Helix unwinding process in the chiral smectic C phase of MHPOBC as observed by conoscopy

Conoscopic studies have been made on the helix unwinding process in the chiral smectic C phase of MHPOBC. The unwinding process is rather unique in the sense that abrupt changes of the biaxiality and apparent tilt angle are followed by further gradual changes before the complete helix unwinding. The process is qualitatively explained by simulating the conoscopic images using the 4 x 4 matrix method with consideration of model molecular distributions, by taking account of both the ferroelectric and dielectric coupling between molecules and a field. The transmittance loss due to selective reflection was also measured under the application of a stepwise d.c. field. The shift of the dip position due to the loss, toward a longer wavelength region, was observed at low field. In contrast, the emergence of a transmittance loss at the same wavelength as that of an unperturbed state was observed. This phenomenon is explained by the ferroelectric deformation of a helix with the pitch unchanged.     

Light diffraction studies on director arrangement in the polymer‐pinned striped pattern obtained via the electric field‐induced Fréedericksz transition of nematics

We have observed an anomalous pattern forming phenomenon in which a striped pattern in a nematic liquid crystal appeared after removing an electric field following a Fréedericksz transition, and this pattern was preserved even in the equilibrium state in zero‐electric field. The nematic director arrangement in the striped pattern was investigated by light diffraction measurements. The stripes are proposed to consist of a periodic distortion of the nematic directors, specifically, tilted directors with the same absolute value of tilt angle but of opposite sign are alternately arrayed. The proposed model of the stripes is in good accord with the experimental results of light diffraction dependence on polarizing direction and light incidence angle.     

Functional Monomers and Polymers. 165. Dehydrochlorination of Head‐to‐Tail 1,4‐rans‐Poly‐(‐1‐Chlorobutadiene) Prepared by Inclusion Polymerization in Deoxycholic Acid Canals

Thermal and chemical dehydrochlorination of head‐to‐tail 1,4‐trans‐poly(‐1‐chlorobutadiene) prepared by inclusion polymerization in deoxycholic acid canals resulted in formation of a trans‐polyacetylene‐type polymer. The dehydrochiorinated polymer was characterized by UV/VIS, IR, Raman, and ESR spectroscopy. The number of conjugated double bonds in the polymer was about 10–20. Doping with iodine was also studied.     

An improved HarshawTLD™ extremity dosimeter – DXTRAD beta ring

An improved HarshawTLD? extremity dosimeter system that is rugged in design and easy to wear is presented. This dosimeter is improved from the earlier version (2008) for personnel beta monitoring while still having full range photon performance. The dosimeter style, referred to as DXTRAD, is small in size and has identification by means of a circular barcode. It consists of a detector composed of a thin 7 mg cm^?2 monolayer of HarshawTLD-700H (⁷LiF:Mg,Cu,P) powder and a ring cap with a 3.3 mg cm^?2 entrance window. The use of the TLD-700H TLD material provides a good beta energy response as well as a flat energy response from low energy x-rays to high energy gamma rays. A new assembly tool that improves the consistency of dosimeter geometry and ruggedness for warm and cold sterilization is also developed. With the optimized design, this dosimeter is capable of meeting the stringent energy and angular response requirements of the Physikalisch Technische Bundesanstalt (PTB) for both betas and photons. Presented in this paper are the ISO-12974 and PTB type tests as well as additional operational tests, such as residue, reuse, warm and cold sterilization, and environmental leakage.     

Cannabinoid exposure during zebra finch sensorimotor vocal learning persistently alters expression of endocannabinoid signaling elements and acute agonist responsiveness

Background  

Previously we have found that cannabinoid treatment of zebra finches during sensorimotor stages of vocal development alters song patterns produced in adulthood. Such persistently altered behavior must be attributable to changes in physiological substrates responsible for song. We are currently working to identify the nature of such physiological changes, and to understand how they contribute to altered vocal learning. One possibility is that developmental agonist exposure results in altered expression of elements of endocannabinoid signaling systems. To test this hypothesis we have studied effects of the potent cannabinoid receptor agonist WIN55212-2 (WIN) on endocannabinoid levels and densities of CB₁ immunostaining in zebra finch brain.     

Optical detector topology for third-generation gravitational wave observatories

The third generation of gravitational wave observatories, with the aim of providing 100 times better sensitivity than currently operating interferometers, is expected to establish the evolving field of gravitational wave astronomy. A key element, required to achieve this ambitious sensitivity goal, is the exploration of new interferometer geometries, topologies and configurations. In this article we review the current status of the ongoing design work for third-generation gravitational wave observatories. The main focus is the evaluation of the detector geometry and detector topology. In addition we discuss some promising detector configurations and potential noise reduction schemes.     

Rapid collapse of spin waves in nonuniform phases of the second Landau level

The spin degree of freedom in quantum phases of the second Landau level is probed by resonant light scattering. The long wavelength spin wave, which monitors the degree of spin polarization, is at the Zeeman energy in the fully spin-polarized state at ν = 3. At lower filling factors, the intensity of the Zeeman mode collapses, indicating loss of polarization. A novel continuum of low-lying excitations emerges that dominates near ν = 8/3 and ν = 5/2. Resonant Rayleigh scattering reveals that quantum fluids for ν < 3 break up into robust domain structures. While the state at ν = 5/2 is considered to be fully polarized, these results reveal unprecedented roles for spin degrees of freedom.     

Magnetite 3D colloidal crystals formed in the early solar system 4.6 billion years ago

Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago. We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.     

Structure and hardness of a-C:H films prepared by middle frequency plasma chemical vapor deposition

a-C:H films were prepared by middle frequency plasma chemical vapor deposition (MF-PCVD) on silicon substrates from two hydrocarbon source gases, CH₄ and a mixture of C₂H₂ + H₂, at varying bias voltage amplitudes. Raman spectroscopy shows that the structure of the a-C:H films deposited from these two precursors is different. For the films deposited from CH₄, the G peak position around 1520 cm⁻¹ and the small intensity ratio of D peak to G peak (I(D)/I(G)) indicate that the C-C sp³ fraction in this film is about 20 at.%. These films are diamond-like a-C:H films. For the films deposited from C₂H₂ + H₂, the Raman results indicate that their structure is close to graphite-like amorphous carbon. The hardness and elastic modulus of the films deposited from CH₄ increase with increasing bias voltage, while a decrease of hardness and elastic modulus of the films deposited from a mixture of C₂H₂ + H₂ with increasing bias voltage is observed.     

Iridium(III) Catalysts with an Amide‐Pendant Cyclopentadienyl Ligand: Double Aromatic Homologation Reactions of Benzamides by Fourfold C−H Activation

The synthesis, characterization, and catalytic performance of iridium(III) catalysts that bear an amide‐pendant cyclopentadienyl ligand ([Cp^AIrI₂]₂) is reported. These [Cp^AIrI₂]₂ catalysts were obtained from the complexation of a Cp^A ligand precursor with [Ir(cod)OAc]₂ followed by oxidation. Double aromatic homologation reactions of benzamides with alkynes by fourfold C?H activation proceeded in good to high yield with these [Cp^AIrI₂]₂ catalysts, demonstrating their superior catalytic performance in this challenging transformation.