Band Intensity Research Articles

Toward the production of biopolyethylene‐based ecocomposites with improved performance: The potential of eggshell particles as an ecological additive

AbstractLow‐density biopolyethylene (BioLDPE) ecocomposites added with particles of eggshell (ES) residue were produced using linear low‐density polyethylene grafted with maleic anhydride (LDPE‐g‐MA) as a compatibilizing agent. BioLDPE/ES and BioLDPE/ES/LDPE‐g‐MA compounds were processed in a twin‐screw extruder, and the specimens were injection molded. Torque rheometry increased and melt flow index reduced more prominently for the BioLDPE/LDPE‐g‐MA biocomposite with 20 phr ES, suggesting higher viscosity. Consequently, there was a higher level of ES particles breakdown, generating greater distribution and dispersion, as verified in optical microscopy and scanning electron microscopy images. This finding was supported by Fourier transform infrared spectroscopy, considering the intense absorption band at 871 cm−1 for BioLDPE/ES (20 phr)/LDPE‐g‐MA biocomposite, indicating a higher level of ES particles dispersion in BioLDPE matrix. Therefore, BioLDPE/ES (20 phr)/LDPE‐g‐MA biocomposite increased the elastic modulus, tensile strength, Shore D hardness, and heat deflection temperature by 51.4%, 16.9%, 16.4%, and 14, 6%, respectively, related to BioLDPE. Additionally, the flexibility was kept as seen in the elongation at break and impact strength, including not fractured during the impact test. Reported results for the biocomposites are valuable mainly for the polymer additive sector, since the ES has the potential to improve BioLDPE properties, expanding the range of applications.

Carbon microspheres/carbon sheets as efficient electromagnetic wave absorbers

To address the issue of weak absorption intensity and narrow frequency band in pure dielectric electromagnetic wave (EMW) absorbing materials, this study adopts a simple method to successfully prepare a pure dielectric EMW absorption material by modifying acrylonitrile–methylmethacrylate copolymer carbon microspheres (co-AN-MMA@CS) with capsaicin-like 3,5-dimethylphenol derivative (DMPD). The introduction of DMPD into the carbon microspheres increases the heteroatoms (N, O) in the carbon material, thus resulting in functional groups (-C-N, –NO, and C–O) that enable energy loss through dipole polarization. Additionally, the special morphology of carbon microspheres attached or embedded in carbon sheets derived from DMPD increases the inhomogeneous interfaces, thereby increasing the interface polarization relaxation and further attenuating EMWs. The resulting carbon material with the optimal structure (denoted as CNO-2) exhibits superior EMW absorption properties. At a thickness of 2.50 mm, the minimum reflection loss (RLmin) reaches −63.10 dB at 13.14 GHz, whereas the maximum effective absorption bandwidth (EABmax) reaches 6.81 GHz (8.95–15.76 GHz). CNO-2 has excellent EMW absorption capabilities due to the controllable complex dielectric constant and multiple attenuation mechanisms, including interfacial polarization, dipole polarization, and conduction loss. The CNO absorbers prepared in this study can be used as efficient microwave absorbers for electromagnetic protection applications.

Intensities of Atmospheric bands of molecular oxygen in the nightglow

The intensities of the Atmospheric bands of molecular oxygen Ivʹvʺ (cm–2s–1) in the nightglow of the Earth’s atmosphere are calculated for different latitudes and seasons. The calculations were performed using experimental data on the profiles of atomic oxygen concentrations for different seasons. The calculated integral intensities of Atmospheric bands are compared with experimental data obtained from the space shuttle (STS transport system), as well as from the Keck I telescope. It is shown that there is good agreement between theoretical calculations and experimental data for the considered latitudes, but better agreement is received with data obtained from Keck I telescope.

Spectroscopic properties and photoluminescence of the Li2B4O7:Mn,Sm glass

The Li2B4O7:Mn,Sm glass containing 1.0 mol.% MnO2 and Sm2O3 were researched by X-ray diffraction (XRD), electron paramagnetic resonance (EPR), and optical spectroscopy methods. The studied glass of high optical quality was obtained by high temperature melting technique. Parameters of the local structure (interatomic distances and coordination numbers) of Li2B4O7:Mn,Sm glass were derived from XRD data analysis. The EPR and optical spectroscopy (absorption, luminescence excitation, emission, decay kinetics) show the presence of Mn2+(3d5) and Mn3+(3d4) impurity ions in the Li2B4O7:Mn,Sm glass. By EPR spectroscopy in the studied glass were identified three types of Mn2+ centres: single Mn2+ (1) centres in the strongly distorted sites (ratio of rhombic and axial constants, |E/D| ≤ 1/3), single Mn2+ (2) centres in the sites with almost cubic symmetry (D ≅ 0, E ≅ 0) as well as Mn2+ pairs and small clusters coupled by magnetic dipolar and exchange interaction, respectively. The Mn2+ EPR spectra parameters in the Li2B4O7:Mn,Sm glass have been determined at T = 295 K. Optical absorption spectrum of the Li2B4O7:Mn,Sm glass contains a very broad intense band peaked at 467 nm belonging to the 5Eg(D) → 5T2g(D) transition of Mn3+ ions and several weak narrow lines corresponding to the 6H5/2 → 6P3/2, 6H5/2 → 6F9/2, 6F7/2, 6F5/2 transitions of Sm3+ (4f5, 6H5/2) ions. Emission spectrum of the Li2B4O7:Mn,Sm glass exhibits a broad band corresponding to the 4T1g(G) → 6A1g(S) transition of Mn2+ ions and three characteristic bands in the yellow-orange-red range belonging to the 4G5/2 → 6H5/2, 6H7/2, 6H9/2 transitions of Sm3+ ions. Photoluminescence spectra (excitation and emission) and decay kinetics of the Mn2+ and Sm3+ ions in the Li2B4O7:Mn,Sm glass are interpreted in comparison with corresponding results for Li2B4O7:Mn and Li2B4O7:Sm glasses. Energy transfer processes Sm3+→Mn2+, Mn3+, and Mn2+→Mn3+ in the studied glass are considered.

Lactiplantibacillus plantarum and Lactiplantibacillus paraplantarum postbiotics: Assessment of the biotic-derived metabolites with cytocompatibility and antitumoral potential

In this study, the postbiotics production ability of Lactiplantibacillus plantarum MIUG BL21 (Lpb.21) and Lactiplantibacillus paraplantarum MIUG BL74 (Lpb.74), was demonstrated through the fermentation of different media based on agri-foods by-products, gluten free flours, and bovine colostrum. Three categories of postbiotics were identified, such as bioactive peptides, a wide spectrum of polyphenols with antioxidant activity and short chain fatty acids. After fermentation, the polypeptides' profile showed different patterns, with more intense bands at about 30 kDa in gluten-free flour based fermentation product (FP) and between 18 and 34 kDa in the colostrum-based FP. The main synthetized organic acids were acetic acid, followed by isovaleric and valeric acid, respectively. The postbiotics production was highly depended on the medium composition and LAB strains, evidencing the presence of isovaleric, valeric acids, isobutyric acid, isorhamnetin, gallic acid, naringin, galangin, syringic acid, p-coumaric acid, ferulic acid, apigenin, abscisic acid, pinocembrin, pinostrobin, hyperoside, caffeic acid, catechin, ellagic acid and hyperoside. The FP derived by agri-food byproducts fermentation highlighted a better antimicrobial activity when compared to the FP obtained through bovine colostrum-based media' fermentation. All the fermented medium showed good cytocompatibility and antitumoral potential, correlated with both the strains fermentative potential and biotechnological conditions, especially with the medium composition.

Luminescence Properties of ZrO2: Ti Ceramics Irradiated with Electrons and High-Energy Xe Ions.

Samples of ZrO2 ceramics with different concentrations of impurity titanium ions were synthesized by mixing zirconium and titanium oxide powders in different mass ratios. The X-ray diffraction analysis was used to determine the phase composition, lattice parameters, and crystallite size of the ceramics with varying dopant concentrations. Upon irradiation of the samples with 220 MeV Xe ions to a fluence of 1010 ions/cm2, a decrease in the intensity of the pulsed cathodoluminescence band at 2.5 eV was observed. Additionally, ion irradiation resulted in the emergence of a new thermoluminescence peak at 450-650 K attributed to radiation-induced traps of charge carriers. Further analysis revealed that the thermoluminescence curves of samples irradiated with electrons and ions comprise a superposition of several elementary peaks. Notably, a complex non-monotonic dependence of cathodo- and thermoluminescence intensity on titanium concentration was observed, suggesting the influence of concentration quenching and the presence of tunneling transitions.

Enhanced upconversion emission in Nd, Yb, Er and Ho tetra-doped Y2O3 phosphor

Yb3+, Nd3+, Er3+ and Ho3+ tetra ions doped Y2O3 upconversion phosphors have been prepared by the combustion route. Crystalline phase purity and cubic phase of prepared samples have been confirmed from powder X-ray diffraction study. Absorbance of samples over spectral range 200–1100 nm has been measured by diffuse reflectance spectroscopy. All samples exhibit large band gaps. Scanning electron micrograph analysis reveals spherical morphology of particles and sizes around 200 nm. Upconversion emission has been studied under a 980 nm diode laser excitation with 166 mW laser power. The Ho3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor show very high emission intensity of a green band centred at around 550 nm and another moderate intensity red band centred on 667 nm, while reverse is the case for Er3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor. Er3+, Ho3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor show enhanced high emission intensity in both green and red bands. These two bands are not visible in Nd3+ and Yb3+ co-doped Y2O3 phosphor but show weak upconversion emission at 549, 568 and 799 nm. Owing to the high emission intensity of green band, Ho3+, Nd3+ and Yb3+ co-doped Y2O3 phosphor may find potential applications in medical and security, while Er3+, Ho3+, Nd3+ and Yb3+ co-doped phosphor showing enhanced upconversion in green and red bands may find applications in white light generation.

Enhancing polyamide 6: Acid hydrolysis for functionalization and amino group quantification

In this study, our primary aim was to increase the presence of amine groups in polyamide 6 fibers. To achieve this, we employed a functionalization process that mainly depended on increasing the number of reactive sites via acid-catalyzed hydrolysis. The effects of several acids were rigorously examined, including hydrochloric acid (HCl), sulfuric acid (H2SO4), and formic acid (HCOOH). Following this comprehensive acid-based treatment, the method that demonstrated the most significant increase in amine groups was selected for further evaluation in dyeing experiments and full characterization. The quantification of amino groups was performed using potentiometry, evaluating the equilibrium state of acid removal from the fibers. To corroborate these results, the acid dye Levaset Blue 2R was employed, which measured the amount of dye bound to the fibers during the dyeing process. Characterization of the polyamide 6 fiber structural changes was conducted using multiple techniques, including tensile tests, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). Among the acid treatments, the 11% HCl treatment exhibited the most significant increase in amine groups, amounting to an approximately 110% increase as measured by potentiometry and an approximately 150% increase using the dyeing method. During the dyeing process, the 11% HCl-treated fibers absorbed 91% of the dye from the dye bath, indicating enhanced color intensity and K/S value, thus affirming the efficacy of the amine group increasing. Tensile testing revealed a decrease in the strength of the functionalized fiber. In the FTIR spectra, there was a notable increase in the intensity of bands associated with the fiber's crystalline regions and hydrogen bonds. DSC tests validated the FTIR results, demonstrating a 9% increase in crystallinity. Furthermore, SEM micrographs depicted surface alterations induced by the hydrolysis process. These results collectively highlight the effectiveness of hydrolysis in introducing functional groups, enhancing color intensity during dyeing with acid dyes, and reducing dye content in the bath. Additionally, the potentiometric method for quantifying amine group demonstrated practicality and accuracy, serving as a valuable contribution to the field.

Influence of Yb3+ percentage on emission of Er3+ doped into GdVO4 matrix

In this study, we used the non-hydrolytic sol–gel methodology to synthesize gadolinium vanadate particles doped with different Er3+ and Yb3+ molar ratios. Er3+ and Yb3+ chlorides and vanadium alkoxide were used as precursors during the sol–gel synthesis. The resulting powders were treated at 800 °C and characterized by x-ray diffraction and photoluminescence. The x-ray diffractogram displayed peaks attributed to the gadolinium vanadate matrix. Photoluminescence helped to evaluate the Fluorescence Intensity Ratio (FIR), which is important for understanding the nanothermometer property. The FIR of the GdVO4:Er3+/Yb3+ samples containing different Er3+ and Yb3+ molar ratios increased as a function of the laser power, which indicated that the local temperature increased. The excitation spectra obtained at fixed wavelengths of 525 and 555 nm displayed bands at 322, 379, and 489 nm, ascribed to the charge transfer band and Er3+ levels. Upon excitation at 321 nm, the emission spectra in the visible region presented intense bands at 525 and 555 nm, due to Er3+ emission, and excitation at 321 nm led to emission in the infrared region, 980 and 1550 nm. In conclusion, the synthesized system can be employed as a temperature sensor.

Multiwalled carbon nanotubes decorated with molybdenum sulphide (MoS2@MWCNTs) for highly selective electrochemical picric acid (PA) determination

Nitrophenols are industrially versatile yet environmentally detrimental compounds. Herein, we have synthesised molybdenum sulphide based dichalcogenide supported multiwalled carbon nanotubes i.e. MoS2@MWCNTs electrocatalyst by simple wet chemical method for PA determination. The successful decoration of MoS2 over MWCNTs were confirmed by various characterizations techniques including scanning electron microscopy (SEM) shows MoS2 layers grown on MWCNTs and having average size is –80 nm. Energy dispersive X-ray analysis (EDAX) reveals elements are homogenously distributed in nanocomposite. High resolution-transmission electron microscopy (HR-TEM) shows increase in average diameter after decoration of MoS2 over MWCNTs from 30 nm to 70 nm. The Fourier transform infrared (FT-IR) analysis suggests the presence of Mo-S stretching frequency at 605 cm−1 in addition to hydroxyl, carbonyl, C–C, C–O stretching frequencies are also observed. In Raman spectrum from apart D and G bands, the characteristic intense bands E2g1 and A1g of MoS2 were pointed towards presence of molybdenum and sulphur. The X-ray diffraction (XRD) confirms synthesised electrocatalyst is in hexagonal crystal structure with P63/mmc space group. The X-ray photoelectron spectroscopy (XPS) reveals that for Mo 3d is found to be two characteristics peaks at 231.2 eV and 233.2 eV corresponds to Mo4+ 3d3/2 and 3d5/2 respectively. The peak at 229 eV corresponds to S 2s. Whereas, the signal appears at 162.7 eV, 165 eV, 169 eV and 170 eV shows sulphur is in 2S3/2 and 2S5/2 states. Electrochemical performance was examined by cyclic voltammetry (CV) tests. The Electrocatalyst is highly selective, having appreciable anti-interference property, lower limit of detection (LoD), i.e., 0.5 μM with wide linear range. The low Rct and high k⁰ pointed that MoS2@MWCNTs performed better towards electrochemical detection of PA.

Experimental Study on the Micro-Structure of Lignite and Its Explosive Solid Residue

ABSTRACT Lignite reserves in the world’s various coal reserves in the first place. To take a qualitative and quantitative analysis on the change characteristics of the microstructure of lignite before and after explosion, the explosive tests took four lignite samples as the research object and were carried out in the 20 L spherical explosive test system. The experimental study was carried out by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectrometer to analyze the change characteristics of the surface morphology and macromolecular structure of lignite before and after explosion. The results indicated that compared with bituminous coal, the surface particles of lignite are less porous after explosion and the morphology is relatively complete. The rich aliphatic hydrocarbon and oxygen-containing structures in the range of 700–1800 cm−1 and 2800–3000 cm−1 contained in lignite were greatly reduced or disappeared after the explosion, while the mineral band at 536 cm−1 were more obvious and the band intensity became stronger. The area of D3 and D4 peak in Raman spectra decreased significantly after the explosion, which means that the CH3 and CH2 structures in the carbon structure of R-O-R’ (ether group) in lignite are significantly reduced. Besides, the intensity ratio of the sum of D3 peak and D4 peak to G peak ((ID3+ID4)/IG) of the solid product after explosion is reduced significantly, close to 0. The change can be applied of coal microstructure groups in the process of explosive reaction is helpful to reveal the reaction mechanism of pulverized coal explosion and provide a reference for identification and analysis the pulverized coal explosion accident.

Reduction in the antigenicity of beta-lactoglobulin in whole milk powder via supercritical CO2 treatment

Cow milk allergy is a common phenomenon experienced in early childhood (<5 yr of age) with an average occurrence rate of roughly 2.5%. The most prevalent allergen in cow milk is believed to be β-LG. The objective of this study was to evaluate the use of hydrophobic supercritical CO2 (ScCO2) to modify the chemical structure β-LG, thus impairing its recognition by antibodies. Whole milk powder (WMP) was selected because of its closest compositional resemblance to bovine fluid milk and its applications in reconstitution and in the beverage (infant, toddler, and adult), confectionary, bakery, and meat industries. For this study, WMP was treated with food-grade CO2 at temperatures of 50, 63, and 75°C under operating pressures of 100, 150, 200, 250, and 300 bar. Proteins in WMP were examined using SDS-PAGE, western blot, and ELISA. Orbitrap Fusion liquid chromatography-tandem MS (LC-MS/MS) and periodic staining was performed to confirm post-translational modifications in β-LG. Functional properties of WMP before and after treatment were assessed by its solubility index, oil holding capacity, emulsion capacity and stability, zeta potential, particle size, and color analysis. SDS-PAGE of treated samples yielded fuzzy bands (variable mobility of molecules due to different molecular weights results in ill-defined bands) indicative of an increase in molecular weight, presumably due to chemical change in the protein, and demonstrated a maximum of 71.13 ± 0.29% decrease in the band intensity of β-LG under treatment conditions of 75°C/300 bar for 30 min. These changes were small with samples treated with heat only. Lighter, diffused bands were observed using western blot analysis. The ELISA tests proved that ScCO2 treatment specifically and significantly affected the antigenicity of β-LG with a reduction of 42.9 ± 2.83% and 54.75 ± 2.43% at 63°C/200 bar and 75°C/300 bar, respectively. Orbitrap fusion detected the presence of fatty acids and sugar moieties bound to β-LG and the latter was confirmed by periodic staining. Functional properties of ScCO2-treated milk powder yielded a decrease in solubility index and an increase in emulsion capacity of WMP was observed under ScCO2 treatment at 75°C/300 bar, with small and insignificant changes at other treatments producing a decrease in antigenicity. Color changes were small for most samples, except at 63°C/200 bar, where a significant increase in yellowness was observed. Zeta potential and particle size measurements indicated that most changes were temperature driven. This study demonstrates 2 approaches to mitigate β-LG antigenicity via fatty acid binding and lactosylation using hydrophobic ScCO2.

A rapid, inexpensive and effective method for the efficient isolation of genomic DNA from Gram-negative bacteria.

Currently, there are several protocols to extract bacterial DNA based on different principles. However, the quantity and the quality of the DNA obtained by each method are highly variable and microorganism dependent. In most of these classical crude methods, highly toxic and hazardous organic solvents such as phenol and chloroform are used for deproteinization, whereas in certain protocols, expensive enzymes including RNases and Proteinases are used. This study was designed to introduce a simple, rapid, inexpensive and effective genomic DNA isolation procedure for Gram-negative bacteria, without the usage of toxic chemicals and costly enzymes. This novel method was compared with another classical method known as the salting-out method, which uses proteinase-K. Concentration and yield of the extracted DNA were determined by gel electrophoresis by comparing the gel band intensity of the sample DNA to that of a DNA quantitation standard and by the Quantus™ fluorometer. According to the results, the yield of extracted DNA was higher in the novel method compared to the salting-out method. Moreover, the entire process was accomplished in less than 2h with the novel method. Purity and integrity of extracted genomic DNA by both methods were similar. In addition, the quality of DNA was determined using Multicopy Associated Filamentation (MAF) gene amplification by polymerase chain reaction (PCR). Thus, the described technique is non-toxic, less time and fund consuming, efficient and a well-suited method for routine DNA isolation from Gram negative bacteria.

Crystal Growth, Optical, Thermal, DFT and Z‐Scan Studies of Imidazolium Hydrogen Fumarate Crystal for Nonlinear Optical Applications

AbstractOrganic imidazolium hydrogen fumarate (IHF) crystals are grown using the slow evaporation method. The IHF has triclinic crystal structure. The 1H NMR spectrum has five chemical shifts for the IHF crystal. The band at 3155 cm−1 in IR occurs due to the presence of O─H stretching vibration of the IHF molecule. The bandgap value of the IHF crystal is determined to be 4.6 eV. The intense violet emission band is noted at 361 nm. The IHF crystal has thermal stability value of 179 °C. Hirshfeld surface is used to find out the different intermolecular interactions of the IHF crystal. The HOMO–LUMO energy gap is determined to be 4.70 eV. The hydrogen atoms have positive potential in the MEP analysis. The high stabilization energy of 56.81 kcal mol−1 is noticed for π*(C1─N7) → π*(C2─C3) interaction. The third‐order NLO susceptibility (χ(3)) of the IHF is 2.08934 × 10−9 esu.

Solid Phase Synthesis and TAR RNA-Binding Activity of Nucleopeptides Containing Nucleobases Linked to the Side Chains via 1,4-Linked-1,2,3-triazole.

Nucleopeptides (NPs) represent synthetic polymers created by attaching nucleobases to the side chains of amino acid residues within peptides. These compounds amalgamate the characteristics of peptides and nucleic acids, showcasing a unique ability to recognize RNA structures. In this study, we present the design and synthesis of Fmoc-protected nucleobase amino acids (1,4-TzlNBAs) and a new class of NPs, where canonical nucleobases are affixed to the side chain of L-homoalanine (Hal) through a 1,4-linked-1,2,3-triazole (HalTzl). Fmoc-protected 1,4-TzlNBAs suitable for HalTzl synthesis were obtained via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) conjugation of Fmoc-L-azidohomoalanine (Fmoc-Aha) and N1- or N9-propargylated nucleobases or their derivatives. Following this, two trinucleopeptides, HalTzlAAA and HalTzlAGA, and the hexanucleopeptide HalTzlTCCCAG, designed to complement bulge and outer loop structures of TAR (trans-activation response element) RNA HIV-1, were synthesized using the classical solid-phase peptide synthesis (SPPS) protocol. The binding between HalTzls and fluorescently labeled 5'-(FAM(6))-TAR UCU and UUU mutant was characterized using circular dichroism (CD) and fluorescence spectroscopy. CD results confirmed the binding of HalTzls to TAR RNA, which was evident by a decrease in ellipticity band intensity around 265 nm during complexation. CD thermal denaturation studies indicated a relatively modest effect of complexation on the stability of TAR RNA structure. The binding of HalTzls at an equimolar ratio only marginally increased the melting temperature (Tm) of the TAR RNA structure, with an increment of less than 2 °C in most cases. Fluorescence spectroscopy revealed that HalTzlAAA and HalTzlAGA, complementary to UUU or UCU bulges, respectively, exhibited disparate affinities for the TAR RNA structure (with Kd ≈ 30 and 256 µM, respectively). Hexamer HalTzlTCCCAG, binding to the outer loop of TARUCU, demonstrated a moderate affinity with Kd ≈ 38 µM. This study demonstrates that newly designed HalTzls effectively bind the TAR RNA structure, presenting a potential new class of RNA binders and may be a promising scaffold for the development of a new class of antiviral drugs.

Structural and spectroscopic correlation in barium-boro-tellurite glass hosts: effects of Dy2O3 doping

In this study, a series of barium-boro-tellurite glass hosts with varying concentration of Dy2O3 doping (0 to 1.25 mol%) were made by melt-quenching method. A study was conducted to investigate how Dy2O3 dopants affect the physical and spectroscopic traits of glasses. Raw materials including barium oxide (BaO), tellurium dioxide (TeO2), boron oxide (B2O3), and dysprosium oxide (Dy2O3) were used to produce these glasses. XRD patterns of the samples showed a broad hump and absence of long-range periodic lattice arrangements, indicating their amorphous nature. The Raman spectral analyses displayed the various vibration modes where the most intense band caused by BaO vibrations at 300 cm-1 and 450 cm-1 corresponding to the symmetric stretching vibration mode of Te–O–Te intra-chain bridges. The peak at 750 cm-1 was due to TeO4 and Te-O-Te vibration modes. The value of optical band gap energy was decreased from 3.155 to 2.1894 eV and then increase at higher Dy2O3 level (0.75 to 1.25 mol%). At Dy3+ contents between 0.25 to 1.25 mol% seven absorption bands were observed at 390, 424, 452, 750, 797, 895 and 1092 nm due to the electronic transitions in Dy3+. The glass refractive indices were raised from 2.3563 to 2.6584 and then decreased at higher Dy2O3 contents which was mainly because of the generation of more bridging oxygen (BO) in the glass matrix. The value of glass electronic polarizability and oxide ions polarizability calculated using LorentzLorenz equation showed a decrease with the rise of Dy2O3 contents, which was ascribed to the presence of fewer non-bridging oxygen (NBO). The optical basicity of the proposed glass hosts was calculated using Duffy and Ingram equation which was decreased with the increase of doping contents. In addition, the optical transmission was increased and reflection loss was reduced with increasing Dy+3 levels. The value of metallization parameter below 1 proved the true amorphous nature of the prepared samples. All the glasses revealed blue and yellow photoluminescence emission peaks due to 4F9/2→ 6H15/2, and 4F9/2 →6H13/2 transitions in Dy3+, respectively. The proposed glass compositions may be beneficial for the advancement of solid-state lasers.

A New Methodological Approach to Study the Interaction of Humic Acids, Minerals and Polyvalent Cations in Soil

ABSTRACT A new methodological approach of humic acid (HA) extraction is applied to study soil samples with contrasting management regimes: natural vegetation (NV) and agricultural (A). This innovative approach involves a modification of the Swift’s method, wherein several steps HCl/HF are replaced by a single-step HCl/HF. This modification enabled us to investigate the ability of HA to retain inorganic constituents. The carbon content was significantly higher in soils under NV (19.8–27.3 g C kg−1) than under A (11.2–13.4 g C kg−1). The same pattern was observed for the HA content. The new methodology revealed that HA from NV soils had a much higher capacity to retain inorganics (ash contents in HA from 12.3–28.3%) than in A soils (ash content in HA from 1.6–2.6%). Similar results were found for Ca+Al+Fe contents in the HA (3.7–2.5 meq g−1 in HA from NV soils; 2.2–.9 meq g−1 in HA from A soils). Some differences were observed in IR spectra, mainly an intense band at around 1050 cm−1 of HA from NV that reflects the high ash content of the HA and its capacity of retaining inorganic material. Ca binding isotherms of HA also showed that the HA differed significantly in their ability to retain inorganic components when extracted. Humic acid from NV was more efficient in retaining metal ions and minerals than HA from A soils. All results point to a better contact between organic and inorganic matter in NV soils, and this contact contributes to the stabilization of organic matter.

Deep-water ambient sound on near-bottom receivers in the New England Seamount Chain

Ambient sound was recorded for about two months by three synchronized, single-hydrophone receivers that were moored at depths of 2573, 2994, and 4443 m on seamount flanks. Hydrophones were located within 5 m from the seafloor. The data reveal the power spectra and intermittency of the ambient sound intensity in a 13-octave frequency band from 0.5 to 4000 Hz. Statistical distribution of pressure amplitude exhibits much heavier tails than the expected Rayleigh distribution throughout the frequency band of observations. Spatial variability of the observed ambient sound is controlled by the seafloor properties, bathymetric shadowing, and nonuniform distribution of the noise sources on the sea surface due to the Gulf Stream and its meanders. Interferometry of the ambient sound recorded by the receivers with the horizontal separations of 7.0 km shows strong variations of the acoustic travel time between the receivers along a surface-reflected path due to the evolution of the Gulf Stream position. The magnitude of the variations of the passively measured acoustic travel time is consistent with the available contact measurements of the sound speed profiles. Environmental inferences derived from the ambient, shipping, and flow noise data will be discussed. [Work supported by the ONR TFO DRI.]

Intensities of the Atmospheric Bands of Molecular Oxygen in the Nightglow

Intensities of the Atmospheric Bands of Molecular Oxygen in the Nightglow

Excitonic feature in CsAg2I3 crystals prepared by Bridgman method

This study investigated the optical spectra of the CsAg2I3 crystals at low temperatures. In the reflection spectrum, remarkable reflection peaks owing to band-edge exciton transitions were observed at approximately 3.8 eV above the fundamental absorption edge at 3.6 eV. Under excitation in the energy region of exciton transitions, an intense luminescence band attributed to a self-trapped exciton (STE) was observed at 3.37 eV. In addition to STE luminescence, a weak luminescence line was observed at 3.77 eV. Because the value of 3.77 eV is practically equal to the lowest exciton transition energy estimated from the reflection spectrum, the luminescence line at 3.77 eV comes from a free exciton (FE). The intensities of the FE and STE luminescence peaks decrease with increasing temperature. The activation energies of the FE and STE were estimated from the quenching of luminescence intensities. The features of the exciton states in the CsAg2I3 crystals are presented.