Spectral Slope Research Articles

Spectrophotometric properties of CoPhyLab’s dust mixtures

ABSTRACT Objective: In the framework of the Cometary Physics Laboratory (CoPhyLab) and its sublimation experiments of cometary surface analogues under simulated space conditions, we characterize the properties of intimate mixtures of juniper charcoal and SiO2 chosen as a dust analogue (Lethuillier et al. 2022). We present the details of these investigations for the spectrophotometric properties of the samples. Methods: We measured these properties using a hyperspectral imager and a radio-goniometer. From the samples’ spectra, we evaluated reflectance ratios and spectral slopes. From the measured phase curves, we inverted a photometric model for all samples. Complementary characterizations were obtained using a pycnometer, a scanning electron microscope and an organic elemental analyser. Results: We report the first values for the apparent porosity, elemental composition, and VIS-NIR spectrophotometric properties for juniper charcoal, as well as for intimate mixtures of this charcoal with the SiO2. We find that the juniper charcoal drives the spectrophotometric properties of the intimate mixtures and that its strong absorbance is consistent with its elemental composition. We find that SiO2 particles form large and compact agglomerates in every mixture imaged with the electron microscope, and its spectrophotometric properties are affected by such features and their particle-size distribution. We compare our results to the current literature on comets and other small Solar system bodies and find that most of the characterized properties of the dust analogue are comparable to some extent with the spacecraft-visited cometary nuclei, as well as to Centaurs, Trojans, and the bluest TNOs.

Coevolution and Nuclear Structure in the Dwarf Galaxy POX 52 Studied by Multiwavelength Data from Radio to X-Ray

The nearby dwarf galaxy POX 52 at z = 0.021 hosts an active galactic nucleus (AGN) with a black hole (BH) mass of M BH ∼ 105–6 M ⊙ and an Eddington ratio of ∼0.1–1. This object provides the rare opportunity to study both AGN and host-galaxy properties in a low-mass highly accreting system. To do so, we collected its multiwavelength data from X-ray to radio. First, we construct a spectral energy distribution, and by fitting it with AGN and host-galaxy components, we constrain AGN-disk and dust-torus components. Then, while considering the AGN-disk emission, we decompose optical Hubble Space Telescope images. As a result, it is found that a classical bulge component is probably present, and its mass (M bulge) is consistent with an expected value from a local relation. Lastly, we analyze new quasi-simultaneous X-ray (0.2–30 keV) data obtained by the Nuclear Spectroscopic Telescope Array and XMM-Newton. The X-ray spectrum can be reproduced by multicolor blackbody, warm and hot coronae, and disk and torus reflection components. Based on this, the spin is estimated to be a spin = 0.998−0.814, which could suggest that most of the current BH mass was achieved by prolonged mass accretion. Given the presence of the bulge, POX 52 would have undergone a galaxy merger, while the M BH–M bulge relation and the inferred prolonged accretion could suggest that AGN feedback occurred. Regarding the AGN structure, the spectral slope of the hot corona, its relative strength to the bolometric emission, and the torus structure are found to be consistent with Eddington-ratio dependencies found for nearby AGNs.

Neural complexity and the spectral slope characterise auditory processing in wakefulness and sleep.

Auditory processing and the complexity of neural activity can both indicate residual consciousness levels and differentiate states of arousal. However, how measures of neural signal complexity manifest in neural activity following environmental stimulation and, more generally, how the electrophysiological characteristics of auditory responses change in states of reduced consciousness remain under-explored. Here, we tested the hypothesis that measures of neural complexity and the spectral slope would discriminate stages of sleep and wakefulness not only in baseline electroencephalography (EEG) activity but also in EEG signals following auditory stimulation. High-density EEG was recorded in 21 participants to determine the spatial relationship between these measures and between EEG recorded pre- and post-auditory stimulation. Results showed that the complexity and the spectral slope in the 2-20 Hz range discriminated between sleep stages and had a high correlation in sleep. In wakefulness, complexity was strongly correlated to the 20-40 Hz spectral slope. Auditory stimulation resulted in reduced complexity in sleep compared to the pre-stimulation EEG activity and modulated the spectral slope in wakefulness. These findings confirm our hypothesis that electrophysiological markers of arousal are sensitive to sleep/wake states in EEG activity during baseline and following auditory stimulation. Our results have direct applications to studies using auditory stimulation to probe neural functions in states of reduced consciousness.

The utility of wearable headband electroencephalography and pulse photoplethysmography to assess cortical and physiological arousal in individuals with stress-related mental disorders.

Several stress-related mental disorders are characterised by disturbed sleep, but objective sleep biomarkers are not routinely examined in psychiatric patients. We examined the use of wearable-based sleep biomarkers in a psychiatric sample with headband electroencephalography (EEG) including pulse photoplethysmography (PPG), with an additional focus on microstructural elements as especially the shift from low to high frequencies appears relevant for several stress-related mental disorders. We analysed 371 nights of sufficient quality from 83 healthy participants and those with a confirmed stress-related mental disorder (anxiety-affective spectrum). The median value of macrostructural, microstructural (spectral slope fitting), and heart rate variables was calculated across nights and analysed at the individual level (N = 83). The headbands were accepted well by patients and the data quality was sufficient for most nights. The macrostructural analyses revealed trends for significance regarding sleep continuity but not sleep depth variables. The spectral analyses yielded no between-group differences except for a group × age interaction, with the normal age-related decline in the low versus high frequency power ratio flattening in the patient group. The PPG analyses showed that the mean heart rate was higher in the patient group in pre-sleep epochs, a difference that reduced during sleep and dissipated at wakefulness. Wearable devices that record EEG and/or PPG could be used over multiple nights to assess sleep fragmentation, spectral balance, and sympathetic drive throughout the sleep-wake cycle in patients with stress-related mental disorders and healthy controls, although macrostructural and spectral markers did not differ between the two groups.

Increased dominance of terrestrial component in dissolved organic matter in Chinese lakes

The source composition of chromophoric dissolved organic matter (CDOM) in lakes is closely related to regional environmental changes, human activities, and the carbon cycle. The spectral slope ratio (SR) is an important parameter of CDOM optical components, and combined with remote sensing technology, the source composition of CDOM can be tracked comprehensively and efficiently in large regions. Here, we proposed a CDOM source tracking remote sensing model (CDOM-SR) based on the hue angle (α) to assess the spatial pattern and long-term trend of the CDOM source composition in Chinese lakes (surface area ≥ 1 km2) from 1986 to 2021. Validation results show that the CDOM-SR model has a good SR estimation performance with a median absolute percentage difference, root mean square deviation, median ratio, and median deviation of 17.91 %, 0.23, 1.02, and 0.03, respectively. We found that the average SR of Chinese lakes presents an obvious spatial pattern of high in the west and low in the east due to the difference in human activity intensity and the natural geographical environment. Additionally, we found that the average SR of Chinese lakes from 1986 to 2021 decreased at a rate of - 0.06/10 years, of which 64.37 % of lakes decreased significantly, 15.42 % of lakes had no significant change, and only 20.20 % of lakes increased. The widespread decrease in the average SR indicates that the increasing human activity discharge of terrestrial organic matter has had an important impact on the source composition of the CDOM in Chinese lakes. Our results provide a new resource for remote sensing monitoring of CDOM sources and important insights into lake carbon cycling under the influence of ongoing human activities.

Activity in Centaur-like Jupiter-family Comet 2023 RN3

We present multi-filter observations of Centaur-like Jupiter-family comet 2023 RN3 conducted as part of the Las Cumbres Observatory Outbursting Objects Key Project, as well as analysis of archival data in which 2023 RN3 was expected to be present. We find clear evidence of comet-like mass loss in the form of an extended morphology on UT 2023 November 16 and 18, and an increase in intrinsic brightness of >4 mag between 2022 September and 2023 November. We also report broadband colors for the coma of , , and , giving a spectral slope of /100 nm.

Near-IR Spectral Observations of the Didymos System: Daily Evolution Before and After the DART Impact Indicates that Dimorphos Originated from Didymos

Ejecta from Dimorphos following the DART mission impact significantly increased the brightness of the Didymos–Dimorphos system, allowing us to examine subsurface material. We report daily near-IR spectroscopic observations of the Didymos system using NASA’s IRTF that follow the evolution of the spectral signature of the ejecta cloud over 1 week, from 1 day before the impact. Overall, the spectral features remained fixed (S-type classification) while the ejecta dissipated, confirming that both Didymos and Dimorphos are constructed from the same silicate material. This novel result strongly supports binary asteroid formation models that include the breaking up of a single body due to rotational breakup of kilometer-wide bodies. At impact time +14 and +38 hr, the spectral slope decreased, but the following nights presented an increasing spectral slope that almost returned to the preimpact slope. However, the parameters of the 1 μm band remained fixed, and no “fresh”/Q-type-like spectrum was measured. We interpret this as follows. (1) The ejecta cloud is the main contributor (60%–70%) to the overall light during the ∼40 hr after impact. (2) Coarser debris (≥100 μm) dominated the ejecta cloud, decreasing the spectral slope (after radiation pressure removed the fine grains ≤10 hr after impact). (3) After approximately 1 week, the ejecta cloud dispersed enough to make the fine grains on Didymos’s surface the dominant part of the light, increasing the spectral slope to the preimpact level. (4) A negligible amount of nonweathered material was ejected from Dimorphos’s subsurface, suggesting that Dimorphos was accumulated from weathered material ejected from Didymos’s surface.

Contrasting optical properties of dissolved organic matter between oceanic regions near the Getz and Dotson ice shelves in the Amundsen Sea, West Antarctica

The Amundsen Sea, located in West Antarctica, is experiencing rapid melting due to the intrusion of Circumpolar Deep Water, which is causing ice sheet thinning and basal melting. The resulting changes can affect the biogeochemical cycle of dissolved organic matter (DOM) by supplying iron from sea ice and/or glacier, thereby influencing primary production and ocean circulation. Therefore, it is crucial to understand the dynamics of the DOM in this region. In this study, our primary focus was to examine the optical properties of DOM in the oceanic regions adjacent to the West Getz Ice Shelf (WGIS) and the Dotson Ice Shelf (DIS). Significant differences in DOM optical properties, including the chromophoric DOM (CDOM) absorption coefficient at 350 nm (a350), spectral slope coefficient (S275–295), and specific UV absorbance at 254 nm (SUVA254), were observed between the WGIS and DIS regions (t-test, p < 0.05). Notably, the WGIS regions exhibited high a350 values. Additionally, the S275–295 and SUVA254 values, which serve as indices of molecular weight, indicated that the DOM pool in the WGIS regions was dominated by high molecular weight compounds with a substantial proportion of aromatic compounds. In contrast, the low values of a350 and SUVA254 along with the high S275–295 values in the DIS region suggested the dominance of low molecular weight CDOM associated with compounds of lower aromaticity. Furthermore, significant negative correlations were found between biomass of Phaeocystis antarctica (P. antarctica) and phosphate (PO4) in the WGIS regions (r2 = 0.82, p < 0.01 for WGIS 1 and r2 = 0.73, p < 0.01 for WGIS 2). However, no significant relationship was observed in the DIS region. These findings suggest that the high value and molecular weight of a350, extending from the surface layer to the deep layer, in the WGIS regions were associated with autochthonous sources, primarily driven by the colony-forming bloom of P. antarctica. These findings demonstrate that the quantity and quality of DOM in the Amundsen Sea are strongly affected by bloom conditions. The results emphasize that a combination of physical and biological processes interacts in complex ways to determine the characteristics of DOM in the Amundsen Sea.

Thyroid nodule characterization using Spectral Detector Computed Tomography (SDCT) in comparison to ultrasound

ObjectiveTo characterize thyroid nodules seen on Spectral Detector computed tomography (SDCT) in respect to their Thyroid Imaging Reporting and Data System (TI-RADS) category on Ultrasound (US). MethodsWe included patients that underwent US examination for the evaluation of thyroid nodules and contrast-enhanced SDCT examination of the neck/thorax, between the years 2018–2020. The SDCT and US were performed within 6 months of each other. Only patients with a visible thyroid nodule on SDCT were included. Attenuation measurements of the nodules in Hounsfield units (HU) were performed on the conventional CT images, virtual non-contrast (VNC) images and virtual monoenergetic images of 40 keV and 100 keV. The Iodine concentration, spectral slope and enhancement estimation results of the nodules were measured. We compared the spectral results between two groups of nodules, according to the US report: TI-RADS 2–3 and TI-RADS 4–5 groups. ResultsThirty-eight nodules were included in the study, 22 nodules in the TI-RADS 2–3 group and 16 in the TI-RADS 4–5 group. The nodules of the TI-RADS 4–5 group had significantly higher Iodine concentration measurement, 4.6 ± 1.8 mg/ml, compared to 2.3 ± 1.2 mg/ml in the TI-RADS 2–3 group; significantly higher estimated enhancement, 3.9 ± 1.5, compared to 2.2 ± 0.7; and significantly higher calculated spectral slope, 5.6 ± 2.2 compared to 2.9 ± 1.5 (p < 0.001). ConclusionSpectral results of SDCT may assist in differentiating intermediate-high risk (TI-RADS 4–5) from low risk (TI-RADS 2–3) thyroid nodules.Advances in knowledge: SDCT offers additional information for the characterization of thyroid nodules.

The apparent quantum yield matrix (AQY-M) of CDOM photobleaching in estuarine, coastal, and oceanic surface waters

The photochemical degradation of chromophoric dissolved organic matter (CDOM) upon solar exposure, known as photobleaching, can significantly alter the optical properties of the surface ocean. By leading to the breakdown of UV- and visible-radiation-absorbing moieties within dissolved organic matter, photobleaching regulates solar heating, the vertical distribution of photochemical processes, and UV exposure and light availability to the biota in surface waters. Despite its biogeochemical and ecological relevance, this sink of CDOM remains poorly quantified. Efforts to quantify photobleaching globally have long been hampered by the inherent challenge of determining representative apparent quantum yields (AQYs) for this process, and by the resulting lack of understanding of their variability in natural waters. Measuring photobleaching AQY is made challenging by the need to determine AQY matrices (AQY-M) that capture the dual spectral dependency of this process (i.e., magnitude varies with both excitation wavelength and response wavelength). A new experimental approach now greatly facilitates the quantification of AQY-M for natural waters, and can help address this problem. Here, we conducted controlled photochemical experiments and applied this new approach to determine the AQY-M of 27 contrasting water samples collected globally along the land-ocean aquatic continuum (i.e., rivers, estuaries, coastal ocean, and open ocean). The experiments and analyses revealed considerable variability in the magnitude and spectral characteristics of the AQY-M among samples, with strong dependencies on CDOM composition/origin (as indicated by the CDOM 275–295-nm spectral slope coefficient, S275–295), solar exposure duration, and water temperature. The experimental data facilitated the development and validation of a statistical model capable of accurately predicting the AQY-M from three simple predictor variables: 1) S275–295, 2) water temperature, and 3) a standardized measure of solar exposure. The model will help constrain the variability of the AQY-M when modeling photobleaching rates on regional and global scales.

Post-training sleep modulates motor adaptation and task-related beta oscillations.

Motor adaptation reflects the ability of the brain's sensorimotor system to flexibly deal with environmental changes to generate effective motor behaviour. Whether sleep contributes to the consolidation of motor adaptation remains controversial. In this study, we investigated the impact of sleep on motor adaptation and its neurophysiological correlates in a novel motor adaptation task that leverages a highly automatised motor skill, that is, typing. We hypothesised that sleep-associated memory consolidation would benefit motor adaptation and induce modulations in task-related beta band (13-30 Hz) activity during adaptation. Healthy young male experts in typing on the regular computer keyboard were trained to type on a vertically mirrored keyboard while brain activity was recorded using electroencephalography. Typing performance was assessed either after a full night of sleep with polysomnography or a similar period of daytime wakefulness. Results showed improved motor adaptation performance after nocturnal sleep but not after daytime wakefulness, and decreased beta power: (a) during mirrored typing as compared with regular typing; and (b) in the post-sleep versus the pre-sleep mirrored typing sessions. Furthermore, the slope of the electroencephalography signal, a measure of aperiodic brain activity, decreased during mirrored as compared with regular typing. Changes in the electroencephalography spectral slope from pre- to post-sleep mirrored typing sessions were correlated with changes in task performance. Finally, increased fast sleep spindle density (13-15 Hz) during the night following motor adaptation training was predictive of successful motor adaptation. These findings suggest that post-training sleep modulates neural activity supporting adaptive motor functions.

Prompt gamma-ray burst emission from internal shocks – new insights

ABSTRACT Internal shocks are a leading candidate for the dissipation mechanism that powers the prompt γ-ray emission in gamma-ray bursts (GRBs). In this scenario a compact central source produces an ultra-relativistic outflow with varying speeds, causing faster parts or shells to collide with slower ones. Each collision produces a pair of shocks – a forward shock (FS) propagating into the slower leading shell and a reverse shock (RS) propagating into the faster trailing shell. The RS’s lab-frame speed is always smaller, while the RS is typically stronger than the FS, leading to different conditions in the two shocked regions that both contribute to the observed emission. We show that optically thin synchrotron emission from both (weaker FS + stronger RS) can naturally explain key features of prompt GRB emission such as the pulse shapes, time evolution of the νFν peak flux and photon energy, and the spectrum. Particularly, it can account for two features commonly observed in GRB spectra: (i) a sub-dominant low-energy spectral component (often interpreted as ‘photospheric’-like), or (ii) a doubly broken power-law spectrum with the low-energy spectral slope approaching the slow-cooling limit. Both features can be obtained while maintaining high-overall radiative efficiency without any fine tuning of the physical conditions.

Neural network spectral relationship to improve an inherent optical properties data processing system for residual error correction.

The residual error was a critical indicator to measure the data quality of ocean color products, which allows a user to decide the valuable envisioned application of these data. To effectively remove the residual errors from satellite remote sensing reflectance (Rrs) using the inherent optical data processing system (IDAS), we expressed the residual error spectrum as an exponential plus linear function, and then we developed neural network models to derive the corresponding spectral slope coefficients from satellite Rrs data. Coupled with the neural network models-based spectral relationship, the IDAS algorithm (IDASnn) was more effective than an invariant spectral relationship-based IDAS algorithm (IDAScw) in reducing the effects of residual errors in Rrs on IOPs retrieval for our synthetic, field, and Chinese Ocean Color and Temperature Scanner (COCTS) data. Particularly, due to the improved spectral relationship of the residual errors, the IDASnn algorithm provided more accurate and smoother spatiotemporal ocean color product than the IDAScw algorithm for the open ocean. Furthermore, we could monitor the data quality with the IDASnn algorithm, suggesting that the residual error was exceptionally large for COCTS images with low effective coverage. The product effective coverage should be rigorously controlled, or the residual error should be accurately corrected before temporal and spatial analysis of the COCTS data. Our results suggest that an accurate spectral relationship of residual errors is critical to determine how well the IDAS algorithm corrects for residual error.

Investigating Diurnal and Seasonal Turbulence Variations of the Martian Atmosphere Using a Spectral Approach

We use a spectral approach to analyze the pressure and wind data from the InSight mission and investigate the diurnal and seasonal trends. Our analyses show that the daytime pressure and wind spectra have slopes of approximately −1.7 and −1.3 and, therefore, do not follow the Kolmogorov scaling (as was also previously reported for a reduced data set in Banfield et al.). We find that the nighttime pressure spectral slope is close to −1 (as reported in Temel et al.), and that the wind speed spectral slope is close to −0.5, flatter than the theoretical slope expected for the shear-dominated regime. We observe strong nocturnal (likely shear-generated) turbulent behavior starting around L s = 150° (InSight sol 440) that shifts to progressively earlier local times before reaching the “5th season” (InSight sols 530–710) identified by Chatain et al.. The diurnal spectral slope analyses indicate an asymmetry in the diurnal behavior of the Martian boundary layer, with a slow growth and fast collapse mechanism. Finally, the low-frequency (5–30 mHz) pressure data exhibit large spectral slope oscillations. These occur particularly during the periods with a highly stable atmosphere and, therefore, may be linked to gravity wave activity.

Compositional properties of planet-crossing asteroids from astronomical surveys

Context. The study of planet-crossing asteroids is of both practical and fundamental importance. As they are closer than asteroids in the Main Belt, we have access to a smaller size range, and this population frequently impacts planetary surfaces and can pose a threat to life. Aims. We aim to characterize the compositions of a large corpus of planet-crossing asteroids and to study how these compositions are related to orbital and physical parameters. Methods. We gathered publicly available visible colors of near-Earth objects (NEOs) from the Sloan Digital Sky Survey (SDSS) and SkyMapper surveys. We also computed SDSS-compatible colors from reflectance spectra of the Gaia mission and a compilation of ground-based observations. We determined the taxonomy of each NEO from its colors and studied the distribution of the taxonomic classes and spectral slope against the orbital parameters and diameter. Results. We provide updated photometry for 470 NEOs from the SDSS, and taxonomic classification of 7401 NEOs. We classify 42 NEOs that are mission-accessible, including six of the seven flyby candidates of the ESA Hera mission. We confirm the perihelion dependence of spectral slope among S-type NEOs, likely related to a rejuvenation mechanism linked with thermal fatigue. We also confirm the clustering of A-type NEOs around 1.5–2 AU, and predict the taxonomic distribution of small asteroids in the NEO source regions in the Main Belt.

Auditory Perceptual Judgement and Acoustical Study of Liquid Sounds in Children Aged 4~6 Years According to Clinical Experience

Purpose: This study examines whether there are differences in the auditory perceptual evaluation of speech produced by children according to the listener’s clinical experience and seeks to find acoustic correlates. Methods: Fifteen speech-language pathologists (SLPs) and 15 students listened to Korean liquids produced by children aged 4 to 6 years and assessed them using a 5-point Likert scale. The relationship between auditory perceptual evaluation and acoustic variables was analyzed. Results: First, there is a difference in auditory perception scores between laterals and flaps at different ages within 4 to 6 years, and there is a difference in auditory perception scores depending on the vowel environment. Second, the SLP group’s auditory-perceptual evaluation was consistent with the child’s general laterals and flaps development pattern, while the student group’s auditory-perceptual evaluation differed from the laterals and flaps development. Third, in the regression analysis, a higher spectral slope was associated with higher auditory perceptual evaluation in the SLP’s data. Conclusion: It was confirmed that clinical experience plays a quite important role in auditory perceptual evaluation. However, various follow-up studies are needed to enhance the accuracy of these evaluations.

EEG spectral slope: A reliable indicator for continuous evaluation of consciousness levels during propofol anesthesia

The level of consciousness undergoes continuous alterations during anesthesia. Prior to the onset of propofol-induced complete unconsciousness, degraded levels of behavioral responsiveness can be observed. However, a reliable index to monitor altered consciousness levels during anesthesia has not been sufficiently investigated. In this study, we obtained 60-channel EEG data from 24 healthy participants during an ultra-slow propofol infusion protocol starting with an initial concentration of 1 μg/ml and a stepwise increase of 0.2 μg/ml in concentration. Consecutive auditory stimuli were delivered every 5 to 6 s, and the response time to the stimuli was used to assess the responsiveness levels. We calculated the spectral slope in a time-resolved manner by extracting 5-second EEG segments at each auditory stimulus and estimated their correlation with the corresponding response time. Our results demonstrated that during slow propofol infusion, the response time to external stimuli increased, while the EEG spectral slope, fitted at 15–45 Hz, became steeper, and a significant negative correlation was observed between them. Moreover, the spectral slope further steepened at deeper anesthetic levels and became flatter during anesthesia recovery. We verified these findings using an external dataset. Additionally, we found that the spectral slope of frontal electrodes over the prefrontal lobe had the best performance in predicting the response time. Overall, this study used a time-resolved analysis to suggest that the EEG spectral slope could reliably track continuously altered consciousness levels during propofol anesthesia. Furthermore, the frontal spectral slope may be a promising index for clinical monitoring of anesthesia depth.

The diagnostic value of dual-layer CT in the assessment of lymph nodes in lymphoma patients with PET/CT as a reference standard

This study aimed to evaluate the diagnostic performances of dual-layer CT (DLCT) for the identification of positive lymph nodes (LNs) in patients with lymphoma and retrospectively included 1165 LNs obtained by biopsy from 78 patients with histologically proven lymphoma, who underwent both pretreatment DLCT and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). According to 18F-FDG PET/CT findings as a reference standard, cases were categorized into the LN-negative and LN-positive groups. LNs were then randomly divided at a ratio of 7:3 into the training (n = 809) and validation (n = 356) cohorts. The patients’ clinical characteristics and quantitative parameters including spectral curve slope (λHU), iodine concentration (IC) on arterial phase (AP) and venous phase (VP) images were compared between the LN-negative and LN-positive groups using Chi-square test, t-test or Mann–Whitney U test for categorical variables or quantitative parameters. Multivariate logistic regression analysis with tenfold cross-validation was performed to establish the most efficient predictive model in the training cohort. The area under the curve (AUC) was used to evaluate the diagnostic value of the predictive model, and differences in AUC were determined by the DeLong test. Moreover, the predictive model was validated in the validation cohort. Repeatability analysis was performed for LNs using intraclass correlation coefficients (ICCs). In the training cohort, long diameter (LD) had the highest AUC as an independent factors compared to other parameter in differentiating LN positivity from LN negativity (p = 0.006 to p < 0.001), and the AUC of predictive model jointly involving LD and λHU-AP was significantly elevated (AUC of 0.816, p < 0.001). While the AUC of predictive model in the validation cohort was 0.786. Good to excellent repeatability was observed for all parameters (ICC > 0.75). The combination of DLCT with morphological and functional parameters may represent a potential imaging biomarker for detecting LN positivity in lymphoma.

Nonlinear Optical Pulses in Media with Asymmetric Gain.

A generic novel model governing optical pulse propagation in a nonlinear dispersive amplifying medium with asymmetric (linear spectral slope) gain is introduced. We examine the properties of asymmetric optical pulses formed in such gain-skewed media, both theoretically and numerically. We derive a dissipative optical modification of the classical shallow water equations that highlights an analogy between this phenomenon and hydrodynamic wave breaking. These findings provide insight into the nature of asymmetric optical pulses capable of accumulating large nonlinear phase without wave breaking, a crucial aspect in the design of nonlinear fiber amplifiers.

Col-OSSOS: The Distribution of Surface Classes in Neptune's Resonances

The distribution of surface classes of resonant trans-Neptunian objects (TNOs) provides constraints on the protoplanetesimal disk and giant planet migration. To better understand the surfaces of TNOs, the Colours of the Outer Solar System Origins Survey acquired multiband photometry of 102 TNOs and found that the surfaces of TNOs can be well described by two surface classifications: BrightIR and FaintIR. These classifications both include optically red members and are differentiated predominantly based on whether their near-infrared spectral slope is similar to their optical spectral slope. The vast majority of cold classical TNOs, with dynamically quiescent orbits, have the FaintIR surface classification, and we infer that TNOs in other dynamical classifications with FaintIR surfaces share a common origin with the cold classical TNOs. Comparison between the resonant populations and the possible parent populations of cold classical and dynamically excited TNOs reveal that the 3:2 has minimal contributions from the FaintIR class, which could be explained by the ν 8 secular resonance clearing the region near the 3:2 before any sweeping capture occurred. Conversely, the fraction of FaintIR objects in the 4:3 resonance, 2:1 resonance, and the resonances within the cold classical belt suggest that the FaintIR surface formed in the protoplanetary disk between ≳34.6 and ≲47 au, though the outer bound depends on the degree of resonance sweeping during migration. The presence and absence of the FaintIR surfaces in Neptune’s resonances provides critical constraints for the history of Neptune’s migration, the evolution of the ν 8, and the surface class distribution in the initial planetesimal disk.