In the early 2000s, Ramakrishna asked the question: for the elliptic curve

\[E\;:\; y^2 = x^3 - x,\]

$a_p(E)$

$E/\mathbb{Q}$

Based on present knowledge of atmospheric composition, a mechanism for the natural formation of vesicles in the lakes of Titan is proposed. It involves precipitation-induced spray droplets coated by a monolayer of amphiphiles. On interaction with the monolayer on the lake’s surface, bilayer membranes are being formed that encapsulate the liquid phase of the original droplet. The resulting vesicles develop thermodynamic stability by continuous compositional selection of various types of amphiphiles in a dynamic equilibrium, leading to an optimized vesicle stability. Different populations of stable vesicles may compete, initiating a long-term evolution process that could eventually result in primitive protocells. The existence of any type of vesicles on Titan would prove that early steps towards increasing order and complexity have taken place, which represent the necessary precondition for abiogenesis. A valid analytical approach could involve a laser device with combined light scattering analysis and surface enhanced Raman spectroscopy. It would allow for very sensitive detection of amphiphiles as well as for the observation of dispersed vesicles.

Eddy currents play a significant role in the evolution of tokamak plasmas and must therefore be correctly taken into account in time-dependent simulations. In this paper, a computational method for solving the evolution of tokamak plasma considering eddy currents utilising VMEC (Hirshman & Whitson, Phys. Fluids, vol. 26, 1983, pp. 3553–3568), a commonly used static magnetohydrodynamic equilibrium solver, is proposed. This method is convenient since it does not modify the equilibrium solver internally and achieves convergence calculation through external processing. By allowing the components of the magnetic field to be treated separately, this method provides convergence for cases with displacements in arbitrary directions, which has been difficult to achieve with the previous methods.

Standard approaches to neoclassical theory do not extend into regions of strong gradients in tokamaks such as the pedestal and internal transport barriers. Here, we calculate the modifications to neoclassical electron physics inside strong gradient regions of large aspect ratio tokamaks in the banana regime. We show that these modifications are due to the different ion flow and the strong poloidal variation of the potential. We also provide a physical interpretation of the mechanisms that drive poloidal asymmetries and hence a poloidal electric field. We apply our model to two specific example cases of pedestal profiles, calculating the neoclassical electron flux and the bootstrap current. We find that, depending on the ion flow, weak gradient neoclassical theory overestimates or underestimates the neoclassical electron transport and the bootstrap current in regions with strong gradients. We show that the determination of the mean parallel flow is more complex than in weak gradient neoclassical theory. For vanishing turbulence, we can determine the radial electric field for a given flow profile in the pedestal.

Here we present the resistance of two halophilic Archaea, Halorubrum (Hrr.) sp. AS12 and Haloarcula (Har.). sp. NS06, isolated from the brine in Lunenburg, Germany, to stress factors including desiccation, radiation and elevated perchlorate concentration. This is the first study to describe the stress resistance of halophilic Archaea isolated from the Lunenburg brine. While Hrr. sp. AS12 tolerates desiccation up to 45 days with a -log3 reduction in survival, Har. sp. NS06 displays a strong decline in viability and no detectable survival following 21 days. In contrast, Hrr. sp. AS12 was more sensitive towards X-Ray irradiation with a significant decline in viability (D10 228,2 ± 8,9 Gy) while Har. sp. NS06 showed a slight decline in survival following exposure to 1 kGy. The resistance of both strains against germicidal UV-C254nm radiation follows a similar pattern when compared to X-ray exposure with Hrr. sp. AS12 displaying more sensitivity to UV-C radiation (F10 111,6 ± 6,4 J/m2) compared to Har. sp. NS06 (F10 194,9 ± 13,7 J/m2). Exposure to He, Ar, and Fe heavy ions up to 500 Gy showed little effect on the survivability; however, the transport control of Hrr. sp. AS12 showed a strong decline (-log3 reduction) in survival. Both strains revealed increased growth in the presence of perchlorates (NaClO4 and MgClO4) with a clear preference to NaClO4 up to 5%. Our results provide a first insight into the stress resistance of these two isolates and will further develop our understanding of the parameters of life on Earth and potentially on other planets.

Studying the diffuse Galactic synchrotron emission (hereafter, DGSE) at arc-minute angular scale is important to remove the foregrounds for the cosmological 21-cm observations. Statistical measurements of the large-scale DGSE can also be used to constrain the magnetic field and the cosmic ray electron density of our Galaxy’s interstellar medium. Here, we have used the Murchison Widefield Array drift scan observations at $154.2 \, \textrm{MHz}$ to measure the angular power spectrum $({\mathcal C}_{\ell})$ of the DGSE of a region of the sky from right ascension $349^{\circ}$ to $70.3^{\circ}$ at the fixed declination $-26.7^{\circ}$. In this RA range, we have chosen 24 pointing centers (PCs), for which we have removed all the bright point sources above $\sim430 \, \textrm{mJy}\,(3\sigma)$, and applied the Tapered Gridded Estimator on residual data to estimate the ${\mathcal C}_{\ell}$. We use the angular multipole range $65 \le \ell \le 650$ to fit the data with a model, ${\mathcal C}^M_{\ell}=A\times \left(\frac{1\,000}{\ell}\right)^{\beta}+C$, where we interpret the model as the combination of a power law $(\propto \ell^{-\beta})$ nature of the DGSE and a constant part due to the Poisson fluctuations of the residual point sources. We are able to fit the model ${\mathcal C}^M_{\ell}$ for six PCs centered at $\alpha=352.5^{\circ}, 353^{\circ}, 357^{\circ}, 4.5^{\circ}, 4^{\circ}$, and $1^{\circ}$. We run the Markov Chain Monte Carlo (MCMC) ensemble sampler to get the best-fit values of the parameters $A, \beta$, and C for these PCs. We see that the values of A vary in the range 155–400 mK$^{2}$, whereas the $\beta$ varies in the range $0.9$–$1.7$. We find that the value of $\beta$ is consistent at $2-\sigma$ level with the earlier measurement of the DGSE at similar frequency and angular scales.

The Indian Pulsar Timing Array (InPTA) employs unique features of the upgraded Giant Metrewave Radio Telescope (uGMRT) to monitor dozens of the International Pulsar Timing Array (IPTA) millisecond pulsars (MSPs), simultaneously in the 300–500 MHz and the 1260–1460 MHz bands. This dual-band approach ensures that any frequency-dependent delays are accurately characterised, significantly improving the timing precision for pulsar observations, which is crucial for pulsar timing arrays. We present details of InPTA’s second data release that involves 7 yr of data on 27 IPTA MSPs. This includes sub-banded times of arrival (ToAs), dispersion measures (DM), and initial timing ephemerides for our MSPs. A part of this dataset, originally released in InPTA’s first data release, is being incorporated into IPTA’s third data release, which is expected to detect and characterise nanohertz gravitational waves (GWs) in the coming years. The entire dataset is reprocessed in this second data release providing some of the highest precision DM estimates so far and interesting solar wind-related DM variations in some pulsars. This is likely to characterise the noise introduced by the dynamic inter-stellar ionised medium much better than the previous release thereby increasing sensitivity to any future GW search.

We investigate the evolution of active galactic nucleus jets on kiloparsec-scales due to their interaction with the clumpy interstellar medium (ISM) of the host galaxy and, subsequently, the surrounding circumgalactic environment. Hydrodynamic simulations of this jet–environment interaction are presented for a range of jet kinetic powers, peak densities of the multiphase ISM, and scale radii of the larger-scale environment – characteristic of either a galaxy cluster or poor group. Synthetic radio images are generated by considering the combination of synchrotron radiation from the jet plasma and free-free absorption from the multiphase ISM. We find that jet propagation is slowed by interactions with a few very dense clouds in the host galaxy ISM, producing asymmetries in lobe length and brightness which persist to scales of tens of kpc for poor group environments. The classification of kiloparsec-scale jets is highly dependent on surface brightness sensitivity and resolution. Our simulations of young active sources can appear as restarted sources, showing double-double lobe morphology, high core prominence (CP $\gt 0.1$), and the expected radio spectra for both the inner- and outer-lobe components. We qualitatively reproduce the observed inverse correlation between peak frequency and source size and find that the peak frequency of the integrated radio spectrum depends on ISM density but not the jet power. Spectral turnover in resolved young radio sources therefore provides a new probe of the ISM.

We present the first radio–continuum detection of the circumstellar shell around the well-known WN8 type Wolf-Rayet star WR16 at 943.5 MHz using the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey. At this frequency, the shell has a measured flux density of 72.2$\pm$7.2 mJy. Using previous Australia Telescope Compact Array (ATCA) measurements at 2.4, 4.8, and 8.64 GHz, as well as the Evolutionary Map of the Universe (EMU) observations of the star itself, we determine a spectral index of $\alpha\,=\,+0.74\pm0.02$, indicating thermal emission. We propose that the shell and star both exhibit thermal emission, supported by the its appearance in near-infrared and H$\alpha$ observations. The latest Gaia parallax is used to determine a distance of 2.28$\pm$0.09 kpc. This star is well known for its surrounding circular nebulosity, and using the distance and an angular diameter of $8.^{\prime}42$, we determine the shell size to be 5.57$\pm$0.22 pc. We use the Gaia proper motion (PM) of WR16 to determine peculiar velocities of the star as $V_{\alpha}(pec) =$ –45.3$\pm$5.4 km s$^{-1}$ and $V_{\delta}(pec) =$ 22.8$\pm$4.7 km s$^{-1}$, which indicates that the star is moving in a north-west direction, and translates to a peculiar tangential velocity to be 50.7$\pm$6.9 km s$^{-1}$. We also use these proper motion (PM) to determine the shell’s origin, estimate an age of $\sim 9500\pm 1300$ yr, and determine its average expansion velocity to be $280\pm40$ km s$^{-1}$. This average expansion velocity suggests that the previous transitional phase is a Luminous Blue Variable (LBV) phase, rather than a Red Super Giant (RSG) phase. We also use the measured flux at 943.5 MHz to determine a mass-loss rate of $1.753\times 10^{-5}\,{\rm M}_\odot\,$yr$^{-1}$, and use this to determine a lower-limit on ionising photons of $N_{UV} \gt 1.406\times 10^{47}\,\textit{s}^{-1}$.

Magnetic reconnection, a fundamental plasma process, is pivotal in understanding energy conversion and particle acceleration in astrophysical systems. While extensively studied in two-dimensional (2-D) configurations, the dynamics of reconnection in three-dimensional (3-D) systems remains under-explored. In this work, we extend the classical tearing mode instability to three dimensions by introducing a modulation along the otherwise uniform direction in a 2-D equilibrium, given by $g(y)$, mimicking a flux-tube-like configuration. We perform linear stability analysis (both analytically and numerically) and direct numerical simulations to investigate the effects of three-dimensionality. Remarkably, we find that a tearing-like instability arises in three dimensions as well, even without the presence of guide fields. Further, our findings reveal that the 3-D tearing instability exhibits reduced growth rates compared with two dimensions by a factor of $\int g(y)^{1/2} {\rm d}y\,/\int {\rm d}y$, with the dispersion relation maintaining similar scaling characteristics. We show that the modulation introduces spatially varying resistive layer properties, which influence the reconnection dynamics.

This study reports on a set of experiments designed to clarify the impact of the rotational transform on confinement quality at the TJ-II stellarator. For this purpose, the net plasma current is controlled using external coils, resulting in the modification of the rotational transform profile. Significant and systematic variations of the edge electron density gradients (up to $50\,\%{-}60\,\%$) and the plasma energy content ($20\,\%{-}30\,\%$) are achieved. The explanation of this behaviour relies on the placement of low-order rational surfaces in relation to the edge gradient region, which affect local turbulence fluctuation levels, facilitating the formation of zonal flows and concomitant transport barriers. This hypothesis is confirmed experimentally on the basis of a broad array of diagnostic measurements. Calculations based on a resistive magnetohydrodynamic turbulence model provide qualitative support for this hypothesis, clarifying the impact on confinement of specific rational surfaces and highlighting the complex nature of magnetically confined fusion plasmas.

The question of whether PCR is reliable sounds strange at first. However, looking at the scientific literature from the 1950s and 60s, one will find many publications on the physicochemistry of DNA that have been forgotten meanwhile. Quite a few of these studies have shown that DNA is thermolabile, which consequently raises the question of whether this thermolability is relevant in the context of PCR, namely in the denaturation phase. However, it can be shown that this is not the case: losses due to thermal hydrolysis are irrelevant for the performance of contemporary PCR protocols and their specificity as well as for the significance of their results. There is now a huge amount of scientifically verified and published data on technical and molecular aspects of PCR, a small selection of which we quote here. In addition, we present some primary data that also clearly demonstrate the reliability of PCR.

Curvature-driven instabilities are ubiquitous in magnetised fusion plasmas. By analysing the conservation laws of the gyrokinetic system of equations, we demonstrate that the well-known spatial localisation of these instabilities to regions of ‘bad magnetic curvature’ can be explained using the conservation law for a sign-indefinite quadratic quantity that we call the gyrokinetic field invariant. Its evolution equation allows us to define the local effective magnetic curvature whose sign demarcates the regions of ‘good’ and ‘bad’ curvature, which, under some additional simplifying assumptions, can be shown to correspond to the inboard (high-field) and outboard (low-field) sides of a tokamak plasma, respectively. We find that, given some reasonable assumptions, electrostatic curvature-driven modes are always localised to the regions of bad magnetic curvature, regardless of the specific character of the instability. More importantly, we also deduce that any mode that is unstable in the region of good magnetic curvature must be electromagnetic in nature. As a concrete example, we present the magnetic-drift mode, a novel good-curvature electromagnetic instability, and compare its properties with the well-known electron-temperature-gradient instability. Finally, we discuss the relevance of the magnetic drift mode for high-$\beta$ fusion plasmas, and in particular its relationship with microtearing modes.

For small-shear helical-axis stellarators, linear ideal-magnetohydrodynamic (MHD) stability calculations and full-torus, nonlinear, electromagnetic gyrokinetic (GK) simulations (the latter with this unprecedented combination of objectives in stellarator GKs) in their linear phase are shown to yield well agreeing spatio-temporal structures of unstable, globally extended perturbations. Likewise, good agreement is found for their dependence on the plasma pressure and the vacuum-field magnetic well in plasma equilibria with identical gradient lengths of the temperature and density profiles. In the nonlinear phase, these perturbations with MHD signatures entail deformations of the magnetic surfaces, growing magnetic islands which rotate in the electron diamagnetic direction and, eventually, lead to ergodisation of a larger part of the magnetic surfaces.

A technique developed to accurately simulate the amplification of back-reflected light through a multi-petawatt laser system is presented. Using the Frantz–Nodvik equation, we developed an iterative algorithm to simulate the amplification of the main beam as it propagates through solid-state multipass amplifiers, while also accounting for back-reflections from experimental targets and the residual gain within the crystals. Our technique builds on the theoretical model by estimating the energy levels after multiple passes through all amplifiers and refining the simulated data using a brute-force optimization algorithm. We also demonstrate an application of this tool aimed at evaluating machine safety: optimizing the laser system to minimize crystal gain in the post-pulse regime and, consequently, the amplification of back-reflections, while taking advantage of the B-integral.