Subungual melanoma: Management in the modern era.

Subungual melanoma is a rare subtype of cutaneous melanoma that arises from the structures of the nail apparatus. It presents most commonly in older patients and at an advanced stage. A retrospective review of all patients with subungual melanoma in a single institution over a 15-year period was performed. In total, 54 patients were included (26 males, average age 62.9 years), of which 28 cases involved the upper limb. Median tumour thickness was 4.5 mm. Eighteen patients had lymph node metastasis at diagnosis, including 11 of 36 patients with positive sentinel lymph node biopsy. Median survival was 4.6 years. Subungual melanoma has a poor prognosis that is strongly associated with presence of nodal disease at diagnosis. Sentinel lymph node biopsy should be considered to determine stage and prognosis.

An FPGA-based instrumentation platform for use at deep cryogenic temperatures.

We describe the operation of a cryogenic instrumentation platform incorporating commercially available field-programmable gate arrays (FPGAs). The functionality of the FPGAs at temperatures approaching 4 K enables signal routing, multiplexing, and complex digital signal processing in close proximity to cooled devices or detectors within the cryostat. The performance of the FPGAs in a cryogenic environment is evaluated, including clock speed, error rates, and power consumption. Although constructed for the purpose of controlling and reading out quantum computing devices with low latency, the instrument is generic enough to be of broad use in a range of cryogenic applications.

Modular cryogenic interconnects for multi-qubit devices.

We have developed a modular interconnect platform for the control and readout of multiple solid-state qubits at cryogenic temperatures. The setup provides 74 filtered dc-bias connections, 32 control and readout connections with -3 dB frequency above 5 GHz, and 4 microwave feed lines that allow low loss (less than 3 dB) transmission 10 GHz. The incorporation of a radio-frequency interposer enables the platform to be separated into two printed circuit boards, decoupling the simple board that is bonded to the qubit chip from the multilayer board that incorporates expensive connectors and components. This modular approach lifts the burden of duplicating complex interconnect circuits for every prototype device. We report the performance of this platform at milli-Kelvin temperatures, including signal transmission and crosstalk measurements.

Raman phonon emission in a driven double quantum dot.

The compound semiconductor gallium-arsenide (GaAs) provides an ultra-clean platform for storing and manipulating quantum information, encoded in the charge or spin states of electrons confined in nanostructures. The absence of inversion symmetry in the zinc-blende crystal structure of GaAs however, results in a strong piezoelectric interaction between lattice acoustic phonons and qubit states with an electric dipole, a potential source of decoherence during charge-sensitive operations. Here we report phonon generation in a GaAs double quantum dot, configured as a single- or two-electron charge qubit, and driven by the application of microwaves via surface gates. In a process that is a microwave analogue of the Raman effect, phonon emission produces population inversion of the two-level system and leads to rapid decoherence of the qubit when the microwave energy exceeds the level splitting. Comparing data with a theoretical model suggests that phonon emission is a sensitive function of the device geometry.

Evaluation of a chronic disease management system for the treatment and management of diabetes in primary health care practices in Ontario: an observational study.

BACKGROUND: Computerized chronic disease management systems (CDMSs), when aligned with clinical practice guidelines, have the potential to effectively impact diabetes care. OBJECTIVE: The objective was to measure the difference between optimal diabetes care and actual diabetes care before and after the introduction of a computerized CDMS. METHODS: This 1-year, prospective, observational, pre/post study evaluated the use of a CDMS with a diabetes patient registry and tracker in family practices using patient enrolment models. Aggregate practice-level data from all rostered diabetes patients were analyzed. The primary outcome measure was the change in proportion of patients with up-to-date "ABC" monitoring frequency (i.e., hemoglobin A1c, blood pressure, and cholesterol). Changes in the frequency of other practice care and treatment elements (e.g., retinopathy screening) were also determined. Usability and satisfaction with the CDMS were measured. RESULTS: Nine sites, 38 health care providers, and 2,320 diabetes patients were included. The proportion of patients with up-to-date ABC (12%), hemoglobin A1c (45%), and cholesterol (38%) monitoring did not change over the duration of the study. The proportion of patients with up-to-date blood pressure monitoring improved, from 16% to 20%. Data on foot examinations, retinopathy screening, use of angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers, and documentation of self-management goals were not available or not up to date at baseline for 98% of patients. By the end of the study, attitudes of health care providers were more negative on the Training, Usefulness, Daily Practice, and Support from the Service Provider domains of the CDMS, but more positive on the Learning, Using, Practice Planning, CDMS, and Satisfaction domains. LIMITATIONS: Few practitioners used the CDMS, so it was difficult to draw conclusions about its efficacy. Simply giving health care providers a potentially useful technology will not ensure its use. CONCLUSIONS: This real-world evaluation of a web-based CDMS for diabetes failed to impact physician practice due to limited use of the system. PLAIN LANGUAGE SUMMARY: Patients and health care providers need timely access to information to ensure proper diabetes care. This study looked at whether a computer-based system at the doctor's office could improve diabetes management. However, few clinics and health care providers used the system, so no improvement in diabetes care was seen.

Dynamical steady States in driven quantum systems.

We derive dynamical equations for a driven, dissipative quantum system in which the environment-induced relaxation rate is comparable to the Rabi frequency, avoiding assumptions on the frequency dependence of the environmental coupling. When the environmental coupling varies significantly on the scale of the Rabi frequency, secular or rotating wave approximations break down. We avoid these approximations, yielding dynamical steady states which account for the interaction between driven quantum dots and their phonon environment. The theory, which is motivated by recent experimental observations, qualitatively and quantitatively describes the transition from asymmetric unsaturated resonances at weak driving to population inversion at strong driving.

Dispersive readout of a few-electron double quantum dot with fast RF gate sensors.

We report the dispersive charge-state readout of a double quantum dot in the few-electron regime using the in situ gate electrodes as sensitive detectors. We benchmark this gate sensing technique against the well established quantum point contact charge detector and find comparable performance with a bandwidth of ∼ 10 MHz and an equivalent charge sensitivity of ∼ 6.3 × 10(-3) e/sqrt[Hz]. Dispersive gate sensing alleviates the burden of separate charge detectors for quantum dot systems and promises to enable readout of qubits in scaled-up arrays.

Dental health in Iron Age Cambodia: Temporal variations with rice agriculture.

The dental health of two Cambodian Iron Age (500 BC to 500 AD) communities is interpreted through an analysis of advanced wear, caries, periapical lesions, and antemortem tooth loss (AMTL). The two communities, Phum Snay and Phum Sophy, just 40km apart, are temporally situated at a time of significant socio-political change prior to the establishment of Angkorian state rule. Dental pathology frequencies are compared between the two communities and with other prehistoric sites throughout Southeast Asia to determine whether dental health was affected by socio-political changes and the intensification of rice agriculture that also occurred at this time. The people of Snay and Sophy, despite their proximity, were found to exhibit significant differences in dental health. When subdivided by age and sex, Sophy older age class teeth had significantly more advanced wear, and older females had more periapical lesions, while the Phum Snay older age dentitions had significantly more AMTL. Caries rates were similar between the samples. When compared in the broader context of the Iron Age in prehistoric Southeast Asia, both Phum Snay and Phum Sophy suggest a trend of declining dental health during the period prior to the rise of the Angkorian state.

Cryogenic high-frequency readout and control platform for spin qubits.

We have developed a cryogenic platform for the control and readout of spin qubits that comprises a high density of dc and radio frequency sample interconnects based on a set of coupled printed circuit boards. The modular setup incorporates 24 filtered dc lines, 14 control and readout lines with bandwidth from dc to above 6 GHz, and 2 microwave connections for excitation to 40 GHz. We report the performance of this platform, including signal integrity and crosstalk measurements and discuss design criteria for constructing sample interconnect technology needed for multi-qubit devices.

Proceedings of the DMS medical ethics symposium.

This article presents the proceedings of a symposium on medical ethics held at the Royal Centre for Defence Medicine in October 2010. The nature of current operations continually generates challenging ethical problems, many of which are unique to the military environment. This article is intended to generate a debate on these difficult issues and readers are encouraged to contribute to this debate by emailing the Editor.

Exchange control of nuclear spin diffusion in a double quantum dot.

The influence of gate-controlled two-electron exchange on the relaxation of nuclear polarization in small ensembles (N∼10(6)) of nuclear spins is examined in a GaAs double quantum dot system. Waiting in the (2,0) charge configuration, which has large exchange splitting, reduces the nuclear diffusion rate compared to that of the (1,1) configuration. Matching exchange to Zeeman splitting significantly increases the nuclear diffusion rate.

Rapid single-shot measurement of a singlet-triplet qubit.

We report repeated single-shot measurements of the two-electron spin state in a GaAs double quantum dot. The readout allows measurement with a fidelity above 90% with a approximately 7 micros cycle time. Hyperfine-induced precession between singlet and triplet states of the two-electron system are directly observed, as nuclear Overhauser fields are quasistatic on the time scale of the measurement cycle. Repeated measurements on millisecond to second time scales reveal the evolution of the nuclear environment.

Measurement of temporal correlations of the overhauser field in a double quantum dot.

In quantum dots made from materials with nonzero nuclear spins, hyperfine coupling creates a fluctuating effective Zeeman field (Overhauser field) felt by electrons, which can be a dominant source of spin qubit decoherence. We characterize the spectral properties of the fluctuating Overhauser field in a GaAs double quantum dot by measuring correlation functions and power spectra of the rate of singlet-triplet mixing of two separated electrons. Away from zero field, spectral weight is concentrated below 10 Hz, with approximately 1/f2 dependence on frequency f. This is consistent with a model of nuclear spin diffusion, and indicates that decoherence can be largely suppressed by echo techniques.

Suppressing spin qubit dephasing by nuclear state preparation.

Coherent spin states in semiconductor quantum dots offer promise as electrically controllable quantum bits (qubits) with scalable fabrication. For few-electron quantum dots made from gallium arsenide (GaAs), fluctuating nuclear spins in the host lattice are the dominant source of spin decoherence. We report a method of preparing the nuclear spin environment that suppresses the relevant component of nuclear spin fluctuations below its equilibrium value by a factor of approximately 70, extending the inhomogeneous dephasing time for the two-electron spin state beyond 1 microsecond. The nuclear state can be readily prepared by electrical gate manipulation and persists for more than 10 seconds.

Analysis of the initial 100 scans from the first CT scanner deployed by the British armed forces in a land environment.

AIMS: To examine usage of the first CT scanner installed in a UK field hospital, BMH Shaibah, over a 13 month period. METHODS: All request forms and reports for the first 100 studies were analysed retrospectively. RESULTS: An average of 7.7 scans per month was performed. Trauma was the most common indication followed by urinary symptoms and headache. Significant pathology was diagnosed in many cases. CONCLUSION: A deployed CT scanner can make a significant contribution to the capability of a field hospital, shaping both the management and disposal of patients. A more easily deployable scanner will be needed in future.

Shot-noise signatures of 0.7 structure and spin in a quantum point contact.

We report simultaneous measurement of shot noise and dc transport in a quantum point contact as a function of source-drain bias, gate voltage, and in-plane magnetic field. Shot noise at zero field exhibits an asymmetry related to the 0.7 structure in conductance. The asymmetry in noise evolves smoothly into the symmetric signature of spin-resolved electron transmission at high field. Comparison to a phenomenological model with density-dependent level splitting yields good quantitative agreement.

Progress in silicon-based quantum computing.

We review progress at the Australian Centre for Quantum Computer Technology towards the fabrication and demonstration of spin qubits and charge qubits based on phosphorus donor atoms embedded in intrinsic silicon. Fabrication is being pursued via two complementary pathways: a 'top-down' approach for near-term production of few-qubit demonstration devices and a 'bottom-up' approach for large-scale qubit arrays with sub-nanometre precision. The 'top-down' approach employs a low-energy (keV) ion beam to implant the phosphorus atoms. Single-atom control during implantation is achieved by monitoring on-chip detector electrodes, integrated within the device structure. In contrast, the 'bottom-up' approach uses scanning tunnelling microscope lithography and epitaxial silicon overgrowth to construct devices at an atomic scale. In both cases, surface electrodes control the qubit using voltage pulses, and dual single-electron transistors operating near the quantum limit provide fast read-out with spurious-signal rejection.