From urban to national heat island: The effect of anthropogenic heat output on climate change in high population industrial countries

The project presented here sought to determine whether changes in anthropogenic thermal emission can have a measurable effect on temperature at the national level, taking Japan and Great Britain as type examples. Using energy consumption as a proxy for thermal emission, strong correlations (mean r2 = 0.90 and 0.89, respectively) are found between national equivalent heat output (HO) and temperature above background levels Δt averaged over 5‐ to 8‐yr periods between 1965 and 2013, as opposed to weaker correlations for CMIP5 model temperatures above background levels Δmt (mean r2 = 0.52 and 0.10). It is clear that the fluctuations in Δt are better explained by energy consumption than by present climate models, and that energy consumption can contribute to climate change at the national level on these timescales

An Emergent Solution to the Strong CP Problem

We construct a theory in which the solution to the strong CP problem is an emergent property of the background of the dark matter in the Universe. The role of the axion degree of freedom is played by multi-body collective excitations similar to spin-waves in the medium of the dark matter of the Galactic halo. The dark matter is a vector particle whose low energy interactions with the Standard Model take the form of its spin density coupled to $G \widetilde{G}$, which induces a potential on the average spin density inducing it to compensate $\overline{\theta}$, effectively removing CP violation in the strong sector in regions of the Universe with sufficient dark matter density. We discuss the viable parameter space, finding that light dark matter masses within a few orders of magnitude of the fuzzy limit are preferred, and discuss the associated signals with this type of solution to the strong CP problem.Comment: 5 pages, 2 figures. Version published in PR

Spin-Related Current Suppression in a Semiconductor-Quantum-Dot Spin-Diode Structure

We experimentally study the transport features of electrons in a spin-diode structure consisting of a single semiconductor quantum dot (QD) weakly coupled to one nonmagnetic (NM) and one ferromagnetic (FM) lead, in which the QD has an artificial atomic nature. A Coulomb stability diamond shows asymmetric features with respect to the polarity of the bias voltage. For the regime of two-electron tunneling, we find anomalous suppression of the current for both forward and reverse bias. We discuss possible mechanisms of the anomalous current suppression in terms of spin blockade via the QD/FM interface at the ground state of a two-electron QD.Comment: 5 pages, 4 figures + 2 appendix figure

Branching mechanism of intergranular crack propagation in three dimensions

We investigate the process of slow intergranular crack propagation by the finite element method model, and show that branching is induced by partial arresting of crack front owing to the geometrical randomness of grain boundaries. A possible scenario for branching instability of crack propagation in disordered continuum medium is also discussed.Comment: 4 pages, submitted to Phys.Rev.E; v2:corrected typos v3: final version to be publishe

Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads

We have fabricated a lateral double barrier magnetic tunnel junction (MTJ) which consists of a single self-assembled InAs quantum dot (QD) with ferromagnetic Co leads. The MTJ shows clear hysteretic tunnel magnetoresistance (TMR) effect, which is evidence for spin transport through a single semiconductor QD. The TMR ratio and the curve shapes are varied by changing the gate voltage.Comment: 4 pages, 3 figure

Osteoblast interactions within a biomimetic apatite microenvironment.

Numerous reports have shown that accelerated apatites can mediate osteoblastic differentiation in vitro and bone formation in vivo. However, how cells interact within the apatite microenvironment remains largely unclear, despite the vast literature available today. In response, this study evaluates the in vitro interactions of a well-characterized osteoblast cell line (MC3T3-E1) with the apatite microenvironment. Specifically, cell attachment, spreading, and viability were evaluated in the presence and absence of serum proteins. Proteins were found to be critical in the mediation of cell-apatite interactions, as adherence of MC3T3-E1 cells to apatite surfaces without protein coatings resulted in significant levels of cell death within 24 h in serum-free media. In the absence of protein-apatite interaction, cell viability could be "rescued" upon treatment of MC3T3-E1 cells with inhibitors to phosphate (PO(4) (3-)) transport, suggesting that PO(4) (3-) uptake may play a role in viability. In contrast, rescue was not observed upon treatment with calcium (Ca(2+)) channel inhibitors. Interestingly, a rapid "pull-down" of extracellular Ca(2+) and PO(4) (3-) ions onto the apatite surface could be measured upon the incubation of apatites with α-MEM, suggesting that cells may be subject to changing levels of Ca(2+) and PO(4) (3-) within their microenvironment. Therefore, the biomimetic apatite surface may significantly alter the microenvironment of adherent osteoblasts and, as such, be capable of affecting both cell survival and differentiation

Enhanced photoluminescence emission from two-dimensional silicon photonic crystal nanocavities

We present a temperature dependent photoluminescence study of silicon optical nanocavities formed by introducing point defects into two-dimensional photonic crystals. In addition to the prominent TO phonon assisted transition from crystalline silicon at ~1.10 eV we observe a broad defect band luminescence from ~1.05-1.09 eV. Spatially resolved spectroscopy demonstrates that this defect band is present only in the region where air-holes have been etched during the fabrication process. Detectable emission from the cavity mode persists up to room-temperature, in strong contrast the background emission vanishes for T > 150 K. An Ahrrenius type analysis of the temperature dependence of the luminescence signal recorded either in-resonance with the cavity mode, or weakly detuned, suggests that the higher temperature stability may arise from an enhanced internal quantum efficiency due to the Purcell-effect

Electric-field control of tunneling magnetoresistance effect in a Ni/InAs/Ni quantum-dot spin valve

We demonstrate an electric-field control of tunneling magnetoresistance (TMR) effect in a semiconductor quantum-dot (QD) spin-valve device. By using ferromagnetic Ni nano-gap electrodes, we observe the Coulomb blockade oscillations at a small bias voltage. In the vicinity of the Coulomb blockade peak, the TMR effect is significantly modulated and even its sign is switched by changing the gate voltage, where the sign of the TMR value changes at the resonant condition.Comment: 3 pages, 3 figure

A Correlation between the Emission Intensity of Self-Assembled Germanium Islands and the Quality Factor of Silicon Photonic Crystal Nanocavities

We present a comparative micro-photoluminescence study of the emission intensity of self-assembled germanium islands coupled to the resonator mode of two-dimensional silicon photonic crystal defect nanocavities. The emission intensity is investigated for cavity modes of L3 and Hexapole cavities with different cavity quality factors. For each of these cavities many nominally identical samples are probed to obtain reliable statistics. As the quality factor increases we observe a clear decrease in the average mode emission intensity recorded under comparable optical pumping conditions. This clear experimentally observed trend is compared with simulations based on a dissipative master equation approach that describes a cavity weakly coupled to an ensemble of emitters. We obtain evidence that reabsorption of photons emitted into the cavity mode is responsible for the observed trend. In combination with the observation of cavity linewidth broadening in power dependent measurements, we conclude that free carrier absorption is the limiting effect for the cavity mediated light enhancement under conditions of strong pumping.Comment: 8 pages, 5 figure