130,453 research outputs found
White Beam Differential Phase and Dark Field Imaging at High Resolution
No full textX-ray phase-contrast imaging (XPCI) can extend the capabilities of conventional radiography and, by
exploiting phase effects, make visible those details that lack enough absorption contrast [1]. Several
approaches have been proposed for XPCI by using synchrotron radiation, microfocal and extended
labortory sources [2]. We focus here on edge illumination [3] in view of its properties of high resolution,
sensitivity, robustness and achromaticity [4-6]. The latter is of particular interest for the study reported
here, where we used the direct beam from a bending magnet, aiming at making use of a spectral
distribution as broad as possible
Kallon laajojen luupuutosten paraneminen kudossiirteiden, kantasolujen, kasvutekijöiden ja biomateriaalien avulla
No full textAbstractBone is a highly vascularized tissue which enables a close interaction between blood vessels and osteoid complexes, including osteoblasts and osteoclasts. Iatrogenic bone loss, caused by a surgical intervention or trauma, disrupts circulation in the bone and leads to hypoxia and even necrosis of the adjacent bone. The mechanisms of the bone tissue healing process by regeneration are highly specific.The most common and predictable way to manage a large-sized skull bone defect has traditionally been using the patient’s own bone tissue graft. The problem with the method is damage and pain of the donor site caused by the operation and healing problems. In paediatric patients, there is a limited availability of adequate autologous bone grafts. For this reason, efforts have been made to develop substitute materials in order to avoid the need for large bone grafts. Autologous stem cells have proven to be promising targets for the development of bone substitutes for cranio-maxillofacial bone defects.The main objective of this study was to examine, by using an experimental animal model, differences in the healing of critical-sized calvarial bone defects, similar to cranioplasty, induced with different types of autogenous bone grafts and with adipose tissue- or bone marrow-derived stem cells grown in two commonly used biomaterials, tricalcium phosphate and bioglass. We also investigated the effect of tissue adhesive, fibrin glue, on the healing process of bone defects. The effect of the stimulating growth factor proteins BMP-2, BMP-7 and VEGF on tissue transplants and ossification was also studied.The results of this study support the previously reported findings of accelerated bone graft resorption associated with autologous bone graft use. In particular, the use of fibrin tissue glue in combination with autologous particulated bone grafts reduced the formation of new bone in calvarial lesions.During the initial healing of calvarial bone defects, tricalcium phosphate granules proved to be more effective than solid bioactive glass scaffolds. Furthermore, in combination with adipose-derived stem cells, tricalcium phosphate showed better bone regeneration than the same cells in combination with a bioactive glass scaffold. Combining bone marrow-derived stem cells with biomaterial did not increase bone formation in calvarial critical-sized defects. In this study, there was no evidence of the positive effect of growth factors on cranial bone healing.TiivistelmäLuu on runsaasti verisuonitettua kudosta, ja se mahdollistaa tiiviin vuorovaikutuksen verisuonten ja luun rakenteen perusyksikön, osteonin, sekä toiminnallisten solujen osteoblastien ja osteoklastien välillä. Kirurgisen toimenpiteen tai trauman aiheuttama luun vaurio häiritsee luun verenkiertoa ja johtaa hapenpuutteeseen ja jopa nekroosiin vaurioituneessa luun osassa. Luukudoksen paranemisen ja uudistumisen mekanismit ovat pitkälle erilaistuneita ja ne tunnetaan erittäin hyvin.Yleisin ja ennusteeltaan luotettavin tapa korjata laajoja kallon luukudoksen puutoksia on perinteisesti ollut potilaan oman luukudossiirteen käyttö. Menetelmän ongelmana on siirteen luovutuskohdan vaurio ja kipu sekä paranemiseen liittyvät ongelmat. Erityisesti lapsipotilailla on haasteena riittävän siirreluumäärän rajoitettu saatavuus. Tästä syystä on pyritty kehittämään korvaavia materiaaleja, jotta vältettäisiin suuriin luusiirteisiin liittyviä ongelmia. Autologiset kantasolut ovat osoittautuneet lupaaviksi kehitettäessä luuta korvaavia hoitomuotoja kallon luupuutosten hoitoon.Tämän tutkimuksen päätavoitteena oli tutkia kokeellisen eläinmallin avulla laajojen, kallokirurgiassa aiheutuvia luupuutoksia vastaavien vaurioalueiden paranemista. Tutkimuksessa testattiin erityyppisiä autogeenisiä luusiirteitä ja rasvakudos- tai luuydinperäisiä kantasoluja, joita kasvatettiin kahden biomateriaalin, trikalsiumfosfaatin ja bioaktiivisen lasin pinnoilla. Tutkimuksessa selvitettiin myös fibriinikudosliiman vaikutusta omakudosluusiirteen paranemiseen. Kudoskasvutekijäproteiinien BMP-2, BMP-7 ja VEGF stimuloivaa vaikutusta kudossiirteiden toimintaan ja luutumiseen selvitettiin myös.Tämän tutkimuksen tulokset tukevat aiemmin raportoituja havaintoja autologisen luusiirrännäisen käyttöön liittyvästä nopeasta resorptiosta. Erityisesti fibriinikudosliiman käytön yhdessä autologisten pienipartikkelisten luusiirteiden kanssa havaittiin heikentävän uuden luun muodostumista kallon luupuutoksissa.Kallon luupuutosten alkuvaiheen paranemisessa rakeinen trikalsiumfosfaatti osoittautui tehokkaammaksi kuin kiinteä säikeinen bioaktiivinen lasi. Samoin rasvakudosperäisten kantasolujen yhdistäminen trikalsiumfosfaattiin lisäsi merkittävästi luun muodostumista verrattuna samaan yhdistelmään bioaktiivisen lasin kanssa. Luuydinperäisiä kantasoluja yhdistettäessä vastaavaa ei voitu tässä tutkimuksessa todeta. Tutkimuksessa kasvutekijöiden käytöllä ei havaittu olevan positiivista vaikutusta kallonluiden paranemiseen.Academic dissertation to be presented with the assent of the Doctoral Training Committee of Health and Biosciences of the University of Oulu for public defence in the Auditorium of Kastelli Research Centre (Aapistie 1), on 11 November 2016, at 12 noonAbstract
Bone is a highly vascularized tissue which enables a close interaction between blood vessels and osteoid complexes, including osteoblasts and osteoclasts. Iatrogenic bone loss, caused by a surgical intervention or trauma, disrupts circulation in the bone and leads to hypoxia and even necrosis of the adjacent bone. The mechanisms of the bone tissue healing process by regeneration are highly specific.
The most common and predictable way to manage a large-sized skull bone defect has traditionally been using the patient’s own bone tissue graft. The problem with the method is damage and pain of the donor site caused by the operation and healing problems. In paediatric patients, there is a limited availability of adequate autologous bone grafts. For this reason, efforts have been made to develop substitute materials in order to avoid the need for large bone grafts. Autologous stem cells have proven to be promising targets for the development of bone substitutes for cranio-maxillofacial bone defects.
The main objective of this study was to examine, by using an experimental animal model, differences in the healing of critical-sized calvarial bone defects, similar to cranioplasty, induced with different types of autogenous bone grafts and with adipose tissue- or bone marrow-derived stem cells grown in two commonly used biomaterials, tricalcium phosphate and bioglass. We also investigated the effect of tissue adhesive, fibrin glue, on the healing process of bone defects. The effect of the stimulating growth factor proteins BMP-2, BMP-7 and VEGF on tissue transplants and ossification was also studied.
The results of this study support the previously reported findings of accelerated bone graft resorption associated with autologous bone graft use. In particular, the use of fibrin tissue glue in combination with autologous particulated bone grafts reduced the formation of new bone in calvarial lesions.
During the initial healing of calvarial bone defects, tricalcium phosphate granules proved to be more effective than solid bioactive glass scaffolds. Furthermore, in combination with adipose-derived stem cells, tricalcium phosphate showed better bone regeneration than the same cells in combination with a bioactive glass scaffold. Combining bone marrow-derived stem cells with biomaterial did not increase bone formation in calvarial critical-sized defects. In this study, there was no evidence of the positive effect of growth factors on cranial bone healing.Tiivistelmä
Luu on runsaasti verisuonitettua kudosta, ja se mahdollistaa tiiviin vuorovaikutuksen verisuonten ja luun rakenteen perusyksikön, osteonin, sekä toiminnallisten solujen osteoblastien ja osteoklastien välillä. Kirurgisen toimenpiteen tai trauman aiheuttama luun vaurio häiritsee luun verenkiertoa ja johtaa hapenpuutteeseen ja jopa nekroosiin vaurioituneessa luun osassa. Luukudoksen paranemisen ja uudistumisen mekanismit ovat pitkälle erilaistuneita ja ne tunnetaan erittäin hyvin.
Yleisin ja ennusteeltaan luotettavin tapa korjata laajoja kallon luukudoksen puutoksia on perinteisesti ollut potilaan oman luukudossiirteen käyttö. Menetelmän ongelmana on siirteen luovutuskohdan vaurio ja kipu sekä paranemiseen liittyvät ongelmat. Erityisesti lapsipotilailla on haasteena riittävän siirreluumäärän rajoitettu saatavuus. Tästä syystä on pyritty kehittämään korvaavia materiaaleja, jotta vältettäisiin suuriin luusiirteisiin liittyviä ongelmia. Autologiset kantasolut ovat osoittautuneet lupaaviksi kehitettäessä luuta korvaavia hoitomuotoja kallon luupuutosten hoitoon.
Tämän tutkimuksen päätavoitteena oli tutkia kokeellisen eläinmallin avulla laajojen, kallokirurgiassa aiheutuvia luupuutoksia vastaavien vaurioalueiden paranemista. Tutkimuksessa testattiin erityyppisiä autogeenisiä luusiirteitä ja rasvakudos- tai luuydinperäisiä kantasoluja, joita kasvatettiin kahden biomateriaalin, trikalsiumfosfaatin ja bioaktiivisen lasin pinnoilla. Tutkimuksessa selvitettiin myös fibriinikudosliiman vaikutusta omakudosluusiirteen paranemiseen. Kudoskasvutekijäproteiinien BMP-2, BMP-7 ja VEGF stimuloivaa vaikutusta kudossiirteiden toimintaan ja luutumiseen selvitettiin myös.
Tämän tutkimuksen tulokset tukevat aiemmin raportoituja havaintoja autologisen luusiirrännäisen käyttöön liittyvästä nopeasta resorptiosta. Erityisesti fibriinikudosliiman käytön yhdessä autologisten pienipartikkelisten luusiirteiden kanssa havaittiin heikentävän uuden luun muodostumista kallon luupuutoksissa.
Kallon luupuutosten alkuvaiheen paranemisessa rakeinen trikalsiumfosfaatti osoittautui tehokkaammaksi kuin kiinteä säikeinen bioaktiivinen lasi. Samoin rasvakudosperäisten kantasolujen yhdistäminen trikalsiumfosfaattiin lisäsi merkittävästi luun muodostumista verrattuna samaan yhdistelmään bioaktiivisen lasin kanssa. Luuydinperäisiä kantasoluja yhdistettäessä vastaavaa ei voitu tässä tutkimuksessa todeta. Tutkimuksessa kasvutekijöiden käytöllä ei havaittu olevan positiivista vaikutusta kallonluiden paranemiseen
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
An experimental approach to optimising refraction sensitivity for lab-based edge illumination phase contrast set-ups
No full textRefraction sensitivity can be optimised for differential x-ray phase contrast (XPC) imaging methods by modifying the set-up. Often, modifications involve changing source/detector parameters, propagation distances, or the design of optical components, i.e. parameters that are not readily changed without non-trivial time investment, replacing components, or performing high-precision recalibrations. The edge illumination (EI) XPC method provides a method of optimising the refraction sensitivity, by exploiting micrometric translations of its periodic masks, that bypasses the constraints listed above. These translations can be performed on-the-fly and allow optimising the refraction signal for specific applications without making significant changes to the set-up. The method can prove advantageous for lab-based systems that make use of larger sources but with limited available set-up space. In this paper, we study how refraction sensitivity varies as a function of illuminated pixel fraction (IPF) under two commonly encountered experimental conditions: (1) at approximately constant detected counts, and (2) at equal exposure time. We compare the standard deviation in the background of reconstructed refraction images at different IPFs and find that refraction sensitivity is optimal at 25% IPF under both conditions. Finally, we demonstrate that refraction sensitivity affects the visibility of weakly refracting features on an insect leg. The results suggest that IPFs lower than 50% can actually be preferable, especially in the case where the statistics is kept constant, and provide experimental validation that phase sensitivity in EI is not fixed once the system parameters are defined
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
The R&D Tax Incentives
No full textThis article sets out some background information and reflections of the author on the R&D tax incentive schemes included in the Common Corporate Tax Base (CCTB) Proposal. In particular the author analyzes the stimulus to private R&D through ad hoc tax incentives included in the CCTB Proposal and dives into the actual provisions included in the Proposal highlighting the most relevant issues connected with their design and interpretation. Moreover, the author explores the interaction between the CCTB Proposal and the granting by Member States of domestic R&D tax incentives
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