Line Intensities Research Articles

Influence of species kinetics on discharge characteristics in oxygen helicon plasma

Abstract Oxygen (O2) helicon plasmas in multiple wave modes were excited by a right-helical antenna with an upper metal endplate at low pressure. Mode transitions were observed at increasing input power or magnetic field, characterized by obvious jumps of plasma parameters. Blue Core appears at high magnetic fields (~700 G) and input powers (~1700 W), with a large radial gradient of plasma density, ion line intensity, and electron temperature. Emission spectra demonstrate that the blue lights originate from O II lines. We found that the intensity ratio of O II to O I of Blue Core in O2 is lower by one order than that in N2 or Ar despite their similar ionization rates and plasma densities in Blue Core area. A high-temperature B-dot probe together with a waveform fitting procedure was used to present the measured oscillating waveforms of m =+1 helicon waves, showing distinct wave structures of different eigenmodes. Cavity mode resonance is suggested to be responsible for the formation of standing waves of discrete eigenmodes. A pressure balance model was developed to estimate the species densities around the central area in different modes, showing massive dissociation of O2 molecules and high density of O atoms locally, so that O2 helicon plasma behaves a species feature of monatomic gas discharge. The obviously low intensity of O II lines compared to O I lines of Blue Core in O2 is related to the quite high excitation threshold of O+ ions (~30 eV) although electron density and temperature are relatively high. The combined effects of dispersed reaction energy distribution, massive molecule dissociation and negative ion creation are considered to be the main causes for requirement of much higher RF power and magnetic field for Blue Core formation in O2 helicon plasma than that in Ar. The calculated radial profile of power deposition and the captured plasma morphology confirm that the dominant central electron heating is the essential reason for the large radial gradients of plasma density and electron temperature which contributes to the serious neutral depletion and Blue Core formation.

The CH3D Absorption Spectrum Near 1.58 μm: Extended Line Lists and Rovibrational Assignments

Monodeuterated methane (CH3D) contributes greatly to absorption in the 1.58 μm methane transparency window. The spectrum is dominated by the 3ν2 band near 6430 cm−1, which is observed in natural methane and used for a number of planetary applications, such as the determination of the D/H ratio. In this work, we analyze the CH3D spectrum recorded by high-sensitivity differential absorption spectroscopy in the 6099–6530 cm−1 region, both at room temperature and at 81 K. Following a first contribution to this topic by Lu et al., the room-temperature line list is elaborated (11,189 lines) and combined with the previous 81 K list (8962 lines) in order to derive about 4800 empirical lower-state energy values from the ratio of the line intensities measured at 81 K and 294 K (2T-method). Relying on the position and intensity agreements with the TheoReTS variational line list, about 2890 transitions are rovibrationally assigned to twenty bands, with fifteen of them being newly reported. Variational positions deviate from measurements by up to 2 cm−1, and the band intensities are found to be in good agreement with measurements. All the reported assignments are confirmed by Ground-State Combination Difference (GSCD) relations; i.e., all the upper-state energies (about 1370 in total) have coinciding determinations through several transitions (up to 8). The energy values, determined with a typical uncertainty of 10−3 cm−1, are compared to their empirical and variational counterparts. The intensity sum of the transitions assigned between 6190 and 6530 cm−1 represents 76.9 and 90.0% of the total experimental intensities at 294 K and 81 K, respectively.

Enhancing silicon spectral emission in LIBS using Tesla coil discharge

Laser-induced breakdown spectroscopy (LIBS) is a powerful technique for elemental analysis, offering rapid analysis, minimal sample preparation, wide elemental coverage, and portability. To enhance the detection sensitivity of LIBS, increasing the spectral emission intensity is crucial. This paper explores the use of Tesla coil (TC) discharge as an alternative to spark discharge in silicon LIBS. The study examines the influence of TC discharge on both time-integrated and time-resolved spectra, with and without TC discharge; the corresponding electron temperature and density are obtained. The results show that TC discharge significantly amplifies the spectral intensity, improving signal sensitivity in LIBS analysis. Specifically, in the laser energy range from 7.4 to 24.0 mJ, TC discharge increased the average spectral line intensities of Si (II) 385.60 nm and Si (I) 390.55 nm by factors of 8.4 and 5.1, respectively. Additionally, the average electron temperature and density were enhanced by approximately 3.2% and 4.2%, respectively, under TC discharge. The advantages of TC discharge include higher energy deposition, extended discharge duration, reduced electrode erosion, and enhanced safety. This research contributes to advancing LIBS technology and expanding its applications in various fields.

Measurements of line parameters for 12C16O2 near λ = 1.05 μm by cavity ring-down spectrometer

The absorption spectra of 12C16O2 within the wavenumber range of 9358–9648 cm−1 have been precisely measured using a continuous-wave cavity ring-down spectrometer at room temperature. Employing synthetic gas mixtures comprising carbon dioxide, nitrogen, and argon, the line parameters, including line intensities and self-, N2- and Ar- broadening coefficients have been retrieved in the 2003r-00001 (r = 1,2,3) bands. This retrieval process was facilitated by a multi-spectral fitting program that utilizes Voigt line profiles. A comparative analysis of our measured line intensities and self-broadening coefficients with those present in established databases, such as HITRAN2020, CDSD296, AMES-2021, and HITEMP2010, has been conducted. The line intensities and self-broadening coefficients for 12C16O2 deviate by an average of less than 1 % from the values reported in the HITRAN2020 database. The J-dependence of N2- and Ar- broadening coefficients has been investigated by comparing this work with experimental results and theoretical predictions from other vibrational bands. This research offers important experimental references for the improvement of computational models and the exploration of Venus and Mars.

Theoretical investigation of iodine plasma through detailed electron impact excitation cross-section calculations and collisional-radiative model analysis

Abstract In the present study, we consider the electron impact excitation of neutral iodine and its application in developing a collisional-radiative model for plasma diagnostics of iodine plasma. Electron impact excitation cross- sections are calculated using fully relativistic distorted wave theory. The required atomic structure calculations for iodine are carried out using the relativistic multi-configuration Dirac-Fock method. The excitation energies obtained are reported and compared with values from the NIST database. The electron impact excitation cross-sections are calculated from the ground (5p5 2P3/2) and first- excited state (5p5 2P1/2) to the several upper fine structure levels. Our cross- section results align well with previous studies, reported by Ambalampitiya et al. [Atoms, 9, 103, 2021] using the Breit-Pauli B-spline R-matrix method. Further calculated cross-section results are incorporated into the collisional-radiative model. Our model also includes electron impact ionization, de-excitation, three- body recombination, and radiative decay. We validate our model using emission spectra from inductively coupled iodine plasma. For this purpose, we used the recorded intensities for the emission lines, 486.23 nm, 511.92 nm, 523.45 nm, 589.40 nm, and 608.24 nm are compared with those obtained from our model to calculate electron temperature and electron density of the iodine plasma.

Forecasts and Statistical Insights for Line Intensity Mapping Cross-correlations: A Case Study with 21 cm × [C ii]

Intensity mapping—the large-scale mapping of selected spectral lines without resolving individual sources—is quickly emerging as an efficient way to conduct large cosmological surveys. Multiple surveys covering a variety of lines (such as the hydrogen 21 cm hyperfine line, carbon-monoxide rotational lines, and [C ii] fine-structure lines, among others) are either observing or will soon be online, promising a panchromatic view of our Universe over a broad redshift range. With multiple lines potentially covering the same volume, cross-correlations have become an attractive prospect, both for probing the underlying astrophysics and for mitigating observational systematics. For example, cross-correlating 21 cm and [C ii] intensity maps during reionization could reveal the characteristic scale of ionized bubbles around the first galaxies, while simultaneously providing a convenient way to reduce independent foreground contaminants between the two surveys. However, many of the desirable properties of cross-correlations in principle emerge only under ideal conditions, such as infinite ensemble averages. In this paper, we construct an end-to-end pipeline for analyzing intensity mapping cross-correlations, enabling instrumental effects, foreground residuals, and analysis choices to be propagated through Monte Carlo simulations to a set of rigorous error properties, including error covariances, window functions, and full probability distributions for power-spectrum estimates. We use this framework to critically examine the applicability of simplifying assumptions such as the independence and Gaussianity of power-spectrum errors. As worked examples, we forecast the sensitivity of near-term and futuristic 21 cm × [C ii] cross-correlation measurements, providing recommendations for survey design.

Integration of ML methods with CR model-based optical diagnostic for the estimation of electron temperature in Ga laser produced plasma

Accelerated diagnostic of plasma plays a significant role in controlling and optimizing plasma-mediated processing, particularly for plasma with higher temporal and spatial gradients, such as laser produced plasma (LPP). In the present work, two advanced machine learning (ML) algorithms, random forest regression, and gradient boosting regression are integrated with noninvasive collisional radiative (CR) model-based optical diagnostics to facilitate accurate diagnostics. A comprehensive fine-structure resolved CR model framework is developed by incorporating our consistent cross section data obtained from the Relativistic Distorted Wave method [Suresh et al., “Fully relativistic distorted wave calculations of electron impact excitation of gallium atom: Cross sections relevant for plasma kinetic modelling,” Spectrochim. Acta B: At. Spectrosc. 213, 106860 (2024)]. An extensive dataset of CR model simulated intensities is created to train and test the ML methods. The present CR model is applied to characterize the Gallium LPP coupling with the optical emission spectroscopic measurements of Guo et al. [“Time-resolved spectroscopy analysis of Ga atom in laser induced plasma,” Laser Phys. 19, 1832–1837 (2009)] at different delay times. Further, a detailed correlation study of the line intensity ratios is performed to observe the qualitative behavior of the plasma parameters. The electron temperature results obtained from the CR model, ML, and line ratio methods were compared and found to be in excellent agreement. Overall, the present study demonstrates diagnostic approaches that can benefit the LPP community significantly by providing a rapid understanding of the plasma behavior across various operating conditions.

Magnetic Field Alignment Relative to Multiple Tracers in the High-mass Star-forming Region RCW 36

We use polarization data from SOFIA HAWC+ to investigate the interplay between magnetic fields and stellar feedback in altering gas dynamics within the high-mass star-forming region RCW 36, located in Vela C. This region is of particular interest as it has a bipolar H ii region powered by a massive star cluster, which may be impacting the surrounding magnetic field. To determine if this is the case, we apply the histogram of relative orientations (HRO) method to quantify the relative alignment between the inferred magnetic field and elongated structures observed in several data sets such as dust emission, column density, temperature, and spectral line intensity maps. The HRO results indicate a bimodal alignment trend, where structures observed with dense gas tracers show a statistically significant preference for perpendicular alignment relative to the magnetic field, while structures probed by the photodissociation region (PDR) tracers tend to align preferentially parallel relative to the magnetic field. Moreover, the dense gas and PDR associated structures are found to be kinematically distinct such that a bimodal alignment trend is also observed as a function of line-of-sight velocity. This suggests that the magnetic field may have been dynamically important and set a preferred direction of gas flow at the time that RCW 36 formed, resulting in a dense ridge developing perpendicular to the magnetic field. However, on filament scales near the PDR region, feedback may be energetically dominating the magnetic field, warping its geometry and the associated flux-frozen gas structures, causing the observed preference for parallel relative alignment.

Toward electron temperature profiles in hot-dense plasmas from x-ray spectral ensembles

High repetition rate laser systems enable new strategies for diagnosing plasma behavior with large datasets. Here, we define an ensemble technique that relies on randomized targeting of x-ray tracer micro-stripes. On each shot, a high-intensity laser pulse is focused on a solid target with Ti tracer stripes embedded in an Al foil, randomly targeting a micro-stripe, a portion of a stripe, or a gap between stripes. High-resolution, time-integrated x-ray spectrometers capture line emission from the portion of the micro-stripe that is heated to sufficiently high electron temperatures. Accumulation of many such cases is used to construct ensemble distributions of x-ray line intensities that encompass all relative offsets of the laser focus to the micro-stripe centers. Synthetic intensity distributions are likewise generated using collisional-radiative modeling. Bayesian fitting of modeled to measured intensity distributions establishes the most likely radial temperature profiles, enabling comparison to hydrodynamic models and calling into question the cylindrical symmetry of these micro-stripe-embedded systems. Ensemble techniques have significant potential for high-energy-density plasma diagnostics, especially with the advent of high repetition rate experiments.

Electron-impact excitation data for W2+ in support of tungsten spectroscopy and re-deposition measurements for magnetically-confined plasmas

Abstract To better understand plasma wall interactions involving tungsten, accurate atomic structure and electron-impact driven collisional processes for near-neutral ion stages of tungsten are required. Complementing existing work on neutral and singly ionised tungsten, atomic structure and collisional calculations for W2+ electron-impact excitation have been completed. These excitation calculations are an important component of S/XB coefficients for near-neutral charge states, which may be used to spectroscopically infer re-deposition of tungsten at the plasma-solid boundary of fusion relevant devices. With W2+ in particular having emission lines that can be observed at ultraviolet (UV) wavelengths, while higher charge states of tungsten are unlikely to have lines possible to observe outside of the vacuum UV range. The atomic structure was generated using the General-purpose Relativistic Atomic Structure Package (GRASP0), implementing the Multi-configuration Dirac Fock approach. This structure was the basis for a subsequent Dirac R-matrix electron-impact excitation calculation to provide Maxwellian averaged rate coefficients. A synthetic spectrum was generated from this data using a collisional-radiative model to predict the strongest W III spectral lines and these lines were compared to emission from the Compact Toroidal Hybrid (CTH) plasma device. Several of the strongest W III lines are observed in CTH and agree well with the modelled line wavelengths and intensities, a table of these lines is provided that could be observed in other devices.

CII] line intensity mapping the epoch of reionization with the Prime-Cam on FYST. II. CO foreground masking based on an external catalog

The Fred Young Submillimeter Telescope (FYST) line intensity mapping (LIM) survey will measure the power spectrum (PS) of the singly ionized carbon 158 $ fine-structure line CII to trace the appearance of the first galaxies that emerged during and right after the epoch of reionization (EoR, $6<z<9$). We aim to quantify the contamination of the (post-)EoR CII LIM signal by foreground carbon monoxide (CO) line emission ($3 < J_ up < 12$) and assess the efficiency to retrieve this CII LIM signal by the targeted masking of bright CO emitters. Using the IllustrisTNG300 simulation, we produced mock CO intensity tomographies based on empirical star formation rate-to-CO luminosity relations. Combining these predictions with the CII PS predictions of the first paper of this series, we evaluated a masking technique where the interlopers are identified and masked using an external catalog whose properties are equivalent to those of a deep Euclid survey. Prior to masking, our CII PS forecast is an order of magnitude lower than the predicted CO contamination in the 225 GHz ( CII emitted at $z=6.8-8.3$) band of the FYST LIM survey, at the same level in its 280 GHz ( CII emitted at $z=5.3-6.3$) and 350 GHz ( CII emitted at $z=4.1-4.8$) bands, and an order of magnitude higher in its 410 GHz ( CII emitted at $z=3.4-3.9$) band. For our fiducial model, the optimal masking depth is reached when less than 10<!PCT!> of the survey volume is masked at 350 and 410 GHz but around 40<!PCT!> at 280 GHz and 60 <!PCT!> at 225 GHz. At these masking depths we anticipate a detection of the CII PS at 350 and 410 GHz, a tentative detection at 280 GHz, whereas at 225 GHz the CO signal still dominates our model. In the last case, alternative decontamination techniques will be needed.

Laser-induced plasma analysis of ammonia-oxygen and ammonia-oxygen-enriched-air flames at elevated pressures

This study employed Laser-induced breakdown spectroscopy (LIBS) to measure the fuel-oxidizer ratio (FOR) of ammonia combustion with oxygen-enriched air and pure oxygen flames at elevated pressures (100 - 300 kPa). The correlations between the spectral line intensity ratios of nitrogen (N), hydrogen (H), oxygen (O), and equivalence ratio were used to quantify the FOR of flames at various pressures. The effect of pressure on the stability and precision of the calibration profiles for the elemental intensity ratios in flames was investigated. It was observed that the H/O correlation decreases with pressure increase for both ammonia flames. N/O correlations decrease with elevated pressure for the ammonia-oxygen flame. Furthermore, the nitrogen (NII) spectral emission lines at 568 nm and 595 nm were used to estimate the plasma temperature, while the hydrogen (Hα) line at 656 nm was used for electron number density measurements.

Variabilities of Methanol Maser and Thermal Molecular Lines from an Accretion Burst Source G358.93-0.03

From 2019 January to June, the high-mass young stellar object G358.93-0.03 underwent a remarkable accretion burst. Detecting variations in the physical and kinematic environments during episodic accretion is essential for exploring such events. Searching for new maser or molecular lines and monitoring their variability during the accretion burst and postburst stages is feasible for such a study. Using the Purple Mountain Observatory 13.7 m telescope, we carried out monitoring of methanol masers and molecular lines toward G358.93-0.03 in the 3 mm band during the burst (2019 March to June) and postburst stages (2022 October). In addition to the previously abundant detection of the methanol maser lines in the burst stage, eight new methanol maser lines were detected, identified from transitions at 85.57, 93.20, 94.54, 94.82, 99.77, 102.96, 104.35, and 104.41 GHz. Their integrated intensity exhibited an exponential decline during the burst stage, likely associated with the decay process of the accretion burst. None of the eight methanol maser lines were detected in the postburst stage. Besides maser lines, 12 thermal molecular lines were detected in both the burst and postburst stages. Variability of some of them was observed in both stages, but most notably, the ratio of HCO+/N2H+ increased significantly in the burst stage compared to the postburst stage. It is likely caused by the changes of both molecular lines during the burst and postburst stages due to the heating process induced by episodic accretion. Therefore, the comparison of their line intensity ratios might offer a new method for tracing episodic accretion bursts.

H2 Fluorescent Emission from the Diffuse Interstellar Medium

Near-IR spectroscopy, which can now be performed at unprecedented sensitivity with the NIRSpec instrument on JWST, can offer a novel probe of diffuse clouds through the observation of H2 fluorescent emissions. Whereas previous observations of interstellar H2 fluorescent emissions were primarily confined to dense clouds lying close to a source of UV radiation, JWST opens the possibility of detecting such emissions from diffuse molecular clouds exposed to the average radiation field in the Galaxy. A simple analytic model is presented to predict the near-IR H2 fluorescent line intensities emitted by diffuse interstellar clouds with a Plummer density profile. It is applicable to sightlines where the column densities of H and H2 have been measured and the peak gas density can be estimated.

Direct estimates of nitrogen abundance for Seyfert 2 nuclei

Abstract We derive the nitrogen and oxygen abundances in the Narrow Line Regions (NLRs) of a sample of 38 local (z < 0.4) Seyfert 2 nuclei. For that, we consider narrow optical emission line intensities and direct estimates of the electron temperatures (Te-method). We obtain a new theoretical expression for the nitrogen Ionization Correction Factor [ICF($\rm N^{+}$)] for NLRs. Applying this new ICF, we unexpectedly find that NLRs and disk H ii regions exhibit similar ICF distributions. We find nitrogen abundances in the range $7.6 \: < \: \rm 12+log(N/H) \: < \: 8.6$ (mean value 8.06 ± 0.22) or $\rm 0.4 \: < \: (N/N_{\odot }) \: < 4.7$, in the metallicity regime $8.3 \: < \: \rm 12+log(O/H) \: < \: 9.0$. Our results indicate that the dispersion in N/H abundance for a fixed O/H value in AGNs of ∼0.2 dex agrees with that for disc H ii regions with similar metallicity. We show that Seyfert 2 nuclei follow a similar (N/O)-(O/H) relation to the one followed by star-forming objects. Finally, we find that active galaxies called as ”nitrogen-loud” observed at very high redshift (z > 5) show N/O values in consonance with those derived for local NLRs. This result indicates that the main star-formation event is completed in the early evolution stages of active galaxies.

Coexistence of H-MAR and N-MAR in divertor simulation experimental module of GAMMA 10/PDX

In a divertor simulation experimental module (D-module) of GAMMA 10/PDX, additional hydrogen seeding induces molecular-activated recombination (H-MAR). However, when seeding of hydrogen and nitrogen is combined, Nitrogen MAR (N-MAR) is observed in D-module. In this work, we experimentally investigate plasma detachment processes in D-module by seeding hydrogen-only and hydrogen + nitrogen in order to de-couple MARs contribution to the measured particle flux reduction. Nitrogen is seeded after the electron density, measured with Langmuir probes installed in D-module, begins to decrease due to hydrogen seeding. In both cases, the electron temperature near the V-shaped target decreases from ∼23 eV to ∼2 eV. A clear rollover is observed in the ion flux to the V-shaped target. When only hydrogen is seeded, the Balmer lines emission ratio (i.e. the intensity of Hα emission line (IHα)/the intensity of Hβ emission line (IHβ)), an indicator of H-MAR, is observed to increase between V-shaped targets installed in D-module as the amount of hydrogen gas increases. However, when both hydrogen and nitrogen are seeded, IHα/ IHβ increase is suppressed, and the region of the largest IHα/ IHβ signal shifts upstream of D-module, as observed by a high-speed camera. These results show for the first time the transition from H-MAR-dominated phase to N-MAR-dominated phase and the coexistence of both MARs in D-module. It is found that nitrogen seeding increases plasma detachment even at already relatively low Te (∼5 eV). The high-speed camera measurements suggest this effect to be related to the increase of NHx neutral density, in line with previous modeling works.

A-347 A Comprehensive Exdia TRF-LFIA for Simultaneous Quantification of GFAP and NT-proBNP in Distinguishing Ischemic and Hemorrhagic Stroke

Abstract Background The goal of this study is to create a highly sensitive time-resolved fluorescence lateral flow immunoassay (TRF-LFIA) capable of concurrently measuring glial fibrillary acidic protein (GFAP) and the N-terminal fragment of B-type natriuretic peptide precursor (NT-proBNP). This assay is designed as a diagnostic tool and aims to provide an algorithm for stroke management, specifically for distinguishing between Ischemic stroke (IS) and Hemorrhagic stroke (HS). However, LFIA to quantify simultaneous serum NT-proBNP and GFAP are not yet available. Methods We have developed and validated a novel TRF-LFIA for the simultaneous quantitative detection of NT-proBNP and GFAP. The sensitivity and reproducibility of the immunoassay were significantly improved by employing specific monoclonal antibodies linked to europium nanoparticles (EuNPs) that specifically target NT-proBNP and GFAP. The detection area on the nitrocellulose membrane featured sandwich-style complexes containing three test lines for NT-proBNP, GFAP, and Control. The fluorescence intensity of these test lines on the nitrocellulose membrane was measured using an in-house developed Exdia TRF-Plus analyzer. As proof-of-concept, we enrolled patients suspected of having a stroke who were admitted within a specific time frame (6 hours). A small amount of clinical specimen (serum) was used with a well-assembled cartridge for the measurement of GFAP and NT-proBNP. Results To optimize the LFIA, an EuNPs conjugated antibodies were investigated to improve the detection sensitivity and decrease the background signal as well shorten the detection time. The Exdia TRF-LFIA cartridge offers a wide linear dynamic detection range, rapid detection, high sensitivity, and specificity. The limit of detection was determined to be 98 pg/mL for NT-proBNP and 68 pg/mL for GFAP, with minimal cross-reactivity. There were 200 clinical human serum samples that were used to evaluate this platform with high correlation. By combining the results of NT-proBNP and GFAP, we formulated an algorithm for the clinical assessment of Ischemic Stroke (IS) and Hemorrhagic Stroke (HS). According to our proposed algorithm, the combination of GFAP and NT-proBNP emerged as the most effective biomarker combination for distinguishing between IS and HS. Conclusions Exdia TRF-LFIA shows great potential as a supplemental method for in vitro diagnostics in the laboratory or in other point-of-care testing (POCT) applications. Its development substantially decreases the diagnosis time for IS and HS. The proposed algorithm not only minimizes treatment delays but also lowers medical costs for patients.

A-346 Evaluating 14-3-3η Detection in Finger Prick Blood Using Lateral Flow Technology: Advancing Clinical Laboratory Diagnostics

Abstract Background The protein 14-3-3η is a critical biomarker in the diagnosis and monitoring of autoimmune rheumatologic disorders, and its early detection is pivotal for patient outcomes. Previous research has established the significance of 14-3-3η as a biomarker, particularly in inflammatory polyarthritis, as well as patients’ and physicians’ interest in near-patient testing. While 14-3-3η is traditionally measured in serum via ELISA, this study explores the innovative use of lateral flow technology (LFT) for its detection in finger prick blood, addressing the urgent need for near-patient testing.This research aims to evaluate the technical and clinical performance of 14-3-3η measurement using LFT in comparison to standard ELISA methods, with an emphasis on its detectability in finger prick blood. Methods This study included two phases of testing involving patient serum and spiked whole blood. In the serum phase, 53 samples (19 NEG, ≤0.19 ng/mL, and 34 POS, 0.27 to 28 ng/mL 14-3-3η) were tested using LFT. LFT results were compared to JOINTstat® ELISA measurements for concordance. For whole blood, recombinant 14-3-3η and ELISA-positive serum samples were spiked into whole blood at increasing concentrations (0.4 to 3.2 ng/mL) and tested with LFT. Concordance criteria included visual inspection of test and control lines, with results captured and analyzed using a reference key card. The study was extended to assess 14-3-3η levels in consented patients with 22 matched finger prick and venous serum samples​​. Results In serum testing, LFT demonstrated 100% positivity in detecting 14-3-3η for POS samples. Among NEG samples, 85% tested negative, with 15% positive, indicating a strong concordance between LFT and ELISA. The LFT's ability to semi-quantitatively measure 14-3-3η was confirmed by a significant Kruskal-Wallis test (p<0.0001) across four intensity groups. In whole blood testing, LFT correctly identified all samples spiked at concentrations ≥0.5 ng/mL. The Spearman correlation showed a strong and significant association (r=0.96 to 0.98, p=0.001) between LFT test line intensity and spiked 14-3-3η levels. Finally, the equivalence testing for finger prick and venous serum samples affirmed the LFT’s reliability, with a strong correlation (p<0.0001), underscoring its potential for near-patient testing​​. Conclusions The study validates LFT as a reliable and semi-quantitative method for detecting 14-3-3η in finger prick blood, demonstrating strong concordance with traditional ELISA measurements. The findings support the feasibility of LFT in near-patient testing for early detection, prognosis, and monitoring of autoimmune diseases, paving the way for enhanced patient accessibility. Future research will focus on integrating this technology into routine clinical care and examining its impact on patient management and outcomes.

Searching for redshifted 2.2 MeV neutron-capture lines from accreting neutron stars: Theoretical X-ray luminosity requirements and INTEGRAL/SPI observations

Accreting neutron stars (NSs) are expected to emit a redshifted 2.2 MeV line due to the capture of neutrons produced through the spallation processes of 4He and heavier ions in their atmospheres. Detecting this emission would offer an independent method for constraining the equation of state of NSs and provide valuable insights into nuclear reactions occurring in extreme gravitational and magnetic environments. Typically, a higher mass accretion rate is expected to result in a higher 2.2 MeV line intensity. However, when the mass accretion rate approaches the critical threshold, the accretion flow is decelerated by the radiative force, leading to a less efficient production of free neutrons and a corresponding drop in the flux of the spectral line. This makes the brightest X-ray pulsars unsuitable candidates for γ-ray line detection. In this work, we present a theoretical framework for predicting the optimal X-ray luminosity required to detect a redshifted 2.2 MeV line in a strongly magnetized NS. As the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) mission nears its conclusion, we have undertaken a thorough investigation of the SPectrometer on board INTEGRAL (SPI) data of this line in a representative sample of accreting NSs. No redshifted 2.2 MeV line was detected. For each spectrum, we have determined the 3σ upper limits of the line intensity, assuming different values of the line width. Although the current upper limits are still significantly above the expected line intensity, they offer valuable information for designing future gamma-ray telescopes aimed at bridging the observational MeV gap. Our findings suggest that advancing our understanding of the emission mechanism of the 2.2 MeV line, as well as the accretion flow responsible for it, will require a substantial increase in sensitivity from future MeV missions. For example, for a bright X-ray binary such as Sco X−1, we would need at least a 3σ line point source sensitivity of ≈10−6 ph cm−2 s−1, that is, about two orders of magnitude better than that currently achieved.

In-situ relative calibration of Bragg crystals with Monte Carlo line ratio analysis.

X-ray line emission spectra can thoroughly characterize hot plasmas, especially when line shapes and ratios convey distinct aspects of plasma conditions. However, the high spectral resolution required for observing line shapes is often at odds with the large bandwidth required to observe many line ratios across a wide spectral range. One strategy to obtain high spectral resolution over a wide bandwidth is to use multiple crystals with calibrated reflectivity so that line intensities across different crystals can be compared. Here, we explore the use of a low-resolution, wide-bandwidth mica survey spectrometer to infer relative reflectivity of two high-resolution, narrow-bandwidth quartz crystals. A Monte Carlo error analysis determines comparable x-ray line ratios measured from both spectrometers, resulting in an in situ calibration factor and associated uncertainty for the relative reflectivity of the high-resolution crystals.