Imaging the homogeneous nucleation during the melting of superheated colloidal crystals

The nucleation process is crucial to many phase transitions, but its kinetics are difficult to predict and measure. We superheated and melted the interior of thermal-sensitive colloidal crystals and investigated by means of video microscopy the homogeneous melting at single-particle resolution. The observed nucleation precursor was local particle-exchange loops surrounded by particles with large displacement amplitudes rather than any defects. The critical size, incubation time, and shape and size evolutions of the nucleus were measured. They deviate from the classical nucleation theory under strong superheating, mainly because of the coalescence of nuclei. The superheat limit agrees with the measured Born and Lindemann instabilities

Simulating quantum statistics with entangled photons: a continuous transition from bosons to fermions

In contrast to classical physics, quantum mechanics divides particles into two classes-bosons and fermions-whose exchange statistics dictate the dynamics of systems at a fundamental level. In two dimensions quasi-particles known as 'anyons' exhibit fractional exchange statistics intermediate between these two classes. The ability to simulate and observe behaviour associated to fundamentally different quantum particles is important for simulating complex quantum systems. Here we use the symmetry and quantum correlations of entangled photons subjected to multiple copies of a quantum process to directly simulate quantum interference of fermions, bosons and a continuum of fractional behaviour exhibited by anyons. We observe an average similarity of 93.6\pm0.2% between an ideal model and experimental observation. The approach generalises to an arbitrary number of particles and is independent of the statistics of the particles used, indicating application with other quantum systems and large scale application.Comment: 10 pages, 5 figure

Quantum Interference of Photon Pairs from Two Trapped Atomic Ions

We collect the fluorescence from two trapped atomic ions, and measure quantum interference between photons emitted from the ions. The interference of two photons is a crucial component of schemes to entangle atomic qubits based on a photonic coupling. The ability to preserve the generated entanglement and to repeat the experiment with the same ions is necessary to implement entangling quantum gates between atomic qubits, and allows the implementation of protocols to efficiently scale to larger numbers of atomic qubits.Comment: 4 pages, 4 figure

Ambipolar Field Effect in Topological Insulator Nanoplates of (BixSb1-x)2Te3

Topological insulators represent a new state of quantum matter attractive to both fundamental physics and technological applications such as spintronics and quantum information processing. In a topological insulator, the bulk energy gap is traversed by spin-momentum locked surface states forming an odd number of surface bands that possesses unique electronic properties. However, transport measurements have often been dominated by residual bulk carriers from crystal defects or environmental doping which mask the topological surface contribution. Here we demonstrate (BixSb1-x)2Te3 as a tunable topological insulator system to manipulate bulk conductivity by varying the Bi/Sb composition ratio. (BixSb1-x)2Te3 ternary compounds are confirmed as topological insulators for the entire composition range by angle resolved photoemission spectroscopy (ARPES) measurements and ab initio calculations. Additionally, we observe a clear ambipolar gating effect similar to that observed in graphene using nanoplates of (BixSb1-x)2Te3 in field-effect-transistor (FET) devices. The manipulation of carrier type and concentration in topological insulator nanostructures demonstrated in this study paves the way for implementation of topological insulators in nanoelectronics and spintronics.Comment: 7 pages, 4 figure

Fully gapped topological surface states in Bi2_2Se3_3 films induced by a d-wave high-temperature superconductor

Topological insulators are a new class of materials, that exhibit robust gapless surface states protected by time-reversal symmetry. The interplay between such symmetry-protected topological surface states and symmetry-broken states (e.g. superconductivity) provides a platform for exploring novel quantum phenomena and new functionalities, such as 1D chiral or helical gapless Majorana fermions, and Majorana zero modes which may find application in fault-tolerant quantum computation. Inducing superconductivity on topological surface states is a prerequisite for their experimental realization. Here by growing high quality topological insulator Bi$_2$Se$_3$ films on a d-wave superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ using molecular beam epitaxy, we are able to induce high temperature superconductivity on the surface states of Bi$_2$Se$_3$ films with a large pairing gap up to 15 meV. Interestingly, distinct from the d-wave pairing of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, the proximity-induced gap on the surface states is nearly isotropic and consistent with predominant s-wave pairing as revealed by angle-resolved photoemission spectroscopy. Our work could provide a critical step toward the realization of the long sought-after Majorana zero modes.Comment: Nature Physics, DOI:10.1038/nphys274

Relationship between Environmental Phthalate Exposure and the Intelligence of School-Age Children

BACKGROUND: Concern over phthalates has emerged because of their potential toxicity to humans. OBJECTIVE: We investigated the relationship between the urinary concentrations of phthalate metabolites and children`s intellectual functioning. METHODS: This study enrolled 667 children at nine elementary schools in five South Korean cities. A cross-sectional examination of urine phthalate concentrations was performed, and scores on neuro-psychological tests were obtained from both the children and their mothers. RESULTS: We measured mono-2-ethylhexyl phthalate (MEHP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), both metabolites of di(2-ethylhexyl)phthalate (DEHP), and mono-n-butyl phthalate (MBP), a metabolite of dibutyl phthalate (DBP), in urine samples. The geometric mean (ln) concentrations of MEHP, MEOHP, and MBP were 21.3 mu g/L [geometric SD (GSD) = 2.2 mu g/L; range, 0.5-445.4], 18.0 mu g/L (GSD = 2.4; range, 0.07-291.1), and 48.9 mu g/L (GSD = 2.2; range, 2.1-1645.5), respectively. After adjusting for demographic and developmental covariates, the Full Scale IQ and Verbal IQ scores were negatively associated with DEHP metabolites but not with DBP metabolites. We also found a significant negative relationship between the urine concentrations of the metabolites of DEHP and DBP and children`s vocabulary subscores. After controlling for maternal IQ, a significant inverse relationship between DEHP metabolites and vocabulary subscale score remained. Among boys, we found a negative association between increasing MEHP phthalate concentrations and the sum of DEHP metabolite concentrations and Wechsler Intelligence Scale for Children vocabulary score; however, among girls, we found no significant association between these variables. CONCLUSION: Controlling for maternal IQ and other covariates, the results show an inverse relationship between phthalate metabolites and IQ scores; however, given the limitations in cross-sectional epidemiology, prospective studies are needed to fully explore these associations.This work was funded by the Eco-Technopia 21 project of Korea Institute of Environmental Science and Technology (091-081-059).Cho SC, 2010, J CHILD PSYCHOL PSYC, V51, P1050, DOI 10.1111/j.1469-7610.2010.02250.xKim BN, 2009, BIOL PSYCHIAT, V66, P958, DOI 10.1016/j.biopsych.2009.07.034Tanida T, 2009, TOXICOL LETT, V189, P40, DOI 10.1016/j.toxlet.2009.04.005Ghisari M, 2009, TOXICOL LETT, V189, P67, DOI 10.1016/j.toxlet.2009.05.004Barnett JH, 2009, AM J PSYCHIAT, V166, P909, DOI 10.1176/appi.ajp.2009.08081251Kim Y, 2009, NEUROTOXICOLOGY, V30, P564, DOI 10.1016/j.neuro.2009.03.012Engel SM, 2009, NEUROTOXICOLOGY, V30, P522, DOI 10.1016/j.neuro.2009.04.001Kamrin MA, 2009, J TOXICOL ENV HEAL B, V12, P157, DOI 10.1080/10937400902729226Brown JS, 2009, SCHIZOPHRENIA BULL, V35, P256, DOI 10.1093/schbul/sbm147Bellinger DC, 2008, NEUROTOXICOLOGY, V29, P828, DOI 10.1016/j.neuro.2008.04.005Wolff MS, 2008, ENVIRON HEALTH PERSP, V116, P1092, DOI 10.1289/ehp.11007van Neerven S, 2008, PROG NEUROBIOL, V85, P433, DOI 10.1016/j.pneurobio.2008.04.006Hatch EE, 2008, ENVIRON HEALTH-GLOB, V7, DOI 10.1186/1476-069X-7-27Zevalkink J, 2008, J GENET PSYCHOL, V169, P72Kolarik B, 2008, ENVIRON HEALTH PERSP, V116, P98, DOI 10.1289/ehp.10498SATHYANARAYANA S, 2008, CURR PROBL PEDIAT AD, V38, P34KHO YL, 2008, J ENV HLTH SCI, V34, P271Huang PC, 2007, HUM REPROD, V22, P2715, DOI 10.1093/humrep/dem205Janjua NR, 2007, ENVIRON SCI TECHNOL, V41, P5564, DOI 10.1021/es0628755Meeker JD, 2007, ENVIRON HEALTH PERSP, V115, P1029, DOI 10.1289/ehp.9852Fromme H, 2007, INT J HYG ENVIR HEAL, V210, P21, DOI 10.1016/j.ijheh.2006.09.005Xu Y, 2007, ARCH TOXICOL, V81, P57, DOI 10.1007/s00204-006-0143-8Pereira C, 2007, ACTA HISTOCHEM, V109, P29, DOI 10.1016/j.acthis.2006.09.008Hauser R, 2006, EPIDEMIOLOGY, V17, P682, DOI 10.1097/01.ede.0000235996.89953.d7Zhu DF, 2006, BRAIN, V129, P2923, DOI 10.1093/brain/awl215Andrade AJM, 2006, TOXICOLOGY, V227, P185, DOI 10.1016/j.tox.2006.07.022Lottrup G, 2006, INT J ANDROL, V29, P172, DOI 10.1111/j.1365-2605.2005.00642.xBreous E, 2005, MOL CELL ENDOCRINOL, V244, P75, DOI 10.1016/j.mce.2005.06.009Wenzel A, 2005, MOL CELL ENDOCRINOL, V244, P63, DOI 10.1016/j.mce.2005.02.008Kato K, 2005, ANAL CHEM, V77, P2985, DOI 10.1021/ac0481248Tanaka T, 2005, FOOD CHEM TOXICOL, V43, P581, DOI 10.1016/j.fct.2005.01.001Duty SM, 2005, HUM REPROD, V20, P604, DOI 10.1093/humrep/deh656Kota BP, 2005, PHARMACOL RES, V51, P85, DOI 10.1016/j.phrs.2004.07.012Hays T, 2005, CARCINOGENESIS, V26, P219, DOI 10.1093/carcin/bgh285Hauser R, 2004, ENVIRON HEALTH PERSP, V112, P1734, DOI 10.1289/ehp.7212Bornehag CG, 2004, ENVIRON HEALTH PERSP, V112, P1393, DOI 10.1289/ehp.7187Ishido M, 2004, J NEUROCHEM, V91, P69, DOI 10.1111/j.1471-4159.2004.02696.xMink PJ, 2004, EPIDEMIOLOGY, V15, P385, DOI 10.1097/01.ede.0000128402.86336.7eBellinger DC, 2004, EPIDEMIOLOGY, V15, P383, DOI 10.1097/01.ede.0000129525.15064.a4Shea KM, 2003, PEDIATRICS, V111, P1467Tanaka T, 2002, FOOD CHEM TOXICOL, V40, P1499, DOI 10.1016/S0278-6915(02)00073-XHoppin JA, 2002, ENVIRON HEALTH PERSP, V110, P515SATTLER JM, 2001, ASSESSMENT CHILDRENRice D, 2000, ENVIRON HEALTH PERSP, V108, P511Bellinger DC, 2000, NEUROTOXICOL TERATOL, V22, P133LIM YR, 2000, KOR J CLIN PSYCHOL, V19, P563Braissant O, 1998, ENDOCRINOLOGY, V139, P2748Peters JM, 1997, CARCINOGENESIS, V18, P2029Baldini IM, 1997, PROG NEURO-PSYCHOPH, V21, P925Roberts RA, 1997, FUND APPL TOXICOL, V38, P107PARK KS, 1996, DEV KEDI WISC INDIVIMONZANI F, 1993, CLIN INVESTIGATOR, V71, P367SILVERSTEIN AB, 1990, J CLIN PSYCHOL, V46, P333HINTON RH, 1986, ENVIRON HEALTH PERSP, V70, P195KIM MK, 1986, SEOUL J PSYCHIAT, V11, P194KAUFMAN AS, 1976, CONTEMP EDUC PSYCHOL, V1, P1801

Anti-epileptic effect of Ganoderma lucidum polysaccharides by inhibition of intracellular calcium accumulation and stimulation of expression of CaMKII a in epileptic hippocampal neurons

Purpose: To investigate the mechanism of the anti-epileptic effect of Ganoderma lucidum polysaccharides (GLP), the changes of intracellular calcium and CaMK II a expression in a model of epileptic neurons were investigated. Method: Primary hippocampal neurons were divided into: 1) Control group, neurons were cultured with Neurobasal medium, for 3 hours; 2) Model group I: neurons were incubated with Mg2+ free medium for 3 hours; 3) Model group II: neurons were incubated with Mg2+ free medium for 3 hours then cultured with the normal medium for a further 3 hours; 4) GLP group I: neurons were incubated with Mg2+ free medium containing GLP (0.375 mg/ml) for 3 hours; 5) GLP group II: neurons were incubated with Mg2+ free medium for 3 hours then cultured with a normal culture medium containing GLP for a further 3 hours. The CaMK II a protein expression was assessed by Western-blot. Ca2+ turnover in neurons was assessed using Fluo-3/AM which was added into the replacement medium and Ca2+ turnover was observed under a laser scanning confocal microscope. Results: The CaMK II a expression in the model groups was less than in the control groups, however, in the GLP groups, it was higher than that observed in the model group. Ca2+ fluorescence intensity in GLP group I was significantly lower than that in model group I after 30 seconds, while in GLP group II, it was reduced significantly compared to model group II after 5 minutes. Conclusion: GLP may inhibit calcium overload and promote CaMK II a expression to protect epileptic neuron

Photolysis of sulphuric acid as the source of sulphur oxides in the mesosphere of Venus

The sulphur cycle plays fundamental roles in the chemistry and climate of Venus. Thermodynamic equilibrium chemistry at the surface of Venus favours the production of carbonyl sulphide and to a lesser extent sulphur dioxide. These gases are transported to the middle atmosphere by the Hadley circulation cell. Above the cloud top, a sulphur oxidation cycle involves conversion of carbonyl sulphide into sulphur dioxide, which is then transported further upwards. A significant fraction of this sulphur dioxide is subsequently oxidized to sulphur trioxide and eventually reacts with water to form sulphuric acid. Because the vapour pressure of sulphuric acid is low, it readily condenses and forms an upper cloud layer at altitudes of 60–70 km, and an upper haze layer above 70 km (ref. 9), which effectively sequesters sulphur oxides from photochemical reactions. Here we present simulations of the fate of sulphuric acid in the Venusian mesosphere based on the Caltech/JPL kinetics model, but including the photolysis of sulphuric acid. Our model suggests that the mixing ratios of sulphur oxides are at least five times higher above 90 km when the photolysis of sulphuric acid is included. Our results are inconsistent with the previous model results but in agreement with the recent observations using ground-based microwave spectroscopy and by Venus Express

Spin-related tunneling through a nanostructured electric-magnetic barrier on the surface of a topological insulator

We investigate quantum tunneling through a single electric and/or magnetic barrier on the surface of a three-dimensional topological insulator. We found that (1) the propagating behavior of electrons in such system exhibits a strong dependence on the direction of the incident electron wavevector and incident energy, giving the possibility to construct a wave vector and/or energy filter; (2) the spin orientation can be tuned by changing the magnetic barrier structure as well as the incident angles and energies

Evaluation of the new rural cooperative medical system in China: is it working or not?

<p>Abstract</p> <p>Background</p> <p>To prove the possibility of implementing the New Rural Cooperative Medical System (NRCMS) at different levels with a premium funding according to their economic level in developed and less developed areas in Guangdong province, and study the insurable inpatients in different types of regions, taking into account limitations of indemnities and loss ratios.</p> <p>Method</p> <p>All data samples were randomly collected from the NRCMS Department, Guangdong Province. Gross domestic product (GDP) at 10000 Yuan per capita was employed to divide Guangdong into two economic levels: (1) economically developed & (2) less economically developed regions. A descriptive analysis about tendency of raising premium and reimbursement ratios of common fund was performed with independent samples and t-test as well as implementing a model to evaluate the differences in premium contribution differences in co-payments, thresholds, and rebates. Also, a qualitative study measured several economic factors to evaluate farmers' financial and social potency in contributing to the NRCMS.</p> <p>Result</p> <p>A higher GDP per capita were found within economically developed regions (p < 0.05) than in less developed areas, with higher tendency for funding capacity and average funding capability in villages and towns within economically developed regions (p < 0.05) than in economically less developed. Maximum benefits between two regions in medical insurance coverage showed significant difference (p < 0.05); differences between basic medical insurance coverage between two regions was insignificant (p > 0.05); nevertheless, economically developed regions showed higher threshold and rebates with less co-payments in the economically developed than less developed.</p> <p>Conclusion</p> <p>Despite some loop holes in the NRCMS, the system is workable, but needs more strengthening by encouraging farmers' participation into NRCMS with a necessity to implement a new reimbursement payment system by health care providers. In addition it is proposed that for maximum benefits another premium funding should be secured.</p