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 1,351 records · Page 75Linked to original sources
PubMedDate not supplied

[The perceptive color space of the rabbit].

Discrimination of colors was studied using instrumental learning paradigm in three rabbits (Oryctolagus cuniculus). The rabbits were able to discriminate all but red stimuli by their color. The red stimulus could not be discriminated from the black one. The confusion matrix composed of probabilities of instrumental reactions was subjected to factor analysis in order to reveal the basic axes of the color perceptual space. The four-dimensional spherical structure of perceptual color space was obtained, which was different from that of trichromatic species in a reduction of color axes in red and yellow parts. The evidence characterizes rabbit as a protanopic animal.

Animals↗
PubMed1984

Subtrochanteric fracture after Garden screw fixation: a review of predisposing factors and management in nine cases.

Nine cases of subtrochanteric fracture are reviewed following 300 fixations of subcapital fractures with Garden screws. In six cases technical operative errors were considered to contribute to the fracture. It is stressed that adequate reduction and suitably placed crossed Garden screws are demanding requirements and that every attempt should be made to avoid making extra holes with guidewires. In two technically satisfactory cases the low position of the lower Garden screw-hole in the femur probably predisposed to the subtrochanteric fracture. A computerized two-dimensional finite analysis confirmed smaller magnitudes of stress at a more proximally positioned lower Garden screw, and in patients at risk, particularly those with a valgus femoral neck or valgus reduction, it is suggested that if this method of internal fixation is to be used, the screws should be crossed less obliquely, with the lower screw more proximally positioned in the femur.

Adult↗
PubMed1997

Multistep denaturation and hierarchy of disulfide bond cleavage of a monoclonal antibody.

A humanized, monoclonal antibody of the IgG4 class was treated with SDS at room temperature. Analysis using SDS-PAGE revealed the progressive formation of a series of denaturation intermediates, of increasing apparent molecular weights. The detectable species migrated with apparent molecular weights of 137, 152, 162, 182, 196, and 210 kDa. Antibody not incubated in SDS had an apparent molecular weight of 137 kDa, while boiling in SDS provoked the immediate conversion of all antibody to the slowest migrating form (210 kDa). A study designed to test if all rungs of the ladder were equally cleavable by mild treatment with mercaptoethanol revealed small amounts of a novel form, and conditions were devised to generate large amounts of this novel form. The novel form, before full denaturation, migrated at the position of unheated, intact antibody (137 kDa), while full denaturation in SDS converted the novel form to a species migrating at about 190 kDa. The novel form, before full denaturation, was identified as HHL ***L, where the asterisks indicate noncovalent binding of one light chain to HHL. This noncovalent complex remains intact during SDS-PAGE. The novel form, after full denaturation, was identified as HHL. This study, with earlier studies, reveals that different pathways of reductive cleavage are taken by different antibodies, and that the most sensitive disulfide bond is different for different antibodies. Our results on antibody denaturation serve as a warning to those who use two-dimensional gels for the analysis of antibodies.

Animals↗
PubMed2001

Strain compounding: spatial resolution and performance on human images.

Compounding has long been used to reduce speckle brightness variations by incoherently combining partially correlated measurements of the same image object. Conventionally, decorrelation between measurements is introduced by imaging from different spatial positions (i.e., spatial compounding) or within different frequency ranges (i.e., frequency compounding). An alternative compounding approach based on speckle decorrelation of an object under different strain conditions was recently proposed. The new approach was referred to as strain compounding. Speckle correlation of strain compounding was previously analyzed using simulations and radiofrequency (RF) data from a gelatin-based phantom. Results indicated that effective speckle reduction is possible at strains potentially achievable in certain clinical situations. In this paper, performance of strain compounding is further analyzed. Potential degradation in spatial resolution of strain compounding is compared to that of conventional approaches using computer simulations. Results show that strain compounding potentially can achieve the same level of speckle reduction, with less degradation in spatial resolution if a large compression can be applied. Performance of strain compounding is also tested using postdetection human images acquired by a commercial imaging system. Two-dimensional (2-D) speckle tracking is performed to correct for tissue motion resulting from external compression and to ensure that the images to be compounded are spatially matched. Thyroid images show that speckle brightness variations can be effectively reduced without significant degradation in spatial resolution. Speckle reduction in liver imaging is also demonstrated. However, speckle reduction is not as significant as in thyroid imaging, due to the fact that a large compression cannot be achieved.

Humans↗
PubMed2005

Intraoperative three-dimensional imaging with a motorized mobile C-arm (SIREMOBIL ISO-C-3D) in foot and ankle trauma care: a preliminary report.

OBJECTIVE: The aim of the study was to assess the feasibility and benefit of the intraoperative use of a mobile C-arm with 3-dimensional imaging (ISO-C-3D). DESIGN: Prospective consecutive clinical study. SETTING: University hospital, level I trauma center. METHODS: The ISO-C-3D was used for intraoperative visualization in foot and ankle trauma care. Conventional C-arms were used to judge the reduction and implant position before the ISO-C-3D was used. Time spent, changes resulting from use of the ISO-C-3D, and surgeons' ratings (visual analogue scale, 0-10 points) were recorded. PATIENTS: Between January 1, 2003 and March 15, 2004, the ISO-C-3D was used in 62 cases (factures: pilon, n = 1; Weber-C ankles, n = 7; isolated dorsal Volkmann, n = 1; talus, n = 3; calcaneus, n = 20; navicular, n = 1; cuboid, n = 1; Lisfranc fracture-dislocation, n = 6; hindfoot arthrodesis with or without correction, n = 12). RESULTS: On average, the operation was interrupted for 440 seconds (range 330-700); 120 seconds, on average, for the ISO-C-3D scan and 210 seconds, on average, for evaluation of the images by the surgeon. In 39% of the cases (24 of 62), the reduction and/or implant position was corrected during the same procedure after the ISO-C-3D scan. The ratings of the 8 surgeons who used the ISO-C-3D were 9.2(5.2-10) for feasibility, 9.5 (6.1-10) for accuracy, and 8.2 (4.5-10) for clinical benefit. CONCLUSION: Intraoperative 3-dimensional visualization with the ISO-C-3D can provide useful information in foot and ankle trauma care that cannot be obtained from plain films or conventional C-arms. During the same procedure, after conventional C-arm scans judged the positioning to be correct and an ISO-C-3D scan was done, the reduction and/or implant position was corrected in 39% of the cases in this study, although not unnecessarily prolonging the operation. The ISO-C-3D appears to be most helpful in procedures with a closed reduction and internal fixation, and/or when axial reformations provide information that is not possible to obtain with a conventional C-arm and/or direct visualization during open reduction and internal fixation.

Ankle Injuries↗
PubMed2006

Data reduction and representation in drug discovery.

Pre-clinical drug discovery relies increasingly on huge volumes of inter-related multivariate data. To make sense of these data and enable quality decision-making based on this plethora of information they must be presented in an interpretable form. Reducing the dimensionality of the data often leaves a data set that is too complex to interpret readily, so intuitive visualization methods are needed. Bioinformatics has provided much of the impetus for visualizing complex data, the cheminformatics community has been aggressive with the data-reduction problem. The increasing appreciation of the inter-related multifactorial nature of pre-clinical drug discovery makes visualization a burgeoning and active field that spans biosciences, mathematics and visual psychology.

Computational Biology↗
PubMed2004

Prostate seed implantation using 3D-computer assisted intraoperative planning vs. a standard look-up nomogram: Improved target conformality with reduction in urethral and rectal wall dose.

PURPOSE: To compare dosimetric outcomes between two real-time prostate seed implantation (PSI) techniques to evaluate the impact of three-dimensional (3D) intraoperative computer planning on target coverage, conformality, and preset urethral and rectal dose constraints. METHODS AND MATERIALS: One hundred and fourteen patients with clinically localized prostate cancer underwent ultrasound-guided transperineal PSI of the prostate with (125)I sources as monotherapy. From 1999 to 2001, 69 patients were implanted in real-time using a standard look-up nomogram (Group 1: NG-PSI). All patients were implanted with a modified peripheral loading technique in which 75-80% of the calculated total activity was delivered to the gland periphery, with the remaining 20-25% activity placed in the gland interior, to achieve a prescribed dose (PD) of 144 Gy to cover the gland with acceptable homogeneity. No preoperative or intraoperative planning was performed to set dose constraints to the urethra or anterior rectal wall. Dosimetric outcome from this group was compared with 45 patients subsequently implanted after 2001 using an intraoperative 3D computer planning system (Group 2: 3D-PSI). A similar modified peripheral loading technique was used as an option in the planning system. Preoperative dose constraints were placed on the urethra (V150 < 35%), prostate (V100 > 95% of PD; D90: 140-180 Gy), and rectal wall (V110 < 1.5 cc) with real-time dosimetric feedback performed after peripheral loading. Manual dose optimization was performed to determine interior needle position and remaining number and placement of (125)I sources to adhere to urethral and rectal constraints and target coverage goals. Both groups underwent postimplant CT analysis to determine dosimetric outcome with regard toV100(prostate), D90(prostate), V150(urethra), and V110(rectum). Univariate and multivariate analysis was performed to determine variables impacting on dosimetric outcome. RESULTS: Analysis of preimplant and postimplant variables demonstrated no difference in the median preimplant gland volume (33 cc vs. 35 cc; p = 0.31), median mCi/seed strengths (0.4 vs. 0.45 mCi; p = 0.23), median V100 (94% vs. 94%), or median D90 at postimplant Day 30 (165 Gy vs. 160 Gy; p = 0.26) between Groups 1 and 2. However, for Group 2 (3D-PSI) the median total mCi implanted (26 vs. 33 mCi; p < 0.0001) and the median number of seeds implanted (67 vs. 83; p < 0.0001) were reduced substantially. The percent of patients exceeding a D90 > 180 Gy was reduced from 29% in Group 1 to 16% in Group 2 (p = 0.08). A reduction was observed in the percent of patients receiving a D90 < 140 Gy (14% Group 1 vs. 9% Group 2, p = 0.56). The median V150(urethra) for Group 2 was reduced dramatically with 3D-PSI compared with NG-PSI (63% vs. 17%; p < 0.0001). A V150(urethra) > 30% was observed in 88% in Group 1 compared with 29% in Group 2, p < 0.0001. Similarly, the median V110(rectum) for Group 1 was significantly higher than that in Group 2 (1.93 vs. 0.26 cc; p < 0.0001). The percent of patients with V110(rectum) > 1.5 cc in Group 1 and Group 2 was 57% and 13%, respectively (p < 0.0001). CONCLUSIONS: The adoption of 3D computer intraoperative dose planning and optimization for prostate seed implantation resulted in dramatic reductions in urethral and rectal wall doses, while consistently producing excellent target coverage with reduced dose variability above 180 Gy and below 140 Gy, compared with the use of a standard look-up nomogram. Additionally, the reduction in total mCi and number of seeds needed to achieve improved conformality was substantial and may have implications for cost savings.

Analysis of Variance↗
PubMedDate not supplied

Different responses of left ventricular systolic function to changes in right ventricular volume and shortening--comparison between aorto-femoral vein and aorto-left atrium shunts in dog hearts.

It has been reported that left ventricular end-systolic volume decreases during arteriovenous shunt and increases during subclavian artery-left atrium shunt at a constant end-systolic pressure. The mechanism of the opposing changes in end-systolic volume during the two types of shunt is not clear. One possible cause is that left ventricular pump function with enhanced right ventricular ejection differs from that without enhancement. To investigate this hypothesis, we studied the two types of shunt (Aorto-femoral vein shunt, AoFV; aorto-left atrium shunt, AoLA) with matched reduction of systemic vascular resistance in open-chest dogs with beta-blockade. Both right and left ventricular volumes and shortenings were assessed from short-axis views by two-dimensional (2D)-echocardiogram. Left ventricular end-systolic short-axis area decreased from 76 +/- 3 to 62 +/- 3% in AoFV shunt (p less than 0.05), but tended to increase in AoLA shunt (76 +/- 4 in control state vs 81 +/- 5% in AoLA, NS) in spite of a similar reduction in left ventricular end-systolic pressure. There was no difference in left ventricular shortening, but significant differences were observed in right ventricular shortening (50 +/- 8 in AoFV vs 24 +/- 7% in AoLA, p less than 0.05) and right ventricular short-axis area at end-diastole (142 +/- 6 in AoFV vs 96 +/- 3% in AoLA, p less than 0.01), and at end-systole (92 +/- 8 in AoFV vs 73 +/- 7% in AoLA, p less than 0.05) between the two types of shunt. We conclude that the different changes in left ventricular end-systolic short-axis area found in the two shunts are not caused by the different left ventricular shortenings, but by the different right ventricular mechanical actions. These findings suggest that left ventricular pumping action in the high output state changes, depending on whether it is accompanied by augmented ejection of the right ventricle or not.

Animals↗
PubMed1989

Database and search techniques for two-dimensional gel protein data: a comparison of paradigms for exploratory data analysis and prospects for biological modeling.

Two-dimensional (2-D) polyacrylamide gel electrophoresis can detect thousands of polypeptides, separating them by apparent molecular weight (Mr) and isoelectric point (pI). Thus it provides a more realistic and global view of cellular genetic expression than any other technique. This technique has been useful for finding sets of key proteins of biological significance. However, a typical experiment with more than a few gels often results in an unwiedly data management problem. In this paper, the GELLAB-II system is discussed with respect to how data reduction and exploratory data analysis can be aided by computer data management and statistical search techniques. By encoding the gel patterns in a "three-dimensional" (3-D) database, an exploratory data analysis can be carried out in an environment that might be called a "spread sheet for 2-D gel protein data". From such databases, complex parametric network models of protein expression during events such as differentiation might be constructed. For this, 2-D gel databases must be able to include data from other domains external to the gel itself. Because of the increasing complexity of such databases, new tools are required to help manage this complexity. Two such tools, object-oriented databases and expert-system rule-based analysis, are discussed in this context. Comparisons are made between GELLAB and other 2-D gel database analysis systems to illustrate some of the analysis paradigms common to these systems and where this technology may be heading.

Algorithms↗
PubMed2001

Reactive dynamics on two-dimensional supports: Monte Carlo simulations and mean-field theory.

Monte Carlo simulations and mean-field models are used for the study of nonequilibrium reactions taking place on the surface of a catalyst. The model represents the catalytic reduction of NO with H2 on a Pt surface. Both Monte Carlo simulations and mean-field results predict the existence of a critical surface in the parameter space where the catalyst remains active for long times. Outside this critical region the catalyst remains active for finite times only. A discrete version of the mean-field model is proposed that takes into account the discrete, two-dimensional nature of the catalyst. For homogeneous initial conditions this improved model provides better quantitative agreement with the Monte Carlo results.

Journal Article↗
PubMed2003

The significance of cardiac doses received during chemoradiation of oesophageal and gastro-oesophageal junctional cancers.

AIM: Although radiation-induced cardiotoxicity has been described in patients with breast cancer and Hodgkin's disease, the effect of oesophageal radiotherapy on the heart has not been evaluated. This study was designed to evaluate the dose received by the heart during chemoradiotherapy (CT-RT) for oesophageal cancer, to assess its impact on cardiac function, and explore methods of reducing this dose. METHODS: Cardiac doses were calculated from dose-volume histograms in 15 patients with carcinoma of mid and lower oesophagus undergoing combined technique treatment, in whom pre- and post-treatment multigated acquisition scans were available. Chemotherapy consisted of cisplatin and 5-fluorouracil with or without paclitaxel. The radiotherapy was delivered in two phases to a total dose of 45-50 Gy in 25 fractions. RESULTS: There was a significant reduction in median ejection fraction after CT-RT (63% to 58%, P = 0.003). The median dose received by the heart using three-dimensional conformal technique was 27.4 Gy (interquartile range 25.8-34.2 Gy). If shielding blocks were not used, as would be the case with conventional planning, the median dose would have been 35 Gy (interquartile range 28.2-37.7 Gy), which is significantly higher (P = 0.002). The use of a three-field technique throughout treatment also reduced the median cardiac dose from 27.4 Gy to 22.7 Gy (P = 0.001) and the volume of heart receiving 70% of total dose from 63.8% to 25% (P = 0.001). CONCLUSION: This study highlights the significant dose of radiation received by the heart during oesophageal CT-RT, with consequent reduction in cardiac ejection fraction. Conformal radiotherapy reduces cardiac doses received. The cardiac, as well as the pulmonary, side effects of CT-RT needs to be borne in mind, especially when using this treatment before radical surgery.

Adult↗
PubMedDate not supplied

Computer-aided design and modeling of workstations and radiology reading rooms for the new millennium.

Three-dimensional (3D) computer modeling, simulation, and rendering techniques were used to redesign the diagnostic workstations and radiology reading rooms for a proposed hospital with particular attention given to lighting conditions, noise reduction, and optimal use of limited workspace. The results were presented to a panel of multidisciplinary experts and iteratively improved and redesigned with the development or addition of new design criteria or requirements. These 3D techniques allowed faster, more efficient design and presentation of multiple options than is possible with traditional two-dimensional drawings, thereby expediting decision making and resulting in significant savings. The current workstation designs can easily be developed and implemented with available technology at a reasonable cost. They can also accommodate anticipated advances in computer and display technology as well as new imaging paradigms (eg, changes in keyboard and control ergonomics such as adjustable virtual keys on touch-sensitive screens, digital drawing tablets for annotations and controls, direct film digitizing, personal identification devices, offline media readers such as compact disks and digital videodisks, and speech recognition and voice activation). Use of 3D techniques in designing other parts of the radiology department (eg, examination rooms, technologists' areas, physicians' offices) could greatly improve and facilitate the design and implementation of complex settings in these work areas.

Computer Simulation↗
PubMed2006

Marginal hepatectomy in the rat: from anatomy to surgery.

OBJECTIVE: Based on the 3-dimensional visualization of vascular supply and drainage, a vessel-oriented resection technique was optimized. The new surgical technique was used to determine the maximal reduction in liver mass enabling a 50% 1-week survival rate. BACKGROUND DATA: Determination of the minimal liver mass is necessary in clinical as well as in experimental liver surgery. In rats, survival seems to depend on the surgical technique applied. Extended hepatectomy with removal of 90% of the liver mass was long regarded as a lethal model. Introduction of a vessel-oriented approach enabled long-term survival in this model. METHODS: The lobar and vascular anatomy of rat livers was visualized by plastination of the whole organ, respectively, by corrosion casts of the portal vein, hepatic artery and liver veins. The three-dimensional models were used to extract the underlying anatomic structure. In 90% partial hepatectomy, the liver parenchyma was clamped close to the base of the respective liver lobes (left lateral, median and right, liver lobe). Piercing sutures were placed through the liver parenchyma, so that the stem of portal vein and the accompanying hepatic artery but also the hepatic vein were included. RESULTS: A 1-week survival rate of 100% was achieved after 90% hepatectomy. Extending the procedure to 95% resection by additional removal of the upper caudate lobe led to a 1-week survival rate of 66%; 97% partial hepatectomy, accomplished by additional resection of the lower caudate lobe only leaving the paracaval parts of the liver behind, resulted in 100% lethality within 4 days. CONCLUSIONS: Using a anatomically based, vessel-oriented, parenchyma-preserving surgical technique in 95% liver resections led to long-term survival. This represents the maximal reduction of liver mass compatible with survival.

Animals↗
PubMed1985

Dimension reduction projection and our perception of evolution.

The evolution of a species can be viewed as a trajectory in multidimensional space. What we perceive is only a low dimensional projection from the total dimensionality necessary to fully describe a species. Motivated by the phenomenon of punctuated equilibria, it is shown that there are projections of gradualistic evolution which will have a punctuated character. However, whether our eyes and minds would choose such a projection of the total phenotype is not resolved.

Animals↗
PubMed1995

The genes encoding the delta subunits of dinitrogenases 2 and 3 are required for mo-independent diazotrophic growth by Azotobacter vinelandii.

vnfG and anfG encode the delta subunits of alternative nitrogenases 2 and 3 in Azotobacter vinelandii, respectively. As a first step towards elucidating the role of these subunits, diazotrophic growth and acetylene reduction studies were conducted on mutants containing alterations in the genes encoding these subunits. Mutants containing a stop codon (C36stop) or an in-frame deletion in anfG were unable to grow in N-free, Mo-deficient medium (Anf-). Mutants in which cysteine 36 of AnfG (a residue conserved between VnfG and AnfG) was changed to Ala or Ser were Anf+. Thus, this conserved cysteine is not essential for the function of AnfG in dinitrogenase 3. A mutant with a stop codon in vnfG (C17stop) grew after a lag of 25 h in N-free, Mo-deficient medium containing V2O5. However, a Nif- Anf- strain with this mutation was unable to grow under these conditions. This shows that the vnfG gene product is required for nitrogenase 2-dependent growth. Strains with mutations in vnfG and anfG reduced acetylene to different degrees. This indicates that the delta subunits are not required for acetylene reduction by nitrogenases 2 and 3.

Acetylene↗
PubMed1998

Dimensional changes during veneering procedures on discoloured teeth.

OBJECTIVES: The aim of the study was to determine the dimensional changes of teeth when veneering procedures are involved. METHODS: Fifteen discoloured central incisors were selected from a group of 180 veneer restorations (VRs) composed of three different types of materials (direct resin composite, indirect resin composite and porcelain). Impressions and dies were made before treatment, after preparation and after placement and finishing the restoration. Contact stylus profilometry and subsequent analysis of the 3-D surface images provided quantitative data of the differences between the various treatment phases. RESULTS: The preparation reduction was the most for indirect resin composite VRs and the least for direct resin composite VRs. All veneer restorations showed nearly the same thickness and dimensional change after treatment, except one, which resulted in an additional increase of volume of the tooth. CONCLUSION: From the results of this study it is concluded that the dimensions of a discoloured tooth treated with a veneer restoration unintentionally increased, resulting in overcontour.

Analysis of Variance↗
PubMed1992

Modulation of protein composition of nuclear lamina. Reduction of lamins B1 and B2 in livers of griseofulvin-treated mice.

Chronic griseofulvin (GF) intoxication of mice leads to severe alterations of the hepatocytic intermediate filament cytoskeleton similar to that found in alcoholic hepatitis in humans (i.e., derangement and diminution of the keratin filament network and appearance of cytoplasmic aggregates of keratin-containing material, termed Mallory bodies). To investigate eventual alterations of nuclear lamins under these pathologic situations monoclonal antibodies were produced. One of these, GL-35, was directed to lamin B1 and lamin B2. Immunofluorescence microscopy revealed in GF-treated livers, in comparison to normal mouse livers, a highly reduced immunoreaction for lamins B1 and B2, whereas the staining for lamins A and C was unchanged. This reduction of both B-type lamins occurred before detectable alterations of keratin filaments and was reversible after cessation of GF intoxication. A diminished content of both B-type lamins in relation to lamins A and C in GF-intoxicated livers was also revealed by analysis of isolated nuclear envelopes on two-dimensional gels. Moreover, there was a clear predominance of more acidic isoelectric variants of lamins B1 and B2. In contrast to the reduced amount of B-type lamin proteins no reduction in the concentration of the mRNA for lamin B1 was found. For lamin B2 even an increase of mRNA was detected in GF-treated livers. These results indicate that GF not only interferes with expression of the keratin intermediate filament skeleton of hepatocytes but also leads to selective alterations of the nuclear lamins, most likely by posttranslational modifications of intermediate filament proteins.

Animals↗
PubMed2001

Manifold reduction of moesin in fetal Down syndrome brain.

Moesin is a member of the ERM family and is involved in plasma membrane-actin cytoskeleton cross-linking, resulting cell adhesion, shape, and motility. Because moesin was shown to be highly expressed in growth cones and moesin/radixin suppression led to impaired structure and function of this key element in brain development, we tested the ERM family, ezrin, radixin, and moesin, in fetal Down syndrome (DS) cortex at the early second trimester. We applied two-dimensional gel electrophoresis with subsequent MALDI detection and identification of protein spots followed by quantification with specific software. Moesin was shown to be significantly and manifold reduced in fetal DS brain, whereas reduction of ezrin and radixin did not reach statistical significance. We therefore propose the involvement of moesin in developmental impairment of DS brain, including deteriorated arborisation, neuritic outgrowth, and neuronal migration. Furthermore, decreased moesin is the second F-actin bundling protein, besides drebrin, that is manifold reduced in fetal DS brain.

Blood Proteins↗