549 research outputs found
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An Investigation of the Material Properties of Laser Sintered Parts Incorporating Conformal Lattice Structures (CLS™) Technology
Cellular materials, including foams, honeycombs, lattices, and similar constructions, offer
the key advantages of high strength-to-weight ratios and favorable energy absorption
characteristics. The concept of designed cellular materials enables customized material
placement to best suit the demands of specific applications or achieve particular performance
targets. The design, generation, and fabrication of conformal lattice structures via laser sintering
are at the center of the disruptive manufacturing technologies proposed by 3D Systems
Corporation. The primary work reported here is the maturation and mechanical testing of the
conformal lattice structure technology developed between 3D Systems Corporation and the
Georgia Institute of Technology.Mechanical Engineerin
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Pyroelectricity and its role in optical damage of potassium titanyl phosphate crystals
The origin of optical damage in potassium titanyl phosphate (KTP) crystals has been vigorously investigated since its introduction as a nonlinear optical material in 1976. It is well known that this material exhibits a laser damage threshold that limits its use in many high average-power applications, especially frequency doubling of Nd-doped lasers. Both photochromic and electrochromic damage can be induced in KTP. Until recently, it was thought that these two types of damage were distinctly different, possibly involving different mechanisms; however, new data show that electrochromic-like damage can be induced in KT? by laser irradiation only, implying the existence of an internal electric field. We have recently observed bursts of light (optical scintillations) when heating KTP crystals at 0.1 - 1.0 K/s in the temperature range 8 - 675 K. The scintillations correspond to molecular nitrogen emission occurring during the electrical breakdown of air near the crystal surface, and imply the existence of pyroelectric fields in KTP exceeding 30 kV/cm. These fields (and concomitant currents) were induced by 10.6 {mu}m laser irradiation. The observation of pyroelectric effects, heretofore not considered in KTP damage models, provides an important new insight into the possible cause of the recently observed {open_quotes}electrochromic-like{close_quotes} photochromic damage in KTP
Enhanced exciton harvesting in a planar heterojunction organic photovoltaic device by solvent vapor annealing
We thank the European Research Council (ERC) for financial support (EXCITON grant 321305). Data supporting this study is available at https://doi.org/10.17630/0e75f92d-6f8a-41be-ad45-ac6d1d890ee2.The singlet exciton diffusion length was measured in a small molecule electron donor material DR3TBDTT using fluorescence quenching at a planar interface with a cross-linked fullerene derivative. The one-dimensional exciton diffusion length was increased from ~16 to ~24 nm by annealing the film in carbon disulfide solvent vapor. Planar heterojunction solar cells were fabricated using bilayers of these materials and it was found that solvent vapor annealing increased the short circuit current density by 46%. This can be explained by improved exciton harvesting in the annealed bilayer.PostprintPeer reviewe
A BODIPY small molecule as hole transporting material for efficient perovskite solar cells
BODIPY-based materials are well known for their outstanding chemical and photo-stability as well as their ease of synthesis and tunability of their frontier molecular orbitals. These are attractive features for hole transporting materials (HTMs) for perovskite solar cells (PSCs) that could help improve device stability and cost. In this paper, we report the straightforward synthesis of a new BODIPY small molecule, PTZ-PTZ-BDP, functionalised with phenothiazine moieties in both the meso and α positions giving rise to a Y-shaped structure. As estimated by DFT calculations, and confirmed by electrochemical and ambient photoemission spectroscopy studies, PTZ-PTZ-BDP presents appropriate energy levels suitable for its use as a HTM in PSCs. Electrochemical measurements also reveal several redox processes with excellent reversibility. Systematic evaluation of its performance as HTM in n–i–p PSC with and without dopants was conducted and the device parameters compared with commonly used HTMs of spiro-OMeTAD and PTAA. The CH3NH3PbI3 based PSCs incorporating simple solution processed PTZ-PTZ-BDP as HTM demonstrated a champion power conversion efficiency of 14.6%, matched in performance and shelf-life stability to complex and expensive state-of-the-art HTMs, showing that BODIPY based HTMs are a promising direction for perovskite solar cells
Possible origins of macroscopic left-right asymmetry in organisms
I consider the microscopic mechanisms by which a particular left-right (L/R)
asymmetry is generated at the organism level from the microscopic handedness of
cytoskeletal molecules. In light of a fundamental symmetry principle, the
typical pattern-formation mechanisms of diffusion plus regulation cannot
implement the "right-hand rule"; at the microscopic level, the cell's
cytoskeleton of chiral filaments seems always to be involved, usually in
collective states driven by polymerization forces or molecular motors. It seems
particularly easy for handedness to emerge in a shear or rotation in the
background of an effectively two-dimensional system, such as the cell membrane
or a layer of cells, as this requires no pre-existing axis apart from the layer
normal. I detail a scenario involving actin/myosin layers in snails and in C.
elegans, and also one about the microtubule layer in plant cells. I also survey
the other examples that I am aware of, such as the emergence of handedness such
as the emergence of handedness in neurons, in eukaryote cell motility, and in
non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue.
Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in
Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec
Technology-Supported Storytelling (TSST) Strategy in Virtual World for Multicultural Education
Learning culture through stories is an effective way for multicultural education, since stories are one of the most powerful and personal ways that we learn about the world. Storytelling, the process of telling stories, is a form of communication and a universal expression of culture. With the development of technology, storytelling emerges out of diverse ways. This study explores the storytelling in virtual worlds for multicultural education, and devises a Technology-Supported storytelling (TSST) strategy by examining and considering the characteristics of virtual worlds which could be incorporated into the storytelling, and then uses this strategy to teach Korean culture to students with different culture background. With this innovative TSST strategy in virtual world, this study expects to provide a guide to practice for teaching multicultural in digital era
Multipolar Reactive DPD: A Novel Tool for Spatially Resolved Systems Biology
This article reports about a novel extension of dissipative particle dynamics
(DPD) that allows the study of the collective dynamics of complex chemical and
structural systems in a spatially resolved manner with a combinatorially
complex variety of different system constituents. We show that introducing
multipolar interactions between particles leads to extended membrane structures
emerging in a self-organized manner and exhibiting both the necessary
mechanical stability for transport and fluidity so as to provide a
two-dimensional self-organizing dynamic reaction environment for kinetic
studies in the context of cell biology. We further show that the emergent
dynamics of extended membrane bound objects is in accordance with scaling laws
imposed by physics.Comment: submitted to CMSB 0
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS
The chi_b(nP) quarkonium states are produced in proton-proton collisions at
the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS
detector. Using a data sample corresponding to an integrated luminosity of 4.4
fb^-1, these states are reconstructed through their radiative decays to
Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks
corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new
structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is
also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes.
This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table,
corrected author list, matches final version in Physical Review Letter
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