Possible indicators for low dimensional superconductivity in the quasi-1D carbide Sc3CoC4

The transition metal carbide Sc3CoC4 consists of a quasi-one-dimensional (1D) structure with [CoC4]_{\inft} polyanionic chains embedded in a scandium matrix. At ambient temperatures Sc3CoC4 displays metallic behavior. At lower temperatures, however, charge density wave formation has been observed around 143K which is followed by a structural phase transition at 72K. Below T^onset_c = 4.5K the polycrystalline sample becomes superconductive. From Hc1(0) and Hc2(0) values we could estimate the London penetration depth ({\lambda}_L ~= 9750 Angstroem) and the Ginsburg-Landau (GL) coherence length ({\xi}_GL ~= 187 Angstroem). The resulting GL-parameter ({\kappa} ~= 52) classifies Sc3CoC4 as a type II superconductor. Here we compare the puzzling superconducting features of Sc3CoC4, such as the unusual temperature dependence i) of the specific heat anomaly and ii) of the upper critical field H_c2(T) at T_c, and iii) the magnetic hysteresis curve, with various related low dimensional superconductors: e.g., the quasi-1D superconductor (SN)_x or the 2D transition-metal dichalcogenides. Our results identify Sc3CoC4 as a new candidate for a quasi-1D superconductor.Comment: 4 pages, 5 figure

Lasers incorporating 2D photonic bandgap mirrors

Semiconductor lasers incorporating a 2D photonic lattice as a one end mirror in a Fabry-Perot cavity are demonstrated. The photonic lattice is a 2D hexagonal close-packed array with a lattice constant of 220 nm. Pulsed threshold currents of 110 mA were observed from a 180 μm laser

Two-dimensional photonic band-gap mirrors at 850 and 980 nm

Summary form only given. Photonic band-gap (PBG) crystals can be fabricated in semiconductor devices through the etching of patterns of holes in the device, resulting in a periodic dielectric structure. One of the more practical uses of photonic crystals in optoelectronic devices is for thin, high-reflectivity mirrors. The use of hexagonal arrays of etched circular holes results in a 2-D photonic band-gap mirror that can be tuned to a specific wavelength by varying the hole radius and the lattice spacing. 2-D mirror characterization is performed by evaluating the light emission from an active waveguide

Cavity ringdown laser absorption spectroscopy and time-of-flight mass spectroscopy of jet-cooled silver silicides

The cavity ringdown technique has been employed for the first spectroscopic characterization of the AgSi molecule, which is generated in a pulsed laser vaporization plasma reactor. A total of 20 rovibronic bands between 365 and 385 nm have been measured and analyzed to yield molecular properties for the X, B, and C 2Sigma states of AgSi. A time-of-flight mass spectrometer simultaneously monitors species produced in the molecular beam and has provided the first direct evidence for the existence of polyatomic silver silicides. Comparison of the AgSi data to our recent results for the CuSi diatom reveals very similar chemical bonding in the two coinage metal silicides, apparently dominated by covalent interactions

Appraisal Processes in Emotion

Usually, people\u27s emotions arise from their perceptions of their circumstances-immediate, imagined, or remembered. This idea has been implicit in many philosophical treatments of emotions (e.g., in Aristotle, Spinoza, and even Descartes and James; see Ellsworth 1994a; Gardiner, Clark-Metcalf, & Beebe-Centa, 1980; Scherer, 2000) and explicit in some (e.g., Hume and Hobbes), and it is the central emphasis of current appraisal theories of emotion. Thinking and feeling are inextricably interrelated most of the time: Certain ways of interpreting one\u27s environment are inherently emotional, few thoughts are entirely free of feelings, and emotions influence thinking. Reason and passion are not independent domains, or are rarely so. Of course there are exceptions: Brain stimulation, hormones, and drugs can produce emotions without external environmental circumstances, just as they can produce sensations, cognitions, and ideas without external environmental circumstances (Penfield, 1975). The fact that exceptions exist does not mean that there is no rule. The general rule suggested by appraisal theorists is that emotions consist of patterns of perception, or rather interpretation, and their correlates in the central and peripheral nervous systems (see Ellsworth, 1994c; Roseman & Smith, 2001; Scherer, 2001a, 2001b). A further assumption is that emotions are fundamentally adaptive, rather than maladaptive. In order to survive, an organism cannot simply understand its situation; it has to be motivated to do something about it. Many species have solved this problem with a mechanism that triggers fixed action patterns in response to appropriate stimuli. Emotions provide a more flexible alternative. They imply action tendencies (Frijda, 1986) without complete rigidity. _Lower organisms respond to stimulus patterns with behavior. Emotions, although they still motivate behavior, decouple . it from the perception of the stimulus so that reconsideration is possible (Scherer, 1984). Fear creates a tendency to flee, but a person may quickly realize that the threat is directed at someone else (reinterpretation of the event) or that an aggressive stance will intimidate the attacker (reinterpretation of response alternatives). Emotions allow flexibility both in event interpretation and in response choice. Emotions, from this point of view, represent an important evolutionary alternative. The phylogenetic expansion of the cerebral cortex enabled an increasing variety of interpretations, emotions, and behavioral options (see Hebb, 1949)

Classical Physics and Quantum Loops

The standard picture of the loop expansion associates a factor of h-bar with each loop, suggesting that the tree diagrams are to be associated with classical physics, while loop effects are quantum mechanical in nature. We discuss examples wherein classical effects arise from loop contributions and display the relationship between the classical terms and the long range effects of massless particles.Comment: 15 pages, 3 figure

Quantum electrodynamics for vector mesons

Quantum electrodynamics for $\rho$ mesons is considered. It is shown that, at tree level, the value of the gyromagnetic ratio of the $\rho^+$ is fixed to 2 in a self-consistent effective quantum field theory. Further, the mixing parameter of the photon and the neutral vector meson is equal to the ratio of electromagnetic and strong couplings, leading to the mass difference $M_{\rho^0}-M_{\rho^\pm}\sim 1 {\rm MeV}$ at tree order.Comment: 4 pages, 2 figures, REVTeX 4, accepted for publication in PR