In this paper, we report 4 different saturable absorbers based on 4 transition metal dichalcogenides (MoS(2), MoSe(2), WS(2), WSe(2)) and utilize them to Q-switch a ring-cavity fiber laser with identical cavity configuration. It is found that MoSe(2) exhibits highest modulation depth with similar preparation process among four saturable absorbers. Q-switching operation performance is compared from the aspects of RF spectrum, optical spectrum, repetition rate and pulse duration. WS(2) Q-switched fiber laser generates the most stable pulse trains compared to other 3 fiber lasers. These results demonstrate the feasibility of TMDs to Q-switch fiber laser effectively and provide a meaningful reference for further research in nonlinear fiber optics with these TMDs materials.
A Bayesian statistical analysis using redshift space distortions data is performed to test a model of Symmetric Teleparallel Gravity where gravity is non-metrical. The cosmological background mimics a $\Lambda$CDM evolution but differences arise in the perturbations. The linear matter fluctuations are numerically evolved and the study of the growth rate of structures is analysed in this cosmological setting. The best fit parameters reveal that the $\sigma_8$ tension between Planck and Large Scale Structure data can be alleviated within this framework.
We consider f(Q) extended symmetric teleparallel cosmologies, where Q is the non-metricity scalar, and constrain its functional form through the order reduction method. By using this technique, we are able to reduce and integrate the field equations and thus to select the corresponding models giving rise to bouncing cosmology. The selected Lagrangian is then used to develop the Hamiltonian formalism and to obtain the Wave Function of the Universe which suggests that classical observable universes can be recovered according to the Hartle Criterion.
An angular analysis of the B^{0}→K^{*0}(→K^{+}π^{-})μ^{+}μ^{-} decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb^{-1} of pp collision data collected with the LHCb experiment. The full set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the K^{+}π^{-} system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters.
Very low frequency communication systems (3 kHz–30 kHz) enable applications not feasible at higher frequencies. However, the highest radiation efficiency antennas require size at the scale of the wavelength (here, >1 km), making portable transmitters extremely challenging. Facilitating transmitters at the 10 cm scale, we demonstrate an ultra-low loss lithium niobate piezoelectric electric dipole driven at acoustic resonance that radiates with greater than 300x higher efficiency compared to the previous state of the art at a comparable electrical size. A piezoelectric radiating element eliminates the need for large impedance matching networks as it self-resonates at the acoustic wavelength. Temporal modulation of this resonance demonstrates a device bandwidth greater than 83x beyond the conventional Bode-Fano limit, thus increasing the transmitter bitrate while still minimizing losses. These results will open new applications for portable, electrically small antennas. Designing high radiation efficiency antennas for portable transmitters in low frequency communication systems remains a challenge. Here, the authors report on using piezoelectricity to more efficiently radiate while achieving a bandwidth eighty three times higher than the passive Bode-Fano limit.
We investigate the impact on cosmological observables of $f(Q)$-gravity, a specific class of modified gravity models in which gravity is described by the nonmetricity scalar, $Q$. In particular we focus on a specific model which is indistinguishable from the $\mathrm{\ensuremath{\Lambda}}$-cold-dark-matter ($\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$) model at the background level, while showing peculiar and measurable signatures at linear perturbation level. These are attributed to a time-dependent Planck mass and are regulated by a single dimensionless parameter, $\ensuremath{\alpha}$. In comparison to the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, we find for positive values of $\ensuremath{\alpha}$ a suppressed matter power spectrum and lensing effect on the cosmic microwave background radiation (CMB) angular power spectrum and an enhanced integrated-Sachs-Wolfe tail of CMB temperature anisotropies. The opposite behaviors are present when the $\ensuremath{\alpha}$ parameter is negative. We also investigate the modified gravitational waves (GWs) propagation and show the prediction of the GWs luminosity distance compared to the standard electromagnetic one. Finally, we infer the accuracy on the free parameter of the model with standard sirens at future GWs detectors.
The scientific production system is crucial in how global challenges are addressed. However, scholars have recently begun to voice concerns about structural inefficiencies within the system, as highlighted, for example, by the replication crisis, the p-value debate and various forms of publication bias. Most suggested remedies tend to address only partial aspects of the system's inefficiencies, but there is currently no unifying agenda in favour of an overall transformation of the system. Based on a critical review of the current scientific system and an exploratory pilot study about the state of student training, we argue that a unifying agenda is urgently needed, particularly given the emergence of artificial intelligence (AI) as a tool in scientific writing and the research discovery process. Without appropriate responses from academia, this trend may even compound current issues around credibility due to limited replicability and ritual-based statistical practice, while amplifying all forms of existing biases. Naïve openness in the science system alone is unlikely to lead to major improvements. We contribute to the debate and call for a system reform by identifying key elements in the definition of transformation pathways towards open, democratic and conscious learning, teaching, reviewing and publishing supported by openly maintained AI tools. Roles and incentives within the review process will have to adapt and be strengthened in relation to those that apply to authors. Scientists will have to write less, learn differently and review more in the future, but need to be trained better in and for AI even today.
Solar- powered irrigation systems (SPIS) are instruments for sustainable energy transition in agriculture. Despite the government of India's efforts, the adoption of SPIS has remained low. This paper uses the Q method to examine shared stakeholder views on the challenges of increasing SPIS adoption. The aim is to understand barriers to and drivers for SPIS adoption, and the necessary institutional setting to scale up adoption. To capture the discourse on challenges to SPIS adoption, a Q sample of 20 statements was extracted after stakeholder interviews and expert ratings. The statements were Q sorted by 22 respondents across SPIS stakeholder groups. Factor analysis identifies two distinct perspectives on constraints to expanding SPIS: (1) economic and financial barriers; and (2) institutional and governance challenges. This calls for re-framing SPIS from the incentive side of things and convergence across concerned implementing agencies.