UHMWPE/CaSiO3 Nanocomposite: Mechanical and Tribological Properties.

This paper studied the effect of additives of 0.5-20 wt.% synthetic CaSiO3 wollastonite on the thermodynamic, mechanical, and tribological characteristics and structure of polymer composite materials (PCM) based on ultra-high-molecular weight polyethylene (UHMWPE). Using thermogravimetric analysis, X-ray fluorescence, scanning electron microscope, and laser light diffraction methods, it was shown that autoclave synthesis in the multicomponent system CaSO4·2H2O-SiO2·nH2O-KOH-H2O allows one to obtain neeindle-shaped nanosized CaSiO3 particles. It was shown that synthetic wollastonite is an effective filler of UHMWPE, which can significantly increase the deformation-strength and tribological characteristics of PCM. The active participation of wollastonite in tribochemical reactions occurring during friction of PCM by infrared spectroscopy was detected: new peaks related to oxygen-containing functional groups (hydroxyl and carbonyl) appeared. The developed UHMWPE/CaSiO3 materials have high wear resistance and can be used as triboengineering materials.

Non-steady-state photo-EMF in ß-Ga2O3 crystals at λ = 457 nm.

The non-steady-state photoelectromotive force is excited in a monoclinic gallium oxide crystal at wavelength λ = 457 nm. The crystal grown in an oxygen atmosphere is insulating and highly transparent for a visible light, nevertheless, the formation of dynamic space-charge gratings and observation of the photo-EMF signal is achieved without application of any electric field to the sample. The dependencies of the signal amplitude on the frequency of phase modulation, light intensity, spatial frequency and light polarization are measured. The material demonstrates the anisotropy along the [100] and [010] directions, namely, there is a small difference in the transport parameters and a pronounced polarization dependence of the signal. The crystal's photoconductivity, responsivity and diffusion length of electrons are estimated for the chosen light wavelength and compared with the ones for other wide-bandgap crystals.

Mapping the refractive index of optically transparent samples by means of optical nanoantenna attached to fiber microaxicon.

We demonstrate analytically and numerically that the detection of the spectral response of a single spherical Au nanoantenna allows one to map very small (down to 5·10(-4) RIU) variations of the refractive index of an optically transparent sample. Spectral shift of the dipole local plasmon resonance wavelength of the nanoantenna and the spectral sensitivity of the method developed was estimated by using simple analytical quasi-static model. A pointed scanning probe based on fiber microaxicon with the Au spherical nanoantenna attached to its tip was proposed to realize the RI mapping method. Finite-difference time-domain numerical simulations of the spectral properties of the proposed probe are in good agreement with the theoretical quasi-electrostatic estimations for a radius of the nanoantenna not exceeding the skin depth of Au.

Occurrence of a silicatein gene in glass sponges (Hexactinellida: Porifera).

Silicatein genes are involved in spicule formation in demosponges (Demospongiae: Porifera). However, numerous attempts to isolate silicatein genes from glass sponges (Hexactinellida: Porifera) resulted in a limited success. In the present investigation, we performed analysis of potential silicatein/cathepsin transcripts in three different species of glass sponges (Pheronema raphanus, Aulosaccus schulzei, and Bathydorus levis). In total, 472 clones of such transcripts have been analyzed. Most of them represent cathepsin transcripts and only three clones have been found to represent transcripts, which can be related to silicateins. Silicatein transcripts were identified in A. schulzei (Hexactinellida; Lyssacinosida; Rosselidae), and the corresponding gene was called AuSil-Hexa. Expression of AuSil-Hexa in A. schulzei was confirmed by real-time PCR. Comparative sequence analysis indicates high sequence identity of the A. schulzei silicatein with demosponge silicateins described previously. A phylogenetic analysis indicates that the AuSil-Hexa protein belongs to silicateins. However, the AuSil-Hexa protein contains a catalytic cysteine instead of the conventional serine.

Fast photogalvanic response of a Bi12SiO20 crystal.

A photoelectric response of a Bi12SiO20 crystal grown in an argon atmosphere on a linearly polarized light (which is referred to as the linear photogalvanic effect) is reported for the first time in the nanosecond-time domain. Optimal geometry for detection of the photo-induced current concerning the orientation of the polarization state of the incident light in respect to the crystallographic axes of a sample was determined considering both the natural optical activity and light absorption of sillenite crystals. Spectral dependence of the photogalvanic current was measured in the visible part (410 - 610 nm) of the spectrum. Temporal shape of light-induced electric-current pulses observed at different experimental conditions is discussed. Obtained results are believed to show that sillenite crystals are very prospective for development of different ultra-fast optoelectronics devices.

Silicatein genes in spicule-forming and nonspicule-forming Pacific demosponges.

Silicatein genes are known to be involved in siliceous spicule formation in marine sponges. Proteins encoded by these genes, silicateins, were recently proposed for nanobiotechnological applications. We studied silicatein genes of marine sponges Latrunculia oparinae collected in the west Pacific region, shelf of Kuril Islands. Five silicatein genes, LoSilA1, LoSilA1a, LoSilA2, and LoSilA3 (silicatein-alpha group), LoSilB (silicatein-beta group), and one cathepsin gene, LoCath, were isolated from the sponge L. oparinae for the first time. The deduced amino acid sequence of L. oparinae silicateins showed high-sequence identity with silicateins described previously. LoCath contains the catalytic triad of amino acid residues Cys-His-Asn characteristic for cathepsins as well as motifs typical for silicateins. A phylogenetic analysis places LoCath between sponge silicateins-beta and L-cathepsins suggesting that the LoCath gene represents an intermediate form between silicatein and cathepsin genes. Additionally, we identified, for the first time, silicatein genes (AcSilA and AcSilB) in nonspicule-forming marine sponge, Acsmall a, Cyrillicnthodendrilla sp. The results suggest that silicateins could participate also in the function(s) unrelated to spiculogenesis.

Fiber sensors multiplexing using vectorial wave mixing in a photorefractive crystal.

We propose a novel multiplexing system for sensing of dynamic strains excited in different multimode optical fibers. Multiplexing of the sensors is implemented by using vectorial wave mixing technique in the reflection geometry of hologram formation in a photorefractive crystal of CdTe:V. We analyzed different mechanisms of the crosstalk between measuring channels and showed that system performance is strongly affected by residual stresses of the photorefractive crystal.