Peak Width Research Articles

Increasing Isolation Efficiency Using a Segmented Quadrupole Mass Filter Operated with Rectangular Waveforms.

The performance of a segmented quadrupole mass filter operated with rectangular waveforms and capacitively coupled rectangular waveforms applied to the prefilters was examined on a home-built quadrupole-Orbitrap platform. For peak widths of 50 m/z, 100% isolation efficiency was achieved, which fell to approximately 20% for 5 m/z peak width for a rectangular waveform of 150 V0-p. Due to a small exit aperture following the mass filter, peak structure was observed in both experimental peak shapes and those simulated using SIMION. A larger radius quadrupole was examined and achieved similar performance. While the segmented quadrupole does remove the defocusing effects of the fringing fields, the ion beam is only slightly refocused due to the low RF voltage which limits achievable gains in isolation efficiency.

Comparison of carrier gases for the separation and quantification of mineral oil hydrocarbon (MOH) fractions using online coupled high performance liquid chromatography-gas chromatography-flame ionisation detection

On-line coupled high performance liquid chromatography-gas chromatography-flame ionisation detection (HPLC-GC-FID) was used to compare the effect of hydrogen, helium and nitrogen as carrier gases on the chromatographic characteristics for the quantification of mineral oil hydrocarbon (MOH) traces in food related matrices. After optimisation of chromatographic parameters nitrogen carrier gas exhibited characteristics equivalent to hydrogen and helium regarding requirements set by current guidelines and standardisation such as linear range, quantification limit and carry over. Though nitrogen expectedly led to greater peak widths, all required separations of standard compounds were sufficient and humps of saturated mineral oil hydrocarbons (MOSH) and aromatic mineral oil hydrocarbons (MOAH) were appropriate to enable quantitation similar to situations where hydrogen or helium had been used. Slightly increased peak widths of individual hump components did not affect shapes and widths of the MOSH and MOAH humps were not significantly affected by the use of nitrogen as carrier gas. Notably, nitrogen carrier gas led to less solvent peak tailing and smaller baseline offset. Overall, nitrogen may be regarded as viable alternative to hydrogen or helium and may even extend the range of quantifiable compounds to highly volatile hydrocarbon eluting directly after the solvent peak.

Distinct Electrogram Features and Ventricular Arrhythmia Induction Modes Between Repolarization and Conduction Heterogeneities

BackgroundRecent clinical studies have indicated the presence of localized electrical abnormalities in idiopathic ventricular fibrillation and J-wave syndrome patients. ObjectivesThis study aims to characterize the specific electrical signatures of localized repolarization and conduction heterogeneities and their respective role in vulnerability to arrhythmias. MethodsOptical mapping was performed in porcine right ventricles with local: 1) repolarization shortening; 2) conduction slowing; or 3) structural heterogeneity induced by locally perfusing: 1) pinacidil (20 μmol/L, n = 13); or 2) flecainide (2 μmol/L, n = 13) via an epicardial catheter; or 3) by local epicardial tissue destruction (9 radiofrequency lesions n = 12). Electrograms were recorded (n = 5 in each group) and spontaneous and induced arrhythmias were quantified and optically mapped. ResultsElectrograms were normal in (1) but showed local fragmentation in 40% of preparations in (2) with greater effects observed at high pacing frequencies dependent on the wavefront direction. In (3), the structural substrate alone increased the width and number of peaks in the electrograms, and addition of flecainide induced pronounced fragmentation (≥3 peaks and ≥70 ms) in all cases. Occurrence of spontaneous arrhythmias was significantly increased in (1) and (2) (P < 0.0001 and 0.05, respectively, vs baseline) and were triggered by ectopies. Vulnerability to arrhythmias at high pacing frequencies (≥2 Hz) was the lowest in (1) and greatest in (2). ConclusionsMicrostructural substrates have the most pronounced impact on electrograms, especially when combined with sodium channel blockers, whereas local action potential duration shortening does not lead to electrogram fragmentation even though it is associated with the highest prevalence of spontaneous arrhythmias.

Three-dimensional information measurement and reconstruction for micro-hole array based on the modified shape from focus

The geometrical characteristics of the micro-holes and the consistency of spatial distribution among the micro-holes in the micro-hole array fabricated by laser beam drilling (LBD) directly influence the cooling performance, reliability, and longevity of the workpiece. It is of great significance to establish the relationship between the LBD processing parameters and the characteristics of the micro-hole array through the three-dimensional (3D) information measurement and reconstruction of the micro-hole array, as well as to guide and improve the LBD processing technology. However, due to the small size and high aspect ratio of the micro-holes in the micro-hole array, the 3D information measurement and reconstruction of the micro-hole array face challenges. The conventional micro-hole measurement methods suffer from low efficiency, high measurement costs, and potentially destructive measurement processes. Furthermore, the conventional micro-hole measurement methods face challenges in simultaneously obtaining the geometrical characteristics of the micro-holes and the spatial distribution among the micro-holes in the micro-hole array. Therefore, a non-contact and non-destructive 3D information measurement and reconstruction method for the micro-hole array based on the modified shape from focus is proposed. A novel focus measure operator based on grayscale difference and adaptive neighborhood size is proposed to accurately evaluate the focus value and obtain the initial focus volume matrix. A novel image processing operator based on the gradient information of the image sequence is proposed to enhance the initial focus volume matrix. The experimental results indicate that the proposed focus measure operator, combined with the novel image processing operator, is more suitable and reliable for detecting the micro-holes due to its better unimodality, higher contrast, and narrower peak width than the conventional focus measure operator. The optimal focus position of each image point is obtained using the modified Gaussian curve fitting method. On this basis, the 3D information measurement and reconstruction of the micro-hole array are realized. By comparing the results with the conventional micro-hole measurement method, the feasibility and accuracy of the proposed method have been confirmed to be an effective measurement method for the micro-hole array.

Patterns of Cross-Peaks in Two-Dimensional Correlation Spectra to Probe Intermolecular Interactions Described by Two Reversible Reactions.

Two-dimensional correlation spectroscopy is used to investigate the intermolecular interaction between two substances dissolved in the same solutions, where the intermolecular interaction is described by two reversible reactions producing two supramolecular aggregates. The severe overlappings expected among the characteristic peaks of the original solute and aggregates make conventional one-dimensional spectra difficult to accurately reflect the physiochemical nature of the intermolecular interaction. The double asynchronous orthogonal sample design (DAOSD) approach is utilized to analyze the simulated data for proof-of-principle demonstration. The patterns of cross-peaks are much more complex compared with the intermolecular interaction described by only a single reaction. Four major groups of cross-peaks with characteristic patterns observed in the pair of DAOSD asynchronous spectra are systematically analyzed and classified. Further analysis of the spectral feature of the cross-peaks of the DAOSD asynchronous spectra is helpful to exact additional information concerning the variation of the peak position and peak width of the aggregates compared with those of the original solute. The result is important to reveal the physicochemical nature of intermolecular interaction between the solutes (e.g., changes in conformation, dynamical behavior, etc.). The pattern of cross-peaks in the corresponding 2D asynchronous spectra may become rather complex when the peak position, peak width, and peak intensity of two supramolecular aggregates change simultaneously. Further work using artificial intelligence techniques to interpret the complex cross-peaks is still being carried out.

Methylation of phase II metabolites of endogenous anabolic androgenic steroids to improve analytical performance.

The study of intact phase II metabolites of endogenous anabolic androgenic steroids (EAAS) gives important information about metabolism and has the potential to improve the detection of doping with testosterone. For analysis with liquid chromatography-mass spectrometry (LC-MS), chemical derivatization at the steroid moiety is a technique to improve the positive ionization efficiency of glucuronidated/sulfated EAAS under collision-induced dissociation (CID) conditions. However, regarding the chromatographic performance, there are still challenges to address, for example, poor peak shape, which is mainly caused by nondefined adsorption in the chromatographic system. Here, we show a novel derivatization technique for the analysis of selected phase II metabolites of EAAS, where the acidic moiety of the glucuronide/sulfate is methylated with different methylation reagents to reduce nondefined adsorption. The methylation reagent trimethylsilyl-diazomethane (TMSD) was preferred over the other tested reagents methyl iodide (MeI) and dimethyl sulfate (DMS). Glucuronidated and sulfated testosterone and epitestosterone were methylated, and their chromatographic performance and CID ion mass spectra obtained in positive ionization mode were investigated. The peak width and peak height were significantly improved for all substances. Methylated testosterone sulfate showed the best results with a 3.5 times narrower peak and 14 times increased intensity compared with underivatized testosterone sulfate. Furthermore, CID ion mass spectra obtained in positive ionization mode showed product ions characteristically for the steroidal backbone for all substances. This preliminary study shows the potential of methylation as a supplementary derivatization technique, which can assist in the development of more sensitive methods due to the improvements in method performance.

Experimental Validation of Comprehensive Calculation for High-Resolution Linear MALDI-TOF Mass Spectrometry.

This work discusses the effectiveness of the previously developed comprehensive calculation model to optimize linear MALDI-TOF mass spectrometers. The model couples space- and velocity-focusing to precisely analyze the flight-time distribution of ions and predict optimal experimental parameters for the highest mass resolving power. Experimental validation was conducted using a laboratory-made instrument to analyze CsI3 and angiotensin I ions in low to medium m/z range. The results indicate that the predicted optimal extraction voltage and delay were reasonably accurate and effective. In the low m/z range, the peak width obtained using optimal parameters reached the sub nanosecond range, corresponding to a mass resolving power of 10 000-17 000, or 20 000-34 000 if shot-to-shot random fluctuations were minimized by the dynamic data correction method. The observed optimal mass resolving power in the current experiment is 4.8-7.8 times that of commercial instruments. Practical limitations resulting in the gap between the observed and theoretical ultimate mass resolving power are discussed.

Simulation study of digital waveform-driven quadrupole mass filter operated in higher stability regions for high-resolution inductively coupled plasma mass spectrometry.

The use of a frequency-scanned digital quadrupole mass filter (QMF) with varying duty cycles shows promise for application as a high-resolution mass analyzer design for inductively coupled plasma mass spectrometry (ICP-MS). High resolution in ICP-MS is important to overcome isobaric polyatomic interferences. Here, we explore the possibility and the characteristics of using a digital quadrupole operating in higher stability regions for ICP-MS. We perform computational simulations in SIMION of a digital QMF that is operated by scanning the frequency of the digital waveform at a fixed driving voltage and various duty cycles. For ions in the atomic mass range (7-238 m/z), we investigate the expected resolution, transmission, fringe field effects, and ion trajectories. We compare different characteristics between sine and digital waveform QMF. Within the capability of current digital waveform generation technology, a digital QMF can produce variable mass resolution, from several hundred to more than 10 000. This mass resolution covers the low, medium, and high resolutions that are typical for sector-field ICP-MS. Additionally, simulations suggest that transmission of the QMF remains high at high resolution. For example, with 87.50/12.50 duty cycle (zone 4,1), resolution at 10% peak width is 10420 for m/z 80. The transmission through the quadrupole, which is constant for all isoenergetic ions, is ~2.5%, and most ion loss is due to the defocusing effects of the fringe field. Compared to sinusoidal QMFs, ions need many fewer cycles in the digital QMF to obtain high resolution. The results demonstrate that the use of a frequency-scanned, duty-cycle-modulated digital QMF as the mass analyzer for ICP-MS has the potential to produce high resolution while maintaining considerable transmission, thus overcoming most spectral interferences in elemental MS.

Convection-diffusion-electromigration coupled numerical simulation of water and chloride in cement-based materials

The transport of chloride in cement-based materials is influenced by various factors, and the chloride diffusion coefficient in numerical models should be the steady-state value under specific conditions, which is difficult to obtain through traditional experiments. In this article, based on an improved non-contact resistivity instrument, the steady-state chloride diffusion coefficient and porosity of cement-based materials are characterized. Considering the acceleration effect of moisture convection and electric field on chloride transport, a numerical model for moisture and chloride transport coupling diffusion, convection, and electromigration is established. Based on the measured steady-state chloride diffusion coefficient and porosity values, the influence of interface transition zone (ITZ), electric field type, chloride binding effect, initial conditions, and boundary conditions on moisture and chloride transport is numerically analyzed. It is found that the increase of ITZ thickness, electric field strength, boundary concentration, and initial concentration can accelerate chloride transport. The chloride concentration distribution curve exhibits a “shoulder peak” caused by chloride binding effect, and its peak height and width are positively correlated with the chloride binding coefficient. In conclusion, this study aims to better understand the ion transport behavior inside cement-based materials under coupling of convection, diffusion, and electromigration, and identify the key factors influencing this behavior, which provide a feasible scheme for durable design of concrete construction in environments rich in erosive media.

Ultra-high order mode-assisted optical differentiator for edge detection with high tunability

An optical spatial differentiator based on the photonic spin Hall effect (PSHE) with high tunability is presented. By utilizing the characteristics of ultra-high order modes in the symmetrical metal cladding waveguide, the Fresnel reflection coefficient spectrum exhibits a narrow peak width and low trough at the resonant incident angles, resulting in high sensitivity to changes in the incident angle-induced spatial shift caused by the PSHE (the highest ∂(|r s /r p |)/∂θ value can reach 107). After polarization transformation and extinction, the output field demonstrates differential operation with respect to the input field. When applied to edge detection, our differentiator can achieve tunable resolution edge images by adjusting the incident angle. Our proposed edge detection scheme has potential applications for cellular and molecular imaging through two-dimensional extension via the target rotation.

Ultrabroad distribution of multiple anelasticities in O-doped refractory multiprincipal element alloys

The Snoek anelastic internal friction (IF) peak due to stress-induced dipole ordering associated with interstitial atoms was well observed in IF curves of single-principal element alloys (SPEAs) as early as in the 1950s, however, its behavior remains elusive in multi-principal element alloys (MPEAs) to date. Here the temperature-dependent IF spectra of NbTiV0.5Zr refractory MPEAs with varying O contents were presented, and the analysis of these data indicates that for O-doped NbTiV0.5Zr MPEAs, the O addition triggers two anelastic IF peaks (the PO1 and PO2), corresponding to the O-Snoek-type relaxation in random solid solution (RSS) and local chemical ordering (LCO) structures, respectively. The half-peak width of the PO1 is 2–3 times broader than that for SPEAs, associated with the wide O migration energy barrier distribution in MPEAs. These phenomena show a striking contrast to the single and narrow Snoek-type peak observed for SPEAs. Our analysis further reveals an approximate linear correlation between the half-peak width of the Snoek-type peak and the mixing entropy. The introduction of O also shifts grain boundary relaxation peaks (PG) towards higher temperatures. Interestingly, high-temperature anomalous modulus changes were observed for the first time in TiV-based lightweight refractory MPEAs, which is suggested to be originated from the order reduction of the body-centered cubic (bcc) structure at elevated temperatures. Moreover, the 1 at.%O doped NbTiV0.5Zr MPEA with a favorable balance between the peak heights of the PO2 and PG, exhibits outstanding specific yield stress (SYS) among refractory MPEAs while maintaining an elongation as high as 20 %. This work provides not only a bridge between the anelastic behavior of SPEAs and MPEAs for upcoming studies and theories concerning bcc MPEAs with interstitial atoms, but contributes to the holistic design of bcc MPEAs with high strength and excellent ductility.

Enhancing Magnetic Material Data Analysis with Genetic Algorithm-Optimized Variational Mode Decomposition

As the application of machine learning technology in predicting and optimizing material performance continues to grow, handling the electromagnetic data of magnetic materials, especially in removing unavoidable data noise and accurately extracting resonance peaks in the imaginary part of electromagnetic information, has become a significant challenge. These steps are crucial for revealing the deep electromagnetic behavior of materials and optimizing their performance. In response to this challenge, this study introduces an innovative approach—Genetic Algorithm-Optimized Variational Mode Decomposition for Signal Enhancement (GAO-VMD-SE). This method, through the Variational Mode Decomposition (VMD) technique optimized by genetic algorithms, not only effectively reduces noise in the data, thereby improving the Signal-to-Noise Ratio (SNR) and reducing the Mean Absolute Error (MAE), but also significantly enhances the hidden resonance peak information in complex permittivity and permeability data to achieve a comprehensive improvement in key performance indicators. Experimental results prove that this method surpasses traditional analysis techniques in key performance metrics such as the peak width ratio, peak overlap ratio, and the number of peaks. Especially in identifying characteristic peaks related to the Snoek limit, GAO-VMD-SE can effectively reveal the peak features hidden in complex data, thus providing important insights for evaluating the performance of materials at specific frequencies. Moreover, the effectiveness of this method in denoising not only enhances the quality and accuracy of material data analysis but also achieves a 1% to 10% enhancement in peak information extraction. This optimized data processing capability and versatility make GAO-VMD-SE not only suitable for evaluating the performance of magnetic materials but also show significant practical application value in processing spectral data and other time series signal data applications.

A simulation study of the ability to detect power distribution perturbations in the texas A&M TRIGA reactor with self-powered neutron detectors

Given the variety of ways that nuclear reactor core power may be perturbed, reactor operators and developers are keen on understanding the accuracy and convergence time during which perturbations in reactor power distribution may be synthesized (i.e., inferred) from an array of in-core radiation detectors. A simulation study was conducted as described herein using a highly detailed model of the Texas A&M Training, Research, Isotopes, General Atomics Reactor, in which an array of self-powered neutron detectors (SPNDs) was considered for input to the power synthesis methodology. The core power synthesis is conducted using a point-based iterative method with an iterative loop built in to ensure working equation consistency. The forward problem of SPND response to simulated perturbations in reactor power was solved for Gaussian peak-type perturbations in the reactor power distribution. These perturbations varied in variance, amplitude, and core location to assess their impact on synthesis error and to determine the number of iterations required for convergence. A relation between the unique resolvability limit and perturbation width was identified such that the maximum synthesis error increased rapidly when the peak width went beneath this limit (a width approximating half the reactor’s fuel pin-to-pin pitch); this resolvability limit is specific to the SPND configuration and fuel segmentation considered herein. The synthesis error increased linearly with perturbation peak amplitude, whereas the convergence time increased nonlinearly. Perturbations located closer to the center of the core were synthesized more accurately, albeit with a higher number of required iterations. These findings provide a qualitative and quantitative understanding of the accuracy and speed at which different types of spatial power perturbations can be resolved in light-water reactors.

Synchro-curvature description of γ-ray light curves and spectra of pulsars: global properties

Abstract This work presents a methodological approach to generate realistic γ-ray light curves of pulsars, resembling reasonably well the observational ones observed by the Fermi-Large Area Telescope instrument, fitting at the same time their high-energy spectra. The theoretical light curves are obtained from a spectral and geometrical model of the synchro-curvature emission. Despite our model relies on a few effective physical parameters, the synthetic light curves present the same main features observed in the observational γ-ray light curve zoo, such as the different shapes, variety in the number of peaks, and a diversity of peak widths. The morphological features of the light curves allows us to statistically compare the observed properties. In particular, we find that the proportion on the number of peaks found in our synthetic light curves is in agreement with the observational one provided by the third Fermi-LAT pulsar catalog. We also found that the detection probability due to beaming is much higher for orthogonal rotators (approaching 100%) than for small inclination angles (less than 20 %). The small variation on the synthetic skymaps generated for different pulsars indicates that the geometry dominates over timing and spectral properties in shaping the gamma-ray light curves. This means that geometrical parameters like the inclination angle can be in principle constrained by gamma-ray data alone independently on the specific properties of a pulsar. At the same time, we find that γ-ray spectra seen by different observers can slightly differ, opening the door to constraining the viewing angle of a particular pulsar.

Two-dimensional time-resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations.

Dosimetry in pre-clinical FLASH studies is essential for understanding the beam delivery conditions that trigger the FLASH effect. Resolving the spatial and temporal characteristics of proton pencil beam scanning (PBS) irradiations with ultra-high dose rates (UHDR) requires a detector with high spatial and temporal resolution. To implement a novel camera-based system for time-resolved two-dimensional (2D) monitoring and apply it in vivo during pre-clinical proton PBS mouse irradiations. Time-resolved 2D beam monitoring was performed with a scintillation imaging system consisting of a 1mm thick transparent scintillating sheet, imaged by a CMOS camera. The sheet was placed in a water bath perpendicular to a horizontal PBS proton beam axis. The scintillation light was reflected through a system of mirrors and captured by the camera with 500 frames per second (fps) for UHDR and 4 fps for conventional dose rates. The raw images were background subtracted, geometrically transformed, flat field corrected, and spatially filtered. The system was used for 2D spot and field profile measurements and compared to radiochromic films. Furthermore, spot positions were measured for UHDR irradiations. The measured spot positions were compared to the planned positions and the relative instantaneous dose rate to equivalent fiber-coupled point scintillator measurements. For in vivo application, the scintillating sheet was placed 1cm upstream the right hind leg of non-anaesthetized mice submerged in the water bath. The mouse leg and sheet were both placed in a 5cm wide spread-out Bragg peak formed from the mono-energetic proton beam by a 2D range modulator. The mouse leg position within the field was identified for both conventional and FLASH irradiations. For the conventional irradiations, the mouse foot position was tracked throughout the beam delivery, which took place through repainting. For FLASH irradiations, the delivered spot positions and relative instantaneous dose rate were measured. The pixel size was 0.1mm for all measurements. The spot and field profiles measured with the scintillating sheet agreed with radiochromic films within 0.4mm. The standard deviation between measured and planned spot positions was 0.26mm and 0.35mm in the horizontal and vertical direction, respectively. The measured relative instantaneous dose rate showed a linear relation with the fiber-coupled scintillator measurements. For in vivo use, the leg position within the field varied between mice, and leg movement up to 3mm was detected during the prolonged conventional irradiations. The scintillation imaging system allowed for monitoring of UHDR proton PBS delivery in vivo with 0.1mm pixel size and 2ms temporal resolution. The feasibility of instantaneous dose rate measurements was demonstrated, and the system was used for validation of the mouse leg position within the field.

Machine-learning descriptor search on the density of states profile of bimetallic alloy systems and comparison with the d-band center theory.

In this study, the electronic density of states (DOSs) calculated with density functional theory (DFT) were analyzed by the machine-learning techniques. More than 400 pure metal and bimetallic alloy systems were calculated with DFT, and obtained the surface DOSs and the CH3 adsorption energy (Ead). By fitting the Gaussian functions to the DOS, multiple descriptors, such as the Gaussian peak positions, heights, and widths were extracted. Several regression methods, such as the least absolute shrinkage of selection operator (LASSO), random-forest, gradient-boosting, and extra-tree were used to find the relationship between these descriptors and the Ead. The results show that the energy position of the peaks in the d-projected DOS is the most important descriptor, in agreement with the previously known d-band center theory. It was also shown that the peak position in d-projected DOS improves the regression model in addition to the d-band center, since it reduces the regression error.

Growth, optical and thermal properties of YbxHo1-xCa4O(BO3)3 crystals

YbxHo1-xCa4O(BO3)3 (Yb:HoCOB, x = 0, 0.1, 0.2, 0.3) crystals were grown by the Bridgman method for the first time. The crystal structure, rocking curve, transmission spectra, absorption spectra, band structure and thermal properties of Yb:HoCOB were characterized in detail. The maximum half peak width (FMHW) of Yb0.1Ho0.9COB and Yb0.2Ho0.8COB is 26.7″ and 23.8″, respectively, and the effective segregation coefficient is greater than 0.9. In addition, the transmittance of Yb:HoCOB is 88 %. New absorption peaks are introduced by doping Yb3+ at 850–1000 nm. The UV absorption cut-off edge of Yb:HoCOB is red-shifted with increasing Yb3+ doping. The thermal diffusivity and thermal conductivity of Yb:HoCOB decrease with increasing temperature. The specific heat increases with the increasing temperature and finally approaches a constant value. The specific heat of Yb:HoCOB crystal are above 0.670 J/gK at room temperature. Yb:HoCOB with good crystallization quality, high transmittance and high specific heat has the application potential in laser frequency and QPCPA. This work provides a useful exploration for the study of nonlinear optical materials in solid state lasers.

Verification of the McStas code using two double axis neutron diffractometers

The Monte Carlo ray-tracing simulation package McStas is verified by modeling two double axis neutron diffractometers, KARL and KANDI-II, located at the Israel Research reactors IRR-1 and IRR-2, respectively. The advantage of simulating these instruments is their simple design and small number of components. We focus on the simulation of a Soller slit collimator as well as Pyrolytic Graphite and Copper single crystal monochromators. The simulation is compared to neutron flux measurements, performed via activation analysis along the neutron beam as well as observed diffraction patterns from different powder samples. Calculated diffraction patterns are found to agree with observations to within 20%–50% in reflection peak width, while calculated attenuation of the neutron beam agrees to within 20% when the entire instrument is considered, and can show a discrepancy of up to 60% for individual components. Finally, a possible optimization of the neutron flux in the KARL diffractometer is presented.

Bamboo and coconut shell based activated carbon: A Raman spectroscopic study

In this paper, we present a detailed report on Raman spectroscopic analysis of activated carbon (AC) samples obtained from two different biomass sources, namely, bamboo and coconut shell. The detailed analysis revealed that the local structure of the precursors was affected differently by the physical and chemical treatments prior to the preparation of AC. This leads to different structural features of the derived AC samples though processed under similar conditions. The influence of preparation methods and temperature on modifications in the D-, G-, and 2D-peak parameters of bamboo and coconut shell based AC (BAC and CSAC) such as peak positions, peak widths and peak intensity ratio were thoroughly described. We experimentally validate the stage-two of the three-stage Ferrari-Robertson phenomenological model of amorphous carbon for these biomass derived AC. We also show that the observed anomalies in the peak parameters are consistent with the stage-two process combined with the networking properties of biomass derived AC. Physically activated BAC and chemically activated CSAC prepared at a temperature of 600 °C showed greater disorder (ID/IG) values of 1.37 and 1.22 in their AC structures, respectively. Further analysis of 2D-peak indicated the greater turbostratic disorder (quasi 2D-continuous random network) in BAC compared to CSAC.

Real-time measurements of breathing dissipative soliton pairs in mode-locked fiber lasers

The emergence of breathing solitons, as well as the breathing soliton molecules undergoing periodic evolution in peak power and spectral width has attracted growing research attentions in dissipative systems. Beyond the intense pulse interactions within tightly-bound states with picoseconds interval, the long-range interplay between pulses separated by nanosecond-scale starts to be investigated in recent years, thus filling the long-standing academic gap between the bound solitons and independent multiple pulses. In this work, we report on the real-time observations of breathing dissipative soliton pairs with nanoseconds’ separations in a fiber laser operating under the threshold of stationary mode locking. Compared with conventional soliton counterpart, here the breathing soliton pair exhibit even more fascinating inter-pulse nonlinear dynamics due to the intriguing self-excited periodic evolutions. The shot-to-shot measurements of pulse intensity profiles, associated with dispersive Fourier transform clearly uncover not only the different breathing phase synchronization and pulse separations among different pulses but also the hysteresis behaviors of the breathing ratio by continuously varying the laser parameters. Moreover, we observed various transient stages in this unstable lasing regime, including the transition between stable single soliton and breathing soliton pair, as well as their long-range breather interaction. These results reveal the breathing multi-pulse state and the instantaneous non-equilibrium dynamics involving the breather pairs, enriching the framework of breathing solitons and opening a novel possibility to explore the internal motions of breathing soliton complex in nonlinear systems.