Acoustic Features of the Impact of Laser Pulses on Metal-Ceramic Carbide Alloy Surface.

Technologies associated with using concentrated energy flows are increasingly used in industry due to the need to manufacture products made of hard alloys and other difficult-to-process materials. This work is devoted to expanding knowledge about the processes accompanying the impact of laser pulses on material surfaces. The features of these processes are reflected in the acoustic emission signals, the parameters of which were used as a tool for understanding the accompanying phenomena. The influence of plasma formations above the material surface on self-oscillatory phenomena and the self-regulation process that affects pulse productivity were examined. The stability of plasma formation over time, its influence on the pulse performance, and changes in the heat flux power density were considered. Experimental data show the change in the power density transmitted by laser pulses to the surface when the focal plane is shifted. Experiments on the impact of laser pulses of different powers and durations on the surface of a hard alloy showed a relationship between the amplitude of acoustic emission and the pulse performance. This work shows the data content of acoustic emission signals and the possibility of expanding the research of concentrated energy flow technologies.

Two Photon Absorption Properties of CBHB and DEABHB Single Crystals for Optical Limiting Applications.

Novel materials of (E)-N'-(4-chlorobenzylidene)-4-hydroxybenzohydrazide (CBHB) and (E)-N'-(4-(diethylamino) benzylidene)-4-hydroxybenzohydrazide (DEABHB) were synthesized by condensation reaction process and solvent evaporation method was employed to grow CBHB and DEABHB single crystals at room temperature. Lattice parameters of CBHB and DEABHB compounds were recorded using single crystal X-ray diffraction method. The presence of functional groups of the synthesized CBHB and DEABHB compounds were confirmed by Fourier transform infrared and Fourier transform Raman spectral analyses. Various intermolecular interactions were studied using Hirshfeld surface analysis. Thermal stability of the hydrazone Schiff base compounds CBHB and DEABHB were studied by thermogravimetric and differential thermal analyses. Third order nonlinear optical properties of CBHB and DEABHB were measured using open aperature Z scan technique. Two photon absorption coefficient and optical limiting properties of the crystals were reported from the Z scan studies.

Stability of spectral estimates in resting-state magnetoencephalography: Recommendations for minimal data duration with neuroanatomical specificity.

The principle of resting-state paradigms is appealing and practical for collecting data from impaired patients and special populations, especially if data collection times can be minimized. To achieve this goal, researchers need to ensure estimated signal features of interest are robust. In electro- and magnetoencephalography (EEG, MEG) we are not aware of any studies of the minimal length of data required to yield a robust one-session snapshot of the frequency-spectrum derivatives that are typically used to characterize the complex dynamics of the brain's resting-state. We aimed to fill this knowledge gap by studying the stability of common spectral measures of resting-state MEG source time series obtained from large samples of single-session recordings from shared data repositories featuring different recording conditions and instrument technologies (OMEGA: N = 107; Cam-CAN: N = 50). We discovered that the rhythmic and arrhythmic spectral properties of intrinsic brain activity can be robustly estimated in most cortical regions when derived from relatively short segments of 30-s to 120-s of resting-state data, regardless of instrument technology and resting-state paradigm. Using an adapted leave-one-out approach and Bayesian analysis, we also provide evidence that the stability of spectral features over time is unaffected by age, sex, handedness, and general cognitive function. In summary, short MEG sessions are sufficient to yield robust estimates of frequency-defined brain activity during resting-state. This study may help guide future empirical designs in the field, particularly when recording times need to be minimized, such as with patient or special populations.

Linear and non-linear analysis of heart rate variability in HIV-positive patients on two different antiretroviral therapy regimens.

BACKGROUND: Cardiac autonomic dysfunction in HIV+ patients on different antiretroviral therapy (ART) regimens has been described. We aimed to characterize parameters of heart rate variability (HRV) and correlate with different classes of ART in HIV+ patients in three experimental conditions: rest, cold face, and tilt tests. METHODS: Cross-sectional study with three groups of age- and gender-matched individuals: group 1, 44 HIV+ patients undergoing combination therapy, with two nucleoside reverse transcriptase inhibitors (NRTI) and one non-nucleoside reverse transcriptase inhibitor (NNRTI); group 2, 42 HIV+ patients using two NRTI and protease inhibitors (PI's); and group 3, 35 healthy volunteers with negative HIV serology (control group). Autonomic function at rest and during cold face- and tilt-tests was assessed through computerized analysis of HRV, via quantification of time- and frequency domains by linear and non-linear parameters in the three groups. RESULTS: Anthropometric and clinical parameters were similar between both HIV groups, except CD4+ T lymphocytes, which were significantly lower in group 2 (p = 0.039). At baseline, time-domain linear HRV parameters, RMSSD and pNN50, and the correlation dimension, a non-linear HRV parameter (p < 0.001; p = 0.018; p = 0.019, respectively), as well as response of RMSSD to cold face test were also lower in the HIV+ group than in the control individuals (p < 0.001), while no differences among groups were detected in HRV parameters during the tilt test. CONCLUSIONS: Despite ART regimens, HIV+ patients presented lower cardiac vagal modulation than controls, whereas no difference was observed among the HIV groups, suggesting that higher cardiovascular risk linked to PIs may be associated with factors other than autonomic dysfunction.

Octadecyl 3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propanoate, an antifungal metabolite of Alcaligenes faecalis strain MT332429 optimized through response surface methodology.

In the current study, a soil bacterial isolate F2 expressed a significant antagonistic activity against Candida albicans ATCC 10231 and Aspergillus niger clinical isolate confirmed through cross streak, dual culture, and agar well diffusion methods. The isolate F2 was identified using phenotypic and molecular approaches as Alcaligenes (A.) faecalis MT332429. The identification and structural characterization of the antifungal compound was performed using advanced spectroscopic techniques including UV absorbance, 1H and 13C NMR and 2D NMR (COSY, HSQC, and HMBC) and was identified as octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate. Response surface methodology (RSM) using a central composite design was employed to optimize the nutritional and cultural variables affecting the antifungal metabolite yield. The optimum conditions were found to be temperature 30 °C, agitation 150 rpm, glucose 1 g/l, peptone 2 g/l, and pH 8. A confirmatory experiment was performed to assess the accuracy of the optimization procedure, where an increase in the antifungal metabolite production by about 2.48-fold was obtained. To the best of our knowledge, this is the first report of octadecyl 3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propanoate recovered from the culture broth of A. faecalis MT332429 with a promising antifungal activity along with its optimized production through RSM. KEY POINTS: • A novel soil bacterial isolate, F2, identified as Alcaligenes faecalis MT332429, showed significant antagonistic activity against Candida albicans ATCC 10231 and Aspergillus niger clinical isolate. • This stable fungicidal extracellular metabolite was identified as octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate. • Optimization using central composite design resulted in 2.48-fold increase in production reaching 213.82 µg/ml.

CDSpecTech: A single software suite for multiple chiroptical spectroscopic analyses.

The program CDSpecTech was developed to facilitate the analysis of chiroptical spectra, which include the following: vibrational circular dichroism (VCD) and corresponding vibrational absorption (VA) spectra; vibrational Raman optical activity (VROA) and corresponding vibrational Raman spectra; electronic circular dichroism (ECD) and corresponding electronic absorption (EA) spectra. In addition, the program allows for generating optical rotatory dispersion (ORD) as the Kramers-Kronig transform of ECD spectra. The simulation of theoretical spectra from transition strengths can be achieved using different bandshape profiles. The experimental and simulated theoretical spectra can be visually compared by displaying them together. A unique feature of CDSpecTech is performing spectral analysis using the ratio spectra; i.e., the dimensionless dissymmetry factor (DF) spectrum, which is the ratio of CD to absorption spectra, and the dimensionless circular intensity difference (CID) spectrum, which is the ratio of VROA to vibrational Raman spectra. The quantitative agreement between experimental and simulated theoretical spectra can also be assessed from the numerical similarity overlap between them. Two different similarity overlap methods are available. The program uses a graphical user interface which allows for ease of use and facilitates the analysis. All these features make CDSpecTech a valuable tool for the analysis of chiroptical spectra. The program is freely available on the World Wide Web.

Age and Interlimb Coordination Complexity Modulate Oscillatory Spectral Dynamics and Large-scale Functional Connectivity.

Interlimb coordination deteriorates as a result of aging. Due to its ubiquity in daily life, a greater understanding of the underlying neurophysiological changes is required. Here, we combined electroencephalography time-frequency spectral power and functional connectivity analyses to provide a comprehensive overview of the neural dynamics underlying the age-related deterioration of interlimb coordination involving all four limbs. Theta, alpha and beta oscillations in the frontal, central and parietal regions were analyzed in twenty younger (18-30 years) and nineteen older adults (65-78 years) during a complex interlimb reaction time task. Reaction time was significantly higher in older adults across all conditions, and the discrepancy between both age groups was largest in the most complex movement condition. Older adults demonstrated enhanced beta event-related desynchronization (i.e., the attenuation of beta power), which further increased along with task complexity and was positively linked to behavioral performance. Theta functional connectivity between frontal, central and parietal regions generally increased with movement complexity, irrespective of age group. In general, frontoparietal alpha band functional connectivity tended to be reduced in older versus younger adults, although these contrasts did not survive multiple comparison corrections. Overall, spectral results suggest that enhanced beta desynchronization in older adults reflects a successful compensatory mechanism to cope with increased difficulty during complex interlimb coordination. Functional connectivity results suggest that theta and alpha band connectivity are prone to respectively task- and age-related modulations. Future work could target these spectral and functional connectivity dynamics through noninvasive brain stimulation to potentially improve interlimb coordination in older adults.

Alterations in the conformation and function of human serum albumin induced by the binding of methyl hydrogen phthalate.

Phthalate esters (PAEs) are widely used as plasticizer components in production. Methyl hydrogen phthalate (MHP) is a metabolite of dimethyl phthalate (DMP, a kind of PAEs), and its toxic residues accumulate in the nature and can enter the human body. Here, the interaction between MHP and human serum albumin (HSA) was probed by using multi-spectral, computer simulations, and biochemical techniques. The results showed that MHP was spontaneously embedded in site I of HSA to form a complex by H-bonds and van der Waals forces (ΔH < 0, ΔS < 0). The binding constant (Ka) of the HSA-MHP system was 1.136 ± 0.026 × 104 M-1 (298 K). The combination of MHP produced conformational variations of HSA, as shown by the 3D fluorescence spectrum, CD spectra, and molecular dynamics simulation. Additionally, molecular docking indicated that MHP was surrounded by multiple residues, such as Lys199, Leu203, Phe206, and Trp214. Specifically, Lys199 and Trp214 exerted a crucial effect on the interaction of HSA and MHP. The residues with important energy contribution were mostly located in site I. The ASA values of the aromatic amino acids of HSA changed after combining with MHP. The Rg and SASA values of HSA increased after adding MHP, suggesting that the structure of HSA was less compact. Moreover, the esterase-like activity of HSA increased after adding MHP to HSA, indicating that MHP may disturb the normal physiological activities in the human body. This study was helpful to understand the biological function of MHP and provided some insights for its side effect in the human body.

Compositional and spectrochemical analyses of Cr-spinels in the Sittampundi Anorthosite Complex, Southern India: Implications for remote observation of spinels on the Moon.

The spectroscopic techniques such as Laser Raman, Fourier Transform Infrared (FTIR), and hyperspectral have been used widely to understand the mineral chemistry and crystal structure and identify the functional phases and organic molecules in geological materials on Earth and other planetary bodies. The present study used these spectroscopic techniques combined with X-ray Diffraction (XRD) and Electron Probe Micro Analysis (EPMA) to understand the spectral-compositional relationships of the Cr-spinel (Chromian spinel) present in chromitite bodies associated with Sittampundi Anorthosite Complex (SAC), southern India. The bands/lenses of Cr-spinel are found as layers (few centimeters to 6 m thick) intercalated with anorthosites and clinopyroxenites of the SAC. The cumulate Cr-spinels of the study area exhibit compositions ranging between Al-chromite and Cr-spinel. Fe-, Al-rich Cr-spinel is a characteristic of the SAC with Cr2O3 content ranging from ~32-37 wt% and Cr# (Cr/[Cr + Al]) in the 0.44 to 0.53 range. The XRD spectra of these Cr-spinels have shown characteristic peaks corresponding to its constituent phases, with the highest peak at 36.11°. The observed longward shift in the Raman A1g peak (~705-714 cm-1) is likely to be caused by the substitution of Al3+ in the spinel structure. The Raman A1g peak position near 705 cm-1 in the spectra is attributed to the coexistence of (Mg, Fe) in the tetrahedral site and (Al, Cr) in the octahedral site. The broader and stronger 2 µm band position in the hyperspectral data is at relatively shorter wavelengths than typical Cr-spinels due to enhanced Al content (Al2O3 ~ 25 wt%) in the SAC samples. The 2 µm band position is observed to have a longward shift with increasing Cr2O3 and Cr# abundances and a corresponding shortward shift with enhanced Al2O3 content in Cr-spinels. The linear relationship between the 2 µm band position and Cr/Al abundances indicates that this absorption band is significant in distinguishing Cr-spinels from Al-spinels. Based on spectral and compositional resemblance, Fe- and Al-rich Cr-spinels in SAC are considered as probable terrestrial (functional) analogues for similar lunar spinel compositions given that evidence-based correlation of intricate processes involved in their formation under the lunar and terrestrial conditions. The present study demonstrates the approach of applying spectrochemical characteristics of terrestrial analogue spinels for remote identification of lunar spinels and retrieving their compositional ranges from the spectral reflectance parameters.

Electrophysiological Frequency Band Ratio Measures Conflate Periodic and Aperiodic Neural Activity.

Band ratio measures, computed as the ratio of power between two frequency bands, are a common analysis measure in neuroelectrophysiological recordings. Band ratio measures are typically interpreted as reflecting quantitative measures of periodic, or oscillatory, activity. This assumes that the measure reflects relative powers of distinct periodic components that are well captured by predefined frequency ranges. However, electrophysiological signals contain periodic components and a 1/f-like aperiodic component, the latter of which contributes power across all frequencies. Here, we investigate whether band ratio measures truly reflect oscillatory power differences, and/or to what extent ratios may instead reflect other periodic changes, such as in center frequency or bandwidth, and/or aperiodic activity. In simulation, we investigate how band ratio measures relate to changes in multiple spectral features, and show how multiple periodic and aperiodic features influence band ratio measures. We validate these findings in human electroencephalography (EEG) data, comparing band ratio measures to parameterizations of power spectral features and find that multiple disparate features influence ratio measures. For example, the commonly applied θ/ß ratio is most reflective of differences in aperiodic activity, and not oscillatory θ or ß power. Collectively, we show that periodic and aperiodic features can create the same observed changes in band ratio measures, and that this is inconsistent with their typical interpretations as measures of periodic power. We conclude that band ratio measures are a non-specific measure, conflating multiple possible underlying spectral changes, and recommend explicit parameterization of neural power spectra as a more specific approach.

Infrared attenuated total reflection spectroscopic analysis and quantitative detection of forage spectral features in ruminant systems.

This study aimed to (1) access protein molecular structure profile and metabolic characteristics of model forages [Foreign sourced-origin (coded as: "FSO", n = 7 vs. Chinese sourced-origin alfalfa hay "CSO", n = 5] in ruminant systems; (2) Quantify the relationship between forage protein molecular structures and protein utilization and availability. Advanced non-invasive vibrational molecular spectroscopic technique (ATR-FTIR: Attenuated Total Reflection Fourier Transform Infrared spectroscopy) with chemometrics was applied to reveal forage protein molecular structure. Both univariate and multivariate molecular spectral analyses were applied to study molecular structure features in model forages. The molecular structure study provided the detailed protein structure profiles of Amide I and Amide II areas and height, total Amide I and II area ratios, Amide I to II height ratio as well as Amide I to II area ratio using ATR-FTIR spectroscopy. The results showed FSO and CSO had similar (P > 0.05) protein rumen degradation kinetics. However, FSO had superior quality than CSO in intestinal (IDP) and total digestible protein (TDP) and truly absorbed nutrient supply (P < 0.05). As intestinal digestion of protein, FSO was higher (P < 0.05) in protein digestion in terms of: intestinal digestibility of rumen undegraded protein (dIDP: 47.5 vs. 38.3 %RUP); Intestinal digestible protein (IDP: 17.6 vs. 13.7 %CP). As truly absorbed nutrient supply, FSO contained higher (P < 0.05) truly absorbed rumen synthesized microbial protein, absorbable rumen undegradable feed protein in the small intestine, total truly digested protein in the small intestine, metabolizable protein and Feed Milk Value (FMVDVE: 1.2 vs. 1.1 g/kg DM). The molecular structure-nutrition interactive relationship study showed that protein molecular structure profiles were highly associated to protein rumen degradation kinetics, significantly correlated to protein subfractions, protein intestinal digestion, and truly absorbed nutrient supply in ruminant systems.

Changes in Sleep Characteristics and Breathing Parameters During Sleep in Early and Late Pregnancy.

STUDY OBJECTIVES: Few studies have objectively evaluated sleep characteristics during pregnancy or investigated the relationship between altered spectral electroencephalogram (EEG) bands and sleep-disordered breathing (SDB). The study aimed to describe changes in sleep as measured by polysomnography (PSG) and spectral EEG bands during pregnancy and to examine the relationship between delta power in non-rapid eye movement (NREM) sleep and SDB. METHODS: This is a secondary analysis of a prospective study. One hundred twenty-three women underwent full PSG in early pregnancy, and 97 repeated PSG in late pregnancy. Spectral analysis of the EEG in NREM sleep was performed. We used linear and logistic mixed-model regression to analyze the sleep measures and linear regression to explore the association between delta power and apnea-hypopnea index (AHI) changes during pregnancy. RESULTS: In late pregnancy, women had shorter sleep duration, poorer sleep efficiency, more awakenings, more stage N2 sleep, less slow wave sleep, less REM sleep, higher AHI, and higher periodic limb movement index compared to early pregnancy. The percentage of stage N1 sleep, sleep latency, REM sleep latency, and arousal index frequency did not change. Regarding EEG-spectra, delta and theta powers decreased, but beta-2 power increased during pregnancy. In multivariable analyses, greater reduction of delta power was associated with larger increases in AHI (ß [95% confidence interval] = -0.038 [-0.073, -0.002], P = .040). Estimates suggest that each one-unit increase in AHI reduces delta power by 4% in late pregnancy. CONCLUSIONS: PSG-measured sleep characteristics change during pregnancy. Delta power decreases when the severity of SDB increases during pregnancy. COMMENTARY: A commentary on this article appears in this issue on page 1095.

Microstructural, Magnetic, and Optical Properties of Pr-Doped Perovskite Manganite La0.67Ca0.33MnO3 Nanoparticles Synthesized via Sol-Gel Process.

We report on microstructural, magnetic, and optical properties of Pr-doped perovskite manganite (La1 - xPrx)0.67Ca0.33MnO3 (LPCMO, x = 0.0-0.5) nanoparticles synthesized via sol-gel process. Structural characterizations (X-ray and electron diffraction patterns, (high resolution) TEM images) provide information regarding the phase formation and the single-crystalline nature of the LPCMO systems. X-ray and electron diffraction patterns reveal that all the LPCMO samples crystallize in perovskite crystallography with an orthorhombic structure (Pnma space group), where the MnO6 octahedron is elongated along the b axis due to the Jahn-Teller effect. That is confirmed by Raman spectra. Crystallite sizes and grain sizes were calculated from XRD and TEM respectively, and the lattice fringes resolved in the high-resolution TEM images of individual LPCMO nanoparticle confirmed its single-crystalline nature. FTIR spectra identify the characteristic Mn-O bond stretching vibration mode near 600 cm- 1, which shifts towards high wavenumbers with increasing post-annealing temperature or Pr-doping concentration, resulting in further distortion of the MnO6 octahedron. XPS revealed dual oxidation states of Mn3+ and Mn4+ in the LPCMO nanoparticles. UV-vis absorption spectra confirm the semiconducting nature of the LPCMO nanoparticles with optical bandgaps of 2.55-2.71 eV. Magnetic measurements as a function of temperature and magnetic field at field cooling and zero-field cooling modes, provided a Curie temperature around 230 K, saturation magnetization of about 81 emu/g, and coercive field of 390 Oe at 10 K. Such magnetic properties and the semiconducting nature of the LPCMO nanoparticles will make them as suitable candidate for magnetic semiconductor spintronics.

Different acquisition systems for heart rate variability analysis may lead to diverse outcomes

Heart rate variability (HRV) is a relevant physiological variable for the estimation of cardiac autonomic function. Although the gold standard for HRV registration is the electrocardiogram (ECG), several applications (APPs) have been increasingly developed. The evaluation carried out by these devices must be compatible with ECG standards. The aim of this study was to compare the data obtained simultaneously with ECG and APP with chest heart rate transmitters. Fifty-six healthy individuals (28 men and 28 women) were evaluated at rest through a short simultaneous HRV measurement with both devices. Data from both acquisition systems were analyzed separately using their own analysis software and exported and analyzed using a validated software. Signal recordings were compatible between the two acquisition systems (Pearson r=0.99; P<0.0001). Although a high correlation was found for the HRV variables obtained in the time domain (Spearman r=0.99; P<0.0001), the correlation decreased in the frequency domain (Pearson r=0.85; P<0.0001) when two software programs were used. Comparison of the averages of spectral analysis parameters also showed differences when HRV data were analyzed separately in each device for low-frequency (LF) and high-frequency (HF) bands. Although the portability of these mobile devices allows for optimal HRV evaluation, the direct analysis obtained from these devices must be carefully evaluated with respect to frequency domain parameters.

Insights into the mercury(II) adsorption and binding mechanism onto several typical soils in China.

To better understand the Hg(II) adsorption by some typical soils and explore the insights about the binding between Hg(II) and soils, a batch of adsorption and characteristic experiments was conducted. Results showed that Hg(II) adsorption was well fitted by the Langmuir and Freundlich. The maximum adsorption amount of cinnamon soil (2094.73 mg kg-1) was nearly tenfold as much as that of saline soil (229.49 mg kg-1). The specific adsorption of Hg(II) on four soil surface was confirmed by X-ray photoelectron spectroscopy (XPS) owing to the change of elemental bonding energy after adsorption. However, the specific adsorption is mainly derived from some substances in the soil. Fourier transform infrared spectroscopy (FTIR) demonstrated that multiple oxygen-containing functional groups (O-H, C=O, and C-O) were involved in the Hg(II) adsorption, and the content of oxygen functional groups determined the adsorption capacity of the soil. Meanwhile, scanning electron microscopy combined with X-ray energy dispersive spectrometer (SEM-EDS) more intuitive revealed the binding of mercury to organic matter, metal oxides, and clay minerals in the soil and fundamentally confirmed the results of XPS and FTIR to further elucidate adsorptive phenomena. The complexation with oxygen-containing functional groups and the precipitation with minerals were likely the primary mechanisms for Hg(II) adsorption on several typical soils. This study is critical in understanding the transportation of Hg(II) in different soils and discovering potential preventative measures.

Threat-induced autonomic dysregulation in panic disorder evidenced by heart rate variability measures.

OBJECTIVE: The objective was to compare autonomic response to threatening stimuli between patients with panic disorder (PD) and healthy volunteers by using 5-min recordings of heart rate variability (HRV). METHODS: Twenty-seven patients with PD and 20 healthy controls were recruited. The first 5-min measurement of HRV was conducted at resting state. HRV measurement during threatening stimuli was conducted while participants were viewing 15 threatening pictures. Spectral analyses measures included high-frequency (HF; 0.15-0.4 HZ) component, low-frequency (LF; 0.04-0.15 Hz) component and LF/HF ratio. RESULTS: There was no significant HRV difference between the two groups at the resting state. During threatening stimuli, the PD group had significantly higher LF power and LF/HF ratio and significantly lower HF power than the healthy controls (for all, P<.01). A two-way analysis of variance was employed to determine the effect of group (patient and control) and condition (threatening and resting) on all three HRV measures. The analysis showed a significant main effect of group (F=12.21; P<.01), condition (F=14.21; P<.001) and interaction effect between group and condition (F=4.83; P<.05) on LF/HF ratio. CONCLUSIONS: The findings from the present study suggest that patients with PD exhibit a sympathetic predominance when faced with threatening stimuli compared with normal control subjects.