Synthesis of N-Alkyl-N'-cyano-N″-4-pyridylguanidines from 4-Pyridyldithiocarbamic Acid via N-Alkyl-N′-4-Pyridylthioureas,or via 4-Pyridylcyaniminothiocarbamic Acid

Several years ago a number of antihypertensive N-alkyl-N′-cyano-N″-pyridylguanidines was prepared by addition of cyanamide to N-alkyl-N′-pyridylcarbodiimides which were obtained from the respective thioureas and phosgene or triphenylphosphine/carbon tetrachloride¹. Recently we have described some attractive synthetic methods for N-alkyl-N′-4-pyridylthioureas², based on 4-pyridyldithiocarbamic acid (1) (Scheme 1). We now report on the synthesis of N-alkyl-N′-cyano-N″-4-pyridylguanidines (4) from (1) by two different routes which ultimately may pass through a common intermediate (3) (Scheme 1).     

Semipolar Sets and Intrinsic Hausdorff Measure

Potential Analysis - Given a “Green function” G on a locally compact space X with countable base, a Borel set A in X is called G-semipolar, if there is no measure ν ≠ 0...     

A spectral method for an elliptic equation with a nonlinear Neumann boundary condition

Numerical Algorithms - Let Ω be an open region in ?d, d ≥ 2, that is diffeomorphic to ??d. Consider solving ?Δu + γu = 0 on Ω with the Neumann...     

Two-phase flow in porous media: dynamical phase transition

We study numerically the behavior of two-phase flow in porous media via the parameters capillary number and viscosity ratio, under steady-state conditions and various levels of saturation. We construct a phase diagram, where the phases are defined according to whether one or both fluids move. We establish a semi-empirical theory for the location of the phase boundaries. The steady-state conditions are obtained by implementing biperiodic boundary conditions.     

Emerging methods and tools for environmental risk assessment, decision-making, and policy for nanomaterials: summary of NATO Advanced Research Workshop

Nanomaterials and their associated technologies hold promising opportunities for the development of new materials and applications in a wide variety of disciplines, including medicine, environmental remediation, waste treatment, and energy conservation. However, current information regarding the environmental effects and health risks associated with nanomaterials is limited and sometimes contradictory. This article summarizes the conclusions of a 2008 NATO workshop designed to evaluate the wide-scale implications (e.g., benefits, risks, and costs) of the use of nanomaterials on human health and the environment. A unique feature of this workshop was its interdisciplinary nature and focus on the practical needs of policy decision makers. Workshop presentations and discussion panels were structured along four main themes: technology and benefits, human health risk, environmental risk, and policy implications. Four corresponding working groups (WGs) were formed to develop detailed summaries of the state-of-the-science in their respective areas and to discuss emerging gaps and research needs. The WGs identified gaps between the rapid advances in the types and applications of nanomaterials and the slower pace of human health and environmental risk science, along with strategies to reduce the uncertainties associated with calculating these risks.     

Size and aerial density distributions of Ge nanocrystals in a SiO2 layer produced by molecular beam epitaxy and rapid thermal processing

We discuss the distribution of size and aerial density of Ge nanocrystals in a metal-oxide-semiconductor (MOS) memory structure fabricated by molecular beam epitaxy combined with rapid thermal processing; the size and aerial density of Ge nanocrystals are controlled by varying the thickness of the deposited Ge layer and the processing time. Variation of tunnel oxide thickness is demonstrated with the extension of the processing time. The effect of processing time and tunnel oxide thickness on the electrical properties of the MOS structures is investigated by high frequency capacitance–voltage measurements. PACS  61.46.+w; 81.07.-b; 81.07.Bc; 81.07.Ta     

The lex property of varieties of lattice ordered groups

Presented by R. S. Pierce.     

A natural abundance 15N NMR investigation of bilirubin IX-α

Natural abundance ¹⁵N NMR spectra have been obtained for bilirubin IX-α using polarization transfer via the INEPT and SINEPT-2 techniques. The resonances for all four nitrogens are clearly resolved. ¹⁵N chemical shifts and ¹⁵N? ¹H coupling constants over one and three bonds are reported. Heteronuclear chemical shift correlation between ¹⁵N and ¹H for the four NH groups has been established by means of the SINEPT-2 pulse sequence.     

Phase locking of two long-pulse, high-power magnetrons

We have phase locked a pair of long-pulse, high-power, secondary-emission magnetrons to an RF-isolated low-power driver via a waveguide directional coupler. With the 3 dB hybrid coupler, the peak and average power sent back towards the driver were lower than the total power by factors of 20 and 100, respectively. A dual-channel, thyratron-switched line-type modulator was used to power the magnetrons in parallel. In this experiment the total microwave power from the pair of phase-locked high-power magnetrons was limited to 48 MW for 700 ns pulses and 46 MW for 900 ns pulses because one of the high-power magnetrons would only operate at or below half power. Experimental results from this repetitively-pulsed (10 Hz) phase-locked magnetron pair are presented which show excellent phase stability of several degrees both during the pulse and from pulse-to-pulse