Subsecond periodic radio oscillations in a microquasar.

Powerful relativistic jets are one of the ubiquitous features of accreting black holes in all scales1-3. GRS 1915 + 105 is a well-known fast-spinning black-hole X-ray binary4 with a relativistic jet, termed a 'microquasar', as indicated by its superluminal motion of radio emission5,6. It has exhibited persistent X-ray activity over the last 30 years, with quasiperiodic oscillations of approximately 1-10 Hz (refs. 7-9) and 34 and 67 Hz in the X-ray band10. These oscillations probably originate in the inner accretion disk, but other origins have been considered11. Radio observations found variable light curves with quasiperiodic flares or oscillations with periods of approximately 20-50 min (refs. 12-14). Here we report two instances of approximately 5-Hz transient periodic oscillation features from the source detected in the 1.05- to 1.45-GHz radio band that occurred in January 2021 and June 2022. Circular polarization was also observed during the oscillation phase.

Speed of Gravitational Waves from Strongly Lensed Gravitational Waves and Electromagnetic Signals.

We propose a new model-independent measurement strategy for the propagation speed of gravitational waves (GWs) based on strongly lensed GWs and their electromagnetic (EM) counterparts. This can be done in two ways: by comparing arrival times of GWs and their EM counterparts and by comparing the time delays between images seen in GWs and their EM counterparts. The lensed GW-EM event is perhaps the best way to identify an EM counterpart. Conceptually, this method does not rely on any specific theory of massive gravitons or modified gravity. Its differential setting (i.e., measuring the difference between time delays in GW and EM domains) makes it robust against lens modeling details (photons and GWs travel in the same lensing potential) and against internal time delays between GW and EM emission acts. It requires, however, that the theory of gravity is metric and predicts gravitational lensing similar to general relativity. We expect that such a test will become possible in the era of third-generation gravitational-wave detectors, when about 10 lensed GW events would be observed each year. The power of this method is mainly limited by the timing accuracy of the EM counterpart, which for kilonovae is around 10^{4} s. This uncertainty can be suppressed by a factor of ∼10^{10}, if strongly lensed transients of much shorter duration associated with the GW event can be identified. Candidates for such short transients include short γ-ray bursts and fast radio bursts.

Effectiveness and safety of non-vitamin K antagonist oral anticoagulant in the treatment of patients with morbid obesity or high body weight with venous thromboembolism: A meta-analysis.

BACKGROUND: Venous thromboembolism (VTE) poses a significant health risk to patients with morbid obesity or high body weight. Non-vitamin K antagonist oral anticoagulants (NOACs) are emerging treatments, but their effectiveness and safety compared with vitamin K antagonists (VKAs) in this population are yet to be thoroughly studied. METHODS: We conducted a systematic review and meta-analysis, adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Four electronic databases were searched for relevant studies comparing the efficacy and safety of NOACs and VKAs in treating patients with VTE with a body mass index > 40 kg/m2 or body weight > 120 kg. Eligible studies were scored for quality using the Newcastle-Ottawa Scale. RESULTS: Thirteen studies were included. The meta-analysis results showed that compared to VKAs, NOACs significantly decreased the risk of VTE occurrence (odds ratio = 0.72, 95% CI: 0.57-0.91, I2 = 0%, P < .001) and were associated with a lower risk of bleeding (odds ratio = 0.74, 95% CI: 0.58-0.95, I2 = 0%, P < .05). Subgroup analysis showed that in the cancer patient subgroup, both risks of VTE occurrence and bleeding were lower in the NOAC group than in the VKA group. In patients without cancer, the risk of VTE was significantly lower in the NOAC group. CONCLUSION: NOACs appear to be more effective and safer than VKAs in patients with morbid obesity or a high body weight with VTE. However, further large-scale randomized controlled trials are required to confirm these findings.

Clinical Reasoning: A 17-Year-Old Girl With Progressive Cognitive Impairment.

A 17-year-old girl presented with a long history of cognitive impairment, personality and behavioral changes, dysarthria, and paroxysmal lower-extremity weakness. She was initially suspected of having mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes because of stroke-like symptoms, such as episodic lower-extremity weakness, as well as abnormal brain MRI findings of generalized cerebral atrophy, extensive high-intensity lesions in the cortex and subcortical white matter on fluid-attenuated inversion recovery images, decreased N-acetyl aspartate/creatine ratio, and a lactate peak in the focal area on spectrum images. However, there were no relatives with similar presentations in the family of the patient. The whole mitochondrial genome and whole-exome sequencing did not suggest pathogenic mutations, and no abnormalities were found in the blood or CSF lactate levels. In this case, we detail the clinical manifestations, diagnostic workup, and imaging findings. This case highlights the importance of assessing cognitive function and the relevant differential diagnoses in an adolescent with cognitive impairment.

Application Effect of the Standard Operating Procedure in the Prevention of Venous Thromboembolism.

OBJECTIVE: To investigate the application effect of the standard operating procedure (SOP) in the prevention of venous thromboembolism (VTE). METHODS: The clinical data of patients admitted to respiratory, cardiovascular, neurological, and geriatric departments in the hospital (November 2020-May 2021) were retrospectively analyzed, and the patients in line with the inclusion criteria were equally randomized into the observation group (OG) and the control group (CG). The CG was treated with the routine nursing, and the OG received the SOP of VTE prevention additionally. After the record of the incidence of VTE and nursing satisfaction of the two groups, scores of VTE awareness were compared. RESULTS: One hundred and twenty patients were included in this study, and no obvious difference was found in the general data of patients (P > 0.05). Compared with the CG, the incidence of VTE of the OG was obviously lower (P < 0.05). After nursing, compared with the CG, scores of VTE awareness in the OG were conspicuously higher (P < 0.001), and scores of VTE awareness of the nursing staff were conspicuously higher than those before nursing (P < 0.001). Compared with the CG, nursing satisfaction of the OG was obviously higher (P < 0.001). CONCLUSION: SOP can reduce the incidence of VTE of patients, improve their disease awareness, and enhance their nursing satisfaction, which should be popularized in practice.

Direct test of the FLRW metric from strongly lensed gravitational wave observations.

The assumptions of large-scale homogeneity and isotropy underly the familiar Friedmann-Lemaître-Robertson-Walker (FLRW) metric that appears to be an accurate description of our Universe. In this paper, we propose a new strategy of testing the validity of the FLRW metric, based on the galactic-scale lensing systems where strongly lensed gravitational waves and their electromagnetic counterparts can be simultaneously detected. Each strong lensing system creates opportunity to infer the curvature parameter of the Universe. Consequently, combined analysis of many such systems will provide a model-independent tool to test the validity of the FLRW metric. Our study demonstrates that the third-generation ground based GW detectors, like the Einstein Telescope (ET) and space-based detectors, like the Big Bang Observer (BBO), are promising concerning determination of the curvature parameter or possible detection of deviation from the FLRW metric. Such accurate measurements of the FLRW metric can become a milestone in precision GW cosmology.

Precision cosmology from future lensed gravitational wave and electromagnetic signals.

The standard siren approach of gravitational wave cosmology appeals to the direct luminosity distance estimation through the waveform signals from inspiralling double compact binaries, especially those with electromagnetic counterparts providing redshifts. It is limited by the calibration uncertainties in strain amplitude and relies on the fine details of the waveform. The Einstein telescope is expected to produce 104-105 gravitational wave detections per year, 50-100 of which will be lensed. Here, we report a waveform-independent strategy to achieve precise cosmography by combining the accurately measured time delays from strongly lensed gravitational wave signals with the images and redshifts observed in the electromagnetic domain. We demonstrate that just 10 such systems can provide a Hubble constant uncertainty of 0.68% for a flat lambda cold dark matter universe in the era of third-generation ground-based detectors.

Publisher Correction: Precision cosmology from future lensed gravitational wave and electromagnetic signals.

The original PDF version of this Article inadvertently highlighted the author surnames and omitted the publication date. These have now been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.

Optical observations of LIGO source GW 170817 by the Antarctic Survey Telescopes at Dome A, Antarctica.

The LIGO detection of gravitational waves (GW) from merging black holes in 2015 marked the beginning of a new era in observational astronomy. The detection of an electromagnetic signal from a GW source is the critical next step to explore in detail the physics involved. The Antarctic Survey Telescopes (AST3), located at Dome A, Antarctica, is uniquely situated for rapid response time-domain astronomy with its continuous night-time coverage during the austral winter. We report optical observations of the GW source (GW 170817) in the nearby galaxy NGC 4993 using AST3. The data show a rapidly fading transient at around 1 day after the GW trigger, with the i-band magnitude declining from 17.23±0.13 magnitude to 17.72±0.09 magnitude in ~1.8 h. The brightness and time evolution of the optical transient associated with GW 170817 are broadly consistent with the predictions of models involving merging binary neutron stars. We infer from our data that the merging process ejected about ∼10-2 solar mass of radioactive material at a speed of up to 30% the speed of light.