Attenuation Length Research Articles

Immunogenicity and cross-protective efficacy induced by delayed attenuated Salmonella with regulated length of lipopolysaccharide in mice

ABSTRACT Non-typhoidal Salmonella enterica (NTS) is a major global foodborne pathogen that poses a major public health concern worldwide, and no vaccines are available for protecting against infection of multiple Salmonella serotypes, therefore, the development of Salmonella vaccines to provide broad protection is valuable. In this work, we aimed to regulate lipopolysaccharide (LPS) synthesis of live Salmonella in vivo for exposing conserved protein antigens on the outer membrane while maintaining smooth LPS patterns in vitro to keep their original ability to invade host cells for inducing cross-protection against infection of multiple Salmonella serotypes. We generated a series of mutants defective in genes to affect the length of LPS. These mutants exhibit in vivo regulated-delayed attenuation and altered length of LPS, and all these mutants were derived from SW067 (ΔpagL7 ΔpagP81::Plpp lpxE ΔlpxR9 Δfur9) containing ∆pagP81::Plpp lpxE mutation to reduce their endotoxic activity. Animal experiments demonstrated that all regulated delayed attenuated mutants exhibited reduced ability to colonize the organs of the mice, and SW114 (waaI), SW116 (waaJ), SW118 (waaL), and SW120 (wbaP) induced a significant production of IgG and IgA against OMPs isolated from S. Typhimurium, S. Enteritidis, and S. Choleraesuis. SW114 (waaI), SW116 (waaJ), and SW118 (waaL) were capable of conferring significant protection against infection of wild-type S. Enteritidis and S. Choleraesuis, with SW118 (waaL) triggering significant CD4+ T-cell responses as well as the B220low IgG+ BM cell. In conclusion, regulated delayed attenuated Salmonella vaccines with the whole core oligosaccharides of LPS showed a goo.d ability to expose conserved outer antigens and to trigger strong cross-immune responses against both homologous and heterologous Salmonella infections. These results give new insight into the development of the Salmonella vaccine against multiple serotypes of Salmonella.

Effect of radiation on the attenuation length of clear fiber

This paper focuses on measuring and describing the attenuation lengths of two types of clear fiber with distinct irradiation doses. By calculating the ratio of the ADC values of each irradiated fiber to that of the non-irradiated fiber, compared with the attenuation length of the non-irradiated fiber, the attenuation lengths of the irradiated fibers are obtained. It is found that the attenuation lengths of both fibers decreased with the irradiation dose, and the slope of the corresponding function is different.

Photodetectors performance of nanostructured materials in antimony III-V InGaAsSb/AlGaAsSb interband cascade structures

The aim of the study is to increase the performance of solar conversion by integrating nanostructured materials within conventional solar cells by employing multi-energy stages (i.e., interband and intersubband) in cascade systems to overcome the absorption length barrier and achieve large photo-generated carrier values. Specifically, InGaAsSb/Al GaAsSb MQWs are investigated with narrow well widths (2-20 nm) and transition energies of the structures are calculated for varied well/barrier widths and depths using numerical modelling. The results show that both interband and intersubband transitions are valuable for improving photovoltaic and photodetection applications, but their mechanisms and applications are distinct, so understanding and controlling these transitions within semiconductor materials is essential for optimising the performance of devices in both areas of optoelectronics, including strain as an important parameter of integrity. The data suggests that a single electron requires multiple photons to be transported, with the formation of a type-I broken-gap alignment between AlGa AsSb (barrier) and InGaAsSb (well). A wide range of wavelengths, from visible to medium infrared (MIR), will greatly enhance solar spectrum absorption. The long-term goal is to combine the thermal properties of antimonies (GaSbInSb) with a low band gap and the optical properties of arsenide (GaAsAlAs) with a large band gap.

CANDLES-III detector: Low-background spectrometer for studying neutrino-less double [formula omitted] decay of 48Ca

The CANDLES-III detector was installed at the Kamioka Observatory in Japan to investigate the double β decay of 48Ca. This system combines an undoped calcium fluoride scintillator with a long attenuation length (larger than 100 cm), and a two-phase liquid scintillator, thereby serving as a larger-mass detector of 305 kg (contains 350 g of 48Ca) while maintaining a high energy resolution (σ=2.6% at Q-value of 48Ca double beta decay). Low-background conditions are achieved in the energy region of interest by improving the light yield and collection efficiency of the detector system, allowing to access a high energy resolution, as well as by installing passive and active radiation shielding, and using pulse-shape analysis. This paper describes the details of the detector including its site and data acquisition system and presents its performance characterization.

LArRI — A new setup for Liquid Argon Refractive index measurement

Liquid argon (LAr), widely used as the active target in neutrino and dark matter experiments, is a scintillator with a light yield of approximately 40 photons/keV. The scintillation spectrum is centered at 128 nm, and the attenuation length is of the order of meters, depending on the purity. The addition of small amounts of dopants allows for shifting the scintillation peak simplifying the light detection and opening the possibility to the development of imaging systems. There is no precise knowledge of the optical properties of LAr in the VUV range, but it could be exploited to improve the performances of liquid argon-based experiments, especially when the involved mass is in the ton scale. LArRI (Liquid Argon Refractive Index) aims to directly measure the refractive index of LAr in the VUV spectrum, using an interferometric technique. The refractive index is obtained by comparing two interference patterns, created in vacuum and liquid, acquired with cryogenic silicon photomultipliers. This work primarily presents the methodology, the preliminary tests, and the analysis strategy, which are intended to be applied to real data shortly.

Performance of large-scale [formula omitted]Li-doped pulse-shape discriminating plastic scintillators

A 6Li-doped plastic scintillator with pulse-shape discrimination capabilities, commercially identified as EJ-299-50, has been developed and produced at the kilogram-scale. A total of 44 kg-scale bars of dimensions 5.5 cm x 5.5 cm x 50 cm of this material have been characterized. Optical properties like light output and effective attenuation length have been found to be comparable to 6Li-doped liquid scintillators. The scintillator EJ-299-50 shows good neutron detection capabilities with an effective efficiency for capture on 6Li of approximately 85%. Stability tests performed on two formulation variations showed no intrinsic degradation in the material or optical properties during several months of observations.

Distillation and gas stripping purification plants for the JUNO liquid scintillator

The optical and radiochemical purification of the scintillating liquid which will fill the detector of the JUNO experiment plays a crucial role in achieving its scientific goals. Given its gigantic mass and dimensions, and an unprecedented target value of about 3% at 1MeV in energy resolution, JUNO has set severe requirements on the parameters of its scintillator, such as attenuation length (Lat>20m at 430nm), light yield, and content of radioactive contaminants (238U,232Th<10-15g/g). To accomplish these needs, the scintillator will be processed using several purification methods, including distillation under vacuum and gas stripping, carried out in two large-scale plants installed at the JUNO site.In this paper, the layout, operating principles, and technical aspects which have driven the design and construction of the distillation and gas stripping plants are reviewed. The distillation is effective in enhancing the optical properties and removing high-boiling radioactive impurities (238U, 232Th, 40K), while the stripping process exploits pure water steam and high-purity nitrogen to extract gaseous contaminants (222Rn, 39Ar, 85Kr, O2) from the scintillator. The plant operating parameters have been tuned during the recent commissioning phase at the JUNO site and several quality control measurements and tests have been performed to evaluate the performances of the plants. Preliminary results on the efficiency of these purification processes will be shown.

High transparency Ce3+-doped oxyfluoride glass scintillator for X-ray imaging and γ-ray detection

High transparency Ce3+-doped dense gadolinium aluminum borosilicate (GSx) glass scintillator was synthesized in reducing atmosphere by melt-quenching process. The transmittance of the glasses exceeds 80%, and the light attenuation length is between 5-20 cm within the range of 400–600 nm. GSx glass shows an photoluminescence (PL) in range of 350–550 nm, with the strongest emission peak around 420 nm. The PL decay time of GSx glasses is around 37 ns, with a maximum PL quantum yield of 44.05%. The integrated X-ray excited luminescence (XEL) intensity of GSS glass is 52.5% compared with BGO crystal. For X-ray imaging, GSL glass based imaging system shows a high spatial resolution of 9 lp/mm, which is comparable to CsI:Tl X-ray detectors. Under γ-ray, the highest light yield of GSS glass is 1235 ph/MeV with an energy resolution of 24.0% at 662 keV, close to that of BSO crystal. The scintillation decay time of GSx glasses is consisted of fast (∼100 ns) and slow (∼560 ns) components. In thermally stimulated luminescence (TSL), GSS glass exhibits a strong TSL peak at approximately 440 K, with low intensity shoulders at about 520 K, implying different types of defects and traps. Therefore, GSx glass has promising prospects for X-ray imaging and high-energy physics applications.

Demonstration of an 8-Gbit/s quadrature-phase-shift-keying coherent underwater wireless optical communication link using coherent heterodyne detection under scattering conditions.

In this paper, we experimentally demonstrate an 8-Gbit/s quadrature-phase-shift-keying (QPSK) coherent underwater wireless optical communication (UWOC) link under scattering conditions at 532 nm. At the transmitter, we generate the 532-nm QPSK signal using second-harmonic generation (SHG), where the 1064-nm signal modulated with four phase levels of an 8-phase-shift-keying (8-PSK) format is phase doubled to produce the 532-nm QPSK signal. To enhance the receiver sensitivity, we utilize a local oscillator (LO) at the receiver from an independent laser source. The received QPSK data beam is mixed with the independent LO for coherent heterodyne detection. Results show that the bit error rates (BERs) of the received QPSK signal can reach below the 7% forward error correction (FEC) limit under turbid water with attenuation lengths (γL) up to 7.4 and 6.1 for 2- and 8-Gbit/s QPSK, respectively. The corresponding receiver sensitivities are -34.0 and -28.4 dBm for 2- and 8-Gbit/s QPSK, respectively.

Informing solar blind radioluminescence imaging through a calibrated spectrum

While direct radiation detection methods offer great insight into the origin of ionizing particles and photons, their use to locate contaminated areas or concealed radioactive sources can lead to undue exposure of personnel and equipment to ionizing radiation or the potential for contamination. These same sources induce ultraviolet (UV) optical photon fluorescence in air – a process referred to as radioluminescence – that may be imaged from low dose regions over larger attenuation lengths than ionizing radiation. However, most optical detection methods are limited to low lighting conditions to image the more abundant ultraviolet-A (UV-A) photons. To extend this capability to room light or daytime conditions, the solar blind region (Ultraviolet-C (UV–C), <280 nm) can be tapped. Though the emission yield of UV-C photons is roughly two orders of magnitude lower than that in the UV-A regime, the UV-C offers dramatic improvements in signal-to-noise ratios under bright lighting conditions due to decreased background interferences. The yield of specific UV-C lines, if present in the literature at all, varies widely, which has a large impact in modeling and analyzing standoff UV-C measurement scenarios. Thus, we have captured improved radioluminescence spectra over 250–400 nm and identified observed emission peaks in ambient air. Many of the UV-C photons produced by ionizing radiation excitation result from high-energy, molecular nitrogen Gaydon-Herman transitions which have had limited study to date for this application. Relating these findings to published UV-A yields, we estimate emissions between 0.15 and 0.19 photons/MeV over 250–280 nm. We also use a commercial corona-discharge imaging camera to demonstrate outdoor UV-C radiation mapping of alpha and gamma emitters from 50 to 75 m standoffs, respectively. The imaged “counts” are compared to optically modeled values and show the same trend over distance.

The Backscatter Gating method for time, energy, and position resolution characterization of long form factor organic scintillators

This work details a Compton-scattering-based methodology, referred to as Backscatter Gating (BSG), for characterizing the time, energy, and position resolutions of long form factor organic scintillators using a single, fairly minimal measurement setup. Such a method can ease the experimental burden in scenarios where many such scintillator elements may need to be individually characterized before assembly into a larger detector system. A thorough theoretical exploration of the systematic parameters is provided, and the BSG method is then demonstrated by a series of experimental measurements. This “complete” characterization via the BSG method is novel, having previously been used primarily for energy resolution characterization. The method also allows for determination of the assembled scintillator's technical attenuation length and provides a means of verifying the presence or absence of flaws within the scintillator or its optical coupling.

Reduction of lidar ranging error in turbulent water based on WT-ICA method

A new signal-processing method for the underwater lidar system based on wavelet transform (WT) and independent component analysis (ICA) is presented in this paper. Turbulence in water causes stronger scattering in underwater lidar returns, which can reduce the ranging accuracy and spatial resolution of the underwater lidar system. The method we proposed combines wavelet decomposition and independent component analysis (ICA), the data sets from wavelet decomposition are used to form the input matrix of ICA. The new method benefits from adaptive filtering of WT and blind source separation of ICA, therefore, the scattering clutters are further reduced. The WT-ICA signal processing algorithm is tested with experimental data. A mirror and a black Polyvinyl chloride (PVC) plate were used as the targets, respectively. Without using the WT-ICA, the ranging error with the mirror was 10.0 cm at 3 m distance when the attenuation coefficient of the water was 2.0 m-1. A pump was used to generate turbulence in the water tank. When the flow rate of the pump was 200 L/min, after using WT-ICA, the ranging error was reduced from 14.0 cm to 4.0 cm. For the PVC plate, the ranging errors were 4.5 cm and 19.0 cm at 6.0 attenuation length with and without the algorithm respectively. In both cases, applying this algorithm can significantly improve the ranging accuracy. When the algorithm is applied, the ranging error and detection probability of target echoes with and without turbulence were similar. These results indicated that the WT-ICA method had the ability to reduce the influence of turbulence.

Status of h-BN quasi-bulk crystals and high efficiency neutron detectors

III-nitrides have fomented a revolution in the lighting industry and are poised to make a huge impact in the field of power electronics. In the III-nitride family, the crystal growth and use of hexagonal BN (h-BN) as an ultrawide bandgap (UWBG) semiconductor are much less developed. Bulk crystals of h-BN produced by the high-temperature/high-pressure and the metal flux solution methods possess very high crystalline and optical qualities but are impractical to serve as substrates or for device implementation as their sizes are typically in millimeters. The development of crystal growth technologies for producing thick epitaxial films (or quasi-bulk or semi-bulk crystals) in large wafer sizes with high crystalline quality is a prerequisite for utilizing h-BN as an UWBG electronic material. Compared to traditional III-nitrides, BN has another unique application as solid-state neutron detectors, which however, also require the development of quasi-bulk crystals to provide high detection efficiencies because the theoretical efficiency (ηi) relates to the detector thickness (d) by ηi=1−e−dλ, where λ denotes the thermal neutron absorption length which is 47 μm (237 μm) for 10B-enriched (natural) h-BN. We provide an overview and recent progress toward the development of h-BN quasi-bulk crystals via hydride vapor phase epitaxy (HVPE) growth and the attainment of thermal neutron detectors based on 100 μm thick 10B-enriched h-BN with a record efficiency of 60%. The thermal neutron detection efficiency was shown to enhance at elevated temperatures. Benchmarking the crystalline and optical qualities of h-BN quasi-bulk crystals with the state-of-the-art mm-sized bulk crystal flakes and 0.5 μm thick epitaxial films identified that reducing the density of native defects such as vacancies remains the most critical task for h-BN quasi-bulk crystal growth by HVPE.

A novel design for 100 meter-scale water attenuation length measurement and monitoring

Water Cherenov detector is a vital part in most of neutrino or cosmic ray research. As detectors grow in size, the water attenuation length (WAL) becomes increasingly essential for detector performance. It is essential to measure or monitor the WAL. There are two ways to measure WAL, one is to take a water sample from the detector and measure it in the WAL measurement device, and the other is to put the device directly into the water Cherenkov detector. For the device in the water, the Super-Kamiokande experiment achieved WAL measurement capability near 100 meters with a moving light source up and down. A novel system has been proposed to address the challenge of investigating long WAL. This system focuses on ample water Cherenkov detectors and features a fixed light source and photomultiplier tubes (PMTs) at varying distances, eliminating the need for moving parts. Each component, including LED, diffuse ball, PMTs, and fibers, is introduced to explain uncertainty control. Based on lab tests, the measurement uncertainty of each PMT channel has been controlled within 5%. Additionally, camera technology is also used during the evaluation of the system uncertainty, which has the potential to replace PMTs in the future for this measurement. Monte Carlo simulations have shown that the system can achieve a 5% uncertainty at WAL of 80 meters and 8% at WAL of 100 meters. This system can be used in experiments with large Cherenkov detectors such as JUNO-water veto and Hyper-K.

Recovering Quasi-Biennial Oscillations from Chaos

Abstract The Quasi-Biennial Oscillation (QBO) is understood to result from wave-mean-flow interactions, but the reasons for its relative stability remain a subject of ongoing debate. In addition, consensus has yet to be reached regarding the respective roles of different equatorial wave types in shaping the QBO’s characteristics. Here we employ Holton-Lindzen-Plumb’s quasilinear model to shed light on the robustness of periodic behavior in the presence of multiple wave forcings. A comprehensive examination of the various dynamical regimes in this model reveals that increased vertical wave propagation at higher altitudes favors periodicity. In the case of single standing wave forcing, enhanced vertical propagation is controlled by the wave attenuation length scale. The occurrence of non-periodic states at high forcing amplitudes is explained by the excitation of high vertical unstable modes. Increasing the attenuation length scale prevents the emergence of such modes. When multiple wave forcing is considered, the mean flow generated by a dominant primary wave facilitates greater vertical propagation of a perturbation wave. Raising the altitude where most of the wave damping occurs favors periodicity by preventing the development of secondary jets responsible for the aperiodic behavior. This mechanism underscores the potential role of internal gravity waves in supporting the periodicity of a QBO primarily driven by planetary waves.

Performance of New Kuraray Wavelength-shifting Fibers with Short Decay Time

Abstract We measure the decay time and the attenuation length of newly developed wavelength-shifting fibers, the YS series, from Kuraray, which have a fast response. Using a 405 nm laser, the decay times of YS-2, 4, and 6 are measured to be 3.64 ± 0.04, 2.15 ± 0.03, and 1.47 ± 0.02 ns, respectively, for a light injection distance of 10 cm. The decay time of Y-11 is measured to be 7.10 ± 0.09 ns using the same system. All fibers are found to have similar attenuation lengths of more than 4 m. When combined with the plastic scintillators EJ-200 and EJ-204, the YS series has better time resolution than Y-11, with light yields of 60–100% of Y-11.

Atomically Contacted Cs3Bi2Br9 QDs@UiO-66 Composite for Photocatalytic CO2 Reduction.

Metal halide perovskite quantum dots (QDs) are widely studied in the field of photocatalytic CO2 due to their strong light absorption and long carrier migration length. However, it can not exhibit high catalytic performance because of the radiative recombination and the lack of effective catalytic sites. Metal organic frameworks (MOFs) encapsulated QDs can not only solve the aforementioned problems, but also maintain their own unique characteristics with ultra-high specific surfaces area and abundant metal sites. In this work, lead-free bismuth-based halide perovskite QDs are encapsulated into Zr-based MOF (UiO-66), which combines the advantages with high power conversion efficiency of QDs and the high surface area and porosity of UiO-66. In addition, benefiting from the close contact between the Cs3Bi2Br9 QDs and the UiO-66 enables the photogenerated electrons in the QDs to be rapidly transferred to the MOF. As a result, the Cs3Bi2Br9@UiO-66 composite exhibits a higher yield for photocatalytic CO2 reduction than that of the prepared large-sized composite of Cs3Bi2Br9 and UiO-66.

Study of polysterene based scintillator ageing in the DANSS experiment

DANSS is a spectrometer for reactor antineutrinos based on plastic scintillator. The sensitive volume of the detector is made of 2500 polystyrene based scintillator plates with wavelength shifting (WLS) fiber readout (strips). We present a study of the light yield of strips during 6.5 years of DANSS continuous running. Overall ageing at the rate 0.55 ± 0.05 (syst.) % per year is observed that is considerably smaller than in other similar experiments. We also observe the WLS fiber attenuation length shortening at the rate 0.26 ± 0.04(stat.) % per year.

A nearby source of ultra-high energy cosmic rays

Recently the Telescope Array collaboration reported an observation of cosmic ray event with very high energy 244 EeV (2.44 × 1020 eV). Importantly, the event is hard to correlate with the matter distribution in the local Universe, even after taking into account deflections in magnetic fields. This implies that the event is likely a nucleus with a large charge. An attenuation length of the nucleus of such a high energy in intergalactic space is quite small, therefore its source should be relatively close to our Galaxy. Using these arguments we derive a new upper bound on a distance to the closest ultra-high energy cosmic ray (UHECR) source and a lower bound on the UHECR source number density in general. The distance to the closest source should not exceed 5 Mpc at 95% C.L. and the 95% C.L. lower-bound on the sources number density is ρ > 1.0 × 10-4 Mpc-3. The number density of UHECR sources emitting heavy nuclei is constrained for the first time.

Extending UWOC System Applications through Photon Transmission Dynamics Study in Harbor Waters

Underwater wireless optical communication (UWOC) in harbor waters can facilitate real-time monitoring underwater instruments for environmental monitoring, underwater inspection, and maintenance tasks. This study delves into the complex dynamics of UWOC in four distinct harbor waters. The research employs Monte Carlo method incorporated with Fournier–Forand scattering phase function for simulating photon transmission. Key parameters such as the Transmitted full divergence angle, received aperture, and Field of View (FOV) are meticulously evaluated for their impact on power loss and time delay spread. Notably, the normalized power loss and time delay spread are found to be more significantly affected by communication distance than water quality, and the traditional Beer–Lambert law is ineffective in harbor water. The power loss of Harbor II, III, and IV are found to be 14.00 dB, 31.59 dB, and 41.59 dB lower than that of Harbor I, and the time delay spread of Harbor II, III, and IV is 30.56%, 9.67%, and 0.49% times that of the Harbor I under certain conditions. In addition, increasing the received aperture and FOV, particularly over longer distance, make little contribution to reduce the power loss and mitigate the time delay spread. Based on the fixed transmitted full divergence angle, the most applicable received FOV range is 1–3.2 rad, and the most ideal received aperture is 0.15–0.4 m. Under these conditions, the variation in normalized power loss is less than 2 dB. Additionally, the time delay spread remains within the same order of magnitude with the attenuation length (AL) held constant. These conclusions hold substantial technical relevance for the engineering design of UWOC systems in harbor waters.