An automated ac-magnetic susceptibility apparatus

We report here both hardware and software for an ac susceptibility measurement system, namely the design and construction of the cryostat, coil system, sample rod assembly and also the automation of the sample rod movement, bridge control and nulling etc with the help of an inexpensive Z-80A microprocessor via a home-made IEEE-488 interface. The variable parameters are temperature, magnitude of the rms field and frequency. An entirely new dynamic bridge nulling algorithm with continuous sample movement, which eliminates to a large extent problems related to time-dependent drifts, has been developed. We also present some experimental data collected with this system.     

α,β-Unsaturated nitroso system—I : The generation and transformations of ω-nitroso camphene

MO calculations predict a pronounced 1,4-dipolar character for the α,β-unsaturated nitroso synthon, much above that for traditional systems like the α,β-unsaturated Nitro and α,β-unsaturated carbonyl. The work on ω-nitroso camphene-generated from interalia ω-Nitrocamphene 3 is in agreement with the expectations. Thus, the 3 → tricyclene aldehyde 4 change is rationalized on the basis of a σ shift and the 5 → 20 and 6 → 21 changes highlight the overwhelming influence of the α,β-unsaturated nitroso synthon over even the enol ether and enamine functions present in 5 and 6. Amongst other noteworthy features are the deep seated 3 → 8 rearrangement and the preparation and transformation of the extraordinarily stable and the first reported bridgehead nitrile oxide 14.     

Enhancement of surface magnetization in antiferromagnetic nanoparticles

We report enhancement of magnetization below the antiferromagnetic ordering temperature T_N in nanoparticles of two antiferromagnets, viz CoRh₂O₄ and Cr₂O₃. The enhancement of magnetization below T_N is systematic, being larger for sample with smaller particle size. Scaling analysis showed that such enhancement of magnetization in CoRh₂O₄ nanoparticles is due to the superparamagnetic type contribution of surface (shell) spins. The present work shows that similar analysis can also be applied in Cr₂O₃ nanoparticles.     

Biocompatible Small Molecules that Enhance Silica Solubilization Under Ambient Conditions: Chemical Profile of Such Complexes,Possible Mechanism for Enhancement,and Their Effect on the Growth and Protection from Pests in the Rice Plant (Oryza sativa L.)

Recent studies suggest that the depletion of silicon available to plants may be a major reason for the yield decline observed for rice cultivation. In the present article, a novel strategy is explored to identify small biocompatible molecules (carriers) that would enhance the solubility of sand (SiO ₂ . nH ₂ O) (here after named silica) in water under ambient conditions. All considerations, notably biocompatibility, make the 20 proteinous amino acids and their simplified analogs the first choice. Among the proteinous amino acids, notable enhancement of silica solubility was seen at 1000 μ mole.L^?1 : Blank: 1; glutamine: 3.5; histidine: 3; alanine: 2.9. Based on the assumption that the observed enhancement is related to proclivity for hydrogen bond formation with water, a large number of varied biocompatible substrates were examined. Among these, notable enhancement of silica solubilization at 1000 μ mole.L^?1 was seen as exemplified with Blank: 1; imidazole: 5; inositol: 4.5; mannitol: 3.9; 3, 4-dihydroxy phenylalanine (DOPA): 3.5. A complementary gravimetric protocol coupled with thermogravimetric analysis (TGA) enabled the estimation of an approximate empirical formula for few of the carrier–silica complexes. A possible mechanism for the interaction of the carrier at the silica–water interface is suggested. Field experiments (reported separately) with selected carriers, monitored in the stem extract by colorimetry and in the leaf by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis showed enhanced levels of silica and were significantly beneficial for the growth and protection from predators of the rice plant.     

Synthesis of the Insect Sex Pheromone of Achroia Grisella via the Novel Synthon, 1-Tetrahydro-Pyranyloxy Dodec 11-Yne

We report the preparation of 1-tetrahydro-pyranyloxy dodec 11-yne(1), from castor oil, with an overall yield of 9.6%, and illustrate its use with the novel and practical synthesis of 1-oxo octadec (z) 11-ene(2), the insect sex pheromone of Achroia grisella, a species of wax moth, which are specific enemies of bees¹. Parenthetically, it has been found that 1 is a good precursor to the surprisingly large number of pheromones that have the structural unit, [sbnd]CH[dbnd]CH[sbnd](CH₂)₉CHXY².     

Asymmetrical hippocampal connectivity in mesial temporal lobe epilepsy: evidence from resting state fMRI

Background

Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform. The amplitude resolution was impoverished by reducing the number of bits to represent the signal samples. Auditory evoked magnetic fields (AEFs) were measured in the left and right hemisphere of sixteen healthy subjects.

Results

We found that the AEF amplitudes increased significantly with stimulus distortion for all stimulus types, which indicates that the right-hemispheric N1m sensitivity is not related exclusively to degradation of acoustic properties of speech. In addition, the P1m and P2m responses were amplified with increasing distortion similarly in both hemispheres. The AEF latencies were not systematically affected by the distortion.

Conclusions

We propose that the increased activity of AEFs reflects cortical processing of acoustic properties common to both speech and non-speech stimuli. More specifically, the enhancement is most likely caused by spectral changes brought about by the decrease of amplitude resolution, in particular the introduction of periodic, signal-dependent distortion to the original sound. Converging evidence suggests that the observed AEF amplification could reflect cortical sensitivity to periodic sounds.