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The C₃H 10T1/2 mouse embryo transformation assay : the role of radiation quality and dose-rateHall, Susan Claire January 1990 (has links)
No description available.
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The biological Effect of Mosquito Larvae by Ultrasound ExposureHu, Shu-Hua 04 September 2003 (has links)
Abstract
The objective of this thesis is to study the biological effects of larvae of Aedes albopictus induced by ultrasound exposure. Ultrasound is widely used in medical and biological techniques, most of them are cell killing or tumor eliminating by high-intensity ultrasound. In order to analyse the influences of ultrasound biological effects in vivo, the larvae of mosquito, in this research, were exposed to continuous-wave ultrasound.
Some preliminary observations were made with 0-day larvae. The oscillation of the trachea in larvae in response to the ultrasound radiation is simulated using Miller¡¦s cylindrical-bubble activation theory. Dimensions of tubes in the respiratory system of larvae were measured by microscope. The resonant frequency of the tracheae were calculated, and its range is about 0.6¡ã1.5 MHz.
It was observed that the tracheae in 0-day larvae were ruptured by ultrasound exposure, and the larvae were dead in the duration of growth, some fourth instar larvae failed to mature into pupae. The maximum mosquito larvae mortality was with 1 MHz irradiation, and it¡¦s in good agreement with the resonant frequency calculated in this paper.
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Investigation of the aggregation of nanoparticles in aqueous medium and their physicochemical interactions at the nano-bio InterfaceLi, Kungang 08 June 2015 (has links)
Owing to their unique physical, chemical, and mechanical properties, nanoparticles (NPs) have been used, or are being evaluated for use, in many fields (e.g., personal care and cosmetics, pharmaceutical, energy, electronics, food and textile). However, concerns regarding the environmental and biological implications of NPs are raised alongside the booming nanotechnology industry. Numerous studies on the biological effect of NPs have been done in the last decade, and many mechanisms have been proposed. In brief, mechanisms underlying the adverse biological effect caused by NPs can be summarized as: (i) indirect adverse effect induced by reactive oxygen species (ROS) generated by NPs, (ii) indirect adverse effect induced by released toxic ions, and (iii) adverse effect induced by direct interactions of NPs with biological systems. Up to now, most efforts have been focused on the first two mechanisms. In contrast, adverse biological effects induced by direct nano-bio interactions are the least researched. This is largely because of the complexity and lack of suitable techniques for characterizing the nano-bio interface.
This dissertation aims at advancing our understanding of the nano-bio interactions leading to the adverse biological effect of NPs. Specifically, it is comprised of three parts. Firstly, because the aggregation of NPs alters particle size and other physicochemical properties of NPs, the property of NPs reaching and interacting with biological cells is very likely different from that of what we feed initially. Consequently, as the first step and an essential prerequisite for understanding the biological effect of NPs, NP aggregation is investigated and models are developed for predicting the stability and the extent of aggregation of NPs. Secondly, interactions between NPs and cell membrane are studied with paramecium as the model cell. Due to the lack of cell wall, the susceptible cell membrane of paramecium is directly exposed to NPs in the medium. The extent and strength of direct nano-cell membrane interaction is evaluated and quantified by calculating the interfacial force/interaction between NPs and cell membrane. A correlation is further established between the nano-cell membrane interaction and the lethal acute toxicity of NPs. We find NPs that have strong association or interaction with the cell membrane tend to induce strong lethal effects. Lastly, we demonstrate systematic experimental approaches based on atomic force microscope (AFM), which allows us to characterize nano-bio interfaces on the single NP and single-molecular level, coupled with modeling approaches to probe the nano-DNA interaction. Using quantum dots (QDs) as a model NP, we have examined, with the novel application of AFM, the NP-to-DNA binding characteristics including binding mechanism, binding kinetics, binding isotherm, and binding specificity. We have further assessed the binding affinity of NPs for DNA by calculating their interaction energy on the basis of the DLVO models. The modeling results of binding affinity are validated by the NP-to-DNA binding images acquired by AFM. The investigation of the relationship between the binding affinity of twelve NPs for DNA with their inhibition effects on DNA replication suggests that strong nano-DNA interactions result in strong adverse genetic effects of NPs.
In summary, this dissertation has furthered our understanding of direct nano-bio interactions and their role in the biological effect of NPs. Furthermore, the models developed in this dissertation lay the basis for building an “ultimate” predictive model of biological effects of NPs that takes into account multiple mechanisms and their interactions, which would save a lot of testing costs and time in evaluating the risk of NPs.
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[en] VERIFICATION OF THE RADIATION LEVELS EMITTED BY ERBS ANTENNAE AND THE PERCEPTION OF HE CLOSE COMMUNITIES / [pt] VERIFICAÇÃO DOS NÍVEIS DE RADIAÇÃO EMITIDOS PELAS ANTENAS DAS ERBS E A PERCEPÇÃO DAS COMUNIDADES PRÓXIMASSIDNEY CARLOS DA CRUZ 31 March 2006 (has links)
[pt] Com a implantação e disseminação de novos sistemas
celulares,principalmente a partir dos anos 80, novas
tecnologias foram desenvolvidas, o número de celulares
cresceu de forma surpreendente, como conseqüência, o
aumento de Estações Radio Base. É fato, também, que as
pessoas, de modo geral, estão expostas às radiações
emitidas pelas ERBs através de suas antenas. Como a
população, a mais interessada na busca de respostas
adequadas e convincentes, não tem qualquer controle
sobre tais níveis, cabe as autoridades a preocupação
maior em garantir que os níveis de exposição não
sejam excedidos. A partir deste quadro preocupante a OMS
estabeleceu em 1996 o International EMF Project para
avaliar as evidências cientificas
existentes sobre possíveis efeitos de campos
eletromagnéticos à saúde,incluindo nestes os efeitos
emitidos pelos próprios aparelhos celulares e por
suas estações rádio-base. Este trabalho pretende
contribuir no equacionamento
desta questão, tão polemica e controversa. Iniciando com
a evolução do número
de celulares no Brasil, mostrando as funções básicas dos
componentes de uma estrutura celular. No momento
seguinte são mostrados alguns efeitos biológicos
relacionados à radiação não-ionizante pesquisados na
literatura. Tais efeitos,
polêmicos e controversos, são amplamente discutidos por
especialistas de diferentes linhas de pesquisa. O
trabalho mostra, também, os resultados de uma
campanha de medidas com as densidades de potência
obtidas através de duas
metodologias. Inclui, também, conceitos e
características de percepção de risco
e alguns resultados da pesquisa qualitativa de campo. Ao
final são apresentadas
as conclusões e sugestões para trabalhos futuros
relacionados ao tema. / [en] With the implantation and spread of new cellular systems,
mainly starting
from the eighties, new technologies were developed, the
number of cellular grew
in a surprising way, as consequence, the Base Stations
increased, too. The
people, in general, are exposed to the radiations emitted
by ERBs antennae. As
the population doesn't have any control on such levels,
people are always looking
for appropriate and convincing answers. So, the
authorities are concerned in
guaranteeing that the exposition levels are not exceeded.
Based on preoccupying
issue, the World Health Organization (WHO) established in
1996 International
EMF Project to verify the scientific evidence of possible
health effects of
Electromagnetic Field. This work intends to contribute in
the set out of this
controversial subject. At first, the cellular number
evolution in Brazil is presented.
In addition, the basic cellular structure components
functions are described. The
following topic presents some biological effects related
to the non-ionizing
radiation are presented according to the literature. Such
controversial effects are
discussed thoroughly by specialists of different research
lines. This work also
shows the power densities results obtained through two
methodologies.
Afterwards, concepts, risk perception characteristics and
some results from a
qualitative research are presented. At the end, the
conclusions and suggestions
for future works related to the same theme are shown.
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Indirect Consequences of Exposure to Radiation in Doses Relevant to Nuclear Incidents and Accidents / INDIRECT CONSEQUENCES OF NUCLEAR INCIDENTS/ACCIDENTSFernando, Chandula 11 1900 (has links)
At low doses, relevant to nuclear incidents and accidental releases of radioactivity, the detriment of radiation extends beyond direct effects. This thesis investigates genomic instability, a subclass of non-targeted effects where damage and lethality is transmitted vertically and expressed in the progeny of cells many generations after initial radiation exposure. Through a series of experiments using clonogenic assay of human and fish cell culture, studies described in this thesis describe lethal mutations, hyper radiosensitivity and increased radioresistance – processes involving repair mechanisms that dictate survival in cells exposed to low doses. Further study investigates the difference in the relative biological effect of alpha particle radiation compared to what is expected at high doses. Results demonstrate increased radioresistance in a human cell line while also revealing increased lethality in a fish cell line confirming the need for consideration of dose-dependence as well as variance in behaviors of different cell lines and species. It is hoped the conclusions of this thesis will inspire the creation of protocols with greater attention to the indirect consequences of exposure to radiation at doses relevant to nuclear incidents and accidents. / Thesis / Master of Science (MSc)
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