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The reliability of age measurements for Young Stellar Objects from Hertzsprung-Russell or color-magnitude diagrams

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Research in Astronomy and Astrophysics 2012年第1期12卷 1-25页

作者： thomas Preibisch Universitts-Sternwarte Mnchen Ludwig-Maximilians-Universitt

The possibility to estimate ages and masses of Young Stellar Objects （YSOs） from their location in the Hertzsprnng-Russell diagram （HRD） or a color- magnitude diagram provides a very important tool for the investigation of fundamen- tal questions related to the processes of star formation and early stellar evolution. Age estimates are essential for studies of the temporal evolution of circumstellar material around YSOs and the conditions for planet formation. The characterization of the age distribution of the YSOs in a star forming region allows researchers to reconstruct the star formation history and provides important information on the fundamental ques- tion of whether star formation is a slow or a fast process. However, the reliability of these age measurements and the ability to detect possible age spreads in the stellar population of star forming regions are fundamentally limited by several factors. The variability of YSOs, unresolved binary components, and uncertainties in the calibra- tions of the stellar parameters cause uncertainties in the derived luminosities that are usually much larger than the typical photometry errors. Furthermore, the pre-main se- quence evolution track of a YSO depends to some degree on the initial conditions and the details of its individual accretion history. I discuss how these observational and model uncertainties affect the derived isochronal ages, and demonstrate how neglect- ing or underestimating these uncertainties can easily lead to severe misinterpretations, gross overestimates of the age spread, and ill-based conclusions about the star for- marion history. These effects are illustrated by means of Monte-Carlo simulations of observed star clusters with realistic observational uncertainties. The most important points are as follows. First, the observed scatter in the HRD must not be confused with a genuine age spread, but is always just an upper limit to the true age spread. Second, histograms of isochronal ages natural

关键词： stars: ages -- stars: pre-main sequence -- stars: formation --Hertzsprung-Russell diagram

What would a US green hydrogen energy economy look like?

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Clean Energy 2023年第5期7卷 1148-1172页

作者： thomas Tonon Independent researcher Ph.D.Aerospace and Mechanical SciencesPrinceton University1971.11 Bolfmar AvenuePrinceton JunctionNJ 08550USA

Detailed description is given for a hypothetical US hydrogen economy with solar and wind energy supplying virtually all current energy needs and with electrolytic hydrogen the energy carrier and storage *** fuels provide nonfuel products(plastics,chemicals,cement and asphalt).Only current technologies are considered and hydrogen storage accommodates generation intermit-tency and variability,using pit storage of high-pressure vessels in open air,yielding daily storage round-trip energy installation costs of 722 and 538$/kWh for electric and thermal,respectively;and for power,2351 and 2240$/kW for electric and thermal,*** long-duration storage,the costs are 94.1 and 23.8$/kWh and 937 and 845$/kW,*** energy generation 20%over baseline accommodates low-season generation,obviates much required storage and ensures that reserves are topped off;96%of US 2022 total energy consumption is provided *** the default scenario(demand energy portions:half photovoltaic,quarter on-shore wind and quarter offshore wind),the surface area for the farms(including offshore surface)requires~4.6%of the US 48-state land *** 350 pit storage sites provide both daily and long-duration storage,with the latter accounting for complete loss of generation for 4 days over a quarter of the *** pipelines and a renewed electric grid transmit and distribute *** installation cost of the public infrastructure is~$27.8 trillion for the default *** scenarios show significant in-frastructure and cost savings when batteries are used for transportation and/or utility storage,provided current insufficiencies can be ***,cost levels in money,surface and infrastructure are within existing levels already achieved in historical events and modern living.

关键词： hydrogen economy renewable energy hydrogen storage hydrogen pipelines sustainable net zero

Injector Quantum Dot Molecule Infrared Photodetector:A Concept for Efficient Carrier Injection

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Nano-Micro Letters 2011年第2期3卷 121-128页

作者： thomas Gebhard thomas Gebhard Photonics InstituteVienna University of Technology

Quantum dot infrared photodetectors are expected to be a competitive technology at high oper ation temperatures in the long and very long wavelength infrared spectral *** the fact that they already achieved notable success,the performance suffers from the thermionic emission of electrons from the quantum dots at elevated temperatures resulting in a decreasing *** order to provide an efficient carrier injection at high temperatures,quantum dot infrared photodetectors can be separated into two parts:an injection part and a detection part,so that each part can be separately *** order to integrate such functionality into a device,a new class of quantum dot infrared photodetectors using quantum dot molecules will be *** addition to a general discussion simulation results suggest a possibility to realize such a device.

关键词： Quantum dot infrared photodetector Injection Quantum dot molecule High temperature operation Responsivity

Recent result from the A2 real photon facility at MAMI

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Chinese Physics C 2009年第12期33卷 1120-1126页

作者： Andreas thomas Institut fr kernphysik University Mainz J.-J. Becherweg 45 D-55099 Mainz Germany

The upgraded MAMI C accelerator is delivering electrons with an energy of 1558 MeV routinely. The A2 collaboration is doing experiments with energy marked polarised real photons produced via ＂Bremsstrahlung＂. Recent results from the GDH-experiment using a longitudinal polarised frozen spin target in combination with the DAPHNE detector and from the Crystal Ball experiment at MAMI are presented.

关键词： photonuclear reactions polarization phenomena in reactions polarized and other targets leptoninduced reactions

Differential transport of a guild of mutualistic root aphids by the ant Lasius flavus

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Current Zoology 2023年第4期69卷 409-417页

作者： thomas Parmentier Research Unit of Environmental and Evolutionary Biology Namur Institute of Complex Systemsand Institute of LifeEarthand the EnvironmentUniversity of NamurRue de Bruxelles 61B-5000 NamurBelgium Terrestrial Ecology Unit(TEREC) Department of BiologyGhent UniversityK.L.Ledeganckstraat 35B-9000 GentBelgium

Mutually beneficial associations are widespread in ecological *** are typically assembled as multispecies guilds of symbionts that compete for one or more host *** ant Lasius flavus engages in an intriguing and obligate mutualistic association with a community of aphids that are cultivated on plant roots in its *** ant displays a repertoire of amicable behaviors toward the aphids,including their transport.I examined whether *** preferentially carried some of the root *** a no-choice and a choice experiment,I comparatively analyzed the transport rate of 5 obligate and one loosely associated species back to the ant nest and used the transport rate of the ant larvae as a *** associated root aphids were carried back to the nest,but in a clear preferential *** utricularia,Forda Formicaria,and Trama rara were rapidly transported,but slower than the own *** ulmi and Geoica setulosa were collected at a moderate rate and the loosely associated Aploneura lentisci was slowly *** contrast,different species of unassociated aphids were not transported and even provoked aggressive behavior in *** study revealed that co-occurring symbionts may induce different degrees of host attraction,which ultimately may affect the coexistence and assembly of ant-symbiont communities.

关键词： competition Formicidae honeydew rescue behavior symbiosis trophobiont

Brauer-Clifford Group of Lie-Rinehart Algebra

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Algebra Colloquium 2022年第1期29卷 99-112页

作者： thomas Guedenon Department of Mathematics University of ZiguinchorSenegal

In this paper we define the notion of Brauer Clifford group for(S,■)-Azumaya algebras when S is a commutative algebra and■is a(k,S)-Lie algebra over a commutative ring *** is the situation that arises in applications having connections to differential *** Brauer-Clifford group turns out to be an example of a Brauer group of *** monoidal category.

关键词： Lie-Rinehart algebras Hopf algebras Brauer groups Brauer-Clifford groups symmetric monoidal categories

A plant-based diet and stroke

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Journal of Geriatric Cardiology 2017年第5期14卷 321-326页

作者： thomas Campbell School of Medicine and Dentistry University of Rochester 601 Elmwood Ave Rochester NY 14642 USA.

Stroke is a leading cause of death and disability in theUnited States and globally. Each year, approxirnately 795,000Americans experience a *** annual costs of stroke,both direct and indirect, amount to $33 billion. Ischemicstroke is predicted to cost more than $2.2 trillion between2005 and 2050. In the United States, 87% of all strokesare ischemic, 10% are due to intracerebral hemorrhage, and3% are due to subarachnoid hemorrhage.

关键词： Anticoagulation Plant-based diet Prevention Stroke Vegan Vegetarian

Non-destructive silkworm pupa gender classification with X-ray images using ensemble learning

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Artificial Intelligence in Agriculture 2022年第1期6卷 100-110页

作者： Sania thomas Jyothi thomas Department of Computer Science and Engineering Christ(Deemed to be University)BangaloreIndia

Sericulture is the process of cultivating silkworms for the production of ***-quality production of silk without mixing with low quality is a great challenge faced in the silk production *** of the possibilities to overcome this issue is by separating male and female cocoons before extracting silk fibers from the cocoons as male cocoon silk fibers are finer than *** study proposes a method for the classification of male and female cocoons with the help of X-ray images without destructing the *** study used popular single hybrid varieties FC1 and FC2 mulberry silkworm *** shape features of the pupa are considered for the classification process and were obtained without cutting the cocoon.A novel point interpolation method is used for the computation of the width and height of the *** dimensionality reduction methods are employed to enhance the performance of the *** preprocessed features are fed to the powerful ensemble learning method AdaBoost and used logistic regression as the base *** model attained a mean accuracy of 96.3%for FC1 and FC2 in cross-validation and 95.3%in FC1 and 95.1%in FC2 for external validation.

关键词： Sericulture Gender classification Stratified k-fold cross-validation Machine learning AdaBoost

Brain IL-1β was involved in reserpine-induced behavioral depression in rats

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Acta Pharmacologica Sinica 2004年第3期25卷 39-42页

作者： thomas R MINOR Bethune MilitaryMedical College China Department of Psychology Los Angeles PsychoneuroimmunolgyLaboratory Shijiazhuang 050081 USA University of California

AIM: To investigate the mechanism of brain interleukin-1β (IL-1β) in reserpine-induced behavioral depression in rats. METHODS: Porsult swim test was used in the measurement of depressive behavior and ElisA was used in measurement of brain IL-1β. RESULTS: Intraperitoneal injection of reserpine (0, 4, 6, and 8 mg/kg, ip) increased floating time in the Porsult swim test in a dose-and time-dependent manner in rats. Intracerebroventricular injection (icv) of IL-1β receptor antagonist (IL-1ra, 6 mg/kg) blocked the increment of floating time in Porsult swim test at 48 and 72 h after reserpine injection, but not at 1 and 24 h after injection. Brain IL-1β increased after reserpine treatment in posterior cortex, hippocampus, and hypothalamus. The increase of IL-1β concentration starts at 24 hours after injection of reserpine and reached the peak at 48 h. CONCLUSION: Reserpine induced behavioral depression partially via brain interleukin-1β generation.

关键词： reserpine depression interleukin-1