Multicolor Monitoring Research Articles

Intraday variations of polarization vector in blazars: a key to the optical jet structure?

AbstractThis report presents the results of optical polarimetric observations carried out with 6-m and 1-m telescopes at SAO RAS. The study of the blazar S5 0716+714 radiation showed the presence of a period of the variability of brightness and polarization vector variations on scales of ∼1.5 hours, constant on a long time scale; multi-colour monitoring of BL Lac polarization before, during and after the flare demonstrates the difference in the patterns of polarization vector variability depending on the wavelength. Several geometrical models and physical descriptions are discussed.

Spore-derived color-tunable multi-doped carbon nanodots as sensitive nanosensors and intracellular imaging agents

Fluorescent carbon dots hold great promise in biomedical real-time tracking due to their outstanding optical properties and biocompatibility. Here, we report a one-pot synthetic strategy to produce multi-doped carbon dots (MCDs) with bright and color-tunable emission. The resultant MCDs are doped by abundant biogenic elements (O, N, P), so that they contain a variety of surface functional groups. Such hetero-doping and functionalization make MCDs display strong fluorescent emission and excitation-wavelength-dependent characteristic, good aqueous solubility as well as high photo-stability and ion-stability. Moreover, the as-prepared MCDs response to the change of pH values and exhibit high selective and sensitive detection of Fe3+ ions under blue light illumination with the limit of detection (LOD) of 15.9 nM. Such a Fe3+ sensing ability is further demonstrated in real water samples and extended to intracellular multi-color monitoring of Fe3+. More interestingly, the MCDs can also sense the gastrointestinal bacteria Escherichia coli, exhibiting linear sensing dependent behavior. With low cytotoxicity and tunable emission, such MCDs hold great potential as efficient multi-color probes and imaging agents for clinical diagnosis.

Multicolor monitoring of cellular organelles by single wavelength excitation to visualize the mitophagy process.

Multiplexed cellular organelle imaging using single wavelength excitation is highly desirable for unravelling cellular functions but remains challenging. This requires the design of organelle specific fluorophores with distinct emission but similar absorption. Herein, we present two unique aggregation-induced emission (AIE) probes to track mitochondria and lysosomes simultaneously with emission colors that can be distinguished from that of the nucleus stain Hoechst 33342 upon single wavelength excitation. Compared to conventional organelle stains, the two AIE probes have larger Stokes shifts and higher photostability, which endow them with the capability to monitor bioprocesses, such as mitophagy with strong and sustained fluorescent signals. Moreover, both probes can also stain intracellular organelles in zebrafish larvae with good cell-penetrating capabilities, showing their great potential to monitor bioprocesses in vivo.

Optical multi-color monitoring of OJ 287 from 2006 to 2012

We present our opticalmulti-colormonitoring of the BL Lac object OJ 287 from January 2006 to December 2012 in the V, R and I bands. A relatively active state in OJ 287 has been found over all monitored epochs, among which the variations of average magnitude in V/R/I bands were measured with ΔV = 1.956 mag, ΔR = 2.067 mag and ΔI = 2.115mag, respectively. No reliable intraday variability is detected, but possible variability is detected on 16 nights. Their relative variation amplitudes fall into the range between 1% and 8%, with the majority between 2% and 4%. No time lags have been detected, but strong correlations exist among light curves in the three wavebands. The bluer-when-brighter trend is dominant over intraday timescales, which supports the shock-in-jet model. When combining with additional V/R band data obtained from SMARTS and the Steward Observatory, we also find a bluer-when-brighter trend over a long-term timescale. Some possible periods of 513, 176, 36, 30, 26, 17 and 14 d are found in all time-series data sets from 2006 to 2017. Possible explanations about these periods are given.

Multicolor Monitoring of the Proteasome’s Catalytic Signature

Multicolor Monitoring of the Proteasome’s Catalytic Signature

Multicolor Monitoring of Dysregulated Protein Kinases in Chronic Myelogenous Leukemia

The Bcr-Abl and Lyn protein tyrosine kinases have been separately linked to the emergence of imatinib resistance in patients with chronic myelogenous leukemia. We have developed fluorescent sensors for these kinases that are enzymatically and photophysically distinct, allowing us to simultaneously, yet separately, visualize the tyrosine kinase activities of both Abl and Lyn. Multicolor monitoring revealed that an imatinib-resistant cell line (MYL-R) displays a remarkable 13-fold enhancement in Lyn kinase activity relative to its imatinib-sensitive counterpart (MYL). By contrast, both cell lines display nearly identical Abl activities. The upregulation of Lyn kinase phosphotransferase activity in MYL-R cells is linked to an overexpression of the Lyn B isoform. Furthermore, MYL-R cells possess a 4-fold higher level of activated Lyn and 5-fold lower level of autoinhibited Lyn than MYL cells. Finally, studies with an activating SH2 ligand revealed that Lyn from imatinib-resistant MYL-R cells is primed and active, whereas Lyn from imatinib-sensitive cells is dependent upon phosphorylated SH2 ligands for activity.

Colour behaviour of the blazar PKS 0735+178 in 1994–2004

Context. The properties of variable sources responsible for blazar activity are still under discussion. Some conclusions can be drawn from analyzing monitoring observations. Aims. The results of multicolour monitoring observations of the blazar PKS 0735+178 are used to study the colour behaviour of the variable source responsible for the blazar activity in 1994−2004. Methods. The method of “flux-flux” diagrams is used to find the SED of the variable source. Results. The SED of the variable source was unchanged on timescales of years and is represented well by a power-law. High observed polarization and power-law spectrum point to the synchrotron nature of the variable source. The achromatic variability can then be explained by variations in the Doppler boosting due to ∼10◦-variations in the angle between the line of sight and the velocity direction of the radiating source. Conclusions. There is no doubt about the synchrotron nature of the variable source. The most probable reason for this variability is the change in the Doppler boosting.

Multicolor Monitoring of Dysregulated Protein Kinases in Chronic Myelogenous Leukemia

Multicolor Monitoring of Dysregulated Protein Kinases in Chronic Myelogenous Leukemia

Capture radius and synchronization of the white dwarf in the unique magnetic cataclysmic system V1432 Aql

Results from two-color VR photometry of the unique cataclysmic magnetic variable star V1432 Aql and a theoretical model of these data are presented. The accuracy is improved by using the “mean-weighted comparison star” method. The derivative of the rotational period is dP/dt = −1.11(±0.016)·10−8. The characteristic synchronization time for the rotational and orbital motions of the white dwarf is 96.7±1.5 years, in good agreement with theory for the acceleration of an asynchronous propeller owing to the angular momentum of accreting matter. A third type of minimum detected in the light curve is interpreted in terms of the presence of an arc, or ring, rather than an accretion disk. A theoretical model is developed for determining the capture radius of accreted matter by the magnetic field of the white dwarf using the phase difference between the two types of minima associated with the axial rotation. This parameter is estimated to be 16–28 times the radius of the white dwarf for an inclined column model. A dependence of the main characteristics of the system on the mass of the white dwarf is derived which yields better values for the range of this quantity than those determined by indirect methods. For the assumed masses (M1 = 0.9 M⊙ and M2 = 0.3 M⊙) the estimated accretion rate is ∼7×10−10 M⊙. It is shown that in a synchronizing polar the contribution to the change in the period by the variation in the angular momentum of the white dwarf is negligible compared to the accretion torque. In the future multicolor monitoring is needed for studying the spin-orbital synchronization and periodic changes in the accretion structure caused by “spinning” of the white dwarf.

The unique magnetic cataclysmic variable V1432 Aql

Results of a CCD study of the variability of the unique magnetic cataclysmic variable V1432 Aql from the Astronomical Observatory of Mallorca are presented. The “multi-comparison star” method had been applied for better accuracy estimates. The linear ephemeris based on 76 timings of orbital eclipses for 1993–2004 is For the wide minima due to the spin variability, the quadratic ephemeris was determined. The rate of the spin-up of the white dwarf corresponds to the synchronization time-scale determined to be (96.7 ± 1.5) years, in an agreement with theoretical model of the accretion torque. A third type of minima was detected that occur with the spin period. It was interpreted as indicating presence of the second accretion column. For adopted values of mass and the estimated accretion rate is ~7 . Further multi-colour monitoring is needed to study of late stages of the “spin-orbital” synchronization and periodic changes of the accretion geometry caused by “idling” of the white dwarf.

The Reverberation Radius of the Central Dust Hole in NGC 5548

The most intensive multicolor monitoring observations in the optical and near-infrared wave bands were carried out for the Seyfert 1 galaxy NGC 5548. During a monitoring period from 2001 March to 2003 July, the V(0.55 μm) and K(2.2 μm) fluxes separately reached a minimum state twice. A delayed response of light variations in the K band to those in the V band was detected, and the lag time Δt was measured by a cross-correlation analysis based on a new technique of simulating the light curves to fill in the sampling gaps. The measured lag time is Δt = 48 days in the first minimum state and Δt = 47 days in the second minimum state. The lag time is interpreted as the light-travel time from the central energy source to the surrounding dust torus, because the K light is emitted from the hot dust heated by absorption of ultraviolet and optical light from the central energy source. Compared with lag measurements of the broad emission lines in the literature, the lag time for such dust reverberation is found to be longer, indicating that the inner radius of the dust torus corresponds to an outer edge of the broad emission line region in NGC 5548. Furthermore, the V light curve exhibits short-timescale variations superposed on its global variation. These variations on timescales of 10 days or less are found to correlate with X-ray variations and delay behind them by 1 or 2 days, indicating the optical reprocessing of X-ray emission in the central accretion flow in NGC 5548.

Visible and infrared blazar monitoring in the Canary Islands - 1986–1998

A programme of visible multi-colour monitoring of blazars was started in the Canary Islands in 1986. Infrared monitoring was added to the programme in 1988. The sample of objects to be observed is deliberately kept small to ensure that each one receives an acceptable level of light curve coverage. The programme was carried out using scheduled telescope time and a small amount of service observations. We describe the aims of the monitoring programme and show some of the results obtained.

DNA analysis and diagnostics on oligonucleotide microchips.

We present a further development in the technology of sequencing by hybridization to oligonucleotide microchips (SHOM) and its application to diagnostics for genetic diseases. A robot has been constructed to manufacture sequencing "microchips." The microchip is an array of oligonucleotides immobilized into gel elements fixed on a glass plate. Hybridization of the microchip with fluorescently labeled DNA was monitored in real time simultaneously for all microchip elements with a two-wavelength fluorescent microscope equipped with a charge-coupled device camera. SHOM has been used to detect beta-thalassemia mutations in patients by hybridizing PCR-amplified DNA with the microchips. A contiguous stacking hybridization technique has been applied for the detection of mutations; it can simplify medical diagnostics and enhance its reliability. The use of multicolor monitoring of contiguous stacking hybridization is suggested for large-scale diagnostics and gene polymorphism studies. Other applications of the SHOM technology are discussed.