Página 1 dos resultados de 4308 itens digitais encontrados em 0.021 segundos

‣ A hybrid method to characterize the mechanical behaviour of biological hyper-elastic tissues

Ribeiro, J.E.; Lopes, H.; Mendonça, B.; Martins, P.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
460.95785%
The increase of interest in the study of human biological tissues led to the characterization of certain biological materials which have a hyper-elastic mechanical behaviour. Traditionally are used experimental tests to characterize such materials, however, these have been replaced by numerical simulations using finite element codes, with advantages from the point of view of saving time and financial costs. The optical experimental field methods have the advantage, such as the assessment of displacement fields without contact with high resolution, using ordinary white light or laser illumination. Both techniques, experimental and numerical, have limitations in the characterization of hyper-elastic biological tissues. The numerical simulation has different constitutive models, but none of them could characterize completely these materials. In the other hand, most of the optical techniques have a high sensibility which is not adequate for hyper-elastic behaviours. Only the digital image correlation (DIC) has the sensibility range that could allow the measurement of such large displacements. However, the strain fields are computed by the differentiation of displacement fields and this technique could amplify the image noise, in this case the quality of strain fields are not adequate. To overcome these limitations the authors of this work have developed a hybrid method which uses the displacement field obtained with DIC applied in the nodes of a finite element model.

‣ Análise enantiosseletiva da zopiclona, suas impurezas e metabólitos em formulações farmacêuticas e materiais biológicos; Enantioselective analysis of zopiclone, its impurities and metabolites in pharmaceutical formulations and biological materials

Tonon, Milena Araújo
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 05/04/2012 Português
Relevância na Pesquisa
553.66797%
Zopiclona (ZO) é um hipnótico não-benzodiazepínico da classe ciclopirrolonas, indicada para o tratamento da insônia. A ZO é um fármaco quiral administrada como uma mistura racêmica; no entanto, a sua atividade farmacológica está principalmente relacionada com o enatiômero (+)-(S)-ZO, também conhecido como eszopiclona. A ZO é extensivamente metabolizada e os metabólitos principais são a N-desmetil zopiclona (N-Des) e zopiclona-N-óxido (N-Ox). A N-Ox também é uma impureza encontrada na matéria prima. Além dessa impureza, outras oriundas do processo de síntese ou devido à degradação também podem ser encontradas: impureza B (RP29307), impureza C (2-amino-5-cloropiridina, ACP ou RP26695) e RP 48497. Sendo assim, o objetivo desse estudo foi desenvolver métodos de análise enantiosseletiva da ZO, metabólitos e impurezas em formulações farmacêuticas e materiais biológicos. Um método empregando a cromatografia líquida de alta eficiência com detecção por espectrometria de massas (LC-MS-MS) foi desenvolvido e validado para a quantificação simultânea da ZO e de seus metabolitos em plasma de ratos. Os analitos foram isolados das amostras por extração líquido-líquido e separados na coluna CHIRALPAK AD-RH...

‣ Solids rheology for dehydrated food and biological materials

Telis, VRN; Telis-Romero, J.; Gabas, A. L.
Fonte: Taylor & Francis Inc Publicador: Taylor & Francis Inc
Tipo: Artigo de Revista Científica Formato: 759-780
Português
Relevância na Pesquisa
457.4395%
Mechanical properties of food products and biological materials are greatly affected by the drying process and are considered one of the most important quality attributes of dehydrated products. The aim of this work was to review theoretical principles and mathematical modeling, analyzing the measurement techniques and major experimental results that exist in the literature about rheological properties of dehydrated foods and biological materials. Different methods of measuring rheological parameters (fundamental and empiric or imitative) are discussed and major experimental results, as well as the rheological models used in their analysis, published in recent years are presented.

‣ Determination of Hg and Se in biological materials by chemical vapor generation electrothermal vaporization inductively coupled plasma mass spectrometry using isotope dilution calibration after microwave-assisted digestion with Aqua Regia

Vieira,Mariana A.; Ribeiro,Anderson S.; Dias,Lúcia F.; Curtius,Adilson J.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2006 Português
Relevância na Pesquisa
560.95785%
A method for the determination of Hg and Se in biological materials by chemical vapor generation electrothermal vaporization inductively coupled plasma mass spectrometry (CVG-ETV-ICP-MS) using isotope dilution calibration after acid digestion is proposed. The samples were digested with aqua regia in a microwave oven. The isotope ratios used for quantification were: 201Hg/202Hg and 77Se/82Se. A NaBH4 solution stabilized with NaOH was used as reducing agent. The retention and vaporization temperatures in the graphite tube were 150 and 2000 ºC, respectively. Six certified biological materials were analyzed and the obtained concentrations were in good agreement with the certified values according to the t-test for a confidence level of 95%. The detection limits in the sample were 0.7 and 3 ng g-1, for Hg and Se respectively. The method is precise, accurate and adequate for the analysis of biological samples in routine and demonstrates the feasibility of using isotope dilution for the proposed system.

‣ Immobilized Biofilm in Thermophilic Biohydrogen Production using Synthetic versus Biological Materials

Wongthanate,Jaruwan; Polprasert,Chongrak
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 Português
Relevância na Pesquisa
560.95785%
Biohydrogen production was studied from the vermicelli processing wastewater using synthetic and biological materials as immobilizing substrate employing a mixed culture in a batch reactor operated at the initial pH 6.0 and thermophilic condition (55 ± 1ºC). Maximum cumulative hydrogen production (1,210 mL H2/L wastewater) was observed at 5% (v/v) addition of ring-shaped synthetic material, which was the ring-shaped hydrophobic acrylic. Regarding 5% (v/v) addition of synthetic and biological materials, the maximum cumulative hydrogen production using immobilizing synthetic material of ball-shaped hydrophobic polyethylene (HBPE) (1,256.5 mL H2/L wastewater) was a two-fold increase of cumulative hydrogen production when compared to its production using immobilizing biological material of rope-shaped hydrophilic ramie (609.8 mL H2/L wastewater). SEM observation of immobilized biofilm on a ball-shaped HBPE or a rope-shaped hydrophilic ramie was the rod shape and gathered into group.

‣ New European guidelines for the use of stored human biological materials in biomedical research

Trouet, C
Fonte: BMJ Group Publicador: BMJ Group
Tipo: Artigo de Revista Científica
Publicado em /02/2004 Português
Relevância na Pesquisa
468.5432%
The increasing possibilities for using tissue for research and development in genetics and biotechnology have made stored human biological materials more important than ever. Using stored human biological materials raises many legal and ethical questions. On an international level however, the use of these materials has not been regulated in a detailed manner so far. The Council of Europe recently declassified the text of the proposal for an instrument on the use of archived human biological materials in biomedical research for public consultation. The purpose of this paper is to comment on this document regarding its primary goal, which is to protect the rights and fundamental freedoms of the individual whose biological materials could be included in a research project. The guidelines offer good basic protection for sources of identifiable human biological materials but, surprisingly, offer no protection to sources of anonymous or anonymised materials.

‣ On optimal hierarchy of load-bearing biological materials

Zhang, Zuoqi; Zhang, Yong-Wei; Gao, Huajian
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
456.35203%
Load-bearing biological materials such as shell, mineralized tendon and bone exhibit two to seven levels of structural hierarchy based on constituent materials (biominerals and proteins) of relatively poor mechanical properties. A key question that remains unanswered is what determines the number of hierarchical levels in these materials. Here we develop a quasi-self-similar hierarchical model to show that, depending on the mineral content, there exists an optimal level of structural hierarchy for maximal toughness of biocomposites. The predicted optimal levels of hierarchy and cooperative deformation across multiple structural levels are in excellent agreement with experimental observations.

‣ An ab-initio Computational Method to Determine Dielectric Properties of Biological Materials

Abeyrathne, Chathurika D.; Halgamuge, Malka N.; Farrell, Peter M.; Skafidas, Efstratios
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 08/05/2013 Português
Relevância na Pesquisa
463.2788%
Frequency dependent dielectric properties are important for understanding the structure and dynamics of biological materials. These properties can be used to study underlying biological processes such as changes in the concentration of biological materials, and the formation of chemical species. Computer simulations can be used to determine dielectric properties and atomic details inaccessible via experimental methods. In this paper, a unified theory utilizing molecular dynamics and density functional theory is presented that is able to determine the frequency dependent dielectric properties of biological materials in an aqueous solution from their molecular structure alone. The proposed method, which uses reaction field approximations, does not require a prior knowledge of the static dielectric constant of the material. The dielectric properties obtained from our method agree well with experimental values presented in the literature.

‣ Image and Spectral Processing for ToF-SIMS Analysis of Biological Materials

Graham, Daniel J.; Castner, David G.
Fonte: The Mass Spectrometry Society of Japan Publicador: The Mass Spectrometry Society of Japan
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
457.4395%
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments can rapidly produce large complex data sets. Within each spectrum, there can be hundreds of peaks. A typical 256×256 pixel image contains 65,536 spectra. If this is extended to a 3D image, the number of spectra in a given data set can reach the millions. The challenge becomes how to process these large data sets while taking into account the changes and differences between all the peaks in the spectra. This is particularly challenging for biological materials that all contain the same types of proteins and lipids, just in varying concentrations and spatial distributions. This data analysis challenge is further complicated by the limitations in the ion yield of higher mass, more chemically specific species, and potentially by the processing power of typical computers. Herein we briefly discuss analysis methodologies including univariate analysis, multivariate analysis (MVA) methods, and some of the limitations of ToF-SIMS analysis of biological materials.

‣ Chemical functionalization of AFM cantilevers; Chemical functionalization of atomic force microscopy cantilevers

Lee, Sunyoung, S.M. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 52 p.; 3055388 bytes; 3056447 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
461.3327%
Atomic force microscopy (AFM) has been a powerful instrument that provides nanoscale imaging of surface features, mainly of rigid metal or ceramic surfaces that can be insulators as well as conductors. Since it has been demonstrated that AFM could be used in aqueous environment such as in water or various buffers from which physiological condition can be maintained, the scope of the application of this imaging technique has been expanded to soft biological materials. In addition, the main usage of AFM has been to image the material and provide the shape of surface, which has also been diversified to molecular-recognition imaging - functional force imaging through force spectroscopy and modification of AFM cantilevers. By immobilizing of certain molecules at the end of AFM cantilever, specific molecules or functionalities can be detected by the combination of intrinsic feature of AFM and chemical modification technique of AFM cantilever. The surface molecule that is complementary to the molecule at the end of AFM probe can be investigated via specificity of molecule-molecule interaction.; (cont.) Thus, this AFM cantilever chemistry, or chemical functionalization of AFM cantilever for the purpose of chemomechanical surface characterization...

‣ BE.442 Molecular Structure of Biological Materials, Fall 2002; Molecular Structure of Biological Materials

Zhang, Shuguang, Dr.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Português
Relevância na Pesquisa
667.0127%
Basic molecular structural principles of biological materials. Molecular structures of various materials of biological origin, including collagen, silk, bone, protein adhesives, GFP, self-assembling peptides. Molecular design of new biological materials for nanotechnology, biocomputing and regenerative medicine. Graduate students are expected to complete additional coursework.

‣ BE.442 Molecular Structure of Biological Materials, Fall 2005; Molecular Structure of Biological Materials

Zhang, Shuguang, Dr.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Português
Relevância na Pesquisa
471.79938%
Basic molecular structural principles of biological materials. Molecular structures of various materials of biological origin, including collagen, silk, bone, protein adhesives, GFP, self-assembling peptides. Molecular design of new biological materials for nanotechnology, biocomputing and regenerative medicine. Graduate students are expected to complete additional coursework. Description from course home page: This course, intended for both graduate and upper level undergraduate students, will focus on understanding of the basic molecular structural principles of biological materials. It will address the molecular structures of various materials of biological origin, such as several types of collagen, silk, spider silk, wool, hair, bones, shells, protein adhesives, GFP, and self-assembling peptides. It will also address molecular design of new biological materials applying the molecular structural principles. The long-term goal of this course is to teach molecular design of new biological materials for a broad range of applications. A brief history of biological materials and its future perspective as well as its impact to the society will also be discussed. Several experts will be invited to give guest lectures.

‣ Nanomechanics and ultrastructural studies of cortical bone : fundamental insights regarding structure-function, mineral-organic force mechanics interactions, and heterogeneity

Tai, Kuangshin
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 256 leaves
Português
Relevância na Pesquisa
459.91836%
Although the mechanics of bone has been studied extensively at the micro- and macro-scale, the nano-scopic level is perhaps the most illuminating as this is the length scale at which the individual constituents interact. Bone is made primarily up of type I collagen, hydroxyapatite mineral, a variety of non-collagenous proteins, and water. A multitechnique experimental and modeling approach methodology was used break down several of the deformation mechanisms that exist in bone at the nanoscale including the effect of mineral content, cohesive-frictional plasticity, increased ductility through mechanical heterogeneity, and intermolecular forces. To show that mineral content had a significant effect on both nanomechanical properties and ultrastructural deformation mechanisms of bone, partial and complete demineralization was carried out to produce samples ranging from -0-58 wt.% mineral content. Nanoindentation experiments perpendicular to the osteonal axis found a 4-6x increase in stiffness for the -58 wt.% sample compared to the completely demineralized -~0 wt.% samples. These results are discussed in the context of in situ and post-mortem AFM imaging studies which shed light on nanoscale mechanisms of deformation including collagen fibril deformation and pressure induced structural transitions of the mineral component.; (cont.) A finite element elastic-plastic continuum model was able to predict the nanomechanical properties of the different samples on loading and unloading. In addition...

‣ Assembly of biological building blocks for nano- and micro-fabrication of materials

Chiang, Chung-Yi
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 137 p.
Português
Relevância na Pesquisa
454.6235%
Experimental studies were performed to fabricate various material structures using genetically engineered M13 bacteriophage. This virus template showed superior controls of material syntheses from nanoscale to microscale. Structures including nanowires, nanoparticle arrays, hetero-particle arrays, and micro-fibers were fabricated using the engineered MI3 virus as the building block and mineralization platform. The mineralization mechanisms were revealed by alternating the types and amounts of peptide motifs displayed on the viral templates. The results showed the importance of a fused peptide motif to mediate the mineralization process of a material, which was dominated by either physical absorption or chemical nucleation. The potential applications of the materials synthesized using the viral template, including energy generation and biosensors, were also demonstrated. For the first time, several types of highly engineered MI 3 virus were used to fabricate nanostructures such as nanowires, nano-arrays, hetero-particle arrays, and complex nanowires. A type 8 phage library was reported to screen peptide motifs for making nanowires. A multi-functionalized viral template, type 8-3 virus, was engineered and demonstrated to create a variety of nano-archietetures. A type 8+8 virus was used to create complex nanowires embedded with different materials. In addition...

‣ Towards rational design of peptides for selective interaction with inorganic materials

Krauland, Eric Mark
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 141 p.
Português
Relevância na Pesquisa
459.53695%
Utilizing molecular recognition and self-assembly, material-specific biomolecules have shown great promise for engineering and ordering materials at the nanoscale. These molecules, inspired from natural biomineralization systems, are now commonly selected against non-natural inorganic materials through biopanning random combinatorial peptide libraries. Unfortunately, the challenge of studying the biological inorganic interface has slowed the understanding of interactions principles, and hence limited the number of downstream applications. This work focuses on the facile study of the peptide-inorganic interface using Yeast Surface Display. The general approach is to use combinatorial selection to suggest interaction principles followed by rational design to refine understanding. In this pursuit, two material groups-II-VI semiconductors and synthetic sapphire (metal oxides)-are chosen as inorganic targets due to their technological relevance and ease of study. First, yeast surface display (YSD) was established as a broadly applicable method for studying peptide-material interactions by screening a human scFv YSD library against cadmium sulfide (CdS), a II-VI semiconductor. The presence of multiple histidine residues was found to be necessary for mediating cell binding to CdS. As a follow-up...

‣ Open vessel microwave extraction of metals in biological and botanical materials.

LOMBARDI, M. C.; COSTA, L.; NOBREGA, J.; NOGUEIRA, A. R. de A.
Fonte: In: ANNUAL CONFERENCE OF THE FEDERATION OF ANALYTICAL CHEMISTRY AND SPECTROSCOPY SOCIETIES - FACSS, 26.; INTERNATIONAL CONFERENCE ON ANALYTICAL SCIENCES AND SPECTROSCOPY - ICASS, 1999, Vancouver. Proceedings...Vancouver: FACSS, 1999. p.223. Publicador: In: ANNUAL CONFERENCE OF THE FEDERATION OF ANALYTICAL CHEMISTRY AND SPECTROSCOPY SOCIETIES - FACSS, 26.; INTERNATIONAL CONFERENCE ON ANALYTICAL SCIENCES AND SPECTROSCOPY - ICASS, 1999, Vancouver. Proceedings...Vancouver: FACSS, 1999. p.223.
Tipo: Resumo em anais de congresso (ALICE)
Português
Relevância na Pesquisa
464.85105%
The complete sample decomposition is not always necessary when measurements are carried out using optical techniques. Depending on both technique employed and sample matrix characteristics, an extraction procedure can be completely suitable for quantitative determinations. To implement this approach is essential to perform a critical evaluation of the behavior of each element, of the extractor solution, and of the temperature and time of extraction. The temperature can be controlled adopting microwave-assisted procedures that guarantee fast heating and repeatability. In this work an open-vessel microwave system (Star 6, CEM) was employed to investigate the efficiency of the extraction procedures. The extraction of Al, Ca, Cu, Fe, Mg, Mn,:and Zn was evaluated in biological (bovine liver, SRM 1577b, NIST) and botanical (apple leaves, SRM 1515, NIST; trace elements in spinach leaves, SR!vf 1570a, NIST; and commercial teas) materials. The extraction procedures were investigated using 1 or 10% v/v hydrochloric or nitric acid solutions. An alkaline solution containing a mixture of water- soluble tertiary amines (CFA-C, Spectrasol) was also tested. All procedures were carried out at temperatures in the range 80-105 oC during time intervals shorter than 10 min. The analytes were determined by flame and graphite furnace atomic absorption spectrophotometry (Intralab...

‣ Determination of Cobalt in Biological Materials by RNAA Via Induced Short-lived 60mCo

REPINC Urska; BENEDIK LJUDMILA; PIHLAR B.
Fonte: SPRINGER WIEN Publicador: SPRINGER WIEN
Tipo: Articles in Journals Formato: Printed
Português
Relevância na Pesquisa
461.85793%
A procedure for determination of cobalt in biological materials using the short-lived induced radionuclide 60mCo is described. 60mCo has been rarely used as an indicator radionuclide in NAA due to low concentrations usually found in biological materials and due to its short-half life (t1/2 = 10.5 min). Using the described procedure, based on dissolution of the irradiated sample, precipitation of Co with C5H10NNaS2*3H2O, extraction of the complexes formed into toluene, purification and counting by gamma spectrometry, Co was determined in biological materials at ng g-1 levels.; JRC.D.4-Isotope measurements

‣ Genetic engineering of bacteriophage and its applications for biomimetic materials

Lee, Soo-Kwan
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 96 leaves
Português
Relevância na Pesquisa
461.98402%
Filamentous bacteriophage (M13) are excellent biological build block due to their multiple peptide display system including type 8 (complete peptide display at pVIII) and type 83 (complete peptide display at both pVIII and pIII) display systems. Unlike the phagemid systems, the advantage of these systems is that we can get homogenous peptide display on pVIII resulting in uniform placement of selected molecules as well as defined length and width. In this thesis, type 8 and type 83 phage were constructed and used as biological scaffolds to meet the following four specific aims. First, the self-assembly of engineered M13 bacteriophage as a template for Co-Pt crystals was demonstrated. An phage library with an octapeptide library on the major coat protein (pVIII) was used for selection of binders to cobalt ions. Fibrous structures with directionally ordered phage were obtained by interaction with cobalt ions. Co-Pt alloys were synthesized on the fibrous scaffold, and their magnetic properties were characterized. The mineralization showed organized nanoparticles on fibrous bundles with superparamagnetic properties. Second, an in vitro molecular selection method in non-biological conditions for inorganic synthesis was introduced.; (cont.) A phage display peptide library which is resistant to ethanol was constructed and used for selection against titania in 90% ethanol. The selected peptide...

‣ Assembly and detection of viruses and biological molecules on inorganic surfaces

Sinensky, Asher Keeling
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 175 p.
Português
Relevância na Pesquisa
463.43016%
This work is composed of three distinct, albeit related, projects. Each project is an exploration of the ways in which interactions between inorganic surfaces and biological molecules can be advantageously exploited. The first project entitled, Biomolecular Recognition of Crystal Defects extended the phage display technique to the detection of crystal defects. The system used is based on the M13 bacteriophage with 7-residue constrained random sequence on protein III. After considerable experimentation a procedure described as 'Diffuse Selection' was developed for selecting defects on crystal surfaces. Challenges occur because it is difficult to drive phage display towards the selection of particular surface features as opposed to whole surfaces. After multiple iterations, diffuse selection was optimized and consensus sequences were achieved. Virus binding was characterized using Atomic Force Microscopy, Fluorescene Microscopy and Titration. Using a simple bimolecular model, the binding sequence identified through this work is shown to have a binding constant 100,000 times better than a random peptide sequence. The second project entitled, Surface Patterning of Genetically Programmed Viruses, developed a generalizable approach to patterning viruses regardless of the genetic modification made to the virus. Genetic modifications are made in order to create viruses which will construct inorganic materials on their bodies in the appropriate chemical environment. Three generalizable virus patterning approaches were developed based on hydrophobic...

‣ The Review of Nuclear Microscopy Techniques: An Approach for Nondestructive Trace Elemental Analysis and Mapping of Biological Materials

Mulware, Stephen Juma
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
457.4395%
The properties of many biological materials often depend on the spatial distribution and concentration of the trace elements present in a matrix. Scientists have over the years tried various techniques including classical physical and chemical analyzing techniques each with relative level of accuracy. However, with the development of spatially sensitive submicron beams, the nuclear microprobe techniques using focused proton beams for the elemental analysis of biological materials have yielded significant success. In this paper, the basic principles of the commonly used microprobe techniques of STIM, RBS, and PIXE for trace elemental analysis are discussed. The details for sample preparation, the detection, and data collection and analysis are discussed. Finally, an application of the techniques to analysis of corn roots for elemental distribution and concentration is presented.