138 research outputs found
-cluster categories and -replicated algebras
Let A be a hereditary algebra over an algebraically closed field. We prove
that an exact fundamental domain for the m-cluster category of A is the m-left
part of the m-replicated algebra of A. Moreover, we obtain a
one-to-one correspondence between the tilting objects in the m-cluster category
(that is, the m-clusters) and those tilting -modules for which all non
projective-injective direct summands lie in the m-left part of .Comment: 28 pages, 2 figure
Focal mechanisms in the southern Aegean from temporary seismic networks – implications for the regional stress field and ongoing deformation processes
The lateral variation of the stress field in the southern Aegean
plate and the subducting Hellenic slab is determined from recordings
of seismicity obtained with the CYCNET and EGELADOS networks in the
years from 2002 to 2007. First motions from 7000 well-located
microearthquakes were analysed to produce 540 well-constrained focal
mechanisms. They were complemented by another 140 derived by
waveform matching of records from larger events. Most of these
earthquakes fall into 16 distinct spatial clusters distributed over
the southern Aegean region. For each cluster, a stress inversion
could be carried out yielding consistent estimates of the stress
field and its spatial variation. At crustal levels, the stress field
is generally dominated by a steeply dipping compressional principal
stress direction except in places where coupling of the subducting
slab and overlying plate come into play. Tensional principal
stresses are generally subhorizontal. Just behind the forearc, the
crust is under arc-parallel tension whereas in the volcanic areas
around Kos, Columbo and Astypalea tensional and intermediate
stresses are nearly degenerate. Further west and north, in the
Santorini–Amorgos graben and in the area of the islands of Mykonos,
Andros and Tinos, tensional stresses are significant and point
around the NW–SE direction. Very similar stress fields are observed
in western Turkey with the tensional axis rotated to
NNE–SSW. Intermediate-depth earthquakes below 100 km in the
Nisyros region indicate that the Hellenic slab experiences
slab-parallel tension at these depths. The direction of tension is
close to east–west and thus deviates from the local NW-oriented slab
dip presumably owing to the segmentation of the slab. Beneath the
Cretan sea, at shallower levels, the slab is under NW–SE
compression.
Tensional principal stresses in the crust exhibit very good alignment with
extensional strain rate principal axes derived from GPS velocities
except in volcanic areas, where both appear to be unrelated,
and in the forearc where compressional principal stresses are
very well aligned with compressional principal strain rates. This finding
indicates that, except for volcanic areas, microseismic activity in
the southern Aegean is not controlled by small-scale local stresses
but rather reflects the regional stress field.
The lateral and depth variations of the stress field
reflect the various agents that influence tectonics in the Aegean:
subduction of the Hellenic slab, incipient collision with
continental African lithosphere, roll back of the slab in the
southeast, segmentation of the slab, arc volcanism and extension of
the Aegean crust
Receiver function images of the Hellenic subduction zone and comparison to microseismicity
New combined P receiver functions and seismicity data obtained from the
EGELADOS network employing 65 seismological stations within the Aegean
constrained new information on the geometry of the Hellenic subduction zone.
The dense network and large data set enabled us to estimate the Moho depth of
the continental Aegean plate across the whole area. Presence of a negative
contrast at the Moho boundary indicating the serpentinized mantle wedge above
the subducting African plate was seen along the entire forearc. Furthermore,
low seismicity was observed within the serpentinized mantle wedge. We found a
relatively thick continental crust (30–43 km) with a maximum thickness of
about 48 km beneath the Peloponnese Peninsula, whereas a thinner crust of
about 27–30 km was observed beneath western Turkey. The crust of the
overriding plate is thinning beneath the southern and central Aegean and
reaches 23–27 km. Unusual low Vp / Vs ratios were estimated beneath the
central Aegean, which most likely represent indications on the pronounced
felsic character of the extended continental Aegean crust. Moreover, P
receiver functions imaged the subducted African Moho as a strong converted
phase down to a depth of about 100 km. However, the converted Moho phase
appears to be weak for the deeper parts of the African plate suggesting nearly
complete phase transitions of crustal material into denser phases. We show the
subducting African crust along eight profiles covering the whole southern and
central Aegean. Seismicity of the western Hellenic subduction zone was taken
from the relocated EHB-ISC catalogue, whereas for the eastern Hellenic
subduction zone, we used the catalogues of manually picked hypocentre
locations of temporary networks within the Aegean. Accurate hypocentre
locations reveal a significant change in the dip angle of the Wadati–Benioff
zone (WBZ) from west (~ 25°) to the eastern part (~ 35°) of the Hellenic
subduction zone. Furthermore, a zone of high deformation can be characterized
by a vertical offset of about 40 km of the WBZ beneath the eastern Cretan Sea.
This deformation zone may separate a shallower N-ward dipping slab in the west
from a steeper NW-ward dipping slab in the east. In contrast to hypocentre
locations, we found very weak evidence for the presence of the slab at larger
depths in the P receiver functions, which may result from the strong
appearance of the Moho multiples as well as eclogitization of the oceanic
crust. The presence of the top of a strong low-velocity zone at about 60 km
depth in the central Aegean may be related to the asthenosphere below the
Aegean continental lithosphere and above the subducting slab. Thus, the Aegean
mantle lithosphere seems to be 30–40 km thick, which means that its thickness
increased again since the removal of the mantle lithosphere about 15 to 35 Ma
ago
SHORT COMMUNICATION: Complementary tumor induction in neural grafts exposed to N-ethyl-N-nitrosourea and an activated myc gene
Using a combination of transplacental carcinogen exposure and retrovirus-mediated oncogene transfer into fetal brain transplants, we have studied complementary transformation by N-ethyl-N-nitrosourea (NEU) and the v-myc oncogene in the nervous system. Previous experiments had demonstrated that both agents will not induce tumors independently whereas simultaneous expression of v-H-ras and v-gag/myc exerted a powerful transforming potential in neural grafts. In order to identify other genetic alterations that co-operate with an activated myc gene, the neurotropic carcinogen NEU was used to generate mutations of cellular genes. On embryonic day 14 (ED14), pregnant donor animals (F344 rats) received a single i.v. dose of NEU (50 mg/kg). Twenty-four hours later (ED15), the fetal brains were removed, triturated and incubated with a retroviral vector carrying the v-gag/myc oncogene. Subsequently, these primary cell suspensions were transplanted stereotactically into the caudate-putamen of syngenic adult recipients. After latency periods of 3-6 months, 5 of 10 recipients harboring ED15 fetal brain transplants developed malignant, poorly differentiated neuroectodermal tumors in the grafts. No tumor development was observed in seven recipients harboring ED16 neural grafts. Cell lines were established from three tumors and the 110 kd gag/myc fusion protein encoded by the retroviral construct was identified in the tumors by Western blotting. Several candidate genes for mutational activation by NEU including the H-ras, K-ras and neu oncogenes were analyzed for specific point mutations by polymerase chain reaction (PCR) and direct DNA sequencing of the PCR products. However, no mutations were found in any of these genes. These findings lend further support to the multistep hypothesis of neoplastic transformation in the brain. The tumors induced in this model provide an interesting tool for the identification of genes that co-operate with an activated myc gene in neurocarcinogenesi
Torsion pairs and rigid objects in tubes
We classify the torsion pairs in a tube category and show that they are in
bijection with maximal rigid objects in the extension of the tube category
containing the Pruefer and adic modules. We show that the annulus geometric
model for the tube category can be extended to the larger category and
interpret torsion pairs, maximal rigid objects and the bijection between them
geometrically. We also give a similar geometric description in the case of the
linear orientation of a Dynkin quiver of type A.Comment: 25 pages, 13 figures. Paper shortened. Minor errors correcte
Chronic viral infection promotes sustained Th1-derived immunoregulatory IL-10 via BLIMP-1
During the course of many chronic viral infections, the antiviral T cell response becomes attenuated through a process that is regulated in part by the host. While elevated expression of the immunosuppressive cytokine IL-10 is involved in the suppression of viral-specific T cell responses, the relevant cellular sources of IL-10, as well as the pathways responsible for IL-10 induction, remain unclear. In this study, we traced IL-10 production over the course of chronic lymphocytic choriomeningitis virus (LCMV) infection in an IL-10 reporter mouse line. Using this model, we demonstrated that virus-specific T cells with reduced inflammatory function, particularly Th1 cells, display elevated and sustained IL-10 expression during chronic LCMV infection. Furthermore, ablation of IL-10 from the T cell compartment partially restored T cell function and reduced viral loads in LCMV-infected animals. We found that viral persistence is needed for sustained IL-10 production by Th1 cells and that the transcription factor BLIMP-1 is required for IL-10 expression by Th1 cells. Restimulation of Th1 cells from LCMV-infected mice promoted BLIMP-1 and subsequent IL-10 expression, suggesting that constant antigen exposure likely induces the BLIMP-1/IL-10 pathway during chronic viral infection. Together, these data indicate that effector T cells self-limit their responsiveness during persistent viral infection via an IL-10-dependent negative feedback loop.This work was supported by an Australian NHMRC Overseas Biomedical Postdoctoral Fellowship (to I.A. Parish); a Yale School of Medicine Brown-Coxe Postdoctoral Fellowship (to I.A. Parish); the Alexander von Humboldt Foundation (SKA2010, to P.A. Lang); a CIHR grant (to P.S. Ohashi); and by the Howard Hughes Medical Institute and NIH grant RO1AI074699 (to S.M. Kaech). P.S. Ohashi holds a Canada Research Chair in Autoimmunity and Tumor immunity
Технология синтеза и очистки гликолида
Данная работа посвящена технологии получения и очистки гликолида, как мономера для биоразлагаемых полимеров. Основные потери продукта происходят на стадии получения и очистки мономера. Потери составляют порядка 50-60 %.
Целью данной работы является выбор оптимального пути и очистки гликолида.
В данной работе проведён и представлен всесторонний литературный обзор по методам получения гликолевой кислоты, гликолида, очистки и полимеризации гликолида. Сравнивались различные катализаторы на стадиях поликонденсации, деполимеризации и полимеризации гликолида.
В работе описаны характеристики сырья, описаны способы получения, очистки и полимеризации гликолида. Изложены методики анализа гликолида.This paper is devoted to the technology of production and purification of glycolide as a monomer for biodegradable polymers. The main product losses occur at the stage of monomer production and purification. Losses are about 50-60%.
The purpose of this work is to choose the optimal path and purification of glycolide.
In this paper, we conducted and presented a comprehensive literature review on methods for producing glycolic acid, glycolide, and purification and polymerization of glycolide. Different catalysts were compared at the stages of glycolide polycondensation, depolymerization, and polymerization.
The work describes the characteristics of the raw materials, describes the methods of production, purification, and polymerization of glycolide
MALT1 is an intrinsic regulator of regulatory T cells.
peer reviewedRegulatory T cells (Tregs) are crucial for the maintenance of immunological self-tolerance and their absence or dysfunction can lead to autoimmunity. However, the molecular pathways that govern Treg biology remain obscure. In this study, we show that the nuclear factor-κB signalling mediator mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is an important novel regulator of both Tregs originating in the thymus ('natural' or nTregs) and Tregs induced to differentiate from naive thymocyte helper (Th) cells in the periphery ('induced' or iTregs). Our examination of mice deficient for MALT1 revealed that these mutants have a reduced number of total Tregs. In young Malt1-/- mice, nTregs are totally absent and iTreg are diminished in the periphery. Interestingly, total Treg numbers increase in older Malt1-/- mice as well as in Malt1-/- mice subjected to experimentally induced inflammation. iTregs isolated from WT and Malt1-/- mice were indistinguishable with respect to their ability to suppress the activities of effector T cells, but Malt1-/- iTregs expressed higher levels of Toll-like receptor (TLR) 2. Treatment of WT and Malt1-/- Th cells in vitro with the TLR2 ligand Pam3Cys strongly enhanced the induction and proliferation of Malt1-/- iTregs. Our data suggest that MALT1 supports nTreg development in the thymus but suppresses iTreg induction in the periphery during inflammation. Our data position MALT1 as a key molecule that contributes to immune tolerance at steady-state while facilitating immune reactivity under stress conditions
On quiver Grassmannians and orbit closures for representation-finite algebras
We show that Auslander algebras have a unique tilting and cotilting module which is generated and cogenerated by a projective-injective; its endomorphism ring is called the projective quotient algebra. For any representation- nite algebra, we use the projective quotient algebra to construct desingularizations of quiver Grassmannians, orbit closures in representation varieties, and their desingularizations. This generalizes results of Cerulli Irelli, Feigin and Reineke
Hirnorganoide – Modellsysteme des menschlichen Gehirns
This is the final version. Available from Deutsche Akademie der Naturforscher Leopoldina via the DOI in this record. Hirnorganoide sind Gewebestrukturen aus dem Labor, die Teile der Hirnfunktion imitieren. Sie eröffnen als vereinfachtes Modellsystem einen experimentellen Zugang zu Fragen rund um die Entwicklung und die Funktion des menschlichen Gehirns. Während die Forschung an menschlichen lebenden Gehirnen aus ethischen Gründen enge Grenzen hat und Tiermodelle viele Fragen nur bedingt beantworten können, bieten Hirnorganoide neue Forschungsmöglichkeiten. In der Stellungnahme „Hirnorganoide ‒ Modellsysteme des menschlichen Gehirns“ der Nationalen Akademie der Wissenschaften Leopoldina beschreiben Wissenschaftlerinnen und Wissenschaftler die Möglichkeiten dieses Forschungsgebietes und erörtern, ob es aus ethischen oder juristischen Gründen stärker reguliert werden sollte
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