Key Experimental Features Research Articles

Light vector bosons and the weak mixing angle in the light of future germanium-based reactor CEνNS experiments

In this work, the sensitivity of future germanium-based reactor neutrino experiments to the weak mixing angle sin2θW, and to the presence of new light vector bosons is investigated. By taking into account key experimental features with their uncertainties and the application of a data-driven and state-of-the-art reactor antineutrino spectrum, the impact of detection threshold and experimental exposure is assessed in detail for an experiment relying on germanium semiconductor detectors. With the established analysis framework, the precision on the Weinberg angle, and capability of probing the parameter space of a universally coupled mediator model, as well as a U(1)B−L-symmetric model are quantified. Our investigation finds the next-generation of germanium-based reactor neutrino experiments in good shape to determine the Weinberg angle sin2θW with < 10% precision using the low-energetic neutrino channel of CEνNS. In addition, the current limits on new light vector bosons determined by reactor experiments can be lowered by about an order of magnitude via the combination of both CEνNS and EνeS. Consequently, our findings provide strong phenomenological support for future experimental endeavours close to a reactor site.

A meta-analysis of microbial thermal inactivation in low moisture foods

Microbial thermal inactivation in low moisture foods is challenging due to enhanced thermal resistance of microbes and low thermal conductivity of food matrices. In this study, we leveraged the body of previous work on this topic to model key experimental features that determine microbial thermal inactivation in low moisture foods. We identified 27 studies which contained 782 mean D-values and developed linear mixed-effect models to assess the effect of microorganism type, matrix structure and composition, water activity, temperature, and inoculation and recovery methods on cell death kinetics. Intraclass correlation statistics (I2) and conditional R2 values of the linear mixed effects models were: E. coli (R2-0.91, I2-83%), fungi (R2-0.88, I2-85%), L. monocytogenes (R2-0.84, I2-75%), Salmonella (R2-0.69, I2-46%). Finally, global response surface models (RSM) were developed to further study the non-linear effect of aw and temperature on inactivation. The fit of these models varied by organisms from R2 0.88 (E. coli) to 0.35 (fungi). Further dividing the Salmonella data into individual RSM models based on matrix structure improved model fit to R2 0.90 (paste-like products) and 0.48 (powder-like products). This indicates a negative relationship between data diversity and model performance.

Bose-Einstein condensation in honeycomb dimer magnets and Yb2Si2O7

An asymmetric Bose-Einstein condensation (BEC) dome was observed in a recent experiment on the quantum dimer magnet ${\mathrm{Yb}}_{2}{\mathrm{Si}}_{2}{\mathrm{O}}_{7}\mathrm{e}$ [G. Hester et al., Phys. Rev. Lett. 123, 027201 (2019)], which is modeled by a ``breathing'' honeycomb lattice Heisenberg model with possible anisotropies. We report a remarkable agreement between key experimental features and predictions from numerical simulations of the magnetic model. Both critical fields, as well as critical temperatures of the BEC dome, can be accurately captured, as well as the occurrence of two regimes inside the BEC phase. Furthermore, we investigate the role of anisotropies in the exchange coupling and the $g$ tensor. While we confirm a previous proposal that anisotropy can induce a zero-temperature phase transition at magnetic fields smaller than the fully polarizing field strength, we find that this effect becomes negligible at temperatures above the anisotropy scale. Instead, the two regimes inside the BEC dome are found to be due to a nonlinear magnetization behavior of the isotropic breathing honeycomb Heisenberg antiferromagnet. Our analysis is performed by combining the density matrix renormalization group (DMRG) method with the finite-temperature techniques of minimally entangled typical thermal states (METTS) and quantum Monte Carlo (QMC).

Mechanism of Bismuth Stimulated Bottom-up Gold Feature Filling

The mechanism underlying -stimulated bottom-up Au filling and self-passivation in trenches and vias in slightly alkaline electrolytes is explored. The impacts of electrolyte components and and potential-dependent kinetic factors on the rate of Au electrodeposition are quantified experimentally. Derived parameters are applied within the surfactant conservation Curvature Enhanced Accelerator Coverage model to simulate the filling of high aspect ratio trenches. It is observed that Bi adsorption accelerates the Au deposition rate with a non-linear dependence occurring around a critical coverage. Further, the impact of electrolyte composition is such that gradients of and derived from reduction of during deposition accentuate deposition farther from the feature opening. These factors and surface area reduction result in Bi enrichment at the bottoms of filling features that localizes active deposition to feature bottoms. Ultimately, weakening of the concentration gradients and associated kinetics as bottom-up feature filling progresses reduces the Bi coverage on the growth front below the critical value and bottom-up growth terminates. Good agreement is observed with key experimental features including the incubation period of conformal deposition, transition to bottom-up growth, subsequent bottom-up filling and finally self-passivation as the growth front nears the field.

Diamagnetic coefficients and g-factors of InAs/InGaAlAs quantum dashes emitting at telecom wavelengths

Semiconductor nanostructures of various material systems are heavily researched for information processing applications as single-photon sources for communication and as a spin memory for storage. Here, exciton, electron, and hole properties in single InAs/InP asymmetric quantum dots (quantum dashes) emitting in a broad spectral range from 0.8 to above 1 eV are studied experimentally and theoretically. Experiments using magneto-microphotoluminescence allowed us to determine g-factor tensor components and diamagnetic coefficients. The growth-axis exciton g-factor is in a 0.0–2.9 range with a constant hole g-factor of 4.5 and variation governed by electron contribution. The in-plane g-factor is more stable with the size of the nanostructure exhibiting values of around −0.7 and −1.6 for holes and electrons, respectively. The diamagnetic coefficients are 13 and 5μeVT2 in the growth and in-plane directions, respectively. Simulations based on the eight-band k⋅p model qualitatively reproduce the key experimental features, including the vanishing of the inverse fine-structure splitting of bright exciton at around 3 T, making these structures prospective for the generation of entangled photons.

Numerical simulation of viscoelastic &amp; thixo-viscoelastoplastic complex flows at highly non-linear regimes

<h2>Abstract</h2> The High Weissenberg Number Problem (HWNP), which is the ceiling posed by the degree of non-linearity a numerical scheme can resolve in the approximation of the solution to a complex flow, is one of the main challenges to the Computational Rheology community (Walters & Webster, 2003). Research on this facet of non-Newtonian Fluids Mechanics has been traditionally focused on increasing resolution and capability to computationally capture non-linear phenomena in complex flow (Walters & Webster, 2003). In this talk, a proposal is presented to increase the critical Weissenberg number <i>Wi</i>_crit a numerical scheme can attain, via the generally applicable ABS-f and the VGR corrections reported previously (López-Aguilar et al., 2015), and their use to predict some experimental and numerical signatures in complex flow. The ABS-f correction acts upon stress-invariants used to promote non-linear features in conventional differential-type constitutive equations for viscoelastic fluids, helping in problem-regularisation and physically consistent material-property calculation in complex deformations (López-Aguilar et al., 2015). The VGR correction deals with proper velocity-gradient estimation, used to impose conservation-of-mass discretely over the flow-domain and to consistently specify velocity-gradient components at boundary symmetry lines (López-Aguilar et al., 2015). Here, predictions with an advanced hybrid finite-element/volume algorithm on the benchmark circular 4:1:4 contraction-expansion flow of concentrated wormlike micellar solutions prove notably extended in their <i>Wi</i>-span, where <i>Wi</i>_crit-adjustment is reported over three orders-of-magnitude from uncorrected variants, and with some cases presenting no limitation (López-Aguilar et al., 2015); (López-Aguilar et al., 2016a). Finally, use of these computational tools is exemplified in various contraction-expansion flow settings through the prediction of key experimental features for Boger fluids (López-Aguilar & Tamaddon-Jahromi, 2020; Webster et al., 2019), thixo-viscoelastoplasticity in sharp-cornered geometries (López-Aguilar et al., 2018) and shear-banding in contraction-expansion flow of highly concentrated wormlike micellar solutions (López-Aguilar et al., 2017a).

Time-Resolved Characterization of Electrochemically-Induced Solid Oxide Cell Microstructure Evolution

Solid oxide cells (SOC) are exciting both for their capability of fuel-flexible electricity generation and their promise in the production of green H2; however, their degradation and long-term performance remain important questions. Operating individual button cells to characterize these changes is prone to cell-to-cell variations, whereas large-area cell/stack life testing requires considerable resources. In both cases, full cell characterization usually must wait until the completion of the life test, which may delay getting results for months or years. While progress has been made in observing microstructural changes over time (termed here time-resolved characterization) using techniques like non-destructive transmission x-ray microscope tomography, such experiments are difficult to implement, especially the effect of current is unexplored due to geometrical and gas environmental limitations of the system.Presented here is a method to rapidly obtain time-resolved microstructural information of the same cell in tandem with electrochemical measurements. While SOC degradation arises due to a range of processes, this work focuses on the microstructural evolution of Ni-YSZ fuel electrodes that occurs during electrolysis operation, which is known to be a key issue. Two key experimental features allowed time-resolved characterization of multiple cells simultaneously: (1) the use of Ni-YSZ symmetric cells allows multiple cells of different size in a single test by avoiding the need for gas seals, and (2) the use of laser milling to allow controlled removal of a portion of each cell during the test.Here we illustrate the method for the case of low steam content and high current density, designed to exacerbate and accelerate electrolysis degradation due to the highly reducing conditions achieved. Tape-cast planar electrode-supported Ni-YSZ symmetric cells were laser cut into precise geometries with well-defined projected areas and easily removable sections. Four cells with projected areas of 1, 1, 0.75, and 0.5 cm2 were connected in series within the same furnace at 800 C and a gas environment of 97% H2 and 3% H2O. A current of 0.75 A was run through three of the cells, resulting in current densities of 0.75, 1.0, and 1.5 A/cm2, while one was maintained with no current. The life test lasted for 500 h, and the microstructure was observed at 0, 200, and 500 hours.Figure 1 shows the microstructures observed at the highest current density by polished cross-sectional SEM and FIB-polished sections under conditions that provided Ni/YSZ contrast. Microstructural degradation had occurred by 200 h and became immense at 500 h, due to high current density in these reducing conditions. By 200 hours, grain boundaries become enriched with Ni, likely due to the formation of Ni-Zr intermetallics in the ultra-low pO2 induced by local overpotential as reported by Chen[1] and Szasz[2]. Additionally, the electrode-electrolyte interface becomes nanoporous and a Ni enriched fracture is present ~2 μm into the electrolyte. By 500 hours, the Ni rich nanoporosity has progressed more than 10 μm into the electrolyte and created islands of large grains surrounded by Ni-rich deposits.Electrochemical impedance spectroscopy measurements show a clear initial decrease in polarization resistance followed by an overall impedance increase by 200 hours. These correspond to the initial electrochemical boost from the production of a nanoporous structure, followed by the deactivation of areas of the cell due to the large fractures through the electrolyte.[1] M. Chen et al., “Microstructural Degradation of Ni/YSZ Electrodes in Solid Oxide Electrolysis Cells under High Current,” J. Electrochem. Soc., vol. 160, no. 8, pp. F883–F891, 2013, doi: 10.1149/2.098308jes.[2] J. Szász et al., “High-Resolution Studies on Nanoscaled Ni/YSZ Anodes,” Chem. Mater., vol. 29, no. 12, pp. 5113–5123, 2017, doi: 10.1021/acs.chemmater.7b00360.Figure 1: Microstructural and electrochemical changes of a symmetric Ni-YSZ SOC undergoing 1.5 A/cm2 in reducing conditions at 0, 200, and 500 hours. Cathode is on the left in all images; anode is on the right. a, b, c) Backscatter electron imaging reveals destruction of the dense YSZ electrolyte over the lifetime of the experiment. Lines of brighter phases on the anode side of fractures are Ni deposits. d, e, f) Focused Ion Beam cross sections reveal nanoporosity forming in the first 10 μm from the cathode-electrolyte interface at 200 and 500 hours. Charging is evident as a result of curtaining from the nanoporous features in the electrolyte. g) Electrochemical impedance spectroscopy shows the initial decrease in resistance from 0 to 48 hours followed by increasing resistance due to microstructure evolution. Figure 1

Asymmetry of synchronisation tongue in persistent sodium plus potassium neuron model

In recent experimental studies, cardio-respiratory synchronisation was observed when the respiration rate was higher than the resting heart rate. Under this condition, there is a strong asymmetry in the synchronisation tongue towards frequencies higher than that of an unperturbed self-oscillator. These experimental results are compelling because they support a novel hypothesis about the interaction of cardiac and respiratory centres in the brain. This hypothesis, however, required further validation; we aimed to observe the key experimental features in related dynamical models. A number of simple self-oscillatory systems under an external driving force have been considered in this work, and a persistent sodium plus potassium neuron model was found to display the strong asymmetry, which is the key feature of the experimental observations. Bifurcations and other changes in the model’s state space were considered by varying the amplitude and frequency of the external force. It was shown that the strong asymmetry in the synchronisation tongue is linked to a non-uniformity of the surface of the non-synchronous invariant torus, and, within a certain range of parameters, to the additional saddle–node bifurcations of cycles. Then, it was demonstrated that the torus non-uniformity leads to changes in the shape of the phase difference potential as the amplitude increases. To illustrate the latter effect, a numerical approach for estimating the one dimensional phase difference profile and providing the corresponding explicit analytical expression is developed. Also, a discrepancy in synchronisation boundaries obtained by two different approaches, one based on bifurcational analysis and the other on a time series technique, was observed. The latter observation stresses the necessity of considering the standard deviation of instantaneous frequency alongside the mean value for the non-ambiguous identification of synchronisation in periodically driven systems.

Significant energy relaxation of quantum dot emitted hot electrons

Mesoscopic quantum dots (QDs) are ubiquitous in quantum devices as reliable sources of hot electrons. However, we have observed an unexpectedly significant energy relaxation of QD-emitted hot electrons up to $\ensuremath{\approx}55%$ of its excitation $\ensuremath{\le}1.5\phantom{\rule{4pt}{0ex}}\mathrm{meV}$ from the Fermi level. The energetics of hot electrons were obtained through transverse magnetic focusing over a few microns using both QD and quantum point contact (QPC) emitters. Unlike the QPC counterparts, QD emissions deviated substantially from Fermi gas predictions---the focusing peak appeared at lower magnetic fields, and excessive broadening was observed. The phenomenon was modeled by a capacitive interaction transferring energy from the hot electron to the QD. Model simulations reproduced the key experimental features, implying the presence of a strong yet overlooked relaxation mechanism that is intrinsic to QD emissions. Our observation calls for the prudent use of QDs as single electron sources.

Insights into Rare-Earth Metal Complex-Mediated Hydroamination

Since the precise understanding of the underlying mechanism is important for the rational design of catalysts, much attention has been paid for hydroamination reactions catalyzed by organolanthanides during the past three decades. Distinct mechanisms were proposed on the basis of some key experimental features. It is a challenge to distinguish these mechanisms. The present study focuses on this controversial topic by synthesizing an almost entire range of rare-earth metal bisalkyl complexes (Py-CH2-Flu)Ln(CH2SiMe3)2(THF)x (Ln = Sc (1), Lu (2), Tm (3), Er (4), Ho (5), Y (6), Dy (7), Tb (8), Gd (9), and Pr (10)) stablized by a pyridine methylene fluorenyl ligand to catalyze intramolecular hydroamination (IAHA) of prototypical 1-amino-2,2-diphenyl-4-pentene and intermolecular hydroamination (IEHA) of styrene and pyrrolidine. Among them, thulium-, terbium-, and gadolinium-based catalysts were investigated for the first time. As observed for all the reported catalytic systems, the rate of IAHA increased almost linearly with increasing metal ion radius, whereas the reactivity pattern in IEHA with respect to the ionic radius size follows the opposite trend. Kinetic studies were carried out to obtain the empirical rate law v = k[Ln]1.0[S]0.0 for IAHA and v = k[Ln]1.0[St]1.0[pyrrolidine]0.0 for IEHA. The zero-order dependence on amine was attributed to the population ratio between the rare-earth metal amido adduct and its precursor being larger than 104. Density functional theory studies on scandium, yttrium, and praseodymium complex-mediated IAHA and IEHA were investigated using a stepwise σ-insertive mechanism and a concerted noninsertive mechanism, respectively. The results suggested the prevailing mechanism to be a stepwise σ-insertive pathway that involves the insertion of C═C into the Ln–N bond and protonolysis of the Ln–C bond. The protonolysis reaction is the turnover-limiting step. The reason behind the influence of the metal ion radius on the catalytic activity was elucidated.

Left Ventricular Thrombus Therapy With Direct Oral Anticoagulants Versus Vitamin K Antagonists: A Systematic Review and Meta-Analysis.

Current guidelines recommend vitamin K antagonists (VKAs) for left ventricular thrombus (LVT) resolution. Direct oral anticoagulants (DOACs) are increasingly evaluated as alternatives to the standard of care in anticoagulation. We performed a systematic review and meta-analysis to assess the use of DOACs vs VKAs for LVT treatment. The occurrence of LVT resolution, systemic embolism (SE) or stroke, and bleeding events were compared during follow-up using random-effects analysis. The 5 included studies were all observational (a total of 828 patients). Of these, 284 patients (34%) were treated with DOACs, and 544 (66%) treated with VKAs. Thrombus resolution was similar for both methods (pooled odds ratio [OR], 0.91; 95% CI, 0.47-1.75; I2 = 63%; P = .78). The incidence of SE or stroke was also similar (pooled OR, 1.59; 95% CI, 0.85-2.97; I2 = 0%; P = .14). Clinically relevant bleeding incidence was similar for both groups (pooled OR, 0.66; 95% CI, 0.31-1.40; I2 = 0%; P = .28), although all bleeding events were less frequent in the DOAC group (pooled OR, 0.49; 95% CI, 0.26-0.90; I2 = 0%; P = .02). Our systematic review and meta-analysis suggests DOACs were as effective as VKAs for LVT resolution, with a similar risk of systemic embolism/stroke and clinically relevant bleeding. These results, obtained from observational studies, are not definitive and hence randomized controlled trials are needed. Nevertheless, our analysis identifies key experimental features required in future studies.

LiNiO2 as a high-entropy charge- and bond-disproportionated glass

Understanding microscopic properties of LiNiO$_2$, a Li-ion battery cathode material with extraordinarily high reversible capacity, has remained a challenge for decades. Based on extensive electronic structure calculations, which reveal a large number of nearly degenerate phases involving local Jahn-Teller effect as well as bond and oxygen-based charge disproportionation, we propose that LiNiO$_2$ exists in a high-entropy charge-glass like state at and below ambient temperatures. Recognizing the glassy nature of LiNiO$_2$ does not only explain its key experimental features, but also opens a new path in designing entropy-stabilized battery cathodes with superb capacities.

On the Interpretation of Force-Induced Unfolding Studies of Membrane Proteins Using Fast Simulations

Single-molecule force spectroscopy has proven extremely beneficial in elucidating folding pathways for membrane proteins. Here, we simulate these measurements, conducting hundreds of unfolding trajectories using our fast Upside algorithm for slow enough speeds to reproduce key experimental features that may be missed using all-atom methods. The speed also enables us to determine the logarithmic dependence of pulling velocities on the rupture levels to better compare to experimental values. For simulations of atomic force microscope measurements in which force is applied vertically to the C-terminus of bacteriorhodopsin, we reproduce the major experimental features including even the back-and-forth unfolding of single helical turns. When pulling laterally on GlpG to mimic the experiment, we observe quite different behavior depending on the stiffness of the spring. With a soft spring, as used in the experimental studies with magnetic tweezers, the force remains nearly constant after the initial unfolding event, and a few pathways and a high degree of cooperativity are observed in both the experiment and simulation. With a stiff spring, however, the force drops to near zero after each major unfolding event, and numerous intermediates are observed along a wide variety of pathways. Hence, the mode of force application significantly alters the perception of the folding landscape, including the number of intermediates and the degree of folding cooperativity, important issues that should be considered when designing experiments and interpreting unfolding data.

A combined fatigue-ductile damage model with optimized parameters for predicting the mechanical response of high-Cr steels at high stress levels

In this paper, a combined fatigue-ductile damage model is presented, which aims to provide accurate predictions on the mechanical response of high-Cr steels at high stress levels. In this model, the Chaboche-type constitutive laws are adopted for the viscoplastic strain and two damage variables (i.e., the fatigue damage and the ductile damage) are incorporated to describe the failure behaviors of high-Cr steels. An efficient scheme is proposed to identify the material parameters in the model, which contains three steps. First, the initial values of the elastic and viscoplastic parameters are determined through a step-by-step procedure. Second, a parameter optimization program is designed and utilized to generate the optimized elastic and viscoplastic parameters. Third, the damage associated parameters are further determined. By adopting one set of optimized parameters, the mechanical response of high-Cr steels in the cyclic loading test, the long-term constant loading test and the loading-dwell test can be predicted at a quantitative level. Some key experimental features (e.g., the minimum strain rate and average rupture time in constant loading test, the stress amplitude evolution curves in the cyclic loading test) can also be properly described. Furthermore, it is revealed that under different loading conditions, the failure behaviors of high-Cr steels are induced by different damage mechanisms. The results obtained in this work are useful for safety design and residual lifetime evaluation of high-Cr steel components in supercritical power plants.

Analyzing test batteries in animal models of psychopathology with MANOVA: One possible approach to increase external validity

In this paper, a combined fatigue-ductile damage model is presented, which aims to provide accurate predictions on the mechanical response of high-Cr steels at high stress levels. In this model, the Chaboche-type constitutive laws are adopted for the viscoplastic strain and two damage variables (i.e., the fatigue damage and the ductile damage) are incorporated to describe the failure behaviors of high-Cr steels. An efficient scheme is proposed to identify the material parameters in the model, which contains three steps. First, the initial values of the elastic and viscoplastic parameters are determined through a step-by-step procedure. Second, a parameter optimization program is designed and utilized to generate the optimized elastic and viscoplastic parameters. Third, the damage associated parameters are further determined. By adopting one set of optimized parameters, the mechanical response of high-Cr steels in the cyclic loading test, the long-term constant loading test and the loading-dwell test can be predicted at a quantitative level. Some key experimental features (e.g., the minimum strain rate and average rupture time in constant loading test, the stress amplitude evolution curves in the cyclic loading test) can also be properly described. Furthermore, it is revealed that under different loading conditions, the failure behaviors of high-Cr steels are induced by different damage mechanisms. The results obtained in this work are useful for safety design and residual lifetime evaluation of high-Cr steel components in supercritical power plants.

Genome-wide prediction of cis-regulatory regions using supervised deep learning methods

BackgroundIn the human genome, 98% of DNA sequences are non-protein-coding regions that were previously disregarded as junk DNA. In fact, non-coding regions host a variety of cis-regulatory regions which precisely control the expression of genes. Thus, Identifying active cis-regulatory regions in the human genome is critical for understanding gene regulation and assessing the impact of genetic variation on phenotype. The developments of high-throughput sequencing and machine learning technologies make it possible to predict cis-regulatory regions genome wide.ResultsBased on rich data resources such as the Encyclopedia of DNA Elements (ENCODE) and the Functional Annotation of the Mammalian Genome (FANTOM) projects, we introduce DECRES based on supervised deep learning approaches for the identification of enhancer and promoter regions in the human genome. Due to their ability to discover patterns in large and complex data, the introduction of deep learning methods enables a significant advance in our knowledge of the genomic locations of cis-regulatory regions. Using models for well-characterized cell lines, we identify key experimental features that contribute to the predictive performance. Applying DECRES, we delineate locations of 300,000 candidate enhancers genome wide (6.8% of the genome, of which 40,000 are supported by bidirectional transcription data), and 26,000 candidate promoters (0.6% of the genome).ConclusionThe predicted annotations of cis-regulatory regions will provide broad utility for genome interpretation from functional genomics to clinical applications. The DECRES model demonstrates potentials of deep learning technologies when combined with high-throughput sequencing data, and inspires the development of other advanced neural network models for further improvement of genome annotations.

The NEXT double beta decay experiment

NEXT (Neutrino Experiment with a Xenon TPC) is a neutrinoless double-beta (ββ0v) decay experiment at Laboratorio Subterraneo de Canfranc (LSC). It is an electroluminescent Time Projection Chamber filled with high pressure 136Xe gas with separated function capabilities for calorimetry and tracking. Energy resolution and background suppression are the two key features of any neutrinoless double beta decay experiment. NEXT has both good energy resolution (< 1% FWHM) and an extra handle for background identification provided by track reconstruction. We expect a background rate of 4 × 10-4 counts keV-1 kg-1 yr-1, and a sensitivity to the Majorana neutrino mass of between 80-160 meV (depending on NME) after a run of 3 effective years of the 100 kg scale NEXT-100 detector. The initial phase of NEXT-100, called NEW, is currently being commissioned at LSC. It will validate the NEXT background rate expectations and will make first measurements of the two neutrino ββ2v mode of 136Xe. Furthermore, the NEXT technique can be extrapolated to the tonne scale, thus allowing the full exploration of the inverted hierarchy of neutrino masses. These proceedings review NEXT R&D results, the status of detector commissioning at LSC and the NEXT physics case.

Backgrounds and sensitivity of the NEXT double beta decay experiment

NEXT (Neutrino Experiment with a Xenon TPC) is a neutrinoless double-beta (ββ0ν) decay experiment that will operate at the Canfranc Underground Laboratory (LSC). It is an electroluminescent high-pressure gaseous xenon Time Projection Chamber (TPC) with separate read-out planes for calorimetry and tracking. Energy resolution and background suppression are the two key features of any neutrinoless double beta decay experiment. NEXT has both good energy resolution (<1% FWHM) at the Q value of 136Xe and an extra handle for background identification provided by track reconstruction. With the background model of NEXT, based on the detector simulation and the evaluation of the detector radiopurity, we can determine the sensitivity to a measurement of the ββ2ν mode in NEW and to a ββ0ν search in NEXT100. In this way we can predict the background rate of 5×10−4 counts/(keV kg yr), and a sensitivity to the Majorana neutrino mass down to 100 meV after a 5-years run of NEXT100.

A mechanistic model for hydrogen activation, spillover, and its chemical reaction in a zeolite-encapsulated Pt catalyst.

The hydrogen (H) spillover phenomenon has attracted considerable attention in the catalysis field. Many researchers have focused on the phenomenon itself, as well as its applications for advanced catalytic systems. In particular, H spillover on non-reducible materials, such as alumina, silica, and zeolites, is a controversial issue owing to the lack of understanding regarding its mechanistic properties. In this study, we use density functional theory calculations to propose the entire mechanism of H spillover from H2 activation on a platinum to its participation in chemical reactions on the external surface of a zeolite. We determined that surface hydroxyl groups of the zeolites, such as Brønsted acid sites, play a role in initiating H spillover, and the Lewis acid sites facilitate the entire process by allowing H to be transferred as a H(+)/e(-) charge pair, as well as providing good binding sites for organic reactants. Theoretical results explain the key experimental features, and we expect that this work will help to elucidate the H spillover phenomenon on non-reducible support materials and to utilize it for catalytic systems.

Computational mechanistic elucidation of the intramolecular aminoalkene hydroamination catalysed by iminoanilide alkaline-earth compounds.

A comprehensive computational exploration of plausible alternative mechanistic pathways for the intramolecular hydroamination (HA) of aminoalkenes by a recently reported class of kinetically stabilised iminoanilide alkaline-earth silylamido compounds [{N^N}Ae{N(SiMe3)2}⋅(thf)n] ({N^N} = iminoanilide; Ae = Ca, Sr, Ba) is presented. On the one hand, a proton-assisted concerted N-C/C-H bond-forming pathway to afford the cycloamine in a single step can be invoked and on the other hand, a stepwise σ-insertive pathway that involves a fast, reversible migratory olefin 1,2-insertion step linked to a less rapid, irreversible metal-C azacycle tether σ-bond aminolysis. Notably, these alternative mechanistic avenues are equally consistent with reported key experimental features. The present study, which employs a thoroughly benchmarked and reliable DFT methodology, supports the prevailing mechanism to be a stepwise σ-insertive pathway that sees an initial conversion of the {N^N}Ae silylamido into the catalytically competent {N^N}Ae amidoalkene compound and involves thereafter facile and reversible insertive N-C bond-forming ring closure, linked to irreversible intramolecular Ae-C tether σ-bond aminolysis at the transient {N^N}Ae alkyl intermediate. Turnover-limiting protonolysis accounts for the substantial primary kinetic isotope effect observed; its DFT-derived barrier satisfactorily matches the empirically determined Eyring parameter and predicts the decrease in rate observed across the series Ca>Sr>Ba correctly. Non-competitive kinetic demands militate against the operation of the concerted proton-assisted pathway, which describes N-C bond-forming ring closure triggered by concomitant amino proton delivery at the C=C linkage evolving through a multi-centre TS structure. Valuable insights into the catalytic structure-activity relationships are unveiled by a detailed comparison of [{N^N}Ae(NHR)] catalysts. Moreover, the intriguingly opposite trends in reactivity observed in intramolecular (Ca>Sr>Ba) and intermolecular (Ca<Sr<Ba) HA catalysis for the studied family of iminoanilide alkaline-earth amido catalysts are rationalised.