Spectroscopic characterization of carbon monoxide activation by neutral chromium carbides.

Spectroscopic characterization of carbon monoxide activation by neutral metal carbides is of essential importance for understanding the structure-reactivity relationships of catalytic sites, but has been proven to be very challenging owing to the difficulty in size selection. Here, we report a size-specific infrared-vacuum ultraviolet spectroscopic study of the reactions between carbon monoxide with neutral chromium carbides. Quantum chemical calculations were carried out to identify the low-lying structures and to interpret the experimental features. The results reveal that the most stable structure of CrC3(CO)2 consists of a CCO ketenylidene unit and that of CrC4(CO)2 has a semi-bridging CO with a very low CO stretching vibrational frequency at 1821 cm-1. The electron structure analyses show that this semi-bridging CO is highly activated through the delocalized Cr-C-C three-center two-electron (3c-2e) interaction between the antibonding orbitals of CO and the metal carbide skeleton. The formation of these metal carbide carbonyls is found to be both thermodynamically exothermic and kinetically facile in the gas phase. The present findings have important implications for the mechanical understanding of the catalytic processes with isolated metal atoms/clusters dispersed on supports.

Spectroscopic Characterization of Highly Excited Neutral Chromium Tricarbonyl.

Spectroscopic characterization of highly excited neutral transition-metal complexes is important for understanding the multifaceted reaction mechanisms between metals and ligands. In this work, the reactions of neutral chromium atoms with carbon monoxide were probed by size-specific infrared spectroscopy. Interestingly, Cr(CO)3 was found to have an unprecedented 7A2″ septet excited state rather than the singlet ground state. A combination of experiment and theory shows that the gas-phase formation of this highly excited Cr(CO)3 is facile both thermodynamically and kinetically. Electronic structure and bonding analyses indicate that the valence electrons of Cr atoms in the septet Cr(CO)3 are in a relatively stable configuration, which facilitate the highly excited structure and the planar geometric shape (D3h symmetry). The observed septet Cr(CO)3 affords a paradigm for exploring the structure, properties, and formation mechanism of a large variety of excited neutral compounds.

Can a "Pandemic Life Adaptation" Digital Technology Curriculum Reduce the Digital Disadvantage of Older Adults During COVID-19? An Intervention Study from Shanghai.

Older adults are at a digital disadvantage because of social stereotypes and a lack of social support; however, smartphones have become a necessary technology to cope with crises and daily life in China, especially during the pandemic. This study aimed to help marginalized older adults take on new tasks by developing digital technology education that used a framework of social cognitive theory in social work. The study followed a quasi-experimental design in which 153 elderly people were recruited from three community service centers; 90 of the participants received 6-weekly intervention. Intent-to-treat analysis, effect size calculations, and sensitivity analysis were conducted. The findings show that digital education significantly enhanced two domains of digital life adaptation abilities: general digital life adaptation abilities [g = .50, 95% CI (.70, 2.69)] and pandemic digital life adaptation abilities [g = .89, 95% CI (.96, 2.07)]. The intervention also improved three domains of digital self-efficacy: sharing and communication [g = .55, 95% CI (.04, .48)], verification [g = .34, 95% CI (.01, .59)], and influencing others [g = .53, 95% CI (.13, .77)]. The study showed that the new intervention approach reduced the harm to vulnerable older adults in the digital wave, especially during the pandemic.

Taurine promotes B-cell activation by interaction with the VH /VL framework regions of B-cell receptor.

Taurine (Tau) is a special sulphur-containing amino acid and has been widely used as a dietary supplement. Although Tau exists in lymphocytes in large quantities, the physiological significance of Tau to modulate human immunity is unknown. In the present study, we first found that Tau regulates the B-cell receptor (BCR)-mediated signal transduction and induces the B cells activation. The IgG production of mice after ovalbumin immunization was also increased by Tau administration. Moreover, the isothermal titration calorimetry and surface plasmon resonance analysis have shown that Tau specifically bound to the IgG2a-BCR. The Tau could bind to IgG F(ab')2 regions via fluorescence spectroscopy analysis. In the molecular docking analysis, Tau bound to the framework regions (FRs) of variable region of the heavy chains (VH ) and in the light chains (VL ) of IgG2a-BCR. Our results suggested that Tau could improve the activation of B cells by interaction with the VH /VL FRs of BCR.

Spectroscopic snapshot for neutral water nonamer (H2O)9: Adding a H2O onto a hydrogen bond-unbroken edge of (H2O)8.

Structural characterization of neutral water clusters is crucial to understanding the structures and properties of water, but it has been proven to be a challenging experimental target due to the difficulty in size selection. Here, we report the size-specific infrared spectra of confinement-free neutral water nonamer (H2O)9 based on threshold photoionization, using a tunable vacuum ultraviolet free-electron laser. Distinct OH stretch vibrational fundamentals in the 3200-3350 cm-1 region are observed, providing unique spectral signatures for the formation of an unprecedented (H2O)9 structure evolved by adding a ninth water molecule onto a hydrogen bond-unbroken edge of the (H2O)8 octamer with D2d symmetry. This nonamer structure coexists with the five previously identified structures that can be viewed as derived by inserting a ninth water molecule into a hydrogen bond-broken edge of the D2d/S4 octamer. These findings provide key microscopic information for systematic understanding of the formation and growth mechanism of dynamical hydrogen-bonding networks that are responsible for the structure and properties of condensed-phase water.

Observation of Confinement-Free Neutral Group Three Transition Metal Carbonyls Sc(CO)7 and TM(CO)8 (TM=Y, La).

Spectroscopic characterization of neutral highly-coordinated compounds is essential in fundamental and applied research, but has been proven to be a challenging experimental target because of the difficulty in mass selection. Here, we report the preparation and size-specific infrared-vacuum ultraviolet (IR-VUV) spectroscopic identification of group-3 transition metal carbonyls Sc(CO)7 and TM(CO)8 (TM=Y, La) in the gas phase, which are the first confinement-free neutral heptacarbonyl and octacarbonyl complexes. The results indicate that Sc(CO)7 has a C2v structure and TM(CO)8 (TM=Y, La) have a D4h structure. Theoretical calculations predict that the formation of Sc(CO)7 and TM(CO)8 (TM=Y, La) is both thermodynamically exothermic and kinetically facile in the gas phase. These highly-coordinated carbonyls are 17-electron complexes when only those valence electrons that occupy metal-CO bonding orbitals are considered, in which the ligand-only 4b1u molecular orbital is ignored. This work opens new avenues toward the design and chemical control of a large variety of compounds with unique structures and properties.

Ligand-Induced Tuning of the Electronic Structure of Rhombus Tetraboron Cluster.

A neutral boron carbonyl complex B4 (CO)3 is generated in the gas phase and is characterized by infrared plus vacuum ultraviolet (IR+VUV) two-color ionization spectroscopy and quantum chemical calculations. The complex is identified to have a planar C2v structure with three CO ligands terminally coordinated to a rhombus B4 core. It has a closed-shell singlet ground state that correlates to an excited state of B4 . Bonding analyses on B4 (CO)3 as well as the previously reported B4 and B4 (CO)2 indicate that the electronic structure of rhombus tetraboron cluster changes from a close-shell singlet to an open-shell singlet in B4 (CO)2 and to a close-shell singlet in B4 (CO)3 , demonstrating that the electronic structures of boron clusters can be effectively tuned via sequential CO ligand coordination.

Aerosol mass spectrometry of neutral species based on a tunable vacuum ultraviolet free electron laser.

A vacuum ultraviolet free electron laser (VUV-FEL) photoionization aerosol mass spectrometer (AMS) has been developed for online measurement of neutral compounds in laboratory environments. The aerosol apparatus is mainly composed of a smog chamber and a reflectron time-of-flight mass spectrometer (TOF-MS). The indoor smog chamber had a 2 m3 fluorinated ethylene propylene film reactor placed in a temperature- and humidity-controlled room, which was used to generate the aerosols. The aerosols were sampled via an inlet system consisting of a 100 µm orifice nozzle and aerodynamic lenses. The application of this VUV-FEL AMS to the α-pinene ozonolysis under different concentrations reveals two new compounds, for which the formation mechanisms are proposed. The present findings contribute to the mechanistic understanding of the α-pinene ozonolysis in the neighborhood of emission origins of α-pinene. The VUV-FEL AMS method has the potential for chemical analysis of neutral aerosol species during the new particle formation processes.

Characterization of neutral metal hydride-hydroxide hydrogen-bonded clusters HMOH(H2O)2 (M = Al and Ga).

Metal hydride-hydroxide hydrogen-bonded clusters HMOH(H2O)n are key intermediates in the reactions of metals with water. However, characterizing the structure of such neutral clusters is a challenging experimental goal due to the difficulty of size selection. Here, neutral HMOH(H2O)2 (M = Al and Ga) clusters were prepared by using a laser-vaporization source and characterized by size-specific infrared-vacuum ultraviolet spectroscopy combined with quantum chemical calculations and ab initio molecular dynamics simulations. The HMOH(H2O)2 (M = Al and Ga) clusters were found to have intriguing hydrogen-bonded network structures. The results indicate that the formation of HMOH(H2O)2 (M = Al and Ga) is both thermodynamically exothermic and kinetically facile in the gas phase. The present system serves as a model for capturing key intermediates in metal-water reactions and also opens up new avenues for systematic studies of a large variety of reactions between neutral metal atoms/clusters and small molecules.

Core fucosylation regulates the ovarian response via FSH receptor during follicular development.

INTRODUCTION: Ovarian low response to follicle-stimulating hormone (FSH) causes infertility featuring hypergonadotropic hypogonadism, ovarian failure, and/or defective ovarian response. OBJECTIVES: N-glycosylation is essential for FSH receptor (FSHR). Core fucosylation catalyzed by fucosyltransferase 8 (FUT8) is the most common N-glycosylation. Core fucosylation level changes between individuals and plays important roles in multiple physiological and pathological conditions. This study aims to elucidate the significance of FUT8 to modulate FSHR function in female fertility. METHODS: Samples from patients classified as poor ovary responders (PORs) were detected with lectin blot and real-time PCR. Fut8 gene knockout (Fut8-/-) mice and FUT8-knockdown human granulosa cell line (KGN-KD) were established and in vitro fertilization (IVF) assay, western blot, molecular interaction, immunofluorescence and immunoprecipitation were applied. RESULTS: Core fucosylation is indispensable for oocyte and follicular development. FSHR is a highly core-fucosylated glycoprotein. Loss of core fucosylation suppressed binding of FSHR to FSH, and attenuated FSHR downstream signaling in granulosa cells. Transcriptomic analysis revealed the downregulation of several transcripts crucial for oocyte meiotic progression and preimplantation development in Fut8-/- mice and in POR patients. Furthermore, loss of FUT8 inhibited the interaction between granulosa cells and oocytes, reduced transzonal projection (TZP) formation and caused poor developmental competence of oocytes after fertilization in vitro. While L-fucose administration increased the core fucosylation of FSHR, and its sensitivity to FSH. CONCLUSION: This study first reveals a significant presence of core fucosylation in female fertility control. Decreased fucosylation on FSHR reduces the interaction of FSH-FSHR and subsequent signaling, which is a feature of the POR patients. Our results suggest that core fucosylation controls oocyte and follicular development via the FSH/FSHR pathway and is essential for female fertility in mammals.

Spectroscopic and Theoretical Identifications of Two Structural Motifs of (H2O)10 Cluster.

Precise characterization of archetypal systems of aqueous hydrogen-bonding networks is essential for developing accurate potential functions and universal models of water. The structures of water clusters (H2O)n (n = 2-9) have been verified recently through size-specific infrared spectroscopy with a vacuum ultraviolet free electron laser (VUV-FEL) and quantum chemical studies. For (H2O)10, the pentagonal prism and butterfly motifs were proposed to be important building blocks and were observed in previous experiments. Here we report the size-specific infrared spectra of (H2O)10 via a joint experimental and theoretical study. Well-resolved spectra provide a unique signature for the coexistence of pentagonal prism and butterfly motifs. These (H2O)10 motifs develop from the dominant structures of (H2O)n (n = 8, 9) clusters. This work provides an intriguing prelude to the diverse structure of liquid water and opens avenues for size-dependent measurement of larger systems to understand the stepwise formation mechanism of hydrogen-bonding networks.

A Flexible Iontronic Capacitive Sensing Array for Hand Gesture Recognition Using Deep Convolutional Neural Networks.

Hand gesture recognition, one of the most popular research topics in human-machine interaction, is extensively used in visual and augmented reality, sign language translation, prosthesis control, and so on. To improve the flexibility and interactivity of wearable gesture sensing interfaces, flexible electronic systems for gesture recognition have been widely studied. However, these systems are limited in terms of wearability, stability, scalability, and robustness. Herein, we report a flexible wearable hand gesture recognition system that is based on an iontronic capacitive pressure sensing array and deep convolutional neural networks. The entire capacitive array is integrated into a flexible silicone wristband and can be comfortably and conveniently wrapped around the wrist. The pressure sensing array, which is composed of an iontronic film sandwiched between two flexible screen-printed electrode arrays, exhibits a high sensitivity (775.8 kPa-1), fast response time (65 ms), and high durability (over 6000 cycles). Image processing techniques and deep convolutional neural networks are applied for sensor signal feature extraction and hand gesture recognition. Several contexts such as intertrial test (average accuracy of 99.9%), intersession rewearing (average accuracy of 93.2%), electrode shift (average accuracy of 83.2%), and different arm positions during measurement (average accuracy of 93.1%) are evaluated.

A Wearable Co-Located Neural-Mechanical Signal Sensing Device for Simultaneous Bimodal Muscular Activity Detection.

The co-located and concurrent measurement of both muscular neural activity and muscular deformation is considered necessary in many applications, such as medical robotics, assistive exoskeletons and muscle function evaluations. Nevertheless, conventional muscle-related signal perception systems either detect only one of these modalities, or are made with rigid and bulky components that cannot provide conformal and flexible interface. Herein, a flexible, easy-to-fabricate, bimodal muscular activity sensing device, which collects neural and mechanical signal at the same muscle location, is reported. The sensing patch includes a screen-printed sEMG sensor, and a pressure-based muscular deformation sensor (PMD sensor) based on a highly sensitive, co-planar iontronic pressure sensing unit. Both sensors are integrated on a super-thin (25 µm) substrate. The sEMG sensor shows a high signal-to-noise ratio of 37.1 dB, and the PMD sensor sensor exhibits a high sensitivity of 70.9 kPa -1. The responses of the sensor to three types of muscle activities (isotonic, isometric, and passive stretching) were analyzed and validated by ultrasound imaging. Bimodal signals during dynamic walking experiments with different level-ground walking speeds were also investigated. The application of the bimodal sensor was verified in gait phase estimation, and results show that the assembly of both modalities significantly reduce (p < 0.05) the average estimation error across all subjects and all walking speeds to 3.82%. Demonstrations show the potential of this sensing device for informative evaluation of muscular activities, and its abilities in human-robot interaction.

Infrared spectroscopic study of solvation and size effects on reactions between water molecules and neutral rare-earth metals.

Elucidating the solvation and size effects on the reactions between water and neutral metals is crucial for understanding the microscopic mechanism of the catalytic processes but has been proven to be a challenging experimental target due to the difficulty in size selection. Here, MO4H6 and M2O6H7 (M = Sc, Y, La) complexes were synthesized using a laser-vaporization cluster source and characterized by size-specific infrared-vacuum ultraviolet spectroscopy combined with quantum chemical calculations. The MO4H6 and M2O6H7 complexes were found to have H˙M(OH)3(H2O) and M2(µ2-OH)2(η1-OH)3(η1-OH2) structures, respectively. A combination of experiments and theory revealed that the formation of H˙M(OH)3(H2O) and M2(µ2-OH)2(η1-OH)3(η1-OH2) is both thermodynamically exothermic and kinetically facile in the gas phase. The results indicated that upon the addition of water to H˙M(OH)3, the feature of the hydrogen radical is retained. In the processes from mononuclear H˙M(OH)3 to binuclear M2(µ2-OH)2(η1-OH)3(η1-OH2), the active hydrogen atom undergoes the evolution from hydrogen radical → bridging hydrogen → metal hydride → hydrogen bond, which is indicative of a reduced reactivity. The present system serves as a model for clarifying the solvation and size effects on the reactions between water and neutral rare-earth metals and offers a general paradigm for systematic studies on a broad class of the reactions between small molecules and metals at the nanoscale.

Inhibition of α2,6-sialyltransferase relieves symptoms of ulcerative colitis by regulating Th17 cells polarization.

Ulcerative colitis (UC) is a chronic, relapsing inflammatory disease that affects human intestines. Immune imbalance is one of the important factors inducing UC. After the activation of CD4+ T cells, pro-inflammatory cytokines are produced to induce colonic inflammation. α2,6-Sialylation, catalyzed by α2,6-sialyltransferase (ST6GAL1), affects the proliferation, activation, and T cell receptor (TCR) signaling of CD4+ T cells, but its role in CD4+ T cell polarization, regulation of Th17 / Treg balance, and its role in UC are still unclear. We found the number of CD4+ T and Th17 cells increased in colonic tissue with UC. The level of α2,6-sialylation of CD4+ T cells in patients with UC was significantly increased. De-α2,6-sialylation significantly reduced the symptoms of UC in rats. ST6GAL1 gene knockout inhibited the polarization of CD4+ T cells to Th17 cells, and promoted the polarization of CD4+ T cells to Treg cells. ST6GAL1 knockout significantly inhibited the IL-17 signaling pathway in CD4+ T cells and inhibited the secretion of pro-inflammatory cytokine IL-17a. ST6GAL1 and IL-17a are highly expressed in patients with UC, and there is a positive correlation between them. In conclusion, reduced α2,6-sialylation inhibits the polarization of CD4+ T cells to Th17 cells, inhibits IL-17a signaling pathway and reduces the level of pro-inflammatory cytokine IL-17a to alleviate the symptoms of UC, which is a potential novel target for the clinical treatment of UC.

Capturing Hydrogen Radicals by Neutral Metal Hydroxides.

Capturing the hydrogen radical is of central importance in various systems ranging from catalysis to biology to astronomy, but it has been proven to be challenging experimentally because of its high reactivity and short lifetime. Here, neutral MO3H4 (M = Sc, Y, La) complexes were characterized by size-specific infrared-vacuum ultraviolet spectroscopy. All these products were determined to be the hydrogen radical adducts in the form of H•M(OH)3. The results indicate that the addition of the hydrogen radical to the M(OH)3 complex is both thermodynamically exothermic and kinetically facile in the gas phase. Moreover, the soft collisions in the cluster growth channel with the helium expansion were found to be demanded for the formation of H•M(OH)3. This work highlights the pivotal roles played by the soft collisions in the formation of hydrogen radical adducts and also opens new avenues toward the design and chemical control of compounds.

Size-Specific Infrared Spectroscopic Study of the Reactions between Water Molecules and Neutral Vanadium Dimer: Evidence for Water Splitting.

Investigation of the reactions between water molecules and neutral metal clusters is important in water splitting but is very challenging due to the inherent difficulty of size selection. Here, we report a size-specific infrared-vacuum ultraviolet spectroscopic study on the reactions of water with neutral vanadium dimer. The V2O3H4 and V2O4H6 products were characterized to have unexpected V2(µ2-OH)(µ2-H)(η1-OH)2 and V2(µ2-OH)2(η1-H)2(η1-OH)2 structures, indicative of a water decomposition. A combination of theory and experiment reveals that the water splitting by V2 is both thermodynamically exothermic and kinetically facile in the gas phase. The present system serves as a model for clarifying the pivotal roles played by neutral metal clusters in water decomposition and also opens new avenues toward systematic understanding of water splitting by a large variety of single-cluster catalysts.

Track-Etch Membranes as Tools for Template Synthesis of Highly Sensitive Pressure Sensors.

Flexible pressure sensors with high sensitivity are highly desired in wearable electronics and human-machine interaction. Introducing the surface microstructures to the capacitive-type sensors can improve sensitivity and reduce response time. However, conventional techniques for the fabrication of highly sensitive and large-area pressure sensors still remain challenging. Here, a template synthesis approach is reported for fabrication of a large-area and low-cost ionic micropillar array templated from track-etch membranes. The pressure sensors based on the ionic micropillars gel dielectric layers exhibit a low limit of detection (∼0.5 Pa) and high sensitivity (14.83 kPa-1) in the low-pressure regime (0-5 kPa) and linear sensitivity (1.96 kPa-1) over a wide pressure range of 24-230 kPa. The versatility of the sensors is demonstrated in various human physiological signal detection scenarios and spatial pressure distribution. Furthermore, a real-time pressure mapping insole was fabricated on the basis of a large-area micropillared ionic gel dielectric layer combined with the screen-printing technique. The scalable and low-cost fabrication of pressure sensors with micropillars templated from a track-etch membrane provides new insights into the future development of health monitoring and human-machine interaction.

Hand Gesture Recognition With Flexible Capacitive Wristband Using Triplet Network in Inter-Day Applications.

Human-machine interfaces for hand gesture recognition across multiple sessions and days of doffing and re-donning while maintaining acceptable recognition accuracy are still challenging. In this paper, a flexible wristband, which was integrated with a highly sensitive capacitive pressure sensing array, was used for inter-day hand gesture recognition. The performance of the entire system was further improved by utilizing a triplet network for deep feature embedding. Seven hand gestures were included into the gesture set, and inter-day experiments which lasted for five consecutive days with three sessions on each day were conducted. Five healthy subjects participated in the experiment. Between each session, the wristband was doffed, and re-donned before the next session. The triplet network achieved an average recognition accuracy of 91.98% across all the sessions of all the subjects, and yielded a higher classification result (p < 0.05) over the convolutional neural network trained with softmax-cross-entropy loss (with an average accuracy of 84.65%). Furthermore, we also found that the capacitive array size had an evident influence on the inter-day classification result. The array with the full size (thirty-two channels) achieved a higher average recognition accuracy over all the down-sampled arrays. This work demonstrated the feasibility of improving the hand gesture recognition performance over days of usage by fabricating a wearable, flexible multi-channel capacitive wristband and implementing the triplet network.

Core Fucosylation Regulates the Function of Pre-BCR, BCR and IgG in Humoral Immunity.

Most of the membrane molecules involved in immune response are glycosylated. N-glycans linked to asparagine (Asn) of immune molecules contribute to the protein conformation, surface expression, stability, and antigenicity. Core fucosylation catalyzed by core fucosyltransferase (FUT8) is the most common post-translational modification. Core fucosylation is essential for evoking a proper immune response, which this review aims to communicate. First, FUT8 deficiency suppressed the interaction between µHC and λ5 during pre-BCR assembly is given. Second, we described the effects of core fucosylation in B cell signal transduction via BCR. Third, we investigated the role of core fucosylation in the interaction between helper T (TH) cells and B cells. Finally, we showed the role of FUT8 on the biological function of IgG. In this review, we discussed recent insights into the sites where core fucosylation is critical for humoral immune responses.