Single half-wavelength ultrasonic particle filter: predictions of the transfer matrix multilayer resonator model and experimental filtration results

The quantitative performance of a "single half-wavelength" acoustic resonator operated at frequencies around 3 MHz as a continuous flow microparticle filter has been investigated. Standing wave acoustic radiation pressure on suspended particles (5-microm latex) drives them towards the center of the half-wavelength separation channel. Clarified suspending phase from the region closest to the filter wall is drawn away through a downstream outlet. The filtration efficiency of the device was established from continuous turbidity measurements at the filter outlet. The frequency dependence of the acoustic energy density in the aqueous particle suspension layer of the filter system was obtained by application of the transfer matrix model [H. Nowotny and E. Benes, J. Acoust. Soc. Am. 82, 513-521 (1987)]. Both the measured clearances and the calculated energy density distributions showed a maximum at the fundamental of the piezoceramic transducer and a second, significantly larger, maximum at another system's resonance not coinciding with any of the transducer or empty chamber resonances. The calculated frequency of this principal energy density maximum was in excellent agreement with the optimal clearance frequency for the four tested channel widths. The high-resolution measurements of filter performance provide, for the first time, direct verification of the matrix model predictions of the frequency dependence of acoustic energy density in the water layer.     

More Precise Pair Correlation of Zeros and Primes in Short Intervals

Goldston and Montgomery proved that the strong pair correlationconjecture and two second moments of primes in short intervalsare equivalent to each other under the Riemann hypothesis. Thepaper obtains the second main terms for each of the above, andit is shown that they are almost equivalent to each other.     

Thermofraktographie zur Schnellanalyse von Kunststoffen. 3. Mitteilung

When heating vinyl polymers within the temperature gradient of 50–450° C, they are fragmented in certain temperature ranges to defined products. These products are fractionated on the TLC-layer and subsequently chromatographed. Based on the thermofractograms obtained identification of the starting material can be made. From polyvinyl esters, e.g., the corresponding acid is obtained and copolymers yield the different acids. Thermolysis of polyvinyl carbazole yields vinyl carbazole and vinyl pyrrolidone and pyrrolidone are obtained from polyvinyl pyrrolidone. Polymethacrylate is fragmented to the corresponding methacrylate, and acrylate if obtained from polyacrylate. Evaluation of the thermofractograms leads in part to new conceptions about structures and cleavage mechanisms of such polymers.     

FTIR studies of O(3P) atom reactions with CSe2, SCSe, and OCSe

The overall rate coefficients of the reactions of CSe2, SCSe, and OCSe with O(3P) atom have been determined to be k(CSe2) = (1.4 +/- 0.2) x 10(-10) cm3 molecule(-1) s(-1), k(SCSe) = (2.8 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1), and k(OCSe) = (2.4 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1) at 301-303 K using Fourier transform infrared (FTIR) absorption spectroscopy. The measurements have been accomplished by calibrating against the literature value of the rate coefficient for O(3P) with CS2 (4 x 10(-12) cm3 molecule(-1) s(-1)). A product channel giving OCSe in 32.0 +/- 4.2% yield has been found for the O + CSe2 reaction. Although CO was also detected, its generation could be attributed to subsequent reactions of OCSe with O atoms. The corresponding reaction for O + SCSe gives OCS and OCSe as observable products, with their yields given as 32.2 +/- 4.5 and 30.2 +/- 3.3%, respectively. Computational studies using UB3LYP/aug-cc-PVTZ methods have been used particularly to determine the reaction pathways for the channels in which OCS or OCSe is produced.     

Structural determinants of CDK4 inhibition and design of selective ATP competitive inhibitors

A number of selective inhibitors of the CDK4/cyclin D1 complex have been reported recently. Due to the absence of an experimental CDK4 structure, the ligand and protein determinants contributing to CDK4 selectivity are poorly understood at present. Here, we report the use of computational methods to elucidate the characteristics of selectivity and to derive the structural basis for specific, high-affinity binding of inhibitors to the CDK4 active site. From these data, the hypothesis emerged that appropriate incorporation of an ionizable function into a CDK2 inhibitor results in more favorable binding to CDK4. This knowledge was applied to the design of compounds in the otherwise CDK2-selective 2-anilino-4-(thiazol-5-yl)pyrimidine pharmacophore that are potent and highly selective ATP antagonists of CDK4/cyclin D1. The findings of this study also have significant implications in the design of CDK4 mimic structures based on CDK2.     

Development of a single‐cell X‐ray fluorescence flow cytometer

An X‐ray fluorescence flow cytometer that can determine the total metal content of single cells has been developed. Capillary action or pressure was used to load cells into hydrophilic or hydrophobic capillaries, respectively. Once loaded, the cells were transported at a fixed vertical velocity past a focused X‐ray beam. X‐ray fluorescence was then used to determine the mass of metal in each cell. By making single‐cell measurements, the population heterogeneity for metals in the µM to mM concentration range on fL sample volumes can be directly measured, a measurement that is difficult using most analytical methods. This approach has been used to determine the metal composition of 936 individual bovine red blood cells (bRBC), 31 individual 3T3 mouse fibroblasts (NIH3T3) and 18 Saccharomyces cerevisiae (yeast) cells with an average measurement frequency of ～4 cells min^?1. These data show evidence for surprisingly broad metal distributions. Details of the device design, data analysis and opportunities for further sensitivity improvement are described.     

A Macrocyclic Ruthenium(III) Complex Inhibits Angiogenesis with Down‐Regulation of Vascular Endothelial Growth Factor Receptor‐2 and Suppresses Tumor Growth In Vivo

A macrocyclic ruthenium(III) complex [Ru^III(N₂O₂)Cl₂]Cl ( Ru‐1 ) is reported as an inhibitor of angiogenesis and an anti‐tumor compound. The complex is relatively non‐cytotoxic towards endothelial and cancer cell lines in vitro, but specifically inhibited the processes of angiogenic endothelial cell tube formation and cancer cell invasion. Moreover, compared with known anti‐cancer ruthenium complexes, Ru‐1 is distinct in that it suppressed the expression of vascular endothelial growth factor receptor‐2 (VEGFR2), and the associated downstream signaling that is crucial to tumor angiogenesis. In addition, in vivo studies showed that Ru‐1 inhibited angiogenesis in a zebrafish model and suppressed tumor growth in nude mice bearing cancer xenografts.     

Approximating reals by sums of two rationals

We generalize Dirichlet's diophantine approximation theorem to approximating any real number α by a sum of two rational numbers with denominators 1?q₁,q₂?N. This turns out to be related to the congruence equation problem with 1?x,y?q1/2+?.