Transport in random correlated fields

A review is given of recent developments in the diffusion properties of particles in the presence of local random fields as well as the conductivity of the analog random resistor network. The effect of long-range ferro- and antiferro-type correlations between the local fields on the diffusion and conductivity properties is considered. A physical realization for such spatial correlations is diffusion on linear polymers in the presence of external uniform bias field. For this case a universal diffusion law was found independent of the fractal dimension of the polymer chain or the Euclidean dimension in which the polymer is embedded. Recent results for diffusion in two dimensions in the presence of a special case of correlated local fields are also reviewed.     

Magnetic moments and general covariance

The principle of general covariance for deriving the passive equations is applied to the group of automorphisms of compact support of a principal bundle acting on the space of Cartan connections. Under an orbital constraint this yields the equations of motion postulated in [11] which have a symplectic character. When specialized to an affine connection these equations become the equations of interaction of spin and torsion studied in [5]. With the incorporation of a Higgs field, a forcing term is added to the equations which, in the case of an electromagnetic field, incorporate the effects of the magnetic moment. The Higgs field is of the character obtained by dimensional reduction.     

Direct flourination of bycyclic molecules

Elemental fluorine substitutes certain tertiary hydrogens of various bicyclo systems via the rare electrophilic pathway.     

A new method for fluorination of sterols

Diethylaminosulfurtrifluoride (DAST) is a good fluorinating reagent for sterols. The fluorinating reactions proceed through SN₂ mechanism, while reactions through free carbonium ion are responsible for rearrangements and eliminations.     

Laplacian and vibrational spectra for homogeneous graphs

A homogeneous graph is a graph togerther with a group that acts transitively on vertices as symmertries of the graph. We consider Laplacians of homogeneous graphs and generalizations of Laplacians whose eigenvalues can be associated with various equilibria of forces in molecules (such as vibrational modes of buckyballs). Methods are given for calculating such eigenvalues by combining concepts and techniques in group representation theory, gauge theory and graph theory.     

Sufficient conditions for boundedness of solutions of linear differential equations

In this paper we obtain sufficient conditions for boundedness of every solution and its derivatives of a linear differential equation. We will also show that our conditions are sharp.     

Reactions of α-chloronitrones with unsaturated ethers

The Ag⁺ induced reaction of α-chloronitrones with unsaturated ethers goes in two parallel competitive directions. On the one hand cycloadducts like 3 are formed and on the other hand oxonium ions like 4. Formation of analogous oxonium compounds occurs also when α-alkoxynitrones are treated with Et₃O⁺BF₄^? in 1,2-dichloroethane. Formation of oxonium compounds with the enol-ethers is practically irreversible and leads to enol-ether fragmentation. With the saturated ethers compounds like 25 were formed and were used as a potential source of N-alkyl-N-vinyl-nitrosonium ions.     

On the determination of free energy in linear viscoelastic solids

Zusammenfassung Der Artikel behandelt die isotherme Verformung eines linear-viskoelastischen Stoffes im einachsigen Spannungszustand. Ein Integralgesetz für die Spannungs-Dehnungsbeziehung wird aufgestellt, in dem der Relaxationsmodul als Summe von Exponentialfunktionen angesetzt wird. Die Möglichkeit, die freie Energie und die Entropieproduktion aus der Kenntnis des Relaxationsmoduls zu bestimmen, wird diskutiert. Im Gegensatz zu früheren Untersuchungen dieses Problems macht der vorliegende Artikel keinen Gebrauch von Modellvorstellungen und stützt sich ausschliesslich auf thermodynamische Überlegungen.

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The results communicated in this paper were obtained in the course of research sponsored by the Office of Naval Research under Contract Nonr 562(10), and by Material Research Program, The Advanced Research Projects Agency, Department of Defense.     

The interactions between doxorubicin and amphiphilic and acidic β-sheet peptides towards drug delivery hydrogels

Amphiphilic β-sheet peptides decorated by acidic amino acids may spontaneously assemble into ordered monolayers at interfaces as well as form hydrogels at near physiological pH values. Here we monitored interactions between the peptide Pro-Asp-(Phe-Asp)(5)-Pro and the mildly amphiphilic chemotherapeutic drug doxorubicin (Dox). The peptide in the form of monolayers at the air water interface was found to enhance Dox adsorption, pointing to favorable interactions between the amphiphilic peptide and Dox. In solutions the fluorescence emission of Dox which was fitted to the Stern-Volmer quenching models suggested the formation of Dox associated forms >25 μM and larger forms at >100 μM. In presence of the peptide these larger associated forms appeared already at Dox concentrations >50 μM, indicating enhanced interactions between Dox and the peptide in the β-sheet conformation. Peptide hydrogels loaded with the drug showed sustained release profiles over several days. Smaller fractions of the drug were released with increase in either peptide or initially loaded drug concentrations. The released Dox was found to retain its cytotoxic activity in vitro. This study provides insights on the interactions between the amphiphilic and acidic peptide and Dox that are useful for the bottom up development of Dox-loaded peptide hydrogels for local drug delivery applications.     

Near IR Fluorescent Polystyrene/Albumin Core/Shell Nanoparticles for Specific Targeting of Colonic Neoplasms

Previous studies have shown that albumin has a high affinity towards tumours, and, as a result, many drug/albumin conjugates, as well as albumin nanoparticles, have been studied as antineoplastic drug carriers. Numerous studies have also shown the high affinity of cyanine dyes for albumin. This work combines the former and the latter for the preparation of NIR fluorescent and photostable nanoparticles as diagnostic biomaterials. Tumour‐specific labelling by NIR fluorescent polystyrene/albumin core/shell nanoparticles is demonstrated, without the presence of additional targeting moieties, and they possess great potential for clinical applications.