16,696 research outputs found
Evaluating Interaction Techniques in an Interactive Workspace: Comparing the Effectiveness of a Textual Interface, Virtual Paths Interface, and ARIS
ARIS is an interface that enables users to visually relocate applications and redirect input among myriad devices in an interactive workspace. While we previously claimed that ARIS is more effective than other interfaces for performing these tasks, this work seeks to empirically validate our claim. We compared the use of ARIS to an interaction design of a text-based and virtual paths interface for relocating applications and redirecting input in an interactive workspace. Results show that (i) users can relocate applications and redirect input faster with ARIS than a text-based interface, (ii) users commit fewer errors with ARIS than a text-based interface, (iii) users experience less workload and are more satisfied with ARIS than a text-based interface, and (iv) ARIS was comparable to the use of a virtual paths interface. ARIS is more effective than an interaction design that requires a user to mentally map and select textual identifiers, while supporting functionality beyond that of a virtual paths interface
New path description for the M(k+1,2k+3) models and the dual Z_k graded parafermions
We present a new path description for the states of the non-unitary
M(k+1,2k+3) models. This description differs from the one induced by the
Forrester-Baxter solution, in terms of configuration sums, of their
restricted-solid-on-solid model. The proposed path representation is actually
very similar to the one underlying the unitary minimal models M(k+1,k+2), with
an analogous Fermi-gas interpretation. This interpretation leads to fermionic
expressions for the finitized M(k+1,2k+3) characters, whose infinite-length
limit represent new fermionic characters for the irreducible modules. The
M(k+1,2k+3) models are also shown to be related to the Z_k graded parafermions
via a (q to 1/q) duality transformation.Comment: 43 pages (minor typo corrected and minor rewording in the
introduction
Particles in RSOS paths
We introduce a new representation of the paths of the Forrester-Baxter RSOS
models which represents the states of the irreducible modules of the minimal
models M(p',p). This representation is obtained by transforming the RSOS paths,
for the cases p> 2p'-2, to new paths for which horizontal edges are allowed at
certain heights. These new paths are much simpler in that their weight is
nothing but the sum of the position of the peaks. This description paves the
way for the interpretation of the RSOS paths in terms of fermi-type charged
particles out of which the fermionic characters could be obtained
constructively. The derivation of the fermionic character for p'=2 and p=kp'+/-
1 is outlined. Finally, the particles of the RSOS paths are put in relation
with the kinks and the breathers of the restricted sine-Gordon model.Comment: 15 pages, few typos corrected, version publishe
Mapping isoprene emissions over North America using formaldehyde column observations from space
We present a methodology for deriving emissions of volatile organic compounds (VOC) using space-based column observations of formaldehyde (HCHO) and apply it to data from the Global Ozone Monitoring Experiment (GOME) satellite instrument over North America during July 1996. The HCHO column is related to local VOC emissions, with a spatial smearing that increases with the VOC lifetime. Isoprene is the dominant HCHO precursor over North America in summer, and its lifetime (≃1 hour) is sufficiently short that the smearing can be neglected. We use the Goddard Earth Observing System global 3-D model of tropospheric chemistry (GEOS-CHEM) to derive the relationship between isoprene emissions and HCHO columns over North America and use these relationships to convert the GOME HCHO columns to isoprene emissions. We also use the GEOS-CHEM model as an intermediary to validate the GOME HCHO column measurements by comparison with in situ observations. The GEOS-CHEM model including the Global Emissions Inventory Activity (GEIA) isoprene emission inventory provides a good simulation of both the GOME data (r2 = 0.69, n = 756, bias = +11%) and the in situ summertime HCHO measurements over North America (r2 = 0.47, n = 10, bias = −3%). The GOME observations show high values over regions of known high isoprene emissions and a day-to-day variability that is consistent with the temperature dependence of isoprene emission. Isoprene emissions inferred from the GOME data are 20% less than GEIA on average over North America and twice those from the U.S. EPA Biogenic Emissions Inventory System (BEIS2) inventory. The GOME isoprene inventory when implemented in the GEOS-CHEM model provides a better simulation of the HCHO in situ measurements than either GEIA or BEIS2 (r2 = 0.71, n = 10, bias = −10%)
Measurement of Gibbs energies of formation of CoF<sub>2</sub> and MnF<sub>2</sub> using a new composite dispersed solid electrolyte
Gibbs energies of formation of CoF2 and MnF2 have been measured in the temperature range from 700 to 1100 K using Al2O3-dispersed CaF2 solid electrolyte and Ni+NiF2 as the reference electrode. The dispersed solid electrolyte has higher conductivity than pure CaF2 thus permitting accurate measurements at lower temperatures. However, to prevent reaction between Al2O3 in the solid electrolyte and NiF2 (or CoF2) at the electrode, the dispersed solid electrolyte was coated with pure CaF2, thus creating a composite structure. The free energies of formation of CoF2 and MnF2 are (± 1700) J mol−1;
ΔG°f(CoF2,s)=-664,010+134.38T(700-980K)
ΔG°f(MnF2,s)=-848.270+129.59T(700-980K)
=-850.200+131.56T(980-1100K)
The third law analysis gives the enthalpy of formation of solid ΔG°f2 as ΔH° (298·15 K) = −672·69 (± 0·1) kJ mol−1, which compares with a value of −671·5 (± 4) kJ mol−1 given in Janaf tables. For solid MnF2, ΔH°(298·15 K) = − 854·97 (± 0·13) kJ mol−1, which is significantly different from a value of −803·3 kJ mol−1 given in the compilation by Barinet al
Mean Field Theory of the Morphology Transition in Stochastic Diffusion Limited Growth
We propose a mean-field model for describing the averaged properties of a
class of stochastic diffusion-limited growth systems. We then show that this
model exhibits a morphology transition from a dense-branching structure with a
convex envelope to a dendritic one with an overall concave morphology. We have
also constructed an order parameter which describes the transition
quantitatively. The transition is shown to be continuous, which can be verified
by noting the non-existence of any hysteresis.Comment: 16 pages, 5 figure
Critical Analysis of Strategies Towards Creating an Adequate Level of Awareness on Cybercrime among the Youth in Gauteng Province
This study aims to determine any measures taken by the South African Police Service (SAPS) to create awareness about cybercrime among the youth in the selected policing areas in the Gauteng province. A qualitative research method was applied using semi-structured interviews to find the views of participants, of measures if any, to create youths’ awareness in the area of cybercrime. A total of 37 participants comprised of 29 youths aged between 19 and 35 years, including an additional eight participants from the SAPS Crime Intelligence Unit who agreed to participate. Among these participants, there were 18 females and 19 males. The findings highlighted that there was a lack of awareness on the measures taken by the SAPS in educating the youth about the risks associated with cybercrime. The other challenges highlighted by the SAPS were a lack of capacity, resources, and training to increase the technical skills amongst the SAPS members to work effectively on cybercrime-related challenges, lack of collaboration among role players to respond adequately to cybercrime, and ineffective implementation of cybercrime policies, therefore, there was a lack of cybercrime-related campaigns. Based on the findings, five themes were explored in this study, including a lack of capacity, resources, and training to increase the technical skills amongst the SAPS members to work effectively on cybercrime-related challenges, lack of collaboration among role players to respond adequately to cybercrime and ineffective implementation of cybercrime policies. The recommendations are provided as a potential step towards tailoring education packages and awareness programs to ensure at-risk groups are equipped with actionable mechanisms to protect themselves against cybercrimes
Novel type of phase transition in a system of self-driven particles
A simple model with a novel type of dynamics is introduced in order to
investigate the emergence of self-ordered motion in systems of particles with
biologically motivated interaction. In our model particles are driven with a
constant absolute velocity and at each time step assume the average direction
of motion of the particles in their neighborhood with some random perturbation
() added. We present numerical evidence that this model results in a
kinetic phase transition from no transport (zero average velocity, ) to finite net transport through spontaneous symmetry breaking of the
rotational symmetry. The transition is continuous since is
found to scale as with
Deficiency of RgpG causes major defects in cell division and biofilm formation, and deficiency of LytR-CpsAPsr family proteins leads to accumulation of cell wall antigens in culture medium by Streptococcus mutans
ABSTRACT
Streptococcus mutans
is known to possess rhamnose-glucose polysaccharide (RGP), a major cell wall antigen.
S. mutans
strains deficient in
rgpG
, encoding the first enzyme of the RGP biosynthesis pathway, were constructed by allelic exchange. The
rgpG
deficiency had no effect on growth rate but caused major defects in cell division and altered cell morphology. Unlike the coccoid wild type, the
rgpG
mutant existed primarily in chains of swollen, “squarish” dividing cells. Deficiency of
rgpG
also causes significant reduction in biofilm formation (
P
< 0.01). Double and triple mutants with deficiency in
brpA
and/or
psr
, genes coding for the LytR-CpsA-Psr family proteins BrpA and Psr, which were previously shown to play important roles in cell envelope biogenesis, were constructed using the
rgpG
mutant. There were no major differences in growth rates between the wild-type strain and the
rgpG brpA
and
rgpG psr
double mutants, but the growth rate of the
rgpG brpA psr
triple mutant was reduced drastically (
P
< 0.001). Under transmission electron microscopy, both double mutants resembled the
rgpG
mutant, while the triple mutant existed as giant cells with multiple asymmetric septa. When analyzed by immunoblotting, the
rgpG
mutant displayed major reductions in cell wall antigens compared to the wild type, while little or no signal was detected with the double and triple mutants and the
brpA
and
psr
single mutants. These results suggest that RgpG in
S. mutans
plays a critical role in cell division and biofilm formation and that BrpA and Psr may be responsible for attachment of cell wall antigens to the cell envelope.
IMPORTANCE
Streptococcus mutans
, a major etiological agent of human dental caries, produces rhamnose-glucose polysaccharide (RGP) as the major cell wall antigen. This study provides direct evidence that deficiency of RgpG, the first enzyme of the RGP biosynthesis pathway, caused major defects in cell division and morphology and reduced biofilm formation by
S. mutans
, indicative of a significant role of RGP in cell division and biofilm formation in
S. mutans
. These results are novel not only in
S. mutans
, but also other streptococci that produce RGP. This study also shows that the LytR-CpsA-Psr family proteins BrpA and Psr in
S. mutans
are involved in attachment of RGP and probably other cell wall glycopolymers to the peptidoglycan. In addition, the results also suggest that BrpA and Psr may play a direct role in cell division and biofilm formation in
S. mutans
. This study reveals new potential targets to develop anticaries therapeutics.
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Nonlocal operator basis from the path representation of the M(k+1,k+2) and the M(k+1,2k+3) minimal models
We reinterpret a path describing a state in an irreducible module of the
unitary minimal model M(k+1,k+2) in terms of a string of charged operators
acting on the module's ground-state path. Each such operator acts non-locally
on a path. The path characteristics are then translated into a set of
conditions on sequences of operators that provide an operator basis. As an
application, we re-derive the vacuum finite fermionic character by constructing
the generating function of these basis states.
These results generalize directly to the M(k+1,2k+3) models, the close
relatives of the unitary models in terms of path description.Comment: 22 pages, new title and abstract; section 1 rewritten and section 2.2
improved; version to appear in J. Phys.
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