Consolidating the concept of low-energy magnetic dipole decay radiation

We have made a thorough study of the low-energy behaviour of the $\gamma$-ray strength function within the framework of the shell model. We have performed large-scale calculations spanning isotopic and isotonic chains over several mass regions, with the purpose of studying the systematic behavior of the low-energy enhancement (LEE) for $M1$ transitions. There are clear trends in the calculations: From being all but absent in the lowest mass region, the LEE becomes steeper and more pronounced as the mass number increases, and for a given mass region it further increases towards shell closures. Moreover, the LEE is found to be steeper in regions near doubly-magic nuclei where proton particles couple to neutron holes. These trends enable us to consolidate several previous works on the LEE into a single, consistent concept. We compare the inferred trends to the available experimental data from the Oslo method, and find suppport for the systematic behaviour. Lastly we have compared the calculations to strength functions compiled from discrete, experimental lifetimes, and find excellent agreement; the discrete data are consistent with a LEE, and indicate that the slope varies as function of mass number.Comment: 11 pages, 13 figure

Hemicellulosic bioethanol production from fast-growing Paulownia biomass

In order to exploit a fast-growing Paulownia hardwood as an energy crop, a xylose-enriched hydrolysate was obtained in this work to increase the ethanol concentration using the hemicellulosic fraction, besides the already widely studied cellulosic fraction. For that, Paulownia elongata x fortunei was submitted to autohydrolysis treatment (210 °C or S0 of 4.08) for the xylan solubilization, mainly as xylooligosaccharides. Afterwards, sequential stages of acid hydrolysis, concentration, and detoxification were evaluated to obtain fermentable sugars. Thus, detoxified and non-detoxified hydrolysates (diluted or not) were fermented for ethanol production using a natural xylose-consuming yeast, Scheffersomyces stipitis CECT 1922, and an industrial Saccharomyces cerevisiae MEC1133 strain, metabolic engineered strain with the xylose reductase/xylitol dehydrogenase pathway. Results from fermentation assays showed that the engineered S. cerevisiae strain produced up to 14.2 g/L of ethanol (corresponding to 0.33 g/g of ethanol yield) using the non-detoxified hydrolysate. Nevertheless, the yeast S. stipitis reached similar values of ethanol, but only in the detoxified hydrolysate. Hence, the fermentation data prove the suitability and robustness of the engineered strain to ferment non-detoxified liquor, and the appropriateness of detoxification of liquor for the use of less robust yeast. In addition, the success of hemicellulose-to-ethanol production obtained in this work shows the Paulownia biomass as a suitable renewable source for ethanol production following a suitable fractionation process within a biorefinery approach.This research was funded by MINECO (Spain) in the framework of the projects “Multistage processes for the integral benefit of macroalgal and vegetal biomass” with reference CTM2015-68503- R,” and “Cutting-edge strategies for a sustainable biorefinery based on valorization of invasive species” with reference PID2019-110031RB-I00, to Consellería de Cultura, Educación e Ordenación Universitaria (Xunta de Galicia) through the contract ED431C 2017/62-GRC to Competitive Reference Group BV1, program partially funded by European Regional Development Fund (FEDER). This study was also supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit.info:eu-repo/semantics/publishedVersio

Shell Evolution towards Ni 78: Low-Lying States in Cu 77

The level structure of the neutron-rich Cu77 nucleus is investigated through β-delayed γ-ray spectroscopy at the Radioactive Isotope Beam Factory of the RIKEN Nishina Center. Ions of Ni77 are produced by in-flight fission, separated and identified in the BigRIPS fragment separator, and implanted in the WAS3ABi silicon detector array, surrounded by Ge cluster detectors of the EURICA array. A large number of excited states in Cu77 are identified for the first time by correlating γ rays with the β decay of Ni77, and a level scheme is constructed by utilizing their coincidence relationships. The good agreement between large-scale Monte Carlo shell model calculations and experimental results allows for the evaluation of the single-particle structure near Ni78 and suggests a single-particle nature for both the 5/21- and 3/21- states in Cu77, leading to doubly magic Ni78. © 2017 American Physical Society

Level densities and thermodynamical properties of Pt and Au isotopes

The nuclear level densities of $^{194-196}$Pt and $^{197,198}$Au below the neutron separation energy have been measured using transfer and scattering reactions. All the level density distributions follow the constant-temperature description. Each group of isotopes is characterized by the same temperature above the energy threshold corresponding to the breaking of the first Cooper pair. A constant entropy excess $\Delta S=1.9$ and $1.1$ $k_B$ is observed in $^{195}$Pt and $^{198}$Au with respect to $^{196}$Pt and $^{197}$Au, respectively, giving information on the available single-particle level space for the last unpaired valence neutron. The breaking of nucleon Cooper pairs is revealed by sequential peaks in the microcanonical caloric curve

Improving QPF by blending techniques at the Meteorological Service of Catalonia

The current operational very short-term and short-term quantitative precipitation forecast (QPF) at the Meteorological Service of Catalonia (SMC) is made by three different methodologies: Advection of the radar reflectivity field (ADV), Identification, tracking and forecasting of convective structures (CST) and numerical weather prediction (NWP) models using observational data assimilation (radar, satellite, etc.). These precipitation forecasts have different characteristics, lead time and spatial resolutions. The objective of this study is to combine these methods in order to obtain a single and optimized QPF at each lead time. This combination (blending) of the radar forecast (ADV and CST) and precipitation forecast from NWP model is carried out by means of different methodologies according to the prediction horizon. Firstly, in order to take advantage of the rainfall location and intensity from radar observations, a phase correction technique is applied to the NWP output to derive an additional corrected forecast (MCO). To select the best precipitation estimation in the first and second hour (t+1 h and t+2 h), the information from radar advection (ADV) and the corrected outputs from the model (MCO) are mixed by using different weights, which vary dynamically, according to indexes that quantify the quality of these predictions. This procedure has the ability to integrate the skill of rainfall location and patterns that are given by the advection of radar reflectivity field with the capacity of generating new precipitation areas from the NWP models. From the third hour (t+3 h), as radar-based forecasting has generally low skills, only the quantitative precipitation forecast from model is used. This blending of different sources of prediction is verified for different types of episodes (convective, moderately convective and stratiform) to obtain a robust methodology for implementing it in an operational and dynamic wa

Measurement of the optical transfer function using a white-dot pattern presented on a liquid-crystal display

The optical transfer function (OTF) and its modulus, the modulation transfer function (MTF), are widely accepted measurements of the quality of optical systems. There are different ways of estimating both OTF and MTF. Random-dot-pattern methods have some advantages when computing MTFs, especially those which present the pattern on a liquid crystal-display (LCD) screen because no additional light source is needed. Nevertheless spatial information is not usually available in the image plane because MTFs are computed for the whole image in a finite number of directions only. We propose a way of providing spatial information by measuring a number of point-spread functions (PSFs). Created by a white-dot pattern on a LCD screen, white pixels operate as point sources and PSFs are calculated to eventually result in the OTF of the system. MTFs in the main directions are computed to compare with reference values obtained by the random-dot method. Sensor and LCD resolutions define the achievable MTF range. Our proposed method is used to characterize a liquid-crystal tunable filter (LCTF) attached to a monochrome camera at different wavelengths. This method, which is both easy to install and to use, achieves results with errors of less than 3%, and has advantages over classical OTF estimation methods: spatial information provided in the image plane, all frequencies and directions covered in a single capture, no additional light source needed and derivative-dependent noise avoided

137,138,139^{137,138,139}La(nn, γ\gamma) cross sections constrained with statistical decay properties of 138,139,140^{138,139,140}La nuclei

The nuclear level densities and $\gamma$-ray strength functions of $^{138,139,140}$La were measured using the $^{139}$La($^{3}$He, $\alpha$), $^{139}$La($^{3}$He, $^{3}$He$^\prime$) and $^{139}$La(d, p) reactions. The particle-$\gamma$ coincidences were recorded with the silicon particle telescope (SiRi) and NaI(Tl) (CACTUS) arrays. In the context of these experimental results, the low-energy enhancement in the A$\sim$140 region is discussed. The $^{137,138,139}$La($n, \gamma)$ cross sections were calculated at $s$- and $p$-process temperatures using the experimentally measured nuclear level densities and $\gamma$-ray strength functions. Good agreement is found between $^{139}$La($n, \gamma)$ calculated cross sections and previous measurements

Completing the nuclear reaction puzzle of the nucleosynthesis of 92Mo

One of the greatest questions for modern physics to address is how elements heavier than iron are created in extreme, astrophysical environments. A particularly challenging part of that question is the creation of the so-called p-nuclei, which are believed to be mainly produced in some types of supernovae. The lack of needed nuclear data presents an obstacle in nailing down the precise site and astrophysical conditions. In this work, we present for the first time measurements on the nuclear level density and average strength function of $^{92}$Mo. State-of-the-art p-process calculations systematically underestimate the observed solar abundance of this isotope. Our data provide stringent constraints on the $^{91}$Nb$(p,{\gamma})^{92}$Mo reaction rate, which is the last unmeasured reaction in the nucleosynthesis puzzle of $^{92}$Mo. Based on our results, we conclude that the $^{92}$Mo abundance anomaly is not due to the nuclear physics input to astrophysical model calculations.Comment: Submitted to PR