1,807 research outputs found
Tilting mutation of weakly symmetric algebras and stable equivalence
We consider tilting mutations of a weakly symmetric algebra at a subset of
simple modules, as recently introduced by T. Aihara. These mutations are
defined as the endomorphism rings of certain tilting complexes of length 1.
Starting from a weakly symmetric algebra A, presented by a quiver with
relations, we give a detailed description of the quiver and relations of the
algebra obtained by mutating at a single loopless vertex of the quiver of A. In
this form the mutation procedure appears similar to, although significantly
more complicated than, the mutation procedure of Derksen, Weyman and Zelevinsky
for quivers with potentials. By definition, weakly symmetric algebras connected
by a sequence of tilting mutations are derived equivalent, and hence stably
equivalent. The second aim of this article is to study these stable
equivalences via a result of Okuyama describing the images of the simple
modules. As an application we answer a question of Asashiba on the derived
Picard groups of a class of self-injective algebras of finite representation
type. We conclude by introducing a mutation procedure for maximal systems of
orthogonal bricks in a triangulated category, which is motivated by the effect
that a tilting mutation has on the set of simple modules in the stable
category.Comment: Description and proof of mutated algebra made more rigorous (Prop.
3.1 and 4.2). Okuyama's Lemma incorporated: Theorem 4.1 is now Corollary 5.1,
and proof is omitted. To appear in Algebras and Representation Theor
H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray Ionization Rate
Using high resolution infrared spectroscopy we have surveyed twenty
sightlines for H3+ absorption. H3+ is detected in eight diffuse cloud
sightlines with column densities varying from 0.6x10^14 cm^-2 to 3.9x10^14
cm^-2. This brings to fourteen the total number of diffuse cloud sightlines
where H3+ has been detected. These detections are mostly along sightlines
concentrated in the Galactic plane, but well dispersed in Galactic longitude.
The results imply that abundant H3+ is common in the diffuse interstellar
medium. Because of the simple chemistry associated with H3+ production and
destruction, these column density measurements can be used in concert with
various other data to infer the primary cosmic-ray ionization rate, zeta_p.
Values range from 0.5x10^-16 s^-1 to 3x10^-16 s^-1 with an average of 2x10^-16
s^-1. Where H3+ is not detected the upper limits on the ionization rate are
consistent with this range. The average value of zeta_p is about an order of
magnitude larger than both the canonical rate and rates previously reported by
other groups using measurements of OH and HD. The discrepancy is most likely
due to inaccurate measurements of rate constants and the omission of effects
which were unknown when those studies were performed. We believe that the
observed column density of H3+ is the most direct tracer for the cosmic-ray
ionization rate due to its simple chemistry. Recent models of diffuse cloud
chemistry require cosmic-ray ionization rates on the order of 10^-16 s^-1 to
reproduce observed abundances of various atomic and molecular species, in rough
accord with our observational findings.Comment: Accepted to ApJ, 35 pages, 5 figures, 5 table
Ozonolysis of a-phellandrene - Part 2 : Compositional analysis of secondary organic aerosol highlights the role of stabilized Criegee intermediates
The molecular composition of secondary organic aerosol (SOA) generated from the ozonolysis of α-phellandrene is investigated for the first time using high pressure liquid chromatography coupled to high-resolution Quadrupole-Orbitrap tandem mass spectrometry. In total, 21 prominent products or isomeric product groups were identified using both positive and negative ionisation modes, with potential formation mechanisms discussed. The aerosol was found to be composed primarily of polyfunctional first- and second-generation species containing one or more carbonyl, acid, alcohol and hydroperoxide functionalities, with the products significantly more complex than those proposed from basic gas-phase chemistry in the companion paper (Mackenzie-Rae et al., 2017a). Mass spectra show a large number of dimeric products are also formed. Both direct scavenging evidence using formic acid, and indirect evidence from double bond equivalency factors, suggests the dominant oligomerisation mechanism is the bimolecular reaction of stabilised Criegee intermediates (SCIs) with non-radical ozonolysis products. Saturation vapour concentration estimates suggest monomeric species cannot explain the rapid nucleation burst of fresh aerosol observed in chamber experiments, hence dimeric species are believed to be responsible for new particle formation, with detected first- and second-generation products driving further particle growth in the system. Ultimately, identification of the major constituents and formation pathways of α-phellandrene SOA leads to a greater understanding of the atmospheric processes and implications of monoterpene emissions and SCIs, especially around Eucalypt forests regions where α-phellandrene is primarily emitted
Sperm repository for a breeding program of the eastern oyster crassostrea virginica: Sample collection, processing, cryopreservation, and data management plan
The Eastern oyster Crassostrea virginica (Family Ostreidae) is one of the most important fishery and aquaculture species in the U.S. and is a keystone species for coastal reefs. A breeding program was initiated in 2019 to support the fastâgrowing aquaculture industry culturing this species in the Gulf of Mexico. Oysters from 17 wild populations in embayment along the U.S. Gulf of Mexico coast from southwest Florida to the Matagorda Bay, Texas were used as broodstock for the program to maximize genetic diversity in the base population. A sperm repository of the broodstock was established to support the breeding project. The goal of this study was to demonstrate the sperm sample collection, processing, cryopreservation, and the data management plan involved in the establishment of a sperm germplasm repository of base populations. The supporting objectives were to: (1) develop a data management plan for the sperm repository; (2) streamline the procedure for sample collection, processing, and cryopreservation; (3) incorporate sperm quality analysis into the procedure, and (4) archive the cryopreserved samples as a repository for future use in the breeding program. This sperm repository included a total of 102 male oysters from the 17 collection sites (six oysters per site). A data management plan was developed with six categories, including sample collection, phenotype, fresh sperm, genotype, cryopreservation, and postâthaw sperm, as guide for data collection. Sperm collection was accomplished by strip spawn, and fresh sperm production, motility, and fertility were recorded for quality analysis. Cryopreserved sperm samples were sorted, labelled, archived, and stored in liquid nitrogen for future use. Postâthaw motility (1â30%) and plasm membrane integrity (15.34â70.36%) were recorded as postâthaw quality parameters. Overall, this study demonstrated a streamlined procedure of oyster sperm collection, processing, and cryopreservation for establishing a sperm repository that can serve as a template for construction of oyster germplasm repositories for breeding programs
Support varieties for selfinjective algebras
Support varieties for any finite dimensional algebra over a field were
introduced by Snashall-Solberg using graded subalgebras of the Hochschild
cohomology. We mainly study these varieties for selfinjective algebras under
appropriate finite generation hypotheses. Then many of the standard results
from the theory of support varieties for finite groups generalize to this
situation. In particular, the complexity of the module equals the dimension of
its corresponding variety, all closed homogeneous varieties occur as the
variety of some module, the variety of an indecomposable module is connected,
periodic modules are lines and for symmetric algebras a generalization of
Webb's theorem is true
A classification method of road transport missions and applications using the operating cycle format
When dealing with customers, original equipment manufacturers (OEMs) classify vehicular usage by resorting to simplified, often colloquial, descriptions that allow for a rough understanding of the operating conditions and the userâs needs. In this way, the information retrieved from the customers is exploited to guide their choices in terms of vehicle design and configuration, based on the characteristics of the transport application, labeled using intuitive metrics. However, a common problem in this context is the absence of any formal connection to lower levels of representation that might effectively be used to assess vehicular energy performance in simulation, or for design optimization using mathematical algorithms. Indeed, both processes require more accurate modeling of the surroundings, including exhaustive information about the local road, weather, and traffic conditions. Therefore, starting with a detailed statistical description of the environment, this paper proposes a method for mathematical classification of transport missions and applications within the theoretical framework of the operating cycle (OC). The approach discussed in the paper combines a collection of statistical models structured hierarchically, called a stochastic operating cycle (sOC), with a birdâs-eye view description of the operating environment. The latter postulates the existence of different classes, which are representative of the usage and whose definition is based on simple metrics and thresholds expressed mathematically in terms of statistical measures. Algebraic expressions, called operating classes in the paper, are derived analytically for all the stochastic models presented. This establishes a connection between the two levels of representation, enabling to simulate longitudinal vehicle dynamics in virtual environments generated based on the characteristics of the intended application, using log data collected from vehicles and/or information provided by customers. Additionally, the relationships between the two descriptions are formalized using elementary probability operators, allowing for an intuitive characterization of a transport operation. An example is adduced to illustrate a possible application of the proposed method, using six sOCs parametrized from log data collected during real-world missions. The proposed approach may facilitate the interaction between OEMs, customers, and road operators, allowing for planning of maintenance, and optimization of transport missions, components, and configurations using standard procedures and routines
Passive and catalytic antibodies and drug delivery
Antibodies are one of the most promising components of the biotechnology repertoire for the purpose of drug delivery. On the one hand, they are proven agents for cell-selective delivery of highly toxic agents in a small but expanding number of cases. This technology calls for the covalent attachment of the cytotoxin to a tumor-specific antibody by a linkage that is reversible under appropriate conditions (antibody conjugate therapy, ACT â"passive deliveryâ). On the other hand, the linker cleavage can be accomplished by a protein catalyst attached to the tumor-specific antibody ("catalytic deliveryâ). Where the catalyst is an enzyme, this approach is known as antibody-directed enzyme prodrug therapy (ADEPT). Where the transformation is brought about by a catalytic antibody, it has been termed antibody-directed abzyme prodrug therapy (ADAPT). These approaches will be illustrated with emphasis on how their demand for new biotechnology is being realized by structure-based protein engineerin
Enhanced Mechanistic Understanding Through the Detection of Radical Intermediates in Organic Reactions
Two applications of a radical trap based on a homolytic substitution reaction (SH2') are presented for the trapping of short-lived radical intermediates in organic reactions. The first example is a photochemical cyanomethylation catalyzed by a Ru complex. Two intermediate radicals in the radical chain propagation have been trapped and detected using mass spectrometry (MS), along with the starting materials, products and catalyst degradation fragments. Although qualitative, these results helped to elucidate the reaction mechanism. In the second example, the trapping method was applied to study the radical initiation catalyzed by a triethylboronoxygen mixture. In this case, the concentration of trapped radicals was sufficiently high to enable their detection by nuclear magnetic resonance (NMR). Quantitative measurements made it possible to characterize the radical flux in the system under different reaction conditions (including variations of solvent, temperature and concentration) where modelling was complicated by chain reactions and heterogeneous mass transfer
Chemical species of migrating radionuclides at commercial shallow land burial sites. Quarterly progress report, July-September 1983
The primary purpose of this project is to develop an understanding of chemical processes that significantly influence the migration of radionuclides at commercial low-level waste burial sites. Chemical measurements of waste trench leachate and identification of chemical changes in leachate during migration will provide a basis for geochemical waste transport models. This project will produce for the US Nuclear Regulatory Commission (NRC) information to support guidance for implementation of 10 CFR 61, particularly in the development of criteria for low level waste disposal site selection, management, permanent closure and monitoring. This project will also produce information needed by the Commonwealth of Kentucky as they finalize plans to stabilize, close and monitor the Maxey Flats site. Current research results are presented for the following tasks: (1) chemical forms inorganic and organic radionuclide species; (2) subsurface migration and infiltration studies; (3) specific radionuclide mapping at Maxey Flats and other commercial shallow land burial sites; (4) ecological monitoring at commercial shallow land burial sites; and (5) technical program coordination for low-level waste research. 17 references, 6 figures, 3 tables
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