On the constancy of the velocity of light

We point out that the acceptance of the relativity principle together with the homogeneity and isotropy of space and the homogeneity of time inevitably leads to the Lorentz spacetime transformation with a universal limiting speed . Speculations on possible new four-dimensional symmetries involving a variable speed of light such as that proposed by Hsu must therefore be dismissed on such a basis alone. In this paper we draw attention to some logical inconsistencies in Hsu's attempt at establishing a new space-light transformation law, and follow with a discussion on why such an attempt must necessarily fail.     

Analysis of the maximum entropy principle “debate”

Jaynes's maximum entropy principle (MEP) is analyzed by considering in detail a recent controversy. Emphasis is placed on the inductive logical interpretation of probability and the concept of total knowledge. The relation of the MEP to relative frequencies is discussed, and a possible realm of its fruitful application is noted.     

Femptovoltmeter (10−15 Volt) based on a double Josphson junction resistive interferometer

A voltmeter of sensitivity is based on direct conversion of the voltage to be measured into a frequency according to the Josephson voltage-frequency relation. Selfpumped parametric amplification in a d.c. biased loop containing two Josephson junctions and a measuring resistanceR _s=4.7×10^–9 amplifies the femptovolt level voltages acrossR _s to microvolt levels that can be observed with a room temperature amplifier. The sensitivity of the femptovoltmeter is determined by Johnson-Nyquist noise voltages at 4.2 K in the 4.7×10^–9 resistance.     

Dipolmomente 1, 6-überbrückter [10]- Annulene

The dipole moments of 1, 6-bridged [10]-annulenes of type I (X = CH₂, O, NH) and of bromo derivatives with X = CH₂, O are in agreement with the previously established structure of these compounds if a partial moment of approximately 0,8 D is assigned to the non-planar π-electron system.     

Fingerprint scaling increases the probability of identifying molecules with similar activity in virtual screening calculations.

Results of systematic virtual screening calculations using a structural key-type fingerprint are reported for compounds belonging to 14 activity classes added to randomly selected synthetic molecules. For each class, a fingerprint profile was calculated to monitor the relative occupancy of fingerprint bit positions. Consensus bit patterns were determined consisting of all bits that were always set on in compounds belonging to a specific activity class. In virtual screening calculations, scale factors were applied to each consensus bit position in fingerprints of query molecules. This technique, called "fingerprint scaling", effectively increases the weight of consensus bit positions in fingerprint comparisons. Although overall prediction accuracy was satisfactory using unscaled calculations, scaling significantly increased the number of correct predictions but only slightly increased the rate of false positives. These observations suggest that fingerprint scaling is an attractive approach to increase the probability of identifying molecules with similar activity by virtual screening. It requires the availability of a series of related compounds and can be easily applied to any keyed fingerprint representation that associates bit positions with specific molecular features.     

Time-dependent master equation simulation of complex elementary reactions in combustion: application to the reaction of 1CH2 with C2H2 from 300-2000 K

Computational simulations of the title reaction are presented, covering a temperature range from 300 to 2000 K. At lower temperatures we find that initial formation of the cyclopropene complex by addition of methylene to acetylene is irreversible, as is the stabilisation process via collisional energy transfer. Product branching between propargyl and the stable isomers is predicted at 300 K as a function of pressure for the first time. At intermediate temperatures (1200 K), complex temporal evolution involving multiple steady states begins to emerge. At high temperatures (2000 K) the timescale for subsequent unimolecular decay of thermalized intermediates begins to impinge on the timescale for reaction of methylene, such that the rate of formation of propargyl product does not admit a simple analysis in terms of a single time-independent rate constant until the methylene supply becomes depleted. Likewise, at the elevated temperatures the thermalized intermediates cannot be regarded as irreversible product channels. Our solution algorithm involves spectral propagation of a symmetrized version of the discretized master equation matrix, and is implemented in a high precision environment which makes hitherto unachievable low-temperature modelling a reality.     

Technetium-99 in Fucusand seawater samples in the Finnish coastal area of the Baltic Sea, 1999

Liquid discharges of ⁹⁹Tc from the Sellafield nuclear facilities increased largely in the mid 90"s. These releases are transported to the Nordic sea areas by the ocean currents. Results of the ⁹⁹Tc activities along the Norwegian coastal areas and in the North Sea have been reported but then again, the spreading of ⁹⁹Tc into Baltic Sea has not been studied thoroughly. Fucus vesiculosus and seawater samples were collected in the summer 1999 from the Finnish coastal areas for measuring ⁹⁹Tc in the Baltic Sea area. A modified analytical method for measuring ⁹⁹Tc in the environmental samples was developed at that time. The method based on extraction chromatography and liquid scintillation measurement of ⁹⁹Tc. The ⁹⁹Tc concentration in the Fucus vesiculosus in the Finnish coast of the Baltic Sea varied from 1.6 to 11.6 Bq/kg (dry weight) being highest at the most northern sampling sites. These values were considerable lower than those in the Danish and Norwegian coasts. The variation in the concentrations observed are probably due to biological factors. The ⁹⁹Tc concentration in the Baltic Sea water studied was below 0.2 Bq/m³.     

The effect of 4-vinylcyclohexene on the degradation of polystyrene and on the polymerisation of styrene

It has previously been postulated that the inhibition of polystyrene degradation observed in the initial stages of the isothermal degradation of polystyrene-polybutadiene blends is partly due to reaction of polystyryl radicals with 4-vinylcyclohexene (4VCH) evolved from the polybutadiene. This hypothesis has been tested by examining the effect of small amounts of 4VCH on polystyrene degradation and on the free radical polymerisation of styrene. The results provide support for the hypothesis: there is an induction period in the degradation and the polymerisation is retarded. From molecular weight measurements on polymers made in the presence of various amounts of 4VCH, a chain transfer constant in styrene polymerisation at 60°C of 117 × 10^?5 has been calculated.     

Lipophilicity determination of some photosynthetic pigments by reversed-phase thin-layer chromatography. The effect of support and the organic phase in the eluent

Summary The lipophilicity of some photosynthetic pigments was determined by reversed-phase thin-layer chromatography using silica, alumina, cellulose, polyamid and diatomaceous earth as supports and acetone and ethanol as organic mobile phase. The R_M value of each compound linearly decreased with increasing concentration of the organic modifier. The supports exerted high impact on the separation: no acceptable separation was achieved on cellulose, polyamid, alumina and diatomaceous earth supports while silica supports produced the best separation. The retention of photosynthetic pigments depended on the origin of silica and on the type of organic mobile phase.     

Crystal and molecular structure of 6b,7,8,8a-tetramethyl-6b,8a-dihydrocyclobut[a]acenaphthylene and 1,2,2a,10b-tetramethyl-2a,10b-dihydrocyclobuta[l]phenanthrene

The crystal and molecular structure of 6b,7,8,8a-tetramethyl-6b,8a-dihydrocyclobut[a]acenaphthylene (I) and 1,2,2a,10b-tetramethyl-2a,10b-dihydrocyclobuta[l]phenanthrene (II) is established by XRD analysis. The C(6b)-C(8a) bond in I is lengthened to 1.603(3) ∢, and the C(2a)-C(10b) bond in II is prolonged to 1.589(6) ∢. The acenaphthene and dihydrophenanthrene frameworks are planar; the rms deviations of atoms from the plane are 0.011 and 0.032 ∢, respectively. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1140–1145, November–December, 1997.