Lower Cleavage Research Articles

Two-dimensional Nowotny-Juza NaZnX (X = P, As, Sb) as high-performance thermoelectric materials

Ideal thermoelectric material requires high power factor and low thermal conductivity. Two-dimensional structuring of bulk thermoelectric materials has been reported to be an effective way to achieving excellent thermoelectric performance. In this work, we proposed three two-dimensional Nowotny-Juza materials: NaZnP, NaZnAs, and NaZnSb. Based on the state-of-the-art first-principles calculations, it is revealed that the monolayers possess high stability, low cleavage energy, and excellent electronic transport performance with power factor of 0.65, 0.15 and 0.06 Wm−1K−2 respectively. Meanwhile, the monolayers exhibited ultra-low thermal conductivities of 1.16, 1.38, and 0.31 W⋅m−1⋅K−1 at 300 K, respectively. Such low thermal conductivities are mainly due to the larger scattering rates, resulting from the special cage structure of NaZnX (X = P, As, Sb) and weak ionic bond. As a result, their ZT values reach 2.59, 1.78, and 0.05 (at 300 K), respectively, and increase further to 6.03, 3.23, and 0.13 (at 700 K), respectively. The exceptional performance of NaZnX monolayers sheds light on their immense potential applications in thermoelectric devices.

Ultrahigh breakdown current density of van der Waals one dimensional PdBr2

One-dimensional (1D) van der Waals (vdW) materials offer nearly defect-free strands as channel materials in the field-effect transistor devices and probably, a better interconnect than conventional copper with higher current density and resistance to electro-migration with sustainable down-scaling. We report a theoretically predicted halide based 1D few-chain atomic thread, PdBr2, isolable from its bulk which crystallizes in a monoclinic space group C2/c. Liquid phase exfoliated nanowires with mean length (20 ± 1)μm transferred onto a SiO2/Si wafer with a maximum aspect ratio (length:width) of ≈5000 confirm the lower cleavage energy perpendicular to the chain direction. Moreover, an isolated nanowire can also sustain a current density of 200 MA/cm2, which is atleast one-order higher than typical copper interconnects. However, local transport measurement via the conducting atomic force microscopy (CAFM) tip along the cross direction of the single chain records a much lower current density due to the anisotropic electronic band structure. While 1D nature of the nanoobject can be linked with a non-trivial collective quantum behavior, vdW nature could be beneficial for possible pathways in an interconnect fabrication strategy with better control of placement in an integrated circuit.

O-105 Chromatin accessibility of oocytes contributes to PCOS transgenerational inheritance

Abstract Study question What is the underlying mechanism contributing to the transgenerational defects of oocytes and embryos of polycystic ovary syndrome (PCOS)? Summary answer The transgenerational inheritance of abnormal chromatin accessibility in the PCOS oocytes is responsible for the defect of oocytes and embryos in transgeneration. What is known already Studies have provided evidence of compromised oocyte quality and related adverse impacts. Observed PCOS animal-model oocyte defects include meiotic abnormalities, mitochondrial dysfunction, and increased oxidative stress. Elevated androgen levels are associated with reduced fertilization rates and lower cleavage rates during in vitro fertilization (IVF) treatment. PCOS could be transgenerationally transmitted, and unique altered gene expression has been observed in metaphase II (MII) oocytes from all offspring in PCOS mice. Study design, size, duration We profiled the transcriptome and chromatin accessibility of oocytes and preimplantation embryos in F0-F2 offspring of PCOS mice, to explored whether the inheritance of chromatin accessibility defects in PCOS oocytes was responsible for the abnormalities of oocytes and embryos in PCOS offspring. Besides, oocytes from 13 healthy women and 8 women with PCOS, 24 blood samples from 24 women with/without PCOS were analyzed to validate the molecular mechanisms of PCOS inheritance. Duration: 2019.5∼2022.12. Participants/materials, setting, methods PCOS mice models were established by means of DHEA-exposure. Smart-seq2 and DNase-seq were utilized to investigate the transcriptome and chromatin accessibility of oocytes and preimplantation embryos in F0-F2 offspring of PCOS mice. Bioinformatic analysis was applied to explore the differential gene expression and chromatin accessibility of oocytes and embryos in PCOS mice and offspring comparing to controls. Common gene signatures in the tissues of PCOS women and PCOS daughters are analyzed compared to control samples. Main results and the role of chance In PCOS mice, we observed transcriptional alteration in oocytes and 2-cell embryos compared to normal mice. There are 4229 and 1197 differentially expressed genes (DEGs) in PCOS oocytes and 2-cell embryos. The DEGs includes both maternal factors and zygotic genome activation (ZGA) genes. Interestingly, in PCOS 2-cell embryos, we observed hundreds of pre-activated genes which are silence in normal 2-cell embryo but expressed in PCOS 2-cell embryos. Notably, many DEGs in the oocytes of PCOS mice were also differentially expressed in the oocytes of F2 PCOS mice compared to control mice, supporting the transgenerational inheritance of transcriptional alteration in PCOS oocytes. Mechanismly, the changes of chromatin accessibility were associated with the DEGs in PCOS oocytes and embryos. In particular, chromatin accessibility of the pre-activated gene promoters is elevated in PCOS oocytes compared to that in normal oocytes. Furthermore, many of the abnormal chromatin accessibility signals detected in F0 PCOS oocytes were also observed in F2 PCOS oocytes. Finally, our data showed that some DEGs in the oocytes of PCOS mice were also differentially expressed in human PCOS oocytes compared to the control oocytes. Common genes identified in PCOS offspring may be used as potential predictors of PCOS phenotype. Limitations, reasons for caution Which factors contribute to the abnormalities of chromatin accessibility in PCOS oocytes are still unknown. Wider implications of the findings The candidate genes may be used as potential predictors of PCOS phenotype and provide the clues for PCOS offspring . Trial registration number not applicable

A family of two-dimensional semiconductors with transition metal Kagome lattice, large power factor and ultralow lattice thermal conductivity

Two-dimensional (2D) materials hold promising application potential in the future, so it is worthy to explore new 2D materials with fascinating structures and functionals. Here we predict a series of 15 stable 2D semiconductors, A2B3C4 (A = K, Rb, Cs; B = Ni, Pd, Pt; C = S, Se), using first-principles calculations. The feasibility of mechanical exfoliation from their bulk phases has been confirmed by low cleavage energies. Interestingly, a perfect Kagome lattice formed by transition metal Ni/Pd/Pt atoms have been revealed in these fifteen monolayers. All A2B3C4 monolayers exhibit indirect band features (1.82 eV to 2.76 eV). More encouragingly, and it is theoretically proven, based on constant relaxation time (CRT) approximation, that the A2B3C4 monolayers possess large n-type power factors (1.77 ∼ 2.10 × 103 μWm-1K−2), which is mainly contributed from the loop formed by the conduction band minima in different directions in energy band structure. Furthermore, ultralow lattice thermal conductivity (0.20 Wm-1K−1 to 3.04 Wm-1K−1) has been confirmed in 2D A2B3C4 at room temperature. Finally, the thermoelectric figure of merit (ZT) of A2B3C4 monolayers has been evaluated based on CRT approximation. These interesting findings make A2B3C4 monolayers promising candidates for low-dimensional electronic devices.

Dysregulation of iron metabolism-linked genes at myocardial tissue and cell levels in dilated cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Fondazione Gigi & Pupa Ferrari ONLUS Italian Ministry of Health-Ricerca Corrente. Background Heart failure (HF) is defined as one of the main clinical and public health burdens with multifactorial symptoms and high worldwide prevalence. Dilated cardiomyopathy (DCM) is one of the leading causes of HF and is responsible for over half of all left ventricular assist device implantations and heart transplantations. DCM is regarded as a multiple disease entity linked to a number of genetic, nutritional, inflammatory, infective, metabolic, and environmental causes. Among the metabolic processes associated with HF, iron metabolism disorders, ranging from iron deficiency to iron overload, are gaining attention. However, the understanding of iron mechanisms, at cardiac level, involved in HF and particularly in DCM, remains elusive. Purpose We aim to evaluate the possible dysregulation of iron metabolism-linked genes in DCM, through a quantitative analysis of public myocardial gene expression data at tissue and cell levels. Methods Bulk RNA sequencing (RNA-seq) and single-nucleus RNA-seq (snRNA-seq) datasets, respectively of 436 and 38 left ventricle samples from adult non-failed (NF) and DCM subjects, were retrieved from public studies. We defined a list of 272 genes directly related to intramyocardial iron metabolism and performed the differential gene expression analysis both at whole cardiac tissue level and in cardiomyocytes, fibroblasts, myeloid, endocardial, and endothelial cells. Results In the overall myocardial tissue, we found 44 iron-linked genes differentially expressed between DCM and NF subjects. To better understand iron genes abnormalities in the myocardium of DCM patients we deepened the analysis from tissue to single-cell level. Among the five considered cell types (cardiomyocytes, fibroblasts, myeloid, endocardial, and endothelial cells) at least 9% of iron-linked expressed genes were significantly regulated in DCM when compared to NF. Specifically, the iron metabolism in DCM cardiomyocytes is altered at several levels (Figure 1), including: 1) imbalance of Fe3+ internalization (SCARA5 down-regulation) and reduction of internal conversion from Fe3+ to Fe2+ (STEAP3 down-regulation), 2) increase of iron consumption to produce hemoglobin (HBA1/2 up-regulation), 3) higher heme synthesis and externalization (ALAS2 and ABCG2 up-regulation), 4) lower cleavage of heme to Fe2+, biliverdin and carbon monoxide (HMOX2 down-regulation), and 5) positive regulation of hepcidin (BMP6 up-regulation). Conclusions In conclusion, the present study provides significant progress in knowledge of iron metabolism changes in DCM disease, which likely have a clinical meaning. Indeed, our data show that regulation of intracellular iron homeostasis is dysfunctional in DCM patients’ cardiac tissues, supporting, but not providing, the hypothesis of a direct effect of iron in the disease progression.

Selection of allosteric dnazymes that can sense phenylalanine by expression-SELEX.

Aptamers are ligand-binding RNA or DNA molecules and have been widely examined as biosensors, diagnostic tools, and therapeutic agents. The application of aptamers as biosensors commonly requires an expression platform to produce a signal to report the aptamer-ligand binding event. Traditionally, aptamer selection and expression platform integration are two independent steps and the aptamer selection requires the immobilization of either the aptamer or the ligand. These drawbacks can be easily overcome through the selection of allosteric DNAzymes (aptazymes). Herein, we used the technique of Expression-SELEX developed in our laboratory to select for aptazymes that can be specifically activated by low concentrations of l-phenylalanine. We chose a previous DNA-cleaving DNAzyme known as II-R1 as the expression platform for its low cleavage rate and used stringent selection conditions to drive the selection of high-performance aptazyme candidates. Three aptazymes were chosen for detailed characterization and these DNAzymes were found to exhibit a dissociation constant for l-phenylalanine as low as 4.8 μM, a catalytic rate constant improvement as high as 20000-fold in the presence of l-phenylalanine, and the ability to discriminate against closely related l-phenylalanine analogs including d-phenylalanine. This work has established the Expression-SELEX as an effective SELEX method to enrich high-quality ligand-responsive aptazymes.

Concomitant Autoimmunity in Endometriosis Impairs Endometrium-Embryo Crosstalk at the Implantation Site: A Multicenter Case-Control Study.

Endometriosis and autoimmune diseases share a hyper-inflammatory state that might negatively impact the embryo-endometrium crosstalk. Inflammatory and immune deregulatory mechanisms have been shown to impair both endometrial receptivity and embryo competence at the implantation site. The aim of this study was to investigate the potential additional impact of co-existing autoimmunity in women affected by endometriosis on the early stages of reproduction. This was a retrospective, multicenter case-control study enrolling N = 600 women with endometriosis who underwent in vitro fertilization-embryo transfer cycles between 2007 and 2021. Cases were women with endometriosis and concomitant autoimmunity matched based on age and body mass index to controls with endometriosis only in a 1:3 ratio. The primary outcome was the cumulative clinical pregnancy rate (cCPR). The study found significantly lower cleavage (p = 0.042) and implantation (p = 0.029) rates among cases. Autoimmunity (p = 0.018), age (p = 0.007), and expected poor response (p = 0.014) were significant negative predictors of cCPR, with an adjusted odds ratio of 0.54 (95% CI, 0.33-0.90) for autoimmunity. These results suggest that the presence of concomitant autoimmunity in endometriosis has a significant additive negative impact on embryo implantation. This effect might be due to several immunological and inflammatory mechanisms that interfere with both endometrial receptivity and embryo development and deserves further consideration.

Simulations Reveal High Efficiency and Confinement of a Population Suppression CRISPR Toxin-Antidote Gene Drive.

Though engineered gene drives hold great promise for spreading through and suppressing populations of disease vectors or invasive species, complications such as resistance alleles and spatial population structure can prevent their success. Additionally, most forms of suppression drives, such as homing drives or driving Y chromosomes, will generally spread uncontrollably between populations with even small levels of migration. The previously proposed CRISPR-based toxin-antidote system called toxin-antidote dominant embryo (TADE) suppression drive could potentially address the issues of confinement and resistance. However, it is a relatively weak form of drive compared to homing drives, which might make it particularly vulnerable to spatial population structure. In this study, we investigate TADE suppression drive using individual-based simulations in a continuous spatial landscape. We find that the drive is actually more confined than in simple models without space, even in its most efficient form with low cleavage rate in embryos from maternally deposited Cas9. Furthermore, the drive performed well in continuous space scenarios if the initial release requirements were met, suppressing the population in a timely manner without being severely affected by chasing, a phenomenon in which wild-type individuals avoid the drive by recolonizing empty areas. At higher embryo cut rates, the drive loses its ability to spread, but a single, widespread release can often still induce rapid population collapse. Thus, if TADE suppression gene drives can be successfully constructed, they may play an important role in control of disease vectors and invasive species when stringent confinement to target populations is desired.

Dysregulation of Iron Metabolism-Linked Genes at Myocardial Tissue and Cell Levels in Dilated Cardiomyopathy.

In heart failure, the biological and clinical connection between abnormal iron homeostasis, myocardial function, and prognosis is known; however, the expression profiles of iron-linked genes both at myocardial tissue and single-cell level are not well defined. Through publicly available bulk and single-nucleus RNA sequencing (RNA-seq) datasets of left ventricle samples from adult non-failed (NF) and dilated cardiomyopathy (DCM) subjects, we aim to evaluate the altered iron metabolism in a diseased condition, at the whole cardiac tissue and single-cell level. From the bulk RNA-seq data, we found 223 iron-linked genes expressed at the myocardial tissue level and 44 differentially expressed between DCM and NF subjects. At the single-cell level, at least 18 iron-linked expressed genes were significantly regulated in DCM when compared to NF subjects. Specifically, the iron metabolism in DCM cardiomyocytes is altered at several levels, including: (1) imbalance of Fe3+ internalization (SCARA5 down-regulation) and reduction of internal conversion from Fe3+ to Fe2+ (STEAP3 down-regulation), (2) increase of iron consumption to produce hemoglobin (HBA1/2 up-regulation), (3) higher heme synthesis and externalization (ALAS2 and ABCG2 up-regulation), (4) lower cleavage of heme to Fe2+, biliverdin and carbon monoxide (HMOX2 down-regulation), and (5) positive regulation of hepcidin (BMP6 up-regulation).

Stability and the electronic and optical properties of two-dimensional iridium trihalides with promising applications in photocatalytic water splitting.

Based on density functional theory (DFT) calculations, we systematically investigate the structural stabilities, mechanical, electronic, and optical properties of an unexplored kind of two-dimensional (2D) material IrX3 (X = Cl, Br, I) monolayers. Calculations reveal that IrX3 monolayers have low cleavage energies, making them feasible to be extracted from their 3D layered bulk counterparts, and possess excellent energetic, dynamical, mechanical, and thermodynamic stabilities. The calculated band gaps fall in the range from 1.796 to 2.410 eV, with the conduction band (CB) edge and valence band (VB) edge straddling between the redox potentials of water. Analysis of optical properties shows that the monolayers exhibit large exciton binding energies and good optical absorption in the visible-light and ultraviolet regions. The van der Waals (vdW) heterostructures IrCl3:IrBr3 and IrBr3:IrI3 have type-II band alignment with enhanced charge separation, narrower band gap, and better visible light absorption, suggesting that the heterostructures hold promising applications in photocatalytic water splitting.

Electronic, mechanical and gas sensing properties of two-dimensional γ-SnSe.

Two-dimensional (2D) materials are excellent candidates for advanced flexible electronics and gas sensors. Herein, we systematically investigate the layer-dependent electronic structures, mechanical properties and gas sensing characteristics of the newly synthesized γ-SnSe based on first-principles calculations. Bulk γ-SnSe is a typical van der Waals layered material with an indirect narrow band gap, while monolayer and multilayer γ-SnSe can be obtained through mechanical exfoliation due to its low cleavage energy. The band gap of γ-SnSe gradually increases with decreasing layers, reaching a value of 2.25 eV for the monolayer due to weakened interlayer coupling. Mechanical analysis reveals strong anisotropy in multilayer γ-SnSe, whereas the monolayer exhibits a negative Poisson's ratio (-0.023/-0.025). Additionally, based on the analysis of electronic structures, adsorption energies and charge transfer of the host materials after adsorption of various gases, it is found that the γ-SnSe monolayer demonstrates enhanced sensitivity and selectivity towards NO, NO2, and SO2 compared to CO, CO2, H2S and NH3. These findings highlight the potential of γ-SnSe as an excellent gas-sensitive material for the detection of nitrogen oxides and sulfur dioxide.

Sperm factors associated with the production of equine blastocysts by intracytoplasmic sperm injection (ICSI) using frozen/thawed semen

Intracytoplasmic Sperm Injection (ICSI) using frozen/thawed sperm is a common procedure to obtain embryos from fertile or subfertile mares and stallions. Stallion-associated factors that impact the efficiency of ICSI have been studied less than those associated with the mare. Three experiments were conducted: Experiment 1: the effect of freezing extender composition and cryoprotectant; Experiment 2: the effect of sperm exposure to seminal plasma prior to freezing (ejaculated vs. epididymal sperm; two-freeze/thaw cycles each); and Experiment 3: the effect of sperm morphologic feature used for fertilization (normal vs. cytoplasmic droplet vs. bent tail); on the blastocyst rate after ICSI. In Experiment 1, stallion sperm was cryopreserved using commercially available extenders containing: a) 2% egg-yolk + milk + 4% glycerol (MFR5); b) 2% egg-yolk + milk + 2% glycerol + 3% methyl formamide (CMMFR5); c) 20% egg-yolk + 4.75% glycerol (LE); or d) 20% egg-yolk + 2% glycerol + 3% methyl formamide (CMLE). Sperm from each of the treatment groups were used for Piezo-driven ICSI on in vitro-matured equine oocytes (n = 321). Extender CMLE resulted in a lower cleavage rate (35%) than the other treatment groups (MFR5: 74%, CMMFR5: 62%, LE: 68%; P < 0.05). Extender MFR5 yielded a higher blastocyst rate per injected oocyte (21/82 [26%]) than the Groups LE (8/77 [10%]), CMLE (4/80 [5%]) or CMMFR5 (4/82 [5%]; P < 0.05). Extender MFR5 also yielded a higher blastocyst rate per cleaved oocyte (34%) than Groups LE, CMLE or CMMFR5 (15%, 14%, 8%; respectively P < 0.05). In Experiment 2, ejaculated (EJ) and epididymal (EPD) sperm from a fertile stallion which was initially cryopreserved in the CMLE extender, was thawed and re-cryopreserved in MFR5 extender for use in ICSI. Sperm from both groups (EJ vs. EPD) were used for ICSI on in vitro matured oocytes (n = 127). Differences were not detected for cleavage rate (EJ: 36/63 [57%] vs. EPD: 49/64 [77%]), blastocyst rate per injected oocyte (EJ: 11/63 [17%] vs. EPD: 11/64 [17%]), or blastocyst rate per cleaved oocyte (EJ: 31% vs. EPD: 22%) between treatment groups (P > 0.05). In Experiment 3, morphologically normal sperm (N), or sperm with proximal droplets (PD) or bent tails (BT), were obtained from a single fertile stallion and were used for ICSI on in vitro matured oocytes (n = 75). No differences were detected among treatment groups for cleavage rate (N: 19/25 [77%] vs. PD: 20/25 [88%] vs. BT: 18/25 [72%]), blastocyst rate per injected oocyte (N: 6/25 [24%] vs. PD: 5/25 [20%] vs. BT: 2/25 [8%]), and blastocyst rate per cleaved oocyte (N: 32% vs. PD: 23% vs. BT: 11%; P > 0.05). In conclusion, the current study indicates that freezing extender composition used for stallion sperm cryopreservation has an impact on the developmental competence of in vitro-matured equine oocytes after ICSI and in vitro culture. Furthermore, we were unable to detect differences on cleavage and blastocyst rates when performing ICSI when using: 1) ejaculated or epididymal sperm; or 2) sperm with different morphologic features. The results from the current study provide additional insight regarding stallion-related factors that should be considered when performing ICSI in horses.

Ab initio study of two-dimensional MgAl2Se4 and MgIn2Se4 with high stability, high electron mobility, and high thermoelectric figure of merit

Various two-dimensional (2D) materials possess low thermal conductivity owing to the predominant quantum effects, making them promising candidates for high-performance thermoelectric devices. Herein, we proposed two 2D materials, MgAl2Se4 and MgIn2Se4, exhibiting low cleavage energies of 0.20 J·m−2 and 0.22 J·m−2, respectively. They are both direct-gap semiconductors with bandgaps of 1.93 eV and 1.37 eV, respectively. Further, they have a high Seebeck coefficient (0.57–0.87 mV·K−1) and electrical conductivity (106–107 Ω−1·m−1). Moreover, owing to strong phonon–phonon anharmonic scattering, the monolayers exhibit low intrinsic lattice thermal conductivities of 1.39 W/m·K and 0.54 W/m·K. Consequently, the ZT values of MgAl2Se4 and MgIn2Se4 reach 0.36 and 0.74 at 300 K and rise even further to 2.58 and 3.06 at 700 K, respectively, indicating potential applications in nanoelectronics and thermoelectric devices.

Influence of delta ferrite on the impact toughness of a PH 13-8 Mo maraging steel

Due to the fact that maraging steels are widely utilized as structural parts for the aerospace industry, high and consistent impact toughness is crucial to ensure reliability under extreme mechanical loads. The toughness of maraging steels is heavily influenced by the martensitic structure and reverted austenite. Another microstructural constituent is residual delta ferrite that originates from non-equilibrium solidification. This work focuses on the effect of delta ferrite on the impact toughness of a PH 13-8 Mo maraging steel, while keeping other toughness-influencing factors as constant as possible. Three-step heat treatments were applied to samples for adjusting different phase fractions of delta ferrite. Charpy impact testing revealed that the impact toughness decreases with an increasing phase fraction of delta ferrite. However, no significant influence on the lower energy shelf, i.e. the impact energies below the ductile-to-brittle transition temperature range, was found. In addition, no decrease in hardness at room temperature was measured when delta ferrite is present in the microstructure. Particle analysis by APT measurements revealed that delta ferrite contains Ni- and Al-rich precipitates. It is assumed that those precipitates in combination with effective solid solution hardening by Cr, Mo and Al significantly contribute to the hardness of delta ferrite, which is in the range of martensite. Furthermore, EDS analysis showed a depletion in Ni in delta ferrite, presumably resulting in a lower cleavage fracture resistance compared to martensite, and, therefore, causing embrittlement. Moreover, the interface between delta ferrite and martensite possibly plays an additional role for crack initiation due to amplified local stresses.

Vacuum Low-Temperature Microwave-Assisted Pyrolysis of Technical Lignins

Cleavage by microwave-assisted pyrolysis is a way to obtain higher-value organic chemicals from technical lignins. In this report, pine kraft lignin (PKL), spruce and beech organosolv lignin (SOSL and BOSL), and calcium lignosulfonates from spruce wood (LS) were pyrolyzed at temperatures between 30 and 280 °C using vacuum low-temperature, microwave-assisted pyrolysis. The mass balance, energy consumption, condensation rate, and pressure changes of the products during the pyrolysis process were recorded. Phenolic condensates obtained at different temperatures during pyrolysis were collected, and their chemical composition was determined by GC-MS and GC-FID. The origin of the technical lignin had a significant influence on the pyrolysis products. Phenolic condensates were obtained in yields of approximately 15% (PKL and SOSL) as well as in lower yields of 4.5% (BOSL) or even 1.7% (LS). The main production of the phenolic condensates for the PKL and SOSL occurred at temperatures of approximately 140 and 180 °C, respectively. The main components of the phenolic fraction of the three softwood lignins were guaiacol, 4-methylguaiacol, 4-ethylguaiacol, and other guaiacol derivatives; however, the quantity varied significantly depending on the lignin source. Due to the low cleavage temperature vacuum, low-temperature, microwave-assisted pyrolysis could be an interesting approach to lignin conversion.

Two novel easily exfoliated quaternary chalcogenides with high performance of photocatalytic hydrogen production

Based on density functional theory calculations, we have disclosed two novel monolayers Tl2SnAs2Q6 (Q = S, Se) with efficient photocatalytic ability. Both Tl2SnAs2S6 and Tl2SnAs2Se6 monolayers (referred to as TSAS and TSASe) show low cleavage energy comparable to that of graphene, which endorses they can be easily exfoliated from their bulk counterparts. Moderate band gaps are observed in TSAS (2.06 eV) and TSASe (1.81 eV) monolayers and both of their absorption peaks reach the order of 105 cm−1 in visible light region. Remarkably, the results of Gibbs free energy changes show that the hydrogen reaction can proceed efficiently without any extra voltage. Superior carrier mobilities with obvious anisotropy are also observed in TSAS and TSASe (∼103 cm2V-1s-1) monolayers, which are much larger than that of MoS2 (200 cm2V-1s-1). In addition, we also studied the adsorption energy of water molecules H2O and hydrogen atoms H on TSAS(Se) substrates, and the kinetic barriers in the process of hydrogen production, which is helpful to further understand the hydrogen evolution process of water splitting. This work demonstrates two novel easily exfoliated monolayers with significant hydrogen evolution performance, making them promising candidates for novel photocatalysts.

Liquid-Phase Exfoliation of Bismuth Telluride Iodide (BiTeI): Structural and Optical Properties of Single-/Few-Layer Flakes.

Bismuth telluride halides (BiTeX) are Rashba-type crystals with several potential applications ranging from spintronics and nonlinear optics to energy. Their layered structures and low cleavage energies allow their production in a two-dimensional form, opening the path to miniaturized device concepts. The possibility to exfoliate bulk BiTeX crystals in the liquid represents a useful tool to formulate a large variety of functional inks for large-scale and cost-effective device manufacturing. Nevertheless, the exfoliation of BiTeI by means of mechanical and electrochemical exfoliation proved to be challenging. In this work, we report the first ultrasonication-assisted liquid-phase exfoliation (LPE) of BiTeI crystals. By screening solvents with different surface tension and Hildebrandt parameters, we maximize the exfoliation efficiency by minimizing the Gibbs free energy of the mixture solvent/BiTeI crystal. The most effective solvents for the BiTeI exfoliation have a surface tension close to 28 mN m–1 and a Hildebrandt parameter between 19 and 25 MPa0.5. The morphological, structural, and chemical properties of the LPE-produced single-/few-layer BiTeI flakes (average thickness of ∼3 nm) are evaluated through microscopic and optical characterizations, confirming their crystallinity. Second-harmonic generation measurements confirm the non-centrosymmetric structure of both bulk and exfoliated materials, revealing a large nonlinear optical response of BiTeI flakes due to the presence of strong quantum confinement effects and the absence of typical phase-matching requirements encountered in bulk nonlinear crystals. We estimated a second-order nonlinearity at 0.8 eV of |χ(2)| ∼ 1 nm V–1, which is 10 times larger than in bulk BiTeI crystals and is of the same order of magnitude as in other semiconducting monolayers (e.g., MoS2).

Effect of enzymatic pro-oxidant and antioxidant systems on bovine oocyte in vitro maturation

Abstract The role of reactive oxygen species (ROS) during oocyte in vitro maturation (IVM) is still controversial. Although an increase in ROS production may cause deleterious effects in cells, these reactive species may also act as signaling molecules influencing different cell functions. The aim of this study was to examine the effect of varying endogenous ROS levels during IVM on the process of bovine oocyte maturation. To do so, different enzymatic antioxidant (catalase, or superoxide dismutase + catalase, or diphenyl iodonium) or pro-oxidant systems (xanthine + xanthine oxidase, or xanthine + xanthine oxidase + catalase) were added to the culture medium. ROS levels were determined by 2′,7′-dichlorodihydrofluorescein diacetate stain, nuclear maturation was evaluated by the presence of the metaphase II chromosome configuration at 22h of IVM and cleavage rate was recorded 48h post- in vitro fertilization. ROS levels were only significantly increased (P&lt;0.05) by the O2 .- generating system (xanthine + xanthine oxidase + catalase), but meiotic maturation rates were significantly lower (P&lt;0.05) in all the evaluated systems compared with the control, except for the diphenyl iodonium group. However, this last group presented a significantly lower (P&lt;0.05) cleavage rate in comparison to the control group. These results indicate that ROS would play an essential role during oocyte maturation, since its increase or decrease beyond a physiological level significantly reduced nuclear or cytoplasmic maturation rates in bovine oocytes.

Nanotribology of SiP nanosheets: Effect of thickness and sliding velocity

Two-dimensional compounds combining group IV A element and group V A element were determined to integrate the advantages of the two groups. As a typical 2D group IV–V material, SiP has been widely used in photodetection and photocatalysis due to its high carrier mobility, appropriate bandgap, high thermal stability, and low interlayer cleavage energy. However, its adhesion and friction properties have not been extensively grasped. Here, large-size and high-quality SiP crystals were obtained by using the flux method. SiP nanosheets were prepared by using mechanical exfoliation. The layer-dependent and velocity-dependent nanotribological properties of SiP nanosheets were systematically investigated. The results indicate the friction force of SiP nanosheets decreases with the increase in layer number and reaches saturation after five layers. The coefficient of friction of multilayer SiP is 0.018. The mean friction force, frictional vibrations, and the friction strengthening effect can be affected by sliding velocity. Specially, the mean friction force increases with the logarithm of sliding velocity at nm/s scale, which is dominated by atomic stick-slip. The influence of frequency on frictional vibration is greater than speed due to the different influences on the change in contact quality. The friction strengthening saturation distance increases with the increase in speed for thick SiP nanosheets. These results provide an approach for manipulating the nanofriction properties of SiP and serve as a theoretical basis for the application of SiP in solid lubrication and microelectromechanical systems.

Theoretical probing the anchoring properties of BNP2 monolayer for lithium-sulfur batteries

Lithium-sulfur (Li-S) battery is blocked to implement as a practical energy storage device ascribes to the shuttle effect during charging and discharging processes. To solve the shuttle effect problem, one feasible method is to design a suitable anchoring material on the electrode. In this study, we explore the potential application of the BNP2 monolayer as an anchoring material through the first-principles calculation method. The results show that BNP2 with adequate adsorption energies (from 0.71 eV to 3.60 eV) can inhibit the shuttle effect without causing lithium polysulfides (LiPSs) decomposition. Then, by analyzing the projected density of states, it can be found that the property of BNP2 has been changed from a semiconductor to metal after adsorbing LiPSs, which is conducive to improving the electrical conductivity of the system. Moreover, due to the low cleavage energy barrier for the conversion of Li2S2 into Li2S, it not only improves the conversion efficiency but also avoids the waste of active substances. Finally, the low energy barrier for the catalytic decomposition of Li2S and the fast diffusion of the Li atom on the substrate accelerates the entire electrochemical process, thereby promoting the cycle performance and coulombic efficiency of Li-S batteries. In view of these advantages, it could expect that the BNP2 monolayer is an excellent anchoring material for Li-S batteries.