EVOLUTION, Issue 6 2000
Michael C. Whitlock
Abstract With a small effective population size, random genetic drift is more important than selection in determining the fate of new alleles. Small populations therefore accumulate deleterious mutations. Left unchecked, the effect of these fixed alleles is to reduce the reproductive capacity of a species, eventually to the point of extinction. New beneficial mutations, if fixed by selection, can restore some of this lost fitness. This paper derives the overall change in fitness due to fixation of new deleterious and beneficial alleles, as a function of the distribution of effects of new mutations and the effective population size. There is a critical effective size below which a population will on average decline in fitness, but above which beneficial mutations allow the population to persist. With reasonable estimates of the relevant parameters, this critical effective size is likely to be a few hundred. Furthermore, sexual selection can act to reduce the fixation probability of deleterious new mutations and increase the probability of fixing new beneficial mutations. Sexual selection can therefore reduce the risk of extinction of small populations. [source]

COMPLICATIONS OF INTERNAL FIXATION IN PAEDIATRIC FRACTURES

ANZ JOURNAL OF SURGERY, Issue 10 2007
Audi B. Widjaja
Background: Most displaced fractures in children can be managed by closed treatment. Internal fixation of fractures is sometimes required to achieve satisfactory reduction with certain fractures. The aim of this study was to document the rate of complications associated with internal fixation of fractures in the paediatric age group. Methods: A retrospective study was carried out on 268 consecutive children who had internal fixation of fractures from January 2000 to July 2004. The complications were categorized as major or minor. Results: The average age was 9.2 years (range, 1.4,16.9). There were 327 fractures. Fifty-nine children had fractures of two bones. Humeral fractures accounted for 45.7% of fractures, forearm fractures 31.3%, tibial and fibular fractures 14.1% and femoral fractures 4.9%. There were 27 children (10%) with major complications and 49 children (18%) with minor complications. There were 18 children (6.7%) with both major and minor complications. A total of 66 (24.6%) children had complications. There were 23 children (8.5%) requiring further surgery. Conclusions: In this study, 24.6% of children had complications associated with internal fixation. The risk of complications should be considered when electing to proceed with surgical treatment. Closed treatment should always be attempted in children unless there is a good indication for internal fixation. [source]

Avoiding Accounting Fixation: Determinants of Cognitive Adaptation to Differences in Accounting Method,

CONTEMPORARY ACCOUNTING RESEARCH, Issue 2 2005
DAVID T. DEARMAN
Abstract Much research over the last 30 years has provided evidence that individuals display accounting fixation; that is, their cognitive process does not appropriately adapt to cross-sectional or temporal differences in an accounting method. This paper presents the results of a quasi-experimental test of the hypothesis that cognitive adaptation to a change in accounting method is an ordinal interactive function of three person characteristics: relevant accounting knowledge, general problem-solving ability, and intrinsic motivation to appropriately engage in the decision task. Based on a product-pricing decision task in which participants are provided with product costs reported by two generally employed product-costing methods (activity-based costing [ABC] and volume-based costing), the results show that the majority of participants did not change their cognitive behavior when there was a change in the costing method. Further, those participants who did adapt to the change in accounting method, and thus avoided accounting fixation, did so by debiasing costs reported by volume-based costing but not by ABC. Finally, these adapters generally exhibited high values for all three of the person characteristics compared with those who did not adapt. [source]

Deep Plane Fixation in Integumental Surgery

DERMATOLOGIC SURGERY, Issue 2 2004
Gerard E. Seery MD
Background. Standard wound closure techniques are prone to complication in the presence of tension. Objective. To show that deep plane fixation (DPF), a surgical modality based on limited undermining and strategic placement of DPF sutures, affects tension-reduced closure in wounds that would otherwise require skin grafts/flaps or tissue expansion. Methods. The study is based on an analysis of over 2000 scalp operations. Results. Two groupings of identical sagittal scalp reductions were done. DPF was used in one and not the other. In the series with DPF, reduced tension closure was consistently possible, as was significantly increased excision, relative to the series without DPF. Conclusions. DPF narrows the wound base and channels tension forces from superficial to deep and/or nonundermined tissues (where they harmlessly dissipate). This allows relatively increased tissue excision and tension-reduced closure. [source]

Desulfotomaculum genus- and subgenus-specific 16S rRNA hybridization probes for environmental studies

ENVIRONMENTAL MICROBIOLOGY, Issue 2 2000
Krassimira R. Hristova
Based on comparative analysis of 16S rRNA sequences and the recently established phylogeny of the genus Desulfotomaculum, a set of phylogenetically nested hybridization probes was developed and characterized. A genus-specific probe targets all known Desulfotomaculum species (with the exception of Desulfotomaculum acetoxidans,), and five specific probes target subclusters within the Desulfotomaculum genus. The dissociation temperature of each probe was determined experimentally. Probe specificities were verified through hybridizations with pure culture rRNA isolated from a wide variety of target and non-target organisms and through an evaluation of probe ,nesting' using samples obtained from four different environments. Fixation and hybridization conditions for fluorescence in situ hybridizations were also optimized. The probes were used in quantitative membrane hybridizations to determine the abundance of Desulfotomaculum species in thermophilic anaerobic digesters, in soil, in human faeces and in pig colon samples. Desulfotomaculum rRNA accounted for 0.3,2.1% of the total rRNA in the digesters, 2.6,6.6% in soil, 1.5,3.3% in human faeces and 2.5,6.2% in pig colon samples. [source]

Fixation of heavy contaminants of a dirty bomb attack: Studies with uranium and metal simulants

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2007
Thomas L. McGehee
Abstract Asphalt emulsions were evaluated as a means to immobilize radiological contaminants deposited on urban surfaces after a dirty bomb attack. Contaminated surfaces would be sprayed with thin coatings of asphalt emulsion to encapsulate the radioactive particles until the site can be safely remediated. This research investigated applications of an asphalt emulsion (Topein C, Encapco Technologies, LLC, Napa, CA) to treat (zero-valent) iron, lead, and uranium powders on various building material surfaces. Initial studies found that some of the building materials (limestone, concrete, and metal) reacted with the emulsion producing gas bubbles, which formed 0.001 to 1 cm vesicles in the cured asphalt emulsion. These vesicles, however, did not expose the building material surface, and the reaction appeared to aid in the setting of the emulsion. Powdered lead did not react with the asphalt emulsion, but iron powder and uranium did. Iron powder and the emulsion formed vesicles up to 0.5 mm (but not exposing the building material surface), while the uranium (U3O8) had a moderate reaction when compared with to the lead and iron powders. Scanning electron micrographs showed that the lead powder formed nonreactive layers adjacent to the concrete surface while iron particles were evenly distributed in the asphalt matrix due to the reaction with the asphalt, indicating that the physical and chemical reactions between the iron metal particles, asphalt, and concrete affected particle distribution in the asphalt matrix. A vertical operation sediment tube was used to determine the flowing shear stress durability of the asphalt/metal/substrate complex. The asphalt treatment with iron had no loss at the shear range tested (0.1,2.5 Pa), while the asphalt stabilized powdered lead lost 8% asphalt and lead at 2.5 Pa mean shear stress applied for 5 h. The chemical reaction between asphalt emulsion and iron increased the resistance of the asphalt/metal/substrate complex to shear when compared with lead. Some hydrogen was formed in reactions with iron, but the amount formed was well below the lower flammability limit. Treatment of uranium indicated that the emulsion was effective at reducing leaching of the uranium 10 fold. These experiments indicate that asphalt emulsions may be a viable means for containing metallic or dense radiological contaminants on common building materials. © 2007 American Institute of Chemical Engineers Environ Prog 26:94,103, 2007 [source]

Localisation and distribution of hyaluronan in normal bone marrow matrix: a novel method to evaluate impending fibrosis?

EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2002
Gunnel Sundström
Abstract: Bone marrow trephine biopsies from 30 healthy volunteers, 10 men and 20 women aged 18,60 yr were obtained for identification and localisation of hyaluronan (HYA). Fixation, decalcification and embedding were performed by two different methods, with identical results in both. For comparison bone marrow trephine biopsies from three patients with different haematological diseases and known fibrosis were studied. All bone marrow specimens were also stained for reticulin grading. HYA was found in the bone marrow specimens from healthy individuals in a pattern that was concordant with the reticulin staining, the common way of visualising bone marrow fibrosis. In bone marrow from the patients with known fibrosis the HYA and reticulin staining were both more intense and abundant. Interestingly, HYA was also found intracellularly in eosinophilic cells in normal bone marrow. HYA is a polysaccharide unique both in structural and biological properties, and in excess it may predict bone marrow fibrosis. [source]

CO2 Fixation and Activation by CuII Complexes of 5,5,-Terpyridinophane Macrocycles

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2008
Begoña Verdejo
Abstract An aza-terpyridinophane receptor containing the polyamine 4,7,10,13-tetraazahexadecane-1,16-diamine linked through methylene groups to the 5,5, positions of a terpyridine unit has been prepared and characterized (L). The acid-base behaviour, CuII speciation and ability to form ternary complexes (CuII -L-carbonate) have been explored by potentiometric titrations in 0.15 M NaClO4 and by UV/Vis and paramagnetic NMR spectroscopy. Comparisons are made with a previously reported terpyridinophane containing the polyamine 4,7,10-triazatridecane-1,13-diamine (L1). For this latter receptor, reductive coupling between indigo and carbon dioxide at indigo-modified electrodes produces carboxylated derivatives via a solid-state reaction under electrochemical activation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Polystyrene-Supported Amino Acids as Efficient Catalyst for Chemical Fixation of Carbon Dioxide

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010
Chaorong Qi
Abstract Four new polystyrene-supported amino acids have been synthesized and applied to the chemical fixation of carbon dioxide for the first time. Two series of experiments with polystyrene-supported threonine (PS-Thr) and polystyrene-supported tyrosine (PS-Tyr) as catalyst, respectively, were conducted to study the effect of the reaction conditions on the carboxylation of propylene oxide/carbon dioxide. There was no considerable decrease in the yield of propylene carbonate after the polystyrene-supported amino acids were used five times, indicating that these catalysts are very stable. It was demonstrated that these catalysts were very efficient in the carboxylation of various epoxides and aziridines with carbon dioxide under mild conditions without any solvents. The mechanism for this carboxylation is also discussed. [source]

Rapid assessment of internodal myelin integrity in central nervous system tissue

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2010
Daniel A. Kirschner
Abstract Monitoring pathology/regeneration in experimental models of de-/remyelination requires an accurate measure not only of functional changes but also of the amount of myelin. We tested whether X-ray diffraction (XRD), which measures periodicity in unfixed myelin, can assess the structural integrity of myelin in fixed tissue. From laboratories involved in spinal cord injury research and in studying the aging primate brain, we solicited "blind" samples and used an electronic detector to record rapidly the diffraction patterns (30 min each pattern) from them. We assessed myelin integrity by measuring its periodicity and relative amount. Fixation of tissue itself introduced ±10% variation in periodicity and ±40% variation in relative amount of myelin. For samples having the most native-like periods, the relative amounts of myelin detected allowed distinctions to be made between normal and demyelinating segments, between motor and sensory tracts within the spinal cord, and between aged and young primate CNS. Different periodicities also allowed distinctions to be made between samples from spinal cord and nerve roots and between well-fixed and poorly fixed samples. Our findings suggest that, in addition to evaluating the effectiveness of different fixatives, XRD could also be used as a robust and rapid technique for quantitating the relative amount of myelin among spinal cords and other CNS tissue samples from experimental models of de- and remyelination. © 2009 Wiley-Liss, Inc. [source]

Fixation of hydroxyapatite-coated revision implants is improved by the surgical technique of cracking the sclerotic bone rim

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2009
Brian Elmengaard
Abstract Revision joint replacement has poorer outcomes that have been associated with poorer mechanical fixation. We investigate a new bone-sparing surgical technique that locally cracks the sclerotic bone rim formed during aseptic loosening. We inserted 16 hydroxyapatite-coated implants bilaterally in the distal femur of eight dogs, using a controlled weight-bearing experimental model that replicates important features of a typical revision setting. At 8 weeks, a control revision procedure and a crack revision procedure were performed on contralateral implants. The crack procedure used a splined tool to perform a systematic local perforation of the sclerotic bone rim of the revision cavity. After 4 weeks, the hydroxyapatite-coated implants were evaluated for mechanical fixation by a push-out test and for tissue distribution by histomorphometry. The cracking revision procedure resulted in significantly improved mechanical fixation, significantly more bone ongrowth and bone volume in the gap, and reduced fibrous tissue compared to the control revision procedure. The study demonstrates that the sclerotic bone rim prevents bone ingrowth and promotes fixation by fibrous tissue. The effect of the cracking technique may be due to improved access to the vascular compartment of the bone. The cracking technique is a simple surgical method that potentially can improve the fixation of revision implants in sclerotic regions important for obtaining the fixation critical for overall implant stability. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 996,1001, 2009 [source]

A new animal model for bone atrophic nonunion: Fixation by external fixator

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 12 2008
Katharina Kaspar
Abstract A new small animal model of bone atrophic nonunion was established for investigating the process of bone regeneration by performing cauterization of the periosteum, removal of the local bone marrow, and stabilization with external fixation. The model allows the creation of an atrophic nonunion without the need for a critical size defect. Furthermore, it provides reproducible, well-defined mechanical conditions and minimized physical interference of the implant with the biological processes in the healing zone. Eighty adult Sprague-Dawley rats received an osteotomy of the left femur, stabilized with an external fixator. In half of the animals, the periosteum proximal and distal to the osteotomy was destroyed by cauterization and the adjacent bone marrow was removed (nonunion group). At 2 and 8 weeks after surgery, radiological, biomechanical, histological, and histomorphometrical analyses showed a typical physiological healing in the control group, while the nonunion group was characterized by resorption of the bone ends with some callus formation distant to the osteotomy. At both time points, the callus was composed of significantly less bone and significantly more connective tissue (p,<,0.001). In addition, the torsional strength of the osteotomized femur was significantly less in the nonunion group than in the control group, which was comparable to that of the intact femur (p,<,0.001). In conclusion, the present model allows the induction of an atrophic nonunion without the need of a critical size defect. It is reproducible, provides standardized biomechanical conditions, and allows minimized interaction of the implant with the healing zone. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source]

mtDNA perspective of chromosomal diversification and hybridization in Peters' tent-making bat (Uroderma bilobatum: Phyllostomidae)

MOLECULAR ECOLOGY, Issue 11 2003
Federico G. Hoffmann
Abstract We compared sequence variation in the complete mitochondrial cytochrome -b gene with chromosomal and geographical variation for specimens of Peters' tent-making bat (Uroderma bilobatum). Three different chromosomal races have been described in this species: a 2n = 42 race from South America east of the Andes, a 2n = 44 from NW Central America and 2n = 38 from the rest of Central America and NW South America. The deepest nodes in the tree were found within the South American race (42 race), which is consistent with a longer history of this race. Average distance among races ranged from 2.5 to 2.9%, with the highest amount of intraracial variation found within the 2n = 42 race (1.7%), intermediate values within the 2n = 38 race (0.9%) and lowest within the 2n = 44 race (0.5%). Variation among chromosomal races accounted for over 55% of molecular variance, whereas variation among populations within races accounted for 6%. The 2n = 38 and 2n = 44 races hybridize in the coastal lowlands of Honduras, near the Gulf of Fonseca. Introgression between these two races is low (two introgressed individuals in 45 examined). Clinal variation across the hybrid zone for the cytochrome -b of U. bilobatum, is similar to clinal variation reported for chromosomes and isozymes of this species. Mismatch distribution analyses suggests that geographical isolation and karyological changes have interplayed in a synergistic fashion. Fixation of the alternative chromosomal rearrangements in geographical isolation and secondary contact is the most likely mechanism accounting for the hybrid zone between the 2n = 38 and 2n = 44 races. If a molecular clock is assumed, with rates ranging from 2.3 to 5.0% per million years, then isolation between these races occurred within the last million years, implying a relatively recent origin of the extant diversity in Uroderma bilobatum. None the less, the three chromosomal races probably represent three different biological species. [source]

Pre-bent elastic stable intramedullary nail fixation for distal radial shaft fractures in children

ORTHOPAEDIC SURGERY, Issue 3 2010
Yi-hua Ge MD
Objective:, To investigate the functional and radiographic outcomes of pre-bent elastic stable intramedullary nail in treatment of distal radial shaft fractures in children. Methods:, From January 2006 to December 2008, 18 children with distal radial shaft fracture were treated by close reduction and internal fixation with a pre-bent elastic stable intramedullary nail. The age range was from 5 years to 15 years, with an average of 9 years and 8 months. The minimum follow-up was 12 months. Results:, All fractures maintained good alignment postoperatively, and 94.4% (17/18) of the patients regained a full range of rotation of the forearm. One patient has limitation of rotation to less than 10°, this had improved by final follow-up. Complications included soft tissue irritation at the site of nail insertion in one patient and transient scar hypersensitivity in another. Conclusion:, Fixation with a pre-bent elastic stable intramedullary nail is an effective, safe and convenient method for treating distal radial shaft fractures in children. [source]

Blue-Violet Excited Autofluorescence Spectroscopy and Imaging of Normal and Cancerous Human Bronchial Tissue after Formalin Fixation

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2007
Tanja Gabrecht
Autofluorescence (AF) imaging is a powerful tool for the detection of (pre-)neoplastic lesions in the bronchi. Several endoscopic imaging systems exploit the spectral and intensity contrast of AF between healthy and (pre-)neoplastic bronchial tissues, yet, the mechanisms underlying these contrasts are poorly understood. In this report, the effect of formalin fixation on the human bronchi AF, hence on the contrast, was studied by spectrofluorometric point measurements and DAFE (Diagnostic AutoFluorescence Endoscopy) broad field imaging. Generally, formalin-fixed samples have higher AF intensity than in vivo, whereas the emission spectral shape is similar. Additionally, the spectrofluorometric data showed a moderate decrease of the AF intensity on (pre-)neoplastic lesions relative to the healthy bronchial samples. However, this decrease was lower than that reported from in vivo measurements. Neither spectral measurements nor imaging revealed spectral contrast between healthy bronchial tissue and (pre-)neoplastic lesions in formalin. These results indicate that epithelial thickening and blood supply in the adjacent lamina propria are likely to play a key role in the generation of the AF contrast in bronchial tissues. Our results show that the AF contrast in bronchial tissues was significantly affected by standard, 10% buffered, formalin fixation. Therefore, these samples are not suited to AF contrast studies. [source]

Visible Light Irradiation of Ethidium Bromide,stained Interphase Nuclei Causes DNA,Protein Linking and Structural Stabilization of Nucleoprotein Complexes,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2003
Andrey N. Prusov
ABSTRACT Fixation of DNA and proteins in the isolated rat hepatocyte nuclei stained with ethidium bromide and irradiated with visible light was analyzed in this study. It was shown that irradiation results in the following modifications of higher-level nucleoprotein complexes of interphase chromatin: (1) the complexes acquire resistance to decondensing treatments, which may be indicative of the formation of links between proteins or proteins and DNA in the chromatin; (2) the linking rate for both DNA and proteins is dose dependent; (3) the irradiation induces intermolecular link formation between DNA molecules, which brings about an increase in the average molecular weight of DNA fragments; (4) some modifications (dimerization, etc.) of histones and nonhistone proteins occur; and (5) histone proteins are not effectively cross-linked to DNA. The structural stabilization of interphase chromatin is possibly mediated by free radical,based mechanisms, whereas disulfide bonds seem to play no significant role in the cross-linking. [source]

Fixation of nitrogen in an electrospray mass spectrometer,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2006
Rodney L. Levine
The formation of an iron-nitrogen compound in an electrospray ionization instrument is reported. The iron was released from the stainless steel electrospray needle by acetic acid added to displace trifluoroacetic acid and the nitrogen was present as the drying gas. The product is an iron nitride ion, [N2FeOH]1+, m/z 100.9438, and is capable of addition to peptides and proteins. Published in 2006 by John Wiley & Sons, Ltd. [source]

Two Subgroups of Stapes Fixation: Otosclerosis and Pseudo-Otosclerosis,

THE LARYNGOSCOPE, Issue 11 2005
Tamás Karosi MD
Abstract Hypothesis: Stapes ankylosis is a disease with variable histopathology and can be caused by otosclerosis or pseudo-otosclerosis. Viral pathogenesis of otosclerosis could be established only by correlative analysis: histologic examination of the stapes footplate and reverse-transcriptase polymerase chain reaction (RT-PCR) amplification of the viral RNA. Background: Presence of the RNA genome of measles virus was demonstrated in the footplates of clinically otosclerotic patients by RT-PCR, and also viral proteins were detected by immunohistochemistry. Methods: Nucleic acids were extracted from ankylotic stapes footplates of clinically stapes fixation patients (n = 104). Measles virus genomic nucleoprotein (NP) RNA was amplified by seminested RT-PCR. Amplification results were correlated to postoperative histologic and audiologic findings. Results: Measles virus RNA was detectable only in histologically otosclerotic stapes footplates (n = 67). Histology for virus negative footplates (n = 37) excluded otosclerosis. Virus negative stapes footplates showed nonotosclerotic, degenerative disorders. Conclusions: Stapes ankylosis is a heterogeneous disease causing conductive hearing loss with different etiologies. Nonotosclerotic stapes fixations could be established as pseudo-otosclerosis and may belong to nonspecific, degenerative disorders with variable and noncharacteristic histopathology. Otosclerosis is an inflammatory disease caused by persisting measles virus infection of the otic cap-sule. [source]

Temporary Intermaxillary Fixation using Individualized Acrylic Splints Permits Image,Data-Based Surgery of the Lower Jaw and Oropharynx

THE LARYNGOSCOPE, Issue 8 2004
Jürgen Hoffmann MD
Abstract Objectives/Hypothesis: Image,data-based surgical navigation is used as a helpful device in the operating room to localize critical structures with a high degree of accuracy. It also enables physicians to plan therapeutic performance. Because it relies on preoperatively acquired computed tomography (CT) or magnetic resonance imaging (MRI) data, there is restricted access for navigation of surgical instruments in areas that show motion uncorrelated with radiologic data. Thus, in the case of moveable structures, for example the lower jaw, navigational procedures could not yet be applied. Study Design: We introduce a new technique using individualized intermaxillary splints that fix the mandible in a reproducible aboccluded position at the time of image-data acquisition and surgery. Methods: Different manufacturing processes were investigated. The feasibility of uni- and bilateral intermaxillary splints was studied under clinical conditions in four patients during different procedures in the mandibular and oropharyngeal regions. Results: The manufacturing of the splints showed was easily performed in a short time. With bilateral fixation, there was a high anatomic target precision of 1.6 to 2.3 mm. Conclusions: The use of bilateral intermaxillary splints that fix the patient's mandible in a reproducible aboccluded position permits an image,data-based navigated surgical approach to the oropharyngeal and mandibular regions. [source]

Rotating Frame for the In-situ Fixation of Large Animals

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 1 2009
F.-V. Salomon
Summary The frame for the in-situ fixation of large animals can be rotated around its longtitudinal axis. Thereby the fixing procedure is improved and the anatomical preparation is easier. [source]

Atmospheric CO2 Fixation by Unsaturated Alcohols Using tBuOI under Neutral Conditions,

ANGEWANDTE CHEMIE, Issue 7 2010
Satoshi Minakata Dr.
Festgehalten: Das Treibhausgas CO2 kann durch Reaktion mit ungesättigten Alkoholen und tBuOI unter Bildung von cyclischen Carbonaten fixiert werden. Gegenüber anderen Verfahren zur CO2 -Fixierung zeichnet sich dieser Prozess durch äußerst milde Bedingungen aus. [source]

Modified technique for varus derotation osteotomy of the proximal femur in children

ANZ JOURNAL OF SURGERY, Issue 11 2001
Andrew J. Wilkinson
Background: The results of a study in which the Richards' intermediate hip screw and the AO (Association for the Study ofInternal Fixation (ASIF)) 908 fixed-angle blade plate were compared for use in proximal femoral osteotomy in children have previously been reported. In that study loss of position at the osteotomy site was reported as a specific complication associated with the use of the Richards' intermediate hip screw. Methods: The authors devised a simple modification of surgical technique using the Richards' intermediate hip screw to enhance the stability of the fixation. In the present article the results of a prospective study of that modified technique are reported and compared with the results of the previous study. Results: During a 2-year period 24 proximal femoral osteotomies were performed on 12 children with cerebral palsy, using the modified technique by two surgeons. Only two of the 12 patients (16%) required postoperative immobilization in a hip spica cast. This represents a significant reduction in the level of spica casting when compared with the previous cohort study (61%). Conclusion: A simple modification of surgical technique improves the stability of fixation in proximal femoral osteotomy in children who have cerebral palsy. This resulted in a decreased need for supplementary hip spica casting and may reduce morbidity. [source]

Combined Wear Behavior and Long-Term Implant-Bone Fixation of Total Knee Replacement: A Novel In Vitro Set-up

ARTIFICIAL ORGANS, Issue 5 2010
Michele Spinelli
Abstract The success of a total knee replacement (TKR) strongly depends on the prosthetic design; this includes on one hand the best choice of the bearing materials to minimize wear, on the other hand a good orientation of the prosthetic components with respect to the loading directions. The aim of this study was to investigate the feasibility of a new experimental setup combining two fundamental aspects for the long-term success of knee implants: wear and micromotions. A novel procedure was used to simulate working conditions as close as possible to in vivo ones and to measure implant-bone micromotion, by means of fixing the femoral component of the prosthesis to the distal part of a synthetic femur to be tested through a knee simulator. Gravimetric wear of the tibial specimens was assessed at regular intervals. Implant-bone inducible micromotions and permanent migrations were measured at three locations throughout the test. Wear patterns on tibial specimens were characterized through a standardized protocol based on digital image analysis; fatigue damage in the cement was quantified. Some initial conditioning was noticed both in the wear process and microcracking distribution within the cement mantle. Similarity in wear tracks observed on tibial inserts and other retrieval studies, coupled with clinically consistent migration patterns for TKR, supports the efficacy of the new in vitro method presented. [source]

Nitrogen Fixation in Bryophytes, Lichens, and Decaying Wood along a Soil-age Gradient in Hawaiian Montane Rain Forest

BIOTROPICA, Issue 1 2003
Virginia Matzek
ABSTRACT We determined rates of acetylene reduction and estimated total nitrogen fixation associated with bryophytes, lichens, and decaying wood in Hawaiian montane rain forest sites with underlying substrate ranging in age from 300 to 4.1 million years. Potential N fixation ranged from ca 0.2 kg/ha annually in the 300-year-old site to ca 1 kg/ha annually in the 150,000-year-old site. Rates of acetylene reduction were surprisingly uniform along the soil-age gradient, except for high rates in symbiotic/associative fixers at the 150,000-year-old site and in heterotrophic fixers at the 2100-year-old site. Low fixation at the youngest site, where plant production is known to be N-limited, suggests that demand for N alone does not govern N fixation. Total N fixation was highest in sites with low N:P ratios in leaves and stem wood, perhaps because epiphytic bryophytes and lichens depend on canopy leachate for mineral nutrients and because heterotrophic fixation is partly controlled by nutrient supply in the decomposing substrate; however, differences in substrate cover, rather than in fixation rates, had the largest effect on the total N input from fixation at these sites. [source]

Hydrogen Production from a Fluidized-bed Coal Gasifier with In Situ Fixation of CO2,Part I: Numerical Model

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2008
J. Lu
Abstract In order to attempt to eliminate global warming effects, it is highly desirable that new technologies with lower or zero emission of CO2 to the environment are developed. In this work, a high-pressure fluidized-bed coal gasifier for H2 production with in situ fixation of CO2 is simulated by a comprehensive two-dimensional model. The Eddy Dissipation Concept (EDC) model is first adopted in the pulverized coal gasification model to simultaneously describe the turbulent mixing and detailed chemical kinetics. The developed model is verified with experimental results. The simulated concentrations for the gas product agree well with the experimental data. The simulated distributions for gas temperature and velocity correlate well with the reaction mechanism and experimental phenomena. [source]

Tibial Bone KPro technique and long term results

ACTA OPHTHALMOLOGICA, Issue 2009
J TEMPRANO
The operation is performed in three stages. The first stage consists in preparing the eye to receive and maintain the keratoprosthesis. For this purpose the anterior surface of the eye is cleaned and regularized, eliminating fibrous tissue and the entire epithelium. Subsequently we obtain a 2 x 3 cm graft of buccal mucosa from the inferior lip comprising the entire mucosal and submucosal thickness. The graft is sutured to cover the anterior pole of the eye to promote revitalization. The second stage consists in preparing the keratoprosthesis. A 10 mm disk of tibial bone from the superior part of the medial face of the tibia is obtained using a crown drill. The posterior part of the piece of bone obtained is then cut with a chisel to obtain a thickness of 3 mm. Subsequently the obtained disk of bone is cleaned and a central opening of 3.5 mm is performed to introduce in this opening a PMMA optic cylinder, 9 mm in length, 3.5 mm in diameter in its narrow portion, 4 mm in the wider portion. Fixation is achieved with cyanoacrylate. This is left to dry and then it is introduced into a palpebral pocket of the inferior lid of the patient. The pocket is closed with sutures and the piece is left in place for three months. For the third stage we remove the keratoprosthesis device from the palpebral pocket and if it is found to be in perfect conditions we dissect the buccal mucous membrane which is covering the cornea and perform a central window with a 4.5 mm trephine to remove the transparent or cataractous lens and perform a total iridectomy. The posterior portion of the optic cylinder is introduced into the anterior chamber. The prosthesis is sutured to the anterior pole of the eye with non-absorbible sutures. Finally the buccal mucosa is replaced, covering the entire area. One point of blepharorraphy is applied. Long term results. We started to use this technique in 1988 and after 21 years of experience we have 80% of anatomically perfect results. In 20 % of the cases the prosthesis extruded due to total or partial resorption of the bone. It has to be emphasized that these were cases without any other possibility of treatment. We did 143 cases during these years. The longest follow-up of a prosthesis "in situ" is 19 years. The earliest extrusion was after one year. The complications are the same as for OOKP (glaucoma, retinal detachment, vitritis, extrusion) The functional results depend on the conditions of the retina and the optic nerve. There were many cases with 20/20 vision. The mean value of retention of the prosthesis is 15 years. [source]

Ionic Liquid as an Efficient Promoting Medium for Fixation of Carbon Dioxide: A Clean Method for the Synthesis of 5-Methylene-1,3-oxazolidin-2-ones from Propargylic Alcohols, Amines, and Carbon Dioxide Catalyzed by Cu(I) under Mild Conditions.

CHEMINFORM, Issue 2 2006
Yanlong Gu
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Chemical Fixation of Carbon Dioxide Catalyzed by Binaphthyldiamino Zn, Cu, and Co Salen-Type Complexes.

CHEMINFORM, Issue 26 2003
Yu-Mei Shen
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

ChemInform Abstract: Chemical Fixation of Carbon Dioxide to Styrene Carbonate under Supercritical Conditions with DMF in the Absence of Any Additional Catalysts.

CHEMINFORM, Issue 5 2001
Hajime Kawanami
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Towards Supramolecular Fixation of NOX Gases: Encapsulated Reagents for Nitrosation

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2005
Yanlong Kang
Abstract The use of simple calix[4]arenes for chemical conversion of NO2/N2O4 gases is demonstrated in solution and in the solid state. Upon reacting with these gases, calixarenes 1 encapsulate nitrosonium (NO+) cations within their cavities with the formation of stable calixarene,NO+ complexes 2. These complexes act as encapsulated nitrosating reagents; cavity effects control their reactivity and selectivity. Complexes 2 were effectively used for nitrosation of secondary amides 5, including chiral derivatives. Unique size,shape selectivity was observed, allowing for exclusive nitrosation of less crowded N -Me amides 5,a,e (up to 95,% yields). Bulkier N -Alk (Alk>Me) substrates 5 did not react due to the hindered approach to the encapsulated NO+ reagents. Robust, silica gel based calixarene material 3 was prepared, which reversibly traps NO2/N2O4 with the formation of NO+ -storing silica gel 4. With material 4, similar size,shape selectivity was observed for nitrosation. The N -Me,N -nitroso derivatives 6,d,e were obtained with ,30,% yields, while bulkier amides were nitrosated with much lower yields (<8,%). Enantiomerically pure encapsulating reagent 2,d was tested for nitrosation of racemic amide 5,t, showing modest but reproducible stereoselectivity and ,15,% ee. Given high affinity to NO+ species, which can be generated by a number of NOX gases, these supramolecular reagents and materials may be useful for NOX entrapment and separation in the environment and biomedical areas. [source]