Covalent organic frameworks derived Single-Atom cobalt catalysts for boosting oxygen reduction reaction in rechargeable Zn-Air batteries

The design and development of high-performance and long-life Pt-free catalysts for the oxygen reduction reaction (ORR) is of great important with respect to metal-air batteries and fuel cells. Herein, a new low-cost covalent organic frameworks (COFs)-derived CoNC single-atoms catalyst (SAC) is fabricated and compared with the engineered nanoparticle (NP) counterpart for ORR activity. The ORR performance of the SAC catalyst (CoSA@NC) surpasses the NP counterpart (CoNP-NC) under the same operation condition. CoSA@NC also achieves improved long-term durability and better methanol tolerance compared with the Pt/C. The zinc-air battery assembled by the CoSA@NC cathode delivers a higher power density and energy density than that of commercial Pt/C catalyst. Molecular dynamics (MD) is performed to explain the spontaneous evolution from clusters to single-atom metal configuration and density functional theory (DFT) calculations find that CoSA@NC possesses lower d-band center, resulting in weaker interaction between the surface and the O-containing intermediates. Consequently, the reductive desorption of OH*, the rate-determine step, is further accelerated.

Selective detection of tricyclazole by optical technique using thiomalic acid-modified Au and Ag nanoparticle mixtures

This study proposes the use of thiomalic acid-modified Au and Ag nanoparticle mixtures (TMA-Au/AgNP mixes) for the selective detection of tricyclazole. Upon the addition of tricyclazole, the color of TMA-Au/AgNP mixes solution changes from orange-red to lavender (red-shift). According to the density-functional theory calculations, tricyclazole-induced aggregation of TMA-Au/AgNP mixes through electron donor-acceptor interactions was proved. The sensitivity and selectivity of the proposed method are affected by the amount of TMA, volume ratio of TMA-AuNPs to TMA-AgNPs, pH value, and buffer concentration. The ratio of absorbance (A₆₅₄/A₅₂₀) of TMA-Au/AgNP mixes solution is proportional to the concentration of tricyclazole over the range 0.1-0.5 ppm with a linear correlation (R² = 0.948). Moreover, the limit of detection was estimated at 0.028 ppm. The practicality of TMA-Au/AgNP mixes was validated for the determination of tricyclazole concentration in real samples (spiked recovery was 97.5%-105.2%), demonstrating its advantages of simplicity, selectivity, and sensitivity.

Atomically dispersed golds on degradable zero-valent copper nanocubes augment oxygen driven Fenton-like reaction for effective orthotopic tumor therapy

Herein, we employ a galvanic replacement approach to create atomically dispersed Au on degradable zero-valent Cu nanocubes for tumor treatments on female mice. Controlling the addition of precursor HAuCl₄ allows for the fabrication of different atomic ratios of Au_xCu_y. X-ray absorption near edge spectra indicates that Au and Cu are the predominant oxidation states of zero valence. This suggests that the charges of Au and Cu remain unchanged after galvanic replacement. Specifically, Au_0.02Cu_0.98 composition reveals the enhanced •OH generation following O₂ → H₂O₂ → •OH. The degradable Au_0.02Cu_0.98 released Cu⁺ and Cu²⁺ resulting in oxygen reduction and Fenton-like reactions. Simulation studies indicate that Au single atoms boot zero-valent copper to reveal the catalytic capability of Au_0.02Cu_0.98 for O₂ → H₂O₂ → •OH as well. Instead of using endogenous H₂O₂, H₂O₂ can be sourced from the O₂ in the air through the use of nanocubes. Notably, the Au_0.02Cu_0.98 structure is degradable and renal-clearable.

Constraints on Sub-GeV Dark Matter-Electron Scattering from the CDEX-10 Experiment

We present improved germanium-based constraints on sub-GeV dark matter via dark matter-electron (χ-e) scattering using the 205.4  kg·day dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted χ-e scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for m_{χ} larger than 80  MeV/c^{2} compared to previous germanium-based χ-e results. We also present the most stringent χ-e cross-section limit to date among experiments using solid-state detectors for m_{χ} larger than 90  MeV/c^{2} with heavy mediators and m_{χ} larger than 100  MeV/c^{2} with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new χ-e detection method with high-purity germanium detectors in ultralow radioactive background.

Recall of B cell memory depends on relative locations of prime and boost immunization

Immunization or microbial infection can establish long-term B cell memory not only systemically but also locally. Evidence has suggested that local B cell memory contributes to early local plasmacytic responses after secondary challenge. However, it is unclear whether locality of immunization plays any role in memory B cell participation in recall germinal centers (GCs), which is essential for updating their B cell antigen receptors (BCRs). Using single B cell culture and fate mapping, we have characterized BCR repertoires in recall GCs after boost immunizations at sites local or distal to the priming. Local boosts with homologous antigen recruit the progeny of primary GC B cells to recall GCs more efficiently than do distal boosts. Recall GCs elicited by local boosts contain significantly more B cells with elevated levels of immunoglobulin (Ig) mutation and higher avidity BCRs. This local preference is unaffected by blocking CD40:CD154 interaction to terminate active, GC responses. Local boosts with heterologous antigens elicit secondary GCs with B cell populations enriched for cross-reactivity to the prime and boost antigens; in contrast, cross-reactive GC B cells are rare after distal boosts. Our results suggest that local B cell memory is retained in the form of memory B cells, GC B cells, and GC phenotype B cells that are independent of organized GC structures and that these persistent "primed B cells" contribute to recall GC responses at local sites. Our findings indicate the importance of locality in humoral immunity and inform serial vaccination strategies for evolving viruses.

Primary germinal center-resident T follicular helper cells are a physiologically distinct subset of CXCR5hiPD-1hi T follicular helper cells

T follicular helper (Tfh) cells are defined by a Bcl6+CXCR5hiPD-1hi phenotype, but only a minor fraction of these reside in germinal centers (GCs). Here, we examined whether GC-resident and -nonresident Tfh cells share a common physiology and function. Fluorescently labeled, GC-resident Tfh cells in different mouse models were distinguished by low expression of CD90. CD90neg/lo GCTfh cells required antigen-specific, MHCII+ B cells to develop and stopped proliferating soon after differentiation. In contrast, nonresident, CD90hi Tfh (GCTfh-like) cells developed normally in the absence of MHCII+ B cells and proliferated continuously during primary responses. The TCR repertoires of both Tfh subsets overlapped initially but later diverged in association with dendritic cell-dependent proliferation of CD90hi GCTfh-like cells, suggestive of TCR-dependency seen also in TCR-transgenic adoptive transfer experiments. Furthermore, the transcriptomes of CD90neg/lo and CD90hi GCTfh-like cells were enriched in different functional pathways. Thus, GC-resident and nonresident Tfh cells have distinct developmental requirements and activities, implying distinct functions.

Theoretical insight into hydroxyl production via H2O2 decomposition over the Fe3O4(311) surface

Fenton's reagent provides a method to produce active hydroxyl radicals (˙OH) for chemical oxidation by mixing iron oxide and hydrogen peroxide, which divides into homogeneous and heterogeneous Fenton's reagent. Heterogeneous Fenton's reagent is fabricated from H₂O₂ and various iron oxide solid materials, such as α-FeOOH, α-Fe₂O₃, and Fe₃O₄. Fe₃O₄ possesses the Fe²⁺/Fe³⁺ mixed valence oxidational state and has been reported to have good catalytic activity. However, the reaction mechanism of H₂O₂ decomposition on Fe₃O₄ surfaces is still unclear. In this work, we performed DFT calculations to investigate the H₂O₂ decomposition mechanisms over the Fe₃O₄(311) surface. There are two iron environments for H₂O₂ adsorption and decomposition on the Fe₃O₄(311) surface, a Fe²⁺/Fe³⁺ environment and a Fe³⁺/Fe³⁺ environment. We found that the H₂O₂ can adsorb on the Fe²⁺/Fe³⁺ environment by molecular adsorption but by dissociative adsorption on the Fe³⁺/Fe³⁺ environment. Our results show that both adsorption structures can produce two OH groups on the Fe₃O₄(311) surface thermodynamically. In addition, based on the electronic property analysis, H₂O₂ on the Fe²⁺/Fe³⁺ environment follows the Haber-Weiss mechanism to form one OH anion and one OH radical. On the other hand, H₂O₂ on the Fe³⁺/Fe³⁺ environment follows the radical mechanism to form two OH radicals. In particular, the OH radical formed on Fe²⁺/Fe³⁺ has energy levels on both sides of the Fermi energy level. It can be expected that this OH radical has good redox activity.

Effects of external electric field on the sensing property of volatile organic compounds over Janus MoSSe monolayer: a first-principles investigation

Janus 2D transition metal dichalcogenide (TMD) is a new generation 2D material with a unique asymmetric structure. This asymmetric structure (or out-off plane symmetric geometry) of Janus 2D TMD has been reported to yield tunable electronic properties through strain and electric field, which can also be applied in gas sensing. In this work, we performed DFT calculations to investigate the gas sensing property of cyclohexane and acetone on MoS2 and Janus MoSSe monolayers under external electric fields. Our results show that cyclohexane possesses slightly larger adsorption energy on pristine MoS2 and Janus MoSSe monolayers than acetone without external electric fields. After applying the external electric fields, the adsorption energy for cyclohexane on MoS2 shows no enhancement. However, the adsorption energy of acetone shows the most substantial enhancement on the Janus MoSSe monolayer. We found that the dipole moment orientations of adsorbates and the monolayer can strongly interact with the external electric fields. Hence, the combination of polar adsorbate and polar material, i.e., acetone and Janus MoSSe, demonstrates the most vital sensitivity under the applied bias. On the other hand, the non-polar adsorbate and non-polar material combination show a negligible effect on external bias. These findings can be applied to the design of gas sensors in the future through polar materials.

Facile Fabrication of Highly Stable and Wavelength-Tunable Tin Based Perovskite Materials with Enhanced Quantum Yield via the Cation Transformation Reaction

Metal halide perovskites have attracted great attention for their superior light energy conversion applications. Herein, we demonstrated a facile synthesis of zero-dimensional Sn²⁺ perovskite Cs_4-xM_xSnBr₆(M = K⁺ and Rb⁺) material through the cation transformation reaction at room temperature. Cs₄SnBr₆ NCs was mixed with pure metal bromide salts (KBr and RbBr) via the mechanochemical process to successfully synthesize Cs_4-xM_xSnBr₆ perovskite where transformation of Cs to mixed Cs/Rb and mixed Cs/K was achieved. By substituting different cations, the bright fluorescence of the Cs_4-xM_xSnBr₆ was tuned from dim green to greenish-cyan while achieving the photoluminescence (PL) quantum yield of ∼39%. The crystal structure of Sn based perovskite with the substitution of K⁺ or Rb⁺ cations was determined by X-ray diffraction (XRD). Moreover, the Cs_4-xM_xSnBr₆ demonstrated superior air stability and exhibited a better photocatalytic activity for CO₂ reduction reaction (CO₂RR) with high selectivity of CH₄ gas with a higher yield rate compared to the pristine Cs₄SnBr₆ NCs.

Combined Density Functional Theory and Microkinetics Study to Predict Optimum Operating Conditions of Si(100) Surface Carbonization by Acetylene for High Power Devices

The Si(100) surface carbonization mechanisms by acetylene are explored using density functional theory calculations combined with microkinetic simulations. The most stable acetylene adsorption geometries and their subsequent decomposition mechanisms to form a carbon dimer on the Si surface are investigated. Microkinetics simulations are further used to examine the optimal reaction conditions for obtaining a single-crystalline silicon carbide (SiC). We find that the carbon dimer (C₂*) as an end-bridge structure can be formed at 560 K, and the maximum of C₂* can be obtained near 640 K. The acetylene adsorbed via the di-σ configuration starts to dehydrogenate when the heating rate is too fast and will form two possible carbon dimers (di-C₂* and C₂*), which will lead to a polycrystalline SiC buffer layer. We predict that 750 K and 10^-6 bar will be the optimum temperature and pressure for obtaining a single-crystalline SiC buffer layer, respectively.

The investigation of methane storage at the Ni-MOF-74 material: a periodic DFT calculation

To develop a high-performance methane storage material, an understanding of the mechanism and electronic interactions between methane and the material is essential. In this study, we performed detailed theoretical analyses to investigate the methane storage capacity of Ni-MOF-74 using a large-scale periodic DFT code CONQUEST. In a single pore of the unit cell, we considered three possible sites, iSBU, L, and P sites, where iSBU is the inorganic secondary building unit with a metal center, and L is the linker consisting of the organic building unit, while the P site is the vacuum site in the center of the pore. It shows that the methane molecule adsorption possesses the largest methane molecule adsorption energy on the iSBU site. Our calculations indicate that both C-HO and weak agostic interactions exist between the methane molecule and the iSBU site. The adsorption energy of one methane molecule on the iSBU site is in good agreement with previous experimental and theoretical studies. The calculation of the stepwise methane molecule adsorption shows that the first six methane molecules can first occupy the iSBU sites via C-HO and weak agostic interactions. The second six methane molecules are adsorbed on the remaining L sites, where the C-Hπ interaction becomes important, leading to the synergistic effect together with the C-HO interaction to enhance the adsorption energy of the methane molecule. Finally, it can adsorb up to sixteen CH4 molecules in a single pore of a unit cell at Ni-MOF-74. Moreover, we conducted DOS and EDD analyses, which clearly show that the interactions play a vital role in the adsorption of a methane molecule on Ni-MOF-74, especially the C-HO interaction.

Computational Study of Janus Transition Metal Dichalcogenide Monolayers for Acetone Gas Sensing

Recently, Janus two-dimensional (2D) transition metal dichalcogenides (TMDs) have been widely investigated and have provided exciting prospects in many fields such as photoelectric materials, photocatalysis, and gas sensors. In this study, we performed density functional theory (DFT) calculations to study the sensitivity of four volatile organic compounds (VOCs), including acetone, methanol, ethanol, and formyl aldehyde, over pristine 2D TMDs and 2D Janus TMD monolayers. We found that MoS2, Janus MoSSe, and Janus MoSTe demonstrated greater sensitivity toward acetone than other VOCs. Furthermore, the band gap values of the Janus MoSSe and Janus MoSTe monolayers dramatically changed after acetone adsorption on their sulfur layers, which was quite larger than the band gap change after acetone adsorption on the MoS2 monolayer. This result also leads to the extremely large conductivity change of Janus MoSSe and Janus MoSTe after sensing acetone. Hence, Janus MoSSe and Janus MoSTe monolayers show much higher sensitivity toward acetone in comparison with the pristine MoS2 monolayer. Finally, our finding indicates that Janus MoSSe and Janus MoSTe monolayers can be proposed as ultrahigh-sensitivity 2D TMD materials for acetone sensors.

Immune checkpoint modulation enhances HIV-1 antibody induction

Eliciting protective titers of HIV-1 broadly neutralizing antibodies (bnAbs) is a goal of HIV-1 vaccine development, but current vaccine strategies have yet to induce bnAbs in humans. Many bnAbs isolated from HIV-1-infected individuals are encoded by immunoglobulin gene rearrangments with infrequent naive B cell precursors and with unusual genetic features that may be subject to host regulatory control. Here, we administer antibodies targeting immune cell regulatory receptors CTLA-4, PD-1 or OX40 along with HIV envelope (Env) vaccines to rhesus macaques and bnAb immunoglobulin knock-in (KI) mice expressing diverse precursors of CD4 binding site HIV-1 bnAbs. CTLA-4 blockade augments HIV-1 Env antibody responses in macaques, and in a bnAb-precursor mouse model, CTLA-4 blocking or OX40 agonist antibodies increase germinal center B and T follicular helper cells and plasma neutralizing antibodies. Thus, modulation of CTLA-4 or OX40 immune checkpoints during vaccination can promote germinal center activity and enhance HIV-1 Env antibody responses.

Elucidation of broadly neutralizing antibodies (bnAb) is a goal in HIV vaccine development. Here, Bradley et al. show that administration of CTLA-4 blocking antibody with vaccine antigens increases HIV-1 envelope antibody responses in macaques and a bnAb precursor mouse model.

B, N-co-doped graphene-supported Ir and Pt clusters for methane activation and C─C coupling: A density functional theory study

Methane conversion by using transition metal catalysts plays in an important role in various usages of the industrial process. The mechanism of methane conversion on B, N-co-doped graphene supported Ir and Pt clusters, BNG-Ir4 and BNG-Pt4, have been investigated using density functional theory calculations. Methane was found to adsorb on BNG-Ir4 and BNG-Pt4 clusters via strong agostic interactions. The first step of methane dehydrogenation on BNG-Ir4 has a lower energy barrier, indicating a facile methane dissociation on BNG-Ir4. In addition, it shows that hydrogen molecule can form on the BNG-Ir4 and hydrogen can desorb from the surface. Besides, the C-C coupling reaction of CH₃ to form ethane is a more thermodynamically favorable process than CH₃ dehydrogenation on BNG-Ir4. Further, ethane is easier to desorb from the surface due to its low desorption energy. Therefore, the BNG-Ir4 cluster is a potential catalyst for activating methane to form ethane and to produce hydrogen. © 2019 Wiley Periodicals, Inc.

Germinal center responses to complex antigens

Germinal centers (GCs) are the primary sites of antibody affinity maturation, sites where B-cell antigen-receptor (BCR) genes rapidly acquire mutations and are selected for increasing affinity for antigen. This process of hypermutation and affinity-driven selection results in the clonal expansion of B cells expressing mutated BCRs and acts to hone the antibody repertoire for greater avidity and specificity. Remarkably, whereas the process of affinity maturation has been confirmed in a number of laboratories, models for how affinity maturation in GCs operates are largely from studies of genetically restricted B-cell populations competing for a single hapten epitope. Much less is known about GC responses to complex antigens, which involve both inter- and intraclonal competition for many epitopes. In this review, we (i) compare current methods for analysis of the GC B-cell repertoire, (ii) describe recent studies of GC population dynamics in response to complex antigens, discussing how the observed repertoire changes support or depart from the standard model of clonal selection, and (iii) speculate on the nature and potential importance of the large fraction of GC B cells that do not appear to interact with native antigen.

c-Maf and STAT3 are essential but distinct regulators of RORγt+ and follicular regulatory T cells

Foxp3+ regulatory T cells (Tregs) must adapt to function within a wide range of tissue environments and types of immune response. This flexibility is achieved through specialization, whereby context-dependent transcriptional changes integrate unique functionality into general Treg programming. In the most well-studied examples, this involves the co-expression of Foxp3 and another “lineage-defining” transcription factor (TF) which confers expression of specific functional genes. Two such specialized populations are RORγt+ Tregs and Bcl-6+ T follicular regulatory (Tfr) cells, which have important functions in regulating colitis and humoral immune responses, respectively. Although the importance of Treg specialization is now clear, the underlying network of signals and TFs driving this process is largely undefined. Here, we identify the TF c-Maf as an essential regulator of Treg specialization for both RORγt+ Tregs and Tfr cells. Importantly, the role of c-Maf in these subsets is highly specific, because deletion of Maf does not affect general Treg development, generation of other specialized Tregs, or expression of suppressive molecules. In vitro, we show that addition of IL-6 to Treg-promoting conditions is sufficient to drive both c-Maf expression and c-Maf-dependent conversion of naïve T cells to RORγt+ Tregs, suggesting that IL-6 might drive c-Maf in vivo. Surprisingly, although STAT3 – the primary downstream effector of IL-6 – is required for development of both RORγt+ Tregs and Tfr cells, we find that Stat3 deletion in vivo does not ablate c-Maf expression and results in Treg defects distinct from Maf deletion. Therefore, c-Maf and STAT3 are cooperative, but distinct regulators of RORγt+ and follicular Treg development.

Germinal center entry not selection of B cells is controlled by peptide-MHCII complex density

B cells expressing high affinity antigen receptors are advantaged in germinal centers (GC), perhaps by increased acquisition of antigen for presentation to follicular helper T cells and improved T-cell help. In this model for affinity-dependent selection, the density of peptide/MHCII (pMHCII) complexes on GC B cells is the primary determinant of selection. Here we show in chimeric mice populated by B cells differing only in their capacity to express MHCII (MHCII^+/+ and MHCII^+/-) that GC selection is insensitive to halving pMHCII density. Alone, both B cell types generate identical humoral responses; in competition, MHCII^+/+ B cells are preferentially recruited to early GCs but this advantage does not persist once GCs are established. During GC responses, competing MHCII^+/+ and MHCII^+/- GC B cells comparably accumulate mutations and have indistinguishable rates of affinity maturation. We conclude that B-cell selection by pMHCII density is stringent in the establishment of GCs, but relaxed during GC responses.

Boerhaave's Syndrome Secondary to Migration of Gastrostomy Tube

Percutaneous endoscopic gastrostomy is a safe procedure for providing nutrition. Complications associated with tube migration such as duodenal obstruction or pancreatitis have been reported. For the first time, we reported a rare complication of gastrostomy tube migration manifested by Boerhaave's syndrome. (Hong Kong j.emerg.med. 2013;20:400-401)

Cutting Edge: c-Maf Is Required for Regulatory T Cells To Adopt RORγt+ and Follicular Phenotypes

Regulatory T cells (Tregs) adopt specialized phenotypes defined by coexpression of lineage-defining transcription factors, such as RORγt, Bcl-6, or PPARγ, alongside Foxp3. These Treg subsets have unique tissue distributions and diverse roles in maintaining organismal homeostasis. However, despite extensive functional characterization, the factors driving Treg specialization are largely unknown. In this article, we show that c-Maf is a critical transcription factor regulating this process in mice, essential for generation of both RORγt⁺ Tregs and T follicular regulatory cells, but not for adipose-resident Tregs. c-Maf appears to function primarily in Treg specialization, because IL-10 production, expression of other effector molecules, and general immune homeostasis are not c-Maf dependent. As in other T cells, c-Maf is induced in Tregs by IL-6 and TGF-β, suggesting that a combination of inflammatory and tolerogenic signals promote c-Maf expression. Therefore, c-Maf is a novel regulator of Treg specialization, which may integrate disparate signals to facilitate environmental adaptation.

The Limit of MHC Class II-driven Selection in Germinal Centers

B cells undergo iterative rounds of proliferation, hypermutation and selection in the germinal centers (GCs) to generate high affinity, protective antibody. It is now thought that GC B cells with higher affinity BCRs acquire more antigen for processing and presenting in association with MHC class II (MHCII) to T follicular helper (TFH) cells than lower affinity competitors. The resulting increase in T-cell help is hypothesized to be the major factor that drives affinity maturation. In this model for GC B cell selection, the density of peptide/MHCII (pMHCII) complexes available on the B-cell membrane is the major determinant of affinity-dependent selection. To quantify the limits of this model for GC selection, we generated short- and long-term chimeric mice with equal numbers of isogenic, mature B cells that differed by their capacity to express MHCII (MHCII+/+ and MHCII+/−). Separately, both B cell types generated virtually identical humoral responses, including affinity maturation, in response to NP-OVA. In competition, MHCII+/+ B cells were preferentially recruited to early GCs consistent with a critical role for pMHCII density in T:B collaboration. However, once established in GCs, no further competitive advantage was observed during the full course (24 days) of the GC response. During this period, both MHCII+/+ and MHCII+/− GC B cells comparably accumulated VH gene segment mutations and exhibited comparable rates of affinity maturation to the NP hapten. These data indicate that B-cell selection determined by MHCII density is more stringent prior to the establishment of GCs than in the GC itself. This observation may be relevant to our recent observation of the persistence of low affinity GC B cells.

Prophylactic Dual Catheter Technique to Prevent Side Branch Snowplowing Complications during Angioplasty and Stenting

Objective

Angioplasty and Stenting of intracranial atherosclerotic lesions have a higher complication rate and a large proportion of this is attributable to side branch arterial occlusion from forceful displacement of the atheroma into the ostia or snowplowing effect. This can result in severe disabilities when it result in small infarcts involving eloquent areas in the posterior circulation or the motor tracts.

Materials and Methods

We present a series of 6 cases utilizing a new dual catheter technique for maintaining the patency of at-risk vessels during angioplasty and stenting. There are several methods previously described to help reduce the incidence of stroke but because they do not have a physical presence in the ostia to protect it, they are unable to guarantee the patency of the vessel.

Results

All 6 patients underwent angioplasty and stenting with the technique. The patients were assessed for complications with post-procedure magnetic resonance imaging and no complications were found.

Conclusion

In this preliminary series, the dual catheter technique appears to safe and effective in preventing occlusion of the adjacent branch arteries. This technique may facilitate the use of the Wingspan stent in the treatment of intracranial atherosclerotic stenotic segments by reducing the risk of peri-procedural stroke.

MRI audit of complications in intracranial stenosis treated with Wingspan device

OBJECTIVES

To evaluate the safety and efficacy of the Wingspan device for the treatment of symptomatic intracranial atherosclerotic stenosis (ICAS).

METHODS

We audited a prospective ongoing database of consecutive patients who received Wingspan stenting between January 2013 and December 2015. All patients underwent MRI to audit any complications during the early follow-up period. We focused on the clinical demographics, lesion characteristics, treatment results, and periprocedural complications. Functional outcomes were measured with the modified Rankin Scale (mRS) at discharge and after 3 months.

RESULTS

Intracranial stenting was performed in 50 patients (100%). Mean stenosis pre-stenting was 76.5±13.1% and post-stenting residual stenosis was 19.8±13.8%. The overall 30-day rate of procedure-related complications was 6.0% (3/50). Two patients (4%) developed in-stent restenosis, one of whom had a dissection at the middle cerebral artery. Interestingly, on the follow-up MRI scan there was a high incidence of asymptomatic diffusion-weighted imaging (DWI) hyperintensities, 46% (23/50) presumed to be due to microembolic causes. At the 90-day, 180-day, and 1-year follow-up, three patients had further strokes resulting in a total complication rate of 12%. 92% had excellent outcomes (mRS 0-1) and only one patient had deterioration of his mRS score.

CONCLUSIONS

ICAS treated by Wingspan stenting using pre-placement balloon angioplasty appears safe and effective with a high technical success rate and favorable outcomes. There is a high incidence of asymptomatic DWI hyperintensites post-procedure, but these do not appear to result in long-term sequelae.

Efficient Culture of Human Naive and Memory B Cells for Use as APCs

The ability to culture and expand B cells in vitro has become a useful tool for studying human immunity. A limitation of current methods for human B cell culture is the capacity to support mature B cell proliferation. We developed a culture method to support the efficient activation and proliferation of naive and memory human B cells. This culture supports extensive B cell proliferation, with ∼10³-fold increases following 8 d in culture and 10⁶-fold increases when cultures are split and cultured for 8 more days. In culture, a significant fraction of naive B cells undergo isotype switching and differentiate into plasmacytes. Culture-derived (CD) B cells are readily cryopreserved and, when recovered, retain their ability to proliferate and differentiate. Significantly, proliferating CD B cells express high levels of MHC class II, CD80, and CD86. CD B cells act as APCs and present alloantigens and microbial Ags to T cells. We are able to activate and expand Ag-specific memory B cells; these cultured cells are highly effective in presenting Ag to T cells. We characterized the TCR repertoire of rare Ag-specific CD4⁺ T cells that proliferated in response to tetanus toxoid (TT) presented by autologous CD B cells. TCR Vβ usage by TT-activated CD4⁺ T cells differs from resting and unspecifically activated CD4⁺ T cells. Moreover, we found that TT-specific TCR Vβ usage by CD4⁺ T cells was substantially different between donors. This culture method provides a platform for studying the BCR and TCR repertoires within a single individual.

TCR Repertoire Analysis of Mouse T Follicular Helper Cells and T Follicular Regulatory Cells Following Immunization

Generation of high-affinity and class-switched antibody requires the germinal center (GC) reaction after infection or immunization. Within the B-cell follicles of secondary lymphoid organs, the GC represents a sophisticated collaboration between antigen-specific B cells, follicular dendritic cells, T follicular helper (TFH) cells and T follicular regulatory (TFREG) cells. Despite intensive interest in the development and effector function of TFH and TFREG cells, little is known regarding the selection of T-cell receptor (TCR) repertoire during polyclonal GC reactions. In order to evaluate native, polyclonal TCR responses elicited by a complex antigen, we developed a sorting strategy to isolate TFH/TFREG cell populations that were activated and expanded after s.c. immunization with NP15-OVA. TCRβ VDJ rearrangements were recovered from highly purified TCRβ+CD4+CXCR5hiPD-1+Bcl-6+FoxP3− TFH cells and TCRβ+CD4+ CXCR5hiPD-1+Bcl-6+FoxP3+ TFREG cells, amplified by PCR, and sequenced. Analysis of the antigen-specific TCR repertoire of TFH/TFREG cells provides important insights into the factors influencing T-cell recruitment and clonal expansion following infection or vaccination, especially when linked to contemporary analysis of the GC B-cell repertoire. These findings may inform rational and selective control strategy of the GC reaction. Vaccine development can accordingly focus on modulating TFH/TFREG responses to facilitate optimal adaptive immune responses.

Oxidation of CO on a carbon-based material composed of nickel hydroxide and hydroxyl graphene oxide, (Ni4(OH)3–hGO) – a first-principles calculation

The mechanism of CO oxidation on a composite of nickel hydroxide and hydroxyl graphene oxide, Ni₄(OH)₃–hGO.

Wired and wireless convergent extended-reach optical access network using direct-detection of all-optical OFDM super-channel signal

We propose and demonstrate the feasibility of using all-optical orthogonal frequency division multiplexing (AO-OFDM) for the convergent optical wired and wireless access networks. AO-OFDM relies on all-optically generated orthogonal subcarriers; hence, high data rate (> 100 Gb/s) can be easily achieved without hitting the speed limit of electronic digital-to-analog and analog-to-digital converters (DAC/ADC). A proof-of-concept convergent access network using AO-OFDM super-channel (SC) is demonstrated supporting 40 - 100 Gb/s wired and gigabit/s 100 GHz millimeter-wave (MMW) ROF transmissions.

Coding for stable transmission of W-band radio-over-fiber system using direct-beating of two independent lasers

We demonstrate experimentally Manchester (MC) coding based W-band (75 - 110 GHz) radio-over-fiber (ROF) system to reduce the low-frequency-components (LFCs) signal distortion generated by two independent low-cost lasers using spectral shaping. Hence, a low-cost and higher performance W-band ROF system is achieved. In this system, direct-beating of two independent low-cost CW lasers without frequency tracking circuit (FTC) is used to generate the millimeter-wave. Approaches, such as delayed self-heterodyne interferometer and heterodyne beating are performed to characterize the optical-beating-interference sub-terahertz signal (OBIS). Furthermore, W-band ROF systems using MC coding and NRZ-OOK are compared and discussed.

OFDM RF power-fading circumvention for long-reach WDM-PON

We propose and demonstrate an orthogonal frequency division multiplexing (OFDM) radio-frequency (RF) power-fading circumvention scheme for long-reach wavelength-division-multiplexed passive-optical-network (LR-WDM-PON); hence the same capacity of 40 Gb/s can be provided to all the optical-networking-units (ONUs) in the LR-WDM-PON. Numerical analysis and proof-of-concept experiment are performed.

Conduction control at ferroic domain walls via external stimuli

Intriguing functionalities at nano-sized domain walls have recently spawned a new paradigm for developing novel nanoelectronics due to versatile characteristics. In this study, we explore a new scenario to modulate the local conduction of ferroic domain walls. Three controlling parameters, i.e., external electrical field, magnetic field and light, are introduced to the 90° domain walls (90° DWs) of BiFeO₃. Electrical modulation is realized by electrical transport, where the mobility of 90° DWs can be altered by gating voltage. We further use the ferromagnetic/antiferromagnetic coupling to reveal the inherent magnetism at the DWs. With an established magnetic nature, magnetotransport has been conducted to introduce magnetic controlling parameter, where a giant positive magnetoresistance change can be observed up to 200%. In addition, light modulated conduction, a core factor for multifunctional applications, is successfully demonstrated (current enhancement by a factor of 2 with 11 W white lamp). These results offer new insights to discover the tunability of domain wall nanoelectronics.

A scalable and continuous-upgradable optical wireless and wired convergent access network

In this work, a scalable and continuous upgradable convergent optical access network is proposed. By using a multi-wavelength coherent comb source and a programmable waveshaper at the central office (CO), optical millimeter-wave (mm-wave) signals of different frequencies (from baseband to > 100 GHz) can be generated. Hence, it provides a scalable and continuous upgradable solution for end-user who needs 60 GHz wireless services now and > 100 GHz wireless services in the future. During the upgrade, user only needs to upgrade their optical networking unit (ONU). A programmable waveshaper is used to select the suitable optical tones with wavelength separation equals to the desired mm-wave frequency; while the CO remains intact. The centralized characteristics of the proposed system can easily add any new service and end-user. The centralized control of the wavelength makes the system more stable. Wired data rate of 17.45 Gb/s and w-band wireless data rate up to 3.36 Gb/s were demonstrated after transmission over 40 km of single-mode fiber (SMF).

Highly effective catalysis of the double-icosahedral Ru(19) cluster for dinitrogen dissociation - a first-principles investigation

The N2 bond cleavage is the rate-limiting step in the synthesis of ammonia, and ruthenium is a catalyst well known for this reaction. The double-icosahedral (D5h) Ru19 cluster is famous as an active catalyst, and has a remarkable stability towards the adsorption of H2, N2 and CO. Using first-principles calculations, we have investigated the adsorption and dissociation of dinitrogen on a double-icosahedral Ru19 cluster. Our results show that the hollow site in the rhombus region (BHB site) of the Ru19 cluster possesses the greatest catalytic activity to dissociate N2, with the reaction barrier of 0.89 eV and an exothermicity of -1.45 eV. Multiple coadsorption of N2 on the cluster (i.e. coadsorption of 2N2 and 3N2 on a single Ru19 cluster) causes the barrier to dissociate N2 to be less on a BHB site than for adsorption of a single N2. To understand the catalytic properties of a Ru19 cluster towards N2 bond cleavage, we calculated the electron population, vibrational wavenumbers and local densities of states; the results are explicable.

Adaptive 84.44-190 Mbit/s phosphor-LED wireless communication utilizing no blue filter at practical transmission distance

We propose and experimentally demonstrate a white-light phosphor-LED visible light communication (VLC) system with an adaptive 84.44 to 190 Mbit/s 16 quadrature-amplitude-modulation (QAM) orthogonal-frequency-division-multiplexing (OFDM) signal utilizing bit-loading method. Here, the optimal analogy pre-equalization design is performed at LED transmitter (Tx) side and no blue filter is used at the Rx side. Hence, the ~1 MHz modulation bandwidth of phosphor-LED could be extended to 30 MHz. In addition, the measured bit error rates (BERs) of < 3.8 × 10(-3) [forward error correction (FEC) threshold] at different measured data rates can be achieved at practical transmission distances of 0.75 to 2 m.

The impact of abnormal muscle tone from hemiplegia on reclining wheelchair positioning: a sliding and pressure evaluation

BACKGROUND

Little is known about the influence of existing muscle tone abnormality on the sitting posture of stroke patients in reclining wheelchairs.

AIM

To investigate the impact of muscle tone abnormality from hemiplegia on the forward sliding and pressure of stroke patients while sitting in reclining wheelchairs.

DESIGN

Experimental study.

SETTING

The Assistive Devices/Technology Center at the Rehabilitation Department of hospital.

POPULATION

14 able-bodied elders and nonambulatory elderly stroke patients with flaccid (N.=12) or spastic hemiplegia (N.=13) participated in this study. Of the 12 patients with flaccid hemiplegia, 8 suffered from left-sided hemiplegia and 4 from right-sided hemiplegia. Of the 13 patients with spastic hemiplegia, 6 suffered from left-sided hemiplegia and 7 from right-sided hemiplegia.

METHODS

We performed 3 reclining cycles in wheelchairs with conventional seats and V-shaped seats for each participant. The sliding along the backrest (BS) plane and the seat (SS) plane, mean sitting pressure (MP), and sacral peak pressure (SPP) of the participants were recorded. The Kruskal-Wallis test was used to compare the difference in BS, SS, MP, and SPP between able-bodied elders and stroke patients.

RESULTS

The BS, SS, and SPP during repetitive reclining were generally greatest in flaccid hemiplegic participants, followed by spastic hemiplegic participants, and finally by able-bodied participants. There was no significant difference in MP among three subject groups on both conventional seats and V-shaped seats in most comparisons. Able-bodied participants' buttocks tended to slide forward on conventional seats but backward on V-shaped seats, whereas hemiplegic participants' buttocks slid forward on both seat types.

CONCLUSION

Stroke patients with flaccid hemiplegia are the most vulnerable to sacral sitting and higher sacral pressure in reclining wheelchairs, followed by patients with spastic hemiplegia. There is a difference in the displacement pattern between participants with normal muscle tone and those with abnormal muscle tone during wheelchair positioning. People who have hemiplegia with spasticity do not have incremental forward sliding with repetitive reclining in the same way as those who have a flaccid hemiplegia.

CLINICAL REHABILITATION IMPACT

The findings are valuable for wheelchair prescription and caregiver education.

Energetics of C-N coupling reactions on Pt(111) and Ni(111) surfaces from application of density-functional theory

We applied density-functional theory (DFT) with the projector-augmented-wave method (PAW) to investigate systematically the energetics of C-N coupling reactions on Pt(111) and Ni(111)surfaces. Our approach includes several steps: the adsorption of reactants and products (CHx, NHy and CHxNHy, x = 0-3, y = 0-2), movement of molecular fragments on the surface, and then C-N coupling. According to our calculations, the energies (ignoring the conventional negative sign) of adsorption of CHx and NHy on Pt(111)/Ni(111) surfaces decrease in the order C > CH > CH2 > CH3 and N > NH > NH2, with values 7.41/6.91, 6.97/6.52, 4.58/4.39, 2.19/2.01 eV and 5.10/5.49, 4.12/4.79, 2.75/2.87 eV, respectively. Regarding the adsorption energies among CHxNHy, the adsorption energy of CNH2 species is the highest on the Pt(111) surface, whereas on the Ni(111) surface CH3N is the most stable. The C-N coupling barriers differ on the two metallic surfaces despite the structures of initial, transition and final states being similar. On the Pt(111) surface, the coupling reaction of CH2 + NH2 has the smallest barrier, whereas CH + NH2 is the most favorable on the Ni(111) surface. The detailed local density of states (LDOS) and electron-localization functions (ELF) were investigated to rationalize the calculated outcomes.

Stable and wavelength-tunable silicon-micro-ring-resonator based erbium-doped fiber laser

In this work, we propose and demonstrate a stable and wavelength-tunable erbium-doped fiber (EDF) ring laser. Here, a silicon-on-insulator (SOI)-based silicon-micro-ring-resonator (SMRR) is used as the wavelength selective element inside the fiber ring cavity. A uniform period grating coupler (GC) is used to couple between the SMRR and single mode fiber (SMF) and serves also as a polarization dependent element in the cavity. The output lasing wavelength of the proposed fiber laser can be tuned at a tuning step of 2 nm (defined by the free spectral range (FSR) of the SMRR) in a bandwidth of 35.2 nm (1532.00 to 1567.20 nm), which is defined by the gain of the EDF. The optical-signal-to-noise-ratio (OSNR) of each lasing wavelength is larger than 42.0 dB. In addition, the output stabilities of power and wavelength are also discussed.

Timing of gangrene tissue debridement after autologous bone marrow cell implantation in patients with superficial femoral arterial occlusion: preliminary experiences

AIM

Although implantation of bone marrow mononuclear cells (BMI) was shown to improve outcomes in patients with severe peripheral arterial occlusive disease (PAOD), little experience has been reported in patients with an arterial occlusion level above the knee, ischemic gangrene, and high cardiovascular risk. This study sought to investigate the timing of gangrene tissue debridement and the safety of BMI in these patients.

METHODS

Six "no-option" PAOD patients were enrolled with an arterial occlusion level above the knee, ischemic gangrene, and 3 systemic diseases related to a high cardiovascular risk. The ischemic status was evaluated by measuring the ankle-brachial index (ABI), transcutaneous oxygen pressure (TcPO2), and wound healing after BMI.

RESULTS

All patients safely underwent the procedures with intravenous general anesthesia by titrating propofol. Major lower extremity amputation, minor debridement amputation, and debridement surgery were performed in 2 (33.3%), 1 (16.7%), and 2 (33.3%) patients, respectively, 3.1 2.8 months after BMI. Compared to the amputation group (N=3), the salvage group (N=3) had a significantly higher baseline ABI (P=0.02) and a shorter distance between the gangrene site and arterial occlusion site (P=0.01). In the 3 patients who underwent debridement, ABI and TcPO2 significantly improved 1 month after BMI, and gangrenous tissues were debrided 3.8 ± 3.6 (range, 1~8) months after BMI with complete healing within 1 month.

CONCLUSION

Autologous BMI therapy is safe in patients at high cardiovascular risk with an arterial occlusion level above the knee and ischemic gangrene. Effective predictors of BMI include the baseline ABI and distance to the ischemia. Gangrene tissue should be debrided at least 1 month after BMI.

Dietary flavonoid naringenin induces regulatory T cells via an aryl hydrocarbon receptor mediated pathway

The aryl hydrocarbon receptor (AhR), a transcription factor mediating xenobiotic detoxification, plays a considerable role in regulatory T cell (Treg) induction. Tregs regulate the immune system, thus suppressing allergies and autoimmune diseases. This study aims to identify new types of antiallergic dietary factors, with focus on the flavonoids with potential AhR agonistic activity. Among 25 dietary flavonoid samples tested using a reporter assay, 8 showed marked induction of AhR-dependent transcriptional activity. The subsequent T cell proliferation suppression assay identified naringenin as the only sample capable of stimulating Treg induction; notably, this induction was eliminated by cotreatment with AhR antagonists. Indeed, naringenin induced CD4(+)Foxp3(+) Tregs, irrespective of the presence of the transforming growth factor-β (TGF-β), indicating that the conventional TGF-β-dependent signaling pathway might not be involved.

Removal of C.I. Reactive Red 2 from aqueous solutions by chitin: an insight into kinetics, equilibrium, and thermodynamics

In this study, C.I. Reactive Red 2 (RR2) was removed from aqueous solutions by chitin. Exactly how the RR2 concentration, chitin dosage, pH, and temperature affected adsorption of RR2 by chitin was then determined. After reaction for 120 min, the amount of 10 and 20 mg/L RR2 absorbed onto chitin was 5.7 and 7.5 mg/g, respectively. The adsorption percentage increased from 56 to 94% when the chitin dosage was increased from 1.5 to 2.5 g/L. Experimental results indicated that the pseudo-second-order model best represents adsorption kinetics. Adsorption of RR2 increased as the temperature increased; however, it decreased with an increased pH. Experimental results further demonstrated that the Freundlich model is superior to the Langmuir model in fitting experimental isotherms. The ΔH° and ΔS° were 16.34 kJ/mol and 152.10 J/mol K, respectively. ΔH° suggested that adsorption of RR2 onto chitin was via physisorption.

Using adaptive four-band OFDM modulation with 40 Gb/s downstream and 10 Gb/s upstream signals for next generation long-reach PON

In this demonstration, we propose and demonstrate an adaptive long-reach passive optical network (LR-PON) using four-band orthogonal frequency division multiplexed (OFDM) channels. The downstream traffic rates from 6.25 to 40 Gb/s (using fixed quadrature amplitude modulation (QAM) level in the four OFDM bands) and from 9.37 to 40.3 Gb/s (using variable QAM levels in the four OFDM bands) can be achieved adaptively in the optical network units (ONUs) depending on different fiber transmission lengths from 0 to 100 km. For the upstream transmission, a 10 Gb/s 16-QAM OFDM signal with pre-emphasis is experimentally performed by using a 2.5 GHz directly modulated laser (DML). Based on the simulation and experimental results, the proposed adaptive four-band OFDM system could be a promising candidate for the future LR-PON.

Imaging findings in mandibular primitive neuroectodermal tumour: a report of a rare case and review of the literature

Primitive neuroectodermal tumours (PNETs) are aggressive undifferentiated tumours that occur mainly in the central nervous system (CNS). Reviewing the literature, only six cases of primary PNET of the mandible have been reported. These rare tumours are usually overlooked in clinical practice. An 18-year-old woman who presented with dental caries and left cheek swelling was initially diagnosed with facial cellulitis, but the swelling persisted despite adequate intravenous antibiotic therapy. Subsequent ultrasound and MR examinations revealed a tumour originating from the left mandibular ramus. The ultrasonography-guided percutaneous core needle biopsy confirmed the diagnosis of peripheral PNET. The radiographic features of mandibular PNETs are similar to those of PNETs in other regions, except for haemorrhage, necrosis and calcification. In addition, this is the first reported case with sonographic and MR images of this rare tumour, and the first case that was diagnosed based on the ultrasonography-guided percutaneous core needle biopsy. Using these image characteristics, mandibular PNETs can be diagnosed more accurately.

Long-reach radio-over-fiber signal distribution using single-sideband signal generated by a silicon-modulator

The integration of passive optical network (PON) and radio-over-fiber (ROF) networks could provide broadband services for both fixed and mobile users in a single and low-cost platform. Combining the long-reach (LR)-PON (>100 km) and the LR-ROF can further reduce the cost by simplifying the network architecture, sharing the same optical components and extending the coverage of ROF network. However, the transmission and distribution of ROF signal in LR network is very challenging due to the chromatic dispersion generated periodic power fading and code time-shifting effects in the optical fiber. In this work, we propose and experimentally demonstrate a LR-ROF signal distribution using single-sideband (SSB)-ROF signal generated by a silicon ring-modulator. The silicon modulator is compact and has low power consumption. Besides, one unique feature of the silicon ring-modulator is that it only modulates the signal wavelength at the resonant null. This makes it very suitable for the generation of the SSB-ROF signal. Numerical comparison of the SSB-ROF with the double-sideband (DSB)-ROF and optical carrier suppress (OCS)-ROF signals; as well as the fabrication of the silicon ring-modulator will be discussed.