80 research outputs found
The Dirac equation without spinors
In the first part of the paper we give a tensor version of the Dirac
equation. In the second part we formulate and analyse a simple model equation
which for weak external fields appears to have properties similar to those of
the 2--dimensional Dirac equation.Comment: 20 pages. Submitted for publication in the proceedings of the
conference `Functional analysis, partial differential equations and
applications', Rostock (Germany) 31 August--4 September 199
Phospholipase A2 Activity in Gingival Crevicular Fluid from Patients with Periodontal Disease: A possible Marker of Disease Activity
The activity of phospholipase A2 in human gingival crevicular fluid
(GCF) associated with periodontal disease was demonstrated. Based
upon the presence or absence of bleeding on probing (BOP), which is
a marker for the disease activity, there were higher levels of the
enzyme activity in BOP positive, than in negative sites. When the
BOP positive sites became negative after periodontal therapy, the
enzyme activity decreased dramatically to almost undetectable
levels. There were no significant differences between the activity
before and after treatment when the BOP positive sites remained
unchanged. These results suggest that the activity in GCF reflects
periodontal disease conditions and that it can be used as a marker
for disease activity
Magnetic oxide semiconductors
Magnetic oxide semiconductors, oxide semiconductors doped with transition
metal elements, are one of the candidates for a high Curie temperature
ferromagnetic semiconductor that is important to realize semiconductor
spintronics at room temperature. We review in this paper recent progress of
researches on various magnetic oxide semiconductors. The magnetization,
magneto-optical effect, and magneto-transport such as anomalous Hall effect are
examined from viewpoint of feasibility to evaluate the ferromagnetism. The
ferromagnetism of Co-doped TiO2 and transition metal-doped ZnO is discussed.Comment: 26 pages, 5 tables, 6 figure
S-Nitrosated alpha-1-acid glycoprotein exhibits antibacterial activity against multidrug-resistant bacteria strains and synergistically enhances the effect of antibiotics
Alpha-1-acid glycoprotein (AGP) is a major acute-phase protein. Biosynthesis of AGP increases markedly during inflammation and infection, similar to nitric oxide (NO) biosynthesis. AGP variant A (AGP) contains a reduced cysteine (Cys149). Previously, we reported that S-nitrosated AGP (SNO-AGP) synthesized by reaction with a NO donor, possessed very strong broad-spectrum antimicrobial activity (IC50 = 10−9-10−6 M). In this study, using a cecal ligation and puncture animal model, we confirmed that AGP can be endogenously S-nitrosated during infection. Furthermore, we examined the antibacterial property of SNO-AGP against multidrug-resistant Klebsiella pneumoniae and Pseudomonas aeruginosa to investigate the involvement of SNO-AGP in the host defense system. Our results showed that SNO-AGP could inhibit multidrug efflux pump, AcrAB-TolC, a major contributor to bacterial multidrug resistance. In addition, SNO-AGP decreased biofilm formation and ATP level in bacteria, indicating that SNO-AGP can revert drug resistance. It was also noteworthy that SNO-AGP showed synergistic effects with the existing antibiotics (oxacillin, imipenem, norfloxacin, erythromycin, and tetracycline). In conclusion, SNO-AGP participated in the host defense system and has potential as a novel agent for single or combination antimicrobial therapy
Constraint-preserving boundary treatment for a harmonic formulation of the Einstein equations
We present a set of well-posed constraint-preserving boundary conditions for
a first-order in time, second-order in space, harmonic formulation of the
Einstein equations. The boundary conditions are tested using robust stability,
linear and nonlinear waves, and are found to be both less reflective and
constraint preserving than standard Sommerfeld-type boundary conditions.Comment: 18 pages, 7 figures, accepted in CQ
Enhanced contribution to quark and neutron electric dipole moments with small mixing of right-handed currents and CKM CP violation
We study the light quark and the neutron electric dipole moments (EDMs) under
the assumptions that the CP source is still in the usual CKM matrix and that
there is a small mixing of right-handed charged currents in the quark sector.
We find that the EDMs arise already at two loop order that are much larger than
the standard model (SM) result even for a small mixing.Comment: 9 pages, revtex, axodraw.sty, 1 figure, published version in Phys.
Rev. D. References updated, minor corrections and typos fixe
Solitary waves in the Nonlinear Dirac Equation
In the present work, we consider the existence, stability, and dynamics of
solitary waves in the nonlinear Dirac equation. We start by introducing the
Soler model of self-interacting spinors, and discuss its localized waveforms in
one, two, and three spatial dimensions and the equations they satisfy. We
present the associated explicit solutions in one dimension and numerically
obtain their analogues in higher dimensions. The stability is subsequently
discussed from a theoretical perspective and then complemented with numerical
computations. Finally, the dynamics of the solutions is explored and compared
to its non-relativistic analogue, which is the nonlinear Schr{\"o}dinger
equation. A few special topics are also explored, including the discrete
variant of the nonlinear Dirac equation and its solitary wave properties, as
well as the PT-symmetric variant of the model
Adaptive and Bounded Investment Returns Promote Cooperation in Spatial Public Goods Games
The public goods game is one of the most famous models for studying the evolution of cooperation in sizable groups. The multiplication factor in this game can characterize the investment return from the public good, which may be variable depending on the interactive environment in realistic situations. Instead of using the same universal value, here we consider that the multiplication factor in each group is updated based on the differences between the local and global interactive environments in the spatial public goods game, but meanwhile limited to within a certain range. We find that the adaptive and bounded investment returns can significantly promote cooperation. In particular, full cooperation can be achieved for high feedback strength when appropriate limitation is set for the investment return. Also, we show that the fraction of cooperators in the whole population can become larger if the lower and upper limits of the multiplication factor are increased. Furthermore, in comparison to the traditionally spatial public goods game where the multiplication factor in each group is identical and fixed, we find that cooperation can be better promoted if the multiplication factor is constrained to adjust between one and the group size in our model. Our results highlight the importance of the locally adaptive and bounded investment returns for the emergence and dominance of cooperative behavior in structured populations
A long non-coding RNA links calreticulin-mediated immunogenic cell removal to RB1 transcription
Logarithmic sensing in Bacillus subtilis aerotaxis
Aerotaxis, the directed migration along oxygen gradients, allows many microorganisms to locate favorable oxygen concentrations.
Despite oxygen’s fundamental role for life, even key aspects of aerotaxis remain poorly understood. In Bacillus subtilis, for example,
there is conflicting evidence of whether migration occurs to the maximal oxygen concentration available or to an optimal
intermediate one, and how aerotaxis can be maintained over a broad range of conditions. Using precisely controlled oxygen
gradients in a microfluidic device, spanning the full spectrum of conditions from quasi-anoxic to oxic (60 n mol/l–1 m mol/l), we
resolved B. subtilis’ ‘oxygen preference conundrum’ by demonstrating consistent migration towards maximum oxygen
concentrations (‘monotonic aerotaxis’). Surprisingly, the strength of aerotaxis was largely unchanged over three decades in oxygen
concentration (131 n mol/l–196 μ mol/l). We discovered that in this range B. subtilis responds to the logarithm of the oxygen
concentration gradient, a rescaling strategy called ‘log-sensing’ that affords organisms high sensitivity over a wide range of
conditions. In these experiments, high-throughput single-cell imaging yielded the best signal-to-noise ratio of any microbial taxis
study to date, enabling the robust identification of the first mathematical model for aerotaxis among a broad class of alternative
models. The model passed the stringent test of predicting the transient aerotactic response despite being developed on steadystate
data, and quantitatively captures both monotonic aerotaxis and log-sensing. Taken together, these results shed new light on
the oxygen-seeking capabilities of B. subtilis and provide a blueprint for the quantitative investigation of the many other forms of
microbial taxis
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