1,291 research outputs found
Potential of Diagnostic Microbiology for Treatment and Prognosis of Dental Caries and Periodontal Diseases
Most evidence suggests that only a finite number of bacteria are responsible for dental caries and periodontal diseases. This knowledge led to the development of microbial tests which can identify suspected pathogens. Current evaluation of the diagnostic power of microbial tests has shown that they have a low sensitivity and a low prognostic value. Despite these shortcomings, there are valid indications for microbiological-based diagnosis. Salivary microbial tests for the detection of mutans streptococci and lactobacilli may be useful, for example, in young children, oligosialic patients, and orthodontic patients. These tests can be used to monitor the success of chemopreventive measures or compliance with dietary recommendations. Microbial diagnosis may also be valuable in the treatment of early-onset periodontitis or in subjects who respond poorly to periodontal therapy. The use of microbial tests to monitor the efficacy of chemotherapy or mechanical treatment is of particular interest.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68094/2/10.1177_10454411960070030401.pd
Morphometric versus densitometric assessment of coronary vasomotor tone-an overview
The main advantage of the morphometric approach is that the spatial orientation of the vessel with respect to the image intensifier is not very important. Its most severe limitations are that reasonable accuracy can only be obtained with circular lumina, and that accuracy decreases rapidly with the vessel diameter. The densitometric approach is much less dependent on the shape of the lumen and on the correct identification of the vessel wall in the image. A further essential advantage is that one measures directly the cross-sectional area of the vessel instead of a ‘diameter' of low haemodynamic relevance. Severe requirements must however be met if the potential accuracy of densitometry is to be fully exploited. The morphometric approach seems thus preferable for absolute or relative diameter measurements on intact vessels, while densitometry is superior in case of irregular or small lumina. Morphometric calibration using the injection catheter can induce non-negligible errors in both approaches. Grid calibration is probably more accurate, but also more tedious. In the densitometric approach, ‘3D-calibration' by help of a cube of known size allows also determination of the spatial orientation of the vessel in space. This solution requires however biplane imagin
Novel method for the analysis of clathrates
Recently various of applications of clathrates, such as the concentration of juices, water desalination and wastewater treatment have gained the attention in industry and research alike. In this paper we present a novel method based on photoacoustic spectroscopy for the analysis of clathrates in aqueous environments. The herein proposed self-referencing method poses a simple and robust approach identifying and determining the formation of clathrates via the measurement of the Grüneisen coefficient using a PVDF-based photoacoustic spectroscope. This research holds high potential for industrial applications of clathrates helping to save time, energy and resources during the clathrate forming process by indicating clathrate formation
Shear-induced reaction-limited aggregation kinetics of Brownian particles at arbitrary concentrations
The aggregation of interacting Brownian particles in sheared concentrated
suspensions is an important issue in colloid and soft matter science per se.
Also, it serves as a model to understand biochemical reactions occurring in
vivo where both crowding and shear play an important role. We present an
effective medium approach within the Smoluchowski equation with shear which
allows one to calculate the encounter kinetics through a potential barrier
under shear at arbitrary colloid concentrations. Experiments on a model
colloidal system in simple shear flow support the validity of the model in the
range considered. By generalizing Kramers' rate theory to the presence of
collective hydrodynamics, our model explains the significant increase in the
shear-induced reaction-limited aggregation kinetics upon increasing the colloid
concentration
Cryo-Preparation and Planar Magnetron Sputtering for Low Temperature Scanning Electron Microscopy
Cryo-preparation is a reliable technique for the structural investigation of food products in low temperature scanning electron microscopy (SEM). Artifacts, such as, the segregation of water/non-water ingredients, occur during the freezing process by the crystallization of ice; they can be helpful for correct interpretation of visualized details, e.g., the detection of water containing compartments. The size of the segregation structures depends on water concentration and specimen thickness. The condensation of water vapor (ice contamination) is influenced by the specimen temperature and the partial pressure of the water inside the vacuum system. Furthermore, the evaporation (sublimation, etching) of specimen water can be regulated by monitoring the specimen temperature. Sublimation under SEM observation, i.e., in situ etching at low acceleration voltage, allows the progress of etching to be observed continuously, prior to the coating of the specimen inside a dedicated cryo-preparation system attached to the SEM. Coating of specimens provides superior structural resolution compared with the observation of uncoated samples. A coating layer of platinum ( ~ 1-2 nm thick), deposited on a cold substrate by planar magnetron sputtering, is almost homogenous and has a density close to that of the solid metal. Its use allows bulk biological specimens to be observed in low temperature SEM with a structural resolution up to the visualization of transmembrane proteins
Homotopy Theory of Strong and Weak Topological Insulators
We use homotopy theory to extend the notion of strong and weak topological
insulators to the non-stable regime (low numbers of occupied/empty energy
bands). We show that for strong topological insulators in d spatial dimensions
to be "truly d-dimensional", i.e. not realizable by stacking lower-dimensional
insulators, a more restrictive definition of "strong" is required. However,
this does not exclude weak topological insulators from being "truly
d-dimensional", which we demonstrate by an example. Additionally, we prove some
useful technical results, including the homotopy theoretic derivation of the
factorization of invariants over the torus into invariants over spheres in the
stable regime, as well as the rigorous justification of replacing by
and by as is common in the current
literature.Comment: 11 pages, 3 figure
Universal scaling behavior at the upper critical dimension of non-equilibrium continuous phase transitions
In this work we analyze the universal scaling functions and the critical
exponents at the upper critical dimension of a continuous phase transition. The
consideration of the universal scaling behavior yields a decisive check of the
value of the upper critical dimension. We apply our method to a non-equilibrium
continuous phase transition. But focusing on the equation of state of the phase
transition it is easy to extend our analysis to all equilibrium and
non-equilibrium phase transitions observed numerically or experimentally.Comment: 4 pages, 3 figure
Ultrasonic field mapping through a multimode optical fibre
Miniaturising ultrasonic field mapping systems could lead to novel endoscopes capable of photoacoustic tomography and other techniques. However, developing high-resolution arrays of sensitive, sub-millimetre scale ultrasound sensors presents a challenge for traditional piezoelectric transducers. To address this challenge, we conceived an ultrasonic detection concept in which an optical ultrasonic sensor array is read out using a laser beam scanned through a 0.24 mm diameter multimode optical fibre using optical wavefront shaping. We demonstrate this system enables ultrasonic field mapping with >2500 measurement points, paving the way to developing miniaturised photoacoustic endoscopes and other ultrasonic systems based on the presented concept
An investigation of standard thermodynamic quantities as determined via models of nuclear multifragmentation
Both simple and sophisticated models are frequently used in an attempt to
understand how real nuclei breakup when subjected to large excitation energies,
a process known as nuclear multifragmentation. Many of these models assume
equilibriumthermodynamics and produce results often interpreted as evidence of
a phase transition. This work examines one class of models and employs standard
thermodynamical procedure to explore the possible existence and nature of a
phase transition. The role of various terms, e.g. Coulomb and surface energy,
is discussed.Comment: 19 two-column format pages with 24 figure
Rapid volumetric photoacoustic tomographic imaging with a Fabry-Perot ultrasound sensor depicts peripheral arteries and microvascular vasomotor responses to thermal stimuli
PURPOSE: To determine if a new photoacoustic imaging (PAI) system successfully depicts (1) peripheral arteries and (2) microvascular circulatory changes in response to thermal stimuli. METHODS: Following ethical permission, 8 consenting subjects underwent PAI of the dorsalis pedis (DP) artery, and 13 completed PAI of the index fingertip. Finger images were obtained after immersion in warm (30-35 °C) or cold (10-15 °C) water to promote vasodilation or vasoconstriction. The PAI instrument used a Fabry-Perot interferometeric ultrasound sensor and a 30-Hz 750-nm pulsed excitation laser. Volumetric images were acquired through a 14 × 14 × 14-mm volume over 90 s. Images were evaluated subjectively and quantitatively to determine if PAI could depict cold-induced vasoconstriction. The full width at half maximum (FWHM) of resolvable vessels was measured. RESULTS: Fingertip vessels were visible in all participants, with mean FWHM of 125 μm. Two radiologists used PAI to correctly identify vasoconstricted fingertip capillary beds with 100% accuracy (95% CI 77.2-100.0%, p < 0.001). The number of voxels exhibiting vascular signal was significantly smaller after cold water immersion (cold: 5263 voxels; warm: 363,470 voxels, p < 0.001). The DP artery was visible in 7/8 participants (87.5%). CONCLUSION: PAI achieves rapid, volumetric, high-resolution imaging of peripheral limb vessels and the microvasculature and is responsive to vasomotor changes induced by thermal stimuli
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