3,526 research outputs found
The role of triplet excitons in enhancing polymer solar cell efficiency: a photo-induced absorption study
Inclusion of heavy metal atoms in a polymer backbone allows transitions
between the singlet and triplet manifolds. Interfacial dissociation of triplet
excitons constitutes a viable mechanism for enhancing photovoltaic (PV)
efficiencies in polymer heterojunction-based solar cells. The PV efficiency
from polymer solar cells utilizing a ladder-type poly (para-phenylene) polymer
(PhLPPP) with trace quantity of Pd atoms and a fullerene derivative (PCBM) is
much higher than its counterpart (MeLPPP) with no Pd atom. Evidence is
presented for the formation of a weak ground-state charge-transfer complex
(CTC) in the blended films of the polymer and PCBM, using photo-induced
absorption (PIA) spectroscopy. The CTC state in MeLPPP:PCBM has a singlet
character to it, resulting in a radiative recombination. In contrast, the CTC
states in PhLPPP:PCBM are more localized with a triplet character. An
absorption peak at 1.65 eV is observed in PhLPPP:PCBM blend in the PIA, which
may be converted to weakly-bound polaron-pairs, contributing to the enhancement
of PV efficiency.Comment: 19 pages, 11 figure
Urbanization and the South Asian Enigma: A Case Study of India
South Asia has the highest rate of child malnutrition in the world, despite rapid economic growth compared to other regions such as sub-Saharan Africa. Known as the ‘South Asian enigma’ this feature is partly attributed to the low status of women in South Asian societies. This paper examines this tenet in the context of India, with particular emphasis on possible differences between rural and urban scenarios. The empirical evidence reveals some important differences, which are relevant for policies relating to women’s empowerment against a backdrop of rapid urbanization.urbanization, women, malnutrition, slums, India
Vibration Studies of Block Type Machine Foundations
Detailed vibration measurements were undertaken at eight block type machine foundations with different supporting soil conditions. These extensive measurements were supplemented by theoretical vibration calculations using principally Barkan\u27s method but, at times, using methods of Reissner, Pauw, Richart and Ford and Haddow. The results of prototype experiments and theoretical studies on various compressor foundations described above as also on similar foundations in the country justify broadly the validity of various theories, particularly Barkan’s method, though these are based on somewhat different concepts. Design criteria for foundations are generally described in terms of limiting values of amplitudes of displacement at the operating conditions. In general, the permissible amplitude of vibration decreases as the frequency increases. Thus, the allowable vibration amplitude has to be considered along with the operating frequency of machine
Magnetic Field resulting from non-linear electrical transport in single crystals of charge-ordered Pr Ca MnO}
In this letter we report that the current induced destabilization of the
charge ordered (CO) state in a rare-earth manganite gives rise to regions with
ferromagnetic correlation. We did this experiment by measurement of the I-V
curves in single crystal of the CO system
PrCaMnO and simultanously measuring the magnetization
of the current carrying conductor using a high T SQUID working at T = 77K.
We have found that the current induced destabilization of the CO state leads to
a regime of negative differential resistance which leads to a small enhancement
of the magnetization of the sample, indicating ferromagnetically aligned
moments.Comment: 4 pages LateX, 4 eps figure
Polarization fluctuation dominated electrical transport processes of polymer based ferroelectric-field-effect transistors
Ferroelectric field-effect transistors (FE-FETs) consisting of tunable
dielectric layers are utilized to investigate interfacial transport processes.
Large changes in the dielectric constant as a function of temperature are
observed in FE-FETs in conjunction with the ferroelectric to paraelectric
transition. The devices offer a test bed to evaluate specific effects of
polarization on the electrical processes. FE-FETs have dominant contributions
from polarization-fluctuation rather than static dipolar disorder prevalent in
high k paraelectric dielectric-based FETs. Additionally, photo-excitation
measurements in the depletion mode reveal clear features in the FET response at
different temperatures, indicative of different transport regimes.Comment: 6 figure
Collider Interplay for Supersymmetry, Higgs and Dark Matter
We discuss the potential impacts on the CMSSM of future LHC runs and possible
electron-positron and higher-energy proton-proton colliders, considering
searches for supersymmetry via MET events, precision electroweak physics, Higgs
measurements and dark matter searches. We validate and present estimates of the
physics reach for exclusion or discovery of supersymmetry via MET searches at
the LHC, which should cover the low-mass regions of the CMSSM parameter space
favoured in a recent global analysis. As we illustrate with a low-mass
benchmark point, a discovery would make possible accurate LHC measurements of
sparticle masses using the MT2 variable, which could be combined with
cross-section and other measurements to constrain the gluino, squark and stop
masses and hence the soft supersymmetry-breaking parameters m_0, m_{1/2} and
A_0 of the CMSSM. Slepton measurements at CLIC would enable m_0 and m_{1/2} to
be determined with high precision. If supersymmetry is indeed discovered in the
low-mass region, precision electroweak and Higgs measurements with a future
circular electron-positron collider (FCC-ee, also known as TLEP) combined with
LHC measurements would provide tests of the CMSSM at the loop level. If
supersymmetry is not discovered at the LHC, is likely to lie somewhere along a
focus-point, stop coannihilation strip or direct-channel A/H resonance funnel.
We discuss the prospects for discovering supersymmetry along these strips at a
future circular proton-proton collider such as FCC-hh. Illustrative benchmark
points on these strips indicate that also in this case FCC-ee could provide
tests of the CMSSM at the loop level.Comment: 47 pages, 26 figure
Explosion Codas and Design Seismic Coefficient
In view of construction of structures in seismic zones like high dams, nuclear power plants etc., evaluation of ‘site dependent design seismic coefficient’ has been of paramount importance. It is thus necessary to assess correctly ‘amplification factor’ of ground motion due to surface geology during earthquakes. This ground amplification factor depends on ‘predominant period’ of site in addition to other factors according to Kanai and others. Though micro tremors have been utilized for estimation of predominant period of site, it has been shown that explosion generated codas could also be used to obtain ground amplification factor useful for estimation of probabilistic site dependent design seismic coefficient from response spectra of probable maximum earthquake magnitude estimated from seismic environment and assumed life of the structure
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