Results are presented from the first underground data run of ZEPLIN-II, a 31 kg two-phase xenon detector developed to observe nuclear recoils from hypothetical weakly interacting massive dark matter particles. Discrimination between nuclear recoils and background electron recoils is afforded by recording both the scintillation and ionisation signals generated within the liquid xenon, with the ratio of these signals being different for the two classes of event. This ratio is calibrated for different incident species using an AmBe neutron source and 60Co γ-ray sources. From our first 31 live days of running ZEPLIN-II, the total exposure following the application of fiducial and stability cuts was 225 kg × days. A background population of radon progeny events was observed in this run, arising from radon emission in the gas purification getters, due to radon daughter ion decays on the surfaces of the walls of the chamber. An acceptance window, defined by the neutron calibration data, of 50% nuclear recoil acceptance between 5 keVee and 20 keVee, had an observed count of 29 events, with a summed expectation of 28.6 ± 4.3 γ-ray and radon progeny induced background events. These figures provide a 90% c.l. upper limit to the number of nuclear recoils of 10.4 events in this acceptance window, which converts to a WIMP nucleon spin-independent cross-section with a minimum of 6.6 × 10-7 pb following the inclusion of an energy-dependent, calibrated, efficiency. A second run is currently underway in which the radon progeny will be eliminated, thereby removing the background population, with a projected sensitivity of 2 × 10-7 pb for similar exposures as the first run

The in situ electrochemical‐conductance method is presented as an important electrochemical characterization tool for gaining insight into the chemical and electrical behavior of π‐conjugated polymers and electroactive materials. Important information about conductivity models, the type of charge carrier, and the carrier‐transport pathways as well as explanations of different phenomena related to charge and mass transport can be extracted from the obtained analyses. Using conveniently modified polymers, this method enables the development of a wide range of conductometric sensory devices. This Minireview summarizes the historical development of the in situ electrochemical‐conductance method, describes the systems used, explains details of the calculations, and discusses recent advances and applications.

We present the first measurements of the electroluminescence response to the emission of single electrons in a two-phase noble gas detector. Single ionization electrons generated in liquid xenon are detected in a thin gas layer during the 31-day background run of the ZEPLIN-II experiment, a two-phase xenon detector for WIMP dark matter searches. Both the pressure dependence and magnitude of the single-electron response are in agreement with previous measurements of electroluminescence yield in xenon. We discuss different photoionization processes as possible cause for the sample of single electrons studied in this work. This observation may have implications for the design and operation of future large-scale two-phase systems.Comment: 11 pages, 6 figure

A hybrid film composed of chiral encoded mesoporous platinum and polypyrrole shows differential wireless actuation as a function of the chiral nature of an enantiomer present in solution.

A key approach for designing bioinspired machines is to transfer concepts from nature to manmade structures by integrating biomolecules into artificial mechanical systems. This allows the conversion of molecular information into macroscopic action. In the present contribution, we describe the design and dynamic behavior of hybrid bioelectrochemical swimmers, which move spontaneously at the air/water interface. Their motion is governed by the diastereomeric interactions between immobilized enantiopure oligomers and the antipodes of a chiral probe molecule present in solution. These dynamic systems are able to convert chiral information present at the molecular level into enantiospecific macroscopic trajectories. Depending on the enantiomer in solution, the swimmers will move clockwise or anti-clockwise and the concept can also be used for the direct visualization of the degree of enantiomeric excess by analyzing the curvature of the trajectories.

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This article reports parents' perspectives on access to mental health services for their children enrolled in a state children's health insurance program (CHIP). Little has been published about mental health services utilization in states' CHIP programs. Focus groups with parents yielded many contextual factors, confirming previous reports about the importance of the primary care interface and cultural competence. In addition, the findings pointed to the importance of taking seriously parents' perception of severity of the child's problem, reducing administrative barriers to accessing treatment, promoting education about mental health to the community, and eliciting regular input from parents about system performance.

Autonomous swimmers have been intensively studied in recent years due to their numerous potential applications in many areas ranging from biomedicine to environmental remediation. Their motion is based either on different self-propulsion mechanisms or on the use of various external stimuli. Herein, the synergy between the ion flux around self-electrophoretic Mg/Pt Janus swimmers and an external magnetic field is proposed as an efficient alternative mechanism to power swimmers on the basis of the resulting Lorentz force. A strong magnetohydrodynamic effect is observed due to the orthogonal combination of magnetic field and spontaneous ionic currents, leading to an increase of the swimmer speed by up to 2 orders of magnitude. Furthermore, the trajectory of the self-propelled swimmers can be controlled by the orientation of the magnetic field, due to the presence of an additional torque force caused by a horizontal cation flux along the swimmer edges, resulting in predictable clockwise or anticlockwise motion. In addition, this effect is independent of the swimmer size, since a similar type of rotational motion is observed for macro- and microscale objects.