697 research outputs found
motifDiverge: a model for assessing the statistical significance of gene regulatory motif divergence between two DNA sequences
Next-generation sequencing technology enables the identification of thousands
of gene regulatory sequences in many cell types and organisms. We consider the
problem of testing if two such sequences differ in their number of binding site
motifs for a given transcription factor (TF) protein. Binding site motifs
impart regulatory function by providing TFs the opportunity to bind to genomic
elements and thereby affect the expression of nearby genes. Evolutionary
changes to such functional DNA are hypothesized to be major contributors to
phenotypic diversity within and between species; but despite the importance of
TF motifs for gene expression, no method exists to test for motif loss or gain.
Assuming that motif counts are Binomially distributed, and allowing for
dependencies between motif instances in evolutionarily related sequences, we
derive the probability mass function of the difference in motif counts between
two nucleotide sequences. We provide a method to numerically estimate this
distribution from genomic data and show through simulations that our estimator
is accurate. Finally, we introduce the R package {\tt motifDiverge} that
implements our methodology and illustrate its application to gene regulatory
enhancers identified by a mouse developmental time course experiment. While
this study was motivated by analysis of regulatory motifs, our results can be
applied to any problem involving two correlated Bernoulli trials
TRUST MANAGEMENT – AN INFORMATION SYSTEMS PERSPECTIVE
The focus of the Information Systems (IS) research on trust has been on the perception of trust and explaining the concept in terms of its antecedents. The merits of this descriptive and explanatory knowledge notwithstanding, the usefulness and applicability of this knowledge for organizations that aim at actively influencing their trust position is limited. In light of recent public scandals in areas such as social media, car manufacturing or financial services, organizations require an understanding of how customer trust can be managed using contemporary information systems solutions. In this paper we propose trust management as an IS theme of increasing relevance and draw upon extant research in IS, psychology, and marketing to bridge the gap between topics such as risk management, compliance management and governance on the one hand and trust management on the other. We utilize Botsman’s concept of uncertainty as a proxy for customer trust to bring together organizational approaches that can objectively reduce uncertainty linked to an organization, its processes, products, and services with the customer’s perception of this uncertainty. We contribute to the further maturity of trust management by providing new foundations and providing explicit advice on how to improve trust in organizations
Alternative glues for the production of ATLAS silicon strip modules for the Phase-II upgrade of the ATLAS Inner Detector
The Phase-II upgrade of the ATLAS detector for the High Luminosity Large
Hadron Collider (HL-LHC) includes the replacement of the current Inner Detector
with an all-silicon tracker consisting of pixel and strip detectors. The
current Phase-II detector layout requires the construction of 20,000 strip
detector modules consisting of sensor, circuit boards and readout chips, which
are connected mechanically using adhesives. The adhesive between readout chips
and circuit board is a silver epoxy glue as was used in the current ATLAS
SemiConductor Tracker (SCT). This glue has several disadvantages, which
motivated the search for an alternative.
This paper presents a study concerning the use of six ultra-violet (UV) cure
glues and a glue pad for use in the assembly of silicon strip detector modules
for the ATLAS upgrade. Trials were carried out to determine the ease of use,
the thermal conduction and shear strength, thermal cycling, radiation hardness,
corrosion resistance and shear strength tests. These investigations led to the
exclusion of three UV cure glues as well as the glue pad.
Three UV cure glues were found to be possible better alternatives. Results
from electrical tests of first prototype modules constructed using these glues
are presented.Comment: 23 pages, to be published in Journal of Instrumentatio
Interference of Clocks: A Quantum Twin Paradox
The phase of matter waves depends on proper time and is therefore susceptible
to special-relativistic (kinematic) and gravitational time dilation (redshift).
Hence, it is conceivable that atom interferometers measure general-relativistic
time-dilation effects. In contrast to this intuition, we show that light-pulse
interferometers without internal transitions are not sensitive to gravitational
time dilation, whereas they can constitute a quantum version of the
special-relativistic twin paradox. We propose an interferometer geometry
isolating the effect that can be used for quantum-clock interferometry.Comment: 9 Pages, 2 Figure
Evolutionarily distant I domains can functionally replace the essential ligand-binding domain of Plasmodium TRAP
Inserted (I) domains function as ligand-binding domains in adhesins that support cell adhesion and migration in many eukaryotic phyla. These adhesins include integrin alpha beta heterodimers in metazoans and single subunit transmembrane proteins in apicomplexans such as TRAP in Plasmodium and MIC2 in Toxoplasma. Here we show that the I domain of TRAP is essential for sporozoite gliding motility, mosquito salivary gland invasion and mouse infection. Its replacement with the I domain from Toxoplasma MIC2 fully restores tissue invasion and parasite transmission, while replacement with the aXI domain from human integrins still partially restores liver infection. Mutations around the ligand binding site allowed salivary gland invasion but led to inefficient transmission to the rodent host. These results suggest that apicomplexan parasites appropriated polyspecific I domains in part for their ability to engage with multiple ligands and to provide traction for emigration into diverse organs in distant phyla
Atom-interferometric test of the universality of gravitational redshift and free fall
Light-pulse atom interferometers constitute powerful quantum sensors for
inertial forces. They are based on delocalised spatial superpositions and the
combination with internal transitions directly links them to atomic clocks.
Since classical tests of the gravitational redshift are based on a comparison
of two clocks localised at different positions under gravity, it is promising
to explore whether the aforementioned interferometers constitute a competitive
alternative for tests of general relativity. Here we present a specific
geometry which together with state transitions leads to a scheme that is
concurrently sensitive to both violations of the universality of free fall and
gravitational redshift, two premises of general relativity. The proposed
interferometer does not rely on a superposition of internal states, but merely
on transitions between them, and therefore generalises the concept of physical
atomic clocks and quantum-clock interferometry. An experimental realisation
seems feasible with already demonstrated techniques in state-of-the-art
facilities.Comment: 8 pages, 4 figure
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