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We report the quantitative assessment of nuclear quantum effects on the strength of a single hydrogen bond formed at a water-salt interface, using tip-enhanced inelastic electron tunneling spectroscopy based on a scanning tunneling microscope. The inelastic scattering cross section was resonantly enhanced by \"gating\" the frontier orbitals of water via a chlorine-terminated tip, so the hydrogen-bonding strength can be determined with high accuracy from the red shift in the oxygen-hydrogen stretching frequency of water. Isotopic substitution experiments combined with quantum simulations reveal that the anharmonic quantum fluctuations of hydrogen nuclei weaken the weak hydrogen bonds and strengthen the relatively strong ones. However, this trend can be completely reversed when a hydrogen bond is strongly coupled to the polar atomic sites of the surface.

Background While Salmonella serotyping is of paramount importance for the disease intervention of salmonellosis, a fast and easy-to-operate molecular serotyping solution remains elusive. We have developed a multiplex ligation reaction based on probe melting curve analysis (MLMA) for the identification of 30 common Salmonella serovars. Methods Serovar-specific primers and probes were designed based on a comparison of gene targets ( wzx and wzy encoding for somatic antigen biosynthesis; fliC and fljB for flagellar antigens) from 5868 Salmonella genomes. The ssaR gene, a type III secretion system component, was included for the confirmation of Salmonella . Results All gene targets were detected and gave expected Tm values during assay evaluation. Cross reactions were not demonstrated between the 30 serovars (n = 211), or with an additional 120 serovars (n = 120) and other Enterobacteriaceae (n = 3). The limit of identification for all targets ranged from using 1.2 ng/μL to 1.56 ng/μL of DNA. The intra- and inter-assay standard deviations and the coefficients of variation were no more than 0.5 °C and less than 1% respectively, indicating high reproducibility. From consecutive outpatient stool samples (n = 3590) collected over a 10-month period at 11 sentinel hospitals in Shenzhen, China, we conducted a multicenter study using the traditional Salmonella identification workflow and the MLMA assay workflow in parallel. From Salmonella isolates (n = 496, 13.8%) derived by both workflows, total agreement (kappa = 1.0) between the MLMA assay and conventional serotyping was demonstrated. Conclusions With an assay time of 2.5 h, this simple assay has shown promising potential to provide rapid and high-throughput identification of Salmonella serovars for clinical and public health laboratories to facilitate timely surveillance of salmonellosis.

The dynamic nature of epidemiology has presented a unique challenge for disease intervention strategies. Despite the continued rise of disease incidence and outbreaks of vibriosis, as well as the global emergence of pandemic clones and serovariants with enhanced virulence, there is a paucity of molecular methods for the serotyping of strains to improve disease surveillance and outbreak investigations. We describe the development of a multiplex ligation reaction based on probe melting curve analysis (MLMA) for the simultaneous identification of 11 clinically most common serotypes spanning a 10-year period. Through extensive sequence analyses using 418 genomes, specific primers and probes were designed for a total of 22 antigen gene targets for the O- and K- serogroups. Additionally, the gene was incorporated into the assay for the confirmation of . All gene targets were detected by the assay and gave expected Tm values, without any cross reactions between the 11 clinically common serotypes or with 38 other serotypes. The limit of identification for all gene targets ranged from 0.1 to 1 ng/μL. The intra- and inter-assay standard deviations and the coefficients of variation were no more than 1°C and <1% respectively, indicating a highly reproducible assay. A multicenter double-blind clinical study was conducted using the traditional identification workflow and the MLMA assay workflow in parallel. From consecutive diarrheal stool specimens ( = 6118) collected over a year at 10 sentinel hospitals, a total of 153 isolates (2.5%) were identified by both workflows. A total agreement (kappa = 1.0) between the serotypes identified by the MLMA assay and conventional serological method was demonstrated. This is the first molecular assay to simultaneously identify multiple clinically important serotypes, which satisfies the acute need for a practical, rapid and robust identification of serotypes to facilitate the timely detection of vibriosis outbreaks and surveillance.

We present SN 2023zaw \\(-\\) a sub-luminous (\\(\\mathrm{M_r} = -16.7\\) mag) and rapidly-evolving supernova (\\(\\mathrm{t_{1/2,r}} = 4.9\\) days), with the lowest nickel mass (\\(\\approx0.002\\) \\(\\mathrm{M_\\odot}\\)) measured among all stripped-envelope supernovae discovered to date. The photospheric spectra are dominated by broad He I and Ca NIR emission lines with velocities of \\(\\sim10\\ 000 - 12\\ 000\\) \\(\\mathrm{km\\ s^{-1}}\\). The late-time spectra show prominent narrow He I emission lines at \\(\\sim\\)1000\\(\\ \\mathrm{km\\ s^{-1}}\\), indicative of interaction with He-rich circumstellar material. SN 2023zaw is located in the spiral arm of a star-forming galaxy. We perform radiation-hydrodynamical and analytical modeling of the lightcurve by fitting with a combination of shock-cooling emission and nickel decay. The progenitor has a best-fit envelope mass of \\(\\approx0.2\\) \\(\\mathrm{M_\\odot}\\) and an envelope radius of \\(\\approx50\\) \\(\\mathrm{R_\\odot}\\). The extremely low nickel mass and low ejecta mass (\\(\\approx0.5\\) \\(\\mathrm{M_\\odot}\\)) suggest an ultra-stripped SN, which originates from a mass-losing low mass He-star (ZAMS mass \\(<\\) 10 \\(\\mathrm{M_\\odot}\\)) in a close binary system. This is a channel to form double neutron star systems, whose merger is detectable with LIGO. SN 2023zaw underscores the existence of a previously undiscovered population of extremely low nickel mass (\\(< 0.005\\) \\(\\mathrm{M_\\odot}\\)) stripped-envelope supernovae, which can be explored with deep and high-cadence transient surveys.

The intergalactic medium represents the dominant reservoir of baryons at high redshift, traces the architecture of the cosmic web dominated by dark matter and fuels ongoing galaxy evolution. The intergalactic medium has been studied using the absorption lines of quasi-stellar objects, including the Lyman-α forest, but these absorption lines are unable to provide the information that emission maps would give. However, because of the low surface brightness and extended, diffuse distribution, direct detection of an emission equivalent to the absorption Lyman-α forest has not been possible with existing instrumentation and observational approaches. Using a purpose-built instrument, with nod-and-shuffle and dual-field subtraction, we have detected an emission Lyman-α forest. The emission forest is highly extended, shows filamentary morphology with filaments connecting galaxies, exhibits statistics like the absorption Lyman-α forest, displays spectra resembling the absorption forest and is correlated with galaxy-traced overdensities consistent with bias like dark matter. We conclude that the emission Lyman-α forest may provide a new tool for tracing a substantial fraction of the cosmic web of baryons and dark matter.A purpose-built instrument to detect the faint emission lines of the Lyman-α forest provides evidence of filaments that connect galaxies and trace the cosmic web.

The recently discovered Pa 30 nebula, the putative type Iax supernova remnant associated with the historical supernova of 1181 AD, shows puzzling characteristics that make it unique among known supernova remnants. In particular, Pa 30 exhibits a complex morphology, with a unique radial and filamentary structure, and it hosts a hot stellar remnant at its center, which displays oxygen-dominated, ultra-fast winds. Because of the surviving stellar remnant and the lack of hydrogen and helium in its filaments, it has been suggested that Pa 30 is the product of a failed thermonuclear explosion in a near- or super-Chandrasekhar white dwarf, which created a sub-luminous transient, a rare sub-type of the Ia class of supernovae called type Iax. We here present a detailed study of the 3D structure and velocities of a full radial section of the remnant. The Integral Field Unit (IFU) observations, obtained with the new red channel of the Keck Cosmic Web Imager spectrograph, reveal that the ejecta are consistent with being ballistic, with velocities close to the free-expansion velocity. Additionally, we detect a large cavity inside the supernova remnant and a sharp inner edge to the filamentary structure, which coincides with the outer edge of a bright ring detected in infrared images. Finally, we detect a strong asymmetry in the amount of ejecta along the line of sight, which might hint to an asymmetric explosion. Our analysis provides strong confirmation that the explosion originated from SN 1181.

Fast radio bursts (FRBs) are enigmatic millisecond-duration signals which encode otherwise unattainable information on the plasma which permeates our Universe, providing insights into magnetic fields and gas distributions. Here we report the discovery of FRB 20240304B originating at redshift 2.148 +/- 0.001 corresponding to just 3 billion years after the Big Bang. FRB 2024030 was detected with the MeerKAT radio telescope and localized to a low-mass, clumpy, star forming galaxy using the James Webb Space Telescope. This discovery doubles the redshift reach of localized FRBs and probes ionized baryons across ~80% of cosmic history. Its sightline, intersecting the Virgo Cluster and a foreground group, reveals magnetic field complexity over many gigaparsec scales. Our observations establish FRB activity during the peak of cosmic star formation and demonstrate that FRBs can probe galaxy formation during the most active era in cosmic time.

Understanding the noise characteristics of high quantum efficiency silicon-based ultraviolet detectors, developed by the Microdevices Lab at the Jet Propulsion Laboratory, is critical for current and proposed UV missions using these devices. In this paper, we provide an overview of our detector noise characterization test bench that uses delta-doped, photon counting, Electron-multiplying CCDs (EMCCDs) to understand the fundamental noise properties relevant to all silicon CCDs and CMOS arrays. This work attempts to identify the source of the dark current plateau that has been previously measured with photon-counting EMCCDs and is known to be prevalent in other silicon-based arrays. It is suspected that the plateau could be due to a combination of detectable photons in the tail of blackbody radiation of the ambient instrument, low-level light leaks, and a non-temperature-dependent component that varies with substrate voltage. Our innovative test setup delineates the effect of the ambient environment during dark measurements by independently controlling the temperature of the detector and surrounding environment. We present the design of the test setup and preliminary results.

We present the pilot study component of the Fluorescent Lyman-Alpha Structures in High-z Environments (FLASHES) Survey; the largest integral-field spectroscopy survey to date of the circumgalactic medium at \\(z=2.3-3.1\\). We observed 48 quasar fields between 2015 and 2018 with the Palomar Cosmic Web Imager (Matuszewski et al. 2010). Extended HI Lyman-\\(\\mathrm{\\alpha}\\) emission is discovered around 42/48 of the observed quasars, ranging in projected, flux-weighted radius from 21-71 proper kiloparsecs (pkpc), with 26 nebulae exceeding \\(100\\mathrm{~pkpc}\\) in effective diameter. The circularly averaged surface brightness radial profile peaks at a maximum of \\(\\mathrm{1\\times 10^{-17}~erg~s^{-1}~cm^{-2}~arcsec^{-2}}\\) (\\(2\\times10^{-15}~\\mathrm{erg~s^{-1}~cm^{-2}~arcsec^{-2}}\\) adjusted for cosmological dimming) and luminosities range from \\(1.9\\times10^{43}~\\mathrm{erg~s^{-1}}\\) to \\(-14.1\\times10^{43}~\\mathrm{erg~s^{-1}}\\). The emission appears to have a highly eccentric morphology and a maximum covering factor of \\(50\\%\\) (\\(60\\%\\) for giant nebulae). On average, the nebular spectra are red-shifted with respect to both the systemic redshift and Ly\\(\\alpha\\) peak of the quasar spectrum. The integrated spectra of the nebulae mostly have single or double-peaked line shapes with global dispersions ranging from \\(167~\\mathrm{km~s^{-1}}\\) to \\(690~\\mathrm{km~s^{-1}}\\), though the individual (Gaussian) components of lines with complex shapes mostly appear to have dispersions \\(\\leq 400\\) \\(\\mathrm{km~s^{-1}}\\), and the flux-weighted velocity centroids of the lines vary by thousands of \\( \\mathrm{km~s^{-1}}\\) with respect to the systemic QSO redshifts. Finally, the root-mean-square velocities of the nebulae are found to be consistent with gravitational motions expected in dark matter halos of mass \\(\\mathrm{M_h \\simeq10^{12.5} M_\\odot}\\). We compare these results to existing surveys at both higher and lower redshift.

FIREBall-2 is a stratospheric balloon-borne 1-m telescope coupled to a UV multi-object slit spectrograph designed to map the faint UV emission surrounding z~0.7 galaxies and quasars through their Lyman-alpha line emission. This spectro-imager had its first launch on September 22nd 2018 out of Ft. Sumner, NM, USA. Because the balloon was punctured, the flight was abruptly interrupted. Instead of the nominal 8 hours above 32 km altitude, the instrument could only perform science acquisition for 45 minutes at this altitude. In addition, the shape of the deflated balloon, combined with a full Moon, revealed a severe off-axis scattered light path, directly into the UV science detector and about 100 times larger than expected. In preparation for the next flight, and in addition to describing FIREBall-2's upgrade, this paper discusses the exposure time calculator (ETC) that has been designed to analyze the instrument's optimal performance (explore the instrument's limitations and subtle trade-offs).