We consider a nonlinear Volterra integral equation with local and/or integral loads on the desired solution given by the Stieltjes integral. The equation contains a bifurcation parameter and has the ...trivial solution for any of the parameter values. Necessary and sufficient conditions are obtained for those values of the parameter (bifurcation points) in the vicinity of which the equation has nontrivial continuous real solutions. The leading terms of the asymptotics of the solution branches are constructed, and a method for their refinement is indicated. Illustrative examples are given. A linearization principle is established that permits one to find bifurcation points using only information about the linear part of the nonlinear equation with a vector load and a vector bifurcation parameter.
An integro-functional equation of the Fredholm type with linear functionals and with a small parameter is considered. Sufficient conditions for the existence of a continuous solution are obtained. A ...method is given for constructing a solution both in the regular case and in the irregular one. In the regular case, the solution is constructed as a Taylor series in powers of the parameter. In the irregular case, the solution is constructed as a Laurent series in powers of the parameter.
This study was aimed at studying the effect of heavy metals and arsenic on the survival and biofilm formation of some saprotrophic microorganisms:
Bacillus megaterium
var.
phosphaticum
,
Bacillus ...mucilaginosus
,
Pectobacterium carotovorum
, and
Escherichia coli
. As a source of heavy metals and arsenic, we used aqueous solutions of NaAsO
2
, Cd(CH
3
COO)
2
, and Pb(NO
3
)
2
(2.5, 25, 250 mg L
−1
). The cultures in the liquid medium had different resistance to the toxicants under study:
B. megaterium
>
B. mucilaginosus
>
P. carotovorum
>
E. coli
. The toxicity of the tested solutions of heavy metals and arsenic for microorganisms can be arranged (decreasing toxicity) as follows: cadmium acetate > lead nitrate > sodium metaarsenite. These experiments revealed some regularities related to the mechanisms of toxic effect of As, Pb, and Cd solutions on the formation of biofilms of soil bacteria, changes in bacterial cellular forms, and their survival.
Bacillus megaterium
strain was the most resistant to high As concentrations and was able to influence the formation of highly structured colonies of bacterial cells with the honeycomb-like structure. The immobilization of heavy metals can be achieved due to their binding into strong compounds with the matrix substances of biofilms and polymeric organic compounds formed during the sporulation of rhizobacteria. It can increase the resistance of bacteria to high concentrations of heavy metals and arsenic. The results obtained can be of great practical importance in the development of biotechnologies related to soil bioremediation, in the field of nanotechnology, crop production, and medicine.
Superconductivity in diamond Sidorov, V. A; Ekimov, E. A; Bauer, E. D ...
Nature,
04/2004, Letnik:
428, Številka:
6982
Journal Article
Recenzirano
Odprti dostop
Diamond is an electrical insulator well known for its exceptional hardness. It also conducts heat even more effectively than copper, and can withstand very high electric fields. With these physical ...properties, diamond is attractive for electronic applications, particularly when charge carriers are introduced (by chemical doping) into the system. Boron has one less electron than carbon and, because of its small atomic radius, boron is relatively easily incorporated into diamond; as boron acts as a charge acceptor, the resulting diamond is effectively hole-doped. Here we report the discovery of superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2,500-2,800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond is a bulk, type-II superconductor below the superconducting transition temperature Tc 4 K; superconductivity survives in a magnetic field up to Hc2(0) ≥ 3.5 T. The discovery of superconductivity in diamond-structured carbon suggests that Si and Ge, which also form in the diamond structure, may similarly exhibit superconductivity under the appropriate conditions.
The cyanobacterial strain
sp. IPPAS B-1200 isolated from Lake Balkhash is characterized by high relative amounts of myristic (30%) and myristoleic (10%) acids. The remaining fatty acids (FAs) are ...represented mainly by palmitic (20%) and palmitoleic (40%) acids. We expressed the genes for lysophosphatidic acid acyltransferase (LPAAT; EC 2.3.1.51) and Δ9 fatty acid desaturase (FAD; EC 1.14.19.1) from
sp. IPPAS B-1200 in
PCC 7942, which synthesizes myristic and myristoleic acids at the level of 0.5-1% and produces mainly palmitic (~60%) and palmitoleic (35%) acids.
cells that expressed foreign LPAAT synthesized myristic acid at 26%, but did not produce myristoleic acid, suggesting that Δ9-FAD of
cannot desaturate FAs with chain lengths less than C16.
cells that co-expressed LPAAT and Δ9-FAD of
synthesized up to 45% palmitoleic and 9% myristoleic acid, suggesting that Δ9-FAD of
is capable of desaturating saturated acyl chains of any length.
The effect of positive thermodiffusion of colloidal particles under convection of magnetic fluids in connected vertical channels of 3.2 × 3.2 mm
2
square cross-section and height 50 mm heated from ...below is analyzed. Below the critical Rayleigh number, particle thermophoresis in vertical generates unstable density stratification in fluid at rest. This leads to rapid bursts (~1 min) of concentration convection arising periodically (~4 h). Under developed convection, above the critical Rayleigh number particle thermophoresis in horizontal direction generates concentration inhomogeneities in the neighborhood of the channel walls and provokes convective flow instability that leads to the periodic change (~1 h) in the direction of convective stream. The reasons of the oscillatory instability of mechanical equilibrium observed experimentally at positive sign of the Soret coefficient are discussed.
Filamentation of ultrashort laser pulses in the atmosphere offers unique opportunities for long-range transmission of high-power laser radiation and standoff detection. With the critical power of ...self-focusing scaling as the laser wavelength squared, the quest for longer-wavelength drivers, which would radically increase the peak power and, hence, the laser energy in a single filament, has been ongoing over two decades, during which time the available laser sources limited filamentation experiments in the atmosphere to the near-infrared and visible ranges. Here, we demonstrate filamentation of ultrashort mid-infrared pulses in the atmosphere for the first time. We show that, with the spectrum of a femtosecond laser driver centered at 3.9 μm, right at the edge of the atmospheric transmission window, radiation energies above 20 mJ and peak powers in excess of 200 GW can be transmitted through the atmosphere in a single filament. Our studies reveal unique properties of mid-infrared filaments, where the generation of powerful mid-infrared supercontinuum is accompanied by unusual scenarios of optical harmonic generation, giving rise to remarkably broad radiation spectra, stretching from the visible to the mid-infrared.
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