PdCu alloy anchored defective titania for photocatalytic conversion of carbon dioxide into methane with 100% selectivity

The photoreduction of CO_(2)into CH_(4)with simultaneous high activity and selectivity is a promising strategy to increase energy supply and alleviate global warming.However,the absence of the active sites that is responsible for the adsorption and activation of CO_(2)and the generation of CO and H2via side reactions often lead to poor efficiency and low selectivity of the catalyst.Herein,Cu,Pd,and PdCu metal clusters cocatalyst-anchored defective TiO_(2)nanotubes(Cu/TiO_(2)-SBO,Pd/TiO_(2)-SBO,and Pd1Cu1/TiO_(2)-SBO)were designed via a simple solution impregnation reduction and applied for photocatalytic conversion of CO_(2)to CH_(4).The Pd1Cu1/TiO_(2)-SBO photocatalyst exhibits excellent catalytic performance among the other catalysts for photoreduction of CO_(2)into CH_(4).More interestingly,the product selectivity of CH_(4)reaches up to 100%with a rate of 25μmol g^(-1)h^(-1).In-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and density functional theory(DFT)simulations indicate that the main reasons for the high selectivity of CH_(4)are attributed to the PdCu alloy and oxygen vacancies,which jointly enhance the photoinduced carrier separation and lower energy barriers of key intermediates.Moreover,due to the tunable d-band center of the Cu site in the PdCu alloy,the generated intermediates can be well prevented from poisoning and promoted to participate in further reactions.Hopefully,the current study will provide insight into the development of new,highly selective photocatalysts for the visible light-catalytic reduction of CO_(2)into CH_(4).

Defective layered Mn-based cathode materials with excellent performance via ion exchange for Li-ion batteries

Defective layered Mn-based materials were synthesized by Li/Na ion exchange to improve their electrochemical activity and Coulombic efficiency.The annealing temperature of the Na precursors was important to control the P3-P2 phase transition,which directly affected the structure and electrochemical characteristics of the final products obtained by ion exchange.The O3-Li_(0.78)[Li_(0.25)Fe_(0.075)Mn_(0.675)]O_(δ) cathode made from a P3-type precursor calcined at 700℃ was analyzed using X-ray photoelectron spectrometry and electron paramagnetic resonance.The results showed that the presence of abundant trivalent manganese and defects resulted in a discharge capacity of 230 mAh/g with an initial Coulombic efficiency of about 109%.Afterward,galvanostatic intermittent titration was performed to examine the Li^(+) ion diffusion coefficients,which affected the reversible capacity.First principles calculations suggested that the charge redistribution induced by oxygen vacancies(OV_(s))greatly affected the local Mn coordination environment and enhanced the structural activity.Moreover,the Li-deficient cathode was a perfect match for the pre-lithiation anode,providing a novel approach to improve the initial Coulombic efficiency and activity of Mn-based materials in the commercial application.

Hepatitis B virus infection:defective surface antigen expression and pathogenesis

Hepatitis B virus(HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.

Defective ZnS nanoparticles anchored in situ on N-doped carbon as a superior oxygen reduction reaction catalyst

Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions.However,the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking.In this study,ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst.These catalysts were prepared via a one-step method at 900℃.Amazingly,the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles.These facilitated the catalyst synthesis,and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium,including a lower onset potential,lower mid-wave potential,four electron transfer process,and better durability compared with 20 wt%Pt/C.More importantly,the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH*from*OO toward oxygen reduction reaction.Therefore,the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells,given the novel catalyst’s resulting performance.

Enhancing Photocatalytic Performance of NH 2-UIO66 by Defective Structural Engineering

NH_(2)-UIO66(NU)is a promising photocatalyst for the reduction of Cr(VI)to low-toxic Cr(III)driven by visible light under ambient conditions.However,the main limitation in this process is the ineffi cient ligand to metal charge transfer(LMCT)of photo-excited electrons,which is caused by inherent energy gap(ΔE_(LMCT)).This study synthesized the defective NU(NUXH,where X is the molar equivalent of the modulator)with reducedΔE_(LMCT)through linkers removal via acid treatment.The electronic structure of NUX-H was systematically investigated,and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms.Furthermore,they substantially lowered the energy of the unoccupied d orbitals(LUMO),which was benefi cial to effi cient LMCT,resulting in an improved photocatalytic activity of NUX-H toward high-concentration(100 mg/L)Cr(VI)reduction.Compared to NU with defect-free structure,the reducing rate of Cr(VI)was increased by 47 times.This work introduced an alternative strategy in terms of designing effi cient photocatalysts for reducing Cr(VI)under ambient conditions.

Ultrathin defective high-entropy layered double hydroxides for electrochemical water oxidation

One of the fundamental driving forces in the materials science community is the hunt for new materials with specific properties that meet the requirements of rapidly evolving technology.

PLASTIC LIMIT LOAD ANALYSIS OF DEFECTIVE PIPELINES

The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemical factories.An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies.A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems.The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure,bending moment and axial force.The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated.Some typical failure modes corresponding to different configurations of slots and loading forms are studied.

心电图Defective T波对成人继发孔型房间隔缺损的诊断价值和形成因素分析

目的:探讨心电图Defective T波(DTW)诊断成人继发孔型房间隔缺损(ASD)的价值及主要形成因素。方法:选取经心脏超声心动图确诊的继发孔型ASD成人患者243例(ASD组)和心脏超声未见明显异常者247例(非ASD组),均描记标准十二导联心电图,观察DTW、不完全性右束支传导阻滞(IRBBB)检出情况,分析DTW对继发孔型ASD的诊断价值和形成因素,观察不同术式前后心电图的变化。结果:ASD组、非ASD组DTW检出率分别为58.02%(141/243)、5.67%(14/247),DTW合并IRBBB检出率分别为51.85%(126/243)、0.81%(2/247),ASD组均高于非ASD组(χ^(2)=155.263、165.363,P<0.001)。DTW诊断继发孔型ASD的敏感度、特异度和准确度分别为58.02%、94.33%和76.33%,DTW合并IRBBB诊断继发孔型ASD的敏感度、特异度和准确度分别为51.85%、99.19%和75.71%。右心室增大、肺动脉收缩压增高是ASD患者DTW形成的主要影响因素[OR(95%CI)分别为1.095(1.020~1.176)、1.040(1.006~1.075)];术前DTW、IRBBB和DTW合并IRBBB阳性的ASD患者经过外科手术或介入手术治疗6个月后均缓解,缓解程度在两种术式组间的差异无统计学意义(P>0.05)。结论:心电图DTW对成人继发孔型ASD的诊断具有较大指导意义,右心室增大、肺动脉收缩压增高是ASD患者DTW的主要形成因素。

Effects of Imperfect Quality and Defective Items on Economic Production Lot Size

The classical EPQ model has been used for a long ti me and is widely accepted and implemented. Nevertheless, the analysis for finding an economic lot size has based on a number of unrealistic assumptions. A common unrealistic assumption in using EPQ is that all units produced are of good quali ty. The classical EPQ model shows that the optimal lot size will generate minimum ma nufacturing cost, thus producing minimum setup cost and inventory cost. However, this is only true if all products manufactured in the process are assumed to be of good quality (i.e. all products are within the specification limits). In rea lity this is not the case, therefore, it is necessary to consider the cost of im perfect quality items, because this cost can influence the economic lot size. Ma ny studies and recent papers have indicated that there is a significant relation ship between economic production lot size and process/product quality. However, their models included either the imperfect quality items (not necessarily de fective) which are to be sold at a discounted price or defective items which can be reworked or rejected. The aim of this paper is to provide a framework to integrate three different sit uations (discounted pricing/rework/reject) into a single model. 100% inspection is performed in order to distinguish the amount of good quality items, imper fect quality items and defective items in each lot. In this paper, a mathematica l model is developed, and a numerical example is presented to illustrate the sol ution procedures. It is found that the economic production lot size tends to inc rease as the average percentage of imperfect quality items and defectives (rejec ted items) increases.

Defective/Doped Graphene-Based Materials as Cathodes for Metal-Air Batteries

Graphene,as a proof-of-concept two-dimensional material,has proven to have excellent physical and chemical properties.Its derivatives,such as defective or doped graphene,are also applied as catalytic materials for metal-air batteries(MABs).MABs have been recognized as possible candidates for new-generation energy storage systems due to their ultra-high theoretical energy density.So far,graphene and its derivatives with optimized structures have been widely explored to improve the electrochemical performance in MABs.Generally speaking,perfect graphene crystalline is inert for many catalytic processes,while defects and heteroatoms can endow graphene with high activity for many electrocatalytic reactions.Under this circumstance,recent progress is summarized for defective/doped graphene as air cathodes in aqueous or organic MABs,which are actually different electrochemical systems with distinct requirements for air cathodes.Also,the relationship is clarified between graphene defects/doping and electrocatalytic mechanisms that can be the guidance for catalyst design.Future directions are also prospected for the development of graphene-based MAB cathodes.

Extreme narrow photonic passbands generated from defective two-segment-connected triangular waveguide networks

In this paper, we investigate the optical transmission properties of perfect and defective two-segment-connected tri- angular waveguide networks （2SCTWNs） and find that after introducing defects in networks, many groups of transparent extreme narrow photonic passbands （ENPPs） will be created in the middle of the transmission spectra, the number for each group and the group number of ENPPs can he adjusted by the matching ratios of waveguide length （MRWLs）, the number of defects, and the number of unit cells of 2SCTWNs. The influences of MRWL, number of defects, and number of unit cells on the number, width, and position of these ENPPs are researched and a series of quantitative rules and prop- erties are obtained. It may be useful for the designing of high-sensitive optical switches, wavelength division multiplexers, extreme-narrowband filters, and other correlative waveguide network devices.

IN situ Confocal Microprobe Raman Spectroscopic Studies on Defective La-based Complex Oxides

The adsorption of O2 over defective La2O3-based OCM catalysts with anionic vacancies , and the reaction of surface oxygen species with CH4 were studied by means of in situ confocal microprobe Raman spectra. The partially reduced oxygen species O2, O , O (O<&<1 ) and even the lattice oxygen ion O2-can be detected on the surface of O2-pretreated La2O3-based catalysts. At lower temperatures (< 573 K) it is peroxide species O- or O- that is more essential for the coupling of methane,while at higher temperature. the superoxide O2 and lattice oxygen species O2-are rather important. It is easier for fluoride-containing La2O3-based catalysts to induce the oxygen species with fewer negative charges and the basicity of the cat- alyst surface is weakened , so that the C2 selectivity for OCM reaction is improved.

Dynamic Control of Defective Gap Mode Through Defect Location

A one dimensional model is developed for defective gap mode（DGM）with two types of boundary conditions：conducting mesh and conducting sleeve.For a periodically modulated system without defect,the normalized width of spectral gaps equals to the modulation factor,which is consistent with previous studies.For a periodic system with local defects introduced by the boundary conditions,it shows that the conducting-mesh-induced DGM is always well confined by spectral gaps while the conducting-sleeve-induced DGM is not.The defect location can be a useful tool to dynamically control the frequency and spatial periodicity of DGM inside spectral gaps.This controllability can be potentially applied to the interaction between gap eigenmodes and energetic particles in fusion plasmas,and optical microcavities and waveguides in photonic crystals.

Thermal conductivity of carbon nanotube superlattices:Comparative study with defective carbon nanotubes

We use molecular dynamics simulation to calculate the thermal conductivities of（5, 5） carbon nanotube superlattices（CNTSLs） and defective carbon nanotubes（DCNTs）, where CNTSLs and DCNTs have the same size. It is found that the thermal conductivity of DCNT is lower than that of CNTSL at the same concentration of Stone–Wales（SW） defects. We perform the analysis of heat current autocorrelation functions and observe the phonon coherent resonance in CNTSLs, but do not observe the same effect in DCNTs. The phonon vibrational eigen-mode analysis reveals that all modes of phonons are strongly localized by SW defects. The degree of localization of CNTSLs is lower than that of DCNTs, because the phonon coherent resonance results in the phonon tunneling effect in the longitudinal phonon mode. The results are helpful in understanding and tuning the thermal conductivity of carbon nanotubes by defect engineering.

An Inventory Model of Production with Level Dependent Demand Allowing Few Defective Items

This paper considers a model regarding the products with finite life which allows defective items in reproduction and causes a small amount of decay. The market demand is assumed to be level dependent linear type. The model has also considered the constant production rate which stops after a desired level of inventories and that is the highest level of it. Due to the market demand, defective item and product’s decay, the inventory reduces to the zero level where again the production cycle starts. With a numerical search procedure, the proof of the proposed model has been shown. The objective of the proposed model is to find out the total optimum inventory cost, optimum ordering cost and optimum ordering cycle.

Management of the Recall of Defective Motor Vehicles in China

The Administrative Regulation on the Recall of Defective Motor Vehicles has officially entered into force on October 1st, 2004, which means the management on defective products has made a substantive progress. The enactment and enforcement of the Administrative Regulation has generated active responses in our society and drawn much attention from the automobile industry. Up to March 2005, there have been 15 domestic and foreign auto manufacturers initiating voluntary recalls since the Administrative Regulation on the Recall of Defective Motor Vehicles was issued in March 2004, and 312864 vehicles have been recalled. All the relevant firms, types, models, numbers and the date are as the following table 1.

Statistical Analysis of Defective Items of Pharmaceutical Wholesale Enterprises

Objective To provide some references and suggestions for promoting the healthy development of pharmaceutical wholesale enterprises,improving the scientific supervision level of the drug regulatory department and ensuring the quality of drugs in the circulation.Methods Retrieving the items on the official websites of the national and provincial drug regulatory departments from 2017 to 2019 that didn’t meet the requirements of the 2016 edition of the Good Supplying Practice in pharmaceutical wholesale enterprises under various inspections,the defective items were summarized and analyzed,and further study of the changes of defective items was conducted.Results and Conclusion 908 pharmaceutical wholesale enterprises had definite defective items,and 218 items violated the Guidelines for On-site Inspection of the Good Supplying Practice,with a cumulative frequency of 3874 defects.Defective items with high-frequency mainly occurred in storage and maintenance,facilities and equipment,personnel and training,general rules and sales.The average defect frequency in each pharmaceutical wholesale enterprises increased year by year,but the proportion of serious defective items decreased significantly.It is recommended that based on improving drug quality,pharmaceutical wholesale enterprises should strengthen personnel training to enhance their awareness of quality responsibility.Besides,the drug regulatory department should increase inspection and crackdown on illegal business operations and the deception of pharmaceutical wholesale enterprises.

Surface-defective FeS2 for electrochemical NH3 production under ambient conditions

In the viewpoint of ammonia economy,electrochemical N2 reduction reaction(NRR)under mild condition is a very promising approach for sustainable development.By virtue of robust activity and low cost,transition-metalbased materials become one kind of the most attractive electrocatalysts in realizing ammonia synthesis to the industrial level.However,the investigation related to NRR electrocatalysts still mainly rely on costly substance or fabrication process,which greatly restrict their large-scale applications.In this work,a simple fabricated FeS2 electrode is adopted as NRR catalysts.The abundant surface defects due to the existence of Cr element,as well as the synergistic effect between FeS2 crystal planes provided excellent electrocatalytic performance with a high NH3 yield rate(11.5μg h^-1mg^-1 Fe)and Faradaic efficiency(14.6%)at-0.2 V vs.reversible hydrogen electrode(RHE)toward NRR under ambient conditions.The superior catalytic performance of such non-precious metal catalysts would strongly promote the application of NRR process industrially.