Complexity factor for charged spherical system

In this paper, we study the complexity factor for a charged anisotropic self-gravitating object. We formulate the Einstein–Maxwell field equations, Tolman–Opphenheimer–Volkoff equation, and the mass function. We form the structure scalars by the orthogonal splitting of the Riemann tensor and then find the complexity factor with the help of these scalars. Finally, we investigate some astrophysical objects for the vanishing of complexity condition. It is found that the presence of the electromagnetic field decreases the complexity of the system.     

Drift of Phase Fluctuations in the ABC Model

In a recent work, Bodineau and Derrida analyzed the phase fluctuations in the ABC model. In particular, they computed the asymptotic variance and, on the basis of numerical simulations, they conjectured the presence of a drift, which they guessed to be an antisymmetric function of the three densities. By assuming the validity of the fluctuating hydrodynamic approximation, we prove the presence of such a drift, providing an analytical expression for it. This expression is then shown to be an antisymmetric function of the three densities. The antisymmetry of the drift can also be inferred from a symmetry property of the underlying microscopic dynamics.     

Drop impact on surfactant films and solutions

Drops impacting on horizontal aqueous surfactant films have been analyzed using a high-speed camera. Drops of either water or aqueous surfactant solutions had a diameter of 2.4?±?0.4 mm and impacted with a velocity of 0.1 to 1.3 m/s. As surfactants, anionic sodium dodecyl sulfate and cationic cetyltrimethyl ammonium bromide were used. Pure water drops impacting on freestanding surfactant films showed coalescence, bouncing, partial bouncing, passing, and partial passing. For bouncing, the concentration of surfactant in the surfactant film must exceed the critical micelle concentration. When surfactant was added to the drop, coalescence and partial passing were suppressed. We attribute the different behavior to different hydrodynamic boundary conditions at the surface of pure water and surfactant solution, leading to different repulsive hydrodynamic forces arising when the air has to flow out of the closing gap between the two liquid surfaces. The boundary condition changes as a function of surfactant concentration from a slip to no-slip, leading to stronger hydrodynamic repulsion. In addition, estimates of the characteristic velocities show that diffusion of air into the water is slow and can only account for the very last thinning of the air gap before coalescence.     

Investigation of the critical scattering at the structural phase transition in RbCaF3 using Mössbauer diffraction

The elastic and inelastic scattering of 14.4 keV Mössbauer gamma-rays from the 1/2(311) reflection of RbCaF₃ was investigated in the critical region. The temperature dependence of both intensities near the phase transition at 193 K is in good agreement with other experiments.     

Libraries of random-sequence polypeptides produced with high yield as carboxy-terminal fusions with ubiquitin

Summary Libraries of random-sequence polypeptides have been shown to be valuable sources of novel molecules possessing a variety of useful biologic-like activities, some of which may hold promise as potential vaccines and therapeutics. Previous random peptide expression systems were limited to low levels of peptide production and often to short sequences. Here we describe a series of libraries designed for increased polypeptide length. Cloned as carboxy-terminal extensions of ubiquitin, the fusions were produced inE. coli at high levels, and were purified to homogeneity. The majority of the extension proteins examined could be cleaved from ubiquitin by treatment with a ubiquitin-fusion hydrolase. The libraries described here are appropriate sources of novel polypeptides with desired binding or catalytic function, as well as tools with which to examine inherent properties of proteins as a whole. Toward the latter goal, we have examined structural properties of random-sequence proteins purified from these libraries. Quite surprisingly, fluorescence emission spectra of intrinsic tryptophan residues in several purified fusion proteins, under native-like and denaturing conditions, often resemble those expected for folded and unfolded states, respectively. The results presented here detail an important expansion in the range of potential uses for random-sequence polypeptide libraries.     

Novel process for generating useful electrophiles from common anions using Selectfluor fluorination agent

In the present work, the electrophile equivalents Cl+, Br+, SCN+, and NO2+ are generated from their respective sodium, potassium, and in some cases ammonium salts (M+X-) by reaction with Selectfluor electrophilic fluorination agent in acetonitrile solution at room temperature. These generated electrophilic species subsequently react in situ with a variety of aromatic substrates containing one or more substituent groups including H, F, Cl, CH3, COOH, C(O)CH3, NO2, and OR' and NR'R' ' where R' and R' ' are H or CH3. The resulting substitution products are, in most cases, isolable as pure compounds in high yield. Variations in the process include the use of other anions, electrophilic fluorination agents, and solvents.     

Highly diastereoselective approach toward (+/-)-tetraponerine T6 and analogues via the double cycloisomerization-reduction of bis-alkynylpyrimidines

A new, short, and efficient approach toward tricyclic alkaloids, involving the double cycloisomerization-reduction of bis-alkynylpyrimidines 3a-m, has been developed. The requisite bis-alkynylpyrimidines 3a-m were readily prepared via regioselective sequential Sonogashira coupling reactions of dibromopyrimidines 1. Bis-alkynylpyrimidines 3a-m were converted into the 5-6-5 tricyclic heteroaromatic cores 4a-m via the Cu(I)-assisted double cycloisomerization reaction. The reaction proceeded stepwise, which was confirmed by the isolation of the mono-pyrrolization intermediate 5. The structure of 5 was assigned by 2D NMR and by independent synthesis. Cycloisomerization of 5 under standard conditions afforded tricyclic 4g in 89% yield. The PtO2-catalyzed hydrogenation of bis-pyrrolopyrimidines 4d, 4g, and 4i in acidic media afforded stable amidinium derivatives, 11a, 11b, and 11c. Further reduction of the latter with LiAlH4 allowed for the highly diastereoselective total synthesis of (+/-)-tetraponerine T6 and its analogues.     

A simple synthesis of some 1,10-phenanthrolines

The reaction of o-phenylenediamine with α,β-unsaturated ketones in the presence of hydrochloric acid smoothly affords alkyl substituted 1,10-phenanthrolines in a one step synthesis.     

A combination of chemical derivatisation and improved bioinformatic tools optimises protein identification for proteomics

The identification of individual protein species within an organism's proteome has been optimised by increasing the information produced from mass spectral analysis through the chemical derivatisation of tryptic peptides and the development of new software tools. Peptide fragments are subjected to two forms of derivatisation. First, lysine residues are converted to homoarginine moieties by guanidination. This procedure has two advantages, first, it usually identifies the C-terminal amino acid of the tryptic peptide and also greatly increases the total information content of the mass spectrum by improving the signal response of C-terminal lysine fragments. Second, an Edman-type phenylthiocarbamoyl (PTC) modification is carried out on the N-terminal amino acid. The renders the first peptide bond highly susceptible to cleavage during mass spectrometry (MS) analysis and consequently allows the ready identification of the N-terminal residue. The utility of the procedure has been demonstrated by developing novel bioinformatic tools to exploit the additional mass spectral data in the identification of proteome proteins from the yeast Saccharomyces cerevisiae. With this combination of novel chemistry and bioinformatics, it should be possible to identify unambiguously any yeast protein spot or band from either two-dimensional or one-dimensional electropheretograms.