Calorimetric analysis of dysprosia and dysprosia-doped zirconia ceramics

Dysprosia (Dy₂O₃) and dysprosia-doped ZrO₂ (~10?wt% Dy₂O₃) samples were subjected to calorimetric and thermal analyses to understand the effect of dysprosia doping on the thermal properties of ZrO₂ and to compare the thermal conductivity of dysprosia-doped ZrO₂ (DySZ) to standard 7YSZ (7?wt% Y₂O₃ in ZrO₂). All doped samples were plasma sprayed and subsequently sintered to ensure material densification (reduced porosity for bulk property analysis) and sufficient diffusion of constituents throughout the samples. Differential scanning calorimetry was used to measure the specific heat capacity values for powder and sintered samples as a function of temperature. The thermal conductivities of sintered samples were measured using laser flash techniques. The results showed that the addition of dysprosia to ZrO₂ has lowered both the specific heat capacity and thermal diffusivity when compared to the standard 7YSZ. The resulting thermal conductivity of DySZ was 75% lower than that of 7YSZ under the sintered condition.     

One-side peano curves of fractal genus 9

This paper completes the analysis (begun by E.V. Shchepin and the author in 2008) of regular Peano curves of genus 9 in search of a curve with the minimum square-to-linear ratio. One-side regular Peano curves of genus 9 are considered, and, among these curves, a class of minimal curves with a square-to-linear ratio of 5 2/3 is singled out. A new language to describe curves is introduced which significantly simplifies the coding of these curves.     

Voltage control for microchip capillary electrophoresis analyses

This paper presents an inexpensive and easy-to-implement voltage sequencer instrument for use in microchip capillary electrophoresis (MCE) actuation. The voltage sequencer instrument takes a 0–5 V input signal from a microcontroller and produces a reciprocally proportional voltage signal with the capability to achieve the voltages required for MCE actuation. The unit developed in this work features four independent voltage channels, measures 105 × 143 × 45 mm (width × length × height), and the cost to assemble is under 60 USD. The system is controlled by a peripheral interface controller and commands are given via universal serial bus connection to a personal computer running a command line graphical user interface. The performance of the voltage sequencer is demonstrated by its integration with a fluorescence spectroscopy MCE sensor using pinched sample injection and electrophoretic separation to detect ciprofloxacin in samples of milk. This application is chosen as it is particularly important for the dairy industry, where fines and health concerns are associated with the shipping of antibiotic-contaminated milk. The voltage sequencer instrument presented represents an effective low-cost instrumentation method for conducting MCE, thereby making these experiments accessible and affordable for use in industries such as the dairy industry.     

Use of hydrophobins in formulation of water insoluble drugs for oral administration

The poor water solubility of many drugs requires a specific formulation to achieve a sufficient bioavailability after oral administration. Suspensions of small drug particles can be used to improve the bioavailability. We here show that the fungal hydrophobin SC3 can be used to make suspensions of water insoluble drugs. Bioavailability of two of these drugs, nifedipine and cyclosporine A (CyA), was tested when administered as a SC3-based suspension. SC3 (in a 1:2 (w/w) drug:SC3 ratio) or 100% PEG400 increased the bioavailability of nifedipine to a similar degree (6 ± 2- and 4 ± 3-fold, respectively) compared to nifedipine powder without additives. Moreover, SC3 (in a 7:1 (w/w) drug:hydrophobin ratio) was as effective as a 20-fold diluted Neoral^® formulation by increasing bioavailability of CyA 2.3 ± 0.3-fold compared to CyA in water. Interestingly, using SC3 in the CyA formulation resulted in a slower uptake (p < 0.001 in T_max) of the drug, with a lower peak concentration (C_max 1.8 mg ml^?1) at a later time point (T_max 9 ± 2 h) compared to Neoral^® (C_max 2.2 mg ml^?1; T_max 3.2 ± 0.2). Consequently, SC3 will result in a more constant, longer lasting drug level in the body. Taken together, hydrophobins are attractive candidates to formulate hydrophobic drugs.     

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Determination of elements in SRM soil 2709a by neutron activation analysis

A combination of instrumental neutron activation analysis (INAA) and prompt gamma-ray activation analysis (PGAA) was used to value assign 35 elements in SRM soil 2709a (San Joaquin Soil). INAA with counting of short-lived radioisotopes was used for determination of Al, Au, Ca, Dy, K, Mg, Mn, Na, Ti, and V. Elements determined by INAA with counting of intermediate and long-lived radioisotopes included As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Nd, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Yb, Zn, and Zr. Thermal neutron PGAA was used for the determination of H, B, Si, K, Ti, Mn, Fe, Cd and Gd. Expanded uncertainties were determined for all values reported.     

Practical synthesis of a renin inhibitor via a diastereoselective Dieckmann cyclization

A scalable synthesis of a potent renin inhibitor (1) is described. The absolute stereochemistry is set via an unprecedented diastereoselective Dieckmann cyclization directed by a remote chiral protecting group. This transformation enables preparation of chiral 1,3-[3.3.1]-diazabicyclononenes by desymmetrization of alkyl-esters, with selectivities ranging from 4 to 17:1.     

The assembly-inducing laulimalide/peloruside a binding site on tubulin: molecular modeling and biochemical studies with [³H]peloruside A

We used synthetic peloruside A for the commercial preparation of [3H]peloruside A. The radiolabeled compound bound to preformed tubulin polymer in amounts stoichiometric with the polymer's tubulin content, with an apparent K(d) value of 0.35 μM. A less active peloruside A analogue, (11-R)-peloruside A and laulimalide acted as competitive inhibitors of the binding of the [3H]peloruside A, with apparent K(i) values of 9.3 and 0.25 μM, respectively. Paclitaxel, epothilone B, and discodermolide had essentially no ability to inhibit [3H]peloruside A binding, confirming that these compounds bind to a different site on tubulin polymer. We modeled both laulimalide and peloruside A into the binding site on β-tubulin that was identified by Huzil et al. (J. Mol. Biol. 2008, 378, 1016-1030), but our model provides a more reasonable structural basis for the protein-ligand interaction. There is a more complete desolvation of the peloruside A ligand and a greater array of favorable hydrophobic and electrostatic interactions exhibited by peloruside A at its β-tubulin binding site. In addition, the protein architecture in our peloruside A binding model was suitable for binding laulimalide. With the generation of both laulimalide and peloruside A binding models, it was possible to delineate the structural basis for the greater activity of laulimalide relative to peloruside A and to rationalize the known structure-activity relationship data for both compounds.