The Arabian-Nubian Shield(ANS)serves as a key geological archive,preserving the tectono-thermal evolution associated with the Rodinia breakup(∼900–800 Ma)and Gondwana formation(∼800–620 Ma).The Katherina Ring Comp...The Arabian-Nubian Shield(ANS)serves as a key geological archive,preserving the tectono-thermal evolution associated with the Rodinia breakup(∼900–800 Ma)and Gondwana formation(∼800–620 Ma).The Katherina Ring Complex(KRC),located in the Sinai Peninsula,Egypt(northern ANS),exemplifies continental growth through multistage magmatism and orogenesis,spanning the Tonian to Ediacaran periods(∼900–530 Ma).Despite its importance,debates persist regarding the nature,age,crustal characteristics,and magma source evolution of its constituent units.Situated in the northwestern part of the KRC,the Wadi Rofaiyed Cu deposit offers an exceptional natural laboratory for investigating continental crust formation during this interval,owing to its superb exposure and preservation.This study integrates detailed fieldwork,petrographic analyses,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon U-Pb-Lu-Hf isotopic data.It aims to(i)establish a robust chronological framework for the unmetamorphosed plutonic rocks of the KRC,(ii)advance the understanding of associated geodynamic processes,and(iii)elucidate the episodic magmatism events.The findings show that Wadi Rofaiyed juvenile crust developed in four main phases:(i)a subduction-accretionary phase(∼755 Ma)characterized by intense calc-alkaline magmatism,originating from the partial melting of mafic lower crust;(ii)a syn-collisional phase(∼630 Ma)occurred during the collision between the Saharan metacraton and the younger ANS crust,producing I-type granitoids formed through magma mixing and crustal anatexis;(iii)a post-collisional phase characterized by intermediate I-type(∼595 Ma)to felsic A-type alkaline magma(∼594 Ma),originated from the partial melting of the overthickened lower crust corresponding to lithospheric delamination;and(iv)an anorogenic phase(∼530 Ma)related to the final amalgamation of Greater Gondwana.Isotopic analyses across all four magmatic phases reveal low initial^(87)Sr/^(86)Sr(0.702648–0.703311)and positiveε_(Hf)(t)(+2.84 to+7.78)andε_(Nd)(t)(+2.61 to+5.21)values,consistent with lower crustal sources with depleted mantle-like signatures.The model ages(T_(DM2))for these magmatic rocks derived from zircon Hf(1.2–1.5 Ga)and whole-rock Nd isotopes(0.96–1.17 Ga)support a predominantly juvenile crustal origin.These findings underscore the multistage tectono-magmatic evolution of the northern ANS,advancing our understanding of obduction-accretion dynamics and crustal development during the Neoproterozoic.展开更多
In addition to syenite ring dykes and multiple alkaline granite stocks, the sub-volcanic Houshihushan alkaline ring complex near Shanhaiguan, Qinhuangdao City, contains cone-sheets of two types： a majority filled wit...In addition to syenite ring dykes and multiple alkaline granite stocks, the sub-volcanic Houshihushan alkaline ring complex near Shanhaiguan, Qinhuangdao City, contains cone-sheets of two types： a majority filled with granite porphyry and a minority filled with quartz syenite porphyry. Many cone sheets show evidence of multiple magma intrusion events. Some granite porphyry sheets＇ multiple chilled margins display magmatic roll structures indicating that turbulent magma flowed up the fractures. In one upward-closing cone-sheet K-feldspar phenocrysts floated up through fluid granite porphyry magma and became concentrated at the top providing direct evidence of shallow-level crystal fractionation, confirmed by published rock analyses. Accreted lapilli with K-feldspar crystal cores occur only in the inner parts of a minority of cone-sheets and field relationships indicate that they must have formed beneath the ground surface. Similar lapilli occur in erupted ignimbrites preserved in the collapsed caldera. Voids between lapilli in cone-sheets indicate the presence of volumes of gas below the surface that could have flowed upwards as fast-moving hot gas streams. We propose a mechanism of formation that began with subterranean magmatic rolls with K-feldspar crystal cores that formed on dyke walls, and became detached. Then they were caught up in rising gas streams and erupted at the surface. Thus accreted lapilli formed underground, were erupted along with blobs of fluid glass in escaping gases, and transported over the surface in nuées ardentes, to settle and cool as ignimbrite flows.展开更多
El-Kahfa complex locates at the intersection of Lat. 24°8′18″ N and Long. 34038′55″ E, South Eastern Desert of Egypt. It comprises an outer ring composed of alkaline syenites, ranging from barrento quartz-bea...El-Kahfa complex locates at the intersection of Lat. 24°8′18″ N and Long. 34038′55″ E, South Eastern Desert of Egypt. It comprises an outer ring composed of alkaline syenites, ranging from barrento quartz-bearing syenites, an inner ring which varies in composition from leucocratic to melanocratic syenites, and a central stock formed essentially of alkali gabbros. These alkali gabbros are cut by small bodies of alkaline syenites, which occasionally grade into nepheline syenites. The country rocks are represented mainly by metavolcanics and epidiorites. El-Kahfa syenites lack any primary hydrous mafic silicates indicating that their magma was anhydrous. Major and trace elements geochemistry of EI-Kahfa rocks reflects the crystallization of early plagioclase followed by Fe-Ti oxides. Salic members in the complex are co-magmatic and related to crystal liquid fractionation. The REE （rare earth elements）＇s tetrad is obvious on the primitive mantle normalized pattern of El-Kahfa rocks. The M-type tetrads clearly appear in the more evolved rocks. These tetrad effects are either a feature of magma-fluid system before crystallization or inherited from external fluid during or after the emplacement of the magma. Generally, El-Kahfa rocks parental magma was probably derived from Nb-enriched or at least under-plate mantle source within the continental East-Africa rift zone, where it may be subjected to minor contamination through their fractional crystallization.展开更多
The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co...The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.展开更多
The Zargat Na’am ring complex crops out 90 km NW of Shalatin City in the Southeastern Desert of Egypt. The ring complex forms a prominent ridge standing high above the surrounding mafic-ultramafic hills. It is cut by...The Zargat Na’am ring complex crops out 90 km NW of Shalatin City in the Southeastern Desert of Egypt. The ring complex forms a prominent ridge standing high above the surrounding mafic-ultramafic hills. It is cut by two sets of joints and faults which strike predominantly NNW-SSE and E-W, and is injected by dikes, porphyritic alkaline syenites, and felsite porphyries. It consists of alkali syenites, alkali quartz syenites, and peralkaline arfvedsonite-bearing granitic and pegmatitic dikes and sills. The complex is characterized locally by extreme enrichments in REEs, wolframite and rare, high field strength metals (HFSM), such as Zr and Nb. The highest concentrations ({1.5} wt% Zr, {0.25} wt% Nb, {0.6} wt% ∑REEs) occur in aegirine-albite aplites that formed around arfvedsonite pegmatites. Quartz-hosted melt inclusions in arfvedsonite granite and pegmatite provide unequivocal evidence that the peralkaline compositions and rare metal enrichments are primary magmatic features. Glass inclusions in quartz crystals also have high concentrations of incompatible trace elements including Nb (750×10+{-6}), Zr (2500×10+{-6}) and REEs (1450×10+{-6}). The REEs, Nb and Zr compositions of the aegirine-albite aplites plot along the same linear enrichment trends as the melt inclusions, and Y/Ho ratios mostly display unfractionated, near-chondritic values. The chemical and textural features of the aegirine-albite aplites are apparently resultant from rapid crystallization after volatile loss from a residual peralkaline granitic melt similar in composition to the melt inclusions.展开更多
New fieldwork, mineralogical and geochemical data and interpretations are presented for the rare-metal bearing A-type granites of the Aja intrusive complex(AIC) in the northern segment of the Arabian Shield. This comp...New fieldwork, mineralogical and geochemical data and interpretations are presented for the rare-metal bearing A-type granites of the Aja intrusive complex(AIC) in the northern segment of the Arabian Shield. This complex is characterized by discontinuous ring-shaped outcrops cut by later faulting. The A-type rocks of the AIC are late Neoproterozoic post-collisional granites, including alkali feldspar granite, alkaline granite and peralkaline granite. They represent the outer zones of the AIC, surrounding a core of older rocks including monzogranite, syenogranite and granophyre granite. The sharp contacts between A-type granites of the outer zone and the different granitic rocks of the inner zone suggest that the AIC was emplaced as different phases over a time interval, following complete crystallization of earlier batches. The A-type granites represent the late intrusive phases of the AIC, which were emplaced during tectonic extension, as shown by the emplacement of dykes synchronous with the granite emplacement and the presence of cataclastic features. The A-type granites consist of K-feldspars, quartz, albite, amphiboles and sodic pyroxene with a wide variety of accessory minerals, including Fe-Ti oxides, zircon, allanite, fluorite, monazite, titanite, apatite, columbite, xenotime and epidote. They are highly evolved(71.3–75.8 wt% SiO2) and display the typical geochemical characteristics of post-collisional, within-plate granites. They are rare-metal granites enriched in total alkalis, Nb, Zr, Y, Ga, Ta, REE with low CaO, MgO, Ba, and Sr. Eu-negative anomalies(Eu/Eu* = 0.17–0.37) of the A-type granites reflect extreme magmatic fractionation and perhaps the effects of late fluid-rock interactions. The chemical characteristics indicate that the A-type granites of the AIC represent products of extreme fractional crystallization involving alkali feldspar, quartz and, to a lesser extent, ferromagnesian minerals. The parent magma was derived from the partial melting of a juvenile crustal protolith with a mantle contribution. Accumulation of residual volatile-rich melt and exsolved fluids in the late stage of the magma evolution produced pegmatite and quartz veins that cut the peripheries of the AIC. Post-magmatic alteration related to the final stages of the evolution of the A-type granitic magma, indicated by alterations of sodic amphibole and sodic pyroxene, hematitization and partial albitization.展开更多
Photosynthesis in nature has been deemed as the most significant biochemical reaction,which maintains a relatively stable content of O_(2) and CO_(2) in the atmosphere.Herein,for a deeper comprehension of natural phot...Photosynthesis in nature has been deemed as the most significant biochemical reaction,which maintains a relatively stable content of O_(2) and CO_(2) in the atmosphere.Herein,for a deeper comprehension of natural photosynthesis,an artificial photosynthesis model reaction of photochemical CO_(2) to CO conversion(CO_(2)+2 H^(+)+2e^(-)→CO+H_(2)O)catalyzed by a homogeneous hexanuclear ring cobalt complex{K_(2)[CoO_(3)PCH_(2)N(CH_(2)CO_(2))_(2)]}_(6)(Co6 complex)is developed.Using the[Ru(bpy)_(3)]^(2+)as a photosensitizer and TEOA as a sacrificial electron donor,an optimal turnover frequency of 503.3 h^(‒1) and an apparent quantum efficiency of 0.81%are obtained.The good photocatalytic CO_(2) reduction performance is attributed to the efficient electron transfer between Co6 complex and[Ru(bpy)_(3)]^(2+),which boosts the photogenerated carriers separation of the photosensitizer.It is confirmed by the j‐V curves,light‐assisted UV‐vis curves,steady‐state photoluminescence spectra and real‐time laser flash photolysis experiments.In addition,the proposed catalytic mechanism for CO_(2) reduction reaction catalyzed by the Co6 complex is explored by the potassium thiocyanate poison experiment,Pourbaix diagram and density functional theory calculations.展开更多
Two types of bifunctional bis（salicylaldimine） ligands（syn-L and anti-L） were designed and synthesized to support bimetallic aluminum complexes. Owing to the rigid anthracene skeleton, syn-L and anti-L successfull...Two types of bifunctional bis（salicylaldimine） ligands（syn-L and anti-L） were designed and synthesized to support bimetallic aluminum complexes. Owing to the rigid anthracene skeleton, syn-L and anti-L successfully locked two Al centers in close proximity（syn-Al2） and far apart（anti-Al2）, respectively. The distance between two Al centers in syn-Al2 was defined by X-ray diffraction as 6.665 ？, which is far shorter than that in anti-Al2. In the presence of stoichiometrical Bn OH, syn-Al2 and anti-Al2 were both efficient for ring-opening polymerization（ROP） of rac-LA with the former being more active. In the presence of excess Bn OH, syn-Al2 showed an efficient and immortal feature, consistent with high conversions, matched Mns, narrow molecular weight distributions and end group fidelity, while anti-Al2 had a much lower activity or even became entirely inactive due to rapid decomposition, indicated by in situ ～1H-NMR experiments of Al complexes with Bn OH.展开更多
A series of bis-ligated zinc complexes supported by Schitt base ligands were successfully synthesized and characterized by 1 H, 13C NMR, elemental analysis, and X-ray crystallography. These zinc complexes can be used ...A series of bis-ligated zinc complexes supported by Schitt base ligands were successfully synthesized and characterized by 1 H, 13C NMR, elemental analysis, and X-ray crystallography. These zinc complexes can be used as catalysts for the polymerization of rac-lactide in solution as well as in molten lactide. The results show that all catalysts exhibited high catalytic activity and obtained moderate heterotactic PLAs with the expected molecular weight. Complex 1 can catalyze the polymerization of rac-lactide under controllable conditions with living and immortal character in toluene solution. In addition, the steric hindrance and electronic effects has a great influence on the catalytic activity and selectivity of catalysts.展开更多
Highly active calcium chloride（CaCl2） doped Zn-Co^Ⅲdouble metal-cyanide（Ca-DMC） catalysts were firstly reported.Ca-DMCs presented a very higher polymer yield（54 kg polymer/g catalyst） at relative low temperatur...Highly active calcium chloride（CaCl2） doped Zn-Co^Ⅲdouble metal-cyanide（Ca-DMC） catalysts were firstly reported.Ca-DMCs presented a very higher polymer yield（54 kg polymer/g catalyst） at relative low temperature（80-115℃） toward ringopening polymerization（ROP） of propylene oxide（PO） than did DMC catalysts without modification.展开更多
In this paper,ring-opening polymerization of trimethylene carbonate(TMC)with rare earth(Nd,Y,La)ρ-tert- butylcalix[n]arene(n=4,6,and 8)complexes as catalysts has been studied.Poly(trimethylene carbonate)(PTMC)with M_...In this paper,ring-opening polymerization of trimethylene carbonate(TMC)with rare earth(Nd,Y,La)ρ-tert- butylcalix[n]arene(n=4,6,and 8)complexes as catalysts has been studied.Poly(trimethylene carbonate)(PTMC)with M_v of 21,400 was produced by bulk polymerization under the conditions as follows:[TMC]_0/[Nd](molar ratio)=1000,80℃, 8 h.Mechanism study reveals that the polymerization proceeds via a coordination mechanism.展开更多
In this paper, we report the preparation of a new tertrahydrosalen-stabilized yttrium complex which was employed as an initiator-precursor for the polymerization of ε-caprolactone （ε-CL） in the presence of NaBH4 t...In this paper, we report the preparation of a new tertrahydrosalen-stabilized yttrium complex which was employed as an initiator-precursor for the polymerization of ε-caprolactone （ε-CL） in the presence of NaBH4 to give interesting hydroxytelechelic poly（ε-caprolactone） （PCL）. The effect of [monomer]/[initiator] （[CL]/[I]）, temperature and time on the polymerization was investigated. It was found that under the condition： [CL]/[I] = 1200, 55℃, toluene： 0.5 mL, ε-CL： 0.5 mL, PCL with Mw = 32,600 and PDI = 1.47 was obtained.展开更多
novel complex composed of chitosan(CS) and neodymium(Nd ) was preparedand the ring opening polymerization of epichlorohydrin(ECH) with a new catalyticsystem comprising this new rare earth polymer complex(CS . Nd) has ...novel complex composed of chitosan(CS) and neodymium(Nd ) was preparedand the ring opening polymerization of epichlorohydrin(ECH) with a new catalyticsystem comprising this new rare earth polymer complex(CS . Nd) has been suc-cessfully carried out for the first time. It has been found that the new catalytic sys-tem composed of CS . Nd-AI (i-Bui,-methyl benzoxylate( Ⅲ) is an excellent cata-lyst for the polymerization of epichlorohydrin which shows a catalytic activity 60times higher tlian that of conventional rare earth catalyst. Under the following re-action conditions : Nd - 1 ×10￣(-6) mo1/g monomer, A1/Nd= 60 molar ratio , Ⅲ/A1=-0. 6 molar ratio, the monomer conversion and PECH molecular weight are as highas 92.9% and 28. 2 × 10￣5 respectively and the polymer prepared has a low crys-tallinity. The kinetics investigation revealed that the polymerization has a short in-duction period of several minutes and the rate of polymerization is of first orderwith respect to the monomer concentration and the catalyst concentration. The acti-vation energy of the polymerization reaction was found to be 25. 5 kJ/mol which islower than that of conimon rare earth catalvst.展开更多
The stability constants of some ternary mixed-ligand complexes, Pt(Phen)(CA)+, where Phen=1,10-phenanthroline and CA- =carboxylate, were determined by means of potentiometric pH titration in aqueous solutions(I=0.1 mo...The stability constants of some ternary mixed-ligand complexes, Pt(Phen)(CA)+, where Phen=1,10-phenanthroline and CA- =carboxylate, were determined by means of potentiometric pH titration in aqueous solutions(I=0.1 mol/L, KNO 3; 25 ℃), and the stability of them was compared with that of the corresponding binary complexes. It was revealed that the ternary complexes containing phenylalkane carboxylates ligands(PCA-) are much more stable than those formed with formate and acetate. The results indicate that there exist the intramolecular aromatic-ring interactions between the phenanthroline ring of Phen and the phenyl moiety of ligand PCA- in the ternary mixed-ligand Pt(Phen)(PCA)- complexes. The extent of the stacking interactions, which depends on the number of methylene groups between the phenyl moieties and the coordinated phenylalkane carboxylate groups, was calculated. The best-fitted stack was obtained for the complexes with 2-phenylacetate and 3-phenylpropionate as the ligands.展开更多
Tetrahydrosalen ligand was employed in the synthesis of gadolinium complex. The ligand was deprotoned by LiBu, and the afforded lithium salt was reacted with anhydrous GdCl3 to produce the gadolinium complex through s...Tetrahydrosalen ligand was employed in the synthesis of gadolinium complex. The ligand was deprotoned by LiBu, and the afforded lithium salt was reacted with anhydrous GdCl3 to produce the gadolinium complex through salt metathesis. This complex was successfully used to initiate the ring-opening polymerization of ε-caprolactone. The initiation conditions in different temperature, monomer-to-initiator ratio and time were investigated. Under the condition： [ε-caprolactone]：[catalyst] = 600, 56 ℃, toluene： 2 ml, poly（ε-caprolactone） （PCL） with Mw = 11,2782 and PDI = 1.96 was achieved.展开更多
The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-,...The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-, in the form of a yellow-green crystalline solid in a yield of 94%. This two-core ruthenium complex is a selective catalyst for ring closing metathesis of unsubstituted terminal dienes. More importantly, no isomerized byproduct was observed for N-substrates when the two-core ruthenium complex was used as the catalyst at an elevated temperature（137 °C）, indicating that the complex is a chemo-selective catalyst for ring closing metathesis reactions.展开更多
Lanthanum complex supported by the heterocyclic Schiff-base ligand of N-(2-pyridyl)-3,5-di-tert-butyl-salicylaldimine was prepared and employed for the ring-opening polymerization(ROP)ofε-caprolactone(ε-CL).The poly...Lanthanum complex supported by the heterocyclic Schiff-base ligand of N-(2-pyridyl)-3,5-di-tert-butyl-salicylaldimine was prepared and employed for the ring-opening polymerization(ROP)ofε-caprolactone(ε-CL).The polymers obtained with this initiator showed a unimodal molecular weight distribution implied that only one active species was present.Mechanism study revealed that the polymerization proceeds via acyl-oxygen bond cleavage.展开更多
The Jabal Hadb Ad Dayheen granitic complex in central Saudi Arabia is an alkaline granitic ring complex associated with a collapsed caldera. It mainly consists of monzogranite in the center, biotite-hornblende porphyr...The Jabal Hadb Ad Dayheen granitic complex in central Saudi Arabia is an alkaline granitic ring complex associated with a collapsed caldera. It mainly consists of monzogranite in the center, biotite-hornblende porphyritic granite, and biotite-aegirine-riebeckite granite, intruded by some felsic and mafic dikes. The petrological and geochemical characteristics show that the granitic suites consist of metalminous-peralkaline A-type granites. The secondary ion mass spectrometry(SIMS) zircon U-Pb analysis yielded ^(206)Pb/^(238)U ages of 613.3 ± 8.1 – 603.8 ± 3.8, 602.4 ± 3.8, 596 ± 5.6 Ma for biotitehornblende porphyritic granite, microgranite, and biotite-aegirine-riebeckite granite, respectively. The trace element characteristics and positive ε_(Hf)(t) values(3.2–12.2) indicate that the granitic rocks of the Dayheen Ring Complex are mainly derived from the juvenile crust with the involvement of mantlederived materials. Combined with the regional tectonic evolution, the formation of the Dayheen Ring Complex mainly covered four periods:(1) subduction initiation and formation of arc terranes(870–620 Ma)—volcanic craters formed during this period provided the channel for alkaline complex intrusion;(2) collision between East and West Gondwana continents and formation of the north East African Orogen(640–613 Ma)—monzogranite stock at the center of the ring complex emplaced during this period;(3) post-collision extension and collapse(613–602 Ma)—red metaluminous biotite-hornblende porphyritic granite and microgranite sheets in the rim of the Dayheen Ring Complex emplaced during this period;(4) within-plate extension(602 – 545 Ma) —white peralkaline biotite-aegirine-riebeckite granite and plenty of felsic and mafic dikes in the rim mainly formed during this period. The granitic rocks of the Dayheen Ring Complex mainly formed during the transitional stage of post-collison to within-plate extension after the collision between East and West Gondwana continents, and part of them formed during the early stage of the within-plate extension. U, Th, Zr, Nb, and rare earth element mineralization mainly formed during the early stage of the last period, having a close relationship with the intrusion of white peralkaline biotite-aegirine-riebeckite granite.展开更多
Ring-opening polymerization of ε-caprolactone has been carried out by using rare earth Schiff base complexes： lanthanide tris（N-phenyl-3,5-di-t-butylsalicylaldiminato）s [Ln（OPBS）3] as single component catalyst f...Ring-opening polymerization of ε-caprolactone has been carried out by using rare earth Schiff base complexes： lanthanide tris（N-phenyl-3,5-di-t-butylsalicylaldiminato）s [Ln（OPBS）3] as single component catalyst for the first time. The influences of different rare earth elements, monomer and catalyst concentration as well as reaction time on the polymerization were investigated. Mechanism studies showed that monomer inserts into the active site with the acyl-oxygen bond scission rather than the break of alkyl-oxygen bond.展开更多
The asymmetric ring-opening of epoxides with dithiophosphorus acids catalyzed by a （salen）Ti（Ⅳ） complex formed in situ from the reaction of Ti（OPr-i）4 and the chiral Schiff base derived from （1R,2R）-（＋）-di...The asymmetric ring-opening of epoxides with dithiophosphorus acids catalyzed by a （salen）Ti（Ⅳ） complex formed in situ from the reaction of Ti（OPr-i）4 and the chiral Schiff base derived from （1R,2R）-（＋）-diaminocyclohexane was realized. The resulting products were obtained with low to good enantioselectivity （up to 73% ee）.展开更多
基金supported by the National Natural Science Foundation of China(No.92162103)the Natural Science Foundation of Hunan Province(No.2022JJ30699,No.2023JJ10064)the Science and Technology Innovation Program of Hunan Province(No.2021RC4055,No.2022RC1182).
文摘The Arabian-Nubian Shield(ANS)serves as a key geological archive,preserving the tectono-thermal evolution associated with the Rodinia breakup(∼900–800 Ma)and Gondwana formation(∼800–620 Ma).The Katherina Ring Complex(KRC),located in the Sinai Peninsula,Egypt(northern ANS),exemplifies continental growth through multistage magmatism and orogenesis,spanning the Tonian to Ediacaran periods(∼900–530 Ma).Despite its importance,debates persist regarding the nature,age,crustal characteristics,and magma source evolution of its constituent units.Situated in the northwestern part of the KRC,the Wadi Rofaiyed Cu deposit offers an exceptional natural laboratory for investigating continental crust formation during this interval,owing to its superb exposure and preservation.This study integrates detailed fieldwork,petrographic analyses,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon U-Pb-Lu-Hf isotopic data.It aims to(i)establish a robust chronological framework for the unmetamorphosed plutonic rocks of the KRC,(ii)advance the understanding of associated geodynamic processes,and(iii)elucidate the episodic magmatism events.The findings show that Wadi Rofaiyed juvenile crust developed in four main phases:(i)a subduction-accretionary phase(∼755 Ma)characterized by intense calc-alkaline magmatism,originating from the partial melting of mafic lower crust;(ii)a syn-collisional phase(∼630 Ma)occurred during the collision between the Saharan metacraton and the younger ANS crust,producing I-type granitoids formed through magma mixing and crustal anatexis;(iii)a post-collisional phase characterized by intermediate I-type(∼595 Ma)to felsic A-type alkaline magma(∼594 Ma),originated from the partial melting of the overthickened lower crust corresponding to lithospheric delamination;and(iv)an anorogenic phase(∼530 Ma)related to the final amalgamation of Greater Gondwana.Isotopic analyses across all four magmatic phases reveal low initial^(87)Sr/^(86)Sr(0.702648–0.703311)and positiveε_(Hf)(t)(+2.84 to+7.78)andε_(Nd)(t)(+2.61 to+5.21)values,consistent with lower crustal sources with depleted mantle-like signatures.The model ages(T_(DM2))for these magmatic rocks derived from zircon Hf(1.2–1.5 Ga)and whole-rock Nd isotopes(0.96–1.17 Ga)support a predominantly juvenile crustal origin.These findings underscore the multistage tectono-magmatic evolution of the northern ANS,advancing our understanding of obduction-accretion dynamics and crustal development during the Neoproterozoic.
基金financially supported by the National Nature Science Foundation of China (No. 41272079)
文摘In addition to syenite ring dykes and multiple alkaline granite stocks, the sub-volcanic Houshihushan alkaline ring complex near Shanhaiguan, Qinhuangdao City, contains cone-sheets of two types： a majority filled with granite porphyry and a minority filled with quartz syenite porphyry. Many cone sheets show evidence of multiple magma intrusion events. Some granite porphyry sheets＇ multiple chilled margins display magmatic roll structures indicating that turbulent magma flowed up the fractures. In one upward-closing cone-sheet K-feldspar phenocrysts floated up through fluid granite porphyry magma and became concentrated at the top providing direct evidence of shallow-level crystal fractionation, confirmed by published rock analyses. Accreted lapilli with K-feldspar crystal cores occur only in the inner parts of a minority of cone-sheets and field relationships indicate that they must have formed beneath the ground surface. Similar lapilli occur in erupted ignimbrites preserved in the collapsed caldera. Voids between lapilli in cone-sheets indicate the presence of volumes of gas below the surface that could have flowed upwards as fast-moving hot gas streams. We propose a mechanism of formation that began with subterranean magmatic rolls with K-feldspar crystal cores that formed on dyke walls, and became detached. Then they were caught up in rising gas streams and erupted at the surface. Thus accreted lapilli formed underground, were erupted along with blobs of fluid glass in escaping gases, and transported over the surface in nuées ardentes, to settle and cool as ignimbrite flows.
文摘El-Kahfa complex locates at the intersection of Lat. 24°8′18″ N and Long. 34038′55″ E, South Eastern Desert of Egypt. It comprises an outer ring composed of alkaline syenites, ranging from barrento quartz-bearing syenites, an inner ring which varies in composition from leucocratic to melanocratic syenites, and a central stock formed essentially of alkali gabbros. These alkali gabbros are cut by small bodies of alkaline syenites, which occasionally grade into nepheline syenites. The country rocks are represented mainly by metavolcanics and epidiorites. El-Kahfa syenites lack any primary hydrous mafic silicates indicating that their magma was anhydrous. Major and trace elements geochemistry of EI-Kahfa rocks reflects the crystallization of early plagioclase followed by Fe-Ti oxides. Salic members in the complex are co-magmatic and related to crystal liquid fractionation. The REE （rare earth elements）＇s tetrad is obvious on the primitive mantle normalized pattern of El-Kahfa rocks. The M-type tetrads clearly appear in the more evolved rocks. These tetrad effects are either a feature of magma-fluid system before crystallization or inherited from external fluid during or after the emplacement of the magma. Generally, El-Kahfa rocks parental magma was probably derived from Nb-enriched or at least under-plate mantle source within the continental East-Africa rift zone, where it may be subjected to minor contamination through their fractional crystallization.
基金the National Natural Science Foundation of China(52275378).
文摘The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.
文摘The Zargat Na’am ring complex crops out 90 km NW of Shalatin City in the Southeastern Desert of Egypt. The ring complex forms a prominent ridge standing high above the surrounding mafic-ultramafic hills. It is cut by two sets of joints and faults which strike predominantly NNW-SSE and E-W, and is injected by dikes, porphyritic alkaline syenites, and felsite porphyries. It consists of alkali syenites, alkali quartz syenites, and peralkaline arfvedsonite-bearing granitic and pegmatitic dikes and sills. The complex is characterized locally by extreme enrichments in REEs, wolframite and rare, high field strength metals (HFSM), such as Zr and Nb. The highest concentrations ({1.5} wt% Zr, {0.25} wt% Nb, {0.6} wt% ∑REEs) occur in aegirine-albite aplites that formed around arfvedsonite pegmatites. Quartz-hosted melt inclusions in arfvedsonite granite and pegmatite provide unequivocal evidence that the peralkaline compositions and rare metal enrichments are primary magmatic features. Glass inclusions in quartz crystals also have high concentrations of incompatible trace elements including Nb (750×10+{-6}), Zr (2500×10+{-6}) and REEs (1450×10+{-6}). The REEs, Nb and Zr compositions of the aegirine-albite aplites plot along the same linear enrichment trends as the melt inclusions, and Y/Ho ratios mostly display unfractionated, near-chondritic values. The chemical and textural features of the aegirine-albite aplites are apparently resultant from rapid crystallization after volatile loss from a residual peralkaline granitic melt similar in composition to the melt inclusions.
基金The authors extend their appreciation to the Deanship of Scientific ResearchHa’il Universityfor supporting this work through research project no.SCB-0150175
文摘New fieldwork, mineralogical and geochemical data and interpretations are presented for the rare-metal bearing A-type granites of the Aja intrusive complex(AIC) in the northern segment of the Arabian Shield. This complex is characterized by discontinuous ring-shaped outcrops cut by later faulting. The A-type rocks of the AIC are late Neoproterozoic post-collisional granites, including alkali feldspar granite, alkaline granite and peralkaline granite. They represent the outer zones of the AIC, surrounding a core of older rocks including monzogranite, syenogranite and granophyre granite. The sharp contacts between A-type granites of the outer zone and the different granitic rocks of the inner zone suggest that the AIC was emplaced as different phases over a time interval, following complete crystallization of earlier batches. The A-type granites represent the late intrusive phases of the AIC, which were emplaced during tectonic extension, as shown by the emplacement of dykes synchronous with the granite emplacement and the presence of cataclastic features. The A-type granites consist of K-feldspars, quartz, albite, amphiboles and sodic pyroxene with a wide variety of accessory minerals, including Fe-Ti oxides, zircon, allanite, fluorite, monazite, titanite, apatite, columbite, xenotime and epidote. They are highly evolved(71.3–75.8 wt% SiO2) and display the typical geochemical characteristics of post-collisional, within-plate granites. They are rare-metal granites enriched in total alkalis, Nb, Zr, Y, Ga, Ta, REE with low CaO, MgO, Ba, and Sr. Eu-negative anomalies(Eu/Eu* = 0.17–0.37) of the A-type granites reflect extreme magmatic fractionation and perhaps the effects of late fluid-rock interactions. The chemical characteristics indicate that the A-type granites of the AIC represent products of extreme fractional crystallization involving alkali feldspar, quartz and, to a lesser extent, ferromagnesian minerals. The parent magma was derived from the partial melting of a juvenile crustal protolith with a mantle contribution. Accumulation of residual volatile-rich melt and exsolved fluids in the late stage of the magma evolution produced pegmatite and quartz veins that cut the peripheries of the AIC. Post-magmatic alteration related to the final stages of the evolution of the A-type granitic magma, indicated by alterations of sodic amphibole and sodic pyroxene, hematitization and partial albitization.
文摘Photosynthesis in nature has been deemed as the most significant biochemical reaction,which maintains a relatively stable content of O_(2) and CO_(2) in the atmosphere.Herein,for a deeper comprehension of natural photosynthesis,an artificial photosynthesis model reaction of photochemical CO_(2) to CO conversion(CO_(2)+2 H^(+)+2e^(-)→CO+H_(2)O)catalyzed by a homogeneous hexanuclear ring cobalt complex{K_(2)[CoO_(3)PCH_(2)N(CH_(2)CO_(2))_(2)]}_(6)(Co6 complex)is developed.Using the[Ru(bpy)_(3)]^(2+)as a photosensitizer and TEOA as a sacrificial electron donor,an optimal turnover frequency of 503.3 h^(‒1) and an apparent quantum efficiency of 0.81%are obtained.The good photocatalytic CO_(2) reduction performance is attributed to the efficient electron transfer between Co6 complex and[Ru(bpy)_(3)]^(2+),which boosts the photogenerated carriers separation of the photosensitizer.It is confirmed by the j‐V curves,light‐assisted UV‐vis curves,steady‐state photoluminescence spectra and real‐time laser flash photolysis experiments.In addition,the proposed catalytic mechanism for CO_(2) reduction reaction catalyzed by the Co6 complex is explored by the potassium thiocyanate poison experiment,Pourbaix diagram and density functional theory calculations.
基金financially supported by the National Natural Science Foundation of China (No. B040102)State Key Laboratory for Modification of Chemical Fibers and Polymer Materials (Donghua University) (No. LK1501)Department of Science and Technology of Qingdao and Shandong Province (Nos. 159181jch and 2015GGX107015)
文摘Two types of bifunctional bis（salicylaldimine） ligands（syn-L and anti-L） were designed and synthesized to support bimetallic aluminum complexes. Owing to the rigid anthracene skeleton, syn-L and anti-L successfully locked two Al centers in close proximity（syn-Al2） and far apart（anti-Al2）, respectively. The distance between two Al centers in syn-Al2 was defined by X-ray diffraction as 6.665 ？, which is far shorter than that in anti-Al2. In the presence of stoichiometrical Bn OH, syn-Al2 and anti-Al2 were both efficient for ring-opening polymerization（ROP） of rac-LA with the former being more active. In the presence of excess Bn OH, syn-Al2 showed an efficient and immortal feature, consistent with high conversions, matched Mns, narrow molecular weight distributions and end group fidelity, while anti-Al2 had a much lower activity or even became entirely inactive due to rapid decomposition, indicated by in situ ～1H-NMR experiments of Al complexes with Bn OH.
基金supported by National Natural Science Foundation of China(Nos.21271092,21171078,and 21401161)the Science Foundation of Gansu Province of China(No.1308RJ2A121)
文摘A series of bis-ligated zinc complexes supported by Schitt base ligands were successfully synthesized and characterized by 1 H, 13C NMR, elemental analysis, and X-ray crystallography. These zinc complexes can be used as catalysts for the polymerization of rac-lactide in solution as well as in molten lactide. The results show that all catalysts exhibited high catalytic activity and obtained moderate heterotactic PLAs with the expected molecular weight. Complex 1 can catalyze the polymerization of rac-lactide under controllable conditions with living and immortal character in toluene solution. In addition, the steric hindrance and electronic effects has a great influence on the catalytic activity and selectivity of catalysts.
基金the financial supports of the National Science Foundation of the People's Republic of China(No.20704034)Provincial Natural Science Foundation of Zhejiang(No.Y4090047)
文摘Highly active calcium chloride（CaCl2） doped Zn-Co^Ⅲdouble metal-cyanide（Ca-DMC） catalysts were firstly reported.Ca-DMCs presented a very higher polymer yield（54 kg polymer/g catalyst） at relative low temperature（80-115℃） toward ringopening polymerization（ROP） of propylene oxide（PO） than did DMC catalysts without modification.
基金This work was financially supported by the Special Fund for Major State Basic Research Project(G1999064801)the National Natural Science Foundation of China(Nos.20174033 and 20434020)
文摘In this paper,ring-opening polymerization of trimethylene carbonate(TMC)with rare earth(Nd,Y,La)ρ-tert- butylcalix[n]arene(n=4,6,and 8)complexes as catalysts has been studied.Poly(trimethylene carbonate)(PTMC)with M_v of 21,400 was produced by bulk polymerization under the conditions as follows:[TMC]_0/[Nd](molar ratio)=1000,80℃, 8 h.Mechanism study reveals that the polymerization proceeds via a coordination mechanism.
基金supports from National Natural Science Foundation(Nos.20674071, 20774078)the Special Funds for Major State Basic Research Projects(No.2005CB623802)
文摘In this paper, we report the preparation of a new tertrahydrosalen-stabilized yttrium complex which was employed as an initiator-precursor for the polymerization of ε-caprolactone （ε-CL） in the presence of NaBH4 to give interesting hydroxytelechelic poly（ε-caprolactone） （PCL）. The effect of [monomer]/[initiator] （[CL]/[I]）, temperature and time on the polymerization was investigated. It was found that under the condition： [CL]/[I] = 1200, 55℃, toluene： 0.5 mL, ε-CL： 0.5 mL, PCL with Mw = 32,600 and PDI = 1.47 was obtained.
文摘novel complex composed of chitosan(CS) and neodymium(Nd ) was preparedand the ring opening polymerization of epichlorohydrin(ECH) with a new catalyticsystem comprising this new rare earth polymer complex(CS . Nd) has been suc-cessfully carried out for the first time. It has been found that the new catalytic sys-tem composed of CS . Nd-AI (i-Bui,-methyl benzoxylate( Ⅲ) is an excellent cata-lyst for the polymerization of epichlorohydrin which shows a catalytic activity 60times higher tlian that of conventional rare earth catalyst. Under the following re-action conditions : Nd - 1 ×10￣(-6) mo1/g monomer, A1/Nd= 60 molar ratio , Ⅲ/A1=-0. 6 molar ratio, the monomer conversion and PECH molecular weight are as highas 92.9% and 28. 2 × 10￣5 respectively and the polymer prepared has a low crys-tallinity. The kinetics investigation revealed that the polymerization has a short in-duction period of several minutes and the rate of polymerization is of first orderwith respect to the monomer concentration and the catalyst concentration. The acti-vation energy of the polymerization reaction was found to be 25. 5 kJ/mol which islower than that of conimon rare earth catalvst.
基金Supported by the Foundation of Academ y L eader of Zhejiang Gongshang U niversity(No.19972 0 0 2 )
文摘The stability constants of some ternary mixed-ligand complexes, Pt(Phen)(CA)+, where Phen=1,10-phenanthroline and CA- =carboxylate, were determined by means of potentiometric pH titration in aqueous solutions(I=0.1 mol/L, KNO 3; 25 ℃), and the stability of them was compared with that of the corresponding binary complexes. It was revealed that the ternary complexes containing phenylalkane carboxylates ligands(PCA-) are much more stable than those formed with formate and acetate. The results indicate that there exist the intramolecular aromatic-ring interactions between the phenanthroline ring of Phen and the phenyl moiety of ligand PCA- in the ternary mixed-ligand Pt(Phen)(PCA)- complexes. The extent of the stacking interactions, which depends on the number of methylene groups between the phenyl moieties and the coordinated phenylalkane carboxylate groups, was calculated. The best-fitted stack was obtained for the complexes with 2-phenylacetate and 3-phenylpropionate as the ligands.
基金The authors acknowledge the financial supports from National Nature Science Foundation（Nos. 20674071, 20774078 and 20434020） ；the Special Funds for Major State Basic Research Projects （No.2005CB623802）.
文摘Tetrahydrosalen ligand was employed in the synthesis of gadolinium complex. The ligand was deprotoned by LiBu, and the afforded lithium salt was reacted with anhydrous GdCl3 to produce the gadolinium complex through salt metathesis. This complex was successfully used to initiate the ring-opening polymerization of ε-caprolactone. The initiation conditions in different temperature, monomer-to-initiator ratio and time were investigated. Under the condition： [ε-caprolactone]：[catalyst] = 600, 56 ℃, toluene： 2 ml, poly（ε-caprolactone） （PCL） with Mw = 11,2782 and PDI = 1.96 was achieved.
基金Supported by the National Natural Science Foundation of China(No.20872108)
文摘The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-, in the form of a yellow-green crystalline solid in a yield of 94%. This two-core ruthenium complex is a selective catalyst for ring closing metathesis of unsubstituted terminal dienes. More importantly, no isomerized byproduct was observed for N-substrates when the two-core ruthenium complex was used as the catalyst at an elevated temperature（137 °C）, indicating that the complex is a chemo-selective catalyst for ring closing metathesis reactions.
文摘Lanthanum complex supported by the heterocyclic Schiff-base ligand of N-(2-pyridyl)-3,5-di-tert-butyl-salicylaldimine was prepared and employed for the ring-opening polymerization(ROP)ofε-caprolactone(ε-CL).The polymers obtained with this initiator showed a unimodal molecular weight distribution implied that only one active species was present.Mechanism study revealed that the polymerization proceeds via acyl-oxygen bond cleavage.
文摘The Jabal Hadb Ad Dayheen granitic complex in central Saudi Arabia is an alkaline granitic ring complex associated with a collapsed caldera. It mainly consists of monzogranite in the center, biotite-hornblende porphyritic granite, and biotite-aegirine-riebeckite granite, intruded by some felsic and mafic dikes. The petrological and geochemical characteristics show that the granitic suites consist of metalminous-peralkaline A-type granites. The secondary ion mass spectrometry(SIMS) zircon U-Pb analysis yielded ^(206)Pb/^(238)U ages of 613.3 ± 8.1 – 603.8 ± 3.8, 602.4 ± 3.8, 596 ± 5.6 Ma for biotitehornblende porphyritic granite, microgranite, and biotite-aegirine-riebeckite granite, respectively. The trace element characteristics and positive ε_(Hf)(t) values(3.2–12.2) indicate that the granitic rocks of the Dayheen Ring Complex are mainly derived from the juvenile crust with the involvement of mantlederived materials. Combined with the regional tectonic evolution, the formation of the Dayheen Ring Complex mainly covered four periods:(1) subduction initiation and formation of arc terranes(870–620 Ma)—volcanic craters formed during this period provided the channel for alkaline complex intrusion;(2) collision between East and West Gondwana continents and formation of the north East African Orogen(640–613 Ma)—monzogranite stock at the center of the ring complex emplaced during this period;(3) post-collision extension and collapse(613–602 Ma)—red metaluminous biotite-hornblende porphyritic granite and microgranite sheets in the rim of the Dayheen Ring Complex emplaced during this period;(4) within-plate extension(602 – 545 Ma) —white peralkaline biotite-aegirine-riebeckite granite and plenty of felsic and mafic dikes in the rim mainly formed during this period. The granitic rocks of the Dayheen Ring Complex mainly formed during the transitional stage of post-collison to within-plate extension after the collision between East and West Gondwana continents, and part of them formed during the early stage of the within-plate extension. U, Th, Zr, Nb, and rare earth element mineralization mainly formed during the early stage of the last period, having a close relationship with the intrusion of white peralkaline biotite-aegirine-riebeckite granite.
基金This work was financially supported by the Key Program of National Natural Science Foundation of China(No.G 20434020)the Special Funds for Major Basic Research Projects(No.G 2005 CB623802)the Committee of Science and Technology of Zhejiang Province.
文摘Ring-opening polymerization of ε-caprolactone has been carried out by using rare earth Schiff base complexes： lanthanide tris（N-phenyl-3,5-di-t-butylsalicylaldiminato）s [Ln（OPBS）3] as single component catalyst for the first time. The influences of different rare earth elements, monomer and catalyst concentration as well as reaction time on the polymerization were investigated. Mechanism studies showed that monomer inserts into the active site with the acyl-oxygen bond scission rather than the break of alkyl-oxygen bond.
基金the National Natural Science Foundation of China(No.20472033)the Ph.D Programs of Ministry of Education of China for generous financial support for our programs.
文摘The asymmetric ring-opening of epoxides with dithiophosphorus acids catalyzed by a （salen）Ti（Ⅳ） complex formed in situ from the reaction of Ti（OPr-i）4 and the chiral Schiff base derived from （1R,2R）-（＋）-diaminocyclohexane was realized. The resulting products were obtained with low to good enantioselectivity （up to 73% ee）.
