Low-noise 0.8-0.96- and 0.96-1.12-THz superconductor-insulator-superconductor mixers for the Herschel Space Observatory

Heterodyne mixers incorporating Nb SIS junctions and NbTiN-SiO/sub 2/-Al microstrip tuning circuits offer the lowest reported receiver noise temperatures to date in the 0.8-0.96- and 0.96-1.12-THz frequency bands. In particular, improvements in the quality of the NbTiN ground plane of the SIS devices' on-chip microstrip tuning circuits have yielded significant improvements in the sensitivity of the 0.96-1.12-THz mixers relative to previously presented results. Additionally, an optimized RF design incorporating a reduced-height waveguide and suspended stripline RF choke filter offers significantly larger operating bandwidths than were obtained with mixers that incorporated full-height waveguides near 1 THz. Finally, the impact of junction current density and quality on the performance of the 0.8-0.96-THz mixers is discussed and compared with measured mixer sensitivities, as are the relative sensitivities of the 0.8-0.96- and 0.96-1.12-THz mixers

Generation of degenerate, factorizable, pulsed squeezed light at telecom wavelengths

We characterize a periodically poled KTP crystal that produces an entangled, two-mode, squeezed state with orthogonal polarizations, nearly identical, factorizable frequency modes, and few photons in unwanted frequency modes. We focus the pump beam to create a nearly circular joint spectral probability distribution between the two modes. After disentangling the two modes, we observe Hong-Ou-Mandel interference with a raw (background corrected) visibility of 86 % (95 %) when an 8.6 nm bandwidth spectral filter is applied. We measure second order photon correlations of the entangled and disentangled squeezed states with both superconducting nanowire single-photon detectors and photon-number-resolving transition-edge sensors. Both methods agree and verify that the detected modes contain the desired photon number distributions

Sideband separating mixer for 600-720 GHz

The ALMA Band 9 receiver cartridge (600-720 GHz) based on Dual Sideband (DSB) superconductor-insulatorsuperconductor (SIS) mixer is currently in full production. In the case of spectral line observations, the integration time to reach a certain signal-to-noise level can be reduced by about a factor of two by rejecting an unused sideband. The goal is to upgrade the current ALMA band 9 cartridge to a full dual-polarization sideband separating (2SB) capability, with minimal-cost upgrade path. A new compact and modular sideband separating mixer was designed, and a prototype manufactured. The individual SIS mixer devices in the 2SB block are implemented as conventional Band 9 DSB mixers, so that existing devices can be reused and tested individually. Any ALMA DSB developments contribute to the 2SB upgrade. The first experimental results demonstrate noise temperature from 300K to 500K over 80% of the band, which will be improved to fit the ALMA requirements. Nevertheless, the frequency response for 2SB is the same as for DSB, showing that the RF design is still valid, even with different SIS mixer devices. The quality of the RF and IF design is confirmed by a sideband rejection ratio of about 15 dB, which is within the ALMA spec (>10dB )

Feasibility of trial procedures for a randomised controlled trial of a community based group exercise intervention for falls prevention for visually impaired older people: the VIOLET study

Background Visually impaired older people (VIOP) have a higher risk of falling than their sighted peers, and are likely to avoid physical activity. The aim was to adapt the existing Falls Management Exercise (FaME) programme for VIOP, delivered in the community, and to investigate the feasibility of conducting a definitive randomised controlled trial (RCT) of this adapted intervention. Methods Two-centre randomised mixed methods pilot trial and economic evaluation of the adapted group-based FaME programme for VIOP versus usual care. A one hour exercise programme ran weekly over 12 weeks at the study sites (Newcastle and Glasgow), delivered by third sector (voluntary and community) organisations. Participants were advised to exercise at home for an additional two hours over the week. Those randomised to the usual activities group received no intervention. Outcome measures were completed at baseline, 12 and 24 weeks. The potential primary outcome was the Short Form Falls Efficacy Scale – International (SFES-I). Participants’ adherence was assessed by reviewing attendance records and self-reported compliance to the home exercises. Adherence with the course content (fidelity) by instructors was assessed by a researcher. Adverse events were collected in a weekly phone call. Results Eighteen participants, drawn from community-living VIOP were screened; 68 met the inclusion criteria; 64 participants were randomised with 33 allocated to the intervention and 31 to the usual activities arm. 94% of participants provided data at the 12 week visit and 92% at 24 weeks. Adherence was high. The intervention was found to be safe with 76% attending nine or more classes. Median time for home exercise was 50 min per week. There was little or no evidence that fear of falling, balance and falls risk, physical activity, emotional, attitudinal or quality of life outcomes differed between trial arms at follow-up. Conclusions The intervention, FaME, was implemented successfully for VIOP and all progression criteria for a main trial were met. The lack of difference between groups on fear of falling was unsurprising given it was a pilot study but there may have been other contributory factors including suboptimal exercise dose and apparent low risk of falls in participants. These issues need addressing for a future trial

Demographic, clinical and antibody characteristics of patients with digital ulcers in systemic sclerosis: data from the DUO Registry

OBJECTIVES: The Digital Ulcers Outcome (DUO) Registry was designed to describe the clinical and antibody characteristics, disease course and outcomes of patients with digital ulcers associated with systemic sclerosis (SSc). METHODS: The DUO Registry is a European, prospective, multicentre, observational, registry of SSc patients with ongoing digital ulcer disease, irrespective of treatment regimen. Data collected included demographics, SSc duration, SSc subset, internal organ manifestations, autoantibodies, previous and ongoing interventions and complications related to digital ulcers. RESULTS: Up to 19 November 2010 a total of 2439 patients had enrolled into the registry. Most were classified as either limited cutaneous SSc (lcSSc; 52.2%) or diffuse cutaneous SSc (dcSSc; 36.9%). Digital ulcers developed earlier in patients with dcSSc compared with lcSSc. Almost all patients (95.7%) tested positive for antinuclear antibodies, 45.2% for anti-scleroderma-70 and 43.6% for anticentromere antibodies (ACA). The first digital ulcer in the anti-scleroderma-70-positive patient cohort occurred approximately 5 years earlier than the ACA-positive patient group. CONCLUSIONS: This study provides data from a large cohort of SSc patients with a history of digital ulcers. The early occurrence and high frequency of digital ulcer complications are especially seen in patients with dcSSc and/or anti-scleroderma-70 antibodies

Sideband separating mixer for 600-720 GHz

The ALMA Band 9 receiver cartridge (600-720 GHz) based on Dual Sideband (DSB) superconductor-insulatorsuperconductor (SIS) mixer is currently in full production. In the case of spectral line observations, the integration time to reach a certain signal-to-noise level can be reduced by about a factor of two by rejecting an unused sideband. The goal is to upgrade the current ALMA band 9 cartridge to a full dual-polarization sideband separating (2SB) capability, with minimal-cost upgrade path. A new compact and modular sideband separating mixer was designed, and a prototype manufactured. The individual SIS mixer devices in the 2SB block are implemented as conventional Band 9 DSB mixers, so that existing devices can be reused and tested individually. Any ALMA DSB developments contribute to the 2SB upgrade. The first experimental results demonstrate noise temperature from 300K to 500K over 80% of the band, which will be improved to fit the ALMA requirements. Nevertheless, the frequency response for 2SB is the same as for DSB, showing that the RF design is still valid, even with different SIS mixer devices. The quality of the RF and IF design is confirmed by a sideband rejection ratio of about 15 dB, which is within the ALMA spec (>10dB ).Kavli Institute of NanoscienceApplied Science

First Results of the Sideband-Separating Mixer for ALMA Band 9 Upgrade

Last year, the design and implementation details of a new modular sideband-separating mixer block, intended as an upgrade for the current single-ended ALMA Band 9 mixers, were presented at this conference. In high-frequency observation bands like ALMA Band 9 (600-720 GHz), which is strongly influenced by atmospheric noise, employment of sideband separating mixers can reduce, by roughly a factor of two, the integration time needed to reach a certain signal-to-noise ratio for spectral line observations. Alternatively, in the same integration time, a sufficiently larger selection of sources can be accessed. Two prototype mixer blocks were produced on a micro milling machine, and equipped with production Band 9 SIS mixer devices that have independently been tested in double-sideband mode. Here, we present the results of the first measurements, notably, the noise temperature, image rejection, LO pumping balance and IF response. We also present in detail a procedure of the image rejection ratio measurement, which is fast and can be used for single sideband mixers, so that a second IF chain is not required

Sideband Separating Mixer for 600-720 GHz

The ALMA Band 9 receiver cartridge (600-720 GHz) based on Dual Sideband (DSB) superconductor-insulator-superconductor (SIS) mixer is currently in full production. In the case of spectral line observations, the integration time to reach a certain signal-to-noise level can be reduced by about a factor of two by rejecting an unused sideband. The goal is to upgrade the current ALMA band 9 cartridge to a full dual-polarization sideband separating (2SB) capability, with minimal-cost upgrade path. A new compact and modular sideband separating mixer was designed, and a prototype manufactured. The individual SIS mixer devices in the 2SB block are implemented as conventional Band 9 DSB mixers, so that existing devices can be reused and tested individually. Any ALMA DSB developments contribute to the 2SB upgrade. The first experimental results demonstrate noise temperature from 300K to 500K over 80% of the band, which will be improved to fit the ALMA requirements. Nevertheless, the frequency response for 2SB is the same as for DSB, showing that the RF design is still valid, even with different SIS mixer devices. The quality of the RF and IF design is confirmed by a sideband rejection ratio of about 15 dB, which is within the ALMA spec (>10dB)