Investigating the intrinsic noise limit of Dayem bridge NanoSQUIDs

NanoSQUIDs made from Nb thin films have been produced with nanometre loop sizes down to 200 nm, using weak-link junctions with dimensions less than 60 nm. These composite (W/Nb) single layer thin film devices, patterned by FIB milling, show extremely good low-noise performance ∼170 nΦ0 at temperatures between 5 and 8.5 K and can operate in rather high magnetic fields (at least up to 1 T). The devices produced so far have a limited operating temperature range, typically only 1–2 K. We have the goal of achieving operation at 4.2 K, to be compatible with the best SQUID series array (SSA) preamplifier available. Using the SSA to readout the nanoSQUIDs provides us with a means of investigating the intrinsic noise of the former. In this paper we report improved white noise levels of these nanoSQUIDs, enabling potential detection of a single electronic spin flip in a 1-Hz bandwidth. At low frequencies the noise performance is already limited by SSA preamplifier noise

Degenerate ground state and anomalous flux hysteresis in an YBa2Cu3O7 grain boundary r.f. SQUID

We report measurements of the flux hysteresis curves and trapped flux distribution in an YBa2Cu3O7 r.f. SQUID containing two closely spaced grain boundary Josephson junctions in parallel. Broadening of the flux distribution from T = 15 K to 30 K is followed by a bifurcation at T = 35 K which corresponds to a degenerate ground state. Above T ~ 40 K the bifurcation disappears, the flux distribution narrows significantly and small secondary loops appear in the hysteresis curves. This behaviour can be modelled qualitatively if we assume a temperature dependent second harmonic term in the current-phase relationship of the junctions.Comment: 10 pages, 7 figure

Microwave intermodulation distortion of MgB2 thin films

The two tone intermodulation arising in MgB2 thin films deposited in-situ by planar magnetron sputtering on sapphire substrates is studied. Samples are characterised using an open-ended dielectric puck resonator operating at 8.8 GHz. The experimental results show that the third order products increase with the two-tone input power with a slope ranging between 1.5 and 2.3. The behaviour can be understood introducing a mechanism of vortex penetration in grain boundaries as the most plausible source of non linearities in these films. This assumption is confirmed by the analysis of the field dependence of the surface resistance, that show a linear behaviour at all temperatures under test.Comment: 13 pages, 3 figures; to be published in Appl. Phys. Let

Preventing adolescents’ externalizing and internalizing symptoms : effects of the Penn Resiliency Program

This study reports secondary outcome analyses from a past study of the Penn Resiliency Program (PRP), a cognitive-behavioral depression prevention program for middle-school aged children. Middle school students (N = 697) were randomly assigned to PRP, PEP (an alternate intervention), or control conditions. Gillham et al., (2007) reported analyses examining PRP’s effects on average and clinical levels of depression symptoms. We examine PRP’s effects on parent-, teacher-, and self-reports of adolescents’ externalizing and broader internalizing (depression/anxiety, somatic complaints, and social withdrawal) symptoms over three years of follow-up. Relative to no intervention control, PRP reduced parent-reports of adolescents’ internalizing symptoms beginning at the first assessment after the intervention and persisting for most of the follow-up assessments. PRP also reduced parent-reported conduct problems relative to no-intervention. There was no evidence that the PRP program produced an effect on teacher- or self-report of adolescents’ symptoms. Overall, PRP did not reduce symptoms relative to the alternate intervention, although there is a suggestion of a delayed effect for conduct problems. These findings are discussed with attention to developmental trajectories and the importance of interventions that address common risk factors for diverse forms of negative outcomes.peer-reviewe

Development and Evaluation of a Pragmatic Measure of Adherence to Dialectical Behavior Therapy: The DBT Adherence Checklist for Individual Therapy

This paper presents two studies conducted to develop and evaluate a new pragmatic measure of therapist adherence to Dialectical Behavior Therapy (DBT): the DBT Adherence Checklist for Individual Therapy (DBT AC-I). Study 1 used item response analysis to select items from the gold standard DBT Adherence Coding Scale (DBT ACS) using archival data from 1271 DBT sessions. Items were then iteratively refined based on feedback from 33 target end-users to ensure relevance, usability, and understandability. Study 2 examined the psychometric properties of the DBT AC-I as a therapist self-report and observer-rated measure in 100 sessions from 50 therapist-client dyads, while also evaluating predictors of therapist accuracy in self-rated adherence. When used as a therapist self-report measure, concordance between therapist and observer ratings was at least moderate (AC1≥0.41) for all DBT AC-I items but overall concordance (ICC=0.09) as well as convergent (r=0.05) and criterion validity (AUC=0.54) with the DBT ACS were poor. Higher therapist accuracy was predicted by greater DBT knowledge and adherence as well as more severe client suicidal ideation. When used by trained observers, the DBT AC-I had excellent interrater reliability (ICC=0.93), convergent validity (r=0.90), and criterion validity (AUC=0.94). While therapists’ self-rated adherence on the DBT AC-I should not be assumed to reflect their actual adherence, some therapists may self-rate accurately. The DBT AC-I offers an effective and relatively efficient method of evaluating adherence to DBT when used by trained observers

Synthetic Compound Libraries Displayed on the Surface of Encoded Bacteriophage

AbstractWe describe a technology for attaching libraries of synthetic compounds to coat proteins of bacteriophage particles such that the identity of the chemical structure is encoded in the genome of the phage, analogous to peptides displayed on phage surfaces by conventional phage-display techniques. This format allows a library of synthetic compounds to be screened very efficiently as a single pool. Encoded phage serve as extremely robust reporters of the presence of each compound, providing exquisite sensitivity for identification of active compounds engaged in complex biological processes such as receptor-mediated endocytosis and transcytosis. To evaluate this approach, we constructed a library of 980 analogs of folic acid displayed on T7 phage, and demonstrated rapid identification of compounds that bind to folate receptor and direct endocytosis of associated phage particles into cells that express the targeted receptor

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