Measurements of the gravitational constant using two independent methods.

The Newtonian gravitational constant, G, is one of the most fundamental constants of nature, but we still do not have an accurate value for it. Despite two centuries of experimental effort, the value of G remains the least precisely known of the fundamental constants. A discrepancy of up to 0.05 per cent in recent determinations of G suggests that there may be undiscovered systematic errors in the various existing methods. One way to resolve this issue is to measure G using a number of methods that are unlikely to involve the same systematic effects. Here we report two independent determinations of G using torsion pendulum experiments with the time-of-swing method and the angular-acceleration-feedback method. We obtain G values of 6.674184 × 10-11 and 6.674484 × 10-11 cubic metres per kilogram per second squared, with relative standard uncertainties of 11.64 and 11.61 parts per million, respectively. These values have the smallest uncertainties reported until now, and both agree with the latest recommended value within two standard deviations.

Multifunctionality promotes the prosperity of riverine planktonic diatoms in plateau.

Interpreting the biogeographic distribution and underlying mechanisms of functional traits not only contributes to revealing the spatiotemporal dynamics of species biodiversity but also helps to maintain ecological stability during environmental variations. However, little is known about the functional profiles of diatom communities over large river systems. Herein, we provided the first blueprints about the spatiotemporal distributions and driving forces of functional traits for both planktonic and sedimentary diatoms over the 6030 km continuum of the Yangtze River, with the help of the high-throughput sequencing and functional identification. By investigating the 28 functional traits affiliated into five categories, we found that planktonic diatom functions showed clearer landform-heterogeneity patterns (ANOSIM R = 0.336) than sedimentary functions (ANOSIM R = 0.172) along the river, represented by life-forms and ecological-guilds prominent in water-plateau as well as cell-sizes and life-forms particularly in sediment-plateau. Planktonic diatom functions also displayed higher richness and network complexity in plateau (richness: 58.70 ± 9.30, network edges: 65) than in non-plateau regions (23.82 ± 13.16, 16), promoting the stability and robustness of diatom functions against the high-radiation and low-temperature plateau environment. Environmental selection (mainly exerted by PAR, UV, and Tw) played crucial roles in determining the functional variations of planktonic diatoms (explaining 80.5%) rather than sedimentary diatoms (14.5%) between plateau and non-plateau regions. Meanwhile, planktonic diatom traits within life-forms were identified to be well responsive to the ecological environment quality (r = 0.56-0.60, P < 0.001) in the Yangtze. This study provided comprehensive insights into the multifunctionality of diatoms and their responses to environmental disturbance and environment quality, which helps to develop effective strategies for maintaining ecological stability in changing river environments.

Immobilization of the Polar Group into an Ultramicroporous Metal-Organic Framework Enabling Benchmark Inverse Selective CO2/C2H2 Separation with Record C2H2 Production.

One-step harvest of high-purity light hydrocarbons without the desorption process represents an advanced and highly efficient strategy for the purification of target substances. The separation and purification of acetylene (C2H2) from carbon dioxide (CO2) by CO2-selective adsorbents are urgently demanded yet are very challenging owing to their similar physicochemical properties. Here, we employ the pore chemistry strategy to adjust the pore environment by immobilizing polar groups into an ultramicroporous metal-organic framework (MOF), achieving one-step manufacture of high-purity C2H2 from CO2/C2H2 mixtures. Embedding methyl groups into prototype stable MOF (Zn-ox-trz) not only changes the pore environment but also improves the discrimination of guest molecules. The methyl-functionalized Zn-ox-mtz thus exhibits the benchmark reverse CO2/C2H2 uptake ratio of 12.6 (123.32/9.79 cm3 cm-3) and an exceptionally high equimolar CO2/C2H2 selectivity of 1064.9 at ambient conditions. Molecular simulations reveal that the synergetic effect of pore confinement and surfaces decorated with methyl groups provides high recognition of CO2 molecules through multiple van der Waals interactions. The column breakthrough experiments suggest that Zn-ox-mtz dramatically achieved the one-step purification capacity of C2H2 from the CO2/C2H2 mixture with a record C2H2 productivity of 2091 mmol kg-1, surpassing all of the CO2-selective adsorbents reported so far. In addition, Zn-ox-mtz exhibits excellent chemical stability under different pH values of aqueous solutions (pH = 1-12). Moreover, the highly stable framework and excellent inverse selective CO2/C2H2 separation performance showcase its promising application as a C2H2 splitter for industrial manufacture. This work paves the way to developing reverse-selective adsorbents for the challenging gas separation process.

Customizing Pore System in a Microporous Metal-Organic Framework for Efficient C2H2 Separation from CO2 and C2H4.

Selective-adsorption separation is an energy-efficient technology for the capture of acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4). However, it remains a critical challenge to effectively recognize C2H2 among CO2 and C2H4, owing to their analogous molecule sizes and physical properties. Herein, we report a new microporous metal-organic framework (NUM-14) possessing a carefully tailored pore system containing moderate pore size and nitro-functionalized channel surface for efficient separation of C2H2 from CO2 and C2H4. The activated NUM-14 (namely NUM-14a) exhibits sufficient pore space to acquire excellent C2H2 loading capacity (4.44 mmol g-1) under ambient conditions. In addition, it possesses dense nitro groups, acting as hydrogen bond acceptors, to selectively identify C2H2 molecules rather than CO2 and C2H4. The breakthrough experiments demonstrate the good actual separation ability of NUM-14a for C2H2/CO2 and C2H2/C2H4 mixtures. Furthermore, Grand Canonical Monte Carlo simulations indicate that the pore surface of the NUM-14a has a stronger affinity to preferentially bind C2H2 over CO2 and C2H4 via stronger C-H···O hydrogen bond interactions. This article provides some insights into customizing pore systems with desirable pore sizes and modifying groups in terms of MOF materials toward the capture of C2H2 from CO2 and C2H4 to promote the development of more MOF materials with excellent properties for gas adsorption and separation.

Combined Test of the Gravitational Inverse-Square Law at the Centimeter Range.

Experiments measuring the Newtonian gravitational constant G can offer uniquely sensitive probes of the test of the gravitational inverse-square law. An analysis of the non-Newtonian effect in two independent experiments measuring G is presented, which permits a test of the 1/r^{2} law at the centimeter range. This work establishes the strongest bound on the magnitude α of Yukawa-type deviations from Newtonian gravity in the range of 5-500 mm and improves the previous bounds by up to a factor of 7 at the length range of 60-100 mm.

Pore-Space Partition through an Embedding Metal-Carboxylate Chain-Induced Topology Upgrade Strategy for the Separation of Acetylene/Ethylene.

Ethylene (C2H4) is one of the most significant substances in the petrochemical industry; however, the capture of acetylene (C2H2) in about 1% from C2H2/C2H4 mixtures is a difficult task because of the similarity of their physical properties. With the aggravation of the energy crisis, using metal-organic framework (MOF) materials to purify C2H4 through adsorptive separation is a promising way to save energy and reduce emission. Pore-space partition (PSP) with the aim of enhancing the density of the binding sites and the strength of the host-guest interactions is an effective means to promote a solution for the challenging gas separation problems. Herein, we report a new embedding metal-carboxylate chain-induced topology upgrade strategy within a MOF to realize PSP and separation of C2H2/C2H4 mixtures. As a proof of concept, we construct a microporous MOF (NUM-12) utilizing the in situ insertion of cobalt terephthalic chains into a pretargeted ant-type framework during synthesis. Because of the attainment of an elaborately tuned aperture size and a specific pore environment through this strategy, NUM-12a (activated NUM-12) not only has a remarkable gas sorption capacity and strong interactions for C2H2 but also possesses an excellent purification performance for C2H2/C2H4 mixtures. Both experiments and simulation calculations clearly reveal that NUM-12 is a promising candidate for the separation of C2H2/C2H4, proving the feasibility of this new strategy for developing newly fashioned MOFs with adjustable structure and performance.

Constraints on the Velocity and Spin Dependent Exotic Interaction at the Micrometer Range.

We report on an experimental test of the velocity and spin dependent exotic interaction that can be mediated by new light bosons. The interaction is searched by measuring the force between a gold sphere and a microfabricated magnetic structure using a cantilever. The magnetic structure consists of stripes with antiparallel electron spin polarization so that the exotic interaction between the polarized electrons in the magnetic structure and the unpolarized nucleons in the gold sphere varies periodically, which helps to suppress the spurious background signals. The experiment sets the strongest laboratory constraints on the coupling constant between electrons and nucleons at the micrometer range with f_{⊥}<5.3×10^{-8} at λ=5 µm.

Improvement for Testing the Gravitational Inverse-Square Law at the Submillimeter Range.

We improve the test of the gravitational inverse-square law at the submillimeter range by suppressing the vibration of the electrostatic shielding membrane to reduce the disturbance coupled from the residual surface potential. The result shows that, at a 95% confidence level, the gravitational inverse-square law holds (|α|≤1) down to a length scale λ=48 µm. This work establishes the strongest bound on the magnitude α of the Yukawa violation in the range of 40-350 µm, and improves the previous bounds by up to a factor of 3 at the length scale λ≈70 µm. Furthermore, the constraints on the power-law potentials are improved by about a factor of 2 for k=4 and 5.

Design of a Carrier Wave for Capacitive Transducer with Large Dynamic Range.

Capacitive transducers are widely used in fundamental physics experiments, seismology, Earth or planetary observations, and space scientific and technical applications because of their high precision, simple structure, and compatibility with various measurements. However, in real applications, there is a trade-off between their resolution and dynamic range. Therefore, this paper is aimed at enlarging the dynamic range while ensuring high resolution. In this paper, a noise analysis of a capacitive transducer is presented, which shows that the amplitude noise of the carrier wave is the main limiting factor. Hence, a new method of generating a carrier wave with lower-amplitude noise is proposed in the paper. Based on the experimental verification, it is found that the carrier wave produced through the new method performed significantly better than the typical digital carrier wave when they were compared in the same sensing circuit. With the carrier wave produced through the new method, the dynamic range of the capacitive transducer can reach 120.7 dB, which is 18.3 dB greater than for the typical direct digital synthesis (DDS) method. In addition, the resolution of the carrier wave is mainly limited by the voltage reference components.

Combined Search for a Lorentz-Violating Force in Short-Range Gravity Varying as the Inverse Sixth Power of Distance.

Precision measurements of the inverse-square law via experiments on short-range gravity provide sensitive tests of Lorentz symmetry. A combined analysis of data from experiments at the Huazhong University of Science and Technology and Indiana University sets simultaneous limits on all 22 coefficients for Lorentz violation correcting the Newton force law as the inverse sixth power of distance. Results are consistent with no effect at the level of 10^{-12} m^{4}.

Test of the Equivalence Principle with Chiral Masses Using a Rotating Torsion Pendulum.

Here we present a new test of the equivalence principle designed to search for the possible violation of gravitational parity using test bodies with different chiralities. The test bodies are a pair of left- and right-handed quartz crystals, whose gravitational acceleration difference is measured by a rotating torsion pendulum. The result shows that the acceleration difference towards Earth Δa_{left-right}=[-1.7±4.1(stat)±4.4(syst)]×10^{-15} m s^{-2} (1-σ statistical uncertainty), correspondingly the Eötvös parameter η=[-1.2±2.8(stat)±3.0(syst)]×10^{-13}. This is the first reported experimental test of the equivalence principle for chiral masses and opens a new way to the search for the possible parity-violating gravitation.

New Test of the Gravitational Inverse-Square Law at the Submillimeter Range with Dual Modulation and Compensation.

By using a torsion pendulum and a rotating eightfold symmetric attractor with dual modulation of both the interested signal and the gravitational calibration signal, a new test of the gravitational inverse-square law at separations down to 295 µm is presented. A dual-compensation design by adding masses on both the pendulum and the attractor was adopted to realize a null experiment. The experimental result shows that, at a 95% confidence level, the gravitational inverse-square law holds (|α|≤1) down to a length scale λ=59 µm. This work establishes the strongest bound on the magnitude α of Yukawa-type deviations from Newtonian gravity in the range of 70-300 µm, and improves the previous bounds by up to a factor of 2 at the length scale λ≈160 µm.

Combined Search for Lorentz Violation in Short-Range Gravity.

Short-range experiments testing the gravitational inverse-square law at the submillimeter scale offer uniquely sensitive probes of Lorentz invariance. A combined analysis of results from the short-range gravity experiments HUST-2015, HUST-2011, IU-2012, and IU-2002 permits the first independent measurements of the 14 nonrelativistic coefficients for Lorentz violation in the pure-gravity sector at the level of 10^{-9} m^{2}, improving by an order of magnitude the sensitivity to numerous types of Lorentz violation involving quadratic curvature derivatives and curvature couplings.

A microporous bismuth-based MOF for efficient separation of acetylene from carbon dioxide.

The separation of acetylene from carbon dioxide is challenging due to their almost identical molecular sizes and volatilities. Metal-organic frameworks (MOFs) in general are strong candidates for the separation of gas mixtures owing to the presence of functional pore surfaces that can selectively capture specific target molecules. Herein, we report a stable and easily synthesized bismuth-based MOF, Bi-BTC, which can achieve the separation of acetylene and carbon dioxide. We performed a detailed analysis of the sorption properties of the Bi-MOF. Bi-BTC shows good adsorption capacities for C2H2 with a capacity of 53.8 cm3 g-1 at 298 K and 1.0 bar, and C2H2/CO2 selectivity of 5.14/7.69 at 298 K and 1.0/0.1 bar. IAST selectivity calculations indicate that Bi-BTC possesses good separation capacity, and dynamic breakthrough experiments were performed to prove the separation of C2H2 and CO2. Bi-MOFs as a group of relatively less studied types of MOFs have interesting adsorption characteristics, and this study on Bi-based MOF will enrich three-dimensional Bi-MOF adsorbents for gas adsorption and separation applications.

A high resolution and wide range valve for micronewton cold gas thrusters.

Numerous scientific satellites require micronewton thrusters for compensating environmental disturbances. The mass flow control proportional valve plays a crucial role in precisely regulating the thrust. To meet the high resolution and wide range requirements of the thrusters, this paper introduces a novel proportional valve with two sets of independently controllable piezoelectric stack. One set of the piezo-stack is used to compensate the stroke loss of the valve core, mainly caused by the deformation of the valve seat. The valve sealing mechanism is carefully analyzed to reduce the stroke loss. Another set of the stack works as the primary actuator, enabling the high mass flow control resolution. Two sets of independently controlled piezoelectric stacks not only expand the range and improve the range ratio but also provide redundancy and enhance reliability. This means that the actuator can still operate at lower ranges even if one piezo-stack is damaged. The piezo-actuators are assembled using U-shaped connectors, creating a compact and space-efficient overall design. Experimental tests have been conducted to verify the performance of the valve, which demonstrated a mass flow range of 0-675 µg/s with a resolution better than 0.1 µg/s and a flow noise below 0.1 µg/s/Hz1/2 at 0.1 mHz-1 Hz.

Effect of metal pollution on the distribution and co-occurrence pattern of bacterial, archaeal and fungal communities throughout the soil profiles.

Metal pollution has raised negative impact on microbes, but little is known about the distribution and co-occurrence pattern of bacterial, fungal and archaeal communities along the soil profiles at multiple metal contamination sites. Here, we characterized the variations of metal concentrations and microbial communities with soil depth along five deep bores at the Tanghe Sewage Reservoir, a typical metal contamination area on the North China Plain. Co, Cd, Mg, Se, and Li were identified as the major contaminants in this area, and the pollution load index was 1.88, 1.54 and 1.62 in the shallow layer (0-0.6 m), deep layer (>2.0 m) and middle layer (0.6-2.0 m), respectively. The diversities and compositions of bacterial, archaeal and fungal communities varied significantly along the soil profiles. Deterministic process played a crucial role in shaping the difference of microbial community compositions among different soil layers, in which metal levels contributed more than soil physiochemical parameters. Furthermore, the interspecific co-occurrence network was most complex in the middle layer, indicating that metal pollution could decrease microbial network complexity. Bacterial keystone species in the co-occurrence networks showed both positive and negative correlations with polluted metals, whereas most archaeal and fungal keystone species were negatively related to multiple metals. These findings increased our understanding of distribution patterns, co-occurrence networks and environmental drivers of microbial communities in metal pollution soils.

Insights into the responses of fungal taxonomy and function to different metal(loid) contamination levels.

Fungi possess prominent tolerance and detoxification capacities in highly metal(loid)-polluted systems, yet little is known about their responding behaviors under different contamination conditions. Here, we systematically investigated the structure and function profiles of fungal communities in an abandoned reservoir mainly contaminated by multiple metal(loid)s such as Al, Be, Cd, Co, Cr, and Cu. This abandoned reservoir consisted of three distinct zones, i.e., Zone I with the shortest deprecation time and the highest metal(loid) contamination; Zone II with the medium deprecation time and medium metal(loid) contamination; and Zone III with the longest abandonment time and the lowest metal(loid)contamination. The lowest pH and the highest contents of OM, TN, and TP were also observed for the high-contamination Zone I, followed by the moderate-contamination Zone II and the low-contamination Zone III. Fungal biodiversity was found to be robust and dominated by many endurable genera in Zone I, and notable cooperative relationships among fungal species facilitated their viability and prosperity under severe metal(loid) contaminations. Differently, the lowest biodiversity and fragile co-occurrence network were identified in Zone II. As metal(loid) contaminations reduced from Zone I to Zone III, dominant fungal functions gradually changed from undefined saprotroph guild to parasites or pathogens of plant-animal (i.e. animal pathogen, endophyte, and plant pathogen). Moreover, metal(loid)s combined with physicochemical properties jointly mediated the fungal taxonomic and functional responses to different metal(loid) contamination levels. Overall, this study not only broadens the understanding of taxonomic and functional repertoires of fungal communities under different metal(loid) contaminated conditions, but also highlights the crucial contributions of specific fungi to bioremediation and management in varying metal(loid)-polluted environments.

Deciphering the dynamics of metal and antibiotic resistome profiles under different metal(loid) contamination levels.

Metal(loid) contaminations pose considerable threats to ecological security and public health, yet little is known about the dynamics of metal resistance genes (MRGs) and antibiotic resistance genes (ARGs) under different metal(loid) contamination levels. Here, we provided a systematic investigation of MRGs and ARGs in three zones (Zones I, II, and III) with different metal(loid) contamination levels across an abandoned sewage reservoir. More diverse MRGs and ARGs were detected from the high-contaminated Zone I and the moderate-contaminated Zone II, while the abundant MGEs (mobile genetic elements) potentially enhanced the horizontal gene transfer potential and the resistome diversity in Zone I. Particularly, resistome hosts represented by Thiobacillus, Ramlibacter, and Dyella were prevalent in Zone II, promoting the vertical gene transfer of MRGs and ARGs. The highest health risk of ARGs was predicted for Zone I (about 7.58% and 0.48% of ARGs classified into Rank I and Rank II, respectively), followed by Zone II (2.11% and 0%) and Zone III (0% and 0%). However, the ARGs co-occurring with MRGs might exhibit low proportions and low health risks (all were Rank IV) in the three zones. Overall, these findings uncovered the dynamic responses of resistomes and their hosts to different metal(loid) contamination levels, contributing to formulating accurate management and bioremediation countermeasures for various metal(loid) contaminated environments.

Structure, stability, and potential function of groundwater microbial community responses to permafrost degradation on varying permafrost of the Qinghai-Tibet Plateau.

The ongoing permafrost degradation under climate warming has modified aboveground biogeochemical processes mediated by microbes, yet groundwater microbial structure and function as well as their response to permafrost degradation remain poorly understood. We separately collect 20 and 22 sub-permafrost groundwater samples from Qilian Mountain (alpine and seasonal permafrost) and Southern Tibet Valley (plateau isolated permafrost) on the Qinghai-Tibet Plateau (QTP) to investigate the effects of permafrost groundwater characteristics on the diversity, structure, stability, and potential function of bacterial and fungal communities. Regional discrepancy of groundwater microbes between two permafrost regions reveals that permafrost degradation might reshape microbial community structure, increase community stability and potential functions relevant to carbon metabolism. Bacterial community assembly in permafrost groundwater is governed by deterministic processes, whereas fungal communities are mainly controlled by stochastic processes, suggesting that bacterial biomarkers might provide the better 'early warning signals' to permafrost degradation in deeper layers. Our study highlights the importance of groundwater microbes in ecological stability and carbon emission on the QTP.

Investigating temperature-induced torque noise of a torsion pendulum based on temperature modulation at different frequencies.

Torsion pendulums are widely used for the measurement of small forces. In this study, we investigated the impact of temperature fluctuations on a torsion pendulum using heating devices to modulate the environmental temperature at different specific frequencies. The response coefficient between the temperature variation and the torque of the torsion pendulum was found to vary at different frequencies, with values from 4 × 10-15 N mK-1 at 0.1 mHz to 3 × 10-13 N mK-1 at 10 mHz. A passive thermal-insulation system was used to reduce the torque response within this frequency band, which is dominated by temperature noise. The results demonstrate that this modulation method provides a useful way to independently investigate the noise in a torsion pendulum resulting from environmental temperature fluctuations over a wide frequency band.