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PubMed1996

Three-dimensional dynamic geometry of the normal canine mitral annulus and papillary muscles.

BACKGROUND: Despite an incomplete knowledge of the geometry and dynamics of the mitral annulus (MA), papillary muscle (PM), and the chordae tendineac, chordal-sparing MVR is popular. METHODS AND RESULTS: The systolic reduction in three-dimensional distance between each PM tip and eight MA sites (DT-A) was measured in nine normal closed-chest dogs by use of surgically implanted radiopaque markers. Three loci (tip, junction, and base) on each PM were also projected onto the MA plane at end diastole and end systole to assess PM dynamics. The anterior PM tip showed significant shortening of DT-A toward the opposite side of the MA or the midanterior MA region (P < .005 or P < .05, respectively, versus same MA side [MANOVA]); conversely, the posterior PM tip DT-A shortened toward the opposite side of the MA near the anterior commissure or the area between the anterior commissure and midposterior MA (P < .005 versus same MA side). Annular projection revealed three-dimensional motion (relative to the MA) of the anterior PM tip, junction, and base toward the right trigone, while posterior PM motion was oriented toward the opposite side of the MA. CONCLUSIONS: Both PMs in normal canine hearts demonstrated systolic relative motion in a direction compatible with the "oblique" chordal configuration, ie, from the anterior PM to the anterior MA near the right trigone and from the posterior PM to the opposite side of the posterior MA. These observations warrant further investigation of three-dimensional PM-MA dynamics with various methods of chorda preservation during MVR to assess their impact on left ventricular systolic and diastolic function.

Animals↗
PubMed2004

Fano factor reduction on the 0.7 conductance structure of a ballistic one-dimensional wire.

We have measured the nonequilibrium current noise in a ballistic one-dimensional wire which exhibits an additional conductance plateau at 0.7x2e(2)/h. The Fano factor shows a clear reduction on the 0.7 structure, and eventually vanishes upon applying a strong parallel magnetic field. These results provide experimental evidence that the 0.7 structure is associated with two conduction channels that have different transmission probabilities.

Journal Article↗
PubMed2004

Reduction of coherent artifacts in dynamic holographic three-dimensional displays by diffraction-specific pseudorandom diffusion.

An electroholographic display based on diffraction-specific computation can reduce speckle by electronic diffusion through selective addition of a pseudorandom sequence. Intensity fluctuation as a result of the introduction of pseudorandom noise does not affect three-dimensional (3-D) images significantly since spatial windows formed by diffused basis fringes do not widen noticeably at low pseudorandom spread, whereas the features of the fluctuation are much smaller than human visual resolution. Experimental results obtained on the Massachusetts Institute of Technology holographic video system confirmed that the diffusion smooths 3-D images and improves the intensity nonuniformity among horizontal holographic lines.

Journal Article↗
PubMed2006

Possible origins of the complex topographic organization of motor cortex: reduction of a multidimensional space onto a two-dimensional array.

We propose that some of the features of the topographic organization in motor cortex emerge from a competition among several conflicting mapping requisites. These competing requisites include a somatotopic map of the body, a map of hand location in space, and a partitioning of cortex into regions that emphasize different complex, ethologically relevant movements. No one type of map fully explains the topography; instead, all three influences (and perhaps others untested here) interact to form the topography. A standard algorithm (Kohonen network) was used to generate an artificial motor cortex array that optimized local continuity for these conflicting mapping requisites. The resultant hybrid map contained many features seen in actual motor cortex, including the following: a rough, overlapping somatotopy; a posterior strip in which simpler movements were represented and more somatotopic segregation was observed, and an anterior strip in which more complex, multisegmental movements were represented and the somatotopy was less segregated; a clustering of different complex, multisegmental movements into specific subregions of cortex that resembled the arrangement of subregions found in the monkey; three hand representations arranged on the cortex in a manner similar to the primary motor, dorsal premotor, and ventral premotor hand areas in the monkey; and maps of hand location that approximately matched the maps observed in the monkey.

Algorithms↗
PubMed2003

Simulation analysis of the ability of different types of multi-electrodes to increase selectivity of detection and to reduce cross-talk.

Selectivity of different one- and two-dimensional multi-electrodes and their ability to reduce cross-talk were analyzed. Signals from an individual motor unit (MU) were calculated as a single convolution of intracellular action potential (IAP) first temporal derivative and spatially filtered MU impulse response. It was shown that the uptake area (irrespective of the way it was defined) could not characterize electrode properties reliably because its estimate depended on the source parameters. Due to the different decline of individual phases of MU signals with depth, electrode should provide higher spatial and temporal resolution of the main phases for better selectivity and greater suppression of the terminal phases for cross-talk reduction. A two-dimensional normal double differentiating (NDD) electrode provided almost the same or slightly lower selectivity but weaker reduction of cross-talk than a longitudinal double differentiating (LDD) electrode. A transversal double differentiating (TDD) electrode provided a lower selectivity and weaker reduction of cross-talk than a LDD electrode. A new, BiTDD multi-electrode (performing difference between signals detected by two TDD electrodes) provided the best selectivity and reduction of cross-talk. To obtain the smallest cross-talk, a BiTDD electrode should be positioned above the end-plate region, while LDD, TDD, or NDD electrodes-above the ends of muscle that produced it. Signal differentiation improved selectivity but increased cross-talk.

Electrodes↗
PubMed1987

Comparison of echocardiographic methods for assessment of left ventricular shortening and wall stress.

M-mode echocardiographic measurement of left ventricular fractional shortening and meridional wall stress has been used extensively alone and in combination to describe left ventricular systolic function. To determine whether the improved dimensional information afforded by two-dimensional echocardiography might result in shortening and stress calculations yielding a different view of left ventricular function, we compared two-dimensional and M-mode echocardiograms in 69 subjects (19 normal, 13 with aortic stenosis, 22 with aortic regurgitation and 15 with congestive cardiomyopathy). Fractional shortening was greater with M-mode than with two-dimensional echocardiography in all subjects, especially in those with cardiomyopathy (p less than 0.05). In aortic stenosis, two-dimensional shortening, at 24 +/- 5%, was reduced (p less than 0.05 versus normal), but M-mode shortening, at 34 +/- 5%, was not. M-mode estimates of meridional stress were higher than two-dimensional values, again especially in cardiomyopathy. Two-dimensional echocardiography enabled determination of long- and short-axis ratios, circumferential stress and the ratio of circumferential to meridional stresses. Circumferential stress was elevated in aortic stenosis at 302 +/- 65 X 10(3) dynes/cm2, suggesting afterload excess as the cause for the observed reduction in two-dimensional shortening. The more spherical cardiomyopathic hearts had a meridional to circumferential stress ratio closer to 1, such that use of meridional stress alone would overestimate effective afterload. It is concluded that M-mode and two-dimensional echocardiographic analyses of left ventricular shortening and stress produce different results. Two-dimensional echocardiographic methods may enhance the assessment of ventricular function, especially in patients with aortic stenosis and cardiomyopathy.

Adult↗
PubMed1991

Randomised trial of chemotherapy versus endocrine therapy in patients presenting with locally advanced breast cancer (a pilot study).

Sixty patients with locally advanced breast cancer, but with no evidence of distant metastases were randomised to receive primary endocrine therapy or chemotherapy after assessment and 'Trucut' biopsy of the primary tumour. After 12 weeks all patients were assessed. Eight out of 30 (27%) of the patients who received chemotherapy showed complete clinical regression of the primary cancer, eight patients' tumours had regressed by more than 50%, and ten showed a 25-50% reduction in bi-dimensional diameter. Only four (13%) patients' tumours failed to reduce in size. Seven patients were judged to require mastectomy at the end of the 12 week period of treatment with chemotherapy. In contrast, only three out of 30 (10%) patients receiving endocrine therapy showed a greater than 50% reduction in tumour size, and four patients had a 25-50% reduction at 12 weeks. The remaining patients' tumours either stabilised (12 patients) or enlarged (11 patients). We conclude that primary chemotherapy in patients with primary breast cancer is more effective in rapidly reducing the size of the primary breast cancer than endocrine therapy (P = 0.001) and alters significantly the future management of these patients. However, at 65 weeks on completion of the follow-up, there is no significant difference in the number of patients' disease-free, locally or distant recurrent, or dead.

Adult↗
PubMed1999

Reducing cardiac dose in post-operative irradiation of breast cancer patients: the relative importance of patient positioning and CT scan planning.

Left-sided post-operative radiotherapy fields for the treatment of breast cancer inevitably encompass the heart within the treatment volume, resulting in late mortality which may negate the cause-specific survival advantage of the therapy. The effect of positioning was studied in 11 patients with left-sided tumours and five with right-sided tumours receiving routine post-operative radiotherapy to the breast or chest wall as part of primary therapy for breast cancer. Using the same arrangement of glancing fields for each patient treatment position, the optimum patient positioning resulted in a reduction in cardiac dose compared to our standard patient treatment position. On the left side the reduction in mean cardiac dose was 60% (p < 0.001) and the reduction in maximum dose was 32% (p < 0.001); on the right it was 17% and 31%, respectively. The volume of cardiac tissue irradiated was also reduced for all patients. Using this optimum treatment position, cardiac dose was investigated in a further 10 patients with left-sided tumours and our standard glancing field set-up was compared with 3-dimensional planning. A further reduction of 12% in the mean cardiac dose was achieved. 5 of 10 patients had a further small reduction of 4.6% in the maximum dose and one patient had a further reduction in maximum dose of 58%. In conclusion, sophisticated radiotherapy planning can reduce cardiac doses, but optimum patient positioning is of greater importance. The general application of such relatively simple measures could have a significant positive effect on overall survival from breast cancer.

Breast Neoplasms↗
PubMed1983

Incomplete filling and incoordinate contraction as mechanisms of hypotension during ventricular tachycardia in man.

We sought to determine mechanisms for decrease of cardiac output and for hypotension during ventricular tachycardia (VT) in man. Two-dimensional and M mode echocardiograms and left ventricular pressure from micromanometer-tipped catheters were obtained in 20 patients before, during, and at the end of induced hypotensive VT. Patients were divided into two groups according to left ventricular function in sinus rhythm as assessed by angiographic ejection fraction (EF) before electrophysiologic study. Group 1 (n = 8) had angiographic EF greater than or equal to 50% in normal sinus rhythm, and group 2 (n = 12) had EF less than or equal to 40%. During VT, left ventricular cavity volume (as indexed by short- and long-axis two-dimensional end-diastolic cavity areas) was markedly reduced in group 1, from 19.7 +/- 2 to 8.6 +/- 2 cm2 (p less than .001) and from 32.0 +/- 8 to 22.5 +/- 7 cm2 (p less than .001), respectively, but was only slightly reduced in group 2, from 34.1 +/- 6 to 31.5 +/- 7 cm2 (p = .044) and from 45.0 +/- 8 to 49.4 +/- 7 cm2 (p = NS), respectively. Conversely, left ventricular systolic function during VT (as indexed by fractional reduction in two-dimensional short- and long-axis areas) was markedly depressed in group 2, from 25.6 +/- 6% to 4.2 +/- 4% (p = .005) and from 13.7 +/- 3% to 1.8 +/- 0.8% (p less than .001), respectively, but remained at control levels in group 1. Left ventricular end-diastolic pressures increased in group 1, from 11.8 +/- 2 to 27.7 +/- 8 mm Hg (p = .005) and did not change in group 2 during VT. Pressure-dimension loops from left ventricular pressure and M mode echocardiographically determined cavity dimensions generated from the end of the VT episodes showed that diastolic pressure-dimension relationships returned to control levels with the first prolonged diastolic interval in group 1 patients, indicating that incomplete relaxation was the mechanism responsible for reduction of cardiac output during VT in these patients. Coordination of contraction and relaxation (indicated by the percent ratio of the pressure-dimension loop area to the area of the rectangle just enclosing the loop) decreased from 37 +/- 11% to 16 +/- 13% in group 2 patients during VT (p = .013) but remained at control levels in group 1 patients. Thus, during VT patients with impaired left ventricular function in sinus rhythm (group 2) developed severe discoordination, and patients with normal or near-normal function (group 1) developed incomplete relaxation to account for stroke volume deterioration and hypotension.

Adolescent↗
PubMed1990

[Left ventricular ejection fraction estimated by 2-dimensional echocardiography].

Visual assessment of the reduction of left ventricular volumes during the cardiac cycle, which is the basis for calculation of the left ventricular ejection fraction followed up from several planes in real time is close to the objectively assessed changes estimated by various time consuming methods from two-dimensional echocardiography by the one- or two-plane method. The author's method makes it possible to assess the left ventricular ejection fraction and to divide it for clinical needs into four groups: normal above 60%, slightly reduced 45-60%, reduced 30-45% and markedly reduced 30% or less. The described echocardiographic examination method is invaluable when practiced by an experienced worker with restricted time for examination.

Echocardiography↗
PubMed2000

Transition from anaerobic to aerobic growth conditions for the sulfate-reducing bacterium Desulfovibrio oxyclinae results in flocculation.

A chemostat culture of the sulfate-reducing bacterium Desulfovibrio oxyclinae isolated from the oxic layer of a hypersaline cyanobacterial mat was grown anaerobically and then subjected to gassing with 1% oxygen, both at a dilution rate of 0.05 h(-1). The sulfate reduction rate under anaerobic conditions was 370 nmol of SO(4)(2-) mg of protein(-1) min(-1). At the onset of aerobic gassing, sulfate reduction decreased by 40%, although viable cell numbers did not decrease. After 42 h, the sulfate reduction rate returned to the level observed in the anaerobic culture. At this stage the growth yield increased by 180% compared to the anaerobic culture to 4.4 g of protein per mol of sulfate reduced. Protein content per cell increased at the same time by 40%. The oxygen consumption rate per milligram of protein measured in washed cell suspensions increased by 80%, and the thiosulfate reduction rate of the same samples increased by 29% with lactate as the electron donor. These findings indicated possible oxygen-dependent enhancement of growth. After 140 h of growth under oxygen flux, formation of cell aggregates 0.1 to 3 mm in diameter was observed. Micrometer-sized aggregates were found to form earlier, during the first hours of exposure to oxygen. The respiration rate of D. oxyclinae was sufficient to create anoxia inside clumps larger than 3 microm, while the levels of dissolved oxygen in the growth vessel were 0.7 +/- 0.5 microM. Aggregation of sulfate-reducing bacteria was observed within a Microcoleus chthonoplastes-dominated layer of a cyanobacterial mat under daily exposure to oxygen concentrations of up to 900 microM. Desulfonema-like sulfate-reducing bacteria were also common in this environment along with other nonaggregated sulfate-reducing bacteria. Two-dimensional mapping of sulfate reduction showed heterogeneity of sulfate reduction activity in this oxic zone.

Aerobiosis↗
PubMed1997

Post-translational modifications of alpha5beta1 integrin by glycosaminoglycan chains. The alpha5beta1 integrin is a facultative proteoglycan.

Cell-fibronectin interactions, mediated through several different receptors, have been implicated in a wide variety of cellular properties. Among the cell surface receptors for fibronectin, integrins are the best characterized, particularly the prototype alpha5beta1 integrin. Using [125I]iodine cell surface labeling or metabolic radiolabeling with sodium [35S]sulfate, we identified alpha5beta1 integrin as the only sulfated integrin among beta1 integrin heterodimers expressed by the human melanoma cell line Mel-85. This facultative sulfation was confirmed not only by immunoprecipitation reactions using specific monoclonal antibodies but also by fibronectin affinity chromatography, two-dimensional electrophoresis, and chemical reduction. The covalent nature of alpha5beta1 integrin sulfation was evidenced by its resistance to treatments with high ionic, chaotrophic, and denaturing agents such as 4 M NaCl, 4 M MgCl2, 8 M urea, and 6 M guanidine HCl. Based on deglycosylation procedures as chemical beta-elimination, proteinase K digestion, and susceptibility to glycosaminoglycan lyases (chondroitinase ABC and heparitinases I and II), it was demonstrated that the alpha5beta1 heterodimer and alpha5 and beta1 integrin subunits were proteoglycans. The importance of alpha5beta1 sulfation was strengthened by the finding that this molecule is also sulfated in MG-63 (human osteosarcoma) and HCT-8 (human colon adenocarcinoma) cells.

Cell Adhesion↗
PubMed2000

Dynamics and control of a multimode laser: Reduction of space-dependent rate equations to a low-dimensional system.

We suggest a quantitatively correct procedure for reducing the spatial degrees of freedom of the space-dependent rate equations of a multimode laser that describe the dynamics of the population inversion of the active medium and the mode intensities of the standing waves in the laser cavity. The key idea of that reduction is to take advantage of the small value of the parameter that defines the ratio between the population inversion decay rate and the cavity decay rate. We generalize the reduction procedure for the case of an intracavity frequency doubled laser. Frequency conversion performed by an optically nonlinear crystal placed inside the laser cavity may cause a pronounced instability in the laser performance, leading to chaotic oscillations of the output intensity. Based on the reduced equations, we analyze the dynamical properties of the system as well as the problem of stabilizing the steady state. The numerical analysis is performed considering the specific system of a Nd:YAG (neodymium-doped yttrium aluminum garnet) laser with an intracavity KTP (potassium titanyl phosphate) crystal.

Journal Article↗
PubMed2001

Improving resolution in fast rotating-frame experiments.

The rapid rotating-frame technique allows significant reduction in data-acquisition time compared with the two-dimensional method by stroboscopic observation of the nuclear magnetization during its evolution in the rotating frame. A onefold reduction in the dimensionality of the original rotating-frame experiment is achieved by using a train of strong radiofrequency pulses separated by short acquisition windows. The penalty for shortening experimental time is a reduction in spectral resolution compared with the two-dimensional method due to relaxation of transverse magnetization components during the observation windows. A variant of the rapid-rotating frame technique for improving spectral resolution based on undersampling and self-phase encoding is presented. An M-fold resolution improvement requires M experiments, thus, making possible a tradeoff between spectral resolution and experimental time. The technique was applied for spatial localization of quadrupole nuclei in powder solids, and resolution improvement is demonstrated on one- and two-dimensional NQR images.

Journal Article↗
PubMed1984

Focal cerebral ischemia in the rat: topography of hemodynamic and histopathological changes.

We studied local cerebral blood flow, as measured by autoradiography with digital image processing and by tissue morphology, in six rats 4 hours after occlusion of the proximal middle cerebral artery. A consistent, three-dimensional pattern of graded reductions in local cerebral blood flow involved the affected hemisphere, with a densely ischemic zone (local cerebral blood flow less than 3 ml/100 gm/min) in the dorsolateral caudate putamen and the adjacent frontoparietal cortex. In the frontoparietal cortex, the normal laminar pattern of local cerebral blood flow was disrupted, and there was a transcortical gradient in flow, with pronounced ischemia in deeper layers and relatively preserved superficial flow. Comparisons of autoradiographic findings with histopathological abnormalities in adjacent frozen sections showed that the region of ischemic damage corresponded closely with the area of greatest reduction in blood flow. Although around this region local cerebral blood flow increased centrifugally, a striking finding was that flow density changed abruptly (a tenfold variation in flow within a 1 to 2 mm interval) at the edge of the pathological lesion. Penumbral conditions may therefore exist in only a very narrow zone 4 hours after onset of focal ischemia. After occlusion of a major cerebral artery, the pattern of local cerebral blood flow changes appears to depend on interactions among vascular architecture, reductions in perfusion pressure, alterations in metabolic demands, and variations in local vascular resistance.

Animals↗
PubMed2006

Spatial arrangement of metal nanoparticles supported by porous polymer substrates studied by transmission electron microtomography.

Fine metal particles (nanoparticles) stabilized on porous (polymeric) substrates can be considered as a model system of a high-performance catalyst. In the present study, the substrate was made using the periodic microphase-separated structure of a block copolymer as the template, and the Pd nanoparticles were formed inside the porous material by reduction of the Pd2+ ions with 1-propanol as the reductant. The three-dimensional morphology of such a polymer-Pd hybrid material was studied by transmission electron microtomography. The characteristic structural parameters of the hybrid, e.g., the penetration of the Pd nanoparticles into the polymer substrate, number density of the Pd nanoparticles, and size distribution of the Pd nanoparticles, were measured for the first time.

Metal Nanoparticles↗
PubMed2001

Critical conditions for phytoplankton blooms.

We motivate and analyse a reaction-advection-diffusion model for the dynamics of a phytoplankton species. The reproductive rate of the phytoplankton is determined by the local light intensity. The light intensity decreases with depth due to absorption by water and phytoplankton. Phytoplankton is transported by turbulent diffusion in a water column of given depth. Furthermore, it might be sinking or buoyant depending on its specific density. Dimensional analysis allows the reduction of the full problem to a problem with four dimensionless parameters that is fully explored. We prove that the critical parameter regime for which a stationary phytoplankton bloom ceases to exist, can be analysed by a reduced linearized equation with particular boundary conditions. This problem is mapped exactly to a Bessel function problem, which is evaluated both numerically and by asymptotic expansions. A final transformation from dimensionless parameters back to laboratory parameters results in a complete set of predictions for the conditions that allow phytoplankton bloom development. Our results show that the conditions for phytoplankton bloom development can be captured by a critical depth, a compensation depth, and zero, one or two critical values of the vertical turbulent diffusion coefficient. These experimentally testable predictions take the form of similarity laws: every plankton-water-light-system characterized by the same dimensionless parameters will show the same dynamics.

Light↗