Notes: A reciprocating cantilever utilizing emitted charges from a millicurie radioisotope thin film is presented. The actuator realizes a direct collected-charge-to-motion conversion. The reciprocation is obtained by self-timed contact between the cantilever and the radioisotope source. A static model balancing the electrostatic and mechanical forces from an equivalent circuit leads to an analytical solution useful for device characterization. Measured reciprocating periods agree with predicted values from the analytical model. A scaling analysis shows that microscale arrays of such cantilevers provide an integrated sensor and actuator platform. © 2002 American Institute of Physics.

Notes: Silicon dioxide (SiO2)/silicon carbide (SiC) structures annealed in nitric oxide (NO) and argon gas ambiences were investigated using x-ray photoelectron spectroscopy (XPS). The XPS depth profile analysis shows a nitrogen pileup of 1.6 at. % close to the NO annealed SiO2/SiC interface. The results of Si 2p, C 1s, O 1s, and N 1s core-level spectra are presented in detail to demonstrate significant differences between NO and Ar annealed samples. A SiO2/SiC interface with complex intermediate oxide/carbon states is found in the case of the Ar annealed sample, while the NO annealed SiO2/SiC interface is free of these compounds. The Si 2p spectrum of the Ar annealed sample is much broader than that of the NO annealed sample and can be fitted with three peaks compared with the two peaks in the NO annealed sample, indicating a more complex interface in the Ar annealed sample. Also the O 1s spectrum of the NO annealed samples is narrow and symmetrical and can be fitted with only one peak whereas that of the Ar annealed sample is broad and asymmetrical and is fitted with two peaks. It is evident that the Ar annealed sample contains some structural defects at the interface, which have been removed from the interface by NO annealing as shown by O 1s spectra. The C 1s spectra at the interface reveal the subtle difference between NO and Ar annealed samples. An additional peak representing the interface oxide/carbon species is observed in the Ar annealed sample. At the interface, the N 1s spectrum is symmetrical and can be fitted with one peak, representing the strong Si(Triple Bond)N bond. However, the N 1s and C 1s XPS spectra acquired in the bulk of the dielectric showed not only the Si(Triple Bond)N bond but also a trace amount of the N–C bond. © 1999 American Institute of Physics.

Notes: The interpretation of Faraday rotation measure maps of active galactic nuclei (AGNs) within galaxy clusters has revealed ordered or coherent regions, Lmag∼50−100 kpc (∼3×1023 cm), that are populated with large, ∼30 μG magnetic fields. The magnetic energy of these coherent regions is Lmag3(B2/8π)∼1059−60 ergs, and the total magnetic energy over the whole cluster (∼1 Mpc across) is expected to be even larger. Understanding the origin and role of these magnetic fields is a major challenge to plasma astrophysics. A sequence of physical processes that are responsible for the production, redistribution, and dissipation of these magnetic fields is proposed. These fields are associated with single AGNs within the cluster and therefore with all galaxies during their AGN (active galactic nucleus or quasar) phase, simply because only the central supermassive black holes (∼108M(sun)) formed during the AGN phase have an accessible energy of formation, ∼1061 ergs, that can account for the magnetic field energy budget. An α–Ω dynamo process has been proposed that operates in an accretion disk around a black hole. The disk rotation naturally provides a large winding number, ∼1011 turns, sufficient to make both large gain and large flux. The helicity of the dynamo can be generated by the differential plume rotation derived from star-disk collisions. This helicity generation process has been demonstrated in the laboratory and the dynamo gain was simulated numerically. A liquid sodium analog of the dynamo is being built. Speculations are that the back reaction of the saturated dynamo will lead to the formation of a force-free magnetic helix, which will carry the energy and flux of the dynamo away from the accretion disk and redistribute the field within the clusters and galaxy walls. The magnetic reconnection of a small fraction of this energy logically is the source of the AGN (active galactic nucleus or quasar) luminosity, and the remainder of the field energy should then dominate the free energy of the present-day universe. The reconnection of this intergalactic field during a Hubble time is the only sufficient source of energy necessary to produce an extragalactic cosmic ray energy spectrum as observed in this galaxy, and at the same time allow this spectrum to escape to the galaxy voids faster than the GZK (blackbody radiation) loss. © 2001 American Institute of Physics.

Notes: Electron/electron instabilities arise in collisionless plasmas when the electron velocity distribution consists of two distinct components with a sufficiently large relative drift speed between them. If the less dense beam component is not too tenuous and sufficiently fast, the electron/electron beam instability is excited over a relatively broad range of frequencies. This instability is often studied in the electrostatic limit, which is appropriate at ωe/|Ωe|(very-much-greater-than)1, where ωe is the electron plasma frequency and Ωe is the electron cyclotron frequency, but is not necessarily valid at ωe/|Ωe|∼1. Here linear Vlasov dispersion theory has been used and fully electromagnetic particle-in-cell simulations have been run in a spatially homogeneous, magnetized plasma model at βe(very-much-less-than)1 and 0.5 ≤ωe/|Ωe|≤4.0. Theory and simulations (run to times of order 100ωe−1) of the electron/electron beam instability show the growth of appreciable magnetic fluctuations at ωe/|Ωe|〈2; these waves bear right-hand elliptical magnetic polarization. The simulations reproduce the well-known slowing and heating of the beam; at ωe/|Ωe|〈1 this heating is predominantly parallel to the background magnetic field, but as ωe/|Ωe| becomes greater than unity the perpendicular heating of the beam increases. The simulations also demonstrate that, for ωe/|Ωe|∼1, electromagnetic fluctuations impart to the more dense electron core component significant heating perpendicular to the background magnetic field. © 2000 American Institute of Physics.

Notes: Discontinuous Atrial Ablations. Introduction: Linear atrial ablations are thought to he necessary to accomplish successful catheter ablation of atrial fibrillation. In order to investigate the conduction characteristics of atrial myocardium in regions of linear lesion discontinuity gaps), we performed activation sequence mapping in gap regions during atrial pacing and atrial fibrillation. Methods and Results. In seven dogs, a linear epicardial ablation was created on the right atrial free wall with a discontinuous segment (gap) in the mid-portion of the lesion. A plaque electrode was used to measure conduction across the gap. Conduction was assessed during (1) atrial pacing from the edge of the plaque electrode during sinus rhythm, and (2) during atrial fibrillation. After each series of measurements, the lesion gap was decreased by creating additional radiofrequency ablations and repeat conduction maps were obtained. The process was repeated until conduction block was observed during atrial pacing. Gap lengths ranged from 0 to 25 mm. During atrial pacing, gaps as narrow as 2 mm demonstrated normal conduction and gaps as large as 5 mm demonstrated block during pacing. Although conduction block was never present across gaps greater than 5 mm, the ability to predict conduction block as a function of gap width was difficult for lesions ≤ 5 mm due to a significant degree of overlap between normal conduction and conduction block in this gap range. During atrial fibrillation, 1/175 (0.6%) mapped wavelets conducted across gaps that demonstrated block during pacing; whereas, 411/600 (68.5%; P 〈 0.0001) wavelets conducted across gaps that did not demonstrate block during pacing (P = NS compared to preablation measurements). Histologically normal atrial myocytes were observed within gaps exhibiting conduction block. Conclusions: Visible gaps 〉 5 mm rarely demonstrate conduction block during atrial pacing and atrial fibrillation; whereas, gaps ≤ 5 mm in length may demonstrate block. Lesion gaps that do not demonstrate conduction block during atrial pacing have no higher rate of functional conduction block during atrial fibrillation than fibrillating atria without ablation lesions.

Notes: Abstract: We have cloned a σ receptor from rat brain and established its functional identity using a heterologous expression system. The cloned cDNA (1,582 bp long) codes for a protein of 223 amino acids that possesses a single putative transmembrane domain. The amino acid sequence of the rat brain σ receptor is highly homologous to that of the σ receptor recently cloned from guinea pig liver and a human placental cell line but is not related to any other known mammalian receptors. When expressed in HeLa cells, the rat brain σ receptor cDNA leads to a two- to threefold increase in haloperidol binding, and this cDNA-induced binding is sensitive to inhibition by several σ receptor-specific ligands. Kinetic analysis using the heterologous expression system has revealed that the rat brain σ receptor interacts with haloperidol with an apparent dissociation constant (KD) of 3 nM. Functional expression of the cloned rat brain σ receptor in HeLa cells also leads to an increase in the binding of two other σ ligands, namely, (+)-pentazocine and (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine (PPP). Pharmacological characterization of the cloned rat brain σ receptor reveals that it exhibits severalfold higher affinity for clorgyline than for 1,3-di(2-tolyl)guanidine, it interacts with progesterone and testosterone, and its interaction with PPP is markedly enhanced by phenytoin. In addition, transfection of MCF-7 cells, which do not express type 1 σ receptor mRNA or activity, with the cloned rat brain cDNA leads to the appearance of haloperidol-sensitive binding of (+)-pentazocine, a selective type 1 σ receptor ligand. These data show that the cloned rat brain cDNA codes for a functional type 1 σ receptor. Northern blot analysis with poly(A)+ RNA isolated from various rat tissues has indicated that the σ receptor-specific transcript, 1.6 kb in size, is expressed abundantly in liver and moderately in intestine, kidney, brain, and lung.

Notes: Abstract: σ receptor is a protein that interacts with a variety of psychotomimetic drugs including cocaine and amphetamines and is believed to play an important role in the cellular functions of various tissues associated with the endocrine, immune, and nervous systems. Here we report on the structure and organization of the human gene coding for this receptor. The gene is ∼7 kbp long and contains four exons, interrupted by three introns. Exon 3 is the shortest (93 bp), and exon 4 is the longest (1,132 bp). Among the introns, intron 3 is the longest (∼1,250 bp). Exon 2 codes for the single transmembrane domain present in the receptor. 5′ rapid amplification of cDNA end reactions with mRNA from the JAR human trophoblast cell line have identified 56 bp upstream of the translation start codon as the initiation site for transcription. This transcription start site has been confirmed by RNase protection analysis. Structural analysis of the 5′ flanking region has revealed that the gene is TATA-less. This region, however, contains a CCAATC box in the reverse complement and several GC boxes that are recognition sites for SP1. There are also consensus sequences for the liver-specific transcription factor nuclear factor-1/L, for a variety of cytokine responsive factors, and for the xenobiotic responsive factor called the arylhydrocarbon receptor. Southern blot analysis of the genomic DNA from Chinese hamster-human and mouse-human hybrid cell lines and fluorescent in situ hybridization with human metaphase chromosome spreads have shown that the gene is located on human chromosome 9, band p13, a region known to be associated with different psychiatric disorders.