The potential of hot water dipping, vapour heating or ultraviolet irradiation to eliminate the use of chemicals for control of sprouting and post-harvest diseases of the potato (Solanum tuberosum L.) was examined. The microorganisms on which these treatments were tested were the fungal dry rot (Fusarium solani) and the bacterial soft rot (Erwinia carotovora pv. carotovora), two major post-harvest pathogens of potatoes. The study focused on short-term storage (three months) at 8$ sp circ$C or 18$ sp circ$C, which are representative of storage temperatures used by producers in northern temperate and semi-arid tropical regions, respectively. / Response surface methodology was used in experimentation to facilitate analysis of data and identification of optimal operating conditions for the treatments. The following parameters were used to assess tuber quality after the treatments and 3-month storage: firmness, color and structure. / It was found possible to obtain 100% control of sprouting and diseases for the three-month storage without resorting to the use of chemicals. This was achieved without significantly altering the quality attributes of the tubers under certain conditions of hot water, ultraviolet radiation or combinations of these two with storage at 8$ sp circ$C for three months. Although 100% control was not possible for the storage at 18$ sp circ$C, treated tubers performed much better than the controls. Vapour heat (50-70$ sp circ$C) was much less effective at controlling sprouting and was therefore not tested on the pathogens. / A numerical model of the heat transfer phenomenon in the tuber was also developed. It was used to predict the transient temperature distribution in the tuber. The model was solved using the line-by-line technique and model simulations were validated against experimental data.

<p>Nanometer-scale metallic structures have been widely and intensively studied over the last decade because of their remarkable plasmonic properties that can enhance local electromagnetic (EM) fields. However, most plasmonic applications are restricted to the visible and near infrared photon energies due to the limitations of the surface plasmon resonance energies of the most commonly used plasmonic metals: Au and Ag. Plasmonic applications in ultraviolet (UV) are of great interest because Raman scattering sections are larger and do not overlap fluorescence spectra. UV plasmonics also benefit from high spatial resolution and low penetration depth. However, an appropriate UV plasmonic material must be identified.</p><p>We proposed and demonstrated that gallium is a highly-promising and compelling material for UV nanoplasmonics through synthesis of size-controlled nanoparticle arrays, EM modeling of local field enhancement, ellipsometric and spatial characterization of the arrays, and analytical measurement of UV- enhanced Raman and fluorescence spectra. Self-assembled arrays of hemispherical gallium nanoparticles deposited by molecular beam epitaxy on a sapphire support are characterized with spatial and ellipsometric measurements. Spin-casting a thin film of crystal violet upon these nanoparticles permitted the demonstration of surface-enhanced Raman spectra, fluorescence, and molecular photodegradation following excitation by a HeCd laser operating at 325 nm (UV). Measured local Raman enhancement factors exceeding 10<super>7</super> demonstrated the potential of gallium nanoparticle arrays for plasmonically-enhanced ultraviolet detection and remediation.</p> / Dissertation

L'origine, la distribution et l'évolution des molécules organiques et de la vie sont les principaux sujets d'un domaine scientifique récent appelé astrobiologie. Un sous-thème intéressant de ce vaste domaine est l'identification des composés organiques et des processus chimiques et physiques dans des lieux autres que la Terre. Un objet particulièrement intéressant de ce point de vue est Titan, la plus grosse lune de Saturne et la seule dans le système solaire pour laquelle on observe la présence d'une épaisse atmosphère composée d'azote et méthane (N2 et CH4), et ayant toutes les caractéristiques d'une atmosphère planétaire. Cette atmosphère est depuis longtemps connue pour être riche en composés organiques présentant un grand intérêt pour l'astrobiologie. La mission Cassini-Huygens (NASA-ESA-ASI) a été conçue pour explorer le système saturnien, avec un intérêt particulier pour Titan. Les instruments de Cassini fournissent de grandes quantités d'informations sur l'atmosphère depuis 2004. Ainsi, les données du Spectromètre de Masse d'Ions et de Molécules Neutres (INMS) et du Spectromètre de Plasma de Cassini(CPS) ont montré l'existence de molécules organiques neutres lourdes (jusqu'à 7 atomes de carbone) et des ions lourds (jusqu'à 13000 Da) dans la thermosphère. Les observations effectuées tout au long de la mission ont par ailleurs montré une variabilité atmosphérique complexe en fonction de nombreuses variables comme, entre autres, l'activité solaire ou les interactions avec la magnétosphère de Saturne. Les molécules organiques dans l'atmosphère donnent lieu à une chimie complexe et conduit à la formation d'aérosols organiques dans les couches stratosphériques inférieures. Ces aérosols précipitent à la surface de Titan où ils continuent leur évolution chimique. C'est une des caractéristiques qui font de Titan un objet intéressant du point de vue astrobiologique

Ultravioletiniai spinduliai veikia daugelį polimerų, tame tarpe ir polipropileną. Darbo tikslas buvo ištirti ultravioletinės spinduliuotės (=254 nm) poveikį polipropilenui. Medžiagos cheminės sudėties pokyčiui nustatyti buvo matuojami infraraudonųjų spindulių absorbcijos spektrai, o fizinių savybių pokytis – matuojant stiprumo ribą, regimosios šviesos praleidimo faktorių, induktyvumą bei kontūro elektrinę talpą. Nustatyta, kad polipropileną veikiant 254 nm bangos ilgio šviesa medžiaga palaipsniui oksiduojasi. UV spinduliuotė generuoja peroksidinių (>CH-O-OH), karbonilinių (>C=O) ir vinilinių (-CH=CH2) grupių susidarymą anglies grandinėse ir jų koncentracija didėja ilginant švitinimo trukmę. Po 160 val. švitinimo prasideda polimero degradacija: keičiasi jo struktūra, prarandamas skaidrumas, elastingumas, didėja trapumas bei mažėja polipropileno plėvelės storis. Polipropileno paviršiuje atsiranda įtrūkimų, plėvelė pageltonuoja. Magnetinių savybių matavimai rodo, kad oksiduojantis polipropilenui didėja laisvųjų radikalų koncentracija propileno grandinėse. Mikroskopiniai tyrimai parodė plėvelės paviršiuje susidariusias destrukcijos juostas. / Wide verily of polymers undergo physicochemical changes. The aim of the paper was to study the effect of ultraviolet radiation (λ= 254 nm) on polypropylene. The chemical changes were measured by the infrared absorption spectra, and the change the physical properties – by measurement of the strength limit, visible light transmittance, polypropilene inductance and capacitance. It is determined that PP exposed to ultraviolet light undergo photo-oxidation and photo-degradation. UV radiation generates formation of peroxide (>CH-O-OH), carbonyl (>C=O) and vinyl (-CH=CH2) groups in the carbon chaines with increasing their concentrations during exposure. After 160 hours UV exposure process of PP destruction gets up: the transparency, elasticity, polypropilene film thickness and strenght is declining. Microscopic demonstrated the cracks on the surface of the films after 160 hours of exposure.

Les lasers solides émettant dans l'UV sont l'objet de nombreux efforts de recherche. Ainsi, deux cristaux non linéaires ont été développés et caractérisés pour réaliser la conversion de fréquences laser dans le domaine UV : Ca5(BO3)3F (CBF) et YAl3(BO3)4 (YAB). Concernant les cristaux de CBF, l'influence des gradients thermiques ainsi que de nouveaux flux ont été étudiés en vue d'améliorer la qualité cristalline. La génération du troisième harmonique à 343 nm en type II a été réalisée pour la première fois dans CBF. 300 mW correspondant à un rendement ? (1030 ' 343 nm) = 1,5 % ont été obtenus. L'utilisation de flux à base de LaB3O6 a permis la synthèse de cristaux de YAB par la méthode TSSG. Les propriétés physiques, structurales ainsi que les défauts de ces cristaux ont été caractérisés. De bonnes performances ont été obtenues dans le cadre de la génération du quatrième harmonique à 266 nm puisqu'un rendement de conversion ? (1064 ' 266 nm) = 12,2 % a été atteint.

Ultraviolet (UV) radiation damages both eukaryotic and prokaryotic cells by causing the formation of free radicals which damage cell membranes and DNA. Antioxidant vitamins have been shown to protect cells from UV-induced damage by scavenging free radicals. The protection of skin and its normal flora is necessary for the health of individuals in resisting diseases caused by microorganisms and delaying the long-term damage caused by UV radiation.This research investigated the effects of the antioxidants vitamin A and ascorbic acid, as well as UV-irradiation on both prokaryotic (Staphylococcus epidermidis) cells and eukaryotic (human fibroblast skin) cells. This information is important in determining the effects of vitamin treatment on skin and its normal flora.Results indicate that ascorbic acid is rapidly (within six hours) degraded after being dissolved in water or medium. Treatment of cells with ascorbic acid must take into account this rapid degradation. S.epidermidis cells were protected from UV-induced damage by treatment with ascorbic acid but were more sensitive to UV-irradiation when treated with vitamin A. Human fibroblast cells treated with ascorbic acid did not exhibit morphological changes when compared to untreated cells. / Department of Biology

No description available.

Tyrimo tikslas. Įvertinti merginų informuotumą apie ultravioletinės spinduliuotės poveikį sveikatai bei sąsajas su deginimosi elgsena Tyrimo metodika. Tyrimas atliktas 2013 - 2014 m. Tyrime dalyvavo Kauno kolegijos Medicinos fakulteto I ir II kurso studentės. Iš viso buvo išdalinta 580 anketų. Duomenys analizuoti naudojant SPSS 20.0 programa, lyginant studenčių deginimosi saulėje įpročius, soliariumų naudojimo ir požiūrio bei žinių apie ultravioletinius spindulius kintamuosius pagal χ2 kriterijų. Skirtumas statistiškai reikšmingas, kai pasikliovimo lygmuo p<0,05. Tyrimo metodas – anoniminė anketinė apklausa. Rezultatai: 68,1 proc. studenčių nuomone saulės spinduliai gali sukelti akių pažeidimus - kataraktą. Merginos turinčios jautresnę I-II odos tipą teigia, kad saulės spinduliai sukelia ne tik odos, tačiau ir akių pažeidimus 75,8 proc. Didžioji dalis merginų 67,8 proc.teigė, kad oda raukšlėjasi saulės poveikyje. Statistiškai reikšmingai dažniau I-II odos tipo merginų 89,6 proc. teigė, kad daugėja raukšlių odoje deginantis soliariume negu mažiau jautrią odą turintis III-IV odos tipas. Apie odos senėjimą saulės poveikyje I-II ir III-IV odos tipų merginos teigė, kad saulė mažina odos elastingumą ir spartina senėjimą 87,9 ir 87,1 proc. pigmentinės dėmės suvokiamos kaip neigiamas veiksnys ir 68,1 proc. merginų teigė, kad būtent saulės poveikyje atsiranda įvairūs pakitimai odoje. Statistiškai reikšmingai dažniau III-IV odos tipų merginų 7,1 proc.teigė, kad soliariumo spinduliai... [toliau žr. visą tekstą] / The purpose of the investigation. To assess the effects of exposure of ultraviolet radiation, to the young women's awareness of health and interfaces with tanning behaviors. Methodology of the Study. Study was carried out in 2013-2014 in the study participated I and II course women of Kaunas College of Medicine faculty. A total of 580 questionnaires were handed out. Data analysed using SPSS program 20.0, comparing female students tanning in the Sun habits, attitudes and the use of ultraviolet rays, according to the knowledge of the variables of x2 criteria. The difference statistically significant when the confidence level p < 0,05. A questionnaire - based survey method to anonymous access. Results: 68,1 percent of the female students think, that sun's rays can lead to cataracts-ocular lesions. Girls having more sensitive skin type I-II argues that the sun's rays causes not only the skin, but also violations of eyes 75,8 percent. The most part of girls 67,8 percent claimed that skin wrinkling sun effecting. Statistically significant more often I-II type of skin girls 89,6 percent said that a growing number of wrinkles in the skin scorching solarium than less sensitive skin with skin type III-IV. About the ageing of the skin of the Sun effecting I-II and III- IV skin types girls claimed that the Sun reduces the elasticity of the skin and accelerates the ageing 87,9 and 87,1 percent pigmented spots seen as a negative factor and 68,1 percent of girls said, that a variety of... [to full text]

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.

While modern epitaxial methods enable precise, monolayer (ML) control of the thin film deposition process, the complexity of certain device structures is ultimately limited by the capability and cost of the fabrication process. The objective of this work is to develop a pathway toward three-dimensional epitaxy (3DE) - the ability to intentionally and dynamically pattern regions of a film during the deposition process - in order to enable novel device concepts unbound by the traditional device fabrication paradigm. This work pioneers UV-assisted metal organic molecular beam epitaxy (MOMBE) as a particularly selective epitaxy technique to create a pathway toward 3DE of a crucial and topical material system - the III-Nitrides. A novel UV-assisted MOMBE system is developed enabling intense UV irradiation of films during growth. High quality, heavily (unintentionally) carbon-doped GaN is successfully grown by NH₃-based MOMBE and for the first time InGaN, AlGaN, and magnesium-doped GaN are demonstrated by NH₃-based MOMBE. Intense UV irradiation of films during NH₃-based MOMBE significantly enhances photo-desorption of species during the growth process, subsequently affecting the resultant InGaN alloy composition, carbon dopant concentration, or magnesium dopant concentration. A digital micromirror device is introduced to pattern incident UV radiation during InGaN growth, demonstrating that the effects of photoexcitation during MOMBE which have been proposed, discovered, and identified by this thesis indeed can be leveraged to deposit an InGaN film that is compositionally patterned within the growth plane. The results demonstrate that the new approach presented herein is possible for the 3DE of III-Nitrides if additional challenges in practical implementation can be overcome.