Gaussian Fitting Research Articles

Estimation of Forest Canopy Height from Spaceborne Full-Waveform LiDAR Data Using a Bisection Approximation Decomposition Method

Forest canopy height (FCH) is a vital indicator for assessing forest health and ecosystem service capacity. Over the past two decades, full-waveform (FW) LiDAR has been widely employed for estimating forest biophysical variables due to its high precision in measuring vertical forest structures. However, the impact of terrain undulations on forest parameter estimation remains challenging. To address this issue, this study proposes a bisection approximation decomposition (BAD) method for processing GEDI L1B data and FCH estimation. The BAD method analyzes the energy composition of simplified echo signals and determines the fitting parameters by integrating overall signal energy, the differences in unresolved signals, and the similarity of inter-forest signal characteristics. FCH is subsequently estimated based on waveform peak positions. By dynamically adjusting segmentation points and Gaussian fitting parameters, the BAD method achieved precise separation of mixed canopy and ground signals, substantially enhancing the physical realism and applicability of decomposition results. The effectiveness and robustness of the BAD method for FCH estimation were evaluated using 2049 footprints across varying slope conditions in the Harvard Forest region of Petersham, Massachusetts. The results demonstrated that digital terrain models (DTMs) extracted using the GEDI data and the BAD method exhibited high consistency with the DTMs derived using airborne laser scanning (ALS) data (coefficient of determination R2 > 0.99). Compared with traditional Gaussian decomposition (GD), wavelet decomposition (WD), and deconvolution decomposition (DD) methods, the BAD method showed significant advantages in FCH estimation, achieved the smallest relative root mean square error (rRMSE) of 17.19% and greatest mean estimation accuracy of 84.57%, and reduced the rRMSE by 10.74%, 21.49%, and 28.93% compared to GD, WD, and DD methods, respectively. Moreover, the BAD method exhibited a significantly stronger correlation with ALS-derived canopy height mode data than the relative height metrics from GEDI L2A products (r = 0.84, p < 0.01). The robustness and adaptability of the BAD method to complex terrain conditions provide great potential for forest parameters using GEDI data.

Designing & optimisation of dual Ca2+ and SO4 2– ionic cross-linked sericin/pectin microbeads using response surface methodology for colon-specific delivery

Ulcerative colitis, a chronic inflammatory condition of the colon, requires precise and targeted treatment, and polysaccharides, with their pH responsiveness and biodegradability, offer an innovative approach for colon-specific drug delivery. This study aims to develop a highly precise drug delivery system with enhanced therapeutic and targeting efficiency for ulcerative colitis, focusing on the preparation, optimisation, and evaluation of dual cross-linked mesalamine-loaded sericin-pectin (DCLSPs) micro-beads. These beads utilise the pH-responsive and microflora biodegradability properties of polysaccharides for targeted colon delivery, employing the Response Surface Methodology. Formulated via the ionotropic gelation method with divalent cross-linking ions (Ca2+ and SO4 2–), the DCLSPs were optimised using a Box-Behnken design to assess the impact of the varying drug, pectin, and sericin polymer proportions. The DCLSPs were evaluated for entrapment efficiency, thermal behaviour, surface morphology, water uptake, swelling, and in-vitro drug release. Results indicated that spherical beads were successfully developed, with encapsulation efficiency ranging from 65.1% to 95.5%, drug loading between 32.5% and 49.9%, bead sizes of 0.75 mm to 0.92 mm, and degrees of swelling from 0.92 to 1.82. Drug release was controlled by both diffusion and swelling mechanisms, as supported by the Higuchi and Korsmeyer-Peppas models. The optimised formulation demonstrated high drug encapsulation efficiency, pH-responsive swelling, and strong adhesion to the colon, ensuring extended retention at the targeted site. Additionally, the incorporation of sericin enhanced the accuracy of Gaussian fitting for particle size distribution. Overall, the dual cross-linked sericin-pectin beads show potential as mucoadhesive carriers for delivering drugs specifically to the colon.

Ultra-wide band near-infrared (NIR) optical thermometry (12-673 K) performance enhanced by Stark sublevel splitting in Er3+ ions near the first biological window in the PbZr0.53Ti0.47O3:Er3+/Yb3+ phosphor.

The fluorescence intensity ratio (FIR) approach, which relies on thermally coupled levels (TCLs), is significantly important for optical thermometry at room temperature and above, but was found to be impractical for low temperature sensing due to limited population density (thermal) or lack of spectrum at extremely low temperatures. Herein, we report a wide temperature range (12-673 K) sensing capability of the PbZr0.53Ti0.47O3:Er3+/Yb3+ (C1:PZT) phosphor utilising the bandwidth of Stark sublevel split near-infrared (NIR) emission bands as one sensing parameter and FIR as another. Motivated by our previous studies on upconversion (UC) and the promising thermometry performance of the C1:PZT phosphor for real time nanothermometer monitoring (using visible TCLs), this work extends to the same thermometry application using UC-NIR emission as TCLs. The temperature-dependent UC spectra were measured across the ranges of 12-313 K and 313-673 K under 980 nm excitation, and their sensing capabilities were thoroughly evaluated. An enveloped single emission band, comprising multiple peaks in the NIR region, was observed and subsequently deconvoluted using Gaussian fitting. These individual peaks were analyzed in relation to Stark sublevel splitting, which was particularly evident at 12 K, and the variations in their full width at half maximum (FWHM) were compared across temperatures up to 313 K. Based on the temperature-dependent bandwidth, two prominent peaks ∼11 655 cm-1 (858 nm) and 11 454 cm-1 (873 nm), were identified as TCL levels, and a sensitivity (Sr) of 0.68 ± 0.01% K-1 at 673 K was observed, making it a suitable thermometer for reading low temperatures using NIR bands.

Application of Gaussian Beam Propagation Theory and Nonlinear Fitting Technology in Automatic Production of Optical Fiber Collimator

Application of Gaussian Beam Propagation Theory and Nonlinear Fitting Technology in Automatic Production of Optical Fiber Collimator

Research on double cubic interpolation combined with Gaussian fitting sub-pixel edge detection method

Research on double cubic interpolation combined with Gaussian fitting sub-pixel edge detection method

Revisiting the Optical Spectrum of the Plutonyl Ion (PuO2)2+ in 1 M HClO4.

The analysis of the solution absorption spectrum of the plutonyl ion in an aqueous environment was given by Eisenstein and Pryce (E&P) in 1968. In 2011 a new spectrum was published of the (PuO2)2+ ion in 1 M HClO4. We have been provided with the original data of this spectrum and have found in the data a previously unreported low-lying transition at 7385 cm-1 which we have assigned as a magnetic dipole transition. We have fit most of the near-infrared and optical transitions with Gaussian fits and tabulated a new energy level list up to 22,000 cm-1 which mostly agrees with the data of E&P. We assumed a crystal field of D∞h (only axial symmetry) and utilized the intensity calculations published for the isoelectronic (NpO2)1+ ion using a complete basis set for the 5f2 problem including the Coulombic, spin-orbit as well as the crystal field Hamiltonian. Our results differ substantially from those of E&P. Subsequently, we used a truncated Hamiltonian to try to establish the effects of assuming the σ antibonding orbitals are at such high energies that we can ignore their contributions to the lower lying φ and δ orbitals.

Development of a full field-of-view spectroscopic single-molecule fluorescence instrument with improved methods for calibration

Abstract We have developed a high-throughput, full field-of-view (FOV) spectroscopic single-molecule fluorescence (sSMF) instrument, overcoming distortion issues with gratings and prisms. Our calibration techniques ensure spectral uniformity across the whole FOV, and our two-step Gaussian fit method enables better than 2 nm precision in spectral peak determination for accurate molecule identification, making it a valuable tool for multi-color single-molecule detection and analysis.

Atmospheric Modulation Transfer Function Calculation and Error Evaluation for the Panchromatic Band of the Gaofen-2 Satellite

In the optical satellite on-orbit imaging quality estimation system, the calculation of Modulation Transfer Function (MTF) is not fully standardized, and the influence of atmosphere is often simplified, making it difficult to obtain completely consistent on-orbit MTF measurements and comparisons. This study investigates the effects of various factors—such as edge angle, edge detection methods, oversampling rate, and interpolation techniques—on the accuracy of MTF calculations in the commonly used slanted-edge method for on-orbit MTF assessment, informed by simulation experiments. A relatively optimal MTF calculation process is proposed, which employs the Gaussian fitting method for edge detection, the adaptive oversampling rate, and the Lanczos (a = 3) interpolation method, minimizing the absolute deviation in the MTF results. A method to quantitatively analyze the atmospheric scattering and absorption MTF is proposed that employs a radiative transfer model. Based on the edge images of GF-2 satellite, images with various atmospheric conditions and imaging parameters are simulated, and their atmospheric scattering and absorption MTF is obtained through comparing the MTFs of the ground and top atmosphere radiance. The findings reveal that aerosol optical depth (AOD), viewing zenith angle (VZA), and altitude (ALT) are the primary factors influencing the accuracy of GF-2 satellite on-orbit MTF measurements in complex scenarios. The on-orbit MTF decreases with the increase in AOD and VZA and increases with the increase in ALT. Furthermore, a collaborative analysis of the main influencing factors of atmospheric scattering and absorption MTF indicates that, taking the PAN band of the GF-2 satellite as an example, the atmospheric MTF values are consistently below 0.7905. Among these, 90% of the data are less than 0.7520, with corresponding AOD conditions ranging from 0 to 0.08, a VZA ranging from 0 to 50°, and an ALT ranging from 0 to 5 km. The results can provide directional guidance for the selection of meteorological conditions, satellite attitude, and geographical location during satellite on-orbit testing, thereby enhancing the ability to accurately measure satellite MTF.

Simulation of nitrate nitrogen concentrations and DOM characteristics in groundwater from Southwest China's Karst Wetlands using an improved GMS model.

Existing models often face limitations in the understanding and prediction of nitrate nitrogen (NO3--N) concentrations in karst groundwater. In this study, to tackle this issue, a Gaussian function model was coupled with the Groundwater Modeling System (GMS) to simulate NO3--N concentration changes in the southwest karst wetland of China. Additionally, fluorescence spectroscopy was employed to measure dissolved organic matter (DOM) components in the groundwater, providing insights into their variation and influence on NO3--N dynamics. The results demonstrated that coupling the Gaussian curve fitting method with the GMS model accurately simulated NO3--N concentration changes in the study area. The simulation revealed lower NO3--N levels in the northern region, with higher concentrations in the central area, peaking at 20.73mg/L at lower elevations. NO3--N was primarily distributed in the southwestern region and upper Mudong Lake, exhibiting a diffusion trend from west to east. DOM analysis indicated significant autochthonous contributions, particularly microbial metabolic by-products. The total fluorescence intensity and DOM components increased downstream, with the lowest values at the source and the highest values at river confluences. The humification index (HIX) was correlated with NO3--N concentrations, where lower NO3--N levels corresponded to lower HIX values, and higher NO3--N levels corresponded to higher HIX values. In conclusion, this study provides valuable insights into NO3--N prediction in groundwater and the role of DOM, offering a reference for groundwater protection in the southwest China karst basin.

Exploring Fission Dynamics through Fission Fragment Spectroscopy

Abstract Fission Fragment Spectroscopy (FFS) measurement technique has been utilized to measure the relative isotopic yield distributions of the even-even correlated fission fragment nuclei produced from 236U* at two different values of excitation energies (E ex ). The fissioning compound nucleus, 236U* was populated at E ex = 6.5 and 21.5 MeV through two different sets of experiments by using the reactions, 235U(n th ,f) and 232Th(α,f), respectively. The experimentally measured relative isotopic yield distributions were further used to obtain the corresponding mass yield distributions. The extracted mass yield distributions of 236U* indicates the transition from asymmetric distribution to bimodal distribution with increase in the values of E ex from 6.5 to 21.5 MeV. The experimental mass yield distribution pattern for the reaction, 232Th(α,f) at E ex = 21.5 MeV could be fitted well through three Gaussian fits as per the prescription based on the Multimodal Random-Neck Rupture Model (MM-RNRM).

Investigation of Individual Pulse Emission Behaviors from Pulsar J1741–0840

We have carried out a detailed study of individual pulse emission from the pulsar J1741−0840 (B1738−08) observed using the Parkes and Effelsberg radio telescopes at the L band. The pulsar exhibits four emission components, which are not well resolved by employing multicomponent Gaussian fitting. The radio emission originates at a height of approximately 1000 km, with the viewing geometry characterized by inclination and impact angles roughly estimated at 81° and 3°, respectively. Fluctuation spectral analysis of single pulse behavior reveals two prominent periodicities, around 32 and five rotation periods. The longer periodic modulation feature is linked to nulling behavior across the entire emission window, with an updated nulling fraction of 23% ± 2% derived from pulse energy distribution via Gaussian mixture modeling. In addition to quasiperiodic nulling, the pulsar also exhibits the presence of subpulse drifting in the trailing component, with the shorter periodic feature in the fluctuation spectra related to the phenomenon of subpulse drifting, and the longitudinal separation estimated to be about 5°. Both periodic modulations show significant temporal evolution with time-dependent fluctuation power. The implications of understanding the radio emission mechanisms are discussed.

Center-to-limb Variations in Solar Plage Using IRIS Observations

The center-to-limb variations (CLV) of transition region line Gaussian fit parameters in solar plage are reported for the first time. The Si iv 1402.77 Å line observed by the Interface Region Imaging Spectrograph is used. The spectral intensity increases linearly from the disk center to the solar limb. Similarly, the nonthermal velocity also increases linearly from 23.6 (at the disk center) to 30.9 km s−1 (at the solar limb). On the other hand, the Doppler velocity decreases from 8.9 ± 1.0 at the disk center to 0.0 km s−1 at the limb. This CLV pattern in solar plages is consistent with the CLV pattern reported in the quiet Sun (QS). However, the average values of the parameters in the solar plage are significantly higher than in the QS. The intensity and nonthermal velocity increase linearly with the magnetic field at the disk center, while the Doppler velocity does not depend on the magnetic field. Due to the line-of-sight effect, the plasma column depth increases toward the solar limb, which leads to a linear increase in the spectral intensity. Further, the increasing plasma column depth toward the solar limb adds more and more unresolved motions, and as a result, the nonthermal velocity increases from the disk center to the solar limb. In the solar plages, the higher plasma density due to the strong magnetic field leads to higher intensity and nonthermal velocity compared to the QS and coronal hole.

Analysis of Atomic Structure Using Spectroscopy: An Emission and Absorption Line Spectrum Study

This research study investigates the emission and absorption spectra of hydrogen, helium, and sodium using modern spectroscopic techniques to gain deeper insights into their atomic structures and electronic transitions. By utilizing high-resolution spectrometry and a Gaussian fitting algorithm, the study systematically compares both emission and absorption spectra under controlled laboratory conditions. The experimental setup included repeated trials to ensure data reliability, with spectral lines captured in terms of peak wavelength, intensity, and full width at half maximum (FWHM). Key findings reveal distinct energy level transitions for each element, with sodium displaying minimal shift between its emission and absorption peaks, indicating efficient electronic transitions. Hydrogen's and helium’s spectra provided further validation of well-established theoretical models, including the Balmer series for hydrogen. This research contributes to filling a literature gap by offering a simultaneous comparison of emission and absorption spectra for the same elements, enhancing the understanding of atomic interactions. The results hold broader implications for various fields, including astrophysics, chemical analysis, and environmental monitoring, where accurate spectral analysis is critical. The study underscores the importance of high-resolution spectroscopy in scientific and industrial applications and paves the way for future advancements in spectroscopic techniques

Nonlinear convolutional sparse filtering with Gaussian fitting for rolling bearings compound fault diagnosis

The operational precision, stability, and lifespan of servo motors are directly influenced by the healthy operation of rolling bearings. Early diagnosis of bearing faults holds significant importance in enhancing the reliability of servo motors and preventing substantial economic losses and personal injuries. However, strong noise interference in industrial environments poses challenges to bearing fault diagnosis. Additionally, the difficulty in detecting single faults in bearings often leads to the occurrence of compound faults. To achieve compound fault diagnosis under intense noise interference in industrial environments, this paper proposes the nonlinear convolutional sparse filtering (NCSF). First, generalized sigmoid and Z-score normalization are utilized to amplify fault features and reduce the influence of irrelevant interference. Subsequently, multidimensional filters are learned based on a nonlinear objective function to achieve the separation of compound faults. Then, the Gaussian function is utilized to fit the trained filters, reducing the impact of low-frequency noise. Finally, the filtered signals are envelope demodulated to analyze fault types. The capability of NCSF to distinguish compound faults amid noise interference is confirmed by both experimental and simulation results. The proposed NCSF is an effective method to realize compound fault diagnosis under strong noise interference.

Temperature and Ge Fraction Dependance of Broad Peaks in Raman Spectra from Ge-Rich Silicon Germanium Thin Films

Background and Objective Silicon-germanium (SiGe) is applied to the next-generation electric and thermoelectric devices because it has higher hole mobility than Si and low thermal conductivity due to the alloy scattering. However, device performance is affected by temperature, strain, and composition. Therefore, it is significant to optimize these properties to improve the device performance. Raman spectroscopy is one of the promising methods to evaluate strain, composition, and thermal properties [1]. In our previous studies, a broad peak was observed at the lower wavenumber side of the Ge-Ge mode in the Raman spectra of Ge-rich SiGe obtained by immersion Raman spectroscopy [2]. This broad peak is considered to be originated in the surface phonon [3] or disorder mode [4]. If the broad peak is derived from the surface phonon of SiGe, it would be sensitive to surface temperature and Ge fraction. Thus, in this study, we evaluated the laser power dependence of broad peak obtained from Ge-rich SiGe films by oil-immersion Raman spectroscopy. Then, we investigated the effect of Ge fraction and temperature variations on the broad peak. Experiments We prepared Ge-rich SiGe thin films with different Ge fractions epitaxially grown on (001) Ge substrate by molecular beam epitaxy (MBE). The Ge fractions of these samples were approximately 75, 85, and 92%, respectively. The SiGe layers were grown less than the critical thickness to suppress strain relaxation and defect generation. We measured Raman spectra of SiGe by using oil-immersion Raman spectroscopy to detect very weak broad peak compared to first-order phonon peaks (Ge-Ge mode). In the oil-immersion Raman spectroscopy measurements, the wavelength of the excitation light source was 532 nm, and the focal length of the spectrometer was 2,000 mm. The numerical aperture of the oil-immersion lens was 1.4, and the reflective index of the oil was 1.5. For each SiGe thin film with different Ge fractions, we varied the laser power from 1 mW to 9 mW in 2 mW increments and evaluated the dependence of Ge fraction and temperature on the broad peak. Results and Discussion Figure 1 shows Raman spectra (Ge-Ge mode) of the Si0.15Ge0.85 layer obtained under the longitudinal optical (LO) and transverse optical (TO) phonon mode active configurations. As a result, we observed the broad peak at the lower wavenumber side of Ge-Ge mode in the TO-active configuration. In general, the TO-active configurations are theoretically Raman inactive condition under the backscattering geometry from the (001) surface with diamond structure. The Ge-Ge mode is excited only by the z-polarized component from the oil-immersion lens, so the contribution of the unintentional Ge-Ge mode is much smaller compared to that in the LO-active configuration. Thus, the broad peak at the shoulder on the lower energy side of the Ge-Ge mode can be clearly observed.Figures 2 and 3 show intensity and laser power dependence of the broad peak for three samples with different Ge fractions, respectively. These broad peaks were extracted by Gaussian fitting. In Fig. 2, the intensity of the broad peak decreases with increasing Ge fraction. In addition, we found that the intensity ratio of the broad peak to the Ge-Ge vibrational mode shifted linearly related to Ge fraction. Therefore, we consider that the Ge fraction can be derived more easily by using the intensity of broad peak than by Raman shift without affected by the complicated strain states. In Fig. 3, the broad peak shifts to the lower wavenumber side with increasing laser power. We consider that frequency reduction due to the thermal expansion of the SiGe thin film caused this shift. The broad peaks shifted more significantly than the spectrum of the Ge-Ge mode, which suggests that the broad peak is sensitive to the local temperature changes.In conclusion, we observed that the intensity of the broad peak decreases with increasing Ge fraction and the Raman shift of the broad peak change with incident laser power compared to Ge-Ge mode. We expect that the broad peak obtained by oil-immersion Raman spectroscopy can be applied to the evaluation of Ge fraction and thermal properties of nanoscale devices. Acknowledgements This work was supported by Grant-in-Aid for Scientific Research (21K14201). Reference [1] B. Stoib et al., Appl. Phys. Lett. 104, 161907 (2014).[2] D. Kosemura et al., Jpn. J. Appl. Phys. 55, 026602 (2016).[3] K. Takeuchi et al., Appl. Phys. Express. 9, 071301 (2016).[4] A. A. Corley-Wiciak et al., Phys. Rev. Appl. 20, 024021 (2023). Figure 1

Deterioration of Polypropylene Random Copolymer Formulations Based on Phenolic Antioxidants and Non‐Phenolic Stabilizers at Elevated Temperatures in Hot Air

ABSTRACTThis article deals with the hot air aging behavior of polypropylene random copolymers additivated with phenolic antioxidants, hindered amine light stabilizers (HALS) and thiosynergists in a wide temperature range from 65°C to 135°C. Various stabilizer mixtures and their interactions were evaluated. To avoid diffusion‐limited oxidation effects, 100 μm thick specimens were prepared from injection molded sheets and examined by Fourier‐transform infrared spectroscopy in transmission mode and tensile testing. In addition to ultimate strain‐at‐break, the aging indicators phenol index (PI), nitroxide index (NI), and ester index (EI) were deduced. Monitoring the phenolic functional groups revealed the formation of splitting‐off derivatives which remained beyond full embrittlement of the micro‐specimen at a relative content of app. 20%. Oxidation of the phenolic stabilizer Irganox 1330 resulted in shifts of the IR‐band associated with single‐ and dual‐oxidized products. Gaussian fitting of the triple peak confirmed the formation of these splitting‐off derivatives. The combination of phenolic antioxidants with HALS led to a significantly faster decay of the phenolic groups. However, this effect was reduced by the addition of thiosynergists. Interestingly, a slower decrease of the phenol, nitroxide and ester indexes representing phenolic‐, amine‐ and thio‐stabilizers, respectively, was ascertained for the PP‐R formulation with the ternary additive mixture leading to higher endurance times by a factor of up to 2.5. The analytical aging indicators did not reflect the time‐to‐embrittlement, especially for complex additive formulations containing HALS.

Low current driven blue-violet light-emitting diodes based on p-GaN/i-Ga2O3/n-Ga2O3:Si structure

This paper reports a low current driven LED with p-GaN/i-Ga2O3/n-Ga2O3:Si structure prepared by radio frequency (RF) magnetron sputtering, the driving current of the device is only 0.02 mA. Compared with the reported drive current of the LEDs, the reduction is 100 or even 1000 times. Through the study of its electrical properties, it was found that it had excellent rectification characteristics at different ambient temperatures and the turn-on voltage was about 1.8 V. In addition, the leakage current was as low as 4.30 × 10-8 mA. Through the electroluminescence test, it was found that the device had the function of emitting in the ultraviolet (363 nm) and visible (425 nm) region, which realized the blue-violet luminescence at room temperature. Furthermore, the device had excellent high temperature color stability and ultra-low color temperature of 1924 K. The color coordinate of the device at room temperature was (0.1905,0.0955). A detailed study was conducted on the electroluminescence mechanism of the device through its band structure, and the causes of the luminescence were analyzed through the Gaussian fitting of the EL spectrum.

Proof-of-Concept Validation of Noninvasive Detection of Cortical Spreading Depolarization with High Resolution Direct Current-Electroencephalography.

Cortical spreading depolarization (SD) is increasingly recognized as a major contributor to secondary brain injury. Monitoring SDs could be used to institute and guide SD-based therapeutics if noninvasive detection methods were available. Our primary objective is to use a high density array of electrodes to compare scalp direct current (DC)-shifts to SDs detected by gold standard electrocorticography (ECoG) to establish proof-of-concept validation that scalp DC-potentials can potentially provide noninvasive SD detection. Our secondary objective is to assess usability and artifact tolerance. An 83×58 mm thermoplastic elastomer array with 29 embedded 6-mm diameter Ag/AgCl 1-cm spaced electrodes, the CerebroPatch™ Proof-of-Concept Prototype, was adhesively placed on the forehead with an intervening electrode gel interface to record DC-electroencephalography in normal volunteers and severe acute brain injury patients in the neuro-intensive care unit some with and some without invasive subdural ECoG electrodes. The scalp and ECoG voltages were collected by a Moberg® Advanced ICU Amplifier. Artifacts were visually identified and usability issues were recorded. SD was scored on ECoG using standard criteria of DC shift with associated suppression of high frequency activity with propagation across the electrode. A six parameter Gaussian plus quadratic baseline model was used to produce time-course ECoG and scalp electrode channel plots and heat-map movies of scalp voltages. The similarity of the noninvasive scalp and invasive ECoG DC-shift time-courses was compared via the Gaussian fit parameters and confirmed if the Coefficient-of-Determination exceeded 0.80. Usability and artifact issues obscured most scalp Prototype device data except for 38 of the 140 ECoG-coded SDs over a period of 11 days in one sub-arachnoid hemorrhage patient. 26 of these DC-shifts were in readable, artifact free portions of scalp recordings and 24 had an acceptable, >0.80 Coefficient-of-Determination (0.98 [0.02], median [IQR]) between invasive ECoG and noninvasive Prototype device DC-shifts. These data suggest that these scalp DC-shifts (peak -457 ± 69 μV [mean ± StD], full-widthhalf maximum 70.9 ± 5.92 sec, area 18.7 ± 2.76 cm2) depicted in the heat-map movies represent noninvasively detected SDs. These results suggest that noninvasive SD detection is possible using scalp DC-potential signals with a high spatial resolution EEG array. Efforts to limit artifact and improve usability in DC-EEG detection are needed in order to improve the reliability of this approach and enable multi-modal monitoring for secondary brain injury.

Calibration of the JAGB method for the Magellanic Clouds and Milky Way from Gaia DR3, considering the role of oxygen-rich AGB stars

The JAGB method is a new way of measuring distances in the Universe with the use of asymptotic giant branch (AGB) that are situated in a selected region in a J versus J − Ks colour–magnitude diagram (CMD), and relying on the fact that the absolute J magnitude is (almost) constant. It is implicitly assumed in the method that the selected stars are carbon-rich AGB stars (carbon stars). However, as the sample selected to determine MJ is purely colour based, there can also be contamination by oxygen-rich AGB stars in principle. As the ratio of carbon-rich to oxygen-rich stars is known to depend on metallicity and initial mass, the star formation history and age–metallicity relation in a galaxy should influence the value of MJ . The aim of this paper is to look at mixed samples of oxygen-rich and carbon-rich stars for the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Milky way (MW) using the Gaia catalogue of long-period variables (LPVs) as a basis. The advantage of this catalogue is that it contains a classification of O- and C-stars based on the analysis of Gaia Rp spectra. The LPV catalogue is correlated with data from the Two Micron All Sky Survey (2MASS) and samples in the LMC, SMC, and the MW are retrieved. Following methods proposed in the literature, we report the mean and median magnitudes of the selected sample using different colour and magnitude cuts and the results of fitting Gaussian and Lorentzian profiles to the luminosity function (LF). For the SMC and LMC, we confirm previous results in the literature. The LFs of the SMC and LMC JAGB stars are clearly different, yet it can be argued that the mean magnitude inside a selection box agrees at the 0.021 mag level. The results of our analysis of the MW sample are less straightforward. The contamination by O-rich stars is substantial for a classical lower limit of (J − Ks)0 = 1.3, and becomes less than 10% only for (J − Ks)0 = 1.5. The sample of AGB stars is smaller than for the MCs for two reasons. Nearby AGB stars (with potentially the best determined parallax) tend to be absent as they saturate in the 2MASS catalogue, and the parallax errors of AGB stars tend to be larger compared to non-AGB stars. Several approaches have been taken to improve the situation but finally the JAGB LF for the MW contains about 130 stars, and the fit of Gaussian and Lorentzian profiles is essentially meaningless. The mean and median magnitudes are fainter than for the MC samples by about 0.4 mag which is not predicted by theory. We do not confirm the claim in the literature that the absolute calibration of the JAGB method is independent of metallicity up to solar metallicity. A reliable calibration of the JAGB method at (near) solar metallicity should await further Gaia data releases, or should be carried out in another environment.

Reaction kinetics dominated by melt decomposition mechanism: Intrinsic pyrolysis of insensitive HTPE polyurethane and the efficient inter-reaction with AP

The novel insensitive HTPE (hydroxyl terminated polyether) adhesive holds a great potential application to develop the insensitive solid propellants. However, the pyrolysis kinetics and reaction mechanism of HTPE polyurethane are remained unclear. In this experimental investigation, the DTG curve of HTPE polyurethane was effectively deconvoluted into two main reaction stages via Gaussian peak fitting method, and the kinetic parameters for each pyrolysis stage were calculated. The calculation of the reaction mechanism functions indicated that both reaction stages follow an n-order reaction model with a very close n value. The overall pyrolysis process can be expressed as f(α) = (1 - α)ⁿ (n = 1.8 or 1.9). The TG-FTIR-GCMS results of online-collected gaseous products demonstrated that the pyrolysis of HTPE polyurethane is gradually decomposed from the outer layer to the inner layer, rather than being completely dominated by the kinetics of different functional groups. Localized melting of HTPE polyurethane was observed at 150 °C, moreover, it would almost completely transform into the liquid phase before the decomposition reaction occurred. Thus, it is suggested that the distinctive melt decomposition process of HTPE polyurethane alters the chemical environment even turns heat and mass transfer models of internal molecules, ultimately leading to its unique pyrolysis kinetics and reaction mechanisms. Furthermore, HTPE polyurethane could delay the first-stage pyrolysis of ammonium perchlorate (AP), but significantly promote its second-stage pyrolysis process. Therefore, HTPE polyurethane is beneficial in reducing the sensitivity of AP under thermal stimulation as well as promoting its concentrated heat release process.