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Dual-mode imaging combining photoacoustic and ultrasound modalities holds great promise for comprehensive tissue characterization. In traditional dual-mode imaging systems, however, the opaque ultrasound transducers are integrated in complex optical and ultrasound paths, leading to compromises in imaging efficiency and sensitivity. To address these challenges, we design and produce highly transparent Pb(Mg,Nb)O3PbTiO3 ceramics with exceptional transparency of 68%, alongside a remarkable ultrahigh piezoelectric d33 of 1500 pC/N. Leveraging this material, we fabricate a high-sensitivity transparent piezoelectric ultrasound transducer (TPUT) with a center frequency of 16 MHz and a bandwidth of 30%, which seamlessly integrating ultrasound and photoacoustic capabilities into one system to achieve simultaneous photoacoustic/ultrasound dual-mode imaging, showcasing a remarkable sensitivity for deep-tissue detection (e.g., 7.5 mm thick chicken breast meat). Additionally, in vivo photoacoustic imaging of subcutaneous microvasculature in a mouse ear was successfully achieved via 28 MHz TPUT. Our innovation not only advances imaging performance but also offers a cost-effective solution, paving the way for transformative biomedical imaging applications.

Abstract Botulinum neurotoxin E (BoNT/E) is one of the major causes of human botulism and paradoxically also a promising therapeutic agent. Here we determined the co-crystal structures of the receptor-binding domain of BoNT/E (HCE) in complex with its neuronal receptor synaptic vesicle glycoprotein 2A (SV2A) and a nanobody that serves as a ganglioside surrogate. These structures reveal that the protein-protein interactions between HCE and SV2 provide the crucial location and specificity information for HCE to recognize SV2A and SV2B, but not the closely related SV2C. At the same time, HCE exploits a separated sialic acid-binding pocket to mediate recognition of an N-glycan of SV2. Structure-based mutagenesis and functional studies demonstrate that both the protein-protein and protein-glycan associations are essential for SV2A-mediated cell entry of BoNT/E and for its potent neurotoxicity. Our studies establish the structural basis to understand the receptor-specificity of BoNT/E and to engineer BoNT/E variants for new clinical applications.

Photoacoustic imaging (PAI) uniquely combines optics and ultrasound, presenting a promising role in biomedical imaging as a non-invasive and label-free imaging technology. As the traditional opaque ultrasound (US) transducers could hinder the transportation of the excitation light and limit the performance of PAI system, piezoelectric transparent ultrasonic transducers (TUTs) with indium tin oxide (ITO) electrodes have been developed to allow light transmission through the transducer and illuminate the sample directly. Nevertheless, without having transparent matching materials with appropriate properties, the bandwidth of those TUTs was generally narrow. In this work, we propose to employ polymethyl methacrylate (PMMA) as the matching layer material to improve the bandwidth of lithium niobate (LN)-based TUTs. The effects of PMMA matching layer on the performance of TUTs have been systematically studied. With the optimized PMMA matching layer, the very wide bandwidth of > 50 % could be achieved for the TUTs even with different transducer frequencies, leading to the great enhancement of axial resolution when compared to the similar reported work. In addition, the imaging performance of the developed TUT prototype has been evaluated in a PAI system and demonstrated by both phantom and in vivo small animal imaging.

Abstract With the rapid development of micro‐energy harvesting technology, noise has great potential as a new type of micro‐energy source by developing a high‐performance acoustic energy harvester (AEH). Nevertheless, the challenges of harvesting energy from noise are low acoustic energy density, multi‐frequency mixed sound, and unstable sound pressure. Piezoelectric‐based AEHs are proposed as a solution, but most reported devices need to work at a certain frequency and very high sound pressure, and exhibit the disadvantages of being bulky and heavy when using an extra sound‐pressure amplifier. Here, the eardrum and cochlea bioinspired polyvinylidene fluoride (PVDF) piezoelectric generator which is lightweight, compact, has a simple structure and is low‐cost, harvests multi‐frequency sound energy. Although using the commercial pure PVDF membrane, the prepared AEH still presents a high acoustoelectric conversion performance with an output power of 8.45 µW and an acoustic sensitivity of 1 V Pa−1 at 200 Hz and 100 dB without using any sound‐pressure amplifier through optimizing the structure–vibration–frequency relationship. More importantly, the bioinspired AEHs do not only exhibit the ability of acoustic energy harvesting function but also have the abilities of frequency recognition and acoustic sensing, which show great potential in the application of self‐powered acoustic sensors.

Light and flexible thermoelectric generators operating at room temperature are highly desirable for wearable microelectronics. Here, flexible thermoelectric composites comprising semiconducting Bi2Te3 particles and conductive polymers exhibit a high output power within a small temperature window around room temperature.

Photoacoustic technology is a promising tool to provide morphological and functional information in biomedical research. To enhance the imaging efficiency, the reported photoacoustic probes have been designed coaxially involving complicated optical/acoustic prisms to bypass the opaque piezoelectric layer of ultrasound transducers, but this has led to bulky probes and has hindered the applications in limited space. Though the emergence of transparent piezoelectric materials helps to save effort on the coaxial design, the reported transparent ultrasound transducers were still bulky. In this work, a miniature photoacoustic probe with an outer diameter of 4 mm was developed, in which an acoustic stack was made with a combination of transparent piezoelectric material and a gradient-index lens as a backing layer. The transparent ultrasound transducer exhibited a high center frequency of ~47 MHz and a −6 dB bandwidth of 29.4%, which could be easily assembled with a pigtailed ferrule of a single-mode fiber. The multi-functional capability of the probe was successfully validated through experiments of fluid flow sensing and photoacoustic imaging.

Botulinum neurotoxins (BoNTs) are among the deadliest of bacterial toxins. BoNT serotype A and B in particular pose the most serious threat to humans because of their high potency and persistence. To date, there is no effective treatment for late post-exposure therapy of botulism patients. Here, we aim to develop single-domain variable heavy-chain (VHH) antibodies targeting the protease domains (also known as the light chain, LC) of BoNT/A and BoNT/B as antidotes for post-intoxication treatments. Using a combination of X-ray crystallography and biochemical assays, we investigated the structures and inhibition mechanisms of a dozen unique VHHs that recognize four and three non-overlapping epitopes on the LC of BoNT/A and BoNT/B, respectively. We show that the VHHs that inhibit the LC activity occupy the extended substrate-recognition exosites or the cleavage pocket of LC/A or LC/B and thus block substrate binding. Notably, we identified several VHHs that recognize highly conserved epitopes across BoNT/A or BoNT/B subtypes, suggesting that these VHHs exhibit broad subtype efficacy. Further, we identify two novel conformations of the full-length LC/A, that could aid future development of inhibitors against BoNT/A. Our studies lay the foundation for structure-based engineering of protein- or peptide-based BoNT inhibitors with enhanced potencies and cross-subtypes properties.

With the popularization of humans working in tandem with robots and artificial intelligence (AI) by Industry 5.0, ultrasonic non-destructive testing (NDT)) technology has been increasingly used in quality inspections in the industry. As a crucial part of handling ultrasonic testing results–signal processing, the current approach focuses on professional training to perform signal discrimination but automatic and intelligent signal optimization and estimation lack systematic research. Though the automated and intelligent framework for ultrasonic echo signal processing has already exhibited essential research significance for diagnosing defect locations, the real-time applicability of the algorithm for the time-of-flight (ToF) estimation is rarely considered, which is a very important indicator for intelligent detection. This paper conducts a systematic comparison among different ToF algorithms for the first time and presents the auto-diagnosis of the ToF approach based on the Defect Peaks Tracking Model (DPTM). The proposed DPTM is used for ultrasonic echo signal processing and recognition for the first time. The DPTM using the Hilbert transform was verified to locate the defect with the size of 2–10 mm, in which the wavelet denoising method was adopted. With the designed mechanical fixture through 3D printing technology on the pipeline to inspect defects, the difficulty of collecting sufficient data could be conquered. The maximum auto-diagnosis error could be reduced to 0.25% and 1.25% for steel plate and pipeline under constant pressure, respectively, which were much smaller than those with the DPTM adopting the cross-correlation. The real-time auto-diagnosis identification feature of DPTM has the potential to be combined with AI in future work, such as machine learning and deep learning, to achieve more intelligent approaches for industrial health inspection.

As the featured material of the superionic thermoelectric (TE) material family, copper-chalcogenide Cu2-xSe is attracting growing research interest for its excellent TE performance derived from the satisfactory power factor and the ultra-low thermal conductivity induced by the superionic effect. Various efforts have been made and proved to be effective to further enhance the TE performance for Cu2-xSe. However, this material is still far from the application stage, which is mainly due to concerns regarding control of the properties and the costly complex fabrication technology. Here we report a scalable pathway to achieve high-performance and tunable Cu2-xSe, utilizing conventional sintering technology and copper (Cu)-vacancy engineering with an effective mass model. The figure of merit zT is a competitive value of 1.0 at 800 K for the optimized binary Cu2-xSe, based on the precise modeling prediction and Cu-vacancy engineering. The changes in TE properties of Cu2-xSe under heating-cooling cycle tests are also revealed. Our work offers the referable method along with the decent parent material for further enhancement of TE performance, paving a possible route for the application and industrialization of Cu2-xSe TE materials. Keywords: Thermoelectric, Copper selenide, Copper-vacancy engineering, Effective mass model

Abstract The presence of defects in thermoelectric materials plays a significant role in the modification their properties by influencing the behavior of electrons and phonons. Dopants with a unique f‐orbital can directly cause distortions in electronic density of states (eDOS) and phonon transport mechanism by intentionally inducing defects in their lattice. The theoretical and experimental outcomes of engineered vacancy defects are investigated by intentional doping of f‐block rare earth elements in β‐Zn4Sb3. Thermoelectric behavior breaks down the inverse relation and results in a parallel increase in Seebeck coefficient and electrical conductivity for β‐(Zn0.997Ce0.003)4Sb3 and β‐(Zn0.997Er0.003)4Sb3. This synergistic response triples the power factor of a thermoelectric β‐Zn4Sb3 system realized by the impurity induced resonant distortion in eDOS. From first principle GGA + U calculations, the above‐mentioned unconventional properties are attributed to the effect of doping induced vacancy formation and the formation of resonant impurity levels. Hence, it is postulated that defect engineering can be a broad strategy to improve the power factor of the system and can be extended to other thermoelectric materials.

Summary: Botulinum neurotoxin (BoNT) is one of the most acutely lethal toxins known to humans, and effective treatment for BoNT intoxication is urgently needed. Single-domain antibodies (VHH) have been examined as a countermeasure for BoNT because of their high stability and ease of production. Here, we investigate the structures and the neutralization mechanisms for six unique VHHs targeting BoNT/A1 or BoNT/B1. These studies reveal diverse neutralizing mechanisms by which VHHs prevent host receptor binding or block transmembrane delivery of the BoNT protease domain. Guided by this knowledge, we design heterodimeric VHHs by connecting two neutralizing VHHs via a flexible spacer so they can bind simultaneously to the toxin. These bifunctional VHHs display much greater potency in a mouse co-intoxication model than similar heterodimers unable to bind simultaneously. Taken together, our studies offer insight into antibody neutralization of BoNTs and advance our ability to design multivalent anti-pathogen VHHs with improved therapeutic properties. : Botulinum neurotoxins (BoNTs) are extremely toxic biothreats. Lam et al. report the crystal structures and neutralizing mechanisms of six unique antitoxin VHHs against BoNT/A1 and BoNT/B1, the two major human pathogenic BoNTs. They then develop a platform for structure-based rational design of bifunctional VHH heterodimers with superior antitoxin potencies. Keywords: botulinum neurotoxin, single-domain antibody, VHH, neutralizing epitope, bifunctional antibody, antitoxin, structure-based design

The translocation domain (HN) of Botulinum neurotoxins (BoNTs) mediates the delivery of the BoNT light chain (LC) into neuronal cytosol. Here the authors provide insights into HN membrane insertion by determining the crystal structure of BoNT/A1 HN at acidic pH, which reveals a molecular switch in HN, where buried α-helices are transformed into surface-exposed hydrophobic β-hairpins.

Abstract Antibody treatment is currently the only available countermeasure for botulism, a fatal illness caused by flaccid paralysis of muscles due to botulinum neurotoxin (BoNT) intoxication. Among the seven major serotypes of BoNT/A-G, BoNT/A poses the most serious threat to humans because of its high potency and long duration of action. Prior to entering neurons and blocking neurotransmitter release, BoNT/A recognizes motoneurons via a dual-receptor binding process in which it engages both the neuron surface polysialoganglioside (PSG) and synaptic vesicle glycoprotein 2 (SV2). Previously, we identified a potent neutralizing antitoxin against BoNT/A1 termed ciA-C2, derived from a camelid heavy-chain-only antibody (VHH). In this study, we demonstrate that ciA-C2 prevents BoNT/A1 intoxication by inhibiting its binding to neuronal receptor SV2. Furthermore, we determined the crystal structure of ciA-C2 in complex with the receptor-binding domain of BoNT/A1 (HCA1) at 1.68 Å resolution. The structure revealed that ciA-C2 partially occupies the SV2-binding site on HCA1, causing direct interference of HCA1 interaction with both the N-glycan and peptide-moiety of SV2. Interestingly, this neutralization mechanism is similar to that of a monoclonal antibody in clinical trials, despite that ciA-C2 is more than 10-times smaller. Taken together, these results enlighten our understanding of BoNT/A1 interactions with its neuronal receptor, and further demonstrate that inhibiting toxin binding to the host receptor is an efficient countermeasure strategy.

Botulinum neurotoxin (BoNT) serotype E is one of three serotypes that cause the preponderance of human botulism cases and is a Tier 1 Select Agent. BoNT/E is unusual among BoNT serotypes for its rapid onset and short duration of intoxication. Here we report two large panels of unique, unrelated camelid single-domain antibodies (VHHs) that were selected for their ability to bind to BoNT/E holotoxin and/or to the BoNT/E light chain protease domain (LC/E). The 19 VHHs which bind to BoNT/E were characterized for their subunit specificity and 8 VHHs displayed the ability to neutralize BoNT/E intoxication of neurons. Heterodimer antitoxins consisting of two BoNT/E-neutralizing VHHs, including one heterodimer designed using structural information for simultaneous binding, were shown to protect mice against co-administered toxin challenges of up to 500 MIPLD50. The 22 unique VHHs which bind to LC/E were characterized for their binding properties and 9 displayed the ability to inhibit LC/E protease activity. Surprisingly, VHHs selected on plastic-coated LC/E were virtually unable to recognize soluble or captured LC/E while VHHs selected on captured LC/E were poorly able to recognize LC/E coated to a plastic surface. This panel of anti-LC/E VHHs offer insight into BoNT/E function, and some may have value as components of therapeutic antidotes that reverse paralysis following BoNT/E exposures.

Botulinum neurotoxin serotype E (BoNT/E) is one of the major causes of human botulism, which is a life-threatening disease caused by flaccid paralysis of muscles. After receptor-mediated toxin internalization into motor neurons, the translocation domain (HN) of BoNT/E transforms into a protein channel upon vesicle acidification in endosomes and delivers its protease domain (LC) across membrane to enter the neuronal cytosol. It is believed that the rapid onset of BoNT/E intoxication compared to other BoNT serotypes is related to its swift internalization and translocation. We recently identified two neutralizing single-domain camelid antibodies (VHHs) against BoNT/E1 termed JLE-E5 and JLE-E9. Here, we report the crystal structures of these two VHHs bound to the LCHN domain of BoNT/E1. The structures reveal that these VHHs recognize two distinct epitopes that are partially overlapping with the putative transmembrane regions on HN, and therefore could physically block membrane association of BoNT/E1. This is confirmed by our in vitro studies, which show that these VHHs inhibit the structural change of BoNT/E1 at acidic pH and interfere with BoNT/E1 association with lipid vesicles. Therefore, these two VHHs neutralize BoNT/E1 by preventing the transmembrane delivery of LC. Furthermore, structure-based sequence analyses show that the 3-dimensional epitopes of these two VHHs are largely conserved across many BoNT/E subtypes, suggesting a broad-spectrum protection against the BoNT/E family. In summary, this work improves our understanding of the membrane translocation mechanism of BoNT/E and paves the way for developing VHHs as diagnostics or therapeutics for the treatment of BoNT/E intoxication.

Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed.

Botulinum neurotoxins (BoNTs), which have been exploited as cosmetics and muscle-disorder treatment medicines for decades, are well known for their extreme neurotoxicity to humans. They pose a potential bioterrorism threat because they cause botulism, a flaccid muscular paralysis-associated disease that requires immediate antitoxin treatment and intensive care over a long period of time. In addition to the existing seven established BoNT serotypes (BoNT/A–G), a new mosaic toxin type termed BoNT/HA (aka type FA or H) was reported recently. Sequence analyses indicate that the receptor-binding domain (HC) of BoNT/HA is ~84% identical to that of BoNT/A1. However, BoNT/HA responds differently to some potent BoNT/A-neutralizing antibodies (e.g., CR2) that target the HC. Therefore, it raises a serious concern as to whether BoNT/HA poses a new threat to our biosecurity. In this study, we report the first high-resolution crystal structure of BoNT/HA-HC at 1.8 Å. Sequence and structure analyses reveal that BoNT/HA and BoNT/A1 are different regarding their binding to cell-surface receptors including both polysialoganglioside (PSG) and synaptic vesicle glycoprotein 2 (SV2). Furthermore, the new structure also provides explanations for the ~540-fold decreased affinity of antibody CR2 towards BoNT/HA compared to BoNT/A1. Taken together, these new findings advance our understanding of the structure and function of this newly identified toxin at the molecular level, and pave the way for the future development of more effective countermeasures.

A study was conducted to explore the electrical and mechanical properties of newly fabricated piezoelectric-metal-cavity (PMC) actuator created by using the lead-free [Bi.sub.0.5][([Na.sub.0.725][K.sub.0.175][Li.sub.0.1]).sub.0.5]Ti[O.sub.3] (BN-KLT) ceramics. The results showed that with good piezoelectric coefficients and low density, the BNKLT ceramic could find potential use as the driving element of the lead-free actuator.

Lead-free multiferroic ceramics of 0.75Bi1-xNdxFeO3 - 0.25BaTiO3 + 1 mol. % MnO2 were prepared by a conventional ceramic technique and their structure, piezoelectricity, and multiferroicity were studied. The ceramics sintered at 890-990 °C possess a pure perovskite structure. A morphotropic phase boundary of rhombohedral and monoclinic phases is formed at x = 0.05. A small amount of Nd improves the ferroelectric and piezoelectric properties of the ceramics. The ferroelectric-paraelectric phase transition becomes gradually diffusive with x increasing. After the addition of Nd, the ferromagnetism of the ceramics is greatly enhanced by ~320%. The increase in sintering temperature improves significantly the ferroelectric, piezoelectric, and ferromagnetic properties of the ceramics. The ceramics with x = 0.05 sintered at 950-990 °C possess improved ferroelectricity, piezoelectricity, magnetism and insulation with Pr of 16.5-17.5 μC/cm-2, d33 of 113-121 pC/N, Mr of 0.127-0.138 emu/g, R of ~ 5 x 109 O·cm and high Tc of 473-482 °C, indicating that the ceramic is a promising candidate for room-temperature multiferroic and high-temperature piezoelectric materials. [ABSTRACT FROM AUTHOR]

Bacterial flagella are rotary nanomachines that contribute to bacterial fitness in many settings, including host colonization. The flagellar motor relies on the multiprotein flagellar motorswitch complex to govern flagellum formation and rotational direction. Different bacteria exhibit great diversity in their flagellar motors. One such variation is exemplified by the motorswitch apparatus of the gastric pathogen Helicobacter pylori, which carries an extra switch protein, FliY, along with the more typical FliG, FliM, and FliN proteins. All switch proteins areneeded for normal flagellation and motility in H. pylori, but the molecular mechanismof their assembly isunknown. To fill this gap, we examined the interactions among these proteins. We found that the C-terminal SpoA domain of FliY (FliYC) is critical to flagellation and forms heterodimeric complexes with the FliN and FliM SpoA domains, which are β-sheet domains of type III secretion system proteins. Surprisingly, unlike in other flagellar switch systems, neither FliY nor FliN self-associated. The crystal structure of the FliYC-FliNC complex revealed a saddle-shaped structure homologous to the FliN-FliN dimer of Thermotoga maritima, consistent with a FliY-FliN heterodimer forming the functional unit. Analysis of the FliYC-FliNC interface indicated that oppositely charged residues specific to each protein drive heterodimer formation. Moreover, both FliYC-FliMCandFliYC-FliNCassociated with the flagellar regulatory protein FliH, explaining their important roles in flagellation. We conclude that H. pylori uses a FliY-FliN heterodimer instead of a homodimer and creates a switch complex with SpoA domains derived from three distinct proteins. [ABSTRACT FROM AUTHOR]

Spinel LiNi0.5Mn1.5O4 cathode materials with Fd3m space group were prepared using the co-precipitation method via adjusting the amount of Na2CO3 precipitant. X-ray diffraction and Rietveld refinement revealed that the impurity phase was effectively inhibited after the addition of more amount of Na2CO3. All samples, including the pristine LiNi0.5Mn1.5O4 sample and that prepared with different extra amounts of Na2CO3, exhibited uniform polyhedron morphology and their average grain sizes increased with the amount of Na2CO3. After adding 5% more Na2CO3, the average grain size of the sample was larger than 500 nm. When compared to other samples, the amount of impurity phase was minimum in the sample prepared with 5% more Na2CO3. Due to the impurity suppression, the LiNi0.5Mn1.5O4 sample prepared with 5% more Na2CO3 exhibited superior electrochemical performance for Li-ion batteries, showing initial discharge capacities of 125.4 mA h g-1 and 126.1 mA h g-1, and high capacity retentions of 90.7% and 87.6% after 200 cycles at 0.1 C and 0.5 C, respectively. It also exhibited the lowest intrinsic resistance and best Li+ diffusion kinetics among all the samples deduced from electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

The extreme toxicity of botulinum neurotoxins (BoNTs) relies on their specific cleavage of SNARE proteins, which eventually leads to muscle paralysis. One newly identified mosaic toxin, BoNT/HA (aka H or FA), cleaves VAMP-2 at a unique position between residues L54 and E55, but the molecular basis underlying VAMP-2 recognition of BoNT/HA remains poorly characterized. Here, we report a ~2.09 Å resolution crystal structure of the light chain protease domain of BoNT/HA (LC/HA). Structural comparison between LC/HA and LC of BoNT/F1 (LC/F1) reveals distinctive hydrophobic and electrostatic features near the active sites, which may explain their different VAMP-2 cleavage sites. When compared to BoNT/F5 that cleaves VAMP-2 at the same site as BoNT/HA, LC/HA displays higher affinity for VAMP-2, which could be caused by their different surface charge properties surrounding a VAMP-2 exosite-binding cleft. Furthermore, systematic mutagenesis studies on VAMP-2 and structural modeling demonstrate that residues R47 to K59 spanning the cleavage site in VAMP-2 may adopt a novel extended conformation when interacting with LC/HA and LC/F5. Taken together, our structure provides new insights into substrate recognition of BoNT/HA and paves the way for rational design of small molecule or peptide inhibitors against LC/HA. [ABSTRACT FROM AUTHOR]

The bacterial flagellar motor is a self-assembling supramolecular nanodevice. Its spontaneous biosynthesis is initiated by the insertion of the MS ring protein FliF into the inner membrane, followed by attachment of the switch protein FliG. Assembly of this multiprotein complex is tightly regulated to avoid nonspecific aggregation, but the molecular mechanisms governing flagellar assembly are unclear. Here, we present the crystal structure of the cytoplasmic domain of FliF complexed with the N-terminal domain of FliG (FliFC-FliGN) from the bacterium Helicobacter pylori. Within this complex, FliFC interacted with FliGN through extensive hydrophobic contacts similar to those observed in the FliFC-FliGN structure from the thermophile Thermotoga maritima, indicating conservation of the FliFC-FliGN interaction across bacterial species. Analysis of the crystal lattice revealed that the heterodimeric complex packs as a linear superhelix via stacking of the armadillo repeat-like motifs (ARM) of FliGN. Notably, this linear helix was similar to that observed for the assembly of the FliG middle domain. We validated the in vivo relevance of the FliGN stacking by complementation studies in Escherichia coli. Furthermore, structural comparison with apo FliG from the thermophile Aquifex aeolicus indicated that FliF regulates the conformational transition of FliG and exposes the complementary ARM-like motifs of FliGN, containing conserved hydrophobic residues. FliF apparently both provides a template for FliG polymerization and spatiotemporally controls subunit interactions within FliG. Our findings reveal that a small protein fold can serve as a versatile building block to assemble into a multiprotein machinery of distinct shapes for specific functions. [ABSTRACT FROM AUTHOR]

The development of the thermoelectric (TE) power generation is rapid, and the applications have extensively been studied. The principle is based on the Seebeck effect, in which the temperature difference between hot and cold sides of the TE material converts to electrical energy. In this paper, a design is proposed to convert the thermal energy between indoor and outdoor of a board to electrical energy by the thermoelectric generator (TEG). Furthermore, the electrical energy generated is charged to supercapacitors as a battery or a power supply to the loads (e.g., lights) of the house. Besides the experimental work, a thermal model and an electrical model of the TEG have been proposed. To study the power generation performance in terms of materials, the simulation of the conversion efficiency of the TE board using materials with different thermal conductance have also been conducted. It was found that, using graphene as the thermally conductive material, the conversion efficiency was enhanced by 1.6% and 1.7%, when the temperature difference was 15 °C and 40 °C, respectively. [ABSTRACT FROM AUTHOR]

The measurement of cell mechanics is crucial for a better understanding of cellular responses during the progression of certain diseases and for the identification of the cell's nature. Many techniques using optical tweezers, atomic force microscopy, and micro-pipettes have been developed to probe and manipulate cells in the spatial domain. In particular, we recently proposed a two-dimensional acoustic trapping method as an alternative technique for small particle manipulation. Although the proposed method may have advantages over optical tweezers, its applications to cellular mechanics have not yet been vigorously investigated. This study represents an initial attempt to use acoustic tweezers as a tool in the field of cellular mechanics in which cancer cell membrane deformability is studied. A press-focused 193-MHz single-element lithium niobate (LiNbO3) transducer was designed and fabricated to trap a 5-μm polystyrene microbead near the ultrasound beam focus. The microbeads were coated with fibronectin, and trapped before being attached to the surface of a human breast cancer cell (MCF-7). The cell membrane was then stretched by remotely pulling a cell-attached microbead with the acoustic trap. The maximum cell membrane stretched lengths were measured to be 0.15, 0.54, and 1.41 μm at input voltages to the transducer of 6.3, 9.5, and 12.6 Vpp, respectively. The stretched length was found to increase nonlinearly as a function of the voltage input. No significant cytotoxicity was observed to result from the bead or the trapping force on the cell during or after the deformation procedure. Hence, the results convincingly demonstrated the possible application of the acoustic trapping technique as a tool for cell manipulation. [ABSTRACT FROM AUTHOR]

Botulinum neurotoxins (BoNTs) are potent bacterial toxins. The high oral toxicity of BoNTs is largely attributed to the progenitor toxin complex (PTC), which is assembled from BoNT and nontoxic neurotoxin-associated proteins (NAPs) that are produced together with BoNT in bacteria. Here, we performed ex vivo studies to examine binding of the highly homogeneous recombinant NAPs to mouse small intestine. We also carried out the first comprehensive glycan array screening with the hemagglutinin (HA) component of NAPs. Our data confirmed that intestinal binding of the PTC is partly mediated by the HA moiety through multivalent interactions between HA and host carbohydrates. The specific HA-carbohydrate recognition could be inhibited by receptor-mimicking saccharides. [ABSTRACT FROM AUTHOR]

Lead magnesium niobate-lead titanate (PMN-PT) ceramic fibres with a nominal composition of 0.65Pb(Mg 1/3 Nb 2/3 )O 3 -0.35PbTiO 3 have been fabricated by a modified sol-gel technique. The ceramic fibres with 100 μm diameter were well-crystallized after being calcined at 850°C and sintered at 1200°C. After being poled, the electromechanical coefficient of the single PMN-PT ceramic fibre is 0.5. The relative permittivity of the single ceramic fibre was higher than that of a ceramic disc while their hysteresis loops are comparable. The characterization of the ceramic fibres reveals that the modified sol-gel method can be used to fabricate PMN-PT ceramic fibres with good piezoelectric and ferroelectric properties. [ABSTRACT FROM AUTHOR]

Abstract The pursuit of supercapacitors with simultaneous high power and energy densities has led to extensive research and successful outcomes through the integration of three‐dimensional (3D) electrodes, encompassing both 3D active materials and 3D porous current collectors. This mini review provides a summary of recent developments in supercapacitors featuring 3D structures. The incorporation of both 3D active materials and 3D current collectors proves effective in enhancing the mass loading of active materials without compromising their specific capacitance. The presence of pores in 3D porous current collectors contributes to additional double‐layer capacitance by offering a large surface area. Moreover, 3D porous transition metal current collectors can provide both double‐layer and faradic capacitances through the in‐situ surface oxidation mechanism. Beyond materials and geometries, this review also discusses synthesis strategies for electrodes, offering insights into the process‐structure‐property relationship crucial for supercapacitors. By combining 3D active materials with 3D current collectors, the energy density of supercapacitors could be substantially improved.

This paper is intended to estimate the spatial averaging effects of the hydrophone in field characterization of focused transducers. The analytical model derived was based on Fresnel approximation and enabled modifications of the results for both on-axis and off-axis measurement arrangements. The axial and lateral field distributions in the focal plane measured by the hydrophone were derived for both non-attenuating and attenuating fluids in the model. The spatial averaging effects result in underestimating the absolute acoustic pressure amplitudes, and overestimating the cross-sectional size of the beam directivity pattern in the focal plane. The validity of the Rayleigh integral and the Fresnel approximation for curved transducers were discussed. The results indicate that, for (where k is the circular wave number, ah is the chord from the center of curved surface to the boundary and b is the effective radius of the hydrophone), the Fresnel approximation remains valid for all locations of the hydrophone in the focused field. Particularly, in the focal plane, the spatial averaging effects of the hydrophone on the directivity pattern of the acoustic beam can be neglected for (where a and lf are the effective radius and focal distance of the focused transducer). [ABSTRACT FROM AUTHOR]

SnSe single crystals have been demonstrated to possess excellent thermoelectric properties. In this work, we demonstrate a grain size control method in growing nanocrystalline SnSe thin films through a glancing angle pulsed-laser deposition approach. Structural characterization reveals that the SnSe film deposited at a normal angle has a preferred orientation along a axis, while by contrast, the SnSe film deposited at an 80° glancing angle develops a nanopillar structure with the growth direction towards the incident atomic flux. The glancing angle deposition greatly reduces the grain size of the thin film due to a shadowing effect to the adatoms, resulting in significantly increased power factor for more than 100%. The maximum Seebeck coefficient and power factor are 498.5μV/K and 18.5μWcm−1K−2, respectively. The enhancement of thermoelectric property can be attributed to the potential barrier scattering at grain boundaries owing to the reduced grain size and increased grain boundaries in the film. Given this enhanced power factor, and considering the fact that the nanopillar structure should have much lower thermal conductivity than a plain film, the zT value of such made SnSe film could be significantly larger than the corresponding single crystal film, making it a good candidate for thin film-based thermoelectric device.