AIM:To investigate the prevalence of clinically unrecognized mitral regurgitation(MR) in lone atrial fibrillation(AF).METHODS:We studied the prevalence and severity of MR by transesophageal echocardiography(TEE) in pa...AIM:To investigate the prevalence of clinically unrecognized mitral regurgitation(MR) in lone atrial fibrillation(AF).METHODS:We studied the prevalence and severity of MR by transesophageal echocardiography(TEE) in patients with "lone" AF as compared to a matched cohort of patients in normal sinus rhythm(NSR) undergoing TEE for other indications besides recognized valvular heart disease.RESULTS:A total of 157 subjects(57 in the AF group and 100 in the NSR group) with structurally normal cardiac valves were included in the study.In the AF group,moderate MR or more was noted in 66% of thepatients,mild MR in 18%,trace or no MR in 16%.In the control group,moderate MR was noted in 6% of patients,mild MR 31%,trace or no MR in 63 % of patients.Moderate MR or greater was significantly more prevalent in the AF group compared to the NSR group(66% vs 6%,P < 0.0001).CONCLUSION:Clinically unrecognized moderate MR is prevalent in "lone" AF-either as an etiologic factor leading to "lone" AF or developing after onset of AF.展开更多
Herein,two antimony sulfates,named RbSb(SO_(4))_(2)(1)and CsSb(SO_(4))_(2)(2),have been successfully synthesized with the introduction of Sb^(3+)cation with stereochemically active lone pairs(SCALP)into sulfates by th...Herein,two antimony sulfates,named RbSb(SO_(4))_(2)(1)and CsSb(SO_(4))_(2)(2),have been successfully synthesized with the introduction of Sb^(3+)cation with stereochemically active lone pairs(SCALP)into sulfates by the conventional hydrothermal method.Both two compounds endow short ultraviolet(UV)absorption edges(281 nm and 278 nm,respectively)and large birefringence(0.171@546 nm and 0.174@546 nm,respectively),which means that they are promising short-wave UV optical materials.Interestingly,though both of the two compounds exhibit similar 1D chained structures,and possess the same functional moieties including SbO4 seesaws and SO4 tetrahedral groups,they exhibit significantly opposite macroscopic symmetries,i.e.,compound 1 crystallizes in a centrosymmetric(CS)manner(P2_(1)/n)and compound 2 in a noncentrosymmetric(NCS)manner(P2_(1)2_(1)2_(1)),due to the size of cations[r(Rb+)=1.56 A˚,r(Cs+)=1.67 A˚]affects the orientation of SCALP of the adjacent Sb^(3+).展开更多
The stereochemically active lone pairs around post-transition metal atoms play an important role in determining distorted lattice structure and optical response.The lone pair electrons are characterized by crystal orb...The stereochemically active lone pairs around post-transition metal atoms play an important role in determining distorted lattice structure and optical response.The lone pair electrons are characterized by crystal orbitals,electron localization function(ELF)and partial density of states(PDOS).Birefringence is evaluated by means of a Born effective charge approach based on modern polarization theory.The origin of the different responses of birefringence and second-harmonic generation(SHG)is explored,as well as the effect of spin-orbit coupling(SOC)on the band structure and optical properties is explored.The study of this paper can help to deeply understand the lone pairs and their contribution to optical property.展开更多
An organic-inorganic hybrid antimony(Ⅲ)oxalate(C_(5)H_(6)ON)_(2)[Sb_(2)O(C_(2)O_(4))_(3)]has been successfully obtained by simultaneous combination of a-conjugated 4-hydroxypyridine and(C_(2)O_(4))^(2-)group with ste...An organic-inorganic hybrid antimony(Ⅲ)oxalate(C_(5)H_(6)ON)_(2)[Sb_(2)O(C_(2)O_(4))_(3)]has been successfully obtained by simultaneous combination of a-conjugated 4-hydroxypyridine and(C_(2)O_(4))^(2-)group with stereochemical active Sb(Ⅲ)cation.The compound features a layered structure,and the equatorial planes of SbO6 units,π-conjugated(C_(2)O_(4))^(2-)and(C5H6ON)+groups are closer to a planar arrangement,representing strong structural anisotropy that favors a large birefringence.As expected,(C_(5)H_(6)ON)_(2)[Sb_(2)O(C_(2)O_(4))_(3)]exhibits a large birefringence of 0.279 at 546 nm.Structural and theoretical analyses indicate that the combination of multipleπ-conjugated units is a feasible approach for designing and exploring new superior birefringent materials.展开更多
Drainage divides along a southern Laramie Range crest area and in the nearby southeast Wyoming Gangplank area (as observed on detailed topographic maps) suggest present-day drainage routes in the Cheyenne Tablelands r...Drainage divides along a southern Laramie Range crest area and in the nearby southeast Wyoming Gangplank area (as observed on detailed topographic maps) suggest present-day drainage routes in the Cheyenne Tablelands region originated as headward erosion of south-oriented valleys (now the downstream Lodgepole, Crow, and Lone Tree Creek valleys) from an actively eroding northeast-oriented South Platte River valley captured flood flow in the south half of a large east-oriented anastomosing channel complex while headward erosion of a north-oriented valley (now the downstream Horse Creek valley) from the southeast-oriented North Platte River valley captured the north half of the same large anastomosing channel complex. The Gangplank, which today serves as a low gradient ramp of Tertiary Ogallala Formation sediments leading from the Great Plains to the Laramie Range erosion surface, is located along the Crow Creek-Lone Tree Creek drainage divide and low points along that divide (referred to here as divide crossings) suggest, prior to headward erosion of what is now its south-oriented downstream Lone Tree Creek valley, upstream east-oriented Lone Tree Creek drainage routes were intertwined with east-oriented Crow Creek drainage routes, which today flow much further in an east direction (than east-oriented upstream Lone Tree Creek drainage routes) before also turning in a south direction to reach the South Platte River. The ability of the commonly accepted regional geomorphology paradigm to explain this topographic map evidence is then compared with a fundamentally different and new regional geomorphology paradigm’s ability to explain the same evidence. While both paradigms offer possible explanations the new paradigm, which requires headward erosion of the valleys to have occurred as massive continental ice sheet melt water floods crossed the region, explains much more of the drainage system evidence and also permits much more detailed explanations.展开更多
Expanding the optical absorption range of photocatalysts is still a key endeavor in graphitic carbon nitride(g-C_(3)N_(4))studies.Here,we report on a novel thiophene group extending the optical property,which is assig...Expanding the optical absorption range of photocatalysts is still a key endeavor in graphitic carbon nitride(g-C_(3)N_(4))studies.Here,we report on a novel thiophene group extending the optical property,which is assigned to n-π^(*)electronic transitions involving the two lone pairs on sulfur(TLPS).The as-prepared samples,denoted as CN-ThAx(where x indicates the amount of ThA added,mg),showed an additional absorption above 500 nm as compared to pristine g-C_(3)N_(4).Further,the thiophene group enhanced charge carrier separation to suppress e‒/h+pair recombination.The experimental results suggest that the thiophene group can obstruct the polymerization of melem to generate a large plane,thus exposing the lone electron pairs on the sulfur.The photocatalytic activity was evaluated in the decomposition of bisphenol A and H2 evolution.Compared with g-C_(3)N_(4),the optimized CN-ThA_(30) sample led to a 6.6-and 2-fold enhancement of the degradation and H2 generation rates,respectively.The CN-ThA_(30) sample allowed for synchronous H2 production and BPA decomposition.展开更多
Background Growing epidemiologic evidence has indicated that genetics can predispose individuals to the occurrence of lone atrial fibrillation （AF）. The angiotensin-converting enzyme 2 （ACE2） gene has been establi...Background Growing epidemiologic evidence has indicated that genetics can predispose individuals to the occurrence of lone atrial fibrillation （AF）. The angiotensin-converting enzyme 2 （ACE2） gene has been established to be associated with hypertension and left ventricular hypertrophy. The objective of our study was to investigate the association of ACE2 gene polymorphisms with lone AF. Methods A total of 265 consecutive lone AF patients and 289 healthy controls were successfully investigated. The polymorphisms rs2106809 and rs2285666 were genotyped by polymerase chain reaction （PCR） and direct sequencing. A Logistic regression model was used to determine the odds ratio （OR） and 95% confidence intervals （CO of variations of ACE2 for lone AF. Results The T allele of rs2106809 conferred an increased risk for lone AF （OR 1.24, 95% CI 1.01-1.52, P=0.03） in males after adjustment for conventional risk factors. SNP at rs2285666 in males was not significantly different between AF patients and controls. No association was found between the two polymorphisms in the female population with lone AF. After （36.3±4.5） months of follow-up, the end point data were obtained： death （cardiac and noncardiac）, ischemic stroke, and heart failure. In the male subgroup, the associations between rs2106809 T male carriers and combined end points including ischemic stroke, heart failure, and death in our study were of significance （OR 3.6, 95% CI 1.0-13.1, P=-0.04）. Conclusions The results indicate that polymorphism at ACE2 gene is associated with male lone AF in a Chinese Han population. Lone AF males who c.arrv the. rs2106809T alle.le, are. associate.d with adverse cardiac, e.ve.nts展开更多
It has been demonstrated that intermolecular interaction,crucial in a plenty of chemical and physical processes,may vary in the presence of metal surface.However,such modification is yet to be quantitatively revealed....It has been demonstrated that intermolecular interaction,crucial in a plenty of chemical and physical processes,may vary in the presence of metal surface.However,such modification is yet to be quantitatively revealed.Here,we present a systematical density functional theory study on adsorbed bis（para-pyridyl）acetylene（BPPA） tetramer on Au（111） surface.We observed unusually high electron density between two head-to-head N atoms,an intermolecular ＂non-bonded＂ region,in adsorbed BPPA tetramer.This exceptional electron density originates from the wavefunction hybridization of the two compressed N lone-electron-pair states of two BPPA,as squeezed by a newly revealed N-Au-N threecenter bonding.This bond,together with the minor contribution from N...H-C intermolecular hydrogen bonding,shortens the N-N distance from over 4 A to 3.30 A and offers an attractive lateral interacting energy of 0.60 eV,effectively to a surface-confined in-plane pressure.The overlapped non-bonding vvavefunction hybridization arising from the effective pressure induced by the N-Au-N three-center bonding,as not been fully recognized in earlier studies,was manifested in non-contact Atomic Force Microscopy.展开更多
Various bond modes of the M-C（C5 ring） exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the ...Various bond modes of the M-C（C5 ring） exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the C5 ring.The tin（Ⅱ） metallocene complexes LSn R（L = HC[CMe（N-2,6-iPr2C6H3）]2,R = cyclopentadienyl,C5H5（1）; indenyl,C9H7（2）; fluorenyl,C（13）H9（3）） stabilized by the β-diketiminato ligand were prepared and utilized in the study on their solid and solution state structures.X-ray single-crystal diffraction data revealed an η~1-mode of the Sn-C（C5 ring） bond in each 1~3.However,the room temperature ~1H NMR spectral studies disclosed such a fluxional bonding mode in solution.The 119 Sn NMR studies suggested a quadruple coordination nature of the Sn center in 1 while the triple coordination manner was for the Sn atom in both 2 and 3.Then the variable-temperature（25~–75 ℃） ~1H NMR spectral studies for each 1~3 were performed,which detected the relaxation state structures of 1~3 at lower temperature.All of these results indicate a stereochemical activity of the lone electron pairs at the tin（Ⅱ） atom that definitely has an electronic interaction with the 6 p-electrons of the C5 ring.The observed Sn-C（C5 ring） bond modes appear influenced by either the metallocene size or the compound state existed.展开更多
First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the gen...First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.展开更多
根据GenBank报道的谷氨酸棒杆菌ATCC13032序列,设计并合成一对引物,获得了全长argB基因片段.将其克隆到pGEM T Easy载体中,经测序鉴定后,以其为DIG标记探针,通过SouthernBlot分析钝齿棒杆菌A.S1.542与谷氨酸棒杆菌ATCC13032,argB基因核...根据GenBank报道的谷氨酸棒杆菌ATCC13032序列,设计并合成一对引物,获得了全长argB基因片段.将其克隆到pGEM T Easy载体中,经测序鉴定后,以其为DIG标记探针,通过SouthernBlot分析钝齿棒杆菌A.S1.542与谷氨酸棒杆菌ATCC13032,argB基因核苷酸同源性高达99%,氨基酸序列95%相同.展开更多
Although fluorobis(phenylsulfonyl)methane(FBSM)and its cyclic analog 2-fluoro-1,3-benzodithiole-1,1,3,3-tetraoxide(FBDT)possess similar physicochemical properties,Shibata et al.found that FBSM failed to undergo nucleo...Although fluorobis(phenylsulfonyl)methane(FBSM)and its cyclic analog 2-fluoro-1,3-benzodithiole-1,1,3,3-tetraoxide(FBDT)possess similar physicochemical properties,Shibata et al.found that FBSM failed to undergo nucleophilic monofluoromethylation of aldehydes regardless of the reaction conditions at-tempted(using various organic and inorganic bases).However,it was later discovered by Hu et al.that the nucleophilic monofluoromethylation could be accomplished by employing lithium hexamethyldisi-lazide(LiHMDS)as a base.Herein,we present an in-depth computational investigation into the intrigu-ing effects of reagent structure and bases on the nucleophilic monofluoromethylation of aldehydes.The computations reveal the 1,4-diazabicyclo[2.2.2]octane(DABCO)catalyzed nucleophilic monofluoromethy-lation of benzaldehyde with acyclic FBSM is a thermodynamically unfavorable process mainly due to the destabilizing O···O lone pair repulsions in FBSM product,whereas such repulsion could be largely avoided in FBDT product because of its constrained five-membered ring structure.Employing LiHMDS as a base can not only facilitate the nucleophilic monofluoromethylation via Li–O interactions but also render the monofluoromethylation of benzaldehyde with FBSM thermodynamically favored.展开更多
In order to develop pure organic single-molecule white-light emitters(SMWLE),the oxidation of thianthrene(TA)was performed on sulfur atoms at different degrees to tune room temperature phosphorescence(RTP)emission.Wit...In order to develop pure organic single-molecule white-light emitters(SMWLE),the oxidation of thianthrene(TA)was performed on sulfur atoms at different degrees to tune room temperature phosphorescence(RTP)emission.With increasing degrees of oxidation from 1OTA,2OTA,3OTA,to 4OTA,monomeric and aggregative RTP emission was gradually suppressed,due to the gradual disappearance of lone pair electrons on sulfur atoms.Among these compounds,monomers and aggregates of 1OTA demonstrated a better intensity match between fluorescence and RTP.展开更多
Two isostructural tellurite phosphates Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)have been synthesized via hydrothermal method.Both of them crystalize in monoclinic space group C2/m(No.12).For Ni_(...Two isostructural tellurite phosphates Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)have been synthesized via hydrothermal method.Both of them crystalize in monoclinic space group C2/m(No.12).For Ni_(2)ZnTe^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4),a=19.3247(10),b=5.9697(3),c=4.7737(2)Å,β=103.637(5)°,V=535.18(5)Å^(3),Z=2,M_(r)=727.94,S=1.103,D_(c)=4.517 g·cm^(-3),μ(Mo Kα)=11.434 mm^(-1) and F(000)=672,the final R=0.0369and wR=0.1086 for 639 observed reflections with I>2σ(I).The crystal structure of Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)features a 3D framework composed of[Ni_(2)O_(2)(PO_(4))_(2)]^(6-)layers interconnected by[MTe_(2)O_(2)(OH)_(4)]^(2+)single chains.Different magnetic susceptibility results at low temperature of the two title compounds confirm that Zn(1)completely occupies the Ni(2)position but not partially substitutes both Ni(1)and Ni(2)position atoms.Additionally,the acentric TeO_(3)(OH)_(2) tetragonal pyramids are aligned in an antiparallel manner,resulting in the crystallization of centrosymmetric(C2/m)crystal structure instead of the non-centrosymmetric crystal structure.The investigation of the origin of centrosymmetric crystal structure with strong dipole moment units provides deeper understanding for future rational design for non-centrosymmetric crystal structure.展开更多
Catassembly is a new concept in molecular assembly that is analogous to catalysis in chemical synthesis. However, for most molecular-assembled processes, the catassembler contributions are rather inconspicuous due to ...Catassembly is a new concept in molecular assembly that is analogous to catalysis in chemical synthesis. However, for most molecular-assembled processes, the catassembler contributions are rather inconspicuous due to the low activation barriers. As a result, few systems dealing with the catassembly are available until now. In this paper, we report that naphthalene diimide coordination networks are formed under the catassembly of lone-pair-bearing catassemblers(e.g., N,N-dimethylacetamide, N-methylpyrrolidin-2-one). During such molecular assembly, a stable transition state between the electron-deficient naphthalene diimide tectons and catassemblers via the less common lone pair-π interactions was observed, which is supposed to play the key role in the enhancement of coordination abilities of organic tectons and thus formation of the final coordination networks.展开更多
Background The CHA 2 DS 2-VASc schema has recently been introduced to complement the CHADS2 score and improve the identification of atrial fibrillation （AF） patients at ＇truly low risk＇ for thromboembolism.We test...Background The CHA 2 DS 2-VASc schema has recently been introduced to complement the CHADS2 score and improve the identification of atrial fibrillation （AF） patients at ＇truly low risk＇ for thromboembolism.We tested the predictive ability of the CHA 2 DS 2-VASc,CHADS2 and van Walraven risk stratification schemes in a cohort of ＇lone＇ AF patients with a 12-year follow-up.Methods and Results We conducted a registry-based,observational cohort study of 345 patients initially diagnosed with ＇lone＇ AF between 1992 and 2007.At baseline,all patients had the CHADS2 and van Walraven scores of 0,and 262 （75.9%） had a CHA 2 DS 2VASc score=0.During follow-up （or within a year prior to stroke）,228 （66.1%）,234 （67.8%） and 150 patients （43.5%） retained the CHADS2,van Walraven and CHA 2 DS 2VASc scores of 0,respectively.The overall rate of ischemic stroke was 0.19 （95%CI：0.18-0.20） per 100 patient-years.In the multivariable analysis,only the CHA 2 DS 2-VASc score of 0 was significantly related to the absence of stroke （OR 5.1,95%CI：1.5-16.8,P=0.008）.Only the CHA 2 DS 2-VASc score had a significant prediction ability （c-statistic 0.72 [0.61-0.84],P=0.031）.Conclusions The CHA 2 DS 2-VASc score reliably identified the ＇lone＇ AF patients who were at ＇truly low risk＇ for thromboembolism,and was the only tested risk stratification scheme with a significant predictive ability for thromboembolism amongst lone AF patients.展开更多
文摘AIM:To investigate the prevalence of clinically unrecognized mitral regurgitation(MR) in lone atrial fibrillation(AF).METHODS:We studied the prevalence and severity of MR by transesophageal echocardiography(TEE) in patients with "lone" AF as compared to a matched cohort of patients in normal sinus rhythm(NSR) undergoing TEE for other indications besides recognized valvular heart disease.RESULTS:A total of 157 subjects(57 in the AF group and 100 in the NSR group) with structurally normal cardiac valves were included in the study.In the AF group,moderate MR or more was noted in 66% of thepatients,mild MR in 18%,trace or no MR in 16%.In the control group,moderate MR was noted in 6% of patients,mild MR 31%,trace or no MR in 63 % of patients.Moderate MR or greater was significantly more prevalent in the AF group compared to the NSR group(66% vs 6%,P < 0.0001).CONCLUSION:Clinically unrecognized moderate MR is prevalent in "lone" AF-either as an etiologic factor leading to "lone" AF or developing after onset of AF.
基金the National Natural Science Foundation of China(Nos.22122106,22071158,21971171)the Fundamental Research Funds from Sichuan University(No.2021SCUNL101).
文摘Herein,two antimony sulfates,named RbSb(SO_(4))_(2)(1)and CsSb(SO_(4))_(2)(2),have been successfully synthesized with the introduction of Sb^(3+)cation with stereochemically active lone pairs(SCALP)into sulfates by the conventional hydrothermal method.Both two compounds endow short ultraviolet(UV)absorption edges(281 nm and 278 nm,respectively)and large birefringence(0.171@546 nm and 0.174@546 nm,respectively),which means that they are promising short-wave UV optical materials.Interestingly,though both of the two compounds exhibit similar 1D chained structures,and possess the same functional moieties including SbO4 seesaws and SO4 tetrahedral groups,they exhibit significantly opposite macroscopic symmetries,i.e.,compound 1 crystallizes in a centrosymmetric(CS)manner(P2_(1)/n)and compound 2 in a noncentrosymmetric(NCS)manner(P2_(1)2_(1)2_(1)),due to the size of cations[r(Rb+)=1.56 A˚,r(Cs+)=1.67 A˚]affects the orientation of SCALP of the adjacent Sb^(3+).
基金supported by the National Natural Science Foundation of the People's Republic of China“Mechanistic study of the influence of ns^(2) cation intrinsic properties and coordination environment on birefringence and frequency doubling effects”(12264047),“The study of the mechanism of the influence of lead-oxygen polyhedra and their coordination environments on the gain of the frequency doubling effect”(11864040)Tianshan Talent Project of Xinjiang Uygur Autonomous Region of China“Design,synthesis and photofunctional study of novel rare earth phosphate materials”(2022TSYCJU0004)。
文摘The stereochemically active lone pairs around post-transition metal atoms play an important role in determining distorted lattice structure and optical response.The lone pair electrons are characterized by crystal orbitals,electron localization function(ELF)and partial density of states(PDOS).Birefringence is evaluated by means of a Born effective charge approach based on modern polarization theory.The origin of the different responses of birefringence and second-harmonic generation(SHG)is explored,as well as the effect of spin-orbit coupling(SOC)on the band structure and optical properties is explored.The study of this paper can help to deeply understand the lone pairs and their contribution to optical property.
基金supported by grants from the National Natural Science Foundation of China(22001142)Natural Science Foundation of Shandong Province(ZR2022MB093)+1 种基金Natural Science Foundation of Hebei Province(A2021208013)Hebei Province Department of Education Fund(QN2022149).
文摘An organic-inorganic hybrid antimony(Ⅲ)oxalate(C_(5)H_(6)ON)_(2)[Sb_(2)O(C_(2)O_(4))_(3)]has been successfully obtained by simultaneous combination of a-conjugated 4-hydroxypyridine and(C_(2)O_(4))^(2-)group with stereochemical active Sb(Ⅲ)cation.The compound features a layered structure,and the equatorial planes of SbO6 units,π-conjugated(C_(2)O_(4))^(2-)and(C5H6ON)+groups are closer to a planar arrangement,representing strong structural anisotropy that favors a large birefringence.As expected,(C_(5)H_(6)ON)_(2)[Sb_(2)O(C_(2)O_(4))_(3)]exhibits a large birefringence of 0.279 at 546 nm.Structural and theoretical analyses indicate that the combination of multipleπ-conjugated units is a feasible approach for designing and exploring new superior birefringent materials.
文摘Drainage divides along a southern Laramie Range crest area and in the nearby southeast Wyoming Gangplank area (as observed on detailed topographic maps) suggest present-day drainage routes in the Cheyenne Tablelands region originated as headward erosion of south-oriented valleys (now the downstream Lodgepole, Crow, and Lone Tree Creek valleys) from an actively eroding northeast-oriented South Platte River valley captured flood flow in the south half of a large east-oriented anastomosing channel complex while headward erosion of a north-oriented valley (now the downstream Horse Creek valley) from the southeast-oriented North Platte River valley captured the north half of the same large anastomosing channel complex. The Gangplank, which today serves as a low gradient ramp of Tertiary Ogallala Formation sediments leading from the Great Plains to the Laramie Range erosion surface, is located along the Crow Creek-Lone Tree Creek drainage divide and low points along that divide (referred to here as divide crossings) suggest, prior to headward erosion of what is now its south-oriented downstream Lone Tree Creek valley, upstream east-oriented Lone Tree Creek drainage routes were intertwined with east-oriented Crow Creek drainage routes, which today flow much further in an east direction (than east-oriented upstream Lone Tree Creek drainage routes) before also turning in a south direction to reach the South Platte River. The ability of the commonly accepted regional geomorphology paradigm to explain this topographic map evidence is then compared with a fundamentally different and new regional geomorphology paradigm’s ability to explain the same evidence. While both paradigms offer possible explanations the new paradigm, which requires headward erosion of the valleys to have occurred as massive continental ice sheet melt water floods crossed the region, explains much more of the drainage system evidence and also permits much more detailed explanations.
文摘Expanding the optical absorption range of photocatalysts is still a key endeavor in graphitic carbon nitride(g-C_(3)N_(4))studies.Here,we report on a novel thiophene group extending the optical property,which is assigned to n-π^(*)electronic transitions involving the two lone pairs on sulfur(TLPS).The as-prepared samples,denoted as CN-ThAx(where x indicates the amount of ThA added,mg),showed an additional absorption above 500 nm as compared to pristine g-C_(3)N_(4).Further,the thiophene group enhanced charge carrier separation to suppress e‒/h+pair recombination.The experimental results suggest that the thiophene group can obstruct the polymerization of melem to generate a large plane,thus exposing the lone electron pairs on the sulfur.The photocatalytic activity was evaluated in the decomposition of bisphenol A and H2 evolution.Compared with g-C_(3)N_(4),the optimized CN-ThA_(30) sample led to a 6.6-and 2-fold enhancement of the degradation and H2 generation rates,respectively.The CN-ThA_(30) sample allowed for synchronous H2 production and BPA decomposition.
基金The study was supported by a grant from the National Natural Science Foundation of China （No. 81100160）. Conflict of interest： none declared.
文摘Background Growing epidemiologic evidence has indicated that genetics can predispose individuals to the occurrence of lone atrial fibrillation （AF）. The angiotensin-converting enzyme 2 （ACE2） gene has been established to be associated with hypertension and left ventricular hypertrophy. The objective of our study was to investigate the association of ACE2 gene polymorphisms with lone AF. Methods A total of 265 consecutive lone AF patients and 289 healthy controls were successfully investigated. The polymorphisms rs2106809 and rs2285666 were genotyped by polymerase chain reaction （PCR） and direct sequencing. A Logistic regression model was used to determine the odds ratio （OR） and 95% confidence intervals （CO of variations of ACE2 for lone AF. Results The T allele of rs2106809 conferred an increased risk for lone AF （OR 1.24, 95% CI 1.01-1.52, P=0.03） in males after adjustment for conventional risk factors. SNP at rs2285666 in males was not significantly different between AF patients and controls. No association was found between the two polymorphisms in the female population with lone AF. After （36.3±4.5） months of follow-up, the end point data were obtained： death （cardiac and noncardiac）, ischemic stroke, and heart failure. In the male subgroup, the associations between rs2106809 T male carriers and combined end points including ischemic stroke, heart failure, and death in our study were of significance （OR 3.6, 95% CI 1.0-13.1, P=-0.04）. Conclusions The results indicate that polymorphism at ACE2 gene is associated with male lone AF in a Chinese Han population. Lone AF males who c.arrv the. rs2106809T alle.le, are. associate.d with adverse cardiac, e.ve.nts
基金supported by the Ministry of Science and Technology(MOST)of China(Nos.2012CB932704,2012CB933001)the National Natural Science Foundation of China(NSFC,Nos.11274380,91433103,21173058,11622437,61674171 and 21203038)supported by the Outstanding Innovative Talents Cultivation Funded Programs 2015 of Renmin University of China
文摘It has been demonstrated that intermolecular interaction,crucial in a plenty of chemical and physical processes,may vary in the presence of metal surface.However,such modification is yet to be quantitatively revealed.Here,we present a systematical density functional theory study on adsorbed bis（para-pyridyl）acetylene（BPPA） tetramer on Au（111） surface.We observed unusually high electron density between two head-to-head N atoms,an intermolecular ＂non-bonded＂ region,in adsorbed BPPA tetramer.This exceptional electron density originates from the wavefunction hybridization of the two compressed N lone-electron-pair states of two BPPA,as squeezed by a newly revealed N-Au-N threecenter bonding.This bond,together with the minor contribution from N...H-C intermolecular hydrogen bonding,shortens the N-N distance from over 4 A to 3.30 A and offers an attractive lateral interacting energy of 0.60 eV,effectively to a surface-confined in-plane pressure.The overlapped non-bonding vvavefunction hybridization arising from the effective pressure induced by the N-Au-N three-center bonding,as not been fully recognized in earlier studies,was manifested in non-contact Atomic Force Microscopy.
基金supported by the National Natural Science Foundation of China(21473142 and 21673191)the National Innovative Research Team of China(IRT_14R31 and J1310024)
文摘Various bond modes of the M-C（C5 ring） exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the C5 ring.The tin（Ⅱ） metallocene complexes LSn R（L = HC[CMe（N-2,6-iPr2C6H3）]2,R = cyclopentadienyl,C5H5（1）; indenyl,C9H7（2）; fluorenyl,C（13）H9（3）） stabilized by the β-diketiminato ligand were prepared and utilized in the study on their solid and solution state structures.X-ray single-crystal diffraction data revealed an η~1-mode of the Sn-C（C5 ring） bond in each 1~3.However,the room temperature ~1H NMR spectral studies disclosed such a fluxional bonding mode in solution.The 119 Sn NMR studies suggested a quadruple coordination nature of the Sn center in 1 while the triple coordination manner was for the Sn atom in both 2 and 3.Then the variable-temperature（25~–75 ℃） ~1H NMR spectral studies for each 1~3 were performed,which detected the relaxation state structures of 1~3 at lower temperature.All of these results indicate a stereochemical activity of the lone electron pairs at the tin（Ⅱ） atom that definitely has an electronic interaction with the 6 p-electrons of the C5 ring.The observed Sn-C（C5 ring） bond modes appear influenced by either the metallocene size or the compound state existed.
文摘First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.
文摘根据GenBank报道的谷氨酸棒杆菌ATCC13032序列,设计并合成一对引物,获得了全长argB基因片段.将其克隆到pGEM T Easy载体中,经测序鉴定后,以其为DIG标记探针,通过SouthernBlot分析钝齿棒杆菌A.S1.542与谷氨酸棒杆菌ATCC13032,argB基因核苷酸同源性高达99%,氨基酸序列95%相同.
基金supported by the Natural Science Foundation of China(Nos.22122104,21933004 and 21702098).
文摘Although fluorobis(phenylsulfonyl)methane(FBSM)and its cyclic analog 2-fluoro-1,3-benzodithiole-1,1,3,3-tetraoxide(FBDT)possess similar physicochemical properties,Shibata et al.found that FBSM failed to undergo nucleophilic monofluoromethylation of aldehydes regardless of the reaction conditions at-tempted(using various organic and inorganic bases).However,it was later discovered by Hu et al.that the nucleophilic monofluoromethylation could be accomplished by employing lithium hexamethyldisi-lazide(LiHMDS)as a base.Herein,we present an in-depth computational investigation into the intrigu-ing effects of reagent structure and bases on the nucleophilic monofluoromethylation of aldehydes.The computations reveal the 1,4-diazabicyclo[2.2.2]octane(DABCO)catalyzed nucleophilic monofluoromethy-lation of benzaldehyde with acyclic FBSM is a thermodynamically unfavorable process mainly due to the destabilizing O···O lone pair repulsions in FBSM product,whereas such repulsion could be largely avoided in FBDT product because of its constrained five-membered ring structure.Employing LiHMDS as a base can not only facilitate the nucleophilic monofluoromethylation via Li–O interactions but also render the monofluoromethylation of benzaldehyde with FBSM thermodynamically favored.
基金supported by the National Natural Science Foundation of China(51873077,91833304,and 51803071)the National Basic Research Program of China(2016YFB0401001)+1 种基金the Postdoctoral Innovation Talent Support Project(BX20180121)the China Postdoctoral Science Foundation(2018M641767),and JLUSTIRT(2019TD-33).
文摘In order to develop pure organic single-molecule white-light emitters(SMWLE),the oxidation of thianthrene(TA)was performed on sulfur atoms at different degrees to tune room temperature phosphorescence(RTP)emission.With increasing degrees of oxidation from 1OTA,2OTA,3OTA,to 4OTA,monomeric and aggregative RTP emission was gradually suppressed,due to the gradual disappearance of lone pair electrons on sulfur atoms.Among these compounds,monomers and aggregates of 1OTA demonstrated a better intensity match between fluorescence and RTP.
基金Supported by the National Natural Science Foundation of China(No.21201144)the Natural Science Foundation of Fujian Province(No.2018J07006)。
文摘Two isostructural tellurite phosphates Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)have been synthesized via hydrothermal method.Both of them crystalize in monoclinic space group C2/m(No.12).For Ni_(2)ZnTe^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4),a=19.3247(10),b=5.9697(3),c=4.7737(2)Å,β=103.637(5)°,V=535.18(5)Å^(3),Z=2,M_(r)=727.94,S=1.103,D_(c)=4.517 g·cm^(-3),μ(Mo Kα)=11.434 mm^(-1) and F(000)=672,the final R=0.0369and wR=0.1086 for 639 observed reflections with I>2σ(I).The crystal structure of Ni_(2)M^(Ⅱ)Te^(Ⅳ)_(2)O_(2)(PO_(4))_(2)(OH)_(4)(M^(Ⅱ)=Ni,Zn)features a 3D framework composed of[Ni_(2)O_(2)(PO_(4))_(2)]^(6-)layers interconnected by[MTe_(2)O_(2)(OH)_(4)]^(2+)single chains.Different magnetic susceptibility results at low temperature of the two title compounds confirm that Zn(1)completely occupies the Ni(2)position but not partially substitutes both Ni(1)and Ni(2)position atoms.Additionally,the acentric TeO_(3)(OH)_(2) tetragonal pyramids are aligned in an antiparallel manner,resulting in the crystallization of centrosymmetric(C2/m)crystal structure instead of the non-centrosymmetric crystal structure.The investigation of the origin of centrosymmetric crystal structure with strong dipole moment units provides deeper understanding for future rational design for non-centrosymmetric crystal structure.
基金supported by the National Natural Science Foundation of China (21202020, 21572032)the Doctoral Fund of Ministry of Education of China (20123514120002)+1 种基金the Natural Science Foundation of Fujian Province (2014J01040)the Science & Technical Development Foundation of Fuzhou University (2012-XQ-10, 2013-XQ-14)
文摘Catassembly is a new concept in molecular assembly that is analogous to catalysis in chemical synthesis. However, for most molecular-assembled processes, the catassembler contributions are rather inconspicuous due to the low activation barriers. As a result, few systems dealing with the catassembly are available until now. In this paper, we report that naphthalene diimide coordination networks are formed under the catassembly of lone-pair-bearing catassemblers(e.g., N,N-dimethylacetamide, N-methylpyrrolidin-2-one). During such molecular assembly, a stable transition state between the electron-deficient naphthalene diimide tectons and catassemblers via the less common lone pair-π interactions was observed, which is supposed to play the key role in the enhancement of coordination abilities of organic tectons and thus formation of the final coordination networks.
文摘Background The CHA 2 DS 2-VASc schema has recently been introduced to complement the CHADS2 score and improve the identification of atrial fibrillation （AF） patients at ＇truly low risk＇ for thromboembolism.We tested the predictive ability of the CHA 2 DS 2-VASc,CHADS2 and van Walraven risk stratification schemes in a cohort of ＇lone＇ AF patients with a 12-year follow-up.Methods and Results We conducted a registry-based,observational cohort study of 345 patients initially diagnosed with ＇lone＇ AF between 1992 and 2007.At baseline,all patients had the CHADS2 and van Walraven scores of 0,and 262 （75.9%） had a CHA 2 DS 2VASc score=0.During follow-up （or within a year prior to stroke）,228 （66.1%）,234 （67.8%） and 150 patients （43.5%） retained the CHADS2,van Walraven and CHA 2 DS 2VASc scores of 0,respectively.The overall rate of ischemic stroke was 0.19 （95%CI：0.18-0.20） per 100 patient-years.In the multivariable analysis,only the CHA 2 DS 2-VASc score of 0 was significantly related to the absence of stroke （OR 5.1,95%CI：1.5-16.8,P=0.008）.Only the CHA 2 DS 2-VASc score had a significant prediction ability （c-statistic 0.72 [0.61-0.84],P=0.031）.Conclusions The CHA 2 DS 2-VASc score reliably identified the ＇lone＇ AF patients who were at ＇truly low risk＇ for thromboembolism,and was the only tested risk stratification scheme with a significant predictive ability for thromboembolism amongst lone AF patients.
