Inspired by the ubiquitous helical structures in nature,research on artificial helices has attracted increasing attention.As a unique and complex three-dimensional(3D)geometry in the microscopic world,the micro-/nano ...Inspired by the ubiquitous helical structures in nature,research on artificial helices has attracted increasing attention.As a unique and complex three-dimensional(3D)geometry in the microscopic world,the micro-/nano helix has significant advantages in wide applications due to its distinctive properties at the micro-scale.Micro-/nanotechnology is advancing rapidly.The geometric complexity of helical structure poses technical challenges for the manufacturing at the micro-/nanoscale,requiring some emerging manufacturing techniques.In this review,we systematically classify and summarize existing manufacturing methods for micro/nano helical structures and their underlying mechanisms.Based on the unique physical properties of helical structures at the microscale,their latest applications are analyzed across different fields.Finally,we conclude the challenges and future research directions of micro-/nano helices in manufacturing methods and applications.展开更多
The novel complex{[Co(bipy)(azpy)_(2)(NCS)_(2)]·H_(2)O}n(where bipy=4,4′bipyridine,azpy=4,4′azobisp yridine)has been synthesized and characterized by elemental analyses,IR,UV,thermal analyses,and variable tempe...The novel complex{[Co(bipy)(azpy)_(2)(NCS)_(2)]·H_(2)O}n(where bipy=4,4′bipyridine,azpy=4,4′azobisp yridine)has been synthesized and characterized by elemental analyses,IR,UV,thermal analyses,and variable temperature magnetic susceptibility.The crystal(C_(32)H_(26)CoN_(12)OS_(2),Mr=717.70)belongs to the orthorhombic,space group Pnna,a=2.21312(16)nm,b=1.40403(10)nm,c=1.14237(8)nm,V=3.5497(4)nm^(3),Z=4,Dc=1.343g·cm^(-3),μ=0.645mm^(-1),F(000)=1476,and final R_(1)=0.0691,wR_(2)=0.1129 for 231 parameters and 1674 observed reflections[I>2.00σ(I)].The Co(Ⅱ)atom is,in a distorted octahedral geometry,coordinated by six nitrogen atoms from two bridging bipy,two monodentate azpy,and two thiocyanate groups.The bridging ligand bipy links Co(Ⅱ)atoms to form the infinite“rod"with terminal coordination azpy ligand acting as sidearms.Unprecedented three parallel interpenetrating two dimensional(4,4)networks and novel infinite triple helices are formed via hydrogen bonding interactions.CCDC:155588.展开更多
In this work, the formation sites, helical parameters and hydrogen bond positions of Konjac glucomannan molecular helices were investigated using molecular dynamic simulation method. To our interest, the KGM chain is ...In this work, the formation sites, helical parameters and hydrogen bond positions of Konjac glucomannan molecular helices were investigated using molecular dynamic simulation method. To our interest, the KGM chain is mainly composed by local left and right helix struetttres. The formation sites of KGM chain might locate at the chain-segments containing acetyl groups, and the left helix is the favorable conformation of KGM. Temperature-dependent molecule conformation study indicates that the right helix is dominant when the temperature is lower than 343 K, above which, however, the left helix is dominating （right helix disappears）. In addition, intramolecular hydrogen bonds in the left helix can be found at the -OH groups on C（2）, C（4） and C（6） of mannose residues; comparably, the intramolecular hydrogen bonds in the right helix can be mainly observed at the -OH groups on C（4） and C（6） of the mannose residues and C（3） of the glucose residues. In conclusion, molecular dynamic simulation is an efficient method for the microscopic conformation study of glucomannan molecular helices.展开更多
A brilliant purple octahedral single crystal is hydrothermally synthesized by the reaction of CoCl26H2O, H3BO3 and H3PO4 in NaOH aqueous solution of CH3(CH2)15N(CH3)3Br, and its crystal structure has been characterize...A brilliant purple octahedral single crystal is hydrothermally synthesized by the reaction of CoCl26H2O, H3BO3 and H3PO4 in NaOH aqueous solution of CH3(CH2)15N(CH3)3Br, and its crystal structure has been characterized by single-crystal X-ray diffraction. The compound, NaCo(H2O)2BP2O8稨2O (Mr = 336.72), belongs to hexagonal, space group P6122 with a = 9.447(5), c = 15.83(1) , V = 1223(1) 3, Dc = 2.742 g/cm3, Z = 6, F(000) = 1002 and m = 2.606 mm-1. The three-dimensional framework in the compound is built up from the linkage tetrahedral ribbons, in which the BO4 and PO4 tetrahedra alternate with CoO6 octahedra. The sodium ions and water molecules are located within the free thread of the helical ribbons.展开更多
The first primary organicamine templated indium iodate with the formula （H2en）KIn（IO3）6-2（H2O） was hydrothermally synthesized via reaction at 100 ℃ for 7 d and characterized by single-crystal X-ray diffraction ...The first primary organicamine templated indium iodate with the formula （H2en）KIn（IO3）6-2（H2O） was hydrothermally synthesized via reaction at 100 ℃ for 7 d and characterized by single-crystal X-ray diffraction and thermal analysis. The compound crystallized in a triclinic system with space group P1, a=0.69803（14） nm, b=0.70863（14） nm, c=1.2091（2） nm, a=76.417（4）°,β=79.953（4）°, γ=72.206（3）°, V=0.55012（19） nm3. Structure determination indicates that it is made up of zero-dimensional units each of which consists of [In（IO3）6]3 anion, potassium, water and ethylenediamine cation. The most striking feature of the compound is that it possesses helical hydrogen bonds formed by organic amine template, water molecules and inorganic network.展开更多
Aquaporin （AQP） is a water channel protein found in various subcellular membranes of both prokaryotic and eukaryotic cells. The physiological functions of AQPs have been elucidated in many organisms. However, unders...Aquaporin （AQP） is a water channel protein found in various subcellular membranes of both prokaryotic and eukaryotic cells. The physiological functions of AQPs have been elucidated in many organisms. However, understanding their biogenesis remains elusive, particularly regarding how they assemble into tetramers. Here, we investigated the amino acid residues involved in the tetramer formation of the Arabidopsis plasma membrane AQP AtPIP2;1 using extensive amino acid substitution mutagenesis. The mutant proteins V41A/ E44A, F51A/L52A, F87A/191A, F92A/193A, V95A/Y96A, and H216A/L217A, harboring alanine substitutions in the transmembrane （TM） helices of AtPIP2;1 polymerized into multiple oligomeric complexes with a vari- able number of subunits greater than four. Moreover, these mutant proteins failed to traffic to the plasma membrane, instead of accumulating in the endoplasmic reticulum （ER）. Structure-based modeling revealed that these residues are largely involved in interactions between TM helices within monomers. These results suggest that inter-TM interactions occurring both within and between monomers play crucial roles in tetramer formation in the AtPIP2;1 complex. Moreover, the assembly of AtPIP2;1 tetramers is critical for their trafficking from the ER to the plasma membrane, as well as water permeability.展开更多
Helix as essential molecular chiral phenomenon at supramolecular level offers an affective method to study chiral characteristic of homochiral coordination polymers(CPs).Herein,two homochiral CPs[Cd((R)-CBA)_(2)(3,5-D...Helix as essential molecular chiral phenomenon at supramolecular level offers an affective method to study chiral characteristic of homochiral coordination polymers(CPs).Herein,two homochiral CPs[Cd((R)-CBA)_(2)(3,5-DIT)]_(n)((R)-H_(2) CBA=(R)-4-(1-carboxyethoxy)benzoic acid,3,5-DIT=3,5-di(1 H-imidazol-1-yl)toluene,1-R)and[Zn((R)-CBA)(3,5-DIT)]_(n)(2-R)were synthesized under hydrothermal conditions.In complex 1-R,only a helical chain was built by chiral ligands(R)-CBA2-,ancillary ligands 3,5-DIT and Cd(Ⅱ)ions.After Cd(Ⅱ)ions were replaced by Zn(Ⅱ)ions under similar reaction system,Zn(Ⅱ),(R)-CBA^(2-)and/or 3,5-DIT formed six types of helices,resulting in complex 2-R.So,the metal ions played a key role in the construction of helical structures.Complexes 1-R and 2-R were also characterized by elemental analysis,PXRD,TGA,CD and UV-visible absorptions.In addition,complexes 1-R and 2-R exhibited different photoluminescence behaviors in solid sate compared to free ligand(R)-H_(2)CBA.展开更多
Autografting is the gold standard for surgical repair of nerve defects>5 mm in length;however,autografting is associated with potential complications at the nerve donor site.As an alternative,nerve guidance conduit...Autografting is the gold standard for surgical repair of nerve defects>5 mm in length;however,autografting is associated with potential complications at the nerve donor site.As an alternative,nerve guidance conduits may be used.The ideal conduit should be flexible,resistant to kinks and lumen collapse,and provide physical cues to guide nerve regeneration.We designed a novel flexible conduit using electrospinning technology to create fibers on the innermost surface of the nerve guidance conduit and employed melt spinning to align them.Subsequently,we prepared disordered electrospun fibers outside the aligned fibers and helical melt-spun fibers on the outer wall of the electrospun fiber lumen.The presence of aligned fibers on the inner surface can promote the extension of nerve cells along the fibers.The helical melt-spun fibers on the outer surface can enhance resistance to kinking and compression and provide stability.Our novel conduit promoted nerve regeneration and functional recovery in a rat sciatic nerve defect model,suggesting that it has potential for clinical use in human nerve injuries.展开更多
Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experim...Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experiment on a three-spiral-pile jacket foundation under deep-buried sandy soil conditions.During the experiment,horizontal displacement was applied to the structure to thoroughly investigate the bearing characteristics of the three-spiral-pile jacket foundation.This study also focused on analyzing the bearing mechanisms of conventional piles compared with spiral piles with different numbers of blades.Three different working conditions were set up and compared,and key data,such as the horizontal bearing capacity,pile shaft axial force,and spiral blade soil pressure,were measured and analyzed.The results show the distinct impacts of the spiral blades on the compressed and tensioned sides of the foundation.Specifically,on the compressed side,the spiral blades effectively enhance the restraint of the soil on the pile foundation,whereas on the tensioned side,an excessive number of spiral blades can negatively affect the structural tensile performance to some extent.This study also emphasizes that the addition of blades to the side of a single pile is the most effective method for increasing the bearing capacity of the foundation.This research aims to provide design insights into improving the bearing capacity of the foundation.展开更多
A numerical simulation analysis is conducted to examine the unsteady hydrodynamic characteristics of vortex-induced vibration(VIV)and the suppression effect of helical strakes on VIV in subsea pipelines.The analysis u...A numerical simulation analysis is conducted to examine the unsteady hydrodynamic characteristics of vortex-induced vibration(VIV)and the suppression effect of helical strakes on VIV in subsea pipelines.The analysis uses the standard k−εturbulence model for 4.5-and 12.75-inch pipes,and its accuracy is verified by comparing the results with large-scale hydrodynamic experiments.These experiments are designed to evaluate the suppression efficiency of VIV with and without helical strakes,focusing on displacement and drag coefficients under different flow conditions.Furthermore,the influence of important geometric parameters of the helical strakes on drag coefficients and VIV suppression efficiency at different flow rates is compared and discussed.Numerical results agree well with experimental data for drag coefficient and vortex shedding frequency.Spring-pipe self-excited vibration experimental tests reveal that the installation of helical strakes substantially reduces the drag coefficient of VIV within a certain flow rate range,achieving suppression efficiencies exceeding 90%with strake heights larger than 0.15D.Notably,the optimized parameter combination of helical strakes,with a pitch of 15D,a fin height of 0.2D,and 45°edge slopes,maintains high suppression efficiency,thereby exhibiting superior performance.This study provides a valuable reference for the design and application of helical strakes and VIV suppression in subsea engineering.展开更多
A series of optically active copolymers with various feed ratios have been synthesized through helix-sense-selective copolymerization catalyzed by[Rh(norbornadiene)Cl]2-triethylamine.This process involves two proline-...A series of optically active copolymers with various feed ratios have been synthesized through helix-sense-selective copolymerization catalyzed by[Rh(norbornadiene)Cl]2-triethylamine.This process involves two proline-derived acetylene monomers,(S)-N-(4-chlorophenyl)carbamoyl-2-ethynyl pyrrolidine(MCl)and(S)-N-(tert-butoxycarbonyl)-2-ethynyl pyrrolidine,followed by acidic deprotection and neutralization.These copolymers adopt helical conformations with a preferred handedness,as demonstrated by nuclear magnetic resonance spectroscopy and a series of spectroscopic analyses.The chiroptical activity intensity of copolymer has been found to increase with MCl content.Consequently,the enantioseparation capabilities of copolymers containing 95 mol%,90 mol%,and 85 mol%MCl units have been assessed as chiral stationary phases in high-performance liquid chromatography because of their good chiroptical activities.These chiral stationary phases effectively enantioseparate racemic alcohols,sulfoxides,amides,and metal complexes.Notably,the copolymer with 90 mol%MCl shows superior chiral recognition ability,especially for 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethanol(α=1.19)and 4-methylbenzenesulfinamide(α=1.47).Insights from molecular dynamic simulation and autodock analysis indicate that hydrogen bonding andπ-πstacking interactions between the chiral stationary phases and enantiomers play a key role for successful chiral separation.Our contribution not only demonstrates the importance of hydrogen bonding donor and copolymer chiroptical activity of chiral stationary phases for chiral resolution,but will also provide valuable insights for the future development of novel stationary phases.展开更多
Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship betw...Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship between configuration and electromagnetic(EM)loss mechanism has remained elusive.Herein,drawing inspiration from the DNA transcription process,we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability.Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn–N4–C configuration,along with cross polarization generated by the helical structure,endow the helical converters with enhanced EM loss.As a result,HMC-8 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.13 dB at an ultralow thickness of 1.29 mm.Through precise tuning of the graphite domain size,HMC-7 achieves an effective absorption bandwidth(EAB)of 6.08 GHz at 2.02 mm thickness.Furthermore,constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm,with the maximum radar cross section reduction value reaching 36.4 dB m2.This innovative approach not only advances the understanding of metal–nonmetal co-doping but also realizes broadband EMWA,thus contributing to the development of EMWA mechanisms and applications.展开更多
Helicene-type compounds are renowned for their unique chiral properties,however,obtaining their enantiomers usually requires laborious and costly chiral separations.Moreover,their chiroptical activity is typically lim...Helicene-type compounds are renowned for their unique chiral properties,however,obtaining their enantiomers usually requires laborious and costly chiral separations.Moreover,their chiroptical activity is typically limited to the ultraviolet spectral range,which restricts their broader applicability.To overcome these limitations,a novel and efficient strategy for synthesizing optically active compounds through the incorporation of an optically pure binaphthol(BINOL)group onto the periphery of β-isoindigo based aza dipyrrometheneboron difluoride(aza-BODIPY)analogues(BIABs)was presented.The resulting(R)/(S)-BINOL-BIABs demonstrate exceptional photostability,deep-red emission,strong Cotton effect(Δε)and high absorbance dissymmetry factor(g_(abs)).Moreover,tunable circularly polarized luminescence(CPL)with high brightness in the deep-red region was achieved.This strategy offers straightforward procedures for synthesizing optically active compounds.展开更多
To get large dissymmetric factor(g_(lum))of organic circularly polarized luminescence(CPL)materials is still a great challenge.Although helical chirality and planar chirality are usual efficient access to enhancement ...To get large dissymmetric factor(g_(lum))of organic circularly polarized luminescence(CPL)materials is still a great challenge.Although helical chirality and planar chirality are usual efficient access to enhancement of CPL,they are not combined together to boost CPL.Here,a new tetraphenylethylene(TPE)tetracycle acid helicate bearing both helical chirality and planar chirality was designed and synthesized.Uniquely,synergy of the helical chirality and planar chirality was used to boost CPL signals both in solution and in helical self-assemblies.In the presence of octadecylamine,the TPE helicate could form helical nanofibers that emitted strong CPL signals with an absolute g_(lum)value up to 0.237.Exceptionally,followed by addition of para-phenylenediamine,the g_(lum)value was successively increased to 0.387 due to formation of bigger helical nanofibers.Compared with that of TPE helicate itself,the CPL signal of the self-assemblies was not only magnified by 104-fold but also inversed,which was very rare result for CPL-active materials.Surprisingly,the interaction of TPE helicate with xylylenediamine even gave a gel,which was transformed into suspension by shaking.Unexpectedly,the suspension showed 40-fold stronger CPL signals than the gel with signal direction inversion each other.Using synergy of the helical chirality and planar chirality to significantly boost CPL intensity provides a new strategy in preparation of organic CPL materials having very large g_(lum)value.展开更多
Cylindrical cross sections are critical components in offshore structures, including jacket platform legs, pipelines, mooring lines, and risers. Thesecylindrical structures are subjected to vortex-induced vibrations (...Cylindrical cross sections are critical components in offshore structures, including jacket platform legs, pipelines, mooring lines, and risers. Thesecylindrical structures are subjected to vortex-induced vibrations (VIV) due to strong ocean currents, where vortices generated during fluid flowresult in significant vibrations in crossflow and in-flow directions. Such vibrations can lead to severe damage to platforms, cables, and risersystems. Consequently, mitigating VIV caused by vortex-induced forces is important. This study investigates the hydrodynamic performance offive strake models relative to a bare cylinder at moderate Reynolds numbers. The models encompass one conventional continuous helical strake(HS) and four helical discrete strake (HDS) with varying segment spacing between the fins. The hydrodynamic performance, specifically liftand drag force coefficients, was computed using a Reynolds averaged Navier –Stokes-based CFD solver and validated with experimentalmeasurements. The conventional HS suppresses 95% of the lift force but increases the drag force by up to a maximum of 48% in measurements.The HDS suppress the lift force by 70%–88% and increase the drag force by 15%–30%, which is less than the increase observed with the HS.Flow visualization showed that HS and HDS cylinders mitigate vortex-induced forces by altering the vortex-shedding pattern along the length ofthe cylinder. The HDS achieves a reduction in drag compared with the conventional continuous HS. The segment spacing is found to significantlyimpact the reduction in vortex-induced forces.展开更多
Protein nanotubes(PNTs)can be regarded as two-dimensional(2D)lattices with p1 or p2 symmetry rolled into tubes.However,attempts to re-assemble their building blocks into stable 2D nanomaterials often fail.Here,startin...Protein nanotubes(PNTs)can be regarded as two-dimensional(2D)lattices with p1 or p2 symmetry rolled into tubes.However,attempts to re-assemble their building blocks into stable 2D nanomaterials often fail.Here,starting from two baculoviral capsid proteins,we screened protein variants for the in vitro assembly of various nanotubes and nanosheets.These high-order assemblies were structurally characterized by cryo-electron microscopy techniques.Interfacial analysis of three groups of PNTs revealed that helical heterogeneity is largely the result of the redundancy of p2 symmetry-related contacting interfaces.The assembled nanosheets showed similar interfacial networks to their nanotubular counterparts.In addition,foreign macromolecules could be efficiently displayed on the sizecontrollable double-layered nanosheets.This study sheds light on the rational design of flexible nanosheets,and it also provides novel 2D protein scaffolds for developing biocompatible materials.展开更多
Sapphire fiber has been widely utilized in ultra-high-temperature environments.A sapphire fiber Bragg grating(SFBG)is a potential high-temperature sensor,but the multimodal behavior results in a broadband reflection s...Sapphire fiber has been widely utilized in ultra-high-temperature environments.A sapphire fiber Bragg grating(SFBG)is a potential high-temperature sensor,but the multimodal behavior results in a broadband reflection spectrum and poor precision.In this article,we report a helical tapered depressed cladding waveguide(HTDCW)by using a femtosecond laser direct writing technique to realize single-mode operation of SFBG.The HTDCW was created using helical negative refractive index modification by forming a depressed cladding.展开更多
Bio-inspired magnetic helical microrobots have great potential for biomedical and micromanipulation applications. Precise interaction with objects in liquid environments is an important prerequisite and challenge for ...Bio-inspired magnetic helical microrobots have great potential for biomedical and micromanipulation applications. Precise interaction with objects in liquid environments is an important prerequisite and challenge for helical microrobots to perform various tasks. In this study, an automatic control method is proposed to realize the axial docking of helical microrobots with arbitrarily placed cylindrical objects in liquid environments. The docking process is divided into ascent, approach, alignment, and insertion stages. First, a 3D docking path is planned according to the positions and orientations of the microrobot and the target object. Second, a steering-based 3D path-following controller guides the helical microrobot to rise away from the container bottom and approach the target along the path. Third, based on path design with gravity compensation and steering output limits, alignment of position and orientation can be accomplished simultaneously. Finally, the helical microrobot completes the docking under the rotating magnetic field along the target orientation. Experiments verified the automatic docking of the helical microrobot with static targets, including connecting with micro-shafts and inserting into micro-tubes. The object grasping of a reconfigurable helical microrobot aided by 3D automatic docking was also demonstrated. This method enables precise docking of helical microrobots with objects, which might be used for capture and sampling, in vivo navigation control, and functional assembly of microrobots.展开更多
Rational tuning of chiral nanostructures of supramolecular assemblies as catalysts and investigating their chiral morphology-enantioselectivity dependence is rarely reported. Herein, we report a series of supramolecul...Rational tuning of chiral nanostructures of supramolecular assemblies as catalysts and investigating their chiral morphology-enantioselectivity dependence is rarely reported. Herein, we report a series of supramolecular M/P-helical nanoribbons(HNs) assembled from the chiral L/D-glutamate-based amphiphiles(L/D-Glu C16) and Cu(Ⅱ) ions, with their helical screw pitches adjusted from 217 nm to 104 nm through the facile regulation of their water/organic solvent assembly environment. They were then used as ideal models to reveal the chiral morphology-enantioselectivity relationship by catalyzing the asymmetric Diels-Alder reaction. Better enantioselectivity was achieved with more twist morphology. Experimental evidences of stronger chiral transfer effect from the supramolecular HNs with more twist to the aza-chalcone as reactant were obtained to understand such dependence. Our study demonstrates a new perspective for designing supramolecular catalysts with higher enantioselectivity.展开更多
Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional load...Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional loaded tooth contact analysis(3D-LTCA)method which can consider tooth modification and coupling assembly errors is proposed,and mesh stiffness calculated by proposed method is verified by MASTA software.Secondly,based on neural network,the surrogate model(SM)that maps the relationship between modification parameters and mesh mechanical parameters is established,and its accuracy is verified.Finally,SM is introduced to establish an optimization model with the target of minimizing mesh stiffness variations and obtaining more even load distribution on mesh surface.The results show that even considering training time,the efficiency of gear pair optimization by surrogate model is still much higher than that by LTCA method.After optimization,the mesh stiffness fluctuation of gear pair with coupling assembly error is reduced by 34.10%,and difference in average contact stresses between left and right regions of the mesh surface is reduced by 62.84%.展开更多
基金supported by the National Key R&D Program of China(Grant No.2022YFB4701200)the National Natural Science Foundation of China(Grant Nos.52335003,52405011 and U22A20176)+3 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022B1515120078 and 2023A1515110313)the Shenzhen Natural Science Fund(the Stable Support Plan Program,Grant No.GXWD20231129161359002)the Shenzhen Science and Technology Program(Grant No.KQTD20210811090146075)Pre-research Task of State Key Laboratory of Robotics and Systems(HIT)(Grant No.SKLRS202421B).
文摘Inspired by the ubiquitous helical structures in nature,research on artificial helices has attracted increasing attention.As a unique and complex three-dimensional(3D)geometry in the microscopic world,the micro-/nano helix has significant advantages in wide applications due to its distinctive properties at the micro-scale.Micro-/nanotechnology is advancing rapidly.The geometric complexity of helical structure poses technical challenges for the manufacturing at the micro-/nanoscale,requiring some emerging manufacturing techniques.In this review,we systematically classify and summarize existing manufacturing methods for micro/nano helical structures and their underlying mechanisms.Based on the unique physical properties of helical structures at the microscale,their latest applications are analyzed across different fields.Finally,we conclude the challenges and future research directions of micro-/nano helices in manufacturing methods and applications.
文摘The novel complex{[Co(bipy)(azpy)_(2)(NCS)_(2)]·H_(2)O}n(where bipy=4,4′bipyridine,azpy=4,4′azobisp yridine)has been synthesized and characterized by elemental analyses,IR,UV,thermal analyses,and variable temperature magnetic susceptibility.The crystal(C_(32)H_(26)CoN_(12)OS_(2),Mr=717.70)belongs to the orthorhombic,space group Pnna,a=2.21312(16)nm,b=1.40403(10)nm,c=1.14237(8)nm,V=3.5497(4)nm^(3),Z=4,Dc=1.343g·cm^(-3),μ=0.645mm^(-1),F(000)=1476,and final R_(1)=0.0691,wR_(2)=0.1129 for 231 parameters and 1674 observed reflections[I>2.00σ(I)].The Co(Ⅱ)atom is,in a distorted octahedral geometry,coordinated by six nitrogen atoms from two bridging bipy,two monodentate azpy,and two thiocyanate groups.The bridging ligand bipy links Co(Ⅱ)atoms to form the infinite“rod"with terminal coordination azpy ligand acting as sidearms.Unprecedented three parallel interpenetrating two dimensional(4,4)networks and novel infinite triple helices are formed via hydrogen bonding interactions.CCDC:155588.
基金supported by the National Natural Science Foundation of China (30871749,30901004)Natural Science Foundation of Fujian Province(2009J01061)
文摘In this work, the formation sites, helical parameters and hydrogen bond positions of Konjac glucomannan molecular helices were investigated using molecular dynamic simulation method. To our interest, the KGM chain is mainly composed by local left and right helix struetttres. The formation sites of KGM chain might locate at the chain-segments containing acetyl groups, and the left helix is the favorable conformation of KGM. Temperature-dependent molecule conformation study indicates that the right helix is dominant when the temperature is lower than 343 K, above which, however, the left helix is dominating （right helix disappears）. In addition, intramolecular hydrogen bonds in the left helix can be found at the -OH groups on C（2）, C（4） and C（6） of mannose residues; comparably, the intramolecular hydrogen bonds in the right helix can be mainly observed at the -OH groups on C（4） and C（6） of the mannose residues and C（3） of the glucose residues. In conclusion, molecular dynamic simulation is an efficient method for the microscopic conformation study of glucomannan molecular helices.
基金NNSFC (No. 20173017) and State Key Basic Program (No. G2000048)
文摘A brilliant purple octahedral single crystal is hydrothermally synthesized by the reaction of CoCl26H2O, H3BO3 and H3PO4 in NaOH aqueous solution of CH3(CH2)15N(CH3)3Br, and its crystal structure has been characterized by single-crystal X-ray diffraction. The compound, NaCo(H2O)2BP2O8稨2O (Mr = 336.72), belongs to hexagonal, space group P6122 with a = 9.447(5), c = 15.83(1) , V = 1223(1) 3, Dc = 2.742 g/cm3, Z = 6, F(000) = 1002 and m = 2.606 mm-1. The three-dimensional framework in the compound is built up from the linkage tetrahedral ribbons, in which the BO4 and PO4 tetrahedra alternate with CoO6 octahedra. The sodium ions and water molecules are located within the free thread of the helical ribbons.
基金Supported by the National Natural Science Foundation of China(Nos.20671040, 20971054 and 90922034)New Century Excellent Talents in University of China and the Key Project of Chinese Ministry of Education(No.2009-49)
文摘The first primary organicamine templated indium iodate with the formula （H2en）KIn（IO3）6-2（H2O） was hydrothermally synthesized via reaction at 100 ℃ for 7 d and characterized by single-crystal X-ray diffraction and thermal analysis. The compound crystallized in a triclinic system with space group P1, a=0.69803（14） nm, b=0.70863（14） nm, c=1.2091（2） nm, a=76.417（4）°,β=79.953（4）°, γ=72.206（3）°, V=0.55012（19） nm3. Structure determination indicates that it is made up of zero-dimensional units each of which consists of [In（IO3）6]3 anion, potassium, water and ethylenediamine cation. The most striking feature of the compound is that it possesses helical hydrogen bonds formed by organic amine template, water molecules and inorganic network.
文摘Aquaporin （AQP） is a water channel protein found in various subcellular membranes of both prokaryotic and eukaryotic cells. The physiological functions of AQPs have been elucidated in many organisms. However, understanding their biogenesis remains elusive, particularly regarding how they assemble into tetramers. Here, we investigated the amino acid residues involved in the tetramer formation of the Arabidopsis plasma membrane AQP AtPIP2;1 using extensive amino acid substitution mutagenesis. The mutant proteins V41A/ E44A, F51A/L52A, F87A/191A, F92A/193A, V95A/Y96A, and H216A/L217A, harboring alanine substitutions in the transmembrane （TM） helices of AtPIP2;1 polymerized into multiple oligomeric complexes with a vari- able number of subunits greater than four. Moreover, these mutant proteins failed to traffic to the plasma membrane, instead of accumulating in the endoplasmic reticulum （ER）. Structure-based modeling revealed that these residues are largely involved in interactions between TM helices within monomers. These results suggest that inter-TM interactions occurring both within and between monomers play crucial roles in tetramer formation in the AtPIP2;1 complex. Moreover, the assembly of AtPIP2;1 tetramers is critical for their trafficking from the ER to the plasma membrane, as well as water permeability.
基金the National Natural Science Foundation of China(No.21761036)。
文摘Helix as essential molecular chiral phenomenon at supramolecular level offers an affective method to study chiral characteristic of homochiral coordination polymers(CPs).Herein,two homochiral CPs[Cd((R)-CBA)_(2)(3,5-DIT)]_(n)((R)-H_(2) CBA=(R)-4-(1-carboxyethoxy)benzoic acid,3,5-DIT=3,5-di(1 H-imidazol-1-yl)toluene,1-R)and[Zn((R)-CBA)(3,5-DIT)]_(n)(2-R)were synthesized under hydrothermal conditions.In complex 1-R,only a helical chain was built by chiral ligands(R)-CBA2-,ancillary ligands 3,5-DIT and Cd(Ⅱ)ions.After Cd(Ⅱ)ions were replaced by Zn(Ⅱ)ions under similar reaction system,Zn(Ⅱ),(R)-CBA^(2-)and/or 3,5-DIT formed six types of helices,resulting in complex 2-R.So,the metal ions played a key role in the construction of helical structures.Complexes 1-R and 2-R were also characterized by elemental analysis,PXRD,TGA,CD and UV-visible absorptions.In addition,complexes 1-R and 2-R exhibited different photoluminescence behaviors in solid sate compared to free ligand(R)-H_(2)CBA.
基金supported by the National Natural Science Foundation of China,No.82202718the Natural Science Foundation of Beijing,No.L212050the China Postdoctoral Science Foundation,Nos.2019M664007,2021T140793(all to ZL)。
文摘Autografting is the gold standard for surgical repair of nerve defects>5 mm in length;however,autografting is associated with potential complications at the nerve donor site.As an alternative,nerve guidance conduits may be used.The ideal conduit should be flexible,resistant to kinks and lumen collapse,and provide physical cues to guide nerve regeneration.We designed a novel flexible conduit using electrospinning technology to create fibers on the innermost surface of the nerve guidance conduit and employed melt spinning to align them.Subsequently,we prepared disordered electrospun fibers outside the aligned fibers and helical melt-spun fibers on the outer wall of the electrospun fiber lumen.The presence of aligned fibers on the inner surface can promote the extension of nerve cells along the fibers.The helical melt-spun fibers on the outer surface can enhance resistance to kinking and compression and provide stability.Our novel conduit promoted nerve regeneration and functional recovery in a rat sciatic nerve defect model,suggesting that it has potential for clinical use in human nerve injuries.
基金The National Natural Science Foundation of China(No.52171274).
文摘Spiral pile foundations,as a promising type of foundation,are of significant importance for the development of offshore wind energy,particularly as it moves toward deeper waters.This study conducted a physical experiment on a three-spiral-pile jacket foundation under deep-buried sandy soil conditions.During the experiment,horizontal displacement was applied to the structure to thoroughly investigate the bearing characteristics of the three-spiral-pile jacket foundation.This study also focused on analyzing the bearing mechanisms of conventional piles compared with spiral piles with different numbers of blades.Three different working conditions were set up and compared,and key data,such as the horizontal bearing capacity,pile shaft axial force,and spiral blade soil pressure,were measured and analyzed.The results show the distinct impacts of the spiral blades on the compressed and tensioned sides of the foundation.Specifically,on the compressed side,the spiral blades effectively enhance the restraint of the soil on the pile foundation,whereas on the tensioned side,an excessive number of spiral blades can negatively affect the structural tensile performance to some extent.This study also emphasizes that the addition of blades to the side of a single pile is the most effective method for increasing the bearing capacity of the foundation.This research aims to provide design insights into improving the bearing capacity of the foundation.
基金Supported by the National Natural Science Foundation of China (Grant No. 52222111)the National Science and Technology Major Project of China “Key Technologies and Equipment for Deepwater Dry Oil and Gas Production and Processing Platforms”(No. 2024ZD1403300)+1 种基金Subproject 5 “Research on Safety Risk Assessment Technology System for Deepwater Dry Oil and Gas Production and Processing Platforms”(No. 2024ZD1403305)the China Scholarship Council (202306440019)。
文摘A numerical simulation analysis is conducted to examine the unsteady hydrodynamic characteristics of vortex-induced vibration(VIV)and the suppression effect of helical strakes on VIV in subsea pipelines.The analysis uses the standard k−εturbulence model for 4.5-and 12.75-inch pipes,and its accuracy is verified by comparing the results with large-scale hydrodynamic experiments.These experiments are designed to evaluate the suppression efficiency of VIV with and without helical strakes,focusing on displacement and drag coefficients under different flow conditions.Furthermore,the influence of important geometric parameters of the helical strakes on drag coefficients and VIV suppression efficiency at different flow rates is compared and discussed.Numerical results agree well with experimental data for drag coefficient and vortex shedding frequency.Spring-pipe self-excited vibration experimental tests reveal that the installation of helical strakes substantially reduces the drag coefficient of VIV within a certain flow rate range,achieving suppression efficiencies exceeding 90%with strake heights larger than 0.15D.Notably,the optimized parameter combination of helical strakes,with a pitch of 15D,a fin height of 0.2D,and 45°edge slopes,maintains high suppression efficiency,thereby exhibiting superior performance.This study provides a valuable reference for the design and application of helical strakes and VIV suppression in subsea engineering.
基金supported by the National Natural Science Foundation of China(Nos.52273002 and 52333008)the funding of Boya Postdoctoral Fellowship at Peking University,BMS Junior Fellow Program and the National Funding Program for Postdoctoral Researchers(No.GZC20230031).
文摘A series of optically active copolymers with various feed ratios have been synthesized through helix-sense-selective copolymerization catalyzed by[Rh(norbornadiene)Cl]2-triethylamine.This process involves two proline-derived acetylene monomers,(S)-N-(4-chlorophenyl)carbamoyl-2-ethynyl pyrrolidine(MCl)and(S)-N-(tert-butoxycarbonyl)-2-ethynyl pyrrolidine,followed by acidic deprotection and neutralization.These copolymers adopt helical conformations with a preferred handedness,as demonstrated by nuclear magnetic resonance spectroscopy and a series of spectroscopic analyses.The chiroptical activity intensity of copolymer has been found to increase with MCl content.Consequently,the enantioseparation capabilities of copolymers containing 95 mol%,90 mol%,and 85 mol%MCl units have been assessed as chiral stationary phases in high-performance liquid chromatography because of their good chiroptical activities.These chiral stationary phases effectively enantioseparate racemic alcohols,sulfoxides,amides,and metal complexes.Notably,the copolymer with 90 mol%MCl shows superior chiral recognition ability,especially for 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethanol(α=1.19)and 4-methylbenzenesulfinamide(α=1.47).Insights from molecular dynamic simulation and autodock analysis indicate that hydrogen bonding andπ-πstacking interactions between the chiral stationary phases and enantiomers play a key role for successful chiral separation.Our contribution not only demonstrates the importance of hydrogen bonding donor and copolymer chiroptical activity of chiral stationary phases for chiral resolution,but will also provide valuable insights for the future development of novel stationary phases.
基金supported by the National Natural Science Foundation of China(22265021)the Aeronautical Science Foundation of China(2020Z056056003)Jiangxi Provincial Natural Science Foundation(20232BAB212004).
文摘Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption(EMWA)materials.However,the relationship between configuration and electromagnetic(EM)loss mechanism has remained elusive.Herein,drawing inspiration from the DNA transcription process,we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability.Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn–N4–C configuration,along with cross polarization generated by the helical structure,endow the helical converters with enhanced EM loss.As a result,HMC-8 demonstrates outstanding EMWA performance,achieving a minimum reflection loss of−63.13 dB at an ultralow thickness of 1.29 mm.Through precise tuning of the graphite domain size,HMC-7 achieves an effective absorption bandwidth(EAB)of 6.08 GHz at 2.02 mm thickness.Furthermore,constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm,with the maximum radar cross section reduction value reaching 36.4 dB m2.This innovative approach not only advances the understanding of metal–nonmetal co-doping but also realizes broadband EMWA,thus contributing to the development of EMWA mechanisms and applications.
文摘Helicene-type compounds are renowned for their unique chiral properties,however,obtaining their enantiomers usually requires laborious and costly chiral separations.Moreover,their chiroptical activity is typically limited to the ultraviolet spectral range,which restricts their broader applicability.To overcome these limitations,a novel and efficient strategy for synthesizing optically active compounds through the incorporation of an optically pure binaphthol(BINOL)group onto the periphery of β-isoindigo based aza dipyrrometheneboron difluoride(aza-BODIPY)analogues(BIABs)was presented.The resulting(R)/(S)-BINOL-BIABs demonstrate exceptional photostability,deep-red emission,strong Cotton effect(Δε)and high absorbance dissymmetry factor(g_(abs)).Moreover,tunable circularly polarized luminescence(CPL)with high brightness in the deep-red region was achieved.This strategy offers straightforward procedures for synthesizing optically active compounds.
基金National Natural Science Foundation of China(Nos.22072050,22372066 and 22301090)the Open Research Fund(No.2024JYBKF05)of Key Laboratory of Material Chemistry for Energy Conversion and Storage(HUST)Ministry of Educationthe China Postdoctoral Science Foundation(No.2023M731189)for financial support,and thank the Analytical and Testing Centre at Huazhong University of Science and Technology for measurement.
文摘To get large dissymmetric factor(g_(lum))of organic circularly polarized luminescence(CPL)materials is still a great challenge.Although helical chirality and planar chirality are usual efficient access to enhancement of CPL,they are not combined together to boost CPL.Here,a new tetraphenylethylene(TPE)tetracycle acid helicate bearing both helical chirality and planar chirality was designed and synthesized.Uniquely,synergy of the helical chirality and planar chirality was used to boost CPL signals both in solution and in helical self-assemblies.In the presence of octadecylamine,the TPE helicate could form helical nanofibers that emitted strong CPL signals with an absolute g_(lum)value up to 0.237.Exceptionally,followed by addition of para-phenylenediamine,the g_(lum)value was successively increased to 0.387 due to formation of bigger helical nanofibers.Compared with that of TPE helicate itself,the CPL signal of the self-assemblies was not only magnified by 104-fold but also inversed,which was very rare result for CPL-active materials.Surprisingly,the interaction of TPE helicate with xylylenediamine even gave a gel,which was transformed into suspension by shaking.Unexpectedly,the suspension showed 40-fold stronger CPL signals than the gel with signal direction inversion each other.Using synergy of the helical chirality and planar chirality to significantly boost CPL intensity provides a new strategy in preparation of organic CPL materials having very large g_(lum)value.
文摘Cylindrical cross sections are critical components in offshore structures, including jacket platform legs, pipelines, mooring lines, and risers. Thesecylindrical structures are subjected to vortex-induced vibrations (VIV) due to strong ocean currents, where vortices generated during fluid flowresult in significant vibrations in crossflow and in-flow directions. Such vibrations can lead to severe damage to platforms, cables, and risersystems. Consequently, mitigating VIV caused by vortex-induced forces is important. This study investigates the hydrodynamic performance offive strake models relative to a bare cylinder at moderate Reynolds numbers. The models encompass one conventional continuous helical strake(HS) and four helical discrete strake (HDS) with varying segment spacing between the fins. The hydrodynamic performance, specifically liftand drag force coefficients, was computed using a Reynolds averaged Navier –Stokes-based CFD solver and validated with experimentalmeasurements. The conventional HS suppresses 95% of the lift force but increases the drag force by up to a maximum of 48% in measurements.The HDS suppress the lift force by 70%–88% and increase the drag force by 15%–30%, which is less than the increase observed with the HS.Flow visualization showed that HS and HDS cylinders mitigate vortex-induced forces by altering the vortex-shedding pattern along the length ofthe cylinder. The HDS achieves a reduction in drag compared with the conventional continuous HS. The segment spacing is found to significantlyimpact the reduction in vortex-induced forces.
基金supported by the National Key Research and Development Program of China(2022YFC2303300 to S.C.)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0490000 to S.C.)+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2022341 to G.R.)the Major Project of the Guangzhou National Laboratory(GZNL2024A01010 to G.R.).
文摘Protein nanotubes(PNTs)can be regarded as two-dimensional(2D)lattices with p1 or p2 symmetry rolled into tubes.However,attempts to re-assemble their building blocks into stable 2D nanomaterials often fail.Here,starting from two baculoviral capsid proteins,we screened protein variants for the in vitro assembly of various nanotubes and nanosheets.These high-order assemblies were structurally characterized by cryo-electron microscopy techniques.Interfacial analysis of three groups of PNTs revealed that helical heterogeneity is largely the result of the redundancy of p2 symmetry-related contacting interfaces.The assembled nanosheets showed similar interfacial networks to their nanotubular counterparts.In addition,foreign macromolecules could be efficiently displayed on the sizecontrollable double-layered nanosheets.This study sheds light on the rational design of flexible nanosheets,and it also provides novel 2D protein scaffolds for developing biocompatible materials.
基金National Key Research and Development Program of China(2023YFB3208600)National Natural Science Foundation of China(62222510,62435012,62375176,T2421003)+1 种基金Guangdong Provincial Department of Science and Technology(2024A1515010108)Ling Chuang Research Project of China National Nuclear Corporation(CNNC-LCKY-2024-067)。
文摘Sapphire fiber has been widely utilized in ultra-high-temperature environments.A sapphire fiber Bragg grating(SFBG)is a potential high-temperature sensor,but the multimodal behavior results in a broadband reflection spectrum and poor precision.In this article,we report a helical tapered depressed cladding waveguide(HTDCW)by using a femtosecond laser direct writing technique to realize single-mode operation of SFBG.The HTDCW was created using helical negative refractive index modification by forming a depressed cladding.
基金supported by the National Natural Science Foundation of China(No.62273117)Pre-research Task(No.SKLRS202418B)of State Key Laboratory of Robotics and Systems(HIT).
文摘Bio-inspired magnetic helical microrobots have great potential for biomedical and micromanipulation applications. Precise interaction with objects in liquid environments is an important prerequisite and challenge for helical microrobots to perform various tasks. In this study, an automatic control method is proposed to realize the axial docking of helical microrobots with arbitrarily placed cylindrical objects in liquid environments. The docking process is divided into ascent, approach, alignment, and insertion stages. First, a 3D docking path is planned according to the positions and orientations of the microrobot and the target object. Second, a steering-based 3D path-following controller guides the helical microrobot to rise away from the container bottom and approach the target along the path. Third, based on path design with gravity compensation and steering output limits, alignment of position and orientation can be accomplished simultaneously. Finally, the helical microrobot completes the docking under the rotating magnetic field along the target orientation. Experiments verified the automatic docking of the helical microrobot with static targets, including connecting with micro-shafts and inserting into micro-tubes. The object grasping of a reconfigurable helical microrobot aided by 3D automatic docking was also demonstrated. This method enables precise docking of helical microrobots with objects, which might be used for capture and sampling, in vivo navigation control, and functional assembly of microrobots.
基金support of this research by the National Natural Science Foundation of China(Nos.22202171,21922202,and 22272146)the Natural Science Foundation of Jiangsu Basic Research Program(No.BK20220559)+1 种基金the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province(No.22KJD150009)the Jiangsu Specially-Appointed Professor Plan(Z.Xi)from the Jiangsu Education Department。
文摘Rational tuning of chiral nanostructures of supramolecular assemblies as catalysts and investigating their chiral morphology-enantioselectivity dependence is rarely reported. Herein, we report a series of supramolecular M/P-helical nanoribbons(HNs) assembled from the chiral L/D-glutamate-based amphiphiles(L/D-Glu C16) and Cu(Ⅱ) ions, with their helical screw pitches adjusted from 217 nm to 104 nm through the facile regulation of their water/organic solvent assembly environment. They were then used as ideal models to reveal the chiral morphology-enantioselectivity relationship by catalyzing the asymmetric Diels-Alder reaction. Better enantioselectivity was achieved with more twist morphology. Experimental evidences of stronger chiral transfer effect from the supramolecular HNs with more twist to the aza-chalcone as reactant were obtained to understand such dependence. Our study demonstrates a new perspective for designing supramolecular catalysts with higher enantioselectivity.
基金Project(11972112)supported by the National Natural Science Foundation of ChinaProject(N2103024)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(J2019-IV-0018-0086)supported by the National Science and Technology Major Project,China。
文摘Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional loaded tooth contact analysis(3D-LTCA)method which can consider tooth modification and coupling assembly errors is proposed,and mesh stiffness calculated by proposed method is verified by MASTA software.Secondly,based on neural network,the surrogate model(SM)that maps the relationship between modification parameters and mesh mechanical parameters is established,and its accuracy is verified.Finally,SM is introduced to establish an optimization model with the target of minimizing mesh stiffness variations and obtaining more even load distribution on mesh surface.The results show that even considering training time,the efficiency of gear pair optimization by surrogate model is still much higher than that by LTCA method.After optimization,the mesh stiffness fluctuation of gear pair with coupling assembly error is reduced by 34.10%,and difference in average contact stresses between left and right regions of the mesh surface is reduced by 62.84%.
