6,608 research outputs found
Ion-water clusters, bulk medium effects, and ion hydration
Thermochemistry of gas-phase ion-water clusters together with estimates of
the hydration free energy of the clusters and the water ligands are used to
calculate the hydration free energy of the ion. Often the hydration
calculations use a continuum model of the solvent. The primitive quasichemical
approximation to the quasichemical theory provides a transparent framework to
anchor such efforts. Here we evaluate the approximations inherent in the
primitive quasichemical approach and elucidate the different roles of the bulk
medium. We find that the bulk medium can stabilize configurations of the
cluster that are usually not observed in the gas phase, while also
simultaneously lowering the excess chemical potential of the ion. This effect
is more pronounced for soft ions. Since the coordination number that minimizes
the excess chemical potential of the ion is identified as the optimal or most
probable coordination number, for such soft ions, the optimum cluster size and
the hydration thermodynamics obtained without account of the bulk medium on the
ion-water clustering reaction can be different from those observed in
simulations of the aqueous ion. The ideas presented in this work are expected
to be relevant to experimental studies that translate thermochemistry of
ion-water clusters to the thermodynamics of the hydrated ion and to evolving
theoretical approaches that combine high-level calculations on clusters with
coarse-grained models of the medium
Virtual EQ â the talent differentiator in 2020?
In an increasingly competitive, globalised world, knowledge-intensive industries/ services are seen as engines for success. Key to this marketplace is a growing army of âtalentâ i.e. skilled and dedicated knowledge workers. These knowledge workers engage in non-routine problem solving through combining convergent, divergent and creative thinking across organizational and company boundaries - a process often facilitated though the internet and social media, consequently forming networks of expertise. For knowledge workers, sharing their learning with others through communities of practice embedded in new information media becomes an important element of their personal identity and the creation of their individual brand or e-social reputation. Part of the new knowledge/skills needed for this process becomes not only emotional intelligence (being attuned to the emotional needs of others) but being able to do this within and through new media, thus the emergence of virtual emotional intelligence (EQ). Our views of current research found that HRD practitioners in 2020 might need to consider Virtual EQ as part of their talent portfolio. However it seems that new technology has created strategies for capturing and managing knowledge that are readily duplicated and that a talent differentiator in 2020 might simply be the ability and willingness to learn
Making identity assurance and authentication strength work for federated infrastructures
In both higher Research and Education (R&E) as well as in research-/ e-infrastructures (in short: infrastructures), federated access and single sign-on by way of national federations, operated in most cases by NRENs, are used as a means to provide users with access to a variety of services. Whereas in national federations institutional accounts, e.g. provided by a university, are typically used to access services, many infrastructures also accept other sources of identity: provided by \u27\u27community identity providers\u27\u27, social identity providers, or governmental IDs. In order to assess and communicate the quality of identities being used and authentications being performed, so called Level of Assurance (LoA) frameworks are used. Because sophisticated LoA frameworks like NIST 800-63-3, Kantara IAF 1420 or eIDAS regulation are often considered too complex to be used in R&E scenarios, the REFEDS Assurance Suite, a more lightweight approach, has been developed. To select an appropriate assurance level, Service Providers need to weigh risks and potential harms in relation to the kind of service they offer. However, the management of risks is often implicitly assumed and little or no guidance to determine the appropriate assurance level is given. In this paper, first, common LoA frameworks and their relation to risk management are investigated. Following that, their components are compared against the REFEDS Assurance Suite using a graphical representation. The focus of this paper lies in providing guidance and best practices based on example scenarios for both Service Providers to request the appropriate REFEDS assurance level, as well as for Identity Provider operators on how to implement REFEDS assurance components
Clusters in the Luminous Giant HII Regions in M101
(Abridged) We have obtained HST WFPC2 observations of three very luminous but
morphologically different giant HII regions (GHRs) in M101, NGC5461, NGC5462,
and NGC5471, in order to study cluster formation in GHRs. The measured (M_F547M
- M_F675W) colors and M_F547M magnitudes are used to determine the ages and
masses of the cluster candidates with M_F547M <= -9.0. NGC5461 is dominated by
a very luminous core, and has been suggested to host a super-star cluster
(SSC). Our observations show that it contains three R136-class clusters
superposed on a bright stellar background in a small region. This tight group
of clusters may dynamically evolve into an SSC in the future, and may appear
unresolved and be identified as an SSC at large distances, but at present
NGC5461 has no SSCs. NGC5462 has loosely distributed HII regions and clusters
without a prominent core. It has the largest number of cluster candidates among
the three GHRs, but most of them are faint and older than 10 Myr. NGC5471 has
multiple bright HII regions, and contains a large number of faint clusters
younger than 5 Myr. Two of the clusters in NGC5471 are older than R136, but
just as luminous; they may be the most massive clusters in the three GHRs. The
fraction of stars formed in massive clusters is estimated from the clusters'
contribution to the total stellar continuum emission and a comparison of the
ionizing power of the clusters to the ionizing requirement of the associated
HII regions. Both estimates show that <~ 50% of massive stars are formed in
massive clusters. The cluster luminosity functions (CLFs) of the three GHRs
show different slopes. NGC5462 has the steepest CLF and the most loosely
distributed interstellar gas, qualitatively consistent with the hypothesis that
massive clusters are formed in high-pressure interstellar environments.Comment: 36 pages (figures not included), 16 figures (3 of them are color
figures). Figures are in JPEG or GIF format with a lower resolution due to
the size limit of the file. For a higher resolution version of the paper,
please download from http://www.astro.uiuc.edu/~c-chen/clusters.pdf. accepted
for ApJ (scheduled for the ApJ 2005 February issue
Managing Dynamic User Communities in a Grid of Autonomous Resources
One of the fundamental concepts in Grid computing is the creation of Virtual
Organizations (VO's): a set of resource consumers and providers that join
forces to solve a common problem. Typical examples of Virtual Organizations
include collaborations formed around the Large Hadron Collider (LHC)
experiments. To date, Grid computing has been applied on a relatively small
scale, linking dozens of users to a dozen resources, and management of these
VO's was a largely manual operation. With the advance of large collaboration,
linking more than 10000 users with a 1000 sites in 150 counties, a
comprehensive, automated management system is required. It should be simple
enough not to deter users, while at the same time ensuring local site autonomy.
The VO Management Service (VOMS), developed by the EU DataGrid and DataTAG
projects[1, 2], is a secured system for managing authorization for users and
resources in virtual organizations. It extends the existing Grid Security
Infrastructure[3] architecture with embedded VO affiliation assertions that can
be independently verified by all VO members and resource providers. Within the
EU DataGrid project, Grid services for job submission, file- and database
access are being equipped with fine- grained authorization systems that take VO
membership into account. These also give resource owners the ability to ensure
site security and enforce local access policies. This paper will describe the
EU DataGrid security architecture, the VO membership service and the local site
enforcement mechanisms Local Centre Authorization Service (LCAS), Local
Credential Mapping Service(LCMAPS) and the Java Trust and Authorization
Manager.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 7 pages, LaTeX, 5 eps figures. PSN
TUBT00
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