Improving gold recovery of Pb–Zn sulfide ore by selective activation with organic acid

Free gold and gold wrapped in sulfides are considered as the object of gold floatation. However,floatation of free gold exhibits more variables in practice.In this study, improving gold recovery of a Pb-Zn sulfide ore from Yunnan Province, China, was investigated. The results show that free gold and auriferous sulfides account for 94.99 % of total gold. Without adding organic acid in floatation, only 82 % recovery of gold could be obtained.Gold recovery in Au/Pb concentrates increases by 9.29 %with oxalate added and by 7.35 % with citric acid added,respectively, while performances of lead and arsenic nearly keep a constant. A possible reason is that free gold is of wonderful selectivity against pyrite with organic activators.A new method to enhance gold recovery is proposed.

Special Issue on Catalytic Activation and Selective Conversion of Energy-Related Molecules

The activation and selective conversion of energy-related molecules is an important research area of energy chemistry.The depletion of petroleum has stimulated research activities into the utilization of non-petroleum carbon resources such as natural gas(including conventional and

Catalytic Performance of Carbon Materials Supported Pd Nanoparticles in Selective Hydrogenation of Acetylene

Pd/C catalysts were prepared by deposited Pd nanoparticles （NPs） on different carbon supports including activated carbon （AC）, graphite oxide （GO）, and reduced graphite oxide （rGO） using sol-immobilization method. Through transmission electron microscopy, powder X-ray di raction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction.

A NEW ACTIVE DIESTER FOR SELECTIVE POLYMERIZATION TO FORM FUNCTIONAL POLYAMIDES

A new synthetic route to polyamides and hydroxyl polyamides was established, based on the selecting (?)-acylation of three novel typical active diesters: the active diester of N-hydroxy- (?) 4-epoxy-5-cyclohexene-2, 3-dicarboximide( HOEC), such as N, N'-(temphthaloyldioxy) bis(1, 4- epoxy - 5 - cyclohexene- 2, 3 - dicarboximide.) ( PBOEC), N, N'- ( isophthaloyl - dioxy) bis (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide)(IPBOEC) and N, N' -(adipoyldioxy) his (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide) ( ADOEC)with aliphatic diamines and 1,3-diamino-2-hydroxypropane. The polycondensation occurs at room temperature in solution without added catalyst. Dipolar aprotic solvents which include dimethyl sulfoxide, N- methyl - 2- pyrrolidone and dimethylformamide were used as solvents for polymerization. The selective N-acylation of two active diesters was performed as a model reaction study.

EFFECT OF STRUCTURE OF FUNCTIONAL POLYMER ACTIVE MATERIALS ON PROPERTIES OF GADOLINIUM ION SELECTIVE ELECTRODE

In this paper,the functional polymeric active materials were prepared by the grafting copolymerization and their structure and properties were studied.The results show that the structure and properties of these ac- tive materials have the relative large effects on the properties of gadolinium ion selective electrodes.

Efficient hydrogen peroxide production enabled by exploring layered metal telluride as two electron oxygen reduction reaction electrocatalyst

It is of great interest to develop the novel transition metal-based electrocatalysts with high selectivity and activity for two electron oxygen reduction reaction(2e^(-) ORR).Herein,the nickel ditelluride(NiTe_(2)) with layered structure was explored as the 2e^(-) ORR electrocatalyst,which not only showed the highest 2e^(-) selectivity more than 97%,but also delivered a slight activity decay after 5000 cycles in alkaline media.Moreover,when NiTe_(2) was assembled as the electrocatalyst in H-type electrolyzer,the on-site yield of H_(2)O_(2) could reach up to 672 mmol h^(-1)g^(-1) under 0.45 V vs.RHE.Further in situ Raman spectra,theoretical calculation and post microstructural analysis synergistically unveiled that such a good 2e^(-) ORR performance could be credited to the intrinsic layered crystal structure,the high compositional stability,as well as the electron modulation on the active site Ni atoms by neighboring Te atoms,leading to the exposure of active sites as well as the optimized adsorption free energy of Ni to –OOH.More inspiringly,such telluride electrocatalyst has also been demonstrated to exhibit high activity and selectivity towards 2e^(-) ORR in neutral media.

Selective leaching of calcium from mechanically activated mixed rare earth concentrate

The loss of rare earths(REs)takes place during the pre-decalcification process of mixed rare earth concentrate.In an effort to reduce such RE loss,a novel idea to improve the leaching selectivity of Ca to REs by applying selective mechanical activation was proposed.First,regarding the key minerals affecting the leaching selectivity of Ca to REs,the differences in the mechanical activation behaviors of CaF_(2) and REFCO_(3) were studied,and we find that the lattice strain of CaF_(2) increases from 0.21%to 0.42%,whereas that of REFCO_(3) increases from 0.31%to 0.40%.Notably,CaF_(2) demonstrates a larger lattice strain than REFCO_(3),indicating greater mechanical activation energy storage and higher leaching activity.Next,the HCl leaching process was studied.A significant leaching selectivity of Ca to REs,from 21.6 to 35.1,is achieved through mechanical activation.The Ca leaching rate reaches 80.7%when the RE loss is 2.3%in the activated sample.This study provides an novel approach for achieving selective extraction of specific components via mechanical activation pretreatment.

LOCALIZATION FOR MOBILE TARGET IN WIRELESS SENSOR NETWORKS

A precise localization for mobile target in wireless sensor networks is presented in this letter,where a geometrical relationship is explored to improve the location estimation for mobile target,in-stead of a simple centroid approach.The equations of location compensation algorithm for mobiletarget are derived based on linear trajectory prediction and sensor selective activation.The resultsbased on extensive simulation experiments show that the compensation algorithm gets better per-formance in metrics of quality of tracking and energy efficiency with the change of sensor sensing range,the ratio of sensing range and sensor activation range,and the data sampling rate than traditionalmethods,which means our proposing can achieve better quality-energy tradeoff for mobile target inwireless sensor networks.

Effects of Vanadium Oxidation Number on Light Olefins Selectivity of FCC Catalyst

Effects of vanadium on light olefins selectivity of FCC catalysts were investigated with vanadium having different oxidation numbers （hereinafter abbreviated as Oxnum）. Molecular modeling studies showed that vanadium with low Oxnum could affect the chemical conversion of large-size hydrocarbon molecules. However, the vanadium deposited on equilibrium catalyst bad high Oxnum because of the oxidation reaction taking place in the regenerator, so an activation method to reduce vanadium Oxnum named ＂selective activation＂ was introduced. It was proved by means of Electron Paramagnetic Resonance （EPR） and Temperature-Programmed Reduction （TPR） methods that the vanadium Oxnum was decreased, when the catalyst was activated. The molecular modeling studies are consistent well with the lab evaluation results. The light olefins selectivity of activated equilibrium catalysts was better than that achieved by the inactivated catalysts. Similar results were observed with the lab vanadium-contaminated catalyst. The light olefins selectivity of the catalyst was optimized when the vanadium Oxnum was close to 2 （VO）.

Influence of alkali metal doping on surface properties and catalytic activity/selectivity of CaO catalysts in oxidative coupling of methane

Surface properties （viz. surface area, basicity/base strength distribution, and crystal phases） of alkali metal doped CaO （alkali metal/Ca= 0.1 and 0.4） catalysts and their catalytic activity/selectivity in oxidative coupling of methane （OCM） to higher hydrocarbons at different reaction conditions （viz. temperature, 700 and 750 ℃; CH4/O2 ratio, 4.0 and 8.0 and space velocity, 5140-20550 cm^3 ·g^-1·h^-1） have been investigated. The influence of catalyst calcination temperature on the activity/selectivity has also been investigated. The surface properties （viz. surface area, basicity/base strength distribution） and catalytic activity/selectivity of the alkali metal doped CaO catalysts are strongly influenced by the alkali metal promoter and its concentration in the alkali metal doped CaO catalysts. An addition of alkali metal promoter to CaO results in a large decrease in the surface area but a large increase in the surface basicity （strong basic sites） and the C2＋ selectivity and yield of the catalysts in the OCM process. The activity and selectivity are strongly influenced by the catalyst calcination temperature. No direct relationship between surface basicity and catalytic activity/selectivity has been observed. Among the alkali metal doped CaO catalysts, Na-CaO （Na/Ca = 0.1, before calcination） catalyst （calcined at 750 ℃）, showed best performance （C2＋ selectivity of 68.8% with 24.7% methane conversion）, whereas the poorest performance was shown by the Rb-CaO catalyst in the OCM process.

Osteoclast-derived microRNA-containing exosomes selectively inhibit osteoblast activity

With the support by the National Natural Science Foundation of China and National Basic Research Program of China,the research team led by Prof.Li Yingxian(李英贤)at the State Key Laboratory of Space Medicine Fundamentals and Application,China Astronaut Research and Training Center,discovered that osteoclast-derived microRNA-containing exosomes selectively inhibited osteoblast activity,which was pub-

Identification of hydrazone moiety-bearing aminopyrimidines as potent antitumor agents with selective inhibition of gefitinib-resistant H1975 cancer cells

Based on our previous work,a series of hydrazone moiety-bearing aminopyrimidines were synthesized.The compounds were evaluated for inhibitory activities against EGFRT790M/L858 R and antiproliferative activities against H1975 and A549 NSCLC cell lines harboring different forms of EGFR.Compounds 7f and7 k exhibited potent and selective activity in inhibition of gefitinib-resistant H1975 cancer cells（IC50;0.45,0.2μmol/L） while were much less active on A549 cancer cells（IC50;52.83,〉100μmol/L）.Both compounds could be served as promising lead compounds for further investigation.

Why 90%of clinical drug development fails and how to improve it?

Ninety percent of clinical drug development fails despite implementation of many successful strategies,which raised the question whether certain aspects in target validation and drug optimization are overlooked?Current drug optimization overly emphasizes potency/specificity using structure-activityrelationship(SAR)but overlooks tissue exposure/selectivity in disease/normal tissues using structure-tissue exposure/selectivity—relationship(STR),which may mislead the drug candidate selection and impact the balance of clinical dose/efficacy/toxicity.We propose structure-tissue exposure/selectivity—activity relationship(STAR)to improve drug optimization,which classifies drug candidates based on drug’s potency/selectivity,tissue exposure/selectivity,and required dose for balancing clinical efficacy/toxicity.ClassⅠdrugs have high specificity/potency and high tissue exposure/selectivity,which needs low dose to achieve superior clinical efficacy/safety with high success rate.ClassⅡdrugs have high specificity/potency and low tissue exposure/selectivity,which requires high dose to achieve clinical efficacy with high toxicity and needs to be cautiously evaluated.ClassⅢdrugs have relatively low(adequate)specificity/potency but high tissue exposure/selectivity,which requires low dose to achieve clinical efficacy with manageable toxicity but are often overlooked.ClassⅣdrugs have low specificity/potency and low tissue exposure/selectivity,which achieves inadequate efficacy/safety,and should be terminated early.STAR may improve drug optimization and clinical studies for the success of clinical drug development.

Virus-inspired surface-nanoengineered antimicrobial liposome:A potential system to simultaneously achieve high activity and selectivity

Enveloped viruses such as SARS-CoV-2 frequently have a highly infectious nature and are considered effective natural delivery systems exhibiting high efficiency and specificity.Since simultaneously enhancing the activity and selectivity of lipopeptides is a seemingly unsolvable problem for conventional chemistry and pharmaceutical approaches,we present a biomimetic strategy to construct lipopeptide-based mimics of viral architectures and infections to enhance their antimicrobial efficacy while avoiding side effects.Herein,a surface-nanoengineered antimicrobial liposome(SNAL)is developed with the morphological features of enveloped viruses,including a moderate size range,lipid-based membrane structure,and highly lipopeptide-enriched bilayer surface.The SNAL possesses virus-like infection to bacterial cells,which can mediate high-efficiency and high-selectivity bacteria binding,rapidly attack and invade bacteria via plasma membrane fusion pathway,and induce a local“burst”release of lipopeptide to produce irreversible damage of cell membrane.Remarkably,viral mimics are effective against multiple pathogens with low minimum inhibitory concentrations(1.6-6.3μg mL1),high bactericidal efficiency of>99%within 2 h,>10-fold enhanced selectivity over free lipopeptide,99.8%reduction in skin MRSA load after a single treatment,and negligible toxicity.This bioinspired design has significant potential to enhance the therapeutic efficacy of lipopeptides and may create new opportunities for designing next-generation antimicrobials.

Cross inhibition improves activity selection when switching incurs time costs

We consider a behavioural model of an animal choosing between two activities, based on positive feedback, and exa- mine the effect of introducing cross inhibition between the motivations for the two activities. While cross-inhibition has pre- viously been included in models of decision making, the question of what benefit it may provide to an animal＇s activity selection behaviour has not previously been studied. In neuroscience and in collective behaviour cross-inhibition, and other equivalent means of coupling evidence-accumulating pathways, have been shown to approximate statistically-optimal decision-making and to adaptively break deadlock, thereby improving decision performance. Switching between activities is an ongoing decision process yet here we also find that cross-inhibition robustly improves its efficiency, by reducing the frequency of costly switches between behaviours .

Observations of carbon–carbon coupling of 4,4''-dibromo-p-terphenyl on Cu(110) surface at molecular level

The carbon–carbon couplings of 4,4＇＇-dibromo-p-terphenyl（DBTP） on Cu（110） surface have been investigated at a single molecular level by scanning tunneling microscopy. After annealing at 353 K, a mixture of parallel non-organometallic and organometallic intermediates of DBTP molecules along the[1–10] direction of the surface has been observed. Further annealing at 393 K causes one group of molecules to form oligomers with para-para and para-meta motifs via Ullmann reaction and the other group of molecules to synthesize oligomers with meta-meta motifs via direct carbon–carbon coupling reaction. Statistical results directly reveal that the occurrence of reaction type is strongly related to the initial binding configuration of DBTP molecules.

Coupling effects of Zn single atom and high curvature supports for improved performance of CO_(2) reduction

Single-atom catalysts(SACs)have emerged as one of the most competitive catalysts toward a variety of important electrochemical reactions,thanks to their maximum atom economy,unique electronic and geometric structures.However,the role of SACs supports on the catalytic performance does not receive enough research attentions.Here,we report an efficient route for synthesis of single atom Zn loading on the N-doped carbon nano-onions(ZnN/CNO).ZnN/CNO catalysts show an excellent high selectivity for CO_(2) electro-reduction to CO with a Faradaic efficiency of CO(FECO)up to 97%at -0.47 V(vs.reversible hydrogen electrode,RHE)and remarkable durability without activity decay.To our knowledge,ZnN/CNO is the best activity for the Zn based catalysts up to now,and superior to single atom Zn loading on the two-dimensional planar and porous structure of graphene substrate,although the graphene with larger surface area.The exact role of such carbon nano-onions(CNO)support is studied systematically by coupling characterizations and electrochemistry with density functional theory(DFT)calculations,which have attributed such good performance to the increased curvature.Such increased curvature modifies the surface charge,which then changes the adsorption energies of key intermediates,and improves the selectivity for CO generation accordingly.

Active Disturbance Rejection Control for PMLM Servo System in CNC Machining

Uncertain friction is a key factor that influences the accuracy of servo system in CNC machine.In this paper,based on the principle of Active Disturbance Rejection Control(ADRC),a control method is proposed,where both the extended state observer(ESO) and the reduced order extended state observer(RESO) are used to estimate and compensate for the disturbance.The authors prove that both approaches ensure high accuracy in theory,and give the criterion for parameters selection.The authors also prove that ADRC with RESO performs better than that with ESO both in disturbance estimation and tracking error.The simulation results on CNC machine show the effectiveness and feasibility of our control approaches.