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Prepenetration Stages of Guignardia psidii in Guava: Effects of Temperature, Wetness Duration and Fruit Age

ESCANFERLA, Maria Eugenia; MORAES, Sylvia Raquel Gomes; SALAROLI, Renato Barbosa; MASSOLA JR., Nelson Sidnei
Fonte: WILEY-BLACKWELL PUBLISHING, INC Publicador: WILEY-BLACKWELL PUBLISHING, INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.46%
This study examined the effects of temperature and wetness duration in vitro and in vivo as well as the effects of fruit age on germination and appressoria formation by conidia of Guignardia psidii, the causal agent of black spot disease in guava fruit. The temperatures tested for in vitro and in vivo experiments were 10, 15, 20, 25, 30, 35 and 40 degrees C. The wetness periods studied were 6, 12, 24, 36 and 48 h in vitro and 6, 12 and 24 h in vivo. Fruit 10, 35, 60, 85 and 110-days old were inoculated and maintained at 25 degrees C, with a wetness period of 24 h. Temperature and wetness duration affected the variables evaluated in vitro and in vivo. All variables reached their maximum values at between 25 and 30 degrees C with a wetness duration of 24 h in vivo and 48 h in vitro. These conditions resulted in 31.3% conidia germination, 33.6% appressoria formation and 32.5% appressoria melanization in vitro, and 50.4% conidia germination and 9.5% appressoria formation in vivo. Fruit age also influenced these factors. As fruit age increased, conidia germination and appressoria formation gradually increased. Conidia germination and appressoria formation were 10.8% and 2.3%, respectively, in 10-day-old fruits. In 110-day-old fruits, conidia germination and appressoria formation were 42.5% and 23.2% respectively.

The effects of occlusal loading on the margins of cervical restorations

FRANCISCONI, Luciana Favaro; GRAEFF, Marcia Sirlene Zardin; MARTINS, Leandro de Moura; FRANCO, Eduardo Batista; MONDELLI, Rafael Francisco Lia; FRANCISCONI, Paulo Afonso Silveira; PEREIRA, Jose Carlos
Fonte: AMER DENTAL ASSOC Publicador: AMER DENTAL ASSOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.45%
Background. Researchers have proposed the restoration of abfraction lesions, but limited information is available about the effects of occlusal loading on the margins of such restorations. Because abfraction is a well-recognized problem, the authors conducted a study to assess the effects of occlusal loading on the margins of cervical restorations. Methods. The authors prepared 40 wedge-shaped cavities in extracted premolars and restored them with a resin-based composite. They subjected specimens to occlusal loading (150 newtons, 101 cycles) on the buccal cusp, on the central fossa or on the lingual cusp, and they stored 1 the control group, specimens in deionized water. The authors used fluorescein to delimit marginal defects and evaluated the defects by using laser scanning confocal microscopy. Results. Results of chi(2) and Kruskal-Wallis tests (P < .05) showed that specimens subjected to occlusal loading had a higher percentage of marginal gaps (53.3 percent) than did the control specimens (10.0 percent). There were no differences between groups in marginal defect formation or in defect location, length or width. Conclusions. Occlusal loading led to a significant increase in gap formation at the margins of cervical resin-based composite restorations. Clinical Implications. The clinician cannot underestimate the effects of occlusal loading When restoring teeth with cervical wedge-shaped lesions. If occlusal loading is the main factor contributing to lesion formation...

Estudo sobre efeitos da participação em programas especiais de formação docente nas trajetórias profissionais de suas egressas; Study of the effects of the participation in special programs of teacher education upon the professional trajectories of the alumni

Amaral, Daniele Kohmoto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/04/2015 PT
Relevância na Pesquisa
75.46%
Com a promulgação da Lei de Diretrizes e Bases da Educação Nacional (LDBEN), de 1996, e impulsionado pela chamada Década da Educação (1997 2007), desencadeou-se um movimento caracterizado pelo desenvolvimento de diversos convênios entre as Secretarias de Educação, universidades públicas e privadas e fundações, com o intuito de certificar em nível superior professores com formação em nível médio. Nesse cenário, intensificou-se a oferta dos Programas Especiais de Formação Docente, sendo assim nomeados em decorrência de seu caráter temporário, avançando as problematizações que os atrelavam às políticas e reformas de cunho neoliberal. Mostravam-se escassas, porém, as reflexões sobre as implicações desse modelo de formação para as trajetórias docentes, colocando-nos diante das seguintes questões: Os Programas Especiais trouxeram implicações para as trajetórias profissionais? O que ficou de mais significativo da experiência de participação em um Programa Especial? Essas foram algumas das indagações que nortearam esta investigação que busca conhecer os efeitos da formação em um Programa Especial nas trajetórias profissionais de suas egressas. Para responder a elas, foi tomado como referente empírico uma das experiências pioneiras realizadas em São Paulo nos âmbitos estadual e municipal: o PEC. Esta pesquisa foi estruturada em três etapas: (1) revisão bibliográfica e sistematização de materiais sobre o Programa Especial...

Reevaluation of the Effects of Brefeldin A on Plant Cells Using Tobacco Bright Yellow 2 Cells Expressing Golgi-Targeted Green Fluorescent Protein and COPI AntiseraW⃞

Ritzenthaler, Christophe; Nebenführ, Andreas; Movafeghi, Ali; Stussi-Garaud, Christiane; Behnia, Leila; Pimpl, Peter; Staehelin, L. Andrew; Robinson, David G.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /01/2002 EN
Relevância na Pesquisa
55.45%
Brefeldin A (BFA) causes a block in the secretory system of eukaryotic cells by inhibiting vesicle formation at the Golgi apparatus. Although this toxin has been used in many studies, its effects on plant cells are still shrouded in controversy. We have reinvestigated the early responses of plant cells to BFA with novel tools, namely, tobacco Bright Yellow 2 (BY-2) suspension-cultured cells expressing an in vivo green fluorescent protein–Golgi marker, electron microscopy of high-pressure frozen/freeze-substituted cells, and antisera against Atγ-COP, a component of COPI coats, and AtArf1, the GTPase necessary for COPI coat assembly. The first effect of 10 μg/mL BFA on BY-2 cells was to induce in <5 min the complete loss of vesicle-forming Atγ-COP from Golgi cisternae. During the subsequent 15 to 20 min, this block in Golgi-based vesicle formation led to a series of sequential changes in Golgi architecture, the loss of distinct Golgi stacks, and the formation of an endoplasmic reticulum (ER)–Golgi hybrid compartment with stacked domains. These secondary effects appear to depend in part on stabilizing intercisternal filaments and include the continued maturation of cis- and medial cisternae into trans-Golgi cisternae, as predicted by the cisternal progression model...

Immunoregulatory and Antimicrobial Effects of Nitrogen Oxides

Mannick, Joan B.
Fonte: American Thoracic Society Publicador: American Thoracic Society
Tipo: Artigo de Revista Científica
Publicado em /04/2006 EN
Relevância na Pesquisa
65.34%
The therapeutic effects of inhaled nitric oxide (NO) therapy are thought to be restricted to the pulmonary vasculature because of rapid inactivation of NO by hemoglobin in the bloodstream. However, recent data suggest that inhaled NO may not only be scavenged by the heme iron of hemoglobin but also may react with protein thiols in the bloodstream, including cysteine-93 of the hemoglobin B subunit. Reaction of NO with protein or peptide thiols is termed S-nitrosylation and results in the formation of relatively stable protein S-nitrosothiols that carry NO bioactivity to distal organs. Thus, inhaled NO-induced protein S-nitrosylation may allow inhaled NO to have multiple as yet undiscovered physiologic and pathophysiologic effects outside of the lung. Here we review the immunoregulatory and antimicrobial functions of NO and the potential effects of inhaled NO therapy on host defense.

Effects of Vitamin K2 on the Development of Osteopenia in Rats as the Models of Osteoporosis

Iwamoto, Jun; Takeda, Tsuyoshi; Sato, Yoshihiro
Fonte: Yonsei University College of Medicine Publicador: Yonsei University College of Medicine
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
55.46%
Vitamin K2 is widely used for the treatment of osteoporosis in Japan. To understand the effects of vitamin K2 on bone mass and bone metabolism, we reviewed its effects on the development of osteopenia in rats, which characterizes models of osteoporosis. Vitamin K2 was found to attenuate the increase in bone resorption and/or maintain bone formation, reduce bone loss, protect against the loss of trabecular bone mass and its connectivity, and prevent the decrease in strength of the long bone in ovariectomized rats. However, combined treatment of bisphosphonates and vitamin K2 had an additive effect in preventing the deterioration of the trabecular bone architecture in ovariectomized rats, while the combined treatment of raloxifene and vitamin K2 improved the bone strength of the femoral neck. The use of vitamin K2 alone suppressed the increase in trabecular bone turnover and endocortical bone resorption, which attenuated the development of cancellous and cortical osteopenia in orchidectomized rats. In addition, vitamin K2 inhibited the decrease in bone formation in prednisolone-treated rats, thereby preventing cancellous and cortical osteopenia. In sciatic neurectomized rats, vitamin K2 suppressed endocortical bone resorption and stimulated bone formation...

Why Hofmeister effects of many salts favor protein folding but not DNA helix formation

Pegram, Laurel M.; Wendorff, Timothy; Erdmann, Robert; Shkel, Irina; Bellissimo, Dana; Felitsky, Daniel J.; Record, M. Thomas
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
55.48%
The majority (∼70%) of surface buried in protein folding is hydrocarbon, whereas in DNA helix formation, the majority (∼65%) of surface buried is relatively polar nitrogen and oxygen. Our previous quantification of salt exclusion from hydrocarbon (C) accessible surface area (ASA) and accumulation at amide nitrogen (N) and oxygen (O) ASA leads to a prediction of very different Hofmeister effects on processes that bury mostly polar (N, O) surface compared to the range of effects commonly observed for processes that bury mainly nonpolar (C) surface, e.g., micelle formation and protein folding. Here we quantify the effects of salts on folding of the monomeric DNA binding domain (DBD) of lac repressor (lac DBD) and on formation of an oligomeric DNA duplex. In accord with this prediction, no salt investigated has a stabilizing Hofmeister effect on DNA helix formation. Our ASA-based analyses of model compound data and estimates of the surface area buried in protein folding and DNA helix formation allow us to predict Hofmeister effects on these processes. We observe semiquantitative to quantitative agreement between these predictions and the experimental values, obtained from a novel separation of coulombic and Hofmeister effects. Possible explanations of deviations...

Experimental and theoretical investigation of the effects of low-frequency sonophoresis on transdermal drug transport; Low-frequency sonophoresis on transdermal drug transport

Tang, Hua, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 276 leaves; 18692067 bytes; 18691821 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.32%
Transdermal drug delivery offers many advantages over traditional drug administration methods such as injections and oral delivery, including increased patient compliance, and avoiding first-pass effects. However, due to the low skin permeability, transdermal drug delivery is currently limited to only a handful of drugs that are hydrophobic and of low molecular weight. The pharmaceutical relevance of many molecules that are excluded from this category, such as proteins, peptides, and DNA, has stimulated the investigation of various skin permeation enhancement methods, among which ultrasound represents a promising skin permeation enhancer. Previous work by our group has shown that ultrasound at a frequency of 20 kHz significantly enhances transdermal transport of drugs, a phenomenon referred to as Low-Frequency Sonophoresis (LFS). The objective of this thesis was to develop a fundamental understanding of the mechanisms of low-frequency sonophoresis (LFS) with an emphasis on the transdermal transport of hydrophilic permeants. An important goal was to utilize this mechanistic understanding to develop guidelines for the rational design of clinical LFS systems. With this in mind, a transport theory was developed to characterize the skin porous pathway of hydrophilic permeants...

Effects of surface properties on solder bump formation by direct droplet deposition

Hsiao, Wen Kai, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 166 leaves; 13354521 bytes; 13376541 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
65.4%
Recent advances in microdroplet generation and deposition processes have made it possible to directly form solder bumps on integrated circuits using micron-sized molten metal droplets. The direct droplet deposition bumping process can potentially produce uniform-sized bumps more economically than the existing processes such as plating and stencil printing. However, the development of this new bumping method is still in its infancy, particularly because of a lack of understanding about the post-impact deposition behavior of molten droplets on solid targets. A deposited molten on the deposition efficiency, as well as on the final bump size and shape. The present study investigates the effects of wetting and surface roughness on droplet bouncing during solder bump formation. The potential for droplet bouncing is modeled based on the energy difference between the maximum spreading and equilibrium sessile stages of a deposited droplet. Validated by experimental results, the model shows that strong droplet-surface wetting can significantly reduce the tendency for a deposited droplet to bounce. The effect of surface droplet can sometimes recoil violently after the initial spreading and rebound off the target surface. Such behavior, known as bouncing...

The effects of deposit thermal history on microstructure produced by uniform droplet spray forming

Cherng, Jean-Pei Jeanie
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 92 leaves; 4418684 bytes; 4418490 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.28%
Uniform droplet spray forming is a process aimed at producing near-net-shape parts directly from the liquid melt by spraying micron-sized droplets onto a movable target. In spray forming, the solidification rate of the deposited material is a key parameter that influences its microstructure formation and consequently, its mechanical properties. Ideal deposit microstructure has fine grain size and minimal segregation. The purpose of this thesis is to quantify the effects of deposit thermal history on the microstructure produced by the UDS forming process. Experiments were conducted with Zn-20wt% Sn alloy droplets using different process parameters to vary the deposit solidification rate from 6⁰C/s to 27⁰C/s immediately after deposition. The temperature of the sprayed deposits was measured in situ with a fiber-optic infrared thermometer and a contact thermocouple. Furthermore, a 2-D axisymmetric finite element model was developed to predict the temperature of the deposit during and after deposition. The simulation results show that radial heat conduction cannot be neglected when the thermal diffusivity of the substrate material is comparable to the diffusivity of the deposit material. Simulation results showed good agreement with the measured temperature data. The resultant deposit microstructures were examined with scanning electron microscopy...

Effects of borehole stability on well log data

Grandi Karam, Samantha, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 150 leaves; 5098661 bytes; 5098470 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.39%
In this thesis we analyze the effects of borehole irregularities on well logs and develop methods to obtain reliable formation properties from such logs. Data from a well in eastern Venezuela are analysed. Borehole irregularities in this well consist mainly of borehole enlargements perpendicular to the borehole axis due to rock failure under high horizontal stresses. They are observed in three forms: as small scale irregularities of the borehole wall, as-near elliptical shapes oriented along the minimum in situ stress direction, and as an increase of borehole diameter at all azimuths due to large scale failure. Breakout data suggest that maximum stress is oriented NNW-SSE. The suite of logs analyzed include lithology, density, dipmeter and full waveform acoustic logs. The standard log processing and interpretation methods fail because of the effects of irregularities. The analysis of the density log indicates that standard corrections are not enough when diameter is severly elongated. Similarly, acoustic logs processed commercially give unreasonable formation velocities. Guided by theoretical models we evaluate the effects of irregularities on different wave types recorded by full waveforms acoustic logs, i.e refracted P and S, pseudo Rayleigh...

Simulations of polymeric membrane formation in 2D and 3D

Zhou, Bo, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 213 p.; 5095015 bytes; 5217969 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.23%
The immersion precipitation process makes most commercial polymeric membranes, which enjoy widespread use in water filtration and purification. In this work, a ternary Cahn-Hilliard formulation incorporating a Flory-Huggins homogeneous free energy function is used to model both initial diffusion and the liquid-liquid demixing stage of the immersion precipitation process, which determines much of the final morphology of membranes. Simulations start with a simple non-solvent/solvent/polymer ternary system with periodic boundary conditions and uniform initial conditions with small random fluctuations in 2D. Results in 2D demonstrate the effects of mobilities (Mij) and gradient penalty coefficients (Kij) on phase separation behavior. A two-layer polymer-solvent/non-solvent initial condition is then used to simulate actual membrane fabrication conditions. 2D simulation results demonstrate an asymmetric structure of membrane morphology, which strongly agrees with the experimental observation. A mass transfer boundary condition is developed to model the interaction between the polymer solution and the coagulation bath more efficiently. Simulation results show an asymmetric membrane with connected top layer.; (cont.) Then a wide range of initial compositions are used in both the polymer solution and the coagulation bath...

Investigation of thermal filamentation instability over Gakona, Alaska

Cohen, Joel (Joel A.), S.B. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 43 p.
ENG
Relevância na Pesquisa
65.23%
The thermal filamentation instability has been invoked to explain the formation of parallel plate waveguides in mid-latitude ionospheric plasmas during Arecibo, Puerto Rico heating experiments in 1997. The geometry of the kilometer-scale parallel plates predicted by thermal filamentation depends on the mode of the transmitted heater wave, as does the threshold to excite this instability. While plasma heating can excite small-scale irregularities via parametric instabilities, thermal filamentation is thought to produce large-scale irregularities. In Arecibo, the threshold for X-mode to induce irregularities was found to be greater than 1 V/m, while for O-mode it was on the order of mV/m. In recent plasma experiments in high-latitude ionospheric plasmas, carried out at the HAARP facility in Gakona, Alaska in summer 2005, spring 2006, and summer 2006, a weakening in ionogram traces was observed during O-mode and X-mode heating, leading to a scenario detailing the effects of thermal filamentation and short-scale irregularities caused by heating. The Gakona experiments using a high power HF heating facility and multiple diagnostic instruments shed light on the important role of the thermal filamentation instability in generating electromagnetic wave-induced plasma turbulence with a broad spectrum of wavelengths...

Effects of water on chemomechanical instabilities in amorphous silica : nanoscale experiments and molecular simulation

Silva, Emílio César Cavalcante Melo da
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 114 leaves
ENG
Relevância na Pesquisa
65.31%
We elucidate the tensile failure mechanism of amorphous silica and the effects of water on the process, combining: (a) atomic force microscope (AFM) bending tests, (b) molecular dynamics (MD) simulation and (c) molecular orbital (MO) simulation. Bending tests of silica nanowires provide validation for the predictions of the simulations, in which we study the failure of dry silica using MD and define a representative system to be studied with the more chemically accurate MO method. We used the AFM to perform bending tests on silica nanowires of diameter D < 1 [mu]m, which have very high surface-to-volume ratio and no microscopic flaws. No size effects on elastic modulus were observed down to 130 nm. For 500 nm wires, water reduces the strength from 10.5 GPa in air to 6.5 GPa in water, results comparable to those reported for micrometer-scale fibers. By probing the strength of silica at this scale, we bring experiments to the length scales accessible to atomistic simulation. Using classical MD, we found that crystalline silica fails globally by crack nucleation, but amorphous silica displays plastic deformation due to the formation of local defects, which cascade into larger compound defects. We extend to amorphous systems the instability criterion for material failure and use the Lanczos iteration method to isolate unstable modes. Failure of these modes create local defects...

Electrospinning of polymeric nanofiber materials : process characterization and unique applications

Yu, Jian Hang, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 156 p.
ENG
Relevância na Pesquisa
65.29%
Electrospinning or electrostatic fiber spinning employs electrostatic force to draw a fiber from a spinneret. This fiber solidifies and lies down on a collector in the form of a non-woven fiber mat. Electrospinning has attracted much attention recently due to the ease with which fine fibers about 10 nanometers to 10 microns in diameter can be produced from both natural and synthetic polymers. Despite the large volume of publications on this technology, few publications discuss the mechanics of electrospinning. Most publications deal with the exploratory works on what material can be electrospun and the potential applications of the electrospun fibers. This work examined the electrohydrodynamics of the electrospinning process and developed this technology for making functional materials. The first part of this dissertation deals with the electrohydrodynamics of the process. The effects of processing parameters and material properties on the size and structure of electrospun fibers were studied. The experimental findings validated the analytical scaling model developed by Fridrikh and co-workers to predict how the final radius or "the terminal jet radius" of the electrospun fiber depends on the processing parameters.; (cont.) The scaling formula is derived from the force balance between surface tension and surface charge repulsion. The scaling model provides a powerful tool for controlling the fiber diameter just by adjusting the surface tension...

Musculoskeletal adaptation to Partial Weight Suspension : studies of Lunar and Mars loading; Musculoskeletal adaptation to PWS

Wagner, Erika Brown
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 257 p.
ENG
Relevância na Pesquisa
65.32%
As human spaceflight extends in both duration and scope, it is critical to better understand the physiologic effects of this novel environment. In the weight bearing structures of the body, bone loss and muscle atrophy far in excess of age-related declines are hallmarks of microgravity adaptation. However, while the physiological effects of such disuse unloading are well-described, the effects of partial weight bearing, such as expected on the moon (16% of Earth's gravity) and Mars (38% of Earth's gravity), have yet to be quantified. In these environments, the risks of musculoskeletal atrophy and accompanying orthopedic injury are uncertain, and a means of further investigation is needed. To address this need, we developed a novel model of Partial Weight Suspension (PWS) that supports investigation of the physiologic effects of chronically reduced quadrupedal loading in mice. Validation of the PWS system was conducted using a gait analysis treadmill and high-precision force platform. These studies showed that peak ground reaction forces were significantly reduced under conditions of partial weightbeari:ng, and changes in gait dynamics were consistent with previous studies of human locomotion. Using the PWS system, we conducted the first known studies of chronic musculoskeletal adaptation to Mars and lunar levels of weight bearing. Adult female BALB/cByJ mice underwent 21 days of partial weight bearing or control treatment. Relative to controls...

Study of particulate matter formation and evolution in near-field aircraft plumes using a one-dimensional microphysical model

Zhang, Jianye, S.M. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 58 p.
ENG
Relevância na Pesquisa
65.36%
Environmental concerns have led to a growing effort to investigate and characterize the particulate matter (PM) emissions from aircraft engines. This thesis presents a one-dimensional microphysics and chemical kinetics model that is used to study the formation and evolution of particulate matter in near field aircraft plumes at ground level. The initial exhaust properties were obtained from engine data and plume mixing profiles were generated using FLUENT®. The initial gas species concentrations were estimated based on a two-step constrained equilibrium process. Parametric studies of the effects of ambient temperature, ambient relative humidity, engine operating conditions and engine design parameters on the aerosol formation were investigated using the one dimensional model following a centerline trajectory up to lkm downstream of the engine exit plane. PM formation and evolution characteristics along trajectories from several radial locations were also investigated and compared to the results from the centerline study. The results from this study show that binary homogeneous H2SO4-H20 nucleation strongly depends on ambient conditions such as ambient temperature and relative humidity whereas the condensational growth of soot particles is most dependent on engine power settings.; (cont.) For example...

Lung tissue engineering : in vitro synthesis of lung tissue from neonatal and fetal rat lung cells cultured in a three-dimensional collagen matrix

Chen, Patty P., 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 77 p.; 4402930 bytes; 4411005 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
65.3%
The focus of this study was to investigate the histology of tissue formed when fetal (16-20 days gestation) and neonatal (2 days old) rat lung cells were grown in a collagen-glycosaminoglycan scaffold. This project employed a collagen-GAG scaffold specifically developed for tissue engineering and investigated the effect of this substratum on the formation of lung histotypic structures in vitro. A cell isolation procedure was developed whereby 19-days gestation type II alveolar cells reaggregated to form alveolar-like structures. The effects of selected scaffold design variables including pore diameter and degradation rate of the substratum on lung tissue regeneration were explored. Lung cell behavior revealed as the cells interact with an analog of the extracellular matrix was also examined. Differences in fetal and neonatal lung cell behavior were identified using histological analysis. Lung cells were obtained from Sprague-Dawley rats after 16-, 19-, and 20-days of gestation and at 2 days after term. These cells were seeded into type I collagen-GAG matrices, sized 8mm in diameter by 2mm in thickness. The medium used, F12K and Ham's nutrient mixture, was supplemented with 10% fetal bovine serum. A seeding density between 1 to 5 million cells per sponge sample was used. Histology studies were performed at termination periods of 2...

Mechanisms of toxicity and carcinogenicity of three alkylanilines

Sun, Hsiao-Lan Patty
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 158 leaves
ENG
Relevância na Pesquisa
55.47%
Alkyl-substituted anilines have been implicated as important etiological agents in human carcinogenesis. Specifically, 2,6-dimethylaniline (2,6-DMA), 3,5-dimethylaniline (3,5-DMA), and 3-ethylaniline (3EA) have been associated with an increased risk of human bladder cancer, independent of cigarette smoking, in a published case-control study. Understanding the metabolic activation of and DNA adduct formation by these chemicals is an important first step in elucidating their mechanisms of carcinogenesis and toxicity. Cytochrome P450-mediated metabolism was profiled based on the hypothesis that N-hydroxylated metabolites are critical intermediates in the formation of DNA adducts. This work was extended to assess in vitro DNA adduct formation with the cell-free and cell-based assays. Accelerator Mass Spectrometry (AMS) was used for detection and semi-quantification of DNA adducts formed by 14C-labeled alkylanilines. Data indicated 3,5-DMA formed high levels of DNA adducts, suggesting that it is a potent carcinogen. Additionally, the levels of adducts exhibited inter-species variation. The effects of phase II metabolism on adduct formation were evaluated by comparing the results obtained from the two types of assays and by assessing the effects of phase II enzyme cofactors on the results of cell-free assay.; (cont.) Results implied that sulfotransferase-mediated metabolism promotes cytotoxicity and mutagenicity of all three alkylanilines; however...

Effects of line-blocking on the non-LTE Fe I spectral line formation.

Collet, Remo; Asplund, Martin; Thevenin, F
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
65.45%
The effects of background line opacity (line-blocking) in statistical equilibrium calculations for Fe in late-type stellar atmospheres have been investigated using an extensive and up-to-date model atom with radiative data primarily from the IRON Project. The background metal line opacities have been computed using data from the MARCS stellar model atmospheres. While accounting for this line opacity is important at solar metallicity, the differences between calculations including and excluding line-blocking at low metallicity are insignificant for the non-local thermodynamic equilibrium (non-LTE) abundance corrections for Fe I lines. The line-blocking has no impact on the non-LTE effects of Fe II lines. The dominant uncertainty in Fe non-LTE calculations for metal-poor stars is still the treatment of the inelastic H I collisions, which here have been included using scaling factors to the classical Drawin formalism, and whether or not thermalisation of the high Fe I levels to Fe II ground state should be enforced. Without such thermalisation, the Fe I non-LTE abundance corrections are substantial in metal-poor stars: about 0.3 dex with efficient (i.e. Drawin-like) H I collisions and ≲0.5 dex without. Without both thermalisation and H I collisions...