Spin and orbital frustration in MnSc_2S_4 and FeSc_2S_4

Crystal structure, magnetic susceptibility, and specific heat were measured in the normal cubic spinel compounds MnSc_2S_4 and FeSc_2S_4. Down to the lowest temperatures, both compounds remain cubic and reveal strong magnetic frustration. Specifically the Fe compound is characterized by a Curie-Weiss temperature \Theta_{CW}= -45 K and does not show any indications of order down to 50 mK. In addition, the Jahn-Teller ion Fe^{2+} is orbitally frustrated. Hence, FeSc_2S_4 belongs to the rare class of spin-orbital liquids. MnSc_2S_4 is a spin liquid for temperatures T > T_N \approx 2 K.Comment: 4 pages, to be published in Physical Review Letter

Hybrid photonic crystal light-emitting diode renders 123% color conversion effective quantum yield

Colloidal quantum dots (QDs) have emerged as promising color conversion light emitters for solid-state lighting applications [Nat. Photonics 7, 13 (2012) [CrossRef] due to their emission tunability and near-unity photoluminescence quantum yields. In the current commercial LEDs, QDs are dispersed into an encapsulation layer in a far-field architecture, where the majority of the light emitted by the LED remains trapped within the epitaxy due to total internal reflection, drastically reducing the out-coupling efficiency. In this paper, we demonstrate a photonic quasi-crystal hybrid LED geometry that allows QD emitters to be placed in close proximity to the multiple quantum wells (MQWs) of the active area. This architecture greatly improves the coupling between MQWs and QDs, simultaneously allowing for a non-radiative resonant energy transfer between the MQWs and the QDs and near-field radiative coupling of trapped (guided) modes in the LED to the emitters. In this configuration, we demonstrate record-breaking effective quantum yields reaching 123% for single-color conversion LEDs and 110% for white light-emitting devices

Meyer's surgical procedure for the treatment of lip carcinoma.

Lip carcinomas are generally treated by surgery. A reconstruction is often required if the resected segment exceeds one-third of the lip. Meyer's plasty is an alternate way of reconstructing the lower or upper lip. The aim of this study is to describe the technique, its indications and results. A retrospective review of all patients who underwent a Meyer's plasty in our institution is presented. Twenty-four consecutive patients were treated in Lausanne for T1 and T2 lip carcinomas between 1983 and 2001. Primary surgery associated with Meyer's plasty was performed in all cases. Data were collected from the medical records, and eight patients were recalled for clinical evaluation. The oncological, functional and aesthetic results were analyzed. The 5-year local control was 100%. Three patients developed metachronous lymph node metastasis. No patient died from the disease. A hindering microstomy was found in three cases, and two patients suffered from temporary oral leakage. No speech difficulty was encountered. The aesthetics was described as satisfying or good in 87% of the patients. Meyer's plasty following lip surgery of the upper or lower lip allows an aesthetic and functional one-stage reconstruction without compromising the oncological outcome

A Novel Sintered Porous Micromixer for the Effective Mixing of Biologics and Scale Model Investigation of Micromixing Mechanisms

This paper presents a parametric investigation of a porous 3D micro-mixer as well as a 10:1 scale model of the same used to examine the influence of the contributions of both diffusion and advection to successful mixing of fluids of different viscosity. Experiments at both scales implement the laser induced fluorescence technique to capture the evolution of concentration gradients at the mixer outlet. Mixing performance strongly increases with flow rate in the micromixing apparatus but only moderately in the scale-up suggesting important scale-dependent manipulation of diffusion

Competing types of quantum oscillations in the 2D organic conductor (BEDT-TTF)8Hg4Cl12(C6H5Cl)2

Interlayer magnetoconductance of the quasi-two dimensional organic metal (BEDT-TTF)8Hg4Cl12(C6H5Cl)2 has been investigated in pulsed magnetic fields extending up to 36 T and in the temperature range from 1.6 to 15 K. A complex oscillatory spectrum, built on linear combinations of three basic frequencies only is observed. These basic frequencies arise from the compensated closed hole and electron orbits and from the two orbits located in between. The field and temperature dependencies of the amplitude of the various oscillation series are studied within the framework of the coupled orbits model of Falicov and Stachowiak. This analysis reveals that these series result from the contribution of either conventional Shubnikov-de Haas effect (SdH) or quantum interference (QI), both of them being induced by magnetic breakthrough. Nevertheless, discrepancies between experimental and calculated parameters indicate that these phenomena alone cannot account for all of the data. Due to its low effective mass, one of the QI oscillation series - which corresponds to the whole first Brillouin zone area - is clearly observed up to 13 K.Comment: 8 pages, 8 figures. To be published in Phys. Rev.

Planck pre-launch status: HFI beam expectations from the optical optimisation of the focal plane

Planck is a European Space Agency (ESA) satellite, launched in May 2009, which will map the cosmic microwave background anisotropies in intensity and polarisation with unprecedented detail and sensitivity. It will also provide full-sky maps of astrophysical foregrounds. An accurate knowledge of the telescope beam patterns is an essential element for a correct analysis of the acquired astrophysical data. We present a detailed description of the optical design of the High Frequency Instrument (HFI) together with some of the optical performances measured during the calibration campaigns. We report on the evolution of the knowledge of the pre-launch HFI beam patterns when coupled to ideal telescope elements, and on their significance for the HFI data analysis procedure

Defect-Free Self-Catalyzed GaAs/GaAsP Nanowire Quantum Dots Grown on Silicon Substrate

The III-V nanowire quantum dots (NWQDs) monolithically grown on silicon substrates, combining the advantages of both one- and zero-dimensional materials, represent one of the most promising technologies for integrating advanced III-V photonic technologies on a silicon microelectronics platform. However, there are great challenges in the fabrication of high-quality III-V NWQDs by a bottom-up approach, that is, growth by the vapor-liquid-solid method, because of the potential contamination caused by external metal catalysts and the various types of interfacial defects introduced by self-catalyzed growth. Here, we report the defect-free self-catalyzed III-V NWQDs, GaAs quantum dots in GaAsP nanowires, on a silicon substrate with pure zinc blende structure for the first time. Well-resolved excitonic emission is observed with a narrow line width. These results pave the way toward on-chip III-V quantum information and photonic devices on silicon platform

The changing information environment for nanotechnology: online audiences and content

The shift toward online communication in all realms, from print newspapers to broadcast television, has implications for how the general public consumes information about nanotechnology. The goal of this study is threefold: to investigate who is using online sources for information and news about science and nanotechnology, to examine what the general public is searching for online with regards to nanotechnology, and to analyze what they find in online content of nanotechnology. Using survey data, we find those who report the Internet as their primary source of science and technology news are diverse in age, more knowledgeable about science and nanotechnology, highly educated, male, and more diverse racially than users of other media. In a comparison of demographic data on actual visits by online users to general news and science Web sites, science sites attracted more male, non-white users from the Western region of the United States than news sites did. News sites, on the other hand, attracted those with a slightly higher level of education. Our analysis of published estimates of keyword searches on nanotechnology reveals people are turning to the Internet to search for keyword searches related to the future, health, and applications of nanotechnology. A content analysis of online content reveals health content dominates overall. Comparisons of content in different types of sites—blogs, government, and general sites—are conducted

Design of an interaction region with head-on collisions for the ILC

An interaction region (IR) with head-on collisions is considered as an alternative to the baseline configuration of the International Linear Collider (ILC) which includes two IRs with finite crossing-angles (2 and 20 mrad). Although more challenging for the beam extraction, the head-on scheme is favoured by the experiments because it allows a more convenient detector configuration, particularly in the forward region. The optics of the head-on extraction is revisited by separating the e+ and e- beams horizontally, first by electrostatic separators operated at their LEP nominal field and then using a defocusing quadrupole of the final focus beam line. In this way the septum magnet is protected from the beamstrahlung power. Newly optimized final focus and extraction optics are presented, including a first look at post-collision diagnostics. The influence of parasitic collisions is shown to lead to a region of stable collision parameters. Disrupted beam and beamstrahlung photon losses are calculated along the extraction elements