Preparative isolation of (+)-beta-eudesmol fromAmyris balsamifera

Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum distillation of the total oil. Step two was a medium pressure LC separation with an AgNO₃ impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related sesquiterpene alcohols (75% of the oil).     

Metal-catalyzed anaerobic disproportionation of hydroxylamine. Role of diazene and nitroxyl intermediates in the formation of N2, N2O, NO+, and NH3

The catalytic disproportionation of NH(2)OH has been studied in anaerobic aqueous solution, pH 6-9.3, at 25.0 degrees C, with Na(3)[Fe(CN)(5)NH(3)].3H(2)O as a precursor of the catalyst, [Fe(II)(CN)(5)H(2)O](3)(-). The oxidation products are N(2), N(2)O, and NO(+) (bound in the nitroprusside ion, NP), and NH(3) is the reduction product. The yields of N(2)/N(2)O increase with pH and with the concentration of NH(2)OH. Fast regime conditions involve a chain process initiated by the NH(2) radical, generated upon coordination of NH(2)OH to [Fe(II)(CN)(5)H(2)O](3)(-). NH(3) and nitroxyl, HNO, are formed in this fast process, and HNO leads to the production of N(2), N(2)O, and NP. An intermediate absorbing at 440 nm is always observed, whose formation and decay depend on the medium conditions. It was identified by UV-vis, RR, and (15)NMR spectroscopies as the diazene-bound [Fe(II)(CN)(5)N(2)H(2)](3)(-) ion and is formed in a competitive process with the radical path, still under the fast regime. At high pH's or NH(2)OH concentrations, an inhibited regime is reached, with slow production of only N(2) and NH(3). The stable red diazene-bridged [(NC)(5)FeHN=NHFe(CN)(5)](6)(-) ion is formed at an advanced degree of NH(2)OH consumption.     

Critical Analysis of Hypothesis Tests in Federal Information Processing Standard (140-2)

This work presents an analysis of the existing dependencies between the tests of the FIPS 140-2 battery. Two main analytical approaches are utilized, the first being a study of correlations through the Pearson’s correlation coefficient that detects linear dependencies, and the second one being a novel application of the mutual information measure that allows detecting possible non-linear relationships. In order to carry out this study, the FIPS 140-2 battery is reimplemented to allow the user to obtain p-values and statistics that are essential for more rigorous end-user analysis of random number generators (RNG).     

A compactness theorem for scalar-flat metrics on manifolds with boundary

Let (M ⁿ , g) be a compact Riemannian manifold with boundary ?M. This paper is concerned with the set of scalar-flat metrics which are in the conformal class of g and have ?M as a constant mean curvature hypersurface. We prove that this set is compact for dimensions n ?? 7 under the generic condition that the trace-free 2nd fundamental form of ?M is nonzero everywhere.     

Number of infections suffered by a focal individual in a two‐strain SIS model with partial cross‐immunity

We study a stochastic model for the spread of two pathogen strains—termed type 1 and type 2—among a homogeneously mixing community consisting of a finite number of individuals. In the model, we assume partial cross‐immunity, exogenous streams of infection, and that the degree of severity of a newly infective individual depends on who this infective individual was infected by. The aim is to characterize the joint probability distribution of the numbers M₁ and M₂ of type‐1 and type‐2 infections suffered by a focal individual during an outbreak of the disease. We present iterative procedures for computing the probability mass function of (M₁,M₂) under the assumption that the initial state of the focal individual is known, and a numerical study of the model is performed to investigate the influence of certain key parameters on the spread of resistant bacteria in hospitals.     

Comparisons of zinc with cadmium in N2S2 coordination and as S-bonded adducts to tungsten carbonyls

The synthesis and characterization of bis-mercaptoethanediazaheptane cadmium(II) is reported and compared to the analogous zinc complex. Of significance is the dimeric form of the [Zn(N(2)S(2))](2) complex achieves penta-coordination about zinc through a bridging thiolate whereas cadmium engages two thiolate as S-bridges resulting in hexa-coordination about cadmium within a coordination polymer whose X-ray crystal structure is reported here. In the presence of W(CO)(5), this polymer breaks up, generating dimeric [Cd(N(2)S(2))](2) with two W(CO)(5) units appended to the terminal thiolates, a feat that is not observed for the zinc dimer analogue. The greater thiophilicity of cadmium over zinc is noted in several features of these complexes.     

Characterization of structured acrylamide/acrylic acid hydrogels by TMDSC and microscopy

The thermal behavior of hydrogels synthesized by solution polymerization between acrylamide, acrylic acid and diglycidyl acrylate (DGA) as a crosslinking agent was investigated. The structure of the hydrogel can be tightly controlled with the reaction temperature. This method produces a new type of hydrogels, which exhibit well defined structures at various scales of length simultaneously. These multi-structured hydrogels are hydrophilic, elastic, water insoluble, and soft polymers with an anisotropic optical response. The structure was observed by scanning electron microscopy (SEM), polarized light microscopy (PLM) and macroscopic visualization (CCD camera). In addition, structural transitions in the hydrogels were monitored by temperature modulated differential scanning calorimetry (TMDSC). Severe heating tests in an adiabatic oven were performed to analyze decomposition of the material. Fourier transform infrared (FTIR) spectroscopy was used to qualitatively analyze the hydrogels samples exposed to a sudden thermal treatment.