43 research outputs found
Learning in Hybrid-Project Systems: The Effects of Project Performance on Repeated Collaboration
This study advances contingency theories of performance-outcome learning in hybrid-project systems, in which both project participants and superordinate organizations influence the formation of project ventures. We propose that performance-outcome learning depends on the perceived relevance of prior performance and on organizational control over project participants. We examine this framework using data on 239 U.S. movie projects from the years 1931-40. In keeping with our theory, higher project performance led to future collaborations with the same partners, contingent on prior collaborations, project similarity, and organizational control. Our findings imply distinct patterns of network evolution and unfolding adaptation of hybrid-project systems through slow-moving, local adjustments
Electrically Conductive PEDOT Coating with Self-Healing Superhydrophobicity
A self-healing electrically conductive
superhydrophobic polyÂ(3,4-ethylenedioxythiophene)
(PEDOT) coating has been prepared by chemical vapor deposition of
a fluoroalkylsilane (POTS) onto a PEDOT film, which was obtained by
electrochemical deposition. The coating not only maintained high conductivity
with a low resistivity of 3.2 × 10<sup>–4</sup> Ω·m,
but also displayed a water contact angle larger than 156° and
a sliding angle smaller than 10°. After being etched with O<sub>2</sub> plasma, the coating showed an excellent self-healing ability,
spontaneously regaining its superhydrophobicity when left under ambient
conditions for 20 h. This superhydrophobicity recovery process was
found to be humidity-dependent, and could be accelerated and completed
within 2 h under a high humidity of 84%. The coating also exhibited
good superhydrophobicity recovering ability after being corroded by
strong acid solution at pH 1 or strong base solution at pH 14 for
3 h
“Fastening” Porphyrin in Highly Cross-Linked Polyphosphazene Hybrid Nanoparticles: Powerful Red Fluorescent Probe for Detecting Mercury Ion
It
is a significant issue to overcome the concentration-quenching
effect of the small fluorescent probes and maintain the high fluorescent
efficiency at high concentration for sensitive and selective fluorescent
mark or detection. We developed a new strategy to “isolate”
and “fasten” porphyrin moieties in a highly cross-linked
polyÂ(tetraphenylporphyrin-<i>co</i>-cyclotriphosphazene)
(TPP–PZS) by the polycondensation of hexachlorocyclotriphosphazene
(HCCP) and 5,10,15,20-tetrakisÂ(4-hydroxyphenyl)Âporphyrin (TPP-(OH)<sub>4</sub>) in a suitable solvent. The resulting TPP–PZS particles
were characterized with transmission electron microscopy (TEM), scanning
electron microscopy (SEM), Fourier transform infrared (FTIR), <sup>31</sup>P nuclear magnetic resonance (NMR), and ultraviolet and visible
(UV–vis) absorption spectra. Remarkably, TPP–PZS particles
obtained in acetone emitted a bright red fluorescence both in powder
state and in solution because the aggregation of porphyrin moieties
in “H-type” (face-to-face) and “J-type”
(edge-to-edge) was effectively blocked. The fluorescent TPP–PZS
particles also showed superior resistance to photobleaching, and had
a high sensitivity and selectivity for the detection of Hg<sup>2+</sup> ions. The TPP–PZS particles were therefore used as an ideal
material for preparing test strips to quickly detect/monitor the Hg<sup>2+</sup> ions in a facile way
Electro-Responsively Reversible Transition of Polythiophene Films from Superhydrophobicity to Superhydrophilicity
An electro-responsively reversible
switching of wettability between
superhydrophobicity and superhydrophilicity has been obtained from
a highly porous structured polythiophene film. The polythiophene film
was prepared by two-step electrochemical deposition on an indium tin
oxide (ITO) substrate. The underlying polyÂ(3,4-ethylenedioxythiophene)
(PEDOT) provides a highly porous structured conductive support, and
polyÂ(3-methylthiophene) (PÂ(3-MTH)) deposited thereon plays the role
of a low-surface-energy conductive coating. The wettability switching
of this double-layer film between superhydrophobicity and superhydrophilicity
has been investigated by doping and dedoping in an electrolyte solution
containing ClO<sub>4</sub><sup>–</sup>. Electrochromism of
the film was also seen to accompany the electrochemical process of
conversion between the two superwetting states. On the basis of this
porous electro-active film, an in situ electro-wetting device was
also demonstrated
Facile Synthesis of Superparamagnetic Fe<sub>3</sub>O<sub>4</sub>@polyphosphazene@Au Shells for Magnetic Resonance Imaging and Photothermal Therapy
Multifunctional nanoparticles were
prepared by directly welding superparamagnetic Fe<sub>3</sub>O<sub>4</sub> nanoparticles and Au shells together with highly cross-linked
polyphosphazene as “glue” in a facile but effective
way. The as-prepared particles can simultaneously take advantages
of both magnetization of Fe<sub>3</sub>O<sub>4</sub> core for magnetic
resonance imaging diagnosis and strong near-infrared absorption of
Au nanoshell for photothermal therapy
Anisotropic Fluorescence Emission of Ionic Complex Induced by the Orientation of Azobenzene Unit
A series
of azobenzene-containing fluorescent complexes with stilbene fluorescent
unit were prepared based on the ionic self-assembly approach. The
incorporation of the stilbene unit did not change the lamellar structure
of the azobenzene-containing complex. Under pulsed laser irradiation,
the azobenzene group oriented in the direction perpendicular to the
laser polarization, and as a result, the fluorescent stilbene unit
was cooperatively oriented following the direction of azobenzene group
orientation. This oriented complex films presented anisotropic emission
of fluorescence, and the anisotropic ratio of fluorescence increases
with the increase of the content of azobenzene unit in the complex
Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries
Compared with artificial vascular grafts, bottom-up tubular
cell
sheets (TCSs) without scaffolds have shown promise for patients with
cardiovascular disease. However, TCS therapy also faces the challenges
of lengthy maturation time, elaborate operation, and weak mechanical
strength. In this work, a structured small-diameter vascular graft
(SDVG), consisting of three layers of TCSs, with different cell types
and arrangements, was fabricated using layer-by-layer assembly of
naturally formed TCSs and further cell culture. To this end, a surface-patterned
collagen-coated cylindrical substrate was designed for the efficient
harvesting of naturally formed and well-aligned TCSs. The patterned
collagen (type I) layer facilitated the adhesion and orientation of
cells, and a continuous tubular cell monolayer was naturally formed
after approximately 4 days in cell culture. Biocompatible near-infrared
(NIR) light was used to trigger the photothermal phase transition
of the collagen coated on the cylindrical substrate to dissociate
the collagen layer. As a result, an intact TCS could be harvested
within a few minutes. These naturally formed and well-aligned TCSs
exhibited outstanding free-standing performance without rugosity,
facilitating their operability and practical application. A ring tensile
test showed that orientation was critical for improving the mechanical
properties of TCSs. The layer-by-layer assembly of SDVGs not only
is easy to manipulate and has a short preparation time but also overcomes
the bottleneck of forming a hierarchically structured vascular graft.
This approach shows promise for repairing damaged blood vessels
Highly Cross-Linked and Biocompatible Polyphosphazene-Coated Superparamagnetic Fe<sub>3</sub>O<sub>4</sub> Nanoparticles for Magnetic Resonance Imaging
Highly
cross-linked and biocompatible polyÂ(cyclotriphosphazene-<i>co</i>-4,4′-sulfonyldiphenol) (PZS) were used to directly
coat hydrophilic superparamagnetic Fe<sub>3</sub>O<sub>4</sub> nanoparticles
by a facile but effective one-pot polycondensation. The obtained core–shell
Fe<sub>3</sub>O<sub>4</sub>@PZS nanohybrids were characterized by
transmission electron microscopy (TEM), scanning electron microscopy
(SEM), Fourier-transform infrared (FTIR) and X-ray diffraction spectra.
Interesting, the size and T<sub>2</sub> relaxivity of Fe<sub>3</sub>O<sub>4</sub>@PZS increased with increasing the mass ratio of Fe<sub>3</sub>O<sub>4</sub> to PZS. All these nanohybrids could be internalized
by HeLa cells but show negligible cytotoxicity. The PZS layer slowly
degraded into less dangerous forms such as 4,4′-sulfonyldiphenol,
phosphate and ammonia at neutral or acid atmosphere. Considering their
excellent water dispersibility, colloidal and chemical stability,
magnetic manipulation, and magnetic resonance imaging (MRI) properties,
Fe<sub>3</sub>O<sub>4</sub>@PZS nanohybrids have great potential in
MRI diagnosis of cancer
Dual-Responsive Ionically Assembled Fluorescent Nanoparticles from Copoly(Ionic Liquid) for Temperature Sensor
A simple copolymer, copolyÂ(ionic liquid), consisting
of <i>N</i>-isopropylacrylamide (NIPAM) and 1-benzyl-4-vinylpyridine
bromide (4-VPBn<sup>+</sup>Br<sup>–</sup>) units as thermo-responsive
and ionic liquid parts, respectively, has been synthesized. Fluorescent
nanoparticles (FNPs) were then formed under the driving forces of
electrostatic interaction between 2-(4-amino-2-hydroxyphenyl) benzothiazole
derivative (AHBTA) and copolyÂ(ionic liquid) due to hydrophilic/hydrophobic
balance. The fluorescent intensity of the FNPs enhanced by a factor
of about 50 times when the pH was increased from 7 to 10, and was
effectively doubled within 1 °C around LCST in pH 9 buffer solution,
thus showing a dramatic pH and thermal dual-dependent property. The
FNPs exhibited reversible fluorescence enhancement/quenching over
more than five cycles, regardless of the heating/cooling process.
Furthermore, the FNPS proved to be much more stable to UV light irradiation
than pure fluorescence molecule AHBTA
Precise Preparation of a Multilayer Tubular Cell Sheet with Well-Aligned Cells in Different Layers to Simulate Native Arteries
Compared with artificial vascular grafts, bottom-up tubular
cell
sheets (TCSs) without scaffolds have shown promise for patients with
cardiovascular disease. However, TCS therapy also faces the challenges
of lengthy maturation time, elaborate operation, and weak mechanical
strength. In this work, a structured small-diameter vascular graft
(SDVG), consisting of three layers of TCSs, with different cell types
and arrangements, was fabricated using layer-by-layer assembly of
naturally formed TCSs and further cell culture. To this end, a surface-patterned
collagen-coated cylindrical substrate was designed for the efficient
harvesting of naturally formed and well-aligned TCSs. The patterned
collagen (type I) layer facilitated the adhesion and orientation of
cells, and a continuous tubular cell monolayer was naturally formed
after approximately 4 days in cell culture. Biocompatible near-infrared
(NIR) light was used to trigger the photothermal phase transition
of the collagen coated on the cylindrical substrate to dissociate
the collagen layer. As a result, an intact TCS could be harvested
within a few minutes. These naturally formed and well-aligned TCSs
exhibited outstanding free-standing performance without rugosity,
facilitating their operability and practical application. A ring tensile
test showed that orientation was critical for improving the mechanical
properties of TCSs. The layer-by-layer assembly of SDVGs not only
is easy to manipulate and has a short preparation time but also overcomes
the bottleneck of forming a hierarchically structured vascular graft.
This approach shows promise for repairing damaged blood vessels