conjugated microporous polymer

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Network formation mechanisms in conjugated microporous polymers

Network formation mechanisms in conjugated microporous polymers

We further investigated the polymers by scanning electron microscopy (SEM). For CMP networks, a strong link exists between polymer morphology and gas sorption properties. 12 Networks prepared in toluene were generally mesoporous and showed the presence of smooth, spherical morphologies by SEM. When synthesised in DMF, the same networks were sig- nificantly more microporous and SEM showed that these net- works consisted of larger fused masses with rough surfaces. We concluded that the change in morphology was a conse- quence of different solubility of reaction intermediates in the solvent. Indeed, spherical morphologies have been reported for aromatic polymers that undergo liquid–liquid phase separ- ation (i.e., premature precipitation of oligomers) during their synthesis. Spherical structures are also observed just after the gel point for rigid polymers such as polyamides. 46 In this work, polymers collected at 60 and 120 minutes exhibit inter- particulate mesoporosity and consist of fused-spherical mor- phologies with smooth surfaces (Fig. 6). These morphologies are similar to the CMP networks prepared in toluene. 12 However, the polymers collected at 300 and 1080 minutes display larger particles with rough surfaces (Fig. 6). These results are akin to the previously reported CMP-1 synthesised in DMF. 12 Hence, the differences in porosity between the poly- mers isolated at 120 minutes and 300 minutes seems to corre- late well with the differences in morphology, as evidenced by SEM, as opposed to the chemical composition. It is not clear, however, whether these changes in morphology affect the Table 4 Summary of gas sorption data for polymers synthesised at
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Low band-gap benzothiadiazole conjugated microporous polymers

Low band-gap benzothiadiazole conjugated microporous polymers

Solid-state UV-vis spectra of the BCMP networks were recorded and are shown in Figure 2. All six polymers show a broad absorption covering almost the whole visible light region. Although the shapes of the spectra are similar, they do show differences in terms of the onset of the absorption, which correlates with the band gap of the conjugated system. TBT- containing CMPs (BCMP-3, BCMP-4, and BCMP-6) show lower bang-gaps than the corresponding BTZ-based CMPs (BCMP-1, BCMP-2, BCMP-5) due to the additional donor- acceptor effect between the thiophene and BTZ units. Whilst the absorption edge is not sharp, optical band gaps can be estimated. For example, the optical band gaps of BCMP-1 and BCMP-3 are approximately 1.98 eV (close to the value estimated by Zhang et al. using cyclic voltammetry 14 ) and 1.75 respectively. BCMP-2
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Functionalized Polymeric Membranes for CO2 Capture

Functionalized Polymeric Membranes for CO2 Capture

[39] O.M. Yaghi, M. O'Keeffe, N.W. Ockwig, H.K. Chae, M. Eddaoudi, J. Kim, Reticular synthesis and the design of new materials, Nature 423 (2003) 705-714. [40] A.I. Cooper, Conjugated microporous polymers, Adv. Mater. 21 (2009) 1291-1295. [41] N.B. McKeown, B. Gahnem, K.J. Msayib, P.M. Budd, C.E. Tattershall, K. Mahmood, S. Tan, D. Book, H.W. Langmi, A. Walton, Towards polymer-based hydrogen storage materials: Engineering ultramicroporous cavities within polymers of intrinsic microporosity, Angew. Chem. Int. Ed. 45 (2006) 1804-1807. [42] T.M. Long, T.M. Swager, Molecular design of free volume as a route to low-k
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Electrospun Nanofiber-Coated Membrane Separators for Lithium-Ion Batteries.

Electrospun Nanofiber-Coated Membrane Separators for Lithium-Ion Batteries.

In recent years, there have been intensive efforts to develop advanced battery separators for lithium-ion rechargeable batteries for use in different applications such as portable electronics, electric vehicles, and other electronic devices [1-3]. A battery separator is considered to be the critical component in a lithium-ion rechargeable battery. The role of the separator is to prevent physical contact between the positive and negative electrodes of the battery and to prevent internal short while allowing the transportation of ions [4-5]. In most commercial lithium-ion rechargeable batteries, separators are made out of polyolefin microporous membranes such as polyethylene (PE), polypropylene (PP), and their combinations. Polyolefin microporous membranes have excellent mechanical strength and good chemical stability [5]. However, increasing demands for higher-performance lithium- ion rechargeable batteries require separators to have excellent electrolyte uptake capacity and enhanced separator-electrode adhesion. High electrolyte uptake is required for the purpose of reducing the cell resistance and enhancing the cell kinetics, while excellent separator- electrode adhesion is critical for ensuring the long-term performance and safety of lithium- ion cells [6-8]. Therefore, there is a need to further explore methods which improve the electrolyte uptake and separator-electrode adhesion of polyolefin microporous membranes in lithium-ion rechargeable batteries.
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Fabrication of Microporous Film and Microspheres Hybrids

Fabrication of Microporous Film and Microspheres Hybrids

Honeycomb films were successfully fabricated from the amphiphilic block copolymer, poly(acrylic acid)-block- polystyrene) prepared via atom transfer radical polymerization followed by the acid catalyzed elimination reac- tion. After drying, the surface of the film was hydrophobic since carboxyl groups went inside the film in order to minimize the surface energy, and hybridization did not occur by immersing the film into slurry of polymer par- ticles. By soaking the film in methanol, the wettability increased, and hybrid films were successfully obtained, where microspheres were embedded in the pore. The embedding efficiency of microspheres modified with amino groups was much higher than that of conventional polystyrene microspheres. Electrostatic interaction plays an important role for the hybridization. With the increase of open pore size, multi-numbers of micro- spheres were embedded in a single pore. It is noteworthy that our process utilizes no special apparatus for the fabrication of hybrids. It is expected that periodic arrangements of aggregates of microspheres can be fabricated using various combinations of pore size of microporous films and diameter of microspheres.
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Low threshold polariton lasing in a highly disordered conjugated polymer

Low threshold polariton lasing in a highly disordered conjugated polymer

Low-threshold, room-temperature polariton lasing is crucial for future application of polaritonic devices. Conjugated polymers are attractive candidates for room-temperature polariton lasers, due to their high exciton binding energy, very high oscillator strength, easy fabrication, and tunability. However, to date, polariton lasing has only been re- ported in one conjugated polymer, ladder-type MeLPPP, whose very rigid structure gives an atypically narrow excitonic linewidth. Here, we observe polariton lasing in a highly disordered prototypical conjugated polymer, poly(9,9-dioctylfluorene), thereby opening up the field of polymer materials for polaritonics. The long-range spatial coherence of the emission shows a maximum fringe visibility contrast of 72%. The observed polariton lasing threshold (27.7 μJ∕cm 2 , corresponding to an absorbed pump fluence of 19.1 μJ∕cm 2 ) is an order of magnitude smaller than for
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Electroosmotic Water Vapor Transport across Novel, Smart, Functionalized Conducting Polymer Microporous Membranes in Active Mode at Very High Rates, with Concomitant Chemical Warfare (CW) Agent Blocking

Electroosmotic Water Vapor Transport across Novel, Smart, Functionalized Conducting Polymer Microporous Membranes in Active Mode at Very High Rates, with Concomitant Chemical Warfare (CW) Agent Blocking

In this communication, we have demonstrated passive as well as active electroosmotic WVT, across unique, func- tionalized CP microporous membranes, the latter for the first time to our knowledge. This occurs together with simultaneous blocking of CW agents and simulants, again for the first time to our knowledge. The membrane assemblies demonstrate typical passive WVT rates more than 2.5 times as high and active rates more than 3.5 times as high as the highest previously reported (passive) WVT rates, for Nylon microporous membranes; these latter of course do not possess any agent blocking capa- bility as our membranes do. Agent blocking was demon- strated with agents. All WVT and other measurements were independently corroborated at external laboratories. The membrane assemblies passed all relevant environ- mental durability tests. They were incorporated into “smart” final-form fabrics. Likely mechanisms of the significantly enhanced electroosmotic transport as well as the CW agents blocking in these membranes were dis- cussed. Many issues relating to field use, such as power consumption and “smart” control were resolved. Gar- ments incorporating these unique membranes are cur- rently under test. The ultimate objective of this work is to create lightweight, comfortable protective garments.
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Modelling drug release from polymer-free coronary stents with microporous surfaces

Modelling drug release from polymer-free coronary stents with microporous surfaces

Polymer-free stents abandon the use of a polymeric drug carrier altogether and instead employ technologies that are usually (though not always) based on directly covering a bare surface of the stent strut with drug (Khan et al., 2013; Chen et al., 2015). This surface may be rela- tively smooth, as in the case of the Amazonia Pax Stent (MINVASYS), or may be specially modi fi ed to receive the drug and modulate its sub- sequent release rate. In the latter case, microporous surface technology is the most commonly used in the manufacture of currently available polymer-free stents. A microporous surface contains pits whose breadth, depth and separation are on the order of micrometres in scale, and the Yukon (Translumina therapeutics, 2016), Yinyi (Yinyi Biotech, 2016), Vestasync (MIV Therapeutics) and Biofreedom (Biosensors In- ternational) stents are all examples of devices that employ this tech- nology. Some nanoporous systems for drug delivery from stents have also been investigated (Kang et al., 2007; Tsujino et al., 2007).
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Structure–Thermodynamic Property Relationships in Cyanovinyl Based Microporous Polymer Networks for the Future Design of Advanced Carbon Capture Materials

Structure–Thermodynamic Property Relationships in Cyanovinyl Based Microporous Polymer Networks for the Future Design of Advanced Carbon Capture Materials

Nitrogen-rich absorbents have been immensely tested for the capture of carbon dioxide yet until this date, the molecular engineering and design rules for solid absorbent materials do not show to be well grounded. We report here a family of cyanovinylene-based microporous polymers synthesized under metal-catalyzed conditions as promising candidates for advanced carbon capture materials. Of paramount importance is the discovery of a structure – property relationship where CO 2 sorption enthalpies have shown to be directly proportional to the

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Tumour-homing chimeric polypeptide-conjugated polypyrrole nanoparticles for imaging-guided synergistic photothermal and chemical therapy of cancer

Tumour-homing chimeric polypeptide-conjugated polypyrrole nanoparticles for imaging-guided synergistic photothermal and chemical therapy of cancer

photothermal therapy in which NIR light can be absorbed and transformed into heat efficiently to ablate cancer cells [2-8]. NIR-absorbing organic nanomaterials are generally less toxic and more biocompatible than inorganic ones [9,10], so several NIR-absorbing conjugated polymers, such as polypyrrole (PPy) [11-15], polyaniline [16] and poly(3,4-ethylenedioxythiophene):poly(4-styre-nesulf onate) (PEDOT:PSS) [17] have recently attracted much attention as a new class of photothermal agents for cancer therapy. Furthermore, conjugated polymer nanoparticles have been explored as drug carriers for combined photothermal and chemical/photo- dynamic/radioisotope therapy of cancer [18-23]. Drugs such as doxorubicin (DOX) and porphyrin can be loaded into these conjugated polymer nanoparticles through π-π stacking. The photothermal effect of the conjugated polymer nanoparticles can be used to not only directly kill cancer cells by hyperthermia, but also trigger the on-demand release of drugs from the nanoparticles or enhance the cellular uptake of drugs loaded in the nanocarriers to significantly improve the efficacy of chemical or photodynamic therapy.
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The fabrication and lithography of conjugated polymer distributed feedback lasers and development of their applications

The fabrication and lithography of conjugated polymer distributed feedback lasers and development of their applications

The polymeric mould is fabricated by blending the co-polymers (supplied by Gelest GmbH) Methylhydrosiloxane-dimethylsiloxane (HMS) and Vinylmethylsiloxane-dimethylsiloxane trimethylsiloxy terminated (VDT) in the ratio of 3.4 parts VDT to 1 part HMS, as per the work conducted by Schmid and Michel [8]. The chemical structures of these polymers are shown below in figure 3.3. A platinum catalyst (Platinum-divinyl tetramethyl-disiloxane complex) is added to the VDT (a few ppm) and stirred in a beaker before adding the HMS. A silica master, which has been previously cleaned in a mixture of sulphuric acid (95 % w/v) and hydrogen peroxide (30 % w/v) to remove any organic residue on the grating surface is placed face up in a small plastic sample container before the co-polymer mixture is poured over the surface. The sample is then cured for 24 hours at a temperature of 70 ° C. After curing, the sample is carefully removed from the mould while the co-polymer is still warm and easily workable. The completed mould is then allowed to cool to room temperature under ambient conditions before use.
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Morphological, chemical, and electronic changes of the conjugated polymer PTB7 with thermal annealing

Morphological, chemical, and electronic changes of the conjugated polymer PTB7 with thermal annealing

changes in molecular packing. Although the cleavage temperature used here is too high to be a viable pro- cessing step for flexible substrates used in OPV, previous work suggests that reduction of cleavage temperature can be achieved through the inclusion of a catalyst (Vahdani et al., 2016) or by appropriately engineered side chains (Hillebrandt et al., 2016). Additional processing steps may be developed to target and remove trap states formed in this reaction, and the decrease of solubility of the polymer backbones without side chains can aid this process. For example, the polymer matrix may be swelled using an appro- priate solvent wash, allowing the release of volatile hydrocarbon by-products. The correlation of side chain cleavage with photoinduced degradation indicates that these same washing procedures may be used to remove the damaging sub-gap trap states that form during burn-in.
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Real time observation of conformational switching in single conjugated polymer chains

Real time observation of conformational switching in single conjugated polymer chains

Polymer-incubated glass substrates were assembled onto the brass chamber and flushed with nitrogen for 1 min and then filled with the corresponding degassed solvent ( o -DCB or DMSO). A steady flux of de- gassed solvent from a reservoir vial was then maintained to avoid fast pho- todegradation of the samples. The flux was controlled by regulating the nitrogen pressure inside the reservoir vial. All solvents were degassed by bubbling nitrogen for at least 1 hour and kept tightly sealed until imaging. For the experiments involving the exchange from one solvent to another, the different solvents were injected into the reservoir vial subsequently when the previous solvent was running out. All samples were excited with a 473-nm laser in continuous wave operation (27 W/cm 2 ) and imaged in epifluorescence mode. The excitation beam was circular- ly polarized to excite as many chromophores as possible. The beam was focused on the back-focal plane of an oil immersion objective (PlanApo, 60×, numerical aperture = 1.42, working distance = 0.17 mm). Any residual excitation light was filtered out with a dichroic beamsplitter (Semrock, 480-nm edge LaserMUX), and the collected PL emission was directed to an electron-multiplying charge-coupled device camera (Andor Ixon Ultra 897) cooled at − 70°C. PL intensity movies of the samples were recorded with integration times of 100 ms.
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Strategic design of conjugated polymer materials for sensors and solid state lighting

Strategic design of conjugated polymer materials for sensors and solid state lighting

Di-ureasils are a subset of a larger group of Class II materials, called polysilsesquioxanes, which are a family of organic-inorganic materials prepared via the hydrolysis and condensation of monomers containing an organic bridging group with two or more functional silyl groups. 4, 5 Through the variety of chemical and structural properties of polysilsesquioxanes accessible by variation of the organic bridging unit or functionalised silyl groups, they have found use in a wide range of applications such as separation membranes, 6 thermal insulation coatings 7 and photo- patternable materials. 8 The inclusion of π-conjugated bridging species, such as 1-cyano-1,2- bisbiphenyl-ethylene derivatives into a Class II hybrid, has led to highly fluorescent materials derived from strong π-π interactions between conjugated species giving rise to aggregation-induced emission. 9 Alternatively, covalently binding carbazole units to a polysiloxane network, to form a phosphorescent OLED with an iridium bis(4,6-difluorophenyl)pyridinato-N,C 2 picolinate (FIrpic) dopant, has been shown to break up the π-π interactions between the chromophoric units giving rise to a host material with high triplet energies. This prevents back energy transfer to the host, confining the triplet exciton on the FIrpic. This gives rise to a phosphorescent organic light- emitting diode with greater maximum quantum efficiency when compared to identical devices with different polymeric host networks. 10, 11
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Solid state optical conjugated polymer amplifier; with ultrafast gain switching

Solid state optical conjugated polymer amplifier; with ultrafast gain switching

The need for organic solid state optical amplifiers is due to the requirements of ultrafast telecommunications networks, polymer optical circuits and digital signal processing. Silica fibre networks can transmit data at a bandwidth of 2.5 Gbits/sec and higher [23]. Bandwidth to offices and homes, however, are at a rate of 4 - 10 Mbits/sec [24]. There is a reduction in the bandwidth at home because copper cables are still used to transmit data from the remote stations to the consumers. Copper cables have only a bandwidth capability of 150 Mbits/sec [23]. They have limited digital transmission capability [25] and are susceptible to electromagnetic interference [25] and result in a bottleneck at the remote stations [26]. A simple solution would be to replace the copper cables with silica fibers, opening the consumers to the full bandwidth currently possible. This however is not possible. A town would require a few hundred fibers, and a city would need up to several thousand fibers and due to the cost of silica fibers this is not viable.
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Nanoparticles Transport in Ceramic Matriсes: A Novel Approach for Ceramic Matrix Composites Fabrication

Nanoparticles Transport in Ceramic Matriсes: A Novel Approach for Ceramic Matrix Composites Fabrication

The results of practical implementation of a new method for porous piezoceramics, and ceramic matrix piezocomposites fabrication were presented. The method was based on nanoparticles transport in ceramic matrices using a polymer nanogranules coated or filled with a various chemicals, with successive porous ceramics fabrication processes. Different types of polymer microgranules filled and coated by metal-containing nanoparticles were used for a pilot samples fab- rication. Polymer microgranules were examined using transmission and scanning electron microscopy as well as by EXAFS and X-ray emission spectroscopy. Pilot samples of nano- and microporous ceramics and composites were fab- ricated using different piezoceramics compositions (PZT, lead potassium niobate and lead titanate) as a ceramic matrix bases. Resulting ceramic matrix piezocomposites were composed by super lattices of closed or open pores filled or coated by nanoparticles of metals, oxides, ferromagnetics etc. embedded in piezoceramic matrix. Dielectric and piezo- electric parameters of pilot samples were measured using piezoelectric resonance analysis method. New family of nano- and microporous piezoceramics and ceramic matrix piezocomposites are characterized by a unique spectrum of the electrophysical properties unachievable for standard PZT ceramic compositions and fabrication methods.
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A miroscopic and spectroscopic characterisation of nanotube/conjugated polymer interactions

A miroscopic and spectroscopic characterisation of nanotube/conjugated polymer interactions

H ow ever, despite the high expectations and progress in these fields o f carbon nanotubes, and conjugated polym ers, there are several problem s hindering their developm ent. Conjugated polym ers do have problem s w ith stability and strength, and consequently com m ercial products have to incorporate extensive protection in their packaging to shield them from damage and the environm ent. In addition, their conductivity is low due to low intrinsic carrier density and m obility. Pure carbon nanotubes are not available in large quantities, and inevitably com e w ith large am ounts o f im purities. Furtherm ore, there is no way to control the distribution o f nanotubes w ithin a sample, w hich come in a wide range o f chiralities and sizes. In addition, technological lim itations m ean that m anipulating these is difficult, and im possible on a repeatable large scale. These lim itations im ply that any applications in the near future will only be able to harness the bulk properties o f carbon nanotubes. These include as bulk reinforcem ent for materials^®, and as m echanical actuators^'.
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Synthesis of Polythiophene Nanoparticles by Surfactant - Assisted Dilute Polymerization Method for High Performance Redox Supercapacitors

Synthesis of Polythiophene Nanoparticles by Surfactant - Assisted Dilute Polymerization Method for High Performance Redox Supercapacitors

potential, the total impedance of the cell gave rise to an initial ohmic drop of the discharge voltage which remained till constant capacitive performances were achieved. However, the initial decrease in capacitance was related to the irreversible charge compensation in faradaic reaction associated with the oxidation/reduction of PTh. The initial sharp change in potential with time, during charging and discharging process was due to the ohmic loss which arose from the internal resistance of the cell. The pseudocapacitance displayed a typical charge/discharge performance with small discharge capacitance at the working voltage of 2.0 V. The power density was evaluated by dividing the energy density by discharge time [29]. To avoid IR drop effect in the discharge capacitance, the slope was calculated after the IR drop portion of discharge curve. The capacitance obtained from AC impedance measurements was lower than charge-discharge measurements, as it was measured at zero potential of charge and the potential amplitude was also very small (5-10 mV). This is mainly due to the diffusion of ions in the microporous polymer electrolyte. The values of the discharge capacitance (C m ) and
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Riechel, Stefan
  

(2002):


	Organic semiconductor lasers with two-dimensional distributed feedback.


Dissertation, LMU München: Fakultät für Physik

Riechel, Stefan (2002): Organic semiconductor lasers with two-dimensional distributed feedback. Dissertation, LMU München: Fakultät für Physik

Probably the most ambitious task is the realization of an injection laser based on disordered organic semiconductors. Despite the rapid progress of OLEDs and optically pumped lasers stimulated emission under electrical excitation has yet to be observed, the two major obstacles being electrode and charge-induced absorption. The development of transparent cathodes together with an optimization of waveguide or microcavity structure might eventually reduce the required laser threshold by an order of magnitude. A completely different approach towards an injection laser makes use of light-emitting field-effect transistors as recently demonstrated with organic molecular crystals 274 . Their employment essentially eliminates the problem of electrode absorption. Even so, this technique is still in its very early stage. Besides that, a number of materials issues need to be addressed. The careful design of heterostructures allows to combine the best available electron and hole conductors with efficient emitter layers. In OLEDs consisting of molecular semiconductors the use of heterostructures is comparatively sophisticated, whereas it has only just begun with conjugated polymers 283 . First and foremost there is a dire need for better electron transporting materials to achieve balanced current transport on a high level, to shift the recombination zone away from the cathode, and to increase the exciton generation rate. As the low mobility of disordered organic semiconductors is directly correlated to their disorder, the use of higher mobilities in oriented regio-regular polymers might offer routes for solving this problem. Simultaneously, crossing of the polymer chains and the lasing mode polarization is a possible way to diminish the effect of charge-induced absorption. Secondly, long lived emitters will allow to accumulate excitations over a long time and thus reach a high excitation density with comparatively low current. To maintain a reasonably high stimulated emission cross-section, narrow-band emitters such as rare-earth atoms seem well suited. Also spiro-type molecules 87 or core-shell nanoparticles might be an alternative 284 . Furthermore the materials have to be thoroughly selected to avoid spectral overlap of charge-induced absorption with the band of stimulated emission. This calls for electric-pump optical-probe experiments to study the optical properties of light-emitting diodes under intense electrical excitation.
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Synthesis of a Conjugated Ladder Polymer for Application in Direct Writing.

Synthesis of a Conjugated Ladder Polymer for Application in Direct Writing.

catalyzed α -arylation to form a processible precursor polymer which then will be chemically converted to an all aromatic ladder polymer... SYNTHESIS OF A CONJUGATED LADDER POLYMER FOR[r]

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