Studies of Zinc Oxide and Zinc Phosphate Nanostructures

In the framework of this dissertation, a microwave-assisted synthesis strategy for the production of zinc oxide nanoparticles, at the lower end of the nanoscale, is presented. The radius of these spherical particles can be adjusted by choosing a reaction temperature between 125 °C and 200 °C in the range of 2.6 nm to 3.8 nm. In this range, semiconductor particles such as those made of zinc oxide, exhibit size-dependent optical and structural properties, and tailor-made particles can aid their detailed investigation. This is demonstrated by the changes in optical band gap, photoluminescence and crystal lattice stress. Due to their functionalisation with oleate, these zinc oxide nanoparticles are hydrophobic and only dispersible in organic solvents such as cyclohexane or tetrahydrofuran. However, some applications -- for example as luminescent probes in biological systems -- may require hydrophilic particles in aqueous dispersion. For this, a phase transfer procedure is presented in which the particles are transferred into an aqueous medium employing the surfactant polysorbate 80. This process is associated with further particle growth, and the final particle size can be adjusted to up to 5.7 nm via the duration of heating this dispersion to 90 °C. In this context, the particle size distributions are determined via small-angle X-ray scattering, which, in contrast to other methods such as electron microscopy, can also be reliably applied in complex media. This is demonstrated with studies on the artificial digestion of zinc oxide nanoparticles. Zinc oxide, as well as other ionic zinc compounds, are added to food and cosmetic products due to their antibacterial effect or as food supplements and are ingested by humans. For this reason, it is essential to examine in detail any changes in the chemical and structural composition of these additives that end up being digested. When zinc oxide and zinc chloride come into contact with artificial saliva, new, small nanoparticles with radii around 3 nm are formed, whereby the size, concentration or functionalisation of the ingested substances has no significant influence on particle formation. After the dissolution of these nanostructures in gastric juice, particles form again in the intestinal juice, but their size distribution could not be determined unambiguously. It is assumed that the newly formed particles consist of zinc phosphate, regardless of which zinc compound is initially ingested. Ion release measurements confirm the findings on the formation and dissolution behaviour of the particles obtained from small-angle X-ray scattering. In order to investigate the particle formation from a zinc chloride solution in artificial saliva more precisely, X-ray scattering and X-ray absorption spectroscopy were employed. Within five minutes of the addition of zinc chloride to artificial saliva, nanoparticles with a radius of 1 nm are formed, and this radius remains constant for at least two weeks. The particles are found as aggregates with a radius of ca. 15 nm, in which a protein layer presumably binds the particles together. It is assumed that the particles initially consist of amorphous zinc phosphate, which begins to crystallise within seven hours. At the same time, the aggregates densify, i.e. the distance between the particles becomes smaller. In the subsequent two weeks, the radius of the aggregate increases to ca. 22 nm as the number of bound particles also increases. In summary, the first part of this dissertation focuses on the synthesis of reference candidate nanoparticles from zinc oxide at the lower end of the nanoscale. These particles, with adjustable size and in turn inherent optical and structural properties, are provided in both polar and apolar solvents. The second half of this dissertation, focuses on the application of small-angle X-ray scattering, and the suitability of the method for the characterisation of nanoparticles in complex media is demonstrated at an artificial digestion process. Thus, a contribution is made to the understanding of biological processes induced by the application of particulate and dissolved zinc compounds in food and cosmetic products

Modulation of Contact Sensitivity Responses by Bacterial Superantigen

Superantigens are potent modulators of the immune system, especially T cells. Therefore, we determined the influence of superantigens on the T-cell-mediated immune response, contact sensitivity. We chose the combination of staphylococcal enterotoxin B (SEB) as superantigen and 2,4-dinitrofluorbenzene (DNFB) as the contact sensitizer, because in BALB/c mice SEB reacts almost exclusively with Vβ8+ T cells, and these cells are capable of transferring contact sensitivity to DNFB from sensitized donors to naive syngeneic recipients. Pretreatment with a single intradermal injection of 50 ng SEB 24 h before DNFB exposure at the same site on the lower abdomen enhanced the induction of contact sensitivity: its intradermal injection permitted sensitization with non-sensitizing concentrations of DNFB as assessed by ear swelling responses after challenge with DNFR. In contrast, pretreatment with repeated intradermal injections of 50 ng SEB every other day over at least 1 week inhibited the induction of contact sensitivity following sensitization. The enhancing effect of SEB may be explained by the creation of a proinflammatory milieu in the skin after a single intradermal injection of the bacterial toxin, whereas the inhibitory effect may be due to tolerization of Vβ8+ T cells. The data indicate that products of skin-colonizing bacteria that can serve as superantigens are able to augment or inhibit the development of contact sensitivity

Influence heat-reflective coating on the decrease of heat losses of window constructions

Developed theoretical and methodological foundations of the optimal choice of space-planning and constructive decisions of low-rise buildings blocked type, aimed at improving efficiency of investment, energy and resource saving, creation of comfortable conditions for the population, ensure sustainable development of low-rise construction in the context of socio-economic priorities in the climatic zoning of the area of construction

Visibility science operations with the Keck Interferometer

The visibility science mode of the Keck Interferometer fully transitioned into operations with the successful completion of its operational readiness review in April 2004. The goal of this paper is to describe this science mode and the operations structure that supports it

Rat Model of Staphylococcal Enterotoxin B-Induced Rhinosinusitis

ObjectivesIt has been proposed that microbial persistence, superantigen (SA) production, and host T-cell response may be involved in the development of chronic rhinosinusitis. According to the SA hypothesis, a single intranasal application of SA such as staphylococcal enterotoxin B (SEB) may induce chronic eosinophilic rhinosinusitis. This study aimed to develop a rat model of rhinosinusitis induced by intranasally applied SEB.MethodsForty µL of SEB (100 µg/mL) or phosphate buffered saline was applied intranasally through each naris in 4 week-old Sprague-Dawley test rats (N=36) and controls (N=16), respectively. Following sacrifice at 1, 5, 14, and 28 days, the obtained nasal cavity and sinuses were prepared for histologic investigation. The histologic sections were examined in a blind manner for the ratio of the sinus spaces occupied by inflammatory cell clusters and the number of inflammatory cells in the lamina propria.ResultsInfiltration of neutrophils in the lamina propria and appearance of neutrophil clusters in the sinus spaces were observed in the SEB-applied rats. The ratio of the sinus spaces occupied by neutrophil clusters and the number of neutrophils infiltrated in the lamina propria increased significantly at day 1 as compared with the control rats.ConclusionIntranasally applied SEB induces acute neutrophilic rhinosinusitis in rats. Eosinophilic inflammation was not demonstrated. The mere presence of SA in the nose does not necessarily induce SA-induced inflammation, as suggested by the SA hypothesis

The dusty AGB star RS CrB: first mid-infrared interferometric observations with the Keck Telescopes

We report interferometric observations of the semi-regular variable star RS CrB, a red giant with strong silicate emission features. The data were among the first long baseline mid-infrared stellar fringes obtained between the Keck telescopes, using parts of the new nulling beam combiner. The light was dispersed by a low-resolution spectrometer, allowing simultaneous measurement of the source visibility and intensity spectra from 8 to 12 microns. The interferometric observations allow a non-ambiguous determination of the dust shell spatial scale and relative flux contribution. Using a simple spherically-symmetric model, in which a geometrically thin shell surrounds the stellar photosphere, we find that ~30% to ~70% of the overall mid-infrared flux - depending on the wavelength - originates from 7-8 stellar radii. The derived shell opacity profile shows a broad peak around 11 microns (tau ~ 0.06), characteristic of Mg-rich silicate dust particles.Comment: Accepted for publication in ApJ Letter

Formation of nanoscale ferromagnetic MnAs crystallites in low-temperature grown GaAs

3 páginas, 3 figuras, 1 tabla.We report the formation of nanosize ferromagnetic MnAs crystallites imbedded in low-temperature grown GaAs using Mn+ ion implantation and subsequent annealing. The structural and magnetic properties of the crystallites have been characterized by transmission electron microscopy, electron beam induced x-ray fluorescence, and superconducting quantum interference device magnetometry. After an optimized thermal annealing at 750 °C, MnAs crystallites of 50 nm in size are formed. These nanomagnets show room temperature ferromagnetism.This work has been supported by QUEST, an NSF Science and Technology center (Grant No. DMR91.20007). P.J.W. is a postdoctoral fellow of the Deutsche Forschungsgemeinschaft (DFG) J.M.G. is a postdoctoral fellow of the Spanish Ministry of Education and Science.Peer reviewe

НАЩАДКИ КОШОВОГО ОТАМАНА ЙОСИПА ГЛАДКОГО

Постать останнього кошового отамана Задунайської запорозької Січі а згодом й Азовського козацького війська Йосипа Михайловича Гладкого не залишилася поза увагою істориків [1] і народної пам’яті [2]. Діяльність цієї, безумовно, харизматичної людини отримала неоднозначну оцінку в попередній і сучасній історіографії. Останнім часом з’явилися ґрунтовні дослідження запорозького історика Людмили Маленко, присвячені історії Азовського козацького війська [3] і персонально діяльності отамана цього війська Й.Гладкого [4]. Дослідниця ввела до наукового обігу потужний корпус нових джерел. У полі зору Л.Маленко опинилася також і генеалогія Гладких. Проте ще наприкінці 1880-х рр. цього питання торкався відомий дослідник Запорожжя Дмитро Іванович Яворницький (1855-1940). Він був чи не першим, хто більш-менш повно висвітлив родинні стосунки Й.Гладкого. Вже у першій своїй великій монографії “Запорожжя в залишках старовини і переказах народу” Д.Яворницький приділив немало рядків Й.Гладкому та його нащадкам [5]. Головним джерелом у цьому дослідженні були документи родинного архіву Гладких. Яворницькому допомагав в цьому питанні його олександрівський приятель і відомий дослідник історії й фольклору місцевого краю Яків Павлович Новицький (1847-1925). В творчому доробку історика є й спеціальна стаття, присвячена Й. Гладкому та його генеалогії [6]