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Isothermal crystallization of poly(glycolic acid) studied by terahertz and infrared spectroscopy and SAXS/WAXD simultaneous measurements
摘要： Isothermal crystallization of poly(glycolic acid) (PGA) has been studied using terahertz (THz) and infrared (IR) spectroscopy and simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements. Changes in the intermolecular interactions in PGA during the isothermal crystallization were monitored using THz spectroscopy, which is an efficient technique for analyzing the higher-order structure of polymers. In the THz spectra, the temporal difference in the intensity observed in the isothermal crystallization is due to the difference in the vibrational origins of two bands at 192 and 65 cm?1. The band at 192 cm?1 primarily originates from the intramolecular vibrational mode (twisting of the local structure of the PGA molecular chain). Furthermore, the band at 65 cm?1 exists due to the intermolecular vibration mode (C = O···H-C hydrogen bonds between polymer chains). In addition, these THz bands appeared after the appearance of the SAXS and WAXD peaks. When a lamellar structure is formed and the molecular chains are oriented, the THz band originating from the intermolecular vibration is observed. It is highly possible that the intermolecular vibration appearing in the THz spectra requires the molecular chains to be oriented.
关键词： Terahertz spectroscopy,Intermolecular interactions,Infrared spectroscopy,Isothermal crystallization,SAXS/WAXD,Poly(glycolic acid)
更新于2025-09-10 09:29:36
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Correlated Materials Characterization via Multimodal Chemical and Functional Imaging
摘要： Multimodal chemical imaging simultaneously offers high resolution chemical and physical information with nanoscale, and in select cases atomic resolution. By coupling modalities that collect physical and chemical information, we can address scientific problems in biological systems, battery and fuel cell research, catalysis, pharmaceuticals, photovoltaics, medicine and many others. The combined systems enable local correlation of material properties with chemical makeup, making fundamental questions in how chemistry and structure drive functionality approachable. In this review we present recent progress and offer a perspective for chemical imaging used to characterize a variety of samples by a number of platforms. Specifically, we present cases in infrared and Raman spectroscopies combined with scanning probe microscopy; optical microscopy and mass spectrometry; nonlinear optical microscopy; and finally, ion, electron and probe microscopies with mass spectrometry. We also discuss the challenges associated with the use of data originated by the combinatorial hardware, analysis, and machine learning as well as processing tools necessary for interpretation of multidimensional data acquired from multimodal studies.
关键词： raman spectroscopy,ion microscopy,nonlinear optical microscopy,mass spectrometry,electron microscopy,infrared spectroscopy,chemical imaging,scanning probe microscopy,data analytics,optical microscopy
更新于2025-09-10 09:29:36
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Spontaneous Low Frequency Oscillations in Acute Ischemic Stroke ? A Near Infrared Spectroscopy (NIRS) Study
摘要： Background and purpose: Continuous wave near infrared spectroscopy (NIRS) is a non-invasive bed-side optical method to detect changes in oxygenated (oxyHb) and deoxygenated hemoglobin (deoxyHb) in the outermost layers of the cerebral cortex. Cortical oxyHb low frequency oscillations (LFOs) in the 0.09-0.11 Hz range are affected by changes in cerebral autoregulation (CA), which is altered following stroke. We examined oxyHb LFOs at bed-side as a marker of CA in the subacute phase in stroke patients with or without recombinant tissue plasminogen activator thrombolytic therapy. Methods: We recruited 29 patients admitted to the stroke unit with symptoms of ischemic stroke. 11/29 patients received thrombolytic therapy. NIRS examination was conducted 2 days (median time) from stroke onset. NIRS optodes were placed on each side of the head with a 3 cm source-detector distance. Using transfer function analysis, inter-hemispheric phase shift and amplitude ratio of the oxyHb oscillations in the 0.09-0.11 Hz range were assessed. Results: The correlation between NIHSS scores at admission and oxyHb parameters revealed a significant positive correlation between stroke severity at admission and inter-hemispheric phase shift (P=0.028). The oxyHb absolute inter-hemispheric phase shift was significantly less in patients receiving thrombolytic therapy compared to non-thrombolytic therapy patients (3° vs. 23°, P=0.005). Conclusions: Stroke severity correlates with the degree of impaired cortical CA and stroke patients receiving thrombolytic therapy might have less severely impaired CA. NIRS detects alteration in cortical oxyHb LFOs between hemispheres in stroke patients in the subacute phase and may be a feasible method to explore changes at bed-side in a stroke unit.
关键词： Stroke,rtPA thrombolytic therapy,Low frequency oscillations,Transfer function analysis,Cerebral autoregulation,Thrombolytic treatment,Near infrared spectroscopy
更新于2025-09-10 09:29:36
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Feasibility of NIRS-based neurofeedback training in social anxiety disorder: behavioral and neural correlates
摘要： Attention biases towards threat signals have been linked to the etiology and symptomatology of social anxiety disorder (SAD). Dysfunction of the dorsolateral prefrontal cortex (dlPFC) may contribute to attention biases in anxious individuals. The aim of this study was to investigate the feasibility of near-infrared spectroscopy (NIRS) neurofeedback (NF) training—targeting the dlPFC—and its effects on threat-related attention biases of individuals with SAD. 12 individuals with SAD participated in the NIRS-NF training lasting 6–8 weeks and including a total of 15 sessions. NF performance increased significantly, while the attention bias towards threat-related stimuli and SAD symptom severity decreased after the training. The individual increase in neurofeedback performance as well as the individual decrease in SAD symptom severity was correlated with decreased responses to social threat signals in the cerebral attention system. Thus, this pilot study does not only demonstrate that NIRS-based NF is feasible in SAD patients, but also may be a promising method to investigate the causal role of the dlPFC in attention biases in SAD. Its effectiveness as a treatment tool might be examined in future studies.
关键词： Social anxiety disorder,Near-infrared spectroscopy,DlPFC,Laughter,Attention bias
更新于2025-09-10 09:29:36
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Removing Task-Induced Superficial-Tissue Hemodynamics and Head Motion-Induced Artifacts in Functional Near-Infrared Spectroscopy
摘要： Functional near-infrared spectroscopy, a neuroimaging tool used to measure brain activity, is associated with two different types of artifacts: (a) task-induced super?cial-tissue hemodynamic artifacts derived from the scalp; and (b) motion artifacts caused by head motions. Recently, a simple and easy-to-use method, based on a general linear model incorporating super?cial hemodynamics model estimated from short-probe distance channels using principal component analysis, was proposed to remove task-induced super?cial-tissue artifacts. In the present study, we examined the effectiveness of this method in removing task-induced and head motion-induced super?cial-tissue hemodynamics. Thus, we conducted a motor experiment where participants were asked to perform grasping movements. During some sessions, head motions were generated in order to introduce motion artifacts. Although the removal of motion artifacts was not perfect, we found that analyses including the ?rst and second principal component (estimated from short-channels) showed a tendency to provide accurate detection of brain activity. This ?nding demonstrated the possibility of conducting effective analysis of functional near-infrared spectroscopy using general linear model and short-channels.
关键词： motion artifact removals,general linear model,functional near-infrared spectroscopy
更新于2025-09-10 09:29:36
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Reaction-probe infrared investigation on drastic change in reactivity of mesoporous silica for acetalization of cyclohexanone with methanol; pore-size dependence
摘要： Small-pored (< 2.5 nm) mesoporous silica showed remarkably higher catalytic activity for cyclohexanone acetalization with methanol than large-pored ones (≥2.5 nm). For the clari?cation of the pore-size e?ect of mesoporous silicas (MCM-41 and SBA-15) on the reactivity, the reaction probe infrared (IR) method was applied. No evident di?erences were observed by conventional IR characterization methods using CO, pyridine and acetonitrile adsorption. IR spectra of methanol, one of the reactants, on small-pored (MCM-41) and large-pored (SBA-15) samples appeared the same. On the other hand, adsorption of cyclohexanone resulted in di?erent IR spectra: a C]O stretching band appeared at lower frequency side on MCM-41 at a small amount of adsorption in addition to that observed on SBA-15. This result indicates the presence of the stronger interaction of cyclohexanone with MCM-41 than that with SBA-15. When the time course of the reaction was observed by in-situ IR observation, the consumption of activated carbonyl groups and the generation of 1,1-dimethoxycyclohexane, the reaction product, were con?rmed. The presence of the activated cyclohexanone was most probably due to the adsorption on two (or more) OH groups in vicinity, while a non-activated species occupied a single OH group. The reaction probe IR method is thus, a direct and e?ective approach to extract the small di?erences in catalysis.
关键词： Pore-size dependence,Acetalization,Infrared spectroscopy,Reaction-probe,Mesoporous silica
更新于2025-09-10 09:29:36
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - A Modified Common Spatial Pattern Algorithm Customized for Feature Dimensionality Reduction in fNIRS-Based BCIs
摘要： Functional near-infrared spectroscopy (fNIRS) is a non-invasive multi-channel imaging tool for assessing brain activities, which has shown its high potential in brain-computer interface (BCI) technique. Most previous studies have focused on constructing high dimensional features from whole channels, adding to the complexity of their classifiers. Another multi-channel source for BCI is electroencephalograph (EEG), which possesses different spatial and temporal features from fNIRS. In EEG field, Common Spatial Pattern (CSP) algorithm is widely used aimed at dimensionality reduction. In our article, we modified it based on the characteristics of fNIRS and evaluated its effectiveness in discriminating Mental Arithmetic (MA) against resting status in an open-access dataset. The Modified Common Spatial Pattern algorithm significantly outperforms CSP algorithm in fNIRS-based BCI and shows its potential in further BCI related explorations.
关键词： Common Spatial Pattern (CSP),Mental Arithmetic (MA),Modified Common Spatial Pattern (MCSP),brain-computer interface (BCI),Functional near-infrared spectroscopy (fNIRS)
更新于2025-09-10 09:29:36
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Antioxidant capacity of Camellia japonica cultivars assessed by near- and mid-infrared spectroscopy
摘要： Main conclusion Camellia japonica antioxidant capacity highly differs among its cultivars and could be successfully predicted by near- and mid-infrared spectroscopy. Camellia japonica is a Theaceae family species which are mainly used as an ornamental plant due to its colourful flowers presenting over than 32,000 recognized cultivars. However, this species have been somehow neglected due to the popular tea source, Camellia sinensis. In this study, the antioxidant profile (total phenolic and flavonoid content and total antioxidant capacity—TPC, TFC and TAC) of 31 C. japonica cultivars leaves was determined and further assessed by near- and mid-infrared spectroscopy. The leaves’ antioxidant profile was revealed to be highly dependent on the cultivars analysed being in some cases distinct even for different trees of the same cultivar. Near- and mid-infrared spectroscopy proved to be suitable techniques to predict the total phenolic and flavonoid content as well as the total antioxidant capacity. The best results were obtained with near-infrared spectroscopy whose root mean square error of the prediction set samples was of 5.7?mg of gallic acid/g dry leaf; 3.5?mg catechin/g dry leaf and 3.3?mM Trolox/g dry leaf for TPC, TFC and TAC (with coefficients of the determinations equal to or higher than 0.93). Moreover, the range error ratios were higher than 15 meaning that the developed partial least-squares models are very good for calibration and quantification determinations according to the guidelines for near-infrared models development and maintenance. In this work, the antioxidant profile of several C. japonica cultivars leaves was determined for the first time, being that a rapid and low cost spectroscopic-based method was also proposed for its determination.
关键词： Antioxidants,Camellia japonica cultivars,Chemometrics,Phenolic compounds,Flavonoids,Infrared spectroscopy
更新于2025-09-10 09:29:36
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Nondestructive Determination of the Compressive Strength of Wood Using Near-Infrared Spectroscopy
摘要： In this study, Xylosma racemosum was selected as the raw material and its compressive strength was predicted through nondestructive methods. The test data consisted of 160 near-infrared (NIR) absorption spectra of the wood samples obtained using an NIR spectrometer, with the wavelength range of 900 to 1900 nm. The original absorption spectra were pre-processed with multiplicative scatter correction (MSC) and Savitzky-Golay (SG) smoothing and divided into several intervals using the backward interval partial least squares (BiPLS) method. The optimal combination of intervals with the smallest root mean square error of cross validation (RMSECV) value was selected, and a genetic algorithm (GA) was used to select featured wavelengths. Finally, a partial least squares (PLS) regression model was established with the featured wavelengths. The BiPLS-GA-PLS model outperformed the other models, resulting in a high prediction correlation coefficient of 0.927 and a root mean square error rate of 4.06. Based on the results, it is feasible to accurately measure the compressive strength of wood processed by different methods using near-infrared spectroscopy.
关键词： Prediction,BiPLS-GA,Compressive strength,Near-infrared spectroscopy
更新于2025-09-10 09:29:36
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Modeling the Vibrational Properties of InSb Diamondoids and Nanocrystals Using Density Functional Theory
摘要： Raman and infrared spectra were used to obtain the vibrational properties of an indium antimonide crystal. The density functional theory of the Perdew, Burke and Ernzerhof functions/3-21G and the functions’ basis of polarization were employed. This study investigates how the vibrational frequencies of InSb diamondoids change with size as compared to the experimental bulk. The results showed that the bond lengths in InSb diamondoids decreased as the number of atoms within increased. Many physical properties were studied, including energy gaps, tetrahedral angles, dihedral angles, atomic charges, and bond lengths. The high reduced mass mode (HRMM) and high force constant mode were found to be larger in octamantane than in diamondoids, at 211.09 cm?1 and 190.17 cm?1, respectively.
关键词： PBE/3-21G,InSb diamondoids,DFT,Raman spectra,Infrared spectroscopy
更新于2025-09-10 09:29:36