Growth of infants delivered by mothers with HIV in Guangxi, China: An 18-month longitudinal follow-up study, 2015-2021.

OBJECTIVES: The prevention of mother-to-child transmission of HIV has been a global success. But little is known about the growth parameters of infants delivered by mothers with HIV or the drug resistance of infants with HIV in China. The study aimed to assess growth parameters and drug resistance in Chinese infants exposed to HIV. METHODS: We conducted an 18-month longitudinal follow-up study of 3283 infants (3222 without HIV; 61 with HIV) born to mothers with HIV in the Guangxi Zhuang Autonomous Region between January 2015 and December 2021. The weight and length of all participants was recorded. In addition, genetic subtypes and drug resistance analysis were performed for infants with HIV. RESULTS: Compared with infants without HIV, those with HIV had significantly lower weight/length Z-scores, except at 18 months of age. The length/age Z-scores of infants with HIV was significantly reduced, except at 1 month of age. The weight/age Z-scores of infants with HIV were significantly lower at all follow-up time points. The weight/length Z-scores of male infants without HIV were significantly lower than for female infants without HIV at all follow-up time points. Male infants without HIV had lower length/age and weight/age Z-scores than female infants at the remaining follow-up points, except at 1 month of age. Of a total of 61 infants with HIV, subtype and drug-resistance data were obtained from 37 (60.66%) samples. Infants with HIV were dominated by the CRF01_AE genotype and showed a diversity of mutation sites dominated by non-nucleoside reverse transcriptase inhibitor resistance. CONCLUSION: Our study demonstrates the growth of infants exposed to HIV in southwest China and provides detailed information on subtype distribution and drug resistance of those with HIV. Nutritional support and drug-resistance surveillance for infants exposed to HIV need to be strengthened.

Self-assembly for preparing nanotubes from monolayer graphyne ribbons on a carbon nanotube.

Graphyne nanotube (GNT), as a promising one-dimensional carbon material, attracts extensive attention in recent years. However, the synthesis of GNT is still challenging even in the laboratory. This study reveals the feasibility of fabricating a GNT by self-assembling a monolayer graphyne (GY) ribbon on a carbon nanotube (CNT) via theoretical and numerical analysis. Triggered by the van der Waals force from the CNT, a GY ribbon near the tube first winds upon the tube and then conditionally self-assembles to form a GNT. The self-assembly process and result are heavily influenced by the ambient temperature, which indicates the thermal vibration of the nanosystem. Molecular dynamic simulation results address the temperature range conducive to successful self-assembly. Different types of GNTs, e.g.α-,ß-, andγ-GNTs with specified chirality (armchair, zigzag, and chiral), length, and radius, can be obtained via self-assembly by controlling the geometry of the GY ribbons and temperature. The present theoretical understanding is helpful for fabricating GNTs with predefined morphology.

Trends in the psychosocial and mental health of HIV-positive women in China from 2015 to 2020: Results from two cross-sectional surveys.

BACKGROUND: The human immunodeficiency virus (HIV) continues to be one of the major public health challenges in the world. Despite the advancement in medication and changes in views towards HIV in Chinese society, little is known about the changes in the psychosocial and mental health of HIV-positive women in recent years. OBJECTIVES: The present study examined the change in depression, anxiety, stigma, relationship with the child, intimacy with a partner, and social support from family, friends, and health professionals, for HIV-positive women in China from 2015 to 2020. METHODS: Two cross-sectional surveys were conducted in 2015 and 2020, and 429 and 382 HIV-positive women were recruited from the Women's Health Department in Yunnan and Guangxi, China between November 2015 to May 2016, and November 2019 to January 2020, respectively. RESULTS: After controlling for significant sociodemographic variables, participants recruited in 2019-2020 had significantly lower levels of depression and anxiety and higher scores on emotional and tangible support from friends. On the other hand, they had lower scores in intimacy with partners and emotional and tangible support from family. No significant changes were found in stigma, relationship with the child, and support from health professionals. CONCLUSION: Results provide important information on the changes in psychosocial and mental health, which offer insights into the design of interventions to promote psychosocial and mental health among HIV-positive women in China. PATIENT OR PUBLIC CONTRIBUTION: HIV-positive women contributed to the data of this study. Health care professionals were involved in the discussion of the methods and results.

Bonding few-layered graphene via collision with high-speed fullerenes.

Graphene, as a typical two-dimensional material, is popular in the design of nanodevices. The interlayer relative sliding of graphene sheets can significantly affect the effective bending stiffness of the few-layered graphene. For restricting the relative sliding, we adopted the atomic shot peening method to bond the graphene sheets together by ballistic C60 fullerenes from its two surfaces. Collision effects are evaluated via molecular dynamics simulations. Results obtained indicate that the fullerenes' incident velocity has an interval, in which the graphene sheet can be bonded after collision while no atoms on the fullerenes escaping from the graphene ribbon after collision. The limits of the interval increase with the layer number. Within a few picoseconds of collision, a stable carbon network is produced at an impacted area. The graphene sheets are bonded via the network and cannot slide relatively anymore. Conclusions are drawn to show the way of potential applications of the method in manufacturing a new graphene-based two-dimensional material that has a high out-of-plane bending stiffness.

A method for designing tunable chiral mechanical carbon networks for energy storage.

A method is proposed for designing tunable chiral nano-networks using partly hydrogenated graphene ribbons and carbon nanotubes (CNTs). In the network, the hydrogenated graphene ribbons (HGRs) act as basic components, which connect each other via CNT joints. Each component contains two HGR segments and an internal graphene joint (G-J2) or CNT joint (CNT-J2). Since the two HGR segments are hydrogenated at opposite surfaces, they may wind in chiral about the internal joint to form a scroll (G-J2-scroll or CNT-J2-scroll) or about the two end joints to form CNT-J4-scrolls. In general, a G-J2-scroll is formed more easily than both a CNT-J4-scroll and a CNT-J2-scroll. Because of scrolling, the surface energy is reduced. This reduction is converted to and stored as deformation potential energy. By means of molecular-dynamics simulations, we studied the final configurations of two types of networks from the same components, the maximum shrinkage, and their capacity of energy storage for potential application of energy storage or as large-deformable components in a nano-device. The results indicate that the network reaches a stable state when the shrinkage reaches 70% of the two in-plane dimensions.

Dynamic Behavior of Rotation Transmission Nano-System in Helium Environment: A Molecular Dynamics Study.

The molecular dynamics (MD) method is used to investigate the influence of the shielding gas on the dynamic behavior of the heterogeneous rotation transmission nano-system (RTS) built on carbon nanotubes (CNTs) and boron nitride nanotube (BNNT) in a helium environment. In the heterogeneous RTS, the inner CNT acts as a rotor, the middle BNNT serves as a motor, and the outer CNT functions as a stator. The rotor will be actuated to rotate by the motor due to the interlayer van der Waals effects and the end effects. The MD simulation results show that, when the gas density is lower than a critical range, a stable signal of the rotor will arise on the output and the rotation transmission ratio (RRT) of RTS can reach 1.0, but as the gas density is higher than the critical range, the output signal of the rotor cannot be stable due to the sharp drop of the RRT caused by the large friction between helium and the RTS. The greater the motor input signal of RTS, the lower the critical working helium density range. The results also show that the system temperature and gas density are the two main factors affecting the RTS transmission behavior regardless of the size of the simulation box. Our MD results clearly indicate that in the working temperature range of the RTS from 100 K to 600 K, the higher the temperature and the lower the motor input rotation frequency, the higher the critical working helium density range allows.

Thermal shrinkage and stability of diamondene nanotubes.

By curving a rectangular diamondene, an sp 2/sp 3 composite carbon film, a diamondene nanotube (DNT) can be formed when the two straight edges are sewn together. In this study, thermal stabilities of DNTs are investigated using molecular dynamics simulation approaches. An interesting thermal shrinkage of damaged DNTs is discovered. Results indicate that DNTs have critical temperatures between 320 K and 350 K. At temperatures higher than the critical value, the interlayer bonds, i.e., the sp 3-sp 3 bonds, may break. The broken ratio of the interlayer bonds mainly depends on the temperature. For the DNT with a high broken ratio of interlayer bonds, it has thermal shrinkage in both the cross section and tube axis. The sp 2-sp 3 bonds in either the inner or the outer surface are much more stable. Even at 900 K, only a few sp 2-sp 3 bonds break. These properties can be used in the design of metamaterials.

Friction effect of stator in a multi-walled CNT-based rotation transmission system.

The rotation transmission system (RTS) made from co-axial multi-walled nanotubes (MWNTs) has the function of regulating the input rotation from a nanomotor. The mechanism for the regulation is that the friction among the tubes during rotation governs the rotation of the rotors in the nanosystem. By integrating a rotary nanomotor and a nanobearing into an MWNT-based RTS, it is discovered that the stator (outer tube) provides relatively greater friction on the rotors by penetrating the motor tube, which has a higher stable rotational frequency. And the output rotation of the rotors in the system depends significantly on the temperature of the system, as the rotor tubes are slightly longer than the motor tube. Briefly, at low temperatures, say 8 K, the rotors rotate synchronously with the motor. However, at high temperatures, the rotors rotate slower than the motor with a bigger difference between their rotational frequencies. Hence, the output rotational frequencies can be adjusted by changing the temperature as well as the input rotational frequency.

Coupling effect of van der Waals, centrifugal, and frictional forces on a GHz rotation-translation nano-convertor.

A nano rotation-translation convertor with a deformable rotor is presented, and the dynamic responses of the system are investigated considering the coupling among the van der Waals (vdW), centrifugal and frictional forces. When an input rotational frequency (ω) is applied at one end of the rotor, the other end exhibits a translational motion, which is an output of the system and depends on both the geometry of the system and the forces applied on the deformable part (DP) of the rotor. When centrifugal force is stronger than vdW force, the DP deforms by accompanying the translation of the rotor. It is found that the translational displacement is stable and controllable on the condition that ω is in an interval. If ω exceeds an allowable value, the rotor exhibits unstable eccentric rotation. The system may collapse with the rotor escaping from the stators due to the strong centrifugal force in eccentric rotation. In a practical design, the interval of ω can be found for a system with controllable output translation.

Thermal Vibration-Induced Rotation of Nano-Wheel: A Molecular Dynamics Study.

By bending a straight carbon nanotube and bonding both ends of the nanotube, a nanoring (or nano-wheel) is produced. The nanoring system can be driven to rotate by fixed outer nanotubes at room temperature. When placing some atoms at the edge of each outer tube (the stator here) with inwardly radial deviation (IRD), the IRD atoms will repulse the nanoring in their thermally vibration-induced collision and drive the nanoring to rotate when the repulsion due to IRD and the friction with stators induce a non-zero moment about the axis of rotational symmetry of the ring. As such, the nanoring can act as a wheel in a nanovehicle. When the repulsion is balanced with the intertubular friction, a stable rotational frequency (SRF) of the rotor is achieved. The results from the molecular dynamics simulation demonstrate that the nanowheel can work at extremely low temperature and its rotational speed can be adjusted by tuning temperature.

Self-assembly of a nanotube from a black phosphorus nanoribbon on a string of fullerenes at low temperature.

A string of fullerenes is used for generating a nanotube by self-assembly of a black phosphorus (BP) nanoribbon at a temperature of 8 K. Among the fullerenes in the string, there are at least two fixed fullerenes placed along the edge of the BP ribbon for keeping its configuration stability during winding. By way of molecular dynamics simulations, it is found that successful generation of a BP nanotube depends on the bending stiffness of the ribbon and the attraction between the fullerenes and the ribbon. When the attraction is strong enough, the two edges (along the zigzag direction) of the BP ribbon will be able to bond covalently to form a nanotube. By the molecular dynamics approach, the maximum width of the BP ribbon capable of forming a nanotube with a perfect length is investigated in three typical models. The maximum width of the BP ribbon becomes larger with the string containing more fullerenes. This finding reveals a way to control the width of the BP ribbon which forms a nanotube. It provides guidance for fabricating a BP nanotube with a specified length, the same as to the width of the ribbon.

Buckling behaviour of composites with double walled nanotubes from carbon and phosphorus.

Due to weak interactions among phosphorus atoms in black phosphorene, a nanotube obtained by curling single-layer black phosphorus is not as stable as a carbon nanotube (CNT) at finite temperature. In the present work, we recommend a new 1D composite material with a double-walled nanotube (DWNT) from a black phosphorus nanotube (BPNT) and a CNT. The dynamic response of the composite DWNTs is simulated using a molecular dynamics approach. Effects of the factors including temperature, slenderness and configurations of DWNTs on dynamic behavior of the composite are discussed. Compared with a single-walled BPNT, the composite DWNTs under uniaxial compression show some unique properties. When a BPNT is embedded in a CNT which will not only isolate the BPNT from the ambient conditions, but also improve the capability of axial deformation of the BPNT, the system will not collapse rapidly even if the BPNT has been buckled.

Biophysical implications of lipid bilayer rheometry for mechanosensitive channels.

The lipid bilayer plays a crucial role in gating of mechanosensitive (MS) channels. Hence it is imperative to elucidate the rheological properties of lipid membranes. Herein we introduce a framework to characterize the mechanical properties of lipid bilayers by combining micropipette aspiration (MA) with theoretical modeling. Our results reveal that excised liposome patch fluorometry is superior to traditional cell-attached MA for measuring the intrinsic mechanical properties of lipid bilayers. The computational results also indicate that unlike the uniform bilayer tension estimated by Laplace's law, bilayer tension is not uniform across the membrane patch area. Instead, the highest tension is seen at the apex of the patch and the lowest tension is encountered near the pipette wall. More importantly, there is only a negligible difference between the stress profiles of the outer and inner monolayers in the cell-attached configuration, whereas a substantial difference (∼30%) is observed in the excised configuration. Our results have far-reaching consequences for the biophysical studies of MS channels and ion channels in general, using the patch-clamp technique, and begin to unravel the difference in activity seen between MS channels in different experimental paradigms.

Sound transmission loss through metamaterial plate with lateral local resonators in the presence of external mean flow.

In the context of sound incident upon a metamaterial plate, explicit formulas for sound transmission loss (STL) are derived in the presence of external mean flow. Metamaterial plate, consisting of homogeneous plate and lateral local resonators (LLRs), is homogenized by using effective medium method to obtain the effective mass density and facilitate the calculation of STL. Results show that (a) vigorously oscillating LLRs lead to higher STL compared with bare plate, (b) increasing Mach number of the external mean flow helps obtain higher STL below the coincidence frequency but decreases STL above the coincidence frequency due to the added mass effect of light fluid loading and aerodynamic damping effect, (c) the coincidence frequency shifts to higher frequency range for the refracted effect of the external mean flow. However, effects of the flow on STL within negative mass density range can be neglected because of the lateral local resonance occurring. Moreover, hysteretic damping from metamaterial can only smooth the transmission curves by lowering higher peaks and filling dips. Effects of incident angles on STL are also examined. It is demonstrated that increasing elevation angle can improve the sound insulation, while the azimuth angle does not.

A nanoengine governor based on the end interfacial effect.

A conceptual design is presented for a nanoengine governor based on the end interfacial effect of two rotary nanotubes. The governor contains a thermal-driven rotary nanomotor made from double-walled carbon nanotubes (DWCNTs) and a coaxially laid out rotary nanotube near one end of the nanomotor rotor. The rotation of the rotor in the nanomotor can be controlled by two features. One is the stator (the outer tube of DWCNTs) which has some end atoms with inward radial deviation (IRD) on the stator. The other is the relative rotation of the neighboring rotary tube of the rotor. As the configuration of the stator is fixed, the end interfacial interaction between the two rotors will govern the dynamic response of the rotor in the nanomotor system. The obtained results demonstrate that the relative rotational speed between the two rotors provides friction on the rotor in the nanomotor system. In particular, higher relative rotational speed will provide lower friction on rotor 1, which is opposite to that between neighboring shells in DWCNTs.

Thermal stability of a free nanotube from single-layer black phosphorus.

Similar to a carbon nanotube fabricated from a graphene sheet, a black phosphorus nanotube (BPNT) can also be theoretically produced by curling rectangular single-layer black phosphorus (SLBP). In the present study, the effect of the thermal vibration of atoms on the failure of a BPNT is investigated using molecular dynamics simulations. Two types of double-shell BPNTs obtained by curling the SLBP along its armchair/pucker and zigzag directions respectively are involved in simulation. At finite temperature, a bond on the outer shell of the tube is under tension due to both the curvature of the tube and the serious thermal vibration of the atoms. As the length of a bond with such elongation approaches its critical value, i.e. 0.279 nm, or the smallest distance between two nonbonding phosphorus atoms is over 0.389 nm caused by a great variation of the bond angle, the tube fails quickly. The critical stable states of either an armchair or a zigzag BPNT at finite temperature are calculated and compared. To achieve a stable BPNT with high robustness, the tube should have a higher radius or should work at a lower temperature. Only when the BPNT has structural stability does it have the potential application as a nanowire in a future nano electro-mechanical system.

Exciton and Trion Dynamics in Bilayer MoS2.

The control of exciton and triondynamics in bilayer MoS2 is demonstrated, via the comodulations by both temperature and electric field. The calculations here show that the band structure of bilayer MoS2 changes from indirect at room temperature toward direct nature as temperature decreases, which enables the electrical tunability of the K-K direct PL transition in bilayer MoS2 at low temperature.

Meshless method with operator splitting technique for transient nonlinear bioheat transfer in two-dimensional skin tissues.

A meshless numerical scheme combining the operator splitting method (OSM), the radial basis function (RBF) interpolation, and the method of fundamental solutions (MFS) is developed for solving transient nonlinear bioheat problems in two-dimensional (2D) skin tissues. In the numerical scheme, the nonlinearity caused by linear and exponential relationships of temperature-dependent blood perfusion rate (TDBPR) is taken into consideration. In the analysis, the OSM is used first to separate the Laplacian operator and the nonlinear source term, and then the second-order time-stepping schemes are employed for approximating two splitting operators to convert the original governing equation into a linear nonhomogeneous Helmholtz-type governing equation (NHGE) at each time step. Subsequently, the RBF interpolation and the MFS involving the fundamental solution of the Laplace equation are respectively employed to obtain approximated particular and homogeneous solutions of the nonhomogeneous Helmholtz-type governing equation. Finally, the full fields consisting of the particular and homogeneous solutions are enforced to fit the NHGE at interpolation points and the boundary conditions at boundary collocations for determining unknowns at each time step. The proposed method is verified by comparison of other methods. Furthermore, the sensitivity of the coefficients in the cases of a linear and an exponential relationship of TDBPR is investigated to reveal their bioheat effect on the skin tissue.

Band gap of shear horizontal waves for one-dimensional phononic crystals with chiral materials.

Extensive applications of chiral lattice structures in the field of acoustic wave manipulation and vibration modulation show the effectiveness of chirality route to the design of phononic crystals. However, how and to what extent the material chirality affects the band gap properties of phononic crystals remains unclear. In this study, one-dimensional phononic crystals made of chiral materials is proposed, and a theoretical model of shear horizontal (SH) wave propagation in the chiral phononic crystals is developed based on the noncentrosymmetric micropolar elasticity theory. Through the transfer matrix method, the dispersion relationship of SH wave propagation is obtained and the effects of material chirality on the band-gap properties are investigated. Our work demonstrates that the change of material chirality can significantly affect the dispersion relationship of phononic crystals, leading to the wide band gap and low frequency. In a unit cell, when the chiral coefficients of the two parts have opposite signs but the same magnitude and the chiral directions are consistent with the vibrational direction, it is the most favorable for the phononic crystals to achieve the lowest frequency and widest band gap. This study suggests that the material chirality can be harnessed to effectively tune the band-gap properties of phononic crystals. The present study provides insight for the chirality route to the design of phononic crystals.

The characterization of bovine compact bone fatigue damage using terahertz spectroscopy.

Fatigue can cause cracks to propagate from the micro- to the macroscale, which results in a decrease of Young's modulus of the bone. Non-destructive measurements of bone fatigue damage are of great importance for bone quality assessment and fracture prevention. Unfortunately, there is still a lack of effective nondestructive methods sensitive to the initial deterioration during damage accumulation, particularly in the field of orthopedics and biomechanics. In this study, terahertz spectroscopy was adopted to evaluate microscale bone damage. Specifically, the refractive index and Young's modulus of bone samples subjected to different degrees of fatigue damage were tested at a fixed area. Both parameters are found to decrease in two stages under cycled fatigue loading, which is attributed to the initial onset and subsequent development of microdamage during fatigue loading. The change in refractive index reflects the accumulation of fatigue damage as well as the decrease in Young's modulus.