27 research outputs found
Shear and Anchorage Behaviour of Fire Exposed Hollow Core Slabs
No full textHollow core (HC) slabs are made of precast concrete with pretensioned strands. These slabs are popular as floor structures in offices and housing. At ambient conditions, the load bearing capacity can be dominated by four different failure modes, i.e. flexure, anchorage, shear compression and shear tension. As the economic production process does not allow for the inclusion of mild reinforcement, the slabs rely on the tensile strength of concrete for the shear and anchorage capacity. When exposed to a fire, the HC slabs have to maintain their load bearing and separating function for a certain time in order to facilitate the fire fighting actions and to provide sufficient time for the users of the building to escape and for rescue teams to search the building. Current design codes consider only flexural failure, while fire tests carried out in the past showed that the other failure modes can dominate the fire behaviour as well. As a result, design codes might overestimate the actual performance of fire exposed HC slabs. However, the experiments might represent a worst case compared to the practice. At least, fatalities caused by a premature collapse of fire exposed HC slabs, have never been reported up to the author's knowledge. Because there is a lack of fundamental understanding of the shear and anchorage behaviour, an optimum design between safety and economics can yet not be achieved. The objective of the research presented in this thesis is to gain a basic understanding of the shear and anchorage behaviour of fire exposed HC slabs and to develop FE models to predict this behaviour. With the models, design measures to improve the behaviour can be evaluated. The field of application is limited to HC slabs in accordance with the European product standard prEN 1168 [1197], exposed to standard fire conditions and simply supported on rigid supports like walls. The results are on the safe side for HC slabs with restraining support conditions.Civil Engineering and Geoscience
Different binding properties and function of CXXC zinc finger domains in Dnmt1 and Tet1
Get PDFSeveral mammalian proteins involved in chromatin and DNA modification contain CXXC zinc finger domains. We compared the structure and function of the CXXC domains in the DNA methyltransferase Dnmt1 and the methylcytosine dioxygenase Tet1. Sequence alignment showed that both CXXC domains have a very similar framework but differ in the central tip region. Based on the known structure of a similar MLL1 domain we developed homology models and designed expression constructs for the isolated CXXC domains of Dnmt1 and Tet1 accordingly. We show that the CXXC domain of Tet1 has no DNA binding activity and is dispensable for catalytic activity in vivo. In contrast, the CXXC domain of Dnmt1 selectively binds DNA substrates containing unmethylated CpG sites. Surprisingly, a Dnmt1 mutant construct lacking the CXXC domain formed covalent complexes with cytosine bases both in vitro and in vivo and rescued DNA methylation patterns in dnmt1⁻/⁻ embryonic stem cells (ESCs) just as efficiently as wild type Dnmt1. Interestingly, neither wild type nor ΔCXXC Dnmt1 re-methylated imprinted CpG sites of the H19a promoter in dnmt1⁻/⁻ ESCs, arguing against a role of the CXXC domain in restraining Dnmt1 methyltransferase activity on unmethylated CpG sites
Data management technology driven and sustained by the eResearch community
No full textThe technology of iRODS (Integrated Rule-Oriented Data System) was first funded by a government grant in 1995 and subsequently developed by several academic institutions that saw data management as a growing problem. The code was open-source from the beginning but the development was done on a volunteer basis. It became clear as the scale of the problem grew that a more formal solution was required. The iRODS Consortium was founded in 2013 as a group of professional developers based at the University of North Carolina at Chapel Hill. This group is sustained by a membership model and, today, the iRODS Consortium has over 30 members spanning the world. These members are both academic and commercial, but they all have similar requirements in their institutions. Today, iRODS technology is a product of both the developers and the community. Code is contributed and regular community meetings are held to highlight the needs of all of the members. Working groups are formed to address the changing requirements of the members as the scale and complexity of data generation and maintenance changes dynamically over time. Decisions regarding the disposition of data can now be automated and based on metadata which can change depending on citation or usage. Data can be automatically gathered from sensors and instruments, sorted by metadata, processed, and the products distributed or published in completely automated workflows.The iRODS community is comprised of academic and commercial researchers but the discourse is active and the resultant product is based upon consensus. Today, worldwide, FAIR discovery and directed dissemination of eResearch information is being accomplished in sites controlling tens of petabytes of data with this open-source technology.ABOUT THE AUTHOR Dave Fellinger is a Data Management Technologist and Storage Scientist with the iRODS Consortium. He has over three decades of engineering experience including film systems, video processing devices, ASIC design and development, GaAs semiconductor manufacture, RAID and storage systems, and file systems. He attended Carnegie-Mellon University and holds patents in diverse areas of technology.</p
DNA methylation requires a DNMT1 ubiquitin interacting motif (UIM) and histone ubiquitination
Get PDFDNMT1 is recruited by PCNA and UHRF1 to maintain DNA methylation after replication. UHRF1 recognizes hemimethylated DNA substrates via the SRA domain, but also repressive H3K9me3 histone marks with its TTD. With systematic mutagenesis and functional assays, we could show that chromatin binding further involved UHRF1 PHD binding to unmodified H3R2. These complementation assays clearly demonstrated that the ubiquitin ligase activity of the UHRF1 RING domain is required for maintenance DNA methylation. Mass spectrometry of UHRF1-deficient cells revealed H3K18 as a novel ubiquitination target of UHRF1 in mammalian cells. With bioinformatics and mutational analyses, we identified a ubiquitin interacting motif (UIM) in the N-terminal regulatory domain of DNMT1 that binds to ubiquitinated H3 tails and is essential for DNA methylation in vivo. H3 ubiquitination and subsequent DNA methylation required UHRF1 PHD binding to H3R2. These results show the manifold regulatory mechanisms controlling DNMT1 activity that require the reading and writing of epigenetic marks by UHRF1 and illustrate the multifaceted interplay between DNA and histone modifications. The identification and functional characterization of the DNMT1 UIM suggests a novel regulatory principle and we speculate that histone H2AK119 ubiquitination might also lead to UIM-dependent recruitment of DNMT1 and DNA methylation beyond classic maintenance
Oracle Corporation 1-2
No full textDuring these sessions, Tom Kyte of Oracle Corporation will cover the following topics:# The Tools Tom uses, # The Top 5 things done wrong over and over again, # Building test cases, # Oracle 10g "cool features" Speaker Bio:Tom Kyte is the Vice President, Core Technologies for Oracle Government, Education and Healthcare. Before starting at Oracle, Tom Kyte worked as a systems integrator building large-scale, heterogeneous databases and applications, mostly for military and government customers. He spends a great deal of his time working with the Oracle database and, more specifically, working with people who are working with the Oracle database. Tom Kyte is the Tom behind the AskTom web site, answering people's questions about the Oracle database and its tools (http://asktom.oracle.com/). He is also the author of the AskTom column in http://www.oracle.com/technology/oramag/oracle/current.html Oracle Magazine, and the author of Expert One-on-One Oracle (Apress, 2003), Beginning Oracle Programming (Wrox Press, 2002), and Effective Oracle by Design (Oracle Press, 2003). These are books about the general use of the Oracle database and how to develop successful Oracle applications
Building a Federated Research Collaborative
No full textThe concept of countrywide and worldwide research collaboratives is relatively new. Several
decades ago it was common for a department head to have multiple vertical file cabinets
with paper folders housing the work of researchers and students in his or her department.
Access and subsequent citations of this work was generally based on the department heads’
knowledge of the works. As digital storage technologies became less expensive and
relatively ubiquitous the vertical files turned into disk storage systems reflecting the work of
each university department. The works were still filed and maintained by standard file
system references such as creation date, name, and access controls. In the many cases, card
catalogs or spreadsheets were used to further describe the titles. The introduction of
ethernet in the late 1970’s largely changed the manner in which research works were
conserved. The deployment of campus-wide data networks enabled universities to establish
and maintain central data repositories. Storage could become a service of the university
where individual colleges or departments no longer had to maintain their own archival
systems. The era of the digital research collaborative was born. In many cases, this
transition took years, and even today, some university departments retain internal storage.
Locating a specific work based upon anything other than title was a challenge and that
problem grew with the number of works that were archived.The Advent of Storage Management TechnologyA digital file system is really just a means for storing and maintaining data like a set of
shelves is a means to hold books. What is actually required is a way to relate descriptive
data to files indicating the contents of a file. This was largely understood for libraries
containing shelves of books starting thousands of years ago dating back to 2000 BC [1]. In
the United States, the Defense Advanced Research Projects Agency (DARPA) funded a
program called the Storage Resource Broker (SRB) in 1995 and 1996 and the first
middleware to identify works based on content and user defined metadata was written. In
2006 the DICE group, a group of research institutions in the US created the Integrated RuleOriented Data System (iRODS) expanding on the concepts of SRB and in 2013 the iRODS
Consortium was formed as a user supported community devoted to the long term
continuation of this open source middleware. This project, that was first launched 25 years ago, has spawned software that is being used to manage data archives worldwide. The
iRODS software can completely virtualize entire file system infrastructures so that storage
purchased from any vendor at any time can be made to appear as one effective file system.
Researchers no longer have to be concerned with the location of data but just the contents.
Data discovery is one of the primary features of iRODS. A researcher can specify search
terms retained in an index that allows other researchers to discover that research work. The
process of building an index does not necessarily require human intervention. Metadata can
be automatically extracted from files at rest or while being ingested to enable
discoverability. In fact, complete workflow automation can be realized with iRODS. Data can
be automatically ingested from numerous sensors and routed, based on content and
policies, to specific compute platforms for analysis. The subsequent data products can then
be distributed based on policy. Data products can be published according to policies
associated with the collections under management. All of this functionality can be audited in
real time to precisely track the operation of a data centerBandwidth Availability Enables Global CollaborationThe deployment of 100Gbps ethernet wide area networks across many universities
launched a new era of research data communication. Initially all data operations were
relegated to one campus or entity simply due to the limitations of communication
technology. While it was possible to transfer files by way of File Transfer Protocol (FTP)
technologies it was not easily possible to create indices that spanned federated collections
allowing data to be discovered or easily accessed. The secure federation capabilities of
iRODS has changed the way that we think of data locality. One of the key focuses of iRODS
development has been to enable federated collaboration. When the administrators of two
iRODS sites share a set of keys, the two sites, with permissions, can appear as one. The
researcher or administrator can assign access controls for local and WAN access. A user in a
remote zone can easily discover data through access to user defined metadata. A file
transfer can then be enabled with the iRODS servers brokering a direct transfer to the
requesting client. A researcher can even share data with a non-iRODS users issuing a secure
ticket for a specific file or files. A New Era of Data Sharing is UnderwayLarge scale iRODS deployments span the world and have enabled collaborations of multinational scientists and researchers. In the US the iPlant Collaborative was formed in 2008
with funding from the National Science Foundation. Data management was based on iRODS
from the start of the project and it initially served the plant science communities primarily in
the US. From its inception, iPlant quickly grew into a mature organization providing
powerful resources and offering scientific and technical support services to researchers nationally and internationally. In 2015, iPlant was rebranded to CyVerse to emphasize an
expanded mission to serve all life sciences [2]. Today CyVerse serves over 47,000 users with
5,690 participating academic institutions and 2,438 non-academic institutions. A major
feature of the collaborative is the Discovery Environment (DE) which allows researchers to
quickly find files of interest relating to their life science discipline. The primary site is in
Tucson Arizona with a mirror at Texas Advanced Computing in Austin Texas. Both data
management and workflow control is enabled by the use of iRODS.In Europe the EUDAT Collaborative Data Infrastructure (CDI) was formed to host the data of
over 50 universities and research institutions in the European Union. The infrastructure is
managed under iRODS and the data covers over 30 scientific disciplines from atmospheric
research to physics, hydro-meteorology, genomics, and ecology. As with CyVerse, a major
feature of EUDAT is data discovery across the entire geography of the EU. The goal is to
provide both data access and re-use for near term needs as well as data preservation to
build a long term archive [3]. In the Netherlands, SURF has built a data management framework based on iRODS.
Countrywide data from several universities is stored at their data site. Besides the service of
offering data storage and management, they also offer data processing and analysis as well
as compute services. All of the data at the site is moved to various platforms and tiers using
iRODS [4]. SURF is a member of the iRODS community as well as several universities in the
Netherlands.In Sweden, The Swedish National Infrastructure for Computing (SNIC) is a national research
infrastructure that makes available large scale high performance computing resources,
storage capacity, and advanced user support, for Swedish researchers. This service is
managed under iRODS control [5]. This service uses the Swedish University Network
(SUNET) which links the infrastructure at the KTH Royal Institute of Technology to other
universities in Sweden with a 100Gbps link to facilitate data movement [6].These are just a few of the iRODS deployments in both the academic and research sectors.
The use of iRODS and its discovery capabilities accelerates scientific research allowing
researchers to quickly find relevant materials while building on them. The power of iRODS to
manage data based on collection policies cannot be overstated as data sets grow and
automation becomes a requirement. Many worldwide universities, libraries, museums, and
companies have chosen iRODS as a technology that allows the “future proofing” of data
collections independent of the evolution of storage. These institutions have realized that
their data policy decisions can be maintained by iRODS at any scale regardless of the change
of data storage or networking technologies over time. ABOUT THE AUTHOR Dave Fellinger is a Data Management Technologist and Storage Scientist with the iRODS
Consortium. In his role at the iRODS Consortium, Dave is working with users in research sites and high
performance computer centers to confirm that a broad range of use cases can be fully
addressed by the iRODS feature set. He helped to launch the iRODS Consortium and was a
member of the founding board. References 1. The history of the card catalog is available from; https://www.vox.com/culture/2017/4/21/15357984/card-catalog-library-ofcongress-history ,accessed 2 November 2019 2. The history of CyVerse is available from; https://www.cyverse.org/about ,accessed 9 October 2019 3. Information regarding EUDAT is available from; https://www.eudat.eu/eudat-cdi ,accessed 8 October 2019 4. Information regarding SURF is available from; https://www.surf.nl/en/research-ict ,accessed 9 October 2019 5. Information regarding SNIC is available from; https://www.snic.se/ ,accessed 9 October 2019 6. Information regarding SUNET is available from; https://www.sunet.se/about-sunet/ ,accessed 9 October 2019 </div
In-plane friction behaviour of a ferrofluid bearing
No full textFerrofluid bearings have been demonstrated to be very interesting for precision positioning systems. The friction of these bearings is free of stick-slip which results in an increase of precision. More knowledge on the friction behaviour of these bearings is important for there application in precision positioning systems. This paper demonstrates that the friction of a ferrofluid bearing can be modelled by a viscous damper model and provides a basic model to predict the friction behaviour of a bearing design. The model consists of a summation of a Couette flow with a Poiseuille flow such that there is no net fluid transport under the bearing pads. The model is experimentally validated on a six degrees of freedom stage using ferrofluid bearings. A stiffness in the form of a closed-loop control gain is introduced in the system to create a resonance peak at the desired frequency. The damping coefficient can be identified from the peak height of the resonance, since the peak height is the ratio of total energy to dissipated energy in the system. The results show that the newly derived model can be used to make an estimate of the damping coefficient for small(∼1mm) stroke translations. Furthermore, the model shows that the load capacity of a ferrofluid pocket bearing is affected during sliding.Mechatronic Systems Desig
