Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Dimensionality Reduction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources
PubMed2003

Evaluation of a conceptual model for the subsurface transport of plutonium involving surface mediated reduction of PuV to PuIV.

A conceptual model is proposed to explain the transport behavior of plutonium in laboratory columns packed with a sandy coastal soil from the U.S. Department of Energy (DOE)'s Savannah River Site. The column transport experiments involved the introduction of a finite step input of plutonium, predominately in the +5 oxidation state, into the columns followed by elution with a low-carbonate solution of 0.02 M NaClO4 at pH 3, 5, and 8. Total plutonium concentrations were measured in the effluent as a function of time. These elution profiles suggest at least two distinct physical/chemical forms of plutonium, each with a different mobility. To explain the observed behavior, the following conceptual model was evaluated: [1] equilibrium partitioning of plutonium (V) and plutonium (IV) between the aqueous and sorbed phases as defined by pH-dependent, oxidation-state specific distribution coefficients and [2] kinetic reduction of plutonium (V) to plutonium (IV) in the sorbed phase. The conceptual model was applied to the column experiments through a one-dimensional advective/dispersive mathematical model, and predictions of the mathematical model were compared with the experimental data. Overall, the model was successful in predicting some of the major features observed in the experiments. It also yielded quantitative estimates of the rate constant for surface mediated reduction of plutonium (V) to plutonium (IV) that were of the same order (10(-4) to 10(-5) s(-1)) as those calculated from batch data both for this soil and for goethite.

Chemical Phenomena↗
PubMed1989

Purification and characterisation of Clostridium difficile toxin A by bovine thyroglobulin affinity chromatography and dissociation in denaturing conditions with or without reduction.

Highly purified toxin A of Clostridium difficile was obtained by bovine thyroglobulin affinity chromatography followed by two sequential anion-exchange chromatography steps on Q Sepharose FF and Mono Q. After Q Sepharose FF chromatography of a thyroglobulin affinity-purified toxin A preparation, two major peaks of cytotoxicity representing toxins A and B were detected. The homogeneity of the final toxin A preparation obtained from Mono Q anion-exchange fast protein liquid chromatography was ascertained by gel electrophoresis developed by silver stain. The mol. wt of toxin A in non-denaturing conditions was estimated to be 520-540 Kda by native polyacrylamide gel electrophoresis (PAGE) developed by silver stain. In contrast, with sodium dodecyl sulphate (SDS)-PAGE under reducing or non-reducing conditions, a major band of 240 Kda and 10 minor and 27 faint bands (non-reduced conditions), or four minor and 31 faint bands (reduced conditions) were detected after silver staining. In two-dimensional PAGE, the seven minor bands of greater than 240 Kda obtained by non-reducing SDS-PAGE migrated to the 240-Kda position after reduction with beta-mercaptoethanol.

Animals↗
PubMed1982

Echocardiographic features of eosinophilic endomyocardial disease.

Nine patients with eosinophilic endomyocardial disease who had undergone angiocardiography with histological staging of their disease, were studied by M-mode and two dimensional echocardiography to determine the extent to which specific features of the disease could be evaluated by these non-invasive methods. In seven patients, amplitude processed two dimensional echocardiography showed regions where the relative intensity of endomyocardial echoes was greater than normal, and their distribution corresponded to known areas of fibrosis. Standard two dimensional echocardiography was normal in all but three patients. In eight patients M-mode echocardiography showed only non-specific abnormalities, but appeared to be useful in assessing the functional consequences of myocardial or mitral valve disease. After digitisation a reduction in the duration and an increase in the peak rate of dimension increase during filling was prolonged. It was concluded that amplitude processed two dimensional echocardiography might be useful in diagnosing the extent and severity of endomyocardial disease in patients with hyperosinophilia. These noninvasive techniques may thus provide a means for the early diagnosis of endomyocardial fibrosis and could be useful in assessing in progression or response to treatment.

Adult↗
PubMed2002

Optimization of unilateral overjet management: three-dimensional analysis by the finite element method.

The main goal of this research was to introduce, evaluate, and mathematically optimize the treatment procedure of unilateral overjet cases. Patients with Class II subdivision malocclusions usually reach a point with canines in a Class I position, and a unilateral overjet remains to be treated at the next stage of treatment. This study tried to prepare an archwire design that combines the midline-shift correction and the unilateral overjet reduction simultaneously. The analyses of displacements were carried out by the finite element method. The upper dental arch was designed three-dimensionally. Three archwire designs that were thought to be useful in these cases were modeled and engaged the dental-arch model separately. Three-dimensional displacements of the mesio- and distoincisolabial point angles of each incisor were assessed. Shortcomings of each design concerning the main treatment objectives were eliminated by optimization. Modeling and optimization of wire ligation methods were the last phase of this study. The use of an archwire containing a closed vertical loop with a helix distal to the lateral incisor on the affected (excess overjet) side and an open vertical loop without a helix distal to the lateral incisor on the normal side (normal overjet) while lacing the four incisors can be suggested as an optimum procedure to treat a unilateral overjet that is combined with a midline shift. The archwire cross-section depends on the initial position of the incisors. This mechanotherapy can be prescribed for both dental arches.

Dental Stress Analysis↗
PubMed2006

Computer-assisted surgical treatment of orbitozygomatic fractures.

Orbitozygomatic fractures pertain to the most common injuries in craniofacial trauma patients. Accurate fracture reduction is of high importance for a successful outcome. This pilot study was performed to assess the potential benefit of surgical navigation to aid in orbitozygomatic fracture reduction. A non-comparative series of five consecutive patients with severely displaced orbitozygomatic fractures was treated using the guidance of computed tomography (CT)-based surgical navigation. Using a previously developed software platform, the fracture was reduced virtually by a three-dimensional shifting of the orbitozygomatic complex within the patient's preoperative multimodal CT data set. This treatment plan was transferred to a navigation system. Fracture reduction was performed according to the treatment plan using surgical navigation. Intraoperative control of fracture reduction by comparing the real with the virtual bone position using surgical navigation showed up as a helpful tool. Accurate treatment planning and immediate evaluation of craniofacial surgery outcome are the benefits of the new approach demonstrated. A major drawback of the presented approach is a high consumption of human and financial resources. A larger clinical series with long-term follow-up will be needed to determine reproducibility and cost-effectiveness. In addition to bone repositioning, a future application may include simulation of craniofacial osteotomies.

Feasibility Studies↗
PubMed1985

Fibrinogen biosynthesis in isolated guinea pig megakaryocytes.

Fibrinogen synthesis was investigated in guinea pig megakaryocytes. Purified megakaryocytes were incubated with 35S-methionine in methionine-free incubation medium for 18 hours. Newly synthesized fibrinogen in megakaryocyte lysates enriched with purified carrier guinea pig fibrinogen was immunoprecipitated with a specific anti-guinea pig fibrinogen antiserum produced in rabbits. Proteins in the immunoprecipitates were analyzed with a 3.5% to 10.0% gradient polyacrylamide slab gel electrophoresis and auto-radiography. Radioactivity was detected in a protein band of 340,000 daltons. In order to verify fibrinogen synthesis, immunoprecipitate was analyzed by two-dimensional slab gel electrophoresis: (1) the first dimension separated unreduced fibrinogen using a 3.5% to 10.0% gradient gel; (2) following reduction by 2-beta-mercaptoethanol, fibrinogen chains were separated in the second dimension using a 10% gel. Alpha, beta, and gamma fibrinogen chains, which represented carrier guinea pig plasma fibrinogen, were visualized by Coomassie brilliant blue. Autoradiography identified the incorporation of radioactivity into the three fibrinogen chains. In control experiments, immunoprecipitates, produced by exposing megakaryocyte lysates to preimmune rabbit serum and goat anti-rabbit IgG, were also analyzed by the two-dimensional gel system. Radioactivity was not detected in sites corresponding to the migration of fibrinogen subunits. The study demonstrates that isolated guinea pig megakaryocytes can synthesize fibrinogen. The electrophoretic mobility of newly synthesized fibrinogen and subunits is similar to that of guinea pig plasma fibrinogen.

Animals↗
PubMed1989

Mathematical shape optimization of hip prosthesis design.

The long-term success of artificial-joint replacement depends partly on the chances for acrylic cement failure and interface disruption. These chances can be diminished by an optimal load-transfer mechanism, whereby stress concentrations are avoided. The present paper introduces a method for numerical shape optimization, whereby the finite element method is used iteratively to determine optimal prosthetic designs, which minimize interface stresses. The method is first applied in a simplified one-dimensional model of a cemented femoral stem fixation, using acrylic cement. The results show that 30-70% cement and interface stress reductions can be obtained in principle with an optimized design. Although the actual optimal shape is susceptible to the characteristics of the joint load, the stem length, stem modulus, cement modulus and bone properties, its general geometrical characteristics are consistent, featuring proximal and distal tapers, and a belly-shaped middle region. These general characteristics are confirmed in a more realistic two-dimensional FEM model. It is concluded that this method of shape optimization can provide a meaningful basis for prosthetic design and analysis activities in general.

Bone Cements↗
PubMed1994

Estimation of in vivo pulses in medical ultrasound.

An algorithm for the estimation of one-dimensional in-vivo ultrasound pulses is derived. The routine estimates a set of ARMA parameters describing the pulse and uses data from a number of adjacent rf lines. Using multiple lines results in a decrease in variance on the estimated parameters and significantly reduces the risk of terminating the algorithm at a local minimum. Examples from use on synthetic data confirms the reduction in variance and increased chance of successful minimization termination. Simulations are also reported indicating the relation between the one-dimensional pulse and the three-dimensional, attenuated ultrasoud field for a concave transducer. Pulses are estimated from in-vivo liver data showing good resemblance to a pulse measured as the response from a planar reflector and then properly attenuated. The main application for the algorithm is to function as a preprocessing stage for deconvolution algorithms using parametric pulses.

Ultrasonography↗
PubMed1985

The organism as bioreactor. Interpretation of the reduction law of metabolism in terms of heterogeneous catalysis and fractal structure.

Organisms and bioreactors are open, dissipative systems in steady state. They are functionally equivalent with respect to turnover and kinetics, and structurally analogous with respect to fractal organization and self-similar scaling. As heterogeneous catalytic systems both are governed by interaction of mass transport and reaction. The structural equivalent to turbulence in the reactor, yielding high efficiency, is the fractal folding and branching of the transport systems of the organism. Dimensionally and in terms of fractals, organisms and reactors are therefore area-volume hybrids. The physiological consequence of this is the reduction law of metabolism. Introducing limits into allometric functions describing scale-up of similar organisms yields probability density distributions of their realization.

Animals↗
PubMedDate not supplied

Comparison of phantom and computer-simulated MR images of flow in a convergent geometry: implications for improved two-dimensional MR angiography.

The signal loss that occurs in regions of disturbed flow significantly decreases the clinical usefulness of MR angiography in the imaging of diseased arteries. This signal loss is most often attributed to turbulent flow; but on a typical MR angiogram, the signal is lost in the nonturbulent upstream region of the stenosis as well as in the turbulent downstream region. In the current study we used a flow phantom with a forward-facing step geometry to model the upstream region. The flow upstream of the step was convergent, which created high levels of convective acceleration. This region of the flow field contributes to signal loss at the constriction, leading to overestimation of the area of stenosis reduction. A computer program was designed to simulate the image artifacts that would be caused by this geometry in two-dimensional time-of-flight MR angiography. Simulated images were compared with actual phantom images and the flow artifacts were highly correlated. The computer simulation was then used to test the effects of different orders of motion compensation and of fewer pixels per diameter, as would be present in MR angiograms of small arteries. The results indicated that the computational simulation of flow artifacts upstream of the stenosis provides an important tool in the design of optimal imaging sequences for the reduction of signal loss.

Arteriosclerosis↗
PubMed1981

Isolation of Drosophila flightless mutants which affect myofibrillar proteins of indirect flight muscle.

A large number of dominant flightless mutants of Drosophila were chemically induced, and their thorax proteins were examined by chemically induced, and their thorax proteins were examined by means of two-dimensional gel electrophoresis (O'Farrell 1975). Among them, 26 lines were found to have deficiency or reduction of some of myofibrillar proteins in indirect flight muscle (IFM). The gel patterns of the mutants could be classified into eleven groups. In general, more than a few polypeptides were either absent or reduced in each mutant line. Although the mutations affect myofibrillar proteins in apparently complex and diverse ways, logical correlations were found among the changes. There are pairs of proteins which always change together when a number of mutants are compared. There are also many pairs in which presence of one protein is necessary, but not sufficient for presence of the other. This suggests that absence of one component leads to disappearance or reduction of others which are either spatially or functionally related to the former. The correlation is possibly due to a hierarchy of the proteins in the myofibrillar assembly processes. Chromosomal loci of eleven typical mutants were examined, and it was found that most of them are located in two small regions of the second and the third chromosomes. IFM myofibrils of these mutants are either abnormal or absent in homozygotes as well as in heterozygotes.

Animals↗
PubMed1991

Further characterization of Trypanosoma cruzi GP57/51 as the major antigen expressed by differentiating epimastigotes.

Study of Trypanosoma cruzi metacyclogenesis under chemically defined conditions showed that the expression of a group of acidic polypeptides with a molecular weight of 45-50 kDa is markedly increased on adhesion of epimastigotes to the culture vessels. Immunochemical analysis revealed that these developmentally regulated polypeptides are structurally related to, and possibly homologous with, a major T. cruzi antigen, namely, GP57/51, a glycoprotein that has recently been characterized as a cysteine proteinase. The differentiation of epimastigotes into metacyclic trypomastigotes is accompanied by a 2- to 5-fold reduction in the concentration of GP57/51 antigen as determined by radioimmunoassays using monoclonal antibodies. Two-dimensional polyacrylamide gel electrophoretic analysis of metabolically labelled parasites indicated that this antigen is synthesized as a precursor with a molecular weight of 60 kDa, which is then processed to a level of 45-50 kDa via the formation of at least one intermediate processing product. The observation that expression of GP57/51-related products increases during epimastigote differentiation suggests an important role for this proteinase during the life cycle of T. cruzi.

Animals↗
PubMed2002

[Osteosynthesis systems in mouth, jaw and facial surgery].

The introduction of stable osteosynthesis of mandibular fractures in the late 1960s for trauma patients meant an increase in quality of life. Intermaxillary immobilization and time in hospital could be reduced significantly. Later on, miniplates became popular in most trauma centers to treat mandibular fractures. Compared to the technique of stable osteosynthesis, miniplating is less demanding and the complication rates are similar. In midfacial fractures, too, miniplate osteosynthesis could guarantee three-dimensional stability. With the help of microplates even the smallest bony structures can be fixed following reduction. Degradable plates, which are available today, are used for craniofacial and midfacial indications; however, up to now degradable plates are not suitable for load-bearing areas.

Biomechanical Phenomena↗
PubMed1982

Partial characterization of bovine salivary proteins by electrophoretic methods.

Electrophoresis in 71/2% polyacrylamide gel separates bovine salivary proteins into 12 bands, and is used as the first step, followed by isoelectrofocusing or electrophoresis in polyacrylamide (15%) gels containing sodium dodecyl sulphate (SDS) or immunoelectrophoresis in two-dimensional separations. Molecular weights of native proteins are determined by electrophoresis on gels of polyacrylamide concentration 10 to 20%. Using these methods, information on native and subunit molecular weights, isoelectric pH values and immunological relationships for bovine salivary proteins has been determined. Enzymic functions for six of the proteins were established by histological methods.

Animals↗
PubMed2005

A sensitive method for the quantitative measurement of protein thiol modification in response to oxidative stress.

The combination of proteomics with highly specific and sensitive affinity techniques is important for the identification of posttranslational modifications by reactive oxygen and nitrogen species (ROS/RNS). One of the most pressing problems with this approach is to determine accurately the extent of modification of specific amino acids, such as cysteine residues, in a complex protein sample. A number of techniques relevant to free radical biology use biotin tagging as a method to follow protein modification with high sensitivity and specificity. To realize the potential of this approach to provide quantitative data, we have prepared a series of biotinylated proteins through the modification of lysine residues. These proteins were then used as quantitative standards in electrophoretic separation of protein samples labeled with biotin-conjugated iodoacetamide. The utility of the approach was assessed by measuring modification of thiols in response to exposure to thiol oxidants, as well as the amount of protein adduct formation with a biotin-tagged electrophilic lipid. Furthermore, using a combination of native and biotin-tagged cytochrome c, this method was used to quantitate the amount of thiol relative to the amount of protein in a given spot on a two-dimensional gel. Thus, we have developed a versatile, cost-effective standard that can be used in proteomic methods to quantitate biotin tags in response to oxidative stress.

Animals↗
PubMed2005

The covalent immobilization of microsomal uridine diphospho-glucuronosyltransferase (UDPGT): initial synthesis and characterization of an UDPGT immobilized enzyme reactor for the on-line study of glucuronidation.

The microsomal fraction of rat liver containing uridine diphospho-glucuronosyltransferase (UDPGT; EC 2.4.1.17) has been covalently immobilized on a high performance chromatographic support. In this study Nucleosil Si-500 silica was converted into diol-bonded silica and subsequently converted into an aldehyde form through oxidation with sodium periodate. The microsomal fraction was immobilized via Schiff base formation followed by reduction with sodium cyanoborohydride. The resulting immobilized enzyme reactor (IMER) was placed in a multi-dimensional chromatographic system which utilized a mixed mode (C18 and anion exchange) column to trap the parent compound and glucuronide and a C18 column to separate the substrate and product. The IMER system was used for the online glucuronidation of 4-methylumbelliferone (4Me7OHC) and acetaminophen (APAP). The Michaelis-Menten kinetic parameters (Km and Vmax) associated with the formation of 4Me7OHC and APAP glucuronides demonstrated that the immobilization had not significantly affected the enzymatic activity of the UDPGT relative to the non-immobilized enzyme. The IMER retained enzymatic activity for more than 6 weeks. The results of this study demonstrate an easy and convenient way to identify compounds which may be glucuronidated and to synthesize and characterize the resulting products.

Animals↗
PubMed2005

Proteomic identification of proteins specifically oxidized in Caenorhabditis elegans expressing human Abeta(1-42): implications for Alzheimer's disease.

Protein oxidation has been shown to lead to loss of protein function, increased protein aggregation, decreased protein turnover, decreased membrane fluidity, altered cellular redox poteintial, loss of Ca2+ homeostaisis, and cell death. There is increasing evidence that protein oxidation is involved in the pathogenesis of Alzheimer's disease and amyloid beta-peptide (1-42) has been implicated as a mediator of oxidative stress in AD. However, the specific implications of the oxidation induced by Abeta(1-42) on the neurodegeneration evident in AD are unknown. In this study, we used proteomic techniques to identify specific targets of oxidation in transgenic Caenorhabditis elegans (C. elegans) expressing human Abeta(1-42). We identified 16 oxidized proteins involved in energy metabolism, proteasome function, and scavenging of oxidants that are more oxidized compared to control lines. These results are discussed with reference to Alzheimer's disease.

Amyloid beta-Peptides↗