Short Light Research Articles

Nondestructive Measurements of the Mechanical and Structural Properties of Nanostructured Metalattices.

Metalattices are artificial 3D solids, periodic on sub-100 nm length scales, that enable the functional properties of materials to be tuned. However, because of their complex structure, predicting and characterizing their properties is challenging. Here we demonstrate the first nondestructive measurements of the mechanical and structural properties of metalattices with feature sizes down to 14 nm. By monitoring the time-dependent diffraction of short wavelength light from laser-excited acoustic waves in the metalattices, we extract their acoustic dispersion, Young's modulus, filling fraction, and thicknesses. Our measurements are in excellent agreement with macroscopic predictions and potentially destructive techniques such as nanoindentation and scanning electron microscopy, with increased accuracy over larger areas. This is interesting because the transport properties of these metalattices do not obey bulk predictions. Finally, this approach is the only way to validate the filling fraction of metalattices over macroscopic areas. These combined capabilities can enable accurate synthesis of nanoenhanced materials.

Improving the Quality of Digital Images Using the Image Averaging Method

Image is a representation (picture), similarity, or imitation of an object. The use of digital images plays an important role as a form of information due to its advantages. Although it is rich in information, not all images have a good visual appearance. This can be due to interference in the form of noise, color intensity that is too contrasting or blurred. Noise itself is a disturbance caused by distorted digital data received by the image data receiver, starting from the movement during shooting by optical devices such as cameras, the use of optical devices that are not in focus, short lighting thereby reducing the number of photos captured by optical devices, or the weather when shooting. Noise can be removed by using the Image Averaging Method

A rotating holographic imager for stationary cloud droplet and ice crystal measurements

An optical cloud droplet and ice crystal measurement system ICEMET (icing condition evaluation method), designed for present icing condition monitoring in field conditions, is presented. The aim in this work has been to develop a simple but precise imaging technique to measure the two often missing parameters needed in icing rate calculations caused by icing clouds—the droplet size distribution (DSD) and the liquid water content (LWC) of the air. The measurement principle of the sensor is based on lens-less digital in-line holographic imaging. Cloud droplets and ice crystals are illuminated by a short laser light pulse and the resulting hologram is digitally sampled by a digital image sensor and the digital hologram is then numerically analyzed to calculate the present DSD and LWC values. The sensor has anti-icing heating power up to 500 W and it is freely rotating by the wind for an optimal sampling direction and aerodynamics. A volume of 0.5 cm3 is sampled in each hologram and the maximum sampling rate is 3 cm3/s. Laboratory tests and simulations were made to ensure the adequate operation of the measurement sensor. Computational flow dynamics simulations showed good agreement with droplet concentration distributions measured from an icing wind tunnel. The anti-icing heating of the sensor kept the sensor operational even in severe icing conditions; the most severe test conditions were the temperature − 15 °C, wind speed 20 m/s and the LWC 0.185 g/m3. The verification measurements made using NIST traceable monodisperse particle standard glass spheres showed that the ICEMET sensor measurement median diameter 25.54 µm matched well with 25.60 µm ± 0.70 µm diameter confidence level given by the manufacturer.

On the timescales of correlated electron dynamics

Recent developments yielding intense and short light pulses in the atto-second regime makes it possible to address fundamental questions on the time evolution of the electron dynamics. We demonstrate in our studies that electron pair emission from surfaces holds the promise to unravel the time scale of correlated electron dynamics. This can be achieved without atto-second light sources. We will discuss two different approaches. First we studied the Auger decay following the emission of a core-electron due to photon absorption. With coincidence spectroscopy, we demonstrate an extensive energy sharing between the Ag 4p photoelectron and the NVV Auger electron exceeding 10 eV. This result is at odds with a sequential emission of first the photoelectron and then the Auger electron. This energy width of the sharing provides access to the time scale of the emission process. We convert this to a timescale of 60 as over which the fluctuations takes place. This value is fair agreement with the theoretical calculation of the timescale to fill an exchange-correlation hole. In a second study we utilized the neutralization of ions near a surface. This is known to be efficient process and leads to electron emission via Auger-type processes. Specifically, the neutralization of He2+ ions makes available the double ionization energy. We demonstrate that the neutralization of a single He2+ ion near an Ir(100) surface leads to the emission of an electron pair. Via coincidence spectroscopy we give evidence that a sizable amount of these electron pairs originate from a correlated single step neutralization of the ion involving a total of 4 electrons from the metal. These correlated electron pairs cannot be explained in the common picture of two consecutive and independent neutralization steps. We infer a characteristic time scale for the correlated electron dynamics in the metal of 40–400 as.

Improved emitter performance of RIE black silicon through the application of in-situ oxidation during POCl3 diffusion

Nano-texture has the potential to reduce the optical losses of crystalline silicon solar cells. RIE fabricated black silicon enables near zero reflectance across a broad range of wavelengths and the angular dependence has been shown to be superior to existing technologies. However, in front-contact cells which are the current industrial mainstream architecture, the emitter is located on the front textured side and is typically realized by POCl3 diffusion. The interaction of this process with the nano-texture is complex, which makes it challenging to optimise the electrical performance of the phosphorus emitter. This paper studies the impact of in-situ oxidation during emitter formation to the electrical performance of a POCl3 diffused RIE nanotextured emitter surface. Additional corona charge was applied on the ALD SiO2/Al2O3 stack to avoid the limitation on the emitter performance due to non-ideal surface passivation conditions. After saturation with surface charge, the results demonstrate in-situ oxidation to be an effective technique to improve the electrical performance. An emitter recombination factor of 147 fA/cm2 was achieved for a 127 Ω/□ emitter formed on reactive-ion etched sample with surface area enhancement factor and effective slope index of 4.19 and 1.63, respectively. Further paths for improvement are identified, particularly relating to the collection of carriers generated by short wavelength light and how that relates to the shape of the texture used.

Applications of Inorganic Nanomaterials in Photothermal Therapy Based on Combinational Cancer Treatment.

BackgroundCancer is one of the major causes of death and is difficult to cure using existing clinical therapies. Clinical cancer treatments [such as surgery, chemotherapy (CHT), radiotherapy (RT) and immunotherapy (IT)] are widely used but they have limited therapeutic effects and unavoidable side effects. Recently, the development of novel nanomaterials offers a platform for combinational therapy (meaning a combination of two or more therapeutic agents) which is a promising approach for cancer therapy. Recent studies have demonstrated several types of nanomaterials suitable for photothermal therapy (PTT) based on a near-infrared (NIR) light-responsive system. PTT possesses favorable properties such as being low in cost, and having high temporospatial control with minimal invasiveness. However, short NIR light penetration depth limits its functions.MethodsIn this review, due to their promise, we focus on inorganic nanomaterials [such as hollow mesoporous silica nanoparticles (HMSNs), tungsten sulfide quantum dots (WS2QDs), and gold nanorods (AuNRs)] combining PTT with CHT, RT or IT in one treatment, aiming to provide a comprehensive understanding of PTT-based combinational cancer therapy.ResultsThis review found much evidence for the use of inorganic nanoparticles for PTT-based combinational cancer therapy.ConclusionUnder synergistic effects, inorganic nanomaterial-based combinational treatments exhibit enhanced therapeutic effects compared to PTT, CHT, RT, IT or PDT alone and should be further investigated in the cancer field.

Degradation of the contrast of a short light pulse in a CPA system

We have calculated the effect of four-wave mixing of the main radiation pulse with the background radiation components on the value of the output radiation contrast in a chirped pulse amplification system of petawatt laser facilities. Formulae are presented that make it possible to quantify the contributions of two mechanisms, i.e. Kerr nonlinearity of the refractive index of the amplifying medium and gain saturation. For typical values of the nonlinear refractive index, both contributions are comparable. The possibility of mutual quenching of nonlinear contributions is noted. The influence of spectral filtering of radiation on the output pulse contrast is considered.

Visibility of hexagonal boron nitride on transparent substrates

The high transmittance and low reflectance of monolayer hexagonal boron nitride (hBN) lead to its invisibility under white-light, causing serious troubles in the search, transfer, and fabrication of 2D material devices. In this work, we demonstrate enhancing the contrast of hBN on a transparent substrate by simulation and experimental observation, where the highest contrast is obtained by using a polymer-based interfacial layer on a polydimethylsiloxane (PDMS) substrate. The simulation result reveals that the contrast under short wavelength light is higher than that under long wavelength. To confirm this, the red-green-blue components are extracted from the optical color image. The blue component image shows an hBN flake clearly on the substrate, while the hBN flake fades on the green and red components. Moreover, the contrast on transparent substrates have only positive value, while opaque substrates cause both negative and positive contrast depending on the thickness of the interfacial layer. Thus, the high contrast (∼4.5%) of hBN on the PDMS substrate enables us to observe mono- and few-layer hBN flakes under white-light illumination by an optical microscope.

Pharmacognostic Standardization and Physicochemical Analysis of Clerodendrum Wallichii (Merr.) Leaves

Background: Presently, the use of herbal medicines is expanding rapidly across the world. While considering source materials, authentication and standardization are prerequisites for herbal formulation in any system of medicine. The plant Clerodendrum Wallichii Merr. (Family: Lamiaceae) has been used for various ailments in traditional systems of medicines, particularly in the treatment of diarrhea, skin infection, inflammation and fever.
 Objectives: The present study was designed to establish the pharmacognostic standards and perform the physicochemical analysis of C. wallichii leaves. Macroscopic and microscopic studies were performed using the simple and trinocular microscope, respectively.
 Methods: The World Health Organization guidelines were followed for the physicochemical analysis of the plant. Fluorescence analysis was observed at daylight, short UV light, and long UV light. The leaves of C. wallichii were found dark green on the upper surface and light green in the lower surface which is odorless and bitter. The leaves are oblong to oblong-lanceolate with a smooth surface. The size of leaves varies from 11 to 18 cm in length and 2.5 to 4 cm in diameter.
 Results: Powdered microscopy showed the various characters like rare multicellular covering trichome, xylem vessels (reticulate), fiber, trichome base, stellate trichome, adaxial epidermal cell (rectangular), abaxial epidermal cell (irregular), vessels, stomata (anisocytic), calcium oxalate crystals (square and cubic). Physicochemical parameters like moisture content of dry powder of the plant was determined 9.3% W/W. The total ash, acid-insoluble, and water-soluble ash values were calculated as 10.48%, 1.08%, and 8.17%, respectively. The loss on drying was calculated as 9.3% W/W.
 Conclusion: Extractive values by cold and hot maceration method were also determined. Our obtained data help to authenticate the plant and establish its pharmacopoeial standards.

Coupling and Decoupling of Surface Plasmon Polaritons with a Double Period Metallic Grating

Herein, a numerical and experimental study of the interaction of a directional beam of light with metallic surfaces with two periodic components is presented. The periods of these two components are chosen in such a way that, through one of them, light is coupled into surface plasmon polaritons (SPPs) and, through the other one, the SPPs are decoupled as a propagating beam in another direction. This interaction can produce a propagating beam of light that involves in its trajectory the passage through an SPP state, providing thus a means of studying the effects of SPP coupling on the state of coherence of the emerging field. These coupling/decoupling effects are studied numerically, and experimental evidence of the generation of such SPP decoupled beams is presented. The effect of this double scattering process on the temporal properties of short light pulses, reflected by a double period metallic grating, is also studied.

Finding 10% hidden electricity in crystalline Si solar cells using PDMS coating and three‐dimensional cell arrays

AbstractOver the decades, solar cells have been developed to achieve higher energy conversion efficiency. However, the fabrication of modules has resulted in electricity production loss, but this has not attracted as much attention as the solar cells. As a result, the improved performance of solar cells has not been fully revealed at the panel scale. Furthermore, the standard testing conditions, such as 1 sun, AM1.5, which is very strong incident light, does not fully reflect the electricity production capabilities of solar panels because of performance degradation under oblique and weak illumination. Simple modification of the module fabrication process, including poly‐dimethylsiloxane (PDMS) coatings and three‐dimensional (3‐D) structured modules by one‐directional angled arrays of each cell, has revealed 13.4% extra hidden electricity in solar panels with some types of crystalline silicon (Si)‐based solar cells through high transmission to short wavelength light, recapture of the light reflected from Si solar cell surface textures by the PDMS coating and enhanced power production under oblique incident light or scattered light through a 3‐D module. Further studies to find hidden electricity should be followed by the development of solar cell device structures to improve electricity production, rather than being restricted to optimizing energy conversion efficiency.

Light deprivation reduces the severity of experimental diabetic retinopathy

Illumination of the retina is a major determinant of energy expenditure by its neurons. However, it remains unclear whether light exposure significantly contributes to the pathophysiology of common retinal disease. Driven by the premise that light exposure reduces the metabolic demand of the retina, recent clinical trials failed to demonstrate a benefit for constant illumination in the treatment of diabetic retinopathy. Here, we instead ask whether light deprivation or blockade of visual transduction could modulate the severity of this common cause of blindness. We randomized adult mice with two different models of diabetic retinopathy to 1-3 months of complete dark housing. Unexpectedly, we find that diabetic mice exposed to short or prolonged light deprivation have reduced diabetes-induced retinal pathology, using measures of visual function, compared to control animals in standard lighting conditions. To corroborate these results, we performed assays of retinal vascular health in diabetic Gnat1−/− and Rpe65−/− mice, which lack phototransduction. Both mutants displayed less diabetes-associated retinal vascular disease compared to respective wild-type controls. Collectively, these results suggest that light-induced visual transduction promotes the development of diabetic retinopathy and implicate photoreceptors as an early source of visual pathology in diabetes.

Endosomolytic and Tumor-Penetrating Mesoporous Silica Nanoparticles for siRNA/miRNA Combination Cancer Therapy

Combination therapies consisting of multiple short therapeutic RNAs, such as small interfering RNA (siRNA) and microRNA (miRNA), have enormous potential in cancer treatment as they can precisely silence a specific set of oncogenes and target multiple disease-related pathways. However, clinical use of siRNA/miRNA combinations is limited by the availability of safe and efficient systemic delivery systems with sufficient tumor penetrating and endosomal escaping capabilities. This study reports on the development of multifunctional tumor-penetrating mesoporous silica nanoparticles (iMSNs) for simultaneous delivery of siRNA (siPlk1) and miRNA (miR-200c), using encapsulation of a photosensitizer indocyanine green (ICG) to facilitate endosomal escape and surface conjugation of the iRGD peptide to enable deep tumor penetration. Increased cell uptake of the nanoparticles was observed in both 3D tumor spheroids in vitro and in orthotopic MDA-MB-231 breast tumors in vivo. Using a galectin-8 recruitment assay, we showed that reactive oxygen species generated by ICG upon light irradiation functioned as an endosomolytic stimulus that caused release of the siRNA/miRNA combination from endosomes. Co-delivery of the therapeutic RNAs displayed combined cell killing activity in cancer cells. Systemic intravenous treatment of metastatic breast cancer with the iMSNs loaded with siPlk1 and miR-200c resulted in a significant suppression of the primary tumor growth and in marked reduction of metastasis upon short light irradiation of the primary tumor. This work demonstrates that siRNA-miRNA combination assisted by the photodynamic effect and tumor penetrating delivery system may provide a promising approach for metastatic cancer treatment.

Habitual physical activity pattern and its association with gender and body composition in healthy adults

An appropriate level of physical activity (PA) is beneficial for health and weight management. This study examines the relationship of habitual PA and activity energy expenditure (AEE) in a typical week with gender and body composition parameters. Data of habitual PA of 72 healthy adults were collected with the heart rate and motion sensor (Actiheart). Total and segmental body fat was measured with bioelectrical impedance analyser. Men were more active in total and on working days and had shorter light and longer moderate and vigorous PA on working days than females (p<0.05). Females had less inactive and sitting time on days off. Inactive and sitting time in working days for both genders correlated positively with visceral fat rating, body and leg fat % (p<0.05). In male’s duration of working days’ moderate PA correlated inversely, but light PA positively with these parameters (p<0.05). Males with more vigorous PA in working day and AEE in days off had lower body fat % (p<0.05). A distinctive PA pattern on working days and days off indicates a gender-related differences. Decrease of time of inactivity and light PA and increase of duration of moderate and vigorous PA was associated with lower body and segmental fat amount.

Comparative Studies on Polyurethane Composites Filled with Polyaniline and Graphene for DLP-Type 3D Printing.

Digital light processing (DLP)-type 3D printing ensures several advantages, such as an easy solution process, a short printing time, high-quality printing, and selective light curing. Furthermore, polyurethane (PU) is among the promising candidates for 3D printing because of its wide range of applications. This work reports comparative studies on the fabrication and optimization of PU composites using a polyaniline (PANI) nanomaterial and a graphene sheet (GS) for DLP-type 3D printing. The morphologies and dispersion of the printed PU composites were studied by field emission scanning electron microscope (FE-SEM) images. Bonding structures in the PU composites were investigated by Fourier-transform infrared (FT-IR) spectroscopy. As-prepared PU/PANI and PU/GS composites with different filler contents were successfully printed into sculptures with different sizes and shapes. The PU/PANI and PU/GS composites exhibit the improved sheet resistance, which is up to 8.57 × 104 times (1.19 × 106 ohm/sq) lower and 1.27 × 105 times (8.05 × 105 ohm/sq) lower, respectively, than the pristine PU (1.02 × 1011 ohm/sq). Moreover, the PU/PANI and PU/GS composites demonstrate 1.41 times (44.5 MPa) higher and 2.19 times (69.3 MPa) higher tensile strengths compared with the pristine PU (31.6 MPa). This work suggests the potential uses of highly conductive PU composites for DLP-type 3D printing.

Photoautotrophic cultures of Chlamydomonas reinhardtii: sulfur deficiency, anoxia, and hydrogen production.

The aim of this work was a comparative study of S-repleted and S-depleted photoautotrophic cultures of Chlamydomonas reinhardtii under aerobic and anoxic conditions with the main focus on PSII activity. For that we used photobioreactor with short light path connected on-line to PAM fluorometer and cultivated microalgae in twice concentrated HS medium to avoid any uncontrolled limitation by mineral elements. Photoautotrophic cultures grown under Ar + CO2 gas mixture did not reach the same Chl (a + b) concentration as control culture (grown under air + CO2). At pO2 40% of air saturation (96µM O2), the actual quantum yield of PSII started to decrease. Under microaerobic conditions when cultures stopped growing, the most significant changes in PSII function were observed. Maximum quantum yield Fv/Fm decreased significantly along with performance index, PIabs. It was accompanied by increase of fluorescence at J point, Vj. Results indicate that microaerobic conditions are stressful for photoautotrophic cultures. Photoautotrophic cultures of microalgae under S-deprivation in aerobic or anaerobic conditions showed similar behavior as photoheterotrophic ones described earlier. However, photoautotrophic cultures during anaerobiosis establishment did not show sharp "switch off" effect of actual quantum yield. We show also that S-deprivation under air or argon as well as the growth under Ar + CO2 cause significant increase of initial rise of fluorescence, which indicates that PSII and oxygen-evolving complex might be disintegrated.

Influence of α-Oscillation Phase-dependent Exogenous Afferent Input on the Powers of Background EEG Rhythms

The study involved 20 healthy volunteers. Visual stimuli in the form of short diffuse light flashes (50 μs) were presented to each subject for 100 times in the ascending or descending phase of ongoing oscillations corresponding to the individual-specific dominating α-rhythm frequency. An EEG was recorded from 14 leads according to the 10/20 system during the test. Stimuli presented in the ascending phase of α oscillations were found to reduce the α-rhythm power in a time period at least 1 min after stimulus presentation. Stimuli presented in the descending phase increased the α-rhythm power.

Distortional analysis of laminated composite box girder: A review

With increase of maintenance and durability issues in bridge industry have motivated researchers to explore laminated composite FRP box girders in bridges. Box beams have good eccentric load distribution and better stability characteristics due to their high torsional stiffness. The combination of box-girder with FRP is perfect for light weight long span bridges. The potential for application of FRP box section has been particularly high in deployable bridges used in defense, temporary bridges, emergency replacement bridges, FOB and short span light loaded vehicular bridges etc. The objective of this paper is to provide highlights of the most important references related to the development of current guide specifications for laminated composite FRP box girder/beam and to understand distortional behavior of thin walled box girder. In this study, an attempt is made to study the significance of the laminated composite FRP box girder & type, distortion effect on thin walled box girder, methods used for distortional analysis of box girder. There are very limited studies in the field of laminated composite FRP box girder. Most of the studies are on distortional behavior of steel box girder. There is not detailed study available on distortional behavior of laminated composite FRP box girder. Thus, there appears to be a dearth of information on the distortional behavior of laminated composite FRP box girder. The present state of art has motivated the interest to contribute towards a better understanding of distortional behavior of laminated composite FRP box girders.

Distribution of Carotenoids and Protective Effects of Zeaxanthin on Retina of Ayu Sweetfish (Plecoglossus altivelis).

Ayu sweetfish (Plecoglossus altivelis) is a diurnal freshwater fish that are surface swimmers and active under broad and short wavelength-dominated light. Biochemical analyses have shown that the ayu fish have abundant carotenoids including zeaxanthin in their integuments. Although zeaxanthin plays an important role in the physiological function of the retina, the amount and location of zeaxanthin in the ayu eye have not been accurately determined. In this study, circular dichroism spectral data and chiral high-performance liquid chromatography analysis showed that zeaxanthin was the primary carotenoid in the ayu eye, and the eye had the highest carotenoid content compared to those in the integuments, subcutaneous fat, and digestive tract. Interestingly, zeaxanthin in the ayu eyeball was expressed in the photoreceptor layer and near the retinal pigmented epithelium. In vitro assays showed that zeaxanthin could protect photoreceptors and retinal pigmented epithelial cell lines against the oxidative stress induced by exposure to L-buthionine-(S,R)-sulfoximine/glutamate. These findings indicate that zeaxanthin plays protective roles against oxidative stress in the vision of wild ayu.

On the Propagation of a Short Light Pulse in a Medium With a Lorentz Contour of the Spectral Gain Line

On the Propagation of a Short Light Pulse in a Medium With a Lorentz Contour of the Spectral Gain Line