Fidelity benchmarks for two-qubit gates in silicon.

Universal quantum computation will require qubit technology based on a scalable platform1, together with quantum error correction protocols that place strict limits on the maximum infidelities for one- and two-qubit gate operations2,3. Although various qubit systems have shown high fidelities at the one-qubit level4-10, the only solid-state qubits manufactured using standard lithographic techniques that have demonstrated two-qubit fidelities near the fault-tolerance threshold6 have been in superconductor systems. Silicon-based quantum dot qubits are also amenable to large-scale fabrication and can achieve high single-qubit gate fidelities (exceeding 99.9 per cent) using isotopically enriched silicon11,12. Two-qubit gates have now been demonstrated in a number of systems13-15, but as yet an accurate assessment of their fidelities using Clifford-based randomized benchmarking, which uses sequences of randomly chosen gates to measure the error, has not been achieved. Here, for qubits encoded on the electron spin states of gate-defined quantum dots, we demonstrate Bell state tomography with fidelities ranging from 80 to 89 per cent, and two-qubit randomized benchmarking with an average Clifford gate fidelity of 94.7 per cent and an average controlled-rotation fidelity of 98 per cent. These fidelities are found to be limited by the relatively long gate times used here compared with the decoherence times of the qubits. Silicon qubit designs employing fast gate operations with high Rabi frequencies16,17, together with advanced pulsing techniques18, should therefore enable much higher fidelities in the near future.

Integrated silicon qubit platform with single-spin addressability, exchange control and single-shot singlet-triplet readout.

Silicon quantum dot spin qubits provide a promising platform for large-scale quantum computation because of their compatibility with conventional CMOS manufacturing and the long coherence times accessible using 28Si enriched material. A scalable error-corrected quantum processor, however, will require control of many qubits in parallel, while performing error detection across the constituent qubits. Spin resonance techniques are a convenient path to parallel two-axis control, while Pauli spin blockade can be used to realize local parity measurements for error detection. Despite this, silicon qubit implementations have so far focused on either single-spin resonance control, or control and measurement via voltage-pulse detuning in the two-spin singlet-triplet basis, but not both simultaneously. Here, we demonstrate an integrated device platform incorporating a silicon metal-oxide-semiconductor double quantum dot that is capable of single-spin addressing and control via electron spin resonance, combined with high-fidelity spin readout in the singlet-triplet basis.

Design and characterization of a dead-time regime enhanced early photon projection imaging system.

Scattering of visible and near-infrared light in biological tissue reduces spatial resolution for imaging of tissues thicker than 100 µm. In this study, an optical projection imaging system is presented and characterized that exploits the dead-time characteristics typical of photon counting modules based on single photon avalanche diodes (SPADs). With this system, it is possible to attenuate the detection of more scattered late-arriving photons, such that detection of less scattered early-arriving photons can be enhanced with increased light intensity, without being impeded by the maximum count rate of the SPADs. The system has the potential to provide transmittance-based anatomical information or fluorescence-based functional information (with slight modification in the instrumentation) of biological samples with improved resolution in the mesoscopic domain (0.1-2 cm). The system design, calibration, stability, and performance were evaluated using simulation and experimental phantom studies. The proposed system allows for the detection of very-rare early-photons at a higher frequency and with a better signal-to-noise ratio. The experimental results demonstrated over a 3.4-fold improvement in the spatial resolution using early photon detection vs. conventional detection, and a 1000-fold improvement in imaging time using enhanced early detection vs. conventional early photon detection in a 4-mm thick phantom with a tissue-equivalent absorption coefficient of µa = 0.05 mm-1 and a reduced scattering coefficient of µs' = 5 mm-1.

Diurnal physiological and immunological responses to a 10-km run in highly trained athletes in an environmentally controlled condition of 6 °C.

PURPOSE: The Clara cell protein CC16, secreted from Clara cells in the lung, is discussed as a potential biomarker for toxic effects on the airways. An increased concentration of CC16 in serum may be caused by increased permeability of the lungs. To investigate the changes in P-CC16 in response to an intense exercise bout performed at different times of day (9 am and 4 pm) of highly trained individuals. METHOD: Using a crossover randomized design, 8 runners (mean VO2max 71 ml kg-1 min-1, SD 6) performed a 10-km time trial run, at 9 am and 4 pm, in an environmental chamber set at 6 °C. Lung function tests and blood sampling occurred at baseline, immediately post and 1 h post time trial. RESULT: Diurnal differences (P < 0.05) were found for blood neutrophil and lymphocyte counts; with higher values at 4 pm. P-CC16 was higher at the pre- and post-trial time point at 9 am compared to 4 pm. Lung function was not different between or within trials. CONCLUSION: Morning trial in cold condition caused more physiological strain compared to the same trial in the evening. However, this extra stress caused by zeitgebers could be a useful strategy for athletes, coaches, and general population to improve their running performance and protect their health in cold conditions in the long-term plan.

Effects of ventilator vs manual hyperinflation in adults receiving mechanical ventilation: a systematic review of randomised clinical trials.

BACKGROUND: Ventilator hyperinflation (VHI) and manual hyperinflation (MHI) are thought to improve secretion clearance, atelectasis and oxygenation in adults receiving mechanical ventilation. However, to the authors' knowledge, a systematic review of their relative effectiveness has not been undertaken previously. OBJECTIVE: To determine whether VHI is more effective than MHI for the improvement of clinical outcomes in adults receiving mechanical ventilation. DATA SOURCES: The electronic databases PubMed, Cochrane Library, CINHAL Plus, Wiley Online Library, ScienceDirect and PEDro were searched from January 1993 until August 2013. OpenGrey, the metaRegister of Controlled Trials (mRCT) and the reference lists of all potentially relevant studies were also searched. STUDY ELIGIBILITY CRITERIA: Full English reports of randomised clinical trials comparing at least one effect of VHI and MHI in adults receiving mechanical ventilation. STUDY SYNTHESIS AND APPRAISAL: Included studies were appraised using the Cochrane risk of bias tool. The findings were synthesised using a purely qualitative approach. RESULTS: All four included studies reported no significant differences in sputum wet weight, dynamic and static pulmonary compliance, oxygenation and cardiovascular stability between VHI and MHI. LIMITATIONS: All of the included studies had considerable limitations related to the protocols, equipment, participants and outcome measures. Furthermore, the overall risk of bias was judged to be high for three studies and unclear for one study. CONCLUSION: Only four studies, all of which had a high or unclear risk of bias and significant additional limitations, have compared the effects of VHI and MHI in adults receiving mechanical ventilation. As such, further research in this area is clearly warranted.

Growth hormone secretion is correlated with neuromuscular innervation rather than motor neuron number in early-symptomatic male amyotrophic lateral sclerosis mice.

GH deficiency is thought to be involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). However, therapy with GH and/or IGF-I has not shown benefit. To gain a better understanding of the role of GH secretion in ALS pathogenesis, we assessed endogenous GH secretion in wild-type and hSOD1(G93A) mice throughout the course of ALS disease. Male wild-type and hSOD1(G93A) mice were studied at the presymptomatic, onset, and end stages of disease. To assess the pathological features of disease, we measured motor neuron number and neuromuscular innervation. We report that GH secretion profile varies at different stages of disease progression in hSOD1(G93A) mice; compared with age-matched controls, GH secretion is unchanged prior to the onset of disease symptoms, elevated at the onset of disease symptoms, and reduced at the end stage of disease. In hSOD1(G93A) mice at the onset of disease, GH secretion is positively correlated with the percentage of neuromuscular innervation but not with motor neuron number. Moreover, this occurs in parallel with an elevation in the expression of muscle IGF-I relative to controls. Our data imply that increased GH secretion at symptom onset may be an endogenous endocrine response to increase the local production of muscle IGF-I to stimulate reinnervation of muscle, but that in the latter stages of disease this response no longer occurs.

Distinct roles for fibroblast growth factor signaling in cerebellar development and medulloblastoma.

Cerebellar granule neurons are the most abundant neurons in the brain, and a critical element of the circuitry that controls motor coordination and learning. In addition, granule neuron precursors (GNPs) are thought to represent cells of origin for medulloblastoma, the most common malignant brain tumor in children. Thus, understanding the signals that control the growth and differentiation of these cells has important implications for neurobiology and neurooncology. Our previous studies have shown that proliferation of GNPs is regulated by Sonic hedgehog (Shh), and that aberrant activation of the Shh pathway can lead to medulloblastoma. Moreover, we have demonstrated that Shh-dependent proliferation of GNPs and medulloblastoma cells can be blocked by basic fibroblast growth factor (bFGF). But while the mitogenic effects of Shh signaling have been confirmed in vivo, the inhibitory effects of bFGF have primarily been studied in culture. Here, we demonstrate that mice lacking FGF signaling in GNPs exhibit no discernable changes in GNP proliferation or differentiation. In contrast, activation of FGF signaling has a potent effect on tumor growth: treatment of medulloblastoma cells with bFGF prevents them from forming tumors following transplantation, and inoculation of tumor-bearing mice with bFGF markedly inhibits tumor growth in vivo. These results suggest that activators of FGF signaling may be useful for targeting medulloblastoma and other Shh-dependent tumors.

The effect of cereal type and enzyme addition on pig performance, intestinal microflora, and ammonia and odour emissions.

Two 2 × 2 factorial experiments were conducted to investigate the interaction between cereal type (wheat v. barley) and exogenous enzyme supplementation (with or without) on odour and ammonia emissions (experiment 1) and growth performance (experiment 2) in grower-finisher pigs. The enzyme supplement used contained endo-1, 3 (4) - ß- glucanase (EC 3.2.1.6) and endo-1, 4 - ß-xylanase (E.C 3.2.1.8). The diets were formulated to contain similar levels of net energy (9.8 MJ/kg) and lysine (10.0 g/kg). The experimental treatments were as follows: (1) wheat-based diet, (2) wheat-based diet containing a ß-glucanase and ß-xylanase mixed enzyme supplement, (3) barley-based diet and (4) barley-based diet containing a ß-glucanase and ß-xylanase mixed enzyme supplement. In experiment 1, the diets were offered to the pigs for 23 days in sealed pens (eight pigs per pen) and this was repeated four times (n = 4). Odour and ammonia emissions were measured on days 9, 11, 14, 16, 21 and 23 of each replicate period. Odour samples were collected in 20-l Nalophan bags and analysed for odour concentration using an ECOMA Yes/No Olfactometer. Ammonia concentrations in the ventilation air were measured using Dräger tubes. In experiment 2, 220 pigs were group fed in mixed sex pens using single-space feeders (11 pigs per feeder, six boars and five gilts) (n = 5). There was a cereal × enzyme interaction in odour emission rates, ammonia emissions and selected microbial populations in the caecum and colon (P < 0.05). The addition of an enzyme supplement to the barley-based diet increased both odour and ammonia emission, however the addition of an enzyme to the wheat-based diet decreased ammonia emission rates and had no effect on odour emission. Pigs offered the unsupplemented barley-based diet had a significantly (P < 0.05) lower population of Enterobacteriaceae spp. and a higher population of Bifidobacteria spp. compared with enzyme-supplemented barley diets. However, there was no effect of enzyme supplementation in wheat-based diets. In the performance experiment, neither cereal type nor enzyme inclusion had an effect on pig performance or carcass characteristics. In conclusion, the inclusion of an enzyme mix to barley-based diets increased odour and ammonia emissions, while the addition of an enzyme mix to wheat-based diets decreased ammonia emissions.

Delta 9-tetrahydrocannabinol induces the apoptotic pathway in cultured cortical neurones via activation of the CB1 receptor.

Delta 9-tetrahydrocannabinol, the principal psychoactive component of marijuana, exerts a variety of effects on the CNS, including impaired cognitive function and neurobehavioural deficits. The mechanisms underlying these neuronal responses to tetrahydrocannabinol are unclear but may involve alterations in neuronal viability. Tetrahydrocannabinol has been shown to influence neuronal survival but the role of the cannabinoid receptors in the regulation of neuronal viability has not been fully clarified. In this study we demonstrate that tetrahydrocannabinol promotes the release of cytochrome c, activates caspase-3, promotes cleavage of the DNA repair enzyme poly-ADP ribose polymerase and induces DNA fragmentation in cultured cortical neurones. These effects of tetrahydrocannabinol were completely abrogated by the CB(1) receptor antagonist AM-251. The findings of this study demonstrate that tetrahydrocannabinol induces apoptosis in cortical neurones in a manner involving the CB1 subtype of cannabinoid receptor.

Genetic testing, Alzheimer disease, and long-term care insurance.

Patients with Alzheimer Disease (AD) often need long-term care, which is poorly covered by private or governmental health insurance. Private long-term care (LTC) insurance is increasingly being marketed to provide some financial support for long term care. LTC insurance does cover AD, but the insurers will not sell policies to people who have already been diagnosed with AD. As a result, LTC insurance might be particularly attractive to individuals who are at heightened risk for developing AD. This makes the issues surrounding predictive genetic testing for AD and the use of test results in determining insurance premiums and eligibility of great concern to patients, clinicians, insurers, ethicists, and patient advocate groups. The paper examines the complexities of these issues.

Harvesting in discrete-time predator-prey systems.

Fisheries for assemblages of interacting species with seasonal recruitment occur throughout temperate and boreal regions of the world ocean. Such systems are conveniently modeled within a difference-equation framework. Here, we examine the dynamic behavior of discrete-time models for an exploited predator-prey system. We contrast the dynamic properties of an aggregate production model and an age-structured model in which recruitment and mortality are explicitly considered. The joint effects of harvesting and interspecific interactions on the stability of the system are defined and contrasted with results for single species systems. We demonstrate that harvesting is a potentially stabilizing factor in the production model and in an age-structured model in which juveniles are harvested and that the relative magnitude of the interaction between predator and prey strongly affects the exploitation levels at which stabilization occurs. In contrast, harvesting is potentially destabilizing (i.e., results in complex dynamics) in an age-structured model with harvesting of adults only; again, the magnitude of the interaction determines the stability boundaries, with stronger interactions leading to a broader range of stable parameter space. In both the aggregate production model and the age-structured model with harvesting of juvenile predator and prey, exploitation effectively reduces the intrinsic rate of increase of the populations; for prey, this effect is amplified by high predation mortality rates. Sustainable levels of exploitation for both predators and prey are lower for the case where juveniles are harvested. Predators and resource harvesters can be viewed as competitors for the prey, and sustainable harvest levels are directly affected by the magnitude of predation mortality. These considerations expand the scope of issues to be resolved in fishery management to include factors such as trade-offs between mean yield and the potential for intrinsic variability and the role of predator-prey interactions in shaping the dynamics of exploited systems.

Interdecadal heterogeneity in mitochondrial DNA of Atlantic haddock (Melanogrammus aeglefinus) from Georges Bank.

Atlantic haddock of Georges Bank are characterized by large fluctuations in population size and a recent collapse of the commercial fishery. DNA extracted from dried scales of Georges Bank haddock, archived by the U.S. National Marine Fisheries Service (NMFS), reveals significant heterogeneity in frequencies of four mitochondrial DNA control region haplotypes between 1975 and 1985 cohorts. Several processes may be responsible for this temporal variation, the most attractive hypothesis being that haddock from other geographic regions episodically contribute to the Georges Bank gene pool. Thus, the population of haddock spawning on Georges Bank may not be genetically discrete and, with respect to Atlantic haddock, Georges Bank may not be viewed as a closed system.

A review of studies of heavy users of psychiatric services.

OBJECTIVES: This paper reviews studies of patients who are heavy users of psychiatric services and identifies areas in which further research and evaluation are indicated. METHODS: Extensive searches were conducted of the English language psychiatric and psychological literature before 1994. Important references from initially identified studies were followed up. More than 200 articles were reviewed, 72 of which are described in this review. The 72 papers were selected because they dealt with three questions: What is heavy service use? What patient characteristics contribute to it? What service delivery characteristics contribute to it? RESULTS AND CONCLUSIONS: Criteria for identifying and defining heavy users of psychiatric services vary among studies. Few studies of heavy service users have attempted to examine use of all psychiatric services, both inpatient and community based. In most studies, 10 to 30 percent of patients are identified as heavy users, those who utilize between 50 and 80 percent of service resources. This group consists of a constantly changing cohort of patients who generally have psychotic illnesses as well as comorbid personality disorders and high levels of drug and alcohol misuse. Few studies have examined social issues such as isolation, homelessness, and social support, although these factors appear to contribute significantly to heavy service use. Few attempts have been made to define heavy-user groups in fiscal terms. More research on heavy users of psychiatric services is clearly needed to improve providers' ability to plan appropriately targeted mental health services for this disabled group of patients who use expensive resources.

Heavy utilization of inpatient and outpatient services in a public mental health service.

OBJECTIVE: The purpose of the study was to develop a descriptive profile of heavy users of services in the South Australian Mental Health Services. METHODS: Case notes for 50 heavy users were reviewed to obtain demographic and diagnostic information and data on service use over a three-year period. To supplement and verify this information, 35 of the patients were given structured interviews. RESULTS: The mean age of the 50 patients was 34.9 years, and there was a slight predominance of females. Most patients had never married and had been unemployed for a long time. All had a low income. The mean number of years of education was ten. The group was seriously disabled by psychiatric illness. The most common diagnosis was schizophrenia, followed by schizoaffective disorder and bipolar disorder. Comorbid axis I disorder and personality disorder or physical illness was common. Drug and alcohol abuse often complicated patient management and patients' ability to live successfully in the community. The average annual cost per patient was $13,598 (Australian), largely from inpatient care. CONCLUSIONS: This study contributes to an emerging global profile of the heavy service user. Such a profile may help service systems identify patients in this subgroup and target management strategies to these often very disadvantaged and challenging patients.