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.     

Callback response of dugongs to conspecific chirp playbacks

Dugongs (Dugong dugon) produce bird-like calls such as chirps and trills. The vocal responses of dugongs to playbacks of several acoustic stimuli were investigated. Animals were exposed to four different playback stimuli: a recorded chirp from a wild dugong, a synthesized down-sweep sound, a synthesized constant-frequency sound, and silence. Wild dugongs vocalized more frequently after playback of broadcast chirps than that after constant-frequency sounds or silence. The down-sweep sound also elicited more vocal responses than did silence. No significant difference was found between the broadcast chirps and the down-sweep sound. The ratio of wild dugong chirps to all calls and the dominant frequencies of the wild dugong calls were significantly higher during playbacks of broadcast chirps, down-sweep sounds, and constant-frequency sounds than during those of silence. The source level and duration of dugong chirps increased significantly as signaling distance increased. No significant correlation was found between signaling distance and the source level of trills. These results show that dugongs vocalize to playbacks of frequency-modulated signals and suggest that the source level of dugong chirps may be manipulated to compensate for transmission loss between the source and receiver. This study provides the first behavioral observations revealing the function of dugong chirps.     

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.     

Hydrogen‐Bonding Catalysis of Alkyl‐Onium Salts

The synthetic utility of alkyl‐onium salt compounds is widely recognized in the field of organic chemistry. Among the wide variety of onium salts, quaternary ammonium, phosphonium, and tertiary sulfonium salts have been the most useful compounds in organic syntheses. These compounds have been very useful reagents in the construction of organic building blocks. In addition, onium salts are known as reliable catalysts, which are used to promote important organic transformations by serving as phase‐transfer and ion‐pair catalysts through the activation of nucleophiles. Although phase‐transfer catalysis is a major direction for onium salt catalysis, hydrogen‐bonding catalysis of alkyl‐onium salts, which is promoted via the activation of electrophiles, has recently become a relevant topic in the field of onium salt chemistry. This Minireview introduces new possibilities and future directions for alkyl‐onium salt chemistry based on its use in hydrogen‐bonding catalysis and on its overall utility.