Storage In Ambient Air Research Articles

Surface analysis of poly(ethylene naphthalate) (PEN) films treated at atmospheric pressure using diffuse coplanar surface barrier discharge in air and in nitrogen

Surface modification of poly(ethylene naphthalate) (PEN) films by Diffuse Coplanar Surface Barrier Discharge (DCSBD) in ambient air and nitrogen at atmospheric pressure was studied at short plasma exposure times from 1 s up to 10 s. Chemical changes in the surface composition after the plasma treatments were studied using a high resolution XPS (X-ray Photoelectron Spectroscopy). The water contact angle was reduced from an initial value of 79° to values of 31° and 20° for the ambient air and nitrogen plasma treatments. After 3 days of storage in ambient air the contact angles were still about 50° and 40°, respectively. The polar component of surface energy was changed by the aging significantly less than the total surface energy. Despite the marked increase in the surface energy, the plasma treatment had no significant influence on the surface morphology.The surface modification in air plasma resulted in significant reduction the OC bond formation on the treated surface. The concentration of oxygen on PEN surface was increased from an initial value of 22 at.% up to 45 at.% already after 5 s air plasma exposure, and this oxygen concentration remained constant for longer plasma treatments. A small presence of nitrogen under 1.5 at.% from the air was also found after the treatments. The nitrogen plasma modified surface composition only by implanted nitrogen up to 5 at.% when the ratio of CO and C–O was not significantly changed. But some new bonds are also expected to be formed in a very low number only.

Incorporation of transparent conducting oxide characteristics and oxygen analysis in vacuum annealed indium oxide films

Indium oxide films prepared by thermal oxidation of In metal films acquire high electrical conductivity and optical transmission on annealing in vacuum. These films, by virtue of their high figure of merit (1.3 × 10 3 Ω −1 cm −1), can function as transparent conducting oxides. Deposition of smooth In metal films is essential for realizing good figure of merit in oxide films. Roughness existing in metallic films persists in oxide films and impairs their properties, in particular, optical transmission. Analyses by Rutherford backscattering spectrometry and 16O(α,α) 16O resonant scattering suggest that vacuum annealing brings about a subtle oxygen deficiency in films and also causes a reduction in their thicknesses. The deficiency of oxygen results from the loss of lattice oxygen and desorption of chemisorbed oxygen, and is responsible for the enhanced electrical conductivity of the films. The reduction in thickness, on the other hand, occurs due to the volatilization of In 2O formed under the reducing environment of vacuum. X-ray photoelectron spectroscopy studies show that vacuum annealing renders films reactive towards oxygen bearing species. These films, as a result, tend to regain the nominal oxide composition on prolonged storage in ambient air, however, their TCO properties remain largely unaffected. The nature of oxygen absorbed in the process is seemingly different from that in air-annealed oxide films.

Dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) thin-film transistors with improved performance and stability

Organic thin-film transistors based on the vacuum-deposited small-molecule conjugated semiconductor dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) have been fabricated and characterized. The transistors have field-effect mobilities as large as 2 cm 2/V s and an on/off ratio of 10 8. Owing to the large ionization potential of DNTT, the TFTs show excellent stability for periods of several months of storage in ambient air. Unipolar ring oscillators based on DNTT TFTs with a channel length of 10 μm oscillate with a signal propagation delay as short as 7 μsec per stage at a supply voltage of 5 V. We also show that DNTT TFTs with usefully small channel width/length ratio are able to drive blue organic LEDs to a brightness well above that required for active-matrix displays.

Environmental Factors and Deactivation Mechanism of Au/α-Fe<SUB>2</SUB>O<SUB>3</SUB> Catalyst during Storage in Ambient Air

Environmental Factors and Deactivation Mechanism of Au/α-Fe<SUB>2</SUB>O<SUB>3</SUB> Catalyst during Storage in Ambient Air

Effect of Origanum Oil and Vinegar on the Maintenance of Postharvest Quality of Tomato

Tomato fruits (Solanum lycopersicum, L.) were exposed to origanum oil, vinegar, or chlorine at 12℃ and 95% RH. Quality-related attributes were examined during or following vapour treatment. Fruit pre-treated with natural volatiles and transferred to ambient air had less decay compared to control fruits. Vinegar-enrichment maintained fruit firmness and acidity during exposure, though the effect was sustained only for acidity following storage in ambient air. Glucose and fructose levels were higher in origanum oil-treated fruit, while ascorbic acid content increased in volatile-treated fruits following transfer/storage in ambient air. Total phenolics declined during vinegar and chlorine exposure but tended to increase following transfer to ambient air. Vinegar and chlorine increased lycopene concentration during exposure to vapours, and this effect persisted only for vinegar following exposure and transfer in ambient air. Origanum oil-treated fruit increased lycopene concentration following exposure and transfer in ambient air. Vapour- treatment did not affect fruit weight and ethylene production. Natural volatiles may maintain fruit quality in addition to the well documented antimicrobial protection during fresh produce storage and transit.

Synthesis and stability of iron nanoparticles for lunar environment studies

Abstract– Simulants of lunar dust are needed when researching the lunar environment. However, unlike the true lunar dust, today’s simulants do not contain nanophase iron. Two different processes have been developed to fabricate nanophase iron to be used as part of a lunar dust simulant. (1) The first is to sequentially treat a mixture of ferric chloride, fluorinated carbon, and soda lime glass beads at about 300 °C in nitrogen, at room temperature in air, and then at 1050 °C in nitrogen. The product includes glass beads that are gray in color, can be attracted by a magnet, and contains α-iron nanoparticles (which seem to slowly lose their lattice structure in ambient air during a period of 12 months). This product may have some similarity to the lunar glassy agglutinate, which contains FeO. (2) The second is to heat a mixture of carbon black and a lunar simulant (a mixed metal oxide that includes iron oxide) at 1050 °C in nitrogen. This process simulates lunar dust reactions with the carbon in a micrometeorite at the time of impact. The product contains a chemically modified simulant that can be attracted by a magnet and has a surface layer whose iron concentration increased during the reaction. The iron was found to be α-iron and Fe3O4 nanoparticles, which appear to grow after the fabrication process. This growth became undetectable after 6 months of ambient air storage, but may last for several years or longer.

Thermal and weathering degradation of poly(propylene carbonate)

High molecular-weight poly(propylene carbonate) (PPC) can remain intact upon storage in ambient air or in water for 8 months once the catalyst is completely removed. Catalyst-free pure PPC is also thermally stable below 180 °C. At 200 °C, degradation occurs, mainly due to attack of the chain-ended hydroxyl group onto a carbonate linkage, through which the molecular weight distribution is broadened by simultaneous formation of low and high molecular weight fractions. Incomplete removal of hydrogen peroxide generated during the catalyst preparation results in a prepared polymer that contains a substantial amount of polymer chains grown biaxially from hydrogen peroxide, which gives rise to more severe thermal degradation. Experiments conducted in a weathering chamber at high temperature (63 °C) and high humidity (50%) revealed another degradation process involving chain scission through an attack of water molecules onto the carbonate linkage, which progressively and temporally lowers molecular weight.

Evolution of porous silicon crystal structure during storage in ambient air

Both double- and triple- crystal X-ray diffraction techniques (X-ray DCD and TCD techniques) together with transmission electron microscopy (TEM) were employed for the investigation of structural changes in porous silicon (PS) layers during prolonged periods (up to 6800 hours) of their storage in ambient air. Apart from the Bragg reflection from the Si substrate, the diffraction pattern contains an additional maximum caused by the presence of the PS layer with an increased lattice parameter. The position of this peak shifts to smaller Bragg angles and its intensity decreases as the time of storage in air increases. In addition, the profiles of such peaks become clearly asymmetric. In this case, Gaussian curves were used to reach a fit to the experimental X-ray rocking curves. All samples were biaxially bent due to compressive stresses that arise as soon as 10 min after electrochemical process. The values of lattice strains along the surface normal (Δd/d)⊥ and lateral deformation (Δd/d)|| were estimated to be ~ +10−3, ~ −10−5 respectively. The analysis of diffraction curve evolution shows a gradual destruction of the crystal lattice caused by the air oxidation process.

Properties of SnO 2 films fabricated using a rectangular filtered vacuum arc plasma source

Transparent and conducting SnO 2 films of 57–200nm thickness were deposited on microscope glass slide substrates, using a rectangular filtered vacuum arc deposition system. The 40 glass slides were equally distributed on a 400 × 420mm substrate carriage, and were exposed to a Sn plasma beam, produced by a rectangular vacuum arc plasma gun with a Sn cathode, and passed through a rectangular magnetic macroparticle filter towards the substrates. The carriage with the substrates was transported past the 94 × 494mm filter outlet. The SnO 2 films were fabricated on the glass substrates at room temperature by maintaining the chamber oxygen background pressure at 0.52Pa. The film composition, and electrical and optical properties were studied as a function of the film thickness. The films were stored under ambient air conditions, and their electrical resistance was measured as a function of storage time over a period of several months. The average resistivity of films was 10–17mΩ cm for films with thickness ( t) less than 100nm, but that of t > 100nm it was 5–9mΩ cm. The resistivity of the films with t > 100nm did not change significantly after 8months of storage in ambient air. The optical transmittance of the films in the visible spectrum was in the range of 75–90%. The optical constants, i.e., the refractive index and the extinction coefficient of the films at wavelength λ = 550nm were in the range of 2.02–2.09 and 0.013–0.023, respectively, and the optical band gap energy was 4.15–4.21eV. Unlike the electrical resistivity, the optical parameters weakly depended on t.

P50 Expression of estrogens, progesterone and c-erbB-2 in patients with recurrent breast cancer in Mexico

Modification of the surface properties of a polypropylene (PP) film using an air dielectric barrier discharge has been studied using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The atmospheric pressure air discharge is found to modify the PP surface in both morphology and composition, as expressed in the following outcomes: the spherulitic features of the surface of the pristine PP film change into randomly-shaped surface protrusions, with the surface roughness increasing as the processing time is extended; heavily oxidized carbon species are found on the plasma-processed surface and the contact angle is also reduced dramatically from 93.7° for the untreated surface to 53.8° post-treatment. After long-term storage in ambient air, the much lowered surface contact angle of the processed PP film is found to in part recover. Effective plasma-induced chemical etching appears to equilibrate after 25% of the surface carbon is oxidized. The CH3 functionalities in the PP are believed to be oxidized preferentially by the air discharge plasma.

Incidence of storage diseases on apples of selected cultivars and advanced selections grown with and without fungicide treatments

In the course of a 3-year study the natural occurrence of storage diseases in ambient air storage with <br />1 to 2°C was evaluated on samples of 30 cultivars and advanced selections that were harvested from orchards with and without the use of fungicide treatments. Based upon the frequency of occurrence, bitter rot and grey mould were the most common diseases in this study followed by blue mould and brown rot. Fungicide treatments applied in the orchard with integrated plant protection reduced total fruit rotting with different cultivars two to four times. Significant losses caused by rotting usually took place in the last quarter of the normal storage life of each cultivar, but in the case of samples treated with fungicides it was mostly during the last month. Cultivars Angold, Gala, Florina, Melodie and Meteor proved to be partially resistant to the storage diseases, but the smallest shares of rotted fruits were recorded on apples of Zuzana andMelrose. Still, five advanced selections proved not to be so affected by fruit rotting asMelrose and Zuzana, from which HL 237 and HL 390 were the most remarkable. The majority of selections with resistance to storage diseases as well as Zuzana cv. contain Glockenapfel cv. in their pedigree.  

Enzymatic and microbiological inhibitory activity in eggshell membranes as influenced by layer strains and age and storage variables

Eggshell membranes (ESM) have been shown to exhibit antibacterial activity. The purpose of this study was to evaluate the enzymatic and biological [decimal reduction times (D-values)] activities of ESM as a function of bird breed, age, and ESM stabilization treatments. Younger White Leghorn (WL) hens produced ESM with 28% higher lysozyme activity than Rhode Island Red (RIR) layers. In contrast, older WL layers produced ESM with 17% less lysozyme activity than ESM from RIR layers. Similarly, β-N-acetylglucosaminidase (β-NAGase) ESM activities differed by hen age within breeds with younger hens yielding 14 to 16% more enzyme activity. D54 degrees C-values of Salmonella Typhimurium cells preexposed to WL ESM did not differ as a function of bird age (33, 50, and 81 wk). The ESM Lysozyme and β-NAGase activities varied somewhat over a 6-mo storage study after treatment with 1 of 5 stabilization methods [i.e., storage at 4 degrees C, -20 degrees C, or ambient air storage after freeze drying, air drying (23 degrees C), or forced-air drying (50 degrees C)]. Both air and forced-air drying yielded significant reductions in β-NAGase and lysozyme ESM activity (ca 12 to 30%) after the initial 24 h and then remained fairly stable during the extended storage. Freeze-dried samples retained the most enzymatic activity (95%) throughout the 6-mo trial, whereas refrigerated ESM lost 20 and 18% of the β-NAGase and lysozyme activities, respectively. Frozen ESM lost 22% of the β-NAGase activity, whereas lysozyme was nearly unaffected after 6 mo. The ESM biological activities against S. Typhimurium were not adversely impacted by layer breed or age. No significant loss in biological activity of ESM was detected 24 h after processing or after 6 mo of storage for refrigerated, frozen, and freeze-dried membranes, whereas significant reductions were observed for air- and heat-dried ESM. These findings demonstrate that ESM enzyme and biological activities are relatively constant across layer breeds and over extended storage. Based on these and other findings, ESM may have potential commercial value as a processing adjuvant in food and pharmaceutical product applications.

Highly Concentrated Ozone Gas for Preparing Wettable Polyimide Surface

Highly concentrated ozone gas, of greater than 20%, was applied, for the first time, in order to obtain a stable wettable polyimide film surface. The water contact angle of the polyimide film surface decreased from 60° to nearly 20° after exposure to the highly concentrated ozone gas. The increase in the small water contact angle during storage in ambient air was very gradual, i.e., 5° for over one month. Scanning electron microscopy and the atomic force microscope showed that surface roughening simultaneously occurred. Since the X-ray photoelectron spectra showed an increase in oxygen concentration at the polyimide film surface, the highly concentrated ozone gas is considered to produce a wettable surface by the significant oxidation of the polyimide film chains on the surface.

A technique for fabricating Au/Ti micro- and nanotubes

For the first time, Au/Ti micro- and nanotubes were prepared by rolling initially planar,strained Au/Ti bifilms, freed from the Si substrates by wet selective etching ofunderlying Al sacrificial layers. Conducting metal tubes with diameters ranging from20 µm to 40 nm weremade from 10 µm wide and 10 cm long metal strips lithographically defined on Si substrates. Also, arrays oftubes rigidly attached to the substrate by unrolled parts of the film were obtained. Fullydetached tubes could be bent to form sharp angles or loops without mechanical failure, dueto their high plasticity. The shape and electric conductivity of the Au/Ti micro- andnanotubes were found to remain unchanged over a more than two-year long storage inambient air.

Study of the surface modification of a Nylon-6,6 film processed in an atmospheric pressure air dielectric barrier discharge

A Nylon-6,6 film has been treated using an atmospheric pressure air dielectric barrier discharge (DBD). The resultant surface modifications were studied using X-ray photoelectron spectroscopy (XPS), contact angle measurement and secondary ion mass spectrometry (SIMS). The surface oxidation arising in the DBD discharge was found to arise in two stages: in the first stage, the creation of the carbon sites singly bonded to oxygen is dominant, the second stage leads to further conversion of such lightly oxidised carbons to those more heavily oxidised. The marked increase found in the hydrophilicity of the surface post-treatment is in the main believed to be associated with the earlier outcome. Partial recovery of the surface contact angle values is found for the treated samples following extended storage in ambient air. The final contact angle obtained for the treated samples was ∼50°, still reduced significantly from that of 83.5° for the untreated material.

Formation of Si/SiOx interface and its influence on photoluminescence of Si nano-crystallites

Photoluminescence (PL), PL excitation and atomic force microscopy investigations of porous silicon (PSi) have been done in as-prepared state and after 1.0 year storage in ambient air. In as-prepared state, PSi layers are characterised by two PL bands peaked at 1.70 and 2.00eV. The complex analysing of the changes of PL parameters during the formation of the Si/SiOx interface give possibility to make conclusion concerning the PL and PL excitation mechanisms for both PL bands in Si-nano-crystallites.

Evolution of the mechanical strength of industrially dried ceramic tiles during storage

Industrially fast-dried ceramic tiles were used to determine the variation of dried tile mechanical strength with storage time in a moisture-free container. Dried tile mechanical strength rose with storage time under these conditions. Under the most favourable conditions, dry mechanical strength increased by up to 60% of the initial value. The reason for the rise in mechanical strength is attributed to the relaxation of stresses that develop during rapid industrial drying. A model was derived making the assumption that on exiting the dryer, the tile acts as a Maxwell linear viscoelastic system. The relation was determined between tile moisture content and mechanical strength, which was shown to be independent of whether tile moisture content was the result of drying wet tiles, or dried tile adsorption of ambient humidity. This relation and the stress relaxation model were used to derive a model that describes the evolution of dried tile mechanical strength during subsequent storage in ambient air very well.

Modification of the surface properties of a polypropylene (PP) film using an air dielectric barrier discharge plasma

Modification of the surface properties of a polypropylene (PP) film using an air dielectric barrier discharge has been studied using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The atmospheric pressure air discharge is found to modify the PP surface in both morphology and composition, as expressed in the following outcomes: the spherulitic features of the surface of the pristine PP film change into randomly-shaped surface protrusions, with the surface roughness increasing as the processing time is extended; heavily oxidized carbon species are found on the plasma-processed surface and the contact angle is also reduced dramatically from 93.7° for the untreated surface to 53.8° post-treatment. After long-term storage in ambient air, the much lowered surface contact angle of the processed PP film is found to in part recover. Effective plasma-induced chemical etching appears to equilibrate after 25% of the surface carbon is oxidized. The CH3 functionalities in the PP are believed to be oxidized preferentially by the air discharge plasma.

515 Chlorophyll Fluorescence as an Indicator of Anaerobic Metabolite Levels for Broccoli in MAP and Subsequent Air Storage

When the gas concentrations of modified atmosphere packaging (MAP) become extreme for broccoli (<2 kPa O2 and >10 kPa CO2), off-odors and off-flavors may develop via anaerobic respiration, rendering it unmarketable. We recently showed that chlorophyll fluorescence decreases when broccoli switches to anaerobic behavior in MAP. The objectives of this study were to determine: 1) if chlorophyll fluorescence returns to normal levels after the package is opened and hence the broccoli is exposed to ambient air, and 2) if chlorophyll fluorescence is related to off-odors that develop. Broccoli heads were held in MAP (2 to 3 kPa O2 and >10 kPa CO2) at 0 to 1 °C for 4, 7, 14, 21, or 28 days, and then 5 days in ambient air at 0 to 1 °C. Chlorophyll fluorescence of the broccoli decreased dramatically in MAP, and remained low during the subsequent 5 days in ambient air. Similarly, off-odors became worse and acetaldehyde, ethanol, and ethyl acetate increased in the broccoli with time in MAP. However, these compounds slightly decreased during the subsequent 5 days of storage in ambient air. Chlorophyll fluorescence parameters correlated negatively with off-odor development and acetaldehyde, ethanol, and ethyl acetate levels in the tissue.

Hydroperoxide formation in irradiated polyethylene

Spectroscopic analysis for hydroperoxide in irradiated ultrahigh molecular weight polyethylene, on the basis of the formation of a nitrate derivative after exposure to dilute nitric oxide, is examined. Hydroperoxide is found to be an important intermediate in the oxidation of polyethylene and is believed to result from hydrogen abstraction reactions by peroxy radicals in a polyethylene matrix. During γ irradiation in air, the rates of bimolecular combination of peroxy radicals on the surface to form ketones or hydrogen abstraction to form hydroperoxides are similar. However, as a result of bimolecular combination, the concentration of peroxy radicals decreases. After irradiation and storage in ambient air, isolated peroxy radicals below the polymer surface induce a slow chain reaction leading to a long-term increase in hydroperoxides and carbonyls. Differences in hydroperoxide and oxygen content for samples irradiated in air or vacuum are primarily confined to or near the surface. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3309–3316, 1999