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Abstract. Copper/zinc superoxide dismutase (CuZnSOD), a 32.5 kDa metalloprotein with a radius of ca. 2.1 nm, catalyses the superoxide to hydrogen peroxide and molecular oxygen. At the femtomolar concentration range, has been sensed through electrochemical catalytic amplification using a Pt ultramicroelectrode. During amperometric (i vs. t) analysis, cathodic and anodic current transitions peaks were seen, in agreement with the metalloprotein catalytic mechanism. The current amplitudes were analyzed and correspond to the CuZnSOD dimensions. Thermal treatment of metalloprotein samples at 80 °C showed larger current spikes suggesting aggregation without losing its catalytic capability. The size was confirmed by transmission electron microscopy. Resumen. Cuprozinc superóxido dismutasa (CuZnSOD), es una metaloproteina de 32.5 kDa con un radio de aproximadamente 2.1 nm. Esta enzima cataliza la reacción de superóxido a peróxido y oxígeno molecular. Por primera vez, esta proteína es detectada a concentraciones femtomolares haciendo uso de la técnica electroquímica conocida como amplificación catalítica y la tecnología de ultra-microelectrodos de Pt. Durante un análisis amperométrico (curvas i vs. t), se observaron picos transitorios de corriente catódica y anódica que concuerdan con el mecanismo catalítico de la enzima. Al analizar la amplitud de la corriente, la misma concuerda con las dimensiones de CuZnSOD. Luego de exponer la proteína a un tratamiento térmico de 80 °C, CuZnSOD mostró picos de corriente transitorias que sugieren aglomeración de la enzima sin perder su capacidad catalítica. El tamaño fue confirmado por microscopía electrónica de transmisión. 

The BUQEYE collaboration (Bayesian Uncertainty Quantification: Errors in Your effective field theory) presents a pedagogical introduction to projection-based, reduced-order emulators for applications in low-energy nuclear physics. The term emulator refers here to a fast surrogate model capable of reliably approximating high-fidelity models. As the general tools employed by these emulators are not yet well-known in the nuclear physics community, we discuss variational and Galerkin projection methods, emphasize the benefits of offline-online decompositions, and explore how these concepts lead to emulators for bound and scattering systems that enable fast and accurate calculations using many different model parameter sets. We also point to future extensions and applications of these emulators for nuclear physics, guided by the mature field of model (order) reduction. All examples discussed here and more are available as interactive, open-source Python code so that practitioners can readily adapt projection-based emulators for their own work. 

Abstract The field of model order reduction (MOR) is growing in importance due to its ability to extract the key insights from complex simulations while discarding computationally burdensome and superfluous information. We provide an overview of MOR methods for the creation of fast & accurate emulators of memory- and compute-intensive nuclear systems, focusing on eigen-emulators and variational emulators. As an example, we describe how ‘eigenvector continuation’ is a special case of a much more general and well-studied MOR formalism for parameterized systems. We continue with an introduction to the Ritz and Galerkin projection methods that underpin many such emulators, while pointing to the relevant MOR theory and its successful applications along the way. We believe that this guide will open the door to broader applications in nuclear physics and facilitate communication with practitioners in other fields. 

The sub-Jovian desert is a region in the mass-period and radius-period parameter space that typically encompasses short-period ranges between super-Earths and hot Jupiters, and exhibits an intrinsic dearth of planets. This scarcity is likely shaped by photoevaporation caused by the stellar irradiation received by giant planets that have migrated inward. We report the detection and characterization of TOI-3568 b, a transiting super-Neptune with a mass of 26.4 ± 1.0 M_⊕, a radius of 5.30 ± 0.27 R_⊕, a bulk density of 0.98 ± 0.15 g cm⁻³, and an orbital period of 4.417965 (5) d situated in the vicinity of the sub-Jovian desert. This planet orbiting a K dwarf star with solar metallicity was identified photometrically by the Transiting Exoplanet Survey Satellite (TESS). It was characterized as a planet by our high-precision radial-velocity (RV) monitoring program using MAROON-X at Gemini North, supplemented with additional observations from the SPICE large program with SPIRou at CFHT. We performed a Bayesian MCMC joint analysis of the TESS and ground-based photometry, and MAROON-X and SPIRou RVs, to measure the orbit, radius, and mass of the planet, as well as a detailed analysis of the high-resolution flux and polarimetric spectra to determine the physical parameters and elemental abundances of the host star. Our results reveal TOI-3568 b to be a hot super-Neptune rich in hydrogen and helium, with a core of heavier elements of between 10 and 25 M_⊕in mass. We analyzed the photoevaporation status of TOI-3568 b and find that it experiences one of the highest extreme-ultraviolet (EUV) luminosities among planets with a mass of M_p< 2 M_Nep, yet it has an evaporation lifetime exceeding 5 Gyr. Positioned in the transition between two significant populations of exoplanets on the mass-period and energy diagrams, this planet presents an opportunity to test theories concerning the origin of the sub-Jovian desert.