Biodegradability patterns of two PHAs: a polymer of 3-hydroxybutyric acid (3-PHB) and a copolymer of 3-hydroxybutyric and 3-hydroxyvaleric acids (3-PHB/3-PHV) containing 11
mol% of hydroxyvalerate, ...were studied in the tropical marine environment, in the South China Sea (Nha Trang, Vietnam). No significant differences have been observed between degradation rates of 3-PHB and 3-PHB/3-PHV specimens; it has been found that under study conditions, biodegradation is rather influenced by the shape of the polymer item and the preparation technique than by the chemical composition of the polymer. Biodegradation rates of polymer films in seawater have been found to be higher than those of compacted pellets. As 3-PHB and 3-PHB/3-PHV are degraded and the specimens lose their mass, molecular weight of both polymers is decreased, i.e. polymer chains get destroyed. The polydispersity index of the PHAs grows significantly. However, the degree of crystallinity of both PHAs remains unchanged, i.e. the amorphous phase and the crystalline one are equally disintegrated. PHA-degrading microorganisms were isolated using the clear-zone technique, by inoculating the isolates onto mineral agar that contained PHA as sole carbon source. Based on the 16S rRNA analysis, the PHA-degrading strains were identified as
Enterobacter sp. (four strains),
Bacillus sp. and
Gracilibacillus sp.
ABSTRACT
Luminous blue variables (LBVs) are massive stars that show strong spectral and photometric variability. The questions of what evolutionary stages they represent and what exactly drives their ...instability are still open, and thus it is important to understand whether LBVs without significant ongoing activity exist, and for how long such dormant LBVs may ‘sleep’. In this paper we investigate the long-term variability properties of the LBV candidate MN 112, by combining its optical and infrared spectral data covering 12 years with photometric data covering nearly a century, as acquired from both modern time-domain sky surveys and historical photographic plates. We analyse the spectra, derive the physical properties of the star by modelling its atmosphere, and use a new distance estimate from Gaia data release 3 (DR3) to determine the position of MN 112 both inside the Galaxy and in the Hertzsprung–Russell diagram. The distance estimation has almost doubled in comparison with Gaia DR2. Because of this, MN 112 moved to upper part of the diagram, and according to our modelling it lies on an evolutionary track for a star with initial mass $M_*=70~\rm M_\odot$ near the Humphreys–Davidson limit. Given the absence of any significant variability, we conclude that the star is a dormant LBV that has now been inactive for at least a century.
The interaction of non-monochromatic radiation with arrays comprising plasmonic and dielectric nanoparticles has been studied using the finite-difference time-domain electrodynamics method. It is ...shown that LiNbO
, TiO
, GaAs, Si, and Ge all-dielectric nanoparticle arrays can provide a complete selective reflection of an incident plane wave within a narrow spectral line of collective lattice resonance with a Q-factor of 10
or larger at various spectral ranges, while plasmonic refractory TiN and chemically stable Au nanoparticle arrays provide high-Q resonances with moderate reflectivity. Arrays with fixed dimensional parameters make it possible to fine-tune the position of a selected resonant spectral line by tilting the array relative to the direction of the incident radiation. These effects provide grounds for engineering novel selective tunable optical high-Q filters in a wide range of wavelengths, from visible to middle-IR.
Tunka-133: Results of 3 year operation Prosin, V.V.; Berezhnev, S.F.; Budnev, N.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2014, Volume:
756
Journal Article
Peer reviewed
Open access
The EAS Cherenkov light array Tunka-133, with ~3km2 geometric area, is taking data since 2009. The array permits a detailed study of cosmic ray energy spectrum and mass composition in the PeV energy ...range. After a short description of the methods of EAS parameter reconstruction, we present the all-particle energy spectrum and results of studying CR composition, based on 3 seasons of array operation. In the last part of the paper, we discuss possible interpretations of the obtained results.
To explain the nature of the high reddening (A
V
≃ 10 mag) towards one of the most luminous stars in the Galaxy – Cyg OB2 #12 (B5 Ia-0), also known as MT304, we carried out spectrophotometric ...observations of 24 stars located in its vicinity. We included five new B-stars among the members of Cygnus OB2, and for five more photometrically selected stars we spectroscopically confirmed their membership. We constructed the map of interstellar extinction within 2.5 arcmin radius and found that interstellar extinction increases towards MT304. According to our results the most reddened OB-stars in the association after MT304 are J203240.35+411420.1 and J203239.90+411436.2, located about 15 arcsec away from it. Interstellar extinction towards these stars is about 9 mag. The increase of reddening towards MT304 suggests that the reddening excess may be caused by the circumstellar shell ejected by the star during its evolution. This shell absorbs 1 mag, but its chemical composition and temperature are unclear. We also report the detection of a second component of MT304, and discovery of an even fainter third component, based on data of speckle interferometric observations taken with the Russian 6-m telescope.
A
bstract
We present the study of the decay
J/ψ
→
ρπ
. The results are based on of 5.2 million
J/ψ
events collected by the KEDR detector at the VEPP-4M collider. The branching fractions are measured ...to be
B
(
J/ψ
→
ρπ
) = (2
.
072 ± 0
.
017 ± 0
.
062) ∙ 10
−
2
and
B
(
J/ψ
→
π
+
π
−
π
0
) = (1
.
878 ± 0
.
013 ± 0
.
051) ∙ 10
−
2
, where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.
Possibilities for optimizing the design of self-cooled radiators were investigated. The SIMP method can be used for topologically optimizing the steady-state thermal conductivity of a flat plate with ...the Dirichlet condition on the lateral edge and uniform heat release throughout the volume. A radiator with optimal topology geometry was constructed using wire EDM cutting technology. The results of the heat removal efficiency comparison for topologically optimized radiators and conventional finned radiators are presented in the form of their temperature fields. Studies have demonstrated the high efficiency of a topologically optimized radiator design heat removal in comparison with finned ones. Recommendations for the practical application of the results obtained are formulated.
The Brownian dynamics method is employed to study the formation of an electrical double layer (EDL) on the metal nanoparticle (NP) surface in hydrosols during adsorption of electrolyte ions from the ...interparticle medium. Also studied is the charge accumulation by NPs in the Stern layer. To simulate the process of the formation of EDL, we took into account the effect of image forces and specific adsorption, dissipative and random forces, and the degree of hydration of adsorbed ions on the EDL structure. The employed model makes it possible to determine the charge of NPs and the structure of EDL. For the first time, the charge of both the diffuse part of EDL and the dense Stern layer has been determined. A decrease in the electrolyte concentration (below
c
< 0.1 mol/l) has been found to result in dramatic changes in the formation of the Stern layer.
Graphical abstract
The use of topological optimization (TO) in most cases is limited to theoretical studies, since the result of solving TO problems, as a rule, is a complex irregular geometry. Advanced additive ...technologies (AT) allow transferring directly to the TO practical application without preliminary engineering study of the solution. A promising AT feature is the possibility of manufacturing a porous internal macrostructure of products, which can be used to optimize their mass when subjected to bending loads. In this study, the problem of minimizing the compliance of a Messerschmitt–Bölkov–Blom (MBB) beam is solved. The topologically optimized design was made of plastic by the method of fused deposition modelling. The reproducibility of product properties was assessed; standard three-point bending tests were implemented for various types of internal porosity and various internal filling fraction values, as well as various orientations of pores in space. It is shown that the use of an internal porous structure is a promising approach that allows reducing the material consumption while maintaining the strength properties of the product.
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