1,240 research outputs found
Challenges and Opportunities at the Dawn of the New Space Age
As space technology evolves due to increased private- and publicsector investments and due to the accelerated pace of innovation, Perry World House hosted a oneday workshop to discuss the novel challenges and opportunities that have emerged at this critical point in the "New Space Age." This new age is characterized by a diversity of actors beyond the nation-state— actors that have greater accessibility and fewer barriers to acquiring a footprint in space. As participant Xavier Pasco of Fondation pour la Recherche Stratégique wrote in his workshop contribution, "Space was born from the Cold War and from the promotion of national interests with the prevalence of foreign policy considerations." The New Space Age has expanded the map to include private actors and "new technological processes and innovative modes of industrialization and commercial exploitation.
Projection-based measurement and identification
A recently developed Projection-based Digital Image Correlation (P-DVC)
method is here extended to 4D (space and time) displacement field measurement
and mechanical identification based on a single radiograph per loading step
instead of volumes as in standard DVC methods. Two levels of data reductions
are exploited, namely, reduction of the data acquisition (and time) by a factor
of 1000 and reduction of the solution space by exploiting model reduction
techniques. The analysis of a complete tensile elastoplastic test composed of
127 loading steps performed in 6 minutes is presented. The 4D displacement
field as well as the elastoplastic constitutive law are identified. Keywords:
Image-based identification, Model reduction, Fast 4D identification, In-situ
tomography measurements. INTRODUCTION Identification and validation of
increasingly complex mechanical models is a major concern in experimental solid
mechanics. The recent developments of computed tomography coupled with in-situ
tests provide extremely rich and non-destructive analyses [1]. In the latter
cases, the sample was imaged inside a tomograph, either with interrupted
mechanical load or with a continuously evolving loading and on-the-fly
acquisitions (as ultra-fast X-ray synchrotron tomography, namely, 20 Hz full
scan acquisition for the study of crack propagation [2]). Visualization of fast
transformations, crack openings, or unsteady behavior become accessible.
Combined with full-field measurements, in-situ tests offer a quantitative basis
for identifying a broad range of mechanical behavior.Comment: SEM 2019, Jun 2019, Reno, United State
Impact of Backbone fluorination on -conjugated polymers in organic photovoltaic devices: a review
Solution-processed bulk heterojunction solar cells have experienced a remarkable
acceleration in performances in the last two decades, reaching power conversion efficiencies above 10%. This impressive progress is the outcome of a simultaneous development of more advanced device architectures and of optimized semiconducting polymers. Several chemical approaches have
been developed to fine-tune the optoelectronics and structural polymer parameters required to reach
high efficiencies. Fluorination of the conjugated polymer backbone has appeared recently to be
an especially promising approach for the development of efficient semiconducting polymers. As a
matter of fact, most currently best-performing semiconducting polymers are using fluorine atoms in their conjugated backbone. In this review, we attempt to give an up-to-date overview of the latest results achieved on fluorinated polymers for solar cells and to highlight general polymer properties’ evolution trends related to the fluorination of their conjugated backbone
Impact of Backbone fluorination on -conjugated polymers in organic photovoltaic devices: a review
Solution-processed bulk heterojunction solar cells have experienced a remarkable
acceleration in performances in the last two decades, reaching power conversion efficiencies above 10%. This impressive progress is the outcome of a simultaneous development of more advanced device architectures and of optimized semiconducting polymers. Several chemical approaches have
been developed to fine-tune the optoelectronics and structural polymer parameters required to reach
high efficiencies. Fluorination of the conjugated polymer backbone has appeared recently to be
an especially promising approach for the development of efficient semiconducting polymers. As a
matter of fact, most currently best-performing semiconducting polymers are using fluorine atoms in their conjugated backbone. In this review, we attempt to give an up-to-date overview of the latest results achieved on fluorinated polymers for solar cells and to highlight general polymer properties’ evolution trends related to the fluorination of their conjugated backbone
Insights into nitromethane combustion from detailed kinetic modeling – Pyrolysis experiments in jet-stirred and flow reactors
International audienceThe pyrolysis of nitromethane highly diluted in helium was studied in a plug flow reactor and in a jet-stirred reactor at 1.07 bar and over the temperature range from 500 to 1100 K. Mole fraction profiles of major products and of intermediates were identified with gas chromatography and Fourier transform infrared spectroscopy. Using these experimental data, as well as published ones, we have developed a newly compiled model for the prediction of the pyrolysis and of the oxidation of nitromethane in jet-stirred and flow reactors, freely propagating, and burner-stabilized premixed flames, as well as in shock-tubes. The experimental results from the present work and from the literature are interpreted with the help of the kinetic model derived here. This study mainly focuses on the analysis of speciation in different reactors. Among the nitrogenous species, NO is found to be a major product for pyrolysis and oxidation. The model suggests that for nitromethane pyrolysis and oxidation the thermal dissociation channel to CH3 and NO2 is the main reaction path for the nitromethane degradation followed by the H-atom abstraction channel. The most sensitive reactions for nitromethane pyrolysis in a flow reactor and during pyrolysis and oxidation in a jet-stirred reactor are found to be CH3NO2(+M) ⇋ CH3 + NO2(+M) and CH3 + NO2 ⇋ CH3O + NO. The reaction CH3 + NO2 ⇋ CH3O + NO is found to be the most important reaction for all conditions studied. In a burner-stabilized premixed flame, as the mixture gets richer, the thermal dissociation channel CH3NO2(+M) ⇋ CH3 + NO2(+M) becomes more important as the contribution of the H-atom abstraction channel is decreased. Furthermore, in the burner-stabilized premixed flames, it was found that NO is mainly formed via NO2: NO2 + H ⇋ NO + OH, NO2 + CH3 ⇋ CH3O + NO. The model provided an overall reasonable agreement with the experimental data. However, for pyrolysis conditions, future work is desirable to improve predictions of intermediate species. This work extends the kinetic database and helps to improve the understanding of nitromethane chemistry. The kinetic model presented in this work can serve as a base model for hydrocarbons and oxygenated fuels higher than C2 and nitrogen-containing compounds higher than C1 as well as for pure nitrogen compounds
Correlation with basic differentiation processes of neurons
The development of the spinal cord involves the proliferation of neurons, their migration to well-defined areas, fiber outgrowth and synapse formation. The present study was designed to correlate the spatiotemporal pattern of expression of synaptophysin, an integral membrane protein of small synaptic vesicles, with these basic processes occurring during the embryonic development of the rat spinal cord.
Thoracic segments of spinal cords from embryonic days 12, 14, 16, 18, 20 and of adult spinal cords were studied. S1 nuclease protection assays and immunoblots revealed minute amounts of specific mRNA and synaptophysin at embryonic day 12. There was a steep increase of mRNA between embryonic days 14 and 16, after which levels reached a plateau. A rise in the amount of synaptophysin in the spinal cord occurred between embryonic days 12 and 14, and the levels changed only slightly until the end of embryonic development. Even higher levels of synaptophysin, found in the adult spinal cord, may indicate that its biosynthesis continued after birth.
In situ hybridization histochemistry revealed the localization of specific synaptophysin mRNA in the neuroepithelium. However, immunocytochemistry failed to detect synaptophysin in the neuroepithelial cells. Following migration of the neuroblasts, synaptophysin was found in neurons concomitantly with the onset of fiber outgrowth. Thus, already at embryonic day 12, outgrowing fibers of the dorsal root sensory neurons and of motoneurons were synaptophysin positive. From embryonic day 14 throughout the prenatal period, strong synaptophysin immunoreactivity was seen in the ventrolateral and dorsal parts of the marginal layer. Most likely this staining pattern indicates transient functional synaptic contacts because, in the adult spinal cord, the corresponding region, the white matter, exhibited only faint synaptophysin immunoreactivity. In the intermediate layer of the embryonic spinal cord, which corresponds to the gray matter of the adult spinal cord, synaptophysin-positive fibers were observed prior to the formation of functional synapses. The latter are most likely permanent, since synaptophysin in the adult spinal cord is mainly confined to the gray matter.
Our data
(i) show transcription and translation of synaptophysin within the neurons of the spinal cord and correlate these processes with proliferation, migration, fiber outgrowth and the formation of transient or permanent synapses, and
(ii) prove that synaptophysin is a marker for fiber outgrowth in addition to synapse formation
Crystal isomorphisms in Fock spaces and Schensted correspondence in affine type A
We are interested in the structure of the crystal graph of level Fock
spaces representations of . Since
the work of Shan [26], we know that this graph encodes the modular branching
rule for a corresponding cyclotomic rational Cherednik algebra. Besides, it
appears to be closely related to the Harish-Chandra branching graph for the
appropriate finite unitary group, according to [8]. In this paper, we make
explicit a particular isomorphism between connected components of the crystal
graphs of Fock spaces. This so-called "canonical" crystal isomorphism turns out
to be expressible only in terms of: - Schensted's classic bumping procedure, -
the cyclage isomorphism defined in [13], - a new crystal isomorphism, easy to
describe, acting on cylindric multipartitions. We explain how this can be seen
as an analogue of the bumping algorithm for affine type . Moreover, it
yields a combinatorial characterisation of the vertices of any connected
component of the crystal of the Fock space
Recommendations for burns care in mass casualty incidents: WHO Emergency Medical Teams Technical Working Group on Burns (WHO TWGB) 2017-2020
Health and logistical needs in emergencies have been well recognised. The last 7 years has witnessed improved professionalisation and standardisation of care for disaster affected communities – led in part by the World Health Organisation Emergency Medical Team (EMT) initiative.
Mass casualty incidents (MCIs) resulting in burn injuries present unique challenges. Burn management benefits from specialist skills, expert knowledge, and timely availability of specialist resources. With burn MCIs occurring globally, and wide variance in existing burn care capacity, the need to strengthen burn care capability is evident. Although some high-income countries have well-established disaster management plans, including burn specific plans, many do not – the majority of countries where burn mass casualty events occur are without such established plans. Developing globally relevant recommendations is a first step in addressing this deficit and increasing preparedness to deal with such disasters.
Global burn experts were invited to a succession of Technical Working Group on burns (TWGB) meetings to:
1) review literature on burn care in MCIs; and
2) define and agree on recommendations for burn care in MCIs.
The resulting 22 recommendations provide a framework to guide national and international specialist burn teams and health facilities to support delivery of safe care and improved outcomes to burn patients in MCIs.publishedVersio
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