The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods.The latter are based upon assumptions that often reveal to be limited for ...The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods.The latter are based upon assumptions that often reveal to be limited for precooler design.In this paper,a refined design method considering the variations of fluid thermophysical properties,flow area and thermal parameters distortion,was proposed to remediate their limitations.Firstly,the precooler was discretized into a fixed number of sub-microtubes based on a new discretization criterion.Next,in-house one-dimensional(1D)and two-dimensional(2D)segmented models were established for rapid thermal design and precooler rating with non-uniform airflow,respectively.The heat transfer experimental studies of supercritical hydrocarbon fuel were performed to verify the Jackson correlation for precooler design and the in-house models were validated against the reported data from open literature.On this basis,the proposed method was employed for the design analysis of hydrocarbon fuel precoolers for precooled-Turbine Based Combined Cycle(TBCC)engines.The results show that the local performance of precoolers is intrinsically impacted by the aforementioned three variations.In the case study,the local heat transfer performance is drastically affected by coolant flow transition.While the circumferential temperature distortion of airflow is weakened by heat transfer.With consideration of additional parameter variations,this novel method improves design accuracy and shortens the design time.展开更多
Lettuce is an important leafy vegetable that represents a significant dietary source of antioxidants and bioactive compounds.However,the levels of metabolites in different lettuce cultivars are poorly characterized.In...Lettuce is an important leafy vegetable that represents a significant dietary source of antioxidants and bioactive compounds.However,the levels of metabolites in different lettuce cultivars are poorly characterized.In this study,we used combined GC×GC-TOF/MS and UPLC-IMS-QTOF/MS to detect and relatively quantify metabolites in 30 lettuce cultivars representing large genetic diversity.Comparison with online databases,the published literature,standards as well using collision cross-section values enabled putative identification of 171 metabolites.Sixteen of these 171 metabolites(including phenolic acid derivatives,glycosylated flavonoids,and one iridoid)were present at significantly different levels in leaf and head type lettuces,which suggested the significant metabolomic variations between the leaf and head types of lettuce are related to secondary metabolism.A combination of the results and metabolic network analysis techniques suggested that leaf and head type lettuces contain not only different levels of metabolites but also have significant variations in the corresponding associated metabolic networks.The novel lettuce metabolite library and novel non-targeted metabolomics strategy devised in this study could be used to further characterize metabolic variations between lettuce cultivars or other plants.Moreover,the findings of this study provide important insight into metabolic adaptations due to natural and human selection,which could stimulate further research to potentially improve lettuce quality,yield,and nutritional value.展开更多
The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives...The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives. The degradation process follows the first-order kinetics. A pH-rate profile exhibits the U-shape and shows the maximum stability of cefixime at pH = 6. The stability in different pure solvents is ranked as acetone 〉 ethanol 〉 methanol 〉 water, while the degradation rate of cefixime exists a maximum at the ratio of 0.6 in water ＋ methanol mixtures. In addition, the degradation rate increases with the temperature increasing and the activation energy of degradation was found to be 27.078 kJ. mol- 1 in acetone ＋ water mixed solvents. The addition of different additives was proven to either inhibit or accelerate the degradation. The degradation products were analyzed using HPLC, LC-MS and infrared spectroscopy, and the possible degradation pathways in acid as well as alkaline environment were proposed to help us understand the degradation behavior of cefixime.展开更多
A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for a...A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.展开更多
Immune function and antioxidant defense play an important role in protecting animals against pathogens and in controlling oxidative stress, respectively. Aldicarb is of great concern for human health due to its toxic ...Immune function and antioxidant defense play an important role in protecting animals against pathogens and in controlling oxidative stress, respectively. Aldicarb is of great concern for human health due to its toxic nature, its extensive usage and consequent pollution. The hypothesis that aldicarb exposure would suppress immune function and antioxidant capacity in Kunming mice was to be tested in the present study. Twenty-three adult male mice were randomly divided into the control (n = 11) and the aldicarb treated (n = 12) groups. Food and water were provided ad libtum for both groups, while the aldicarb treated mice drank aldicarb solution (0.097 mg/L) for 22 days. Cellular immunity assessed by phytohaemagglutinin (PHA) response did not differ between the control and the aldicarb treated groups. Similarly, white blood cells were not influenced by aldicarb treatment. Moreover, aldicarb exposure had not significant effect on body mass, all organ masses detected. However, aldicarb treatment suppressed total antioxidant capacity in liver but not in kidneys. In summary, aldicarb treatment did not affect immune function, but suppressed liver antioxidant capacity in Kunming mice.展开更多
Three kerogen samples(JJZG-1,JJZG-2 and JJZG-3)isolated from the Permian Lucaogou shales of varying biodegradation levels(BLs≈0,3 and 7,respectively)were subjected to sequential stepwise pyrolysis combined with on-li...Three kerogen samples(JJZG-1,JJZG-2 and JJZG-3)isolated from the Permian Lucaogou shales of varying biodegradation levels(BLs≈0,3 and 7,respectively)were subjected to sequential stepwise pyrolysis combined with on-line detection of gas chromatography-mass spectrometry(GC-MS).Occluded fractions(bitumenⅡ)released at low-temperature steps(≥410℃)show consistent biodegradative signatures with that reported for solvent-extracted fractions(bitumenⅠ)of the original shales,e.g.,broad range of abundant n-alkanes,isoprenoids and regular hopanes for the non-biodegraded JJZG-1;trace n-alkanes and abundant hopanes for the moderately biodegraded JJZG-2;and no n-alkanes but still prominent hopanes including the microbially produced 25-nohopanes for the severely biodegraded JJZG-3.This consistency between bitumenⅡand bitumenⅠfractions indicates the biodegradability of the kerogenoccluded bitumenⅡwith limited protection from host kerogen.A minor level of protection was suggested by the trace distribution of n-alkanes in the bitumenⅡof JJZG-2,whereas the bitumenⅠhad no nalkanes.The kerogen itself was more resistant to biodegradation as reflected by the persistence of high abundances of both n-alkanes and hopanes in the high temperature(≥460℃)products of all three kerogen samples.However,the relative abundances of these product groups did show some evidence of biodegradation alteration,e.g.,ratios of n-C_(15)alkene/C_(27)hop-17(21)-ene at 510℃pyrolysis decreased by order of magnitude from the non-biodegraded(JJZG-1=27.4)to highly biodegraded(0.3 for JJZG-3)samples.The reduced biodegradation impact on the kerogen fraction(Cf.bitumen fractions)was also evident by the absence of 25-norhopanes in the high-temperature analysis of the JJZG-3 kerogen.展开更多
A metallic binary-groove gratings, which can be exploited to absorb light at C-band and sense materials with refractive index (1.0 - 1.2), is proposed and investigated numerically. Both ultra-high absorption (99.937%)...A metallic binary-groove gratings, which can be exploited to absorb light at C-band and sense materials with refractive index (1.0 - 1.2), is proposed and investigated numerically. Both ultra-high absorption (99.937%) and sensitivity (1600 nm/RIU) are achieved.展开更多
Let G be a graph. A bipartition of G is a bipartition of V (G) with V (G) = V<sub>1</sub> ∪ V<sub>2</sub> and V<sub>1</sub> ∩ V<sub>2</sub> = ∅. If a bipartition satis...Let G be a graph. A bipartition of G is a bipartition of V (G) with V (G) = V<sub>1</sub> ∪ V<sub>2</sub> and V<sub>1</sub> ∩ V<sub>2</sub> = ∅. If a bipartition satisfies ∥V<sub>1</sub>∣ - ∣V<sub>2</sub>∥ ≤ 1, we call it a bisection. The research in this paper is mainly based on a conjecture proposed by Bollobás and Scott. The conjecture is that every graph G has a bisection (V<sub>1</sub>, V<sub>2</sub>) such that ∀v ∈ V<sub>1</sub>, at least half minuses one of the neighbors of v are in the V<sub>2</sub>;∀v ∈ V<sub>2</sub>, at least half minuses one of the neighbors of v are in the V<sub>1</sub>. In this paper, we confirm this conjecture for some bipartite graphs, crown graphs and windmill graphs.展开更多
Lithium(Li)is considered one of the most promising anode materials for next-generation batteries.However,Li dendrites and uncontrollable volume changes emerge during cycling,which severely restrict their commercial ap...Lithium(Li)is considered one of the most promising anode materials for next-generation batteries.However,Li dendrites and uncontrollable volume changes emerge during cycling,which severely restrict their commercial application.To achieve efficient and stable Li storage,we proposed an insitu lithiophilic strategy based on three-dimensional graphite(3D-G)current collectors.Specifically,we prepared the 3D-G rapidly with a high specific surface area(∼190.3 m2 g−1)using a freeze-drying technology.During an electrochemical prelithiation process,Li ions first intercalated into graphite to form a lithiophilic Li intercalated compound,and transformed into Li0,filling the pores,which weakened the local electron/ion mismatching during direct Li+→Li0 reaction and provided a smooth initial nucleation.Even at a high rate,the nucleation reaction under synchronous intercalation also promoted a superior nucleation process.Therefore,the LiFePO4||3D-G@Li battery maintained a capacity retention rate of 86%and a discharge specific capacity of 118.7mAh g−1 after 1000 cycles at 1 C.Furthermore,a finite element analysis showed that 3D-G exerted a uniform Li+distribution and a low local current density,conducive to the uniform deposition of Li.展开更多
Hutchinson-Gilford progeria syndrome(HGPS)is a rare progeroid disorder,and approximately 90%of cases are caused by LMNA mutation that yields the lamin A/C variant progerin.Progerin is toxic,and its clearance and disru...Hutchinson-Gilford progeria syndrome(HGPS)is a rare progeroid disorder,and approximately 90%of cases are caused by LMNA mutation that yields the lamin A/C variant progerin.Progerin is toxic,and its clearance and disruption have positive benefits on HGPS cells and mice and even HGPS patients.However,accelerating progerin clearance is still an unaddressed issue.Here,we report that primary cells from HGPS patients displayed lysosome defects and that counteracting lysosome defects via the activation of lysosome biogenesis promoted progerin clearance and accordingly alleviated cellular senescence in HGPS.We revealed that nucleus-localized progerin was expelled into the cytoplasm via nuclear envelope(NE)budding and degraded through autophagy in HGPS cells.Lysosome defects occurred in HGPS cells and impaired progerin clearance.Activating lysosome biogenesis via the protein kinase C(PKC)activator phorbol 12-myristate 13-acetate(PMA)or the m TORC1 inhibitor Torin 1 promoted progerin clearance and accordingly mitigated DNA damage,cell cycle arrest,low proliferation ability and senescence-associated secretory phenotype(SASP)in HGPS cells.Overall,we propose that,in HGPS,lysosomes exhibit defects and that activating lysosome biogenesis can accelerate progerin clearance and alleviate cellular senescence.These findings highlight the anti-senescence roles of PKC activation and lysosome biogenesis and provide new insights for understanding and treating HGPS.展开更多
Bulk synthesis of single-walled carbon nanotubes(SWNTs)using solid catalyst has been challenging,despite of recent breakthrough in the chirality-specific growth on the flat substrate surface.In this work,we propose a ...Bulk synthesis of single-walled carbon nanotubes(SWNTs)using solid catalyst has been challenging,despite of recent breakthrough in the chirality-specific growth on the flat substrate surface.In this work,we propose a porous magnesia support rhenium catalyst for bulk synthesis of SWNTs.It is found that the well-dispersed catalyst with a high melting point and the optimal chemical vapor deposition reaction conditions account for the growth of SWNTs.Detailed characterizations reveal the produced SWNTs are dominant in(n,n−1)and(n,n−2)species.Furthermore,by using a multicolumn chromatography post-growth separation method,SWNTs with three defined diameter ranges were obtained.This work guides the design of porous oxide supported catalyst for bulk synthesis and diameter-dependent sorting of SWNTs,which will ultimately help harness the extraordinary properties of SWNTs.展开更多
We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasi- continuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a...We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasi- continuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a linear phase gradient and realizes both full 2Jr phase shift and high transmission efficiency in the operating wavelength range from 740 to 780 nm. At the central wavelength around 751 nm, the total transmission efficiency is up to 88.0% and the section of the desired anomalous refraction is 80.4%. The anomalous refraction angle is 29.62°, and larger refraction angle can be achieved by changing the period of the super cell. We demonstrate a refraction angle as large as 38.59°, and the anomalous transmission efficiency reaches 76.6% at wavelength of 741 nm. It is worth mentioning that the structure is much simpler than conventional metasurfaces based on arrays of discrete nanoantennas. Our research may pave the way for designing efficient all-dielectric phase-gradient metasurfaces and applying them in integrated optical devices for wavefront control.展开更多
Metasurfaces have pioneered a new avenue for advanced wave-front engineering.Among the various types of metasurfaces,Huygens'metasurfaces are thought to be a novel paradigm for flat optical devices.Enabled by spec...Metasurfaces have pioneered a new avenue for advanced wave-front engineering.Among the various types of metasurfaces,Huygens'metasurfaces are thought to be a novel paradigm for flat optical devices.Enabled by spectrally overlapped electric resonance and magnetic resonance,Huygens'metasurfaces are imparted with high transmission and full phase coverage of 2π,which makes them capable of realizing high-efficiency wave-front control.However,a defect of Huygens'metasurfaces is that their phase profiles and transmissive responses are often sensitive to the interaction of neighboring Huygens'elements.Consequently,the original assigned phase distribution can be distorted.In this work,we present our design strategy of transmissive Huygens'metasurfaces performing anomalous refraction.We illustrate the investigation of Huygens'elements,realizing the overlapping between an electric dipole and magnetic dipole resonance based on cross-shaped structures.We find that the traditional discrete equidistant-phase design method is not enough to realize a transmissive Huygens'surface due to the interaction between neighboring Huygens'elements.Therefore,we introduce an extra optimization process on the element spacing to palliate the phase distortion resulting from the element interaction.Based on this method,we successfully design unequally spaced three-element transmissive metasurfaces exhibiting anomalous refraction effect.The anomalous refractive angle of the designed Huygens'metasurface is 30°,which exceeds the angles of most present transmissive Huygens'metasurfaces.A transmissive efficiency of 83.5%is numerically derived at the operating wavelength.The far-field electric distribution shows that about 93%of transmissive light is directed along the 30°refractive direction.The deflection angle can be tuned by adjusting the number of Huygens'elements in one metasurface unit cell.The design strategies used in this paper can be inspiring for other functional Huygens'metasurface schemes.展开更多
One-step deposition approaches have been widely applied and developed in the fabrication of quasi-2D perovskites.However,the regulation of quantum wells(QWs)and crystalline orientation is difficult and complicated whe...One-step deposition approaches have been widely applied and developed in the fabrication of quasi-2D perovskites.However,the regulation of quantum wells(QWs)and crystalline orientation is difficult and complicated when using this methodology.Sequential deposition is another widespread synthetic approach for preparing perovskite films and perovskite dimension engineering.In this article,δ-CsPbI_(3)intermediate phase assisted sequential(IPAS)deposition is successfully carried out to fabricate MA-free quasi-2D ACI perovskites.The amount of theδ-CsPbI_(3)intermediate phase in the PbI2 layer and the concentration of GAI molecule in the IPA solution both play important roles in the production of MA-free quasi-2D ACI perovskite films.The n value of the MA-free quasi-2D ACI perovskites can be adjusted,which affects the photovoltaic performance and device stability.Compared with one-step deposition,the MA-free quasi-2D ACI perovskites prepared via IPAS deposition have opposite reverse-graded QW distribution and improved vertical orientation,leading to a remarkable PEC of up to 18.86%and allowing the preparation of unpackaged devices with prominent working stability(80%,400 h).The underlying mechanism and crystallization pathway of IPAS deposition confirm that sequential deposition has unique superiority in regulating the QW distribution and crystalline orientation of quasi-2D perovskites.展开更多
A novel scheme for the design of an ultra-compact and high-performance optical switch is proposed and investigated numerically. Based on a standard silicon(Si) photonic stripe waveguide, a section of hyperbolic metama...A novel scheme for the design of an ultra-compact and high-performance optical switch is proposed and investigated numerically. Based on a standard silicon(Si) photonic stripe waveguide, a section of hyperbolic metamaterials(HMM) consisting of 20-pair alternating vanadium dioxide (VO_2)∕Si thin layers is inserted to realize the switching of fundamental TE mode propagation. Finite-element-method simulation results show that, with the help of an HMM with a size of 400 nm × 220 nm × 200 nm(width × height × length), the ON/OFF switching for fundamental TE mode propagation in an Si waveguide can be characterized by modulation depth(MD) of5.6 d B and insertion loss(IL) of 1.25 dB. It also allows for a relatively wide operating bandwidth of 215 nm maintaining MD > 5 dB and IL < 1.25 dB. Furthermore, we discuss that the tungsten-doped VO_2 layers could be useful for reducing metal-insulator-transition temperature and thus improving switching performance. In general, our findings may provide some useful ideas for optical switch design and application in an on-chip all-optical communication system with a demanding integration level.展开更多
In spite of the great progress of wound healing materials,the development of dressing with moisture permeabil-ity,stretchable capability,and adhesive performance remains a huge challenge.In this study,gelatin-dopamine...In spite of the great progress of wound healing materials,the development of dressing with moisture permeabil-ity,stretchable capability,and adhesive performance remains a huge challenge.In this study,gelatin-dopamine(GT-DA)nanofiber membrane was prepared by introducing dopamine(DA)into gelatin(GT)via electrospinning followed by in-situ reaction.The effects of DA dosage,crosslinking condition and crosslinking time on the mechanical properties of the fiber membrane were studied systematically.The resultant GT-DA nanofibrous hydrogels exhibited integrated stress strength of 1.96 MPa,good water absorption of 700%,and water vapor transmission(WVT:4.3 kg m^(-2)d^(-1)),which were superior than those of Mepiform■,a commercial adhesive silicone dressing.In addition,Fe^(3+)were introduced into one side of the nanofiber membrane.A stronger adhesion strength of 2.5 KPa on the porcine skin,which was 1.6 times higher than that of Mepiform■was achieved.Our research showed that the prepared nanofibrous hydrogel has potential as wound dressing and could be used in post-traumatic tissue healing engineering.This work presented a type of breathable,stretchable and adhesive nanofibrous hydrogels,which would ensure the stable attachment on wounds during movement as a wound healing material.展开更多
This paper uses ideas from biological evolution to analyze the evolution of the securities market in which rational and irrational traders coexist.A market evolutionary model is developed to describe the dynamic traje...This paper uses ideas from biological evolution to analyze the evolution of the securities market in which rational and irrational traders coexist.A market evolutionary model is developed to describe the dynamic trajectories of rational and irrational traders'wealth.The main question is,are irrational traders eliminated as the securities market evolves.The paper considers the impact of new entrants on the security market long-term equilibrium.In addition,it discusses the existence and uniqueness of the long-term equilibrium The paper finds that,under some market conditions,irrational traders could survive in the long run.展开更多
Background:A sudden outbreak of the coronavirus disease 2019(COVID-19)started in December 2019 in Wuhan,China.Up-to-date,there have been limited studies examining the anxiety status of Chinese individuals in the early...Background:A sudden outbreak of the coronavirus disease 2019(COVID-19)started in December 2019 in Wuhan,China.Up-to-date,there have been limited studies examining the anxiety status of Chinese individuals in the early phase of the pandemic period(January 30,2020–February 15,2020).This survey aimed to compare the level of anxiety of the medical staff with that of the public and to provide a theoretical basis for developing an effective psychological intervention.Method:Questionnaires were sent on the Internet(http://www.wjx.cn)during this period.The anxiety levels of Chinese people were investigated using the Self-Rating Anxiety Scale(SAS),and the demographic data were collected simultaneously.Results:A total of 1110 participants were enrolled in this study,with an effective response rate of 100%.A total of 482 respondents were medical staff(43.4%),while 628 were members of the general public(56.6%).The medical staff itself had a higher SAS score than the general public(48.36±13.40 vs.45.74±11.79,P<0.01),while the medical staff in Wuhan were more anxious than the public in Wuhan with a higher SAS score(54.17±14.08 vs.48.53±11.92,P<0.01).Conclusion:The COVID-19 pandemic has had a significant impact on the anxiety levels of the medical staff and the public,with the medical personnel showing a higher anxiety level than the public,especially female medical staff in Wuhan.Therefore,urgent intervention programs to reduce anxiety should be implemented.展开更多
基金co-supported by the Specialized Research Foundation of Civil Aircraft,China(MJ-2016-D-35)the Advanced Jet Propulsion Creativity Center,AEAC,China(HKCX2019-01-004)。
文摘The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods.The latter are based upon assumptions that often reveal to be limited for precooler design.In this paper,a refined design method considering the variations of fluid thermophysical properties,flow area and thermal parameters distortion,was proposed to remediate their limitations.Firstly,the precooler was discretized into a fixed number of sub-microtubes based on a new discretization criterion.Next,in-house one-dimensional(1D)and two-dimensional(2D)segmented models were established for rapid thermal design and precooler rating with non-uniform airflow,respectively.The heat transfer experimental studies of supercritical hydrocarbon fuel were performed to verify the Jackson correlation for precooler design and the in-house models were validated against the reported data from open literature.On this basis,the proposed method was employed for the design analysis of hydrocarbon fuel precoolers for precooled-Turbine Based Combined Cycle(TBCC)engines.The results show that the local performance of precoolers is intrinsically impacted by the aforementioned three variations.In the case study,the local heat transfer performance is drastically affected by coolant flow transition.While the circumferential temperature distortion of airflow is weakened by heat transfer.With consideration of additional parameter variations,this novel method improves design accuracy and shortens the design time.
基金This work was supported by the National Natural Science Foundation of China(No.61233006)the Seed Industry Development Project of Shanghai,China(Grant No.2016,1-8)+1 种基金Shanghai Agriculture Applied Technology Development Program,China(Grant No.20170304)X.Y.was supported by the State Scholarship Fund of China Scholarship Council(No.201706230173).
文摘Lettuce is an important leafy vegetable that represents a significant dietary source of antioxidants and bioactive compounds.However,the levels of metabolites in different lettuce cultivars are poorly characterized.In this study,we used combined GC×GC-TOF/MS and UPLC-IMS-QTOF/MS to detect and relatively quantify metabolites in 30 lettuce cultivars representing large genetic diversity.Comparison with online databases,the published literature,standards as well using collision cross-section values enabled putative identification of 171 metabolites.Sixteen of these 171 metabolites(including phenolic acid derivatives,glycosylated flavonoids,and one iridoid)were present at significantly different levels in leaf and head type lettuces,which suggested the significant metabolomic variations between the leaf and head types of lettuce are related to secondary metabolism.A combination of the results and metabolic network analysis techniques suggested that leaf and head type lettuces contain not only different levels of metabolites but also have significant variations in the corresponding associated metabolic networks.The novel lettuce metabolite library and novel non-targeted metabolomics strategy devised in this study could be used to further characterize metabolic variations between lettuce cultivars or other plants.Moreover,the findings of this study provide important insight into metabolic adaptations due to natural and human selection,which could stimulate further research to potentially improve lettuce quality,yield,and nutritional value.
基金Supported by the National Natural Science Foundation of China(81361140344 and21376164)National High Technology Reseach and Development Program of China(863Program,2015AA021002)Major National Scientific Instrument Development Project(21527812)
文摘The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives. The degradation process follows the first-order kinetics. A pH-rate profile exhibits the U-shape and shows the maximum stability of cefixime at pH = 6. The stability in different pure solvents is ranked as acetone 〉 ethanol 〉 methanol 〉 water, while the degradation rate of cefixime exists a maximum at the ratio of 0.6 in water ＋ methanol mixtures. In addition, the degradation rate increases with the temperature increasing and the activation energy of degradation was found to be 27.078 kJ. mol- 1 in acetone ＋ water mixed solvents. The addition of different additives was proven to either inhibit or accelerate the degradation. The degradation products were analyzed using HPLC, LC-MS and infrared spectroscopy, and the possible degradation pathways in acid as well as alkaline environment were proposed to help us understand the degradation behavior of cefixime.
基金This work was financially supported by the "973" National Basic Research Program of China (No. 2003CB314901)the National "863" High Technology Project of China (No. 2003AA311070)the Open Project of State Key Laboratory on Integrated Opto-electronics.
文摘A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on （001） substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.
文摘Immune function and antioxidant defense play an important role in protecting animals against pathogens and in controlling oxidative stress, respectively. Aldicarb is of great concern for human health due to its toxic nature, its extensive usage and consequent pollution. The hypothesis that aldicarb exposure would suppress immune function and antioxidant capacity in Kunming mice was to be tested in the present study. Twenty-three adult male mice were randomly divided into the control (n = 11) and the aldicarb treated (n = 12) groups. Food and water were provided ad libtum for both groups, while the aldicarb treated mice drank aldicarb solution (0.097 mg/L) for 22 days. Cellular immunity assessed by phytohaemagglutinin (PHA) response did not differ between the control and the aldicarb treated groups. Similarly, white blood cells were not influenced by aldicarb treatment. Moreover, aldicarb exposure had not significant effect on body mass, all organ masses detected. However, aldicarb treatment suppressed total antioxidant capacity in liver but not in kidneys. In summary, aldicarb treatment did not affect immune function, but suppressed liver antioxidant capacity in Kunming mice.
基金supported by the National Natural Science Foundation of China(grants No.41972163 and 42173055).
文摘Three kerogen samples(JJZG-1,JJZG-2 and JJZG-3)isolated from the Permian Lucaogou shales of varying biodegradation levels(BLs≈0,3 and 7,respectively)were subjected to sequential stepwise pyrolysis combined with on-line detection of gas chromatography-mass spectrometry(GC-MS).Occluded fractions(bitumenⅡ)released at low-temperature steps(≥410℃)show consistent biodegradative signatures with that reported for solvent-extracted fractions(bitumenⅠ)of the original shales,e.g.,broad range of abundant n-alkanes,isoprenoids and regular hopanes for the non-biodegraded JJZG-1;trace n-alkanes and abundant hopanes for the moderately biodegraded JJZG-2;and no n-alkanes but still prominent hopanes including the microbially produced 25-nohopanes for the severely biodegraded JJZG-3.This consistency between bitumenⅡand bitumenⅠfractions indicates the biodegradability of the kerogenoccluded bitumenⅡwith limited protection from host kerogen.A minor level of protection was suggested by the trace distribution of n-alkanes in the bitumenⅡof JJZG-2,whereas the bitumenⅠhad no nalkanes.The kerogen itself was more resistant to biodegradation as reflected by the persistence of high abundances of both n-alkanes and hopanes in the high temperature(≥460℃)products of all three kerogen samples.However,the relative abundances of these product groups did show some evidence of biodegradation alteration,e.g.,ratios of n-C_(15)alkene/C_(27)hop-17(21)-ene at 510℃pyrolysis decreased by order of magnitude from the non-biodegraded(JJZG-1=27.4)to highly biodegraded(0.3 for JJZG-3)samples.The reduced biodegradation impact on the kerogen fraction(Cf.bitumen fractions)was also evident by the absence of 25-norhopanes in the high-temperature analysis of the JJZG-3 kerogen.
文摘A metallic binary-groove gratings, which can be exploited to absorb light at C-band and sense materials with refractive index (1.0 - 1.2), is proposed and investigated numerically. Both ultra-high absorption (99.937%) and sensitivity (1600 nm/RIU) are achieved.
文摘Let G be a graph. A bipartition of G is a bipartition of V (G) with V (G) = V<sub>1</sub> ∪ V<sub>2</sub> and V<sub>1</sub> ∩ V<sub>2</sub> = ∅. If a bipartition satisfies ∥V<sub>1</sub>∣ - ∣V<sub>2</sub>∥ ≤ 1, we call it a bisection. The research in this paper is mainly based on a conjecture proposed by Bollobás and Scott. The conjecture is that every graph G has a bisection (V<sub>1</sub>, V<sub>2</sub>) such that ∀v ∈ V<sub>1</sub>, at least half minuses one of the neighbors of v are in the V<sub>2</sub>;∀v ∈ V<sub>2</sub>, at least half minuses one of the neighbors of v are in the V<sub>1</sub>. In this paper, we confirm this conjecture for some bipartite graphs, crown graphs and windmill graphs.
基金supported by the National Natural Science Foundation of China(grant no.22479060)the State Key Laboratory of Catalysis(grant no.2024SKL-A-004)the Major Science and Technology Projects for Independent Innovation of China First Automotive Works(FAW)Group Co.,Ltd.(grant nos.20220301018GX and 20220301019GX).
文摘Lithium(Li)is considered one of the most promising anode materials for next-generation batteries.However,Li dendrites and uncontrollable volume changes emerge during cycling,which severely restrict their commercial application.To achieve efficient and stable Li storage,we proposed an insitu lithiophilic strategy based on three-dimensional graphite(3D-G)current collectors.Specifically,we prepared the 3D-G rapidly with a high specific surface area(∼190.3 m2 g−1)using a freeze-drying technology.During an electrochemical prelithiation process,Li ions first intercalated into graphite to form a lithiophilic Li intercalated compound,and transformed into Li0,filling the pores,which weakened the local electron/ion mismatching during direct Li+→Li0 reaction and provided a smooth initial nucleation.Even at a high rate,the nucleation reaction under synchronous intercalation also promoted a superior nucleation process.Therefore,the LiFePO4||3D-G@Li battery maintained a capacity retention rate of 86%and a discharge specific capacity of 118.7mAh g−1 after 1000 cycles at 1 C.Furthermore,a finite element analysis showed that 3D-G exerted a uniform Li+distribution and a low local current density,conducive to the uniform deposition of Li.
基金supported by the National Natural Science Foundation of China(92254305,32130026,32070714)。
文摘Hutchinson-Gilford progeria syndrome(HGPS)is a rare progeroid disorder,and approximately 90%of cases are caused by LMNA mutation that yields the lamin A/C variant progerin.Progerin is toxic,and its clearance and disruption have positive benefits on HGPS cells and mice and even HGPS patients.However,accelerating progerin clearance is still an unaddressed issue.Here,we report that primary cells from HGPS patients displayed lysosome defects and that counteracting lysosome defects via the activation of lysosome biogenesis promoted progerin clearance and accordingly alleviated cellular senescence in HGPS.We revealed that nucleus-localized progerin was expelled into the cytoplasm via nuclear envelope(NE)budding and degraded through autophagy in HGPS cells.Lysosome defects occurred in HGPS cells and impaired progerin clearance.Activating lysosome biogenesis via the protein kinase C(PKC)activator phorbol 12-myristate 13-acetate(PMA)or the m TORC1 inhibitor Torin 1 promoted progerin clearance and accordingly mitigated DNA damage,cell cycle arrest,low proliferation ability and senescence-associated secretory phenotype(SASP)in HGPS cells.Overall,we propose that,in HGPS,lysosomes exhibit defects and that activating lysosome biogenesis can accelerate progerin clearance and alleviate cellular senescence.These findings highlight the anti-senescence roles of PKC activation and lysosome biogenesis and provide new insights for understanding and treating HGPS.
基金the National Key Research and Development Program of China(Nos.2020YFA0714700 and 2018YFA0208402)the National Natural Science Foundation of China(Nos.51972184,51820105002,11634014,and 51872320)+3 种基金the Key Basic Research Project of Shandong Province(No.ZR2019ZD49)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB33030100)the Key Research Program of Frontier Sciences,CAS(No.QYZDBSSW-SYS028)the Youth Innovation Promotion Association of CAS(No.2020005).
文摘Bulk synthesis of single-walled carbon nanotubes(SWNTs)using solid catalyst has been challenging,despite of recent breakthrough in the chirality-specific growth on the flat substrate surface.In this work,we propose a porous magnesia support rhenium catalyst for bulk synthesis of SWNTs.It is found that the well-dispersed catalyst with a high melting point and the optimal chemical vapor deposition reaction conditions account for the growth of SWNTs.Detailed characterizations reveal the produced SWNTs are dominant in(n,n−1)and(n,n−2)species.Furthermore,by using a multicolumn chromatography post-growth separation method,SWNTs with three defined diameter ranges were obtained.This work guides the design of porous oxide supported catalyst for bulk synthesis and diameter-dependent sorting of SWNTs,which will ultimately help harness the extraordinary properties of SWNTs.
基金National Key R&D Program of China(2016YFA0301300)National Natural Science Foundation of China(NSFC)(61275201,61372037)+2 种基金BUPT Excellent Ph.D.Students Foundation(CX2016204,CX2017401)Fundamental Research Funds for the Central Universities(2016RC24)Fund of State Key Laboratory of Information Photonics and Optical Communications(IPOC20172204)
文摘We propose and numerically investigate an efficient transmission-mode metasurface that consists of quasi- continuous trapezoid-shaped crystalline silicon nanoantennas on a quartz substrate. This metasurface provides a linear phase gradient and realizes both full 2Jr phase shift and high transmission efficiency in the operating wavelength range from 740 to 780 nm. At the central wavelength around 751 nm, the total transmission efficiency is up to 88.0% and the section of the desired anomalous refraction is 80.4%. The anomalous refraction angle is 29.62°, and larger refraction angle can be achieved by changing the period of the super cell. We demonstrate a refraction angle as large as 38.59°, and the anomalous transmission efficiency reaches 76.6% at wavelength of 741 nm. It is worth mentioning that the structure is much simpler than conventional metasurfaces based on arrays of discrete nanoantennas. Our research may pave the way for designing efficient all-dielectric phase-gradient metasurfaces and applying them in integrated optical devices for wavefront control.
基金National Key RD Program of China(2016YFA0301300)National Natural Science Foundation of China(61671090,61875021)+3 种基金Guangxi Key Laboratory of Wireless Wideband Communication and Signal ProcessingNatural Science Foundation of Beijing Municipality(2192036)Fundamental Research Funds for the Central UniversitiesFund of State Key Laboratory of IPOC(BUPT)(IPOC2019ZZ03)
文摘Metasurfaces have pioneered a new avenue for advanced wave-front engineering.Among the various types of metasurfaces,Huygens'metasurfaces are thought to be a novel paradigm for flat optical devices.Enabled by spectrally overlapped electric resonance and magnetic resonance,Huygens'metasurfaces are imparted with high transmission and full phase coverage of 2π,which makes them capable of realizing high-efficiency wave-front control.However,a defect of Huygens'metasurfaces is that their phase profiles and transmissive responses are often sensitive to the interaction of neighboring Huygens'elements.Consequently,the original assigned phase distribution can be distorted.In this work,we present our design strategy of transmissive Huygens'metasurfaces performing anomalous refraction.We illustrate the investigation of Huygens'elements,realizing the overlapping between an electric dipole and magnetic dipole resonance based on cross-shaped structures.We find that the traditional discrete equidistant-phase design method is not enough to realize a transmissive Huygens'surface due to the interaction between neighboring Huygens'elements.Therefore,we introduce an extra optimization process on the element spacing to palliate the phase distortion resulting from the element interaction.Based on this method,we successfully design unequally spaced three-element transmissive metasurfaces exhibiting anomalous refraction effect.The anomalous refractive angle of the designed Huygens'metasurface is 30°,which exceeds the angles of most present transmissive Huygens'metasurfaces.A transmissive efficiency of 83.5%is numerically derived at the operating wavelength.The far-field electric distribution shows that about 93%of transmissive light is directed along the 30°refractive direction.The deflection angle can be tuned by adjusting the number of Huygens'elements in one metasurface unit cell.The design strategies used in this paper can be inspiring for other functional Huygens'metasurface schemes.
基金supported by the National Natural Science Foundation of China(Grant/Award Numbers:52262033,51862017,51962015,52162028,and 21603086)the Science and Technology Department of Hubei Province(Grant/Award Number:2019AAA020)The authors also acknowledge the financial support by the Natural Science Foundation of Hunan Province(No.2022JJ40551).
文摘One-step deposition approaches have been widely applied and developed in the fabrication of quasi-2D perovskites.However,the regulation of quantum wells(QWs)and crystalline orientation is difficult and complicated when using this methodology.Sequential deposition is another widespread synthetic approach for preparing perovskite films and perovskite dimension engineering.In this article,δ-CsPbI_(3)intermediate phase assisted sequential(IPAS)deposition is successfully carried out to fabricate MA-free quasi-2D ACI perovskites.The amount of theδ-CsPbI_(3)intermediate phase in the PbI2 layer and the concentration of GAI molecule in the IPA solution both play important roles in the production of MA-free quasi-2D ACI perovskite films.The n value of the MA-free quasi-2D ACI perovskites can be adjusted,which affects the photovoltaic performance and device stability.Compared with one-step deposition,the MA-free quasi-2D ACI perovskites prepared via IPAS deposition have opposite reverse-graded QW distribution and improved vertical orientation,leading to a remarkable PEC of up to 18.86%and allowing the preparation of unpackaged devices with prominent working stability(80%,400 h).The underlying mechanism and crystallization pathway of IPAS deposition confirm that sequential deposition has unique superiority in regulating the QW distribution and crystalline orientation of quasi-2D perovskites.
基金Ministry of Science and Technology of the People's Republic of China(MOST)(2016YFA0301300)National Natural Science Foundation of China(NSFC)(61275201,61372037)+2 种基金Beijing University of Posts and Telecommunications(BUPT)Excellent Ph.D.Students Foundation(CX2016204)Fundamental Research Funds for the Central Universities(2016RC24)Beijing Excellent Ph.D.Thesis Guidance Foundation(20131001301)
文摘A novel scheme for the design of an ultra-compact and high-performance optical switch is proposed and investigated numerically. Based on a standard silicon(Si) photonic stripe waveguide, a section of hyperbolic metamaterials(HMM) consisting of 20-pair alternating vanadium dioxide (VO_2)∕Si thin layers is inserted to realize the switching of fundamental TE mode propagation. Finite-element-method simulation results show that, with the help of an HMM with a size of 400 nm × 220 nm × 200 nm(width × height × length), the ON/OFF switching for fundamental TE mode propagation in an Si waveguide can be characterized by modulation depth(MD) of5.6 d B and insertion loss(IL) of 1.25 dB. It also allows for a relatively wide operating bandwidth of 215 nm maintaining MD > 5 dB and IL < 1.25 dB. Furthermore, we discuss that the tungsten-doped VO_2 layers could be useful for reducing metal-insulator-transition temperature and thus improving switching performance. In general, our findings may provide some useful ideas for optical switch design and application in an on-chip all-optical communication system with a demanding integration level.
基金supported by the National Natural Science Foundation of China(81771338 and 52073055)Natural Science Foundation of Shanghai(19ZR1470500)+1 种基金the Fundamental Research Funds for the Central UniversitiesDHU Distinguished Young Professor Program.
文摘In spite of the great progress of wound healing materials,the development of dressing with moisture permeabil-ity,stretchable capability,and adhesive performance remains a huge challenge.In this study,gelatin-dopamine(GT-DA)nanofiber membrane was prepared by introducing dopamine(DA)into gelatin(GT)via electrospinning followed by in-situ reaction.The effects of DA dosage,crosslinking condition and crosslinking time on the mechanical properties of the fiber membrane were studied systematically.The resultant GT-DA nanofibrous hydrogels exhibited integrated stress strength of 1.96 MPa,good water absorption of 700%,and water vapor transmission(WVT:4.3 kg m^(-2)d^(-1)),which were superior than those of Mepiform■,a commercial adhesive silicone dressing.In addition,Fe^(3+)were introduced into one side of the nanofiber membrane.A stronger adhesion strength of 2.5 KPa on the porcine skin,which was 1.6 times higher than that of Mepiform■was achieved.Our research showed that the prepared nanofibrous hydrogel has potential as wound dressing and could be used in post-traumatic tissue healing engineering.This work presented a type of breathable,stretchable and adhesive nanofibrous hydrogels,which would ensure the stable attachment on wounds during movement as a wound healing material.
基金We gratefully acknowledge editors of Journal of Systems Scienence and Systems Engineering,and two anonymous referees for their valuable comments and suggestions.This paper is supported by the National Natural Science Foundation of China under Grant No.71790594 and Program for interdisciplinary direction team in Zhongyuan University of Technology,China.
文摘This paper uses ideas from biological evolution to analyze the evolution of the securities market in which rational and irrational traders coexist.A market evolutionary model is developed to describe the dynamic trajectories of rational and irrational traders'wealth.The main question is,are irrational traders eliminated as the securities market evolves.The paper considers the impact of new entrants on the security market long-term equilibrium.In addition,it discusses the existence and uniqueness of the long-term equilibrium The paper finds that,under some market conditions,irrational traders could survive in the long run.
文摘Background:A sudden outbreak of the coronavirus disease 2019(COVID-19)started in December 2019 in Wuhan,China.Up-to-date,there have been limited studies examining the anxiety status of Chinese individuals in the early phase of the pandemic period(January 30,2020–February 15,2020).This survey aimed to compare the level of anxiety of the medical staff with that of the public and to provide a theoretical basis for developing an effective psychological intervention.Method:Questionnaires were sent on the Internet(http://www.wjx.cn)during this period.The anxiety levels of Chinese people were investigated using the Self-Rating Anxiety Scale(SAS),and the demographic data were collected simultaneously.Results:A total of 1110 participants were enrolled in this study,with an effective response rate of 100%.A total of 482 respondents were medical staff(43.4%),while 628 were members of the general public(56.6%).The medical staff itself had a higher SAS score than the general public(48.36±13.40 vs.45.74±11.79,P<0.01),while the medical staff in Wuhan were more anxious than the public in Wuhan with a higher SAS score(54.17±14.08 vs.48.53±11.92,P<0.01).Conclusion:The COVID-19 pandemic has had a significant impact on the anxiety levels of the medical staff and the public,with the medical personnel showing a higher anxiety level than the public,especially female medical staff in Wuhan.Therefore,urgent intervention programs to reduce anxiety should be implemented.
