936 resultados para Crystal growth from melt
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This study firstly describes the epidemiology of malaria in Roraima, Amazon Basin in Brazil, in the years from 1991 to 1993: the predominance of plasmodium species, distribution of the blood slides examined, the malaria risk and seasonality; and secondly investigates whether population growth from 1962 to 1993 was associated with increasing risk of malaria. Frequency of malaria varied significantly by municipality. Marginally more malaria cases were reported during the dry season (from October to April), even after controlling for by year and municipality. Vivax was the predominant type in all municipalities but the ratio of plasmodium types varied between municipalities. No direct association between population growth and increasing risk of malaria from 1962 to 1993 was detected. Malaria in Roraima is of the "frontier" epidemiological type with high epidemic potential.
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Dissertação de mestrado em Comunicação, Arte e Cultura
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Enantioseparation, enantioselective crystallization, structurally related impurity, counter enantiomer, crystallization kinetics, crystal growth, chiral purity, crystal shape, mandelic acid, threonine
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BACKGROUND: In late-diagnosed transposition of the great arteries (TGA), the left ventricle (LV) involutes as it pumps against low resistance and needs retraining by applying a pulmonary artery band (PAB) in preparation for an arterial switch operation. We report our experience with a telemetrically adaptable band compared with classic banding. METHODS: Ten patients underwent retraining of the LV, 4 patients with an adaptable band and progressive weekly tightening of the band (group 1) and 6 patients with a traditional band (group 2). RESULTS: Mean weight and age at pulmonary band placement was 5.8 ± 2.36 kg and 11.7 ± 11.1 months for group 1 and 5.0 ± 2.3 kg and 6.4 ± 7.6 months for group 2. Time between palliation and switch procedure was 4.2 months in both groups. Group 1 showed an initial mean pulmonary gradient of 25.5 ± 4.43 mm Hg with a 5% closure of the device. The mean gradient increased with progressive closure to 63.5 ± 9.8 mm Hg at the time of the arterial switch operation. There were no reinterventions or deaths in this group. In group 2, the mean pulmonary gradient increased with growth from 49 ± 21.4 mm Hg to 68.4 ± 7.86 mm Hg at the time of the switch procedure. However, 4 of these patients required reoperations during retraining: 2 needed 1 reoperation and 2 needed 2 reoperations. Two patients died-1 after banding and 1 after the switch operation. CONCLUSIONS: Retraining of the LV by the adaptable device allows precise control of the tightening, avoids repetitive operations, and diminishes morbidity.
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We communicate a detailed study of the epitaxial growth of CeO2 on MgO. The key feature of the growth is the dependence of the in¿plane orientation of the CeO2 epitaxial layer on the MgO surface morphology. Atomic force microscopic (AFM) measurements, x¿ray analyses, as well as high¿resolution transmission electron microscopy (HRTEM) investigations reveal that on rough substrates a cube¿on¿cube growth of CeO2 on MgO occurs while on smooth substrates the CeO2 unit cell is rotated around the surface normal by 45° with respect to the MgO unit cell when the deposition rate is low (~0.3 Å/s) during the first stages of growth. This growth mechanism can be used for a defined fabrication of 45° grain boundaries in the CeO2 layer by controlling the surface roughness of the MgO substrate. This report demonstrates that these 45° grain boundaries may be used to fabricate YBa2Cu3O7¿x Josephson junctions.
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We find that even very low Ni doping levels of high-quality Bi2Sr2Ca1Cu2O8 single crystals strongly affect the transition temperature T(c). We also observed that T(c) is not related to the total Ni concentration, but only to that of Ni engaged in NiO-type bonds. By controlling the temperature during crystal growth, one can modify the relative weight of Ni in NiO-type bonds with respect to other configurations-and therefore T(c).
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In breast cancer, brain metastases are often seen as late complications of recurrent disease and represent a particularly serious condition, since there are limited therapeutic options and patients have an unfavorable prognosis. The frequency of brain metastases in breast cancer is currently on the rise. This might be due to the fact that adjuvant chemotherapeutic and targeted anticancer drugs, while they effectively control disease progression in the periphery, they only poorly cross the blood-brain barrier and do not reach effectively cancer cells disseminated in the brain. It is therefore of fundamental clinical relevance to investigate mechanisms involved in breast cancer metastasis to the brain. To date experimental models of breast cancer metastasis to the brain described in literature are based on the direct intracarotid or intracardiac injection of breast cancer cells. We recently established a brain metastasis breast cancer model in immunocompetent mice based on the orthotopic injection of 4T1 murine breast carcinoma cells in the mammary gland of syngeneic BALB/c mice. 4T1-derived tumors recapitulate the main steps of human breast cancer progression, including epithelial-to-mesenchymal transition, local invasion and metastatic spreading to lung and lymph nodes. 4T1 cells were engineered to stably express firefly Luciferase allowing noninvasive in vivo and ex vivo monitoring of tumor progression and metastatic spreading to target organs. Bioluminescence imaging revealed the appearance of spontaneous lesions to the lung and lymph nodes and, at a much lower frequency, to the brain. Brain metastases were confirmed by macroscopic and microscopic evaluation of the brains at necropsy. We then isolated brain metastatic cells, re-injected them orthotopically in new mice and isolated again lines from brain metastases. After two rounds of selection we obtained lines metastasizing to the brain with 100% penetrance (named 4T1-BM2 for Brain Metastasis, 2nd generation) compared to lines derived after two rounds of in vivo growth from primary tumors (4T1-T2) or from lung metastases (4T1-LM2). We are currently performing experiments to unravel differences in cell proliferation, adhesion, migration, invasion and survival of the 4T1-BM2 line relative to the 4T1-T2 and 4T1-LM2 lines. Initial results indicate that 4T1-BM2 cells are not more invasive or more proliferative in vitro and do not show a more mesenchymal phenotype. Our syngeneic (BALB/c) model of spontaneous breast carcinoma metastasis to the brain is a unique and clinically relevant model to unravel the mechanisms of metastatic breast cancer colonization of the brain. Genes identified in this model represent potentially clinically relevant therapeutic targets for the prevention and the treatment of brain metastases in breast cancer patients.
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Enterococcal implant-associated infections are difficult to treat because antibiotics generally lack activity against enterococcal biofilms. We investigated fosfomycin, rifampin, and their combinations against planktonic and adherent Enterococcus faecalis (ATCC 19433) in vitro and in a foreign-body infection model. The MIC/MBClog values were 32/>512 μg/ml for fosfomycin, 4/>64 μg/ml for rifampin, 1/2 μg/ml for ampicillin, 2/>256 μg/ml for linezolid, 16/32 μg/ml for gentamicin, 1/>64 μg/ml for vancomycin, and 1/5 μg/ml for daptomycin. In time-kill studies, fosfomycin was bactericidal at 8× and 16× MIC, but regrowth of resistant strains occurred after 24 h. With the exception of gentamicin, no complete inhibition of growth-related heat production was observed with other antimicrobials on early (3 h) or mature (24 h) biofilms. In the animal model, fosfomycin alone or in combination with daptomycin reduced planktonic counts by ≈4 log10 CFU/ml below the levels before treatment. Fosfomycin cleared planktonic bacteria from 74% of cage fluids (i.e., no growth in aspirated fluid) and eradicated biofilm bacteria from 43% of cages (i.e., no growth from removed cages). In combination with gentamicin, fosfomycin cleared 77% and cured 58% of cages; in combination with vancomycin, fosfomycin cleared 33% and cured 18% of cages; in combination with daptomycin, fosfomycin cleared 75% and cured 17% of cages. Rifampin showed no activity on planktonic or adherent E. faecalis, whereas in combination with daptomycin it cured 17% and with fosfomycin it cured 25% of cages. Emergence of fosfomycin resistance was not observed in vivo. In conclusion, fosfomycin showed activity against planktonic and adherent E. faecalis. Its role against enterococcal biofilms should be further investigated, especially in combination with rifampin and/or daptomycin treatment.
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Fatigue life assessment of weldedstructures is commonly based on the nominal stress method, but more flexible and accurate methods have been introduced. In general, the assessment accuracy is improved as more localized information about the weld is incorporated. The structural hot spot stress method includes the influence of macro geometric effects and structural discontinuities on the design stress but excludes the local features of the weld. In this thesis, the limitations of the structural hot spot stress method are discussed and a modified structural stress method with improved accuracy is developed and verified for selected welded details. The fatigue life of structures in the as-welded state consists mainly of crack growth from pre-existing cracks or defects. Crack growth rate depends on crack geometry and the stress state on the crack face plane. This means that the stress level and shape of the stress distribution in the assumed crack path governs thetotal fatigue life. In many structural details the stress distribution is similar and adequate fatigue life estimates can be obtained just by adjusting the stress level based on a single stress value, i.e., the structural hot spot stress. There are, however, cases for which the structural stress approach is less appropriate because the stress distribution differs significantly from the more common cases. Plate edge attachments and plates on elastic foundations are some examples of structures with this type of stress distribution. The importance of fillet weld size and weld load variation on the stress distribution is another central topic in this thesis. Structural hot spot stress determination is generally based on a procedure that involves extrapolation of plate surface stresses. Other possibilities for determining the structural hot spot stress is to extrapolate stresses through the thickness at the weld toe or to use Dong's method which includes through-thickness extrapolation at some distance from the weld toe. Both of these latter methods are less sensitive to the FE mesh used. Structural stress based on surface extrapolation is sensitive to the extrapolation points selected and to the FE mesh used near these points. Rules for proper meshing, however, are well defined and not difficult to apply. To improve the accuracy of the traditional structural hot spot stress, a multi-linear stress distribution is introduced. The magnitude of the weld toe stress after linearization is dependent on the weld size, weld load and plate thickness. Simple equations have been derived by comparing assessment results based on the local linear stress distribution and LEFM based calculations. The proposed method is called the modified structural stress method (MSHS) since the structural hot spot stress (SHS) value is corrected using information on weld size andweld load. The correction procedure is verified using fatigue test results found in the literature. Also, a test case was conducted comparing the proposed method with other local fatigue assessment methods.
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Työssä tutkittiin leijupetikiteyttimen toimivuutta sulfatiatsolikiteiden kasvunopeuksien mittaamisessa. Sulfatiatsoli on lääkeaine, jota käytetään antibioottina. Kirjallisuusosassa on käsitelty kiteytyksen perusteita sekä olosuhteiden vaikutuksia kidemorfologiaan. Koska kyseessä on lääkeaine, on työssä myös selvitetty tekijöitä, jotka vaikuttavat syntyvän kiteen polymorfimuotoon. Näitä ovat mm. siemenkiteen polymorfimuoto sekä käytetty liuotin. Kirjallisuusosassa on myös esitelty teollisia ja laboratoriomittakaavan leijupetikiteyttimiä. Kokeellisessa osassa on keskitytty testaamaan leijupetikiteyttimen toimintaa sekä etsimään sopivia olosuhteita kasvukokeiden suorittamiselle. Kokeissa tutkittiin ylikylläisyyden vaikutusta sulfatiatsolikiteen kasvuun. Kiteen kasvun seurantaan pyrittiin etsimään sopivia hiukkaskokoanalysaattoreita. Mittauksissa käytetyt laitteistot olivat PIA 4000 mod LUT on-line-videomikroskooppi ja laserdiffraktioon perustuva Coulter LS 130 off-line-partikkelikokoanalysaattori.
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Työssä on tutkittu epäpuhtauksien vaikutusta kastelulannoitesuolojen monokaliumfosfaatin, kaliumnitraatin ja ureafosfaatin kiteytyksessä. Kirjallisuusosassa on käsitelty kastelulannoiteprosessit ja epäpuhtauksien vaikutus kastelulannoitteiden valmistuksessa. Kiteytys ja kiteenkasvu on esitetty perusyhtälöin, joissa on otettu epäpuhtauksien vaikutus huomioon. Tarkemmin on perehdytty monokaliumfosfaatin kiteytykseen ja kolmenarvoisten kationeiden, Al3+, Fe3+ ja Cr3+, vaikutukseen kiteiden kasvuun. Kolmenarvoiset metalli-ionit adsorboituvat kiteen pintaan haitaten kiteenkasvua, mikä vaikuttaa erityisesti kiteen prismapinnan kasvuun. Lisäksi on esitelty muita kiteenkasvuun vaikuttavia olosuhteita. Lopuksi on käsitelty kompleksinmuodostajia metalli-ionien haitallisten vaikutusten ehkäisijöinä. Kokeellisessa osassa suoritettiin liukoisuuskokeita monokaliumfosfaatin liukoisuuden selvittämiseksi eri pH-olosuhteissa. Suoritetuissa yksikidekokeissa tutkittiin pH:n ja kolmenarvoisten kationeiden; Al3+, Fe3+ ja Cr3+, vaikutus monokaliumfosfaattikiteen pituus- ja leveyskasvuun ja kidemuotoon eri ylikylläisyyksillä. Lisäksi tutkittiin voidaanko lämpötilaa ja pH muuttamalla tai pyrofosfaattia lisäämällä poistaa raudan kasvua inhiboima vaikutus. Kiteytyslämpötilaa nostamalla voidaan poistaa raudan haitallinen vaikutus kiteen kasvuun.
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Monikulttuurinen johtaminen on globalisaation ja nopean kansainvälistymisen takia erittäin ajankohtainen aihe. Suomessa sitä on kuitenkin tutkittu vasta vähän. Tämän tutkimuksen tarkoituksena on tutkia Suomen suurlähetystöjenmonikulttuurista johtamista Aasian eri kohdemaissa ja kulttuureissa sekä ottaa osaa tieteelliseen keskusteluun monikulttuurisesta johtamisesta. Tutkimuksen kohdemaiksi on valittu neljä Aasian maata, jotka ovat tällä hetkellä hyvin ajankohtaisia nopean talouskasvunsa takia. Itä-Aasiasta mukana ovat Etelä-Korea (Korean tasavalta), Japani ja Kiinan kansantasavalta sekä Kaakkois-Aasiasta tutkimuksessa mukana on Malesia. Tämä tutkimus on laadullinen tutkimus, jonka aineisto koostuu kahdesta laadulliselle tutkimukselle poikkeuksellisesta avoimesta kyselystä, jotka on lähetetty edellä mainittujen maiden suurlähettiläille eri kohdemaihin. Analyysissä menetelmänä on käytetty teemoittelua, jonka avulla on voitu jäsentää saatua aineistoa. Näin teemojen vertailu on myös ollut helpompaa. Tutkimuksen tuloksista kävi ilmi, että monikulttuurinen johtaminen on erittäin haasteellista kansallisten kulttuurien eroista johtuen. Arvot ovat hyvin keskeisessä osassa kulttuuria tutkittaessa ja niiden erot voivat vaikeuttaa kanssakäymistä eri kulttuureista tulevien ihmisten kesken, koska asioiden merkitykset jäävät usein arvoituksiksi vieraasta kulttuurista tuleville henkilöille. Kansallisen kulttuurin tekijöistä kieli, arvot ja uskonto ovat merkittäviä monikulttuurisen johtamisen kannalta. Tutkimuksesta kävi myös ilmi, että Itä- Aasian maissa konfutselaisuudella on suuri merkitys yhteiskuntafilosofiana. Se on muokannut yhteiskunnan arvoja, tapoja ja rakenteita. Vanhempien ja ylempiarvoisten ihmisten arvostus ja vahvasti hierarkkinen yhteiskuntarakenne ovat tyypillisiä konfutselaisuuden piirteitä. Kulttuurin ulottuvuuksista merkityksellisempiä tämän tutkimuksen kannalta ovat yksilöllisyys vs. kollektiivisuus, valtaetäisyys ja konfutselaisuuden dynamiikka (lyhyen vs. pitkän aikavälin suuntautuminen). Kaikki tämän tutkimuksen maat ovat kollektiivisia sekä niissä valtaetäisyys on myös korkea. Tämä tuo haasteita monikulttuuriseen johtamiseen Suomen suurlähetystöissä, koska suomalainen kulttuuri on useimpien länsimaiden tapaan yksilöllinen ja valtaetäisyys on suhteellisen matala. Konfutselaisuuden dynamiikka vaikuttaa lähinnä vain Itä-Aasian maissa tuoden mukanaan erittäin vahvan hierarkian, jota ei voi sivuuttaa. Tutkimuksen aineistoa käsitellään näytenäkökulmasta, eikä sitä ei voisuoraan verrata muihin organisaatioihin tai kulttuureihin. Toisaalta jokaisen kansallisen kulttuurin ihmiset toimivat tietyllä tavalla tietyssä kontekstissa, riippumatta siitä, missä organisaatiossa he työskentelevät. Kulttuuri ohjaa ihmisen toimintaa ja kansallinen kulttuuri on yrityskulttuuria voimakkaampi tekijä.
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The aim of this work is to systematically explore the effect of the synthesis conditions of ZnO structures, immobilized on different substrates by hydrothermal treatment, in its photocatalytic activity. A circumscribed central composite design of experiments was used to analyze the effects of reagents stoichiometry, reaction time and temperature, covering a wide range of these variables. The substrates used were etched glass, copper and zinc foils. The photocatalytic activity of the as-obtained ZnO samples was evaluated through photocatalytic degradation of rhodamine B (RhB) in aqueous solution under UV irradiation. Zinc foils presented the best immobilized film quality and the maximum dye removal was 80% in one hour of UV exposure.
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Temporal dynamics of the chaetophoracean green algae Chaetophora elegans (Roth) C.A. Agardh and Stigeoclonium amoenum Kützing populations was investigated biweekly during late autumn trhough early spring (April to October) in two tropical streams from northwestern São Paulo State, southeastern Brazil. Abundances of one population of each species was evaluated by the quadrat technique in terms of percent cover and frequency. The fluctuations were related to the following stream variables: temperature, turbidity, specific conductance, pH, oxygen saturation, depth, substratum type, current velocity, irradiance and nutrients. Percent cover and frequency of C. elegans had lower values throughout the study period and was positively correlated to rainfall. Other correlations (i.e. positive of percent cover with depth and current velocity and negative with irradiance) were consistently found, reinforcing the strong influence of rainfall. On the other hand, percent cover and frequency of S. amoenum had higher values, with maximum growth from June to September. Percent cover was negatively correlated to rainfall. Results suggest the precipitation regime as the most important driving force to temporal changes in both populations, but playing different roles in each one. The gelatinous thallus of C. elegans seem to be favored by the increment of current velocity, since higher flows can improve the nutrient uptake by means of reduction in diffusion shell without promoting excessive drag force. In contrast, tufts of S. amoenum are, presumably, more exposed to drag force, and, consequently, more susceptible to mechanical damage effects due to higher current velocities.