Effect of Surface Potential Barrier on the Electron Energy Distribution of NEA Photocathodes

By calculating the energy distribution of electrons reaching the photocathode surface and solving the Schrodinger equation that describes the behavior of an electron tunneling through the surface potential barrier,we obtain an equation to calculate the emitted electron energy distribution of transmission-mode NEA GaAs photocathodes. Accord- ing to the equation,we study the effect of cathode surface potential barrier on the electron energy distribution and find a significant effect of the barrier-Ⅰ thickness or end height,especially the thickness,on the quantum efficiency of the cath- ode. Barrier Ⅱ has an effect on the electron energy spread, and an increase in the vacuum level will lead to a narrower electron energy spread while sacrificing a certain amount of cathode quantum efficiency. The equation is also used to fit the measured electron energy distribution curve of the transmission-mode cathode and the parameters of the surface barri- er are obtained from the fitting. The theoretical curve is in good agreement with the experimental curve.

“阴火”之我见

金元时期著名医学家李东垣以《内经》为理论基础,通过长期的医疗实践,提出了脾胃内伤学说、而“阴火”理论则是其学术思想的重要组成部分,但是由于历史条件的限制,其对“阴火”概念的阐述尚欠清晰,使后世在认识上多有歧见,笔者通过反复学习,对“阴火”有了一定的认识,今不揣浅陋,试述如下,以求正于学者.

Synthesis of Schiff Base Bearing Phenolic Hydroxy Group and Its Anion Recognition

A new anion receptor bearing phenolic hydroxy group based on 3,5- ditertbutylsalicylaldehyde-p-nitrophenylhydrazone （1） was designed and synthesized. Upon addition of AcO- and F-, the receptor exhibited visible color changes from deep yellow to purple. However, no obvious color changes were observed on addition of the other anions tested （H2PO4-, Cl-, Br-, I-）. The binding properties of the receptor with anions such as AcO and F- were investigated by UV-Vis and fluorescent titrations. The result indicated that the receptor 1 had a higher affinity to AcO- and F- and a 1：1 host-guest complex was formed through H-bond interactions between 1 and anions.

Structural and Optical Performance of GaN Thick Film Grown by HVPE

Thick GaN films were grown on GaN/sapphire template in a vertical HVPE reactor. Various material characterization techniques,including AFM, SEM, XRD, RBS/Channeling, CL, PL, and XPS, were used to characterize these GaN epitaxial films. It was found that stepped/terraced structures appeared on the film surface,which were indicative of a nearly step-flow mode of growth for the HVPE GaN despite the high growth rate. A few hexagonal pits appeared on the surface, which have strong light emission. After being etched in molten KOH, the wavy steps disappeared and hexagonal pits with {1010} facets appeared on the surface. An EPD of only 8 ×10^6cm^-2 shows that the GaN film has few dislocations. Both XRD and RBS channeling indicate the high quality of the GaN thick films. Sharp band-edge emission with a full width at half maximum（FWHM）of 67meV was observed, while the yellow and infrared emissions were also found. These emissions are likely caused by native defects and C and O impurities.

High-Integrated-Photosensitivity Negative-Electron-Affinity GaAs Photocathodes with Multilayer Be-Doping Structures

The effect of changing Be doping concentration in GaAs layer on the integrated photosensitivity for nega- tive-electron-affinity GaAs photocathodes is investigated. Two GaAs samples with the monolayer structure and the muhilayer structure are grown by molecular beam epitaxy. The former has a constant Be concentration of 1 × 10^19 cm^-3, while the latter includes four layers with Be doping concentrations of 1 × 10^19, 7 × 10^18, 4 × 10^18, and 1 × 10^18 cm^-3 from the bottom to the surface. Negative-electron-affinity GaAs photocathodes are fabricated by exciting the sample surfaces with alternating input of Cs and O in the high vacuum system. The spectral response results measured by the on-line spectral response measurement system show that the integrated photosensitivity of the photocathode with the muhilayer structure enhanced by at least 50% as compared to that of the monolayer structure. This attributes to the improvement in the crystal quality and the increase in the surface escape probability. Different stress situations are observed on GaAs samples with monolayer structure and muhilayer structure, respectively.

Preliminary Study on Leaf Color Development and Photosynthetic Characteristics of Golden-leaf Ginkgo

[Objective]The aim of this study is to research leaf color development and photosynthetic characteristics of golden-leaf ginkgo.[Method]With one-year-old grafted seedlings of golden-leaf ginkgo as the materials,the changes of leaf color,chlorophyll content（Chl）,carotenoid（x.c）content and rate of chlorophyll and carotenoid content,as well as photosynthetic characteristics under full sunlight and overshadowing were all investigated in this study.[Result]Sprouts of golden-leaf ginkgo were pale-yellow,and changed from orange to golden in April,to light yellow-green in May,to yellow-green from June to October,to yellow in November.The chlorophyll and carotenoid contents and the rates of chlorophyll and carotenoid contents of yellow-leaf were significantly lower than that of green-leaf,while the rate of Chla/x.c and Chlb/x.c was obviously lower than the corresponding pigment content of green-leaf.During the leaf color development,Chla,Chlb and x.c content as well as the rate of Chla/x.c and Chlb/x.c of yellow-leaf ginkgo all increased.The saturation light intensity of ginkgo leaf under natural light was higher than that under overshadowing.Maximum net photosynthetic rate,light compensation point and dark respiration rate of yellow leaf were all significantly higher than that of green leaf.Chla/x.c,Chlb/x.c and Chla＋b/x.c of yellow-leaf ginkgo under overshadowing were higher than the corresponding pigment rate of leaf under natural light.[Conclusion]The best ornamental duration of golden-leaf ginkgo is April and May.The major reason for showing yellow leaf is that Chla/x.c and Chlb/x.c of yellow-leaf is obviously lower than that of green-leaf.During the leaf color development,the major reason for yellow-leaf turning to yellow-green is that the rate of Chla/x.c and Chlb/x.c increases.Chlb content of yellow-leaf under overshadowing is higher than that under natural light,which is an adaptive response to overshadowing.Chla/x.c,Chlb/x.c and Chla＋b/x.c of yellow-leaf under overshadowing are relatively higher,which is one of the reasons why yellow-leaf under overshadowing becomes yellow-green or green.

Dynamic Change Laws of Chlorophyll Fluorescence Parameters in Different Parts of Leaves of Ginkgo biloba

[Objective] The aim was to explore the dynamic change laws of chlorophyll fluorescence parameters in different parts of leaves of Ginkgo biloba.[Method] The G.biloba cultivated in North China was used as materials in this study to explore the law of daily change and ten-day change of the chlorophyll fluorescence parameters of leaves in different parts of leaves.[Result] The daily change of Fm（maximal fluorescence）,Fv（variable fluorescence）,Fv/Fm,Fm/Fo（electron transfer rate）,Fv/Fo（potential activity of PSⅡ）in leaves of G.biloba obviously presented a descending-ascending trend,the lowest value was at 12：00 and the NPQ（non-photochemical quenching）of sunny leaves arrived at the maximum at noon.The values of Fm,Fv,Fv/Fm,Fm/Fo,Fv/Fo in shade leaves of G.biloba were obviously higher than those in sunny leaves,but the peak value of NPQ of shade leaves presented earlier and higher,suggesting that the shade leaves might have more sensitive hot dissipation mechanism.Comparing to sunny leaves,shade leaves had the higher PSⅡ potential activity and inner light energy translation efficiency.[Conclusion] This study had provided theoretical basis for the protection of G.biloba resources.

Characterization and photoelectrochemical performance of Zn-doped TiO_2 films by sol-gel method

Zn-doped TiO2 (Zn?TiO2) thin films were prepared by the sol?gel method on titanium substrates with heat treatment at different temperatures. The effects of heat treatment temperatures and Zn doping on the structure, photocathodic protection and photoelectrochemical properties of TiO2 thin films were investigated. It is indicated that the photoelectrical performance of the Zn?TiO2 films is enhanced with the addition of Zn element compared with the pure-TiO2 film and the largest decline by 897 mV in the electrode potential is achieved under 300 °C heat treatment. SEM?EDS analyses show that Zn element is unevenly distributed in Zn?TiO2 films; XRD patterns reveal that the grain size of Zn?TiO2 is smaller than that of pure-TiO2; FTIR results indicate that Zn - O bond forms on Zn?TiO2 surface. Ultraviolet visible absorption spectra prove that Zn?TiO2 shifts to visible light region.Mott?Shottky curves show that the flat-band potential of Zn?TiO2 is more negative and charge carrier density is bigger than that ofpure-TiO2, implying that under the synergy of the width of the space-charge layer, carrier density and flat-band potential, Zn?TiO2 with 300 °C heat treatment displays the best photocathodic protection performance.

Stabilizing CuO photocathode with a Cu_(3)N protection shell

CuO,as a promising photocathode material,suffers from severe photocorrosion in photoelectrochemical water splitting applications.Herein,a Cu_(3)N protection shell was used to protect the CuO photocathode for the first time to effectively suppress the photocorrosion of CuO.Consequently,the Cu_(3)N‐protected CuO photocathode shows improved stability,retaining 80% of its initial current density in a 20‐min test,while only 10%of the initial current density can be retained for the bare photocathode.This work may provide an important strategy for using Cu_(3)N shells to stabilize unstable photocathodes.

Photoelectrochemical nitrogen reduction:A step toward achieving sustainable ammonia synthesis

Industrial NH3 production mainly employs the well‐known Haber‐Bosch(H‐B)process,which is associated with significant energy consumption and carbon emissions.Photoelectrochemical nitro‐gen reduction reaction(PEC‐NRR)under ambient conditions is considered a promising alternative to the H‐B process and has been attracting increasing attention owing to its associated energy effi‐ciency and environmentally friendly characteristics.The performance of a PEC‐NRR system,such as the NH_(3) yield,selectivity,and stability,is essentially determined by its key component,the photo‐cathode.In this review,the latest progress in the development of photocathode materials employed in PEC‐NRR is evaluated.The fundamental mechanisms and essential features required for the PEC‐NRR are introduced,followed by a discussion of various types of photocathode materials,such as oxides,sulfides,selenides,black silicon,and black phosphorus.In particular,the PEC‐NRR reac‐tion mechanisms associated with these photocathode materials are reviewed in detail.Finally,the present challenges and future opportunities related to the further development of PEC‐NRR are also discussed.This review aims to improve the understanding of PEC‐NRR photocathode materials while also shedding light on the new concepts and significant innovations in this field.

Dry-Matter Partitioning, Yield and Leaf Nutrient Contents of Tomato Plants as Influenced by Shading at Different Growth Stages

Pot-grown tomato plants (Lycopersicon esculentum Mill. cv. Maofen) was used to study the effects of three shading levels (0, 75% and 40%) for 8 days on dry matter partitioning, contents of nitrogen (N), phosphorus (P) and potassium (K) in leaves arid yield at three growth stages (early flowering (EF), peak flowering (PF) and later flowering (LF)). Shading reduced the dry weight of root and stem tissues at the EF and PF stages, but the 40% shading increased root dry weight and stem dry weight by 43.2% and 21.6%, respectively, at the LF stage. The influence of shading on the dry weight of leaves was very small at most growth stages. Shading had no effects on total leaf N, P and K contents at the EF and PF stages, showing that N, P and K absorption were regulated by the carbon assimilation at these two stages. The leaf N, P and K contents of 40% shaded plants at the LF stage were significantly increased. There were no obvious differences in leaf N and K contents between 75% and 40% shading treatments, but significant difference in leaf P contents was found between them at the LF stage. Shading significantly enhanced the fruit yield of 40% shaded tomato plants at the LF stage, but failed to affect the fruit yield of shaded plants at the EF stage. These showed that tomato could grow well and a better yield could be obtained if some moderate shading (i.e., 40% shading) was applied at the LF stage at summer midday.

Clinical significance of colposcopy on screening cervical intraepithelial neoplasia in cytological negative and smooth cervices

Objective： The aim of the study was to evaluate the clinical value of the video colposcopy in screening cervical intraepithelial neoplasia （CIN） in cytological negative and smooth cervices by optically gynecological examination. Methods： The 1050 women, whose cervices had been shown smooth and cytological negative by optical examine, were examined with electronic colposcopy in gynecological clinic, and biopsy was taken when the double abnormality of aceto-white epithelium and iodine negative, and other abnormal images were shown. A retrospective analysis of these cases was performed. Re. suits： （1） The 514 samples from 458 cases, including 458 samples of abnormal tissues under colposcopy and 56 samples of polyp or polypoid tumors by optically, were examined by biopsy. Among them, 68 samples were found to be CIN, including 11 cases of CINII/CINIII; （2） The 72 of 1050 cases showed the double-abnormality of aceto-white epithelium and iodine nega- tive. Among them, 64 cases were CIN determined by biopsy. And the positive predictive value of the double-abnormality of aceto-white epithelium and iodine negative under colposcopy was 88.9%, with a false negative rate of 3.3%; （3） Among 458 women examined by biopsy, only one of 350 samples from cervical polyp tissue was CIN （0.3%）, while 67 of 164 samples from the tissues with abnormal colposcopic images were found to be CIN （40.9%）, indicating the close relation between abnormal colposcopic findings and CIN; （4） The results of age-distribution analysis showed that, in the 164 cases with abnormal features under colposcopy, the incidence of double abnormality of aceto-white epithelium and iodine negative was higher in the age of sexual activity, just the same as the age distribution feature of CIN; while single abnormality of iodine negative appeared more in the age of over 50 years. Conclusion： Abnormal features displayed by colposcopy, especially the double abnormality of aceto-white epithelium and iodine negative, has an important significance for the screening of cervical precancerous lesions such as CIN. For this purpose, colposcopy examination is necessary even for the cases of cytological negative and smooth cervices.

Studies on Biologically Active Principles of Huangqi,Root of Astragalus membranaceous,Isolation and Detection of Constituents Scavenging Superoxide Anion

本文使用黄嘌呤-黄嘌呤氧化酶—鲁米诺化学发光体系和化学发光检测法研究了黄芪中各成分的清除超氧阴离子自由基的能力,以药物抑制发光强度50%的浓度(IC_(50))为指标。经研究证明,黄芪总皂甙部分(N)具有较强的活性,IC_(50)为185μg/ml,再经进一步导向分离并鉴定证明,黄芪甙Ⅲ,Ⅳ和Ⅵ的 IC)_(50)分别为80、50和11μg/ml,从而证明黄芪的抗心力衰竭的有效成分可能为黄芪总皂甙部分。

Control of the Interface between Tris (8-quinolinolato) Aluminum and Aluminum Layers in an Organic Electroluminescent devices

A bilayer Al 2O 3/Al is used as a cathode for organic electroluminescent devices. Six times higher electroluminescent efficiency is obtained without increasing the threshold voltage. The improvement is believed to be due to increasing injecting electron density, which improves the balanced injection of carriers, and declines the exciton-quenching and carrier-trapping centers that are intrinsic to the interface between of emitting layer and cathode.

Resolution Characteristics of GaAs/GaAlAs Transmission Photocathode

The resolution characteristic of GaAs/GaAlAs transmission photocathode is an important parameter in third generation intensifiers. The modulation transfer function of GaAs/GaAlAs transmission photocathode is derived from a simple two-dimensional diffusion equation. The theoretical resolution characteristic of a 2 μm thick GaAs/GaAlAs transmission photocathode is calculated. The relationship between resolution and parameters in GaAs/GaAlAs transmission photocathode is discussed. A conclusion is shown that one can design the GaAs/GaAlAs transmission photocathode for maximum quantum efficiency, since the sacrifice in the resolution doesn't limit system performances.

Mean Transverse Energy of Electrons Emitted from GaAs/GaAlAs Transmission Photocathode

A GaAs/GaAlAs transmission photocathode surface topography is examined with a scanning electron microscope(SEM) in the secondary emission mode.The contributions of photocathode surface topography to mean transverse energy of electrons emitted from the photocathode are calculated. Measurement is made of the variation of mean transverse emission energy with activating time during the course of activation. It is shown that the scattering of the photoelectrons in the Cs/O layer is the primary cause of the unexpectant high values of the mean transverse energy of electrons emitted from GaAs/GaAlAs photocathode. A method is proposed for the reduction of the mean transverse energy of electrons emitted from the photocathode.

Characteristics analysis and library development for piezoelectric transformer to drive a ballast for a 35 W class fluorescent lamp using PSPICE modeling

PSPICE model driven by an electric equivalent circuit of a piezoelectric circuit is presented. In order to confirm this model to be effective, an independent model of cold cathode fluorescent lamp(CCFL) driving circuit is used to conduct simulations, leading to a precise modeling. A library is configured through modeling and its accuracy is verified through simulations for widely used and representative lamps such as CCFL, fluorescent lamps, HID lamps, and electrodeless fluorescent lamps. On the basis of experiments, a lamp simulation is also performed using PSPICE, which allows us to take advantage of the lamp library easily. Also, PSPICE model driven by an electric equivalent circuit of a piezoelectric transformer is presented. In order to confirm this model to be effective, an independent model of CCFL driving circuit is used to conduct simulations, leading to a precise modeling. In addition, a new type of electronic ballast is proposed, which allows 35 W-class(T5-class) fluorescent lamp to work. This system is built by a rectifier which has improved power factor and half-bridge series resonant inverter. Also, with size of 27.5 mm high, 27.5 mm wide and 2.5 mm thick, the produced piezoelectric transformer has a high step-up ratio, through which it is possible for the electric ballast circuit to be lighter, smaller and more efficient. After the produced ballast is used to drive the fluorescent lamp for 25 min, it yields 0.95 in power factor correction, 86% in efficiency, 35.07 W in output voltage and 20.5 °C in temperature increase while meeting the characteristics of the 35 W-class fluorescent lamp.

STUDY ON DETERMINATION OF TRACE Fe BY Fe(Ⅱ)-VA THIN LAYER RESIN PHASE SPECTROPHOTOMETRY

A new method for the determination of Fe by thin layer resin phase spectrophotometry in alkali condition was reported. The complex anion formed by Fe（Ⅱ） and VA was absorbed on the 717w resin and Fe was determined by making thin layer. This method had a high sensitivity （ε620= 3.0×10^5L/mol.cm）, which was 15 times higher than that of liquid phase spectrophotometry. It had been proved a satisfactory precision （5.01μg Fe, n=6, RSD=1.8%）. The trace Fe in natural water was determined and the recovery was 97%.

Identification of Fucans from Four Species of Sea Cucumber by High Temperature ~1H NMR

Acidic polysaccharide, which has various biological activities, is one of the most important components of sea cucumber. In the present study, crude polysaccharide was extracted from four species of sea cucumber from three different geographical zones, Pearsonothuria graeffei(Pg) from Indo-Pacific, Holothuria vagabunda(Hv) from Norwegian Coast, Stichopus tremulu(St) from Western Indian Ocean, and Isostichopus badionotu(Ib) from Western Atlantic. The polysaccharide extract was separated and purified with a cellulose DEAE anion-exchange column to obtain corresponding sea cucumber fucans(SC-Fucs). The chemical property of these SC-Fucs, including molecular weight, monosaccharide composition and sulfate content, was determined. Their structure was compared simply with fourier infrared spectrum analyzer and identified with high temperature 1H nuclear magnetic resonance spectrum analyzer(NMR) and room temperature 13 C NMR. The results indicated that Fuc-Pg obtained from the torrid zone mainly contained 2,4-O-disulfated and non-sulfated fucose residue, whereas Fuc-Ib from the temperate zone contained non-, 2-O- and 2,4-O-disulfated fucose residue; Fuc-St from the frigid zone and Fuc-Hv from the torrid zone contained mainly non-sulfated fucose residue. The proton of SC-Fucs was better resolved via high temperature 1H NMR than via room temperature 1H NMR. The fingerprint of sea cucumber in different sea regions was established based on the index of anomer hydrogen signal in SC-Fucs. Further work will help to understand whether there exists a close relationship between the geographical area of sea cucumber and the sulfation pattern of SC-Fucs.

Ultrathin 3D radial tandem‐junction photocathode with a high onset potential of 1.15 V for solar hydrogen production

Combining a progressive tandem junction design with a unique Si nanowire(SiNW)framework paves the way for the development of high‐onset‐potential photocathodes and enhancement of solar hydrogen production.Herein,a radial tandem junction(RTJ)thin film water‐splitting photo‐cathode has been demonstrated experimentally for the first time.The photocathode is directly fab‐ricated on vapor‐liquid‐solid‐grown SiNWs and consists of two radially stacked p‐i‐n junctions,featuring hydrogenated amorphous silicon(a‐Si:H)as the outer absorber layer,which absorbs short wavelengths,and hydrogenated amorphous silicon germanium(a‐SiGe:H)as the inner layer,which absorbs long wavelengths.The randomly distributed SiNW framework enables highly efficient light‐trapping,which facilitates the use of very thin absorber layers of a‐Si:H(~50 nm)and a‐SiGe:H(~40 nm).In a neutral electrolyte(pH=7),the three‐dimensional(3D)RTJ photocathode delivers a high photocurrent onset of 1.15 V vs.the reversible hydrogen electrode(RHE),accompanied by a photocurrent of 2.98 mA/cm^(2) at 0 V vs.RHE,and an overall applied‐bias photon‐to‐current effi‐ciency of 1.72%.These results emphasize the promising role of 3D radial tandem technology in developing a new generation of durable,low‐cost,high‐onset‐potential photocathodes capable of large‐scale implementation。