Violet Side Research Articles

Microplastics as potential carriers of viruses could prolong virus survival and infectivity

Microplastics are emerging contaminants in various aquatic environments, leading to human and environmental health concerns. Viruses have also been ubiquitously detected in aquatic environments, and there is an unknown risk of microplastics-mediated virus migration through adsorption. This study applied polystyrene microplastics as the carrier and the T4 bacteriophage (or phage) as the virus model, and a violet side scatter/green fluorescence double-gated flow cytometry approach to investigate the adsorption capacity of viruses on microplastics. Our results show that up to 98.6±0.2% of the dosed viruses can be adsorbed by microplastics, and such adsorptions are dependent on size and surface functional groups. Both Fourier-transform infrared spectroscopy and fluorescence-labelled confocal microscopy confirmed that the virus can successfully adsorb onto microplastics. Zeta potential characterisation revealed that the electrostatic interaction is the primary adsorption mechanism associated with the adsorption of viruses. UV-aging was found to enhance the adsorption capacities of viruses on microplastics. Both pristine and UV-aged microplastics were found to significantly prolong the infectivity of the adsorbed viruses, even under elevated temperatures. Collectively, our findings highlight that microplastics are associated with the biological risks of water-borne viral transmission through virus adsorption.

Enhanced resolution of marine viruses with violet side scatter.

Marine viruses make up an essential compartment of the marine ecosystem. They are the most abundant organisms and represent one of the biggest sources of unknown biodiversity. Viruses also have an important impact on bacterial and algal mortality in the ocean, and as such have a major influence on microbial diversity and biogeochemical cycling. However, little is known about the abundance and distribution patterns of viruses across the oceans and seas. Over the last 20 years, flow cytometry has been the technique of choice to detect and count the viral particles in natural samples. Nevertheless, due to their small size, the detection of marine viruses is still extremely challenging. In this article we describe how a new generation of flow cytometer which uses the side scatter (SSC) of violet photons from a 405 nm laser beam helps to improve the resolution for detecting marine viruses. To the best of our knowledge, this is the first report where virioplankton has been detected in aquatic samples using flow cytometry with a 405 nm violet SSC instead of a 488 nm blue SSC.

Nanosecond switchable localized surface plasmons through resettable contact angle behavior in silver nanoparticles

In this article, we show nanosecond switchable localized surface plasmon resonance (LSPR) dipole and quadrupole modes from silver (Ag) nanoparticles on fused quartz substrates. Near-spherical Ag nanoparticles (contact angle of 166°± 9 ) were synthesized by Ultra Violet (UV) laser dewetting of Ag thin films under a glycerol fluid environment. Under a single 9 nanosecond laser pulse irradiation of the particles in air, the particles were changed into a near-hemispherical shape (with contact angle of 103°± 7 ). The resulting changes in particle contact area and volume fraction in the dielectric media resulted in substantial shift in the wavelength and intensity of the dipolar and quadrupolar LSPR modes to the violet side of visible spectrum. This switching of the plasmon resonance wavelength position could be repeated over multiple cycles by resetting the contact angle by laser re-irradiation under glycerol. This reusable nanoparticle system with reversible plasmonic properties within nanosecond time scales could prove a cost-effective way of designing high speed plasmonic devices in desired wavelength regions.

A Novel Semiconductor-Based Flow Cytometer with Enhanced Light-Scatter Sensitivity for the Analysis of Biological Nanoparticles

The CytoFLEX is a novel semiconductor-based flow cytometer that utilizes avalanche photodiodes, wavelength-division multiplexing, enhanced optics, and diode lasers to maximize light capture and minimize optical and electronic noise. Due to an increasing interest in the use of extracellular vesicles (EVs) as disease biomarkers, and the growing desire to use flow cytometry for the analyses of biological nanoparticles, we assessed the light-scatter sensitivity of the CytoFLEX for small-particle detection. We found that the CytoFLEX can fully resolve 70 nm polystyrene and 98.6 nm silica beads by violet side scatter (VSSC). We further analyzed the detection limit for biological nanoparticles, including viruses and EVs, and show that the CytoFLEX can detect viruses down to 81 nm and EVs at least as small as 65 nm. Moreover, we could immunophenotype EV surface antigens, including directly in blood and plasma, demonstrating the double labeling of platelet EVs with CD61 and CD9, as well as triple labeling with CD81 for an EV subpopulation in one donor. In order to assess the refractive indices (RIs) of the viruses and EVs, we devised a new method to inversely calculate the RIs using the intensity vs. size data together with Mie-theory scatter efficiencies scaled to reference-particle measurements. Each of the viruses tested had an equivalent RI, approximately 1.47 at 405 nm, which suggests that flow cytometry can be more broadly used to easily determine virus sizes. We also found that the RIs of EVs increase as the particle diameters decrease below 150 nm, increasing from 1.37 for 200 nm EVs up to 1.61 for 65 nm EVs, expanding the lower range of EVs that can be detected by light scatter. Overall, we demonstrate that the CytoFLEX has an unprecedented level of sensitivity compared to conventional flow cytometers. Accordingly, the CytoFLEX can be of great benefit to virology and EV research, and will help to expand the use of flow cytometry for minimally invasive liquid biopsies by allowing for the direct analysis of antigen expression on biological nanoparticles within patient samples, including blood, plasma, urine and bronchoalveolar lavages.

Spatial and temporal variations of K Ca II line profile shapes in different structures of the solar chromosphere. I. Features of individual profiles

We have studied Ca II K line profiles, using two time series of spectrograms taken in two regions near the solar disk center. In each of the regions, the spectrograph slit cut out several areas of the quiet region and a plage. For the selected chromospheric structures, we have derived K line profiles and have defined a number of parameters that characterize the spatial and temporal variations of the profiles. The analysis of profile shapes in different structures belonging to the same moment of time has shown that there are structures whose profiles differ only slightly from each other in the photosphere, but differ dramatically in the chromosphere. The structures begin to differ from the level of formation of K1 and continue to differ further in the chromosphere. There are, however, structures which begin to differ at the level of the photosphere and continue to differ in the chromosphere. The difference between profile shapes in different structures is likely to be associated both with different thermodynamic conditions and with different magnetic field topology at a given point at a given time. We have examined temporal variations of the K Ca II line profiles in structural chromospheric elements, which are caused by the process of K2v-grains. In most of the studied areas of the chromospheric structures, the brightening of the K2v peak develops according to the “common” scenario: at the time of maximum bright-ness, the line shifts toward the red side. There are, however, cases when the brightening of the K2v peak occurs with a shift of the line to the violet side or with no shift at all. We have constructed scatter plots for some pairs of profile parameters related to intensities at characteristic points of the profile and their shifts. A correlation has been found between intensities in the center and wings of the K line. The correlation between shifts of the K2v and K2r peaks is very weak or completely absent.

Пространственные и временные вариации формы контуров линии K Ca II в различных структурных образованиях солнечной хромосферы. I. Особенности индивидуальных контуров

We have studied Ca II K line profiles, using two time series of spectrograms taken in two regions near the solar disk center. In each of the regions, the spectrograph slit cut out several areas of the quiet region and a plage. For the selected chromospheric structures, we have derived K line profiles and have defined a number of parameters that characterize the spatial and temporal variations of the profiles. The analysis of profile shapes in different structures belonging to the same moment of time has shown that there are structures whose profiles differ only slightly from each other in the photosphere, but differ dramatically in the chromosphere. The structures begin to differ from the level of formation of K1 and continue to differ further in the chromosphere. There are, however, structures which begin to differ at the level of the photosphere and continue to differ in the chromosphere. The difference between profile shapes in different structures is likely to be associated both with different thermodynamic conditions and with different magnetic field topology at a given point at a given time. We have examined temporal variations of the K Ca II line profiles in structural chromospheric elements, which are caused by the process of K2v-grains. In most of the studied areas of the chromospheric structures, the brightening of the K2v peak develops according to the “common” scenario: at the time of maximum bright-ness, the line shifts toward the red side. There are, however, cases when the brightening of the K2v peak occurs with a shift of the line to the violet side or with no shift at all. We have constructed scatter plots for some pairs of profile parameters related to intensities at characteristic points of the profile and their shifts. A correlation has been found between intensities in the center and wings of the K line. The correlation between shifts of the K2v and K2r peaks is very weak or completely absent.

Platelet Detection in Unaltered Whole Blood

Abstract Platelets are non-nucleated cellular fragments circulating in the peripheral blood, derived from megakaryocytes. They are critical in the maintenance of hemostasis. Alterations in their function are associated with a range of clinical conditions. Using flow cytometry, light scatter signals from platelets typically overlap signals from red blood cells (RBC). Since RBC outnumber platelets by more than an order of magnitude in whole blood, platelets are typically studied by depleting samples of RBCs by centrifugation methods or selective RBC cell lysis. These sample preparation procedures require manipulations that may affect platelet health and function, and result in loss of cells. Additionally, lysed samples require labeling of the platelets with a fluorescent marker to adequately resolve the platelets from debris/noise. We present a novel technique for resolving leukocytes and platelets from RBC in whole blood using orthogonal light scatter from 2 lasers. This method exploits the differences in light-scattering properties between RBCs and platelets and white blood cells (WBC). Hemoglobin readily absorbs 405 nm laser light, reducing the scatter signal from RBC relative to WBCs and platelets, resulting in a reproducible scatter pattern when analyzing human whole blood with both blue (488 nm) and violet (405 nm) side scatter. Using this approach, a distinct platelet population can be discerned in unaltered whole blood, requiring only dilution of whole blood in buffer. Combining this approach with acoustic cytometry allows great flexibility in determining optimal dilution and sample collection rates for minimal coincidence and rapid analysis. For research use only. Not for use in diagnostic procedures.

Ultraviolet 320 nm laser excitation for flow cytometry.

Although multiple lasers and high-dimensional analysis capability are now standard on advanced flow cytometers, ultraviolet (UV) lasers (usually 325-365 nm) remain an uncommon excitation source for cytometry. This is primarily due to their cost, and the small number of applications that require this wavelength. The development of the Brilliant Ultraviolet (BUV fluorochromes, however, has increased the importance of this formerly niche excitation wavelength. Historically, UV excitation was usually provided by water-cooled argon- and krypton-ion lasers. Modern flow cytometers primary rely on diode pumped solid state lasers emitting at 355 nm. While useful for all UV-excited applications, DPSS UV lasers are still large by modern solid state laser standards, and remain very expensive. Smaller and cheaper near UV laser diodes (NUVLDs) emitting at 375 nm make adequate substitutes for 355 nm sources in many situations, but do not work as well with very short wavelength probes like the fluorescent calcium chelator indo-1. In this study, we evaluate a newly available UV 320 nm laser for flow cytometry. While shorter in wavelength that conventional UV lasers, 320 is close to the 325 nm helium-cadmium wavelength used in the past on early benchtop cytometers. A UV 320 nm laser was found to excite almost all Brilliant Ultraviolet dyes to nearly the same level as 355 nm sources. Both 320 nm and 355 nm sources worked equally well for Hoechst and DyeCycle Violet side population analysis of stem cells in mouse hematopoetic tissue. The shorter wavelength UV source also showed excellent excitation of indo-1, a probe that is not compatible with NUVLD 375 nm sources. In summary, a 320 nm laser module made a suitable substitute for conventional 355 nm sources. This laser technology is available in a smaller form factor than current 355 nm units, making it useful for small cytometers with space constraints. © 2017 International Society for Advancement of Cytometry.

Numerical calculation of laser-induced collisional energy transfer in Ba-Sr system

Based on the existing four-level model of laser-induced collisional energy transfer, the collision process in Ba-Sr system in both weak and strong fields is calculated by immediate integration of the equation of motion, and profiles of laser-induced transition probability and collision cross section under both conditions are obtained. Numerical results for the weak field are in fair to good agreement with former analytical results, while the ones for the strong field show that the effect of laser-induced collision is enhanced when the transfer laser intensity increases. Moreover, the peak of the laser-induced collisional energy transfer spectrum shows an evident shift from resonant frequency to the violet side in strong field, and full width at half maximum (i.e. tuning range) of the spectrum becomes obviously narrower compared with that in weak field.

Characteristic frequency of the magnetic radiation of spinor condensates

The magnetic radiation of the fully condensed states of spinor condensates has been studied. A narrow characteristic spectral line together with a strong background at its violet side have been found. For the condensate of $N={10}^{12}$ atoms of $^{23}\mathrm{Na}$ confined in an isotropic and harmonic trap with frequency ${\ensuremath{\omega}}_{o}=300\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$, for instance, the photon energy of the characteristic line is $127.9\ensuremath{\hbar}{\ensuremath{\omega}}_{o}$ with width $<1.\ensuremath{\hbar}{\ensuremath{\omega}}_{o}$ and the probability of transition is $1.44\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}34}\phantom{\rule{0.3em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. The photon energy and probability have been found to be proportional to ${N}^{2∕5}$ and ${N}^{17∕5}$, respectively. It implies that magnetic radiations with higher photon energies and much larger probabilities can be obtained if numerous atoms are trapped. A technique developed by the authors, namely, the analytical forms of the fractional parentage coefficients, was used to calculate analytically the matrix elements between the spin states that conserve the total spin and its $Z$ component.

Numerical study of laser-induced collision process in Eu-Sr in strong field

Theoretically based on the four-level model, one LICET process in Eu-Sr system in both weak and strong fields was calculated by immediate numerical integrations. Numerical results in weak field are in fair to good agreement with analytical ones. Numerical results in strong field show that: (a) the peak of the LICET profiles moves to the violet side and the tuning range of the profiles obviously becomes narrower when the laser field intensity increases; and (b) numerical results in strong field differ a lot from analytical ones, which indicates that in strong field, the analytical expressions are not applicable any longer.

THE STELLAR WINDS IN BETA LYRAE.

ABSTRACT High signal-to-noise ratio observations of the He I λ5876 feature are presented for the interacting binary β Lyrae. Inspection of these and previously published data on the strong optical He I and Balmer lines during primary eclipse leads to a new interpretation of the phase variable nature of these lines. Arguments are presented to suggest that the majority of the emission in the highly variable violet side, and a similar amount of red emission, is produced in a stellar wind from the primary star. This wind is occulted during primary eclipse to cause the dramatic variations in the optical emission-line profiles. The remainder, and majority, of the red-side emission originates in an expanding shell surrounding the entire system which also produces the P Cygni-like emission lines in the far ultraviolet.

Optical absorption spectrum of Cr3+ in natural ruby

Two sharp line-like bands calledN andR lines on the red side, a close doublet (B lines) on the violet side and two broad bands are observed for natural ruby. At liquid air temperature the splitting ofR line was found and also three sharp-bands calledR, R′ andB lines are identified with spin-forbidden transitions of2E,2T1 and2T2. The two broad bands calledU band andY band are assigned accordingly to the spin-allowed transitions4T2 and4T1 respectively. The observed bands of natural ruby have been attributed to Cr3+ ion in an octahedral environment with trigonal distortion. The crystal field parameters which gave a good fit to the observed band positions areB=732 cm−1,C=4.25B,Dq=1830 cm−1,V=−1996 cm−1 andλ=34 cm−1.

On the nuclear spectrum of NGC 1365

AAT long-slit spectroscopic observations of the nucleus of the barred ‘hot-spot’ galaxy NGC 1365, taken in good seeing, reveal a central nucleus with a spectrum resembling that of an intermediate Seyfert galaxy and a surrounding region of about 400 pc radius with a spectrum having several characteristics of a Seyfert 2. Surrounding this, in turn, are normal H II regions of low excitation suggesting an O/H abundance ratio exceeding that of the Sun. The Seyfert 1 nucleus has asymmetric broad Balmer components, which are unusual in having greater extensions on the violet side, as well as a non-thermal continuum and broad Fe II emssion features. All the emission-line systems are heavily reddened. The importance of allowing for possible non-thermal excitation in the derivation of abundances from emission lines in galactic nuclei is emphasized.

Spectral and time decay analysis of photoluminescence excited in the A band region in KCl:Pb

AbstractThe A band spectral region in KCl:Pb is studied from the point of view of the optical absorption spectra, photoluminescence (emission and excitation) spectra, and the luminescence lifetime measurements in the temperature range 15 to 320 K. The sensitive ITC technique is exploited as a parallel tool to monitor and check the solution state of the impurity in order to rule out the additional and unwanted complications arising from the presence of aggregates. As a consequence only very dilute (4 to 6 ppm) and quenched samples are chosen to perform the detailed and systematic analysis of the photoluminescence spectra. The emission and excitation spectra do not depend significantly on the wavelength of the exciting and emitted light respectively, while their shape depends strongly on the temperature. The careful analysis of the emission spectrum, which looks asymmetric and apparently structureless, suggests that two Gaussians are contributing to it (main band and red side band, with associated average phonons of 1.25 × 10−2 and 1.6 × 10−2 eV, respectively) for T < 120 K, while a third weaker component seems to increase on the high energy side (violet side band) for T > 120 K. The luminescence time decay is complex exhibiting three distinct lifetimes: the length of two of them (τ1 = 30 and τ2 = 160 ns) is temperature independent, while the third one τ3 is strongly temperature‐dependent. The comparison between the intensity behaviour versus temperature both, of the time decay components and of the emission spectral components brings to a tentative attribution of τ1 to the main band, τ2 to the violet side band, and τ3 to the red side band. A scheme for the excited state energy levels, from which the emission excited by A light takes place is discussed both, by taking into account the dynamical Jahn‐Teller effect and the role of the neighbouring cation vacancy.

Isotopically selective dissociation of CCl4molecules by highpower NH3laser radiation

Isotopically selective many-photon dissociation of the CCl4 molecules was achieved for the first time in the field of radiation emitted from an NH3 molecular laser pumped optically by a CO2 laser. The dependence of the dissociation rate on the initial pressure of CCl4 was unusual: the rate first fell on increase of the pressure (as in all other known cases) and then it rose. The ratio of the dissociation rates of 12CCl4 and 13CCl4 was 4.4±0.3. Two-frequency excitation by the weak resonant field of the NH3 laser and dissociation by the strong nonresonant field of the CO2 laser (λl = 9.29 μ) was achieved. The detuning on the violet side was 300 cm−1, which was considerably greater than in the published experiments on the dissociation of SF6 by CO2 laser radiation.

H and He II spectra of Of stars

view Abstract Citations (187) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS H and He II spectra of Of stars. Klein, R. I. ; Castor, J. I. Abstract Previously developed dynamical models of Of stars are used as the basis of a set of statistical equilibrium calculations for hydrogen and ionized helium, on the hypothesis of radiative equilibrium in the stellar envelope. A number of spectral lines of these species are observed in the expanding envelopes of Of stars, and thus they provide diagnostic information about the stellar wind. It is found that the H-alpha line has a strength that is quite sensitive to the rate of mass loss by the star, and comparison with observation indicates loss rates as high as 0.00001 solar mass/yr. The ratio H-alpha/He II 4686-A as observed is in agreement with one of the two sets of theoretical values that are computed; the choice is allowed by uncertainties in the treatment of He II 304-A. Other lines of He II, for which the data are more fragmentary, give only factor-of-2 agreement with theory. The computed profiles of H-alpha and 4686-A are in qualitative agreement with observation, but certain systematic differences exist; the effect of absorption on the violet side of the emission profile is generally more marked in the theoretical profile. The effect of assuming a higher electron temperature in the stellar wind is considered. The primary change would be an upward adjustment in the inferred rates of mass loss, with some worsening of agreement between theory and observation of the H-alpha/4686-A ratio in the later subclasses. Publication: The Astrophysical Journal Pub Date: March 1978 DOI: 10.1086/155980 Bibcode: 1978ApJ...220..902K Keywords: Helium Ions; Hydrogen Atoms; O Stars; Stellar Envelopes; Stellar Models; Stellar Spectra; Atomic Spectra; Dynamic Models; Line Spectra; Stellar Mass Ejection; Stellar Winds; Astrophysics; Envelopes:Of Stars; Mass Loss:Of Stars; Of Stars:Spectra; Of Stars:Stellar Winds full text sources ADS | data products SIMBAD (14)

Experimental investigation of the dependences of the collision broadening and shift of the emission line of a mercury laser on He and Ne pressures

An experimental investigation was made of the impact (collision) broadening and shift of a mercury laser emission line representing the 6p'$sup 3$P$sup 0$$sub 2$$Yields$7s$sup 3$S$sub 1$ (lambda=1.53 $mu$) transition as a function of helium and neon pressures. The boradening of the mercury line varied at a rate of 16 MHz/mm Hg with the helium pressure and at a rate of 10.5 MHz/mm Hg with the neon pressure. Direct measurements indicated that the line was shifted in the direction of the violet side of the spectrum. The rate of shift with the helium pressure was 1.8 MHz/mm Hg and that with the neon pressure was 1.2 MHz/mm Hg. A comparison of the Hg--He and Hg--Ne interactions indicated that in both cases this interaction was the same and was described by the Lennard-- Jones potential. Simultaneous measurements of the broadening and shift gave the values of the phenomenological constants C$sub 6$ and C$sub 12$, whose orders of magnitude were in agreement with the impact (collision) theory. An estimate was obtained of the lifetime of the 6p'$sup 3$P$sup 0$$sub 2$ level, which was approx.2times10$sup -7$ sec.

Characteristics of the Ca ii K-line profiles in the quiet Sun

Feature-to-feature identification is made on simultaneous Ca ii K-line spectrograms (SG) and K2v spectroheliograms (SHG). The line profiles in plages and in the network boundary nearly always have double-peaked reversal in the core, while those inside the cells present all possibilities: double-peaked, single-peaked on violet side, single-peaked on red side, and unreversed absorption. Statistics of the profiles in the quiet chromosphere show that 50% are K232 double-peaked, 20% are K2v single-peaked, 10% are K2r single-peaked, and 20% show only incipient reversal or even totally lack any reversal. We call attention to the nontrivial contribution of these absorption profiles which are formed in ‘dark regions’ shown on SHG's.

Polarization Investigations of Localized Exciton States of Doped Benzene Crystals

AbstractThe absorption spectra of localized exciton states of benzene crystals doped with heterocyclic compounds are studied at T = 4.2 °K using polarized light. When the localized level approaches the exciton A‐band edge, the intensity of the localized absorption is shown to increase anomalously in the a‐component and to decrease in the c‐component of the absorption spectrum. Simultaneously the A‐band is partly depolarized and shifts towards the violet side. The experimental results obtained favour certain conclusions about the exciton band structure and the exciton effective mass and are qualitatively interpreted on the basis of current theories of localized states.