Infrared laser based on the principle of melt crystallization or vapor condensation. Why not?

The paper discusses a possibility of new effects in quantum electronics: amplification of certain frequency infrared beams in supersaturated vapors or super-cooled melts as well as design of infrared lasers based on a new type of pumping. The basis of these effects is the existence of characteristic infrared radiation accompanying phase transitions of the first order, especially crystallization and condensation. Experimental results of the author and other researchers concerning characteristic infrared emission detection during crystallization from the melt of some substances (alkali halides, sapphire, tellurium, ice, etc.) are presented, as well as condensation of water vapor. The author has critically analyzed these experimental data in terms of correspondence to the theoretical models. The last ones are based on the assumption that the particle (atom, molecule or cluster), during transition from higher energetic level (vapor or melt) to the lower energetic level (crystal), emits one or more photons depending on the latent energy of the transition. Based on the experimental data, the author postulates a transparency window appearance for the characteristic radiation in the substances where first-order phase transitions take place.     

Zum gerichtlich-chemischen Nachweis von Quecksilber

Ohne Zusammenfassung     

Topological obstructions to nonnegative curvature

We find new obstructions to the existence of complete Riemannian metric of nonnegative sectional curvature on manifolds with infinite fundamental groups. In particular, we construct many examples of vector bundles whose total spaces admit no nonnegatively curved metrics. Received February 11, 2000 / Published online February 5, 2001     

Nucleation ability of multiwall carbon nanotubes in polypropylene composites

The nonisothermal crystallization of multiwall carbon nanotube (MWNT)/isotactic polypropylene (iPP) nanocomposites was investigated. The results derived from the differential scanning calorimetry curves (onset temperature, melting point, supercooling, peak temperature, half‐time of crystallization, and enthalpy of crystallization) were compared with those of neat iPP. The data were also processed according to Ozawa's theory and Dobreva's approach. These results and X‐ray diffraction data showed that the MWNTs acted as α‐nucleating agents in iPP. Accordingly, MWNT/iPP was significantly different from neat iPP: A fibrillar morphology was observed instead of the usual spherulites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 520–527, 2003     

Phonon spectromicroscopy of carbon nanostructures with atomic resolution

The vibrational properties of single-wall carbon nanotubes have been probed locally with atomic-scale resolution by inelastic electron tunneling spectroscopy with a low-temperature scanning tunneling microscope. The high spatial resolution has allowed the unraveling of changes in the local phonon spectrum related to topological defects. We demonstrated that the radial breathing mode is suppressed within tube segments of lengths below approximately 3 nm, and that in the cap region phonon modes characteristic of the fullerene hemisphere are emerging. Phonon spectromicroscopy should lead to a better understanding of the mechanisms that limit the transport of heat or electrical charge inside nanostructured carbon materials.     

Line narrowing in methyl-TROSY using zero-quantum 1H-13C NMR spectroscopy

An enhanced sensitivity zero-quantum correlation experiment is proposed for recording (1)H-(13)C correlations of methyl groups in highly deuterated, methyl protonated large proteins. The zero-quantum spectra benefit from TROSY-effects in which both intra- and inter-methyl dipolar relaxation interactions are minimized. Applications to malate synthase G at 5 degrees C (81 kDa single polypeptide chain enzyme, correlation time of 118 ns) and lysine decarboxylase at 45 degrees C (810 kDa decameric enzyme) are presented showing significant improvements in resolution relative to corresponding HMQC data sets, with only slight decreases (approximately 10%) in sensitivity.     

Ordering effects in InGaP/GaAs and InGaAsP/GaAs heterostructures grown by LP-MOVPE

Summary The cationic ordering in InGaP epilayers grown by low-pressure vapour phase epitaxy on GaAs substrates has been investigated by X-ray diffraction. The effects of both the substrate miscut and the doping with Si and Zn have been studied. It has been found that ordering effects occur inside relatively small domains on (1–11) and (−111) planes; however, by increasing the miscut angle the domains of the first kind tend to increase their dimensions, while the second ones tend to disappear. Moreover, doping with impurities substituting cations is seen to destroy the order. Photoluminescence anomalies have been revealed and correlated to the size and ordering degree of the ordered domain.     

Fungal colonization on stoneworks. Interaction fungi-powdered stone samples

The microbial activity plays an important role in the biodegradative processes implied in stonework decay. In natural environments it is not possible to separate the damage produced by microorganisms from damage caused by physical and chemical agents. In vitro assays carried out with microbes isolated from weathered stones are required in order to understand the biological mechanisms involved in stone deterioration. We have described, as commented in the text, how fungal colonization observed on scaglia may be the result of the fine grain size of rock, whereas inhibition of growth on marble may depend on the surface characteristics of calcite grains after grinding. The extent of microbial growth clearly depends on the quantity of cations released in solution. However, fungal growth may, in turn, induce a decrease in pH, thus promoting mineral chemical attack. These observation points to selective action of fungal species in promoting weathering well evidenced by the presence of different extents of cations released in suspension from the same sample. Detailed studies are in progress in order to go into this question.     

Production of vancomycin aglycone conjugated to a peptide carrier domain derived from a biosynthetic non-ribosomal peptide synthetase

A method for attaching the vancomycin aglycone to a peptide carrier domain (PCD) is reported which involves reacting the apo-PCD produced in Escherichia coli with vancomycin aglycone-coenzyme A thioester, catalyzed by the phosphopantetheinyl transferase Sfp from Bacillus subtilis.