Thermo Desorption Research Articles

Analysis of volatile organic compounds in Korean-bred strawberries: insights for improving fruit flavor.

The strawberry industry in South Korea has witnessed a significant 65% growth over the past decade, surpassing other fruits and vegetables in production value. While sweetness and acidity are well-recognized flavor determinants, the role of volatile organic compounds (VOCs) in defining the desirable flavor profiles of strawberries is also crucial. However, existing research has predominantly concentrated on a limited range of commercial cultivars, neglecting the broader spectrum of strawberry varieties. This study embarked on developing a comprehensive VOC database for a diverse array of strawberry cultivars sourced both domestically and internationally. A total of 61 different strawberry cultivars from Korea (45), the USA (7), Japan (8), and France (1) were analyzed for their VOC content using Tenax TA Thermo Desorption tubes and Gas Chromatography-Mass Spectrometry (GC-MS). In addition to VOC profiling, heritability was assessed using one-way ANOVA to compare means among multiple groups, providing insights into the genetic basis of flavor differences. The analysis identified 122 compounds categorized into esters, alcohols, terpenes, and lactones, with esters constituting the majority (46.5%) of total VOCs in Korean cultivars. 'Arihyang', 'Sunnyberry', and 'Kingsberry' exhibited the highest diversity of VOCs detected (97 types), whereas 'Seolhong' showed the highest overall concentration (57.5mg·kg-1 FW). Compared to the USA cultivars, which were abundant in γ-decalactone (a peach-like fruity aroma), most domestic cultivars lacked this compound. Notably, 'Misohyang' displayed a high γ-decalactone content, highlighting its potential as breeding germplasm to improve flavor in Korean strawberries. The findings underscore the importance of a comprehensive VOC analysis across different strawberry cultivars to understand flavor composition. The significant variation in VOC content among the cultivars examined opens avenues for targeted breeding strategies. By leveraging the distinct VOC profiles, particularly the presence of γ-decalactone, breeders can develop new strawberry varieties with enhanced flavor profiles, catering to consumer preferences for both domestic and international markets.

Comparative study on the degradation of HDPE, LLDPE and LDPE during multiple extrusions

Stricter regulations of plastics waste and the enforcement of higher recycling quotas has led to an increasing interest in recycling. One of the most prominent recycling strategies is mechanical recycling, which is based on sorting, pre-treatment and remelting of plastics waste. As repeated reprocessing, may be associated with a reduced quality of the obtained recyclates, approaches for the characterization of these materials by analytical techniques need to be developed. These should help to identify recyclates that will not fulfil the requirements but also to provide data allowing to take countermeasures (such as addition of a certain percentage of virgin material and/or polymer stabilizers). Three different polyethylene (PE) types (high-density (HDPE), linear low-density (LLDPE) and low-density (LDPE)) were subjected to long-time extrusion experiments in order to gain a better understanding of degradation occurring during multiple recycling steps (as expected in a circular economy). Unstabilized material as well as PE with two different stabilizers, Irganox 1010 (IX1010) and Irgafos 168 (IF168) were investigated, employing high temperature gel permeation chromatography with infrared spectroscopic detection (HT-GPC-IR), thermo desorption gas chromatography-mass spectrometry (TD-GC-MS) and high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (HPLC-qTOF-MS) (the latter primarily used for analysing stabilizer degradation). The direct comparison of the PE types revealed significant differences regarding the degradative behaviour. One main conclusion is the possible use of short n-alkanes (below 30 carbon atoms) as a quality markers in the recycling process, as unique trends in the breakdown of polymer chains were found for each PE type. Both HDPE and LLDPE showed an increase in odd numbered n-alkanes, but only HDPE showed a constant decrease in the even numbered ones. For LDPE odd and the even numbered n-alkanes were increasing during extrusion. Focusing on the effect of the added stabilizers, IF168 alone had little to no impact, whereas the presence of IX 1010 showed a beneficial influence on polymer degradation – a trend that was even intensified when both stabilizers were combined. Also, in this case differences between the three PE types could be observed. In HDPE and LDPE stabilizers were consumed during extrusion to a higher extent than in LLDPE.

Quantification of UV protecting additives in ethylene-vinyl acetate copolymer encapsulants for photovoltaic modules with pyrolysis-gas chromatography-mass spectrometry

Reliability of polymeric encapsulants is being assured using suitable additives. Especially UV absorbers and UV stabilizers are important to protect the encapsulants from solar radiation. Identifying the additives and their quantities is essential for quality control and lifetime predictions. In this work a new method for quantitative additive characterization by pyrolysis-gas chromatography-mass spectrometry (PY-GCMS) is presented. A general workflow for qualitative analysis and additive quantification is proposed which is based on solvent-free sample preparation. A series of polymer film samples has been prepared with different additive concentrations for method development and validation. Using the two-step thermo desorption extraction all admixed additives can be detected. Furthermore, it was shown that the desorption behavior of the UV protecting additives dissolved in n-hexane strongly differs from the desorption of additives bound inside the polymer matrix. Thus, the use of reference samples is required for calibration. Finally, using verification samples as well as one commercial polymer film, the determination of the mass fractions of the studied UV absorber and UV stabilizer was shown to be possible with high accuracy. While this work is focused on ethylene-vinyl acetate copolymer (EVA) as encapsulant for photovoltaic modules, the derived methodology is very likely directly transferable to other encapsulant and additive compositions.

Structural characterization and hydrogen storage properties of the Ti31V26Nb26Zr12M5 (M = Fe, Co, or Ni) multi-phase multicomponent alloys

Structure and hydrogen storage properties of three Ti31V26Nb26Zr12M5 multicomponent alloys with M = Fe, Co and Ni are investigated. The alloys synthesized by arc melting are characterized via X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The as-cast ingots present multi-phase dendritic structures composed mainly of BCC phases and small amounts of C14 Laves phases. Upon hydrogenation, each alloy absorbs around 1.9 H/M (number of hydrogen atoms per metal atoms) at room temperature. XRD of fully hydrogenated samples shows the formation of multi-phase structures composed of FCC and C14 hydrides. Thermo Desorption Spectroscopy (TDS) shows that the hydrogenated alloys present multi-step desorption processes with wide temperature ranges and low onset temperatures. XRD of partially hydrogenated samples indicate the presence of intermediate BCC hydrides. XRD of desorbed samples suggest reversible reactions of absorption/desorption: BCC + C14 alloy ↔ intermediate BCC hydride + C14 hydride ↔ FCC + C14 hydrides.

The ideal treatment for heart failer

The acid-base characteristics of the catalyst material are frequently linked to catalytic activity. Metal-organic frameworks (MOFs) have been tested as catalysts for a variety of processes. Based on the observed performance in diverse catalytic processes, Cu-BTC (with a well-defined crystalline structure) and Fe-BTC (with a gel-like porous structure) have both shown the presence of Lewis surface acid sites. In this study, researchers used Inverse Gas Chromatography (IGC) and n-butylamine thermal desorption analysis to assess the acid-base characteristics of both materials. Using acidic, basic, and amphoteric molecules, IGC experiments can access the acid-base characteristics of the material surface. The n-butylamine thermal desorption measurements, on the other hand, allow quantification of those acid and basic sites from the n-butylamine desorption curves of a sample previously saturated with that probe molecule. The Lewis acid properties obtained by both methodologies showed to be more pronounced for the Fe-BTC MOF sample. The IGC measurements exhibited values of acidity constants (KA) of 0.81 and 0.60 for Fe-BTC and Cu-BTC, respectively. Furthermore the n-butylamine thermo desorption experiments indicate total acidities of 2.06 and 0.49 mmol g−1 for Fe-BTC and Cu-BTC, respectively.

Can Sediments Contaminated by Mining be a Source of Mercury in the Coastal Environment Due to Dredging? Evidence from Thermo-Desorption and Chemical Speciation

The sediments in the Gulf of Trieste (northern Adriatic Sea, Italy) are contaminated by mercury (Hg) due to historic mining which took place in Idrija (Slovenia). Despite many studies having been done regarding Hg, no information is available on the potential impact of dredging required along the main channel approaching the Port of Monfalcone. Sixteen surface sediment samples were collected along the channel to determine both total Hg concentration and chemical species using the thermo-desorption (TD) technique. Six samples were also chosen to apply a selective sequential extraction (SSE). The TD technique showed the maximum Hg release approximately at 260 and 335°C, corresponding to metacinnabar (β-HgS) and cinnabar (α-HgS), respectively. The SSE demonstrated that Hg was mainly associated with poorly soluble or insoluble compounds (98.7%). A resuspension event over a limited period of time can be considered of negligible impact to the water column due to the scarce Hg mobility from sediments.

Design of TiVNb-(Cr, Ni or Co) multicomponent alloys with the same valence electron concentration for hydrogen storage

Recently, it has been hypothesized that the hydrogen sorption properties of body-centered cubic (BCC) multicomponent alloys might be related to the alloy’s valence electron concentration (VEC). In this work, we employed CALPHAD method to design three BCC alloys with the same VEC to evaluate this hypothesis. The (TiVNb)85Cr15, (TiVNb)95.3Co4.7 and (TiVNb)96.2Ni3.8 multicomponent alloys with VEC = 4.87 were produced by arc melting. Although some amount of segregation could not be avoided, the as-cast microstructures were composed of a BCC phase with highly homogeneous chemical composition. The alloys quickly absorb hydrogen at room temperature and formed FCC hydrides with high capacities of 2 H/M (3.1–3.2 wt%). For the three alloys, it was observed a two-step hydrogenation sequence indicating the formation of an intermediate BCC monohydride prior to the formation of the FCC dihydride. Moreover, the three alloys presented very similar values of enthalpy and entropy of hydrogenation, showing that the initial hypothesis seems to hold for the thermodynamic properties. The alloys hydrogenation/dehydrogenation cycling behavior were also evaluated. (TiVNb)85Cr15 had a small and continuous drop in capacity over cycling that was addressed to incomplete transformation of the BCC monohydride to the FCC dihydride, whereas (TiVNb)95.3Co4.7 and (TiVNb)96.2Ni3.8 showed a more stable behavior achieving a reversible capacity of 1.76 H/M (2.77 wt%) after 20 cycles. The desorption is strongly affected by absorption/desorption cycling for all alloys, as revealed by thermo desorption spectroscopy (TDS). The onset temperature of desorption depends on the alloys’ composition as well as the number of hydrogenation/dehydrogenation cycles. The results suggest that cycling and desorption properties of the alloys are less related to their VEC.

Formaldehyde Total Oxidation on Manganese-Doped Hydroxyapatite: The Effect of Mn Content

An aqueous impregnation method using manganese (II) nitrate precursor, followed by calcination at 400 °C, was carried out for the preparation of manganese doped hydroxyapatite catalysts (MnxHap; x = Mn wt.%: 2.5, 5.0, 10, 20, and 30 based on MnO2). Methods of characterization including inductively coupled plasma spectroscopy (ICP), N2 physisorption, X-ray Diffraction (XRD), Fourier-Transform Transmission Infrared (FT-IR), Raman, and Thermal gravimetric analysis (TGA/MS) analysis were used for the identification of Mn species and its surrounding environment. Raman spectroscopy indicated the presence of the ε-MnO2 phase for Mn20Hap and Mn30Hap in agreement with the XRD results and the presence of β-MnOOH species for Mn5Hap and Mn10Hap. The formaldehyde total oxidation was investigated on these catalysts and it was shown that Mn5Hap was the most active catalyst, achieving a normalized rate of formaldehyde (HCHO) conversion into CO2 per mole of Mn of 0.042 h−1 at a temperature of 145 °C. The well dispersed oxidized manganese species on Hap with a medium Mn AOS (average oxidation state) were mainly responsible for this performance. Since HCHO was retained on the surface of all catalysts during the catalytic test, the combined Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) experiment at room temperature and thermodesorption (TD)-FTIR identified formate species as their oxidation consumed surface OH groups. A stability test and moisture effect study showed that the presence of water vapor has a beneficial effect on the performances of the catalyst.

Surface and Structural Properties of Clay Materials Based on Natural Saponite

AbstractBecause they are so widespread, the use of saponites is significant in many industries. The modification of saponite-rich clay minerals is known to improve their existing characteristics and may provide new functional properties. The objective of the present paper was to characterize the effects of adding nanosized graphene-like molybdenum (Mo) and tungsten (W) sulfides on the textural and surface characteristics of composites based on native saponite and saponite pre-modified with nanoscale magnetite. The textural characteristics were investigated by the nitrogen adsorption-desorption method and scanning electron microscopy. The total acidity, Hammett Brönsted centers, and Quasi-Equilibrium Thermo Desorption (QE-TD) Lewis centers were characteristics used to probe the acid-base properties of the modified composites. In all cases, modification proved to have a significant effect on both the surface and textural properties of the clay matrix. Modification of the native saponite by graphene-like Mo and W sulfides resulted in a decrease in the specific surface area, except a slight increase in the surface area of the magnetite-containing saponite was observed. Analysis of the acid-base characteristics of native and magnetite-modified saponite (MMS) indicated the ability of modified MoS2 and WS2 additives to alter the acid-base state of the surface. The addition of graphene-like Mo and W sulfides increased the total acidity of native and MMS, with MoS2 modification being more promising because, in almost all the samples, saponite composite materials increased the number of both Brönsted and Lewis active centers compared with WS2, which was determined by the corresponding methods. The acid-base characteristics of the saponite-containing samples, which were studied in an aqueous medium by various methods, are in good correlation with each other, and are consistent with the sorption activity of cationic and anionic dyes.

Surface acid-base properties of Cu-BTC and Fe-BTC MOFs. An inverse gas chromatography and n-butylamine thermo desorption study

Catalytic activity is usually related to the acid-base properties of the catalyst material. Metal-organic frameworks (MOFs) have been evaluated as potential catalysts for several reactions. Cu-BTC (with a well-defined crystalline structure) and Fe-BTC (with a gel-like porous structure) have both shown the presence of Lewis surface acid sites based on the observed performance in different catalytic reactions. In this work, experiments of Inverse Gas Chromatography (IGC) and n-butylamine thermo desorption analysis were carried out in order to determine the acid-base properties of both materials. The IGC measurements allow to access the acid-base properties of the material surface by using acidic, basic and amphoteric molecules. Otherwise the n-butylamine thermo desorption measurements allow the quantification of those acid and basic sites from the n-butylamine desorption curves of a sample previously saturated with that probe molecule. The Lewis acid properties obtained by both methodologies showed to be more pronounced for the Fe-BTC MOF sample. The IGC measurements exhibited values of acidity constants (KA) of 0.81 and 0.60 for Fe-BTC and Cu-BTC, respectively. Furthermore the n-butylamine thermo desorption experiments indicate total acidities of 2.06 and 0.49 mmol g−1 for Fe-BTC and Cu-BTC, respectively.

The potential wildfire effects on mercury remobilization from topsoils and biomass in a smelter-polluted semi-arid area

Wildfires can be responsible for significant mercury (Hg) emissions especially in contaminated areas. Here, we investigated the Hg distribution in topsoils and vegetation samples and temperature-dependent Hg mobilization from biomass-rich topsoils collected near a copper (Cu) smelter in Tsumeb (semi-arid Namibia), where Hg-rich Cu concentrates are processed. The thermo-desorption (TD) experiments conducted on representative biomass-rich topsoils (3.9–7.7 mg Hg/kg) indicated that more than 91% of the Hg was released at ∼340 °C, which corresponds to the predominant grassland-fire conditions. The mineralogical investigation indicated that the Hg comes mainly from the deposited smelter emissions because no distinct Hg-rich microparticles corresponding to the windblown dust from the nearby disposal sites of the technological materials (concentrates, slags, tailings) were found. A comparison with the TD curves of the Hg reference compounds confirmed that the Hg in the biomass-rich topsoils occurs as a mixture of Hg bound to the organic matter and metacinnabar (black HgS), which exhibits similarities with the TD pattern of smelter flue dust residue. Despite the installation of a sulfuric acid plant in the smelter in 2015 and a calculated drop in the estimated Hg emissions (from 1301 ± 457 kg/y for the period 2004–2015 to 67 ± 5 kg/y after 2015), the Hg legacy pool in the smelter surroundings can potentially be re-emitted back to the atmosphere by wildfire. Using the Hg spatial distribution data in the area (184 km2), the estimates indicate that up to 303 kg and 1.3 kg can be remobilized from the topsoils and vegetation, respectively.

Occupational exposure to gaseous and particulate contaminants originating from additive manufacturing of liquid, powdered, and filament plastic materials and related post-processes

The aim of this study was to measure the concentrations of gaseous and particulate contaminants originated from additive manufacturing operations and post-processes in an occupational setting when plastics were used as feedstock materials. Secondary aims were to evaluate the concentration levels based on proposed exposure limits and target values and to propose means to reduce exposure to contaminants released in additive manufacturing processes. Volatile organic compounds were sampled with Tenax TA adsorption tubes and analyzed with a thermo desorption gas chromatography-mass spectrometry instrument. Carbonyl compounds were sampled with DNPH-Silica cartridges and analyzed with a high-performance liquid chromatography device. Particles were measured with P-Trak instrument and indoor air quality was sampled with IAQ-Calc instrument. Dust mass concentrations were measured simultaneously with a DustTrak DRX instrument and IOM-samplers. Particle concentrations were highest (2070-81 890 #/cm3 mean) during manufacturing with methods where plastics were thermally processed. Total volatile organic compounds concentrations, in contrast, were low (113–317 µg/m3 mean) during manufacturing with such methods, and vat photopolymerization. However, total volatile organic compounds concentrations of material jetting and multi jet fusion methods were higher (1,114–2,496 µg/m3 mean), perhaps because of material and binder spraying, where part of the spray can become aerosolized. Chemical treatment of manufactured objects was found to be a severe volatile organic compounds source as well. Formaldehyde was detected in low concentrations (3–40 µg/m3) in all methods except for material jetting method, in addition to several other carbonyl compounds. Notable dust concentrations (1.4–9.1 mg/m3) were detected only during post-processing of powder bed fusion and multi jet fusion manufactured objects. Indoor air quality parameters were not found to be notably impacted by manufacturing operations. Only low concentrations (below 2 ppm) of CO were detected during several manufacturing processes. All studied additive manufacturing operations emitted potentially harmful contaminants into their environments, which should be considered in occupational additive manufacturing and workplace design. According to the measured contaminant levels it is possible that adverse additive manufacturing related health effects may occur among exposed workers.

Analysis of Non-polar Organic Compounds in PM2.5 by Rapid Thermo-desorption Method Coupled with GC/MS

Non-polar organic compounds (NPOCs) associated with PM2.5 in the atmosphere were analyzed by automated thermo-desorption (TD) coupled with gas chromatography/mass spectrometry (TD-GC/MS). The analyses for a total of 72 NPOCs were reviewed, including 34 PAHs, one Debenzothiophene, 27 alkanes (C10-C34), 5 hopanes and 5 steranes. Through this improved TD method, operation of filter loadings, TD condition and sample introduction were optimized. The MDL were 0.01-1.0, 0.1-8.0 and 0.50-2.0 ng·m-3 for PAHs, alkanes, hopanes and steranes, respectively. Calibration curve linearities were above 0.9 for all compounds. The TD efficiencies were 95%-100% for PAHs, 81%-100% for alkanes and 83.1%-100% for hopanes and steranes. PM2.5 samples were pretreated by TD and ultrasonic extraction methods separately and analyzed by GC/MS in two laboratories. Results from these two methods were comparable, as the relative biases were less than 30% for most compounds. Analysis results of PM2.5 samples from Linan and Shanghai showed that NPOCs were higher in winter than that in summer. Alkanes were predominant among NPOCs, followed by PAHs. Source analysis by PAH characteristic ratios indicated that fossil fuel burning and coal burning were the main sources of NPOCs in the two sites during the sampling periods.

Investigation of the hydrogen embrittlement susceptibility of T24 boiler tubing in the context of stress corrosion cracking of its welds

For the membrane and spiral walls of the new USC boilers, the advanced T24 material was developed. In 2010, however, extensive T24 tube weld cracking during the commissioning phase of several newly built boilers was observed. As the dominant root cause, Hydrogen Induced - Stress Corrosion Cracking was reported. An investigation into the interaction of the T24 material with hydrogen was launched, in order to compare its hydrogen embrittlement susceptibility with that of the T12 steel commonly used for older boiler evaporators. Both base materials and simulated Heat Affected Zone (HAZ) microstructures were tested. Total and diffusible hydrogen in the materials after electrochemical charging were measured. Thermo Desorption Spectrometry was used to gain insights into the trapping behaviour and the apparent diffusion coefficient at room temperature was determined. Based on the hardness and the diffusible hydrogen pick-up capacity of the materials, it was concluded that T12 is less susceptible to hydrogen embrittlement than T24, as base material as well as in the HAZ condition and that the HAZ of T24 is more susceptible to hydrogen embrittlement than the base material, both in the as welded and in the Post Weld Heat Treated (PWHT) condition. However, based on the results of this investigation it could not be determined if the T24 HAZ is less susceptible to hydrogen embrittlement after PWHT.

Propane oxidation by vanadium supported on activated carbon from sugarcane straw

A high surface area activated carbon was obtained from sugar cane straw by chemical activation with phosphoric acid and was used for the first time as a support for vanadium catalysts. This work aims to investigate the vanadium oxide species in a low surface density (up to 1Vatomnm−2) on this new support, especially applied to propane oxidation reaction. Moreover, commercial activated carbon materials were used as support for comparison. The discussion is conducted in terms of catalyst textural properties, nature and concentration of surface vanadium oxide species, surface functional groups, and their structure/reactivity relationship. All samples were characterized by adsorption-desorption of N2 (BET), scanning electron microscopy, coupled with energy dispersive microscopy (SEM-EDS), thermal analysis (TG-DTA), Boehm titration, ammonia thermo desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), Laser Raman spectroscopy (RS) and X-ray diffraction (XRD). The obtained results show that vanadium oxide species, even at a very low density, are capable of converting propane (30%), producing propylene (10%), but still producing a high amount of COx products. However, it is worth noting that V-P bonds are the key factor for the Oxidative Dehydrogenation of Propane activity.

Rapid screening of explosives in ambient environment by aerodynamic assisted thermo desorption mass spectrometry

Now, more than at any other time in history, the ability to accurately and reliably detect the presence of explosives is critical, both in civilian and military environments. Currently dogs are used to keep bombs out of airports and off planes by sniffing passengers, their baggage and plane's cargo to identify potential threats. K-9s are also used in a military setting to locate unexploded landmines and improvised explosive devices (IEDs). Although the K-9 remains the gold standard for explosive vapor detection even today, mass spectrometrists are actively working to develop strategies that promise to overtake animal olfaction at the method of choice. The K-9 “specialized detection device” has set a high bar for performance with respect to sensitivity, selectivity, speed, simplicity and transportability, but instrument-based alternatives are needed because olfactory performance changes over time, dogs get tired, and detection can be compromised in environments rich with movement and scents. For example, recent reports in the popular press highlight occasional failures of dog teams to find explosives at major U.S. airports and note the all-too-frequent false alarms that could result in unnecessary airport evacuations. The feature article this issue illustrates the potential of aerodynamic assisted thermo-desorption mass spectrometry to achieve “long distance” detection of non-volatile explosives including commonly used non-volatile explosives such as TNT, RDX and C4. The ongoing development and improvement of instrumental methods is an important priority in the battle to overcome existing challenges and to equip us for those we may face in the future. This article provides insights into one groups effort to develop a powerful and broadly applicable mass spectrometric approach to screen people, packages and luggage for threats such as non-volatile explosives.

Rapid screening of explosives in ambient environment by aerodynamic assisted thermo desorption mass spectrometry.

Rapid, direct, and trace detection of explosives in an open environment is of particular need in homeland and/or transportation security. In this work, an aerodynamic assisted thermo desorption mass spectrometry method was developed for the direct quantitative analyses of explosives from a distance. Remote non-volatile explosive sensing was achieved for 2, 4, 6-trinitrotoluene, trinitrohexahydro-1, 3, 5-triazine, 8701 (main ingredient: RDX 98.5%), and C4 (a type of plastic explosive) with a distance of 0.65 m. Furthermore, a close to 324 cm2 effective sampling area could be achieved, and the limits of detection are in the ng range. This device can be deployed in airports and subway stations for high-throughput and automatic luggage/personnel screening of prohibited articles, such as explosives and illicit drugs. Copyright © 2016 John Wiley & Sons, Ltd.

Computer Simulation of Hydrogen Thermodesorption

In the context of problems of hydrogen and thermonuclear power engineering intensive research is being conducted into ways to protect construction materials against hydrogen corrosion, chemical reactor design, materials suitable for hydrogen storage and transporting. Mathematical models help to specify physical-chemical ideas about the interaction of hydrogen and its isotopes with solids, to discover the limiting factors and to significantly reduce the expenses of experimental research by means of numerical simulation for different parameters and experimental conditions (including extreme ones). Classical diffusion models are often insufficient. The paper is devoted to the model and numerical solution of the boundary-value problems of hydrogen thermo desorption taking into account nonlinear sorption-desorption dynamics on the surface and its reversible capture in the bulk. Computational algorithms based on difference approximations and the results of computer simulation of the hydrogen thermo desorption flux from a structural material sample are presented. KeywordsHydrogen Interaction with Solids; Surface Processes; Thermo Desorption Method; Nonlinear Dynamical Boundary-value Problems; Finite-difference Schemes; Computer Simulation

Scents and scentsitivity - what scents (may) spell out and ways to read it

Chemically, scent marks and natural flavours mostly consist of complex mixtures of chemical compounds, which are neither easily recorded nor interpreted. The facts that the size of a signal in the chemical detection (mass spectrometer) does not necessarily relate to the size in perceptual space and that a signal can just as well be encoded as bouquet of compounds than depending on presence and absence of multiple or single components complicate matters even further. In a recent project on European otters and an ongoing EU project on fruit and vegetable flavours we addressed these issues by using novel approaches in data evaluation and sample collection and data acquisition. In both projects the essential first steps in data processing involved construction of retention-indexed custom mass spectral libraries, which were subsequently used for deconvolution, putative identification and integration of GC-MS data. Retention indexing proved to be essential for reliable re-identification of components between samples and for putative identification of chemicals from NIST library. In the case of European otters, we had access to a large inventory (> 600) of scent glands collected by the Cardiff University Otter Project during post mortem examination of otters found dead in England and Wales over the past decade, which were complemented by a wealth of information on e.g. sex, age, developmental stage, health. More traditional multivariate methods, e.g. discriminate function analysis enabled us to discriminate sex, age and developmental stages after SPME sampling of headspace, GC-MS analysis and data processing. For subsequent evaluation involving genetic data sets we did change the statistical methods using approaches developed for ecological datasets, such as PerMANOVA, which allow direct comparison of bouquets. This general approach is currently followed and refined in the EC project QUAFETY, in which we aim to identify markers for quality and safety of ready-to-eat fresh-cut fruit and vegetable. Because of the perishable nature of the odour sources (melon and rocket) we decided to sample headspace on thermodesorption (TD) tubes and devised a simple, easy to use and robust sampling protocol, which was successfully used by our consortium partner organizations across Europe to sample headspace alongside their own experiments. In addition to the use of TD analyses were carried out on GCtime-of-flightMS, which increased sensitivity on average by a factor of 50. The analytical set-up and application of PerMANOVA and canonical analysis of principle ordinates for evaluation of the data allowed successful discrimination of complete scent profiles from 100 mL of headspace of melon samples according to age and cut size. Currently we are in the process of applying further statistical methods, e.g. weighted correlation network analysis with the aim to identify subsets of compounds, which correlated with single traits and conditions.

Resist outgassing assessment for multi electron beams lithography

The outgassing of e-beam resist materials has to be carefully considered in the research and development of multi e-beams lithography. The release of hydrocarbonaceous species by outgassing in high-vacuum e-beam exposure tool is indeed unavoidable and may lead to premature contamination of optics projection systems. Such a contamination may affect the incident electrons path and hence the final imaging performances. In this work, we present an experimental methodology for the purpose of e-beam resist outgassing qualification. A specific experimental setup was designed in CEA-Leti in order to perform electron bombardment of the e-beam resists coated on 100mm silicon wafers and to monitor the induced outgassing phenomena. The wafer stage was designed in order to allow suitable displacements of the resist coated surface with respect to the incident e-beam. In addition, the wafer can be exposed through specific silicon micromachined membranes (called mimic) that are representative of the optics projection system usually embedded in real multi e-beam exposure tools. Finally, a Quadrupole Mass Spectrometer (QMS) is plugged into the vacuum chamber and enables in situ analysis of the by-products outgassing. Combining this tool with the Thermo Desorption–Gas Chromatography coupled to Mass Spectroscopy and Flame Ion Detector (TD/GC/MS–FID) analysis, we could not only determine the outgassing amount of four different resists but also identify all by-products outgassed and their origin. This paper also shows that the use of a thin top-coat can considerably reduce the outgassing. The outgassing amount as well as the top-coat efficiency was shown to be dependent on the resist chemical properties.