89,402 research outputs found
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Web-based information systems development and dynamic organisational change: the need for emergent development tools
This paper considers contextual issues relating to the problem of developing web-based information
systems in and for emergent organisations. It postulates that the methods available suffer because of
sudden and unexpected changing characteristics within the organisation. The Theory of Deferred
Action is used as the basis for the development of an emergent development tool. Many tools for
managing change in a continuously changing organisation are susceptible to inadequacy. The insights
proposed are believed to assist designers in developing functional and relevant approaches within
dynamic organisational contexts
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Changes in forward light scatter parameters as a function of refractive error in young adults
Background/aims
Some aspects of visual performance worsen with increasing myopia. Whilst the underlying causes are not always clear, reduction in retinal image quality is often attributed to structural changes in the posterior myopic eye. Forward light scatter, originating principally from the cornea and lens, is known to produce veiling glare which subsequently reduces retinal image contrast. It is therefore of interest to investigate whether forward light scatter varies with refractive error.
Methods
Thirteen young-adult subjects (18–25 years), with mean spherical errors (MSE ± sd, D) RE, − 1.69 ± 2.02 (range 0.38 to − 4.75); LE, − 1.91 ± 1.94 (range 0.50 to − 4.63) underwent binocular assessment of forward light scatter using the AVOT light scatter test. Five glare annuli, with effective eccentricities ranging from 2 to 10°, were used to estimate parameters, k and n, which define the light scatter function of the eye. These were then used to calculate the area under the light scatter function (k′) and the total volume of light scatter (k″).
Results
Significant correlation was found between increasing myopia and k′ values (RE, p  0.05 for both eyes). Axial length was also not correlated with any of the light scatter parameters measured.
Conclusion
The preliminary data from this study provide evidence that some light scatter parameters may be correlated with refractive error. Further studies are needed to characterize how changes in the anterior media of the eye, and inclusion of a wider range of refractive errors, may affect forward light scatter
Discrete symmetries for electroweak natural type-I seesaw mechanism
The naturalness of electroweak scale in the models of type-I seesaw mechanism
with Yukawa couplings requires TeV scale masses for the fermion
singlets. In this case, the tiny neutrino masses have to arise from the
cancellations within the seesaw formula which are arranged by fine-tuned
correlations between the Yukawa couplings and the masses of fermion singlets.
We motivate such correlations through the framework of discrete symmetries. In
the case of three Majorana fermion singlets, it is shown that the exact
cancellation arranged by the discrete symmetries in seesaw formula necessarily
leads to two mass degenerate fermion singlets. The remaining fermion singlet
decouples completely from the standard model. We provide two candidate models
based on the groups and and discuss the generic
perturbations to this approach which can lead to the viable neutrino masses.Comment: 26 pages, 4 figures; references added, matches published versio
Interpreting 750 GeV diphoton excess in SU(5) grand unified theory
The ATLAS and CMS experiments at the LHC have found significant excess in the
diphoton invariant mass distribution near 750 GeV. We interpret this excess in
a predictive nonsupersymmetric SU(5) grand unified framework with a singlet
scalar and light adjoint fermions. The 750 GeV resonance is identified as a
gauge singlet scalar. Both its production and decays are induced by 24
dimensional adjoint fermions predicted within SU(5). The adjoint fermions are
assumed to be odd under symmetry which forbids their direct coupling to
the standard model fermions. We show that the observed diphoton excess can be
explained with sub-TeV adjoint fermions and with perturbative Yukawa coupling.
A narrow width scenario is more preferred while a simultaneous explanation of
observed cross section and large total decay width requires some of the adjoint
fermions lighter than 375 GeV. The model also provides a singlet fermion as a
candidate of cold dark matter. The gauge coupling unification is achieved in
the framework by introducing color sextet scalars while being consistent with
the proton decay constraint.Comment: Discussion added, conclusion unchanged; Matches published version in
Physics Letters
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