Proximity effect thermometer for local temperature measurements on mesoscopic samples

Using the strong temperature dependent resistance of a normal metal wire in proximity to a superconductor, we have been able to measure the local temperature of electrons heated by flowing a dc current in a metallic wire to within a few tens of millikelvin at low temperatures. By placing two such thermometers at different parts of a sample, we have been able to measure the temperature difference induced by a dc current flowing in the sample. This technique may provide a flexible means of making quantitative thermal and thermoelectric measurements on mesoscopic metallic samples

DNA-Mediated Excitonic Upconversion FRET Switching

Excitonics is a rapidly expanding field of nanophotonics in which the harvesting of photons, ensuing creation and transport of excitons via Förster resonant energy transfer (FRET), and subsequent charge separation or photon emission has led to the demonstration of excitonic wires, switches, Boolean logic and light harvesting antennas for many applications. FRET funnels excitons down an energy gradient resulting in energy loss with each step along the pathway. Conversely, excitonic energy upconversion via upconversion nanoparticles (UCNPs), although currently inefficient, serves as an energy ratchet to boost the exciton energy. Although FRET-based upconversion has been demonstrated, it suffers from low FRET efficiency and lacks the ability to modulate the FRET. We have engineered an upconversion FRET-based switch by combining lanthanide-doped UCNPs and fluorophores that demonstrates excitonic energy upconversion by nearly a factor of 2, an excited state donor to acceptor FRET efficiency of nearly 25%, and an acceptor fluorophore quantum efficiency that is close to unity. These findings offer a promising path for energy upconversion in nanophotonic applications including artificial light harvesting, excitonic circuits, photovoltaics, nanomedicine, and optoelectronics

Origin of atomic clusters during ion sputtering

Previous studies have shown that the size distributions of small clusters ( n<=40 n = number of atoms/cluster) generated by sputtering obey an inverse power law with an exponent between -8 and -4. Here we report electron microscopy studies of the size distributions of larger clusters ( n>=500) sputtered by high-energy ion impacts. These new measurements also yield an inverse power law, but one with an exponent of -2 and one independent of sputtering yield, indicating that the large clusters are produced when shock waves, generated by subsurface displacement cascades, ablate the surface

Argon hollow cathode

An interest in alternate propellants for ion-bombardment thrusters, together with ground applications of this technology, has prompted consideration of argon. Several variations of conventional hollow cathode designs were tried, but the bulk of the testing used a hollow tube with an internal tungsten emitter and an orifice at one end. The optimum cathode tube diameter was found to be in the range of 1.0-2.5 cm, somewhat larger than those used for cesium and mercury. Optimum orifice diameter depended on operating conditions, and varied from 0.5 to 5 mm. Biasing the internal emitter negative relative to the cathode chamber reduced the external coupling voltage and should therefore improve orifice lifetime. The expected effect of this bias on emitter lifetime was less clear. Lifetime tests were not conducted as part of this investigation, but several designs show promise of long lifetime in specific applications

Report of the QCD Working Group

The activities of the QCD working group concentrated on improving the understanding and Monte Carlo simulation of multi-jet final states due to hard QCD processes at LEP, i.e. quark-antiquark plus multi-gluon and/or secondary quark production, with particular emphasis on four-jet final states and b-quark mass effects. Specific topics covered are: relevant developments in the main event generators PYTHIA, HERWIG and ARIADNE; the new multi-jet generator APACIC++; description and tuning of inclusive (all-flavour) jet rates; quark mass effects in the three- and four-jet rates; mass, higher-order and hadronization effects in four-jet angular and shape distributions; b-quark fragmentation and gluon splitting into b-quarks.Comment: 95 pages, 48 figures, contribution to Proceedings of the LEP2 Monte Carlo Workshop. References for NLO 4-jet matrix elements adde

Epidemiološki studij učinaka herbicida

A preliminary study of 324 Swedish railway workers exposed to herbicides between the years 1957-1971 showed 2 excess lung cancer cases, 1 adenocarcinoma and 1 oatcellcancer. Although the number of subjects was small, especially the number of cancers, the possibility that amitrole and combinations together with smoking might have caused the excess lung cancers cannot be ruled out.U ovom preliminarnom epidemiološkom istraživanju, autori su analizirali uzroke smrti među 324 radnika koji su u razdoblju od 1957. do 1971. godine bili izvrgnuti različitim herbicidima tijekom ukupno više od 46 dana. Autori su u račun uzimali incidenciju u općem i specifičnom mortalitetu švedske populacije pa su uspoređivali broj očekivanih i broj utvrđenih smrtnih slučajeva među eksponiranim radnicima. Premda su sveukupni brojevi maleni, ne može se isključiti mogućnost da je amitrol sam ili s pušenjem uvjetovao veći broj karcinoma pluća u eksponiranih radnika

Are there gender differences in the geography of alcohol-related mortality in Scotland? An ecological study

<b>Background</b> There is growing concern about alcohol-related harm, particularly within Scotland which has some of the highest rates of alcohol-related death in western Europe. There are large gender differences in alcohol-related mortality rates in Scotland and in other countries, but the reasons for these differences are not clearly understood. In this paper, we aimed to address calls in the literature for further research on gender differences in the causes, contexts and consequences of alcohol-related harm. Our primary research question was whether the kind of social environment which tends to produce higher or lower rates of alcohol-related mortality is the same for both men and women across Scotland. <b>Methods</b> Cross-sectional, ecological design. A comparison was made between spatial variation in men's and women's age-standardised alcohol-related mortality rates in Scotland using maps, Moran's Index, linear regression and spatial analyses of residuals. Directly standardised mortality rates were derived from individual level records of death registration, 2000–2005 (n = 8685). <b>Results</b> As expected, men's alcohol-related mortality rate substantially exceeded women's and there was substantial spatial variation in these rates for both men and women within Scotland. However, there was little spatial variation in the relationship between men's and women's alcohol-mortality rates (r2 = 0.73); areas with relatively high rates of alcohol-related mortality for men tended also to have relatively high rates for women. In a small number of areas (8 out of 144) the relationship between men's and women's alcohol-related mortality rates was significantly different. <b>Conclusion</b> In as far as geographic location captures exposure to social and economic environment, our results suggest that the relationship between social and economic environment and alcohol-related harm is very similar for men and women. The existence of a small number of areas in which men's and women's alcohol-related mortality had an different relationship suggests that some places may have unusual drinking cultures. These might prove useful for further investigations into the factors which influence drinking behaviour in men and women

CP asymmetry in B→ϕKSB \to \phi K_S in a general two-Higgs-doublet model with fourth-generation quarks

We discuss the time-dependent CP asymmetry of decay $B \to \phi K_S$ in an extension of the Standard Model with both two Higgs doublets and additional fourth-generation quarks. We show that although the Standard Model with two-Higgs-doublet and the Standard model with fourth generation quarks alone are not likely to largely change the effective $\sin 2 \beta$ from the decay of $B \to \phi K_S$, the model with both additional Higgs doublet and fourth-generation quarks can easily account for the possible large negative value of $\sin 2 \beta$ without conflicting with other experimental constraints. In this model, additional large CP violating effects may arise from the flavor changing Yukawa interactions between neutral Higgs bosons and the heavy fourth generation down type quark, which can modify the QCD penguin contributions. With the constraints obtained from $b \to s \bar{s} s$ processes such as $B \to X_s \gamma$ and $\Delta m_{B_s^0}$, this model can lead to the effective $\sin 2 \beta$ to be as large as $- 0.4$ in the CP asymmetry of $B \to \phi K_S$.Comment: 13 pages, 5 figures, references added, to appear in Eur.Phys.J.