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PubMed2005

[Radial basis function networks and IR spectrometry applied for identification of official rhubarb samples].

The Fourier transform infrared spectrometry (FTIRS) and radial basis function neural network (RBF-NN) have been applied to develop classification models for identifying official and unofficial rhubarb samples. The original data were compressed from 775 variables to 49 variables by using wavelet transformation method. The compressed spectra with reduced variables maintain the characteristics of the IR spectra and speed up the network training process. The effects of network parameters including error goal and spread constant, were investigated. The rate of correct classification is up to 97.78% at optimized conditions. Results show that the combination of IRS and ANN can be used as fast and convenient tool for identification of Chinese herbal samples.

Algorithms↗
PubMed2003

Using a modified standard microscope to generate virtual slides.

A standard microscope was reconfigured as a virtual slide generator by adding a Prior Scientific H101 robotic stage with H29 controller and 0.1 microm linear scales and a Hitachi HV-C20 3CCD camera. Media Cybernetics Image Pro Plus version 4 (IP4) software controlled stage movement in the X-, Y-, and Z-axis, whereas a Media Cybernetics Pro-Series Capture Kit captured images at 640 x 480 pixels. Stage calibration, scanning algorithms, storage requirements, and viewing modes were standardized. IP4 was used to montage the captured images into a large virtual slide image that was subsequently saved in TIF or JPEG format. Virtual slides were viewed at the workstation using the IP4 viewer as well as Adobe Photoshop and Kodak Imaging. MGI Zoom Server delivered the virtual slides to the Internet, and MicroBrightField's Neuroinformatica viewing software provided a browser-based virtual microscope interface together with labeling tools for annotating virtual slides. The images were served from a Windows 2000 platform with 2 GB RAM, 500 GB of disk storage, and a 1.0 GHz P4 processor. To conserve disk space on the image server, TIF files were converted to the FlashPix (FPX) file format using a compression ratio of 10:1. By using 4x, 10x, 20x, and 40x objectives, very large gigapixel images of tissue whole-mounts and tissue arrays with high quality and morphologic detail are now being generated for teaching, publication, research, and morphometric analysis. Technical details and a demonstration of our system can be found on the Web at http://virtualmicroscope.osu.edu.

Anatomy, Cross-Sectional↗
PubMed2005

Characterization of the mechanical properties of polymeric chromatographic particles by micromanipulation.

Chromatographic particles should not possess only desirable surface chemical properties but also mechanical properties. The latter determine the deformation of the particles under hydrodynamic conditions of packed beds and further the pressure drop. Understanding the mechanical properties of chromatographic particles is essential to successful design and operation of such processing equipment. The mechanical properties of single chromatographic particles made of different formulations and with different surface modifications were characterized by a novel micromanipulation technique. The principle of this technique is to compress single particles between two parallel surfaces. The force being imposed on the particles and their deformation under compression are measured simultaneously. The particles range from 30 to 300 microm, depending on their formulation. 10-30 particles from each sample were compressed up to a particle deformation of 70% in order to get statistically representative data. Particles for hydrophobic interaction chromatography were proved more stable than resins for ion exchange or gel filtration. The difference is remarkable in dry state and is less in wet state. Water seems to "level out" the differences in mechanical stability of resins. The stability seems to be also dependent on the speed of water release out of the resins.

Algorithms↗
PubMed2003

Preterm premature rupture of the membranes.

Preterm premature rupture of membranes (PROM) affects over 120,000 pregnancies annually in the United States and is associated with significant maternal, fetal, and neonatal risk. Management of PROM requires an accurate diagnosis as well as evaluation of the risks and benefits of continued pregnancy or expeditious delivery. An understanding of gestational age-dependent neonatal morbidity and mortality is important in determining the potential benefits of conservative management of preterm PROM at any gestation. Where possible, the treatment of pregnancies complicated by PROM remote from term should be directed towards conserving the pregnancy and reducing perinatal morbidity due to prematurity while monitoring closely for evidence of infection, placental abruption, labor, or fetal compromise due to umbilical cord compression. Current evidence suggests aggressive adjunctive antibiotic therapy to reduce gestational age-dependent and infectious infant morbidity. Similarly, review of evaluable data indicates that antenatal corticosteroid administration in this setting enhances neonatal outcome without increasing the risk of perinatal infection. It is not clear that tocolysis in the setting of preterm PROM remote from term reduces infant morbidity. When preterm PROM occurs near term, particularly if fetal pulmonary maturity is evident, the patient is generally best served by expeditious delivery.

Algorithms↗
PubMed2003

A biologic model for assessment of osseous strain patterns and plating systems in the human maxilla.

PURPOSE: This study was conducted to examine a biomechanical model and to help answer fundamental questions that relate to rigid plate fixation in the maxilla. Specifically, we sought to elucidate the principal strain patterns generated in the maxilla secondary to masticatory forces as well as the amount of permanent deformational changes incurred due to these loading forces. MATERIALS AND METHODS: Cadaveric heads with the mandible removed were defleshed and placed in a 2-part testing rig to hold and position the skull for testing in a standard material testing system. Rosette strain gages were attached at predefined points on the skull, and an Instron machine was used to load the skull through the loading port on the tray. A Le Fort I osteotomy was then performed on the skull, and a Walter Lorenz Ultra-Micro plating system was applied by a surgeon to reconnect the upper jaw. A 2-mm gap was left at the line of the osteotomy, and a transducer was attached to measure closure of the gap. Again the skull was loaded with the Instron (Canton, MA) machine. RESULTS: The results indicate a linear relationship exists with both maximum (tensile) and minimum (compressive) strain patterns relative to incremental load placement on the intact maxilla. The strain patterns after the Le Fort I osteotomy and plating were different and less linear. The differential variable reluctance transducer data showed a low rate of closure or transient increase in the gap at low loads (0 to 15 kilopond [kp] range) and a steeper slope of closure during high loads (15 to 60 kp range). It is also evident that axial loading forces cause permanent deformation and failure of osseous plating systems predominantly through bending. CONCLUSIONS: This model provides a foundation of knowledge regarding biomechanical strains in the maxilla subjected to static compressive loads in the force range of mastication. In addition, it serves as a comparative reference to assess rigidity of various craniofacial plating systems and to validate proposed standardized synthetic models. With the advent of increasingly precise surgery and new plating systems, this model can be used to help guide placement and design of plating systems; thereby allowing for ideal stabilization and optimizing surgical outcome.

Aged↗
PubMed1996

An investigation of the mechanics of tactile sense using two-dimensional models of the primate fingertip.

Tactile information about an object in contact with the skin surface is contained in the spatio-temporal load distribution on the skin, the corresponding stresses and strains at mechanosensitive receptor locations within the skin, and the associated pattern of electrical impulses produced by the receptor population. At present, although the responses of the receptors to known stimuli can be recorded, no experimental techniques exist to observe either the load distribution on the skin or the corresponding stress-state at the receptor locations. In this paper, the role of mechanics in the neural coding of tactile information is investigated using simple models of the primate fingertip. Four models that range in geometry from a semi-infinite medium to a cylindrical finger with a rigid bone, and composed of linear elastic media, are analyzed under plane strain conditions using the finite element method. The results show that the model geometry has a significant influence on the surface load distribution as well as the subsurface stress and strain fields for a given mechanical stimulus. The elastic medium acts like a spatial low pass filter with the property that deeper the receptor location, the more blurred the tactile information. None of the models predicted the experimentally observed surface deflection profiles under line loads as closely as a simple heterogeneous waterbed model that treated the fingerpad as a membrane enclosing an incompressible fluid (Srinivasan, 1989). This waterbed model, however, predicted a uniform state of stress inside the fingertip and thus failed to explain the spatial variations observed in the neural response. For the cylindrical model indented by rectangular gratings, the maximum compressive strain and strain energy density at typical receptor locations emerged as the two strain measures that were directly related to the electrophysiologically recorded response rate of slowly adapting type I (SAI) mechanoreceptors. Strain energy density is a better candidate to be the relevant stimulus for SAIs, since it is a scalar that is invariant with respect to receptor orientations and is a direct measure of the distortion of the receptor caused by the loads imposed on the skin.

Algorithms↗
PubMed2001

NO2 interfacial transfer is reduced by phospholipid monolayers.

Nitrogen dioxide (NO2) is a ubiquitous, pollutant gas that produces a broad range of pathological and physiological effects on the lung. Absorption of inhaled NO2 is coupled to near-interfacial reactions between the solute gas and constituents of the airway and alveolar epithelial lining fluid. Although alveolar surfactant imparts limited resistance to respiratory gas exchange compared with that contributed by either the pulmonary membrane or uptake in red blood cells, resistance to NO2 flux could have a significant effect on NO2 absorption kinetics. To investigate the effect of interfacial surfactant on NO2 absorption, we designed an apparatus permitting exposure of variably compressed monolayers. Our results suggest that compressed monolayers enriched in 1,2-dipalmitoyl-sn-3-glycero-phosphocholine present significant resistance to NO2 absorption even at surface tensions greater than those achieved in vivo. However, monolayers composed of pure unsaturated phospholipids failed to alter NO2 absorption significantly when compressed, in spite of similar reductions in surface tension. The results demonstrate that phospholipid monolayers appreciably limit NO2 absorption and further that monolayer-induced resistance to NO2 flux is related to physicochemical properties of the film itself rather than alterations within the aqueous and gas phases. On the basis of these findings, we propose that pulmonary surfactant may influence the intrapulmonary gas phase distribution of inhaled NO2.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2006

Design and evaluation of colon specific drug delivery system containing flurbiprofen microsponges.

The purpose of this study was to design novel colon specific drug delivery system containing flurbiprofen (FLB) microsponges. Microsponges containing FLB and Eudragit RS 100 were prepared by quasi-emulsion solvent diffusion method. Additionally, FLB was entrapped into a commercial Microsponge 5640 system using entrapment method. Afterwards, the effects of drug:polymer ratio, inner phase solvent amount, stirring time and speed and stirrer type on the physical characteristics of microsponges were investigated. The thermal behaviour, surface morphology, particle size and pore structure of microsponges were examined. The colon specific formulations were prepared by compression coating and also pore plugging of microsponges with pectin:hydroxypropylmethyl cellulose (HPMC) mixture followed by tabletting. In vitro dissolution studies were done on all formulations and the results were kinetically and statistically evaluated. The microsponges were spherical in shape, between 30.7 and 94.5microm in diameter and showed high porosity values (61-72%). The pore shapes of microsponges prepared by quasi-emulsion solvent diffusion method and entrapment method were found as spherical and cylindrical holes, respectively. Mechanically strong tablets prepared for colon specific drug delivery were obtained owing to the plastic deformation of sponge-like structure of microsponges. In vitro studies exhibited that compression coated colon specific tablet formulations started to release the drug at the 8th hour corresponding to the proximal colon arrival time due to the addition of enzyme, following a modified release pattern while the drug release from the colon specific formulations prepared by pore plugging the microsponges showed an increase at the 8th hour which was the time point that the enzyme addition made. This study presents a new approach based on microsponges for colon specific drug delivery.

Algorithms↗
PubMed2004

Formulation and characterisation of tetracycline-containing bioadhesive polymer networks designed for the treatment of periodontal disease.

This study described the drug release, rheological (dynamic and flow) and textural/mechanical properties of a series of formulations composed of 15% w/w polymethylvinylether-co-maleic anhydride (PMVE-MA), 0-9% w/w polyvinylpyrrolidone (PVP) and containing 1-5% w/w tetracycline hydrochloride, designed for the treatment of periodontal disease. All formulations exhibited pseudoplastic flow with minimal thixotropy. Increasing the concentration of PVP sequentially increased the zero-rate viscosity (derived from the Cross model) and the hardness and compressibility of the formulations (derived from texture profile analysis). These affects may be accredited to increased polymer entanglement and, in light of the observed synergy between the two polymers with respect to their textural and rheological properties, interaction between PVP and PMVE-MA. Increasing the concentration of PVP increased the storage and loss moduli yet decreased the loss tangent of all formulations, indicative of increased elastic behaviour. Synergy between the two polymers with respect to their viscoelastic properties was observed. Increased adhesiveness, associated with increased concentrations of PVP was ascribed to the increasing bioadhesion and tack of the formulations. The effect of increasing drug concentration on the rheological and textural properties was dependent on PVP concentration. At lower concentrations (0, 3% w/w) no effect was observed whereas, in the presence of 9% w/w PVP, increasing drug concentration increased formulation elasticity, zero rate viscosity, hardness and compressibility. These observations were ascribed to the greater mass of suspended drug in formulations containing the highest concentration of PVP. Drug release from formulations containing 6 and 9% PVP (and 5% w/w drug) was prolonged and swelling/diffusion controlled. Based on the drug release, rheological and textural properties, it is suggested that the formulation containing 15% w/w PMVE-MA, 6% w/w PVP and tetracycline hydrochloride (5% w/w) may be useful for the treatment of periodontal disease.

Algorithms↗
PubMed1989

Spontaneous rates, thresholds and tuning of auditory-nerve fibers in the gerbil: comparisons to cat data.

Characteristics of 245 auditory nerve fibers in eleven Mongolian gerbils are described in terms of spontaneous rates, thresholds, and tuning curves. The animals were reared in a low-noise environment and had similar hearing thresholds across frequency. Tuning curves were obtained with an algorithm developed to characterize the tuning of auditory fibers in cat, thereby allowing direct comparisons to published data from cat. The results demonstrate that basic similarities exist between gerbil and cat data, although some minor differences are also apparent. Tuning curve bandwidths, as measured 10 and 40 dB above the thresholds at the characteristic frequency (CF), follow trends found in cat data. Like cat, auditory nerve fibers in the gerbil have a range of spontaneous rates. In individual gerbils, fibers associated with low spontaneous rates have higher thresholds than do fibers of similar CF with high rates. Five of the eleven gerbils showed profiles of spontaneous rate across frequency reminiscent of those obtained from quiet-raised young cats. The profiles of the remaining gerbils tended to be compressed to a smaller range of spontaneous rates for characteristic frequencies above about five kHz, much like older cats with unknown noise histories. The cause of the spontaneous compression is not obvious. The correspondence between cat and gerbil with regard to spontaneous rate and CF threshold implies the presence of fundamental mechanisms that are common to mammalian auditory systems.

Action Potentials↗
PubMed2002

Survival to discharge following open chest cardiac compression (OCCC). A 4-year retrospective audit in a cardiothoracic specialist centre--Royal Brompton and Harefield NHS Trust, United Kingdom.

OBJECTIVE: To review the use of Open Chest Cardiac Compression (OCCC) techniques in postcardiac surgical patients in one specialist cardiothoracic centre in the UK. METHODS: A 4-year retrospective audit (April 1995--March 1999) of all cardiac arrest victims and resuscitation practice across two specialist cardiothoracic hospitals. Audit outcomes related to initial survival and survival to discharge, arrest rhythm, reasons for resternotomy, surgical procedure prior to resternotomy and time elapsed from original surgery to resternotomy. RESULTS: Seventy-two patients (adult and paediatric) suffering cardiac arrest received OCCC following cardiac surgery. Thirty-three patients initially survived (46%) and 12 patients survived to discharge (17%). DISCUSSION AND RECOMMENDATIONS: In the absence of current European Resuscitation Council guidelines, we adopted recommendations for resternotomy to be performed after 5 min of unsuccessful conventional CPR and OCCC initiated. An adapted ERC algorithm incorporating these recommendations can provide much needed direction in postcardiac surgery cardiac arrest victims.

Adult↗
PubMed2004

Frequency Finder: a multi-source web application for collection of public allele frequencies of SNP markers.

Publicly available single nucleotide polymorphism (SNP) allele frequencies are an important resource for the selection of genetic markers that may be most useful for gene mapping and association studies. Data mining these allele frequencies through disparate public databases and Websites is time consuming and can result in inconsistent findings. We have developed a web-based software tool, Frequency Finder, to acquire SNP allele frequencies from multiple public data sources and return a summarized result to the user. Our software optimizes and automates the search of candidate markers, decreasing the amount of time it would take to extract pertinent data manually. We have included several methods to output the data, including on-screen and as a compressed text file. We show that Frequency Finder accurately retrieves available frequency data from the available sources. Using this tool, we detect significant differences between Asian, African and Caucasian populations in the allele frequency spectra of 246 097 SNPs. While limited to public databases that provide web-based access to allele frequencies, Frequency Finder provides a single, user-friendly interface for retrieving allele frequencies for large batches of SNPs from multiple data sources.

Algorithms↗
PubMed1993

High flow priapism: a spectrum of disease.

We describe 4 cases of high flow arterial priapism, ranging from 1 week to 3 years in duration. The mode of presentation, evaluation using a duplex scanner, treatment and ultimate resolution are discussed. In 1 patient treated with ice compression the erection subsided spontaneously. One patient underwent percutaneous embolization and achieved detumescence. In 2 men a vascular pseudocapsule formed around the site of the ruptured cavernous artery that provided an important anatomical landmark for intraoperative localization. The ruptured branch of the cavernous artery was ligated in an open procedure. Based on these cases and a review of the literature, we outline a modified diagnostic and therapeutic approach for patients with high flow arterial priapism.

Adolescent↗
PubMed1999

What causes pre-eclampsia?

Pre-eclampsia remains a leading cause of maternal and fetal morbidity and mortality. Despite extensive research, the mechanisms that cause pre-eclampsia are unknown and it has been considered to be the 'disease of theories'. Hippocrates wrote in one of his Aphorisms that 'convulsions take place from either repletion or depletion'. Since then, obstetricians have been divided on the question of which factor accounted for the convulsions observed during childbirth. Some considered that a sudden reduction in intra-abdominal pressure at delivery led to a pooling of blood diverted from the brain, causing collapse of the cerebral blood vessels and convulsions. Others postulated that cerebral congestion, secondary to compression of the abdominal organs by the large uterus, diverted blood to the brain, causing eclamptic convulsions. It is the purpose of this review to examine those theories about the cause of pre-eclampsia for which modern evidence is available. At present, it is believed that the pathological chain of events leading to pre-eclampsia is scheduled in two steps: an absolute or relative placental ischaemia is followed by a diffuse endothelial cell activation, which causes the clinical features of the disease.

Algorithms↗
PubMed2000

Management of congenital pseudarthrosis of the tibia by excision of the pseudarthrosis, onlay grafting, and intramedullary nailing.

Fourteen skeletally immature children with congenital pseudarthrosis of the tibia were treated by excision of the pseudarthrosis, double onlay autogenous cortical bone grafting, and intramedullary nailing. Union was achieved in 12 patients, and no refractures occurred at the site of the original pseudarthrosis. In three patients, a fresh pseudarthrosis developed at a different site; these united after repeat onlay grafting. Five skeletally mature patients were treated by excision of the pseudarthrosis, compression at the site, and limb lengthening by callotasis. Union was achieved in three. Gain in tibial length ranged from 6 to 13 cm, with no significant complications during lengthening. The authors conclude that union can be achieved and refractures prevented in a significant proportion of skeletally immature children with congenital pseudarthrosis of the tibia by excision of the pseudarthrosis, dual onlay bone grafting, and intramedullary nailing. Any residual shortening of the limb can be treated at skeletal maturity.

Adolescent↗
PubMed2001

A neural network model for optimizing vowel recognition by cochlear implant listeners.

Due to the variability in performance among cochlear implant (CI) patients, it is becoming increasingly important to find ways to optimally fit patients with speech processing strategies. This paper proposes an approach based on neural networks, which can be used to automatically optimize the performance of CI patients. The neural network model is implemented in two stages. In the first stage, a neural network is trained to mimic the CI patient's performance on the vowel identification task. The trained neural network is then used in the second stage to adjust a free parameter to improve vowel recognition performance for each individual patient. The parameter examined in this study was a weighting function applied to the compressed channel amplitudes extracted from a 6-channel continuous interleaved sampling (CIS) strategy. Two types of weighting functions were examined, one which assumed channel interaction, and one which assumed no interaction between channels. Results showed that the neural network models closely matched the performance of five Med-EI/CIS-Link implant patients. The resulting weighting functions obtained after neural network training improved vowel performance, with the larger improvement (4%) attained by the weighting function which modeled channel interaction.

Algorithms↗
PubMed1987

Mechanism of penile erection in the dog. Pressure-flow study combined with morphological observation of vascular casts.

A pressure-flow study of the corpus cavernosum penis in the dog was performed during the flaccid, tumescent, erect and rigid stages. Perfusion was selectively made into the penile deep artery. The erect stage was induced with the local administration of papaverine hydrochloride, and the rigid stage by electrostimulation of the ischiocavernous muscle during the erect stage. Concurrently, vascular casts of the penis at each stage of erection were observed under a scanning electron microscope for the anatomical analysis of the mechanisms controlling cavernous pressure. In the pressure-flow study, it was demonstrated that a combination of decreased arterial resistance and restricted venous outflow was essential to both cause and maintain the erect state. The rigid stage was generated by contraction of the ischiocavernous muscle tightly compressing the crus penis. In the rigid stage, the cavernous pressure was elevated as high as five times the perfusion pressure; nevertheless, no backflow from the cavernous sinus to the deep artery was recognized. By use of the casts, it was confirmed that venous outflow restriction in the erect and rigid stages was due to compression of the postcavernous venules and penetrating veins in the tunica albuginea. The deep artery was occluded in the tunica albuginea in the casts made during the rigid stage, suggesting that the backflow from the corpus cavernosum penis to the deep artery was prevented by this occlusion. Therefore, in the rigid stage, the arterial and venous occlusion isolated the cavernous sinus from the systemic circulation; this mechanism seems to account for the maintenance of the extremely high cavernous pressure.

Algorithms↗
PubMed2004

Using image and curve registration for measuring the goodness of fit of spatial and temporal predictions.

Conventional measures of model fit for indexed data (e.g., time series or spatial data) summarize errors in y, for instance by integrating (or summing) the squared difference between predicted and measured values over a range of x. We propose an approach which recognizes that errors can occur in the x-direction as well. Instead of just measuring the difference between the predictions and observations at each site (or time), we first "deform" the predictions, stretching or compressing along the x-direction or directions, so as to improve the agreement between the observations and the deformed predictions. Error is then summarized by (a) the amount of deformation in x, and (b) the remaining difference in y between the data and the deformed predictions (i.e., the residual error in y after the deformation). A parameter, lambda, controls the tradeoff between (a) and (b), so that as lambda-->infinity no deformation is allowed, whereas for lambda=0 the deformation minimizes the errors in y. In some applications, the deformation itself is of interest because it characterizes the (temporal or spatial) structure of the errors. The optimal deformation can be computed by solving a system of nonlinear partial differential equations, or, for a unidimensional index, by using a dynamic programming algorithm. We illustrate the procedure with examples from nonlinear time series and fluid dynamics.

Algorithms↗