4,414 research outputs found
Marine copepod fecal pellets: Production, preservation and sedimentation
Production, preservation and sedimentational aspects of common marine copepod fecal pellets were studied in order to understand the transport of organic and inorganic material from the surface to the deep sea. Fecal pellets were obtained from laboratory cultures of Calanus finmarchicus, Acartia tonsa and A. clausi fed several species of coccolithophores (approximately 10 µm in diameter) and diatoms (approximately 6 µm and 50 µm in diameter)...
Synthesis of highly substituted alkenes by sulfur-mediated olefination of N-tosylhydrazones
Tetraphenylethylenes (TPEs) are well-known for their aggregation-induced emission properties. The synthesis of TPE derivatives, as well as other highly substituted olefins, generally requires the use of hazardous reagents, such as metalorganic compounds, to overcome the high activation energies caused by the sterically congested double bond. Herein, we present an efficient and metal-free procedure for the synthesis of tetraarylethylenes via alkylidene-homocoupling of N-tosylhydrazones, derived from readily available benzophenones, in excellent yields. The method relies only on cheap and benign additives, i.e. elemental sulfur and potassium carbonate, and easily competes with other established procedures in terms of scope, yield and practicability. A mechanistic study revealed a diazo compound, a thioketone and a thiirane as key intermediates in the pathway of the reaction. Based on this, a modified method, which allows for selective alkylidene-cross-coupling, generating a broader scope of tri- and tetrasubstituted olefins in good yields, is showcased as well
Novel Access to Known and Unknown Thiourea Catalyst via a Multicomponent-Reaction Approach
Thioureas are frequently used in organocatalysis and typically rely on 3,5‐bis(trifluoromethyl) phenyl moieties motifs to enhance their catalytic activity. In this work, these common motifs were replaced with tailorable functional groups, such as ester or sulfone aryls, applying elemental sulfur in a multicomponent reaction (MCR) strategy for the first time for thiourea catalyst synthesis. First, several thioureas bearing aryl, benzylic or aliphatic moieties were synthesized and tested for their hydrogen bonding strength by evaluating thiourea phosphine oxide complexes via P NMR and their catalytic activity in an Ugi four‐component reaction (U‐4CR). Finally, ester and sulfone aryl thioureas were tested in the aminolysis of propylene carbonate, leading to conversions similar to those previously reported in the literature using the 3,5‐bis(trifluoromethyl)phenyl moiety, proving that these groups are suitable alternatives for the trifluoromethyl group
Socionic Multi-Agent Systems Based on Reflexive Petri Nets and Theories of Social Self-Organisation
This contribution summarises the core results of the transdisciplinary ASKO project, part of the German DFG's programme Sozionik, which combines sociologists' and computer scientists' skills in order to create improved theories and models of artificial societies. Our research group has (a) formulated a social theory, which is able to explain fundamental mechanisms of self-organisation in both natural and artificial societies, (b) modelled this in a mathematical way using a visual formalism, and (c) developed a novel multi-agent system architecture which is conceptually coherent, recursively structured (hence non-eclectic) and based on our social theory. The article presents an outline of both a sociological middle-range theory of social self-organisation in educational institutions, its formal, Petri net based model, including a simulation of one of its main mechanisms, and the multi-agent system architecture SONAR. It describes how the theory was created by a re-analysis of some grand social theories, by grounding it empirically, and finally how the theory was evaluated by modelling its concepts and statements.Multi-Agents Systems, Petri Nets, Self-Organisation, Social Theories
First Operation of a Resistive Shell Liquid Argon Time Projection Chamber -- A new Approach to Electric-Field Shaping
We present a new technology for the shaping of the electric field in Time
Projection Chambers (TPCs) using a carbon-loaded polyimide foil. This
technology allows for the minimisation of passive material near the active
volume of the TPC and thus is capable to reduce background events originating
from radioactive decays or scattering on the material itself. Furthermore, the
high and continuous electric resistivity of the foil limits the power
dissipation per unit area and minimizes the risks of damages in the case of an
electric field breakdown. Replacing the conventional field cage with a
resistive plastic film structure called 'shell' decreases the number of
components within the TPC and therefore reduces the potential points of failure
when operating the detector. A prototype liquid argon (LAr) TPC with such a
resistive shell and with a cathode made of the same material was successfully
tested for long term operation with electric field values up to about 1.5
kV/cm. The experiment shows that it is feasible to successfully produce and
shape the electric field in liquefied noble-gas detectors with this new
technology.Comment: 13 page
Toward Comprehensive Specification of Distributed Systems
A new approach to modelling distributed systems is presented. It uses sequential processes and event synchronization as building blocks to construct a cohesive picture of the interdependent requirements for the functionality, architecture, scheduling policies, and performance attributes of a distributed system. A language called CSPS (an extension of Hoare\u27s CSP) is used in the illustration of the approach. Employing CSP as a base allows modelled systems to be verified using techniques already developed for verifying CSP programs and leads to the emergence of a uniform incremental strategy for verifying both logical and performance properties of distributed systems. Several small distributed systems have been modelled using this approach. These exercises enabled us to evaluate the notation system and to gain some expertise on how to approach the specification of distributed systems. This paper describes one of the models and the modelling strategy that has emerged from these exercises
In planta expression of A. cellulolyticus Cel5A endocellulase reduces cell wall recalcitrance in tobacco and maize
The glycoside hydrolase family 5 endocellulase, E1 (Cel5A), from Acidothermus cellulolyticus was transformed into both Nicotiana tabacum and Zea mays with expression targeted to the cell wall under a constitutive promoter. Here we explore the possibility that in planta expression of endocellulases will allow these enzymes to access their substrates during cell wall construction, rendering cellulose more amenable to pretreatment and enzyme digestion. Tobacco and maize plants were healthy and developed normally compared with the wild type (WT). After thermochemical pretreatment and enzyme digestion, transformed plants were clearly more digestible than WT, requiring lower pretreatment severity to achieve comparable conversion levels. Furthermore, the decreased recalcitrance was not due to post-pretreatment residual E1 activity and could not be reproduced by the addition of exogenous E1 to the biomass prior to pretreatment, indicating that the expression of E1 during cell wall construction altered the inherent recalcitrance of the cell wall
Effect of histology on stereotactic body radiotherapy for non-small cell lung cancer oligometastatic pulmonary lesions
BACKGROUND: Stereotactic body radiotherapy (SBRT) is commonly used to provide targeted treatment to metastatic lung disease. Investigation is needed to understand the influence of histology on treatment outcomes. We report how tumor histology affects local control (LC) in a cohort of patients with non-small cell lung cancer (NSCLC) receiving SBRT for oligometastatic and recurrent pulmonary lesions.
METHODS: Patients who received SBRT to recurrent or oligometastatic NSCLC pulmonary lesions from 2015-2019 at our institution were included in this retrospective cohort study. Minimum follow-up was 2 months. Kaplan-Meier (KM) analysis was performed to assess local progression-free survival (LPFS). Local failure cumulative incidence curves using death as a competing risk factor were also generated.
RESULTS: A total of 147 treated lesions from 83 patients were included: 95 lesions from 51 patients with lung adenocarcinoma and 52 lesions from 32 patients with lung squamous cell carcinoma (SqCC). Median follow-up was 23 [interquartile range (IQR): 9.5-44.5] months for adenocarcinoma, and 11.5 (6-32.25) months for SqCC. Two-year LC was 89% for adenocarcinoma and 77% for SqCC (P=0.04). Median overall survival (OS) was 24.5 (10-46.25) months for adenocarcinoma and 14.5 (7.75-23.25) months for SqCC. Adenocarcinoma had improved LPFS over SqCC (P=0.014). SqCC was associated with increased local failure risk that approached statistical significance (P=0.061) with death as a competing risk. Overall toxicity incidence was 8.2% with no G3+ toxicities.
CONCLUSIONS: For SBRT-treated oligometastatic or recurrent NSCLC pulmonary lesions, adenocarcinoma histology is associated with improved 2-year LC and LPFS compared to SqCC and reduced incidence of local recurrence (LR) with death as a competing risk
Inappropriate Use of Radioactive Iodine for Low-Risk Papillary Thyroid Cancer Is Most Common in Regions with Poor Access to Healthcare
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140266/1/thy.2015.0112.pd
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