Deep Reinforcement Learning for Optimizing Restricted Access Window in IEEE 802.11ah MAC Layer.

The IEEE 802.11ah standard is introduced to address the growing scale of internet of things (IoT) applications. To reduce contention and enhance energy efficiency in the system, the restricted access window (RAW) mechanism is introduced in the medium access control (MAC) layer to manage the significant number of stations accessing the network. However, to achieve optimized network performance, it is necessary to appropriately determine the RAW parameters, including the number of RAW groups, the number of slots in each RAW, and the duration of each slot. In this paper, we optimize the configuration of RAW parameters in the uplink IEEE 802.11ah-based IoT network. To improve network throughput, we analyze and establish a RAW parameters optimization problem. To effectively cope with the complex and dynamic network conditions, we propose a deep reinforcement learning (DRL) approach to determine the preferable RAW parameters to optimize network throughput. To enhance learning efficiency and stability, we employ the proximal policy optimization (PPO) algorithm. We construct network environments with periodic and random traffic in an NS-3 simulator to validate the performance of the proposed PPO-based RAW parameters optimization algorithm. The simulation results reveal that using the PPO-based DRL algorithm, optimized RAW parameters can be obtained under different network conditions, and network throughput can be improved significantly.

Biohybrid Urchin-Like ZnO-Based Microspheres with Tunable Hierarchical Structures and Enhanced Photoelectrocatalytic Properties.

Microorganisms have attracted much attention to act as biotemplates for fabricating micro/nanostructured functional particles. However, it is still challenging to produce tunable hierarchical particles based on microorganisms with intricate architectures and superior stability. Herein, a novel strategy is developed to fabricate biohybrid urchin-like magnetic ZnO microspheres based on Chlorella (Ch.) with tunable hierarchical core-shell structures. Using Ch. cells as microspherical templates, Fe3 O4 nanoparticles and ZnO nanorod (NR) arrays are deposited in sequence to form the final biohybrid heterostructure microspheres (Ch.@Fe3 O4 @ZnO NRs). Ordered growth and structural regulation of 3D ZnO NR arrays are achieved via a facile and controllable manner. Compared with the prepared microspheres with diverse structure configurations of ZnO shells, the Ch.@Fe3 O4 @ZnO NRs possess excellent light absorption and photoelectrocatalysis performance toward tetracycline degradation (normalized apparent rate constant, k = 366.3 h-1 g-1 ), which is significantly larger than that of ZnO nanoflower/nanoparticle loaded types. It also proves that the synergistic enhancement of well-oriented ZnO NR arrays, heterojunction structures, and biomass features is the fundamental reason for outstanding photoelectrocatalytic activity. Due to the remarkable stability and versatility, this work provides abundant opportunities to construct biohybrid multilevel micro/nanostructures with significant potentials for practical applications.

Incidence and risk factors of venous thromboembolism in kidney transplantation patients: a prospective cohort study.

To investigate the incidence and explore the risk factors of venous thromboembolism (VTE) within 6 months after kidney transplantation. Total of 331 kidney transplant recipients were assessed by venous ultrasonography for VTE at 14 days, 1 month, 3 months, and 6 months post-transplantation. Cox forward regression were used to identify the independent risk factors of VTE. This study registration number is ChiCTR1900020567 and the date of registration was 2019/01/08. The cumulative incidence of VTE was 2.72% (9/331) within 6 months after transplant. 77.8% (7/9) of VTEs occurred in the first 3 months post-transplantation. 88.9% (1/9) of VTEs were asymptomatic, 66.7% (6/9) of VTEs were mural thromboses and in the right lower extremity. Central vena catheterization (HR = 6.94) and severe pulmonary disease (including pneumonia) (HR = 57.35) were the risk factors for VTE in kidney transplantation recipients. KT patients are the high risk population of VTE. Future interventions should be strengthen for KT patients to receive a minimum of 3-month of precautionary measures for VTE, including infection prevention, and strengthening thromboprophylaxis on the CVC or transplanted side of lower extremity.

State Transition Graph-Based Spatial-Temporal Attention Network for Cell-Level Mobile Traffic Prediction.

Mobile traffic prediction enables the efficient utilization of network resources and enhances user experience. In this paper, we propose a state transition graph-based spatial-temporal attention network (STG-STAN) for cell-level mobile traffic prediction, which is designed to exploit the underlying spatial-temporal dynamic information hidden in the historical mobile traffic data. Specifically, we first identify the semantic context information over different segments of the historical data by constructing the state transition graphs, which may reveal different patterns of random fluctuation. Then, based on the state transition graphs, a spatial attention extraction module using graph convolutional networks (GCNs) is designed to aggregate the spatial information of different nodes in the state transition graph. Moreover, a temporal extraction module is employed to capture the dynamic evolution and temporal correlation of the state transition graphs over time. Such a spatial-temporal attention network can be further integrated with a parallel long short-term memory (LSTM) module to improve the accuracy of mobile traffic prediction. Extensive experiments demonstrate that the STG-STAN can better exploit the spatial-temporal information hidden in the state transition graphs, achieving superior performance compared with several baselines.

Assessing the Assisted Six-Minute Cycling Test as a Measure of Endurance in Non-Ambulatory Patients with Spinal Muscular Atrophy (SMA).

Assessing endurance in non-ambulatory individuals with Spinal Muscular Atrophy (SMA) has been challenging due to limited evaluation tools. The Assisted 6-Minute Cycling Test (A6MCT) is an upper limb ergometer assessment used in other neurologic disorders to measure endurance. To study the performance of the A6MCT in the non-ambulatory SMA population, prospective data was collected on 38 individuals with SMA (13 sitters; 25 non-sitters), aged 5 to 74 years (mean = 30.3; SD = 14.1). The clinical measures used were A6MCT, Revised Upper Limb Module (RULM), Adapted Test of Neuromuscular Disorders (ATEND), and Egen Klassifikation Scale 2 (EK2). Perceived fatigue was assessed using the Fatigue Severity Scale (FSS), and effort was assessed using the Rate of Perceived Exertion (RPE). Data were analyzed for: (1) Feasibility, (2) Clinical discrimination, and (3) Associations between A6MCT with clinical characteristics and outcomes. Results showed the A6MCT was feasible for 95% of the tested subjects, discriminated between functional groups (p = 0.0086), and was significantly associated with results obtained from RULM, ATEND, EK2, and Brooke (p < 0.0001; p = 0.029; p < 0.001; p = 0.005). These findings indicate the A6MCT's potential to evaluate muscular endurance in non-ambulatory SMA individuals, complementing clinician-rated assessments. Nevertheless, further validation with a larger dataset is needed for broader application.

Superconducting, Topological, and Transport Properties of Kagome Metals CsTi3Bi5 and RbTi3Bi5.

The recently discovered ATi3Bi5 (A=Cs, Rb) exhibit intriguing quantum phenomena including superconductivity, electronic nematicity, and abundant topological states. ATi3Bi5 present promising platforms for studying kagome superconductivity, band topology, and charge orders in parallel with AV3Sb5. In this work, we comprehensively analyze various properties of ATi3Bi5 covering superconductivity under pressure and doping, band topology under pressure, thermal conductivity, heat capacity, electrical resistance, and spin Hall conductivity (SHC) using first-principles calculations. Calculated superconducting transition temperature (Tc) of CsTi3Bi5 and RbTi3Bi5 at ambient pressure are about 1.85 and 1.92 K. When subject to pressure, Tc of CsTi3Bi5 exhibits a special valley and dome shape, which arises from quasi-two-dimensional compression to three-dimensional isotropic compression within the context of an overall decreasing trend. Furthermore, Tc of RbTi3Bi5 can be effectively enhanced up to 3.09 K by tuning the kagome van Hove singularities (VHSs) and flat band through doping. Pressures can also induce abundant topological surface states at the Fermi energy (EF) and tune VHSs across EF. Additionally, our transport calculations are in excellent agreement with recent experiments, confirming the absence of charge density wave. Notably, SHC of CsTi3Bi5 can reach up to 226ℏ ·(e· Ω ·cm)-1 at EF. Our work provides a timely and detailed analysis of the rich physical properties for ATi3Bi5, offering valuable insights for further experimental verifications and investigations in this field.

Observation of flat band, Dirac nodal lines and topological surface states in Kagome superconductor CsTi3Bi5.

Kagome lattices of various transition metals are versatile platforms for achieving anomalous Hall effects, unconventional charge-density wave orders and quantum spin liquid phenomena due to the strong correlations, spin-orbit coupling and/or magnetic interactions involved in such a lattice. Here, we use laser-based angle-resolved photoemission spectroscopy in combination with density functional theory calculations to investigate the electronic structure of the newly discovered kagome superconductor CsTi3Bi5, which is isostructural to the AV3Sb5 (A = K, Rb or Cs) kagome superconductor family and possesses a two-dimensional kagome network of titanium. We directly observe a striking flat band derived from the local destructive interference of Bloch wave functions within the kagome lattice. In agreement with calculations, we identify type-II and type-III Dirac nodal lines and their momentum distribution in CsTi3Bi5 from the measured electronic structures. In addition, around the Brillouin zone centre, [Formula: see text] nontrivial topological surface states are also observed due to band inversion mediated by strong spin-orbit coupling.

Nursing workforce allocation in the intensive care units of COVID-19-designated hospitals: A nationwide cross-sectional survey in China.

AIM: To explore the nursing workforce allocation in intensive care units (ICUs) of COVID-19-designated hospitals during the epidemic peak in China. DESIGN: A nationwide cross-sectional online survey. METHODS: A total of 37 head nurses and 262 frontline nurses in 37 ICUs of COVID-19-designated tertiary hospitals located in 22 cities of China were surveyed. The self-reported human resource allocation questionnaire was used to assess the nursing workforce allocation. RESULTS: The average patient-to-nurse ratio was 1.89 ± 1.14, and the median working hours per shift was 5 h. The top four majors of front-line nurses in ICUs were respiratory (31.30%), lemology (27.86%), intensive care (21.76%) and emergency (17.18%). We also found that a smaller average patient-to-nurse ratio (odds ratio [OR]: 0.328, 95% CI: 0.108, 1.000), longer average weekly rest time per person (OR: 0.193, 95% CI: 0.051, 0.729) and larger proportion of 6-9 working years (OR: 0.002, 95% CI: 0.001, 1.121) decreased the occurrence of nursing adverse events.

Topological superconductivity and large spin Hall effect in the kagome family Ti6X4 (X = Bi, Sb, Pb, Tl, and In).

Topological superconductors (TSC) become a focus of research due to the accompanying Majorana fermions. However, the reported TSC are extremely rare. Recent experiments reported kagome TSC AV3Sb5 (A = K, Rb, and Cs) exhibit unique superconductivity, topological surface states (TSS), and Majorana bound states. More recently, the first titanium-based kagome superconductor CsTi3Bi5 with nontrivial topology was successfully synthesized as a perspective TSC. Given that Cs contributes little to electronic structures of CsTi3Bi5 and binary compounds may be easier to be synthesized, here, by first-principle calculations, we predict five stable nonmagnetic kagome compounds Ti6X4 (X = Bi, Sb, Pb, Tl, and In) which exhibit superconductivity with critical temperature Tc = 3.8 K - 5.1 K, nontrivial Z 2 band topology, and TSS close to the Fermi level. Additionally, large intrinsic spin Hall effect is obtained in Ti6X4, which is caused by gapped Dirac nodal lines due to a strong spin-orbit coupling. This work offers new platforms for TSC and spintronic devices.

Colonization of Fusobacterium nucleatum is an independent predictor of poor prognosis in gastric cancer patients with venous thromboembolism: a retrospective cohort study.

BACKGROUND: Fusobacterium nucleatum (F. nucleatum) often colonizes cancerous gastric tissues and is characterized by the promotion of platelet aggregation and the development of visceral thrombosis. Venous thromboembolism (VTE) leads to a significant increase in the mortality of gastric cancer (GC) patients. However, the relationship between the colonization of F. nucleatum and the prognosis of GC patients is still unknown. AIM: The aim of this study was to explore whether the colonization of F. nucleatum is related to the prognosis of GC patients complicated with VTE and to explore other potential risk factors. METHODS: From 2017-2021, the data of 304 patients with new VTEs during the treatment of GC at the Affiliated Cancer Hospital of Zhengzhou University were collected. Fluorescence in situ hybridization of F. nucleatum was performed on pathological sections of cancer tissues from the patients. Survival analysis methods, including the Kaplan‒Meier method and Cox proportional hazard model, were performed. RESULTS: F. nucleatum colonization was significantly associated with splanchnic vein thrombosis, higher platelet-lymphocyte ratio (PLR), and lower absolute lymphocyte count. In the multivariable Cox model, F. nucleatum colonization was found to be an independent risk factor for the prognosis of GC, with an adjusted HR of 1.77 (95% CI, 1.17 to 2.69 [P = 0.007]). In addition, patients with high PLR (HR: 2.65, P = 0.004) or VTE occurring during four cycles of chemotherapy (HR: 2.32, P = 0.012) exhibited shorter survival. Conversely, those experiencing VTE later (HR per month from diagnosis of GC: 0.95, P = 0.006) or using IVC filters (HR: 0.27, P = 0.011) had longer survival. CONCLUSION: Colonization of F. nucleatum in GC tissues was associated with lower absolute lymphocyte count and higher PLR in GC patients with VTE. F. nucleatum colonization also appeared to be associated with the development of VTE in specific sites, in particular the splanchnic vein. Colonization of F. nucleatum may potentially represent an independent predictor of poor prognosis in GC patients. Additional research is necessary to validate these findings.

Semiparametric distributed lag quantile regression for modeling time-dependent exposure mixtures.

Studying time-dependent exposure mixtures has gained increasing attentions in environmental health research. When a scalar outcome is of interest, distributed lag (DL) models have been employed to characterize the exposures effects distributed over time on the mean of final outcome. However, there is a methodological gap on investigating time-dependent exposure mixtures with different quantiles of outcome. In this paper, we introduce semiparametric partial-linear single-index (PLSI) DL quantile regression, which can describe the DL effects of time-dependent exposure mixtures on different quantiles of outcome and identify susceptible periods of exposures. We consider two time-dependent exposure settings: discrete and functional, when exposures are measured in a small number of time points and at dense time grids, respectively. Spline techniques are used to approximate the nonparametric DL function and single-index link function, and a profile estimation algorithm is proposed. Through extensive simulations, we demonstrate the performance and value of our proposed models and inference procedures. We further apply the proposed methods to study the effects of maternal exposures to ambient air pollutants of fine particulate and nitrogen dioxide on birth weight in New York University Children's Health and Environment Study (NYU CHES).

Enhanced Room Temperature Ferromagnetism in Highly Strained 2D Semiconductor Cr2Ge2Te6.

Emergent magnetism in van der Waals materials offers exciting opportunities in fabricating atomically thin spintronic devices. One pertinent obstacle has been the low transition temperatures (Tc) inherent to these materials, precluding room temperature applications. Here, we show that large structural gradients found in highly strained nanoscale wrinkles in Cr2Ge2Te6 (CGT) lead to significant increases of Tc. Magnetic force microscopy was utilized in characterizing multiple strained CGT nanostructures leading to experimental evidence of elevated Tc, depending on the strain percentage estimated from finite element analysis. Our findings are further supported by ab initio and DFT studies of the strained material, which indicates that strain directly augments the ferromagnetic coupling between Cr atoms in CGT, influenced by superexchange interaction; this provides strong insight into the mechanism of the enhanced magnetism and Tc.

Variability and correlations of synthetic chemicals in urine from a New York City-based cohort of pregnant women.

Fetal exposure to environmental chemicals has been associated with adverse health outcomes in children and later into adulthood. While several studies have examined correlations and variability of non-persistent chemical exposures throughout pregnancy, many do not capture more recent exposures, particularly in New York City. Our goal was to characterize exposure to phthalates, bisphenols, polycyclic aromatic hydrocarbons, and organophosphate pesticides among pregnant women residing in New York City who enrolled in the New York University Children's Health and Environment Study (NYU CHES) between 2016 and 2018. We measured urinary chemical metabolite concentrations in 671 women at early, mid, and late pregnancy (median 10.8, 20.8, and 29.3 weeks, respectively). We calculated Spearman correlation coefficients among chemical concentrations at each measurement time point. We compared changes in population-level urinary metabolites at each stage using paired Wilcoxon signed-rank tests and calculated intraclass correlation coefficients (ICCs) to quantify intra-individual variability of metabolites across pregnancy. Geometric means and ICCs were compared to nine other pregnancy cohorts that recruited women in 2011 or later as well as nationally reported levels from women of child-bearing age. Compared with existing cohorts, women in NYU CHES had higher geometric means of organophosphate pesticides (Σdiethylphosphates = 28.7 nmol/g cr, Σdimethylphosphates = 57.3 nmol/g cr, Σdialkyl phosphates = 95.9 nmol/g cr), bisphenol S (0.56 µg/g cr), and 2-naphthalene (8.98 µg/g cr). Five PAH metabolites and two phthalate metabolites increased between early to mid and early to late pregnancy at the population level. Spearman correlation coefficients for chemical metabolites were generally below 0.50. Intra-individual exposures varied over time, as indicated by low ICCs (0.22-0.88, median = 0.38). However, these ICCs were often higher than those observed in other pregnancy cohorts. These results provide a general overview of the chemical metabolites measured in NYU CHES in comparison to other contemporary pregnancy cohorts and highlight directions for future studies.

Engineering Novel (R)-Selective Transaminase for Efficient Symmetric Synthesis of d-Alanine.

d-Alanine belongs to nonessential amino acids that have diverse applications in the fields of food and health care. (R)-transaminase [(R)-TA]-catalyzed asymmetric amination of pyruvate is a feasible alternative for the synthesis of d-alanine, but low catalytic efficiency and thermostability limit enzymatic utilization. In this work, several potential (R)-TAs were discovered using NCBI database mining synchronously with enzymatic structure-function analysis, among which Capronia epimyces TA (CeTA) showed the highest activity for amination of pyruvate using (R)-α-methylbenzylamine as the donor. Furthermore, enzymatic residues surrounding a large catalysis pocket were subjected to saturation and combinatorial mutagenesis, and positive mutant F113T showed dramatic improvement in activity and thermostability. Molecular modeling indicated that the substitution of phenylalanine with threonine afforded alleviation of steric hindrance in the pocket and induced formation of additional hydrogen bonds with neighboring residues. Finally, using recombinant cells containing F113T as a biocatalyst, the conversion yield of amination of 100 mM pyruvate to d-alanine achieved up to 95.2%, which seemed to be the highest level in the literature regarding synthesis of d-alanine using TAs. The inherent characteristics rendered CeTA F113T a promising platform for efficient preparation of d-alanine operating with high productivity. IMPORTANCE d-Alanine is an important compound with many valuable applications. Its asymmetric synthesis employing (R)-ω-TA is considered an attractive choice. According to the stereoselectivity, ω-TAs have either (R)- or (S)-enantiopreference. There has been a variety of literature regarding screening, characterizing, and molecular modification of (S)-ω-TAs; in contrast, the research about (R)-ω-TA has lagged behind. In this work, we identify several (R)-ω-TAs and succeeded in creating mutant F113T, which showed not only better efficiency toward pyruvate but also higher thermostability compared with the original enzyme. The obtained original enzymes and positive mutants displayed important application value for pushing symmetric synthesis of d-alanine to a higher level.

The p-orbital magnetic topological states on a square lattice.

Honeycomb or triangular lattices were extensively studied and thought to be proper platforms for realizing the quantum anomalous Hall effect (QAHE), where magnetism is usually caused by d orbitals of transition metals. Here we propose that a square lattice can host three magnetic topological states, including the fully spin-polarized nodal loop semimetal, QAHE and the topologically trivial ferromagnetic semiconductor, in terms of the symmetry and k · p model analyses that are material independent. A phase diagram is presented. We further show that the above three magnetic topological states can indeed be implemented in the two-dimensional (2D) materials ScLiCl5, LiScZ5 (Z=Cl, Br) and ScLiBr5, respectively. The ferromagnetism in these 2D materials is microscopically revealed from p electrons of halogen atoms. This present study opens a door to explore the exotic topological states as well as quantum magnetism from p-orbital electrons by means of the material-independent approach.

Two-dimensional layered lithium lanthanum titanium oxide/graphene-like composites as electrodes for lithium-ion batteries.

Perovskite-structured (ABO3) lithium lanthanum titanate (LixLa(2-x)/3TiO3, LLTO) is widely used in all solid state lithium ion batteries due to its high ionic conductivity. In this study, a two-dimensional LLTO nanosheet/graphene (LLTO/C) nanosheet composite has been designed as an electrode material for lithium-ion batteries (LIBs). LLTO/C not only exhibits the ionic conductivity properties of perovskite-type LLTO, but the graphene between the layers of LLTO nanosheets also endows the material with additional electronic conductivity. Moreover, LLTO@C-600 exhibits an excellent rate capability as the electrode for delithiation with a high specific capacity of 350 mA h g-1 at 20 mA g-1, and 70% of the specific capacity can be maintained at 1.0 A g-1 after 800 cycles. The excellent electrochemical performances can be attributed to the superior interficial capacitive Li+ storage capability.

Determinants of phthalate exposures in pregnant women in New York City.

Previous studies have provided data on determinants of phthalates in pregnant women, but results were disparate across regions. We aimed to identify the food groups and demographic factors that predict phthalate exposure in an urban contemporary pregnancy cohort in the US. The study included 450 pregnant women from the New York University Children's Health and Environment Study in New York City. Urinary concentrations of 22 phthalate metabolites, including metabolites of di-2-ethylhexylphthalate (DEHP), were determined at three time points across pregnancy by liquid chromatography coupled with tandem mass spectrometry. The Diet History Questionnaire II was completed by pregnant women at mid-pregnancy to assess dietary information. Linear mixed models were fitted to examine determinants of urinary phthalate metabolite concentrations. Using partial-linear single-index (PLSI) models, we assessed the major contributors, among ten food groups, to phthalate exposure. Metabolites of DEHP and its ortho-phthalate replacement, diisononyl phthalate (DiNP), were found in >90% of the samples. The sum of creatinine-adjusted DiNP metabolite concentrations was higher in older and single women and in samples collected in summer. Hispanic and non-Hispanic Black women had lower urinary concentrations of summed metabolites of di-n-octyl phthalate (DnOP), but higher concentrations of low molecular weight phthalates compared with non-Hispanic White women. Each doubling of grain products consumed was associated with a 20.9% increase in ∑DiNP concentrations (95%CI: 4.5, 39.9). PLSI models revealed that intake of dried beans and peas was the main dietary factor contributing to urinary ∑DEHP, ∑DiNP, and ∑DnOP levels, with contribution proportions of 76.3%, 35.8%, and 27.4%, respectively. Urinary metabolite levels of phthalates in pregnant women in NYC varied by age, marital status, seasonality, race/ethnicity, and diet. These results lend insight into the major determinants of phthalates levels, and may be used to identify exposure sources and guide interventions to reduce exposures in susceptible populations.

Tuning the Defects of Two-Dimensional Layered Carbon/TiO2 Superlattice Composite for a Fast Lithium-Ion Storage.

Defect engineering is one of the effective ways to improve the electrochemical property of electrode materials for lithium-ion batteries (LIB). Herein, an organic functional molecule of p-phenylenediamine is embedded into two-dimensional (2D) layered TiO2 as the electrode for LIB. Then, the 2D carbon/TiO2 composites with the tuning defects are prepared by precise control of the polymerization and carbothermal atmospheres. Low valence titanium in metal oxide and nitrogen-doped carbon nanosheets can be obtained in the carbon/TiO2 composite under a carbonization treatment atmosphere of N2/H2 gas, which can not only increase the electronic conductivity of the material but also provide sufficient electrochemical active sites, thus producing an excellent rate capability and long-term cycle stability. The prepared composite can provide a high capacity of 396.0 mAh g-1 at a current density of 0.1 A g-1 with a high capacitive capacity ratio. Moreover, a high specific capacity of 80.0 mAh g-1 with retention rate of 85% remains after 10,000 cycles at 3.0 A g-1 as well as the Coulomb efficiency close to 100%. The good rate-capability and cycle-sustainability of the layered materials are ascribed to the increase of conductivity, the lithium-ion transport channel, and interfacial capacitance due to the multi-defect sites in the layered composite.

Emergent Kagome Electrides.

In a two-dimensional (2D) Kagome lattice, the ideal Kagome bands including Dirac cones, van Hove singularities, and a flat band are highly expected, because they can provide a promising platform to investigate novel physical phenomena. However, in the reported Kagome materials, the complex 3D and multiorder electron hoppings result in the disappearance of the ideal Kagome bands in these systems. Here, we propose an alternative way to achieve the ideal Kagome bands in non-Kagome materials by confining excess electrons in the system to the crystal interstitial sites to form a 2D Kagome lattice, coined as a Kagome electride. Then, we predict two novel stable 2D Kagome electrides in hexagonal materials Li5Si and Li5Sn, whose band structures are similar to the ideal Kagome bands, including topological Dirac cones with beautiful Fermi arcs in their surface states, van Hove singularities, and a flat band. In addition, Li5Si is revealed to be a low-temperature superconductor at ambient pressure, and its superconducting transition temperature Tc can be increased from 1.1 K at 0 GPa to 7.2 K at 100 GPa. The high Tc is unveiled to be the consequence of strong electron-phonon coupling originated from the sp-hybridized phonon-coupled bands and phonon softening caused by strong Fermi nesting. Due to the strong Fermi nesting, the charge density wave phase transition occurs at 110 GPa with the lattice reconstructed from hexagonal to orthorhombic, accompanied with the increase of Tc to 10.5 K. Our findings pave an alternative way to fabricate more real materials with Kagome bands in electrides.

Phosphorylation at Ser68 facilitates DCAF11-mediated ubiquitination and degradation of CENP-A during the cell cycle.

CENP-A (centromeric protein A), a histone H3 variant, specifies centromere identity and is essential to centromere maintenance. Little is known about how protein levels of CENP-A are controlled in mammalian cells. Here, we report that the phosphorylation of CENP-A Ser68 primes the ubiquitin-proteasome-mediated proteolysis of CENP-A during mitotic phase in human cultured cells. We identify two major polyubiquitination sites that are responsible for this phosphorylation-dependent degradation. Substituting the two residues, Lys49 and Lys124, with arginines abrogates proper CENP-A degradation and results in CENP-A mislocalization to non-centromeric regions. Furthermore, we find that DCAF11 (DDB1 and CUL4 associated factor 11/WDR23) is the E3 ligase that specifically mediates the observed polyubiquitination. Deletion of DCAF11 hampers CENP-A degradation and causes its mislocalization. We conclude that the Ser68 phosphorylation plays an important role in regulating cellular CENP-A homeostasis via DCAF11-mediated degradation to prevent ectopic localization of CENP-A during the cell cycle.