scholarly journals Stability of carbonaceous dust analogues and glycine under UV irradiation and electron bombardment

2014 ◽  
Vol 168 ◽  
pp. 267-285 ◽  
Author(s):  
Belén Maté ◽  
Isabel Tanarro ◽  
Miguel A. Moreno ◽  
Miguel Jiménez-Redondo ◽  
Rafael Escribano ◽  
...  
Keyword(s):  
Electron Bombardment ◽  
Point Of View ◽  
Reaction Products ◽  
High Fluences ◽  
Gradual Disappearance ◽  
Diffuse Cloud ◽  
Energetic Point ◽  
Uv Photons ◽  
Uv Photoproducts ◽  
Hydrogenated Amorphous

The effect of UV photon (120–200 nm) and electron (2 keV) irradiation of analogues of interstellar carbonaceous dust and of glycine were investigated by means of IR spectroscopy. Films of hydrogenated amorphous carbon (HAC), taken as dust analogues, were found to be stable under UV photon and electron bombardment. High fluences of photons and electrons, of the order of 1019cm−2, were needed for a film depletion of a few percent. UV photons were energetically more effective than electrons for depletion and led to a certain dehydrogenation of the HAC samples, whereas electrons led seemingly to a gradual erosion with no appreciable changes in the hydrocarbon structure. The rates of change observed may be relevant over the lifetime of a diffuse cloud, but cannot account for the rapid changes in hydrocarbon IR bands during the evolution of some proto-planetary nebulae. Glycine samples under the same photon and electron fluxes decay at a much faster rate, but tend usually to an equilibrium value different from zero, especially at low temperatures. Reversible reactions re-forming glycine, or the build-up of less transparent products, could explain this behavior. CO2and methylamine were identified as UV photoproducts. Electron irradiation led to a gradual disappearance of the glycine layers, also with formation of CO2. No other reaction products were clearly identified. The thicker glycine layers (a few hundred nm) were not wholly depleted, but a film of the order of the electron penetration depth (80 nm), was totally destroyed with an electron fluence of ∼1 × 1018cm−2. A 60 nm ice layer on top of glycine provided only partial shielding from the 2 keV electrons. From an energetic point of view, 2 keV electrons are less efficient than UV photons and, according to literature data, much less efficient than MeV protons for the destruction of glycine. The use of keV electrons to simulate effects of cosmic rays on analogues of interstellar grains should be taken with care, due to the low penetration depths of electrons in many samples of interest.

scholarly journals Photochemistry of 1-Phenyl-4-Allyl-Tetrazol-5-One: A Theoretical Study Contribution towards Mechanism Elucidation

2021 ◽  
Vol 11 (9) ◽  
pp. 4045
Author(s):  
Amilcar Duque-Prata ◽  
Carlos Serpa ◽  
Pedro J. S. B. Caridade
Keyword(s):  
Density Functional ◽  
Reaction Pathway ◽  
Intramolecular Proton Transfer ◽  
Polarizable Continuum Model ◽  
Uv Spectra ◽  
Point Of View ◽  
Basis Set ◽  
Pathway Evolution ◽  
Photodegradation Mechanism ◽  
Energetic Point

The photodegradation mechanism of 1-phenyl-4-allyl-tetrazol-5-one has been studied using (time-dependent) density functional theory with the M06-HF, B3LYP, and PBE0 functionals and the VDZ basis set. All calculations have been carried out using the polarizable continuum model to simulate the solvent effects of methanol. The reaction pathway evolution on the triplet state has been characterised to validate a previously postulated experimental-based mechanism. The transition states and minimums have been initially located by local scanning in partial constrained optimisation, followed by a fully relaxed search procedure. The UV spectra has shown to be better described with PBE0 functional when compared with the experimental results, having the M06-HF a shift of 40 nm. From the energetic point of view, the postulated mechanism has been validated in this work showing a concerted photoextrusion of the N2 molecule. The intramolecular proton transfer occurs at a later stage of the mechanism after cyclization of the allyl group on a triplet biradical intermediate. The photoproduct observed experimentally, a pyrimidinone, has been characterised. The infrared spectroscopic reaction profile has also been proposed.

Color Reactions of Rubber and Gutta-Percha

1930 ◽  
Vol 3 (1) ◽  
pp. 22-23
Author(s):  
F. Kirchhof
Keyword(s):  
Carbon Tetrachloride ◽  
Absorption Spectra ◽  
Aluminum Chloride ◽  
Point Of View ◽  
Previous Article ◽  
Reaction Products ◽  
Characteristic Absorption ◽  
Iron Aluminum ◽  
Gutta Percha ◽  
Color Reactions

Abstract A previous article of mine entitled “Observations on Color Reactions of Rubber and Gutta-Percha” has led to the question whether intensely colored reaction products which are obtained by fusion of phenols with bromides of hydrocarbons give characteristic absorption spectra. I have carried out a few preliminary experiments on this subject, which appear to confirm my earlier point of view that the cause of the different colorations is to be found in dispersion color reactions. It is well known that when rubber bromide or gutta-percha bromide is suspended in carbon tetrachloride and is heated with phenol until the carbon tetrachloride is eliminated, a red-violet to blue fusion mixture is obtained, which gives colors of various stabilities depending upon the solvent into which the fusion mixture is dropped. Thus the blue and violet colorations in chloroform are stable for some time, but they change gradually to green and then to brown, with separation of a flocculent precipitate. Yellow-brown reaction products (hydroxyphenylhydrorubber and gutta-percha) are however obtained in the presence of catalysts (iron, aluminum chloride) or by the action of alkalies (NH3, KOH) or by pouring the blue-violet fusion mixtures into ether.

Sulfur Linkage in Vulcanized Rubber. Reaction of Methyl Iodide with Sulfur Compounds

1949 ◽  
Vol 22 (1) ◽  
pp. 1-7
Author(s):  
M. L. Selker
Keyword(s):  
Methyl Iodide ◽  
Room Temperature ◽  
Sulfur Compounds ◽  
Point Of View ◽  
Secondary Reaction ◽  
Reaction Products ◽  
Sulfide Sulfur ◽  
Vulcanized Rubber ◽  
Allyl Sulfide

Abstract The work described here is an extension of the study of the reaction of methyl iodide with sulfur compounds originally begun with the purpose of using such data in determining the sulfur linkage in vulcanized rubber. A previous paper dealt with the reactions of methyl iodide with propanethiol, propyl sulfide, propyl disulfide, allyl sulfide, and thiophene. This article adds to the list, n-butyl methallyl sulfide, allyl disulfide, allyl tetrasulfide, n-propyl tetrasulfide, and trithiane. The removal of combined sulfur from vulcanized rubber as trimethylsulfonium iodide on treatment with methyl iodide at room temperature was persuasive evidence of the presence of sulfide sulfur linked to allylic type residues. The evidence offered, however, did not constitute exclusive proof because it was not known whether still other types of sulfur linkage would also yield trimethylsulfonium iodide. To shed more light on this question, the sulfur linkages most likely to occur in vulcanizates—the allyl-alkyl monosulfide, diallyl and dialkyl di- and polysulfide—were investigated. The trithiane reaction is of interest mostly from the point of view of the reaction of overcured stocks or secondary reaction products stemming from the original polysulfides. The reactions were carried out using the method described in a previous paper.

scholarly journals A 6-Components Mechanistic Model of Cutting Actions in Milling

2021 ◽  
Author(s):  
Maël Jeulin ◽  
Olivier Cahuc ◽  
Philippe Darnis ◽  
Raynald Laheurte
Keyword(s):  
Energy Balance ◽  
Experimental Model ◽  
Cutting Forces ◽  
Mechanistic Model ◽  
Cutting Parameters ◽  
Point Of View ◽  
Stress Fields ◽  
Mechanistic Modelling ◽  
Cutting Zone ◽  
Energetic Point

Abstract Most of the cutting models developed in the literature attest only to the presence of cutting forces in the balance of mechanical actions resulting from cutting. However, several studies have highlighted the presence of cutting moments during machining, and particularly 3D cutting in milling. The objective of this paper is to characterise phenomena associated with cutting moments by performing experimental mechanistic modelling in 3D cutting. For this purpose, several modelling factors will be investigated, such as the 3D cutting reference frame, the undeformed chip section, the cutting parameters, the cutting zone, etc. The predictive model of this study proves to be relatively efficient for an experimental model and allows a global prediction of cutting moments in milling. Furthermore, beyond the aspect of stress fields in the workpiece caused by cutting moments, this paper gives perspectives from an energetic point of view for which the share of moments in the energy balance could be substantial for monobloc tools.

Investigation on the Intake Process for a Theoretical Twin Opposite Piston Compressor Using R744 Refrigerant

2016 ◽  
Vol 823 ◽  
pp. 75-78
Author(s):  
Doru Groza ◽  
Dan Mihai Dogariu
Keyword(s):  
Air Conditioning ◽  
Piston Compressor ◽  
Environmental Issues ◽  
Point Of View ◽  
Vapor Compression ◽  
Household Appliances ◽  
Intake Process ◽  
Vapor Compression Refrigeration ◽  
Energetic Point ◽  
Air Conditioning Systems

This study aims to validate the use of R744 for a resonant twin piston compressor for domestic applications. The vapor-compression refrigeration is the most commonly approached method for cooling household appliances such as refrigerators and air conditioning systems. The R134a refrigerant is one of the most suitable refrigerants from an energetic point of view. R744 (CO2) compressors are less efficient, but the fact that the R134a raises serious environmental issues pushes commercial trend towards the usage of R744 [1]-[3]. Use of R744 in household appliances is currently an open topic and no company has switched yet to the environmental-friendly alternative. In this paper the fill efficiency will be simulated in order to validate if a conventional compressor such as the opposite twin piston compressor is capable of filling with refrigerant when operating at a 50Hz frequency. Such a validation can enable further investigations regarding the replacement of R134a with R744.

scholarly journals Occurrence of Furosine and Hydroxymethylfurfural in Breakfast Cereals. Evolution of the Spanish Market from 2006 to 2018

Foods ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 158 ◽  
Author(s):  
Marta Mesías ◽  
Laura Sáez-Escudero ◽  
Francisco J. Morales ◽  
Cristina Delgado-Andrade
Keyword(s):  
Manufacturing Process ◽  
Protein Quality ◽  
Sugar Content ◽  
Point Of View ◽  
Maillard Reaction Products ◽  
Reaction Products ◽  
Breakfast Cereal ◽  
Breakfast Cereals ◽  
Damage Indices ◽  
Amadori Compounds

The demand for healthier products has led the breakfast cereal sector to develop new formulations to improve the nutritional profile of breakfast cereals; however, the increase in chemical risks should also be evaluated. Amadori compounds and 5-hydroxymethylfurfural (HMF) are Maillard reaction products applied as heat damage indices in breakfast cereals. Furosine (a synthetic amino acid formed by acid hydrolysis of Amadori compounds) is linked to the loss of protein quality, while HMF has exhibited toxicological effects in cells and animals. Furosine and HMF content was evaluated in Spanish breakfast cereals whereas the effect of protein, fibre, and sugar content, the type of grain, the presence of honey, and the manufacturing process were discussed, as well as compared with a previous prospective study. The average furosine and HMF contents were 182 mg/kg and 21.7 mg/kg, respectively. Protein and fibre content were directly related to the furosine content, whereas sugar level, honey addition, and the manufacturing process affected the content of HMF. Occurrence of furosine and HMF decreased nearly 40% in a decade (2006–2018). These findings are relevant in terms of nutritional score, since lysine availability is preserved, but also from a toxicological point of view, due to the decreased daily exposure to both compounds, which dropped 30%.

The Quality of Brazed Ceramic and Cemented Carbide Joints - A Mechanical and Metallurgical Assessment

2010 ◽  
Vol 64 ◽  
pp. 108-114 ◽  
Author(s):  
Wolfgang Tillmann ◽  
Lukas Wojarski ◽  
Benjamin Lehmert
Keyword(s):  
Thermal Stresses ◽  
Mechanical Performance ◽  
Ceramic Materials ◽  
Mechanical Tests ◽  
Point Of View ◽  
Cemented Carbides ◽  
Full Potential ◽  
Ceramic Surface ◽  
Reaction Products

The availability of adequate joining technologies is of major importance in order to exploit the full potential of ceramic materials. The same is true for joints between cemented carbides and their counterparts. Such joints are not easy to manufacture due to wetting and bonding problems as well as induced thermal stresses. Currently, active brazing is a potential approach for fabricating such joints. The filler alloy contains reactive agents such as Titanium or Hafnium etc. that interact by forming wettable reaction layers on the ceramic surface. It is self-evident that they function very well on cemented carbides as well. The paper describes potential wetting and bonding reactions from a metallurgical point of view. Ceramics, superabrasive and cemented carbides are investigated with respect to interfacial reactions. The quality of the reaction products is of crucial importance regarding the mechanical performance of the joints, as their immanent brittleness can lead to a significant weakening. Apart from metallurgical assessments, mechanical tests are conducted in order to deliver data for their integration in hybrid structures. FE methods can be applied to assess the stress situation in the final joint. Thus it is possible to adjust the design accordingly.

scholarly journals Effect of Hydrogen Content in Intrinsic a-Si:H on Performances of Heterojunction Solar Cells

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Yun-Shao Cho ◽  
Chia-Hsun Hsu ◽  
Shui-Yang Lien ◽  
Dong-Sing Wuu ◽  
In-Cha Hsieh
Keyword(s):  
Solar Cells ◽  
Hydrogen Content ◽  
Crystalline Silicon ◽  
Phase Particle ◽  
Optical Emission ◽  
Point Of View ◽  
Experimental Result ◽  
Heterojunction Solar Cells ◽  
Hydrogenated Amorphous ◽  
Silane Plasma

Influences of hydrogen content in intrinsic hydrogenated amorphous silicon (i-a-Si:H) on performances of heterojunction (HJ) solar cells are investigated. The simulation result shows that in the range of 0–18% of the i-layer hydrogen content, solar cells with higher i-layer hydrogen content can have higher degree of dangling bond passivation on single crystalline silicon (c-Si) surface. In addition, the experimental result shows that HJ solar cells with a low hydrogen content have a poor a-Si:H/c-Si interface. The deteriorate interface is assumed to be attributed to (i) voids created by insufficiently passivated c-Si surface dangling bonds, (ii) voids formed by SiH2clusters, and (iii) Si particles caused by gas phase particle formation in silane plasma. The proposed assumption is well supported and explained from the plasma point of view using optical emission spectroscopy.

Simulation and Field Experiments With an Agricultural Tractor of a Robust Control for a Complete Fluid Power Circuit Using a New Electro-Hydraulic Pump: Part II—Control

2010 ◽  
Author(s):  
Pandeli Borodani ◽  
Davide Colombo ◽  
Marco Forestello ◽  
Patrizio Turco ◽  
Riccardo Morselli
Keyword(s):  
Field Experiments ◽  
Optimization Techniques ◽  
Point Of View ◽  
Hydraulic Pump ◽  
Power Circuit ◽  
Control Approach ◽  
New Device ◽  
Displacement Pump ◽  
Variable Displacement ◽  
Energetic Point

The plant under control is the hydraulic circuit arranged by CNH in a prototype agriculture tractor of medium segment, where instead of the conventional main hydraulic pump, a new device electronically piloted, is installed. The main purpose is basically to obtain some advantages according to the energetic point of view, by means of an appropriate control structure, managing the electronic variable displacement pump. The frontier of the new systems requires the employment of the advanced control techniques, in order to assure the levels of precision, reliability, robustness demanded from systems. The control design methodology employed in the present case is based on robust H∞ optimization techniques, where robust stability properties are guaranteed in presence of unaccountable dynamics and other destabilizing factors. The effectiveness of the proposed control approach is tested on the demonstrative tractor realized from the CNH Agriculture at Modena plants, in all real conditions.

scholarly journals Biomass conversion into valuable products within the integrated management of bio-resources

2019 ◽  
Vol 85 ◽  
pp. 07008 ◽  
Author(s):  
Gabriela Ionescu ◽  
Cora Bulmău
Keyword(s):  
Biomass Conversion ◽  
Integrated Management ◽  
Point Of View ◽  
Biomass Waste ◽  
Waste Valorisation ◽  
Energetic Point ◽  
Biomass Availability ◽  
By Products

The present research proposes two scenarios for the biomass conversion into valuable products within the integrated management of bio-resources. The scenarios have been developed considering: the biomass availability, material and by-products characteristics and the comprehensive combination of the primary technologies used for the conversion of the biomass mixtures into energy. In scenario 1 the biomass waste valorisation is made via integrated pyrolysis and combustion treatment, while in scenario 2 the biomass conversion in done considering the integration of the pyrolysis, gasification and combustion treatments into the conversion chain. The results revealed that all analysed scenarios purposed are self-independent from the energetic point of view.

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