Inflationary Cosmology with Two-component Fluid and Thermodynamics

We present a simple and self-consistent cosmology with a phenomenological model of quantum creation of radiation and matter due to the decay of the cosmological constant . The decay drives a non-isentropic inflationary epoch, which exits smoothly to the radiation-dominated era, without reheating, and then evolves to the dust era. The initial vacuum for radiation and matter is a regular Minkowski vacuum. The created radiation and matter obeys standard thermodynamic laws, and the total entropy produced is consistent with the accepted value. This paper is an extension of the model with the decaying cosmological constant considered in [1]. We compare our model with the quantum field theory approach to creation of particles in curved space.     

Enzyme-like acceleration for the hydrolysis of a DNA model promoted by a dinuclear Zn(II) catalyst in dilute aqueous ethanol

The rates and products of cleavage of methyl (2-chloro-4-nitrophenyl) phosphate (2) promoted by a dinuclear Zn(II) complex (3) of 1,3-bis-N,N'(1,5,9-triazacyclododecyl)propane along with 1 equiv of ethoxide were investigated in ethanol solution containing small amounts of water (8 mM or=1.6 x 10(17) times relative to the background hydroxide reaction, suggesting that complex 3 promotes the hydrolysis at least 1000 times more effectively than ethanolysis.     

DNA double helices recognize mutual sequence homology in a protein free environment

The structure and biological function of the DNA double helix are based on interactions recognizing sequence complementarity between two single strands of DNA. A single DNA strand can also recognize the double helix sequence by binding in its groove and forming a triplex. We now find that sequence recognition occurs between intact DNA duplexes without any single-stranded elements as well. We have imaged a mixture of two fluorescently tagged, double helical DNA molecules that have identical nucleotide composition and length (50% GC; 294 base pairs) but different sequences. In electrolytic solution at minor osmotic stress, these DNAs form discrete liquid-crystalline aggregates (spherulites). We have observed spontaneous segregation of the two kinds of DNA within each spherulite, which reveals that nucleotide sequence recognition occurs between double helices separated by water in the absence of proteins, consistent with our earlier theoretical hypothesis. We thus report experimental evidence and discuss possible mechanisms for the recognition of homologous DNAs from a distance.     

Superarming the S-benzoxazolyl glycosyl donors by simple 2-O-benzoyl-3,4,6-tri-O-benzyl protection

The strategic placement of common protecting groups led to the discovery of a new method for "superarming" glycosyl donors. Conceptualized from our previous studies on the O-2/O-5 Cooperative Effect, it was determined that S-benzoxazolyl glycosyl donors possessing both a participating moiety at C-2 and an electronically armed lone pair at O-5, such as the superarmed glycosyl donor shown above, were exceptionally reactive.     

Solution and asymptotic/blow-up behaviour of a class of nonlinear dissipative systems

In this paper, we consider a three-parameter class of Liénard type nonlinear dissipative systems of the form . Since such dissipative systems admit an eight-parameter Lie group of point transformations, it follows that there exists a (complex) point transformation mapping such a system into the free particle system . Normally, such an explicit point transformation cannot be found. Here we find such an explicit point transformation through exploiting the group properties of the determining equations that lead to it. Consequently, we obtain the explicit general solution of such dissipative systems. Moreover, we completely characterize the asymptotic and/or finite time blow-up behaviour of such systems in terms of their three parameters and initial data.     

Oxygen K-edge XANES investigation of NicMg(1-c)O solid solutions

A series of Ni(c)Mg(1-c)O solid solutions are characterized by means of synchrotron radiation X-ray diffraction and X-ray absorption near-edge-structure spectroscopy at oxygen K-edge (532 eV). A dramatic drop of the pre-edge peak intensity is observed in the Ni(c)Mg(1-c)O system upon dilution. It can be attributed to a decrease of 3d(8)(Ni(2+))-2p(O(2-)) mixing upon dilution with magnesium ions due to a decrease of the number of 3d vacancies as nickel ion is replaced by magnesium ion. Similarly, the decrease of the number of 4s and 4p vacancies also leads to a decrease of 4s4p(Ni(2+))-2p(O(2-)) hybridization, and hence a drop of intensities of features B and C. The features E and F are more sensitive to the increase of the degree of disorder upon dilution than feature D, revealing that the latter is mainly dependent by the medium-range order.     

Kinetic resolution of esters via metal catalyzed methanolysis reactions

Some chiral lanthanide complexes of the Schiff base adducts of: a) bis(2-pyridylcarboxaldehyde) and (1R),(2R)-trans-1,2-diaminocyclohexane (Pyr-R,R'-chxn: 3); b) 6-methyl-2-pyridylcarboxaldehyde and (1R),(2R)-trans 1,2-diaminocyclohexane (MePyr-chxn, 4); and c) 2,6-pyridyldicarboxaldehyde and (1R),(2R)-trans-1,2-diaminocyclohexane ((Pyr-R,R'-chxn)(2), 5) have been screened for their utility to promote kinetic resolution via metal catalyzed alcoholyses of the p-nitrophenyl esters of chiral D- and L-Boc-protected glutamine and phenylalanine. Solvents were varied to optimize the kinetic selectivity values, defined as k(2)(L)/k(2)(D) or k(2)(D)/k(2)(L), for the methanolysis and in some cases, ethanolysis of these substrates. At ambient temperature the greatest selectivity was found for the ethanolysis of Boc-Gln-OPNP, catalyzed by 3:Yb(3+):((-)OEt) (k(2)(L)/k(2)(D) = 7.2). The greatest selectivity for Boc-Phe-OPNP is k(2)(D)/k(2)(L) = 3.9 for its methanolysis promoted by 5:La(3+):((-)OMe). A kinetic method is introduced for the determination of both d and l rate constants for catalyzed alcoholysis from a single kinetic experiment. The activation parameters DeltaH(double dagger) and DeltaS(double dagger) were determined for the metal catalyzed methanolysis and ethanolysis of the Boc-Gln-OPNP substrates, and selectivity factors were found to increase at lower temperatures. A low temperature time course for the ethanolysis of racemic Boc-Gln-OPNP catalyzed by 3:Yb(3+):((-)OEt) at -15 degrees C indicated that after 3 hours 60% residual d-enantiomer was observed having an enantiomeric excess of >95% ee. The activation parameters for the ethanolysis of the same substrate catalyzed by (Pyr-R,R'-chxn)(2):La(3+):((-)OEt) predict a k(2)(D)/k(2)(L) = 40.4 at -40 degrees C with a large ee of >99% with approximately 80% of l isomer remaining at that temperature which has been experimentally confirmed.     

Pressure-induced restructuring of a monolayer film nanojunction produces threshold and power law conduction

The electrical conduction of metal-molecule-metal junctions formed between Au-supported self-assembled monolayers of structurally different 1-hexanethiol, 1-decanethiol, and ferrocenyl-1-undecanethiol and a Pt-coated atomic force microscope (AFM) tip has been measured under different compression forces using conducting-probe AFM. The observed junction resistance had two distinct power law scaling changes with the compression force. Different scaling regions were assigned to the change in the contact area, tunneling distance, number of conduction pathways, and structure of the film under compression.     

A theoretical approach to the interpretation of the transient data in scanning laser ablation inductively coupled plasma mass spectrometry: Consideration of the geometry of the scanning area

This paper represents a further development of the theoretical basis for the interpretation of transient data obtained by scanning laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to overcome the non-linear distortion of the transient signal as well as to improve spatial resolution. The reconstruction of the relative concentration profile from transient data is suggested in terms of simple models of analytical information gathering for extreme cases of depth distribution of the analyte. The main attention is focused on the geometry of the overlap between the laser spot and the concentration profile, the consideration of which allows defining explicitly the response function necessary for the deconvolution procedure. The profile of the transient signal simulated according the proposed model for a real system (copper conductor lines in polymer matrix) is in good agreement with the measured data. The feasibility of the deconvolution procedure to reconstruct the relative concentration profile for a model system is demonstrated. The suggested analytical framework is intended to overcome certain limitations of scanning LA-ICP-MS which are caused by the measuring process independently from the optimization of hardware and experimental conditions.     

Intelligent gels and cryogels with entrapped emulsions

Smart thermoresponsive gels and cryogels with incorporated emulsions have been synthesized and studied. The gels were obtained by three-dimensional copolymerization of N-isopropylacrylamide and N,N'-methylene-bis-acrylamide or N,N'-bis(acryloyl)cystamine in the presence of dispersion of tetradecane stabilized with sodium dodecylsulfate. Polymerization was performed at room temperature and below the water crystallization temperature. Both composite gels and cryogels were capable of heat-induced collapse. The extent of the collapse of the composite gel prepared at room temperature was much smaller and without squeezing of the lipophilic phase out of the shrunk composite gel. In contrast, shrinking of the composite cryogel was accompanied by release of tetradecane emulsion.