5,446 research outputs found
Superconducting fluctuations in organic molecular metals enhanced by Mott criticality
Unconventional superconductivity typically occurs in materials in which a
small change of a parameter such as bandwidth or doping leads to
antiferromagnetic or Mott insulating phases. As such competing phases are
approached, the properties of the superconductor often become increasingly
exotic. For example, in organic superconductors and underdoped
high- cuprate superconductors a fluctuating superconducting state
persists to temperatures significantly above . By studying alloys
of quasi-two-dimensional organic molecular metals in the
-(BEDT-TTF)X family, we reveal how the Nernst effect, a sensitive
probe of superconducting phase fluctuations, evolves in the regime of extreme
Mott criticality. We find strong evidence that, as the phase diagram is
traversed through superconductivity towards the Mott state, the temperature
scale for superconducting fluctuations increases dramatically, eventually
approaching the temperature at which quasiparticles become identifiable at all.Comment: 19 pages, 4 figures, 1 tabl
Dissipation in the superconducting state of kappa-(BEDT-TTF)2Cu(NCS)2
We have studied the interlayer resistivity of the prototypical
quasi-two-dimensional organic superconductor -(BEDT-TTF)Cu(NCS)
as a function of temperature, current and magnetic field, within the
superconducting state. We find a region of non-zero resistivity whose
properties are strongly dependent on magnetic field and current density. There
is a crossover to non-Ohmic conduction below a temperature that coincides with
the 2D vortex solid -- vortex liquid transition. We interpret the behaviour in
terms of a model of current- and thermally-driven phase slips caused by the
diffusive motion of the pancake vortices which are weakly-coupled in adjacent
layers, giving rise to a finite interlayer resistance.Comment: Four pages, three figure
Tetrahydroabietic Acid, a Reduced Abietic Acid, Inhibits the Production of Inflammatory Mediators in RAW264.7 Macrophages Activated with Lipopolysaccharide
Abietic acid (AA), the main component of the rosin fraction of oleoresin synthesized by conifer species, has been reported to have anti-inflammatory effects. AA is a weak contact allergen; however, compounds resulting from its oxidation by air elicit stronger allergic response. Hydrogenation of the conjugated double bonds of AA, as in tetrahydroabietic acid (THAA), decreases its susceptibility to air oxidation and would thus reduce the allergenicity of AA. The aim of this study was to investigate whether THAA could exert anti-inflammatory effects to the same extent as AA in RAW264.7 macrophages activated with the endotoxin lipopolysaccharide (LPS). THAA and AA inhibited the production of nitric oxide (NO) and prostaglandin E2 by suppressing the expression of inducible NO synthase and cyclooxygenase-2, respectively, in LPS-activated RAW264.7 macrophages. They also inhibited the LPS-induced production of interleukin (IL)-1ÎČ, IL-6, and tumor necrosis factor-α. Both THAA and AA prevented the LPS-induced nuclear translocation of the nuclear factor-ÎșB/p65 subunit, suggesting that THAA may inhibit the production of pro-inflammatory mediators through the same mechanism as AA. In comparison, the anti-inflammatory effects of THAA and AA were almost identical, indicating that THAA retains the anti-inflammatory activity of AA at least in LPS-activated RAW264.7 macrophages
Evaluation of Various Packaging Systems on the Activity of Antioxidant Enzyme, and Oxidation and Color Stabilities in Sliced Hanwoo (Korean Cattle) Beef Loin during Chill Storage
The effects of various packaging systems, vacuum packaging (VACP), medium oxygen-modified atmosphere packaging (50% O2/20% CO2/30% N2, MOMAP), MOMAP combined with vacuum skin packaging (VSP-MOMAP), high oxygen-MAP (80% O2/20% CO2/0% N2, HOMAP), and HOMAP combined with VSP (VSP-HOMAP), on the activity of antioxidant enzyme, and oxidation and color stabilities in sliced Hanwoo (Korean cattle) beef loin were investigated at 4°C for 14 d. Higher (p<0.05) superoxide dismutase activity and total reducing ability were maintained in VSP-MOMAP beef than in HOMAP beef. Lipid oxidation (2-thiobarbituric acid reactive substances, TBARS) was significantly (p<0.05) retarded in MOMAP, VSP-MOMAP, and VSP-HOMAP beef compared with HOMAP beef. Production of nonheme iron content was lower (p<0.05) in VSP-MOMAP beef than in HOMAP beef. Red color (a*) was kept higher (p<0.05) in VSP-MOMAP beef compared with MOMAP, HOMAP, and VSP-HOMAP beef. However, VACP beef was found to have the most positive effects on the antioxidant activity, oxidation and red color stabilities among the various packaged beef. These findings suggested that VSP-MOMAP was second to VACP in improving oxidation and color stabilities in sliced beef loin during chill storage
TSLP Induces Mast Cell Development and Aggravates Allergic Reactions through the Activation of MDM2 and STAT6
Thymic stromal lymphopoietin (TSLP) is known to promote T helper type 2 cellâassociated inflammation. Mast cells are major effector cells in allergic inflammatory responses. We noted that the population and maturation of mast cells were reduced in TSLP-deficient mice (TSLP-/-). Thus, we hypothesized that TSLP might affect mast cell development. We found that TSLP induced the proliferation and differentiation of mast cells from bone marrow progenitors. TSLP-induced mast cell proliferation was abolished by depletion of mouse double minute 2 (MDM2) and signal transducers and activators of transcription 6 (STAT6), as an upstream activator of MDM2. TSLP-/-, in particular, had a considerable deficit in the expression of MDM2 and STAT6. Also, the TSLP deficiency attenuated mast cellâmediated allergic reactions through the downregulation of STAT6 and MDM2. In an antibody microarray chip analysis, MDM2 expression was increased in atopic dermatitis patients. These observations indicate that TSLP is a factor for mast cell development, and that it aggravates mast cellâmediated immune responses
Surface acoustic wave devices on bulk ZnO at low temperature
Surface acoustic wave (SAW) devices based on thin films of ZnO are a well
established technology. However, SAW devices on bulk ZnO crystals are not
practical at room temperature due to the significant damping caused by finite
electrical conductivity of the crystal. Here, by operating at low temperatures,
we demonstrate effective SAW devices on the (0001) surface of bulk ZnO
crystals, including a delay line operating at SAW wavelengths of {\lambda} = 4
and 6 {\mu}m and a one-port resonator at a wavelength of {\lambda} = 1.6
{\mu}m. We find that the SAW velocity is temperature dependent, reaching km/s at 10mK. Our resonator reaches a maximum quality factor of
, demonstrating that bulk ZnO is highly viable for
low temperature SAW applications. The performance of the devices is strongly
correlated with the bulk conductivity, which quenches SAW transmission above
about 200 K.Comment: 4 pages, 3 figure
- âŠ