethe--Salpeter equation, we first present the axial
--, -- and meson exchange Feynman amplitudes that satisfy
the partial conservation of the axial current. Employing these amplitudes, we
derive the corresponding weak axial heavy meson exchange currents in the
leading order in the 1/M expansion ( is the nucleon mass), suitable for the
nuclear physics calculations beyond the threshold energies and with wave
functions obtained by solving the Schr\"odinger equation with one--boson
exchange potentials. The constructed currents obey the nuclear form of the
partial conservation of the axial current. We apply the space component of
these currents in calculations of the cross sections for the disintegration of
deuterons by low energy (anti)neutrinos. The deuteron and the final state
nucleon--nucleon wave functions are derived (i) from a variant of the OBEPQB
potential, and (ii) from the Nijmegen 93 and Nijmegen I nucleon-nucleon
interaction. The extracted values of the constant , entering the
axial exchange currents of the pionless effective field theory, are in a
reasonable agreement with its value predicted by the dimensional analysis.Comment: 34 pages, 3 figures, 11 table
STUDIES ON KINETICS OF INHIBITION AND BINDING OF XIIIa BY A CROSS-REACTING ANTIFIBRINOGEN ANTIBODY*
Coagulation factor XIIIa, plasma transglutaminase(endo-g-glutamine:e-lysine transferase EC 2.3.2.13) cata-lyzes isopeptide bond formation between glutamine andlysine residues and rapidly cross-links fibrin clots. Amonoclonal antibody (5A2) directed to a fibrinogen Aa-chain segment 529 –539 was previously observed fromanalysis of end-stage plasma clots to block fibrina-chaincross-linking. This prompted the study of its effect onnonfibrinogen substrates, with the prospect that 5A2was inhibiting XIIIa directly. It inhibited XIIIa-cata-lyzed incorporation of the amine donor substrate dan-sylcadaverine into the glutamine acceptor dimethylca-sein in an uncompetitive manner with respect todimethylcasein utilization and competitively with re-spect to dansylcadaverine. Uncompetitive inhibitionwas also observed with the synthetic glutamine sub-strate, LGPGQSKVIG. Theoretically, uncompetitive in-hibition arises from preferential interaction of the in-hibitor with the enzyme-substrate complex but is alsofound to inhibitg-chain cross-linking. The conjunctionof the uncompetitive and competitive modes of inhibi-tion indicates in theory that this bireactant system in-volves an ordered reaction in which docking of the glu-tamine substrate precedes the amine exchange. Thepresence of substrate enhanced binding of 5A2 to XIIIa,an interaction deemed to occur through a C-terminalsegment of the XIIIa A-chain (643– 658,GSDMTVTVQFT-NPLKE), 55% of which comprises sequences occurring inthe fibrinogen epitope Aa-(529 –540) (GSESGIFTNTKE).Removal of the C-terminal domain from XIIIa abolishesthe inhibitory effect of 5A2 on activity. Crystallographicstudies on recombinant XIIIa place the segment 643– 658in the region of the groove through which glutaminesubstrates access the active site and have predicted thatfor catalysis, a conformational change may accompanyglutamine-substrate binding. The uncompetitive inhibi-tion and the substrate-dependent binding of 5A2 pro-vide evidence for the conformational change
The Axial-Vector Current in Nuclear Many-Body Physics
Weak-interaction currents are studied in a recently proposed effective field
theory of the nuclear many-body problem. The Lorentz-invariant effective field
theory contains nucleons, pions, isoscalar scalar () and vector
() fields, and isovector vector () fields. The theory exhibits a
nonlinear realization of chiral symmetry and has three
desirable features: it uses the same degrees of freedom to describe the
axial-vector current and the strong-interaction dynamics, it satisfies the
symmetries of the underlying theory of quantum chromodynamics, and its
parameters can be calibrated using strong-interaction phenomena, like hadron
scattering or the empirical properties of finite nuclei. Moreover, it has
recently been verified that for normal nuclear systems, it is possible to
systematically expand the effective lagrangian in powers of the meson fields
(and their derivatives) and to reliably truncate the expansion after the first
few orders. Here it is shown that the expressions for the axial-vector current,
evaluated through the first few orders in the field expansion, satisfy both
PCAC and the Goldberger--Treiman relation, and it is verified that the
corresponding vector and axial-vector charges satisfy the familiar chiral
charge algebra. Explicit results are derived for the Lorentz-covariant,
axial-vector, two-nucleon amplitudes, from which axial-vector meson-exchange
currents can be deduced.Comment: 32 pages, REVTeX 4.0 with 12pt.rtx, aps.rtx, revsymb.sty,
revtex4.cls, plus 14 figures; two sentences added in Summary; two references
adde
Observation of time-reversal symmetry breaking in the band structure of altermagnetic RuO
Altermagnets are an emerging third elementary class of magnets. Unlike
ferromagnets, their distinct crystal symmetries inhibit magnetization while,
unlike antiferromagnets, they promote strong spin polarization in the band
structure. The corresponding unconventional mechanism of timereversal symmetry
breaking without magnetization in the electronic spectra has been regarded as a
primary signature of altermagnetism, but has not been experimentally visualized
to date. We directly observe strong time-reversal symmetry breaking in the band
structure of altermagnetic RuO by detecting magnetic circular dichroism in
angle-resolved photoemission spectra. Our experimental results, supported by ab
initio calculations, establish the microscopic electronic-structure basis for a
family of novel phenomena and functionalities in fields ranging from
topological matter to spintronics, that are based on the unconventional
time-reversal symmetry breaking in altermagnets
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