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Mineralogy of Changa??e-4 landing site: preliminary results of visible and near-infrared imaging spectrometer
摘要： The exploration of ma?c anomaly in South Pole-Aitken (SPA, the largest con?rmed) basin on the Moon provides important insights into lunar interior. The landing of Chang’e-4 (CE-4) and deployment of Yutu-2 rover on the discontinuous ejecta from Finsen crater enabled in-situ measurements of the unusual mineralogy in the central portion of SPA basin with visible and near-infrared imaging spectrometer (VNIS). Here we present detailed processing procedures based on the level 2B data of CE-4 VNIS and preliminary mineralogical results at the exploration area of Yutu-2 rover. A systematic processing pipeline is developed to derive credible re?ectance spectra, based on which several spectral and mineral indices are calculated to constrain the ma?c mineralogy. The ma?c components in the soils and boulder around CE-4 landing site are concluded as clinopyroxene-bearing with intermediate composition and probably dominated by pigeonite although the possibility of mixing orthopyroxen (OPX) and calcic clinopyroxene (CPX) also exists. These mineralogical results are more consistent with a petrogenesis that the CE-4 regolith and rock fragment are derived from rapid-cooling magmatic systems and we interpret that the materials at the CE-4 landing site ejected from Finsen crater are probably recrystallized from impact melt settings.
关键词： Chang’e-4,the Moon,visible and near-infrared spectroscopy,mineralogy,impact melt
更新于2025-09-23 15:19:57
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Infrared Spectroscopic and Kinetic Characterization on the Photolysis of Nitrite in Alcohol-Containing Aqueous Solutions
摘要： Nitrite is regarded as a potential OH and NO precursor in aqueous solution upon ultraviolet photolysis. A step-scan Fourier-transform interferometer was employed to collect the transient infrared difference spectra upon excitation of the sodium nitrite aqueous solution in the presence of methanol and ethanol upon 355 nm pulsed excitation. The photolytic intermediates were proposed to be NO and NO2 via the direct dissociation from NO2? and the rapid reaction of OH and NO2?, respectively. Coupled with the theoretical calculations of the absolute energies and harmonic wavenumbers of relevant species using B3LYP density functional theory with the C-PCM model to account for the medium effect of H2O, a transient band at 1860?2030 cm?1 could be attributed to dissolved N2O3 isomers that could be quickly generated from NO + NO2. On the basis of the predicted thermodynamics, the reactions of alcohols with N2O3 were less thermodynamically favorable than that of water, resulting in a slightly decelerated depletion rate of N2O3 in alcohol-containing aqueous solution. Comparing the transient population of N2O3 in the absence and presence of CH3OH or C2H5OH, the upper-bound bimolecular rate coefficient of NO or NO2 with alcohols is reported as 7.3 × 103 M?1 s?1 for the first time. The spectroscopic and kinetic evidence of the reactivity of alcohols with NO, NO2, and N2O3 are provided to augment the roles of alcohols and NxOy in solution or in aqueous aerosol photochemistry.
关键词： Alcohols,Kinetics,Nitrite,Infrared spectroscopy,Aqueous solution,Photolysis
更新于2025-09-23 15:19:57
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Emergence of two-magnon modes below spin-reorientation transition and phonon-magnon coupling in bulk BiFeO3: An infrared spectroscopic study
摘要： We have studied the low-temperature magnetic and infrared measurements on the BiFeO3 ceramic sample to investigate the behavior of phonons and magnon-phonon coupling below 300 K. From the magnetic study, we noticed two magnetic transitions near 150 and 257 K due to the spin-reorientation. Besides, this sample is found to be a mean-field system rather than a glassy system. In our assignment of the infrared modes, all the 13 allowed phonon modes are accounted for rhombohedral BiFeO3 at room temperature itself. Almost all the modes show anomalous behavior in their frequency dependence, close to the observed magnetic transitions. In addition, the emergence of two-magnon modes at 106 and 111 cm-1 below 160 K is observed due to a modification in the noncollinear spin structure. These results indicate the presence of magnon-phonon coupling in multiferroic BiFeO3 below room temperature.
关键词： infrared spectroscopy,Multiferroics,magnetic properties,magnon-phonon coupling
更新于2025-09-23 15:19:57
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The laser power effect on the performance of gas leak detector based on laser photo-acoustic spectroscopy
摘要： The use of a homemade gas leak detector based on laser photo-acoustic spectroscopy for fast and sensitive trace gas detection is reported. To obtain optimal acoustic resonator dimensions, resonant frequency variations in terms of resonator's length and radius were simulated, and then a gas leak detector based on photo-acoustic theory was designed and fabricated. The system limit of detection to trace NO2, SO2 and SF6 was 92, 270 and 8 ppb respectively. Therefore, this system can be used as a sensitive gas sensor for detecting partial leakage of some environmental and industrial pollutants. Variations of the resonant frequency versus various concentrations of NO2, SO2 and SF6 in the presence different buffer gases were studied, and results showed that the lighter buffer gas gives a higher resonance frequency. Also, variations of the photo-acoustic signal and SNR of these gas samples in terms of various CO2 laser power at the presence different buffer gases were investigated, and the saturation laser power for each experiment was obtained. Finally, it was shown that experimental results are in good agreement with photo-acoustic theory.
关键词： Photo-acoustic signal,CO2 laser power,gas leak detector,resonant frequency,Infrared spectroscopy
更新于2025-09-23 15:19:57
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Establishment of optimal exercise therapy using near-infrared spectroscopy monitoring of tissue muscle oxygenation after therapeutic angiogenesis for patients with critical limb ischemia: A multicenter, randomized, controlled trial
摘要： Critical limb ischemia (CLI) is a potentially life-threatening condition that involves severely reduced blood flow to the peripheral arteries due to arteriosclerosis obliterans (ASO) of the limbs or a similar condition. CLI patients must undergo revascularization to avoid amputation of the lower limbs and improve their survival prognosis. However, the outcomes of conventional surgical revascularization or endovascular therapy are inadequate; therefore, establishing further effective treatment methods is an urgent task. We perform therapeutic angiogenesis using autologous bone marrow-derived mononuclear cells in clinical practice and demonstrated its safety and efficacy for CLI patients for whom conventional treatments failed or are not indicated. Exercise therapies must be devised for CLI patients who have undergone therapeutic angiogenesis to save their limbs and improve survival. Because evidence regarding the efficacy and safety of exercise therapy for CLI patients is lacking, we plan to perform a prospective trial of the efficacy and safety of optimal exercise therapy following therapeutic angiogenesis for CLI patients.
关键词： Optimal exercise therapy,Critical limb ischemia,Near-infrared spectroscopy,Arteriosclerosis obliterans,Tissue muscle oxygen saturation,Therapeutic angiogenesis
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 21st Electronics Packaging Technology Conference (EPTC) - Singapore, Singapore (2019.12.4-2019.12.6)] 2019 IEEE 21st Electronics Packaging Technology Conference (EPTC) - A Process Study of Laser Patterning of Different Conductive Layers for Printed Electronics
摘要： Stress-induced psychological and somatic diseases are virtually endemic nowadays. Written self-report anxiety measures are available; however, these indices tend to be time consuming to acquire. For medical patients, completing written reports can be burdensome if they are weak, in pain, or in acute anxiety states. Consequently, simple and fast non-invasive methods for assessing stress response from neurophysiological data are essential. In this paper, we report on a study that makes predictions of the state-trait anxiety inventory (STAI) index from oxyhemoglobin and deoxyhemoglobin concentration changes of the prefrontal cortex using a two-channel portable near-infrared spectroscopy device. Predictions are achieved by constructing machine learning algorithms within a Bayesian framework with nonlinear basis function together with Markov Chain Monte Carlo implementation. In this paper, prediction experiments were performed against four different data sets, i.e., two comprising young subjects, and the remaining two comprising elderly subjects. The number of subjects in each data set varied between 17 and 20 and each subject participated only once. They were not asked to perform any task; instead, they were at rest. The root mean square errors for the four groups were 6.20, 6.62, 4.50, and 6.38, respectively. There appeared to be no significant distinctions of prediction accuracies between age groups and since the STAI are defined between 20 and 80, the predictions appeared reasonably accurate. The results indicate potential applications to practical situations such as stress management and medical practice.
关键词： blood oxygenation,prevention medicine,Anxiety index,neuronal activity,regional cerebral blood flow,translational engineering,near infrared spectroscopy,health and safety,prediction methods,oxyhemoglobin
更新于2025-09-23 15:19:57
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The Supplementary Motor Area Responsible for Word Retrieval Decline After Acute Thalamic Stroke Revealed by Coupled SPECT and Near-Infrared Spectroscopy
摘要： Damage to the thalamus may affect cognition and language, but the underlying mechanism remains unknown. In particular, it remains a riddle why thalamic aphasia occasionally occurs and then mostly recovers to some degree. To explore the mechanism of the affected cognition and language, we used two neuroimaging techniques—single-photon emission computed tomography (SPECT), suitable for viewing the affected brain distribution after acute thalamic stroke, and functional near-infrared spectroscopy (f-NIRS), focusing on hemodynamic responses of the supplementary motor area (SMA) responsible for speech production in conjunction with the frontal aslant tract (FAT) pathway. SPECT yielded common perfusion abnormalities not only in the fronto–parieto–cerebellar loop, but also in the SMA, IFG and surrounding language-relevant regions. In NIRS sessions during a phonemic verbal fluency task, we found significant word retrieval decline in acute thalamic patients relative to age-matched healthy volunteers. Further, NIRS showed strong correlation between word retrieval and posterior SMA responses. In addition, follow-up NIRS exhibited increased bilateral SMA responses linked to improving word retrieval ability. The findings suggest that cognitive dysfunction may be related to the fronto–parieto–cerebellar loop, while language dysfunction is attributed to the SMA, IFG and language-related brain areas. SMA may contribute to the recovery of word retrieval difficulty and aphasia after thalamic stroke.
关键词： SPECT,hemodynamic response,perfusion,verbal fluency test,thalamic aphasia,FAT: frontal aslant tract,cerebro-cerebellar diaschisis,functional near-infrared spectroscopy (f-NIRS)
更新于2025-09-23 15:19:57
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Investigation of GaAsBi epitaxial layers for THz emitters pumped by long-wavelength fiber lasers
摘要： Herein we report the studies on the GaBiAs terahertz emitters. The molecular beam epitaxy grown thin films were subjected to structural and optical characterization. Inhomogeneity of Bi concentration in the samples is confirmed by XRD, PL and EDS studies. Investigations on the generation characteristics of the fabricated bow-tie photoconductive antennas were carried out via the Fourier Transform Infrared Spectroscopy. The collected data indicate a pattern of change in the shape of the spectra with increasing bismuth concentration, namely, a sharp drop in the low-frequency part (0.1–0.2 THz) simultaneously with a noticeable increase in intensity in the range 0.3–1 THz with a pronounced maximum at frequencies of ~0.4 THz. The deterioration of the THz power to average photocurrent ratio can be explained by a general decrease in the electron mobility, caused both by a large number of structural defects and by a large local heating of the crystal.
关键词： terahertz emitters,photoconductive antennas,molecular beam epitaxy,GaBiAs,Fourier Transform Infrared Spectroscopy
更新于2025-09-23 15:19:57
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Localized Nanoscale Heating Leads to Ultrafast Hydrogel Volume-Phase Transition
摘要： The rate of the volume-phase transition for stimuli-responsive hydrogel particles ranging in size from millimeters to nanometers is limited by the rate of water transport, which is proportional to the surface area of the particle. Here, we hypothesized that the rate of volume-phase transition could be accelerated if the stimulus is geometrically controlled from the inside-out, thus facilitating outward water ejection. To test this concept, we applied transient absorption spectroscopy, laser temperature-jump spectroscopy and finite-element analysis modeling to characterize the dynamics of the volume-phase transition of hydrogel particles with a gold nanorod core. Our results demonstrate that nanoscale heating of the hydrogel particle core led to an ultrafast, 60 ns particle collapse, which is 2-3 orders of magnitude faster than the response generated from conventional heating. This is the fastest recorded response time of a hydrogel material, thus opening potential applications for such stimuli-responsive materials.
关键词： infrared spectroscopy,dynamic light scattering,nanorods,volume-phase transition,hydrogel,transient absorption
更新于2025-09-23 15:19:57
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Dowsing for nodal lines in a topological semimetal
摘要： In PNAS, Shao et al. (1) report a spectroscopic search for line degeneracies in the electronic bands of NbAs2, a topological semimetal (TSM). TSMs have attracted great interest recently as exemplars of the emergent physics that can arise in quantum condensed matter (2). They host quasiparticle excitations that cannot occur in the vacuum but do occur in solid-state realizations when protected by discrete symmetries (3). This search is particularly fascinating because the spectroscopic features they uncover are, by any reasonable measure, completely hidden. First, the nodal lines in question are energy dispersive and nearly completely submerged within a Fermi sea, where they are inaccessible to transport measurements. Second, even if the nodal lines could be energy-flattened and floated to the Fermi surface, they would remain hidden. This is because spin-orbit coupling in this material removes the Dirac line degeneracy on an experimentally relevant energy scale. The title of their paper, “Optical signatures of Dirac nodal lines in NbAs2,” is thus a curious misnomer, since there are actually no Dirac nodal lines in this material! Nonetheless, by using infrared spectroscopy, this group detects the fingerprints of these hidden features, which turn up in frequency-scaling relations for the infrared conductivity. One can compare their method to dowsing, the folklore practice of searching for underground water, minerals, or anything invisible indirectly by observing the motion of a pointer or the changes in direction of a pendulum (https://en.wikipedia.org/wiki/Dowsing). In the case of Shao et al. (1), their method actually works and is interpreted using a theory of the scaling relations. As a bonus, the authors suggest that the nascent nodal lines might explain an unusually strong magnetoresistance of the family of related dipnictides, XPn2, where X = {Ta, Nb} and Pn = {P, As, Sb} (4–6).
关键词： Dirac nodal lines,infrared spectroscopy,NbAs2,nodal lines,topological semimetal
更新于2025-09-23 15:19:57