Short Time Delay Research Articles

An upper limit on the spins of merging binary black holes formed through isolated binary evolution

As the sensitivity of ground-based gravitational wave detectors progressively increases, observations of black hole mergers will provide us with the joint distribution of their masses and spins. This will be a critical benchmark to validate different formation scenarios. Merging binary black holes formed through the evolution of isolated binary systems require both components to be stripped of their hydrogen envelopes before core-collapse. The rotation rates of such stripped stars are constrained by the critical rotation limit at their surface, including its deviation from the Keplerian value owing to the outward force provided by radiation. This sets a restriction on their angular momentum content at core-collapse. We aim to determine if this restriction plays a role in the spins of binary black hole mergers. We used detailed calculations of stripped stars with the MESA code at low metallicities ($Z=Z_ $Z_ and $Z_ to determine the dimensionless spins of black holes produced by critically rotating stellar progenitors. To study how such progenitors can arise, we considered their formation through chemically homogeneous evolution (CHE) in binary stars. We used a semi-analytical model to study the physical processes that determine the final angular momentum of CHE binaries, and compared our results against available population synthesis models that rely on detailed binary evolution calculations. We find that above black hole masses of $ 25M_ the dimensionless spin parameter of critically rotating stripped stars ($a=Jc/(GM^2)$) is below unity. This results in an exclusion region at high chirp masses and effective spins that cannot be populated by isolated binary evolution. CHE can produce binaries where both black holes hit this limit, producing a pileup at the boundary of the excluded region. High-spin black holes arise from very low-metallicity CHE systems with short delay times, which merge at higher redshifts. On the other hand, the contribution of CHE to merging binary black holes detected in the third observing run of the LVK collaboration is expected to be dominated by systems with low spins ($ eff <0.5$) that merge near redshift zero. Owing to its higher projected sensitivity and runtime, the fourth observing run of the LVK collaboration can potentially place constraints on the high-spin population and the existence of a limit set by critical rotation.

Rapid and quantitative CEST-MRI sequence using water presaturation.

Despite the significant potential for in vivo metabolic imaging in preclinical and clinical applications, CEST MRI suffers from long scan time and inaccurate quantification. This study aims to suppress the contaminations among signals under different frequencies, which could shorten the TR and thereby facilitate CEST imaging acceleration and quantification. A novel sequence is proposed by applying a water-presaturation (WPS) module at the beginning of each TR. WPS CEST quickly knocks down the residual signal from previous TRs so that the magnetization of all TRs recovers from zero, which aligns well with the formula of quasi-steady-state theorem and enables accurate quantification within shorter TR. WPS CEST was assessed by simulations, creatine phantom, and healthy human brain scans at 3 T. In simulation and phantom experiment, WPS CEST allows accurate estimation of exchange rate (ksw) using omega plot and using shorter delay time (Td) and saturation time (Ts) (e.g., 1 s/1 s) compared with the conventional CEST. Simulations further showed that WPS CEST could obtain consistent spin-lock relaxation (R1ρ) values over varied Tds and Tss. Six human scans indicated that R1ρ collected from conventional sequences showed significant differences between two groups with Td and Ts of (1 s/1 s) and (2 s/2 s) (amide: 1.721 ± 0.051 s-1 vs. 1.622 ± 0.050 s-1, p = 0.001; nuclear Overhauser enhancement: 1.792 ± 0.046 s-1 vs. 1.687 ± 0.053 s-1, p = 0.004), whereas WPS CEST scans using these 2 Td/Ts values obtained the same mean R1ρ (amide: 1.616 ± 0.053 s-1 vs. 1.616 ± 0.048 s-1, p = 0.862; nuclear Overhauser enhancement: 1.688 ± 0.064 s-1 vs. 1.684 ± 0.054 s-1, p = 0.544). WPS CEST demonstrated accurate quantitation within shorter TR compared with conventional sequences, and thereby may allow rapid quantitative CEST scans in various situations.

The Rise of the r-process in the Gaia-Sausage/Enceladus Dwarf Galaxy ∗

Neutron star mergers (NSMs) produce r-process elements after a time-delayed inspiral process. Once a significant number of NSMs are present in a galaxy, r-process elements, such as Eu, are expected to significantly increase with time. Yet, there have been limited observational data in support of Eu increasing within Local Group galaxies. We have obtained high-resolution Magellan/MIKE observations of 43 metal-poor stars in the Gaia-Sausage/Enceladus (GSE) tidally disrupted galaxy with −2.5 < [Fe/H] < −1. For the first time, we find a clear rise in [Eu/Mg] with increasing [Mg/H] within one galaxy. We use a simple chemical evolution model to study how such a rise can result from the interplay of prompt and delayed r-process enrichment events. Delayed r-process sources are required to explain the rise and subsequent leveling off of [Eu/Mg] in this disrupted galaxy. However, the rise may be explained by delayed r-process sources with either short (∼10 Myr) or long (∼500 Myr) minimum delay times. Future studies on the nature of r-process sources and their enrichment processes in the GSE will require additional stars in the GSE at even lower metallicities than the present study.

Delaying an Electromagnetic Pulse with a Reflective High-Integration Meta-Platform.

Delaying an electromagnetic (EM) wave pulse on a thin screen for a significant time before releasing it is highly desired in many applications, such as optical camouflage, information storage, and wave-matter interaction boosting. However, available approaches to achieve this goal either require thick and complex systems or suffer from low efficiencies and a short delay time. This paper proposes an ultra-thin meta-platform that can significantly delay an EM-wave pulse after reflection. Specifically, our meta-platform consists of three meta-surfaces integrated together, of which two are responsible for efficiently coupling incident EM-wave pulse into surface waves (SWs) and vice versa, and the third one supports SWs exhibiting significantly reduced group velocity. We employ theoretical model analyses, full-wave simulations, and microwave experiments to validate the proposed concept. Our experiments demonstrate a 13 ns delay of an EM pulse centered at 12.975 GHz, enabled by a λ/8-thick and 38-λ-long meta-device with an efficiency of 32% (or 70%) with (or without) material loss taken into account. A larger delay time can be enabled by devices with larger sizes considering that the SWs group velocity of our device can be further reduced via dispersion engineering. These findings establish a new road for delaying an EM-wave pulse with ultra-thin screens, which may lead to many promising applications in integration optics.

The Mass Density of Merging Binary Black Holes over Cosmic Time

The connection between the binary black hole (BBH) mergers observed by LIGO-Virgo-KAGRA and their stellar progenitors remains uncertain. Specifically, the fraction ϵ of stellar mass that ends up in BBH mergers and the delay time τ between star formation and merger carry information about the astrophysical processes that produce merging BBHs. We model the merger rate in terms of cosmic star formation, coupled with a metallicity-dependent efficiency ϵ and a distribution of delay times τ, and infer these parameters with data from the Third Gravitational-Wave Transient Catalog. The progenitors to merging BBHs preferentially form in low-metallicity environments with a low-metallicity efficiency of log10ϵ<Zt=−3.99−0.87+0.68 and a high-metallicity efficiency of log10ϵ<Zt=−4.60−0.34+0.30 at 90% credibility. The data also prefer short delay times. For a power-law distribution p(τ) ∝ τ α , we find τmin<1.9Gyr and α < −1.32 at 90% credibility. Our model allows us to extrapolate the mass density in BBHs to high redshifts. We cumulatively integrate our density rate over time to get the total density of merging stellar-mass BBHs as a function of redshift. Today, BBH mergers are only ∼0.01% of the total stellar-mass density created by >10 M ⊙ progenitors. However, because massive stars are short lived, there may be more mass in merging BBHs than in living massive stars as early as ∼2.5 Gyr ago. We also compare to the mass in supermassive black holes, finding that the densities were comparable ∼12.5 Gyr ago, but their densities quickly increased to ∼75 times the density in merging stellar-mass BBHs by z ∼ 1.

Understanding the synergistic effect in green propellants 2-azido-N,N-dimethylethanamine and tetramethylethylenediamine: From drop test to gas-phase autoignition

2-Azido-N,N-Dimethylethanamine (DMAZ) and tetramethylethylenediamine (TMEDA) are promising green propellants for hypergolic applications, and blending DMAZ with TMEDA can achieve short ignition delay time (IDT) and comparable specific impulse to hydrazine-based fuels simultaneously. There are reports of a synergistic effect between DMAZ and TMEDA, but its mechanism is not well understood. In this work, drop tests and gas-phase autoignition experiments were combined to provide insights of this synergistic effect from different aspects. The drop tests of DMAZ/TMEDA blends with white-fuming nitric acid were conducted in a confined transparent chamber with controlled O2 concentration. Results show that the hypergolic ignition is much faster for blends with 20–40 wt% DMAZ under all O2 concentration conditions, and higher concentration of O2 in the environment significantly promotes the hypergolic ignition process. To further investigate the chemistry between DMAZ/TMEDA with O2, gas-phase IDTs were measured using a rapid compression machine and a shock tube in a wide temperature range of 500–1100 K and at pressure of 10 bar. TMEDA shows a higher reactivity at lower temperatures (<690 K), while the autoignition of DMAZ is much faster at higher temperatures (>690 K). A synergistic effect between DMAZ and TMEDA was also observed in the gas-phase autoignition, i.e., fuel blend with 30 % DMAZ showed equal or even lower IDTs than pure TMEDA at lower temperatures. The newly measured IDTs of DMAZ/TMEDA were further adopted to validate a previously developed chemical kinetic model for pure TMEDA and DMAZ, which exhibits good predictions for the blending effects nonetheless. Kinetic analyses reveal that the low-temperature reactivity contributed from the TMEDA can be enhanced by the heat release from DMAZ decomposition, causing the synergistic effect in gas-phase autoignition of DMAZ/TMEDA blends.

Superfast Lombard response in free-flying, echolocating bats

Acoustic cues are crucial to communication, navigation, and foraging in many animals, which hence face the problem of detecting and discriminating these cues in fluctuating noise levels from natural or anthropogenic sources. Such auditory dynamics are perhaps most extreme for echolocating bats that navigate and hunt prey on the wing in darkness by listening for weak echo returns from their powerful calls in complex, self-generated umwelts.1,2 Due to high absorption of ultrasound in air and fast flight speeds, bats operate with short prey detection ranges and dynamic sensory volumes,3 leading us to hypothesize that bats employ superfast vocal-motor adjustments to rapidly changing sensory scenes. To test this hypothesis, we investigated the onset and offset times and magnitude of the Lombard response in free-flying echolocating greater mouse-eared bats exposed to onsets of intense constant or duty-cycled masking noise during a landing task. We found that the bats invoked a bandwidth-dependent Lombard response of 0.1-0.2 dB per dB increase in noise, with very short delay and relapse times of 20ms in response to onsets and termination of duty-cycled noise. In concert with the absence call time-locking to noise-free periods, these results show that free-flying bats exhibit a superfast, but hard-wired, vocal-motor response to increased noise levels. We posit that this reflex is mediated by simple closed-loop audio-motor feedback circuits that operate independently of wingbeat and respiration cycles to allow for rapid adjustments to the highly dynamic auditory scenes encountered by these small predators.

N-Alkyl-1,2,4-triazole–Borane Complexes as High-Density Hypergolic Materials

AbstractHydrazine and its derivatives have served as a conventional bipropellant fuel for several decades. However, their extremely acute toxicity and carcinogenicity, high volatility, and environmental impact have attracted significant attention. In order to synthesize green bipropellant fuels with high density, high specific impulse, and good thermal stability, three novel N-alkyl-1,2,4-triazole–borane complexes were successfully synthesized by reacting alkylated 1,2,4-triazole coordinated with sodium borohydride in the presence of ammonium sulfate. During the droplet test with white fuming nitric acid, there was a relatively short ignition delay time of 98 ms. Additionally, these hypergolic fuels possessed a high density exceeding 1.10 g cm–3, and the specific impulse is ranging from 187 to 199 s, and the highest decomposition temperature reaches 153.4 °C. These results demonstrate their great potential as hypergolic fuels or hypergolic ionic liquid additives in the field of hypergolic materials.

Tunneling field-effect transistors with two-dimensional BiN as the channel semiconductor

The lack of suitable channel semiconductor materials has been a limiting factor in the development of tunneling field-effect transistor (TFET) architectures due to the stringent criteria of both air stability and excellent gate-tunable electronic properties. Here, we report the performance limits of sub-10-nm double-gated monolayer (ML) BiN TFETs by utilizing first-principles quantum-transport simulations. We find that ML BiN possesses an indirect bandgap of 0.8 eV and effective masses of 0.24m0 and 2.24m0 for electrons and holes, respectively. The n-type BiN TFETs exhibit better performance than the p-type ones, and the on-state current can well satisfy the requirements of the International Roadmap for Devices and Systems for both high-performance and low-power standards. Notably, we find that the BiN TFETs exhibit distinguished gate controllability with an ultra-low subthreshold swing below 60 mV/decade even with a small gate length of 6 nm, which is superior to the existing field-effect transistors, such as black phosphorus TFETs, GeSe TFETs, and BiN metal–oxide–semiconductor field-effect transistors. Furthermore, the BiN TFETs are endowed with the potential to realize high switching speed and low-power consumption applications because of their extremely short delay time and ultra-low power-delay product. Our results reveal that the ML BiN is a highly competitive channel material for the next-generation TFETs.

Searching for late-time interaction signatures in Type Ia supernovae from the Zwicky Transient Facility

The nature of the progenitor systems and explosion mechanisms that give rise to Type Ia supernovae (SNe Ia) are still debated. The interaction signature of circumstellar material (CSM) being swept up by the expanding ejecta can constrain the type of system from which it was ejected. However, most previous studies have focussed on finding CSM ejected shortly before the SN Ia explosion, which still resides close to the explosion site resulting in short delay times until the interaction starts. We used a sample of 3\,627 SNe Ia from the Zwicky Transient Facility (ZTF) that were discovered between 2018 and 2020 and searched for interaction signatures greater than 100 days after peak brightness. By binning the late-time light curve data to push the detection limit as deep as possible, we identified potential late-time rebrightening in three SNe Ia (SN 2018grt, SN 2019dlf, and SN 2020tfc). The late-time optical detections occur between 550 and 1450\,d after peak brightness, have mean absolute r -band magnitudes of $-$16.4 to $-$16.8 mag, and last up to a few hundred days, which is significantly brighter than the late-time CSM interaction discovered in the prototype, SN 2015cp. The late-time detections in the three objects all occur within 0.8 kpc of the host nucleus and are not easily explained by nuclear activity, another transient at a similar sky position, or data quality issues. This is suggestive of environment or specific progenitor characteristics playing a role in the production of potential CSM signatures in these SNe Ia. Through simulating the ZTF survey, we estimate that $&lt;$0.5 per cent of normal SNe Ia display a late-time ($&gt;100$ d post peak) strong CSM interaction. This is equivalent to an absolute rate of $ to $54_ $ Gpc$^ $ yr$^ $ assuming a constant SN Ia rate of $2.4 $ Mpc$^ $ yr$^ $ for $z 0.1$. Weaker interaction signatures of emission, more similar to the strength seen in SN 2015cp, could be more common but are difficult to constrain with our survey depth.

Neutron star mergers and their impact on second generation star formation in the early universe

ABSTRACT The exact evolution of elements in the Universe, from primordial to heavier elements produced via the r-process, is still under scrutiny. The supernova deaths of the very first stars led to the enrichment of their local environments, and can leave behind neutron stars (NSs) as remnants. These remnants can end up in binary systems with other NSs, and eventually merge, allowing for the r-process to occur. We study the scenario where a single NS merger (NSM) enriches a halo early in its evolution to understand the impact on the second generation of stars and their metal abundances. We perform a suite of high-resolution cosmological zoom-in simulations using enzo where we have implemented a new NSM model varying the explosion energy and the delay time. In general, an NSM leads to significant r-process enhancement in the second generation of stars in a galaxy with a stellar mass of ∼105 M⊙ at redshift 10. A high explosion energy leads to a Population II (Pop II) mass fraction of 72 per cent being highly enhanced with r-process elements, while a lower explosion energy leads to 80 per cent being enhanced, but only 14 per cent being highly enhanced. When the NSM has a short delay time of 10 Myr, only 5 per cent of the mass fraction of Pop II stars is highly enhanced, while 64 per cent is highly enhanced for the longest delay time of 100 Myr. This work represents a stepping stone towards understanding how NSMs impact their environments and the metal abundances of descendant generations of stars.

Coherent optical response driven by non-equilibrium electron–phonon dynamics in a layered transition-metal dichalcogenide

Layered transition-metal dichalcogenides (TMDs) are model systems to explore ultrafast many-body interactions and various nonlinear optical phenomena. For the application of TMD-based optoelectronic devices capable of ultrafast response, it is essential to understand how characteristic electron–hole and electron–phonon couplings modify ultrafast electronic and optical properties under photoexcitation. Here, we investigate the sub-picosecond optical responses of layered semiconductor 2H–MoTe2 in the presence of an electron–hole (e–h) plasma and a long-lived coherent phonon. Transient reflectivity measurements depending on photon energy reveal that the optical response for short-time delays (&amp;lt; 1ps) was significantly modified by band-gap renormalization and state filling due to the presence of the e–h plasma. Furthermore, octave, sum, and difference phonon frequencies transiently appeared for the early time delays (&amp;lt; 2ps). The emergent multiple phonon frequencies can be described as higher-order optical modulations due to deformation-potential electron–phonon coupling under resonant photoexcitation conditions. This work provides comprehensive insights into fundamental physics and the application of non-equilibrium quasiparticle generations on TMDs under time-periodic phonon driving forces.

Treatment seeking delay and associated factors in adult heart failure patients admitted to Debre Tabor comprehensive specialized hospital, North West, Ethiopia

ObjectivesThis study was aimed at assessing the magnitude of treatment-seeking delay in adult heart failure patients and identifying factors that contribute to it. DesignAn institution-based cross-sectional study with a consecutive sampling technique was conducted at Debre Tabor Comprehensive Specialized Hospital from February 1 to November 1, 2021. SettingThe study was conducted in the medical ward of the hospital. ParticipantsA total of 187 patients aged 18 and above admitted with a diagnosis of heart failure, and able to provide information were included. ResultsThe median delay time of adult heart failure patients admitted to the hospital was 15 days. The mean length of delay was also calculated to be 25.02 days. Urban residents and those who live at a ten or less-kilometer distance from healthcare facilities were found to be less likely to delay seeking care. Presenting with shortness of breath or paroxysmal nocturnal dyspnea, perceiving the cause to be heart-related, and getting positive responses from significant others were also associated with a relatively short delay time. ConclusionTreatment-seeking delay was found to be a major problematic issue in heart failure patients. Therefore, patients, patient families, and the community at large must be taught about the symptoms of heart failure and the need for timely care.

Thermal runaway aspect of ultrahigh-nickel cathode-based lithium-ion batteries at increasing charge states

High-nickel cathode-based lithium-ion batteries (LIBs) are the core of sustainable innovation in electric vehicles (EV). However, there exists a fire hazard associated with thermal runaway (TR) during charging due to chemical instability of the abundant nickel oxides produced. While the subject of TR in LIBs has been considered in the past, research on the ultrahigh-nickel (Ni content >90 wt%) cathode materials subjected to a wide range of state of charge (SOC) is limited. The LIB is transforming towards going ultrahigh in Ni content to improve the performance of EVs, and ultimately resolving safety issues associated with TR related fire accidents is an immediate goal. The current study presents a correlation amongst the LIB components, SOCs, and Ni contents on two classes of cathodes, namely high-Ni at 88 % and ultrahigh-Ni at 91 % Ni. The exothermic reaction involving anode and electrolyte in a full cell was intensified at SOCs >75 %, leading to the dissociation of cathode materials and a significant self-heating via repeated reactions. When self-heating rate exceeded 1000 °C/min, the reaction developed into a TR, elucidating that a 3 % increase from 88 % to 91 % Ni content brought forward the likelihood of TR with a much shorter delay time.

Changes in the Optical Properties of Rubber Exposed to High-Pressure Hydrogen Using Pulsed Terahertz Waves.

In this study, we investigated how high-temperature, high-pressure hydrogen affects the optical properties of three kinds of sealing rubber (chloroprene rubber, ethylene propylene diene monomer, and acrylonitrile butadiene rubber) using pulsed terahertz waves. The optical properties of the rubber samples were analyzed before and after exposure to hydrogen (80 °C and 200 bar) for 72 h. The results showed that the terahertz waves had a shorter time delay and a lower signal intensity for all rubber types. The exposure response intensity, refractive index, and absorption rate also changed in the frequency domain. Raman and Fourier transform infrared spectroscopy were used for comparison, and a few peak shifts were observed. However, the Raman spectra had low signal quality, and the laser damaged the specimen. The study demonstrates that terahertz waves can be used as a non-contact non-destructive testing technique to evaluate the changes in sealing rubbers after hydrogen exposure.

On the loss of image contrast in double-inversion-recovery prepared T2* MRI of Intramyocardial hemorrhage

PurposeStudies have shown that double-inversion-recovery (DIR) prepared dark-blood T2*-weighted images result in lower SNR, CNR and diagnostic accuracy for intramyocardial hemorrhage (IMH) detection compared to non-DIR-prepared (bright-blood) T2*-weighted images; however, the mechanism contributing to this observation has not been investigated and explained in detail. This work tests the hypothesis that the loss of SNR on dark-blood cardiac T2*-weighted images of IMH stems from spin-relaxation during the long RF pulses in double inversion preparation, as a result, compromising image contrast for intramyocardial hemorrhage detection. MethodsPhantom and in-vivo animal studies were performed to test the hypothesis of the study. An agar phantom was imaged with multi-gradient-echo T2* imaging protocols with and without double-inversion-recovery (DIR) preparation. Image acquisitions were placed at different delay times (TD) after DIR preparation. SNR, T2* and Coefficient of Variation (COV) were measured and compared between DIR-prepared and non-DIR-prepared images. Canines with hemorrhagic myocardial infarctions were scanned at 3.0 T with DIR-prepared (dark-blood) and non-DIR-prepared (bright-blood) T2* imaging protocols. DIR-prepared T2* images were acquired with short, medium, and long delay times (TD). SNR, CNR, intramyocardial hemorrhage (IMH) extent, T2* and COV were measured and compared between DIR-prepared T2* images with short, medium, and long delay times (TD) to non-DIR-prepared bright-blood T2* images. ResultsPhantom studies confirmed the hypothesis that the SNR loss on DIR-prepared T2* images originated from signal loss during DIR preparation. SNR followed T1 recovery curve with increased delay times (TD) indicating that SNR can be recovered with longer time delay between DIR and image acquisition. Myocardial T2* values were not affected by DIR preparation but COV of T2* was elevated. Animal studies supported the hypothesis and showed that DIR-prepared T2* images with insufficient delay time (TD) had impaired sensitivity for IMH detection due to lower SNR and CNR, and higher COV. ConclusionWe conclude that lower SNR and CNR on DIR-prepared T2* images originate from signal loss during DIR preparation and insufficient recovery between DIR preparation and image acquisition. Although, the impaired sensitivity can be recovered by extending delay time (TD), it will extend the scan time. Bright-blood T2* imaging protocols should remain the optimal choice for assessment of intramyocardial hemorrhage. DIR-prepared dark-blood T2* imaging protocols should be performed with extra attention on image signal-to-noise ratio when used for intramyocardial hemorrhage detection.

Numerical modelling of rock fragmentation under high in-situ stresses and short-delay blast loading

Since the invention of electronic detonators with a delay accuracy within 1 ms, short-delay blasting technology has been used in mining and tunnelling engineering to improve rock fracturing and control blast-caused vibration. However, the fragmentation characteristics of pre-stressed rock under short-delay blast loading have not been studied in detail. In this study, the interaction between the short-delay blast loading and static in-situ stress is investigated using a FEM-based modelling method and image-processing approach. Firstly, single-hole blasting tests were conducted in an underground roadway with a burial depth of 620 m. Subsequently, a single-hole blasting model was developed in LS-DYNA and validated against one of the experimental results, a two-hole delay blasting model was established to simulate rock fracture and fragmentation under different delay times and in-situ stresses. Finally, the underlying mechanism of in-situ stress affecting the optimum delay time was theoretically analyzed and an analytical solution for optimum delay was proposed. The tested results show that under a borehole length and charge weight of 1 m and 1.5 kg, respectively, the average fragment size is approximately 10.5 cm, and the crater radius and depth are 0.67 m and 0.96 m, respectively. The numerical results indicate that both of average fragment size and fragment size distribution range significantly increase with the increase of in-situ stress, while they first decrease and then increase with the increase of short delay times. Moreover, there is a specific delay window ranging from 0.5 to 3 ms where short-delay blasting improves fragmentation performance, and the optimum delay time increases with the increase of in-situ stress. The findings of this study can aid in improving the efficiency and safety of blasting operations in deep hard rock mining.

Analysis of dual laser Thomson scattering signals on W7-X

A dual laser Thomson scattering has been developed at W7-X: a unique system employing, in combination with a 1064 nm laser, a 1319 nm Nd:YAG laser. Dual-laser Thomson scattering (DLTS) is an advanced diagnostic technique in which two laser pulses of different wavelengths are sent to the plasma with a very short time delay and the two scattered signals are separately and independently measured with the same set of polychromators. For the first time during OP2.1, a dual laser Thomson scattering system was operated stably during the entire experimental campaign. In this work, the dual-wavelength signals recorded in several W7-X discharges are analyzed with different methods and the resulting electron temperature profiles and the experimental errors are discussed, with the aim of identifying the capabilities of this technique.

Lensed Type Ia supernovae in light of SN Zwicky and iPTF16geu

ABSTRACT Strong gravitationally lensed supernovae (glSNe) are a powerful probe to obtain a measure of the expansion rate of the Universe, but they are also extremely rare. To date, only two glSNe with multiple images strongly lensed by galaxies have been found, but their short time delays make them unsuitable for cosmography. Here, we simulate a realistic catalogue of lensed supernovae and study the characteristics of the population of detectable systems for different surveys. Compared to previous studies, our simulations also account for the effect of microlensing and its impact on the glSNe yields. We show that the properties of glSNe in shallow surveys (such as the Zwicky Transient Facility) are determined by the need for large magnifications, which favours systems of four images with short time delays and low image separations. This picture is consistent with the properties of iPTF16geu and SN Zwicky, but is not representative of the population found in deeper surveys, which are limited by the volume of the Universe that is strongly lensed. For deeper surveys, such as the Legacy Survey of Space and Time (LSST), glSNe show longer time delays and greater angular separations, and the inclusion of microlensing results in 8 per cent of glSNe becoming demagnified under the detection threshold. In the 10 yr of the survey LSST should be able to find ≈180 systems, of which 70 will be suited for cosmography enabling a ≈1.2 per cent precision H0 measurement with LSST glSNe.

Paravascular fluid dynamics reveal arterial stiffness assessed using dynamic diffusion-weighted imaging.

Paravascular cerebrospinal fluid (pCSF) surrounding the cerebral arteries within the glymphatic system is pulsatile and moves in synchrony with the pressure waves of the vessel wall. Whether such pulsatile pCSF can infer pulse wave propagation-a property tightly related to arterial stiffness-is unknown and has never been explored. Our recently developed imaging technique, dynamic diffusion-weighted imaging (dynDWI), captures the pulsatile pCSF dynamics in vivo and can explore this question. In this work, we evaluated the time shifts between pCSF waves and finger pulse waves, where pCSF waves were measured by dynDWI and finger pulse waves were measured by the scanner's built-in finger pulse oximeter. We hypothesized that the time shifts reflect brain-finger pulse wave travel time and are sensitive to arterial stiffness. We applied the framework to 36 participants aged 18-82 years to study the age effect of travel time, as well as its associations with cognitive function within the older participants (N =15, age > 60 years). Our results revealed a strong and consistent correlation between pCSF pulse and finger pulse (mean CorrCoeff = 0.66), supporting arterial pulsation as a major driver for pCSF dynamics. The time delay between pCSF and finger pulses (TimeDelay) was significantly lower (i.e., faster pulse propagation) with advanced age (Pearson's r = -0.44, p = 0.007). Shorter TimeDelay was further associated with worse cognitive function in the older participants. Overall, our study demonstrated pCSF as a viable pathway for measuring intracranial pulses and encouraged future studies to investigate its relevance with cerebrovascular functions.