2,788 research outputs found
Diffusion local time storage
In this paper we study a storage process or a liquid queue in which the input
process is the local time of a positively recurrent stationary diffusion in
stationary state and the potential output takes place with a constant
deterministic rate. For this storage process we find its stationary
distribution and compute the joint distribution of the starting and ending
times of the busy and idle periods. This work completes and extends to a more
general setting the results in Mannersalo, Norros, and Salminen (2003).Comment: 24 pages; to appear in Stoch. Proc. App
On inversions and Doob -transforms of linear diffusions
Let be a regular linear diffusion whose state space is an open interval
. We consider a diffusion which probability law is
obtained as a Doob -transform of the law of , where is a positive
harmonic function for the infinitesimal generator of on . This is the
dual of with respect to where is the speed measure of
. Examples include the case where is conditioned to stay above
some fixed level. We provide a construction of as a deterministic
inversion of , time changed with some random clock. The study involves the
construction of some inversions which generalize the Euclidean inversions.
Brownian motion with drift and Bessel processes are considered in details.Comment: 19 page
Optimal stopping of oscillating Brownian motion
We solve optimal stopping problems for an oscillating Brownian motion, i.e. a diffusion with positive piecewise constant volatility changing at the point x=0. Let σ1 and σ 2 denote the volatilities on the negative and positive half-lines, respectively. Our main result is that continuation region of the optimal stopping problem with reward
((1+x)+)2 can be disconnected for some values of the discount rate when 2 σ 21 <σ22. Based on the fact that the skew Brownian motion in natural scale is an oscillating Brownian motion, the obtained results are translated into corresponding results for the skew Brownian motion
ASO Author Reflections : Registry-Based Analysis of Radiation-Associated Angiosarcoma of the Breast Provides Unbiased Insights into this Disease
Non peer reviewe
Kick Scooter Injuries in Children and Adolescents : Minor Fractures and Bruise
Background: Kick scooters are popular among children in both transportation and recreational activities. The aim of this retrospective study was to assess the incidence of and injury patterns associated with kick scooter accidents in school-aged children and adolescents. Methods: All 171 patients at the age of 7-15 years who were treated for kick scooter-related injuries in the metropolitan Helsinki area, Southern Finland from January 2008 to December 2013 were included. Electronic medical records were reviewed and Pediatric Trauma Scores and Injury Severity Scores were utilized to assess the injuries. Results: The annual number of patients increased from 7 in 2008 to 55 in 2013. Almost all patients (94%, n = 161) were injured after a fall from their own height. Most patients (n = 118; 69%) were diagnosed with a fracture but only 26 patients (15%) required surgical procedures under general anesthesia. Pediatric Trauma Scores were low and only one patient had an Injury Severity Score > 15 which can be considered major trauma. Conclusion: Most injuries acquired from kick scooter injuries were easily treatable fractures and bruises. Considering the background population of 105,000 in the respective age group and the 6-year period of data collection from tertiary care, scooting seems a safe means of increasing the physical activity levels of school-aged children and adolescents.Peer reviewe
On -transforms of one-dimensional diffusions stopped upon hitting zero
For a one-dimensional diffusion on an interval for which 0 is the
regular-reflecting left boundary, three kinds of conditionings to avoid zero
are studied. The limit processes are -transforms of the process stopped
upon hitting zero, where 's are the ground state, the scale function, and
the renormalized zero-resolvent. Several properties of the -transforms are
investigated
Mouse MIM, a tissue-specific regulator of cytoskeletal dynamics, interacts with ATP-actin monomers through its C-terminal WH2 domain
The WH2 (WASP homology domain-2) is a small actin monomer-binding motif and is found in many proteins that regulate the actin cytoskeleton, including the beta-thymosins, ciboulot, WASP, and verprolin/WIP (WASP-interacting protein). In sequence database searches we identified a novel mouse protein containing a WH2 domain in its C-terminal region. This mouse gene also shows strong sequence homology to human MIM (Missing in Metastasis), a cDNA fragment that is present in non-metastatic but absent in metastatic bladder cancer cell lines. Northern blot and in situ hybridizations show that MIM is strongly expressed in the developing neurons and skeletal and cardiac muscles in mouse embryos. In adult mice, the strongest expression of MIM mRNA is in liver, outer layers of the kidney, and in the Purkinje cells of the brain. Recombinant MIM protein interacts with actin monomers and inhibits actin filament nucleation in vitro. However, the MIM/ATP-G-actin complex can participate in actin filament assembly at the barbed end. MIM binds ATP-G-actin with a higher affinity (K-D = 0.06 muM) than ADP-G-actin (K-D = 0.3 muM) and inhibits the nucleotide exchange on actin monomers. Site-directed mutagenesis demonstrates that the actin monomer-binding site resides in the C-terminal WH2 domain of MIM. Overexpression of mouse MIM in NIH 3T3 cells results in the disappearance of actin stress fibers and appearance of abnormal actin filament structures. These data show that MIM is an ATP-G-actin binding protein that regulates cytoskeletal dynamics in specialized mammalian cell-types
Cyclase-associated protein 1 (CAP1) promotes cofilin-induced actin dynamics in mammalian nonmuscle cells
Cyclase-associated proteins (CAPs) are highly conserved actin monomer binding proteins present in all eukaryotes. However, the mechanism by which CAPs contribute to actin dynamics has been elusive. In mammals, the situation is further complicated by the presence of two CAP isoforms whose differences have not been characterized. Here, we show that CAP1 is widely expressed in mouse nonmuscle cells, whereas CAP2 is the predominant isoform in developing striated muscles. In cultured NIH3T3 and 1316171 cells, CAP1 is a highly abundant protein that colocalizes with cofilin-1 to dynamic regions of the cortical actin cytoskeleton. Analysis of CAP1 knockdown cells demonstrated that this protein promotes rapid actin filament depolymerization and is important for cell morphology, migration, and endocytosis. Interestingly, depletion of CAP1 leads to an accumulation of cofilin-1 into abnormal cytoplasmic aggregates and to similar cytoskeletal defects to those seen in cofilin-1 knockdown cells, demonstrating that CAP1 is required for proper subcellular localization and function of ADF/cofilin. Together, these data provide the first direct in vivo evidence that CAP promotes rapid actin dynamics in conjunction with ADF/cofilin and is required for several central cellular processes in mammals
Travertine precipitation in the Paleoproterozoic Kuetsjärvi Sedimentary Formation, Pechenga Greenstone Belt, NE Fennoscandian Shield
PES was supported by Väisälä Foundation (Finnish Academy of Science and Letters) and the Finnish Doctoral Program in Geology. ATB was supported by NERC grant NE/G00398X/1. VAM was supported by NFR grant 191530/V30 (projects 331000 and 802795). This is a contribution (paper) # 18 to the ICDP FAR-DEEP project.Peer reviewedPublisher PD
ABBA regulates plasma-membrane and actin dynamics to promote radial glia extension
Radial glia play key roles in neuronal migration, axon guidance, and neurogenesis during development of the central nervous system. However, the molecular mechanisms regulating growth and morphology of these extended cells are unknown. We show that ABBA, a novel member of the IRSp53-MIM protein family, is enriched in different types of radial glia. ABBA binds ATP-actin monomers with high affinity and deforms PtdIns(4,5)P2-rich membranes in vitro through its WH2 and IM domains, respectively. In radial-glia-like C6-R cells, ABBA localises to the interface between the actin cytoskeleton and plasma membrane, and its depletion by RNAi led to defects in lamellipodial dynamics and process extension. Together, this study identifies ABBA as a novel regulator of actin and plasma membrane dynamics in radial glial cells, and provides evidence that membrane binding and deformation activity is critical for the cellular functions of IRSp53-MIM-ABBA family proteins
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