arXiv Physics @arxiv_physics@qoto.org

In the search for neutrinoless double beta decay ($0νββ$) experiments, common methods for sensitivity calculations include the counting method and the spectrum fitting method. This research compares their difference in sensitivity under various energy resolutions. Additionally, the performance of high and low Q-value $0νββ$ isotopes is compared. The results of this research could provide guidance on the choice of methods for sensitivity calculations, energy resolution and $0νββ$ isotopes for future $0νββ$ experiments.

Background: we develop the concept of a Micromegas (MICRO-MEsh GAseous Structure) readout plane with an additional GEM (Gas Electron Multiplier) preamplification stage placed a few mm above it, to increase the maximum effective gain of the combined readout. We implement it and test it in realistic conditions for its application to low-background dark matter searches like the TREX-DM experiment. Methods: for this, we use a Micromegas of microbulk type, built with radiopure materials. A small test chamber allowing for systematic scanning of voltages and pressures is used. In addition, a TREX-DM full-scale set-up has also been built and tested, featuring a replica of the fully-patterned TREX-DM microbulk readout. Results: we report on GEM effective extra gain factors of about 90, 50 and 20 in 1, 4 and 10 bar of Ar-1%iC$_{4}$H$_{10}$. Conclusions: the results here obtained show promise to lower the threshold of the experiment down to 50 eV$_{ee}$, corresponding to substantially enhanced sensitivity to low-mass WIMPs (Weakly Interacting Massive Particles).

A differential frequency microwave sensor for angular displacement detection is reported. A metal strip-loaded cylindrical dielectric resonator (SLCDR) is excited with a 50 ohm microstrip transmission line through a rectangular slot made on its ground plane. Analysis of the transmission coefficient (|S21|) of the circuit shows that for the parallel alignment of SLCDR, dual-transmission zeros are excited at frequencies fL and fH, while for the perpendicular alignment, a single transmission zero is excited at f0 such that fL < f0 < fH. In the range, frequency fL increases towards f0 while fH decreases towards f0. Based on this trend, a differential frequency parameter f = fH-fL is framed as the indicator of the angular displacement following a simulation study with ANSYS HFSS. Subsequent prototype fabrication and VNA measurement confirm the simulations with 15.5 MHz/0 sensitivity over the sensitivity over 900 dynamic range with excellent linearity. Subsequently, using linear inverse regression, the measured differential frequencies are mapped to the angular displacement, and the calculated regression metrics prove very good mapping.

In the Felsenkeller shallow-underground site, protected from cosmic muons by a 45 m thick rock overburden, a research laboratory including a 5 MV Pelletron ion accelerator and a number of radioactivity-measurement setups is located. The laboratory and its installations are described in detail. The background radiation has been studied, finding suppression factors of 40 for cosmic-ray muons, 200 for ambient neutrons, and 100 for the background in germanium $γ$-ray detectors. Using an additional active muon veto, typically the background is just twice as high as in very deep underground laboratories. The properties of the accelerator including its external and internal ion sources and beam line are given. For the radioactivity counting setup, detection limits in the 10$^{-4}$ Bq range have been obtained. Practical aspects for the usage of the laboratory by outside scientific users are discussed.

Intrinsically disordered proteins and regions are increasingly appreciated for their abundance in the proteome and the many functional roles they play in the cell. In this short review, we describe a variety of approaches used to obtain biological insight from the structural ensembles of disordered proteins, regions, and complexes and the integrative biology challenges that arise from combining diverse experiments and computational models. Importantly, we highlight findings regarding structural and dynamic characterization of disordered regions involved in binding and phase separation, as well as drug targeting of disordered regions, using a broad framework of integrative modeling approaches.

In this paper, an analytical technique is proposed to obtain the forced response of a cantilevered tube conveying fluid. By considering the pipe subjected to an arbitrary harmonic force, either distributed or concentrated, an analytical solution is found using the Green's function method. The closed-form solution obtained satisfies the differential equations governing the vibrating tube conveying fluid. The proposed method, which provides exact solutions, is more accurate than the classical eigenfunction expansion or Galerkin's method and eliminates the need for eigenfunctions, eigenvalues, or infinite series.

The purpose of this study is to develop a model for the flow of suspensions consisting of Herschel-Bulkley fluid mixed with spherical particles. In particular, the focus is to investigate the effect of non- Newtonian rheology of the carrying fluid on the flow behavior of a suspension. Two-dimensional steady flow problem in a vertical channel is considered, in which both the pressure gradient and gravity drive the suspension flow. Dependence of the velocity profile and particle concentration across the channel on the fluid rheology parameters and orientation of the pressure gradient is investigated. It is found that the non-uniform particle distribution in the flow across the channel leads to the non-uniform density of the suspension, which causes sinkage of the denser regions and promotes downward migration of the particles even without slip velocity. Particle and suspension fluxes are calculated for various fluid rheologies and pressure gradient orientations. The effect of slip velocity between the phases is added via filtration term that captures fluid flow once particles reach the maximum concentration and stall, and via the settling term that describes gravitational particle settling.

A scheme for treating the Second Law of thermodynamics as a constraint and accounting for the approximate nature of constitutive assumptions in continuum thermomechanics is discussed. An unconstrained, concave, variational principle is designed for solving the resulting mathematical problem. Cases when the Second Law becomes an over-constraint on the mechanical model, as well as when it serves as a necessary constraint, are discussed.

Measurement uncertainty is key to assessing, stating and improving the reliability of measurements. An understanding of measurement uncertainty is the basis for confidence in measurements and is required by many communities; among others in national metrology institutes, accreditation bodies, calibration and testing laboratories, as well as in legal metrology, at universities and in different metrology fields. An important cornerstone to convey an understanding of measurement uncertainty is to provide training. This article identifies the status and the needs for training on measurement uncertainty in each of the above communities as well as among those teaching uncertainty. It is the first study to do so across many different disciplines, and it merges many different sources of information with a focus on Europe. As a result, awareness on the training needs of different communities is raised and teachers of uncertainty are supported in addressing their audiences' needs, in improving their uncertainty-specific pedagogical knowledge and by suggestions for training materials and tools. The three needs that are most commonly encountered in the communities requiring an understanding of measurement uncertainty, are 1) to address a general lack of training on measurement uncertainty, 2) to gain a better overview of existing training on measurement uncertainty in several communities, and 3) to deliver more training on specific technical topics including use of a Monte Carlo method for propagating probability distributions and treating multivariate measurands and measurement models. These needs will serve to guide future developments in uncertainty training and will, ultimately, contribute to increasing the understanding of uncertainty.

Generative Artificial Intelligence (GenAI) has emerged as a valuable assistant in many fields such as marketing, finance, project management, and education. In education, many GenAI tools have been developed to aid teachers in preparing proper educational material and offering personalized learning to their students, tailored to their educational needs. In this paper, we present a custom GPT (IBL Educator GPT) that is designed and developed based on Inquiry-based Learning and offers physics teachers a framework in which they can interact with ChatGPT and design educational strategies. The utilization of the IBL Educator GPT has led to an improvement in teachers' perspectives regarding the adoption of artificial intelligence-based tools for personalizing teaching.

As originally designed [Zhang & Donahue (2024), Acta Cryst. A80, 2370248.], after one cycle of calculation, the single-atom R1 (sR1) method required a user to intelligently determine a partial structure to start the next cycle. In this paper, a lottery scheme has been designed to randomly split a parent model into two child models. This allows the calculation to be carried out in care-free manner. By chance, one child model may have higher amounts of "good" atoms than the parent model. Thus, its expansion in the next cycle favors an improved model. These "lucky" results are carried onto the next cycles. while "unlucky" results in which no improvements occur are discarded. Furthermore, unchanged models are carried onto the next cycles in those "unlucky" occasions. On average a child model has the same fraction of "good" atoms as the parent. Only a substantial statistical fluctuation results in appreciable deviation. This lottery scheme works because such fluctuations do happen. Indeed, test applications with the computing power accessibly by the author have demonstrated that the designed scheme can drive an sR1 calculation to or close to reaching a correct structure solution.

Simulating atomic-scale processes, such as protein dynamics and catalytic reactions, is crucial for advancements in biology, chemistry, and materials science. Machine learning force fields (MLFFs) have emerged as powerful tools that achieve near quantum mechanical accuracy, with promising generalization capabilities. However, their practical use is often limited by long inference times compared to classical force fields, especially when running extensive molecular dynamics (MD) simulations required for many biological applications. In this study, we introduce BoostMD, a surrogate model architecture designed to accelerate MD simulations. BoostMD leverages node features computed at previous time steps to predict energies and forces based on positional changes. This approach reduces the complexity of the learning task, allowing BoostMD to be both smaller and significantly faster than conventional MLFFs. During simulations, the computationally intensive reference MLFF is evaluated only every $N$ steps, while the lightweight BoostMD model handles the intermediate steps at a fraction of the computational cost. Our experiments demonstrate that BoostMD achieves an eight-fold speedup compared to the reference model and generalizes to unseen dipeptides. Furthermore, we find that BoostMD accurately samples the ground-truth Boltzmann distribution when running molecular dynamics. By combining efficient feature reuse with a streamlined architecture, BoostMD offers a robust solution for conducting large-scale, long-timescale molecular simulations, making high-accuracy ML-driven modeling more accessible and practical.

In this paper, we present the solutions of the Schrödinger equation and the thermodynamic properties of generalized hyperbolic Hulthen and Woods-Saxon potential. The eigenvalues and eigenfunctions were found using the parametric Nikiforov-Uvarov method (PNUM). The clean energies of the molecules HCl, NiC, CO, I$_2$, H$_2$, LiH, CuLi and CrH are calculated for certain values of $n$ and $\ell$. They are positive and close to the energy of the ground state ($n= \ell= 0$) in the case of the atomic unit (whose energies become negative for $n=2$). The figures show that the proper energies decrease as $n$, $\ell$, $α$ increase, while they increase as $m$ increases, which confirms the results obtained in the literature. The obtained energy was used to calculate the partition function from which thermodynamic properties such as average energy, specific heat capacity, entropy and free energy are calculated. Numerical results are generated for this generalized hyperbolic Hulthen and Woods-Saxon potential. This study showed that the disorder decreases if the temperature decreases and this decrease is more rapid for HCl and H$_{2}$ molecules.

The tris(2,4,6-trichlorophenyl)methyl radical (TTM) has inspired the synthesis of several luminescent diradicals and diradicaloids, providing an extraordinary opportunity to control the nature of the low-lying excited states by fine-tuning the diradical character. However, the photophysical properties of TTM-derived diradicals remain not fully understood yet. Here we present a comprehensive theoretical investigation on a series of symmetric TTM-derived diradicals, featuring radical moieties separated by pi-conjugated spacers of different length with distinct conjugation extension. All these diradicals exhibit a singlet electronic ground state. The nature of the lowest excited electronic states that control the pho-tophysical behavior of the diradicals, is discussed in detail. The theoretical study is complemented by a complete spectro-scopic characterization of the TTM-TTM diradical, synthesized using a novel, simpler and more efficient procedure ex-ploiting the unique reactivity of TTM. The lowest excited states of the diradicals differ qualitatively from those of TTM: two novel low-lying states emerge in the diradical, due to charge resonance (CR) between the two radical units. The low-est CR state is a dark state for symmetric diradicals. The CR nature explains the blue-shifted emission observed by in-creasing the distance between the radical centres as seen in TTM-ph-TTM. This insight suggests different design strate-gies to improve the luminescence properties of TTM-derived diradicals.

We have developed a Time-to-Digital Converter (TDC) application in a Xilinx Kintex-7 Field Programmable Gate Array (FPGA). This TDC, based on the Tapped-Delay Line (TDL) and Wave Union A (WU-A) techniques, achieves an independent time measurement on 32-channel rising edges and 32-channel falling edges. The average time resolution or the Least Significant Bit (LSB) of the 64 channels is measured to be 3 ps level, with an average root mean square (RMS) precision of 4.77 ps, and a maximum RMS below 8 ps. We also propose an online processing scheme that handles the bubble issues caused by clock region skew.

Homogeneity and efficient oxygen transfer are crucial for aerobic cultures, which is popularly performed in Stirred Tank Bioreactors, through internal mechanical agitation of the impellers.Although there are a number of impeller designs for achieving this purpose, there are still concerns about the ability of the impellers to yield homogeneity and mitigate or eliminate stagnant zones.In this study, a novel impeller design, with auxiliary agitators in form of vents, was introduced and evaluated for small lab-scale bioreactors. For the evaluation, 3D models of a single and double impeller configurations, placed in two different bioreactors were developed. Computational fluid dynamics was employed to carry out the hydrodynamic simulation using k-epsilon standard model in the bioreactors.Computational variables such as the flow velocity, streamlines, pressure and wall shear stress on the shaft and impellers, eddy viscosity, turbulence eddy dissipation and turbulence kinetic energy were obtained and compared in both bioreactors to evaluate the performances at speeds of 50, 100, and 150 revolutions per minute.A comparison of the results with traditional segment-segment and segment-Rushton impellers shows that our double impeller configuration performs more desirably at speeds ranging from 100 to 150 RPM. Homogeneity was also achieved in both bioreactors, and there was significant reduction of stagnant zone less than 99 percentage in the double impeller configuration and significant mitigation in the single impeller agitation.

We introduce a systematic approach that enables two robust methods for performing terahertz time-domain spectroscopy in reflection geometry. Using the Kramers-Kronig relations in connection to accurate experimental measurements of the amplitude of the terahertz electric field, we show how the correct phase of the same field can be retrieved, even in the case of partly misaligned measurements. Our technique allows to accurately estimate the optical properties of in principle any material that reflects terahertz radiation. We demonstrate the accuracy of our approach by extracting the complex refractive index of InSb, a material with a strong plasma resonance in the low-terahertz range. Our technique applies to arbitrary incidence angles and polarization states.

Turbulent transport driven by trapped electron modes (TEMs) is believed to drive significant heat and particle transport in quasihelically symmetric stellarators. Two three-dimensionally-shaped magnetic configurations with suppressed trapped-electron-mode (TEM)-driven turbulence were generated through optimization that targeted quasihelical symmetry and the available energy of trapped electrons. Initial equilibria have flux surface shapes with a helically rotating negative triangularity (NT) and positive triangularity (PT). In gyrokinetic simulations, TEMs are suppressed in the reduced-TEM NT and PT configurations, showing that negative triangularity does not have the same beneficial turbulence properties over positive triangularity as seen in tokamaks. Heat fluxes from TEMs are also suppressed. Without temperature gradients and with a strong density gradient, the most unstable modes at low $k_y$ were consistent with toroidal universal instabilities (UIs) in the NT case and slab UIs in the PT case. Nonlinear simulations show that UIs drive substantial heat flux in both the NT and PT configurations. A moderate increase in $β$ halves the heat flux in the NT configuration, while suppressing the heat flux in the PT geometry. Based on the present work, future optimizations aimed at reducing electrostatic drift wave-driven turbulent transport will need to consider UIs if $β$ is sufficiently small.

In this paper, we experimentally and theoretically show the improvement in noise characteristics in a distributed Raman amplifier (DRA) system for wavelength division multiplexing (WDM) transmission, utilizing our proposed pumping technique. We show that forward (Fwd) pumping is clearly superior to backward (Bwd) pumping in terms of noise figure (NF) defined by amplified spontaneous emission (ASE) noise and gain. We also show that bi-directional pumping is a more desirable configuration for NF improvement. However, it is known that Bwd pumping is preferable to Fwd pumping in suppressing signal quality degradation caused by nonlinear optical effects, especially the interaction between signal and pump light. To compare these advantages and disadvantages of Fwd pumping, we conducted WDM transmission experiments using a recirculating loop including DRA and erbium doped fiber amplifiers. We measured the Q-factors of 9-channel 131.6-GBaud polarization division multiplexed probabilistically shaped 32-quadrature amplitude modulation signals while changing the ratio of Fwd pumping to Bwd pumping in the DRA. By introducing the previously proposed low-noise Fwd pumping technique, a higher Q-factor could be achieved with a lower signal launch power, even when the total Raman gain remained constant. A Q-factor improvement of 0.4 dB and signal launch power reduction of more than 3.4 dB were simultaneously achieved. We also show that when Fwd pumping was performed with a conventional pump light source, the disadvantage of Fwd pumping was more noticeable than its advantage.