536 research outputs found
Quantum transport in weakly coupled superlattices at low temperature
We report on the study of the electrical current flowing in weakly coupled
superlattice (SL) structures under an applied electric field at very low
temperature, i.e. in the tunneling regime. This low temperature transport is
characterized by an extremely low tunneling probability between adjacent wells.
Experimentally, I(V) curves at low temperature display a striking feature, i.e
a plateau or null differential conductance. A theoretical model based on the
evaluation of scattering rates is developed in order to understand this
behaviour, exploring the different scattering mechanisms in AlGaAs alloys. The
dominant interaction in usual experimental conditions such as ours is found to
be the electron-ionized donors scattering. The existence of the plateau in the
I(V) characteristics is physically explained by a competition between the
electric field localization of the Wannier-Stark electron states in the weakly
coupled quantum wells and the electric field assisted tunneling between
adjacent wells. The influence of the doping concentration and profile as well
as the presence of impurities inside the barrier are discussed
âLet Us Make ŚŚŚâ: An Edenic Model of Personal Ontology
Personal ontology studies human constitution and human nature, an increasingly debated topic in Christian theology. Historically, the most prominent models of personal ontology in Christian theology have been substance dualist models. More recently, physicalist models have offered prominent alternatives.
This dissertation studies the conflict of interpretations between these two major model groupings. By applying a canonical theology, it then presents an Edenic model of personal ontology that can address the current conflict of interpretations. To achieve this end, the dissertation briefly analyzes substance dualism and physicalism according to the rubrics of constitution and nature, using a model methodology. It then compares the advantages and challenges each offers, and asks whether a model based solely on the normative source of the biblical canon might prove beneficial to the current debate. This question is explored next through a close reading of the Eden narrative (Gen 1-3), which is the biblical pericope that is most foundational to a study of personal ontology. Utilizing the final-form canonical approach and phenomenological-exegetical analysis, this reading delivers answers to the questions of constitution and nature and reveals an Edenic model of personal ontology. In short, the Edenic model highlights both the physicality and the uniqueness of human ontology. It points to a human constitution that is physical, and yet it does not compromise humansâ unique identity or place in Godâs creation. This is because the text shows the image of God to be the mark of human identity. This imago Dei is manifested in every function of human nature (all of which are physically constituted), and enables humans to fulfill Godâs commission to them.
Next, we compare the Edenic model with substance dualism and physicalism, using the same two rubrics of constitution and nature, to see which models may have higher explanatory powers in dealing with current questions of personal ontology. We see that a model of personal ontology that arises from the Eden narrative emphasizes both human physicality and human uniqueness. Such a twin emphasis proves helpful in the current debate in Christian theology, whereas substance dualism emphasizes human identity, and physicalism often highlights human physicality more than human identity.
The dissertation ends by encouraging Christian theologians to explore further the new questions about personal ontology that are being raised, but to do so within these twin parameters and on the basis of a model that arises from Scripture. This approach will not only have implications for a study of personal ontology, but likely for an array of Christian beliefs and practices
Spectral properties of the largest asteroids associated with Taurid Complex
We obtained spectra of six of the largest asteroids (2201, 4183, 4486, 5143,
6063, and 269690) associated with Taurid complex. The observations were made
with the IRTF telescope equipped with the spectro-imager SpeX. Their taxonomic
classification is made using Bus-DeMeo taxonomy. The asteroid spectra are
compared with the meteorite spectra from the Relab database. Mineralogical
models were applied to determine their surface composition. All the spectral
analysis is made in the context of the already published physical data.
Five of the objects studied in this paper present spectral characteristics
similar to the S taxonomic complex. The spectra of ordinary chondrites
(spanning H, L, and LL subtypes) are the best matches for these asteroid
spectra. {\bf The asteroid} (269690) 1996 RG3 presents a flat featureless
spectrum which could be associated to a primitive C-type object. The increased
reflectance above 2.1 microns constrains its geometrical albedo to a value
around 0.03.
While there is an important dynamical grouping among the Taurid Complex
asteroids, the spectral data of the largest objects do not support a common
cometary origin. Furthermore, there are significant variations between the
spectra acquired until now.Comment: Accepted for publication in A&
Aortic injuries following stents in bariatric surgery: our experience
Background: Due to the large number of laparoscopic sleeve gastrectomy (LSG) performed over the last decade, the management of the leak following LSG has been increasingly reported. The role of covered Self Expandable Metal Stents (cSEMS) for the treatment of the leak is still controversial because of the poor tolerance and high risk of complications. Objectives: The aim of the present study was to analyze the foregut wall perforation and aorta injuries, a very rare but potentially fatal complication, related to the treatment of the leak following LSG using cSEMS. Setting: Private hospital, France. Methods: An audit was conducted in 2 French tertiary bariatric endoscopic centers focusing on aortic injuries after cSEMS use for leak. We examined and classified the initial procedure, leak characteristics, primary endoscopic treatment, and outcome of endoscopic complication for each eligible case. Results: A total of 5 patients were identified with foregut wall perforation and aorta injuries. All stents were deployed for staple line leak following LSG. The recorded mortality in case of esophageal-aortic injuries related to cSEMS use was 80%. Conclusion: cSEMS are potentially effective tools for the management of foregut leaks in bariatric surgery. The biggest challenges with this approach are stent migration and poor quality of life. Caution is required due to the risk of fatal complications such as foregut wall perforation and aortic injury
Near-infrared colors of minor planets recovered from VISTA - VHS survey (MOVIS)
The Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer
(WISE) provide information about the surface composition of about 100,000 minor
planets. The resulting visible colors and albedos enabled us to group them in
several major classes, which are a simplified view of the diversity shown by
the few existing spectra. We performed a serendipitous search in VISTA-VHS
observations using a pipeline developed to retrieve and process the data that
corresponds to solar system objects (SSo). The colors and the magnitudes of the
minor planets observed by the VISTA survey are compiled into three catalogs
that are available online: the detections catalog (MOVIS-D), the magnitudes
catalog (MOVIS-M), and the colors catalog (MOVIS-C). They were built using the
third data release of the survey (VISTA VHS-DR3). A total of 39,947 objects
were detected, including 52 NEAs, 325 Mars Crossers, 515 Hungaria asteroids,
38,428 main-belt asteroids, 146 Cybele asteroids, 147 Hilda asteroids, 270
Trojans, 13 comets, 12 Kuiper Belt objects and Neptune with its four
satellites. The colors found for asteroids with known spectral properties
reveal well-defined patterns corresponding to different mineralogies. The
distributions of MOVIS-C data in color-color plots shows clusters identified
with different taxonomic types. All the diagrams that use (Y-J) color separate
the spectral classes more effectively than the (J-H) and (H-Ks) plots used
until now: even for large color errors (<0.1), the plots (Y-J) vs (Y-Ks) and
(Y-J) vs (J-Ks) provide the separation between S-complex and C-complex. The end
members A, D, R, and V-types occupy well-defined regions.Comment: 19 pages, 16 figure
Nonlinear sigma model study of a frustrated spin ladder
A model of two-leg spin-S ladder with two additional frustrating diagonal
exchange couplings J_{D}, J_{D}' is studied within the framework of the
nonlinear sigma model approach. The phase diagram has a rich structure and
contains 2S gapless phase boundaries which split off the boundary to the fully
saturated ferromagnetic phase when J_{D} and J_{D}' become different. For the
S=1/2 case, the phase boundaries are identified as separating two topologically
distinct Haldane-type phases discussed recently by Kim et al.
(cond-mat/9910023).Comment: revtex 4 pages, figures embedded (psfig
Long Exciton Dephasing Time and Coherent Phonon Coupling in CsPbBrCl Perovskite Nanocrystals
Fully-inorganic cesium lead halide perovskite nanocrystals (NCs) have shown
to exhibit outstanding optical properties such as wide spectral tunability,
high quantum yield, high oscillator strength as well as blinking-free single
photon emission and low spectral diffusion. Here, we report measurements of the
coherent and incoherent exciton dynamics on the 100 fs to 10 ns timescale,
determining dephasing and density decay rates in these NCs. The experiments are
performed on CsPbBrCl NCs using transient resonant three-pulse four-wave
mixing (FWM) in heterodyne detection at temperatures ranging from 5 K to 50 K.
We found a low-temperature exciton dephasing time of 24.51.0 ps, inferred
from the decay of the photon-echo amplitude at 5 K, corresponding to a
homogeneous linewidth (FWHM) of 545 {\mu}eV. Furthermore, oscillations in
the photon-echo signal on a picosecond timescale are observed and attributed to
coherent coupling of the exciton to a quantized phonon mode with 3.45 meV
energy
Surface Reaction Films from Amine-Based Organic Friction Modifiers and Their Influence on Surface Fatigue and Friction
Surface reactive additives are crucial in the lubrication of surfaces experiencing cyclic contact. The combination of additives in the lubricant, on the material surface and the complex tribo-contact conditions hinders the design of additive packages which can simultaneously protect steel surfaces from wear and fatigue. Amine-based Organic Friction Modifiers (OFMs) influence the tribological performance of steel surfaces. This study investigates the tribochemical impact of three amine-based OFMs in combination with Zinc DialkylDithioPhosphate (ZDDP) on tribological performance, particularly surface fatigue, for steel surfaces in severe rollingâsliding contacts. The thickness of reaction films was tracked throughout experiments and the chemistry of reaction films was examined using X-ray Photoelectron Spectroscopy (XPS). Results highlight the impact of the OFM polar moiety on tribological performance and its influence on chemical composition of tribo-reaction films and their formation kinetics. The combination of selected OFMs with ZDDP reduces frictional forces and can mitigate surface fatigue under certain conditions
THEORETICAL ASPECTS OF THE AERATION DRYING PROCESS WITH APPLICATION IN THE HAY TECHNOLOGY
In the current context of the development of mechanized agriculture in several directionsĂÂ in the field of feed storage needs appear in the effective implementation of the drying methodĂÂ used. In terms of maintaining higher production achieved by reducing losses of fodderĂÂ harvesting and secondly by increasing the number of cycles of harvest due to reduced time ofĂÂ harvest (representing the time elapsed mowing fodder plant and to store hay), outline theĂÂ need for a more careful study of the drying process. This paper presents some theoreticalĂÂ aspects that determine and control the drying process used in technology of hay
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