Spectral Monitoring Research Articles

A Facile Approach to Upconversion Crystalline CaF2:Yb3+,Tm3+@mSiO2 Nanospheres for Tumor Therapy.

A new facile approach, namely chemical-assisted sol-gel growth (CASGG), was successfully developed to induce the formation of fine CaF2:Yb3+, Tm3+ nanocrytals within the pore channels of mesoporous silica (mSiO2) nanoparticles. A series of upconversion photoluminescent crystalline CaF2:Yb3+,Tm3+@mSiO2 nanospheres with controlled diameters from ~65 nm to ~290 nm were fabricated. All nanospheres presented sound cyto-compatibility and unique ratiometric spectral monitoring functionalities for drug release kinetics. The nanospheres with smallest dimension (UCNP-2.5, ~65nm) induced the most sustained DOX release kinetics. More importantly, the in-vitro study demonstrated that the DOX loaded UCNP-2.5 nanopheres presented the strongest anti-cancer efficacy to MCF-7 human breast cancer cells due to its stronger penetration ability to cell nuclei due to the size effect.

Kinetics of the ClO + CH3O2 reaction over the temperature range T = 250-298 K.

The kinetics of the potentially atmospherically important ClO + CH3O2 reaction (1) have been studied over the range T = 250-298 K at p = 760 Torr using laser flash photolysis radical generation, coupled with time resolved ultraviolet absorption spectroscopy, employing broad spectral monitoring using a charge coupled device detector array. ClO radicals were monitored unequivocally using this technique, and introduction of CH3O2 precursors ensured known initial methylperoxy radical concentrations. ClO temporal profiles were thereafter analysed to extract kinetic parameters for reaction (1). A detailed sensitivity analysis was also performed to examine any potential systematic variability in k1 as a function of kinetic or physical uncertainties. The kinetic data recorded in this work show good agreement with the most recent previous study of this reaction, reported by Leather et al. The current work reports an Arrhenius parameterisation for k1, given by: . This work therefore concurs with that of Leather et al. implying that the title reaction is potentially less significant in the atmosphere than inferred from preceding studies. However, reaction (1) is evidently a non-terminating radical reaction, whose effects upon atmospheric composition therefore need to be ascertained through atmospheric model studies.

Interaction of Fullerenes with Organosilanes in the Ionization Chamber of a Mass Spectrometer under Electron Impact and the Reaction of C60with Tetraphenylsilane in Solution under UV Irradiation

C60was shown to react with organosilanes Me4Si, Ph2SiH2, Ph2MeSiH, Ph4Si, andα-naphthylphenylmethylsilane in the electron ionization ion source of a mass spectrometer with the transfer of the corresponding organic radicals (Me, Ph, andα-naphthyl) from the silanes to the fullerene. The reactions were accompanied by hydrogen addition to some products and hydrogen loss from them. C70reacted with Me4Si analogously. A reaction mechanism involving homolytic dissociation of the silanes under electron impact to the corresponding organic radicals, which react further with C60at the surface of the ionization chamber of the mass spectrometer to give the respective adducts, was offered. A mechanistic study of the reaction of C60with Me4Si supported it. No silicon containing derivatives of the fullerenes were found. C60reacted with Ph4Si in solution under UV irradiation in a similar fashion furnishing phenyl derivatives of the fullerene. These results provide an additional support to the hypothesis formulated earlier thatthe homolytic reactive mass spectrometry of fullerenes (the reactions of fullerenes with other species in the ionization chambers of mass spectrometers and their mass spectral monitoring)can predict the reactivity of them toward the same reagents in solution to a significant extent.

Mechatronic System for Spectral Monitoring of the Crops Vegetation Status

This paper presents a mechatronic solution for monitoring the crops vegetation status. A data acquisition system containing different types of sensors (multispectral, temperature, plant height, GPS) is placed on a terrestrial mechatronic platform that is carried by a tractor or on an UAV (Unmanned Aerial Vehicle). The multispectral sensor offers information about the reflectance, for discrete wavelengths, necessary to compute the so called vegetation indices. They are correlated with the degree of development and plant health, thermal and water stress, pests, fertilizer need and so on. Knowing these information, a timely intervention is possible, allowing to supply water, pesticide and fertilizer in the proper quantity, at the proper time and in the precise place, leading to major economic impact and significant environmental protection. Geographical information are used for geo-referencing the acquired data, so that the thematic maps to be generated.

Sensitive metal layer-assisted guided-mode resonance SU8 nanopillar array for label-free optical biosensing

A novel polymer nanopillar lattice architecture for label-free optical biosensing based on the metal layer assisted guided-mode resonance (MaGMR) effect is presented. The device consists of a 2D array of SU8 nanopillars fabricated by e-beam lithography (EBL) on an optically-thick aluminum layer. EBL proximity effect, that is, the influence of the electron irradiation in the regions adjacent to those exposed by the e-beam – which is usually considered an undesirable fabrication issue – is positively used to create a non-uniform thickness, crosslinked SU8 film among the SU8 nanopillars on the aluminum layer. The optical response of the resulting SU8 nanostructure array exhibits a MaGMR under normally incident light interrogation. Spectral reflectance monitoring of the MaGMR upon the adsorption of water, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and bovine serum albumin (BSA) molecules is employed to evaluate the surface sensing characteristics of the resonant nanostructure. The figure of merit of the device, defined as the quotient of the surface sensitivity and the resonance spectral width, is increased by two orders of magnitude (0.127nm−1 versus 0.009nm−1) as compared with previous SU8 nanopillar array surface sensing architectures because of the high sensitivity and narrow spectral width of the MaGMR feature.

High-frequency variations of spectral lines in cromospherically active stars 61 cyg AB

We report on the detection of rapid variability in subsecond mode in the Balmer lines of hydrogen, lines Ca II H,K, and b Mg I triplet in chromospherically active stars 61 Cyg A, B. The spectral observations of 61 Cyg A, B were performed with MMCS spectrograph in Cassegrain’s focus of the 2-m telescope at peak Terskol (R = 13000), with a grating spectrograph mounted on a 60-cm telescope at peak Terskol (R ≈ 100), and a 60-cm telescope of the Andrushivka Observatory (R ≈ 200). The observations were carried out in the framework of international campaign of observations of variable stars using the Synchronous Network of Telescopes. The high-resolution spectra were obtained with intervals of approximately 2 minutes. The low-resolution spectra were obtained with intervals from 2 to 3 seconds. Spectral monitoring lasted from 30 minutes to 2 hours. We found that chromospherically active dwarf stars 61 Cyg A, B, having extensional spots on their surfaces exhibit rapid variations in the hydrogen lines, lines CaII H, K of ionized calcium and chromospheric triplet b Mg I on a time scale from approximately 2 seconds to approximately 2 minutes. Variations in the intensity of lines range from 1.5% in the Balmer series of hydrogen to approximately 0.5% in the lines of b Mg I triplet. These variations are well described by the shot noise model in the form of random elementary pulses with the frequency of occurrence of a few fractions of events per second to a few events per second. Comparison of rapid variations in chromospheric lines with different time intervals demonstrates the transient nature of this activity both on short (subsecond) and long-time scales.

Spectral Monitoring of the Crops Vegetation Status in Precision Agriculture

This paper proposes an analysis of spectral monitoring processes of the crop vegetation status. In terms of the extensive implementation of precision agriculture, the performant agricultural management must ensure the monitoring of crop vegetation. In this context, determination and interpretation of vegetation indices, based on spectral data, plays a very important role. The performed research revealed the characteristics of monitoring the status of vegetation in order to obtain the necessary information, ie structure, actions and performances required to achieve an efficient system of monitoring the state of vegetation resources and to obtain the application maps for a precision crop management.precision crop management. This complex system ensures data acquisition and processing, thematic and application maps realization and decision generating on obtaining large productions and quality, on optimizing the economic profits, achieving of an integrated environmental protection and increasing of the sustainability of agricultural systems.

Water spectral pattern as holistic marker for water quality monitoring

Online water quality monitoring technologies have been improving continuously. At the moment, water quality is defined by the respective range of few chosen parameters. However, this strategy requires sampling and it cannot provide evaluation of the entire water molecular system including various solutes. As it is nearly impossible to monitor every single molecule dissolved in water, the objective of our research is to introduce a complimentary approach, a new concept for water screening by observing the water molecular system changes using aquaphotomics and Quality Control Chart method. This approach can continuously provide quick information about any qualitative change of water molecular arrangement without taking into account the reason of the alteration of quality. Different species and concentrations of solutes in aqueous systems structure the water solvent differently. Aquaphotomics investigates not the characteristic absorption bands of the solute in question, but the solution absorption at vibrational bands of water's covalent and hydrogen bonds that have been altered by the solute. The applicability of the proposed concept is evaluated by monitoring the water structural changes in different aqueous solutions such as acid, sugar, and salt solutions at millimolar concentration level and in ground water. The results show the potential of the proposed approach to use water spectral pattern monitoring as bio marker of water quality. Our successful results open a new venue in water quality monitoring by offering a quick and cost effective method for continuous screening of water molecular arrangement. Instead of the regular analysis of individual physical or chemical parameters, with our method – as a complementary tool – the structural changes of water molecular system used as a mirror reflecting even small disturbances in water can indicate the necessity of further detailed analysis by conventional methods.

High spectral resolution monitoring of Nova V339 Delphini with TIGRE

Aims. We investigate the early development of the classical nova V339 Del (Nova Delphini 2013) through high-resolution optical spectroscopy. To study the structure of the ejecta, we focus on the evolution of the absorption and emission features and the changes within the line profiles.Methods. We obtained spectra with the robotic 1.2 m telescope TIGRE equipped with the HEROS spectrograph (R = 20 000, wavelength coverage from 3800 to 8800 A). Our data set covers the outburst from 3 until 121 days after discovery. Results. We provide a qualitative analysis of the spectra, describing the line profiles evolution and providing a rich list of identified lines. During the optically thick phase, we detected several blue-shifted absorption features from s-processed elements, whose origin is unclear. The presence of strong lines from C/O and the absence of Neon features confirm that the nature of the central white dwarf is a CO type. The later “nebular” phase spectra show evidence of the non-spherical, inhomogeneous structure of the ejecta. The detailed evolution of the line profiles and appearance of high ionization species (e.g. N III, O III, He II, [Fe VII]) are direct consequences of the re-ionization of the ejecta during the peak of the soft X-ray emission.

Simultaneous monitoring the real and imaginary parts of the analyte refractive index using liquid-core photonic bandgap Bragg fibers.

We demonstrate simultaneous monitoring of the real and imaginary parts of the liquid analyte refractive index by using a hollow-core Bragg fiber. We apply this two-channel fiber sensor to monitor concentrations of various commercial cooling oils. The sensor operates using spectral monitoring of the fiber bandgap center wavelength, as well as monitoring of the fiber transmission amplitude at mid-bandgap position. The sensitivity of the fiber sensor to changes in the real part of the core refractive index is found to be 1460nm/Refractive index unit (RIU). By using spectral modality and effective medium theory, we determine the concentrations of the two commercial fluids from the measured refractive indices with an accuracy of ~0.57% for both low- and high-loss oils. Moreover, using an amplitude-based detection modality allows determination of the oil concentration with accuracy of ~1.64% for low-loss oils and ~2.81% for the high-loss oils.

Radiation-Induced Glycogen Accumulation Detected by Single Cell Raman Spectroscopy Is Associated with Radioresistance that Can Be Reversed by Metformin.

Altered cellular metabolism is a hallmark of tumor cells and contributes to a host of properties associated with resistance to radiotherapy. Detection of radiation-induced biochemical changes can reveal unique metabolic pathways affecting radiosensitivity that may serve as attractive therapeutic targets. Using clinically relevant doses of radiation, we performed label-free single cell Raman spectroscopy on a series of human cancer cell lines and detected radiation-induced accumulation of intracellular glycogen. The increase in glycogen post-irradiation was highest in lung (H460) and breast (MCF7) tumor cells compared to prostate (LNCaP) tumor cells. In response to radiation, the appearance of this glycogen signature correlated with radiation resistance. Moreover, the buildup of glycogen was linked to the phosphorylation of GSK-3β, a canonical modulator of cell survival following radiation exposure and a key regulator of glycogen metabolism. When MCF7 cells were irradiated in the presence of the anti-diabetic drug metformin, there was a significant decrease in the amount of radiation-induced glycogen. The suppression of glycogen by metformin following radiation was associated with increased radiosensitivity. In contrast to MCF7 cells, metformin had minimal effects on both the level of glycogen in H460 cells following radiation and radiosensitivity. Our data demonstrate a novel approach of spectral monitoring by Raman spectroscopy to assess changes in the levels of intracellular glycogen as a potential marker and resistance mechanism to radiation therapy.

TANAMI: Multiwavelength and multimessenger observations of active galaxies

AbstractExtragalactic jets launched from the immediate vicinity of supermassive black holes in radio‐loud active galactic nuclei (AGN) are key objects in modern astronomy and astroparticle physics. AGN jets carry a fraction of the total gravitational energy released during the accretion of matter onto supermassive black holes and are prime suspects as possible sources of ultrahigh‐energy cosmic rays and the recently detected extraterrestrial neutrinos at PeV energies. TANAMI (Tracking Active galactic Nuclei with Austral Milliarcsecond Interferometry) is a multiwavelength program monitoring AGN jets of the southern sky. It combines high‐resolution imaging and spectral monitoring at radio wavelengths with higher‐frequency observations at IR, optical/UV, X‐ray, and γ‐ray energies. We review recent results of the TANAMI program, highlighting AGN candidate neutrino‐emitters in the error circles of the IceCube PeV neutrino events. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

ULTRAVIOLET/X-RAY VARIABILITY AND THE EXTENDED X-RAY EMISSION OF THE RADIO-LOUD BROAD ABSORPTION LINE QUASAR PG 1004+130

We present the results of recent Chandra, XMM-Newton, and Hubble Space Telescope observations of the radio-loud (RL), broad absorption line (BAL) quasar PG 1004+130. We compare our new observations to archival X-ray and UV data, creating the most comprehensive, high signal-to-noise, multi-epoch, spectral monitoring campaign of a RL BAL quasar to date. We probe for variability of the X-ray absorption, the UV BAL, and the X-ray jet, on month–year timescales. The X-ray absorber has a low column density of when it is assumed to be fully covering the X-ray emitting region, and its properties do not vary significantly between the four observations. This suggests that the observed absorption is not related to the typical "shielding gas" commonly invoked in BAL quasar models, but is likely due to material further from the central black hole. In contrast, the C iv BAL shows strong variability. The equivalent width (EW) in 2014 is , showing a fractional increase of from the 2003 observation, 3183 days earlier in the rest-frame. This places PG 1004+130 among the most highly variable BAL quasars. By combining Chandra observations we create an exposure that is 2.5 times deeper than studied previously, with which to investigate the nature of the X-ray jet and extended diffuse X-ray emission. An X-ray knot, likely with a synchrotron origin, is detected in the radio jet (30 kpc) from the central X-ray source with a spatial extent of (15 kpc). No similar X-ray counterpart to the counterjet is detected. Asymmetric, non-thermal diffuse X-ray emission, likely due to inverse Compton scattering of Cosmic Microwave Background photons, is also detected.

Survey of emission spectra of the plasma of chlorine, hydrogen chloride, argon, and hydrogen

Survey emission spectra of plasma-forming gases such as chlorine, hydrogen chloride, argon, and hydrogen, as well as the spectral composition of these gases, are investigated in the presence of the gallium arsenide semiconductor plate. The reference lines and bands for the spectral etching rate monitoring by the emission intensity of the lines and bands of the etching products are selected. It is assumed that the relation between the emission intensity of the etching products of GaAs and the etching rate in the plasma of chlorine, hydrogen chloride, and their mixtures with argon and hydrogen is described by the directly proportional dependence, which points to the possibility of the real-time control of etching using the spectral method.

Structural conversion of a cyclic d-Penicillaminato tripalladium(II) complex by pyridine or 2-pyridinethiol

Structural conversion of a tripalladium(II) complex with a chair-type Pd3S3 metallacycle, [Pd3(d-pen-N,O,S)3] (1; H2pen = penicillamine), triggered by the coordination of pyridine (py) or 2-pyridinethiol (Hpyt) was reported. Treatment of 1 with py in water produced a tripalladium(II) complex with a boat-type Pd3S3 metallacycle, [Pd3(d-pen-N,O,S)(d-pen-N,S)2(py)2] 2, in which two of three PdII centers are each coordinated by a py ligand through N atom. On the other hand, similar treatment of 1 with Hpyt induced a ring-expansion to form a cyclic tetrapalladium(II) complex with a twist-boat-type Pd4S4 metallacycle, [Pd4(d-Hpen-N,S)(d-pen-N,S)3(Hpyt-S)2(pyt-N,S)] 3, in which two of four PdII centers are bridged by a deprotonated pyt– ligand through N and S atoms and the remaining two PdII centers are each coordinated by a protonated Hpyt ligand through an S atom. The 1H NMR spectral monitoring of each reaction solution showed that the structural conversion to 2 is considerably slower than that to 3.

Field-scale time-domain spectral induced polarization monitoring of geochemical changes induced by injected CO2 in a shallow aquifer

Contamination of potable groundwater by leaking [Formula: see text] is a potential risk of carbon sequestration. With the help of a field experiment, we investigated whether surface monitoring of direct current (DC) electric resistivity and induced polarization (IP) could detect geochemical changes induced by [Formula: see text] in a shallow aquifer. For this purpose, we injected [Formula: see text] at depths of 5 and 10 m and monitored its migration using 320 electrodes on a [Formula: see text] surface grid. Measured resistances and IP decay curves found a clear signal associated with the injected [Formula: see text] and rebounded to preinjection values after the end of the injection. Full-decay 2D DC-IP inversion was used to invert for the subsurface distribution in Cole-Cole parameters and changes to these parameter fields over time. The time-lapse inversions found plumes of decreased resistivity and increased normalized chargeability. The two plumes were of different shapes, with the resistivity anomaly being larger. Comparison with measurements of electric conductivity and aluminum (Al) concentrations indicated that two geochemical processes were imaged. We interpreted the change in resistivity to be associated with the increase in free ions directly caused by the dissolution of [Formula: see text], whereas the change in normalized chargeability was most likely linked to persistent acidification and best indicated by Al concentrations. The results highlight the potential for monitoring of field scale geochemical changes by means of surface DC-IP measurements. Especially the different developments of the DC resistivity and normalized chargeability anomalies and the different associated geochemical processes highlight the added value of IP to resistivity monitoring.

THE MEGAMASER COSMOLOGY PROJECT. VI. OBSERVATIONS OF NGC 6323

We present observations of the H2O megamasers in the accretion disk of NGC 6323. By combining interferometric and spectral monitoring data, we estimate H$_{0} = 73^{+26}_{-22}$ km/s/Mpc, where the low strength of the systemic masers (<15 mJy) limits the accuracy of this estimate. The methods developed here for dealing with weak maser emission provide guidance for observations of similar sources, until significant increases in radio telescope sensitivity, such as anticipated from the next generation Very Large Array, are realized.

Preparation of surface-enhanced Raman scattering(SERS)-active optical fiber sensor by laser-induced Ag deposition and its application in bioidentification of biotin/avidin

A surface-enhanced Raman scattering(SERS) optical fiber sensor was prepared by the laser-induced deposition of Ag nanoparticle membrane on a silica optical fiber tip, which was applied to the real time SERS spectral monitoring on the biorecognition of biotin/avidin. The bioidentification of biotin/avidin was carried out through a indirect method, in which the bioidentification is based on the SERS response signal of a labeled dye(Atto610) after its fluorescence has been quenched totally by the deposited Ag nanoparticle membrane. By SERS monitoring the bioidentification process of biotin/avidin, it has been found that this recognition process is finished in 40 min. The lowest detection concentration of biotin is 1.0×10−7 mg/mL. This research is promising in the application of immunoassays on line and in vivo.

Spectral Monitoring CH/C2 Ratio of Methane Plasma for Growing Single‐Layer Graphene on Cu

Single‐layer graphene was grown on copper at a low temperature of 600°C by plasma‐assisted thermal chemical vapor deposition. Its growth mechanism was discussed with reference to the emission spectra of the plasma. The methane plasma produces the active species (Hx, CHx, and Cx) without the addition of flowing hydrogen, and the amounts of hydrogen‐containing species can be controlled by varying the plasma power. The effective distance was found between the plasma initial stage and the deposition stage for the single‐layer graphene synthesis. The results reveal that high‐quality graphene can be synthesized using methane plasma at a suitable plasma power.

Developing an aqueous approach for synthesizing Au and M@Au (M = Pd, CuPt) hybrid nanostars with plasmonic properties.

Anisotropic Au nanoparticles show unique localized surface plasmon resonance (LSPR) properties, which make them attractive in optical, sensing, and biomedical applications. In this contribution, we report a general and facile strategy towards aqueous synthesis of Au and M@Au (M = Pd, CuPt) hybrid nanostars by reducing HAuCl4 with ethanolamine in the presence of cetyltrimethylammonium bromide (CTAB). According to electron microscopic observations and spectral monitoring, we found that the layered epitaxial growth mode (i.e., the Frank-van der Merwe mechanism) contributes to the enlargement of the core, while the random attachment of Au nanoclusters onto the cores accounts for the formation of the branches. Both of them are indispensable to the formation of the nanostars. The LSPR properties of the Au nanoparticles have been well investigated with morphology control via the precursor amount and growth temperature. The Au nanostars showed improved surface-enhanced Raman spectroscopy (SERS) performance for rhodamine 6G due to their sharp edges and tips, which were therefore confirmed as good SERS substrates to detect trace amounts of molecules.