A portable remote methane detector using an InGaAsP DFB laser

A portable remote methane detector based on infrared-absorption spectroscopy using an InGaAsP distributed-feedback laser is described. This equipment transmits a laser beam and detects a fraction of the backscatter reflected from the target. From this, the detector thereby measures the integrated methane concentration between the detector and the target. The equipment operator can easily detect methane clouds at a distance by hand-scanning the laser beam. To achieve a high sensitivity of detection, wavelength-modulation spectroscopy is applied to the infrared-absorption measurement for methane. The wavelength of the light source is modulated at a frequency of 10 kHz, and the center wavelength is stabilized at the center of the 2₃ band R(3) line of methane (1.65372 m). When used with typical targets at distances up to 10 m, the detector has a detection limit of less than 5 ppm-m. To the best of the authors knowledge, the detector is the only hand-held product capable of remote methane detection. Recently, this novel equipment was commercially introduced into the Japanese market as a product named the Portable Remote Methane Detector (PRMD). Some PRMD units were in research use for detecting methane emissions from garbage landfills, although the PRMD was mainly developed for remote detection of leaks from natural gas pipelines. The author expects that the PRMD could become the standard equipment for field measurements of methane emissions from land.     

岩石化探样中微量铀 钍的XRFA法测定

本文提出以粉末样品直接压饼法测定岩石化探样品中的微量U,Th,其方法简便、快速,适用于各类地质样品,尤其是岩石化探样品测量。     

Relationship between statistical thermal alteration index and vitrinite reflectance for sedimentary rocks in northern Japan with reference to effects for unconformity,faulting, and contact metamorphism

Two organic maturity indices, the statistical thermal alteration index (stTAI) and vitrinite reflectance (R_O), are used to gain insight into the geological histories of sequences of Tertiary and Upper Cretaceous sediments in northern Japan that contain an unconformity and which are affected by faulting and contact metamorphism. The stTAI is based on the brightness, or gray level, of fossil pollen of Pinus, Podocarpus, Abies, and Picea species. Pollen brightness is measured using a transmitted‐light microscope equipped with a computer‐driven digital image processor. The stTAI represents the mean value of the modes for the complete array of indigenous pollen in rock samples. The stTAI indicates the level of organic maturation for Neogene sedimentary rocks of Japan, from incipient diagenesis to early catagenesis (R_O ≤1.0%). With the progressive diagenesis and catagenesis of sedimentary rocks, stTAI values generally show a progressive decrease, whereas R_O values increase. The effects of an unconformity and faulting are more clearly recorded in stTAI trends than in R_O trends. During early stages of organic maturation (R_O ≤0.7%), stTAI shows a rapid decrease, while R_O shows a rapid increase during the mature and post‐mature stages (R_O ≥0.8%). The occurrence of a range in R_O values for a given level of organic maturity makes it difficult to determine the influence of the unconformity on the increasing R_O trend. R_O values show a progressive increase toward an igneous dyke, but this trend is not apparent in stTAI values. Measurements of Tertiary and Upper Cretaceous rocks in Japan reveal that stTAI is more sensitive to heating duration than R_O, although R_O is more sensitive to heating temperature.     

Optical constants of amorphous and crystalline H2O-ice in the near infrared from 1.1 to 2.6 μm

Using new laboratory spectra, we have calculated the real and imaginary parts of the index of refraction of amorphous and crystalline H₂O-ice from 20 to 150 K in the frequency range 9000-3800 cm⁻¹ (1.1-2.6 μm) at a spectral resolution of 1 cm⁻¹. These optical constants can be used to create model spectra for comparison to spectra from Solar System objects. We also analyzed the differences between the amorphous and crystalline H₂O-ice spectra, including weakening of bands and shifting of bands to shorter wavelength in amorphous H₂O-ice spectra. We have also observed two spectrally distinct phases of amorphous H₂O-ice.     

四川盆地东北地区古地温梯度模拟

四川盆地东北地区古地温梯度一直缺乏研究。以普光气田已有的实测反射率数据为依据,应用EasyRo模拟计算方法,研究了该区主要生烃期的古地温梯度。结果表明,对川东北地区主要埋藏与生烃期(三叠纪—早白垩世)进行的成熟度模拟计算,应用古地温梯度为3.0℃/100m的古地温模式计算所得的结果与实测结果非常吻合。进一步提出了该区的简化古地温模式为[3.0℃/100m(96Ma)—2.8℃/100m(65Ma)—2.2℃/100m(0Ma)]。     

Europa’s disk-resolved ultraviolet spectra: Relationships with plasma flux and surface terrains

The full set of high-resolution observations from the Galileo Ultraviolet Spectrometer (UVS) is analyzed to look for spectral trends across the surface of Europa. We provide the first disk-resolved map of the 280 nm SO₂ absorption feature and investigate its relationship with sulfur and electron flux distributions as well as with surface features and relative surface ages. Our results have implications for exogenic and endogenic sources. The large-scale pattern in SO₂ absorption band depth is again shown to be similar to the pattern of sulfur ion implantation, but with strong variations in band depth based on terrain. In particular, the young chaos units show stronger SO₂ absorption bands than expected from the average pattern of sulfur ion flux, suggesting a local source of SO₂ in those regions, or diapiric heating that leads to a sulfur-rich lag deposit.While the SO₂ absorption feature is confined to the trailing hemisphere, the near UV albedo (300-310 nm) has a global pattern with a minimum at the center of the trailing hemisphere and a maximum at the center of the leading hemisphere. The global nature of the albedo pattern is suggestive of an exogenic source, and several possibilities are discussed. Like the SO₂ absorption, the near UV albedo also has local variations that depend on terrain type and age.     

Two‐dimensional speckle spectroscopy of Hα features

In May 2002, the solar chromosphere was observed with a two‐dimensional spectrometer which is mounted in the German Vacuum Tower Telescope (VTT) at the Observatorio del Teide/Tenerife. The aim of this observation was to investigate the fine structure of the solar chromosphere seen in Hα. We took narrow‐band filtergrams (Δλ ≈ 72 mÅ) by scanning through this line. Broad‐band images taken strictly simultaneously with the narrow‐band filtergrams were restored by speckle methods. The instantaneous optical transfer function from this restoration procedure was used for the reconstruction of the narrow‐band images. Some results of this high spatial resolution observation are presented below.     

PARASOL/POLDER3卫星数据的海洋上空云检测

在卫星海洋遥感中,云作为海气耦合系统最重要的调节器之一,其检测结果对海洋上空云微物理特性的反演精度有较大影响。因此,快速而准确识别海洋上空的云像元是卫星遥感数据处理过程中首要解决的关键问题。以PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar)卫星搭载的POLDER3载荷遥感数据为研究对象,提出一种改进的海洋上空云检测方法。首先剔除海洋耀光;接着利用有云与晴空区近红外反射率差异检验识别有云像元,并利用偏振反射率检验进一步识别低反射率的云像元;然后利用近红外与可见光反射率比值检验识别晴空像元;最后建立多角度云检测结果空间融合规则,重新标记有云、晴空和未定像元。以印度洋海区为例进行实验分析,将云检测结果与Buriez方法进行对比,发现检测精度基本相当,而有云像元的识别速度却平均提高约3倍。结果表明:该方法能有效的检测出海洋上空的云像元,满足业务化数据处理的高精度及时效性要求,为后续云微物理特性反演提供可靠的数据源。     

Microanalysis of Fe3+/ΣFe in oxide and silicate minerals by investigation of electron energy-loss near-edge structures (ELNES) at the Fe M 2,3 edge

The Fe M _2,3-edge spectra of solid solutions of garnets (almandine-skiagite Fe₃(Al_1–xFe_x)₂[SiO₄]₃ and andradite-skiagite (Fe_1–xCa_x)₃Fe₂[SiO₄]₃), pyroxenes (acmite-hedenbergite (Ca_1–xNa_x)(Fe²⁺ _1−xFe³⁺ _x)Si₂O₆), and spinels (magnetite-hercynite Fe(Al_1–xFe_x)₂O₄) have been measured using the technique of parallel electron energy-loss spectroscopy (EELS) conducted in a transmission electron microscope (TEM). The Fe M _2,3 electron energy-loss near-edge structures (ELNES) of the minerals exhibit a characteristic peak located at 4.2 eV and 2.2 eV for trivalent and divalent iron, respectively, prior to the main maximum at about 57 eV. The intensity and energy of the pre-edge feature varies depending on Fe³⁺/ΣFe. We demonstrate a new quantitative method to extract the ferrous/ferric ratio in minerals. A systematic relationship between Fe³⁺/ΣFe and the integral intensity ratio of the main maximum and the pre-edge peak of the Fe M _2,3 edge is observed. Since the partial cross sections of the Fe M _2,3 edges are some orders of magnitude higher than those of the Fe L _2,3 edges, the Fe M _2,3 edges are interesting for valence-specific imaging of Fe. The possibility of iron valence-specific imaging is illustrated by Fe M _2,3-ELNES investigations with high lateral resolution from a sample of ilmenite containing hematite exsolution lamellae that shows different edge shapes consistent with variations in the Fe³⁺/ΣFe ratio over distances on the order of 100 nm. Received: 14 April 1998 / Revised, accepted: 8 March 1999     

Intracrystalline fractionation of Fe in synthetic (Fe, Mg, Zn) - bearing staurolite: a Mössbauer spectroscopic study

⁵⁷Fe-Mössbauer spectra of eleven Fe-Mg-bearing staurolite samples, synthesized at 5, 20 and 25 kbar and 680°C, ranging in composition from x_Fe?=1.00 to x_Fe?=0.15, and of two Zn-Fe-bearing staurolite samples, synthesized at 20 kbar and 700°C with x_Fe?=0.10 and x_Fe?=0.32 were collected at room temperature. The spectra reveal that about 80% of Fe_tot (in case of Fe-Mg-bearing staurolite) and about 70% of Fe_tot (in case of Fe-Zn-bearing staurolite) are located as Fe²⁺ at the three subsites Fe1, Fe2 and Fe3 of the tetrahedral T2-site. The refinement of the spectra results in almost identical values for the isomer shift (IS) (±1.0 mm/s) but significantly different values for the quadropole splitting (QS) for the three subsites which is in accordance with the different distortions of these sites. About 8% of Fe_tot (in case of Fe-Mg-bearing staurolite) and 13% of Fe_tot (in case of Fe-Zn-bearing staurolite) are located as Fe²⁺ at the octahedral M4 site, while the remainder percents of Fe_tot indistinguishably occur as Fe²⁺ at the octahedral M1 and M2 sites of the kyanite-like part of the structure. Within the whole Fe-Mg-staurolite solid solution series the Mössbauer parameters QS of the sites M4 and (M1, M2) vary systematically with composition whereas IS remains constant. There is a high negative correlation of the total Mg-content with Fe-occupation of all the Fe-bearing sites indicating a continuous substitution of Fe²⁺ by Mg on all these sites. Synthetic Fe-staurolites show no increasing occupation of the octahedral sites by two-valent cations with pressure, as was assumed by several authors.