A wide star-black-hole binary system from radial-velocity measurements.

All stellar-mass black holes have hitherto been identified by X-rays emitted from gas that is accreting onto the black hole from a companion star. These systems are all binaries with a black-hole mass that is less than 30 times that of the Sun1-4. Theory predicts, however, that X-ray-emitting systems form a minority of the total population of star-black-hole binaries5,6. When the black hole is not accreting gas, it can be found through radial-velocity measurements of the motion of the companion star. Here we report radial-velocity measurements taken over two years of the Galactic B-type star, LB-1. We find that the motion of the B star and an accompanying Hα emission line require the presence of a dark companion with a mass of [Formula: see text] solar masses, which can only be a black hole. The long orbital period of 78.9 days shows that this is a wide binary system. Gravitational-wave experiments have detected black holes of similar mass, but the formation of such massive ones in a high-metallicity environment would be extremely challenging within current stellar evolution theories.

[Relationship between dietary nutrients and hypertension, overweight and obesity in pupil grades 3 to 6 in Wuhan City].

OBJECTIVE: To explore the relationship between children's dietary nutrient intakes and hypertension, overweight and obesity. METHODS: In April 2016, 1033 children aged 9 to 12 from grades 3 to 6 in two primary schools in Hongshan District of Wuhan City were selected by cluster sampling method, with an average age of(10.55±1.10) years, including 545 boys(52.8%) and 488 girls(47.2%), for physical examination and dietary survey. Physical examination included height, weight, blood pressure, etc. Dietary survey was conducted using a 3-day 24 h retrospective method. Principal component factor analysis was used to explore the dietary nutrient patterns of children, and logistic regression was used to analyze the effects of different dietary nutrient patterns on children's hypertension, overweight and obesity. RESULTS: In terms of M(P25, P75), compared with normal blood pressure group, hypertensive group had higher energy intake(1761.97(1617.17, 1940.43)kcal vs.1730.95(1556.06, 1905.71)kcal, P=0.011). Compared with normal weight group, overweight and obese group had higher carbohydrate(250.65(226.55, 281.29)g vs.244.41(220.04, 273.01)g, P=0.011), vitamin B_1(0.29(0.22, 0.36)mg vs.0.27(0.22, 0.34)mg, P=0.022), vitamin B_2(0.45(0.33, 0.60)mg vs.0.39(0.32, 0.51)mg, P=0.001), iron(12.64(11.06, 14.48)mg vs.12.39(10.57, 14.21)mg, P=0.033), zinc(5.11(4.00, 6.77)mg vs.4.60(3.87, 5.84)mg, P<0.001)intakes, lower calcium intake(185.52(136.92, 264.73)mg vs.207.39(141.25, 300.92)mg, P=0.007). Low cholesterol, low vitamin, high calcium pattern(OR=0.644, 95%CI 0.421-0.985) and Q2 of low protein, low fat and low cholesterol(OR=0.626, 95%CI 0.412-0.951) were protective factors for overweight and obesity. CONCLUSION: High carbohydrate may be a risk factor for overweight and obesity, while high calcium, low fat and low cholesterol may be protective factors for overweight and obesity.

The missing link in gravitational-wave astronomy: A summary of discoveries waiting in the decihertz range.

Since 2015 the gravitational-wave observations of LIGO and Virgo have transformed our understanding of compact-object binaries. In the years to come, ground-based gravitational-wave observatories such as LIGO, Virgo, and their successors will increase in sensitivity, discovering thousands of stellar-mass binaries. In the 2030s, the space-based LISA will provide gravitational-wave observations of massive black holes binaries. Between the ∼ 10 -103 Hz band of ground-based observatories and the ∼ 1 0 - 4 -10- 1 Hz band of LISA lies the uncharted decihertz gravitational-wave band. We propose a Decihertz Observatory to study this frequency range, and to complement observations made by other detectors. Decihertz observatories are well suited to observation of intermediate-mass ( ∼ 1 0 2 -104 M ⊙) black holes; they will be able to detect stellar-mass binaries days to years before they merge, providing early warning of nearby binary neutron star mergers and measurements of the eccentricity of binary black holes, and they will enable new tests of general relativity and the Standard Model of particle physics. Here we summarise how a Decihertz Observatory could provide unique insights into how black holes form and evolve across cosmic time, improve prospects for both multimessenger astronomy and multiband gravitational-wave astronomy, and enable new probes of gravity, particle physics and cosmology.

Testing the Universality of Free Fall towards Dark Matter with Radio Pulsars.

The violation of the weak equivalence principle (EP) in the gravitational field of Earth, described by the Eötvös parameter η_{⊕}, was recently constrained to the level |η_{⊕}|≲10^{-14} by the MICROSCOPE space mission. The Eötvös parameter η_{DM}, pertaining to the differential couplings of dark matter (DM) and ordinary matter, was only tested to the level |η_{DM}|≲10^{-5} by the Eöt-Wash group and lunar laser ranging. This test is limited by the EP-violating driving force in the solar neighborhood that is determined by the galactic distribution of DM. Here we propose a novel celestial experiment using the orbital dynamics from radio timing of binary pulsars, and obtain a competing limit on η_{DM} from a neutron-star-white-dwarf (NS-WD) system, PSR J1713+0747. The result benefits from the large material difference between the NS and the WD and the large gravitational binding energy of the NS. If we can discover a binary pulsar within ∼10 pc of the galactic center, where the driving force is much larger in the expected DM spike, precision timing will improve the test of the universality of free fall towards DM and constrain various proposed couplings of DM to the standard model by several orders of magnitude. Such a test probes the hypothesis that gravity is the only long-range interaction between DM and ordinary matter.

Tests of local Lorentz invariance violation of gravity in the standard model extension with pulsars.

The standard model extension is an effective field theory introducing all possible Lorentz-violating (LV) operators to the standard model and general relativity (GR). In the pure-gravity sector of minimal standard model extension, nine coefficients describe dominant observable deviations from GR. We systematically implemented 27 tests from 13 pulsar systems to tightly constrain eight linear combinations of these coefficients with extensive Monte Carlo simulations. It constitutes the first detailed and systematic test of the pure-gravity sector of minimal standard model extension with the state-of-the-art pulsar observations. No deviation from GR was detected. The limits of LV coefficients are expressed in the canonical Sun-centered celestial-equatorial frame for the convenience of further studies. They are all improved by significant factors of tens to hundreds with existing ones. As a consequence, Einstein's equivalence principle is verified substantially further by pulsar experiments in terms of local Lorentz invariance in gravity.

A freely precessing magnetar following an X-ray outburst.

Magnetars-highly magnetized neutron stars-are thought to be the most likely progenitors for fast radio bursts (FRBs). Freely precessing magnetars are further invoked to explain the repeating FRBs. We report here on new high-cadence radio observations of the magnetar XTE J1810-197 recorded shortly after an X-ray outburst. We interpret the polarization variations of the magnetar radio emission as evidence for the magnetar undergoing free precession following the outburst while its magnetosphere slowly untwists. The observations of precession being damped on a timescale of months argue against the scenario of freely precessing magnetars as the origin of repeating FRBs. Using free-precession models based on relaxing ellipticity with a decay of the wobble angle, we find the magnetar ellipticity to be in good agreement with theoretical predictions from nuclear physics. Our precise measurement of the magnetar's geometry can also further help in refining the modelling of X-ray light curves and constrain the star's compactness.

Ultra-purification of heavy metals and robustness of calcium silicate hydrate (C-S-H) nanocomposites.

For the sake of remediating the contamination of heavy metal ions (HMs) that poses high risk to the global environment, a novel inorganic nanocomposite with excellent robustness, calcium silicate hydrate (C-S-H), is synthesized at extremely low cost yet presents rapid adsorption rate and superhigh adsorption capacity. High concentrations of Cu(Ⅱ), Cd(Ⅱ), Co(Ⅱ) and Cr(Ⅲ) in wastewater can be purified to ultra-low level (∼0.008 mg L-1) within 60 min at low C-S-H dosage, the concentration and pH indexes of which meet the standard for direct discharge in China. The adsorption processes are spontaneous, following the Langmuir adsorption isotherm model, and its kinetics conforms to pseudo-second order model. Meanwhile, C-S-H presents excellent anti-interference performance during the ultra-purification of HMs when exposed to the acid environments, solutions with various HMs as well as high salinity. The ultra-purification of HMs and robustness of C-S-H is realized through multiple mechanisms based on adsorption, involving hydrolysis of HMs, electrostatic interaction, chemical microprecipitation, surface complexation and interlayer complexation, among which interlayer complexation is dominant. All these verify the robust performance and broad applicability of C-S-H to complex aqueous systems.

Caregiver Perceptions of Child Diet Quality: What Influenced Their Judgment.

This study aimed at assessing the correctness of a caregiver's perception of their child's diet status and to determine the factors which may influence their judgment. 815 child-caregiver pairs were recruited from two primary schools. 3-day 24-h recall was used to evaluate children's dietary intake, Chinese Children Dietary Index (CCDI) was used to evaluate the dietary quality. Multivariate logistic regression models were used to explore the factors that could influence the correctness of caregiver's perception. In the current study, 371 (62.1%) children with "high diet quality" and 35 (16.1%) children with "poor diet quality" were correctly perceived by their caregivers. Children who were correctly perceived as having "poor diet quality" consumed less fruits and more snacks and beverages than those who were not correctly perceived (p < 0.05). Obese children were more likely to be correctly identified as having "poor diet quality" (OR = 3.532, p = 0.040), and less likely to be perceived as having "high diet quality", even when they had a balanced diet (OR = 0.318, p = 0.020). Caregivers with a high level of education were more likely to correctly perceive children's diet quality (OR = 3.532, p = 0.042). Caregivers in this study were shown to lack the ability to correctly identify their children's diet quality, especially amongst children with a "poor diet quality". Obesity, significantly low consumption of fruits or high consumption of snacks can raise caregivers' awareness of "poor diet quality".

First-digit law in nonextensive statistics.

Nonextensive statistics, characterized by a nonextensive parameter q, is a promising and practically useful generalization of the Boltzmann statistics to describe power-law behaviors from physical and social observations. We here explore the unevenness of the first-digit distribution of nonextensive statistics analytically and numerically. We find that the first-digit distribution follows Benford's law and fluctuates slightly in a periodical manner with respect to the logarithm of the temperature. The fluctuation decreases when q increases, and the result converges to Benford's law exactly as q approaches 2. The relevant regularities between nonextensive statistics and Benford's law are also presented and discussed.