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Enhanced Charge Carrier Transport in 2D Perovskites by Incorporating Single-Walled Carbon Nanotubes or Graphene
Two-dimensional (2D) organic-inorganic (hybrid) perovskites are considered promising candidates to replace conventional three-dimensional (3D) perovskites for solar cell applications as they have good resistance against moisture and UV light. However, the use of 2D perovskite is associated with a significant decrease in power efficiency resulting from their low photogenerated charge carrier density and poor charge transport. To improve power efficiency in 2D perovskites, highly crystalline films (near-single-crystal quality) of 2D perovskite need to be synthesized where the alignment of the inorganic perovskite components is controlled to have vertical alignment with respect to the contacts to improve charge transport. In this work, we explored strategies to overcome this limitation by integrating 2D perovskite with single-walled carbon nanotubes or graphene to enable more efficient extraction of charge carriers toward electric contacts. Longer carrier lifetimes were achieved after the incorporation of the carbon nanostructures in the films, and at the cell level, power efficiency increased by 2-fold
Sex differences in the genetic architecture of lifespan in a seed beetle: extreme inbreeding extends male lifespan
<p>Abstract</p> <p>Background</p> <p>Sex differences in lifespan are ubiquitous throughout the animal kingdom but the causes underlying this phenomenon remain poorly understood. Several explanations based on asymmetrical inheritance patterns (sex chromosomes or mitochondrial DNA) have been proposed, but these ideas have rarely been tested experimentally. Alternatively, sexual dimorphism in lifespan could result from sex-specific selection, caused by fundamental differences in how males and females optimize their fitness by allocating resources into current and future reproduction.</p> <p>Results</p> <p>Here we used sex-specific responses to inbreeding to study the genetic architecture of lifespan and mortality rates in <it>Callosobruchus maculatus</it>, a seed beetle that shows sexual dimorphism in lifespan. Two independent assays revealed opposing sex-specific responses to inbreeding. The combined data set showed that inbred males live longer than outbred males, while females show the opposite pattern. Both sexes suffered reduced fitness measured as lifetime reproductive success as a result of inbreeding.</p> <p>Conclusion</p> <p>No model based on asymmetrical inheritance can explain increased male lifespan in response to inbreeding. Our results are however compatible with models based on sex-specific selection on reproductive strategies. We therefore suggest that sex-specific differences in lifespan in this species primarily result from sexually divergent selection.</p
QCD-scale modified-gravity universe
A possible gluon-condensate-induced modified-gravity model with f(R) \propto
|R|^{1/2} has been suggested previously. Here, a simplified version is
presented using the constant flat-spacetime equilibrium value of the QCD gluon
condensate and a single pressureless matter component (cold dark matter, CDM).
The resulting dynamical equations of a spatially-flat and homogeneous
Robertson-Walker universe are solved numerically. This simple empirical model
allows, in fact, for a careful treatment of the boundary conditions and does
not require a further scaling analysis as the original model did. Reliable
predictions are obtained for several observable quantities of the homogeneous
model universe. In addition, the estimator E_{G}, proposed by Zhang et al. to
search for deviations from standard Einstein gravity, is calculated for linear
sub-horizon matter-density perturbations. The QCD-scale modified-gravity
prediction for E_{G}(z) differs from that of the LambdaCDM model by about \pm
10 % depending on the redshift z.Comment: 24 pages; v7: published versio
Validity of the question for the given name in psychoanalysis
La brĂşjula que guiará este escrito, que se inscribe en el proyecto de investigaciĂłn denominado “Modalidades contemporáneas de la sexualidad humana. Desarrollos actuales en psicoanálisis” y acreditado por la Secretaria de Ciencia y TĂ©cnica de la UNLP, será delimitar relaciones posibles entre el nombre propio y la identificaciĂłn, tal como la considera el psicoanálisis, es decir no desde la semejanza, sino, a la luz de la nociĂłn lacaniana de significante; esto es, desde la diferencia.The compass that will guide this writing, which is part of the research project called “Contemporary modalities of human sexuality. Current developments in psychoanalysis” -accredited by the Secretary of Science and Technology of the UNLP-, will be to delimit possible relationships between the proper name and identification, as considered by psychoanalysis, that is, not from the similarity, but, in the light of the Lacanian notion of significant, that is, from the difference.Facultad de PsicologĂ
The White Dwarf in EM Cygni: Beyond The Veil
We present a spectral analysis of the FUSE spectra of EM Cygni, a Z Cam DN
system. The FUSE spectrum, obtained in quiescence, consists of 4 individual
exposures (orbits): two exposures, at orbital phases phi ~ 0.65 and phi ~ 0.90,
have a lower flux; and two exposures, at orbital phases phi =0.15 and 0.45,
have a relatively higher flux. The change of flux level as a function of the
orbital phase is consistent with the stream material (flowing over and below
the disk from the hot spot region to smaller radii) partially masking the white
dwarf. We carry out a spectral analysis of the FUSE data, obtained at phase
0.45 (when the flux is maximual, using the codes TLUSTY and SYNSPEC. Using a
single white dwarf spectral component, we obtain a white dwarf temperature of
40,000K, rotating at 100km/s. The white dwarf, or conceivably, the material
overflowing the disk rim, shows suprasolar abundances of silicon, sulphur and
possibly nitrogen. Using a white dwarf+disk composite model, we obtain that the
white dwarf temperature could be even as high as 50,000K, contributing more
than 90% of the FUV flux, and the disk contributing less than 10% must have a
mass accretion rate reaching 1.E-10 Msun/yr.In both cases, however, we obtain
that the white dwarf temperature is much higher than previously estimated.Comment: accepted for publication in ApJ, 3 Tables, 12 Figures (including
color figures), 33 pages in present format (possibly 10 pages in ApJ format
An International Ultraviolet Explorer Archival Study of Dwarf Novae in Outburst
We present a synthetic spectral analysis of nearly the entire far ultraviolet
International Ultraviolet Explorer (IUE) archive of spectra of dwarf novae in
or near outburst. The study includes 46 systems of all dwarf nova subtypes both
above and below the period gap. The spectra were uniformly analyzed using
synthetic spectral codes for optically thick accretion disks and stellar
photospheres along with the best-available distance measurements or estimates.
We present newly estimated accretion rates and discuss the implications of our
study for disk accretion physics and CV evolution.Comment: Accepted for publication in the ApJ, Part
Solar PV and solar water heaters in China: Different pathways to low carbon energy.
This review paper examines pathways towards solar energy in China by examining two different solar energy technologies, namely solar photovoltaic (PV) and solar water heaters (SWH). The paper investigates these two case studies to understand how different pathways for low carbon innovation are promoted and challenged by China's changing financing and policy-making, and how they relate to changing practices among producers and consumers. The paper finds two distinct approaches to solar energy. Chinese solar PV is predominantly produced for the export market, relies on intellectual property-intensive technology and has received much financial and political support from the central and provincial governments. On the other side, solar water heaters are an indigenous Chinese technology that is found everywhere across China, especially in rural areas. They have developed from grass-roots levels to mass products with very little central government support. Although being largely absent from high-level discussions and policies, solar water heaters could contribute a lot to China's low carbon transitions that are driven at the local level
Nighttime chlorine monoxide observations by the Odin satellite and implications for the ClO/Cl2O2 equilibrium
We use measurements of chlorine monoxide (ClO) by the SMR instrument onboard the Odin satellite to study the nighttime thermal equilibrium between ClO and its dimer Cl2O2. Observations performed in the polar vortex during the 2002–2003 Arctic winter showed enhanced amounts of nighttime ClO over a wide range of stratospheric temperatures (185 < T < 225 K). Odin/SMR measurements are here compared to three-dimensional model calculations using various published estimations of the Keq equilibrium constant between ClO and Cl2O2. Our results show that the value of Keq currently recommended by JPL (Sander et al., 2003) leads to a large underestimation of the observed nighttime ClO amounts, and that a realistic estimation of Keq must lie between the values determined by Cox and Hayman (1988) and Von Hobe et al. (2005)
Vortex arrays in neutral trapped Fermi gases through the BCS–BEC crossover
Vortex arrays in type-II superconductors reflect the translational symmetry of an infinite system. There are cases, however, such as ultracold trapped Fermi gases and the crust of neutron stars, where finite-size effects make it complex to account for the geometrical arrangement of vortices. Here, we self-consistently generate these arrays of vortices at zero and finite temperature through a microscopic description of the non-homogeneous superfluid based on a differential equation for the local order parameter, obtained by coarse graining the Bogoliubov–de Gennes (BdG) equations. In this way, the strength of the inter-particle interaction is varied along the BCS–BEC crossover, from largely overlapping Cooper pairs in the Bardeen–Cooper–Schrieffer (BCS) limit to dilute composite bosons in the Bose–Einstein condensed (BEC) limit. Detailed comparison with two landmark experiments on ultracold Fermi gases, aimed at revealing the presence of the superfluid phase, brings out several features that make them relevant for other systems in nature as well
Photometry and membership for low mass stars in the young open cluster NGC 2516
We present the results of a 0.86 square degree CCD photometric survey of the
open cluster NGC 2516, which has an age of about 150 Myr and may have a much
lower metallicity than the similarly-aged Pleiades. We select a preliminary
catalogue of 1254 low mass (between 0.2 and 2.0M_{sun}) cluster candidates, of
which about 70--80 percent are expected to be genuine. The mass function is
metallicity dependent, but consistent with a Salpeter-like law (dN/dlog M ~
M^{-alpha}, alpha=+1.47+/-0.11 or alpha=+1.67+/-0.11 for solar and half-solar
metallicities) between 0.7 and 3.0M_{sun}. At lower masses (between 0.3 and
0.7M_{sun}) there is a sharp fall in the mass function, with alpha=-0.75+/-0.20
(solar metallicity) or alpha=-0.49+/-0.13 (half-solar metallicity), which seems
inconsistent with the much flatter mass functions seen in the Pleiades and
field populations. We explain this by demonstrating that mass segregation has
been at work in NGC 2516 -- more than half the cluster low mass stars are
expected to lie outside out survey. The mass of NGC 2516 stars with mass
greater than 0.3M_{sun} inside our survey is 950-1200M_{sun}, depending on
metallicity and what corrections are applied for unresolved binarity.
Correcting for mass segregation increases this to ~1240-1560M_{sun}, about
twice the total mass of the Pleiades.Comment: 27 pages, accepted for Astronomy & Astrophysic
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