Non-contact method for measurement of the microwave conductivity of graphene

We report a non-contact method for conductivity and sheet resistance measurements of graphene samples using a high Q microwave dielectric resonator perturbation technique, with the aim of fast and accurate measurement of microwave conductivity and sheet resistance of monolayer and few layers graphene samples. The dynamic range of the microwave conductivity measurements makes this technique sensitive to a wide variety of imperfections and impurities and can provide a rapid non-contacting characterisation method. Typically the graphene samples are supported on a low-loss dielectric substrate, such as quartz, sapphire or SiC. This substrate is suspended in the near-field region of a small high Q sapphire puck microwave resonator. The presence of the graphene perturbs both centre frequency and Q value of the microwave resonator. The measured data may be interpreted in terms of the real and imaginary components of the permittivity, and by calculation, the conductivity and sheet resistance of the graphene. The method has great sensitivity and dynamic range. Results are reported for graphene samples grown by three different methods: reduced graphene oxide (GO), chemical vapour deposition (CVD) and graphene grown epitaxially on SiC. The latter method produces much higher conductivity values than the others.Comment: 8 pages, 2 figures and 2 table

Tunable coaxial cavity resonator for linear and nonlinear microwave characterization of superconducting wires

We discuss experimental results obtained using a tunable cylindrical coaxial cavity constituted by an outer Cu cylinder and an inner Pb-BSCCO wire. We have used this device for investigating the microwave response of the superconducting wire, both in the linear and nonlinear regimes. In particular, by tuning the different modes of the cavity to make them resonant at exactly harmonic frequencies, we have detected the power emitted by the superconducting inner wire at the second- and third-harmonic frequency of the driving field. The results obtained in the nonlinear regime, whether for the microwave surface impedance or the harmonic emission, are qualitatively accounted for considering intergrain fluxon dynamics. The use of this kind of device can be of strong interest to investigate and characterise wires of large dimensions to be used for implementing superconducting-based microwave devices.Comment: 14 pages, 6 embedded figures, accepted for publication in Supercond. Sci. Techno

Untangling free carrier and exciton dynamics in layered hybrid perovskites using ultrafast optical and terahertz spectroscopy

\ua9 2024 The Author(s). Published by IOP Publishing Ltd.Layered hybrid perovskites (LPKs) are promising as alternatives or additives to 3D metal halide perovskites for optoelectronic applications including photovoltaic cells, LEDs and lasers due to their increased stability. However, high exciton binding energies in these materials mean that excitons are the majority species under the operating conditions of many devices. Although the efficiency of devices that incorporate LPKs has been increasing, much is still unknown about the interplay of excitons and free charge-carriers in these materials, which is vital information for understanding how optoelectronic properties dictate device efficiency. In this work, we employ optical pump/THz probe spectroscopy (OPTP) and visible transient absorption spectroscopy (TAS) to analyse the optoelectronic properties and charge-carrier dynamics of phenylethylammonium lead iodide (PEA)2PbI4. By combining these techniques, we are able to disentangle the contributions from excitons and free charge-carriers. We observe fast cooling of free charge-carriers and exciton formation on a timescale of ∼400 fs followed by slower bimolecular recombination of residual free charge-carriers with a rate constant k 2 ∼ 109 cm3s−1. Excitons recombine via two monomolecular processes with lifetimes t 1 ∼ 11 ps and t2 ∼ 83 ps. Furthermore, we detect signatures of exciton-phonon coupling in the transient absorption kinetic traces. These findings provide new insight into the interplay between free charge-carriers and excitons as well as a possible mechanism to further understand the charge-carrier dynamics in LPKs

Micro-SQUIDs based on MgB2 nano-bridges for NEMS readout

We show the results obtained from the fabrication and characterisation of MgB2 loops with two nano-bridges as superconducting weak links. These ring structures are made to operate as superconducting quantum interference devices and are investigated as readout system for cryogenics NEMS resonators. The nano-constrictions are fabricated by EBL and ion beam milling. The SQUIDs are characterised at different temperatures and measurements of the noise levels have been performed. The devices show high critical current densities and voltage modulations under applied magnetic field, close to the critical temperatures

Social preference weights for treatments in Fabry disease in the UK : a discrete choice experiment

Abstract Objective: Fabry disease is a rare inherited lysosomal storage disorder caused by deficiency of α-galactosidase A. Effective enzyme replacement therapies are available that are administered intravenously. However, a new oral treatment is being developed as an alternative option for patients with amenable mutations. This study was designed to understand the value that people place on the different features of treatments for Fabry disease. Research design and methods: A discrete choice experiment (DCE) was designed to assess the importance of different aspects of treatments for Fabry disease. The attributes included overall survival, mode of administration, treatment related reactions, treatment related headaches and risk of antibody formation. Attributes were combined using a published orthogonal array into choice sets. A research panel was used to survey the UK general public. The mixed logit model was used to estimate strength of preference for the attributes and marginal rates of substitution (MRSs). Disutilities were estimated from the DCE data for changes in each attribute. Results: The sample (n = 506) was broadly representative of UK demographics. The logit model revealed that all attributes were significant predictors of choice. Participants were significantly more likely to choose a treatment which meant an increase in their life expectancy by 1 year (odds ratio = 1.574; 95% CI = 1.504–1.647) and significantly less likely to choose self-administered intravenous (IV) treatment compared to an every other day tablet (OR = 0.426 95% CI = 0.384–0.474). Estimated disutilities were −0.0543 (self-administered infusion), treatment related headaches 12 times a year (−0.0361) and infusion reactions six times a year (−0.0202). Conclusions: The survey revealed a significant preference for oral treatment compared with IV even in the context of a treatment that can extend overall survival. MRSs were used as a basis for estimating disutilities associated with changes in attribute levels which could be used to weight QALYs. It is possible that other important treatment attributes are missing from this research which may have provided further insights. It would also be useful to extend this research to include Fabry disease patients so their preferences can be assessed against the societal perspective

Plasma sTNFR1 and IL8 for prognostic enrichment in sepsis trials: a prospective cohort study.

BackgroundEnrichment strategies improve therapeutic targeting and trial efficiency, but enrichment factors for sepsis trials are lacking. We determined whether concentrations of soluble tumor necrosis factor receptor-1 (sTNFR1), interleukin-8 (IL8), and angiopoietin-2 (Ang2) could identify sepsis patients at higher mortality risk and serve as prognostic enrichment factors.MethodsIn a multicenter prospective cohort study of 400 critically ill septic patients, we derived and validated thresholds for each marker and expressed prognostic enrichment using risk differences (RD) of 30-day mortality as predictive values. We then used decision curve analysis to simulate the prognostic enrichment of each marker and compare different prognostic enrichment strategies.Measurements and main resultsAn admission sTNFR1 concentration > 8861 pg/ml identified patients with increased mortality in both the derivation (RD 21.6%) and validation (RD 17.8%) populations. Among immunocompetent patients, an IL8 concentration > 94 pg/ml identified patients with increased mortality in both the derivation (RD 17.7%) and validation (RD 27.0%) populations. An Ang2 level > 9761 pg/ml identified patients at 21.3% and 12.3% increased risk of mortality in the derivation and validation populations, respectively. Using sTNFR1 or IL8 to select high-risk patients improved clinical trial power and efficiency compared to selecting patients with septic shock. Ang2 did not outperform septic shock as an enrichment factor.ConclusionsThresholds for sTNFR1 and IL8 consistently identified sepsis patients with higher mortality risk and may have utility for prognostic enrichment in sepsis trials

Long-Term Effects From A School-Based Trial Comparing Interpersonal Psychotherapy-Adolescent Skills Training To Group Counseling

Adolescence represents a vulnerable developmental period for depression and an opportune time for prevention efforts. In this study, 186 adolescents with elevated depressive symptoms (M age = 14.01, SD = 1.22; 66.7% female; 32.2% racial minority) were randomized to receive either Interpersonal Psychotherapy–Adolescent Skills Training (IPT-AST; n = 95) delivered by research clinicians or group counseling (GC; n = 91) delivered by school counselors. We previously reported the short-term outcomes of this school-based randomized controlled trial: IPT-AST youth experienced significantly greater improvements in depressive symptoms and overall functioning through 6-month follow-up. Here, we present the long-term outcomes through 24 months postintervention. We examined differences in rates of change in depressive symptoms and overall functioning and differences in rates of depression diagnoses. Youth in both conditions showed significant improvements in depressive symptoms and overall functioning from baseline to 24-month follow-up, demonstrating the efficacy of school-based depression prevention programs. However, the two groups did not differ in overall rates of change or in rates of depression diagnoses from baseline to 24-month follow-up. Although IPT-AST demonstrated advantages over GC in the short term, these effects dissipated over long-term follow-up. Specifically, from 6- to 24-month follow-up, GC youth showed continued decreases in depressive symptoms, whereas IPT-AST youth showed a nonsignificant increase in symptoms. GC youth remained relatively stable in overall functioning, whereas IPT-AST youth experienced a small but statistically significant worsening in functioning. This study highlights the potential of school-based depression prevention efforts and the need for further research

The origins of the Selden map of China: scientific analysis of the painting materials and techniques using a holistic approach

Since the 'rediscovery' of the Selden map of China, an early seventeenth century map of Asia, in the Bodleian Library in Oxford, the importance of the map in our understanding of globalisation in the early seventeenth century has been recognised. One of the unresolved questions is the origin of the map. This paper addresses the question through material evidence provided by a holistic approach using a suite of complementary analytical techniques. The map was examined in situ and non-invasively by a remote spectral imaging instrument (PRISMS) modified for close range imaging, which was followed by a range of complementary techniques applied to a number of detached fragments, though most of the techniques are non-invasive and can be applied to the map directly in the future. The binding medium was found to be a gum, almost certainly gum Arabic, rather than the animal glue commonly used in Chinese paintings. Some of the pigments and their usage were found to be at odds with the common practice in paintings from China. The detection of gum Arabic, a binding medium used by the Europeans, South and West Asians and the use of a mixture of orpiment and indigo, commonly found in European, South and West Asian paintings gives further evidence on the unusual origins of this map. The likely detection of a basic copper chloride, such as atacamite, in the green areas suggests an influence from the South and West Asian rather than the European tradition. Detailed analysis of the various spectral bands of the spectral image cube along with visual inspection of the large scale colour image showed that the map was not fully planned at the beginning but rather painted in stages, at times by trial and error and that it was unfinished. A new hypothesis for the origin of the Selden map in Aceh Sumatra is proposed based on the new evidences

On waiting for something to happen

This paper seeks to examine two particular and peculiar practices in which the mediation of apparently direct encounters is made explicit and is systematically theorized: that of the psychoanalytic dialogue with its inward focus and private secluded setting, and that of theatre and live performance, with its public focus. Both these practices are concerned with ways in which “live encounters” impact on their participants, and hence with the conditions under which, and the processes whereby, the coming-together of human subjects results in recognizable personal or social change. Through the rudimentary analysis of two anecdotes, we aim to think these encounters together in a way that explores what each borrows from the other, the psychoanalytic in the theatrical, the theatrical in the psychoanalytic, figuring each practice as differently committed to what we call the “publication of liveness”. We argue that these “redundant” forms of human contact continue to provide respite from group acceptance of narcissistic failure in the post-democratic era through their offer of a practice of waiting

Prototyping of petalets for the Phase-II Upgrade of the silicon strip tracking detector of the ATLAS Experiment

In the high luminosity era of the Large Hadron Collider, the HL-LHC, the instantaneous luminosity is expected to reach unprecedented values, resulting in about 200 proton-proton interactions in a typical bunch crossing. To cope with the resultant increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The ITk consists of a silicon pixel and a strip detector and exploits the concept of modularity. Prototyping and testing of various strip detector components has been carried out. This paper presents the developments and results obtained with reduced-size structures equivalent to those foreseen to be used in the forward region of the silicon strip detector. Referred to as petalets, these structures are built around a composite sandwich with embedded cooling pipes and electrical tapes for routing the signals and power. Detector modules built using electronic flex boards and silicon strip sensors are glued on both the front and back side surfaces of the carbon structure. Details are given on the assembly, testing and evaluation of several petalets. Measurement results of both mechanical and electrical quantities are shown. Moreover, an outlook is given for improved prototyping plans for large structures.Comment: 22 pages for submission for Journal of Instrumentatio