811 research outputs found
Interferometric baseline performance estimations for multistatic synthetic aperture radar configurations derived from GRACE GPS observations
No full textRecent studies have demonstrated the usefulness
of global positioning system (GPS) receivers for relative positioning
of formation-flying satellites using dual-frequency
carrier-phase observations. The accurate determination of
distances or baselines between satellites flying in formation
can provide significant benefits to a wide area of geodetic
studies. For spaceborne radar interferometry in particular,
such measurements will improve the accuracy of interferometric
products such as digital elevation models (DEM)
or surface deformation maps. The aim of this study is to
analyze the impact of relative position errors on the interferometric
baseline performance of multistatic synthetic aperture
radar (SAR) satellites flying in such a formation. Based
on accuracy results obtained from differential GPS (DGPS)
observations between the twin gravity recovery and climate
experiment (GRACE) satellites, baseline uncertainties are
derived for three interferometric scenarios of a dedicated
SAR mission. For cross-track interferometry in a bistatic
operational mode, a mean 2D baseline error (1σ) of 1.4mm
is derived, whereas baseline estimates necessary for a monostatic
acquisition mode with a 50 km along-track separation
reveal a 2D uncertainty of approximately 1.7mm. Absolute
orbit solutions based on reduced dynamic orbit determination
techniques using GRACE GPS code and carrier-phase data
allows a repeat-pass baseline estimation with an accuracy
down to 4 cm (2D 1σ). To assess the accuracy with respect to
quality requirements of high-resolution DEMs, topographic
height errors are derived from the estimated baseline uncertainties.
Taking the monostatic pursuit flight configuration as
the worst case for baseline performance, the analysis reveals
that the induced low-frequency modulation (height bias) fulfills
the relative vertical accuracy requirement
(σ smaller than 1 m linear point-to-point error) according to the digital terrain elevation
data level 3 (DTED-3) specifications for most of the baseline
constellations. The use of a GPS-based reduced dynamic
orbit determination technique improves the baseline performance
for repeat-pass interferometry. The problem of fulfilling
the DTED-3 horizontal accuracy requirements is still an
issue to be investigated. DGPS can be used as an operational
navigation tool for high-precision baseline estimation if a
geodetic-grade dual-frequency spaceborne GPS receiver is
assumed to be the primary instrument onboard the SAR satellites.
The possibility of using only single-frequency receivers,
however, requires further research effort
Interaction of the developmental regulator SALL1 with UBE2I and SUMO-1
No full textMutations in the SALL1 gene on chromosome 16q12.1 cause Townes- Brocks syndrome (TBS). This autosomal dominantly inherited disorder is characterized by typical malformations of the thumbs, the ears, and the anus, and also commonly affects the kidneys and other organ systems. SALL1 has recently been shown to localize to chromocenters and other heterochromatin foci in murine fibroblasts and to interact with the telomere-repeat- binding factor TRF1/PIN2. Here, we show that the ubiquitin- conjugating enzyme 21 (UBE2I), the human homolog of S. cerevisiae UBC9, and the small ubiquitin-like modifier-1 (SUMO- 1) interact with SALL1 in the yeast two-hybrid system. The interaction of SALL1 and UBE21 was confirmed in a glutathione S-transferase (GST) pull-down experiment. In an in vitro assay, it could be demonstrated that SALL1 is covalently modified by at least two SUMO-1 molecules in the presence of UBA2/AOS1 and UBE21. Mutation of lysine 1086 of SALL1 to arginine abrogates SALL1 sumoylation, suggesting the presence of a polymeric SUMO- I chain in the wild type state. (C) 2002 Elsevier Science (USA). All rights reserved
Editorial Annals of Regional Science
No full textThere is no tradition in Annals of Regional Science that the editors write editorials. However, as of 2020, the editors will each year write an editorial in which we report as well as reflect on recent developments of the journal. We hope that this will be of interest for our readers. This editorial is the first one and marks the start of the strategy to write a yearly editorial.We, i.e., Martin Andersson (Sweden), Hong Sok Kim (South Korea) and Janet Kohlhase (USA), are by some standards a rather new constellation of editors-in-chief (EICs). Janet Kohlhase became an editor in 2011, replacing professor Roger Stough.1 Martin Andersson joined as editor in 2014 and replaced professor Börje Johansson. Hong Sok (Brian) Kim became an editor in 2019 by replacing profes-sor Euijune Kim. The former EICs continue to be part of the journal in the capacity as members of the advisory board of former editors. We are all delighted to serve as EICs and are committed to maintain as well as to further develop the journal’s tradition of publishing high-quality and influential research that pushes the field of regional science forward.open access</p
The Townes-Brocks syndrome gene SALL1 is a transcriptional repressor and interacts with UBC9 and SUMO-1.
No full textThe Townes-Brocks syndrome gene SALL1 is a transcriptional repressor and interacts with UBC9 and SUMO-1.
No full textDefining the heterochromatin localization and repression domains of SALL1
No full textAbstractSALL1 has been identified as one of four human homologues of the Drosophila region-specific homeotic gene spalt (sal), encoding zinc finger proteins of characteristic structure. Mutations of SALL1 on chromosome 16q12.1 cause Townes–Brocks syndrome (TBS, OMIM 107480). We have shown previously that SALL1 acts as a strong transcriptional repressor in mammalian cells when fused to a heterologous DNA-binding domain. Here, we report that SALL1 contains two repression domains, one located at the extreme N-terminus of the protein and the other in the central region. SALL1 fragments with the central repression domain exhibited a punctate nuclear distribution pattern at pericentromeric heterochromatin foci in murine NIH-3T3 cells, suggesting an association between repression and heterochromatin localization. The implications of these findings for the pathogenesis of Townes–Brocks syndrome are discussed
Unique family with Townes-Brocks syndrome, SALL1 mutation, and cardiac defects
No full textTownes-Brocks syndrome (TBS) is a condition with imperforate anus, hand anomalies, and ear malformations with sensorineural hearing loss. Many cases are sporadic. Within and between families, the phenotype displays striking variability. Recently, the disease-causing gene for TBS was identified as SALL1, a zinc finger transcription factor. Here, we report a three-generation family with seven affected individuals who have a novel SALL1 mutation. Unique cardiac anomalies seen in this family include lethal truncus arteriosus in one patient and a lethal complicated defect, including pulmonary valve atresia, in a second patient. These severe cardiac anomalies have not previously been reported in a familial case of TBS. This family and a review of the literature indicate that cardiac evaluation is warranted in all individuals with this disorder. In addition, hypoplastic thumbs were seen in two individuals in this family and should, therefore, be considered a true feature of TBS. (C) 2001 Wiley-Liss. Inc
Higher--Order Coloured Unification and Natural Language Semantics
No full textIn this paper, we show that Higher--Order Coloured Unification -- a form of unification developed for automated theorem proving -- provides a general theory for modeling the interface between the interpretation process and other sources of linguistic, non semantic information. In particular, it provides the general theory for the Primary Occurrence Restriction which (Dalrymple et al., 1991)'s analysis called for. 1 Introduction It is well known that Higher--Order Unification (HOU) can be used to construct the semantics of Natural Language: (Dalrymple et al., 1991) -- henceforth, DSP -- show that it allows a treatment of VP-- Ellipsis which successfully captures the interaction of VPE with quantification and nominal anaphora; (Pulman, 1995; Gardent and Kohlhase, 1996) use HOU to model the interpretation of focus and its interaction with focus sensitive operators, adverbial quantifiers and second occurrence expressions; (Gardent et al., 1996) shows that HOU yields a simple but precise ..
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