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Retrieving vertical ozone profiles from measurements of global spectral irradiance
摘要： A new method is presented to determine vertical ozone profiles from measurements of spectral global (direct Sun plus upper hemisphere) irradiance in the ultraviolet. The method is similar to the widely used Umkehr technique, which inverts measurements of zenith sky radiance. The procedure was applied to measurements of a high-resolution spectroradiometer installed near the centre of the Greenland ice sheet. Retrieved profiles were validated with balloon-sonde observations and ozone profiles from the space-borne Microwave Limb Sounder (MLS). Depending on altitude, the bias between retrieval results presented in this paper and MLS observations ranges between ?5 and +3 %. The magnitude of this bias is comparable, if not smaller, to values reported in the literature for the standard Dobson Umkehr method. Total ozone columns (TOCs) calculated from the retrieved profiles agree to within 0.7±2.0 % (±1σ) with TOCs measured by the Ozone Monitoring Instrument on board the Aura satellite. The new method is called the “Global-Umkehr” method.
关键词： atmospheric composition,spectral irradiance,ozone profiles,UV monitoring,Umkehr technique
更新于2025-09-09 09:28:46
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Exploring the applicability and limitations of selected optical scattering instruments for PM mass measurement
摘要： Two optical scattering instruments for particle mass measurement, the Thermo Personal Data RAM (PDR-1500) and the TSI Environmental DustTrak DRX (Model 8543) were evaluated by (1) using poly- and mono-disperse test aerosol in the laboratory, and (2) sampling ambient aerosol. The responses of these optical scattering instruments to different particle characteristics (size, composition, concentration) were compared with responses from reference instruments. A Mie scattering calculation was used to explain the dependence of the optical instruments’ response to aerosol size and composition. Concurrently, the detection efficiency of one Alphasense Optical Particle Counter (OPC-N2) was evaluated in the laboratory as well. The relationship between aerosol mass concentration and optical scattering was determined to be strongly dependent on aerosol size and to a lesser extent on aerosol composition (as reflected in the refractive indices of the materials tested) based on ambient measurements. This confirms that there is no simple way to use optical scattering instruments over a wide range of conditions without adjustments based on knowledge of aerosol size and composition. In particular, a test period measuring ambient aerosol with optical scattering instruments and a mass based method (an Aerodyne Aerosol Mass Spectrometer) determined that roughly two thirds of the variance (R2 = 0.64) of the optical to mass signal ratio is explained by the aerosol mass median diameter alone. These observations and calculations help evaluate the applicability and limitations of these optical scattering instruments, and provide guidance to designing suitable applications for each instrument by considering aerosol sources and aerosol size.
关键词： aerosol composition,optical scattering instruments,aerosol size,PM mass measurement,Mie scattering calculation
更新于2025-09-09 09:28:46
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Raman and infrared spectroscopy reveal that proliferating and quiescent human fibroblast cells age by biochemically similar but not identical processes
摘要： Dermal fibroblast cells can adopt different cell states such as proliferation, quiescence, apoptosis or senescence, in order to ensure tissue homeostasis. Proliferating (dividing) cells pass through the phases of the cell cycle, while quiescent and senescent cells exist in a non-proliferating cell cycle-arrested state. However, the reversible quiescence state is in contrast to the irreversible senescence state. Long-term quiescent cells transit into senescence indicating that cells age also when not passing through the cell cycle. Here, by label-free in vitro vibrational spectroscopy, we studied the biomolecular composition of quiescent dermal fibroblast cells and compared them with those of proliferating and senescent cells. Spectra were examined by multivariate statistical analysis using a PLS-LDA classification model, revealing differences in the biomolecular composition between the cell states mainly associated with protein alterations (variations in the side chain residues of amino acids and protein secondary structure), but also within nucleic acids and lipids. We observed spectral changes in quiescent compared to proliferating cells, which increased with quiescence cultivation time. Raman and infrared spectroscopy, which yield complementary biochemical information, clearly distinguished contact-inhibited from serum-starved quiescent cells. Furthermore, the spectra displayed spectral differences between quiescent cells and proliferating cells, which had recovered from quiescence. This became more distinct with increasing quiescence cultivation time. When comparing proliferating, (in particular long-term) quiescent and senescent cells, we found that Raman as well as infrared spectroscopy can separate these three cellular states from each other due to differences in their biomolecular composition. Our spectroscopic analysis shows that proliferating and quiescent fibroblast cells age by similar but biochemically not identical processes. Despite their aging induced changes, over long time periods quiescent cells can return into the cell cycle. Finally however, the cell cycle arrest becomes irreversible indicating senescence.
关键词： PLS-LDA classification model,Raman spectroscopy,infrared spectroscopy,quiescence,senescence,proliferation,fibroblast cells,biomolecular composition
更新于2025-09-09 09:28:46
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Innovative low temperature plasma approach for deposition of alumina films
摘要： Alumina films were deposited from a new plasma method using aluminum acetylacetonate (AAA) powder as precursor. The AAA was sputtered in argon and oxygen plasma mixtures. It was investigated the effect of the oxygen proportion (O2%) on the properties of the coatings. Deposition rate was derived from the layer height measured by profilometry. The elemental composition and molecular structure of the films were determined by Rutherford backscattering and infrared spectroscopies, respectively. Grazing incidence X-ray diffraction was used to investigate the microstructure of the films while hardness was determined by nanoindentation technique. Inspections on the surface morphology and on the film composition were conducted associating scanning electron microscopy and energy dispersive spectroscopy. Incorporation of oxygen affects the plasma kinetics and consequently the properties of the coatings. As moderated concentrations of oxygen (< 25%) are added, the structure is predominantly organic containing stoichiometric amorphous alumina. On the other hand, as high O2% (> 25%) are incorporated, the structure become rich in metallic aluminum with carbon rising at low proportions. The deposited layer is not homogeneous in thickness once the chemical composition of the precursor is changed by the action of the reactive oxygen plasma. Oxygen ablation on the film surface also contributes to the lack of homogeneity of the structure, especially as high oxygen proportions are imposed. Hardness data (0.5-2.0 GPa) corroborated the idea of an amorphous structure. Based on the results presented here it was possible to identify the oxygen concentration in the plasma atmosphere which mostly removed organics while preserving the stoichiometric alumina precipitation, subject of great relevance as one considers the reduction in the energy necessary for the creation of fully oxide coatings.
关键词： composition,reactive plasma sputtering,aluminum acetylacetonate,morphology,alumina,structure
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - Kuala Lumpur (2018.8.15-2018.8.17)] 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - Effect of ZnO Composition on the Electrical Properties of MEH-PPV: ZnO Nanocomposites Thin film via Spin Coating
摘要： Organic semiconductor have been commercialized for optoelectronic device application particularly in organic light emitting diodes (OLEDs). Poly [2-methoxy-5(2’ – ethylhexyloxy)-1, 4- phenylenevinylene), MEH-PPV used in optoelectronic devices because it is easily synthesized and deposited in high molecular weight and good purity. The MEH-PPV: ZnO nanocomposites was prepared by spin coating method at room temperature. The MEH-PPV: ZnO nanocomposites thin film was investigated at different ZnO compositions. The electrical properties showed the ZnO composition at 0.2 wt% exhibits the highest conductivity of nanocomposites thin film (7.40 x 10-1 S. cm-1) and suitable applied in optoelectronic devices.
关键词： MEH-PPV: ZnO nanocomposites thin film,electrical properties,spin coating,ZnO composition
更新于2025-09-04 15:30:14
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Investigating Zinc Ketoiminates as a New Class of Precursors for Solution Deposition of ZnO Thin Films
摘要： Zinc oxide (ZnO) has been recognized as one of the most promising metal oxide semiconductor material for processing low-cost thin film transistors (TFTs). Within the scope of this work, we demonstrate a simple, stabilizer free and very efficient chemical solution deposition (CSD) route to grow high quality ZnO layers. The identification of a highly soluble zinc ketoiminate precursor that undergoes hydrolysis under ambient conditions with the facile cleavage of the ligands was the key to develop a simple and straightforward process for ZnO thin films under mild process conditions. Upon heat treatment at moderate temperatures, the precursor decomposes cleanly yielding polycrystalline ZnO thin films, which was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composition was investigated employing complementary techniques such as X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) which revealed high purity ZnO layers. The functional properties in terms of transparency and optical band gap were determined by ultraviolet-visible (UV-Vis) spectroscopy. The transparent ZnO semiconductor thin films serve as active channel layer of thin film transistors (TFT) which was demonstrated by spin coating of the precursor. Subsequent curing in ambient air, yields a 10 nm film that is sufficient to fabricate working TFTs test structures.
关键词： Oxide Semiconductors,Additive-Free Solution Processing,Composition,Thin Film Transistors
更新于2025-09-04 15:30:14
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Spectral analysis of atmospheric composition: application to surface ozone model-measurement comparisons
摘要： Models of atmospheric composition play an essential role in our scientific understanding of atmospheric processes and in providing policy strategies to deal with societally relevant problems such as climate change, air quality and ecosystem degradation. The fidelity of these models needs to be assessed against observations to ensure that errors in model formulations are found and that model limitations are understood. A range of approaches are necessary for these comparisons. Here, we apply a spectral analysis methodology for this comparison. We use the Lomb-Scargle Periodogram, a method similar to a Fourier transform, but better suited to dealing with the gapped data sets typical of observational data. We apply this methodology to long-term hourly ozone observations and the equivalent model (GEOS-Chem) output. We show that the spectrally transformed observational data shows a distinct power spectrum with regimes indicative of meteorological processes (weather, macroweather) and specific peaks observed at the daily and annual timescales together with corresponding harmonic peaks at half, third etc. of these frequencies. Model output shows corresponding features. A comparison between the amplitude and phase of these peaks introduces a new comparison methodology between model and measurements. We focus on the amplitude and phase of diurnal and seasonal cycles and present observational/model comparisons and discuss model performance. We find large biases notably for the seasonal cycle in the mid-latitude northern hemisphere where the amplitudes are generally overestimated by up to 16 ppb, and phases are too late on the order of 1-5 months. This spectral methodology can be applied to a range of model-measurement applications and is highly suitable for Multimodel Intercomparison Projects (MIPs).
关键词： Lomb-Scargle Periodogram,ozone,spectral analysis,GEOS-Chem,model-measurement comparisons,atmospheric composition
更新于2025-09-04 15:30:14
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Mg-doping towards enhancing the composition-phase-structural stability of Li-La-zirconate based cubic garnet upon exposure to air
摘要： Mg, as a new dopant, has been found to stabilize the desired cubic garnet structure (Ia3d) of Li-La-zirconate (LLZO) and lead to Li-ion conductivities similar to those obtained with the same level of Al-doping. More importantly, Mg-doping, as opposed to Al-doping, suppresses the deleterious reactions with the atmospheric moisture/CO2, leading to stability in the composition-phase-structure upon exposure to air. Accordingly, when exposed to air, even though Al-doped LLZO pellets get spontaneously fractured/disintegrated, accompanied by reduction in ionic conductivity by ~3 orders of magnitude, Mg-doped LLZO shows no sign of cracking and almost retains the ionic conductivity measured prior to exposure.
关键词： Ionic conductivity,Mg-doping,Composition-phase-structural stability,Lithium garnet,Solid electrolyte
更新于2025-09-04 15:30:14
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Archaeological applications of spectroscopic measurements. Compatibility of analytical methods in comparative measurements of historical Polish coins
摘要： The ED-XRF (energy-dispersive X-ray fluorescence) compact system was used to analyze selected Polish historical coins. The compact X-ray tube developed in the National Centre for Nuclear Research (NCBJ) was used as an X-ray source in the system designed for the ED-XRF studies. The XRF spectra were recorded with the Amptek SDD spectrometer. The elemental compositions of the coins have been determined using above mentioned system and the results were compared to those obtained with WD-XRF method. Other techniques such as SEM-EDX and XRD were also included into this work for comparison. The experimental data show that the X-ray system with transmission type X-ray tube with silver anode operating at 50 kV/30 mA which was developed in NCBJ together with the Amptek SDD spectrometer is an effective tool for chemical composition analyze of historical coins and can be successfully used in archaeometry.
关键词： Elemental composition,Energy-dispersive X-ray fluorescence,X-ray powder diffraction,Scanning electron microscope with Energy Dispersive X-Ray Spectroscopy,Wavelength-dispersive X-ray fluorescence
更新于2025-09-04 15:30:14
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High-performance GaAs nanowire cathode for photon-enhanced thermionic emission solar converters
摘要： GaAs nanowire cathodes with exponential doping and graded Al composition structures are proposed for photon-enhanced thermionic emission (PETE) devices. The conversion ef?ciency models with these two nanowire cathodes are deduced on the basis of one-dimensional continuity equations. The conversion ef?ciency as a function of wire length, wire width, Al composition distribution, cathode temperature, emissive surface and back interface recombination velocity are also simulated, respectively. Results show that exponential doping and graded Al composition cathode structures can obviously improve the conversion ef?ciency of devices through introducing a built-in electric ?eld along the growth direction of nanowire. Besides, the optimum wire length and wire width range are 300–340 nm and 5.9–6.4 lm, respectively. Moreover, wider Al composition range is bene?cial to achieve higher conversion ef?ciency. These simulations provide an interesting attempt to explore the working mechanism of GaAs nano-based PETE devices and are expected to be veri?ed by the experimental results in the future.
关键词： exponential doping,graded Al composition,photon-enhanced thermionic emission,GaAs nanowire,conversion efficiency
更新于2025-09-04 15:30:14