Nepal Himalaya Offers Considerable Potential for Pumped Storage Hydropower

There is a pressing need for a transition from fossil-fuel to renewable energy to meet the increasing energy demands and reduce greenhouse gas emissions. The Nepal Himalaya possesses substantial renewable energy potential that can be harnessed through hydropower projects due to its peculiar topographic characteristics and abundant water resources. However, the current exploitation rate is low owing to the predominance of run-of-river hydropower systems to support the nation's power system. The utility-scale storage facility is crucial in the load scenario of an integrated Nepalese power system to manage diurnal variation, peak demand, and penetration of intermittent energy sources. In this study, we first identify the potential of pumped storage hydropower across the country under multiple configurations by pairing lakes, hydropower projects, rivers, and available flat terrains. We then identify technically feasible pairs from those of potential locations. Infrastructural, environmental, operational, and other technical constraints govern the choice of feasible locations. We find the flat land-to-river configuration most promising over other configurations for Nepal. Our results provide insight into the potential of pumped storage hydropower and are of practical importance in planning sustainable power systems in the Himalayas

Condensed-Phase Photochemistry in the Absence of Radiation Chemistry

We report post-irradiation photochemistry studies of condensed ammonia using photons of energies below condensed ammonia’s ionization threshold of ~ 9 eV. Hydrazine (N2H4), diazene (also known as diimide and diimine) (N2H2), triazane (N3H5), and one or more isomers of N3H3 are detected as photochemistry products during temperature-programmed desorption. Product yields increase monotonically with (1) photon fluence and (2) film thickness. In the studies reported herein, the energies of photons responsible for product formation are constrained to less than 7.4 eV. Previous post-irradiation photochemistry studies of condensed ammonia employed photons sufficiently energetic to ionize condensed ammonia and initiate radiation chemistry. Such studies typically involve ion-molecule reactions and electron-induced reactions in addition to photochemistry. Although photochemistry is cited as a dominant mechanism for the synthesis of prebiotic molecules in interstellar ices, to the best of our knowledge, ours is one of the first astrochemically-relevant studies that has found unambiguous evidence for condensed-phase chemical synthesis induced by photons in the absence of ionization

Breaking Functional Connectivity into Components: A Novel Approach Using an Individual-Based Model, and First Outcomes

Landscape connectivity is a key factor determining the viability of populations in fragmented landscapes. Predicting ‘functional connectivity’, namely whether a patch or a landscape functions as connected from the perspective of a focal species, poses various challenges. First, empirical data on the movement behaviour of species is often scarce. Second, animal-landscape interactions are bound to yield complex patterns. Lastly, functional connectivity involves various components that are rarely assessed separately. We introduce the spatially explicit, individual-based model FunCon as means to distinguish between components of functional connectivity and to assess how each of them affects the sensitivity of species and communities to landscape structures. We then present the results of exploratory simulations over six landscapes of different fragmentation levels and across a range of hypothetical bird species that differ in their response to habitat edges. i) Our results demonstrate that estimations of functional connectivity depend not only on the response of species to edges (avoidance versus penetration into the matrix), the movement mode investigated (home range movements versus dispersal), and the way in which the matrix is being crossed (random walk versus gap crossing), but also on the choice of connectivity measure (in this case, the model output examined). ii) We further show a strong effect of the mortality scenario applied, indicating that movement decisions that do not fully match the mortality risks are likely to reduce connectivity and enhance sensitivity to fragmentation. iii) Despite these complexities, some consistent patterns emerged. For instance, the ranking order of landscapes in terms of functional connectivity was mostly consistent across the entire range of hypothetical species, indicating that simple landscape indices can potentially serve as valuable surrogates for functional connectivity. Yet such simplifications must be carefully evaluated in terms of the components of functional connectivity they actually predict

Fetal ascites mimicking maternal ovarian tumor: a rare cause of obstructed labour

Fetal ascites has been diagnosed more frequently these days because of routine ultrasound scanning in pregnancy. However as a cause of dystocia in labour, it is very rare. Twenty four years second gravida of 28 weeks 6 days of gestation presented to labour room with preterm obstructed labour. Abdominal examination revealed less readily palpable fetal parts and distantly localized fetal heart sounds. An urgent ultrasound showed huge maternal ovarian cyst. She then underwent emergency cesarean section; delivered a male baby with grossly distended abdomen. However, the ovaries were normal looking. Routine antenatal ultrasounds help in identifying maternal and congenital fetal anomalies. They also guide in planning the most appropriate management. Whenever fetal ascites is diagnosed antenatally, possibility of dystocia in labour should be kept in mind

Amplitude-Mode Spectroscopy of Charge Excitations in PTB7 π-Conjugated Donor-Acceptor Copolymer for Photovoltaic Applications

We measure the spectra of resonant Raman scattering and doping-induced absorption of pristine films of the pi-conjugated donor-acceptor (D-A) copolymer, namely, thieno[3,4 b] thiophene-alt-benzodithiophene (PTB7), as well as photoinduced absorption spectrum in a blend of PTB7 with fullerene phenyl-C61-butyric acid methyl ester molecules used for organic photovoltaic (OPV) applications. We find that the D-A copolymer contains six strongly coupled vibrational modes having relatively strong Raman-scattering intensity, which are renormalized upon adding charge polarons onto the copolymer chains either by doping or photogeneration. Since the lower-energy charge-polaron absorption band overlaps with the renormalized vibrational modes, they appear as antiresonance lines superposed onto the induced polaron absorption band in the photoinduced absorption spectrum but less so in the doping-induced absorption spectrum. We show that the Raman-scattering, doping-, and photoinduced absorption spectra of PTB7 are well explained by the amplitude mode model, where a single vibrational propagator describes the renormalized modes and their related intensities in detail. From the relative strengths of the induced infrared activity of the polaron-related vibrations and electronic transitions, we obtain the polaron effective kinetic mass in PTB7 using the amplitude mode model to be approximately 3.8m*, where m* is the electron effective mass. The enhanced polaronic mass in PTB7 may limit the charge mobility, which, in turn, reduces the OPV solar-cell efficiency based on the PTB7-fullerene blend.Air Force Office of Scientific Research (AFOSR) [FA9550-16-1-0207]; National Science Foundation-Materials Research, Science, and Engineering Center (NSF-MRSEC) [DMR 1121252]; Space Exploration and Optical Solutions Technology Research Initiative Fund at the University of ArizonaThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Imaging of π-conjugated polymer/fullerene blends used in organic photovoltaics by nonlinear photoluminescence emission

A number of image microscopies have been applied to films of p-conjugated polymers and their fullerene blends used in photovoltaic applications; however, they seldom are able to map the polymer/fullerene grain interfaces and detect microscopic defects in the blend films. We have conducted multiphoton microscopy using a 65-fs mode-locked laser at 1.56 mu m for spectroscopy and mapping of films of two prototype p-conjugated polymers, namely MEHPPVand P3HT combined with their blends of PCBM fullerene molecules. The pristine polymer films have shown third harmonic generation and three-photon photoluminescence emission bands that are used for mapping the film topography with micrometer spatial resolution. Since the nonlinear photoluminescence band of the photogenerated charge transfer excitons (CTE) at the polymer/fullerene interfaces in films of polymer/fullerene blends is substantially redshifted compared to that of the excitons in pristine polymers, we could readily map the polymer/fullerene grain interfaces using the nonlinear CTE photoluminescence emission. From the multiphoton imaging of the polymer/fullerene films, we show that the polymer super-grains in MEH-PPV/PCBM are substantially larger than those in P3HT/PCBM, which may be detrimental to charge transport and, in turn, to photovoltaic applications, in agreement with smaller power conversion efficiencies obtained for solar cells based on the former blend. In addition, we also found second harmonic generation emission bands in the MEH-PPV/PCBM blend that result from micron-size embedded defects that do not possess inversion symmetry that forms during the film deposition process at ambient conditions. Multiphoton microscopy and spectroscopy are valuable additions to the tools of organic semiconductor films and devices for investigating the properties and growth of polymer/fullerene blends used for photovoltaic applications with micron spatial resolution. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE).AFOSR [FA9550-16-1-0207]; Space Exploration and Optical Solutions Technology Research Initiative Fund (TRIF)This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Electronic and vibrational spectroscopy studies of PffBT4T π-conjugated donor–acceptor copolymer

We used a variety of optical spectroscopies to investigate the charge excitations and correlated infrared (IR)-active and Raman-active vibrations in poly[(difluoro-benzothiadiazoldiyl)-alt-(di(2-octyldodecyl)-quaterthiophen-diyl)], PffBT4T, a pi-conjugated donor-acceptor (DA) copolymer, which, when blended with fullerene PCBM molecules, serves as an active layer in high-performance photovoltaic solar cells. The applied optical spectroscopies in films of pristine PffBT4T and PffBT4T/PCBM blend include absorption, photoluminescence, electroabsorption, photoinduced absorption (PA), and resonant Raman scattering. We found that the PffBT4T copolymer chain contains 11 strongly coupled Raman-active vibrational modes, which are renormalized upon photogeneration of charge polarons onto the chain. As the lower energy polaron absorption band overlaps with the renormalized vibrational modes, they appear in the PA spectrum as antiresonance (AR) lines superposed onto the induced polaron absorption band. We show that the Raman scattering, doping induced, and photoinduced AR spectra in PffBT4T are well explained by the amplitude mode model (AMM), where a single vibrational propagator describes the renormalized Raman modes and their related photoinduced AR intensities in detail. Surprisingly, we found that two of the IR-active modes in the pristine copolymer must be included in the AMM propagator for explaining the complete photoinduced AR spectrum. This feature is unique to DA-copolymers and indicates that some intrachain C-2v symmetry breaking occurs because of the different electron affinities of the donor and acceptor moieties. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)Space Exploration and Optical Solutions Technology Research Initiative Fund; AFOSR [FA9550-16-1-0207]; NSF-MRSEC [DMR 1121252]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]