AIM: To track the short-term neck narrowing changes in Birmingham metal-on-metal hip resurfacing(MOMHR) patients. METHODS: Since 2001, the Center for Hip and Knee Replacement started a registry to prospectively collec...AIM: To track the short-term neck narrowing changes in Birmingham metal-on-metal hip resurfacing(MOMHR) patients. METHODS: Since 2001, the Center for Hip and Knee Replacement started a registry to prospectively collect data on hip and knee replacement patients. From June 2006 to October 2008, 139 MOMHR were performed at our center by two participate surgeons using Birmingham MOMHR prosthesis(Smith Nephew, United States). It is standard of care for patients to obtain low, anteriorposterior(LAP) pelvis radiographs immediately after MOMHR procedure and then at 3 mo, 1 year and 2 year follow up office visits. Inclusion criteria for the present study included patients who came back for follow up office visit at above mentioned time points and got LAP radiographs. Exclusion criteria include patients who missed more than two follow up time points and those with poor-quality X-rays. Two orthopaedic residency trained research fellows reviewed the X-rays independently at 4 time points, i.e., immediate after surgery, 3 mo, 1 year and 2 year. Neck-to-prosthesis ratio(NPR) was used as main outcome measure. Twenty cases were used as subjects to identify the reliability between two observers. An intraclass correlation coefficient at 0.8 was considered as satisfied. A paired t-test was used to evaluate the significant difference between different time points with P < 0.05 considered to be statistically significant.RESULTS: The mean NPRs were 0.852 ± 0.056, 0.839 ± 0.052, 0.835 ± 0.051, 0.83 ± 0.04 immediately, 3 mo, 1 year and 2 years post-operatively respectively. At 3 mo, NPR was significantly different from immediate postoperative X-ray(P < 0.001). There was no difference between 3 mo and 1 year(P = 0.14) and 2 years(P = 0.53). Femoral neck narrowing(FNN) exceeding 10% of the diameter of the neck was observed in only 4 patients(5.6%) at two years follow up. None of these patients developed a femoral neck fracture(FNF). CONCLUSION: Femoral neck narrowing after MOMHR occurred as early as 3 mo postoperatively, and stabilized thereafter. Excessive FNN was not common in patients within the first two years of surgery and was not correlated with risk of FNF.展开更多
This study considered whether the narrowing of the upper （broad and wandering） reaches of the Lower Yellow River could result in a reduction in sedimentation and even an increase in channel erosion in both the upper...This study considered whether the narrowing of the upper （broad and wandering） reaches of the Lower Yellow River could result in a reduction in sedimentation and even an increase in channel erosion in both the upper and the lower （narrow and meandering） reaches. Analysis of field data and numerical modeling results both justify the proposal to narrow the channel. A positive correlation was found between channel eroded-area and the channel width. Therefore narrowing under conditions of low flow will reduce the amount of erosion in the reach, which, in turn, will reduce the amount of sediment transported into the lower channel. This will reduce the amount of siltation in the lower reaches of the river. However, narrowing under conditions of high flow with a low concentration of sediment will reduce both the extent of flood attenuation along the narrowed channel and the amount of lateral channel bank collapse, which results in increased flows and less sedimentation in the lower channel, leading to increased erosion. When flows with a high concentration of sediment are released from the Xiaolangdi Reservoir, both the lower narrow channel and the upper channel can transport a large amount of the sediment load. It is concluded that the narrowing of the upper broad channel will result in a reduction in sedimentation, or even in channel erosion, in both the upper and the lower channels if the reservoir is operated such that the volume of sediment added during low flows is balanced by the volume eroded during high flows with a low concentration of sediment.展开更多
A new layered Cu-based oxychalcogenide Ba_3Fe_2O_5Cu_2S_2 has been synthesized and its magnetic and electronic properties were revealed. Ba_3Fe_2O_5Cu_2S_2 is built up by alternatively stacking [Cu_2S_2]^（2-） layers...A new layered Cu-based oxychalcogenide Ba_3Fe_2O_5Cu_2S_2 has been synthesized and its magnetic and electronic properties were revealed. Ba_3Fe_2O_5Cu_2S_2 is built up by alternatively stacking [Cu_2S_2]^（2-） layers and iron perovskite oxide[（FeO_2）（BaO）（FeO_2）]^（2-）layers along the c axis that are separated by barium ions with Fe^（3＋） fivefold coordinated by a square-pyramidal arrangement of oxygen. From the bond valence arguments, we inferred that in layered CuC h-based（Ch =S, Se, Te） compounds the ＋3 cation in perovskite oxide sheet prefers a square pyramidal site, while the lower valence cation prefers the square planar sites. The studies on susceptibility, transport, and optical reflectivity indicate that Ba_3Fe_2O_5Cu_2S_2 is an antiferromagnetic semiconductor with a Ne′el temperature of 121 K and an optical bandgap of 1.03 eV. The measurement of heat capacity from 10 K to room temperature shows no anomaly at 121 K. The Debye temperature is determined to be 113 K. Theoretical calculations indicate that the conduction band minimum is predominantly contributed by O 2p and 3 d states of Fe ions that antiferromagnetically arranged in FeO_2 layers. The Fe 3d states are located at lower energy and result in a narrow bandgap in comparison with that of the isostructural Sr_3Sc_2O_5Cu_2S_2.展开更多
Nitrogen(N)doping has been widely adopted to improve the light absorption of TiO_(2).However,the newly introduced N-2p states are largely localized thus barely overlap with O-2p states in the valence band of TiO_(2),r...Nitrogen(N)doping has been widely adopted to improve the light absorption of TiO_(2).However,the newly introduced N-2p states are largely localized thus barely overlap with O-2p states in the valence band of TiO_(2),resulting in a shoulder-like absorption edge.To realize an apparent overlap between N-2p and O-2p states,charge compensation between N^(3-)and O^(2-)via electron transfer from oxygen vacancies(VO)to N dopants is one possible strategy.To verify this,in numerous doping configurations of N/VO-codoped anatase TiO_(2),we identified two types of VOposition independent N-dopant spatial orderings by efficient screening enabled with a newly designed structural descriptor.Compared with others,these two types of the N-dopant spatial orderings are highly beneficial for charge compensation to produce an apparent overlap between N-2p and O-2p states,therefore achieving a large bandgap narrowing.Furthermore,the two types of the N-dopant spatial orderings can also be generalized to N/VO-codoped rutile TiO_(2)for bandgap narrowing.展开更多
We investigate the resonance fluorescence spectrum of an atomic three-level ladder system driven by two laser fields. We show that such a system emulates to a large degree a V-type atom with parallel dipole moments-th...We investigate the resonance fluorescence spectrum of an atomic three-level ladder system driven by two laser fields. We show that such a system emulates to a large degree a V-type atom with parallel dipole moments-the latter being a system that exhibits spontaneously generated coherence and can display ultrasharp spectral lines. We find a suitable energy scheme in a SSRb atom and experimentally observe the narrowing of the central peak in a rubidium atomic beam. The corresponding spectrum can convindngiy demonstrate the existence of spontaneously generated coherence.展开更多
This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency （EIT） in a thin vapour film of A-type atoms confined between two dielectric walls whose thickness ...This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency （EIT） in a thin vapour film of A-type atoms confined between two dielectric walls whose thickness is comparable with the wavelength of the probe field. The absorptive lines of the weak probe field exhibit strong reductions and very narrow EIT dips, which mainly results from the velocity slow-down effects and transient behaviour of atoms in a confined system. It is also shown that the lines are modified by the strength of the coupling field and the ratio of L/λ, with L the film thickness and λthe wavelength of the probe field. A simple robust recipe for EIT in a thin medium is achievable in experiment.展开更多
We present a quantum-theoretical treatment of cavity linewidth narrowing with intracavity electromagnetically in- duced transparency （EIT）. By means of intracavity EIT, the photons in the cavity are in the form of c...We present a quantum-theoretical treatment of cavity linewidth narrowing with intracavity electromagnetically in- duced transparency （EIT）. By means of intracavity EIT, the photons in the cavity are in the form of cavity polaritons： bright-state polariton and dark-state polariton. Strong coupling of the bright-state polariton to the excited state induces an effect known as vacuum Rabi splitting, whereas the dark-state polariton decoupled from the excited state induces a narrow cavity transmission window. Our analysis would provide a quantum theory of linewidth narrowing with a quantum field pulse.展开更多
Inequality in distribution has become an issue of public concern in China. Incomes of the Chinese people have grown year after year ever since the reform and opening era began in the late 1970s. Meanwhile, the income ...Inequality in distribution has become an issue of public concern in China. Incomes of the Chinese people have grown year after year ever since the reform and opening era began in the late 1970s. Meanwhile, the income gap between urban and rural residents has widened constantly, from 1.8:1 in the mid-1980s to 3.2:1 in 2003. In a report entitled Analysis and Forecast of China's Social Conditions 2004-2005, experts with the Chinese Academy of Social Sciences listed the widening income gaps as the second most serious of the six problems China is facing. The report notes that such gaps have kept widening not only between individual workers in the same profession but also between workers in different industries and regions. In view of this, the national economic work conference held in early January called for effort to improve the order of income distribution and readjust the distribution of national wealth in an appropriate manner. How to view the problem of inequality in distribution as we see now? How the divide of the rich and the poor affects the improvement of human rights? What should be done to narrow the gap between the rich and the poor? We have dis- cussed these questions with two leading social scientists in China, Sun Guohua, pro- fessor of law at the Renmin University of China and Prof. Hu Angang of Qinghua University, a noted expert in study of the conditions in China.展开更多
For a three-level atom, two nondegenerate(even microwave and optical) electric dipole transitions are usually allowed;for either of these, the fluorescence spectra are well-described in terms of spontaneous transition...For a three-level atom, two nondegenerate(even microwave and optical) electric dipole transitions are usually allowed;for either of these, the fluorescence spectra are well-described in terms of spontaneous transitions from a triplet of dressed sublevels to an adjacent lower-lying triplet. When the three dressed sublevels are equally spaced from each other, a remarkable feature known as degenerate cascade fluorescence takes place, which displays a five-peaked structure. We show that a single cavity can make all the spectral lines extremely narrow, whether they arise from cavity-coupled or cavity-free transitions. This effect is based on intrinsic cascade lasing feedback and makes it possible to use a single microwave cavity(even a bad cavity) to narrow the spectral lines in the optical frequency regime.展开更多
Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other...Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.展开更多
Stable laser emission with narrow linewidth is of critical importance in many applications,including coherent communications,LIDAR,and remote sensing.In this work,the physics underlying spectral narrowing of self-inje...Stable laser emission with narrow linewidth is of critical importance in many applications,including coherent communications,LIDAR,and remote sensing.In this work,the physics underlying spectral narrowing of self-injection-locked on-chip lasers to Hz-level lasing linewidth is investigated using a composite-cavity structure.Heterogeneously integrated III–V/SiN lasers operating with quantum-dot and quantum-well active regions are analyzed with a focus on the effects of carrier quantum confinement.The intrinsic differences are associated with gain saturation and carrier-induced refractive index,which are directly connected with 0-and 2-dimensional carrier densities of states.Results from parametric studies are presented for tradeoffs involved with tailoring the linewidth,output power,and injection current for different device configurations.Though both quantum-well and quantum-dot devices show similar linewidth-narrowing capabilities,the former emits at a higher optical power in the self-injection-locked state,while the latter is more energy-efficient.Lastly,a multi-objective optimization analysis is provided to optimize the operation and design parameters.For the quantum-well laser,minimizing the number of quantum-well layers is found to decrease the threshold current without significantly reducing the output power.For the quantum-dot laser,increasing the quantum-dot layers or density in each layer increases the output power without significantly increasing the threshold current.These findings serve to guide more detailed parametric studies to produce timely results for engineering design.展开更多
The effect of negative bias temperature instability （NBTI） on a single event transient （SET） has been studied in a 130 nm bulk silicon CMOS process based on 3D TCAD device simulations. The investigation shows that...The effect of negative bias temperature instability （NBTI） on a single event transient （SET） has been studied in a 130 nm bulk silicon CMOS process based on 3D TCAD device simulations. The investigation shows that NBTI can result in the pulse width and amplitude of SET narrowing when the heavy ion hits the PMOS in the high-input inverter; but NBTI can result in the pulse width and amplitude of SET broadening when the heavy ion hits the NMOS in the low-input inverter. Based on this study, for the first time we propose that the impact of NBTI on a SET produced by the heavy ion hitting the NMOS has already been a significant reliability issue and should be of wide concern, and the radiation hardened design must consider the impact of NBTI on a SET.展开更多
Heavy doping of the base in HBTs brings about a bandgap narrowing （BGN） effect, which modifies the intrinsic carrier density and disturbs the band offset, and thus leads to the change of the currents. Based on a the...Heavy doping of the base in HBTs brings about a bandgap narrowing （BGN） effect, which modifies the intrinsic carrier density and disturbs the band offset, and thus leads to the change of the currents. Based on a thermionic-field-diffusion model that is used to the analyze the performance of an abrupt HBT with a heavydoped base, the conclusion is made that, although the BGN effect makes the currents obviously change due to the modification of the intrinsic carrier density, the band offsets disturbed by the BGN effect should also be taken into account in the analysis of the electrical characteristics of abrupt HBTs. In addition, the BGN effect changes the bias voltage for the onset of Kirk effects.展开更多
In this article, we apply the first elliptic function equation to find a new kind of solutions of nonlinear partial differential equations （PDEs） based on the ho- mogeneous balance method, the Jacobi elliptic expans...In this article, we apply the first elliptic function equation to find a new kind of solutions of nonlinear partial differential equations （PDEs） based on the ho- mogeneous balance method, the Jacobi elliptic expansion method and the auxiliary equation method. New exact solutions to the Jacobi elliptic functions of a nonlinear PDE describing pulse narrowing nonlinear transmission lines are given with the aid of computer program, e.g. Maple or Mathematica. Based on Kirchhoff＇s current law and Kirchhoff＇s voltage law, the given nonlinear PDE has been derived and can be reduced to a nonlinear ordinary differential equation （ODE） using a simple transformation. The given method in this article is straightforward and concise, and can be applied to other nonlinear PDEs in mathematical physics. Further results may be obtained.展开更多
The generation of mid-infrared pulsed lasers was achieved in a Ho3+:YAG laser pumped gain-switched Cr^2+:Cd Se laser system with the shortest pulse duration of 4.15 ns.With a pump pulse duration of 50 ns and pump powe...The generation of mid-infrared pulsed lasers was achieved in a Ho3+:YAG laser pumped gain-switched Cr^2+:Cd Se laser system with the shortest pulse duration of 4.15 ns.With a pump pulse duration of 50 ns and pump power of 2.7 W,the gain-switched Cr^2+:Cd Se laser achieved over 10 times pulse narrowing,obtaining the maximum peak power of 5.7 k W.The optical-to-optical conversion efficiency was 3.7%,which could be further improved with better crystal surface polishing quality.The laser central wavelength was measured to be 2.65μm with a bandwidth(FWHM)of 50 nm.In addition,the parameter optimization for suppressing the pulse tail was discussed,while the long cavity and high output transmissivity contributed to obtaining the single-peak pulses.展开更多
A tunable single-longitudinal-mode（SLM） semiconductor optical amplifier（SOA）-based fiber laser based on a dispersion-shifted fiber（DSF） is proposed and successfully demonstrated. SLM operation is obtained due to...A tunable single-longitudinal-mode（SLM） semiconductor optical amplifier（SOA）-based fiber laser based on a dispersion-shifted fiber（DSF） is proposed and successfully demonstrated. SLM operation is obtained due to the spectral narrowing effect resulting from inverse four-wave mixing in a DSF. A tunable optical filter performs wavelength selection function. By inserting a length of DSF in the laser cavity, SLM lasing can possibly be obtained when laser oscillation is stably established after traveling through the DSF many roundtrips. Stable tunable SLM oscillation with a signal-to-noise ratio as high as 65 dB over a wavelength range of about 35 nm is achieved experimentally, and each spectral linewidth is less than 6.5 kHz.展开更多
BACKGROUND Early esophageal neuroendocrine carcinoma(E-NEC)is a rare but aggressive malignancy with poorly understood endoscopic features.Despite advancements in multi-model endoscopy,including white light endoscopy,m...BACKGROUND Early esophageal neuroendocrine carcinoma(E-NEC)is a rare but aggressive malignancy with poorly understood endoscopic features.Despite advancements in multi-model endoscopy,including white light endoscopy,magnifying end-oscopy narrow-band imaging(NBI),and endoscopic ultrasonography(EUS),the diagnostic characteristics of early E-NEC remain unclear.Comprehensive evalu-ation using these techniques can improve early detection and guide clinical management.This study aimed to investigate the endoscopic features of early E-NEC using multiple imaging modalities.We hypothesized that specific endos-copic patterns,such as irregular microvascular morphology or signs of submu-cosal invasion,could reliably distinguish early E-NEC from other esophageal lesions.AIM To characterize early E-NEC using multi-model endoscopy and identify diag-nostic endoscopic features.METHODS Clinical data of four patients with esophageal submucosal lesions identified by gastroscopy and pathologically diagnosed as E-NEC in the Department of Gastroenterology,The First Affiliated Hospital of Zhejiang University School of Medicine between January 2020 and August 2024 were retrospectively analyzed,and their manifestations under multi-model endoscopy were observed.Grayscale values of ultrasound images in three patients with E-NEC and eight with esophageal leiomyoma were calculated using Image J software and compared using the Mann-Whitney U test.Neuroendocrine neoplasms(NENs)are a rare heterogeneous group of epithelial tumors that originate from peptidergic neurons and neuroendocrine cells,and are characterized by neuroendocrine differentiation.NENs include well-differen-tiated neuroendocrine tumors(NETs),poorly differentiated neuroendocrine carcinomas(NECs),and mixed neuroen-docrine-non-NENs[1],which exhibit a wide range of biological behaviors,from indolent,slow-growing lesions to highly aggressive and metastatic malignancies[2].NENs have the capacity for whole-body distribution,with gastroenteropan-creatic NENs comprising approximately 60%-75%of cases,followed by those in the lungs and mediastinum[3].Eso-phageal NENs(E-NENs)are extremely rare,accounting for only approximately 1.6%of all NENs and occurring far less frequently than other gastrointestinal NENs[4].However,with advancements in early cancer screening and diagnostic techniques,the incidence of E-NENs has gradually increased in recent decades[5].Among E-NENs,<1%are well-differ-entiated NETs,with the vast majority being poorly differentiated small cell NECs[6,7].Nevertheless,esophageal NEC(E-NEC)accounts for only 0.05%-7.6%of all esophageal malignant tumors[8,9],and is characterized by aggressive behavior,rapid progression,and early metastasis.E-NEC primarily affects middle-aged and older individuals,with a higher prevalence in males[10].The tumor-node-metastasis staging system of E-NEC mirrors that of esophageal squamous cell carcinoma(ESCC)[11,12].Early E-NEC is defined as lesions limited to the mucosal or submucosal layer(stages T1a and T1b),with or without nodal metastasis.Clinically,we found that early E-NEC often presents with absent or non-specific symptoms,such as mild dysphagia or retrosternal discomfort,which are easily overlooked or mistaken for benign esophageal conditions such as leiomyoma.Conventional imaging and tumor markers frequently fail to detect early lesions,and endoscopic biopsy results may be inconclusive due to submucosal tumor growth and the overlying normal epithelium[13].As a result,E-NEC is frequently diagnosed at an advanced stage(31%-90%of cases)when regional lymph node or distant metastases have already occurred,contributing to its poor prognosis[2,13,14].Studies have reported a median survival of approximately 11 months and 5-year survival rate of<10%[14].Given these challenges,early detection using endoscopy is essential for improving patient outcomes.展开更多
Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past decade.To understand their emergent quantum phenomena,high-quality single crystals of substantial size are ess...Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past decade.To understand their emergent quantum phenomena,high-quality single crystals of substantial size are essential.Here,we report the synthesis of single crystals of the Kitaev quantum spin liquid candidate RuBr_(3),achieving millimeter-sized crystals through a self-flux method under high pressure and high temperature conditions.The crystals exhibit well-defined cleavage planes with a lustrous appearance.Transport characterizations exhibit a narrow band-gap semiconducting behavior with 0.13 eV and 0.11 eV band-gap in ab plane and along𝑐axis,respectively.Magnetic measurement shows a transition to antiferromagnetic(AFM)state at approximately 29K both in ab plane and along the c axis.Notably,the N′eel temperature increases to 34K with an applied magnetic field of up to 7T in the ab plane,but without any change along𝑐axis.The large size and high quality of RuBr3 single crystals provide a valuable platform for investigating various interactions,particularly the Kitaev interaction,and for elucidating the intrinsic physical properties of Kitaev quantum spin liquids.展开更多
文摘AIM: To track the short-term neck narrowing changes in Birmingham metal-on-metal hip resurfacing(MOMHR) patients. METHODS: Since 2001, the Center for Hip and Knee Replacement started a registry to prospectively collect data on hip and knee replacement patients. From June 2006 to October 2008, 139 MOMHR were performed at our center by two participate surgeons using Birmingham MOMHR prosthesis(Smith Nephew, United States). It is standard of care for patients to obtain low, anteriorposterior(LAP) pelvis radiographs immediately after MOMHR procedure and then at 3 mo, 1 year and 2 year follow up office visits. Inclusion criteria for the present study included patients who came back for follow up office visit at above mentioned time points and got LAP radiographs. Exclusion criteria include patients who missed more than two follow up time points and those with poor-quality X-rays. Two orthopaedic residency trained research fellows reviewed the X-rays independently at 4 time points, i.e., immediate after surgery, 3 mo, 1 year and 2 year. Neck-to-prosthesis ratio(NPR) was used as main outcome measure. Twenty cases were used as subjects to identify the reliability between two observers. An intraclass correlation coefficient at 0.8 was considered as satisfied. A paired t-test was used to evaluate the significant difference between different time points with P < 0.05 considered to be statistically significant.RESULTS: The mean NPRs were 0.852 ± 0.056, 0.839 ± 0.052, 0.835 ± 0.051, 0.83 ± 0.04 immediately, 3 mo, 1 year and 2 years post-operatively respectively. At 3 mo, NPR was significantly different from immediate postoperative X-ray(P < 0.001). There was no difference between 3 mo and 1 year(P = 0.14) and 2 years(P = 0.53). Femoral neck narrowing(FNN) exceeding 10% of the diameter of the neck was observed in only 4 patients(5.6%) at two years follow up. None of these patients developed a femoral neck fracture(FNF). CONCLUSION: Femoral neck narrowing after MOMHR occurred as early as 3 mo postoperatively, and stabilized thereafter. Excessive FNN was not common in patients within the first two years of surgery and was not correlated with risk of FNF.
文摘This study considered whether the narrowing of the upper （broad and wandering） reaches of the Lower Yellow River could result in a reduction in sedimentation and even an increase in channel erosion in both the upper and the lower （narrow and meandering） reaches. Analysis of field data and numerical modeling results both justify the proposal to narrow the channel. A positive correlation was found between channel eroded-area and the channel width. Therefore narrowing under conditions of low flow will reduce the amount of erosion in the reach, which, in turn, will reduce the amount of sediment transported into the lower channel. This will reduce the amount of siltation in the lower reaches of the river. However, narrowing under conditions of high flow with a low concentration of sediment will reduce both the extent of flood attenuation along the narrowed channel and the amount of lateral channel bank collapse, which results in increased flows and less sedimentation in the lower channel, leading to increased erosion. When flows with a high concentration of sediment are released from the Xiaolangdi Reservoir, both the lower narrow channel and the upper channel can transport a large amount of the sediment load. It is concluded that the narrowing of the upper broad channel will result in a reduction in sedimentation, or even in channel erosion, in both the upper and the lower channels if the reservoir is operated such that the volume of sediment added during low flows is balanced by the volume eroded during high flows with a low concentration of sediment.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51472266,51202286,and 91422303)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB07020100)the ICDD
文摘A new layered Cu-based oxychalcogenide Ba_3Fe_2O_5Cu_2S_2 has been synthesized and its magnetic and electronic properties were revealed. Ba_3Fe_2O_5Cu_2S_2 is built up by alternatively stacking [Cu_2S_2]^（2-） layers and iron perovskite oxide[（FeO_2）（BaO）（FeO_2）]^（2-）layers along the c axis that are separated by barium ions with Fe^（3＋） fivefold coordinated by a square-pyramidal arrangement of oxygen. From the bond valence arguments, we inferred that in layered CuC h-based（Ch =S, Se, Te） compounds the ＋3 cation in perovskite oxide sheet prefers a square pyramidal site, while the lower valence cation prefers the square planar sites. The studies on susceptibility, transport, and optical reflectivity indicate that Ba_3Fe_2O_5Cu_2S_2 is an antiferromagnetic semiconductor with a Ne′el temperature of 121 K and an optical bandgap of 1.03 eV. The measurement of heat capacity from 10 K to room temperature shows no anomaly at 121 K. The Debye temperature is determined to be 113 K. Theoretical calculations indicate that the conduction band minimum is predominantly contributed by O 2p and 3 d states of Fe ions that antiferromagnetically arranged in FeO_2 layers. The Fe 3d states are located at lower energy and result in a narrow bandgap in comparison with that of the isostructural Sr_3Sc_2O_5Cu_2S_2.
基金financially supported by the National Natural Science Foundation of China(Nos.51972312,51825204,21633009)。
文摘Nitrogen(N)doping has been widely adopted to improve the light absorption of TiO_(2).However,the newly introduced N-2p states are largely localized thus barely overlap with O-2p states in the valence band of TiO_(2),resulting in a shoulder-like absorption edge.To realize an apparent overlap between N-2p and O-2p states,charge compensation between N^(3-)and O^(2-)via electron transfer from oxygen vacancies(VO)to N dopants is one possible strategy.To verify this,in numerous doping configurations of N/VO-codoped anatase TiO_(2),we identified two types of VOposition independent N-dopant spatial orderings by efficient screening enabled with a newly designed structural descriptor.Compared with others,these two types of the N-dopant spatial orderings are highly beneficial for charge compensation to produce an apparent overlap between N-2p and O-2p states,therefore achieving a large bandgap narrowing.Furthermore,the two types of the N-dopant spatial orderings can also be generalized to N/VO-codoped rutile TiO_(2)for bandgap narrowing.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB921603)the National Natural Science Foundation of China (Grant Nos. 11074097,10904048,10974071,and 11004080)
文摘We investigate the resonance fluorescence spectrum of an atomic three-level ladder system driven by two laser fields. We show that such a system emulates to a large degree a V-type atom with parallel dipole moments-the latter being a system that exhibits spontaneously generated coherence and can display ultrasharp spectral lines. We find a suitable energy scheme in a SSRb atom and experimentally observe the narrowing of the central peak in a rubidium atomic beam. The corresponding spectrum can convindngiy demonstrate the existence of spontaneously generated coherence.
文摘This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency （EIT） in a thin vapour film of A-type atoms confined between two dielectric walls whose thickness is comparable with the wavelength of the probe field. The absorptive lines of the weak probe field exhibit strong reductions and very narrow EIT dips, which mainly results from the velocity slow-down effects and transient behaviour of atoms in a confined system. It is also shown that the lines are modified by the strength of the coupling field and the ratio of L/λ, with L the film thickness and λthe wavelength of the probe field. A simple robust recipe for EIT in a thin medium is achievable in experiment.
基金supported by the National Natural Science Foundation of China(Grants Nos.11204080,11274112,91321101,and 61275215)the Fundamental Research Fund for the Central Universities of China(Grants No.WM1313003)
文摘We present a quantum-theoretical treatment of cavity linewidth narrowing with intracavity electromagnetically in- duced transparency （EIT）. By means of intracavity EIT, the photons in the cavity are in the form of cavity polaritons： bright-state polariton and dark-state polariton. Strong coupling of the bright-state polariton to the excited state induces an effect known as vacuum Rabi splitting, whereas the dark-state polariton decoupled from the excited state induces a narrow cavity transmission window. Our analysis would provide a quantum theory of linewidth narrowing with a quantum field pulse.
文摘Inequality in distribution has become an issue of public concern in China. Incomes of the Chinese people have grown year after year ever since the reform and opening era began in the late 1970s. Meanwhile, the income gap between urban and rural residents has widened constantly, from 1.8:1 in the mid-1980s to 3.2:1 in 2003. In a report entitled Analysis and Forecast of China's Social Conditions 2004-2005, experts with the Chinese Academy of Social Sciences listed the widening income gaps as the second most serious of the six problems China is facing. The report notes that such gaps have kept widening not only between individual workers in the same profession but also between workers in different industries and regions. In view of this, the national economic work conference held in early January called for effort to improve the order of income distribution and readjust the distribution of national wealth in an appropriate manner. How to view the problem of inequality in distribution as we see now? How the divide of the rich and the poor affects the improvement of human rights? What should be done to narrow the gap between the rich and the poor? We have dis- cussed these questions with two leading social scientists in China, Sun Guohua, pro- fessor of law at the Renmin University of China and Prof. Hu Angang of Qinghua University, a noted expert in study of the conditions in China.
基金supported by the National Natural Science Foundation of China (Grants Nos. 61875067 and 61178021)。
文摘For a three-level atom, two nondegenerate(even microwave and optical) electric dipole transitions are usually allowed;for either of these, the fluorescence spectra are well-described in terms of spontaneous transitions from a triplet of dressed sublevels to an adjacent lower-lying triplet. When the three dressed sublevels are equally spaced from each other, a remarkable feature known as degenerate cascade fluorescence takes place, which displays a five-peaked structure. We show that a single cavity can make all the spectral lines extremely narrow, whether they arise from cavity-coupled or cavity-free transitions. This effect is based on intrinsic cascade lasing feedback and makes it possible to use a single microwave cavity(even a bad cavity) to narrow the spectral lines in the optical frequency regime.
基金financially supported by the Key Research and Development Program of Ningbo(Grant No.2023Z098)Natural Science Foundation of Inner Mongolia(Grant No.2023MS05040)+1 种基金Shenyang Collaborative Innovation Center Project for Multiple Energy Fields Composite Processing of Special Materials(Grant No.JG210027)Shenyang Key Technology Special Project of The Open Competition Mechanism to Select the Best Solution(Grant Nos.2022210101000827,2022-0-43-048).
文摘Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.
基金supported by King Abdullah University of Science and Technology(KAUST)Research Funding(KRF)under Award No.ORA-2022-5314Advanced Research Projects Agency-Energy(ARPA-E)No.DE-AR000067+1 种基金the U.S.Department of Energy under Contract No.DE-AC04-94AL85000the American Institute for Manufacturing(AIM)Integrated Photonics.
文摘Stable laser emission with narrow linewidth is of critical importance in many applications,including coherent communications,LIDAR,and remote sensing.In this work,the physics underlying spectral narrowing of self-injection-locked on-chip lasers to Hz-level lasing linewidth is investigated using a composite-cavity structure.Heterogeneously integrated III–V/SiN lasers operating with quantum-dot and quantum-well active regions are analyzed with a focus on the effects of carrier quantum confinement.The intrinsic differences are associated with gain saturation and carrier-induced refractive index,which are directly connected with 0-and 2-dimensional carrier densities of states.Results from parametric studies are presented for tradeoffs involved with tailoring the linewidth,output power,and injection current for different device configurations.Though both quantum-well and quantum-dot devices show similar linewidth-narrowing capabilities,the former emits at a higher optical power in the self-injection-locked state,while the latter is more energy-efficient.Lastly,a multi-objective optimization analysis is provided to optimize the operation and design parameters.For the quantum-well laser,minimizing the number of quantum-well layers is found to decrease the threshold current without significantly reducing the output power.For the quantum-dot laser,increasing the quantum-dot layers or density in each layer increases the output power without significantly increasing the threshold current.These findings serve to guide more detailed parametric studies to produce timely results for engineering design.
基金Project supported by the Key Program of the National Natural Science Foundation of China(No.60836004)the National Natural Science Foundation of China(Nos.61006070,61076025)
文摘The effect of negative bias temperature instability （NBTI） on a single event transient （SET） has been studied in a 130 nm bulk silicon CMOS process based on 3D TCAD device simulations. The investigation shows that NBTI can result in the pulse width and amplitude of SET narrowing when the heavy ion hits the PMOS in the high-input inverter; but NBTI can result in the pulse width and amplitude of SET broadening when the heavy ion hits the NMOS in the low-input inverter. Based on this study, for the first time we propose that the impact of NBTI on a SET produced by the heavy ion hitting the NMOS has already been a significant reliability issue and should be of wide concern, and the radiation hardened design must consider the impact of NBTI on a SET.
基金supported by the State Key Development Program for Basic Research of China (No. 2003CB314901)
文摘Heavy doping of the base in HBTs brings about a bandgap narrowing （BGN） effect, which modifies the intrinsic carrier density and disturbs the band offset, and thus leads to the change of the currents. Based on a thermionic-field-diffusion model that is used to the analyze the performance of an abrupt HBT with a heavydoped base, the conclusion is made that, although the BGN effect makes the currents obviously change due to the modification of the intrinsic carrier density, the band offsets disturbed by the BGN effect should also be taken into account in the analysis of the electrical characteristics of abrupt HBTs. In addition, the BGN effect changes the bias voltage for the onset of Kirk effects.
文摘In this article, we apply the first elliptic function equation to find a new kind of solutions of nonlinear partial differential equations （PDEs） based on the ho- mogeneous balance method, the Jacobi elliptic expansion method and the auxiliary equation method. New exact solutions to the Jacobi elliptic functions of a nonlinear PDE describing pulse narrowing nonlinear transmission lines are given with the aid of computer program, e.g. Maple or Mathematica. Based on Kirchhoff＇s current law and Kirchhoff＇s voltage law, the given nonlinear PDE has been derived and can be reduced to a nonlinear ordinary differential equation （ODE） using a simple transformation. The given method in this article is straightforward and concise, and can be applied to other nonlinear PDEs in mathematical physics. Further results may be obtained.
基金supported by the National Key Research and Development Program of China(No.2017YFB1104500)the China Postdoctoral Science Foundation(No.2018M630355)the National Natural Science Foundation of China(Nos.61905128 and61905150)。
文摘The generation of mid-infrared pulsed lasers was achieved in a Ho3+:YAG laser pumped gain-switched Cr^2+:Cd Se laser system with the shortest pulse duration of 4.15 ns.With a pump pulse duration of 50 ns and pump power of 2.7 W,the gain-switched Cr^2+:Cd Se laser achieved over 10 times pulse narrowing,obtaining the maximum peak power of 5.7 k W.The optical-to-optical conversion efficiency was 3.7%,which could be further improved with better crystal surface polishing quality.The laser central wavelength was measured to be 2.65μm with a bandwidth(FWHM)of 50 nm.In addition,the parameter optimization for suppressing the pulse tail was discussed,while the long cavity and high output transmissivity contributed to obtaining the single-peak pulses.
基金supported by the National Natural Science Foundation of China(No.61475065)the Guangdong Natural Science Foundation of China(No.2015A030313322)
文摘A tunable single-longitudinal-mode（SLM） semiconductor optical amplifier（SOA）-based fiber laser based on a dispersion-shifted fiber（DSF） is proposed and successfully demonstrated. SLM operation is obtained due to the spectral narrowing effect resulting from inverse four-wave mixing in a DSF. A tunable optical filter performs wavelength selection function. By inserting a length of DSF in the laser cavity, SLM lasing can possibly be obtained when laser oscillation is stably established after traveling through the DSF many roundtrips. Stable tunable SLM oscillation with a signal-to-noise ratio as high as 65 dB over a wavelength range of about 35 nm is achieved experimentally, and each spectral linewidth is less than 6.5 kHz.
基金Supported by National Natural Science Foundation of China,No.82370570.
文摘BACKGROUND Early esophageal neuroendocrine carcinoma(E-NEC)is a rare but aggressive malignancy with poorly understood endoscopic features.Despite advancements in multi-model endoscopy,including white light endoscopy,magnifying end-oscopy narrow-band imaging(NBI),and endoscopic ultrasonography(EUS),the diagnostic characteristics of early E-NEC remain unclear.Comprehensive evalu-ation using these techniques can improve early detection and guide clinical management.This study aimed to investigate the endoscopic features of early E-NEC using multiple imaging modalities.We hypothesized that specific endos-copic patterns,such as irregular microvascular morphology or signs of submu-cosal invasion,could reliably distinguish early E-NEC from other esophageal lesions.AIM To characterize early E-NEC using multi-model endoscopy and identify diag-nostic endoscopic features.METHODS Clinical data of four patients with esophageal submucosal lesions identified by gastroscopy and pathologically diagnosed as E-NEC in the Department of Gastroenterology,The First Affiliated Hospital of Zhejiang University School of Medicine between January 2020 and August 2024 were retrospectively analyzed,and their manifestations under multi-model endoscopy were observed.Grayscale values of ultrasound images in three patients with E-NEC and eight with esophageal leiomyoma were calculated using Image J software and compared using the Mann-Whitney U test.Neuroendocrine neoplasms(NENs)are a rare heterogeneous group of epithelial tumors that originate from peptidergic neurons and neuroendocrine cells,and are characterized by neuroendocrine differentiation.NENs include well-differen-tiated neuroendocrine tumors(NETs),poorly differentiated neuroendocrine carcinomas(NECs),and mixed neuroen-docrine-non-NENs[1],which exhibit a wide range of biological behaviors,from indolent,slow-growing lesions to highly aggressive and metastatic malignancies[2].NENs have the capacity for whole-body distribution,with gastroenteropan-creatic NENs comprising approximately 60%-75%of cases,followed by those in the lungs and mediastinum[3].Eso-phageal NENs(E-NENs)are extremely rare,accounting for only approximately 1.6%of all NENs and occurring far less frequently than other gastrointestinal NENs[4].However,with advancements in early cancer screening and diagnostic techniques,the incidence of E-NENs has gradually increased in recent decades[5].Among E-NENs,<1%are well-differ-entiated NETs,with the vast majority being poorly differentiated small cell NECs[6,7].Nevertheless,esophageal NEC(E-NEC)accounts for only 0.05%-7.6%of all esophageal malignant tumors[8,9],and is characterized by aggressive behavior,rapid progression,and early metastasis.E-NEC primarily affects middle-aged and older individuals,with a higher prevalence in males[10].The tumor-node-metastasis staging system of E-NEC mirrors that of esophageal squamous cell carcinoma(ESCC)[11,12].Early E-NEC is defined as lesions limited to the mucosal or submucosal layer(stages T1a and T1b),with or without nodal metastasis.Clinically,we found that early E-NEC often presents with absent or non-specific symptoms,such as mild dysphagia or retrosternal discomfort,which are easily overlooked or mistaken for benign esophageal conditions such as leiomyoma.Conventional imaging and tumor markers frequently fail to detect early lesions,and endoscopic biopsy results may be inconclusive due to submucosal tumor growth and the overlying normal epithelium[13].As a result,E-NEC is frequently diagnosed at an advanced stage(31%-90%of cases)when regional lymph node or distant metastases have already occurred,contributing to its poor prognosis[2,13,14].Studies have reported a median survival of approximately 11 months and 5-year survival rate of<10%[14].Given these challenges,early detection using endoscopy is essential for improving patient outcomes.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFA1406000 and 2022YFA1403800)the National Natural Science Foundation of China(Grant Nos.12474002,22171283,22203031,12434005,12204515,and 12074175)support of the Young Elite Scientists Sponsorship Program by CAST(Grant No.2022QNRC001)。
文摘Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past decade.To understand their emergent quantum phenomena,high-quality single crystals of substantial size are essential.Here,we report the synthesis of single crystals of the Kitaev quantum spin liquid candidate RuBr_(3),achieving millimeter-sized crystals through a self-flux method under high pressure and high temperature conditions.The crystals exhibit well-defined cleavage planes with a lustrous appearance.Transport characterizations exhibit a narrow band-gap semiconducting behavior with 0.13 eV and 0.11 eV band-gap in ab plane and along𝑐axis,respectively.Magnetic measurement shows a transition to antiferromagnetic(AFM)state at approximately 29K both in ab plane and along the c axis.Notably,the N′eel temperature increases to 34K with an applied magnetic field of up to 7T in the ab plane,but without any change along𝑐axis.The large size and high quality of RuBr3 single crystals provide a valuable platform for investigating various interactions,particularly the Kitaev interaction,and for elucidating the intrinsic physical properties of Kitaev quantum spin liquids.
