306 research outputs found
Nucleon Mass Splitting at Finite Isospin Chemical Potential
We investigate nucleon mass splitting at finite isospin chemical potential in
the frame of two flavor Nambu--Jona-Lasinio model. It is analytically proved
that, in the phase with explicit isospin symmetry breaking the proton mass
decreases and the neutron mass increases linearly in the isospin chemical
potential.Comment: 3 pages and no figure
1S0 pairing correlation in symmetric nuclear matter with Debye screening effects
AbstractThe 1S0 pairing of symmetric nuclear matter is discussed in the framework of relativistic nuclear theory with Dyson–Schwinger equations (DSEs). The in-medium nucleon and meson propagators are treated in a more self-consistent way through meson polarizations. The screening effects on mesons due to in-medium nucleon excitation are found to reduce the 1S0 pairing gap and shift remarkably the gap peak to low density region
Sigma Decay at Finite Temperature and Density
Sigma decay and its relation with chiral phase transition are discussed at
finite temperature and density in the framework of the Nambu-Jona-Lasinio
model. The decay rate for the process sigma -> 2 pions to first order in a
1/N_c expansion is calculated as a function of temperature T and baryon density
n_b. In particular, only when the chiral phase transition happens around the
tricritical point, the sigma decay results in a non-thermal enhancement of
pions in the final state distributions in relativistic heavy ion collisions.Comment: 6 pages, 3 Postscript figures, submitted to Chin. Phys. Let
Non-Abelian Medium Effects in Quark-Gluon Plasma
Based on the kinetic theory, the non-Abelian medium property of hot
Quark-Gluon Plasma is investigated. The nonlinearity of the plasma comes from
two aspects: The nonlinear wave-wave interaction and self-interaction of color
field. The non-Abelian color permittivity is obtained by expanding the kinetic
equations to third order. As an application, the nonlinear Landau damping rate
and the nonlinear eigenfrequency shift are calculated in the longwave length
limit.Comment: 12 pages(Revtex), no figure
Engineering cofactor metabolism for improved protein and glucoamylase production in Aspergillus niger
Background: Nicotinamide adenine dinucleotide phosphate (NADPH) is an important cofactor ensuring intracellular redox balance, anabolism and cell growth in all living systems. Our recent multi-omics analyses of glucoamylase (GlaA) biosynthesis in the filamentous fungal cell factory Aspergillus niger indicated that low availability of NADPH might be a limiting factor for GlaA overproduction. Results: We thus employed the Design-Build-Test-Learn cycle for metabolic engineering to identify and prioritize effective cofactor engineering strategies for GlaA overproduction. Based on available metabolomics and 13C metabolic flux analysis data, we individually overexpressed seven predicted genes encoding NADPH generation enzymes under the control of the\ua0Tet-on gene switch in two A. niger recipient strains, one carrying a single and one carrying seven glaA gene copies, respectively, to test their individual effects on GlaA and total protein overproduction. Both strains were selected to understand if a strong pull towards glaA biosynthesis (seven gene copies) mandates a higher NADPH supply compared to the native condition (one gene copy). Detailed analysis of all 14 strains cultivated in shake flask cultures uncovered that overexpression of the gsdA gene (glucose 6-phosphate dehydrogenase), gndA gene (6-phosphogluconate dehydrogenase) and maeA gene (NADP-dependent malic enzyme) supported GlaA production on a subtle (10%) but significant level in the background strain carrying seven glaA gene copies. We thus performed maltose-limited chemostat cultures combining metabolome analysis for these three isolates to characterize metabolic-level fluctuations caused by cofactor engineering. In these cultures, overexpression of either the gndA or maeA gene increased the intracellular NADPH pool by 45% and 66%, and the yield of GlaA by 65% and 30%, respectively. In contrast, overexpression of the gsdA gene had a negative effect on both total protein and glucoamylase production. Conclusions: This data suggests for the first time that increased NADPH availability can indeed underpin protein and especially GlaA production in strains where a strong pull towards GlaA biosynthesis exists. This data also indicates that the highest impact on GlaA production can be engineered on a genetic level by increasing the flux through the pentose phosphate pathway (gndA gene) followed by engineering the flux through the reverse TCA cycle (maeA gene). We thus propose that NADPH cofactor engineering is indeed a valid strategy for metabolic engineering of A. niger to improve GlaA production, a strategy which is certainly also applicable to the rational design of other microbial cell factories.[Figure not available: see fulltext.]
On the Ground State of Two Flavor Color Superconductor
The diquark condensate susceptibility in neutral color superconductor at
moderate baryon density is calculated in the frame of two flavor
Nambu-Jona-Lasinio model. When color chemical potential is introduced to keep
charge neutrality, the diquark condensate susceptibility is negative in the
directions without diquark condensate in color space, which may be regarded as
a signal of the instability of the conventional ground state with only diquark
condensate in the color 3 direction.Comment: 4 pages, 2 figure
In-medium meson effects on the equation of state of hot and dense nuclear matter
The influence of the in-medium mesons on the effective nucleon mass and in
turn on the equation of state of hot/dense nuclear matter is discussed in the
Walecka model. Due to the self-consistent treatment of couplings between
nucleons and and mesons, the temperature and density
dependence of the effective hadron masses approaches more towards the Brown-Rho
scaling law, and the compression modulus is reduced from in mean
field theory to an accepted value .Comment: 5 pages, 6 figures in Revtex. Final version to be publishe
Spectral Function of rho in Dense and Hot Hadronic Matter
The spectral function of rho meson in hot/dense hadronic matter is studied by
taking into account the nucleon-loop on quantum hadrondynamics model level.
Different from the hot pion gas effect which changes the spectral function
slightly, the nucleon-antinucleon polarization (Dirac sea) makes the spectral
function very sharp and shifted towards the low invariant mass region
significantly due to the decreasing effective nucleon mass.Comment: Revised version to be published, 10 pages, 8 figure
Current indications for acute total hip arthroplasty in older patients with acetabular fracture: Evidence in 601 patients from 2002 to 2021
PurposeOlder patient population with acetabular fractures is increasing rapidly, requiring enhanced recovery. Acute total hip arthroplasty (THA) is a good option for these patients, and it is becoming increasing popular. However, acute THA has different indications in different studies. Therefore, a systematic review is needed to assess and comprehend the indications for acute THA in older patients.MethodsA systematic literature review was conducted to identify a retrospective series or prospective studies in older patients (>60 years) with acetabular fractures. The search timeline was from database construction till December 2021; PubMed, Embase, and Cochrane Library databases were searched. Two trained professional reviewers independently read the full text of documents that met the inclusion criteria and extracted information on the specific methods used and indication information based on the research design.ResultsIn total, there were 601 patients with acetabular fractures aged >60 years from 33 studies were obtained. Twenty-eight studies reported that THA was a feasible treatment option for acetabular fractures in geriatric patients with good outcome. The primary indications were dome impaction, irreducible articular comminution, femoral head injury, and pre-existing osteoarthritis or avascular necrosis. The most common patterns were anterior column and posterior hemitransverse, posterior wall, both columns, and T-type.ConclusionAcute THA is an effective treatment strategy for older patients with acetabular fractures and should be considered when the abovementioned indications are observed on preoperative images. (PROSPERO: CRD42022329555)
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