Pharmacological inhibition of STING reduces neuroinflammation-mediated damage post-traumatic brain injury

BACKGROUND AND PURPOSE

Traumatic brain injury (TBI) remains a major public health concern worldwide with unmet effective treatment. Stimulator of interferon genes (STING) and its downstream type-I interferon (IFN) signalling are now appreciated to be involved in TBI pathogenesis. Compelling evidence have shown that STING and type-I IFNs are key in mediating the detrimental neuroinflammatory response after TBI. Therefore, pharmacological inhibition of STING presents a viable therapeutic opportunity in combating the detrimental neuroinflammatory response after TBI.

EXPERIMENTAL APPROACH

This study investigated the neuroprotective effects of the small-molecule STING inhibitor n-(4-iodophenyl)-5-nitrofuran-2-carboxamide (C-176) in the controlled cortical impact mouse model of TBI in 10- to 12-week-old male mice. Thirty minutes post-controlled cortical impact surgery, a single 750-nmol dose of C-176 or saline (vehicle) was administered intravenously. Analysis was conducted 2 h and 24 h post-TBI.

KEY RESULTS

Mice administered C-176 had significantly smaller cortical lesion area when compared to vehicle-treated mice 24 h post-TBI. Quantitative temporal gait analysis conducted using DigiGait™ showed C-176 administration attenuated TBI-induced impairments in gait symmetry, stride frequency and forelimb stance width. C-176-treated mice displayed a significant reduction in striatal gene expression of pro-inflammatory cytokines Tnf-α, Il-1β and Cxcl10 compared to their vehicle-treated counterparts 2 h post-TBI.

CONCLUSION AND IMPLICATIONS

This study demonstrates the neuroprotective activity of C-176 in ameliorating acute neuroinflammation and preventing white matter neurodegeneration post-TBI. This study highlights the therapeutic potential of small-molecule inhibitors targeting STING for the treatment of trauma-induced inflammation and neuroprotective potential.

Deep phenotyping of the neuroimaging and skeletal features in KBG syndrome: a study of 53 patients and review of the literature

BACKGROUND

KBG syndrome is caused by haploinsufficiency of ANKRD11 and is characterised by macrodontia of upper central incisors, distinctive facial features, short stature, skeletal anomalies, developmental delay, brain malformations and seizures. The central nervous system (CNS) and skeletal features remain poorly defined.

METHODS

CNS and/or skeletal imaging were collected from molecularly confirmed individuals with KBG syndrome through an international network. We evaluated the original imaging and compared our results with data in the literature.

RESULTS

We identified 53 individuals, 44 with CNS and 40 with skeletal imaging. Common CNS findings included incomplete hippocampal inversion and posterior fossa malformations; these were significantly more common than previously reported (63.4% and 65.9% vs 1.1% and 24.7%, respectively). Additional features included patulous internal auditory canal, never described before in KBG syndrome, and the recurrence of ventriculomegaly, encephalic cysts, empty sella and low-lying conus medullaris. We found no correlation between these structural anomalies and epilepsy or intellectual disability. Prevalent skeletal findings comprised abnormalities of the spine including scoliosis, coccygeal anomalies and cervical ribs. Hand X-rays revealed frequent abnormalities of carpal bone morphology and maturation, including a greater delay in ossification compared with metacarpal/phalanx bones.

CONCLUSION

This cohort enabled us to describe the prevalence of very heterogeneous neuroradiological and skeletal anomalies in KBG syndrome. Knowledge of the spectrum of such anomalies will aid diagnostic accuracy, improve patient care and provide a reference for future research on the effects of ANKRD11 variants in skeletal and brain development.

The Complexity of the cGAS-STING Pathway in CNS Pathologies

Neuroinflammation driven by type-I interferons in the CNS is well established to exacerbate the progression of many CNS pathologies both acute and chronic. The role of adaptor protein Stimulator of Interferon Genes (STING) is increasingly appreciated to instigate type-I IFN-mediated neuroinflammation. As an upstream regulator of type-I IFNs, STING modulation presents a novel therapeutic opportunity to mediate inflammation in the CNS. This review will detail the current knowledge of protective and detrimental STING activity in acute and chronic CNS pathologies and the current therapeutic avenues being explored.

The involvement of microglia in Alzheimer's disease: a new dog in the fight

First described clinically in 1906, Alzheimer's disease (AD) is the most common neurodegenerative disease and form of dementia worldwide. Despite its prevalence, only five therapies are currently approved for AD, all dealing with the symptoms rather than the underlying causes of the disease. A multitude of experimental evidence has suggested that the once thought inconsequential process of neuroinflammation does, in fact, contribute to the AD pathogenesis. One such CNS cell type critical to this process are microglia. Plastic in nature with varied roles, microglia are emerging as key contributors to AD pathology. This review will focus on the role of microglia in the neuroinflammatory response in AD, highlighting recent studies implicating aberrant changes in microglial function in disease progression. Of critical note is that with these advances, a reconceptualization of the framework in which we view microglia is required. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

Generation and characterisation of a parkin-Pacrg knockout mouse line and a Pacrg knockout mouse line

Mutations in PARK2 (parkin) can result in Parkinson's disease (PD). Parkin shares a bidirectional promoter with parkin coregulated gene (PACRG) and the transcriptional start sites are separated by only ~200 bp. Bidirectionally regulated genes have been shown to function in common biological pathways. Mice lacking parkin have largely failed to recapitulate the dopaminergic neuronal loss and movement impairments seen in individuals with parkin-mediated PD. We aimed to investigate the function of PACRG and test the hypothesis that parkin and PACRG function in a common pathway by generating and characterizing two novel knockout mouse lines harbouring loss of both parkin and Pacrg or Pacrg alone. Successful modification of the targeted allele was confirmed at the genomic, transcriptional and steady state protein levels for both genes. At 18-20 months of age, there were no significant differences in the behaviour of parental and mutant lines when assessed by openfield, rotarod and balance beam. Subsequent neuropathological examination suggested there was no gross abnormality of the dopaminergic system in the substantia nigra and no significant difference in the number of dopaminergic neurons in either knockout model compared to wildtype mice.

Efimov States of Strongly Interacting Photons

We demonstrate the emergence of universal Efimov physics for interacting photons in cold gases of Rydberg atoms. We consider the behavior of three photons injected into the gas in their propagating frame, where a paraxial approximation allows us to consider them as massive particles. In contrast to atoms and nuclei, the photons have a large anisotropy between their longitudinal mass, arising from dispersion, and their transverse mass, arising from diffraction. Nevertheless, we show that, in suitably rescaled coordinates, the effective interactions become dominated by s-wave scattering near threshold and, as a result, give rise to an Efimov effect near unitarity. We show that the three-body loss of these Efimov trimers can be strongly suppressed and determine conditions under which these states are observable in current experiments. These effects can be naturally extended to probe few-body universality beyond three bodies, as well as the role of Efimov physics in the nonequilibrium, many-body regime.

Threshold Dynamics of a Semiconductor Single Atom Maser

We demonstrate a single atom maser consisting of a semiconductor double quantum dot (DQD) that is embedded in a high-quality-factor microwave cavity. A finite bias drives the DQD out of equilibrium, resulting in sequential single electron tunneling and masing. We develop a dynamic tuning protocol that allows us to controllably increase the time-averaged repumping rate of the DQD at a fixed level detuning, and quantitatively study the transition through the masing threshold. We further examine the crossover from incoherent to coherent emission by measuring the photon statistics across the masing transition. The observed threshold behavior is in agreement with an existing single atom maser theory when small corrections from lead emission are taken into account.

Precise spatio-temporal control of rapid optogenetic cell ablation with mem-KillerRed in Zebrafish

The ability to kill individual or groups of cells in vivo is important for studying cellular processes and their physiological function. Cell-specific genetically encoded photosensitizing proteins, such as KillerRed, permit spatiotemporal optogenetic ablation with low-power laser light. We report dramatically improved resolution and speed of cell targeting in the zebrafish kidney through the use of a selective plane illumination microscope (SPIM). Furthermore, through the novel incorporation of a Bessel beam into the SPIM imaging arm, we were able to improve on targeting speed and precision. The low diffraction of the Bessel beam coupled with the ability to tightly focus it through a high NA lens allowed precise, rapid targeting of subsets of cells at anatomical depth in live, developing zebrafish kidneys. We demonstrate that these specific targeting strategies significantly increase the speed of optoablation as well as fish survival.

Type-I interferon signalling through IFNAR1 plays a deleterious role in the outcome after stroke

Neuroinflammation contributes significantly to the pathophysiology of stroke. Here we test the hypothesis that the type I interferon receptor (IFNAR1) plays a critical role in neural injury after stroke by regulating the resultant pro-inflammatory environment. Wild-type and IFNAR1^-/- primary murine neurons and glia were exposed to oxygen glucose deprivation (OGD) and cell viability was assessed. Transient cerebral ischemia/reperfusion injury was induced by mid-cerebral artery occlusion (MCAO) in wild-type and IFNAR1^-/- and IFNAR2^-/- mice in vivo, and infarct size, and molecular parameters measured. To block IFNAR1 signalling, wild-type mice were treated with a blocking monoclonal antibody directed to IFNAR1 (MAR-1) and MCAO was performed. Quantitative PCR confirmed MCAO in wild-type mice induced a robust type-I interferon gene regulatory signature. Primary cultured IFNAR1-deficient neurons were found to be protected from cell death when exposed to OGD in contrast to primary cultured IFNAR1-deficient glial cells. IFNAR1^-/- mice demonstrated a decreased infarct size (24.9 ± 7.1 mm³ n = 8) compared to wild-type controls (65.1 ± 4.8 mm³ n = 8). Western blot and immunohistochemistry showed alterations in Akt and Stat-3 phosphorylation profiles in the IFNAR1^-/- brain. MAR-1 injection into WT mice (i.v. 0.5 mg 60 min prior to MCAO) resulted in a 60% decrease in infarct size when compared to the IgG control. IFNAR2^-/- mice failed to display the neuroprotective phenotype seen in IFNAR1^-/- mice after MCAO. Our data proposes that central nervous system signalling through IFNAR1 is a previously unrecognised factor that is critical to neural injury after stroke.

Observation of optomechanical buckling transitions

Correlated phases of matter provide long-term stability for systems as diverse as solids, magnets and potential exotic quantum materials. Mechanical systems, such as buckling transition spring switches, can have engineered, stable configurations whose dependence on a control variable is reminiscent of non-equilibrium phase transitions. In hybrid optomechanical systems, light and matter are strongly coupled, allowing engineering of rapid changes in the force landscape, storing and processing information, and ultimately probing and controlling behaviour at the quantum level. Here we report the observation of first- and second-order buckling transitions between stable mechanical states in an optomechanical system, in which full control of the nature of the transition is obtained by means of the laser power and detuning. The underlying multiwell confining potential we create is highly tunable, with a sub-nanometre distance between potential wells. Our results enable new applications in photonics and information technology, and may enable explorations of quantum phase transitions and macroscopic quantum tunnelling in mechanical systems.

Optomechanical systems could form logic gates, but key requirements are two stable static states and the ability to switch between them. Here, the authors observe radiation-pressure induced buckling transitions in an optomechanical system, and control this transition by varying laser power and detuning.

Sisyphus Thermalization of Photons in a Cavity-Coupled Double Quantum Dot

We investigate the nonclassical states of light that emerge in a microwave resonator coupled to a periodically driven electron in a nanowire double quantum dot (DQD). Under certain drive configurations, we find that the resonator approaches a thermal state at the temperature of the surrounding substrate with a chemical potential given by a harmonic of the drive frequency. Away from these thermal regions we find regions of gain and loss, where the system can lase, or regions where the DQD acts as a single-photon source. These effects are observable in current devices and have broad utility for quantum optics with microwave photons.

Type-1 interferons contribute to the neuroinflammatory response and disease progression of the MPTP mouse model of Parkinson's disease

Type-1 interferons (IFNs) are pleiotropic cytokines with a critical role in the initiation and regulation of the pro-inflammatory response. However, the contribution of the type-1 IFNs to CNS disorders, specifically chronic neuropathologies such as Parkinson's disease is still unknown. Here, we report increased type-1 IFN signaling in both post mortem human Parkinson's disease samples and in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) mouse model. In response to MPTP, mice lacking the type-1 IFN receptor (IFNAR1(-/-) ) displayed decreased type-1 IFN signaling, an attenuated pro-inflammatory response and reduced loss of dopaminergic neurons. The neuroprotective potential of targeting the type-1 IFN pathway was confirmed by reduced neuroinflammation and DA cell death in mice treated with a blocking monoclonal IFNAR1 (MAR-1) antibody. The MPTP/MAR-1 treated mice also displayed increased striatal dopamine levels and improved behavioural outcomes compared to their MPTP/IgG controls. These data, implicate for the first time, a deleterious role for the type-1 IFNs as key modulators of the early neuroinflammatory response and therefore the neuronal cell death in Parkinson's disease. GLIA 2016;64:1590-1604.

Deletion of the type-1 interferon receptor in APPSWE/PS1ΔE9 mice preserves cognitive function and alters glial phenotype

A neuro-inflammatory response is evident in Alzheimer’s disease (AD), yet the precise mechanisms by which neuro-inflammation influences the progression of Alzheimer’s disease (AD) remain poorly understood. Type-1 interferons (IFNs) are master regulators of innate immunity and have been implicated in multiple CNS disorders, however their role in AD progression has not yet been fully investigated. Hence, we generated APP_SWE/PS1_ΔE9 mice lacking the type-1 IFN alpha receptor-1 (IFNAR1, APP_SWE/PS1_ΔE9 x IFNAR1^−/−) aged to 9 months to investigate the role of type-1 IFN signaling in a well-validated model of AD. APP_SWE/PS1_ΔE9 x IFNAR1^−/− mice displayed a modest reduction in Aβ monomer levels, despite maintenance of plaque deposition. This finding correlated with partial rescue of spatial learning and memory impairments in the Morris water maze in comparison to APP_SWE/PS1_ΔE9 mice. Q-PCR identified a reduced type-1 IFN response and modulated pro-inflammatory cytokine secretion in APP_SWE/PS1_ΔE9 x IFNAR1^−/− mice compared to APP_SWE/PS1_ΔE9 mice. Interestingly, immunohistochemistry displayed enhanced astrocyte reactivity but attenuated microgliosis surrounding amyloid plaque deposits in APP_SWE/PS1_ΔE9 x IFNAR1^−/− mice in comparison to APP_SWE/PS1_ΔE9 mice. These APP_SWE/PS1_ΔE9 x IFNAR1^−/− microglial populations demonstrated an anti-inflammatory phenotype that was confirmed in vitro by soluble Aβ1-42 treatment of IFNAR1^−/− primary glial cultures. Our findings suggest that modulating neuro-inflammatory responses by suppressing type-1 IFN signaling may provide therapeutic benefit in AD.

Evidence for the recruitment of autophagic vesicles in human brain after stroke

Autophagy is a homeostatic process for recycling proteins and organelles that is increasingly being proposed as a therapeutic target for acute and chronic neurodegenerative diseases, including stroke. Confirmation that autophagy is present in the human brain after stroke is imperative before prospective therapies can begin the translational process into clinical trials. Our current study using human post-mortem tissue observed an increase in staining in microtubule-associated protein 1 light chain 3 (LC3), sequestosome 1 (SQSTM1; also known as p62) and the increased appearance of autophagic vesicles after stroke. These data confirm that alterations in autophagy take place in the human brain after stroke and suggest that targeting autophagic processes after stroke may have clinical significance.

The contribution of neuroinflammation to amyloid toxicity in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the most common cause of dementia. Deposition of amyloid-β (Aβ) remains a hallmark feature of the disease, yet the precise mechanism(s) by which this peptide induces neurotoxicity remain unknown. Neuroinflammation has long been implicated in AD pathology, yet its contribution to disease progression is still not understood. Recent evidence suggests that various Aβ complexes interact with microglial and astrocytic expressed pattern recognition receptors that initiate innate immunity. This process involves secretion of pro-inflammatory cytokines, chemokines and generation of reactive oxygen species that, in excess, drive a dysregulated immune response that contributes to neurodegeneration. The mechanisms by which a neuroinflammatory response can influence Aβ production, aggregation and eventual clearance are now becoming key areas where future therapeutic intervention may slow progression of AD. This review will focus on evidence supporting the combined neuroinflammatory-amyloid hypothesis for pathogenesis of AD, describing the key cell types, pathways and mediators involved. Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the leading cause of dementia worldwide. Deposition of intracellular plaques containing amyloid-beta (Aβ) is a hallmark proteinopathy of the disease yet the precise mechanisms by which this peptide induces neurotoxicity remains unknown. A neuroinflammatory response involving polarized microglial activity, enhanced astrocyte reactivity and elevated pro-inflammatory cytokine and chemokine load has long been implicated in AD and proposed to facilitate neurodegeneration. In this issue we discuss key receptor systems of innate immunity that detect Aβ, drive pro-inflammatory cytokine and chemokine production and influence Aβ aggregation and clearance. Evidence summarized in this review supports the combined neuroinflammatory-amyloid hypothesis for pathogenesis of AD and highlights the potential of immunomodulatory agents as potential future therapies for AD patients.

Optical Control of Donor Spin Qubits in Silicon

We show how to achieve optical, spin-selective transitions from the ground state to excited orbital states of group-V donors (P, As, Sb, Bi) in silicon. We consider two approaches based on either resonant, far-infrared (IR) transitions of the neutral donor or resonant, near-IR excitonic transitions. For far-IR light, we calculate the dipole matrix elements between the valley-orbit and spin-orbit split states for all the goup-V donors using effective mass theory. We then calculate the maximum rate and amount of electron-nuclear spin-polarization achievable through optical pumping with circularly polarized light. We find this approach is most promising for Bi donors due to their large spin-orbit and valley-orbit interactions. Using near-IR light, spin-selective excitation is possible for all the donors by driving a two-photon Λ-transition from the ground state to higher orbitals with even parity. We show that externally applied electric fields or strain allow similar, spin-selective Λ-transition to odd-parity excited states. We anticipate these results will be useful for future spectroscopic investigations of donors, quantum control and state preparation of donor spin qubits, and for developing a coherent interface between donor spin qubits and single photons.

Injection Locking of a Semiconductor Double Quantum Dot Micromaser

Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models.

Tibiotalocalcaneal arthrodesis with a compressive retrograde nail: A retrospective study of 59 nails

BACKGROUND

Tibiotalocalcaneal arthrodesis is an important salvage method for patients with complex hindfoot problems. This study reports the elective results of combined subtalar and ankle arthrodesis using one design of retrograde intramedullary compression nail.

METHODS

Retrospective review identified 58 patients undergoing 59 tibiotalocalcaneal arthrodesis procedures. Mean follow up was 9.15 (3-36) months with average age 60.7 (22-89) years. A function and subjective patient satisfaction questionnaire was achieved in 89%.

RESULTS

53 patients (93%) achieved union at a mean time of 4.17 months. Four patients (8%) subjectively thought the procedure was of no benefit while 42 (84%) had an excellent or good result. The mean visual analogue scale (VAS) score for preoperative functional pain was 7.46 compared to 1.98 post-operatively (p<0.001).

CONCLUSIONS

This device and technique offers an effective treatment of hindfoot pathology giving reliable compression and subsequent fusion with excellent patient satisfaction and pain relief.

LEVEL OF EVIDENCE

IV case series.

Phonon-assisted gain in a semiconductor double quantum dot maser

We develop a microscopic model for the recently demonstrated double-quantum-dot maser. In characterizing the gain of this device we find that, in addition to the direct stimulated emission of photons, there is a large contribution from the simultaneous emission of a photon and a phonon, i.e., the phonon sideband. We show that this phonon-assisted gain typically dominates the overall gain, which leads to masing. Recent experimental data are well fit with our model.

The contribution of astrocytes and microglia to traumatic brain injury

Traumatic brain injury (TBI) represents a major cause of death and disability in developed countries. Brain injuries are highly heterogeneous and can also trigger other neurological complications, including epilepsy, depression and dementia. The initial injury often leads to the development of secondary sequelae; cellular hyperexcitability, vasogenic and cytotoxic oedema, hypoxia-ischaemia, oxidative stress and inflammation, all of which influence expansion of the primary lesion. It is widely known that inflammatory events in the brain following TBI contribute to the widespread cell death and chronic tissue degeneration. Neuroinflammation is a multifaceted response involving a number of cell types, both within the CNS and in the peripheral circulation. Astrocytes and microglia, cells of the CNS, are considered key players in initiating an inflammatory response after injury. These cells are capable of secreting various cytokines, chemokines and growth factors, and following injury to the CNS, undergo changes in morphology. Ultimately, these changes can influence the local microenvironment and thus determine the extent of damage and subsequent repair. This review will focus on the roles of microglia and astrocytes following TBI, highlighting some of the key processes, pathways and mediators involved in this response. Additionally, both the beneficial and the detrimental aspects of these cellular responses will be examined using evidence from animal models and human post-mortem TBI studies.

Transcription of the Rous sarcoma virus genome in vitro and in vivo

RNA-directed DNA synthesis by detergent-disrupted virions of Rous sarcoma virus (RSV) initiates by the covalent attachment of pdA to the 3'-terminal rA of a 4S RNA hydrogen-bonded to the 70S RNA template. This 4S "primer" has structural features of tRNA and can be aminoacylated with methionine. Synthesis and integration of provirus DNA can be monitored in both permissive (duck) and nonpermissive (mouse) cells acutely infected with RSV. The results of these studies, as well as data obtained with RSV-infected mammalian cells which have reverted from a transformed to a pheno-typically normal state, indicate that integration of viral genes into the host chromosome is not sufficient cause for transformation. Pertinent features of virus-specific RNA-directed DNA synthesis in vitro and in vivo are reviewed and compared.

Smoking, internalized heterosexism, and HIV disease management among male couples

High rates of cigarette smoking have been observed among HIV-positive individuals. Smoking has been linked to HIV-related medical complications and non-AIDS defining cancers and negatively impacts on immune function and virologic control. Although internalized heterosexism has been related to smoking behaviors, little is known about associations between partners' reports of smoking, internalized heterosexism, and HIV medication management in male couples with HIV. A sample of 266 male couples completed baseline assessments for a cohort study examining relationship factors and HIV treatment. A computer-based survey assessed self-reported smoking behaviors, alcohol use, internalized heterosexism, and antiretroviral therapy (ART) adherence. HIV-positive men also provided blood samples to assess viral load. Approximately 30% of the sample reported that they are currently smoking cigarettes. After adjusting for demographic characteristics, men in a primary relationship with a partner who reported currently smoking had more than five-fold greater odds of reporting smoking. Higher levels of internalized heterosexism and financial hardship were each independently associated with greater odds of reporting smoking. Among HIV-positive men on ART (n = 371), having a partner who reported smoking was associated with almost three-fold greater odds of having a detectable viral load. Our findings add new support to the evidence of romantic partners influencing each other's health behaviors, and demonstrate an association between smoking and disease management within male couples. Future research should explore the interpersonal and social contexts of smoking in order to develop interventions that meet the unique needs of male couples.

Topologically robust transport of photons in a synthetic gauge field

Electronic transport is localized in low-dimensional disordered media. The addition of gauge fields to disordered media leads to fundamental changes in the transport properties. We implement a synthetic gauge field for photons using silicon-on-insulator technology. By determining the distribution of transport properties, we confirm that waves are localized in the bulk and localization is suppressed in edge states. Our system provides a new platform for investigating the transport properties of photons in the presence of synthetic gauge fields.

Photon emission from a cavity-coupled double quantum dot

We study a voltage biased InAs double quantum dot (DQD) that is coupled to a superconducting transmission line resonator. Inelastic tunneling in the DQD is mediated by electron phonon coupling and coupling to the cavity mode. We show that electronic transport through the DQD leads to photon emission from the cavity at a rate of 10 MHz. With a small cavity drive field, we observe a gain of up to 15 in the cavity transmission. Our results are analyzed in the context of existing theoretical models and suggest that it may be necessary to account for inelastic tunneling processes that proceed via simultaneous emission of a phonon and a photon.

Ultra-sensitive chip-based photonic temperature sensor using ring resonator structures

Resistance thermometry provides a time-tested method for taking temperature measurements. However, fundamental limits to resistance-based approaches has produced considerable interest in developing photonic temperature sensors to leverage advances in frequency metrology and to achieve greater mechanical and environmental stability. Here we show that silicon-based optical ring resonator devices can resolve temperature differences of 1 mK using the traditional wavelength scanning methodology. An even lower noise floor of 80 μK for measuring temperature difference is achieved in the side-of-fringe, constant power mode measurement.

Personal or relational? Examining sexual health in the context of HIV serodiscordant same-sex male couples

Couples' ability to adopt a "we" orientation has been associated with optimal health outcomes. This study examined how personal and relational motivations are uniquely associated with unprotected anal intercourse (UAI), protected anal intercourse (PAI), and the absence of sexual activity within HIV-serodiscordant same-sex male couples. HIV-positive men and their HIV-negative partners (N = 116 couples, 232 men) completed questionnaires and HIV-positive men had blood drawn for viral load. Results of a multinomial logistic regression illustrated that sexual satisfaction was positively associated with PAI among HIV-negative partners and negatively associated with PAI among HIV-positive partners. Endorsing a "we" orientation was positively associated with PAI among HIV-positive partners. Findings suggest that HIV-positive partners who espouse a "we" orientation may be willing to forgo their personal interests to protect their HIV-negative partners from HIV transmission. Couples-based interventions are warranted to help strengthen relationship dynamics to enhance the sexual health of serodiscordant couples.

Personal or relational? Examining sexual health in the context of HIV serodiscordant same-sex male couples

Couples' ability to adopt a "we" orientation has been associated with optimal health outcomes. This study examined how personal and relational motivations are uniquely associated with unprotected anal intercourse (UAI), protected anal intercourse (PAI), and the absence of sexual activity within HIV-serodiscordant same-sex male couples. HIV-positive men and their HIV-negative partners (N = 116 couples, 232 men) completed questionnaires and HIV-positive men had blood drawn for viral load. Results of a multinomial logistic regression illustrated that sexual satisfaction was positively associated with PAI among HIV-negative partners and negatively associated with PAI among HIV-positive partners. Endorsing a "we" orientation was positively associated with PAI among HIV-positive partners. Findings suggest that HIV-positive partners who espouse a "we" orientation may be willing to forgo their personal interests to protect their HIV-negative partners from HIV transmission. Couples-based interventions are warranted to help strengthen relationship dynamics to enhance the sexual health of serodiscordant couples.

Long-term clinical and functional outcome following treatment for Paget–Schroetter syndrome

Background

Effort-related thrombosis of the axillosubclavian vein (Paget–Schroetter syndrome, PSS) is uncommon. It tends to affect young, active individuals and yet consensus on management is lacking. The aim here was to analyse late outcomes in a series of patients treated for PSS using a standard protocol.

Methods

The medical records of patients treated for PSS over 16 years were analysed. Patients were divided into four groups according to their management. Clinical and functional outcomes were analysed regarding residual venous defects after treatment, and Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire scores, respectively.

Results

Some 117 patients (52 men and 65 women, mean age 32 years) were included. Catheter-directed thrombolysis was successful in 42 of 56 treated patients. Thoracic outlet decompression surgery was performed in 95 patients. DASH scores improved significantly in patients treated surgically (P &lt; 0.001 to P = 0·009); early surgery had a better outcome than delayed surgery (P = 0·040). Patients who were managed conservatively showed no improvement (P = 0·116). Where venoplasty was necessary, it was successful in 18 of 25 patients. A short duration of lysis (less than 24 h) increased the risk of rethrombosis (P = 0·020). The method of postoperative anticoagulation had no influence on the rate of rethrombosis.

Conclusion

Patients treated surgically for PSS had better functional outcomes than those managed conservatively. Prompt thrombolysis and surgery was superior to delayed management with respect to rethrombosis and functional outcome.

Self-consistent measurement and state tomography of an exchange-only spin qubit

Quantum-dot spin qubits characteristically use oscillating magnetic or electric fields, or quasi-static Zeeman field gradients, to realize full qubit control. For the case of three confined electrons, exchange interaction between two pairs allows qubit rotation around two axes, hence full control, using only electrostatic gates. Here, we report initialization, full control, and single-shot readout of a three-electron exchange-driven spin qubit. Control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in less than 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements and non-orthogonal control axes.

Electrically protected resonant exchange qubits in triple quantum dots

We present a modulated microwave approach for quantum computing with qubits comprising three spins in a triple quantum dot. This approach includes single- and two-qubit gates that are protected against low-frequency electrical noise, due to an operating point with a narrowband response to high frequency electric fields. Furthermore, existing double quantum dot advances, including robust preparation and measurement via spin-to-charge conversion, are immediately applicable to the new qubit. Finally, the electric dipole terms implicit in the high frequency coupling enable strong coupling with superconducting microwave resonators, leading to more robust two-qubit gates.

Quantum-dot-based resonant exchange qubit

We introduce a solid-state qubit in which exchange interactions among confined electrons provide both the static longitudinal field and the oscillatory transverse field, allowing rapid and full qubit control via rf gate-voltage pulses. We demonstrate two-axis control at a detuning sweet spot, where leakage due to hyperfine coupling is suppressed by the large exchange gap. A π/2-gate time of 2.5 ns and a coherence time of 19 μs, using multipulse echo, are also demonstrated. Model calculations that include effects of hyperfine noise are in excellent quantitative agreement with experiment.

Performance of coagulation tests in patients on therapeutic doses of dabigatran: a cross-sectional pharmacodynamic study based on peak and trough plasma levels

BACKGROUND

Knowledge of anticoagulation status during dabigatran therapy may be desirable in certain clinical situations.

OBJECTIVE

To determine the coagulation tests that are most useful for assessing dabigatran's anticoagulant effect.

METHODS

Peak and trough blood samples from 35 patients taking dabigatran 150 mg twice daily, and one sample each from 30 non-anticoagulated individuals, were collected. Mass spectrometry and various coagulation assays were performed. 'Therapeutic range' was defined as the range of plasma dabigatran concentrations determined by mass spectrometry between the 2.5th and 97.5th percentiles of all values.

RESULTS

The therapeutic range was 27-411 ng mL(-1) . The prothrombin time (PT) and activated partial thromboplastin time (APTT), determined with multiple reagents, and activated clotting time (ACT) were insensitive to therapeutic dabigatran: 29%, 18% and 40% of samples had a normal PT, APTT, and ACT, respectively. However, normal PT, ACT and APTT ruled out dabigatran levels above the 75th percentile. The thrombin clotting time (TCT) correlated well and linearly with dabigatran levels below the 50th percentile, but was unmeasurable above it. The dilute thrombin time, ecarin clotting time and ecarin chromogenic assay showed linear correlations with dabigatran levels over a broad range, and identified therapeutic and supratherapeutic levels.

CONCLUSIONS

The prothrombin time, APTT and ACT are often normal in spite of therapeutic dabigatran plasma levels. The TCT is useful for detecting minimal dabigatran levels. The dilute thrombin time and chromogenic and clotting ecarin assays accurately identify therapeutic and supratherapeutic dabigatran levels. This trial is registered at www.clinicaltrials.gov (#NCT01588327).

Cardiac damage induced by immunization with heat-killed Trypanosoma cruzi is not antibody mediated

Cardiac inflammation that develops during infection with Trypanosoma cruzi may result in part from autoimmunity, which may occur after bystander activation, after parasite-induced cardiomyocyte damage, or molecular mimicry. A/J mice infected with T. cruzi or immunized with heat-killed T. cruzi (HKTC) develop strong autoimmunity accompanied by cardiac damage. To determine whether this cardiac damage occurs via an antibody-dependent mechanism, we analysed T. cruzi-infected and HKTC-immunized mice for the presence of autoantibodies, cardiac antibody deposition, and serum cardiac troponin I as a measure of cardiac damage. We also performed a serum transfer experiment in which sera from T. cruzi-infected and T. cruzi-immunized mice (and controls) were transferred into naïve recipients, which were then analysed for the presence of antibodies and serum troponin. Unlike T. cruzi-infected mice, T. cruzi-immunized mice did not show significant antibody deposition in the myocardium. These results indicate that antibody deposition does not precede cardiac damage and inflammation in mice immunized with or infected with T. cruzi. Serum adoptive transfer did not induce cardiac damage in any recipients. Based on these findings, we conclude that the cardiac damage induced by immunization with HKTC is not mediated by antibodies.

Simultaneous spin-charge relaxation in double quantum dots

We investigate phonon-induced spin and charge relaxation mediated by spin-orbit and hyperfine interactions for a single electron confined within a double quantum dot. A simple toy model incorporating both direct decay to the ground state of the double dot and indirect decay via an intermediate excited state yields an electron spin relaxation rate that varies nonmonotonically with the detuning between the dots. We confirm this model with experiments performed on a GaAs double dot, demonstrating that the relaxation rate exhibits the expected detuning dependence and can be electrically tuned over several orders of magnitude. Our analysis suggests that spin-orbit mediated relaxation via phonons serves as the dominant mechanism through which the double-dot electron spin-flip rate varies with detuning.

Nonlinear optics quantum computing with circuit QED

One approach to quantum information processing is to use photons as quantum bits and rely on linear optical elements for most operations. However, some optical nonlinearity is necessary to enable universal quantum computing. Here, we suggest a circuit-QED approach to nonlinear optics quantum computing in the microwave regime, including a deterministic two-photon phase gate. Our specific example uses a hybrid quantum system comprising a LC resonator coupled to a superconducting flux qubit to implement a nonlinear coupling. Compared to the self-Kerr nonlinearity, we find that our approach has improved tolerance to noise in the qubit while maintaining fast operation.

Quantum interface between an electrical circuit and a single atom

We show how to bridge the divide between atomic systems and electronic devices by engineering a coupling between the motion of a single ion and the quantized electric field of a resonant circuit. Our method can be used to couple the internal state of an ion to the quantized circuit with the same speed as the internal-state coupling between two ions. All the well-known quantum information protocols linking ion internal and motional states can be converted to protocols between circuit photons and ion internal states. Our results enable quantum interfaces between solid state qubits, atomic qubits, and light, and lay the groundwork for a direct quantum connection between electrical and atomic metrology standards.

Laser cooling and optical detection of excitations in a LC electrical circuit

We explore a method for laser cooling and optical detection of excitations in a room temperature LC electrical circuit. Our approach uses a nanomechanical oscillator as a transducer between optical and electronic excitations. An experimentally feasible system with the oscillator capacitively coupled to the LC and at the same time interacting with light via an optomechanical force is shown to provide strong electromechanical coupling. Conditions for improved sensitivity and quantum limited readout of electrical signals with such an "optical loud speaker" are outlined.

Nanoscale optical electrometer

We propose and demonstrate an all-optical approach to single-electron sensing using the optical transitions of a semiconductor quantum dot. The measured electric-field sensitivity of 5 (V/m)/√Hz corresponds to detecting a single electron located 5 μm from the quantum dot-nearly 10 times greater than the diffraction limited spot size of the excitation laser-in 1 s. The quantum-dot-based electrometer is more sensitive than other devices operating at a temperature of 4.2 K or higher and further offers suppressed backaction on the measured system.

Coupling nitrogen-vacancy centers in diamond to superconducting flux qubits

We propose a method to achieve coherent coupling between nitrogen-vacancy (NV) centers in diamond and superconducting (SC) flux qubits. The resulting coupling can be used to create a coherent interaction between the spin states of distant NV centers mediated by the flux qubit. Furthermore, the magnetic coupling can be used to achieve a coherent transfer of quantum information between the flux qubit and an ensemble of NV centers. This enables a long-term memory for a SC quantum processor and possibly an interface between SC qubits and light.

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.

Dynamic nuclear polarization in double quantum dots

We theoretically investigate the controlled dynamic polarization of lattice nuclear spins in GaAs double quantum dots containing two electrons. Three regimes of long-term dynamics are identified, including the buildup of a large difference in the Overhauser fields across the dots, the saturation of the nuclear polarization process associated with formation of so-called "dark states", and the elimination of the difference field. We show that in the case of unequal dots, buildup of difference fields generally accompanies the nuclear polarization process, whereas for nearly identical dots, buildup of difference fields competes with polarization saturation in dark states. The elimination of the difference field does not, in general, correspond to a stable steady state of the polarization process.

Repetitive readout of a single electronic spin via quantum logic with nuclear spin ancillae

Robust measurement of single quantum bits plays a key role in the realization of quantum computation and communication as well as in quantum metrology and sensing. We have implemented a method for the improved readout of single electronic spin qubits in solid-state systems. The method makes use of quantum logic operations on a system consisting of a single electronic spin and several proximal nuclear spin ancillae in order to repetitively readout the state of the electronic spin. Using coherent manipulation of a single nitrogen vacancy center in room-temperature diamond, full quantum control of an electronic-nuclear system consisting of up to three spins was achieved. We took advantage of a single nuclear-spin memory in order to obtain a 10-fold enhancement in the signal amplitude of the electronic spin readout. We also present a two-level, concatenated procedure to improve the readout by use of a pair of nuclear spin ancillae, an important step toward the realization of robust quantum information processors using electronic- and nuclear-spin qubits. Our technique can be used to improve the sensitivity and speed of spin-based nanoscale diamond magnetometers.

Optical binding mechanisms: a conceptual model for Gaussian beam traps

Optical binding interactions between laser-trapped spherical microparticles are familiar in a wide range of trapping configurations. Recently it has been demonstrated that these experiments can be accurately modeled using Mie scattering or coupled dipole models. This can help confirm the physical phenomena underlying the inter-particle interactions, but does not necessarily develop a conceptual understanding of the effects that can lead to future predictions. Here we interpret results from a Mie scattering model to obtain a physical description which predict the behavior and trends for chains of trapped particles in Gaussian beam traps. In particular, it describes the non-uniform particle spacing and how it changes with the number of particles. We go further than simply demonstrating agreement, by showing that the mechanisms "hidden" within a mathematically and computationally demanding Mie scattering description can be explained in easily-understood terms.

Qubit protection in nuclear-spin quantum dot memories

We present a mechanism to protect quantum information stored in an ensemble of nuclear spins in a semiconductor quantum dot. When the dot is charged the nuclei interact with the spin of the excess electron through the hyperfine coupling. If this coupling is made off-resonant, it leads to an energy gap between the collective storage states and all other states. We show that the energy gap protects the quantum memory from local spin-flip and spin-dephasing noise. Effects of nonperfect initial spin polarization and inhomogeneous hyperfine coupling are discussed.