Substituent Effects in the Carbon NMR of Aliphatic bis(Amidinohydrazones) ['Bis(Guanylhydrazones)']. Construction of a set of Quantitative Empirical Rules. Unambiguous Assignment of Several Previously Unassigned Carbon Resonances

The effects of substituents on the ¹³C chemical shifts of the various carbons of aliphatic 1,2-bis(amidinohydrazones) have been systematically studied using previously published experimental data as the basis. Mathematical formulae have been constructed that describe the effects of various structural features of the molecules on the chemical shifts of the carbons and that also make possible an accurate prediction of the spectra of compounds belonging to this class. It is also shown that the effects of side chains on the chemical shifts of the two carbons of the glyoxal moiety are strictly additive. A mathematical model has been constructed that makes possible a very accurate prediction of the chemical shift of each one of the glyoxal carbons of symmetrical as well as unsymmetrical bis(amidinohydrazones). In the case of ethylmethylglyoxal bis(amidinohydrazone) free base dissolved in dimethyl sulfoxide, the theory predicts that the glyoxal carbons resonate at 157.45 ppm (the one connected to the ethyl group) and 151.21 ppm, while the experimental values are 157.30 and 151.29 ppm. This has, for the first time, made possible the unambiguous individual assignment of the resonances of the glyoxal carbons of unsymmetrical dialkylglyoxal bis(amidinohydrazones). The results also indicate that in all such compounds so far studied, that one of the glyoxal carbons that bears the longer alkyl side chain resonates more downfield than does the other one. This result is in total agreement with conclusions derived from relaxation time measurements.     

One-step method for measuring the effect of humidity on powder resistivity

We present a method for measuring powder resistivity as a function of moisture using a one-step process. The developed new resistivity cell consists of narrow horizontal electrode surrounded by a grounded guard electrode and simultaneous measurement of humidity within the powder bed. The system was modeled using computer simulations. As an example, resistivities of three different lactoses, wheat flour and quartz are presented. Resistivity was found to decrease several orders of magnitude between 10 RH% and 90 RH%. Simulated results showed that if no guard plate is used, measurement errors caused by humidity gradient are of order of magnitude.     

Dual-capillary electroencapsulation of mesoporous silicon drug carrier particles for controlled oral drug delivery

The feasibility of electroencapsulation of mesoporous silicon (PSi) micro- and nanoparticles as a method to seal the PSi particles in mechanically processable solid units, and to facilitate time and site specific drug release from the pores of PSi particles, is of interest in the present work. Suitable microcapsules and micromatrix particles were produced in a single-step process using a setup with two electrospraying nozzles kept at high electric potentials of opposite polarities. The structures of the produced particles were analyzed by microscope and X-ray micro- and nanotomography imaging, and optimization of the electroencapsulation process production efficiency is discussed.     

A characterization of a limit solution for finite horizon bargaining problems

We investigate a two-person random proposer bargaining game with a deadline. A bounded time interval is divided into bargaining periods of equal length and we study the limit of the subgame perfect equilibrium outcomes as the number of bargaining periods goes to infinity while the deadline is kept fixed. This limit is close to the discrete Raiffa solution when the time horizon is very short. If the deadline goes to infinity the limit outcome converges to the time preference Nash solution. Regarding this limit as a bargaining solution under deadline, we provide an axiomatic characterization.     

Signed-rank tests for location in the symmetric independent component model

The so-called independent component (IC) model states that the observed p-vector X is generated via X=ΛZ+μ, where μ is a p-vector, Λ is a full-rank matrix, and the centered random vector Z has independent marginals. We consider the problem of testing the null hypothesis H₀:μ=0 on the basis of i.i.d. observations X₁,…,X_n generated by the symmetric version of the IC model above (for which all ICs have a symmetric distribution about the origin). In the spirit of [M. Hallin, D. Paindaveine, Optimal tests for multivariate location based on interdirections and pseudo-Mahalanobis ranks, Annals of Statistics, 30 (2002), 1103-1133], we develop nonparametric (signed-rank) tests, which are valid without any moment assumption and are, for adequately chosen scores, locally and asymptotically optimal (in the Le Cam sense) at given densities. Our tests are measurable with respect to the marginal signed ranks computed in the collection of null residuals , where is a suitable estimate of Λ. Provided that is affine-equivariant, the proposed tests, unlike the standard marginal signed-rank tests developed in [M.L. Puri, P.K. Sen, Nonparametric Methods in Multivariate Analysis, Wiley & Sons, New York, 1971] or any of their obvious generalizations, are affine-invariant. Local powers and asymptotic relative efficiencies (AREs) with respect to Hotelling’s T² test are derived. Quite remarkably, when Gaussian scores are used, these AREs are always greater than or equal to one, with equality in the multinormal model only. Finite-sample efficiencies and robustness properties are investigated through a Monte Carlo study.     

Expression of iron-related genes in human brain and brain tumors

Background  

Defective iron homeostasis may be involved in the development of some diseases within the central nervous system. Although the expression of genes involved in normal iron balance has been intensively studied in other tissues, little is known about their expression in the brain. We investigated the mRNA levels of hepcidin (HAMP), HFE, neogenin (NEO1), transferrin receptor 1 (TFRC), transferrin receptor 2 (TFR2), and hemojuvelin (HFE2) in normal human brain, brain tumors, and astrocytoma cell lines. The specimens included 5 normal brain tissue samples, 4 meningiomas, one medulloblastoma, 3 oligodendrocytic gliomas, 2 oligoastrocytic gliomas, 8 astrocytic gliomas, and 3 astrocytoma cell lines.     

Anomalous birefringence of light in free-standing samples of porous silicon

The birefringence of light in freely suspended samples of porous silicon is observed and investigated. The effect is interpreted as “shape birefringence,” i.e., the effect caused by the structure of a material consisting of anisotropic formations with sizes less than the wavelength of the light and with a predominant orientation. It is checked experimentally that the samples do not possess optical activity or optical anisotropy in the plane of the porous-silicon film. It is determined that the effect is observed for polarization of incident light that rules out the possibility of observing birefringence in a uniform optical medium, and it is not observed in the conventional experimental geometry. Qualitative explanations are given for the anomalous character of the observed defect.     

On- and off-resonance spin-lock MR imaging of normal human brain at 0.1 T: possibilities to modify image contrast

The aim of the present investigation was to determine spin lock (SL) relaxation parameters for the normal brain tissues and thus, to provide basis for optimizing the imaging contrast at 0.1 T. 68 healthy volunteers were included. On-resonance spin lock relaxation time (T_1ρ) and off-resonance spin lock relaxation parameters (T_1ρ^off, M_e/M_o), MT parameters (T_1sat, M_s/M_o), and T₁, T₂ were determined for the cortical gray matter, and for the frontal and parietal white matters. The T_1ρ for the frontal and parietal white matters ranged from 110 to 133 ms and from 122 to 155 ms with locking field strengths from 50 μT to 250 μT, respectively. Accordingly, the values for the gray matter ranged from 127 to 155 ms. With a locking field strength of 50 μT, T_1ρ^off for the frontal and parietal white matters were from 114 to 217 ms and from 126 to 219 ms, and for the gray matter from 136 to 267 ms with the angle between the effective magnetic field (B_eff) and the z-axis (θ) ranging from 60° to 15°, respectively. The T_1ρ of the white and gray matters increased significantly with increasing locking field amplitude (p < 0.001). The T_1ρ^off decreased significantly with increasing θ (p < 0.001). T_1ρ and T_1ρ^off with θ ≥ 30° were statistically significantly shorter in the frontal than in the parietal white matters (p < 0.05). The duration, amplitude and θ of the locking pulse provide additional parameters to optimize contrast in brain SL imaging.