Thermodynamic,thermogravimetric and permittivity studies of hausmannite (Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>) in air

Some manganese oxides are considered hyperactive under microwave irradiation because of their extremely high heating rates in air. In order to further understand this hyperactivity, thermodynamic calculations, thermogravimetric analysis and both real and imaginary permittivity determinations were performed for hausmannite (Mn₃O₄) as a function of temperature in an air atmosphere. The thermodynamic results demonstrated reasonable agreement with the thermogravimetric analysis data. A comparison of the derivative thermogravimetric analysis data with the derivative of both the real and the imaginary permittivities confirmed that the extremely high values of the permittivities were due to the conversion of the hausmannite to bixbyite (Mn₂O₃). The microwave hyperactivity of the manganese oxides in air is explained in terms of the high permittivities of bixbyite.     

Electroanalytical applications of boron-doped diamond microelectrode arrays

The electrochemical characteristics of a novel all diamond fabricated boron-doped diamond microelectrode array (BDD-MEA) are critically appraised. The voltammetric response of simple electron transfer processes has been investigated and found to generate sigmoidal voltammetric curves. Furthermore, the device has been utilized for various analytical applications including, the direct detection of 4-nitrophenol over the concentration range 1.8-9.2 μM, manganese over the range 0.1-4.8 μM and the indirect determination of sulfide producing a limit of detection of 23 μM.     

Diffusion changes precede size reduction in neoadjuvant treatment of breast cancer

Traditionally, tumor response has been assessed via tumor size measurements during the course of a treatment. However, changes in these morphologically based measures occur relatively late in the course of a treatment. Alternative biomarkers are currently being evaluated to enable an earlier assessment of treatment to facilitate early cessation and cost savings. Diffusion-weighted imaging (DWI) has been identified by preclinical studies to be a likely alternative to tumor size measurements. In this study, 10 patients were examined prior to and after the first and second chemotherapy cycle time points. Longest diameter tumor measurements and apparent diffusion coefficients (ADCs) were recorded at each exam. An increase in the mean (normalized) ADC was noted as early as the first cycle time point. However, a reduction in the mean (normalized) longest diameter was only noted at the second cycle time point. Significant alterations from the baseline value were noted for ADC at the first (P=.005) and second cycle time points (P=.004). Longest diameter measurements only achieved a borderline significance at the second time point (P=.057). These results indicate that DWI may provide a suitable biomarker capable of providing an indication of response to treatment prior to tumor size measurements.     

Dynamics and properties of chiral cosmic strings

Chiral cosmic strings naturally arise in many particle physics models, in particular in supersymmetric theories with a D-term. These strings have a single fermion zero mode in the core. We derive the general equation of motion for such strings. In Minkowski space we give the self-intersections for an arbitrary varying current on the loop, showing that the self-intersection probability is dominated by the fraction of loop with maximal charge. We show how to relate the charge to the fermion condensation temperature, arguing that strings which become current carrying at formation will automatically have a maximal charge. Any daughter loops produced are likely to have the same charge as the parent loop. Possible models for chiral cosmic strings are also discussed and consequences for D-term inflation mentioned.     

Simple Zeros of the Riemann Zeta-Function

Assuming the Riemann Hypothesis, Montgomery showed by meansof his pair correlation method that at least two-thirds of thezeros of Riemann's zeta-function are simple. Later he and Taylorimproved this to 67.25 percent and, more recently, Cheer andGoldston increased the percentage to 67.2753. Here we proveby a new method that if the Riemann and Generalized LindelöofHypotheses hold, then at least 70.3704 percent of the zerosare simple and at least 84.5679 percent are distinct. Our methoduses mean value estimates for various functions defined by Dirichletseries sampled at the zeros of the Riemann zeta-function. 1991Mathematics Subject Classification: 11M26.     

Quantum Zeno and anti-Zeno paradoxes

Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox). We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure change of state: an anti-Zeno paradox.     

粉粒体两相流的电容层析成象测量

粉粒体系统中的固相浓度分布的在线测量是十分困难的问题．电容层析成象技术是一种近年来发展起来的非侵入式快速浓度场测量技术．它不干扰流场，不受流动中颗粒浓度、加速度、不透明等因素的制约．本文讨论其测量原理、应用、近期进展、存在的主要问题及其解决的对策．