Página 1 dos resultados de 5411 itens digitais encontrados em 0.023 segundos

‣ The mismatch negativity: A review of underlying mechanisms

Garrido, Marta I.; Kilner, James M.; Stephan, Klaas E.; Friston, Karl J.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /03/2009 Português
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The mismatch negativity (MMN) is a brain response to violations of a rule, established by a sequence of sensory stimuli (typically in the auditory domain) [Näätänen R. Attention and brain function. Hillsdale, NJ: Lawrence Erlbaum; 1992]. The MMN reflects the brain’s ability to perform automatic comparisons between consecutive stimuli and provides an electrophysiological index of sensory learning and perceptual accuracy. Although the MMN has been studied extensively, the neurophysiological mechanisms underlying the MMN are not well understood. Several hypotheses have been put forward to explain the generation of the MMN; amongst these accounts, the “adaptation hypothesis” and the “model adjustment hypothesis” have received the most attention. This paper presents a review of studies that focus on neuronal mechanisms underlying the MMN generation, discusses the two major explanatory hypotheses, and proposes predictive coding as a general framework that attempts to unify both.

‣ Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy

Carriles, Ramón; Schafer, Dawn N.; Sheetz, Kraig E.; Field, Jeffrey J.; Cisek, Richard; Barzda, Virginijus; Sylvester, Anne W.; Squier, Jeffrey A.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artigo de Revista Científica
Português
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We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences.

‣ Invited Review Article: Review of centrifugal microfluidic and bio-optical disks

Nolte, David D.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artigo de Revista Científica
Português
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Spinning biodisks have advantages that make them attractive for specialized biochip applications. The two main classes of spinning biodisks are microfluidic disks and bio-optical compact disks (BioCD). Microfluidic biodisks take advantage of noninertial pumping for lab-on-a-chip devices using noninertial valves and switches under centrifugal and Coriolis forces to distribute fluids about the disks. BioCDs use spinning-disk interferometry, under the condition of common-path phase quadrature, to perform interferometric label-free detection of molecular recognition and binding. The optical detection of bound molecules on a disk is facilitated by rapid spinning that enables high-speed repetitive sampling to eliminate 1∕f noise through common-mode rejection of intensity fluctuations and extensive signal averaging. Multiple quadrature classes have been developed, such as microdiffraction, in-line, phase contrast, and holographic adaptive optics. Thin molecular films are detected through the surface dipole density with a surface height sensitivity for the detection of protein spots that is approximately 1 pm. This sensitivity easily resolves a submonolayer of solid-support immobilized antibodies and their antigen targets. Fluorescence and light scattering provide additional optical detection techniques on spinning disks. Immunoassays have been applied to haptoglobin using protein A∕G immobilization of antibodies and to prostate specific antigen. Small protein spots enable scalability to many spots per disk for high-throughput and highly multiplexed immonoassays.

‣ Clear Cell Entities of the Head and Neck: A Selective Review of Clear Cell Tumors of the Salivary Glands

Said-Al-Naief, Nasser; Klein, Michael J.
Fonte: Humana Press Inc Publicador: Humana Press Inc
Tipo: Artigo de Revista Científica
Português
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Clear cell changes may be observed in virtually any benign or malignant tumor of epithelial, mesenchymal, melanocytic and hematopoeitic derivation not be attributed to variable etiologies. In general, benign and malignant clear cell neoplasms of the head and neck are rare. They may involve various regions and may be of diverse derivations, with only 1–2% of tumors of the salivary glands, jaws and oral mucosa are primarily or almost exclusively composed of clear cells (Maiorano et al., Semin Diagn Pathol 14:203–212, 1997). This review will selectively discuss the clinicopathological features of salivary gland tumors with clear cell changes, which, at times, may pose a diagnostic challenge and dilemma.

‣ The periodontal – endodontic continuum: A review

Sunitha V, Raja; Emmadi, Pamela; Namasivayam, Ambalavanan; Thyegarajan, Ramakrishnan; Rajaraman, Vijayalakshmi
Fonte: Medknow Publications Publicador: Medknow Publications
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
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Periodontal therapy deals with many aspects of the supporting structures, including the prevention and repair of lesions of the gingival sulcus. Endodontics deals primarily with disease of the pulp and periapical tissues. The success of both periodontal and endodontic therapy depends on the elimination of both disease processes, whether they exist separately or as a combined lesion. The relationship between periodontal and endodontic disease has been a subject of speculation for many years. This paper aims at presenting a comprehensive review of several aspects of perio-endo lesions.

‣ Stem cell therapy – Hype or hope? A review

Nadig, Roopa R
Fonte: Medknow Publications Publicador: Medknow Publications
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
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While the regeneration of a lost tissue is known to mankind for several years, it is only in the recent past that research on regenerative medicine/dentistry has gained momentum and eluded the dramatic yet scientific advancements in the field of molecular biology. The growing understanding of biological concepts in the regeneration of oral/dental tissues coupled with experiments on stem cells is likely to result in a paradigm shift in the therapeutic armamentarium of dental and oral diseases culminating in an intense search for “biological solutions to biological problems.” Stem cells have been successfully isolated from variety of human tissues including orofacial tissues. Initial evidence from pioneering studies has documented the likely breakthrough that stem cells offer for various life-threatening diseases that have so far defeated modern medical care. The evidence gathered so far has propelled many elegant studies exploring the role of stem cells and their manifold dental applications. This review takes you on a sojourn of the origin of stem cells, their properties, characteristics, current research, and their potential applications. It also focuses on the various challenges and barriers that we have to surmount before translating laboratory results to successful clinical applications heralding the dawn of regenerative dentistry.

‣ Electrosurgery in aesthetic and restorative dentistry: A literature review and case reports

Bashetty, Kusum; Nadig, Gururaj; Kapoor, Sandhya
Fonte: Medknow Publications Publicador: Medknow Publications
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
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Electrosurgery has been used in dentistry for more than half a century. There is abundant literature on electrosurgery dating back more than a century. During the past three decades, a substantial increase in minimally invasive surgery and microvascular surgery prompted greater use of electrosurgery. Although this surge in utilization has resulted in new applications, equipment features, problems and solutions, the use of electrosurgery in the field of restorative dentistry has remained relatively unchanged. The presence of conflicting and sometimes confusing information on electrosurgical wound healing in the dental literature is the most likely reason. This article briefly explains the literature review of electrosurgery and clinical application of electrosurgery in aesthetic and restorative dentistry.

‣ Role of titanium tetrafluoride (TiF4) in conservative dentistry: A systematic review

Wahengbam, Pragya; Tikku, A P; Lee, Wahengbam Bruce
Fonte: Medknow Publications Publicador: Medknow Publications
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
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The role of fluoride to reduce demineralization and enhance remineralization of dental hard tissue has been well documented. Different forms of fluoride solutions have been topically used in dentistry as prophylactic agents against tooth decay. In the recent past, metal fluorides, especially titanium tetrafluoride, have become popular in the fraternity of dental research due to their unique interaction with dental hard tissue. Many studies on titanium tetrafluoride, with positive and negative conclusions, have been published in many research journals. This gives the reader a plethora of inconclusive results with one study neutralizing the outcome of other, which confuses us regarding the present status of titanium tetrafluoride in the field of dentistry. This is an endeavor to organize and present the various studies of this unique compound, to provide us with a lucid overall review of its versatile potential application in dentistry, along with its fallacy/drawbacks. We have discussed its role as a cariostatic agent, pit and fissure sealant, tooth desensitizer, against dental erosion, as a root canal irrigant and others.

‣ Human Papillomavirus in Non-Oropharyngeal Head and Neck Cancers: A Systematic Literature Review

Isayeva, Tatyana; Li, Yufeng; Maswahu, Daniel; Brandwein-Gensler, Margaret
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 03/07/2012 Português
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Perhaps one of the most important developments in head and neck oncology of the past decade is the demonstration that patients with human papillomavirus (HPV)-mediated oropharyngeal cancers have significantly improved outcomes, compared to HPV-negative counterpart patients. This has become the basis for clinical trials investigating the impact on “treatment deintensification” for patients with HPV-mediated oropharyngeal cancers. Unfortunately, the significance of HPV in non-oropharyngeal head and neck cancers is much less certain. Our goal is to systematically review the published data regarding the role HPV in carcinomas of the oral cavity, larynx, sinonasal tract and nasopharynx with respect to HPV detection frequency, viral activity, and association with outcome. We also present preliminary data on HPV16/18 transcriptional status in oral cavity carcinomas, as well as salivary gland neoplasia, as determined by nested reverse transcription PCR for HPV E6/E7 RNA. The weighted prevalence (WP) of HPV DNA detection in 4,195 oral cavity cancer patients is 20.2 %, (95 % CI 16.0 %, 25.2 %). HPV16 is the most common type detected. Importantly, no data currently demonstrates a significant association between the presence of HPV DNA and improved outcome. The WP of HPV DNA in 1...

‣ Review of “orthopaedic biomechanics” edited by Beth A. Winkelstein

Samuel, Solomon P; Tiedeken, Nathan C
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 18/04/2013 Português
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This article is a review of the book “orthopaedic biomechanics” edited by Beth A. Winkelstein. This book (hardcover) was published by CRC Press, Taylor & Francis Group, FL in 2012. The contents of the book and its relevance to orthopedic research or practice is discussed in this invited review.

‣ Book review of “Joining and assembly of medical materials and devices” edited by Y. (Norman) Zhou and Mark D. Breyen

Samuel, Solomon P; Tiedeken, Nathan C
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 08/09/2013 Português
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This article is a review of the book “Joining and assembly of medical materials and devices” edited by Y. (Norman) Zhou and Mark D. Breyen. This book (hardcover) was published by Woodhead Publishing, Cambridge, UK in 2013. The contents of the book and its relevance to medical device design and education are discussed in this invited review.

‣ Invited Review Article: Methods for imaging weak-phase objects in electron microscopy

Glaeser, Robert M.
Fonte: AIP Publishing LLC Publicador: AIP Publishing LLC
Tipo: Artigo de Revista Científica
Português
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Contrast has traditionally been produced in electron-microscopy of weak phase objects by simply defocusing the objective lens. There now is renewed interest, however, in using devices that apply a uniform quarter-wave phase shift to the scattered electrons relative to the unscattered beam, or that generate in-focus image contrast in some other way. Renewed activity in making an electron-optical equivalent of the familiar “phase-contrast” light microscope is based in part on the improved possibilities that are now available for device microfabrication. There is also a better understanding that it is important to take full advantage of contrast that can be had at low spatial frequency when imaging large, macromolecular objects. In addition, a number of conceptually new phase-plate designs have been proposed, thus increasing the number of options that are available for development. The advantages, disadvantages, and current status of each of these options is now compared and contrasted. Experimental results that are, indeed, superior to what can be accomplished with defocus-based phase contrast have been obtained recently with two different designs of phase-contrast aperture. Nevertheless, extensive work also has shown that fabrication of such devices is inconsistent...

‣ Book review of “Imaging in Cellular and Tissue Engineering” edited by Y Hanry Yu and Nur Aida Abdul Rahim

Brey, Eric Michael
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 23/06/2014 Português
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This article is a review of the book “Imaging in Cellular and Tissue Engineering” (ISBN-13: 978-1439848036, $149.95, 298 Pages, 114 Illustrations) edited by Y Hanry Yu and Nur Aida Abdul Rahim published by the CRC Press (Taylor&Francis) in 2013. The contents of the book and its relevance to tissue engineering and regenerative medicine are discussed in this invited review.

‣ Characterization of Dietary Energy in Swine Feed and Feed Ingredients: A Review of Recent Research Results

Velayudhan, D. E.; Kim, I. H.; Nyachoti, C. M.
Fonte: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST) Publicador: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST)
Tipo: Artigo de Revista Científica
Publicado em /01/2015 Português
Relevância na Pesquisa
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Feed is single most expensive input in commercial pork production representing more than 50% of the total cost of production. The greatest proportion of this cost is associated with the energy component, thus making energy the most important dietary in terms of cost. For efficient pork production, it is imperative that diets are formulated to accurately match dietary energy supply to requirements for maintenance and productive functions. To achieve this goal, it is critical that the energy value of feeds is precisely determined and that the energy system that best meets the energy needs of a pig is used. Therefore, the present review focuses on dietary supply and needs for pigs and the available energy systems for formulating swine diets with particular emphasis on the net energy system. In addition to providing a more accurate estimate of the energy available to the animal in an ingredient and the subsequent diet, diets formulated using the this system are typically lower in crude protein, which leads to additional benefits in terms of reduced nitrogen excretion and consequent environmental pollution. Furthermore, using the net energy system may reduce diet cost as it allows for increased use of feedstuffs containing fibre in place of feedstuffs containing starch. A brief review of the use of distiller dried grains with solubles in swine diets as an energy source is included.

‣ Auditory hallucinations: A review of the ERC “VOICE” project

Hugdahl, Kenneth
Fonte: Baishideng Publishing Group Inc Publicador: Baishideng Publishing Group Inc
Tipo: Artigo de Revista Científica
Português
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In this invited review I provide a selective overview of recent research on brain mechanisms and cognitive processes involved in auditory hallucinations. The review is focused on research carried out in the “VOICE” ERC Advanced Grant Project, funded by the European Research Council, but I also review and discuss the literature in general. Auditory hallucinations are suggested to be perceptual phenomena, with a neuronal origin in the speech perception areas in the temporal lobe. The phenomenology of auditory hallucinations is conceptualized along three domains, or dimensions; a perceptual dimension, experienced as someone speaking to the patient; a cognitive dimension, experienced as an inability to inhibit, or ignore the voices, and an emotional dimension, experienced as the “voices” having primarily a negative, or sinister, emotional tone. I will review cognitive, imaging, and neurochemistry data related to these dimensions, primarily the first two. The reviewed data are summarized in a model that sees auditory hallucinations as initiated from temporal lobe neuronal hyper-activation that draws attentional focus inward, and which is not inhibited due to frontal lobe hypo-activation. It is further suggested that this is maintained through abnormal glutamate and possibly gamma-amino-butyric-acid transmitter mediation...

‣ Invited Review: Decoding the pathophysiological mechanisms that underlie RNA dysregulation in neurodegenerative disorders: a review of the current state of the art

Walsh, M J; Cooper-Knock, J; Dodd, J E; Stopford, M J; Mihaylov, S R; Kirby, J; Shaw, P J; Hautbergue, G M
Fonte: BlackWell Publishing Ltd Publicador: BlackWell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
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Altered RNA metabolism is a key pathophysiological component causing several neurodegenerative diseases. Genetic mutations causing neurodegeneration occur in coding and noncoding regions of seemingly unrelated genes whose products do not always contribute to the gene expression process. Several pathogenic mechanisms may coexist within a single neuronal cell, including RNA/protein toxic gain-of-function and/or protein loss-of-function. Genetic mutations that cause neurodegenerative disorders disrupt healthy gene expression at diverse levels, from chromatin remodelling, transcription, splicing, through to axonal transport and repeat-associated non-ATG (RAN) translation. We address neurodegeneration in repeat expansion disorders [Huntington's disease, spinocerebellar ataxias, C9ORF72-related amyotrophic lateral sclerosis (ALS)] and in diseases caused by deletions or point mutations (spinal muscular atrophy, most subtypes of familial ALS). Some neurodegenerative disorders exhibit broad dysregulation of gene expression with the synthesis of hundreds to thousands of abnormal messenger RNA (mRNA) molecules. However, the number and identity of aberrant mRNAs that are translated into proteins – and how these lead to neurodegeneration – remain unknown. The field of RNA biology research faces the challenge of identifying pathophysiological events of dysregulated gene expression. In conclusion...

‣ Stellar magnetic activity and Star-Planet Interactions (invited review)

Poppenhaeger, K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/11/2014 Português
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Stellar magnetic activity is an important factor in the formation and evolution of exoplanets. Magnetic phenomena like stellar flares, coronal mass ejections, and high-energy emission affect the exoplanetary atmosphere and its mass loss over time. One major question is whether the magnetic evolution of exoplanet host stars is the same as for stars without planets; tidal and magnetic interactions of a star and its close-in planets may play a role in this. Stellar magnetic activity also shapes our ability to detect exoplanets with different methods in the first place, and therefore we need to understand it properly to derive an accurate estimate of the existing exoplanet population. Here I review recent theoretical and observational results, as well as outline some avenues for future progress.; Comment: Invited review for the CoRoT Symposium 3 / Kepler KASC-7 joint meeting, Toulouse, July 2014. To be published by EPJ Web of Conferences

‣ X-rays of Stellar Coronae with Chandra and XMM-Newton: Flares and Elemental Composition in Stellar Atmospheres (Invited review)

Audard, Marc
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/09/2004 Português
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Observations of magnetically active stars with Chandra and XMM-Newton have deepened our knowledge of the physics of the atmospheres in late-type stars. In this review paper, I discuss two topics that have profited significantly from Chandra and XMM-Newton. Of particular interest, studies of the elemental composition of stellar coronae have taken advantage of the high spectral resolution available with the grating instruments on board these satellites. I summarize the status of our knowledge and discuss the elemental composition in a variety of stellar coronae. I also focus on the topic of flares in stellar coronae, and review the contributions made by XMM-Newton and Chandra to X-ray and multi-wavelength studies.; Comment: Invited review to appear in "Proc. 13th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun", Hamburg (Germany), 5-9 July 2004, F.Favata et al., eds. (ESA-SP, in press). This is a low-resolution paper; a high-resolution PDF is available at http://www.astro.columbia.edu/~audard/publ/cs13/review.pdf

‣ Multiple star systems observed with CoRoT and Kepler (invited review)

Southworth, John
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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The CoRoT and Kepler satellites were the first space platforms designed to perform high-precision photometry for a large number of stars. Multiple systems display a wide variety of photometric variability, making them natural benefactors of these missions. I review the work arising from CoRoT and Kepler observations of multiple systems, with particular emphasis on eclipsing binaries containing giant stars, pulsators, triple eclipses and/or low-mass stars. Many more results remain untapped in the data archives of these missions, and the future holds the promise of K2, TESS and PLATO.; Comment: Invited review for the CoRoT Symposium 3 / Kepler KASC-7 joint meeting, Toulouse, July 2014. To be published by EPJ Web of Conferences. Version 2 corrects errors with 4 references, and also changes the format for all references because they were not indexed by NASA ADS

‣ Observational studies of transiting extrasolar planets (invited review)

Southworth, John
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/11/2014 Português
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The study of transiting extrasolar planets is only 15 years old, but has matured into a rich area of research. I review the observational aspects of this work, concentrating on the discovery of transits, the characterisation of planets from photometry and spectroscopy, the Homogeneous Studies project, starspots, orbital obliquities, and the atmospheric properties of the known planets. I begin with historical context and conclude with a glance to a future of TESS, CHEOPS, Gaia and PLATO.; Comment: Invited review paper presented at Living Together: Planets, Host Stars and Binaries (Litomysl, Czech Republic, September 2014). 15 pages, 9 figures, to be published in ASP Conf. Ser. TEPCat is available at: http://www.astro.keele.ac.uk/jkt/tepcat/