154 research outputs found
Covalent Attachment of TADF Chromophores to Thermally Stable Poly(arylene ether)s
The covalent attachment of a blue emitting, benzothiazole based TADF chromophore into poly(arylene ether) backbone polymers was explored. A benzothiazole derivative, 2-(2,4-difluorophenyl)-benzothiazole (2,4-diF-BTZ), was synthesized to form the electrophilic component of the host polymer. Two polymers were synthesized to have chromophore incorporated, using 2,4-diFBTZ and 4,4-dihydroxydiphenyl ether (DPE) or 4,4â-biphenol (BP). The chromophore was covalently incorporated at a 10% molar ratio into the polymer backbone by copolymerization with 2,4-diF-BTZ and BP, utilizing nucleophilic aromatic substitution (NAS). Structural characterization was provided via NMR spectroscopy and GC/MS analysis. The polymer syntheses provided high molecular weight materials that were able to be cast into somewhat brittle films. The copolymers possessed glass transitions temperatures (Tg) in excess of 200°C. Photophysical analysis of the copolymers revealed the copolymers emitted light in the blue-green region of the visible spectrum, from 400 nm to 550 nm when excited at 365 nm
Signals of a superlight gravitino at hadron colliders when the other superparticles are heavy
If the gravitino (G) is very light and all the other supersymmetric particles
are above threshold, supersymmetry may still be found at colliders, by looking
at processes with only gravitinos and ordinary particles in the final state. We
compute here the cross-sections for some distinctive signals at hadron
colliders: photon plus missing energy, induced by (q antiquark -> G G photon),
and jet plus missing energy, induced by (q antiquark -> G G g), (q g -> G G q),
and (g g -> G G g). From the present Tevatron data, we estimate the bound
m_{3/2} > 2.3 10^-5 eV on the gravitino mass, corresponding to the bound
sqrt{F} > 310 GeV on the supersymmetry-breaking scale. We foresee that the
upgraded Tevatron and the LHC will be sensitive to values of m_{3/2} up to 4.0
10^-5 eV and 6.2 10^-4 eV, corresponding to sqrt{F} up to 410 GeV and 1.6 TeV,
respectively.Comment: 19 pages, Latex, epsfig, 13 figures This revised version supersedes
that published in Nucl. Phys. B526 (1998) 136, and contains important
changes. The correction of a sign error modifies the relevant partonic
cross-sections. The sensitivity to the supersymmetry-breaking scale
(gravitino mass) is only slightly weakene
Summary Talk at the 3rd KEK Topical Conference on CP Violation
A summary of the contributions to this topical conference is presented. The
topics discussed ranged from detailing what we know about CP violation, to what
we hope to learn in the future, to still unsolved mysteries in the subject.Comment: 12 pages, UCLA/TEP/16; figures will be FAXed on request by e-mailing
[email protected]
Dark energy interacting with two fluids
A cosmological model of dark energy interacting with dark matter and another
general component of the universe is investigated. We found general constraints
on these models imposing an accelerated expansion. The same is also studied in
the case for holographic dark energy
Shifts in wood anatomical traits after a major hurricane
âą1. Trait variation across individuals and species influences the resistance and resilience of ecosystems to disturbance, and the ability of individuals to capitalize on postdisturbance conditions. In trees, the anatomical structure of xylem directly affects plant function and, consequently, it is a valuable lens through which to understand resistance and resilience to disturbance.
âą2. To determine how hurricanes affect wood anatomy of tropical trees, we characterized a set of anatomical traits in wood produced before and after a major hurricane for 65 individuals of 10 Puerto Rican tree species. We quantified variation at different scales (among and within species, and within individuals) and determined trait shifts between the pre- and posthurricane periods. We also assessed correlations between traits and growth rates.
âą3. While the majority of anatomical trait variation occurred among species, we also observed substantial variation within species and individuals. Within individuals, we found significant shifts for some traits that generally reflected increased hydraulic conductivity in the posthurricane period. We found weak evidence for an association between individual xylem anatomical traits and diameter growth rates.
âą4. Ultimately, within-individual variation of xylem anatomical traits observed in our study could be related to posthurricane recovery and overall growth (e.g. canopy filling). Other factors, however, likely decouple a relationship between xylem anatomy and diameter growth. While adjustments of wood anatomy may enable individual trees to capitalize on favourable postdisturbance conditions, these may also influence their future responses or vulnerability to subsequent disturbances
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Microsecond Carrier Lifetimes, Controlled p-Doping, and Enhanced Air Stability in Low-Bandgap Metal Halide Perovskites.
Mixed lead-tin halide perovskites have sufficiently low bandgaps (âŒ1.2 eV) to be promising absorbers for perovskite-perovskite tandem solar cells. Previous reports on lead-tin perovskites have typically shown poor optoelectronic properties compared to neat lead counterparts: short photoluminescence lifetimes (<100 ns) and low photoluminescence quantum efficiencies (<1%). Here, we obtain films with carrier lifetimes exceeding 1 ÎŒs and, through addition of small quantities of zinc iodide to the precursor solutions, photoluminescence quantum efficiencies under solar illumination intensities of 2.5%. The zinc additives also substantially enhance the film stability in air, and we use cross-sectional chemical mapping to show that this enhanced stability is because of a reduction in tin-rich clusters. By fabricating field-effect transistors, we observe that the introduction of zinc results in controlled p-doping. Finally, we show that zinc additives also enhance power conversion efficiencies and the stability of solar cells. Our results demonstrate substantially improved low-bandgap perovskites for solar cells and versatile electronic applications.EPSRC (EP/M005143/1 and DTP funding)
Royal Society
ER
Advances in Microfluidics and Lab-on-a-Chip Technologies
Advances in molecular biology are enabling rapid and efficient analyses for
effective intervention in domains such as biology research, infectious disease
management, food safety, and biodefense. The emergence of microfluidics and
nanotechnologies has enabled both new capabilities and instrument sizes
practical for point-of-care. It has also introduced new functionality, enhanced
sensitivity, and reduced the time and cost involved in conventional molecular
diagnostic techniques. This chapter reviews the application of microfluidics
for molecular diagnostics methods such as nucleic acid amplification,
next-generation sequencing, high resolution melting analysis, cytogenetics,
protein detection and analysis, and cell sorting. We also review microfluidic
sample preparation platforms applied to molecular diagnostics and targeted to
sample-in, answer-out capabilities
Plant Power:Opportunities and challenges for meeting sustainable energy needs from the plant and fungal kingdoms
Societal Impact Statement
Bioenergy is a major component of the global transition to renewable energy technologies. The plant and fungal kingdoms offer great potential but remain mostly untapped. Their increased use could contribute to the renewable energy transition and addressing the United Nations Sustainable Development Goal 7 âEnsure access to affordable, reliable, sustainable and modern energy for all.â Current research focuses on species cultivated at scale in temperate regions, overlooking the wealth of potential new sources of smallâscale energy where they are most urgently needed. A shift towards diversified, accessible bioenergy technologies will help to mitigate and adapt to the threats of climate change, decrease energy poverty, improve human health by reducing indoor pollution, increase energy resilience of communities, and decrease greenhouse gas emissions from fossil fuels.
Summary
Bioenergy derived from plants and fungi is a major component of the global transition to renewable energy technologies. There is rich untapped diversity in the plant and fungal kingdoms that offers potential to contribute to the shift away from fossil fuels and to address the United Nations Sustainable Development Goal 7 (SDG7) âEnsure access to affordable, reliable, sustainable and modern energy for all.â Energy povertyâthe lack of access to modern energy servicesâis most acute in the Global South where biodiversity is greatest and least investigated. Our systematic review of the literature over the last 5 years (2015â2020) indicates that research efforts have targeted a very small number of plant species cultivated at scale, mostly in temperate regions. The wealth of potential new sources of bioenergy in biodiverse regions, where the implementation of SDG7 is most urgently needed, has been largely overlooked. We recommend next steps for bioenergy stakeholdersâresearch, industry, and governmentâto seize opportunities for innovation to alleviate energy poverty while protecting biodiversity. Smallâscale energy production using native plant species in bioenergy landscapes overcomes many pitfalls associated with bioenergy crop monocultures, such as biodiversity loss and conflict with food production. Targeted traitâbased screening of plant species and biological screening of fungi are required to characterize the potential of this resource. The benefits of diversified, accessible bioenergy go beyond the immediate urgency of energy poverty as more diverse agricultural landscapes are more resilient, store more carbon, and could also reduce the drivers of the climate and environmental emergencies
Lambda and Sigma0 Pair Production in Two-Photon Collisions at LEP
Strange baryon pair production in two-photon collisions is studied with the
L3 detector at LEP. The analysis is based on data collected at e+e-
centre-of-mass energies from 91 GeV to 208 GeV, corresponding to an integrated
luminosity of 844 pb-1. The processes gamma gamma -> Lambda Anti-lambda and
gamma gamma -> Sigma0 Anti-sigma0 are identified. Their cross sections as a
function of the gamma gamma centre-of-mass energy are measured and results are
compared to predictions of the quark-diquark model
Proton-Antiproton Pair Production in Two-Photon Collisions at LEP
The reaction e^+e^- -> e^+e^- proton antiproton is studied with the L3
detector at LEP. The analysis is based on data collected at e^+e^-
center-of-mass energies from 183 GeV to 209 GeV, corresponding to an integrated
luminosity of 667 pb^-1. The gamma gamma -> proton antiproton differential
cross section is measured in the range of the two-photon center-of-mass energy
from 2.1 GeV to 4.5 GeV. The results are compared to the predictions of the
three-quark and quark-diquark models
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