The β-moments for the second-forbidden β-decay from137Cs,the CVC theory,and the residual interactions

Theβ-moments of the 7/2⁺(1.176 MeVβ ^?)3/2⁺ transition in the decay of¹³⁷Cs have been extracted from the available experimental data. We have obtained the following values: 〈R _ij 〉/R ²=0.035±0.020, 〈iT _ij 〉/R ²=0.067±0.036, and ?0.085≦〈S _ijk ～>/R ²≦0.085. These results show that theβ-moments are reduced with respect to those evaluated by means of the conventional pairing model. These quenching effects are similar to those previously found in the analyses of first-forbiddenβ-decays and are attributed to residual charge-exchange interactions. The results forΛ(=?〈iA _ij 〉/ξ〈R _ij 〉) are discussed in the light of the predicitons of the CVC theory.     

Effect of water content on electrical conductivity of fish skin collagen

The increased interest in fish skin collagen results from the risk of BSE disease and the production of native collagen by the acidic hydration method. As a material, FSC derived by the novel acidic hydration method was used. The bovine Achilles tendon (BAT) collagen type I was applied as a control material. Measurements were carried out at the temperature range 2980 K-510 K. Each sample was heated twice. During the first heating run for FSC, to 380 K, the maximum was localized at 343 K, at electrical conductivity of 7 · 10⁻⁶ S/m. In the second heating run to 510 K, the maximum was observed at 443 K for FSC, and at 487 K for BAT collagen. The peaks revealed in the temperature range 320-350 K were related to the free water and bound water release, alike for FSC and BAT collagen. The process of water removal for both types of collagen takes place in similar temperature ranges.     

Optical and X-ray emission spectroscopy of high-power laser-induced dielectric breakdown in molecular gases and their mixtures

Large-scale plasma was created in molecular gases (CO, CO2, N2, H2O) and their mixtures by high-power laser-induced dielectric breakdown (LIDB). Compositions of the mixtures used are those suggested for the early earth's atmosphere of neutral and/or mildly reducing character. Time-integrated optical spectra emitted from the laser spark have been measured and analyzed. The spectra of the plasma generated in the CO-containing mixtures are dominated by emission of both C2 and CN radicals. A vibrational temperature of approximately 10(4) K was determined according to an intensity distribution in a vibronic structure of the CN (B2Sigma(+)u-X2Sigma(+)g) violet band. For comparison, the NH3-CH4-H2-H2O mixture has been irradiated as a model of the strongly reducing version of the early earth's atmosphere. In this mixture, excited CN seems to be significantly less abundant than C2. The LIDB experiments were in the molecular gases carried out not only in the static cell but also using a large, double stream pulse jet (gas puff target) placed in the vacuum interaction chamber. The obtained soft X-ray emission spectra indicate the presence of highly charged atomic ions in the hot core of high-power laser sparks.     

Anti-Stokes Yb3+ emission--valuable structure information in spectra of rare earth compounds measured with FT-Raman spectrometers

Raman spectroscopy is a powerful and simple method which proved to be very useful in studies of solids. The most widely used Raman spectrometers are FT-Raman instruments with YAG:Nd(3+) laser as an excitation source. However, in the case of samples containing rare earth elements, the quality of FT-Raman spectra is often low due to strong fluorescence effects. We show that, in such cases, anti-Stokes part of the Raman spectra often contains strong, well resolved bands identified as multiphonon-assisted emission bands of Yb(3+) present as an impurity. We show on several examples that analysis of these bands may provide useful structure information, similar to that obtained by "Eu structure probe" method in optical spectroscopy. The Yb(3+) emission can be also measured using standard luminescence detection systems. However, the application of FT-Raman system allows one to obtain good quality spectra in a much cheaper, easier and faster way (in times as short as a few seconds). Moreover, high-sensitivity of FT-Raman spectrometers allows to detect even very small amounts of Yb(3+) impurity.     

Automorphisms of endomorphism semigroups of reflexive digraphs

A reflexive digraph is a pair (X, ρ), where X is an arbitrary set and ρ is a reflexive binary relation on X. Let End (X, ρ) be the semigroup of endomorphisms of (X, ρ). We determine the group of automorphisms of End (X, ρ) for: digraphs containing an edge not contained in a cycle, digraphs consisting of arbitrary unions of cycles such that cycles of length ≥2 are pairwise disjoint, and some circulant digraphs (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Eddy current measurements of surface roughness

The paper proposes a method for simultaneous measurements of the material conductivity and its surface roughness for non-ferromagnetic materials. The method takes advantage of the effect exercised by eddy currents onto impedance of a contact coil. The essence of the method is to eliminate the influence of the surface unevenness onto measurements of conductivity by the calculation of a correcting factor that serves as a specific equivalent of the surface roughness. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nontrivial solutions for Neumann problems with an indefinite linear part

In this paper, we consider a semilinear Neumann problem with an indefinite linear part and a Carathéodory nonlinearity which is superlinear near infinity and near zero, but does not satisfy the Ambrosetti-Rabinowitz condition. Using an abstract existence theorem for C¹-functions having a local linking at the origin, we establish the existence of at least one nontrivial smooth solution.     

Stochastic differential equations with jump reflection at time-dependent barriers

We study existence, uniqueness and approximation of solutions of stochastic differential equations with jump reflection at time-dependent barriers. The basic idea in proofs consists in applying new existence and stability theorems on deterministic one-dimensional Skorokhod problem. Our results are new even in the classical case of one reflecting barrier.     

Cationic Porphyrin-Graphene Oxide Hybrid: Donor-Acceptor Composite for Efficient Photoinduced Electron Transfer

Non-covalent nanohybrids composed of cationic 5,10,15,20-tetra(4-trimethylammoniophenyl)porphyrin tetra(p-toluenesulfonate) (TMAP) and the graphene oxide sheets were prepared under two pH values (6.2 vs. 1.8). The TMAP molecule was positively charged, regardless of the pH value during preparation. However, protonation of the imino nitrogens increased the overall charge of the porphyrin molecule from +4 to +6 (TMAP⁴⁺ and TMAP⁶⁺). It was found that at acidic pH, interaction of TMAP⁶⁺ with GO was largely suppressed. On the other hand, results of FTIR, Raman spectroscopy, thermogravimetric analysis, atomic force microscopy (AFM) and elemental analysis confirmed effective non-covalent functionalization of graphene oxide with cationic porphyrin at pH 6.2. The TMAP⁴⁺-GO hybrids exhibited well defined structure with a monolayer of TMAP⁴⁺ on the GO sheets as confirmed by AFM. Formation of the ground-state TMAP⁴⁺-GO complex in solution was monitored by the red-shift of the porphyrin Soret absorption band. This ground-state interaction between TMAP⁴⁺ and GO is responsible for the static quenching of the porphyrin emission. Fluorescence was not detected for the nanohybrid which indicated that a very fast deactivation process had to take place. Ultrafast time-resolved transient absorption spectroscopy clearly demonstrated the occurrence of electron transfer from the photoexcited TMAP⁴⁺ singlet state to GO sheets, as proven by the formation of a porphyrin radical cation.     

Polyelectrolyte-compression forces between spherical DNA brushes

Optical tweezers are employed to measure the forces of interaction within a single pair of DNA-grafted colloids, dependent on the molecular weight of the DNA chains, and the concentration and valence of the surrounding ionic medium. The resulting forces are short range and set in as the surface-to-surface distance between the colloidal cores reaches the value of the brush height. The measured force-distance relation is analyzed by means of a theoretical treatment that quantitatively describes the effects of compression of the chains on the surface of the opposite-lying colloid. Quantitative agreement with the experiment is obtained for all parameter combinations.