End-stapled homo and hetero collagen triple helices: a click chemistry approach

A CuAAC reaction was established for modular synthesis of end-stapled homo- and hetero-triple helical peptides, generating "clicked" macro-assemblies with enhanced thermal stability.     

Physical interpretation of the phase asymmetry of a slant-pathtransmission matrix

The phase asymmetry of a 20-GHz slant-path transmission matrix during ice events is modeled in terms of two layers consisting of plate- and needle-type crystals. The microwave propagation data are consistent with the meteorological reports that the plate forms are usually predominant at higher altitudes than the needle forms     

Propagation theory in adaptive cancellation of cross-polarization

The application of propagation theory to the structure and control of adaptive networks designed to cancel hydrometeor-induced cross-polarization in microwave communication links is summarized. When adaptive cross-coupling networks are realized at radio frequency as variable waveguide polarizers, desirable simplifications are to make them lossless devices with at most two free parameters. Performance calculations for such simplified forms are fully reviewed. Several new approaches to the design of controllers for the cancelling networks are also made possible. New results are presented on the performance of systems which use only one pilot tone, or even dispense with cross-polar measurement completely. It is also shown that the reciprocity of the hydrometeor medium, an apparently safe assumption, makes possible an extract precorrection of a transmitted polarization if control is based on a beacon signal of the orthogonal polarization sent back from the receiving point.     

Causality in Inflationary Universes with Positive Spatial Curvature

We show that in the case of positively-curved Friedmann-Lemaître universes (k = +1), an inflationary period in the early universe will for most initial conditions not solve the horizon problem, no matter how long inflation lasts. It will only do so for cases where inflation starts in an almost static state, corresponding to an extremely high value of , 1, at the beginning of inflation. For smaller values, it is not possible to solve the horizon problem because the relevant integral asymptotes to a finite value (as happens also in the de Sitter universe in a k = +1 frame). Thus, for these cases, the causal problems associated with the near-isotropy of the Cosmic Background Radiation have to be solved already in the Planck era. Furthermore both compact space sections and event horizons will exist in these universes even if the present cosmological constant dies away in the far future, raising potential problems for M-theory as a theory of gravity.     

Crosspolarisation from high-altitude hydrometeors on a 20 GHz satellite radio path

20 GHz signals received from the ATS6 satellite show much higher crosspolarisation than expected from rain alone. Radar data indicate the cause to be hydrometeors above, rather than in, the melting band. During thunderstorms, the crosspolar level can change abruptly at the moment of a lightning discharge.     

Crosspolarisation and gain reduction due to sand or dust on microwave reflector antennas

A model describing the effect of a sand/dust accretion on the aperture field and gain of a reflector antenna is checked experimentally and extended to predict enhanced crosspolarisation. The largest effects theoretically occur for accretion layers that are uniformly thick but only cover part of the reflector.     

OTS propagation measurements during thunderstorms

Ots propagation measurements are described which comprise a complete determination of the incoming polarizations for both linearly and circularly polarized beacons. Auxiliary equipment includes radars, E-field sensors and a microphone array. General trends in the propagation data are discussed and two basic models are proposed for the observed correlations between electrostatic field and cross-polarization. A detailed analysis, with radar data, is now given for one thunderstorm. A method for the prediction of the linear cross-polarization from the circular is shown to work well for this ice-dominated event. Fast lightning-induced, cross-polar jumps are described, and by relating them to acoustic thunder location data, the physical models for particle alignment are discussed.     

Alcohol in breath and blood: a selected ion flow tube mass spectrometric study

In this paper we compare the amounts of ethanol in breath and in blood after ingestion of whisky using analysis by selected ion flow tube mass spectrometry (SIFT-MS). Blood ethanol concentrations were also obtained using standard hospital forensic procedures for blood alcohol analyses. We demonstrate the quantitative nature of SIFT-MS analysis by correlating the observed alcohol content of the headspace above 5-mL amounts of venous blood and aqueous solution to which known trace amounts of alcohol have been added. This procedure provides a Henry's Law coefficient for ethanol in aqueous solution at 298 +/- 3 K of 209 +/- 7 mol/kg*bar. We also demonstrate that measurement of the ethanol concentration in the alveolar portion of a single breath using the SIFT-MS technique gives an accurate measure of blood alcohol and could obviate the need for blood samples in forensic processing. The storage performance of breath samples in Mylar bags with a volume greater than 1 L has been shown to maintain the mixture integrity for ethanol but not for some other species.     

Association reactions at low pressure. III. The C2H2+/C2H2 system

The association reactions, C4H2(+) + C2H2 and C4H3(+) + C2H2 have been examined at pressures between 8 x 10(-8) and 1 x 10(-4) Torr at 298 K in an ion cyclotron resonance mass spectrometer. Association occurred via two different mechanisms. At pressures below approximately 2 x 10(-6) Torr, the association was bimolecular having rate coefficients k2 = 2.7 x 10(-10) cm3 s-1 and 2.0 x 10(-10) cm3 s-1 for C4H2+ and C4H3+, respectively. At pressures above approximately 2 x 10(-6) Torr, termolecular association was observed with rate coefficients, k3 = 5.7 x 10(-23) cm6 s-1 and 1.3 x 10(-23) cm6 s-1 for C4H2+ and C4H3+, respectively, when M = C2H2. The termolecular rate constants with N2, Ar, Ne, and He as the third body, M, are also reported. We propose that the low pressure bimolecular association process was the result of radiative stabilization of the complex and the termolecular association process was the result of collisional stabilization. Elementary rate coefficients were obtained and the lifetime of the collision complex was > or = 57 microseconds for (C6H4+)* and > or = 18 microseconds for (C6H5+)*. At pressures below 1 x 10(-6) Torr, approximately 11% of the (C6H4+)* were stabilized by photon emission and the remaining approximately 89% reverted back to reactants, while approximately 24% of the (C6H5+)* were stabilized by photon emission and the remaining approximately 76% reverted back to reactants. The ionic products of the C2H2(+) + C2H2 reaction, C4H2+ and C4H3+, were found to be formed with enough internal energy that they did not react by the radiative association channel until relaxed by several nonreactive collisions with the bath gas.