Pleba\'nski-Demia\'nski-like solutions in metric-affine gravity

We consider a (non--Riemannian) metric--affine gravity theory, in particular its nonmetricity--torsion sector ``isomorphic'' to the Einstein--Maxwell theory. We map certain Einstein--Maxwell electrovacuum solutions to it, namely the Pleba\'nski--Demia\'nski class of Petrov type D metrics.Comment: 12 pages of a LaTeX-fil

Independent Component Analysis to Detect Clustered Microcalcification Breast Cancers

The presence of clustered microcalcifications is one of the earliest signs in breast cancer detection. Although there exist many studies broaching this problem, most of them are nonreproducible due to the use of proprietary image datasets. We use a known subset of the currently largest publicly available mammography database, the Digital Database for Screening Mammography (DDSM), to develop a computer-aided detection system that outperforms the current reproducible studies on the same mammogram set. This proposal is mainly based on the use of extracted image features obtained by independent component analysis, but we also study the inclusion of the patient's age as a nonimage feature which requires no human expertise. Our system achieves an average of 2.55 false positives per image at a sensitivity of 81.8% and 4.45 at a sensitivity of 91.8% in diagnosing the BCRP_CALC_1 subset of DDSM

The Cotton tensor in Riemannian spacetimes

Recently, the study of three-dimensional spaces is becoming of great interest. In these dimensions the Cotton tensor is prominent as the substitute for the Weyl tensor. It is conformally invariant and its vanishing is equivalent to conformal flatness. However, the Cotton tensor arises in the context of the Bianchi identities and is present in any dimension. We present a systematic derivation of the Cotton tensor. We perform its irreducible decomposition and determine its number of independent components for the first time. Subsequently, we exhibit its characteristic properties and perform a classification of the Cotton tensor in three dimensions. We investigate some solutions of Einstein's field equations in three dimensions and of the topologically massive gravity model of Deser, Jackiw, and Templeton. For each class examples are given. Finally we investigate the relation between the Cotton tensor and the energy-momentum in Einstein's theory and derive a conformally flat perfect fluid solution of Einstein's field equations in three dimensions.Comment: 27 pages, revtex

Supersymmetric minisuperspace with non-vanishing fermion number

The Lagrangean of $N=1$ supergravity is dimensionally reduced to one (time-like) dimension assuming spatial homogeneity of any Bianchi type within class A of the classification of Ellis and McCallum. The algebra of the supersymmetry generators, the Lorentz generators, the diffeomorphism generators and the Hamiltonian generator is determined and found to close. In contrast to earlier work, infinitely many physical states with non-vanishing even fermion number are found to exist in these models, indicating that minisuperspace models in supergravity may be just as useful as in pure gravity.Comment: 4 page

White dwarfs as test objects of Lorentz violations

In the present work the thermodynamical properties of bosonic and fermionic gases are analyzed under the condition that a modified dispersion relation is present. This last condition implies a breakdown of Lorentz symmetry. The implications upon the condensation temperature will be studied, as well, as upon other thermodynamical variables such as specific heat, entropy, etc. Moreover, it will be argued that those cases entailing a violation of time reversal symmetry of the motion equations could lead to problems with the concept of entropy. Concerning the fermionic case it will be shown that Fermi temperature suffers a modification due to the breakdown of Lorentz symmetry. The results will be applied to white dwarfs and the consequences upon the Chandrasekhar mass--radius relation will be shown. The possibility of resorting to white dwarfs for the testing of modified dispersion relations is also addressed. It will be shown that the comparison of the current observations against the predictions of our model allows us to discard some values of one of the parameters appearing in the modifications of the dispersion relation.Comment: Accepted in Classical and Quantum Gravitatio

Technical Note: A new device for cervical insemination of sheep - design and field test1

Deep semen deposition, avoiding retrograde flow, lesions and stress, has proved to be very important in the success of sheep AI. The objective of the present study was to develop a new, suitable antiretrograde flow device for sheep cervical AI (DARIO) that enables deep deposition of semen into the cervix without any modifications to the procedures currently used, and to compare the fertility, fecundity, and prolificacy rates between DARIO and a traditional catheter. Field tests were performed on 16 farms actively participating in the non-profit National Association of Rasa Aragonesa Breeders genetic selection scheme and where sheep management was similar. A total of 242 AI lots were considered, including 1, 299 ewes; 126 lots (662 ewes) were inseminated using DARIO, and 116 lots (637 ewes) using a traditional commercially-available catheter (control group). Several factors affecting AI results were included in the model for mean comparison between DARIO and control groups (farm and ram as random factors; catheter, year and photoperiod as fixed effects; catheter vó photoperiod interaction). The type of catheter had a significant effect on fertility (P < 0.01) and fecundity rates (P < 0.01) but no significant effect was detected on the prolificacy rate (P = 0.45). For fertility rate (percentage of ewes lambing after AI), means ¬± SE for DARIO and control groups were 59.44 ¬± 2.13% and 49.60 ¬± 2.48%, respectively; for fecundity rates, means ¬± SE for DARIO and control groups were 0.99 ¬± 0.04 and 0.82 ¬± 0.05 lambs/inseminated ewe, respectively, and, for prolificacy rates, means ¬± SE for DARIO and control groups were 1.68 ¬± 0.04 and 1.63 ¬± 0.04 lambs/ewe lambing, respectively. Fertility rate was greater in the decreasing photoperiod (P = 0.01). Significant effects were found for both year (P < 0.05) and farm (P < 0.01) on fertility, fecundity, and prolificacy rates. Neither ram nor catheter vó photoperiod showed any significant effects on the variables investigated (P > 0.05). Overall, the use of DARIO instead of the traditional commercially-available catheter increased both fertility and fecundity rates; the marginal mean differences were 9.05 pregnant ewes per 100 inseminated and 0.15 lambs per inseminated ewe, respectively

Corrosion resistance of protective coatings against molten nitrate salts for thermal energy storage and their environmental impact in CSP technology

Sol-gel ZrO2–3%molY2O3 coating deposited by means of a dip-coating application on P91 steel was statically tested at 500 °C in contact with Solar Salt (60% wt.% NaNO3/40 wt.% of KNO3) for 1000 h. This work assessed the behaviour of the coated P91 steel both from a technical and environmental point of view. Both studies were compared to those obtained with AISI 304 steel, which is currently used in commercial CSP plants. In terms of corrosion evaluation, the behaviour of the coated P91 was directly comparable to that of the uncoated AISI 304, SEM micrographs revealing the better behaviour of coated samples and the maintenance of a compact coating layer, with a thickness ranging between 1 and 1.4 μm. Furthermore, environmental analyses revealed the environmental benefits obtained by using lower Cr-Ni content steel coated with ZrO2–Y2O3 compared to AISI 304 alloy, since this coating had a negligible environmental impact (its influence is below 0.03%). Thus, the proposed scenario seems to be workable in CSP high-temperature applications both from technical and environmental points of view. The linked technical-environmental quantification provided in this paper highlights the importance of considering the whole assessment when conducting material selection for CSP applications.Publicad

Ab initio calculation of the 66 low lying electronic states of HeH+^+: adiabatic and diabatic representations

We present an ab initio study of the HeH$^+$ molecule. Using the quantum chemistry package MOLPRO and a large adapted basis set, we have calculated the adiabatic potential energy curves of the first 20 $^1 \Sigma^+$, 19 $^3\Sigma^+$, 12 $^1\Pi$, 9 $^3\Pi$, 4 $^1\Delta$ and 2 $^3\Delta$ electronic states of the ion in CASSCF and CI approaches. The results are compared with previous works. The radial and rotational non-adiabatic coupling matrix elements as well as the dipole moments are also calculated. The asymptotic behaviour of the potential energy curves and of the various couplings between the states is also studied. Using the radial couplings, the diabatic representation is defined and we present an example of our diabatization procedure on the $^1\Sigma^+$ states.Comment: v2. Minor text changes. 28 pages, 18 figures. accepted in J. Phys.

Operation Allelopathy: An Experiment Investigating an Alternative to Synthetic Agrochemicals

Synthetic herbicides represent a serious problem in modern agriculture because they are not biodegradable and can accumulate in the soil and in the groundwater, a situation that allows them to enter the trophic chain and ultimately leads to human exposure. Allelopathic chemicals offer an effective alternative to the synthetic compounds. The aim of this experiment is to highlight the differences between chemical and biological control of diseases in crops and to demonstrate the use of natural fungicides and herbicides as alternatives to synthetic chemicals. The experiment involves an evaluation by students of the potential of plant extracts as an alternative to synthetic agrochemicals to identify new ecological farming techniques that could be applied in agriculture. In an effort to encourage 1800 students in high school (14 to 16 years old) to have an interest in science, technology, and innovation, the third edition of the Summer Science Campus was organized by the Spanish Foundation for Science and Technology and the Ministry of Education, Culture, and Sports with support from the foundation Obra Social “la Caixa”

The Radio - 2 mm Spectral Index of the Crab Nebula Measured with GISMO

We present results of 2 mm observations of the Crab Nebula, obtained using the Goddard-IRAM Superconducting 2 Millimeter Observer (GISMO) bolometer camera on the IRAM 30 m telescope. Additional 3.3 mm observations with the MUSTANG bolometer array on the Green Bank Telescope are also presented. The integrated 2 mm flux density of the Crab Nebula provides no evidence for the emergence of a second synchrotron component that has been proposed. It is consistent with the radio power law spectrum, extrapolated up to a break frequency of log(nu_{b} [GHz]) = 2.84 +/- 0.29 or nu_{b} = 695^{+651}_{-336} GHz. The Crab Nebula is well-resolved by the ~16.7" beam (FWHM) of GISMO. Comparison to radio data at comparable spatial resolution enables us to confirm significant spatial variation of the spectral index between 21 cm and 2 mm. The main effect is a spectral flattening in the inner region of the Crab Nebula, correlated with the toroidal structure at the center of the nebula that is prominent in the near-IR through X-ray regime.Comment: Accepted for publication in the Ap