Near degeneracy and pseudo Jahn-Teller effects in mixed-valence ladders: the phase transition in NaV2_2O5_5

We analyze the electronic structure of a mixed-valence ladder system. We find that structural anisotropy and complex electron correlations lead to on-rung charge localization and insulating character. Charge fluctuations within the rung of the ladder interact strongly to the lattice degrees of freedom, which gives rise to large pseudo Jahn--Teller effects. The phase transition in NaV$_2$O$_5$ should be driven by this kind of mechanism.Comment: 5 pages, 2 figures, 1 table, submitted to PR

TLR2 expression is increased in rosacea and stimulates enhanced serine protease production by keratinocytes.

A diverse environment challenges skin to maintain temperature, hydration, and electrolyte balance while also maintaining normal immunological function. Rosacea is a common skin disease that manifests unique inflammatory responses to normal environmental stimuli. We hypothesized that abnormal function of innate immune pattern recognition could explain the enhanced sensitivity of patients with rosacea, and observed that the epidermis of patients with rosacea expressed higher amounts of Toll-like receptor 2 (TLR2) than normal patients. Increased expression of TLR2 was not seen in other inflammatory skin disorders such as atopic dermatitis or psoriasis. Overexpression of TLR2 on keratinocytes, treatment with TLR2 ligands, and analysis of TLR2-deficient mice resulted in a calcium-dependent release of kallikrein 5 from keratinocytes, a critical protease involved in the pathogenesis of rosacea. These observations show that abnormal TLR2 function may explain enhanced inflammatory responses to environmental stimuli and can act as a critical element in the pathogenesis of rosacea

College Students and Hookup Behavior

College environments have been expected to provide a time of experimentation. This study focuses on college students’ involvement in brief sexual encounters which are considered hookups and compares hookup behaviors of seniors and freshmen and males and females at different stages of their undergraduate education. This survey examines hookup behavior in relation to drug and alcohol use, contraception, self-esteem, regret, emotional reactions, and the Problem Behavior Inventory which is a screening device for depression, anxiety, and symptoms of common psychological distress. 105 students were surveyed, 60 were female and 45 were male. 54 participants were seniors and 51 were freshmen. Analyses revealed that few differences exist between freshmen and seniors and males and females in regards to hookup behavior

The 1996 U.S. Purse Seine Fishery for Tropical Tunas in the Central-Western Pacific Ocean

The U.S. tropical tuna purse seine fleet has fished the central-western Pacific Ocean under the South Pacific Tuna Treaty since 1988. The 1996 fishery was the poorest since the start ofthe Treaty. Fishing effort declined due to the financial collapse of a large fishing enterprise. Catches reached record lows for yellowfin tuna, Thunnus albacares, and skipjack tuna, Katsuwonus pelamis, and continued a declining trend that started in 1995. Catch rates also decreased to the lowest levels since 1991. Whether this declining trend in catch rates is due to reduced availability of fish caused by cyclic ocean environmental changes affecting vulnerability or to reduced abundance from excessive fishing pressure is not yet known and needs to be assessed

Electron correlations and bond-length fluctuations in copper oxides: from Zhang--Rice singlets to correlation bags

We perform first principles, multiconfiguration calculations on clusters including several CuO$_6$ octahedra and study the ground-state electron distribution and electron--lattice couplings when holes are added to the undoped $d^9 p^6$ configuration. We find that the so-called Zhang--Rice state on a single CuO$_4$ plaquette is nearly degenerate with a state whose leading configuration is of the form Cu $d^9$-- O $p^5$-- Cu $d^9$. A strong coupling between the electronic and nuclear motion gives rise to large inter-site charge transfer effects for half-breathing displacements of the oxygen ions. Under the assumption of charge segregation into alternating hole-free and hole-rich stripes of Goodenough \cite{jbg_02,jbg_03}, our results seem to support the vibronic mechanism and the traveling charge-density wave model from Refs.\cite{jbg_02,jbg_03} for the superconductivity in copper oxides.Comment: submitted to Phys. Rev.

Rosacea as a Disease of Cathelicidins and Skin Innate Immunity

Rosacea is a common and chronic inflammatory skin disease most frequently seen in groups of genetically related individuals. Although the symptoms of rosacea are heterogeneous, they are all related by the presence of characteristic facial or ocular inflammation involving both the vascular and tissue stroma. Until recently, the pathophysiology of this disease was limited to descriptions of a wide variety of factors that exacerbate or improve disease. Recent molecular studies show a common link between the triggers of rosacea and the cellular response, and these observations suggest that an altered innate immune response is involved in disease pathogenesis. Understanding rosacea as a disorder of innate immunity explains the benefits of current treatments and suggests new therapeutic strategies for alleviating this disease

Half-Metallic Ferromagnetism and the spin polarization in CrO2_2

We present electronic structure calculations in combination with local and non-local many-body correlation effects for the half-metallic ferromagnet CrO$_2$. Finite-temperature Dynamical Mean Field Theory results show the existence of non-quasiparticle states, which were recently observed as almost currentless minority spin states near the Fermi energy in resonant scattering experients. At zero temperatures, Variational Cluster Approach calculations support the half-metallic nature of CrO$_2$ as seen in superconducting point contact spectroscopy. The combination of these two techniques allowed us to qualitatively describe the spin-polarization in CrO$_2$.Comment: 5 pages, 3 figure

The electronic structure and the phases of BaVS3

BaVS3 is a moderately correlated d-electron system with a rich phase diagram. To construct the corresponding minimal electronic model, one has to decide which d-states are occupied, and to which extent. The ARPES experiment presented here shows that the behavior of BaVS3 is governed by the coexistence of wide-band (A_1g) and narrow-band (twofold degenerate E) d-electrons. We sketch a lattice fermion model which may serve as a minimal model of BaVS3. This serves foremost for the understanding of the metal-insulator in pure BaVS3 and its absence in some related compounds. The nature of the low temperature magnetic order differs for several systems which may be described in terms of the same electron model. We describe several recent experiments which give information about magnetic order at high pressures. In particular, we discuss field-induced insulator-to-metal transition at slightly subcritical pressures, and an evidence for magnetic order in the high-pressure metallic phase. The phase diagram of Sr-doped BaVS3 is also discussed. The complexity of the phases of BaVS3 arises from the fact that it is simultaneously unstable against several kinds of instabilities.Comment: Presented at the International Conference on Magnetism 2006 (Kyoto), 6 pages, 9 figure

Ka-band Ga-As FET noise receiver/device development

The development of technology for a 30 GHz low noise receiver utilizing GaAs FET devices exclusively is discussed. This program required single and dual-gate FET devices, low noise FET amplifiers, dual-gate FET mixers, and FET oscillators operating at Ka-band frequencies. A 0.25 micrometer gate FET device, developed with a minimum noise figure of 3.3 dB at 29 GHz and an associated gain of 7.4 dB, was used to fabricate a 3-stage amplifier with a minimum noise figure and associated gain of 4.4 dB and 17 dB, respectively. The 1-dB gain bandwidth of this amplifier extended from below 26.5 GHz to 30.5 GHz. A dual-gate mixer with a 2 dB conversion loss and a minimum noise figure of 10 dB at 29 GHz as well as a dielectric resonator stabilized FET oscillator at 25 GHz for the receiver L0. From these components, a hybrid microwave integrated circuit receiver was constructed which demonstrates a minimum single-side band noise figure of 4.6 dB at 29 GHz with a conversion gain of 17 dB. The output power at the 1-dB gain compression point was -5 dBm