Reflection Interference Research Articles

Single depolymerizing and transport kinesins stabilize microtubule ends.

Microtubules are highly dynamic cellular filaments and an accurate control of their length is important for many intracellular processes like cell division. Among other factors, microtubule length is actively modulated by motors from the kinesin superfamily. For example, yeast kinesin-8, Kip3, motors depolymerize microtubules by a cooperative, force- and length-dependent mechanism. However, whether single motors can also depolymerize microtubules is unclear. Here, we measured how single kinesin motors influenced the stability of microtubules in an in vitro assay. Using label-free interference reflection microscopy, we determined the spontaneous microtubule depolymerization rate of stabilized microtubules in the presence of kinesins. Surprisingly, we found that both single Kip3 and nondepolymerizing kinesin-1 transport motors, used as a control, stabilized microtubules further. For Kip3, this behavior is contrary to the collective force-dependent depolymerization activity of multiple motors. Because of the control measurement, the finding may hint at a more general stabilization mechanism. The complex, concentration-dependent interaction with microtubule ends provides new insights into the molecular mechanism of kinesin-8 and its regulatory function of microtubule length.

Color fundamentals

Abstract Colors are only created in the human brain. During this process, light rays from the environment reach the retina of the eye. There they trigger an optical stimulus, which is transmitted to the brain. And the brain translates this stimulus into colors. The perception of color is influenced by multiple factors, which is why it is highly subjective. Originally, the light rays come from the sun. They are described by the color spectrum, which comprises rays visible to us from 400 to 700 nm. These light rays can be influenced by different pigments that manipulate the light rays. This manipulation can happen by absorption, reflection and refraction and interference.

Novel Retroreflective Structural Color Films Based on Total Internal Reflection Interference

Structural color materials have tremendous applications and been extensively investigated in the past decades. Most of them involve either nanoscale periodic photonic crystal structure or film interference mechanisms. Herein, we report a novel retroreflective structural color film (RSCF) based on a combined effect of interference and total internal reflection (TIR). The RSCF is consisted of a microscale polymer hemisphere array formed on the same polymer matrix. When exposed to white light illumination, the non-hemisphere-side of the film exhibits non-iridescent color under coaxial illumination and observation, and iridescent color under noncoaxial illumination and observation. In contrary, the hemisphere-side of the film does not show any colors regardless of coaxial or noncoaxial illumination and observation. Furthermore, an elastic polyurethane-based RSCF can exhibit dynamically and reversibly changing colors during uniaxial tensile/compressive deformation.

Application of optical narrow-band mirrors in sensor of concentration of dust in coal mines

The article presents a new design of the sensor for measuring dust, which is based on the effect of absorption of optical radiation passing through the dust layer. Fundamentally new is the use of a powerful low-cost LED, the spectral part of the radiation range required for measurement of which is formed by the structure of auxiliary reflective optical interference filters. A technique based on the introduced stability criterion of the synthesized interference coating is developed, which makes it possible to study the transformation of the spectra with real errors in the film thicknesses.

DC bipolar anodization of aluminum: Wider anode area than expected on the bipolar electrodes

In this study, the electrical potential distributions on aluminum bipolar electrodes (BPEs) subjected to bipolar anodization in a direct current (DC) electric field were investigated. Aluminum sheets were used as BPEs, suspended in an electrolyte solution, and positioned either vertically or horizontally at the center of a cell. The results of reflective interference measurements, depth-profiling analysis, and re-anodization clearly revealed that the thicknesses of the porous alumina films and barrier layers near the aluminum substrates can be taken to represent the potential distributions on the horizontally located BPEs; the thickest anodic alumina was formed at the edge of the anodic pole of the BPE, and its thickness continuously decreased in the direction of the cathodic pole. Furthermore, the area of the anodic reaction was much larger than expected, accounting for 90% of the BPE.

ARHGAP45 controls naïve T- and B-cell entry into lymph nodes and T-cell progenitor thymus seeding

T and B cells continually recirculate between blood and secondary lymphoid organs. To promote their trans-endothelial migration (TEM), chemokine receptors control the activity of RHO family small GTPases in part via GTPase-activating proteins (GAPs). T and B cells express several RHO-GAPs, the function of most of which remains unknown. The ARHGAP45 GAP is predominantly expressed in hematopoietic cells. To define its in vivo function, we describe two mouse models where ARHGAP45 is ablated systemically or selectively in T cells. We combine their analysis with affinity purification coupled to mass spectrometry to determine the ARHGAP45 interactome in T cells and with time-lapse and reflection interference contrast microscopy to assess the role of ARGHAP45 in T-cell polarization and motility. We demonstrate that ARHGAP45 regulates naïve T-cell deformability and motility. Under physiological conditions, ARHGAP45 controls the entry of naïve T and B cells into lymph nodes whereas under competitive repopulation it further regulates hematopoietic progenitor cell engraftment in the bone marrow, and T-cell progenitor thymus seeding. Therefore, the ARGHAP45 GAP controls multiple key steps in the life of T and B cells.

Magnetic field measurement based on a fiber laser oscillation circuit merged with a polarization-maintaining fiber Sagnac interference structure.

A compact optical magnetic field sensor based on a fiber laser oscillator circuit merged with a Sagnac loop that contains a polarization-maintaining fiber (PMF) and a magnetostrictive rod is proposed. The combination of the PMF-Sagnac loop and fiber laser oscillation circuit significantly increases the signal-to-noise ratio of the reflection spectrum in the system, which is a mixed spectrum that includes interference fringes and lasers. For the proposed system, an erbium-doped fiber amplifier is used to provide gain, a dispersion compensating fiber is used to compensate for dispersion in the system, a PMF is inserted in the Sagnac loop as a microwave filter, while a section of the PMF is bonded to a magnetostrictive rod to achieve magnetic field sensing. The proposed system is shown experimentally to produce a fine reflection interference spectrum. The highest intensity reflection interference peak (from the laser) is over 40 dB with a -3 dB line-width of about 0.03 nm. The system can provide magnetic field sensitivities of 0.07 nm/mT and 0.076 nm/mT for sensor head lengths of 1 m and 2 m, respectively, and exhibits a stability of ±0.029 nm over 1 h. The proposed sensing system has advantages of low cost, high sensitivity, compact structure, and can produce a fine and stable reflection spectrum.

Biofunctionalization of carbon nanotubes for reversible site-specific protein immobilization

Carbon nanotubes (CNTs) emerge as biosensors due to their extraordinary electrical transport properties. Such applications depend on interfacing proteins with CNTs in an oriented manner while maintaining their structural and functional integrity, opening versatile opportunities for one-dimensional alignment and high-sensitivity sensing of protein interactions and conformational dynamics. Here, we devised a novel surface architecture for reversible protein immobilization on CNTs via a short peptide tag for fabrication of reusable biosensors for multiple protein analysis. To this end, we conjugated pyrene-poly(ethylene glycol) with tris-nitrilotriacetic acid (Py-PEG-tris-NTA) for site-specific immobilization of oligohistidine(His)-tagged proteins. We demonstrate spontaneous self-assembly of Py-PEG-tris-NTA on CNTs and graphene, as well as specific capturing of His-tagged green fluorescent protein after loading the NTA chelators with Ni(II) ions. The protein binding capacity of tris-NTA-functionalized CNTs could be restored by an imidazole wash, allowing for repeated immobilization cycles. Reflectance interference spectroscopy and fluorescence lifetime analysis confirmed a specific and reversible binding of proteins on CNT-coated silica substrates as well as close interfacing to the CNT surface.

Morphological, mechanical, and electromagnetic interference shielding effectiveness characteristics of glass fiber/epoxy resin/MWCNT buckypaper composites

AbstractGlass fiber/epoxy resin composites (GF/EP) using one and three multi‐walled carbon nanotube buckypapers (BP) were obtained and their complex parameters, reflectivity, and electromagnetic interference (EMI) shielding effectiveness (SE) at X‐band (8.2–12.4 GHz) and Ku‐band (12.4–18 GHz) were evaluated. The preparation of BP used polyacrylonitrile (PAN) nanofibers (PF These composites show both large storage and energy loss capacity in both bands revealing promising results related to EMI SE applications. Besides, a high attenuation of around 67% and 72% were achieved for BP based composites. The cross‐section view of the buckypaper and the laminates was analyzed by scanning electron microscopy (SEM). The incorporation of the CNT film into the laminates showed no improvements in the elastic properties through dynamic mechanical analyses (DMA). Nevertheless, a decrease in the shear properties by the compression shear test (CST) and interlaminar shear strength (ILSS) has been observed. GF/EP/BP/PF composite presented a reduction of 29 and 39% in its ILSS properties compared to the base laminate (GF/EP). Also, the decrease was even more significant, revealing a steep reduction in its CST properties. On the other hand, the removal of the pan nanofiber (PF) led to better mechanical properties for GF/EP/BP/RPF composites. Results have shown ILSS values of 47.4 ± 2.2 MPa which are close to the base laminate (52.4 ± 3.1 MPa). The removal of the PF provided larger porous in the CNT network, making the impregnation by epoxy easier in the BP/RPF which resulted in improved shear properties compared to GF/EP/BP/PF samples.

Spreading and Migration of Nasopharyngeal Normal and Cancer Cells on Microgratings.

Cell spreading and migration play a pivotal role in many diseases such as tumor metastasis. In particular, nasopharyngeal tumor cells have known of their tendency of migration to pterygoid muscles and further distant metastasis. Although existing studies revealed key characteristics of the nasopharyngeal tumor cells, their migration preference is yet to be thoroughly understood, especially in the physical aspects including the microtopographical factors. Researchers have developed techniques in recent years to study microtopography-related cell behaviors but they are not yet applied in investigating the nasopharyngeal tumor cells. In this work, we elaborate the spreading and migration characteristics of normal and cancerous nasopharyngeal cells on micrograting substrates mimicking the microtopography of myotubes of the pterygoid muscles. We further apply interference reflection microscopy (IRM) to visualize the cell-substrate adhesion dynamics. We are interested in examining the microtopography-related cell spreading and migration behaviors and their correlations, providing insights for deeper understanding and more promising prediction on the nasopharyngeal tumor metastasis.

CD8 Co-Receptor Enhances T-Cell Activation without Any Effect on Initial Attachment.

The scanning of surrounding tissues by T lymphocytes to detect cognate antigens requires high speed, sensitivity and specificity. T-cell receptor (TCR) co-receptors such as CD8 increase detection performance, but the exact mechanism remains incompletely understood. Here, we used a laminar flow chamber to measure at the single molecule level the kinetics of bond formation and rupture between TCR- transfected CD8+ and CD8− Jurkat cells and surfaces coated with five peptide-exposing major histocompatibility antigens (pMHCs) of varying activating power. We also used interference reflection microscopy to image the spreading of these cells dropped on pMHC-exposing surfaces. CD8 did not influence the TCR–pMHC interaction during the first few seconds following cell surface encounter, but it promoted the subsequent spreading responses, suggesting that CD8 was involved in early activation rather than binding. Further, the rate and extent of spreading, but not the lag between contact and spreading initiation, depended on the pMHC. Elucidating T-lymphocyte detection strategy may help unravel underlying signaling networks.

Imaging and Quantifying the Formation of Single Nanobubbles at Single Platinum Nanoparticles during the Hydrogen Evolution Reaction.

While numerous efforts have been made toward the design of sustainable and efficient nanocatalysts of the hydrogen evolution reaction, there is a need for the operando observation and quantification of the formation of gas nanobubbles (NBs) involved in this electrochemical reaction. It is achieved herein through interference reflection microscopy coupled to electrochemistry and optical modeling. In addition to analyzing the geometry and growth rate of individual NBs at single nanocatalysts, the toolbox offered by superlocalization and quantitative label-free optical microscopy allows analyzing the geometry (contact angle and footprint with surface) of individual NBs and their growth rate. It turns out that, after a few seconds, NBs are steadily growing while they are fully covering the Pt nanoparticles that allowed their nucleation and their pinning on the electrode surface. It then raises relevant questions related to gas evolution catalysts, such as, for example, does the evaluation of NB growth at the single nanocatalyst really reflect its electrochemical activity?

Microtubule Growth Is Slowed through Transient Exposure of GDP Tubulin

Microtubule plus-end growth dynamics are determined by a kinetic race dictated by tubulin on- and off-rates at the microtubule tip. The apparent tubulin on- and off-rates can be estimated by measuring the mean plus-end growth rate across a range of free tubulin concentrations. However, when growth phases are studied at higher temporal resolution, fluctuations around the average growth rate are observed, implying more complex dynamics. To understand growth dynamics at the microtubule plus-end, we used Interference Reflection Microscopy (IRM) to quantify time-dependent variations in microtubule growth using GMPCPP, a non-hydrolyzable GTP analog. We found an expected linear dependence of the average growth rate on tubulin concentration. However, there was also a linear relationship between growth variance and tubulin concentration. Utilizing these measured values, we were able to constrain a biochemical model of microtubule growth with an on-rate of 0.7/ μM/pf/s. To determine the degree to which growth in GMPCPP mimics the GTP cap, we repeated the measurements in GTP. We again found a linear dependence of the average growth rate on tubulin; but found a much higher tubulin-dependent growth variance than expected from the GMPCPP experiments. When the growth variance was normalized to growth rate for each condition, there was a 5-fold increase in the relative growth variance in GTP compared to GMPCPP. This result suggests that GTP hydrolysis impacts tubulin binding kinetics at the microtubule plus-end. Consistent with this hypothesis, we then artificially varied the hydrolysis rates from 0 to 0.15 s−1 in the biochemical model. Increasing the hydrolysis rate increased the growth variance, and transient suppression of growth coincided with increasing numbers of exposed GDP tubulin at the plus-end. This work suggests that during growth, exposure of terminal GDP tubulin slows growth until a terminal GTP is restored.

Understanding the Role of Membrane Fluctuation and Tension During Cell Fusion of Myogenesis

During myogenesis, mononucleated proliferating cells undergo cell to cell fusion to form multinucleated myotubes and finally striated skeletal muscle. Does membrane tension need to be regulated to achieve proper fusion during initial stages of fusion and how? Does it need to be changed for the whole cell or only locally? We use interference reflection microscopy to answer some of these questions using C2C12 cells which are tracked at the single cell level through 5 days of differentiation. We find that a global increase in tension is the outcome of differentiation while an interim drop in tension and spatial heterogeneities may facilitate the initial stages.

Correlating Interference Reflection Microscopy with 3D Superresolution Fluorescence Microscopy

Interference reflection microscopy (IRM) is a widely used technique to study cell adhesion and membrane topography on coverslips due to its easy implementation. It relies on the interference of two reflections, one from the coverslip-buffer interface and the second from the buffer-membrane interface, to produce interference patterns that depend on the distance of the membrane from the coverslip. Additional effects like multiple reflections from more membrane interfaces, tilt of the membrane surface in respect to the coverslip and higher order interference minima and maxima, however, make it hard to correctly interpret the resulting images [1].

Facile, Electrochemical Chlorination of Graphene from an Aqueous NaCl Solution.

We report a facile approach to directly chlorinate graphene from an aqueous sodium chloride solution under ambient conditions. By applying a moderate anodic voltage to substrate-supported monolayer graphene, the resultant chlorine radicals generated at the graphene surface enable efficient chlorination: X-ray photoelectron spectrum confirms the formation of C-Cl bonds, and reaction voltage-tunable Cl:C atomic ratios of up to 17% are achieved. In comparison, we find the corresponding electrochemical graphene bromination and iodination reactions much less viable. Electrical and Raman characterizations show substantial p-doping for the chlorinated graphene, yet good basal-plane integrity and electrical properties are maintained. Interference reflection microscopy and pH-dependent experiments next help elucidate the competition between the radical-mediated electrochemical chlorination and oxidation in the process, and rationalize acidic conditions for optimal chlorination. Reaction in a mixed NaCl-NaN3 solution shows the electrochemical chlorination to be fully suppressed by azidation, yet a sequential, two-step chlorination-azidation approach permits facile bifunctionalization.

All-polymeric high-Q optofluidic Fabry-Perot resonator.

A full polymeric optofluidic Fabry-Perot (FP) resonator with a high quality factor (Q) is proposed and tested. The device is based on multilayer optical polymeric films that act as high reflectivity interference mirrors. The all-polymeric laminated structure avoids any deposition or etching process, simplifying the fabrication procedure while retaining a high quality optical surface. The measured quality factor of the FP resonator is 3.03×104, and the finesse is 91 around 700 nm. The refractometric sensing properties have been measured, and a sensitivity of 314 nm/RIU with a limit of detection of 2.55×10-5RIU could be achieved. The device exhibits a very high figure of merit of 1.36×104RIU-1 that is comparable with the performance attainable with sensors based on photonic crystal and whispering gallery mode resonators.

The Centerline Extraction Algorithm of Weld Line Structured Light Stripe Based on Pyramid Scene Parsing Network

Based on the good feature learning ability of the pyramid scene parsing network, a method for extracting the centerline of structured light stripes of weld lines based on the pyramid scene parsing network and Steger algorithm is proposed. This method avoids the traditional complex weld image preprocessing technology, and simplifies the operation steps of extracting the centerline of the structured light stripe of the weld image line. In this paper, the pyramid scene parsing network is used to predict the pixels containing weld feature information. Through the pyramid pooling module, the local and global context feature information is fused to supplement the feature information of the weld edge, and then the Steger algorithm is used to extract the weld feature centerline. The results show that the method in this paper can accurately extract the centerline position of the structured light stripe of the weld line under the interference of reflection, and the average value reaches 86.8% on the accuracy evaluation index mean intersection over union, the 18.93 pixels on the weld extraction accuracy index root mean square error, and the average time of extracting the center line of structured light stripe of weld line is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.188s$ </tex-math></inline-formula> .

Multi-Tone Phase Coding of Interaural Time Difference for Sound Source Localization With Spiking Neural Networks

Mammals exhibit remarkable capability of detecting and localizing sound sources in complex acoustic environments by using binaural cues in the spiking manner. Emulating the auditory process for sound source localization (SSL) by mammals, we propose a computational model for accurate and robust SSL under the neuromorphic spiking neural network (SNN) framework. The center of this model is a Multi-Tone Phase Coding (MTPC) scheme, which encodes the interaural time difference (ITD) between binaural pure tones into discriminative spike patterns that can be directly classified by SNNs. As such, SSL can be implemented as an event-driven task on highly efficient, neuromorphic parallel processors. We evaluate the proposed computational model on a directional audio dataset recorded from a microphone array in a realistic acoustic environment with background noise, obstruction, reflection, and other interferences. We report superior localization capability with a mean absolute error (MAE) of 1.02 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> or 100% classification accuracy with an angle resolution of 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , which surpasses other SNN-based biologically plausible neuromorphic approaches by a relatively large margin and on par with human performance in similar tasks. This study opens up many application opportunities in human-robot interaction where energy efficiency is crucial. As a case study, we successfully deploy the proposed SSL system in a robotic platform to track the speaker and orient the robot's attention.

Manipulation of topological beam splitter based on honeycomb photonic crystals

The intriguing discoveries of quantum spin Hall effect of electrons and its analogy in photon systems have renovated several concepts in condensed matter physics. Here we emulate topological edge states at microwave frequencies utilizing honeycomb photonic crystals with elliptical rods made of silicon material, and a novel topological beam splitter is implemented and analyzed. Robustness against perturbations provides the beam splitter with extremely strong transmission stability. Noticeably, suppressing the backward transmission of electromagnetic wave mitigates undesirable reflection interference. The numerical analysis results reveal that the splitting ratio obtained is in the range of 0.5–1.5 and the maximum transmittance value can reach up to 97% in this system. Besides, by appropriately adjusting the configuration parameters of photonic crystals, the location of operating frequency can be tuned to match different cases. The proposed structure has tremendous potential applications in the field of all-optical integrated circuits and will promote the practicability of photonic topological insulators in the communication domain