Differential Absorption Technique Research Articles

Comparative Study on the Total Phenolics, Total Flavonoids, and Biological Activities of Papaver rhoeas L. Extracts from Different Geographical Regions of Morocco

In this research, a comparative analysis was carried out to characterize the content of phenolics and biological activities of the whole plant of Papaver rhoeas L. (P. rhoeas) from different geographical regions of Morocco, as well as to determine the synergistic antimicrobial and antioxidant effects of all parts of P. rhoeas. The determination of total polyphenol content (TPC), total flavonoid content (TFC), and total anthocyanin content (TA) in extracts of whole plants of P. rhoeas from three different geographical regions: Taounate (P1E), Fez (P2E), and Sefrou (P3E) were estimated by the Folin–Ciocalteu reaction, the aluminum trichloride method and the differential pH absorption technique, respectively. Two tests were used to evaluate the antioxidant power of our samples: the DPPH test and the TAC test. Using two methods, disk diffusion and microdilution, antimicrobial activity was studied against four pathogenic bacteria and one yeast. The results of TPC, TFC, and TA show that the P3E sample is the richest in polyphenols, flavonoids, and anthocyanins, with values 37.33 ± 1.307 mg GAE/g, 4.72 ± 0.346 QE/g, and 1.77 ± 0.026 CGE/g, respectively. In addition, P3E showed the best antioxidant activity with an IC50 = 0.27 ± 0.001 mg/mL and TAC = 9.99 ± 0.768 mg AAE/g, respectively. The results of antimicrobial activity showed significant activity on almost all the tested strains. The lowest MIC was recorded for P3E against E. coli ATCC 25922 and E. coli CIP 53126 strains at 0.78 and 0.78 mg/mL, respectively. These results show that the geographical region can influence the plant’s phytochemistry and then these biological activities.

Spectroscopic, conductivity and voltammetric investigations of interaction of sulfamethoxazole alone and in combination with trimethoprim with self-assembled structures

The demand and urgency of new drug design and discovery is facing new challenges in the wake of spread and persistence of serious global threat of antibiotic resistance. One of the major hurdles in the development of new drugs that are more aqueous soluble and passively diffusible is the paucity of knowledge regarding their physicochemical interactions with biological membranes. Being chemical-mimics of biomembranes, surfactant-based micellar systems present excellent pseudo-membrane models to study biophysical interactions of drugs with biological membranes in vitro. The present research focuses on physicochemical interaction of sulfamethoxazole (SMZ) alone and in combination with trimethoprim (TMP) with cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulfate (SDS). UV–visible spectroscopy, electrical conductivity and cyclic voltammetric techniques were employed to quantitate different drug-surfactant interaction parameters. UV–visible spectroscopic was used to evaluate critical micelle concentration (CMC) of CTAB and SDS in the presence of SMZ, TMP and their binary mixture in aqueous medium (pH 7.0). Differential absorption technique was used to determine partition coefficient (Kc ) and binding constant (Kb ) of SMZ and (SMZ + TMP) mixture with ionic micelles. Thermodynamic parameters of micellization such as and of CTAB and SDS in the presence SMZ and its mixed form with TMP were calculated in deionized water. Further, voltammetric investigations depict the strong binding of SMZ and its TMP mixture with CTAB micelles relative to SDS micelles.

Wintertime Saharan dust transport towards the Caribbean: an airborne lidar case study during EUREC<sup>4</sup>A

Abstract. Wintertime Saharan dust plumes in the vicinity of Barbados are investigated by means of airborne lidar measurements. The measurements were conducted in the framework of the EUREC4A (Elucidating the Role of Cloud-Circulation Coupling in Climate) field experiment upstream the Caribbean island in January–February 2020. The combination of the water vapor differential absorption and high spectral resolution lidar techniques together with dropsonde measurements aboard the German HALO (High Altitude and Long-Range) research aircraft enable a detailed vertical and horizontal characterization of the measured dust plumes. In contrast to summertime dust transport, mineral dust aerosols were transported at lower altitudes and were always located below 3.5 km. Calculated backward trajectories affirm that the dust-laden layers have been transported in nearly constant low-level altitude over the North Atlantic Ocean. Only mixtures of dust particles with other aerosol species, i.e., biomass-burning aerosol from fires in West Africa and marine aerosol, were detected by the lidar. No pure mineral dust regimes were observed. Additionally, all the dust-laden air masses that were observed during EUREC4A came along with enhanced water vapor concentrations compared with the free atmosphere above. Such enhancements have already been observed during summertime and were found to have a great impact on radiative transfer and atmospheric stability.

Temperature and spatial dependence of carrier lifetime and luminescence intensity in Ge0.95Sn0.05 layer

In this work we present a study of spatial and temperature dependencies of carrier lifetime and photoluminescence in pseudomorphic Ge0.95Sn0.05 layer on silicon by applying contactless time-resolved differential absorption and photoluminescence techniques. The observed small lifetime and photoluminescence intensity spatial variations (~10%) indicate for good material homogeneity. Differential transmission kinetics exhibit fast bleaching and slow absorption components related to thermalization (few hundreds of picoseconds) and surface recombination (few tens of nanoseconds) processes. Temperature dependent photo-luminescence measurements indicate activation of carriers from L to Γ valley, governing dominant direct photoluminescence emission band at 1850 nm at 300 K. These direct transitions explain more efficient and blue-shifted by 150 nm photoluminescence emission at room temperature. At low temperatures direct emission is related to non-thermalized carriers, while indirect one is caused by depopulation of light hole band with temperature.

Retrieval of Daytime Total Column Water Vapour from OLCI Measurements over Land Surfaces

A new retrieval of total column water vapour (TCWV) from daytime measurements over land of the Ocean and Land Colour Instrument (OLCI) on-board the Copernicus Sentinel-3 missions is presented. The Copernicus Sentinel-3 OLCI Water Vapour product (COWa) retrieval algorithm is based on the differential absorption technique, relating TCWV to the radiance ratio of non-absorbing band and nearby water vapour absorbing band and was previously also successfully applied to other passive imagers Medium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS). One of the main advantages of the OLCI instrument regarding improved TCWV retrievals lies in the use of more than one absorbing band. Furthermore, the COWa retrieval algorithm is based on the full Optimal Estimation (OE) method, providing pixel-based uncertainty estimates, and transferable to other Near-Infrared (NIR) based TCWV observations. Three independent global TCWV data sets, i.e., Aerosol Robotic Network (AERONET), Atmospheric Radiation Measurement (ARM) and U.S. SuomiNet, and a German Global Navigation Satellite System (GNSS) TCWV data set, all obtained from ground-based observations, serve as reference data sets for the validation. Comparisons show an overall good agreement, with absolute biases between 0.07 and 1.31 kg/m2 and root mean square errors (RMSE) between 1.35 and 3.26 kg/m2. This is a clear improvement in comparison to the operational OLCI TCWV Level 2 product, for which the bias and RMSEs range between 1.10 and 2.55 kg/m2 and 2.08 and 3.70 kg/m2, respectively. A first evaluation of pixel-based uncertainties indicates good estimated uncertainties for lower retrieval errors, while the uncertainties seem to be overestimated for higher retrieval errors.

Improvement of the timing properties of Ce-doped oxyorthosilicate LYSO scintillating crystals

The aim of this work has been to improve the time resolution of radiation detectors for future high-energy physics experiments and medical imaging applications. Ce-doped oxyorthosilicate Lu2SiO5:Ce (LSO) and mixed oxyorthosilicate Lu1.6Y0.4SiO5:Ce (LYSO) have been investigated as prospective scintillators for such high-time-resolution applications. A differential optical absorption technique with sub-picosecond time resolution upon selective excitation of Ce3+ ions to different excited states has been adopted to study carrier dynamics in these scintillators, and coincidence time resolution measured using 511 keV γ-quanta has been exploited to test their timing properties. A delay in population of the emitting level of Ce3+ has been observed, and is interpreted in terms of electron trapping, which is more pronounced in mixed yttrium-containing LYSO crystals due to composition fluctuations. It is shown that the delay, which affects the luminescence response time, can be eliminated by co-doping of LYSO:Ce with calcium at concentrations as low as 5 ppm. The faster kinetics of electron transfer correlates with a better coincidence time resolution. Thermalization and spatial distribution of non-equilibrium carriers has been studied theoretically to link the results obtained by the time-resolved differential optical absorption technique with the behavior of the non-equilibrium carriers generated by irradiation.

CO laser sum-frequency comb for atmosphere sensing

Sum-frequency spectrum of non-selective (multi-line) CO laser radiation generated in ZnGeP2 crystal under noncritical spectral phase-matching conditions was experimentally studied with spectral resolution of ∼0.1 cm−1. The number of spectral lines for this spectrum was found to be about an order of magnitude larger than for previously reported one. Its spectral structure looked like a broadband mid-IR comb of multi-line groups having complicated substructure. That is attractive for the atmosphere sounding by both differential absorption technique and absorption line profile spectroscopy. A list of the atmosphere gases and pollutants that could be detected by these procedures was considered. An opportunity of absorption line profile measuring by means of CO laser sum-frequency comb was experimentally demonstrated for CO2 molecules.

Timing properties of Ce-doped YAP and LuYAP scintillation crystals

Abstract The timing performance of radiation detectors based on Ce-doped perovskites YAlO3 (YAP) and (Lu 1−x - Y x )AlO3 (LuYAP) coupled with near-UV sensitive silicon photomultipliers (NUV-HD SiPMs) have been compared in coincidence time resolution (CTR) experiments. The single-detector time resolution full width at half maximum (FWHM) of YAP was found to be 169 ps, i.e., by a factor of two better than that observed earlier with photomultiplier readout. Introduction of lutetium into YAP structure deteriorates the time resolution to 286 ps and 309 ps for a Lu/Y atomic ratio of 1:1 and 0.7:0.3, respectively. The study of the dynamics of Ce 3 + excited state population after selective optical excitation with short (200 fs) pulses by using the differential absorption technique in pump and probe configuration evidenced the importance of electron trapping, which is enhanced by antisite Lu Al defects having favorable conditions to occur in LuAP.

Data Processing and Analysis Approach to Retrieve Carbon Dioxide Weighted-Column Mixing Ratio and 2-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m Reflectance With an Airborne Laser Absorption Spectrometer

We describe the data processing and analysis algorithms used for high-precision retrievals of CO2 weighted-column mixing ratio and 2- $\mu \text{m}$ surface reflectance from the Carbon Dioxide Laser Absorption Spectrometer (CO2LAS). The CO2LAS at the Jet Propulsion Laboratory, Pasadena, CA, USA, is one of the instruments designed to demonstrate capabilities needed for the NASA Active Sensing over Nights, Days, and Seasons mission concept. The integrated path differential absorption technique is used in CO2 retrieval. The along-track spatial resolution for the airborne measurements described here ranges from 10 m to 1 km. Our approach employs heterodyne detection of two laser signals reflected off earth’s surface. Frequency domain processing enables return signal peak detection and high-fidelity power estimation. We compensate for range to ground variations using a digital elevation model and emphasize the importance of reflectance weighting in time averaging of the surface elevation. Quality control filters are applied, as well as a statistical methodology to filter laser speckle fluctuations. Reflectance is also retrieved on the scale of a few meters of ground track. Our data processing workflow and example retrievals are presented.

Lidar Complex for Measurement of Vertical Ozone Distribution in the Upper Troposphere–Stratosphere

A lidar complex designed at V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (Tomsk) and used at the Siberian Lidar Station (56.5° N, 85.0° W) for the study of ozone dynamics near tropopause and for tracking global ozonosphere changes is presented. It allows measurements of ozone vertical distribution in the upper troposphere–stratosphere when sounding using the differential absorption technique at the wavelength pairs 299/341 and 308/353 nm. The lidar complex covers altitudes from ∼5 to ∼45 km.

Atmospheric Column Water Vapor Retrieval From Hyperspectral VNIR Data Based on Low-Rank Subspace Projection

The knowledge of atmospheric column water vapor concentration is crucial for compensating water absorption effects in remote sensing data. Several algorithms for the estimation of such a parameter were proposed in the past. One of the most effective algorithms is the atmospheric precorrected differential absorption (APDA) technique. APDA relies on a simplified radiative transfer model (RTM) that does not account for the spatial variability of the adjacency effects. In this paper, we study the impact of the simplified RTM assumption on the performance of the algorithm by exploiting a more realistic and well-established RTM. Starting from such a model, we derive a new water retrieval algorithm called low-rank subspace projection-based water estimator. It exploits the high degree of spectral correlation experienced in the reflectances of most of the existing materials. An extensive experimental analysis is carried out on simulated data in order to assess and compare the performance of the two algorithms. Simulation results allow the critical analysis of the two algorithms by highlighting their strengths and drawbacks.

Structural, thermal and optical investigations of Dy3+-doped B2O3–WO3–ZnO–Li2O–Na2O glasses for warm white light emitting applications

Optically transparent Dy3+-doped borate glasses with the chemical composition (60-x) B2O3-10 WO3-10 ZnO-10 Li2O-10 Na2O-x Dy2O3 (x=0.1, 0.25, 0.5, 0.75, 1.0, and 1.5mol %) have been synthesized by melt quenching technique and were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy and Energy Dispersive X-ray Analysis (SEM-EDX), Attenuated Total reflectance-Fourier transform Infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, Thermo-gravimetric analysis (TGA), Differential scanning calorimetry (DSC), optical absorption and luminescence techniques. The amorphous nature of the prepared glasses has been confirmed through XRD and SEM measurements, and the EDX spectra show all the elements present in the respective glasses. The vibrational features of various functional groups like stretching vibrations of BO linkages in BO4 tetrahedra, asymmetric stretching vibrations of BO bond in trigonal BO3 units, stretching vibrations of W–O–W in WO4 or WO6 units, vibrations of Zn–O bonds from ZnO4 groups, bending modes of ZnO4 units, and vibrational modes of BO3 and BO4 due to alkali borates were identified by ATR-FTIR and Raman spectroscopy. For the prepared glasses; weight loss, and the glass transition (Tg), onset crystallization (Tx), crystallization (Tc) and melting (Tm) temperatures were determined from TGA and DSC measurements, respectively. Following the obtained Tg, Tx, Tc, and Tm values, the thermal stability (∆T) and Hruby's values (HR) were determined, the calculated ∆T values increased in the temperature range 131–143°C and HR values varied in the range 0.766–1.014 with Dy3+ concentration increment from 0.1 to 1.5mol %, and the increasing stability of the glasses shows that they are thermally resistant. The optical properties of the titled glasses have been explored from the absorption, photoluminescence excitation (PLE) and photoluminescence (PL) spectra. For the 0.5mol % Dy3+-doped glass, to obtain the information concerning the nature of the ligand field environment around the Dy3+ ions, the Judd-Ofelt (JO) intensity parameters Ωλ (λ=2, 4 and 6) were evaluated from the measured oscillator strengths (f) of various absorption bands. Further, the radiative parameters such as radiative transition probabilities (AR), branching ratios (βR), and the radiative lifetimes (τR) of 4F9/2→6H15/2, 4F9/2→6H13/2, 4F9/2→6H11/2 and 4F9/2→6H9/2 main emission transitions were calculated by using JO parameters. The photoluminescence properties were examined under ultraviolet (UV)/near UV (NUV) and blue excitations. Luminescence spectra measured for different concentrations of Dy3+-doped glasses by exciting the glasses at 350, 364, 386, 400, 425 and 452nm wavelengths show concentration quenching beyond 0.5mol% and the luminescence quenching has been explained by using cross-relaxation (CR) channels and resonant energy transfer (RET). For the 0.5mol% Dy3+-doped glass, the measured decay lifetime and the evaluated quantum efficiency values are ~211.8μs and 68.1%, respectively. Following the luminescence spectra, the yellow-to-blue (Y/B) luminescence intensity ratios, color chromaticity coordinates (x, y) and correlated color temperatures (CCT) of the glasses have also been estimated to evaluate the white light generation with respect to Dy3+ ion concentration. The color coordinates and CCT values for 0.5mol% Dy3+-doped glass (optimum concentration) represent the warm white light region for all the selected UV and blue excitation wavelengths. The obtained results indicate that the optimized 0.5mol% Dy3+-doped glass may be useful for the warm white light emitting applications as well as for solid state yellow laser emission and luminescent display devices.

APDA Water Vapor Retrieval Validation for Sentinel-2 Imagery

Water vapor is one of the main parameters for atmospheric correction of Sentinel-2 imagery. Together with the aerosol retrieval it determines the accuracy of the surface reflectance product. Since Sentinel-2A and soon Sentinel-2B are operational satellites with a free data policy there is great interest in processing this data and using it for environmental studies. This contribution performs a validation of Sentinel-2 retrieved water vapor over land by comparing the scene-derived water vapor column with the AERONET measurement as an independent source. The validation is performed for a large range of AERONET site elevations and solar zenith angles using the atmospheric precorrected differential absorption (APDA) technique. Results show a high correlation with a low RMSE of about 0.1 cm for water vapor values from 0.2 to 5 cm.

Concentration dependent structural, thermal, and optical features of Pr3+-doped multicomponent tellurite glasses

Tuning the structural, thermal, and optical properties of low phonon energy glasses such as tellurite glasses (phonon energy ∼750 cm−1) with suitable rare earth dopants is a key issue in the fabrication of solid state lasers and optical amplifiers. In this work, (70-x) TeO2-10 WO3-10 ZnO-5 TiO2-5 Na2O-(x) Pr2O3 (x = 1.0–5.0 mol %) glasses were synthesized with high optical quality and characterized using X-ray diffraction (XRD), Scanning electron microscopy and Energy dispersive X-ray analysis (SEM-EDAX), Attenuated total reflectance-Fourier transform infrared (ATR-FTIR), Raman spectroscopy, Thermo-gravimetric analysis (TGA), Differential scanning calorimetry (DSC), optical absorption and luminescence techniques. The XRD and SEM measurements reveal the amorphous nature of all the prepared glasses and EDAX confirms all the elements present in the respective glasses. The presence of various functional groups such as stretching vibrations of Te–O bonds in the [TeO4] trigonal bi-pyramid units, symmetrical stretching or bending vibrations of Te–O–Te or O–Te–O linkages at corner sharing sites along the chains of TeO4, TeO3 and TeO3+1, stretching vibrations of W–O– and WO bonds in WO4 tetragonal or WO6 octagonal units, vibrations of Zn–O bonds from ZnO4 groups, including non-hygroscopic nature of the glasses are confirmed by ATR-FTIR and Raman spectra, respectively. For Pr3+-doped glasses, from the DSC profiles the glass transition temperature (Tg), onset crystallization temperature (Tx), crystallization temperature (Tc), and melting temperature (Tm) are identified and the evaluated thermal stability values varied in the temperature range of 169–220 °C with increasing Pr3+ doping concentration. Further, the Pr3+ -doped tellurite glasses demonstrate excellent glass stability with higher criterion of Hruby’s value (HR) between 1.9 and 3.9. From the measured optical absorption spectrum, experimental oscillator strengths are calculated and used to evaluate three phenomenological Judd-Ofelt (J-O) intensity parameters Ωλ (λ = 2, 4 and 6) and respective radiative properties such as radiative transition probabilities (AR), the branching ratios (βR), and the radiative lifetime (τR) of metastable states for 1.0 mol % Pr3+-doped glass. Five main emission transitions at 3P0 → 3H5 (530 nm; green) with a shoulder at 543 nm, a weak band at 1D2 → 3H4 (592 nm; orange), 3P0 → 3H6 (615 nm; orange), 3P0 → 3F2 (649 nm; red), and 3P0 → 3F3 (686 nm; red) upon exciting at 486 nm (3H4 → 3P0) wavelength are observed from the luminescence spectra of Pr3+-doped tellurite glasses. Following the energy level diagram, Pr3+ ion concentration quenching on the luminescence intensity has been explained by a non-radiative energy transfer between the ions through cross-relaxation and energy migration processes. The concentration dependent structural, thermal, and optical behaviors of Pr 3+-doped tellurite glasses are understood and our systematic analysis could contribute towards the development of suitable optical devices fabrication.

Concentration and pressure measurement of water vapor in sealed glass containers based on tunable diode laser absorption spectroscopy

Water vapor in a sealed glass container processed by lyophilization is a main factor for drug metamorphism. The key to knowing whether there is a leakage occurring in the container is how to detect water concentration and pressure in the sealed container quickly and accurately. In the present paper, a strong absorption line of H2O near 1.39 m is carefully selected to avoid the interference of neighboring transitions. A distributed feedback laser semiconductor laser near 1.396 m is employed as the light source with a power of 10 mW and typical linewidth of 2 MHz by combining with tunable diode laser absorption spectroscopy technique, the concentrations and pressures of water vapor in the sealed container are successfully detected under static condition and dynamic condition. In order to isolate the interference absorption from the ambient water vapor in the air, a differential absorption technique is employed in our experiment, which makes our system simpler than routine nitrogen purging based system. During the measurement, the second harmonic signal is utilized for measuring the concentration and pressure, the concentration is retrieved by the peak value while the pressure is calculated by the full width at half maximum. For the measurement of concentration ranging from 0.2% to 12%, the linear correlation coefficient between the real values and the inversed values and the standard deviation ratio are 0.9978 and 4.81%, respectively. For the measurement of pressure, the correlation coefficient and standard deviation ratio are 0.982 and 5.6%, respectively. The minimum detection limits of the concentration and pressure are 400 ppm and 2.5 Torr, respectively. Moreover, in order to test the system for on-line applications in the pharmaceutical industry, measurements are performed in vials which are placed on a rotary stage to simulate the process of the assemble line. In particular, the amplitude of sinuous signal without absorption is used as the reference signal to validate whether the vial is in the optical path. Besides, this amplitude is also utilized to normalize the laser power. The results show that our system can handle about 300 bottles in one minute, which can meet well the requirements for rapid and real-time detections. This system can be applied directly to the medicine bottle on-line detection, and multicomponent detection can also be realized by employing two or more lasers (e.g. H2O, oxygen, etc.). In the future, we plan to build a system for detecting water vapor and oxygen simultaneously, as oxygen is another import indicator for drug metamorphism.

Volcanic CO2 detection with a DFM/OPA-based lidar.

The DFM/OPA-based lidar BILLI was used to investigate the volcanic plume released by the hydrothermal vent of Pisciarelli, in the Campi Flegrei volcano. BILLI remotely measured CO2 concentrations in cross-sections of the near-vent plume using the differential absorption technique. To our knowledge, this is the first example of lidar-based measurement of volcanic CO2. The spatial resolution was 1.5m and the temporal resolution 20s.

Differential laser absorption spectroscopy of uranium in an atmospheric pressure laser-induced plasma

A two-beam differential laser absorption technique is used to measure 238U absorption spectra with high signal-to-noise ratios in an atmospheric pressure laser-induced plasma. High-resolution absorption spectra are presented for the 238U 861 nm transition in the presence of dry air at pressures up to 760 Torr. A spectral linewidth (FWHM) of 2.23±0.13 GHz was found for the 238U line in dry air at 760 Torr. Absorption spectrum measurements using a low 238U concentration NIST glass standard were used to demonstrate sensitivity of the approach.

Calculation of the Absorption Cross Sections of Some Molecules from GEISA Database at the Wavelengths of Isotopically Different CO2 Lasers

A calculation of the absorption cross section of some molecules (NH3, C2H4, CO2, O3, NO2, PH3, HNO3, SF6, CH3OH, HCOOH, OCS, CH3CN, C2H6, SO2, and H2O) at the wavelengths transmitted by a CO2 laser filled with different isotopes (12C16O2, 13C16O2, 12C18O2, 14C16O2, 14C18O2, 13C18O2, and 12C16O18O) is presented. The spectroscopical parameters for the molecules from GEISA database have been used. Hence the selection of the molecules was substantially based on the availability of the parameters in the database. The results of the calculations may be used in designing the differential absorption technique for remote monitoring of these molecules. The pressure and temperature dependence of the cross sections are described by and coefficients; these coefficients were calculated for the largest absorption cross sections for each molecule. The absorption cross sections of CH3OH and HCOOH at low pressures for all these CO2 lasers are also presented. These calculations are provided for design of new CO2-laser-pumped far-infrared lasers.

Airborne measurements of CO2 column absorption and range using a pulsed direct-detection integrated path differential absorption lidar

We report on airborne CO(2) column absorption measurements made in 2009 with a pulsed direct-detection lidar operating at 1572.33 nm and utilizing the integrated path differential absorption technique. We demonstrated these at different altitudes from an aircraft in July and August in flights over four locations in the central and eastern United States. The results show clear CO(2) line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The lidar measurement statistics were also calculated for each flight as a function of altitude. The optical depth varied nearly linearly with altitude, consistent with calculations based on atmospheric models. The scatter in the optical depth measurements varied with aircraft altitude as expected, and the median measurement precisions for the column varied from 0.9 to 1.2 ppm. The altitude range with the lowest scatter was 8-10 km, and the majority of measurements for the column within it had precisions between 0.2 and 0.9 ppm.

Calibration and quality assurance procedures at the far UV linear and circular dichroism experimental station DISCO

Circular and Linear dichroism spectroscopy used in biophysics, are both differential absorption techniques, which explore the chirality of complex macromolecular structures such as proteins and nucleic acids in solution. In the past two decades synchrotron radiation facilities throughout the world, have accommodated circular dichroism (SRCD) experiments. These intense VUV light sources have greatly expanded the wavelength range exploitable (down to 120nm) at high constant photon flux improving signal to noise ratio and data acquisition speed. Here we present the calibration procedure for the circular and linear dichroism experiments explored on the SRCD beam line DISCO at the synchrotron SOLEIL as well as the specially designed automated sample rotation chamber.