西藏地面太阳总辐射与紫外线的观测

地面太阳光谱记录了太阳光经历大气层的烙印与信息,为大气环境、生态保护等研究提供实地依据。西藏高原空气稀薄,地面太阳辐射超强,观测西藏地面太阳光谱为太阳能利用提供实地数据。文章较系统地报道了西藏地面太阳光谱的实地观测结果,为相关高原科学研究提供高精度数据。利用RAMSES光谱仪、CMP6太阳总辐射仪和NILU-UV太阳紫外辐射仪对西藏不同地区、不同季节太阳光谱、太阳总辐射和太阳紫外线进行了全方位的实地观测研究。观测研究了高海拔的西藏拉萨和那曲以及低海拔的北京和成都的光谱特征;研究了拉萨二分二至当地正午（北京时间13:55时）太阳光谱观测结果;对西藏地面光谱与AM1.5和AM0标准光谱进行了对比研究。观测研究了西藏拉萨和那曲太阳总辐射、太阳紫外线强度特征。研究发现拉萨夏季可见和红外区光谱光强度甚至超过AM0光谱相应波长的强度,即：拉萨地面可见光和红外光强度偶尔超过大气层顶部的相应波长光强,是由部分云的反射增量所致;拉萨光谱谱峰出现在波长476.6 nm左右,在2017年的夏至观测到的最大值为2.331 W·m-2·nm-1。然而,对太阳紫外线（280～400 nm）光谱的观测发现地面太阳紫外区的光谱强度总是明显低于AM0光谱相应区光强,表明短波的紫外光被大气臭氧有效吸收。虽然拉萨海拔3 680 m,但通过对拉萨当地正午太阳紫外光谱分析发现拉萨地面波长小于300 nm的太阳紫外光谱强度几乎为零,表明波长小于300 nm的太阳紫外线被大气层吸收,没有到达地面。同时,研究了西藏高海拔太阳光谱与北京、成都低海拔太阳光谱特征,揭示了各地大气成分、含量等诸多信息。报道了2010年7月-2013年12月期间西藏太阳总辐射的观测结果;结果显示拉萨当日太阳总辐射最大值中约18%超过了太阳常数（1 367 W·m-2）。观测发现拉萨太阳总辐射瞬时最大值达到了1 756.09 W·m-2（2011年6月24日）。报道了2008年7月-2013年12月期间西藏太阳紫外线的观测结果;结果显示拉萨和那曲UVA日最大值平均值约为67 W·m-2,UVB日最大值平均值约为5.1 W·m-2;拉萨和那曲当日太阳紫外线A和紫外线B最大值变化趋势保持了很好的一致性,在5年多的观测期间紫外线强度没有出现明显的增强或减弱趋势。     

Benzisoxazole 2‐oxides as novel UV absorbers and photooxidation inhibitors

Compounds with strong absorptions in the ultraviolet (UV) region of the spectrum, particularly the UVA and UVB, have seen much interest as UV screeners or absorbers in a wide variety of commercial products. A series of benzisoxazole 2‐oxides have been synthesized and characterized by UV–vis spectroscopy. A number of derivatives have been shown to posses moderate to strong molar absorption coefficients in the UVB range (ca. 300 nm), the strongest being those derived from benzophenones. Three other derivatives containing additional electron withdrawing groups showed strong molar absorption coefficients in the UVA (ca. 340 nm). Solvent effects on the parent derivatives show changes in the molar absorption coefficients with little changes in the λ_max values. Preliminary studies of these compounds as potential additives to prevent photooxidation of polystyrene showed considerable inhibition of polymer degradation with the parent unsubstituted benzisoxazole 2‐oxide compounds being the most effective. Copyright © 2013 John Wiley & Sons, Ltd.     

The vegetative arctic freshwater green alga Zygnema is insensitive to experimental UV exposure

The physiological performance and ultrastructural integrity of the vegetative freshwater green alga Zygnema sp., growing under ambient polar day solar radiation and after exposure to experimentally low radiation, but with high UVR:PAR ratio were investigated. In the laboratory, algae were exposed to low photosynthetic active radiation (PAR = P, 400–700 nm, 20 μmol m⁻² s⁻¹), PAR + UV-A = PA (320–400 nm, 4.00 W m⁻² = UV-A) and PAR + UV-A + UV-B = PAB (280–320 nm, 0.42 W m⁻² = UV-B) for 24 h at 7 °C. Photosynthetic performance and ultrastructure of ambient solar radiation-exposed (field control) and experimentally treated Zygnema samples were assessed using chlorophyll fluorescence, and transmission electron microscopy (TEM). No significant treatment effect was observed in the photosynthesis–irradiance curve parameters. Exclusion of the UV-B spectrum in the laboratory treatment caused significantly lower effective photosynthetic quantum yield compared to samples exposed to the whole radiation spectrum. TEM revealed no obvious differences in the ultrastructure of field control and laboratory P-, PA- and PAB-exposed samples. Substantial amounts of lipid bodies, visualized by Sudan IV staining, were observed in all samples. Chloroplasts contained numerous plastoglobules. Organelles like mitochondria, Golgi bodies and the nucleus remained unaffected by the radiation exposures. Zygnema is well adapted to ambient solar radiation, enabling the alga to cope with experimental UV exposure and it is expected to persist in a scenario with enhanced UV radiation caused by stratospheric ozone depletion.     

Chemical and photochemical reactivity of 6‐hydroxymethyl‐7,8‐dihydropterin in aqueous solutions

6‐Hydroxymethyl‐7,8‐dihydropterin (H₂Hmp) is an intermediate in the biosynthesis of folate, a precursor of coenzymes involved in the metabolism of nucleotides and amino acids. In this work, we have investigated the reactions undergone by H₂Hmp in aqueous solutions at physiological pH, in the absence and in the presence of UV‐A radiation (320–400 nm). In air‐equilibrated solutions, H₂Hmp undergoes slow thermal oxidation (half‐life 37 h) to yield 7,8‐dihydroxanthopterin (H₂Xap) as the main product. The reaction of H₂Hmp with hydrogen peroxide also yields H₂Xap as a main product. In contrast, UV‐A excitation of H₂Hmp leads to the formation of a dimer identified by electrospray ionization mass spectrometry. The corresponding quantum yield of H₂Hmp consumption (Φ_?R) was independent of O₂ and reactant concentration and has a value of 0.10 (±0.02), more than twice higher than that measured for other 6‐subtituted 7,8‐dihydropterins. Copyright © 2012 John Wiley & Sons, Ltd.     

近红外高光谱的活体玉米叶片水分成像研究

无损检测植物叶片水分对植物生理生化研究及灌溉管理和旱情监测等均具有重要意义。利用Gaia Sorter近红外高光谱仪(900～1 700 nm),以不同生育期的60个鲜活玉米叶片为试验材料,对叶肉不同区域的平均光谱及烘干称重法得到的水分含量分别用偏最小二乘法(PLS)及逐步多元线性回归(SMLR)进行建模分析。结果表明,验证集决定系数/标准偏差分别为0.975/1.18和0.980/1.02,均取得较好的预测效果,可实现单个玉米叶片平均含水量的测定;SMLR优选的特征波长(1 406和1 692 nm)建模预测结果表明,利用高通量近红外相机结合滤光片方法实现玉米叶片冠层或高空遥感测量的可行性。同时,进行了叶片不同区域水分含量的成像分析,结果表明,验证集中6个叶片的叶肉与主叶脉区域水分含量的参考均值和预测均值的相关系数均达到0.85以上,预测结果与实际情况相符合。     

High‐gain Zn1–xMgx O‐based ultraviolet photodetectors on Al2O3 and LiGaO2 substrates

We report the fabrication and characterization of highly responsive ZnMgO‐based ultraviolet (UV) photodetectors in the metal–semiconductor–metal (MSM) configuration for solar‐blind/visible‐blind optoelectronic application. MSM devices were fabricated from wurtzite Zn_1–xMg_x O/ZnO (x ～ 0.44) thin‐film heterostructures grown on sapphire (α‐Al₂O₃) substrates and w‐Zn_1–xMg_x O (x ～ 0.08), grown on nearly lattice‐matched lithium gallate (LiGaO₂) substrates, both by radio‐frequency plasma‐assisted molecular beam epitaxy (PAMBE). Thin film properties were studied by AFM, XRD, and optical transmission spectra, while MSM device performance was analyzed by spectral photoresponse and current–voltage techniques. Under biased conditions, α‐Al₂O₃ grown devices exhibit peak responsivity of ～7.6 A/W at 280 nm while LiGaO₂ grown samples demonstrate peak performance of ～119.3 A/W, albeit in the UV‐A regime (～324 nm). High photoconductive gains (76, 525) and spectral rejection ratios (～10³, ～10⁴) were obtained for devices grown on α‐Al₂O₃ and LiGaO₂, respectively. Exemplary device performance was ascribed to high material quality and in the case of lattice‐matched LiGaO₂ films, decreased photocarrier trapping probability, presumably due to low‐density of dislocation defects. To the best of our knowledge, these results represent the highest performing ZnO‐based photodetectors on LiGaO₂ yet fabricated, and demonstrate both the feasibility and substantial enhancement of photodetector device performance via growth on lattice‐matched substrates. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Narrow-band UV radiation (250–260 nm) from intracavity doubling a single-mode ring dye laser

Generation of continuous-wave, tunable UV radiation (250–260 nm) by intracavity doubling a coumarin-515 ring dye laser is described. A cooled (200–280 K) ADP crystal with end faces cut at Brester's angle is placed inside the laser ring cavity which has been compensated for astigmatism and coma. UV output powers at 254 nm of 120 μW and 60 μW are achieved with the laser operating multimode (bandwidth ? 20 GHz) and single-mode (bandwidth ? 50 MHz), respectively. Continuous single-mode scans over the 253.7 nm mercury profile demonstrate sub-Doppler resolution of the Hg 6s6p ³P^O₁ - 6s²¹S₀ transition.     

Effectiveness of full spectrum light soaking on solar cell degradation analysis

This study examined the effect of UV-spectrum light soaking on solar cell degradation tests. An indoor light soaking test was evaluated over three different spectral ranges: “UV only”, “UV blocked” and “Full spectrum”. a-Si:H and poly-crystalline silicon solar cell technologies were studied by light soaking tests with the same optical filter configurations.The I–V measurement results demonstrated that “UV only” irradiated solar cells exhibited the smallest output power degradation, which was only half of a percent variation compared with the full spectrum light soaking case. Using a filter that excluded the effect of the UV spectral range on light soaking, the “UV blocked” case also exhibited a significant output power degradation of the solar cells. A comparative analysis of the solar cell response, based on the I–V characteristics and the diode ideality factor under these different light soaking spectra, demonstrated the importance of the full spectrum light soaking test in the evaluation of the long-term performance of solar cells.     

An attempt of molecular design and synthesis of 3,4′/4,3′‐disubstituted benzylideneanilines with specified UV–Vis absorption maximum wavelength

Thirty‐one samples of 3,4′/4,3′‐disubstituted benzylideneanilines (XBAY) with specified UV–Vis absorption maximum wavelength (λ_max) were designed and synthesized by applying the equation (Eqn 1 ) which was abstracted from the UV–Vis absorption maximum wavelength energy (ν_max = 1/λ_max) of 4,4′‐disubstituted benzylideneanilines. Then, the UV–Vis data (λ_max) of the designed compounds were measured in anhydrous ethanol. The predicted UV–Vis data of designed compounds are in agreement with the experimental ones, in which the mean absolute error is 2.9 nm. The results show that Eqn 1 is applicative for the prediction of UV–Vis absorption λ_max values of both 4,4′‐disubstituted benzylideneanilines and 3,4′/4,3′‐disubstituted benzylideneanilines. For a same pair of groups (X and Y), one can at least get four disubstituted benzylideneaniline compounds which have different λ_max values. It perhaps provides a convenient method to design an optical material for benzylideneaniline compounds. Copyright © 2014 John Wiley & Sons, Ltd.     

Visualization of mouse spinal cord intramedullary arteries using phase‐ and attenuation‐contrast tomographic imaging

Many spinal cord circulatory disorders present the substantial involvement of small vessel lesions. The central sulcus arteries supply nutrition to a large part of the spinal cord, and, if not detected early, lesions in the spinal cord will cause irreversible damage to the function of this organ. Thus, early detection of these small vessel lesions could potentially facilitate the effective diagnosis and treatment of these diseases. However, the detection of such small vessels is beyond the capability of current imaging techniques. In this study, an imaging method is proposed and the potential of phase‐contrast imaging (PCI)‐ and attenuation‐contrast imaging (ACI)‐based synchrotron radiation for high‐resolution tomography of intramedullary arteries in mouse spinal cord is validated. The three‐dimensional vessel morphology, particularly that of the central sulcus arteries (CSA), detected with these two imaging models was quantitatively analyzed and compared. It was determined that both PCI‐ and ACI‐based synchrotron radiation can be used to visualize the physiological arrangement of the entire intramedullary artery network in the mouse spinal cord in both two dimensions and three dimensions at a high‐resolution scale. Additionally, the two‐dimensional and three‐dimensional vessel morphometric parameter measurements obtained with PCI are similar to the ACI data. Furthermore, PCI allows efficient and direct discrimination of the same branch level of the CSA without contrast agent injection and is expected to provide reliable biological information regarding the intramedullary artery. Compared with ACI, PCI might be a novel imaging method that offers a powerful imaging platform for evaluating pathological changes in small vessels and may also allow better clarification of their role in neurovascular disorders.     

Identification of two Ag‐2,2′:6′,2″‐terpyridine surface species on Ag nanoparticle surfaces by excitation wavelength dependence of SERS spectra and factor analysis: evidence for chemical mechanism contribution to SERS of Ag(0)–tpy

Measurement and interpretation of the excitation wavelength dependence of surface‐enhanced Raman scattering (SERS) spectra of molecules chemisorbed on plasmonic, e.g. Ag nanoparticle (NP) surfaces, are of principal importance for revealing the charge transfer (CT) mechanism contribution to the overall SERS enhancement. SERS spectra, their excitation wavelength dependence in the 445–780‐nm range and factor analysis (FA) were used for the identification of two Ag‐2,2′:6′,2″‐terpyridine (tpy) surface species, denoted Ag⁺–tpy and Ag(0)–tpy, on Ag NPs in systems with unmodified and/or purposefully modified Ag NPs originating from hydroxylamine hydrochloride‐reduced hydrosols. Ag⁺–tpy is a spectral analogue of [Ag(tpy)]⁺ complex cation, and its SERS shows virtually no excitation wavelength dependence. By contrast, SERS of Ag(0)–tpy surface complex generated upon chloride‐induced compact aggregate formation and/or in strongly reducing ambient shows a pronounced excitation wavelength dependence attributed to a CT resonance (the chemical mechanism) contribution to the overall SERS enhancement. Both the resonance (λ_exc = 532 nm) and off‐resonance (λ_exc = 780 nm) pure‐component spectra of Ag(0)–tpy obtained by FA are largely similar to surface‐enhanced resonance Raman scattering (λ_exc = 532 nm in resonance with singlet metal to ligand CT (¹ MLCT) transition) and SERS (λ_exc = 780 nm) spectra of [Fe(tpy)₂]²⁺ complex dication. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterization of Gafchromic EBT3 films for ultraviolet radiation dosimetry

A newly released processless Gafchromic EBT3 film was investigated for its response to ultraviolet radiation (UVR) at three different wavelengths: 365 (UVA), 302 (UVB) and 254 nm (UVC). The change in the film's optical density was dependent on the radiance exposure and UV wavelength and was found to correlate with the UV intensity. The dynamic range of the EBT3 films is ～5 to ～60 J/cm² for UVA and UVB and ～5 to ～300 J/cm² for UVC. The dose sensitivity of EBT3 films for UVA and UVB radiation was approximately 10 times higher than that for UVC radiation. The results indicate the suitability of EBT3 films for quantitative and qualitative measurements of UVR exposure.     

Spectral response of radiochromic gel detector in the near-ultraviolet region (200–400 nm)

Tissue-equivalent radiochromic gel detector is sensitive in the regions of ultraviolet radiation (UVR) and gamma and X-rays. This study aims to investigate the spectral response and other optical properties of the ferrous sulphate, xylenol orange and gelatin (FXG) radiochromic gel dosimeter at particular UVR wavelengths. A total of nine monochromatic wavelengths were selected in the range of 240–400 nm with an increment of 20 nm. The FXG spectral response was estimated from the variation of spectral absorbance at 560 nm resulting from 1 h exposure to UVR beam at each chosen wavelength. Experimental results show that the FXG responsivity depends on the wavelength of the radiation and the optical path in the gel material. UVC and UVB photons have relatively higher photochemical effect than UVA; however, UVA penetration is deeper. Investigations showed that the FXG gel response is relatively constant between 240 and 320 nm, but it varies rapidly with wavelength in the UVA range and takes a minimal value at 360 nm. UVR spectral absorbance curves for different gel sample thicknesses were examined. The experiment showed that 6 mm of neutral gelatin or FXG gel samples was capable of absorbing >99.7% of the beam in the UV range of 240–290 nm.     

Improved performance of silicon‐nanoparticle film‐coated dye‐sensitized solar cells

Silicon (Si) nanoparticles with average size of 13 nm and orange–red luminescence under UV absorption were synthesized using electrochemical etching of silicon wafers. A film of Si nanoparticles with thickness of 0.75 µm to 2.6 µm was coated on the glass (TiO₂ side) of a dye‐sensitized solar cell (DSSC). The cell exhibited nearly 9% enhancement in power conversion efficiency (η) at film thickness of ～2.4 µm under solar irradiation of 100 mW/cm² (AM 1.5) with improved fill factor and short‐circuit current density. This study revealed for the first time that the Si‐nanoparticle film converting UV into visible light and helping in homogeneous irradiation, can be utilized for improving the efficiency of the DSSCs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Isolation and characterization of conformational isomers of N,N′‐bis(3,5‐dichlorosalicylidene)‐2,2′‐ethylenedianiline: crystal structure,photoluminescence, and density functional theory calculation

We have isolated two isomeric solids 1 and 2 of N,N′‐bis(3,5‐dichlorosalicylidene)‐2,2′‐ethylenedianiline and characterized by IR, UV/Vis, X‐ray powder diffraction, thermogravimetric analysis/differential thermal analysis, and X‐ray crystallography. Although the solids are same formulas, each shows different colors and crystal structures. Orange solid ( 1 ) shows endo conformation while yellow solid ( 2 ) exhibits exo form depending on packing modes. UV/Vis spectra of 1 and 2 appear very similar patterns in the solid state; however, the bands of 1 are slightly red‐shifted compared with those of 2 . 1 displays a strong fluorescent emission band at ~582 nm while 2 shows an intense fluorescent signal at ~563 nm. The charge density populations of 1 and 2 have been studied by computational simulations using density functional theory at pbe1pbe/6‐311G** level. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies of 1 and 2 confirm that charge transfer occurs within the organic molecules. The energy difference of HOMO‐LUMO in 1 is smaller slightly than that of 2 about 0.05 eV (~17 nm). Copyright © 2014 John Wiley & Sons, Ltd.     

紫外像增强器辐射灵敏度测量系统

紫外像增强器是紫外探测系统的核心器件,是一种电真空成像器件,可将微弱的紫外光图像转换并增强为肉眼可见、亮度可见的光图像,其研制与应用是微光夜视技术的重要发展方向。辐射灵敏度是评价紫外像增强器的重要参数,直接决定了紫外探测系统的性能。介绍了紫外像增强器辐射灵敏度的测量原理,采用紫外辐射光源、光栅单色仪系统、测试暗箱、微电流计、计算机及测量软件组建了辐射灵敏度测量系统。对3只紫外像增强器在260 nm、280 nm及320 nm波长下的辐射灵敏度进行了测量,并分析了其测量不确定度。该测量系统的建立,将辐射灵敏度测量系统的光谱范围拓展至200 nm～400 nm,弥补了现有系统的不足,具有广泛的应用前景。     

星载太阳紫外光谱监视器的地面辐射定标

星载太阳紫外光谱监视器是一种小型化、高精度紫外-真空紫外光谱辐射计,它有两种工作模式,即探测太阳紫外光谱辐照度的太阳模式和探测大气的太阳后向散射紫外光谱辐亮度的大气模式。对应这两种工作模式分别建立了紫外-真空紫外光谱辐照度和紫外光谱辐亮度定标装置。光谱辐照度标准灯直接辐照仪器的漫反射板进行仪器的光谱辐照度响应度定标,光谱辐照度标准灯辐照标准漫反射板形成朗伯面光源进行仪器的光谱辐亮度响应度定标。误差分析表明:160~250 nm光谱辐照度绝对定标误差为6.5%,250~400 nm为4.3%;250~400 nm光谱辐亮度绝对定标误差为5.9%。星载太阳紫外光谱监视器获得的地外太阳紫外光谱辐照度与大气的太阳后向散射光谱辐亮度数据,同国际上的观测结果相比一致性达±10%。     

Structure and vibrational analysis of 1‐hydroxy naphthalene based on density functional theory calculations

The solid phase mid‐FTIR and FT‐Raman spectra of 1‐hydroxy naphthalene (HNP) were recorded in the regions 4000–400 and 4000–50 cm, respectively. The spectra were interpreted with the help of normal coordinate analysis following full structure optimization and force field calculations based on the density functional theory (DFT) using the standard B3LYP/6‐31G** method and basis set combination. The results of the calculations were applied to simulate infrared and Raman spectra of the title compound which showed excellent agreement with the observed spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Role of gemini surfactants (m‐s‐m type; m = 16, s = 4–6) on the reaction of [Zn(II)‐Gly‐Phe]+ with ninhydrin

In the present paper, reaction of zinc‐glycylphenylalanine ([Zn(II)‐Gly‐Phe]⁺) with ninhydrin has been investigated in gemini (m‐s‐m type; m = 16, s = 4–6) surfactants at temperature (70 °C) and pH (5.0). Monitoring the appearance of product at 400 nm was used to follow the kinetics, spectrophotometrically. The order of the reaction with respect to [Zn(II)‐Gly‐Phe]⁺ was unity while with respect to [ninhydrin] was fractional. The reaction constants involved in the mechanism were obtained. In addition to the rate constant (k_Ψ) increase and leveling‐off regions are observed with the geminis, just like as seen with conventional surfactant hexadecyltrimethylammonium bromide (CTAB), the former produced a third region of increasing k_Ψ at higher concentrations. A close agreement between observed and calculated rate constants was found under varying experimental conditions. A suitable mechanism consistent with the experimental findings has been proposed. Copyright © 2014 John Wiley & Sons, Ltd.     

A planetary environment and analysis chamber (PEACh) for coordinated Raman–LIBS–IR measurements under planetary surface environmental conditions

A planetary environment and analysis chamber (PEACh) has been developed at Washington University in St. Louis, in order to perform in situ multiple spectroscopic measurements on geological samples under relevant planetary environmental conditions and to support future planetary missions, with particular interest on Mars. The pressure in the chamber can range from ambient to 3 × 10⁻² mbar. The simulated atmospheric composition and pressure are regulated via a combination of needle and ball valves connecting the chamber with containers filled with premixed gas. The temperature of the samples can be controlled in a range from ambient to − 100 °C. The in situ analytical techniques implemented (and to be implemented) are laser Raman spectroscopy, laser‐induced breakdown spectroscopy (LIBS), near‐IR reflectance spectroscopy, mid‐IR attenuated total reflectance spectroscopy, and microscopic imaging. The coordinated spectroscopic sensing on the same geological sample under well‐controlled atmospheric conditions in the PEACh establishes a way to link the results from the laboratory experiments to the spectral data obtained by landed and orbital planetary exploration missions, which will facilitate understanding the surface processes by which mineral phases occur and their association with atmospheric changes. Copyright © 2011 John Wiley & Sons, Ltd.