1,147 research outputs found
Tissue engineering of a tracheal substitute
No full textLectin histochemistry and scanning electron microscopy (SEM) was used to assess the growth and characterise the differentiation of human respiratory epithelial cells (REC) cultured on two biomaterial scaffolds. The first scaffold, based on a hyaluronic acid derivative, was observed to be non-adhesive for REC. This lack of adhesion was found to be unrelated to the presence of the hyaluronic acid binding domain on the surface of isolated REC. The other scaffold, consisting of equine collagen, was observed to encourage REC spreading and adhesion. Positive Ulex Europaeus agglutinin (UEA) lectin staining of this preparation indicated the presence of ciliated REC on the scaffold surface. However, the marked decrease in peanut agglutinin (PNA) positive staining, relative to that of control cultures and native tissue, indicates a dedifferentiation of the secretory cells in monolayer. SEM analysis of REC cultured on the collagen scaffold confirmed the presence of ciliated cells thereby validating the UEA positive staining. The presence of both established and developing cilia was also verified. This indicates that collagen biomaterials are appropriate for the tissue engineering of REC. Furthermore, that UEA and PNA staining is a useful tool in the characterisation of cells cultured on biomaterials, therefore helpful in identifying biomaterials that are suitable for specific tissue engineering purposes.
The culture of REC at an air liquid interface (ALI) was investigated. Both conventional ALI inserts and the Biofleece scaffold were used. The cells grown the on conventional inserts became multilayered and showed some degree of ciliation after the period of ten days. The cells grown on the Biofleece scaffold became necrotic and died due to nutrient deprivation. The use of ALI culture techniques on scaffold materials needs to be adjusted to allow for sufficient nutrient supply to the cells.
The Biofleece scaffold was found to be suitable for the tissue engineering of cartilage in vitro. Constructs with a cartilage-like morphology were generated with the scaffold after two weeks in culture. The tissue-engineered cartilage was found to contain a higher number of cells and less extracellular matrix (ECM) than the native tissue controls. Suction seeding techniques were used to improve the distribution of cells within the scaffold and thereby increase the overall efficiency of cartilage tissue engineering within the scaffold. Alcian blue (AB) and Papanicolau (PN) stains of the tissue engineered cartilage described two distinct regions within the constructs, namely the developed cartilage-like region and the developing region. The latter is thought to be areas in which the cartilage cells are yet to fully remodel the scaffold material and deposit their own “native” ECM. However, the Biofleece scaffold material was observed to loose 40-50% of its initial volume during the tissue engineering process over a period of two weeks. Thus the degradation of the Biofleece scaffold exceeds the rate of maturation of the cartilage tissue within the scaffold. This rapid biodegradation is most likely a result of matrixmetalloproteinase (MMP), in particular collagenase, production by the maturing chondrocytes. This reduction in size means that the Biofleece scaffold is not an appropriate material for the tissue engineering of a trachea. The optimal biomaterial for the tissue engineering of a trachea would degrade at a rate equal too, or slower than, the time taken for the cells within the scaffold to mature into functional tissue.
The co-culture of REC and chondrocytes was achieved through the use of matrigel as a basement membrane replacement (note that direct growth of REC on cartilage tissue has been observed to be difficult). The co-cultured constructs were not stable because the Biofleece scaffold degrades at a high rate in the presence of both cell types. The constructs were observed to shrink to approximately 35-30% of the original dimensions in a period of 3-7 days. The reason for this accelerated degradation is not known but is most likely the result of severe MMP production by the two cell types when in combination.
It was concluded that the characterisation procedures used in this study (histochemical staining, fluorescent staining and scanning electron microscopy) for both REC and chondrocyte tissue engineered constructs are appropriate for this and further studies. The chondrocyte seeding methodologies in particular are a useful tool for tissue engineering. This study succeeds in many ways to investigate the tissue engineering of a tracheal substitute by detailing how REC and chondrocytes can be cultured on biomaterials and assessed for tissue development. However, the study does not deliver such a viable substitute as an end product. The primary reason for this outcome is the rapid degradation of the Biofleece scaffold materialLectin Histochemie und Elektronenmikroskopie wurden benutzt, um das Wachstum von humanen respiratorischen Epithelzellen (RECs), welche auf zwei Biomaterialien kultiviert wurden, festzusetzen und ihren Differenzierungsgrad zu bestimmen. Das erste Trägermaterial, welches auf einem Hyaluronsäurederivat basiert, ließ keine Anheftung der RECs zu. Diese fehlende Anheftung ließ sich jedoch nicht zurückführen auf das Vorhandensein der Hyaluronsäure bindenden Domaine auf der Oberfläche isolierter RECs. Das andere Trägermaterial, aus Pferdekollagen hergestellt, zeigte dagegen eine verstärkte Teilungsaktivität und Anheftung der REC. Die positive Ulex Europaeus Agglutinin (UEA) Lectin Färbung dieser Proben ließ die Anwesenheit von mit Zilien versehenen RECs auf der Trägerstoffoberfläche vermuten. Darüber hinaus weist das im Vergleich zu Kontrollkulturen und nativem Gewebe deutliche Nachlassen der positiven Peanut Agglutinin–Färbereaktion auf eine Dedifferenzierung der sekretorischen Zellen in der Monolayer-Kultur hin. Die rasterelektronenmikroskopische Untersuchung der auf dem Kollagenbiomaterial kultivierten RECs bestätigte das Auftreten von Zellen mit Zilien und damit auch die Aussagekräftigkeit der positiven UEA–Färbung. Dies zeigt somit, dass Biomaterialien aus Kollagen für das Tissue Engineering von RECs geeignet sind und dass sowohl die UEA–als auch die PNA–Färbung geeignete Methoden zur Charakterisierung von Zellen darstellen, die auf Biomaterialien kultiviert wurden. Somit helfen sie bei der Identifizierung von Biomaterialien für bestimmte Einsatzgebiete im Tissue Engineering.
Des weiteren wurde die Kultivierung von RECs auf einem Air liquid interface (ALI) untersucht, wobei sowohl der konventionelle ALI–Einsatz als auch das Biovliesmaterial zum Einsatz kamen. Dabei wuchsen die Zellen auf dem konventionellen Einsatz in Multilayern und zeigten nach einem Zeitraum von 10 Tagen einen bestimmten Anteil an Ziliierung. Die Zellen auf dem Biovlies dagegen wurden nekrotisch und gingen schließlich an Nahrungsmangel ein. Deshalb muss der Einsatz von ALI–Kulturtechniken bei Trägermaterialien dementsprechend modifiziert werden, dass eine ausreichende Versorgung der Zellen mit Nährstoffen gewährleistet ist.
Für das in vitro–Tissue Engineering von Knorpel erwies sich das Biovlies jedoch als geeignet. Mit ihm konnten nach zwei Wochen Kulturzeit Konstrukte mit einer knorpelähnlichen Morphologie erzeugt werden. Dabei zeigte sich, dass der Tissue Engineering–Knorpel eine höhere Zellzahl bei reduzierter extrazellulärer Matrix (ECM) aufwies als vergleichbares natives Kontrollgewebe. Dabei wurden Saugtechniken benutzt, um die Verteilung der Zellen im Trägerstoff zu verbessern. Die Alzian – Blau – Färbung (AB) und Papanicolau – Färbung (PN) zeigten bei dem Tissue Engineering–Knorpel zwei unterschiedliche Regionen innerhalb des Konstrukts, nämlich eine knorpelähnliche bereits entwickelte Region und eine sich entwickelnde Region. Bei letzterer dürfte es sich wohl um Gebiete handeln, in denen Zellen noch im Begriff sind, den Trägerstoff vollends umzubauen und ihre eigene „native“ ECM abzulagern. Nichtsdestoweniger büßte das Biovlies während des Tissue Engineering Prozesses über einen Zeitraum von zwei Wochen annähernd 40-50 % seines anfänglichen Volumens ein. Somit übersteigt das Ausmaß der Degradation des Biovlieses das des Heranreifens von Knorpelgewebe in dem Trägermaterial. Diese schnelle Biodegradation ist am ehesten das Ergebnis der Aktivität von Matrixmetalloproteinasen (MMP), insbesondere der Kollagenase, welche von reifenden Chondrozyten produziert wird. Diese Schrumpfung bedeutet also, dass das Biovlies kein geeignetes Material für das Tissue Engineering der Trachea darstellt. Denn ein optimales Biomaterial für das Tissue Engineering der Trachea sollte sich innerhalb derselben Zeit bzw. über einen längeren Zeitraum hinweg abbauen, als innerhalb desjenigen, den die sich in dem Trägermaterial befindlichen Zellen benötigen, um zu funktionalem Gewebe heranzureifen.
Durch den Einsatz von Matrigel als Ersatz für die Basalmembran konnte eine Kokultur aus RECs und Chondrozyten etabliert werden (wobei anzumerken ist, dass sich direktes Wachstum von RECs auf Knorpelgewebe als problematisch erweist). Die Konstrukte aus Kokulturen waren nicht stabil, da das Biovlies in Anwesenheit beider Zelltypen hochgradig abgebaut wird. Innerhalb von 3–7 Tagen schrumpften die Konstrukte auf ca. 35–50 % ihrer Ausgangsgröße zusammen. Der Grund für diesen beschleunigten Abbau ist unbekannt, jedoch ist am ehesten eine ausgeprägte Produktion von MMP durch die beiden Zellarten anzunehmen, sobald diese in Kombination vorliegen.
Insgesamt lässt sich sagen, dass die Methoden zur Zell- und Gewebecharakterisierung, welche in dieser Studie benutzt wurden (histochemische Färbungen, Fluoreszenzfärbung und Elektronenmikroskopie) sowohl für mit RECs als auch mit Chondrozyten hergestellte Konstrukte für die vorliegende Arbeit als auch zukünftige Studien als geeignet anzusehen sind. Diese Studie hat in vielerlei Hinsicht erfolgreich das Tissue Engineering einer Luftröhre untersuchen können, indem sie im Detail aufzeigt, wie RECs und Chondrozyten auf Biomaterialien kultiviert und für das Tissue Engineering eingesetzt werden können. Trotzdem kann diese Arbeit kein einsetzbares Ersatzmaterial als Endprodukt liefern. Der Hauptgrund für dieses Ergebnis ist in erster Linie in dem schnellen Abbau des Biovlieses als Trägermaterial zu sehen
The REC Indemnity: ‘Throwing the Kitchen Sink’ at the Committees?
No full text In this article, the author contends that the current indemnity provided to REC members is unfair and is so badly drafted that it cannot be described as an indemnity at all. He contends that the Appointing Authorities should give guidance to clarify the scope of the indemnity or replace it. The author discusses potential legal claims by REC members against their Appointing Authority if this is not provided. The legal liability of REC members for negligence and other claims is also discussed. The author provides a solution in a simpler form of indemnity framed by reference to actual claims that can be made against a REC member. </jats:p
Operational semantics for SPARQL Update
No full textConcurrent fine grained updates are essential for using RDF stores in dynamic modern Web applications, where users increasingly contribute content as often as they read content. SPARQL Update is a language proposed by the W3C for fine grained updates for RDF stores. In this work we propose an operational semantics for an update language for RDF, which models core features of SPARQL Update. Firstly, an abstract syntax for RDF and updates is presented. Secondly, the operational semantics is defined using relations over the abstract syntax. The operational semantics specifies all possible operational behaviours of updates in the presence of an RDF store. The specification is useful as a common reference for compiler engineers and as a foundation for the static analysis of updates
Recenzja książki: Nicholas P. Roberts, Political Islam and the Invention of Tradition, New Academia Publishing, Washington, DC 2015, ss. 245
No full text[rec.] Nicholas P. Roberts, Political Islam and the
Invention of Tradition, New Academia Publishing,
Washington, DC 2015, ss. 245Nicholas P. Roberts w pracy Political Islam and the Invention of Tradition poddał analizie intelektualną historię islamu, by dzięki historycznej kontekstualizacji przeciwstawić się najczęstszym stereotypom odnoszącym się tak do islamu, jak i do islamizmu. W szczególności jest to odparcie poglądu, że islam, a więc także islamizm, jest wrogi wobec współczesnych rządów, dążąc w istocie do zamierzchłej barbarzyńskiej przeszłości
Direct numerical simulation of the flow around a wing section at moderate Reynolds numbers
No full textA three dimensional direct numerical simulation has been performed to study the flow around the asymmetric NACA-4412 wing at a moderate chord Reynolds number (Rec = 400, 000) with an angle of attack of 5◦ . The flow case under investigation poses numerous challenges for a numerical method due to the wide range of scales and complicated flow physics induced by the geometry. The mesh is optimized and well resolved to account for such varying scales in the flow. An unsteady volume force is used to trip the flow to turbulence on both sides of the wing at 10% chord. Full turbulent statistics are computed on the fly to further investigate the complicated flow features around the wing. The present simulation shows the potential of high-order methods in simulating complex external flows at moderately high Reynolds numbers
Resource Description Framework (RDF)
No full textThe Resource Description Framework (RDF) is the standard knowledge representation language for the Semantic Web, an evolution of the World Wide Web that aims to provide a well-founded infrastructure for publishing, sharing and querying structured data. This article provides an introduction to RDF and its related vocabulary definition language RDF Schema, and explains its relationship with the OWL Web Ontology Language. Finally, it provides an overview of the historical development of RDF and related languages for Web metadata
Authorisation in Grid Computing
No full textThis paper briefly surveys how authorisation in Grid computing has evolved during the last few years, and presents the latest developments in which Grid applications can utilise a policy controlled authorisation infrastructure to make decisions about which users are allowed to perform which actions on which Grid resources. The paper describes the Global Grid Forum SAML interface for connecting policy based authorisation infrastructures to Grid applications, and then describes the PERMIS authorisation infrastructure which has implemented this interface. The paper concludes with suggestions about how this work will evolve in the future
Rhodopseudomonas palustris TIE-1
No full textRaw data files of Rhodopseudomonas palustris TIE-1<strong>Tilt Series Date:</strong> 2012-05-09</p>
<strong>Data Taken By:</strong> Alasdair McDowall</p>
<strong>Species / Specimen:</strong> Rhodopseudomonas palustris</p>
<strong>Strain:</strong> None</p>
<strong>Tilt Series Settings:</strong> Single Axis, tilt range: (-60.0°, 60.0°), step: 1°, constant angular increment, dosage: 100.0 eV/Ų, defocus: None μm, magnification: 22500x. </p>
<strong>Acquisition Software:</strong> UCSFTomo</p>
<strong>Upload Method:</strong> pipeline</p>
<strong>Processing Software Used:</strong> raptor</p>
<strong>Collaborators and Roles:</strong> Nicholas ShikumaDianne Newman</p>
<strong>Purification / Growth Conditions / Treatment:</strong> wild type and shc mutantgrown by photoheterotrophic anaerobic exponential and stationary</p>
<strong>Sample Preparation:</strong> vitrobot</p>
amw2012-05-09-12_slicer4846.jpg: nested vesicle amw2012-05-09-12_slicer4848.jpg: REZ . Granules amw2012-05-09-12_slicer4852.jpg: Unknown amw2012-05-09-12_slicer4855.jpg: Double membrane vesicleFiles available via S3 at https://renc.osn.xsede.org/ini210004tommorrell/tomography_archive/amw2012-05-09-12</p>WT_expo0009.mrc, Tilt Series (Pixel Size 0.9 nm), 1.0 GB
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WT_expo0009_part122_7.rec, Reconstruction (Pixel Size 1.8 nm), 516.1 MB
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WT_expo0009_part122_7.rec, Reconstruction (Pixel Size 1.8 nm), 516.1 MB
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Rhodopseudomonas palustris TIE-1
No full textRaw data files of Rhodopseudomonas palustris TIE-1<strong>Tilt Series Date:</strong> 2012-05-09</p>
<strong>Data Taken By:</strong> Alasdair McDowall</p>
<strong>Species / Specimen:</strong> Rhodopseudomonas palustris</p>
<strong>Strain:</strong> None</p>
<strong>Tilt Series Settings:</strong> Single Axis, tilt range: (-60.0°, 60.0°), step: 1°, constant angular increment, dosage: 100.0 eV/Ų, defocus: None μm, magnification: 22500x. </p>
<strong>Acquisition Software:</strong> UCSFTomo</p>
<strong>Upload Method:</strong> pipeline</p>
<strong>Processing Software Used:</strong> raptor</p>
<strong>Collaborators and Roles:</strong> Nicholas ShikumaDianne Newman</p>
<strong>Purification / Growth Conditions / Treatment:</strong> wild type and shc mutantgrown by photoheterotrophic anaerobic exponential and stationary</p>
<strong>Sample Preparation:</strong> vitrobot</p>
amw2012-05-09-5_slicer4809.jpg: Unknown patchesFiles available via S3 at https://renc.osn.xsede.org/ini210004tommorrell/tomography_archive/amw2012-05-09-5</p>SHC_stat_m1.mrc, Tilt Series (Pixel Size 0.9 nm), 1.0 GB
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SHC_stat_m1_part122_1.rec, Reconstruction (Pixel Size 1.8 nm), 516.1 MB
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> <i class="download icon"></i> Download </a></p>
Rhodopseudomonas palustris TIE-1
No full textRaw data files of Rhodopseudomonas palustris TIE-1<strong>Tilt Series Date:</strong> 2012-05-09</p>
<strong>Data Taken By:</strong> Alasdair McDowall</p>
<strong>Species / Specimen:</strong> Rhodopseudomonas palustris</p>
<strong>Strain:</strong> None</p>
<strong>Tilt Series Settings:</strong> Single Axis, tilt range: (-60.0°, 60.0°), step: 1°, constant angular increment, dosage: 100.0 eV/Ų, defocus: None μm, magnification: 22500x. </p>
<strong>Acquisition Software:</strong> UCSFTomo</p>
<strong>Upload Method:</strong> pipeline</p>
<strong>Processing Software Used:</strong> raptor</p>
<strong>Collaborators and Roles:</strong> Nicholas ShikumaDianne Newman</p>
<strong>Purification / Growth Conditions / Treatment:</strong> wild type and shc mutantgrown by photoheterotrophic anaerobic exponential and stationary</p>
<strong>Sample Preparation:</strong> vitrobot</p>
amw2012-05-09-3_slicer4801.jpg: Parallel membrane sheet . GranuleFiles available via S3 at https://renc.osn.xsede.org/ini210004tommorrell/tomography_archive/amw2012-05-09-3</p>shc_expo_m3.mrc, Tilt Series (Pixel Size 0.9 nm), 1.0 GB
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shc_expo_m3_part122_5.rec, Reconstruction (Pixel Size 1.8 nm), 516.1 MB
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