Characterization and evaluation of silk protein hydrogels for drug delivery

The objective of this study was to characterize and evaluate the physicochemical properties and drug release profiles of hydrogels composed of silk protein (SP) polymers. SPs with a low MW (SPL, ca. 18 kDa) and a high MW (SPH, ca. 76 kDa) were used for preparing hydrogels. Both the random coil form and beta-sheet conformation simultaneously existed in the hydrogels according to Fourier-transformed IR determination. Morphologically, the hydrogels showed a sponge-like cross-linked structure produced by physical entanglement as well as chemical hydrogen and covalent bindings. The in vitro buprenorphine delivery from SPH hydrogels showed a slow-release effect, and a zero-order rate was obtained for all preparations. Drug release could be controlled by varying the SPH concentrations or incorporation of SPL into the systems. SP hydrogels showed a stronger barrier property for hydrophilic solutes than for hydrophobic solutes. The incorporation of SPH into Pluronic F-127 (PF-127) hydrogels changed the gel structure from amorphous micelles to a regularly interconnected texture with pores. Furthermore, SPH as an adjuvant polymer in PF-127 and chitosan hydrogels lowered and controlled the amount of drug released from those systems.     

Compact representations of BL-algebras

In this paper we define sheaf spaces of BL-algebras (or BL-sheaf spaces), we study completely regular and compact BL-sheaf spaces and compact representations of BL-algebras and, finally, we prove that the category of non-trivial BL-algebras is equivalent with the category of compact local BL-sheaf spaces. Mathematics Subject Classification (2000):08A72, 03G25, 54B40, 06F99, 06D05     

AC-2 Invers-voltammetrische Bestimmung von Quecksilber in Harn

Zusammenfassung Es wird ein spezielles Verfahren zur Probenvorbereitung beschrieben, durch welches Verluste an Quecksilber weitgehend vermieden werden. Die invers-voltammetrische Bestimmung des Quecksilbers erfolgt an einer rotierenden Goldelektrode. Durch Messung der Signale der 2. harmonischen Welle der Wechselstrom-Voltammetrie werden Störungen der Grundlinie weitgehend eliminiert.

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AC-2 anodic stripping voltammetric determination of mercury in urine

Summary A special method for sample preparation avoiding losses of mercury is described. A rotating gold electrode is used for the anodic-stripping voltammetric determination of mercury. In order to suppress base-line disturbances, the signal of the 2nd harmonic wave of AC-voltammetry is employed.

     

Approximate Self-Consistent Molecular Orbital Theory I S-P Separation Model Modification of CNDO-MO

A newly developed approximate self-consistent molecular orbital formulation, so called: ‘s–p separation model CNDO-MO method’, is proposed. The Pariser Parr¹⁾ and Nishimoto Mataga²⁾ approximations are separately applied to the ns and np (n=l to 3) AO's. The MO's of both closed and open shell cases are formulated. It seems to be a good method for molecular structure interpretation for both polar and nonpolar compounds.     

Differential cross sections of proton compton scattering at photon laboratory energies between 700 and 1000 MeV

Differential cross sections of proton Compton scattering have been measured at the Bonn 2.5 GeV synchrotron. 78 data points are presented as angular distributions at photon lab energies of 700, 750, 800, 850, 900, and 950MeV. The c.m. scattering angle ranges from 40°–130°, corresponding to a variation of the four momentum transfer squared betweent=?0.10 tot=?0.96 GeV² at 700 and 950 MeV, respectively. Two additional differential cross sections have been measured at 1000MeV, 35.6° and 47.4°. The angular distributions show forward peaks whose extrapolations to 0° are consistent with calculated forward cross sections taken from literature. The small angle data (|t| ?0.2 GeV²) together with the calculated cross sections at 0° are also consistent with the assumption of a slope parameterB of 5 GeV^?2. For the first time a rerise of the angular distributions towards backward angles has been observed. It becomes less steep with increasing energy. The most interesting feature of the angular distributions is a sharp structure which appears betweent=?0.55 GeV² at 700MeV andt=?0.72 GeV² at 950 MeV. Such a rapid varation of the differential cross section witht has never been ovserved in elastic hadron-hadron scattering or photoproduction processes. It indicates the existence of a dynamical mechanism which could be a peculiarity of Compton scattering.     

Cyclopentadienyl chromium complexes with halide, methyl, isothiocyanate and isoselenocyanate ligands: Structures of [η-(C5H4-COOCH3)]Cr(NO)2(Br) and [η-(C5H4-COOCH3)]Cr(NO)2(NCS)

Bromination/nitrosylation of [η⁵-(carbomethoxy)cyclopentadienyl]dicarbonylnitrosylchromium (8) (hereafter called carbomethoxycynichrodene) with hydrogen bromide/isoamyl nitrite gives bromo [η⁵-(carboxymethoxy)cyclopentadienyl]dinitrosylchromium (10) in 84%. Compounds 15 in 74% and 16 in 90% were obtained from the corresponding cynichrodene derivatives via the same method. Compounds [η⁵-(carbomethoxy)cyclopentadienyl](isothiocyanato)dinitrosylchromium (13) and [η⁵-(carbomethoxy)cyclopentadienyl](isoselenocyanato)dinitrosylchromium (14) were prepared from [η⁵-(carbomethoxy)cyclopentadienyl]chlorodinitrosylchromium (9) with excess potassium thiocyanate and selenocyanate, respectively, after detaching the chloride by the action of silver nitrate. One of the nitrosyl groups in each compound is located at the site away from the exocyclic carbonyl carbon of the Cp(Cr) ring with twist angles of 168.5° and 172.3°, respectively. The chemical shifts of C(2)-C(5) carbon atoms of a series of substituted-cyclopentadienyldinitrosylchromium derivatives, [η⁵-(C₅H₄-sub)]Cr(NO)₂X, have been assigned using two-dimensional HetCOR NMR spectroscopy. The assigned chemical shifts were compared with the NMR data of their analogues of ferrocene, and the opposite correlation on the assignments was observed. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of ¹³C NMR data and those of 10 and 13 are compared with the calculations via density functional B3LYP correlation-exchange method.     

Intramolecular charge transfer in donor‐bridge‐acceptor compounds with paired linearly conjugated or cross‐conjugated pathways

An understanding of intramolecular charge transfer in 2‐D linearly conjugated and cross‐conjugated compounds is necessary for the rational design of molecular electronics, improved solar energy devices, semi‐conducting polymers, and materials with nonlinear optical properties. In this work, the femtosecond transient absorption spectra and kinetics of several donor‐bridge‐acceptor compounds containing cross‐conjugated or linearly conjugated bridging groups were obtained. The veratrole group was used as the donor, and the phthalimide group was used as an acceptor. 2‐D conjugation was achieved by involving two bridging groups arranged cyclically between the donor and acceptor. The donor and acceptor were bridged by m‐phenylene in the cross‐conjugated compounds or 2,5‐thiophene in the linearly conjugated compounds. We found slower charge separation times and slower charge recombination times in the compounds containing cyclic cross‐conjugated bridging groups than in those containing the cyclic linearly conjugated groups in polar solvent. Charge separation rates that were found to be dependent on solvent were observed in the donor‐bridge‐acceptor compounds. Copyright © 2014 John Wiley & Sons, Ltd.     

Analytical investigation for true and spurious eigensolutions of multiply-connected membranes containing elliptical boundaries using the dual BIEM

It is well known that the boundary element method may induce spurious eigenvalues while solving eigenvalue problems. The finding that spurious eigenvalues depend on the geometry of inner boundary and the approach utilized has been revealed analytically and numerically in the literature. However, all the related efforts were focused on eigenproblems involving circular boundaries. On the other hand, the extension to elliptical boundaries seems not straightforward and lacks of attention. Accordingly, this paper performs an analytical investigation of spurious eigenvalues for a confocal elliptical membrane using boundary integral equation methods (BIEM) in conjunction with separable kernels and eigenfunction expansion. To analytically study this eigenproblem, the elliptic coordinates and Mathieu functions are adopted. The fundamental solution is expanded into the separable kernel by using the elliptic coordinates and the boundary densities are expanded by using the eigenfunction expansion. The Jacobian terms may exist in the separable kernel, boundary density and boundary contour integration and they can cancel each other out. Therefore, the orthogonal relations are reserved in the boundary contour integration. In this way, a similar finding about the mechanism of spurious eigenvalues is found and agrees with those corresponding to the annular case. To verify this finding, the boundary element method and the commercial finite-element code ABAQUS are also utilized to provide eigensolutions, respectively, for comparisons. Good agreement is observed from comparisons. Based on the adaptive observer system, the present approach can deal with eigenproblems containing circular and elliptical boundaries at the same time in a semi-analytical manner. By using the BIEM, it is found that spurious eigenvalues are the zeros of the modified Mathieu functions which depend on the inner elliptical boundary and the integral formulation. Finally, several methods including the CHIEF method, the SVD updating technique and the Burton & Miller method are employed to filter out the spurious eigenvalues, respectively. In addition, the efficiency of the CHIEF method is better than those of the SVD updating technique and the Burton & Miller approach, since not only hypersingularity is avoided but also computation effort is saved.