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2D transition-metal dichalcogenides have been reported to possess piezoelectricity due to their lack of inversion symmetry; thus, they are potentially applicable as electromechanical energy harvesters. Herein, the authors propose a lithography-free piezoelectric energy harvester composed of centimeter-scale MoS

We have developed a high-speed and high-resolution multimodal nonlinear optical microscope, which can acquire in vivo label and label-free 3D images. Using this microscope, we could successfully observe dynamic images of the zebrafish heartbeat with 33-millisecond intervals without staining process, indicating 1.68 beats per second. In addition, we show that the label-free, high-speed, real-time images can be obtained during somatic cell divisions in the zebrafish’s embryo.

Five-dimensional (5D) recording and decoding is demonstrated by using femtosecond direct laser writing in a silver-containing commercial glass. In particular, laser intensities and ellipse orientations generated by anamorphic focusing are employed to produce 5D data storage unit (3D for XYZ, 1D for the orientation of the elliptically-shaped data storage unit and 1D for its fluorescence intensity). In the recording process, two different images of a 4-bit bitmap format were simultaneously embedded in the medium by multiplexing the elliptical orientation of the laser focus and its intensity so as to access oriented elliptical patterns with independent fluorescence intensity. In the decoding process, two merged original images were successfully reconstructed by comparing each data storage unit with a fabricated calibration matrix of 16 &times, 16 levels for elliptic orientations and fluorescence intensities. We believe this technique can be applied to semi-permanent high-density data storage device.

The effect of corner rounding in a binary surface-relief grating on its diffraction efficiency is investigated by using a rigorous coupled-wave analysis. A super-Gaussian function is adopted to model the profiles of rectangular gratings with rounded corners. In particular, the diffraction efficiencies for transverse electric polarization are found to change significantly with the profile shapes of the reflection gratings while the transverse magnetic polarization causes clearly distinctive change in the efficiency for the transmission gratings.

Electrical stimulation through direct electrical activation has been widely used to recover the function of neurons, primarily through the extracellular application of thin film electrodes. However, studies using extracellular methods show limited ability to reveal correlations between the cells and the electrical stimulation due to interference from external sources such as membrane capacitance and culture medium. Here, we demonstrate long-term intracellular electrical stimulation of undamaged pheochromocytoma (PC-12) cells by utilizing a vertical nanowire electrode array (VNEA). The VNEA was prepared by synthesizing silicon nanowires on a Si substrate through a vapor-liquid-solid (VLS) mechanism and then fabricating them into electrodes with semiconductor nanodevice processing. PC-12 cells were cultured on the VNEA for 4 days with intracellular electrical stimulation and then a 2-day stabilization period. Periodic scanning via two-photon microscopy confirmed that the electrodes pierced the cells without inducing damage. Electrical stimulation through the VNEA enhances cellular differentiation and neurite outgrowth by about 50% relative to extracellular stimulation under the same conditions. VNEA-mediated stimulation also revealed that cellular differentiation and growth in the cultures were dependent on the potential used to stimulate them. Intracellular stimulation using nanowires could pave the way for controlled cellular differentiation and outgrowth studies in living cells.

A video-rate multimodal microscope, which can obtain second- and third- harmonic generation (SHG and THG) images simultaneously, is developed for investigating cellular and tissue structures in mouse ear skin. By utilizing in-vivo video-rate epi-detected SHG and THG microscopy, we successfully demonstrate that combined images of subcutaneous cellular components and peripheral nerve fibers, together with the collagen fiber, in the mouse ear pinna can be obtained without employing fluorescent probes. We also show that the flow of red blood cells and the diameter change of arteriole-like blood vessels can be visualized with femtosecond laser pulses with a wavelength of 1036 nm. In particular, the epi-THG contrast images of the blood-vessel walls display clearly the difference between the arteriole-like and the venule capillary-like blood-vessel types. We should emphasize that our newly-developed microscope system has a unique feature in that it can produce simultaneous in-vivo label-free SHG and THG images in contrast to the conventional confocal and two-photon microscopes.

Nonlinear optical microscopy has enabled the possibility to explore inside the living organisms. It utilizes ultrashort laser pulse with long wavelength (greater than 800nm). Ultrashort pulse produces high peak power to induce nonlinear optical phenomenon such as two-photon excitation fluorescence (TPEF) and harmonic generations in the medium while maintaining relatively low average energy pre area. In plant developmental biology, confocal microscopy is widely used in plant cell imaging after the development of biological fluorescence labels in mid-1990s. However, fluorescence labeling itself affects the sample and the sample deviates from intact condition especially when labelling the entire cell. In this work, we report the dynamic images of Arabidopsis thaliana root cells. This demonstrates the multimodal nonlinear optical microscopy is an effective tool for long-term plant cell imaging.

Unlike those of other ordinary laser scanning microscopies in the past, nonlinear optical laser scanning microscopy (SHG, THG microscopy) applied ultrafast laser technology which has high peak powers with relatively inexpensive, low-average-power. It short pulse nature reduces the ionization damage in organic molecules. And it enables us to take bright label-free images. In this study, we measured cell division of zebrafish egg with ultrafast video images using multimodal nonlinear optical microscope. The result shows in-vivo cell division label-free imaging with sub-cellular resolution.

The mixed liquor of organic wastes (MLOW) produced from a 1,4-butanediol production process was tested as an external carbon source for denitrification in the biological nutrient removal (BNR) process. The fraction of non-biodegradable chemical oxygen demand (NBDCOD) in the MLOW was estimated to be approximately 0.2% by measuring the oxygen uptake rate (OUR). The specific denitrification rate (SDNR) of MLOW and methanol from a nitrate utilization rate (NUR) test was confirmed to be approximately 13.02 and 12.68 mgN/gVSS/hr, respectively. The results indicated that the denitrification capability of microorganisms applying the MLOW was similar to that of using methanol as an external carbon source for the BNR process. The feasibility of MLOW for a stainless steel wastewater treatment plant (WWTP) was investigated. The low concentration of effluent nitrogen indicated a denitrification capability for MLOW similar to that for methanol. These results support the potential of MLOW as a substitute for methanol in the BNR process.

Reproducibility obtained by a minimum-volume cell for photoacoustic (PA) signals is strongly dependent upon the sealing materials and sealing efficiency. Therefore, we have proposed, designed, and constructed an apparatus to enhance the sealing efficiency, and we have examined the reproducibility of amplitude and phase of PA signals with a minimum-volume cell. In particular, we have measured the PA signal as a function of modulation frequency for various rubber O-rings by using our apparatus. The results show that a silicon rubber O-ring can improve the reproducibility of the PA signal and phase by up to 53.4% and 80.4%, respectively, compared to that obtained by using the conventional sealing material, vacuum grease.

There are technical difficulties in measuring the numerical apertures of multi-mode gradient-index plastic optical fibers (GI-POFs) due to their strong speckle noise originating from dopants, non-uniformity of gradient-index profile, and multi-mode interference. Therefore, we propose a new method of obtaining the numerical aperture by controlling the size of the incident laser beam and measuring the numerical aperture of GI-POF. The results show that we can get a value for the numerical aperture of GI-POF very similar to that measured by the conventional method. We can also obtain the optimum launching condition of input beam and maximum coupling efficiency.

We report the impact of a copper hexadecafluorophthalocyanine (F 16 CuPc) layer inserted between the electrode (Ag and Au) and the pentacene active layer in organic thin-film transistors (OTFTs). The electrical characteristics of the transistor are highly improved with the insertion of F 16 CuPc in devices having either an Ag or an Au electrode. The threshold voltage was reduced remarkably from −26.20 V to −3.72 V after inserting the F 16 CuPc layer in the device with an Ag electrode. In order to examine the effect of the F 16 CuPc layer, we evaluated the energy level alignments at the interfaces of pentacene/Ag and pentacene/F 16 CuPc/Ag by in situ ultraviolet photoelectron spectroscopy. The hole-injection barrier from the Ag electrode to the pentacene layer is 0.55 eV with F 16 CuPc, while it is 0.80 eV without F 16 CuPc. The enhancements in the threshold and turn-on voltages are understood with the energy level alignments at the electrode–pentacene interface.

We propose a simple nondestructive method to obtain refractive-index profiles of a graded-index (GRIN) light-focusing rod by means of a diffraction grating. In our proposed method, a laser beam is illuminated through a diffraction grating perpendicular to the axis of the GRIN lens and the separation between the zeroth and first-order diffraction peaks is measured and analyzed. The results demonstrate that the refractive-index profiles of commercially available GRIN lenses can be successfully reconstructed.

We report on the fabrication self-assembled tandem (pyramidal- holed) InGaAs nanostructures on GaAs (311)A in comparison with the nanostructures on (100) surface. Under an identical growth condition, the fabricated nanostructures are characteristically dissimilar; ring-shaped nanostructures on GaAs (100) and pyramidal-holed nanostructures on (311)A. The underlying formation mechanism of these interesting nanostructures can be understood in terms of intermixing, dissolution of GaAs substrate and surface diffusion driven by a surface reconstruction. The size and density of nanostructures can be controlled by modifying the droplet size, density, and thermal energy applied during the fabrication of droplets and nanostructures. These unique InGaAs nanostructures can offer promising applications in optoelectronics.

We have examined the self-assembled membrane-bound aggregates of two annexin V (A5) dye conjugates and compared them to those from native A5. Native A5 and FITC-labeled A5 (A5-FITC) both formed discrete well-defined crystalline monolayer domains of p6 symmetry. However, A5-FITC also showed additional domains with a corrugated appearance not observed in native A5. In contrast, Cy3-labeled A5 (A5-Cy3) showed a mixture of crystalline monolayer and irregular multilayered domains, with the ratio of the two types varying significantly from sample to sample, and also required a much longer incubation time than native A5 and A5-FITC. When A5-FITC and A5-Cy3 were co-incubated on the same bilayer, well-defined crystalline monolayer domains containing both A5-FITC and A5-Cy3 were consistently observed at a much shorter incubation time than that of pure A5-Cy3 alone, indicating that A5-FITC facilitates the inclusion of A5-Cy3. These results suggest that dye labels can affect A5 2D self-assembly and crystal formation on membrane surfaces.

The frequency-dependent photoacoustic (PA) signals and phase spectra of GaAs samples with different doping densities are measured and analyzed. In particular, we find that the magnitude differences of the PA signal and phase between intrinsic GaAs and doped GaAs materials decrease linearly with the doping density in the frequency region of nonradiative bulk recombination. The results show that the PA spectroscopic technique can be used to measure doping density in bulk semiconductors with reasonable accuracy.

Nonlinear optical microcopy has become an important tool in investigating biomaterials due to its various advantages such as label-free imaging capabilities. In particular, it has been shown that third-harmonic generation (THG) signals can be produced at interfaces between an aqueous medium (e.g. cytoplasm, interstitial fluid) and a mineralized lipidic surface. In this work, we have demonstrated that label-free high-contrast THG images of the mycobacterium tuberculosis can be obtained using THG microscopy.

International audience; Third harmonic generation microscopy is described in the frame work of the theory of harmonic generation with Gaussian focused beams inside a bulk material as well as at the vicinity of an interface. This model is then applied to characterize different types of materials in terms of electronic third-order susceptibility. Examples of bulk glasses, poled glasses, laser-induced modifications in glasses and nanoparticles in solution are given in order to give a survey of the broad application field of THG microscopy in material characterization.

Biofiltration is a simple, effective, economically viable and the most widely used gas treatment technique for treating malodors at low concentrations and high flow rates. This paper reports the performance of two lab scale immobilized cell biofilters operated in continuous mode for hydrogen sulfide () and ammonia () removal. The removal efficiency (RE, %) and the elimination capacity (EC, ) profiles were monitored by subjecting the biofilters to different loading rates of (0.3 to ) and (0.3 to ). The removal efficiencies were greater than 99% when inlet loading rate to the biofilters were upto and respectively. The performance of the biofilters were also ascertained by conducting shock loading studies at a loading rate of and . The results from this study show high removal efficiency, good recuperating potential and stability of the immobilized microbial consortia to transient shock loads.

Directional couplers of gradient-index plastic optical fibers were fabricated and characterized. In particular, we have employed a core-facet technique to make the directional couplers, which require mechanical side polishing and linkage. We have measured insertion loss, excess loss, and coupling ratio of the fabricated couplers as a function of polishing depth and coupling length. We found that polishing depth of $\~300{\mu}m$ and coupling length of $\~35mm$ are optimum conditions for minimizing the insertion and excess losses and for achieving 1: 1 coupling ratio.

CdS semiconductor quantum dot (QD) structures in aqueous solution are fabricated by using a gamma- ray irradiation technique and their optical absorption spectra are investigated. Cadmium sulfate solution, 2-mercap- toethanol solution, and reducing agent e aq − are employed to produce CdS molecules, leading to CdS quantum dots. The measured linear absorption spectra before and after γ-ray irradiation clearly show exciton peaks between 300 nm and 400 nm, which indicate the formation of CdS QD's. It is also obs erved that the exciton peaks are red-shifted with increasing the γ-ray irradiation time from 5 min to 15 min. Therefore, it is concluded that the mean QD sizes can be systematically controlled with the dosage of the γ-ray irradiation.

The influence of an aerobic fixed-biofilm activity, microbial ecosystem and mass transfer with respect to HRT variation in a BNR (biological nutrient removal) system has been investigated in this study. The process used in this study was an anoxic (1)/aerobic (1)/anoxic (2)/aerobic (2) system. The study was demonstrated by several kinds of techniques such as INT-dehydrogenase activity (DHA), INT (2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetra-zolium chloride), DAPI (4’,6’-diamidino-2-phenylindole hydrochloride), and microelectrode. The study used by synthetic wastewater and HRT variation demonstrated that the DHA activity, density and heterotrophs/autotrophs ratio increased, as the HRT decreased from 8 hr to 4 hr. In comparing two aerobic reactors in fixed-biofilm process, the first aerobic reactor of the higher C/N ratio showed higher heterotrophs/autotrophs ratio and microbial activity than the second aerobic reactor. It was therefore concluded that the heterotrophs/autotrophs ratio and microbial activity were a greater influence on the first aerobic reactor, as organic loading rate was increased by HRT variation.

A simplified phase-shifting moire interferometer for generating moire fringes from projected linear gratings and computer generated grid patterns without using a low-pass filter is presented. In particular, it is demonstrated that moire fringes can be successfully obtained even when there is no clear frequency separation between the moire fringe and the grid pattern. It is also pointed out that our proposed method produces fewer phase jumps than conventional phase-measuring profilometry, enabling us to realize more robust phase unwrapping.

Simultaneous determination of concentrations for four major components in human blood serum was investigated using a Fourier-transform mid-infrared spectroscopy. Infrared spectra of human blood serum were measured in 8.404 ∼ 10.25 ${\mu}m$ range where the highest absorption peaks of glucose are located. A partial least square (PLS) algorithm was utilized to establish a calibration model for determining total protein, albumin, globulin and glucose levels which are commonly measured metabolites. The standard error of cross validation obtained from our multivariate calibration model was 0.24 g/dL for total protein, 0.15 g/dL for albumin, 0.17 g/dL for globulin, and 6.68 mg/dL for glucose, which are comparable with or meet the criteria for clinical use. The results indicate that the infrared absorption spectroscopy can be used to predict the concentrations of clinically important metabolites without going through a chemical process with a reagent.

We propose a novel stereoscopic display technique which uses only a single wedge prism. It can provide good depth perception from a stereoscopic pair image displayed on a computer monitor. One element of the stereoscopic pair image is inversely distorted to correct the deformation induced by the wedge prism. The computer simulation and experimental demonstration show that this technique can be successfully applied to the Internet environment.

We report that the shape and size of fluorescent patterns can be controlled by the focused laser intensity distribution, which depends on irradiation conditions as well as on the spin and orbital angular momenta being carried by light, inducing the formation of silver cluster patterns in a silver-containing zinc phosphate glass. In particular, we demonstrate that sub-diffraction-limited inner structures of fluorescent patterns can be generated by direct laser writing (DLW) with tightly focused femtosecond laser vortex beams as Laguerre-Gauss modes (LG0l) with linear and left-handed circular polarizations. We believe this technique, further combined with dual-color DLW, can be useful and powerful for developing structured light enabled nanostructures.

The single living cell action potential was measured in an intracellular mode by using a vertical nanoelectrode. For intracellular interfacing, Si nanowires were vertically grown in a controlled manner, and optimum conditions, such as diameter, length, and nanowire density, were determined by culturing cells on the nanowires. Vertical nanowire probes were then fabricated with a complimentary metal-oxide-semiconductor (CMOS) process including sequential deposition of the passivation and electrode layers on the nanowires, and a subsequent partial etching process. The fabricated nanowire probes had an approximately 60-nm diameter and were intracellular. These probes interfaced with a GH3 cell and measured the spontaneous action potential. It successfully measured the action potential, which rapidly reached a steady state with average peak amplitude of approximately 10 mV, duration of approximately 140 ms, and period of 0.9 Hz.

Waveguide writing using a train of femtosecond laser pulses at 850 nm, in the transparent spectral region of bulk As40S60 glasses is reported. Waveguides were written by translating the glass sample along the optical axis of a strongly focussed laser beam. Refractive index variation, linear absorption spectra, and Raman spectra of the exposed region were measured. The chemical mechanism responsible for the index variation has been correlated to a breakage of the glass' As–S bonds and formation of As–As and S–S bonds and increase of the “disorder” of the glass network. The nonlinear optical origin leading to this phenomenon has been shown, and possible mechanisms are discussed.

We report measurements of the dispersion in the linear optical properties (linear absorption coefficient and refractive index) of polydiacetylene para -toluene sulfonate (PDA–PTS) single crystal waveguide films prepared by thermal polymerization of the monomer free floating in solution and subsequent attachment of the film to the substrate. A maximum absorption coefficient >10 5 cm −1 at a wavelength of 620 nm is measured for polarization parallel to the polymer chains, in agreement with previous measurements. The refractive index parallel to the polymer axis is significantly lower in these thin films as compared to bulk PDA–PTS crystals, whereas the index perpendicular to the chains is comparable to that of bulk crystals. Sellmeier parameters describing the dispersion of the refractive index in the near-infrared spectral range are given.

In this letter, we report bending and strain sensitivities of helicoidal long-period fiber gratings fabricated by twisting single-mode fibers during CO2 laser irradiation. Linear spectral shifts of the resonant wavelengths under the bending and tensile strain were observed with the sensitivities of -11.7 nm/m-1 and -1.1 pm/muepsiv, respectively. The corresponding transmission power variations at the resonance wavelength were 4.1 dB/m-1 and 2.2 times 10-4 dB/muepsiv, respectively. Detailed measurement techniques and sensor applications are discussed.

Nonlinear optical properties of an unsaturated polymer (poly trifluroethy dipropargy malonate) are investigated by using a passive Q-switched Nd:YAG laser. Double-peaked structure of phase conjugate signals due to the two-photon-absorption induced thermal effect is clearly is clearly observed and a simple method to remove the thermal effect from the overall phase-conjugate signals is demonstrated.

Photoluminescence characteristics and the energy transfer between Ce3+ and Eu2+ in CaAl12O19 host lattice have been investigated. A series of concentrations of Ce3+ ion with a fixed Eu2+ concentration in doubly doped CaAl12O19 : Ce3+Eu2+ have been studied. The indirect energy transfer has been observed between Ce3+ and Eu2+ through the Ce3+OMe complex in CaAl12O19 host lattice. The two nonradiative relaxation processes from the excited levels of Ce3+OMe complex; one, to the lower emitting level of Ce3+OMe complex themselves and the other, to the Eu2+ site are competing processes.

A quantum well electroabsorption waveguide modulator utilizing a field-induced refractive index change was designed and fabricated. The on/off ratios of the device were investigated as a function of wavelength over the spectral range of 850 nm to 910 nm for the various reverse biases. The field-induced refractive index variations associated with quantum-confined Stark effect was theoretically obtained based on the measured on/off ratios. The resulting maximum refractive index change( ${\DELTA}n) of ~7.5 {\times} 10^{-4}$ at -8 V was estimated.

Ceramide molecules in water-based solutions readily attract each other to form molecular crystals, which seriously hampers to diversify their formulations. This paper describes a facile method that allows fabrication of stable ceramide emulsions through an effective molecular association with a lipid having an asymmetric molecular geometry. The lipid considered in this study is mannosylerythritol lipid (MEL). MEL is specialized in having a unique molecular structure containing sugar alcohol erythritol as a hydrophilic part and two alkyl chains with different number of carbons as hydrophobic moieties. Our particular interest has been focused on experimentally demonstrating how MEL interacts with pseudo-ceramide molecules by observing phase properties, emulsion morphology, and suspension stability. The pseudo-ceramide emulsions prepared with MEL show remarkably improved dispersion stability without either formation of molecular crystals or changes in particle sizes even after storing them for a long time. This suggests that MEL readily associates with the pseudo-ceramide due to the hydrophobic interaction, while it makes a break in the continuity of the molecular assembly of the pseudo-ceramide molecules themselves due to the geometric hindrance coming from MEL's asymmetric molecular structure.

Spectral imaging of luminescent centers in InGaN/GaN multiple quantum wells was performed. In particular, peak energy and linewidth mappings were simultaneously performed in order to evaluate the influence of the In mole fraction.

The effects of the saturable absorber absorption on the pulse duration and stability of active-passively mode-locked YAlO3:Nd3+ laser were investigated. The optimum conditions for energy stability and pulse duration were obtained at the absorption coefficient of α0 = 10.5 cm-1. The energy stability of the steady-state part of the pulse train, containing approximately 60 pulses, was achieved to be less than ±1% r.m.s.. The nonlinear behavior of the passive negative feedback element was also observed.

ICMCB, CNRS, 87 av. Dr. Schweitzer, 33608 Pessac cedex, University Bordeaux I, FranceReceived April 13, 2004Key Words : Quantum dot, Metal-semiconductor composite quantum dot, Plasmon resonance, Gamma rayirradiation, Quantum-confined Stark shiftThere have been great interests in the optical, electrical,and chemical properties of quantized nanoparticles, such assemiconductor quantum dots (QDs).