Deconvolution methods for mitigation of transverse blurring in optical coherence tomography.

Imaging resolution in optical coherence tomography (OCT) is a key determinant for acquiring clinically useful optical biopsies of tissues. In contrast to light or confocal microscopy, the axial and transverse resolutions in OCT are independent and each can be analyzed individually. A method for mitigating transverse blurring and the apparent loss of transverse resolution in OCT by means of Gaussian beam deconvolution is presented. Such a method provides better representation of a specimen by using known physical parameters of a lens. To implement this method, deconvolution algorithms based on a focal-dependent kernel are investigated. First, the direct inverse problem is investigated using two types of regularization, truncated singular value decomposition, and Tikhonov. Second, an iterative expectation maximization algorithm, the Richardson-Lucy algorithm, with a beam-width-dependent iteration scheme is developed. A dynamically iterative Richardson-Lucy algorithm can reduce transverse blurring by providing an improvement in the transverse point-spread-function for sparse scattering samples in regions up to two times larger than the confocal region of the lens. These deblurring improvements inside and outside of the confocal region, which are validated experimentally, are possible without introducing new optical imaging hardware or acquiring multiple images of the same specimen. Implementation of this method in sparse scattering specimens, such as engineered tissues, has the potential to improve cellular detection and categorization.     

Multimer formation as a consequence of separate homodimerization domains: the human c-Jun leucine zipper is a transplantable dimerization module

The eighth sentences shpuld read as follows. rFosLZ–GSTweakly associates beyond a dimer (K_a –4x10⁴ M^–1)and rJunLZ–GST associates indefinitely (K^a –4x10⁵M^–1), consistent with an isodesmic model of association.     

Mass determination of the fatty acids released from tannin-stimulated rabbit alveolar macrophages

Previous studies with macrophages that had been prelabeled with [¹⁴C]arachidonic acid (20∶4) have shown that condensed tannin is a potent agonist for the release of arachidonic acid. However, it has not been demonstrated that the percentage release of [¹⁴C]20∶4 accurately reflects the metabolic activity of the endogenous 20∶4 pool. In order to measure the 20∶4 mass release relative to the total cellular 20∶4 pool, the free fatty acids of freshly isolated alveolar macrophages were derivatized with a fluorescent reagent, and then separated and quantified by high-performance liquid chromatography. The amounts of esterified fatty acids were measured by gas chromatography of the methyl esters. Free fatty acid levels were compared to those of the total esterified plus unesterified fatty acids to determine the actual percentage released of each fatty acid. Tannin-stimulated release of 20∶4 mass reflected that previously reported for the release of [¹⁴C]20∶4 label but at a slower rate and at a much lower percentage indicating that [¹⁴C]20∶4 had been incorporated into part of a more reactive pool. The specificity of the fatty acid release induced by tannin and β-1,3-glucan, a known agonist for 20∶4 release, was also examined. Both agonists promoted an increase in the levels of free 20∶4 and of other fatty acids. A comparison of the absolute increases of each of the fatty acids indicated that tannin caused a preferential increase in the mass of free 20∶4, whereas β-1,3-glucan evoked a selective increase in the mass of 16∶0. Deceased.     

Multimer formation as a consequence of separate homodimerization domains: the human c-Jun leucine zipper is a transplantable dimerization module

Human c-Jun and c-Fos leucine zipper domains were examined fortheir ability to serve as autonomous dimerization domains aspart of a heterologous protein construct. Schistosoma japonicumglutathione S-transferase (GST) was fused to recombinant Junleucine zipper (rJunLZ) and Fos leucine zipper (rFosLZ) domains.SDS–PAGE ‘snapshot’ analyses based on disulphidelinkage of monomers demonstrated the ability of rJunLZ to functionas a dimerization motif in a foreign protein environment. Sterichindrance prevented formation of rJunLZ–GST::rFosLZ–GSTheterodimers whereas rJunLZ–GST::rFosLZ and rJunLZ::rFosLZ–GSTformed readily. Furthermore, rJunLZ–GST generated homodimerssuggesting fusion protein heterodimers interact differentlyto homodimers. Gel filtration chromatography confirmed thatGST is a dimer in solution and that attachment of a leucinezipper domain allows further interactions to take place. Sedimentationequilibrium analyses showed that GST is a stable dimer (K_a >10⁶ M^-1) with no higher multimeric forms. rFosLZ–GST weaklyassociates beyond a dimer (K_a {small tilde}4x10⁵ M^-1) and rJunLZ–GSTassociates indefinitely (K_a {small tilde}4x10⁶ M^-1), consistentwith an isodesmic model of association. The interaction of theseleucine zippers independently of GST association demonstratestheir utility in the modification of proteins when multimerformation is desired.     

Carrier capture and escape times in In/sub 0.35/Ga/sub 0.65/As-GaAs multiquantum-well lasers determined from high-frequency electrical impedance measurements

We present experimental results on the high-frequency electrical impedance of In/sub 0.35/Ga/sub 0.65/As-GaAs multiquantum-well lasers with varied p-doping levels in the active region. The analysis of the data, using a simple three rate equation model, provides information about the dynamical time constants (the carrier lifetime, the effective carrier capture and escape times) under the laser operation conditions. The addition of p-doping increases the carrier escape time at threshold from 0.7 ns, extracted for the undoped devices, up to a value higher than 2 ns for the p-doped lasers. The effective capture time is estimated to be between 2 and 5 ps.     

Cell wall structure and wood properties determined by acoustics—a selective review

The cell wall of wood tracheids is made up of various layers, distinguished from one other by the alignment of the innumerable, fine crystalline cellulose microfibrils within each layer that helically wind about the cell lumen. Microfibrils themselves are embedded in a more compliant, water-reactive matrix of amorphous lignin and hemicelluloses. The average inclination of microfibrils relative to the axis of the cell affects axial rigidity and dimensional stability of wood which are the two most important properties of wood. High and variable microfibril angles can be found in juvenile and compression wood, thus resulting in variations in product performance of forest products. For instance, seemingly identical trees in a plantation can have moduli of elasticity that differ by a factor of two or more. This is why the future is often seen in engineered wood products, where wood may be chipped, fiberised and blended before being glued together again: the average property values are little changed, but the range—the variability—is greatly reduced. There is the opportunity for better wood allocation and processing of timber, if averaged values for individual log characteristics, such as average microfibril angle, can be identified before the processing. In parallel there is genetic potential to select trees with low average microfibril angles. Unfortunately, determination of the average microfibril angle is a time-consuming, laboratory-based task. Preferably, a non-destructive, simple, field-hardened method should be employed that reflects the average microfibril angle in a given piece of wood. For this reason, acoustic methods have been developed to measure the velocity of sound propagation directly related to the stiffness of wood and in turn is dependent on the ultrastructure of the tracheid cell wall. In the fundamental equation, E_dynamic=V², the acoustic modulus is derived from two components, density, , and velocity of sound, V. The latter relates to the intrinsic wood quality and ultrastructure of the tracheid wall. It is shown that acoustic methods can sort and grade trees and logs according to their suitability for structural lumber and for a range of fiber properties of interest to papermakers. Thus, acoustic methods have applications in tree breeding, harvesting, and wood processing.

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Zellwandstruktur und Holzeigenschaften durch akustische Methoden bestimmt

Zusammenfassung Die Zellwand von Holztracheiden besteht aus verschiedenen Schichten, die sich von einander durch eine Aneinanderreihung von unzähligen feinen kristallinen Zellulose-Mikrofibrillen in jeder der Schichten unterscheiden, die sich helikal um das Zelllumen winden. Die Mikrofibrillen selbst sind in eine wasser-reaktive Matrix aus amorphem Lignin und Hemizellulosen eingebettet. Der durchschnittliche Neigungswinkel der Mikrofibrillen relativ zur Achse der Zellen beeinflusst die axiale Steifigkeit und die Dimensionsstabilität des Holzes, die beiden wichtigsten technischen Eigenschaften von Holz. Steile und variable Mikrofibrillenwinkel können in juvenilem und Druckholz gefunden werden, wodurch sich Unterschiede in der Verarbeitung von Holzwerkstoffen ergeben. Beispielsweise können scheinbar identische Bäume in einer Plantage Elastizitätsmoduli aufweisen, die sich durch einen Faktor von zwei und mehr unterscheiden. Aus diesem Grund wird die Zukunft oft in technischen Holzprodukten gesehen, wo Holz zerspant, zerfasert und gemischt wird, bevor man es wieder zusammenleimt: die durchschnittlichen Eigenschaften werden wenig verändert, aber die Bandbreite—die Variabilität—wird stark reduziert. Können durchschnittliche Werte für individuelle Holzbalkencharakteristika, wie der Durchschnitts-Mikrofibrillenwinkel vorher bestimmt werden, besteht die Gelegenheit für eine bessere Holzauswahl und -verarbeitung. Parallel dazu gibt es ein genetisches Potential, um Bäume mit niedrigen Durchschnitts-Mikrofibrillenwinkeln zu selektieren. Leider ist die Bestimmung der Durchschnitts-Mikrofibrillenwinkel eine zeitaufwendige, auf das Labor bezogene Aufgabe. Vorzugsweise sollte eine zerstörungsfreie, einfache außen erprobte Methode eingesetzt werden, die den Durchschnitts-Mikrovibrillenwinkel in einem gegebenen Holzstück reflektiert. Aufgrund dessen wurden akustische Methoden entwickelt, um die Geschwindigkeit der Schallausbreitung zu messen, die direkt mit der Festigkeit des Holzes korreliert und damit auch abhängig ist von der Ultrastruktur der Zellwand. In der Grundgleichung, E_dynamic=V², wird der akustische Modulus von zwei Komponenten abgeleitet, der Dichte, , und der Schallgeschwindigkeit, V. Letztere bezieht sich auf die intrinsische Holzqualität und die Ultrastruktur der Tracheiden-Wand. Es wird gezeigt, dass die akustische Methode in der Lage ist, Bäume und Rundholz gemäß ihrer Eignung für Bauholz und für eine Bandbreite von Fasereigenschaften, im Interesse der Papierhersteller, zu sortieren und einzuteilen. Auf diese Weise finden akustische Methoden Anwendung bei der Aufzucht von Bäumen, ihrer Abholzung und Verarbeitung.

     

Apoptosis in interface membranes of aseptically loose total hip arthroplasty

The terminal events leading to periprosthetic osteolysis are multifactorial in nature and modulation of this process after the stage of osteolytic mediator release has been futile. Recently, the demonstration of the ability of bisphosphonates to inhibit bone resorption that is mediated by particle-stimulated macrophages and their induction of osteoclast apoptosis suggests a potent area for modulation of osteolysis at the prosthesis-bone interface. The purpose of this study was to determine the mode of cell death that occurs at the osteolytic interface of failed total hip arthroplasty (THA). TUNEL staining, DNA laddering, and immunodetection of poly(ADP-ribose)polymerase (PARP) protein were used to identify the presence of apoptosis in interface membranes from 25 patients aged 28–88 years old (mean, 58 years) harvested at the time of hip revision surgery. Our results demonstrated positive TUNEL stain in 100% of specimens with an average 37% of cells (range 12–60%) positively stained for TUNEL whereas less than 8% of control tissue cells showed positive staining. DNA laddering, a characteristic feature of apoptotic cells, was observed in 82% (28/34) of specimens studied at both the acetabular and femoral side of aseptically loose THAs. No laddering was observed in control tissues. Finally, using Western blot analysis, we observed the appearance of the 89 kDa PARP fragment associated with apoptosis in 92% of specimens (30/33). Our results demonstrate the presence of apoptotic cell death in interface membranes of THAs suggesting that apoptosis-related events are indeed associated with periprosthetic osteolysis and could serve as a specific target point for therapeutic modulation. © 2001 Kluwer Academic Publishers     

Investigation of the role of interfacial chemistry on particle interactions, sedimentation and electroosmotic dewatering of model kaolinite dispersions

The influence of pulp chemistry on particle interactions and dewatering behaviour of colloidal kaolinite dispersions has been investigated under coagulation conditions. The dispersion shear yield stress, settling rate and consolidation showed strong dependence upon pH and ionic strength, indicating a maximum at ∼pH 3.2 which was established as the isoelectric point (iep) by particle zeta potential analysis. A “gel point” solid concentration at which the dispersion began to be significantly networked and gravity-driven consolidation of the pulp was completely suppressed, occurred at 13 vol.% (∼28 wt.%). The dewatering rates due to coagulation were significantly lower than those commonly achieved by polymeric flocculation, however the sediment consolidation was ∼25% higher when compared with flocculated pulps. Electroosmosis was found to be effective in consolidating pre-sedimented pulps to spadeable pastes (∼30 vol.%) at pH values away from the iep where zeta potential was higher and ionic strength low (10^− 3 M). This pulp consistency or markedly improved consolidation behavior is not achievable under coagulation and/or flocculation conditions.