In 1994, the Beijing Arts and Crafts Import and Export Corporation has spared no efforts to expand its export trade by making fully use all of its particular resources, such as funds, personnel, access to overseas mar...In 1994, the Beijing Arts and Crafts Import and Export Corporation has spared no efforts to expand its export trade by making fully use all of its particular resources, such as funds, personnel, access to overseas markets and links with customers and overseas businesses, etc. In the first half of this year, the corporation exported展开更多
The Capital Iron and Steel Corporation (Shou Gang) is one of the eight major iron and steel companies in China and one of the first state-owned enterprises to be selected as a testing ground for the reform programme, ...The Capital Iron and Steel Corporation (Shou Gang) is one of the eight major iron and steel companies in China and one of the first state-owned enterprises to be selected as a testing ground for the reform programme, since it was authorized to manage its own foreign trade in 1981, the Corporation’s export trade has expanded steadily. Especially since 1992, its development in foreign trade has skyrocketed because China Shou Gang International Trade Construction Company was approved to be set up. In 1993, it exported 239,700 tons of steel. Its foreign exchange income reached US$630 million, of which the Shou Gang’s self-managed exports took up US$96.98 million. During the展开更多
BACKGROUND To prevent mother to child transmission(MTCT)of human immunodeficiency virus(HIV),sustained maternal viral load suppression(VLS)and early HIV testing among HIV exposed infants(HEI)is critical.AIM To investi...BACKGROUND To prevent mother to child transmission(MTCT)of human immunodeficiency virus(HIV),sustained maternal viral load suppression(VLS)and early HIV testing among HIV exposed infants(HEI)is critical.AIM To investigate maternal viral load results and infant HIV testing uptake at 6-weeks,and 9-months and 18-months in Rwanda.METHODS Between 2015 and 2022,VLS(<200 copies/mL)was measured among pregnant women living with HIV(WLHIV)from 38-healthcare facilities.Viral loads(VL)were measured at 6-months,12-months and 24-months,respectively.For maternal VL,the unit of analysis was visit-pair,and the pairs were created to define those with VL<200 copies/mL at two consecutive visits as having sustained VLS,persistent viremia(VL≥200 copies/mL at two consecutive visits),viral rebound(VL<200 copies/mL at prior visit only)and newly suppressed(VL<200 copies/mL at subsequent visit only).HEI were considered to have persistent HIV testing if they had all three HIV tests.Poisson regression models with generalized estimating equations were used to estimate the adjusted incidence rate ratio(aIRR)and 95%CI for factors associated with sustained VLS and persistent HIV testing.RESULTS A total of 1145 mother-infant pairs were analyzed.Infant HIV testing uptake at 6-weeks,9-months and 18-months was 1145(100.0%),1089(95.1%),1006(87.9%)respectively.Nine hundred ninety-nine HEI(87.3%)tested for HIV persistently.At 18-months,the incidence of HIV among HEI was 8(0.7%).Of 1145 mothers,1076(94.0%)had≥2 VL results making a total of 2010 visit-pairs(142-single;934-double visit-pairs).The incidence rate of sustained VLS,persistent viremia,viral rebound and new suppression were 91.0%,1.3%,3.6%and 4.0%respectively.Maternal disclosure of HIV status(aIRR=1.08,95%CI:1.02-1.14)was associated with increased likelihood of sustained VLS.Having peer support(aIRR=1.0595%CI:1.01-1.10)was associated with persistent HIV testing among HEI.CONCLUSION Sustained VLS is high among pregnant WLHIV in Rwanda.The low incidence of HIV among HEI may be attributed to high VLS levels.Targeted interventions,including enhanced HIV disclosure and peer support,are crucial for improving sustained VLS and increasing infant HIV testing uptake to reduce MTCT.展开更多
The China Pavilion has consistently been the primary vehicle for China's participation in World Expos over the years.From the first China Pavilion at the 1876 Philadelphia Expo to the 2025 China Pavilion at the on...The China Pavilion has consistently been the primary vehicle for China's participation in World Expos over the years.From the first China Pavilion at the 1876 Philadelphia Expo to the 2025 China Pavilion at the ongoing Osaka Expo,nearly 150 years have passed.During this span,the China Pavilion at the Expos.展开更多
Rational tuning of crystallographic surface and metal doping were effective to enhance the catalytic performance of metal organic frameworks,but limited work has been explored for achieving modulation of crystal facet...Rational tuning of crystallographic surface and metal doping were effective to enhance the catalytic performance of metal organic frameworks,but limited work has been explored for achieving modulation of crystal facets and metal doping in a single system.MIL-68(In)was promising for photocatalytic applications due to its low toxicity and excellent photoresponsivity.However,its catalytic activity was constrained by severe carrier recombination and a lack of active sites.Herein,increased(001)facet ratio and active sites exposure were simultaneously realized by cobalt doping in MIL-68(In)through a one-pot solvothermal strategy.Optimized MIL-68(In/Co)-2.5 exhibited remarkable catalytic performance in comparison with pristine MIL-68(In)and other MIL-68(In/Co).The reaction kinetic constant and degradation efficiency of MIL-68(In/Co)were approximately twice and 17%higher than the pristine MIL-68(In)in 36 min reaction,respectively.Density functional theory calculations revealed that Co dopant could modulate the orientation of MIL-68(In)facets,facilitate the exchange of electrons and reduce the adsorption energy of peroxymonosulfate(PMS).This work provides a novel pathway for improvement of In-based MOFs in PMS/vis system,it also promotes the profound comprehension of the correlation between crystal facet regulation and catalytic activation in the PMS/vis system.展开更多
This article presents a new multichannel medium access control (MAC) protocol to solve the exposed-terminal (ET) problem for efficient channel sharing in multi-hop wireless networks. It uses request-to-send and clear-...This article presents a new multichannel medium access control (MAC) protocol to solve the exposed-terminal (ET) problem for efficient channel sharing in multi-hop wireless networks. It uses request-to-send and clear-to-send (RTS/CTS) dialogue on a common channel and flexibly opts for conflict-free traffic channels to carry out the data packet transmission on the basis of a new channel selection scheme. The acknowledgment (ACK) packet for the data packet transmission is sent back to the sender over another ...展开更多
Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. S...Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.展开更多
上期的第二个话题“跳槽”是目前普遍存在的现象,对此人们看法不一。有些人认为这在国外并非什么新鲜事,中国人也开始这样做说明人们的思想解放了.打破了过去那种在一个单位干一辈子的传统观念.这是社会的进步。也有人把“跳槽”看做是...上期的第二个话题“跳槽”是目前普遍存在的现象,对此人们看法不一。有些人认为这在国外并非什么新鲜事,中国人也开始这样做说明人们的思想解放了.打破了过去那种在一个单位干一辈子的传统观念.这是社会的进步。也有人把“跳槽”看做是人的私欲膨胀,是对金钱和物质利益的过分追求,不利于一个企业或部门的发展,不应提倡。考生如同意后一种观点就可以说:“I don’t think it is reasonable for aperson to change his(her)job frequently.A展开更多
In current underground mining, the stability of the exposed backfill face is a basic issue associated with mining design and has been the subject of considerable research in mining safety and efficiency. In this study...In current underground mining, the stability of the exposed backfill face is a basic issue associated with mining design and has been the subject of considerable research in mining safety and efficiency. In this study, an improved analytical solution for evaluating the safety of vertically exposed faces in backfilling was proposed. Based on a differential slice method, the proposed solution emphasizes the arching effect as having the advantages of more rigor and wider scalability. Feasibility of the proposed solution was validated with classic centrifuge results. Good agreement between compared results indicated that the proposed solution skillfully predicts the behavior of the paste centrifuge model. Additionally, calculation of exposed face safety in sequential filling was presented. The proposed solution has practical significance in mine backfill design.展开更多
The ultimately exposed roof area(UERA)of goaf is crucial to the safety and economics of underground mining.The prediction models do not consider the mechanical weakness of rock mass and ignore the influence of the joi...The ultimately exposed roof area(UERA)of goaf is crucial to the safety and economics of underground mining.The prediction models do not consider the mechanical weakness of rock mass and ignore the influence of the joint damage factor,causing a large predicted exposure area with a high roof falling risk.This work adopted joint damage factor to derive a new UERA prediction model.The relationships between the UERA(S)and the span ratio(m),the density(k)and the diameter of fracture(d)were analysed by the new prediction model.The results showed that the exposed area S and the span ratio m have a U-shaped curve relationship.The S decreases with the increase of m and then increases when m is beyond 2.The exposed roof area S is in an inversely proportional power-law relationship with the fracture surface density k,and the curvature of the S-k relationship curve decreases when d=0.5 and k>7,and S is close to 0.There is a negative correlation between S and the fracture surface diameter d,the curvature of the S-d curve decreases with the increase of d and k,and the variation rate increases first and then decreases with the increase of d;when k=0.5 and d>9,S is close to 0.The predicted values of the UERA prediction model are 119.3,112.8,and 114.6 m2 with different joint damage parameters,which are slightly smaller than the actual critical exposure area of a roof(S=120 m2).The case study shows that the alternative prediction model is reasonable and acceptable and provides new theoretical support for the underground mining safety of sedimentary bauxite ore.展开更多
The present report evaluates the effects of formaldehyde (FA) exposure on peripheral lymphocytes by using heth genetic and immunological parameters. Twenty-three non-smoking students in the study had inhalation exposu...The present report evaluates the effects of formaldehyde (FA) exposure on peripheral lymphocytes by using heth genetic and immunological parameters. Twenty-three non-smoking students in the study had inhalation exposure to 0.508 ±0. 299 mg/m3 of FA for a Period of 8 weeks (3h × 3 times each week) during anatomy classes. As for composition of lymphocyte subsets after FA exposare,significant increase was found in the percentage of CD19(B cells), while sighficant decrease was observed in CD3(total T cells), CD4(T helper-inducer cells), and CD8(T cytotoxic-suppressior cells) with a P<0 .01. Increase in the ratio of T-helper-inducer cells to T-cytotoxic-suppressor cells (T4 / T8) was also observed with statistical sighcance after exposure (P < 0.001). In the meanwhile,no significant difference (P > 0 .05) was reported between lymphocyte prolifendion rate and sisterchromatid exchange (SCE) at the exposure level and duration. It is suggested that the lymphocyte subsets may be most susceptible to the effects of FA, though a single immunological endpoint is rarely related with pathophysiological interpretation.展开更多
The Lower Triassic Feixianguan Formation in the Daxian-Xuanhan region, northeastern Sicbuan is interpreted to be a carbonate platform intermediate between the West Hubei-East Cbongqing marine basin and Guangyuan-Wangc...The Lower Triassic Feixianguan Formation in the Daxian-Xuanhan region, northeastern Sicbuan is interpreted to be a carbonate platform intermediate between the West Hubei-East Cbongqing marine basin and Guangyuan-Wangcang marine basin. Outcrops, well logs and seismic data have disclosed that three sedimentary facies can be identified for the formation： open platform, platform exposed shoal and restricted platform facies. During the early stage of deposition of the Feixianguan Formation, there existed a sedimentary framework all the same as the Late Permian one： open platform in the west, and platform exposed shoal, restricted platform and open platform eastwards. The gradual increase of the shoal area permitted eastward migration of the shoal facies. During the deposition of the third member of the Feixianguan Formation, the study area was invaded by temporary transgressions. Till the deposition of the fourth member of the formation, the study area was prevailed over the unified restricted platform deposits, as indicated by the sedimentary model for the typical carbonate platform shoal deposits. The reservoir rocks in the Feixianguan Formation consist mostly of solution opening dolostone, and the rock types are assembled by oolitic dolostone, residual oolitic dolostone and sucrosic residual oolitic medium- to coarse-grained dolostone. The deep and shallow dual laterologs show relatively high resistivity, clear amplitude differences and time difference saltation of acoustic waves in some intervals. The seismic responses are indicated by low-frequency and highly variable amplitudes and chaotic reflection configurations. The reservoir rocks are characterized by high porosity-high permeability and medium porosity-medium permeability, showing a marked correlation between porosity and permeability. Solution openings are extremely developed in the reservoir rocks, including cast pores, intergranular solution openings, intercrystal pores, intercrystal solution openings, solution openings （caves） and minute fissures. Macropores and coarse pore throats are common. The reservoir rocks are apparently controlled by sedimentary facies in distribution patterns. Vertically, they occur dominantly in the second and first members of the Feixianguan Formation, and laterally in the platform exposed shoals and restricted platforms, where good natural gas potential is expected.展开更多
High efficiency, environmental protection and sustainability have become the main theme of the development of the protection engineering, requiring that the components not only meet the basic functions, but also have ...High efficiency, environmental protection and sustainability have become the main theme of the development of the protection engineering, requiring that the components not only meet the basic functions, but also have chemical properties such as acid and alkali corrosion resistance and aging resistance. Polyisocyanate-oxazodone(POZD) polymer has the above characteristics, it also has the advantages of strong toughness, high strength and high elongation. The concrete slab sprayed with POZD material has excellent anti-blast performance. In order to explore the damage characteristics of POZD sprayed concrete slabs under the action of contact explosion thoroughly, the contact explosion test of POZD concrete slabs with different charges were carried out. On the basis of experimental verification,numerical simulation were used to study the influence of the thickness of the POZD on the blast resistance of the concrete slab. According to the test and numerical simulation results that as the thickness of the coating increases, the anti-blast performance of the concrete slab gradually increases,and the TNT equivalent required for critical failure is larger. Based on the above analysis, empirical expressions on normalized crater diameter, the normalized spall diameter and normalized spall diameter are obtained.展开更多
Photocatalytic degradation of gaseous pollutants on Bi-based semiconductors under solar lightirradiation has attracted significant attention.However,their application in gaseous straight-chainalkane purification is st...Photocatalytic degradation of gaseous pollutants on Bi-based semiconductors under solar lightirradiation has attracted significant attention.However,their application in gaseous straight-chainalkane purification is still rare.Here,a series of Bi/BiOBr composites were solvothermally synthe-sized and applied in solar-light-driven photocatalytic degradation of gaseous n-hexane.The charac-terization results revealed that both increasing number of functional groups of alcohol solvent(from methanol and ethylene glycol to glycerol)and solvothermal temperature(from 160 and 180to 200℃)facilitated the in-situ formation of metallic Bi nanospheres on BiOBr nanoplates withexposed(110)facets.Meanwhile,chemical bonding between Bi and BiOBr was observed on theseexposed facets that resulted in the formation of surface oxygen vacancy.Furthermore,the synergis-tic effect of optimum surface oxygen vacancy on exposed(110)facets led to a high visible light re-sponse,narrow band gap,great photocurrent,low recombination rate of the charge carriers,andstrong·O2-and h*formation,all of which resulted in the highest removal efficiency of 97.4%within120 min of 15 ppmv of n-hexane on Bi/BiOBr.Our findings efficiently broaden the application ofBi-based photocatalysis technology in the purification of gaseous straight-chain pollutants emittedby the petrochemical industry.展开更多
BACKGROUND Aplasia cutis congenita (ACC) in newborns is a condition in which congenital defects or hypoplasia is present in part of the epidermis,dermis and even subcutaneous tissue (including muscle and bones).First ...BACKGROUND Aplasia cutis congenita (ACC) in newborns is a condition in which congenital defects or hypoplasia is present in part of the epidermis,dermis and even subcutaneous tissue (including muscle and bones).First reported by Cordon in 1767,ACC is a rare disease with a low incidence of 1/100000 to 3/10000.Currently,there are 500 cases reported worldwide.ACC can be accompanied by other malformations.The onset mechanism of the disease remains unknown but is thought to be correlated to factors such as genetics,narrow uterus,foetal skin and amniotic membrane adhesion,use of teratogenic drugs in early pregnancy and viral infection.CASE SUMMARY In August 2018,we treated a newborn with ACC on the left lower limbs using a combination of ionic silver dressing and moist exposed burn ointment (MEBO) and achieved a satisfactory treatment outcome.The skin defects were observed on the external genitals and on areas from the left foot to 3/4 of the upper left side.Subcutaneous tissue and blood vessels were observed in the regions with skin defects.The following treatments were provided.First,the wound was rinsed with 0.9% sodium chloride solution followed by disinfection with povidone-iodine twice.And then MEBO was applied to the wound at a thickness of approximately 1 mm.After applying ionic silver dressing,the wound was covered with sterile gauze.The wound dressing was replaced every 2-3 d.At the 4-mo follow-up,the treatment outcome was satisfactory.There was minimal scar tissue formation,and limb function was not impaired.CONCLUSION The combination of ionic silver dressing and MEBO to ACC is helpful.展开更多
The frequency of micronuclei (MN) in cells of the nasal mucosa, oral mucosa and in lym-phocytes was evaluated for 25 students in anatomy classes exposed to formaldehyde (FA) overan 8-week period. Each student served a...The frequency of micronuclei (MN) in cells of the nasal mucosa, oral mucosa and in lym-phocytes was evaluated for 25 students in anatomy classes exposed to formaldehyde (FA) overan 8-week period. Each student served as his or her own control. The time-weighted averageconcentration (TWA) of fOrmaldehyde in anatomical laboratories and in students' dormitorieswas 0. 508 ± 0. 299 mg/m3 and 0. 012 ± 0. 0025mg/m3, respectively. A higher frequency ofmicronuclei was observed in nasal and oral exfoliative cells after formaldehyde exposure (3. 85± 1. 48 vs 1 .20± 0. 676 and 0. 857 ± 0. 558 vs 0. 568 ± 0. 317, paired-t test: P< 0. 001and P < 0. 01, respectively). No significant increase in the frequency of lymphocyte micronu-clei was found after formaldehyde exposure (P >0. 05 ). The present study shows that nasalmucosa cel1s exposed through respiration are the chief target of FA-induced genotoxic effects展开更多
文摘In 1994, the Beijing Arts and Crafts Import and Export Corporation has spared no efforts to expand its export trade by making fully use all of its particular resources, such as funds, personnel, access to overseas markets and links with customers and overseas businesses, etc. In the first half of this year, the corporation exported
文摘The Capital Iron and Steel Corporation (Shou Gang) is one of the eight major iron and steel companies in China and one of the first state-owned enterprises to be selected as a testing ground for the reform programme, since it was authorized to manage its own foreign trade in 1981, the Corporation’s export trade has expanded steadily. Especially since 1992, its development in foreign trade has skyrocketed because China Shou Gang International Trade Construction Company was approved to be set up. In 1993, it exported 239,700 tons of steel. Its foreign exchange income reached US$630 million, of which the Shou Gang’s self-managed exports took up US$96.98 million. During the
文摘BACKGROUND To prevent mother to child transmission(MTCT)of human immunodeficiency virus(HIV),sustained maternal viral load suppression(VLS)and early HIV testing among HIV exposed infants(HEI)is critical.AIM To investigate maternal viral load results and infant HIV testing uptake at 6-weeks,and 9-months and 18-months in Rwanda.METHODS Between 2015 and 2022,VLS(<200 copies/mL)was measured among pregnant women living with HIV(WLHIV)from 38-healthcare facilities.Viral loads(VL)were measured at 6-months,12-months and 24-months,respectively.For maternal VL,the unit of analysis was visit-pair,and the pairs were created to define those with VL<200 copies/mL at two consecutive visits as having sustained VLS,persistent viremia(VL≥200 copies/mL at two consecutive visits),viral rebound(VL<200 copies/mL at prior visit only)and newly suppressed(VL<200 copies/mL at subsequent visit only).HEI were considered to have persistent HIV testing if they had all three HIV tests.Poisson regression models with generalized estimating equations were used to estimate the adjusted incidence rate ratio(aIRR)and 95%CI for factors associated with sustained VLS and persistent HIV testing.RESULTS A total of 1145 mother-infant pairs were analyzed.Infant HIV testing uptake at 6-weeks,9-months and 18-months was 1145(100.0%),1089(95.1%),1006(87.9%)respectively.Nine hundred ninety-nine HEI(87.3%)tested for HIV persistently.At 18-months,the incidence of HIV among HEI was 8(0.7%).Of 1145 mothers,1076(94.0%)had≥2 VL results making a total of 2010 visit-pairs(142-single;934-double visit-pairs).The incidence rate of sustained VLS,persistent viremia,viral rebound and new suppression were 91.0%,1.3%,3.6%and 4.0%respectively.Maternal disclosure of HIV status(aIRR=1.08,95%CI:1.02-1.14)was associated with increased likelihood of sustained VLS.Having peer support(aIRR=1.0595%CI:1.01-1.10)was associated with persistent HIV testing among HEI.CONCLUSION Sustained VLS is high among pregnant WLHIV in Rwanda.The low incidence of HIV among HEI may be attributed to high VLS levels.Targeted interventions,including enhanced HIV disclosure and peer support,are crucial for improving sustained VLS and increasing infant HIV testing uptake to reduce MTCT.
文摘The China Pavilion has consistently been the primary vehicle for China's participation in World Expos over the years.From the first China Pavilion at the 1876 Philadelphia Expo to the 2025 China Pavilion at the ongoing Osaka Expo,nearly 150 years have passed.During this span,the China Pavilion at the Expos.
基金supported by the National Natural Science Foundation of China(Nos.52100087,52170079,U20A20322)Science and Technology Development Program of Jilin Province,China(Nos.20220508100RC,20230402035GH).
文摘Rational tuning of crystallographic surface and metal doping were effective to enhance the catalytic performance of metal organic frameworks,but limited work has been explored for achieving modulation of crystal facets and metal doping in a single system.MIL-68(In)was promising for photocatalytic applications due to its low toxicity and excellent photoresponsivity.However,its catalytic activity was constrained by severe carrier recombination and a lack of active sites.Herein,increased(001)facet ratio and active sites exposure were simultaneously realized by cobalt doping in MIL-68(In)through a one-pot solvothermal strategy.Optimized MIL-68(In/Co)-2.5 exhibited remarkable catalytic performance in comparison with pristine MIL-68(In)and other MIL-68(In/Co).The reaction kinetic constant and degradation efficiency of MIL-68(In/Co)were approximately twice and 17%higher than the pristine MIL-68(In)in 36 min reaction,respectively.Density functional theory calculations revealed that Co dopant could modulate the orientation of MIL-68(In)facets,facilitate the exchange of electrons and reduce the adsorption energy of peroxymonosulfate(PMS).This work provides a novel pathway for improvement of In-based MOFs in PMS/vis system,it also promotes the profound comprehension of the correlation between crystal facet regulation and catalytic activation in the PMS/vis system.
基金National Natural Science Foundation of China (10577005, 60532030)National Outstanding Youth Science Foundation of China (60625102)NSBS Program of Beijing University of Aeronau-tics and Astronautics, China (221235)
文摘This article presents a new multichannel medium access control (MAC) protocol to solve the exposed-terminal (ET) problem for efficient channel sharing in multi-hop wireless networks. It uses request-to-send and clear-to-send (RTS/CTS) dialogue on a common channel and flexibly opts for conflict-free traffic channels to carry out the data packet transmission on the basis of a new channel selection scheme. The acknowledgment (ACK) packet for the data packet transmission is sent back to the sender over another ...
基金supported by the National Natural Science Foundation of China (21263015)the Education Department of Jiangxi Province (KJLD14005)the Natural Science Foundation of Jiangxi Province(20151BBE50006,20122BAB203009)~~
文摘Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.
文摘上期的第二个话题“跳槽”是目前普遍存在的现象,对此人们看法不一。有些人认为这在国外并非什么新鲜事,中国人也开始这样做说明人们的思想解放了.打破了过去那种在一个单位干一辈子的传统观念.这是社会的进步。也有人把“跳槽”看做是人的私欲膨胀,是对金钱和物质利益的过分追求,不利于一个企业或部门的发展,不应提倡。考生如同意后一种观点就可以说:“I don’t think it is reasonable for aperson to change his(her)job frequently.A
基金financially supported by the China Scholarship Council (No. 201506420049)
文摘In current underground mining, the stability of the exposed backfill face is a basic issue associated with mining design and has been the subject of considerable research in mining safety and efficiency. In this study, an improved analytical solution for evaluating the safety of vertically exposed faces in backfilling was proposed. Based on a differential slice method, the proposed solution emphasizes the arching effect as having the advantages of more rigor and wider scalability. Feasibility of the proposed solution was validated with classic centrifuge results. Good agreement between compared results indicated that the proposed solution skillfully predicts the behavior of the paste centrifuge model. Additionally, calculation of exposed face safety in sequential filling was presented. The proposed solution has practical significance in mine backfill design.
基金This work is supported by the National Natural Science Foundation of China(51974135,51704094)the National Key Research and Development Program of China(2016YFC0600802).
文摘The ultimately exposed roof area(UERA)of goaf is crucial to the safety and economics of underground mining.The prediction models do not consider the mechanical weakness of rock mass and ignore the influence of the joint damage factor,causing a large predicted exposure area with a high roof falling risk.This work adopted joint damage factor to derive a new UERA prediction model.The relationships between the UERA(S)and the span ratio(m),the density(k)and the diameter of fracture(d)were analysed by the new prediction model.The results showed that the exposed area S and the span ratio m have a U-shaped curve relationship.The S decreases with the increase of m and then increases when m is beyond 2.The exposed roof area S is in an inversely proportional power-law relationship with the fracture surface density k,and the curvature of the S-k relationship curve decreases when d=0.5 and k>7,and S is close to 0.There is a negative correlation between S and the fracture surface diameter d,the curvature of the S-d curve decreases with the increase of d and k,and the variation rate increases first and then decreases with the increase of d;when k=0.5 and d>9,S is close to 0.The predicted values of the UERA prediction model are 119.3,112.8,and 114.6 m2 with different joint damage parameters,which are slightly smaller than the actual critical exposure area of a roof(S=120 m2).The case study shows that the alternative prediction model is reasonable and acceptable and provides new theoretical support for the underground mining safety of sedimentary bauxite ore.
文摘The present report evaluates the effects of formaldehyde (FA) exposure on peripheral lymphocytes by using heth genetic and immunological parameters. Twenty-three non-smoking students in the study had inhalation exposure to 0.508 ±0. 299 mg/m3 of FA for a Period of 8 weeks (3h × 3 times each week) during anatomy classes. As for composition of lymphocyte subsets after FA exposare,significant increase was found in the percentage of CD19(B cells), while sighficant decrease was observed in CD3(total T cells), CD4(T helper-inducer cells), and CD8(T cytotoxic-suppressior cells) with a P<0 .01. Increase in the ratio of T-helper-inducer cells to T-cytotoxic-suppressor cells (T4 / T8) was also observed with statistical sighcance after exposure (P < 0.001). In the meanwhile,no significant difference (P > 0 .05) was reported between lymphocyte prolifendion rate and sisterchromatid exchange (SCE) at the exposure level and duration. It is suggested that the lymphocyte subsets may be most susceptible to the effects of FA, though a single immunological endpoint is rarely related with pathophysiological interpretation.
文摘The Lower Triassic Feixianguan Formation in the Daxian-Xuanhan region, northeastern Sicbuan is interpreted to be a carbonate platform intermediate between the West Hubei-East Cbongqing marine basin and Guangyuan-Wangcang marine basin. Outcrops, well logs and seismic data have disclosed that three sedimentary facies can be identified for the formation： open platform, platform exposed shoal and restricted platform facies. During the early stage of deposition of the Feixianguan Formation, there existed a sedimentary framework all the same as the Late Permian one： open platform in the west, and platform exposed shoal, restricted platform and open platform eastwards. The gradual increase of the shoal area permitted eastward migration of the shoal facies. During the deposition of the third member of the Feixianguan Formation, the study area was invaded by temporary transgressions. Till the deposition of the fourth member of the formation, the study area was prevailed over the unified restricted platform deposits, as indicated by the sedimentary model for the typical carbonate platform shoal deposits. The reservoir rocks in the Feixianguan Formation consist mostly of solution opening dolostone, and the rock types are assembled by oolitic dolostone, residual oolitic dolostone and sucrosic residual oolitic medium- to coarse-grained dolostone. The deep and shallow dual laterologs show relatively high resistivity, clear amplitude differences and time difference saltation of acoustic waves in some intervals. The seismic responses are indicated by low-frequency and highly variable amplitudes and chaotic reflection configurations. The reservoir rocks are characterized by high porosity-high permeability and medium porosity-medium permeability, showing a marked correlation between porosity and permeability. Solution openings are extremely developed in the reservoir rocks, including cast pores, intergranular solution openings, intercrystal pores, intercrystal solution openings, solution openings （caves） and minute fissures. Macropores and coarse pore throats are common. The reservoir rocks are apparently controlled by sedimentary facies in distribution patterns. Vertically, they occur dominantly in the second and first members of the Feixianguan Formation, and laterally in the platform exposed shoals and restricted platforms, where good natural gas potential is expected.
基金the financial support from National Natural Science Foundation of China (Grant Nos. 11302261 and 11972201)supported by the project of Key Laboratory of Impact and Safety Engineering (Ningbo University),Ministry of Education. The project number is CJ202011。
文摘High efficiency, environmental protection and sustainability have become the main theme of the development of the protection engineering, requiring that the components not only meet the basic functions, but also have chemical properties such as acid and alkali corrosion resistance and aging resistance. Polyisocyanate-oxazodone(POZD) polymer has the above characteristics, it also has the advantages of strong toughness, high strength and high elongation. The concrete slab sprayed with POZD material has excellent anti-blast performance. In order to explore the damage characteristics of POZD sprayed concrete slabs under the action of contact explosion thoroughly, the contact explosion test of POZD concrete slabs with different charges were carried out. On the basis of experimental verification,numerical simulation were used to study the influence of the thickness of the POZD on the blast resistance of the concrete slab. According to the test and numerical simulation results that as the thickness of the coating increases, the anti-blast performance of the concrete slab gradually increases,and the TNT equivalent required for critical failure is larger. Based on the above analysis, empirical expressions on normalized crater diameter, the normalized spall diameter and normalized spall diameter are obtained.
文摘Photocatalytic degradation of gaseous pollutants on Bi-based semiconductors under solar lightirradiation has attracted significant attention.However,their application in gaseous straight-chainalkane purification is still rare.Here,a series of Bi/BiOBr composites were solvothermally synthe-sized and applied in solar-light-driven photocatalytic degradation of gaseous n-hexane.The charac-terization results revealed that both increasing number of functional groups of alcohol solvent(from methanol and ethylene glycol to glycerol)and solvothermal temperature(from 160 and 180to 200℃)facilitated the in-situ formation of metallic Bi nanospheres on BiOBr nanoplates withexposed(110)facets.Meanwhile,chemical bonding between Bi and BiOBr was observed on theseexposed facets that resulted in the formation of surface oxygen vacancy.Furthermore,the synergis-tic effect of optimum surface oxygen vacancy on exposed(110)facets led to a high visible light re-sponse,narrow band gap,great photocurrent,low recombination rate of the charge carriers,andstrong·O2-and h*formation,all of which resulted in the highest removal efficiency of 97.4%within120 min of 15 ppmv of n-hexane on Bi/BiOBr.Our findings efficiently broaden the application ofBi-based photocatalysis technology in the purification of gaseous straight-chain pollutants emittedby the petrochemical industry.
文摘BACKGROUND Aplasia cutis congenita (ACC) in newborns is a condition in which congenital defects or hypoplasia is present in part of the epidermis,dermis and even subcutaneous tissue (including muscle and bones).First reported by Cordon in 1767,ACC is a rare disease with a low incidence of 1/100000 to 3/10000.Currently,there are 500 cases reported worldwide.ACC can be accompanied by other malformations.The onset mechanism of the disease remains unknown but is thought to be correlated to factors such as genetics,narrow uterus,foetal skin and amniotic membrane adhesion,use of teratogenic drugs in early pregnancy and viral infection.CASE SUMMARY In August 2018,we treated a newborn with ACC on the left lower limbs using a combination of ionic silver dressing and moist exposed burn ointment (MEBO) and achieved a satisfactory treatment outcome.The skin defects were observed on the external genitals and on areas from the left foot to 3/4 of the upper left side.Subcutaneous tissue and blood vessels were observed in the regions with skin defects.The following treatments were provided.First,the wound was rinsed with 0.9% sodium chloride solution followed by disinfection with povidone-iodine twice.And then MEBO was applied to the wound at a thickness of approximately 1 mm.After applying ionic silver dressing,the wound was covered with sterile gauze.The wound dressing was replaced every 2-3 d.At the 4-mo follow-up,the treatment outcome was satisfactory.There was minimal scar tissue formation,and limb function was not impaired.CONCLUSION The combination of ionic silver dressing and MEBO to ACC is helpful.
文摘The frequency of micronuclei (MN) in cells of the nasal mucosa, oral mucosa and in lym-phocytes was evaluated for 25 students in anatomy classes exposed to formaldehyde (FA) overan 8-week period. Each student served as his or her own control. The time-weighted averageconcentration (TWA) of fOrmaldehyde in anatomical laboratories and in students' dormitorieswas 0. 508 ± 0. 299 mg/m3 and 0. 012 ± 0. 0025mg/m3, respectively. A higher frequency ofmicronuclei was observed in nasal and oral exfoliative cells after formaldehyde exposure (3. 85± 1. 48 vs 1 .20± 0. 676 and 0. 857 ± 0. 558 vs 0. 568 ± 0. 317, paired-t test: P< 0. 001and P < 0. 01, respectively). No significant increase in the frequency of lymphocyte micronu-clei was found after formaldehyde exposure (P >0. 05 ). The present study shows that nasalmucosa cel1s exposed through respiration are the chief target of FA-induced genotoxic effects
