Optical properties of polarization-dependent geometrical phase elements with partially polarized light

International Nuclear Information System (INIS)

Gorodetski, Y.; Biener, G.; Niv, A.; Kleiner, V.; Hasman, E.

2005-01-01

Full Text:The behavior of geometrical phase elements illuminated with partially polarized monochromatic beams is being theoretically as well as experimentally investigated. The element discussed in this paper is composed of wave plates with retardation and space-variant orientation angle. We found that a beam emerging from such an element comprises two polarization orders of right and left-handed circularly polarized states with conjugate geometrical phase modification. This phase equals twice the orientation angle of the space-variant wave plate comprising the element. Apart from the two polarization orders, the emerging beam coherence polarization matrix comprises a matrix termed as the vectorial interference matrix. This matrix contains the information concerning the correlation between the two orthogonal circularly polarized portions of the incident beam. In this paper we measure this correlation by a simple interference experiment. Furthermore, we found that the equivalent mutual intensity of the emerging beam is being modulated according to the geometrical phase induced by the element. Other interesting phenomena along propagation will be discussed theoretically and experimentally demonstrated. We demonstrate experimentally our analysis by using a spherical geometrical phase element, which is realized by use of space-variant sub wavelength grating and illuminated with a CO 2 laser radiation of 10.6μm wavelength

Isotropic differential phase contrast microscopy for quantitative phase bio-imaging.

Science.gov (United States)

Chen, Hsi-Hsun; Lin, Yu-Zi; Luo, Yuan

2018-05-16

Quantitative phase imaging (QPI) has been investigated to retrieve optical phase information of an object and applied to biological microscopy and related medical studies. In recent examples, differential phase contrast (DPC) microscopy can recover phase image of thin sample under multi-axis intensity measurements in wide-field scheme. Unlike conventional DPC, based on theoretical approach under partially coherent condition, we propose a new method to achieve isotropic differential phase contrast (iDPC) with high accuracy and stability for phase recovery in simple and high-speed fashion. The iDPC is simply implemented with a partially coherent microscopy and a programmable thin-film transistor (TFT) shield to digitally modulate structured illumination patterns for QPI. In this article, simulation results show consistency of our theoretical approach for iDPC under partial coherence. In addition, we further demonstrate experiments of quantitative phase images of a standard micro-lens array, as well as label-free live human cell samples. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatiotemporal polarization modulation microscopy with a microretarder array

Science.gov (United States)

Ding, Changqin; Ulcickas, James R. W.; Simpson, Garth J.

2018-02-01

A patterned microretarder array positioned in the rear conjugate plane of a microscope enables rapid polarizationdependent nonlinear optical microscopy. The pattern introduced to the array results in periodic modulation of the polarization-state of the incident light as a function of position within the field of view with no moving parts or active control. Introduction of a single stationary optical element and a fixed polarizer into the beam of a nonlinear optical microscope enabled nonlinear optical tensor recovery, which informs on local structure and orientation. Excellent agreement was observed between the measured and predicted second harmonic generation (SHG) of z-cut quartz, selected as a test system with well-established nonlinear optical properties. Subsequent studies of spatially varying samples further support the general applicability of this relatively simple strategy for detailed polarization analysis in both conventional and nonlinear optical imaging of structurally diverse samples.

Optofluidic time-stretch quantitative phase microscopy.

Science.gov (United States)

Guo, Baoshan; Lei, Cheng; Wu, Yi; Kobayashi, Hirofumi; Ito, Takuro; Yalikun, Yaxiaer; Lee, Sangwook; Isozaki, Akihiro; Li, Ming; Jiang, Yiyue; Yasumoto, Atsushi; Di Carlo, Dino; Tanaka, Yo; Yatomi, Yutaka; Ozeki, Yasuyuki; Goda, Keisuke

2018-03-01

Innovations in optical microscopy have opened new windows onto scientific research, industrial quality control, and medical practice over the last few decades. One of such innovations is optofluidic time-stretch quantitative phase microscopy - an emerging method for high-throughput quantitative phase imaging that builds on the interference between temporally stretched signal and reference pulses by using dispersive properties of light in both spatial and temporal domains in an interferometric configuration on a microfluidic platform. It achieves the continuous acquisition of both intensity and phase images with a high throughput of more than 10,000 particles or cells per second by overcoming speed limitations that exist in conventional quantitative phase imaging methods. Applications enabled by such capabilities are versatile and include characterization of cancer cells and microalgal cultures. In this paper, we review the principles and applications of optofluidic time-stretch quantitative phase microscopy and discuss its future perspective. Copyright © 2017 Elsevier Inc. All rights reserved.

A novel fibrous duct structure discovered in the brain meninges by using polarized light microscopy

Science.gov (United States)

Nam, Min-Ho; Jung, Sharon Jiyoon; Soh, Kwang-Sup; Lim, Jaekwan; Seo, Eunseok; Lim, Jun; Baek, Miok; Lee, Sang Joon

2016-05-01

We have previously reported the discovery of a novel fibrous structure (NFS) consisting of unidirectionally arranged collagen fibers in the spinal pia mater. Due to its unique structure, it was easily detected using polarized light microscopy. In the current study, we describe the discovery of a similar NFS in the brain meninges of rats by using polarized light microscopy. This NFS is located beneath the superior sagittal sinus. Initially, we systemically analyzed the polarization properties of the NFS. The change in the light intensity of the NFS, with respect to the polarization angle, was eight times greater than that of blood vessels, showing that the collagen fibers are oriented in a particular direction with almost perfect parallelism (0.99). The orientation angle of the polarization ellipse confirmed the orientation of the collagen fibers in the NFS. Histological studies further confirmed that the unidirectionally arranged collagen fibers were responsible for this distinct polarization property. Surprisingly, X-ray microtomography and 3D confocal imaging revealed that the NFS contains within it a duct structure, a putative primo vessel. In conclusion, we report a NFS in the brain meninges, detected by using polarized light microscopy, that provides space for a putative primo vessel, not a blood vessel.

Biological applications of phase-contrast electron microscopy.

Science.gov (United States)

Nagayama, Kuniaki

2014-01-01

Here, I review the principles and applications of phase-contrast electron microscopy using phase plates. First, I develop the principle of phase contrast based on a minimal model of microscopy, introducing a double Fourier-transform process to mathematically formulate the image formation. Next, I explain four phase-contrast (PC) schemes, defocus PC, Zernike PC, Hilbert differential contrast, and schlieren optics, as image-filtering processes in the context of the minimal model, with particular emphases on the Zernike PC and corresponding Zernike phase plates. Finally, I review applications of Zernike PC cryo-electron microscopy to biological systems such as protein molecules, virus particles, and cells, including single-particle analysis to delineate three-dimensional (3D) structures of protein and virus particles and cryo-electron tomography to reconstruct 3D images of complex protein systems and cells.

Polar phase transitions in heteroepitaxial stabilized La0.5Y0.5AlO3 thin films

Science.gov (United States)

Liu, Shenghua; Zhang, Chunfeng; Zhu, Mengya; He, Qian; Chakhalian, Jak; Liu, Xiaoran; Borisevich, Albina; Wang, Xiaoyong; Xiao, Min

2017-10-01

We report on the fabrication of epitaxial La0.5Y0.5AlO3 ultrathin films on (001) LaAlO3 substrates. Structural characterizations by scanning transmission electron microscopy and x-ray diffraction confirm the high quality of the film with a - b + c - AlO6 octahedral tilt pattern. Unlike either of the nonpolar parent compound, LaAlO3 and YAlO3, second harmonic generation measurements on the thin films suggest a nonpolar-polar phase transition at T c near 500 K, and a polar-polar phase transition at T a near 160 K. By fitting the angular dependence of the second harmonic intensities, we further propose that the two polar structures can be assigned to the Pmc2 1 and Pmn2 1 space group, while the high temperature nonpolar structure belongs to the Pbnm space group.

Noninvasive assessment of articular cartilage surface damage using reflected polarized light microscopy

Science.gov (United States)

Huynh, Ruby N.; Nehmetallah, George; Raub, Christopher B.

2017-06-01

Articular surface damage occurs to cartilage during normal aging, osteoarthritis, and in trauma. A noninvasive assessment of cartilage microstructural alterations is useful for studies involving cartilage explants. This study evaluates polarized reflectance microscopy as a tool to assess surface damage to cartilage explants caused by mechanical scraping and enzymatic degradation. Adult bovine articular cartilage explants were scraped, incubated in collagenase, or underwent scrape and collagenase treatments. In an additional experiment, cartilage explants were subject to scrapes at graduated levels of severity. Polarized reflectance parameters were compared with India ink surface staining, features of histological sections, changes in explant wet weight and thickness, and chondrocyte viability. The polarized reflectance signal was sensitive to surface scrape damage and revealed individual scrape features consistent with India ink marks. Following surface treatments, the reflectance contrast parameter was elevated and correlated with image area fraction of India ink. After extensive scraping, polarized reflectance contrast and chondrocyte viability were lower than that from untreated explants. As part of this work, a mathematical model was developed and confirmed the trend in the reflectance signal due to changes in surface scattering and subsurface birefringence. These results demonstrate the effectiveness of polarized reflectance microscopy to sensitively assess surface microstructural alterations in articular cartilage explants.

Quantitative analysis with advanced compensated polarized light microscopy on wavelength dependence of linear birefringence of single crystals causing arthritis

Science.gov (United States)

Takanabe, Akifumi; Tanaka, Masahito; Taniguchi, Atsuo; Yamanaka, Hisashi; Asahi, Toru

2014-07-01

To improve our ability to identify single crystals causing arthritis, we have developed a practical measurement system of polarized light microscopy called advanced compensated polarized light microscopy (A-CPLM). The A-CPLM system is constructed by employing a conventional phase retardation plate, an optical fibre and a charge-coupled device spectrometer in a polarized light microscope. We applied the A-CPLM system to measure linear birefringence (LB) in the visible region, which is an optical anisotropic property, for tiny single crystals causing arthritis, i.e. monosodium urate monohydrate (MSUM) and calcium pyrophosphate dihydrate (CPPD). The A-CPLM system performance was evaluated by comparing the obtained experimental data using the A-CPLM system with (i) literature data for a standard sample, MgF2, and (ii) experimental data obtained using an established optical method, high-accuracy universal polarimeter, for the MSUM. The A-CPLM system was found to be applicable for measuring the LB spectra of the single crystals of MSUM and CPPD, which cause arthritis, in the visible regions. We quantitatively reveal the large difference in LB between MSUM and CPPD crystals. These results demonstrate the usefulness of the A-CPLM system for distinguishing the crystals causing arthritis.

Photoassisted Kelvin probe force microscopy at GaN surfaces: The role of polarity

Science.gov (United States)

Wei, J. D.; Li, S. F.; Atamuratov, A.; Wehmann, H.-H.; Waag, A.

2010-10-01

The behavior of GaN surfaces during photoassisted Kelvin probe force microscopy is demonstrated to be strongly dependant on surface polarity. The surface photovoltage of GaN surfaces illuminated with above-band gap light is analyzed as a function of time and light intensity. Distinct differences between Ga-polar and N-polar surfaces could be identified, attributed to photoinduced chemisorption of oxygen during illumination. These differences can be used for a contactless, nondestructive, and easy-performable analysis of the polarity of GaN surfaces.

Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

International Nuclear Information System (INIS)

Figuera, Juan de la; Vergara, Lucía; N'Diaye, Alpha T.; Quesada, Adrian; Schmid, Andreas K.

2013-01-01

Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along directions. ► Magnetic domain wall structures include wide Néel-caps

Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); Vergara, Lucía [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); N' Diaye, Alpha T. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Quesada, Adrian [Instituto de Cerámica y Vidrio, CSIC, Calle Kelsen 5, 28049, Madrid (Spain); Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2013-07-15

Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along <110> directions. ► Magnetic domain wall structures include wide Néel-caps.

Polarized differential-phase laser scanning microscope

International Nuclear Information System (INIS)

Chou Chien; Lyu, C.-W.; Peng, L.-C.

2001-01-01

A polarized differential-phase laser scanning microscope, which combines a polarized optical heterodyne Mach-Zehnder interferometer and a differential amplifier to scan the topographic image of a surface, is proposed. In the experiment the differential amplifier, which acts as a PM-AM converter, in the experiment, converting phase modulation (PM) into amplitude modulation (AM). Then a novel, to our knowledge, phase demodulator was proposed and implemented for the differential-phase laser scanning microscope. An optical grating (1800 lp/mm) was imaged. The lateral and the depth resolutions of the imaging system were 0.5 μm and 1 nm, respectively. The detection accuracy, which was limited by the reflectivity variation of the test surface, is discussed

Photo electron emission microscopy of polarity-patterned materials

International Nuclear Information System (INIS)

Yang, W-C; Rodriguez, B J; Gruverman, A; Nemanich, R J

2005-01-01

This study presents variable photon energy photo electron emission microscopy (PEEM) of polarity-patterned epitaxial GaN films, and ferroelectric LiNbO 3 (LNO) single crystals and PbZrTiO 3 (PZT) thin films. The photo electrons were excited with spontaneous emission from the tunable UV free electron laser (FEL) at Duke University. We report PEEM observation of polarity contrast and measurement of the photothreshold of each polar region of the materials. For a cleaned GaN film with laterally patterned Ga- and N-face polarities, we found a higher photoelectric yield from the N-face regions compared with the Ga-face regions. Through the photon energy dependent contrast in the PEEM images of the surfaces, we can deduce that the threshold of the N-face region is less than ∼4.9 eV while that of the Ga-face regions is greater than 6.3 eV. In both LNO and PZT, bright emission was detected from the negatively poled domains, indicating that the emission threshold of the negative domain is lower than that of the positive domain. For LNO, the measured photothreshold was ∼4.6 eV at the negative domain and ∼6.2 eV at the positive domain, while for PZT, the threshold of the negative domain was less than 4.3 eV. Moreover, PEEM observation of the PZT surface at elevated temperatures displayed that the domain contrast disappeared near the Curie temperature of ∼300 deg. C. The PEEM polarity contrast of the polar materials is discussed in terms of internal screening from free carriers and defects and the external screening due to adsorbed ions

Photo electron emission microscopy of polarity-patterned materials

Science.gov (United States)

Yang, W.-C.; Rodriguez, B. J.; Gruverman, A.; Nemanich, R. J.

2005-04-01

This study presents variable photon energy photo electron emission microscopy (PEEM) of polarity-patterned epitaxial GaN films, and ferroelectric LiNbO3 (LNO) single crystals and PbZrTiO3 (PZT) thin films. The photo electrons were excited with spontaneous emission from the tunable UV free electron laser (FEL) at Duke University. We report PEEM observation of polarity contrast and measurement of the photothreshold of each polar region of the materials. For a cleaned GaN film with laterally patterned Ga- and N-face polarities, we found a higher photoelectric yield from the N-face regions compared with the Ga-face regions. Through the photon energy dependent contrast in the PEEM images of the surfaces, we can deduce that the threshold of the N-face region is less than ~4.9 eV while that of the Ga-face regions is greater than 6.3 eV. In both LNO and PZT, bright emission was detected from the negatively poled domains, indicating that the emission threshold of the negative domain is lower than that of the positive domain. For LNO, the measured photothreshold was ~4.6 eV at the negative domain and ~6.2 eV at the positive domain, while for PZT, the threshold of the negative domain was less than 4.3 eV. Moreover, PEEM observation of the PZT surface at elevated temperatures displayed that the domain contrast disappeared near the Curie temperature of ~300 °C. The PEEM polarity contrast of the polar materials is discussed in terms of internal screening from free carriers and defects and the external screening due to adsorbed ions.

Humidity effects on scanning polarization force microscopy imaging

Energy Technology Data Exchange (ETDEWEB)

Shen, Yue, E-mail: shenyue@isl.ac.cn [Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008 (China); Key Laboratory of Interfacial Physics and Technology of Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhou, Yuan, E-mail: zhouy@isl.ac.cn [Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008 (China); Sun, Yanxia; Zhang, Lijuan [Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Ying; Hu, Jun; Zhang, Yi [Key Laboratory of Interfacial Physics and Technology of Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

2017-08-01

Highlights: • The humidity dramatically affects the contrast of scanning polarization force microscopy (SPFM) imaging on mica surface. • This influence roots in the sensitive dielectric constant of mica surface to the humidity change. • A strategy of controllable and repeatable imaging the local dielectric properties of nanomaterials with SPFM is proposed. - Abstract: Scanning polarization force microscopy (SPFM) is a useful surface characterization technique to visually characterize and distinguish nanomaterial with different local dielectric properties at nanometer scale. In this paper, taking the individual one-atom-thick graphene oxide (GO) and reduced graphene oxide (rGO) sheets on mica as examples, we described the influences of environmental humidity on SPFM imaging. We found that the apparent heights (AHs) or contrast of SPFM imaging was influenced significantly by relative humidity (RH) at a response time of a few seconds. And this influence rooted in the sensitive dielectric constant of mica surface to the RH change. While dielectric properties of GO and rGO sheets were almost immune to the humidity change. In addition, we gave the method to determine the critical humidity at which the contrast conversion happened under different conditions. And this is important to the contrast control and repeatable imaging of SPFM through RH adjusting. These findings suggest a strategy of controllable and repeatable imaging the local dielectric properties of nanomaterials with SPFM, which is critically important for further distinguishment, manipulation, electronic applications, etc.

Synchronous-digitization for video rate polarization modulated beam scanning second harmonic generation microscopy

Science.gov (United States)

Sullivan, Shane Z.; DeWalt, Emma L.; Schmitt, Paul D.; Muir, Ryan D.; Simpson, Garth J.

2015-03-01

Fast beam-scanning non-linear optical microscopy, coupled with fast (8 MHz) polarization modulation and analytical modeling have enabled simultaneous nonlinear optical Stokes ellipsometry (NOSE) and linear Stokes ellipsometry imaging at video rate (15 Hz). NOSE enables recovery of the complex-valued Jones tensor that describes the polarization-dependent observables, in contrast to polarimetry, in which the polarization stated of the exciting beam is recorded. Each data acquisition consists of 30 images (10 for each detector, with three detectors operating in parallel), each of which corresponds to polarization-dependent results. Processing of this image set by linear fitting contracts down each set of 10 images to a set of 5 parameters for each detector in second harmonic generation (SHG) and three parameters for the transmittance of the fundamental laser beam. Using these parameters, it is possible to recover the Jones tensor elements of the sample at video rate. Video rate imaging is enabled by performing synchronous digitization (SD), in which a PCIe digital oscilloscope card is synchronized to the laser (the laser is the master clock.) Fast polarization modulation was achieved by modulating an electro-optic modulator synchronously with the laser and digitizer, with a simple sine-wave at 1/10th the period of the laser, producing a repeating pattern of 10 polarization states. This approach was validated using Z-cut quartz, and NOSE microscopy was performed for micro-crystals of naproxen.

Gas-phase synthesis of magnesium nanoparticles: A high-resolution transmission electron microscopy study

International Nuclear Information System (INIS)

Kooi, B. J.; Palasantzas, G.; De Hosson, J. Th. M.

2006-01-01

Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg(1010) facets. Oxidation of Mg yields a MgO shell (∼3 nm thick), which has an orientation relation with the Mg. Inhomogeneous facet oxidation influences their growth kinetics resulting in a relatively broad size and shape distribution. Faceted voids between Mg and MgO shells indicate a fast outward diffusion of Mg and vacancy rearrangement into voids. The faceting of polar (220) planes is assisted by electron irradiation

Phase-Modulation Laser Interference Microscopy

DEFF Research Database (Denmark)

Brazhe, Alexey; Brazhe, Nadezda; Maximov, G. V.

2008-01-01

We describe how phase-modulation laser interference microscopy and wavelet analysis can be applied to noninvasive nonstained visualization and study of the structural and dynamical properties of living cells. We show how phase images of erythrocytes can reveal the difference between various...... erythrocyte forms and stages of hemolysis and how phase images of neurons reveal their complex intracellular structure. Temporal variations of the refractive index are analyzed to detect cellular rhythmic activity on different time scales as well as to uncover interactions between the cellular processes....

Spin-filter scanning tunneling microscopy : a novel technique for the analysis of spin polarization on magnetic surfaces and spintronic devices

NARCIS (Netherlands)

Vera Marun, I.J.

2010-01-01

This thesis deals with the development of a versatile technique to measure spin polarization with atomic resolution. A microscopy technique that can measure electronic spin polarization is relevant for characterization of magnetic nanostructures and spintronic devices. Scanning tunneling microscopy

Polarization-sensitive second harmonic generation microscopy of α-quartz like GeO2 (α-GeO2) polycrystal

International Nuclear Information System (INIS)

Kawamura, Ibuki; Imakita, Kenji; Kitao, Akihiro; Fujii, Minoru

2014-01-01

The usefulness of polarized second harmonic generation (SHG) microscopy to determine crystallographic orientations of domains in polycrystalline films was demonstrated. Orientation of α-quartz like GeO 2 (α-GeO 2 ) domains in polycrystalline films were investigated by using polarized SHG and Raman microscopy. It was found that the SHG intensity of a α-GeO 2 polycrystalline film depends strongly on measurement points and excitation and detection polarizations, while the Raman intensity was almost uniform in the whole mapping area. Analyses of the SHG mappings in different polarization conditions allowed us to determine not only the size and shape of crystalline domains, but also the crystallographic orientations. (paper)

Phase equilibrium in a polarized saturated 3He-4He mixture

International Nuclear Information System (INIS)

Rodrigues, A.; Vermeulen, G.

1997-01-01

We present experimental results on the phase equilibrium of a saturated 3 He- 4 He mixture, which has been cooled to a temperature of 10-15 mK and polarized in a 4 He circulating dilution refrigerator to a stationary polarization of 15 %, 7 times higher than the equilibrium polarization in the external field of 7 T. The pressure dependence of the polarization enhancement in the refrigerator shows that the molar susceptibilities of the concentrated and dilute phase of a saturated 3 He- 4 He mixture are equal at p = 2.60 ± 0.04 bar. This result affects the Fermi liquid parameters of the dilute phase. The osmotic pressure in the dilute phase has been measured as a function of the polarization of the coexisting concentrated phase up to 15 %. We find that the osmotic pressure at low polarization ( < 7 % ) agrees well with thermodynamics using the new Fermi liquid parameters of the dilute phase

Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

Science.gov (United States)

Phatak, C.; Petford-Long, A. K.; Beleggia, M.; De Graef, M.

2014-06-01

Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift computation for a uniformly polarized prolate ellipsoid with varying aspect ratio in the absence of screening charges.

Spin-polarized scanning tunneling microscopy: breakthroughs and highlights.

Science.gov (United States)

Bode, Matthias

2012-01-01

The principle of scanning tunneling microscopy, an imaging method with atomic resolution capability invented by Binnig and Rohrer in 1982, can be adapted for surface magnetism studies by using magnetic probe tips. The contrast mechanism of this so-called spin-polarized scanning tunneling microscopy, or SP-STM, relies on the tunneling magneto-resistance effect, i.e. the tip-sample distance as well as the differential conductance depend on the relative magnetic orientation of tip and sample. To illustrate the working principle and the unique capabilities of SP-STM, this compilation presents some key experiments which have been performed on various magnetic surfaces, such as the topological antiferromagnet Cr(001), a double-layer of Fe which exhibits a stripe- domain pattern with about 50 nm periodicity, and the Mn monolayer on W(110), where the combination of experiment and theory reveal an antiferromagnetic spin cycloid. Recent experimental results also demonstrate the suitability of SP-STM for studies of dynamic properties, such as the spin relaxation time of single magnetic nanostructures.

Analysis of human knee osteoarthritic cartilage using polarization sensitive second harmonic generation microscopy

Science.gov (United States)

Kumar, Rajesh; Grønhaug, Kirsten M.; Romijn, Elisabeth I.; Drogset, Jon O.; Lilledahl, Magnus B.

2014-05-01

Osteoarthritis is one of the most prevalent joint diseases in the world. Although the cause of osteoarthritis is not exactly clear, the disease results in a degradation of the quality of the articular cartilage including collagen and other extracellular matrix components. We have investigated alterations in the structure of collagen fibers in the cartilage tissue of the human knee using mulitphoton microscopy. Due to inherent high nonlinear susceptibility, ordered collagen fibers present in the cartilage tissue matrix produces strong second harmonic generation (SHG) signals. Significant morphological differences are found in different Osteoarthritic grades of cartilage by SHG microscopy. Based on the polarization analysis of the SHG signal, we find that a few locations of hyaline cartilage (mainly type II collagen) is being replaced by fibrocartilage (mainly type I cartilage), in agreement with earlier literature. To locate the different types and quantify the alteration in the structure of collagen fiber, we employ polarization-SHG microscopic analysis, also referred to as _-tensor imaging. The image analysis of p-SHG image obtained by excitation polarization measurements would represent different tissue constituents with different numerical values at pixel level resolution.

An elliptically-polarizing undulator with phase adjustable energy and polarization

International Nuclear Information System (INIS)

Lidia, S.

1993-08-01

The authors present a planar helical undulator designed to produce elliptically polarized light. Helical magnetic fields may be produced by a variety of undulators with four parallel cassettes of magnets. In their design, all cassettes are mounted in two planes on slides so that they may be moved parallel to the electron beam. This allows the undulator to produce x-rays of left- or right-handed elliptical or circular polarization as well as horizontal or vertical linear polarization. In model calculations, they have found that by sliding the top pair of rows with respect to the bottom pair, or the left pair with respect to the right pair, they retain the polarization setting but change the magnetic field strength, and hence the x-ray energy. This allows them to select both energy and polarization by independent phase adjustments alone, without changing the gap between the rows. Such a design may be simpler to construct than an adjustable gap machine. The authors present calculations that model its operation and its effects on an electron beam

[Polarized light microscopy for evaluation of oocytes as a prognostic factor in the evolution of a cycle in assisted reproduction].

Science.gov (United States)

González-Ortega, C; Cancino-Villarreal, P; Alonzo-Torres, V E; Martínez-Robles, I; Pérez-Peña, E; Gutiérrez-Gutiérrez, A M

2016-04-01

Identification of the best embryos to transfer is a key element for success in assisted reproduction. In the last decade, several morphological criteria of oocytes and embryos were evaluated with regard to their potential for predicting embryo viability. The introduction of polarization light microscopy systems has allowed the visualization of the meiotic spindle and the different layers of the zona pellucida in human oocytes on the basis of birefringence in a non-destructive way. Conflicting results have been reported regarding the predictive value in ICSI cycles. To assess the predictive ability of meiotic spindle and zona pellucida of human oocytes to implant by polarized microscopy in ICSI cycles. Prospective and observational clinical study. 903 oocytes from 94 ICSI cycles were analyzed with polarized microscopy. Meiotic spindle visualization and zona pellucida birefringence values by polarized microscopy were correlated with ICSI cycles results. Meiotic spindle visualization and birefringence values of zona pellucida decreased in a direct basis with increasing age. In patients aged over the 35 years, the percentage of a visible spindle and mean zona pellucida birefringence was lower than in younger patients. Fertilization rate were higher in oocytes with visible meiotic spindle (81.3% vs. 64%; p vs. 39%; p=0.01). Fertilization rate was higher in oocytes with positive values of birefringence (77.5 % vs. 68.5% p=0.005) with similar embryo quality. Conception cycles showed oocytes with higher mean value of zona birefringence and visible spindle vs. no-conception cycles (pPolarized light microscopy improves oocyte selection, which significantly impacts in the development of embryos with greater implantation potential. The use of polarized light microscopy with sperm selection methods, blastocyst culture and deferred embryo transfers will contribute to transfer fewer embryos without diminishing rates of live birth and single embryo transfer will be more feasible.

A portable microscopy system for fluorescence, polarized, and brightfield imaging

Science.gov (United States)

Gordon, Paul; Wattinger, Rolla; Lewis, Cody; Venancio, Vinicius Paula; Mertens-Talcott, Susanne U.; Coté, Gerard

2018-02-01

The use of mobile phones to conduct diagnostic microscopy at the point-of-care presents intriguing possibilities for the advancement of high-quality medical care in remote settings. However, it is challenging to create a single device that can adapt to the ever-varying camera technologies in phones or that can image with the customization that multiple modalities require for applications such as malaria diagnosis. A portable multi-modal microscope system is presented that utilizes a Raspberry Pi to collect and transmit data wirelessly to a myriad of electronic devices for image analysis. The microscopy system is capable of providing to the user correlated brightfield, polarized, and fluorescent images of samples fixed on traditional microscopy slides. The multimodal diagnostic capabilities of the microscope were assessed by measuring parasitemia of Plasmodium falciparum-infected thin blood smears. The device is capable of detecting fluorescently-labeled DNA using FITC excitation (490 nm) and emission (525 nm), the birefringent P. falciparum byproduct hemozoin, and detecting brightfield absorption with a resolution of 0.78 micrometers (element 9-3 of a 1951 Air Force Target). This microscopy system is a novel portable imaging tool that may be a viable candidate for field implementation if challenges of system durability, cost considerations, and full automation can be overcome.

The impact of structural relaxation on spin polarization and magnetization reversal of individual nano structures studied by spin-polarized scanning tunneling microscopy.

Science.gov (United States)

Sander, Dirk; Phark, Soo-Hyon; Corbetta, Marco; Fischer, Jeison A; Oka, Hirofumi; Kirschner, Jürgen

2014-10-01

The application of low temperature spin-polarized scanning tunneling microscopy and spectroscopy in magnetic fields for the quantitative characterization of spin polarization, magnetization reversal and magnetic anisotropy of individual nano structures is reviewed. We find that structural relaxation, spin polarization and magnetic anisotropy vary on the nm scale near the border of a bilayer Co island on Cu(1 1 1). This relaxation is lifted by perimetric decoration with Fe. We discuss the role of spatial variations of the spin-dependent electronic properties within and at the edge of a single nano structure for its magnetic properties.

Macroscopic polarization in crystalline dielectrics: the geometric phase approach

International Nuclear Information System (INIS)

Resta, R.

1994-01-01

The macroscopic electric polarization of a crystal is often defined as the dipole of a unit cell. In fact, such a dipole moment is ill defined, and the above definition is incorrect. Looking more closely, the quantity generally measured is differential polarization, defined with respect to a ''reference state'' of the same material. Such differential polarizations include either derivatives of the polarization (dielectric permittivity, Born effective charges, piezoelectricity, pyroelectricity) or finite differences (ferroelectricity). On the theoretical side, the differential concept is basic as well. Owing to continuity, a polarization difference is equivalent to a macroscopic current, which is directly accessible to the theory as a bulk property. Polarization is a quantum phenomenon and cannot be treated with a classical model, particularly whenever delocalized valence electrons are present in the dielectric. In a quantum picture, the current is basically a property of the phase of the wave functions, as opposed to the charge, which is a property of their modulus. An elegant and complete theory has recently been developed by King-Smith and Vanderbilt, in which the polarization difference between any two crystal states--in a null electric field--takes the form of a geometric quantum phase. This gives a comprehensive account of this theory, which is relevant for dealing with transverse-optic phonons, piezoelectricity, and ferroelectricity. Its relation to the established concepts of linear-response theory is also discussed. Within the geometric phase approach, the relevant polarization difference occurs as the circuit integral of a Berry connection (or ''vector potential''), while the corresponding curvature (or ''magnetic field'') provides the macroscopic linear response

Wide-field imaging of birefringent synovial fluid crystals using lens-free polarized microscopy for gout diagnosis

Science.gov (United States)

Zhang, Yibo; Lee, Seung Yoon Celine; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

2016-06-01

Gout is a form of crystal arthropathy where monosodium urate (MSU) crystals deposit and elicit inflammation in a joint. Diagnosis of gout relies on identification of MSU crystals under a compensated polarized light microscope (CPLM) in synovial fluid aspirated from the patient’s joint. The detection of MSU crystals by optical microscopy is enhanced by their birefringent properties. However, CPLM partially suffers from the high-cost and bulkiness of conventional lens-based microscopy, and its relatively small field-of-view (FOV) limits the efficiency and accuracy of gout diagnosis. Here we present a lens-free polarized microscope which adopts a novel differential and angle-mismatched polarizing optical design achieving wide-field and high-resolution holographic imaging of birefringent objects with a color contrast similar to that of a standard CPLM. The performance of this computational polarization microscope is validated by imaging MSU crystals made from a gout patient’s tophus and steroid crystals used as negative control. This lens-free polarized microscope, with its wide FOV (>20 mm2), cost-effectiveness and field-portability, can significantly improve the efficiency and accuracy of gout diagnosis, reduce costs, and can be deployed even at the point-of-care and in resource-limited clinical settings.

Polarization states encoded by phase modulation for high bit rate quantum key distribution

International Nuclear Information System (INIS)

Liu Xiaobao; Tang Zhilie; Liao Changjun; Lu Yiqun; Zhao Feng; Liu Songhao

2006-01-01

We present implementation of quantum cryptography with polarization code by wave-guide type phase modulator. At four different low input voltages of the phase modulator, coder encodes pulses into four different polarization states, 45 o , 135 o linearly polarized or right, left circle polarized, while the decoder serves as the complementary polarizers

Modeling optical behavior of birefringent biological tissues for evaluation of quantitative polarized light microscopy

NARCIS (Netherlands)

Turnhout, van M.C.; Kranenbarg, S.; Leeuwen, van J.L.

2009-01-01

Quantitative polarized light microscopy (qPLM) is a popular tool for the investigation of birefringent architectures in biological tissues. Collagen, the most abundant protein in mammals, is such a birefringent material. Interpretation of results of qPLM in terms of collagen network architecture and

Drive frequency dependent phase imaging in piezoresponse force microscopy

International Nuclear Information System (INIS)

Bo Huifeng; Kan Yi; Lu Xiaomei; Liu Yunfei; Peng Song; Wang Xiaofei; Cai Wei; Xue Ruoshi; Zhu Jinsong

2010-01-01

The drive frequency dependent piezoresponse (PR) phase signal in near-stoichiometric lithium niobate crystals is studied by piezoresponse force microscopy. It is clearly shown that the local and nonlocal electrostatic forces have a great contribution to the PR phase signal. The significant PR phase difference of the antiparallel domains are observed at the contact resonances, which is related to the electrostatic dominated electromechanical interactions of the cantilever and tip-sample system. Moreover, the modulation voltage induced frequency shift at higher eigenmodes could be attributed to the change of indention force depending on the modulation amplitude with a piezoelectric origin. The PR phase of the silicon wafer is also measured for comparison. It is certificated that the electrostatic interactions are universal in voltage modulated scanning probe microscopy and could be extended to other phase imaging techniques.

Electrostatic force microscopy: imaging DNA and protein polarizations one by one

International Nuclear Information System (INIS)

Mikamo-Satoh, Eriko; Yamada, Fumihiko; Takagi, Akihiko; Matsumoto, Takuya; Kawai, Tomoji

2009-01-01

We present electrostatic force microscopy images of double-stranded DNA and transcription complex on an insulating mica substrate obtained with molecular resolution using a frequency-mode noncontact atomic force microscope. The electrostatic potential images show that both DNA and transcription complexes are polarized with an upward dipole moment. Potential differences of these molecules from the mica substrate enabled us to estimate dipole moments of isolated DNA and transcription complex in zero external field to be 0.027 D/base and 0.16 D/molecule, respectively. Scanning capacitance microscopy demonstrates characteristic contrast inversion between DNA and transcription complex images, indicating the difference in electric polarizability of these molecules. These findings indicate that the electrostatic properties of individual biological molecules can be imaged on an insulator substrate while retaining complex formation.

Topology optimization of piezo modal transducers with null-polarity phases

DEFF Research Database (Denmark)

Donoso, A.; Sigmund, O.

2016-01-01

Piezo modal transducers in 2d can be designed theoretically by tailoring polarity of the surface electrodes. However, it is also necessary to include null-polarity phases of known width separating areas of opposite polarity in the manufacturing process in order to avoid short-circuiting. Otherwise...... the performance of such devices could be spoiled. In this work, we propose an appropriate topology optimization interpolation function for the electrode profile such that the effect of this new phase (hereafter gap-phase) is included in the formulation of the design problem. The approach is density-based, where...... the interface is controlled by including the gradient norm in the electrode profile interpolation. Through a detailed case study in 1d, conclusions on how to control the width of this gap-phase are extracted, and subsequently extended to the 2d case....

Mapping the local organization of cell membranes using excitation-polarization-resolved confocal fluorescence microscopy.

Science.gov (United States)

Kress, Alla; Wang, Xiao; Ranchon, Hubert; Savatier, Julien; Rigneault, Hervé; Ferrand, Patrick; Brasselet, Sophie

2013-07-02

Fluorescence anisotropy and linear dichroism imaging have been widely used for imaging biomolecular orientational distributions in protein aggregates, fibrillar structures of cells, and cell membranes. However, these techniques do not give access to complete orientational order information in a whole image, because their use is limited to parts of the sample where the average orientation of molecules is known a priori. Fluorescence anisotropy is also highly sensitive to depolarization mechanisms such as those induced by fluorescence energy transfer. A fully excitation-polarization-resolved fluorescence microscopy imaging that relies on the use of a tunable incident polarization and a nonpolarized detection is able to circumvent these limitations. We have developed such a technique in confocal epifluorescence microscopy, giving access to new regions of study in the complex and heterogeneous molecular organization of cell membranes. Using this technique, we demonstrate morphological changes at the subdiffraction scale in labeled COS-7 cell membranes whose cytoskeleton is perturbed. Molecular orientational order is also seen to be affected by cholesterol depletion, reflecting the strong interplay between lipid-packing regions and their nearby cytoskeleton. This noninvasive optical technique can reveal local organization in cell membranes when used as a complement to existing methods such as generalized polarization. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Defect-Induced Hedgehog Polarization States in Multiferroics

Science.gov (United States)

Li, Linze; Cheng, Xiaoxing; Jokisaari, Jacob R.; Gao, Peng; Britson, Jason; Adamo, Carolina; Heikes, Colin; Schlom, Darrell G.; Chen, Long-Qing; Pan, Xiaoqing

2018-03-01

Continuous developments in nanotechnology require new approaches to materials synthesis that can produce novel functional structures. Here, we show that nanoscale defects, such as nonstoichiometric nanoregions (NSNRs), can act as nano-building blocks for creating complex electrical polarization structures in the prototypical multiferroic BiFeO3 . An array of charged NSNRs are produced in BiFeO3 thin films by tuning the substrate temperature during film growth. Atomic-scale scanning transmission electron microscopy imaging reveals exotic polarization rotation patterns around these NSNRs. These polarization patterns resemble hedgehog or vortex topologies and can cause local changes in lattice symmetries leading to mixed-phase structures resembling the morphotropic phase boundary with high piezoelectricity. Phase-field simulations indicate that the observed polarization configurations are mainly induced by charged states at the NSNRs. Engineering defects thus may provide a new route for developing ferroelectric- or multiferroic-based nanodevices.

Hierarchical super-structure identified by polarized light microscopy, electron microscopy and nanoindentation: Implications for the limits of biological control over the growth mode of abalone sea shells

Directory of Open Access Journals (Sweden)

Schneider Andreas S

2012-09-01

Full Text Available Abstract Background Mollusc shells are commonly investigated using high-resolution imaging techniques based on cryo-fixation. Less detailed information is available regarding the light-optical properties. Sea shells of Haliotis pulcherina were embedded for polishing in defined orientations in order to investigate the interface between prismatic calcite and nacreous aragonite by standard materialographic methods. A polished thin section of the interface was prepared with a defined thickness of 60 μm for quantitative birefringence analysis using polarized light and LC-PolScope microscopy. Scanning electron microscopy images were obtained for comparison. In order to study structural-mechanical relationships, nanoindentation experiments were performed. Results Incident light microscopy revealed a super-structure in semi-transparent regions of the polished cross-section under a defined angle. This super-structure is not visible in transmitted birefringence analysis due to the blurred polarization of small nacre platelets and numerous organic interfaces. The relative orientation and homogeneity of calcite prisms was directly identified, some of them with their optical axes exactly normal to the imaging plane. Co-oriented "prism colonies" were identified by polarized light analyses. The nacreous super-structure was also visualized by secondary electron imaging under defined angles. The domains of the super-structure were interpreted to consist of crystallographically aligned platelet stacks. Nanoindentation experiments showed that mechanical properties changed with the same periodicity as the domain size. Conclusions In this study, we have demonstrated that insights into the growth mechanisms of nacre can be obtained by conventional light-optical methods. For example, we observed super-structures formed by co-oriented nacre platelets as previously identified using X-ray Photo-electron Emission Microscopy (X-PEEM [Gilbert et al., Journal of the

Calcium hydroxylapatite treatment of human skin: evidence of collagen turnover through picrosirius red staining and circularly polarized microscopy

Directory of Open Access Journals (Sweden)

Zerbinati N

2018-01-01

Full Text Available Nicola Zerbinati,1 Alberto Calligaro2 1Department of Surgical and Morphological Sciences, University of Insubria (Varese and Polyspecialist Medical Center, Pavia, 2Department of Public Health, Experimental and Forensic Medicine, Unit of Histology and Embryology, University of Pavia, Pavia, Italy Background: Calcium hydroxylapatite (CaHA, Radiesse® is a biocompatible, injectable filler for facial soft-tissue augmentation that provides volume to tissues, followed by a process of neocollagenesis for improved skin quality. Objective: To examine the effects of CaHA treatment on the molecular organization of collagen using a combination of picrosirius red staining and circularly polarized light microscopy.Methods: Five subjects received subdermal injection of 0.3 mL of CaHA in tissues scheduled for removal during abdominoplasty 2 months later. Tissue specimens from the CaHA injection site and a control untreated area were obtained from excised skin at the time of surgery. Processed tissue sections were stained with picrosirius red solution 0.1% and visualized under circularly polarized light microscopy for identification of thick mature (type I and thin newly formed (type III collagen fibers. Pixel signals from both the control and CaHA-treated areas were extracted from the images, and morphometric computerized hue analysis was performed to provide a quantitative evaluation of mature and newly formed collagen fibers.Results: Under picrosirius red staining and circularly polarized light microscopy, green/yellow areas (thin newly formed collagen type III were visible among the collagen fibers in tissue sections from the area of CaHA injection. In contrast, the majority of the collagen fibers appeared red (thick mature collagen type I in control tissues. Morphometric analysis confirmed that, following CaHA treatment, the proportion of fibers represented by thin newly formed collagen type III increased significantly (p<0.01 in comparison with the

Effects of phase change on reflection in phase-measuring interference microscopy

OpenAIRE

Dubois , Arnaud

2004-01-01

International audience; We show by analytical and numerical calculations that the phase change on reflection that occurs in interference microscopy is almost independent of the numerical aperture of the objective. The shift of the microscope interferogram response due to the phase change on reflection, however, increases with the numerical aperture. Measurements of the interferogram shift are made with a Linnik interference microscope equipped with various numerical-aperture objectives and ar...

Influence of Oxygen Pressure on the Domain Dynamics and Local Electrical Properties of BiFe0.95Mn0.05O3 Thin Films Studied by Piezoresponse Force Microscopy and Conductive Atomic Force Microscopy

Directory of Open Access Journals (Sweden)

Kunyu Zhao

2017-11-01

Full Text Available In this work, we have studied the microstructures, nanodomains, polarization preservation behaviors, and electrical properties of BiFe0.95Mn0.05O3 (BFMO multiferroic thin films, which have been epitaxially created on the substrates of SrRuO3, SrTiO3, and TiN-buffered (001-oriented Si at different oxygen pressures via piezoresponse force microscopy and conductive atomic force microscopy. We found that the pure phase state, inhomogeneous piezoresponse force microscopy (PFM response, low leakage current with unidirectional diode-like properties, and orientation-dependent polarization reversal properties were found in BFMO thin films deposited at low oxygen pressure. Meanwhile, these films under high oxygen pressures resulted in impurities in the secondary phase in BFMO films, which caused a greater leakage that hindered the polarization preservation capability. Thus, this shows the important impact of the oxygen pressure on modulating the physical effects of BFMO films.

Quantitative DIC microscopy using an off-axis self-interference approach.

Science.gov (United States)

Fu, Dan; Oh, Seungeun; Choi, Wonshik; Yamauchi, Toyohiko; Dorn, August; Yaqoob, Zahid; Dasari, Ramachandra R; Feld, Michael S

2010-07-15

Traditional Normarski differential interference contrast (DIC) microscopy is a very powerful method for imaging nonstained biological samples. However, one of its major limitations is the nonquantitative nature of the imaging. To overcome this problem, we developed a quantitative DIC microscopy method based on off-axis sample self-interference. The digital holography algorithm is applied to obtain quantitative phase gradients in orthogonal directions, which leads to a quantitative phase image through a spiral integration of the phase gradients. This method is practically simple to implement on any standard microscope without stringent requirements on polarization optics. Optical sectioning can be obtained through enlarged illumination NA.

Nonequilibrium phase transitions, fluctuations and correlations in an active contractile polar fluid.

Science.gov (United States)

Gowrishankar, Kripa; Rao, Madan

2016-02-21

We study the patterning, fluctuations and correlations of an active polar fluid consisting of contractile polar filaments on a two-dimensional substrate, using a hydrodynamic description. The steady states generically consist of arrays of inward pointing asters and show a continuous transition from a moving lamellar phase, a moving aster street, to a stationary aster lattice with no net polar order. We next study the effect of spatio-temporal athermal noise, parametrized by an active temperature TA, on the stability of the ordered phases. In contrast to its equilibrium counterpart, we find that the active crystal shows true long range order at low TA. On increasing TA, the asters dynamically remodel, concomitantly we find novel phase transitions characterized by bond-orientational and polar order upon "heating".

Quantitative assessment of spinal cord injury using circularly polarized coherent anti-Stokes Raman scattering microscopy

Science.gov (United States)

Bae, Kideog; Zheng, Wei; Huang, Zhiwei

2017-08-01

We report the quantitative assessment of spinal cord injury using the circularly polarized coherent anti-Stokes Raman scattering (CP-CARS) technique together with Stokes parameters in the Poincaré sphere. The pump and Stokes excitation beams are circularly polarized to suppress both the linear polarization-dependent artifacts and the nonresonant background of tissue CARS imaging, enabling quantitative CP-CARS image analysis. This study shows that CP-CARS imaging uncovers significantly increased phase retardance of injured spinal cord tissue as compared to normal tissue, suggesting that CP-CARS is an appealing label-free imaging tool for determining the degree of tissue phase retardance, which could serve as a unique diagnostic parameter associated with nervous tissue injury.

Analysis of Septin Reorganization at Cytokinesis Using Polarized Fluorescence Microscopy

Directory of Open Access Journals (Sweden)

Molly McQuilken

2017-05-01

Full Text Available Septins are conserved filament-forming proteins that act in diverse cellular processes. They closely associate with membranes and, in some systems, components of the cytoskeleton. It is not well understood how filaments assemble into higher-order structures in vivo or how they are remodeled throughout the cell cycle. In the budding yeast S. cerevisiae, septins are found through most of the cell cycle in an hourglass organization at the mother-bud neck until cytokinesis when the collar splits into two rings that disassemble prior to the next cell cycle. Experiments using polarized fluorescence microscopy have suggested that septins are arranged in ordered, paired filaments in the hourglass and undergo a coordinated 90° reorientation during splitting at cytokinesis. This apparent reorganization could be due to two orthogonal populations of filaments disassembling and reassembling or being preferentially retained at cytokinesis. In support of this idea, we report a decrease in septin concentration at the mother-bud neck during cytokinesis consistent with other reports and the timing of the decrease depends on known septin regulators including the Gin4 kinase. We took a candidate-based approach to examine what factors control reorientation during splitting and used polarized fluorescence microscopy to screen mutant yeast strains deficient in septin interacting proteins. Using this method, we have linked known septin regulators to different aspects of the assembly, stability, and reorganization of septin assemblies. The data support that ring splitting requires Gin4 activity and an anillin-like protein Bud4, and normal accumulation of septins at the ring requires phosphorylation of Shs1. We found distinct regulatory requirements for septin organization in the hourglass compared to split rings. We propose that septin subpopulations can vary in their localization and assembly/disassembly behavior in a cell-cycle dependent manner at cytokinesis.

Detection of secondary phases in duplex stainless steel by magnetic force microscopy and scanning Kelvin probe force microscopy

Energy Technology Data Exchange (ETDEWEB)

Ramírez-Salgado, J. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Domínguez-Aguilar, M.A., E-mail: madoming@imp.mx [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Castro-Domínguez, B. [University of Tokyo, Department of Chemical System Engineering, Faculty of Engineering Bldg. 5, 7F 722, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113–8656 (Japan); Hernández-Hernández, P. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Newman, R.C. [University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Toronto M5S 3E5 (Canada)

2013-12-15

The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite was detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a “ghosted” effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: • Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. • As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. • AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA.

In-line phase retarder and polarimeter for conversion of linear to circular polarization

Energy Technology Data Exchange (ETDEWEB)

Kortright, J.B.; Smith, N.V.; Denlinger, J.D. [Lawrence Berkeley National Lab., CA (United States)] [and others

1997-04-01

An in-line polarimeter including phase retarder and linear polarizer was designed and commissioned on undulator beamline 7.0 for the purpose of converting linear to circular polarization for experiments downstream. In commissioning studies, Mo/Si multilayers at 95 eV were used both as the upstream, freestanding phase retarder and the downstream linear polarized. The polarization properties of the phase retarder were characterized by direct polarimetry and by collecting MCD spectra in photoemission from Gd and other magnetic surfaces. The resonant birefringence of transmission multilayers results from differing distributions of s- and p-component wave fields in the multilayer when operating near a structural (Bragg) interference condition. The resulting phase retardation is especially strong when the interference is at or near the Brewster angle, which is roughly 45{degrees} in the EUV and soft x-ray ranges.

Synergistic promotion of polar phase crystallization of PVDF by ionic liquid with PEG segment

Science.gov (United States)

Xu, Pei; Fu, Weijia; Cui, Zhaopei; Ding, Yunsheng

2018-06-01

To investigate the effect of imidazolium ionic liquid with poly(ethylene glycol) segment (IL) on the polar phase crystallization behavior of poly(vinylidene fluoride) (PVDF), a series of PVDF/IL composites were prepared using solution-cast method. The crystallization peak temperature of PVDF composites and the growth speed of samples decrease with increasing of IL. The >CF2 groups in amorphous region are retained and >CF2 groups in crystalline region are liberated by the PEG long soft segments of IL. The intensity of peaks represented as α phase reduces, moreover polar phase content increases with increasing of IL. The interaction between the >CF2 and the imidazolium cation can induce the polar phase, and the interaction between the >CF2 and PEG soft segment can strengthen polar crystalline induction. PVDF/12IL composite can form big γ spherulite circled by β phase.

Single beam Fourier transform digital holographic quantitative phase microscopy

Energy Technology Data Exchange (ETDEWEB)

Anand, A., E-mail: arun-nair-in@yahoo.com; Chhaniwal, V. K.; Mahajan, S.; Trivedi, V. [Optics Laboratory, Applied Physics Department, Faculty of Technology and Engineering, M.S. University of Baroda, Vadodara 390001 (India); Faridian, A.; Pedrini, G.; Osten, W. [Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart (Germany); Dubey, S. K. [Siemens Technology and Services Pvt. Ltd, Corporate Technology—Research and Technology Centre, Bangalore 560100 (India); Javidi, B. [Department of Electrical and Computer Engineering, U-4157, University of Connecticut, Storrs, Connecticut 06269-2157 (United States)

2014-03-10

Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.

Holography microscopy as an artifact-free alternative to phase-contrast.

Science.gov (United States)

Pastorek, Lukáš; Venit, Tomáš; Hozák, Pavel

2018-02-01

Artifact-free microscopic images represent a key requirement of multi-parametric image analysis in modern biomedical research. Holography microscopy (HM) is one of the quantitative phase imaging techniques, which has been finding new applications in life science, especially in morphological screening, cell migration, and cancer research. Rather than the classical imaging of absorbing (typically stained) specimens by bright-field microscopy, the information about the light-wave's phase shifts induced by the biological sample is employed for final image reconstruction. In this comparative study, we investigated the usability and the reported advantage of the holography imaging. The claimed halo-free imaging was analyzed compared to the widely used Zernike phase-contrast microscopy. The intensity and phase cross-membrane profiles at the periphery of the cell were quantified. The intensity profile for cells in the phase-contrast images suffers from the significant increase in intensity values around the cell border. On the contrary, no distorted profile is present outside the cell membrane in holography images. The gradual increase in phase shift values is present in the internal part of the cell body projection in holography image. This increase may be related to the increase in the cell internal material according to the dry mass theory. Our experimental data proved the halo-free nature of the holography imaging, which is an important prerequisite of the correct thresholding and cell segmentation, nowadays frequently required in high-content screening and other image-based analysis. Consequently, HM is a method of choice whenever the image analysis relies on the accurate data on cell boundaries.

TESTING MODELS FOR THE SHALLOW DECAY PHASE OF GAMMA-RAY BURST AFTERGLOWS WITH POLARIZATION OBSERVATIONS

Energy Technology Data Exchange (ETDEWEB)

Lan, Mi-Xiang; Dai, Zi-Gao [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Wu, Xue-Feng, E-mail: dzg@nju.edu.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2016-08-01

The X-ray afterglows of almost one-half of gamma-ray bursts have been discovered by the Swift satellite to have a shallow decay phase of which the origin remains mysterious. Two main models have been proposed to explain this phase: relativistic wind bubbles (RWBs) and structured ejecta, which could originate from millisecond magnetars and rapidly rotating black holes, respectively. Based on these models, we investigate polarization evolution in the shallow decay phase of X-ray and optical afterglows. We find that in the RWB model, a significant bump of the polarization degree evolution curve appears during the shallow decay phase of both optical and X-ray afterglows, while the polarization position angle abruptly changes its direction by 90°. In the structured ejecta model, however, the polarization degree does not evolve significantly during the shallow decay phase of afterglows whether the magnetic field configuration in the ejecta is random or globally large-scale. Therefore, we conclude that these two models for the shallow decay phase and relevant central engines would be testable with future polarization observations.

Compact diffraction phase microscopy for quantitative visualization of cells in biomedical applications

International Nuclear Information System (INIS)

Talaikova, N A; Ryabukho, V P

2016-01-01

We consider a simplified and compact scheme of interference phase microscopy using a diffraction grating and spatial filtering of the diffracted field, i.e., diffraction phase microscopy. The scheme and the parameters of the device with the possibility of using the optical system of a smartphone and its software are analysed. The results of experimental determination of the spatial structure parameters of erythrocytes are presented. (paper)

Comparison of fabric analysis of snow samples by Computer-Integrated Polarization Microscopy and Automatic Ice Texture Analyzer

Science.gov (United States)

Leisinger, Sabine; Montagnat, Maurine; Heilbronner, Renée; Schneebeli, Martin

2014-05-01

Accurate knowledge of fabric anisotropy is crucial to understand the mechanical behavior of snow and firn, but is also important for understanding metamorphism. Computer-Integrated Polarization Microscopy (CIP) method used for the fabric analysis was developed by Heilbronner and Pauli in the early 1990ies and uses a slightly modified traditional polarization microscope for the fabric analysis. First developed for quartz, it can be applied to other uniaxial minerals. Up to now this method was mainly used in structural geology. However, it is also well suited for the fabric analysis of snow, firn and ice. The method is based on the analysis of first- order interference colors images by a slightly modified optical polarization microscope, a grayscale camera and a computer. The optical polarization microscope is featured with high quality objectives, a rotating table and two polarizers that can be introduced above and below the thin section, as well as a full wave plate. Additionally, two quarter-wave plates for circular polarization are needed. Otherwise it is also possible to create circular polarization from a set of crossed polarized images through image processing. A narrow band interference filter transmitting a wavelength between 660 and 700 nm is also required. Finally a monochrome digital camera is used to capture the input images. The idea is to record the change of interference colors while the thin section is being rotated once through 180°. The azimuth and inclination of the c-axis are defined by the color change. Recording the color change through a red filter produces a signal with a well-defined amplitude and phase angle. An advantage of this method lies in the simple conversion of an ordinary optical microscope to a fabric analyzer. The Automatic Ice Texture Analyzer (AITA) as the first fully functional instrument to measure c-axis orientation was developed by Wilson and other (2003). Most recent fabric analysis of snow and firn samples was carried

Single-shot quantitative phase microscopy with color-multiplexed differential phase contrast (cDPC.

Directory of Open Access Journals (Sweden)

Zachary F Phillips

Full Text Available We present a new technique for quantitative phase and amplitude microscopy from a single color image with coded illumination. Our system consists of a commercial brightfield microscope with one hardware modification-an inexpensive 3D printed condenser insert. The method, color-multiplexed Differential Phase Contrast (cDPC, is a single-shot variant of Differential Phase Contrast (DPC, which recovers the phase of a sample from images with asymmetric illumination. We employ partially coherent illumination to achieve resolution corresponding to 2× the objective NA. Quantitative phase can then be used to synthesize DIC and phase contrast images or extract shape and density. We demonstrate amplitude and phase recovery at camera-limited frame rates (50 fps for various in vitro cell samples and c. elegans in a micro-fluidic channel.

Fiber-based coherent polarization beam combining with cascaded phase-locking and polarization-transforming controls

Science.gov (United States)

Yang, Yan; Geng, Chao; Li, Feng; Huang, Guan; Li, Xinyang

2018-05-01

In this paper, the fiber-based coherent polarization beam combining (CPBC) with cascaded phase-locking (PL) and polarization-transforming (PT) controls was proposed to combine imbalanced input beams where the number of the input beams is not binary, in which the PL control was performed using the piezoelectric-ring fiber-optic phase compensator, and the PT control was realized by the dynamic polarization controller, simultaneously. The principle of the proposed CPBC was introduced. The performance of the proposed CPBC was analyzed in comparison with the CPBC based on PL control and the CPBC based on PT control. The basic experiment of CPBC of three laser beams was carried out to validate the feasibility of the proposed CPBC, where cascaded controls of PL and PT were implemented based on stochastic parallel gradient descent algorithm. Simulation and experimental results show that the proposed CPBC incorporates the advantages of the two previous CPBC schemes and performs well in the closed loop. Moreover, the expansibility and the application of the proposed CPBC were validated by scaling the CPBC to combine seven laser beams. We believe that the proposed fiber-based CPBC with cascaded PL and PT controls has great potential in free space optical communications employing the multi-aperture receiver with asymmetric structure.

Piezoelectricity and rotostriction through polar and non-polar coupled instabilities in bismuth-based piezoceramics.

Science.gov (United States)

Acosta, Matias; Schmitt, Ljubomira A; Cazorla, Claudio; Studer, Andrew; Zintler, Alexander; Glaum, Julia; Kleebe, Hans-Joachim; Donner, Wolfgang; Hoffman, Mark; Rödel, Jürgen; Hinterstein, Manuel

2016-07-01

Coupling of order parameters provides a means to tune functionality in advanced materials including multiferroics, superconductors, and ionic conductors. We demonstrate that the response of a frustrated ferroelectric state leads to coupling between order parameters under electric field depending on grain orientation. The strain of grains oriented along a specific crystallographic direction, 〈h00〉, is caused by converse piezoelectricity originating from a ferrodistortive tetragonal phase. For 〈hhh〉 oriented grains, the strain results from converse piezoelectricity and rotostriction, as indicated by an antiferrodistortive instability that promotes octahedral tilting in a rhombohedral phase. Both strain mechanisms combined lead to a colossal local strain of (2.4 ± 0.1) % and indicate coupling between oxygen octahedral tilting and polarization, here termed "rotopolarization". These findings were confirmed with electromechanical experiments, in situ neutron diffraction, and in situ transmission electron microscopy in 0.75Bi1/2Na1/2TiO3-0.25SrTiO3. This work demonstrates that polar and non-polar instabilities can cooperate to provide colossal functional responses.

Characterization of polarization-independent phase modulation method for practical plug and play quantum cryptography

International Nuclear Information System (INIS)

Kwon, Osung; Lee, Min-Soo; Woo, Min Ki; Park, Byung Kwon; Kim, Il Young; Kim, Yong-Su; Han, Sang-Wook; Moon, Sung

2015-01-01

We characterized a polarization-independent phase modulation method, called double phase modulation, for a practical plug and play quantum key distribution (QKD) system. Following investigation of theoretical backgrounds, we applied the method to the practical QKD system and characterized the performance through comparing single phase modulation (SPM) and double phase modulation. Consequently, we obtained repeatable and accurate phase modulation confirmed by high visibility single photon interference even for input signals with arbitrary polarization. Further, the results show that only 80% of the bias voltage required in the case of single phase modulation is needed to obtain the target amount of phase modulation. (paper)

Intrinsically stable phase-modulated polarization encoding system for quantum key distribution

Energy Technology Data Exchange (ETDEWEB)

Liu Xiaobao [Laboratory of Photonic Information Technology, School for Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China); Liao Changjun [Laboratory of Photonic Information Technology, School for Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China)], E-mail: chliao@scnu.edu.cn; Mi Jinglong; Wang Jindong; Liu Songhao [Laboratory of Photonic Information Technology, School for Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China)

2008-12-22

We demonstrate experimentally an intrinsically stable polarization coding and decoding system composed of optical-fiber Sagnac interferometers with integrated phase modulators for quantum key distribution. An interference visibility of 98.35% can be kept longtime during the experiment without any efforts of active compensation for coding all four desired polarization states.

Direct imaging of phase objects enables conventional deconvolution in bright field light microscopy.

Directory of Open Access Journals (Sweden)

Carmen Noemí Hernández Candia

Full Text Available In transmitted optical microscopy, absorption structure and phase structure of the specimen determine the three-dimensional intensity distribution of the image. The elementary impulse responses of the bright field microscope therefore consist of separate absorptive and phase components, precluding general application of linear, conventional deconvolution processing methods to improve image contrast and resolution. However, conventional deconvolution can be applied in the case of pure phase (or pure absorptive objects if the corresponding phase (or absorptive impulse responses of the microscope are known. In this work, we present direct measurements of the phase point- and line-spread functions of a high-aperture microscope operating in transmitted bright field. Polystyrene nanoparticles and microtubules (biological polymer filaments serve as the pure phase point and line objects, respectively, that are imaged with high contrast and low noise using standard microscopy plus digital image processing. Our experimental results agree with a proposed model for the response functions, and confirm previous theoretical predictions. Finally, we use the measured phase point-spread function to apply conventional deconvolution on the bright field images of living, unstained bacteria, resulting in improved definition of cell boundaries and sub-cellular features. These developments demonstrate practical application of standard restoration methods to improve imaging of phase objects such as cells in transmitted light microscopy.

Frequency dependence of polarization phase difference

International Nuclear Information System (INIS)

Rao, K.S.; Rao, Y.S.; Wang, J.R.

1993-09-01

Polarimetric AIRSAR data of July 13, 1990 acquired over Mahatango watershed area was processed for the identification of corn fields an forested areas. Polarization Phase Difference (PPD) values were computed for the corn fields at P-, L- and C- bands and studied as a function of frequency. The results compare well with the model calculations at 24 deg. incidence angle where as the locations of corn fields were computed to be at 35 deg. incidence angle. The discrepancy is attributed to lack of accurate ground truth and the undulating topography of the corn fields. Another study reported here deals with the usefulness of Polarization Index (PI) for the study of vegetation. PI was found to be dependent on frequency for corn fields where as for forest trees no such dependence was noticed. PI HH,HV is more useful parameter compared to PI HH,VV even for the study of corn fields. (author). 19 refs, 7 figs

Identification of crystals in Hanford nuclear waste using polarized light microscopy

International Nuclear Information System (INIS)

Herting, D.L.

1984-09-01

The use of polarized light microscopy for identifying crystals encountered in Rockwell Hanford Operations chemical studies is described. Identifying characteristics and full-color photographs are presented for crystals commonly found in Hanford Site nuclear waste, including sodium nitrate, sodium nitrite, sodium aluminate, sodium phosphate, sodium fluoride, ammonium heptafluorozirconate, sodium sulfate, sodium carbonate, and ammonium nitrate. These characteristics are described in terms of birefringence, extinction position, interference figure, sign of elongation, optic sign, and crystal morphology. Background information on crystal optics is presented so that these traits can be understood by the nonmicroscopist. Detailed operational instructions are given so that the novice microscope user can make the proper adjustments of the instrument to search for and observe the identifying features of the crystals

Comparative Study of Clinical Staging of Oral Submucous Fibrosis with Qualitative Analysis of Collagen Fibers Under Polarized Microscopy.

Science.gov (United States)

Modak, Neha; Tamgadge, Sandhya; Tamgadge, Avinash; Bhalerao, Sudhir

2015-01-01

Oral submucous fibrosis (OSMF) is a condition where excessive deposition of dense collagen fibers occurred in the connective tissue of oral mucosa. An alteration of collagen necessitates an in depth understanding of collagen in oral tissues as no breakthrough studies have been reported. T herefore the aim was to correlate the clinical, functional and histopathological staging and to analyze the polarization colors and thickness of the collagen fibers in different stages of OSMF using picrosirius red stain under polarizing microscopy so as to assess the severity of disease. The study was conducted in the department of Oral Pathology and Microbiology at Padm. Dr. D. Y Patil Dental and Hospital, Navi Mumbai, India (2012-13). A sample size was of a total 40 subjects, of which 30 patients had OSMF, and 10 were in control group. Clinical, functional and histopathological staging were done depending upon definite criteria. Collagen fibers were analyzed for polarizing colors and thickness. Further clinical, functional and histopathological stages as well as qualitative parameters of collagen fibers were compared. The correlation between clinical and functional staging was not significant ( P >0.05) whereas the comparison of the functional staging with histopathological staging was more reliable ( P qualitative change in the collagen fibers of OSMF patients using polarized microscopy would help to assess its role in diagnostic evaluation, to determine the prognosis of the disease as well as to provide useful predictive treatment modalities to them.

Quantification of flexoelectricity in PbTiO3/SrTiO3 superlattice polar vortices using machine learning and phase-field modeling.

Science.gov (United States)

Li, Q; Nelson, C T; Hsu, S-L; Damodaran, A R; Li, L-L; Yadav, A K; McCarter, M; Martin, L W; Ramesh, R; Kalinin, S V

2017-11-13

Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO 3 /SrTiO 3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory and experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO 3 and SrTiO 3 . Our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics.

Transmission Magnitude and Phase Control for Polarization-Preserving Reflectionless Metasurfaces

Science.gov (United States)

Kwon, Do-Hoon; Ptitcyn, Grigorii; Díaz-Rubio, Ana; Tretyakov, Sergei A.

2018-03-01

For transmissive applications of electromagnetic metasurfaces, an array of subwavelength Huygens' meta-atoms are typically used to eliminate reflection and achieve a high-transmission power efficiency together with a wide transmission phase coverage. We show that the underlying principle of low reflection and full control over transmission is asymmetric scattering into the specular reflection and transmission directions that results from a superposition of symmetric and antisymmetric scattering components, with Huygens' meta-atoms being one example configuration. Available for oblique illumination in TM polarization, a meta-atom configuration comprising normal and tangential electric polarizations is presented, which is capable of reflectionless, full-power transmission and a 2 π transmission phase coverage as well as full absorption. For lossy metasurfaces, we show that a complete phase coverage is still available for reflectionless designs for any value of absorptance. Numerical examples in the microwave and optical regimes are provided.

Stability of superfluid phases in the 2D spin-polarized attractive Hubbard model

Science.gov (United States)

Kujawa-Cichy, A.; Micnas, R.

2011-08-01

We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LPs) with increasing attraction, in the presence of the Zeeman magnetic field (h) for d=2, within the spin-polarized attractive Hubbard model. The broken symmetry Hartree approximation as well as the strong coupling expansion are used. We also apply the Kosterlitz-Thouless (KT) scenario to determine the phase coherence temperatures. For spin-independent hopping integrals (t↑=t↓), we find no stable homogeneous polarized superfluid (SCM) state in the ground state for the strong attraction and obtain that for a two-component Fermi system on a 2D lattice with population imbalance, phase separation (PS) is favoured for a fixed particle concentration, even on the LP (BEC) side. We also examine the influence of spin-dependent hopping integrals (mass imbalance) on the stability of the SCM phase. We find a topological quantum phase transition (Lifshitz type) from the unpolarized superfluid phase (SC0) to SCM and tricritical points in the h-|U| and t↑/t↓-|U| ground-state phase diagrams. We also construct the finite temperature phase diagrams for both t↑=t↓ and t↑≠t↓ and analyze the possibility of occurrence of a spin-polarized KT superfluid.

Light-free magnetic resonance force microscopy for studies of electron spin polarized systems

International Nuclear Information System (INIS)

Pelekhov, Denis V.; Selcu, Camelia; Banerjee, Palash; Chung Fong, Kin; Chris Hammel, P.; Bhaskaran, Harish; Schwab, Keith

2005-01-01

Magnetic resonance force microscopy is a scanned probe technique capable of three-dimensional magnetic resonance imaging. Its excellent sensitivity opens the possibility for magnetic resonance studies of spin accumulation resulting from the injection of spin polarized currents into a para-magnetic collector. The method is based on mechanical detection of magnetic resonance which requires low noise detection of cantilever displacement; so far, this has been accomplished using optical interferometry. This is undesirable for experiments on doped silicon, where the presence of light is known to enhance spin relaxation rates. We report a non-optical displacement detection scheme based on sensitive microwave capacitive readout

Enhancement of polar crystalline phase formation in transparent PVDF-CaF{sub 2} composite films

Energy Technology Data Exchange (ETDEWEB)

Lee, Sang Goo; Ha, Jong-Wook, E-mail: jongwook@krict.re.kr; Sohn, Eun-Ho; Park, In Jun; Lee, Soo-Bok

2016-12-30

Highlights: • The crystalline phase in transparent PVDF-CaF{sub 2} composite films was investigated. • CaF{sub 2} promoted the formation of polar crystalline phases in PVDF matrix. • Ordered γ-phase was obtained by thermal treatment of as-cast films at the vicinity of its melting temperature. - Abstract: We consider the influence of calcium fluoride (CaF{sub 2}) nanoparticles on the crystalline phase formation of poly(vinylidene fluoride) (PVDF) for the first time. The transparent PVDF-CaF{sub 2} composite films were prepared by casting on PET substrates using N,N-dimethylacetamide (DMAc) as a solvent. It was found that CaF{sub 2} promoted the formation of polar crystalline phase of PVDF in composites, whereas nonpolar α-phase was dominant in the neat PVDF film prepared at the same condition. The portion of polar crystalline phase increased in proportional to the weight fraction of CaF{sub 2} in the composite films up to 10 wt%. Further addition of CaF{sub 2} suppressed completely the α-phase formation. Polar crystalline phase observed in as-cast composite films was a mixture of β- and γ-polymorph structures. It was also shown that much ordered γ-phase could be obtained through thermal treatment of as-cast PVDF-CaF{sub 2} composite film at the temperatures above the melting temperature of the composite films, but below that of γ-phase.

Imaging of phase change materials below a capping layer using correlative infrared near-field microscopy and electron microscopy

Science.gov (United States)

Lewin, M.; Hauer, B.; Bornhöfft, M.; Jung, L.; Benke, J.; Michel, A.-K. U.; Mayer, J.; Wuttig, M.; Taubner, T.

2015-10-01

Phase Change Materials (PCM) show two stable states in the solid phase with significantly different optical and electronic properties. They can be switched reversibly between those two states and are promising candidates for future non-volatile memory applications. The development of phase change devices demands characterization tools, yielding information about the switching process at high spatial resolution. Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) allows for spectroscopic analyses of the different optical properties of the PCMs on the nm-scale. By correlating the optical s-SNOM images with transmission electron microscopy images of the same sample, we unambiguously demonstrate the correlation of the infrared optical contrast with the structural state of the phase change material. The investigated sample consists of sandwiched amorphous and crystalline regions of Ag 4 In 3 Sb 67 Te 26 below a 100 nm thick ( ZnS ) 80 - ( SiO2 ) 20 capping layer. Our results demonstrate the sensitivity of s-SNOM to small dielectric near-field contrasts even below a comparably thick capping layer ( 100 nm ).

Vectorial mapping of noncollinear antiferromagnetic structure of semiconducting FeSe surface with spin-polarized scanning tunneling microscopy

Energy Technology Data Exchange (ETDEWEB)

Zhang, K. F.; Yang, Fang; Song, Y. R. [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang, Xiaole [Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240 (China); The State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Chen, Xianfeng [The State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu, Canhua; Qian, Dong; Gao, C. L., E-mail: clgao@sjtu.edu.cn; Jia, Jin-Feng [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing (China); Luo, Weidong, E-mail: wdluo@sjtu.edu.cn [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing (China)

2016-02-08

Antiferromagnetic semiconductors gain increasing interest due to their possible application in spintronics. Using spin polarized scanning tunneling microscopy operating in a vector field, we mapped the noncollinear antiferromagnetic spin structure of a semiconducting hexagonal FeSe surface on the atomic scale. The surface possesses an in-plane compensated Néel structure which is further confirmed by first-principles calculations.

Vectorial mapping of noncollinear antiferromagnetic structure of semiconducting FeSe surface with spin-polarized scanning tunneling microscopy

International Nuclear Information System (INIS)

Zhang, K. F.; Yang, Fang; Song, Y. R.; Zhang, Xiaole; Chen, Xianfeng; Liu, Canhua; Qian, Dong; Gao, C. L.; Jia, Jin-Feng; Luo, Weidong

2016-01-01

Antiferromagnetic semiconductors gain increasing interest due to their possible application in spintronics. Using spin polarized scanning tunneling microscopy operating in a vector field, we mapped the noncollinear antiferromagnetic spin structure of a semiconducting hexagonal FeSe surface on the atomic scale. The surface possesses an in-plane compensated Néel structure which is further confirmed by first-principles calculations

Characterization and quantitative determination of calcium aluminate clinker phases through reflected light microscopy

International Nuclear Information System (INIS)

Marciano Junior, E.; Cunha Munhoz, F.A. da; Splettstoser Junior, J.; Placido, W.F.

1989-01-01

The identification and quantitative determination of phases in calcium aluminate clinker is of great importance to the producer, as it enables a better understanding of the cement and concrete properties, specially those concerning setting time and compressive strenght. Polished sections of three electrofused clinkers, one experimental and two industrial, were used to select the most suitable etchings in order to identify by microscopy the main phases (Ca, CA 2 , C 2 AS, C 12 A 7 , α-Al 2 O 3 ). Quantitative phases determinations by reflected light microscopy showed good results when compared to X-ray diffractometry measurements [pt

Berry phase and shot noise for spin-polarized and entangled electrons

International Nuclear Information System (INIS)

Wang Pei; Tang Weihua; Lu Dinghui; Jiang Lixia; Zhao Xuean

2007-01-01

Shot noise for entangled and spin-polarized states in a four-probe geometric setup has been studied by adding two rotating magnetic fields in an incoming channel. Our results show that the noise power oscillates as the magnetic fields vary. The singlet, entangled triplet and polarized states can be distinguished by adjusting the magnetic fields. The Berry phase can be derived by measuring the shot noise power

Bragg transmission phase plates for the production of circularly polarized x-rays

International Nuclear Information System (INIS)

Lang, J.C.; Srajer, G.

1994-01-01

A thin-crystal Si (400) Bragg transmission x-ray phase plate has been constructed for the production of 5 to 12 keV circularly polarized x-rays. Using multiple beam diffraction from a GaAs crystal, a direct measurement of the degree of circular polarization as a function of off-Bragg position was made. These measurements indicated nearly complete circular polarization (|P c | ≥ 0.95) and full helicity reversal on opposite sides of the rocking curve

A Small Ku-Band Polarization Tracking Active Phased Array for Mobile Satellite Communications

Directory of Open Access Journals (Sweden)

Wei Shi

2013-01-01

Full Text Available A compact polarization tracking active phased array for Ku-band mobile satellite signal reception is presented. In contrast with conventional mechanically tracking antennas, the approach presented here meets the requirements of beam tracking and polarization tracking simultaneously without any servo components. The two-layer stacked square patch fed by two probes is used as antenna element. The impedance bandwidth of 16% for the element covers the operating frequency range from 12.25 GHz to 12.75 GHz. In the presence of mutual coupling, the dimensional parameters for each element of the small 7 × 7 array are optimized during beam scanning and polarization tracking. The compact polarization tracking modules based on the low-temperature cofired ceramic (LTCC system-in-package (SiP technology are proposed. A small active phased array prototype with the size of 120 mm (length × 120 mm (width × 55 mm (height is developed. The measured polarization tracking patterns of the prototype are given. The polarization tracking beam can be steered in the elevation up to 50°. The gain of no less than 16.0 dBi and the aperture efficiency of more than 50% are obtained. The measured and simulated polarization tracking patterns agreed well.

Interface-induced chiral domain walls, spin spirals and skyrmions revealed by spin-polarized scanning tunneling microscopy.

Science.gov (United States)

von Bergmann, Kirsten; Kubetzka, André; Pietzsch, Oswald; Wiesendanger, Roland

2014-10-01

The spin textures of ultra-thin magnetic layers exhibit surprising variety. The loss of inversion symmetry at the interface of the magnetic layer and substrate gives rise to the so-called Dzyaloshinskii-Moriya interaction which favors non-collinear spin arrangements with unique rotational sense. Here we review the application of spin-polarized scanning tunneling microscopy to such systems, which has led to the discovery of interface-induced chiral domain walls and spin spirals. Recently, different interface-driven skyrmion lattices have been found, and the writing as well as the deleting of individual skyrmions based on local spin-polarized current injection has been demonstrated. These interface-induced non-collinear magnetic states offer new exciting possibilities to study fundamental magnetic interactions and to tailor material properties for spintronic applications.

Bandwidth broadening of a graphene-based circular polarization converter by phase compensation.

Science.gov (United States)

Gao, Xi; Yang, Wanli; Cao, Weiping; Chen, Ming; Jiang, Yannan; Yu, Xinhua; Li, Haiou

2017-10-02

We present a broadband tunable circular polarization converter composed of a single graphene sheet patterned with butterfly-shaped holes, a dielectric spacer, and a 7-layer graphene ground plane. It can convert a linearly polarized wave into a circularly polarized wave in reflection mode. The polarization converter can be dynamically tuned by varying the Fermi energy of the single graphene sheet. Furthermore, the 7-layer graphene acting as a ground plane can modulate the phase of its reflected wave by controlling the Femi energy, which provides constructive interference condition at the surface of the single graphene sheet in a broad bandwidth and therefore significantly broadens the tunable bandwidth of the proposed polarization converter.

Wide-field synovial fluid imaging using polarized lens-free on-chip microscopy for point-of-care diagnostics of gout (Conference Presentation)

Science.gov (United States)

Zhang, Yibo; Lee, Seung Yoon; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

2016-03-01

Gout and pseudogout are forms of crystal arthropathy caused by monosodium urate (MSU) and calcium pyrophosphate dehydrate (CPPD) crystals in the joint, respectively, that can result in painful joints. Detecting the unique-shaped, birefringent MSU/CPPD crystals in a synovial fluid sample using a compensated polarizing microscope has been the gold-standard for diagnosis since the 1960's. However, this can be time-consuming and inaccurate, especially if there are only few crystals in the fluid. The high-cost and bulkiness of conventional microscopes can also be limiting for point-of-care diagnosis. Lens-free on-chip microscopy based on digital holography routinely achieves high-throughput and high-resolution imaging in a cost-effective and field-portable design. Here we demonstrate, for the first time, polarized lens-free on-chip imaging of MSU and CPPD crystals over a wide field-of-view (FOV ~ 20.5 mm2, i.e., gout and pseudogout. Circularly polarizer partially-coherent light is used to illuminate the synovial fluid sample on a glass slide, after which a quarter-wave-plate and an angle-mismatched linear polarizer are used to analyze the transmitted light. Two lens-free holograms of the MSU/CPPD sample are taken, with the sample rotated by 90°, to rule out any non-birefringent objects within the specimen. A phase-recovery algorithm is also used to improve the reconstruction quality, and digital pseudo-coloring is utilized to match the color and contrast of the lens-free image to that of a gold-standard microscope image to ease the examination by a rheumatologist or a laboratory technician, and to facilitate computerized analysis.

Dispersions of Goethite Nanorods in Aprotic Polar Solvents

Directory of Open Access Journals (Sweden)

Delphine Coursault

2017-10-01

Full Text Available Colloidal suspensions of anisotropic nanoparticles can spontaneously self-organize in liquid-crystalline phases beyond some concentration threshold. These phases often respond to electric and magnetic fields. At lower concentrations, usual isotropic liquids are observed but they can display very strong Kerr and Cotton-Mouton effects (i.e., field-induced particle orientation. For many examples of these colloidal suspensions, the solvent is water, which hinders most electro-optic applications. Here, for goethite (α-FeOOH nanorod dispersions, we show that water can be replaced by polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP and dimethylsulfoxide (DMSO, without loss of colloidal stability. By polarized-light microscopy, small-angle X-ray scattering and electro-optic measurements, we found that the nematic phase, with its field-response properties, is retained. Moreover, a strong Kerr effect was also observed with isotropic goethite suspensions in these polar aprotic solvents. Furthermore, we found no significant difference in the behavior of both the nematic and isotropic phases between the aqueous and non-aqueous dispersions. Our work shows that goethite nanorod suspensions in polar aprotic solvents, suitable for electro-optic applications, can easily be produced and that they keep all their outstanding properties. It also suggests that this solvent replacement method could be extended to the aqueous colloidal suspensions of other kinds of charged anisotropic nanoparticles.

LORENTZ PHASE IMAGING AND IN-SITU LORENTZ MICROSCOPY OF PATTERNED CO-ARRAYS

International Nuclear Information System (INIS)

VOLKOV, V.V.; ZHU, Y.

2003-01-01

Understanding magnetic structures and properties of patterned and ordinary magnetic films at nanometer length-scale is the area of immense technological and fundamental scientific importance. The key feature to such success is the ability to achieve visual quantitative information on domain configurations with a maximum ''magnetic'' resolution. Several methods have been developed to meet these demands (Kerr and Faraday effects, differential phase contrast microscopy, magnetic force microscopy, SEMPA etc.). In particular, the modern off-axis electron holography allows retrieval of the electron-wave phase shifts down to 2π/N (with typical N = 10-20, approaching in the limit N ∼ 100) in TEM equipped with field emission gun, which is already successfully employed for studies of magnetic materials at nanometer scale. However, it remains technically demanding, sensitive to noise and needs highly coherent electron sources. As possible alternative we developed a new method of Lorentz phase microscopy [1,2] based on the Fourier solution [3] of magnetic transport-of-intensity (MTIE) equation. This approach has certain advantages, since it is less sensitive to noise and does not need high coherence of the source required by the holography. In addition, it can be realized in any TEM without basic hardware changes. Our approach considers the electron-wave refraction in magnetic materials (magnetic refraction) and became possible due to general progress in understanding of noninterferometric phase retrieval [4-6] dealing with optical refraction. This approach can also be treated as further development of Fresnel microscopy, used so far for imaging of in-situ magnetization process in magnetic materials studied by TEM. Figs. 1-3 show some examples of what kind information can be retrieved from the conventional Fresnel images using the new approach. Most of these results can be compared with electron-holographic data. Using this approach we can shed more light on fine details of

Hard-x-ray phase-difference microscopy with a low-brilliance laboratory x-ray source

International Nuclear Information System (INIS)

Kuwabara, Hiroaki; Yashiro, Wataru; Harasse, Sebastien; Momose, Atsushi; Mizutani, Haruo

2011-01-01

We have developed a hard-X-ray phase-imaging microscopy method using a low-brilliance X-ray source. The microscope consists of a sample, a Fresnel zone plate, a transmission grating, and a source grating creating an array of mutually incoherent X-ray sources. The microscope generates an image exhibiting twin features of the sample with opposite signs separated by a distance, which is processed to generate a phase image. The method is quantitative even for non-weak-phase objects that are difficult to be quantitatively examined by the widely used Zernike phase-contrast microscopy, and it has potentially broad applications in the material and biological science fields. (author)

Quantifying migration and polarization of murine mesenchymal stem cells on different bone substitutes by confocal laser scanning microscopy.

Science.gov (United States)

Roldán, J C; Chang, E; Kelantan, M; Jazayeri, L; Deisinger, U; Detsch, R; Reichert, T E; Gurtner, G C

2010-12-01

Cell migration is preceded by cell polarization. The aim of the present study was to evaluate the impact of the geometry of different bone substitutes on cell morphology and chemical responses in vitro. Cell polarization and migration were monitored temporally by using confocal laser scanning microscopy (CLSM) to follow green fluorescent protein (GFP)±mesenchymal stem cells (MSCs) on anorganic cancellous bovine bone (Bio-Oss(®)), β-tricalcium phosphate (β-TCP) (chronOS(®)) and highly porous calcium phosphate ceramics (Friedrich-Baur-Research-Institute for Biomaterials, Germany). Differentiation GFP±MSCs was observed using pro-angiogenic and pro-osteogenic biomarkers. At the third day of culture polarized vs. non-polarized cellular sub-populations were clearly established. Biomaterials that showed more than 40% of polarized cells at the 3rd day of culture, subsequently showed an enhanced cell migration compared to biomaterials, where non-polarized cells predominated (ppolarization predominated at the 7th day of culture (p=0.001). This model opens an interesting approach to understand osteoconductivity at a cellular level. MSCs are promising in bone tissue engineering considering the strong angiogenic effect before differentiation occurs. Copyright © 2010 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Polarization Switching and Light-Enhanced Piezoelectricity in Lead Halide Perovskites.

Science.gov (United States)

Coll, Mariona; Gomez, Andrés; Mas-Marza, Elena; Almora, Osbel; Garcia-Belmonte, Germà; Campoy-Quiles, Mariano; Bisquert, Juan

2015-04-16

We investigate the ferroelectric properties of photovoltaic methylammonium lead halide CH3NH3PbI3 perovskite using piezoelectric force microscopy (PFM) and macroscopic polarization methods. The electric polarization is clearly observed by amplitude and phase hysteresis loops. However, the polarization loop decreases as the frequency is lowered, persisting for a short time only, in the one second regime, indicating that CH3NH3PbI3 does not exhibit permanent polarization at room temperature. This result is confirmed by macroscopic polarization measurement based on a standard capacitive method. We have observed a strong increase of piezoelectric response under illumination, consistent with the previously reported giant photoinduced dielectric constant at low frequencies. We speculate that an intrinsic charge transfer photoinduced dipole in the perovskite cage may lie at the origin of this effect.

Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers.

Science.gov (United States)

Kumar, Krishan; Moudgil, R K

2012-10-17

We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

Single particle analysis based on Zernike phase contrast transmission electron microscopy.

Science.gov (United States)

Danev, Radostin; Nagayama, Kuniaki

2008-02-01

We present the first application of Zernike phase-contrast transmission electron microscopy to single-particle 3D reconstruction of a protein, using GroEL chaperonin as the test specimen. We evaluated the performance of the technique by comparing 3D models derived from Zernike phase contrast imaging, with models from conventional underfocus phase contrast imaging. The same resolution, about 12A, was achieved by both imaging methods. The reconstruction based on Zernike phase contrast data required about 30% fewer particles. The advantages and prospects of each technique are discussed.

Phases of a polar spin-1 Bose gas in a magnetic field

International Nuclear Information System (INIS)

Kis-Szabo, Krisztian; Szepfalusy, Peter; Szirmai, Gergely

2007-01-01

The two Bose-Einstein condensed phases of a polar spin-1 gas at nonzero magnetizations and temperatures are investigated. The Hugenholtz-Pines theorem is generalized to this system. Crossover to a quantum phase transition is also studied. Results are discussed in a mean field approximation

Phase modulation mode of scanning ion conductance microscopy

Energy Technology Data Exchange (ETDEWEB)

Li, Peng; Zhang, Changlin [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Lianqing, E-mail: lqliu@sia.cn, E-mail: gli@engr.pitt.edu; Wang, Yuechao; Yang, Yang [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); Li, Guangyong, E-mail: lqliu@sia.cn, E-mail: gli@engr.pitt.edu [Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 (United States)

2014-08-04

This Letter reports a phase modulation (PM) mode of scanning ion conductance microscopy. In this mode, an AC current is directly generated by an AC voltage between the electrodes. The portion of the AC current in phase with the AC voltage, which is the current through the resistance path, is modulated by the tip-sample distance. It can be used as the input of feedback control to drive the scanner in Z direction. The PM mode, taking the advantages of both DC mode and traditional AC mode, is less prone to electronic noise and DC drift but maintains high scanning speed. The effectiveness of the PM mode has been proven by experiments.

The orientation of eosin-5-maleimide on human erythrocyte band 3 measured by fluorescence polarization microscopy.

Science.gov (United States)

Blackman, S M; Cobb, C E; Beth, A H; Piston, D W

1996-01-01

The dominant motional mode for membrane proteins is uniaxial rotational diffusion about the membrane normal axis, and investigations of their rotational dynamics can yield insight into both the oligomeric state of the protein and its interactions with other proteins such as the cytoskeleton. However, results from the spectroscopic methods used to study these dynamics are dependent on the orientation of the probe relative to the axis of motion. We have employed polarized fluorescence confocal microscopy to measure the orientation of eosin-5-maleimide covalently reacted with Lys-430 of human erythrocyte band 3. Steady-state polarized fluorescence images showed distinct intensity patterns, which were fit to an orientation distribution of the eosin absorption and emission dipoles relative to the membrane normal axis. This orientation was found to be unchanged by trypsin treatment, which cleaves band 3 between the integral membrane domain and the cytoskeleton-attached domain. this result suggests that phosphorescence anisotropy changes observed after trypsin treatment are due to a rotational constraint change rather than a reorientation of eosin. By coupling time-resolved prompt fluorescence anisotropy with confocal microscopy, we calculated the expected amplitudes of the e-Dt and e-4Dt terms from the uniaxial rotational diffusion model and found that the e-4Dt term should dominate the anisotropy decay. Delayed fluorescence and phosphorescence anisotropy decays of control and trypsin-treated band 3 in ghosts, analyzed as multiple uniaxially rotating populations using the amplitudes predicted by confocal microscopy, were consistent with three motional species with uniaxial correlation times ranging from 7 microseconds to 1.4 ms. Images FIGURE 4 FIGURE 8 FIGURE 9 PMID:8804603

Cholesteric lyomesophases based on sodium N-lauroyl asparte: characterization of new system by nuclear magnetic resonance and polarizing microscopy

International Nuclear Information System (INIS)

Melo, M.V.M.C. de.

1982-01-01

Lyomesophases based on di-sodium N-lauroyl aspartate (SNLA), bi-carboxilated amphiphile obtained from the reaction of n-lauroyl chloride with aspartic acid in racemic or levo form are studies. The different mesophases were characterized by 2 H and 23 Na NMR and by polarizing microscopy. (M.J.C.) [pt

Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy

International Nuclear Information System (INIS)

Yang, H. F.; Liu, Z. T.; Fan, C. C.; Xiang, P.; Zhang, K. L.; Li, M. Y.; Liu, J. S.; Yao, Q.; Shen, D. W.

2016-01-01

By means of the state-of-the-art reactive oxide molecular beam epitaxy, we synthesized (001)- and (111)-orientated polar LaNiO 3 thin films. In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO 3 and iso-polarity LaAlO 3 substrates were chosen to achieve high-quality (001)-orientated films in a layer-by-layer growth mode. For largely polar (111)-orientated films, we showed that iso-polarity LaAlO 3 (111) substrate was more suitable than Nb-doped SrTiO 3 . In situ reflection high-energy electron diffraction, ex situ high-resolution X-ray diffraction, and atomic force microscopy were used to characterize these films. Our results show that special attentions need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO 3 based superlattices.

Concomitant use of polarization and positive phase contrast microscopy for the study of microbial cells

Czech Academy of Sciences Publication Activity Database

Žižka, Zdeněk; Gabriel, Jiří

2014-01-01

Roč. 60, č. 6 (2014), s. 545-550 ISSN 0015-5632 Institutional support: RVO:61388971 Keywords : microbial cells * microscopy * microorganism Subject RIV: EE - Microbiology, Virology Impact factor: 1.000, year: 2014

Identification of 6H-SiC polar faces with pull-off force of atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Gan, Di; Song, Youting; Yang, Junwei; Chen, Hongxiang [Research & development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Guo, Liwei, E-mail: lwguo@iphy.ac.cn [Research & development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Chen, Xiaolong, E-mail: chenx29@iphy.ac.cn [Research & development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

2016-12-30

Highlights: • A new method is proposed and demonstrated to distinguish the polar faces of 6H-SiC by pull-off forces which are clearly different on the Si-face and the C-face of 6H-SiC. • The reliability of this method is confirmed on 6H-SiC samples treated with different surface processing procedures. • The essence of different pull-off forces on different polar faces of 6H-SiC is that the surface energies between them are obviously different. • Theoretical calculations are consistent with our experimental results. - Abstract: Distinguishing SiC (0001) Si-face from SiC (000-1) C-face without any damages is extremely important because the two polar faces have different physical and chemical properties which seriously influence the quality of a homoepitaxy or heteroepitaxy thin film on it. Here, a convenient and nondestructive detection method is developed to distinguish the Si-face and C-face of a (0001) oriented SiC wafer by employing a pull-off force measurement using atomic force microscopy. It is found that the pull-off force from a Si-face of 6H-SiC is about two times of that from a C-face, no matter it is a two-face chemical mechanical polishing or etched 6H-SiC wafer. The method developed here is suitable to identify polar faces of materials only if the two polar faces having different surface energy.

Improved cancer risk stratification and diagnosis via quantitative phase microscopy (Conference Presentation)

Science.gov (United States)

Liu, Yang; Uttam, Shikhar; Pham, Hoa V.; Hartman, Douglas J.

2017-02-01

Pathology remains the gold standard for cancer diagnosis and in some cases prognosis, in which trained pathologists examine abnormality in tissue architecture and cell morphology characteristic of cancer cells with a bright-field microscope. The limited resolution of conventional microscope can result in intra-observer variation, missed early-stage cancers, and indeterminate cases that often result in unnecessary invasive procedures in the absence of cancer. Assessment of nanoscale structural characteristics via quantitative phase represents a promising strategy for identifying pre-cancerous or cancerous cells, due to its nanoscale sensitivity to optical path length, simple sample preparation (i.e., label-free) and low cost. I will present the development of quantitative phase microscopy system in transmission and reflection configuration to detect the structural changes in nuclear architecture, not be easily identifiable by conventional pathology. Specifically, we will present the use of transmission-mode quantitative phase imaging to improve diagnostic accuracy of urine cytology and the nuclear dry mass is progressively correlate with negative, atypical, suspicious and positive cytological diagnosis. In a second application, we will present the use of reflection-mode quantitative phase microscopy for depth-resolved nanoscale nuclear architecture mapping (nanoNAM) of clinically prepared formalin-fixed, paraffin-embedded tissue sections. We demonstrated that the quantitative phase microscopy system detects a gradual increase in the density alteration of nuclear architecture during malignant transformation in animal models of colon carcinogenesis and in human patients with ulcerative colitis, even in tissue that appears histologically normal according to pathologists. We evaluated the ability of nanoNAM to predict "future" cancer progression in patients with ulcerative colitis.

Investigation of Polarization Phase Difference Related to Forest Fields Characterizations

Science.gov (United States)

Majidi, M.; Maghsoudi, Y.

2013-09-01

The information content of Synthetic Aperture Radar (SAR) data significantly included in the radiometric polarization channels, hence polarimetric SAR data should be analyzed in relation with target structure. The importance of the phase difference between two co-polarized scattered signals due to the possible association between the biophysical parameters and the measured Polarization Phase Difference (PPD) statistics of the backscattered signal recorded components has been recognized in geophysical remote sensing. This paper examines two Radarsat-2 images statistics of the phase difference to describe the feasibility of relationship with the physical properties of scattering targets and tries to understand relevance of PPD statistics with various types of forest fields. As well as variation of incidence angle due to affecting on PPD statistics is investigated. The experimental forest pieces that are used in this research are characterized white pine (Pinus strobus L.), red pine (Pinus resinosa Ait.), jack pine (Pinus banksiana Lamb.), white spruce (Picea glauca (Moench Voss), black spruce (Picea mariana (Mill) B.S.P.), poplar (Populus L.), red oak (Quercus rubra L.) , aspen and ground vegetation. The experimental results show that despite of biophysical parameters have a wide diversity, PPD statistics are almost the same. Forest fields distributions as distributed targets have close to zero means regardless of the incidence angle. Also, The PPD distribution are function of both target and sensor parameters, but for more appropriate examination related to PPD statistics the observations should made in the leaf-off season or in bands with lower frequencies.

INVESTIGATION OF POLARIZATION PHASE DIFFERENCE RELATED TO FOREST FIELDS CHARACTERIZATIONS

Directory of Open Access Journals (Sweden)

M. Majidi

2013-09-01

Full Text Available The information content of Synthetic Aperture Radar (SAR data significantly included in the radiometric polarization channels, hence polarimetric SAR data should be analyzed in relation with target structure. The importance of the phase difference between two co-polarized scattered signals due to the possible association between the biophysical parameters and the measured Polarization Phase Difference (PPD statistics of the backscattered signal recorded components has been recognized in geophysical remote sensing. This paper examines two Radarsat-2 images statistics of the phase difference to describe the feasibility of relationship with the physical properties of scattering targets and tries to understand relevance of PPD statistics with various types of forest fields. As well as variation of incidence angle due to affecting on PPD statistics is investigated. The experimental forest pieces that are used in this research are characterized white pine (Pinus strobus L., red pine (Pinus resinosa Ait., jack pine (Pinus banksiana Lamb., white spruce (Picea glauca (Moench Voss, black spruce (Picea mariana (Mill B.S.P., poplar (Populus L., red oak (Quercus rubra L. , aspen and ground vegetation. The experimental results show that despite of biophysical parameters have a wide diversity, PPD statistics are almost the same. Forest fields distributions as distributed targets have close to zero means regardless of the incidence angle. Also, The PPD distribution are function of both target and sensor parameters, but for more appropriate examination related to PPD statistics the observations should made in the leaf-off season or in bands with lower frequencies.

Analyzer-based x-ray phase-contrast microscopy combining channel-cut and asymmetrically cut crystals

International Nuclear Information System (INIS)

Hoennicke, M. G.; Cusatis, C.

2007-01-01

An analyzer-based x-ray phase-contrast microscopy (ABM) setup combining a standard analyzer-based x-ray phase-contrast imaging (ABI) setup [nondispersive 4-crystal setup (Bonse-Hart setup)] and diffraction by asymmetrically cut crystals is presented here. An attenuation-contrast microscopy setup with conventional x-ray source and asymmetrically cut crystals is first analyzed. Edge-enhanced effects attributed to phase jumps or refraction/total external reflection on the fiber borders were detected. However, the long exposure times and the possibility to achieve high contrast microscopies by using extremely low attenuation-contrast samples motivated us to assemble the ABM setup using a synchrotron source. This setup was found to be useful for low contrast attenuation samples due to the low exposure time, high contrast, and spatial resolution found. Moreover, thanks to the combination with the nondispersive ABI setup, the diffraction-enhanced x-ray imaging algorithm could be applied

Polarization contrast in photon scanning tunnelling microscopy combined with atomic force microscopy

NARCIS (Netherlands)

Propstra, K.; Propstra, K.; van Hulst, N.F.

1995-01-01

Photon scanning tunnelling microscopy combined with atomic force microscopy allows simultaneous acquisition and direct comparison of optical and topographical images, both with a lateral resolution of about 30 nm, far beyond the optical diffraction limit. The probe consists of a modified

Photoluminescence Polarization Anisotropy in a Single Heterostructured III-V Nanowire with Mixed Crystal Phases

International Nuclear Information System (INIS)

Moses, A. F.; Hoang, T. B.; Ahtapodov, L.; Dheeraj, D. L.; Fimland, B. O.; Weman, H.; Helvoort, A. T. J. van

2011-01-01

Low temperature (10 K) micro-photoluminescence (μ-PL) of single GaAs/AlGaAs core-shell nanowires with single GaAsSb inserts were measured. The PL emission from the zinc blende GaAsSb insert is strongly polarized along the nanowire axis while the PL emission from the wurtzite GaAs nanowire is perpendiculary polarized to the nanowire axis. The result indicates that the crystal phase, through the optical selection rules, has significant effect on the polarization of the PL from NWs besides the dielectric mismatch. The analysis of the PL results based on the electronic structure of these nanowires supports the correlation between the crystal phase and the PL emission.

Helicity-Selective Phase-Matching and Quasi-Phase matching of Circularly Polarized High-Order Harmonics: Towards Chiral Attosecond Pulses

Science.gov (United States)

2016-05-23

2 Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA 3Department of Physics and Optical Engineering, Ort Braude...polarized high harmonic generation, phase matching, ultrafast chiral physics, attosecond pulses (Some figures may appear in colour only in the online...temporal resolution and in spectral regions unavailable to circular polarization thus far. Acknowledgments This work was supported by the USA –Israel

Efficient Phase Unwrapping Architecture for Digital Holographic Microscopy

Directory of Open Access Journals (Sweden)

Wen-Jyi Hwang

2011-09-01

Full Text Available This paper presents a novel phase unwrapping architecture for accelerating the computational speed of digital holographic microscopy (DHM. A fast Fourier transform (FFT based phase unwrapping algorithm providing a minimum squared error solution is adopted for hardware implementation because of its simplicity and robustness to noise. The proposed architecture is realized in a pipeline fashion to maximize through put of thecomputation. Moreover, the number of hardware multipliers and dividers are minimized to reduce the hardware costs. The proposed architecture is used as a custom user logic in a system on programmable chip (SOPC for physical performance measurement. Experimental results reveal that the proposed architecture is effective for expediting the computational speed while consuming low hardware resources for designing an embedded DHM system.

Holography microscopy as an artifact-free alternative to phase-contrast

Czech Academy of Sciences Publication Activity Database

Pastorek, Lukáš; Venit, Tomáš; Hozák, Pavel

2018-01-01

Roč. 149, č. 2 (2018), s. 179-186 ISSN 0948-6143 R&D Projects: GA MŠk(CZ) LM2015062 Institutional support: RVO:68378050 Keywords : Holography microscopy * Phase-contrast * Halo effect Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Cell biology Impact factor: 2.553, year: 2016

Universal holonomic single quantum gates over a geometric spin with phase-modulated polarized light.

Science.gov (United States)

Ishida, Naoki; Nakamura, Takaaki; Tanaka, Touta; Mishima, Shota; Kano, Hiroki; Kuroiwa, Ryota; Sekiguchi, Yuhei; Kosaka, Hideo

2018-05-15

We demonstrate universal non-adiabatic non-abelian holonomic single quantum gates over a geometric electron spin with phase-modulated polarized light and 93% average fidelity. This allows purely geometric rotation around an arbitrary axis by any angle defined by light polarization and phase using a degenerate three-level Λ-type system in a negatively charged nitrogen-vacancy center in diamond. Since the control light is completely resonant to the ancillary excited state, the demonstrated holonomic gate not only is fast with low power, but also is precise without the dynamical phase being subject to control error and environmental noise. It thus allows pulse shaping for further fidelity.

Time-resolved imaging refractometry of microbicidal films using quantitative phase microscopy.

Science.gov (United States)

Rinehart, Matthew T; Drake, Tyler K; Robles, Francisco E; Rohan, Lisa C; Katz, David; Wax, Adam

2011-12-01

Quantitative phase microscopy is applied to image temporal changes in the refractive index (RI) distributions of solutions created by microbicidal films undergoing hydration. We present a novel method of using an engineered polydimethylsiloxane structure as a static phase reference to facilitate calibration of the absolute RI across the entire field. We present a study of dynamic structural changes in microbicidal films during hydration and subsequent dissolution. With assumptions about the smoothness of the phase changes induced by these films, we calculate absolute changes in the percentage of film in regions across the field of view.

New generation quantitative x-ray microscopy encompassing phase-contrast

International Nuclear Information System (INIS)

Wilkins, S.W.; Mayo, S.C.; Gureyev, T.E.; Miller, P.R.; Pogany, A.; Stevenson, A.W.; Gao, D.; Davis, T.J.; Parry, D.J.; Paganin, D.

2000-01-01

Full text: We briefly outline a new approach to X-ray ultramicroscopy using projection imaging in a scanning electron microscope (SEM). Compared to earlier approaches, the new approach offers spatial resolution of ≤0.1 micron and includes novel features such as: i) phase contrast to give additional sample information over a wide energy range, rapid phase/amplitude extraction algorithms to enable new real-time modes of microscopic imaging widespread applications are envisaged to fields such as materials science, biomedical research, and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to X-ray projection microscopy using synchrotron sources

Practical aspects of Boersch phase contrast electron microscopy of biological specimens

Energy Technology Data Exchange (ETDEWEB)

Walter, Andreas [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany); Muzik, Heiko; Vieker, Henning; Turchanin, Andrey; Beyer, Andre; Goelzhaeuser, Armin [University of Bielefeld, Physics of Supramolecular Systems and Surfaces, Universitaetsstr. 25, D-33615 Bielefeld (Germany); Lacher, Manfred; Steltenkamp, Siegfried; Schmitz, Sam; Holik, Peter [Caesar Research Center, Ludwig-Erhard-Allee 2, D-53175 Bonn (Germany); Kuehlbrandt, Werner [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany); Rhinow, Daniel, E-mail: daniel.rhinow@biophys.mpg.de [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany)

2012-05-15

Implementation of physical phase plates into transmission electron microscopes to achieve in-focus contrast for ice-embedded biological specimens poses several technological challenges. During the last decade several phase plates designs have been introduced and tested for electron cryo-microscopy (cryoEM), including thin film (Zernike) phase plates and electrostatic devices. Boersch phase plates (BPPs) are electrostatic einzel lenses shifting the phase of the unscattered beam by an arbitrary angle. Adjusting the phase shift to 90 Degree-Sign achieves the maximum contrast transfer for phase objects such as biomolecules. Recently, we reported the implementation of a BPP into a dedicated phase contrast aberration-corrected electron microscope (PACEM) and demonstrated its use to generate in-focus contrast of frozen-hydrated specimens. However, a number of obstacles need to be overcome before BPPs can be used routinely, mostly related to the phase plate devices themselves. CryoEM with a physical phase plate is affected by electrostatic charging, obliteration of low spatial frequencies, and mechanical drift. Furthermore, BPPs introduce single sideband contrast (SSB), due to the obstruction of Friedel mates in the diffraction pattern. In this study we address the technical obstacles in detail and show how they may be overcome. We use X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to identify contaminants responsible for electrostatic charging, which occurs with most phase plates. We demonstrate that obstruction of low-resolution features is significantly reduced by lowering the acceleration voltage of the microscope. Finally, we present computational approaches to correct BPP images for SSB contrast and to compensate for mechanical drift of the BPP. -- Highlights: Black-Right-Pointing-Pointer Various obstacles need to be overcome before Boersch phase plates can be used routinely. Black-Right-Pointing-Pointer Technical problems include

Practical aspects of Boersch phase contrast electron microscopy of biological specimens

International Nuclear Information System (INIS)

Walter, Andreas; Muzik, Heiko; Vieker, Henning; Turchanin, Andrey; Beyer, André; Gölzhäuser, Armin; Lacher, Manfred; Steltenkamp, Siegfried; Schmitz, Sam; Holik, Peter; Kühlbrandt, Werner; Rhinow, Daniel

2012-01-01

Implementation of physical phase plates into transmission electron microscopes to achieve in-focus contrast for ice-embedded biological specimens poses several technological challenges. During the last decade several phase plates designs have been introduced and tested for electron cryo-microscopy (cryoEM), including thin film (Zernike) phase plates and electrostatic devices. Boersch phase plates (BPPs) are electrostatic einzel lenses shifting the phase of the unscattered beam by an arbitrary angle. Adjusting the phase shift to 90° achieves the maximum contrast transfer for phase objects such as biomolecules. Recently, we reported the implementation of a BPP into a dedicated phase contrast aberration-corrected electron microscope (PACEM) and demonstrated its use to generate in-focus contrast of frozen–hydrated specimens. However, a number of obstacles need to be overcome before BPPs can be used routinely, mostly related to the phase plate devices themselves. CryoEM with a physical phase plate is affected by electrostatic charging, obliteration of low spatial frequencies, and mechanical drift. Furthermore, BPPs introduce single sideband contrast (SSB), due to the obstruction of Friedel mates in the diffraction pattern. In this study we address the technical obstacles in detail and show how they may be overcome. We use X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to identify contaminants responsible for electrostatic charging, which occurs with most phase plates. We demonstrate that obstruction of low-resolution features is significantly reduced by lowering the acceleration voltage of the microscope. Finally, we present computational approaches to correct BPP images for SSB contrast and to compensate for mechanical drift of the BPP. -- Highlights: ► Various obstacles need to be overcome before Boersch phase plates can be used routinely. ► Technical problems include electrostatic charging, mechanical drift, and image artefacts. �

Three-dimensional motion-picture imaging of dynamic object by parallel-phase-shifting digital holographic microscopy using an inverted magnification optical system

Science.gov (United States)

Fukuda, Takahito; Shinomura, Masato; Xia, Peng; Awatsuji, Yasuhiro; Nishio, Kenzo; Matoba, Osamu

2017-04-01

We constructed a parallel-phase-shifting digital holographic microscopy (PPSDHM) system using an inverted magnification optical system, and succeeded in three-dimensional (3D) motion-picture imaging for 3D displacement of a microscopic object. In the PPSDHM system, the inverted and afocal magnification optical system consisted of a microscope objective (16.56 mm focal length and 0.25 numerical aperture) and a convex lens (300 mm focal length and 82 mm aperture diameter). A polarization-imaging camera was used to record multiple phase-shifted holograms with a single-shot exposure. We recorded an alum crystal, sinking down in aqueous solution of alum, by the constructed PPSDHM system at 60 frames/s for about 20 s and reconstructed high-quality 3D motion-picture image of the crystal. Then, we calculated amounts of displacement of the crystal from the amounts in the focus plane and the magnifications of the magnification optical system, and obtained the 3D trajectory of the crystal by that amounts.

New insights into nano-magnetism by spin-polarized scanning tunneling microscopy

Energy Technology Data Exchange (ETDEWEB)

Sander, Dirk, E-mail: sander@mpi-halle.de [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle/Saale (Germany); Oka, Hirofumi; Corbetta, Marco; Stepanyuk, Valeri; Kirschner, Jürgen [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle/Saale (Germany)

2013-08-15

Highlights: ► We measure the magnetization reversal of individual nm small Co island by spin-STM. ► We identify an inhomogeneous magnetic anisotropy within a single Co island. ► The magnetic anisotropy near the rim is negligible as compared to 0.148 meV/atom at the island center. ► A crossover of the magnetization reversal from an exchange-spring behavior to domain wall formation is suggested. ► The impact of the observed spatial variation of the spin-dependent electronic properties on reversal is discussed. -- Abstract: We study the magnetization reversal and the position dependence of the spin-dependent electronic properties of nm small bilayer Co islands on Cu(1 1 1) by spin-polarized scanning tunneling microscopy in magnetic fields at low temperatures of 8 K. The analysis of the energy barrier of magnetization reversal from measurements of the switching field suggests a crossover of the magnetization reversal mode with increasing island size around 7500 atoms from exchange-spring behavior to domain wall formation. The quantitative analysis of the island size dependence of the energy barrier indicates an inhomogeneous magnetic anisotropy of the island. The island rim is magnetically soft, whereas the center shows a pronounced effective anisotropy of 0.148 meV/atom. We speculate that this inhomogeneity of the magnetic anisotropy might be a consequence of the spatial dependence of the spin-dependent electronic properties. We measure a spin-polarization and a tunnel magneto resistance ratio of opposite sign at the rim as compared to the island center.

New insights into nano-magnetism by spin-polarized scanning tunneling microscopy

International Nuclear Information System (INIS)

Sander, Dirk; Oka, Hirofumi; Corbetta, Marco; Stepanyuk, Valeri; Kirschner, Jürgen

2013-01-01

Highlights: ► We measure the magnetization reversal of individual nm small Co island by spin-STM. ► We identify an inhomogeneous magnetic anisotropy within a single Co island. ► The magnetic anisotropy near the rim is negligible as compared to 0.148 meV/atom at the island center. ► A crossover of the magnetization reversal from an exchange-spring behavior to domain wall formation is suggested. ► The impact of the observed spatial variation of the spin-dependent electronic properties on reversal is discussed. -- Abstract: We study the magnetization reversal and the position dependence of the spin-dependent electronic properties of nm small bilayer Co islands on Cu(1 1 1) by spin-polarized scanning tunneling microscopy in magnetic fields at low temperatures of 8 K. The analysis of the energy barrier of magnetization reversal from measurements of the switching field suggests a crossover of the magnetization reversal mode with increasing island size around 7500 atoms from exchange-spring behavior to domain wall formation. The quantitative analysis of the island size dependence of the energy barrier indicates an inhomogeneous magnetic anisotropy of the island. The island rim is magnetically soft, whereas the center shows a pronounced effective anisotropy of 0.148 meV/atom. We speculate that this inhomogeneity of the magnetic anisotropy might be a consequence of the spatial dependence of the spin-dependent electronic properties. We measure a spin-polarization and a tunnel magneto resistance ratio of opposite sign at the rim as compared to the island center

Quantitative tracking of tumor cells in phase-contrast microscopy exploiting halo artifact pattern

Science.gov (United States)

Kang, Mi-Sun; Song, Soo-Min; Lee, Hana; Kim, Myoung-Hee

2012-03-01

Tumor cell morphology is closely related to its invasiveness characteristics and migratory behaviors. An invasive tumor cell has a highly irregular shape, whereas a spherical cell is non-metastatic. Thus, quantitative analysis of cell features is crucial to determine tumor malignancy or to test the efficacy of anticancer treatment. We use phase-contrast microscopy to analyze single cell morphology and to monitor its change because it enables observation of long-term activity of living cells without photobleaching and phototoxicity, which is common in other fluorescence-labeled microscopy. Despite this advantage, there are image-level drawbacks to phase-contrast microscopy, such as local light effect and contrast interference ring, among others. Thus, we first applied a local filter to compensate for non-uniform illumination. Then, we used intensity distribution information to detect the cell boundary. In phase-contrast microscopy images, the cell normally appears as a dark region surrounded by a bright halo. As the halo artifact around the cell body is minimal and has an asymmetric diffusion pattern, we calculated the cross-sectional plane that intersected the center of each cell and was orthogonal to the first principal axis. Then, we extracted the dark cell region by level set. However, a dense population of cultured cells still rendered single-cell analysis difficult. Finally, we measured roundness and size to classify tumor cells into malignant and benign groups. We validated segmentation accuracy by comparing our findings with manually obtained results.

Polarization Imaging Apparatus for Cell and Tissue Imaging and Diagnostics, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — This work proposes to capitalize on our Phase I success in a novel visible-near infrared Stokes polarization imaging technology based on high performance fast...

Vortex phase-induced changes of the statistical properties of a partially coherent radially polarized beam.

Science.gov (United States)

Guo, Lina; Chen, Yahong; Liu, Xianlong; Liu, Lin; Cai, Yangjian

2016-06-27

Partially coherent radially polarized (PCRP) beam was introduced and generated in recent years. In this paper, we investigate the statistical properties of a PCRP beam embedded with a vortex phase (i.e., PCRP vortex beam). We derive the analytical formula for the cross-spectral density matrix of a PCRP vortex beam propagating through a paraxial ABCD optical system and analyze the statistical properties of a PCRP vortex beam focused by a thin lens. It is found that the statistical properties of a PCRP vortex beam on propagation are much different from those of a PCRP beam. The vortex phase induces not only the rotation of the beam spot, but also the changes of the beam shape, the degree of polarization and the state of polarization. We also find that the vortex phase plays a role of resisting the coherence-induced degradation of the intensity distribution and the coherence-induced depolarization. Furthermore, we report experimental generation of a PCRP vortex beam for the first time. Our results will be useful for trapping and rotating particles, free-space optical communications and detection of phase object.

Incremental lines in root cementum of human teeth: An approach to their role in age estimation using polarizing microscopy

Directory of Open Access Journals (Sweden)

Aggarwal Pooja

2008-01-01

Full Text Available Age estimation is an important factor in the identification of an individual in forensic science. The hard tissues of the human dentition are able to resist decay and degradation long after other tissues are lost. This resistance has made teeth useful indicators for age calculation. Recent research indicates that tooth cementum annulations (TCA may be used more reliably than any other morphological or histological traits of the adult skeleton for age estimation. The purpose of this study was to examine the correlation between age and the number of incremental lines in human dental cementum and to ascertain the best method of studying cementum with respect to different forms of microscopy. Thirty nonrestorable teeth were extracted from 20 people, and longitudinal ground section of each tooth was prepared. Photomicrographs of the area at the junction of apical and middle third of the root under light and polarized microscope were taken. The cementum was composed of multiple light and dark bands that were counted on the photomicrograph with the help of image analysis software and added to the average eruption time of individual tooth. The predicted age of the individual was thus obtained. Results showed a significant correlation between the predicted age and actual chronological age of the individual. These data indicate that quantitation of cementum annuli is a moderately reliable means for age estimation in humans and polarizing microscopy is a better means of visualizing incremental lines of cementum compared to light microscopy.

Resonance Polarization and Phase-Mismatched CARS of Pheophytin b Excited in the Qy Band

NARCIS (Netherlands)

de Boeij, W.P.; Lucassen, G.W.; Lucassen, Gerald; Otto, Cornelis; Greve, Jan

1993-01-01

Resonance polarization and phase-mismatched coherent anti-Stokes Raman scattering (CARS) measurements were performed on pheophytin b dissolved in acetone excited in the Qy absorption band, where strong broad fluorescence makes spontaneous Raman spectroscopy impossible. The phase-mismatching

Real time quantitative phase microscopy based on single-shot transport of intensity equation (ssTIE) method

Science.gov (United States)

Yu, Wei; Tian, Xiaolin; He, Xiaoliang; Song, Xiaojun; Xue, Liang; Liu, Cheng; Wang, Shouyu

2016-08-01

Microscopy based on transport of intensity equation provides quantitative phase distributions which opens another perspective for cellular observations. However, it requires multi-focal image capturing while mechanical and electrical scanning limits its real time capacity in sample detections. Here, in order to break through this restriction, real time quantitative phase microscopy based on single-shot transport of the intensity equation method is proposed. A programmed phase mask is designed to realize simultaneous multi-focal image recording without any scanning; thus, phase distributions can be quantitatively retrieved in real time. It is believed the proposed method can be potentially applied in various biological and medical applications, especially for live cell imaging.

Flipping interferometry and its application for quantitative phase microscopy in a micro-channel.

Science.gov (United States)

Roitshtain, Darina; Turko, Nir A; Javidi, Bahram; Shaked, Natan T

2016-05-15

We present a portable, off-axis interferometric module for quantitative phase microscopy of live cells, positioned at the exit port of a coherently illuminated inverted microscope. The module creates on the digital camera an interference pattern between the image of the sample and its flipped version. The proposed simplified module is based on a retro-reflector modification in an external Michelson interferometer. The module does not contain any lenses, pinholes, or gratings and its alignment is straightforward. Still, it allows full control of the off-axis angle and does not suffer from ghost images. As experimentally demonstrated, the module is useful for quantitative phase microscopy of live cells rapidly flowing in a micro-channel.

Live cell refractometry using Hilbert phase microscopy and confocal reflectance microscopy.

Science.gov (United States)

Lue, Niyom; Choi, Wonshik; Popescu, Gabriel; Yaqoob, Zahid; Badizadegan, Kamran; Dasari, Ramachandra R; Feld, Michael S

2009-11-26

Quantitative chemical analysis has served as a useful tool for understanding cellular metabolisms in biology. Among many physical properties used in chemical analysis, refractive index in particular has provided molecular concentration that is an important indicator for biological activities. In this report, we present a method of extracting full-field refractive index maps of live cells in their native states. We first record full-field optical thickness maps of living cells by Hilbert phase microscopy and then acquire physical thickness maps of the same cells using a custom-built confocal reflectance microscope. Full-field and axially averaged refractive index maps are acquired from the ratio of optical thickness to physical thickness. The accuracy of the axially averaged index measurement is 0.002. This approach can provide novel biological assays of label-free living cells in situ.

Investigations of a Cretaceous limestone with spectral induced polarization and scanning electron microscopy

DEFF Research Database (Denmark)

Johansson, Sara; Sparrembom, Charlotte; Fiandaca, Gianluca

2017-01-01

limestone was carried out in the Kristianstad basin, Sweden. The time domain IP data was processed with a recently developed method in order to suppress noise from the challenging urban setting in the survey area. The processing also enabled extraction of early decay times resulting in broader spectra...... in early time ranges for bedrock characterization. The inverted sections showed variations within the limestone that could be caused by variations in texture and composition. Samples from a deep drilling in the Kristianstad basin were investigated with scanning electron microscopy and energy dispersive X......Characterization of varying bedrock properties is a common need in various contexts, ranging from large infrastructure pre-investigations to environmental protection. A direct current resistivity and time domain induced polarization (IP) survey aiming to characterize properties of a Cretaceous...

Fluorescence confocal polarizing microscopy: Three-dimensional ...

Indian Academy of Sciences (India)

journal of. August 2003 physics pp. 373–384. Fluorescence confocal polarizing ... and focal conic domains in flat samples of lamellar LCs are practically indistinguishable. ... or less) LC layer confined between two transparent plates. ... in studies of electro-optic effects such as the Frederiks effect, defects, surface anchoring,.

Classification of M1/M2-polarized human macrophages by label-free hyperspectral reflectance confocal microscopy and multivariate analysis.

Science.gov (United States)

Bertani, Francesca R; Mozetic, Pamela; Fioramonti, Marco; Iuliani, Michele; Ribelli, Giulia; Pantano, Francesco; Santini, Daniele; Tonini, Giuseppe; Trombetta, Marcella; Businaro, Luca; Selci, Stefano; Rainer, Alberto

2017-08-21

The possibility of detecting and classifying living cells in a label-free and non-invasive manner holds significant theranostic potential. In this work, Hyperspectral Imaging (HSI) has been successfully applied to the analysis of macrophagic polarization, given its central role in several pathological settings, including the regulation of tumour microenvironment. Human monocyte derived macrophages have been investigated using hyperspectral reflectance confocal microscopy, and hyperspectral datasets have been analysed in terms of M1 vs. M2 polarization by Principal Components Analysis (PCA). Following PCA, Linear Discriminant Analysis has been implemented for semi-automatic classification of macrophagic polarization from HSI data. Our results confirm the possibility to perform single-cell-level in vitro classification of M1 vs. M2 macrophages in a non-invasive and label-free manner with a high accuracy (above 98% for cells deriving from the same donor), supporting the idea of applying the technique to the study of complex interacting cellular systems, such in the case of tumour-immunity in vitro models.

Control phase shift of spin-wave by spin-polarized current and its application in logic gates

International Nuclear Information System (INIS)

Chen, Xiangxu; Wang, Qi; Liao, Yulong; Tang, Xiaoli; Zhang, Huaiwu; Zhong, Zhiyong

2015-01-01

We proposed a new ways to control the phase shift of propagating spin waves by applying a local spin-polarized current on ferromagnetic stripe. Micromagnetic simulation showed that a phase shift of about π can be obtained by designing appropriate width and number of pinned magnetic layers. The ways can be adopted in a Mach-Zehnder-type interferometer structure to fulfill logic NOT gates based on spin waves. - Highlights: • Spin-wave phase shift can be controlled by a local spin-polarized current. • Spin-wave phase shift increased with the increasing of current density. • Spin-wave phase shift can reach about 0.3π at a particular current density. • The ways can be used in a Mach-Zehnder-type interferometer to fulfill logic gates

IPRT polarized radiative transfer model intercomparison project - Three-dimensional test cases (phase B)

Science.gov (United States)

Emde, Claudia; Barlakas, Vasileios; Cornet, Céline; Evans, Frank; Wang, Zhen; Labonotte, Laurent C.; Macke, Andreas; Mayer, Bernhard; Wendisch, Manfred

2018-04-01

Initially unpolarized solar radiation becomes polarized by scattering in the Earth's atmosphere. In particular molecular scattering (Rayleigh scattering) polarizes electromagnetic radiation, but also scattering of radiation at aerosols, cloud droplets (Mie scattering) and ice crystals polarizes. Each atmospheric constituent produces a characteristic polarization signal, thus spectro-polarimetric measurements are frequently employed for remote sensing of aerosol and cloud properties. Retrieval algorithms require efficient radiative transfer models. Usually, these apply the plane-parallel approximation (PPA), assuming that the atmosphere consists of horizontally homogeneous layers. This allows to solve the vector radiative transfer equation (VRTE) efficiently. For remote sensing applications, the radiance is considered constant over the instantaneous field-of-view of the instrument and each sensor element is treated independently in plane-parallel approximation, neglecting horizontal radiation transport between adjacent pixels (Independent Pixel Approximation, IPA). In order to estimate the errors due to the IPA approximation, three-dimensional (3D) vector radiative transfer models are required. So far, only a few such models exist. Therefore, the International Polarized Radiative Transfer (IPRT) working group of the International Radiation Commission (IRC) has initiated a model intercomparison project in order to provide benchmark results for polarized radiative transfer. The group has already performed an intercomparison for one-dimensional (1D) multi-layer test cases [phase A, 1]. This paper presents the continuation of the intercomparison project (phase B) for 2D and 3D test cases: a step cloud, a cubic cloud, and a more realistic scenario including a 3D cloud field generated by a Large Eddy Simulation (LES) model and typical background aerosols. The commonly established benchmark results for 3D polarized radiative transfer are available at the IPRT website (http

Dynamics of space and polarization charges of ferroelectric thin films measured by atomic force microscopy

International Nuclear Information System (INIS)

Oh, Y.J.; Lee, J.H.; Jo, W.

2006-01-01

Retention behavior and local hysteresis characteristics in Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films on Pt electrodes have been investigated by electrostatic force microscopy (EFM). A sol-gel method is used to synthesize PZT thin films and drying conditions are carefully explored over a wide range of temperature. Decay and retention mechanisms of single-poled and reverse-poled regions of the ferroelectric thin films are explained by space charge redistribution. Trapping behavior of space charges is dependent on the nature of interface between ferroelectric thin films and bottom electrodes. Local measurement of polarization-electric field curves by EFM shows inhomogeneous space charge entrapment

Invited Review Article: Methods for imaging weak-phase objects in electron microscopy

International Nuclear Information System (INIS)

Glaeser, Robert M.

2013-01-01

Contrast has traditionally been produced in electron-microscopy of weak phase objects by simply defocusing the objective lens. There now is renewed interest, however, in using devices that apply a uniform quarter-wave phase shift to the scattered electrons relative to the unscattered beam, or that generate in-focus image contrast in some other way. Renewed activity in making an electron-optical equivalent of the familiar “phase-contrast” light microscope is based in part on the improved possibilities that are now available for device microfabrication. There is also a better understanding that it is important to take full advantage of contrast that can be had at low spatial frequency when imaging large, macromolecular objects. In addition, a number of conceptually new phase-plate designs have been proposed, thus increasing the number of options that are available for development. The advantages, disadvantages, and current status of each of these options is now compared and contrasted. Experimental results that are, indeed, superior to what can be accomplished with defocus-based phase contrast have been obtained recently with two different designs of phase-contrast aperture. Nevertheless, extensive work also has shown that fabrication of such devices is inconsistent, and that their working lifetime is short. The main limitation, in fact, appears to be electrostatic charging of any device that is placed into the electron diffraction pattern. The challenge in fabricating phase plates that are practical to use for routine work in electron microscopy thus may be more in the area of materials science than in the area of electron optics

Polarity Control in Group-III Nitrides beyond Pragmatism

Science.gov (United States)

Mohn, Stefan; Stolyarchuk, Natalia; Markurt, Toni; Kirste, Ronny; Hoffmann, Marc P.; Collazo, Ramón; Courville, Aimeric; Di Felice, Rosa; Sitar, Zlatko; Vennéguès, Philippe; Albrecht, Martin

2016-05-01

Controlling the polarity of polar semiconductors on nonpolar substrates offers a wealth of device concepts in the form of heteropolar junctions. A key to realize such structures is an appropriate buffer-layer design that, in the past, has been developed by empiricism. GaN or ZnO on sapphire are prominent examples for that. Understanding the basic processes that mediate polarity, however, is still an unsolved problem. In this work, we study the structure of buffer layers for group-III nitrides on sapphire by transmission electron microscopy as an example. We show that it is the conversion of the sapphire surface into a rhombohedral aluminum-oxynitride layer that converts the initial N-polar surface to Al polarity. With the various AlxOyNz phases of the pseudobinary Al2O3 -AlN system and their tolerance against intrinsic defects, typical for oxides, a smooth transition between the octahedrally coordinated Al in the sapphire and the tetrahedrally coordinated Al in AlN becomes feasible. Based on these results, we discuss the consequences for achieving either polarity and shed light on widely applied concepts in the field of group-III nitrides like nitridation and low-temperature buffer layers.

Polarized phase shift mask: concept, design, and potential advantages to photolithography process and physical design

Science.gov (United States)

Wang, Ruoping; Grobman, Warren D.; Reich, Alfred J.; Thompson, Matthew A.

2002-03-01

In this paper we introduce the concept and design of a novel phase shift mask technology, Polarized Phase Shift Mask (P:PSM). The P:PSM technology utilizes non-interference between orthogonally polarized light sources to avoid undesired destructive interference seen in conventional two-phase shift mask technology. Hence P:PSM solves the well-known 'phase edge' or 'phase conflict' problem. By obviating the 2nd exposure and 2nd mask in current Complementary Phase Shift Mask (C:PSM) technology, this single mask/single exposure technology offers significant advantages towards photolithography process as well as pattern design. We use examples of typical design and process difficulties associated with the C:PSM technology to illustrate the advantages of the P:PSM technology. We present preliminary aerial image simulation results that support the potential of this new reticle technology for enhanced design flexibility. We also propose possible mask structures and manufacturing methods for building a P:PSM.

LIMITS ON OPTICAL POLARIZATION DURING THE PROMPT PHASE OF GRB 140430A

Energy Technology Data Exchange (ETDEWEB)

Kopac, D.; Mundell, C. G.; Arnold, D. M.; Steele, I. A.; Kobayashi, S.; Lamb, G. P.; Smith, R. J.; Virgili, F. J. [Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool, L3 5RF (United Kingdom); Japelj, J.; Gomboc, A. [Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Guidorzi, C.; Dichiara, S. [Department of Physics and Earth Sciences, University of Ferrara, via Saragat 1, I-44122, Ferrara (Italy); Harrison, R. M. [Department of Astrophysics, School of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv (Israel); Melandri, A. [INAF—Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy); Castro-Tirado, A. J.; Gorosabel, J.; Sánchez-Ramírez, R.; Oates, S. R. [Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomia s/n, E-18008 Granada (Spain); Järvinen, A. [AIP—Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Jelínek, M., E-mail: drejc.kopac@fmf.uni-lj.si [ASU-CAS—Astronomical Institute of the Czech Academy of Sciences, Fričova 298, 251 65 Ondřejov (Czech Republic)

2015-11-01

Gamma-ray burst GRB 140430A was detected by the Swift satellite and observed promptly with the imaging polarimeter RINGO3 mounted on the Liverpool Telescope, with observations beginning while the prompt γ-ray emission was still ongoing. In this paper, we present densely sampled (10-s temporal resolution) early optical light curves (LCs) in 3 optical bands and limits to the degree of optical polarization. We compare optical, X-ray, and gamma-ray properties and present an analysis of the optical emission during a period of high-energy flaring. The complex optical LC cannot be explained merely with a combination of forward and reverse shock emission from a standard external shock, implying additional contribution of emission from internal shock dissipation. We estimate an upper limit for time averaged optical polarization during the prompt phase to be as low as P < 12% (1σ). This suggests that the optical flares and early afterglow emission in this GRB are not highly polarized. Alternatively, time averaging could mask the presence of otherwise polarized components of distinct origin at different polarization position angles.

LIMITS ON OPTICAL POLARIZATION DURING THE PROMPT PHASE OF GRB 140430A

International Nuclear Information System (INIS)

Kopac, D.; Mundell, C. G.; Arnold, D. M.; Steele, I. A.; Kobayashi, S.; Lamb, G. P.; Smith, R. J.; Virgili, F. J.; Japelj, J.; Gomboc, A.; Guidorzi, C.; Dichiara, S.; Harrison, R. M.; Melandri, A.; Castro-Tirado, A. J.; Gorosabel, J.; Sánchez-Ramírez, R.; Oates, S. R.; Järvinen, A.; Jelínek, M.

2015-01-01

Gamma-ray burst GRB 140430A was detected by the Swift satellite and observed promptly with the imaging polarimeter RINGO3 mounted on the Liverpool Telescope, with observations beginning while the prompt γ-ray emission was still ongoing. In this paper, we present densely sampled (10-s temporal resolution) early optical light curves (LCs) in 3 optical bands and limits to the degree of optical polarization. We compare optical, X-ray, and gamma-ray properties and present an analysis of the optical emission during a period of high-energy flaring. The complex optical LC cannot be explained merely with a combination of forward and reverse shock emission from a standard external shock, implying additional contribution of emission from internal shock dissipation. We estimate an upper limit for time averaged optical polarization during the prompt phase to be as low as P < 12% (1σ). This suggests that the optical flares and early afterglow emission in this GRB are not highly polarized. Alternatively, time averaging could mask the presence of otherwise polarized components of distinct origin at different polarization position angles

Analysis of enamel microbiopsies in shed primary teeth by Scanning Electron Microscopy (SEM) and Polarizing Microscopy (PM)

International Nuclear Information System (INIS)

Costa de Almeida, Glauce Regina; Molina, Gabriela Ferian; Meschiari, Cesar Arruda; Barbosa de Sousa, Frederico; Gerlach, Raquel Fernanda

2009-01-01

The aims of this study were 1) to verify how close to the theoretically presumed areas are the areas of enamel microbiopsies carried out in vivo or in exfoliated teeth; 2) to test whether the etching solution penetrates beyond the tape borders; 3) to test whether the etching solution demineralizes the enamel in depth. 24 shed upper primary central incisors were randomly divided into two groups: the Rehydrated Teeth Group and the Dry Teeth Group. An enamel microbiopsy was performed, and the enamel microbiopsies were then analyzed by Scanning Electron Microscopy (SEM) and Polarizing Microscopy (PM). Quantitative birefringence measurements were performed. The 'true' etched area was determined by measuring the etched enamel using the NIH Image analysis program. Enamel birefringence was compared using the paired t test. There was a statistically significant difference when the etched areas in the Rehydrated teeth were compared with those of the Dry teeth (p = 0.04). The etched areas varied from - 11.6% to 73.5% of the presumed area in the Rehydrated teeth, and from 6.6% to 61.3% in the Dry teeth. The mean percentage of variation in each group could be used as a correction factor for the etched area. Analysis of PM pictures shows no evidence of in-depth enamel demineralization by the etching solution. No statistically significant differences in enamel birefringence were observed between values underneath and outside the microbiopsy area in the same tooth, showing that no mineral loss occurred below the enamel superficial layer. Our data showed no evidence of in-depth enamel demineralization by the etching solution used in the enamel microbiopsy proposed for primary enamel. This study also showed a variation in the measured diameter of the enamel microbiopsy in nineteen teeth out of twenty four, indicating that in most cases the etching solution penetrated beyond the tape borders.

Diffraction phase microscopy realized with an automatic digital pinhole

Science.gov (United States)

Zheng, Cheng; Zhou, Renjie; Kuang, Cuifang; Zhao, Guangyuan; Zhang, Zhimin; Liu, Xu

2017-12-01

We report a novel approach to diffraction phase microscopy (DPM) with automatic pinhole alignment. The pinhole, which serves as a spatial low-pass filter to generate a uniform reference beam, is made out of a liquid crystal display (LCD) device that allows for electrical control. We have made DPM more accessible to users, while maintaining high phase measurement sensitivity and accuracy, through exploring low cost optical components and replacing the tedious pinhole alignment process with an automatic pinhole optical alignment procedure. Due to its flexibility in modifying the size and shape, this LCD device serves as a universal filter, requiring no future replacement. Moreover, a graphic user interface for real-time phase imaging has been also developed by using a USB CMOS camera. Experimental results of height maps of beads sample and live red blood cells (RBCs) dynamics are also presented, making this system ready for broad adaption to biological imaging and material metrology.

Quantitative phase imaging with scanning holographic microscopy: an experimental assesment

Directory of Open Access Journals (Sweden)

Tada Yoshitaka

2006-11-01

Full Text Available Abstract This paper demonstrates experimentally how quantitative phase information can be obtained in scanning holographic microscopy. Scanning holography can operate in both coherent and incoherent modes, simultaneously if desired, with different detector geometries. A spatially integrating detector provides an incoherent hologram of the object's intensity distribution (absorption and/or fluorescence, for example, while a point detector in a conjugate plane of the pupil provides a coherent hologram of the object's complex amplitude, from which a quantitative measure of its phase distribution can be extracted. The possibility of capturing simultaneously holograms of three-dimensional specimens, leading to three-dimensional reconstructions with absorption contrast, reflectance contrast, fluorescence contrast, as was previously demonstrated, and quantitative phase contrast, as shown here for the first time, opens up new avenues for multimodal imaging in biological studies.

Identification of stacking faults in silicon carbide by polarization-resolved second harmonic generation microscopy.

Science.gov (United States)

Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Polychroniadis, Efstathios K; Stanciu, George A

2017-07-07

Although silicon carbide is a highly promising crystalline material for a wide range of electronic devices, extended and point defects which perturb the lattice periodicity hold deep implications with respect to device reliability. There is thus a great need for developing new methods that can detect silicon carbide defects which are detrimental to device functionality. Our experiment demonstrates that polarization-resolved second harmonic generation microscopy can extend the efficiency of the "optical signature" concept as an all-optical rapid and non-destructive set of investigation methods for the differentiation between hexagonal and cubic stacking faults in silicon carbide. This technique can be used for fast and in situ characterization and optimization of growth conditions for epilayers of silicon carbide and similar materials.

Valley polarized quantum Hall effect and topological insulator phase transitions in silicene

KAUST Repository

Tahir, M.; Schwingenschlö gl, Udo

2013-01-01

encountered for graphene, in particular the zero band gap and weak spin orbit interaction. We demonstrate a valley polarized quantum Hall effect and topological insulator phase transitions. We use the Kubo formalism to discuss the Hall conductivity and address

Direct observation of fatigue in epitaxially grown Pb(Zr,Ti)O3 thin films using second harmonic piezoresponse force microscopy

Science.gov (United States)

Murari, Nishit M.; Hong, Seungbum; Lee, Ho Nyung; Katiyar, Ram. S.

2011-08-01

Here, we present a direct observation of fatigue phenomena in epitaxially grown Pb(Zr0.2Ti0.8)O3 (PZT) thin films using second harmonic piezoresponse force microscopy (SH-PFM). We observed strong correlation between the SH-PFM amplitude and phase signals with the remnant piezoresponse at different switching cycles. The SH-PFM results indicate that the average fraction of switchable domains decreases globally and the phase delays of polarization switching differ locally. In addition, we found that the fatigue developed uniformly over the whole area without developing region-by-region suppression of switchable polarization as in polycrystalline PZT thin films.

Circularly Polarized Planar Helix Phased Antenna Array for 5G Mobile Terminals

DEFF Research Database (Denmark)

Syrytsin, Igor A.; Zhang, Shuai; Pedersen, Gert F.

2017-01-01

In this paper, a planar helix mobile phased antenna array is proposed for 5th generation communication systems with operating frequency of 28GHz. The proposed array displays circular polarization in the endfire direction. Over 65 degrees of axial ratio beamwidth and 7GHz of axial ratio bandwidth...... has been achieved in the proposed design. The coverage performance of the proposed phased antenna array has also been studied by using the coverage efficiency metric. Coverage efficiency of 50 % at 5 dBi gain is achieved by the proposed phased mobile antenna array....

Analysis of peripheral thermal damage after laser irradiation of dentin using polarized light microscopy and synchrotron radiation infrared spectromicroscopy

Science.gov (United States)

Dela Rosa, Alfredo; Sarma, Anupama V.; Le, Charles Q.; Jones, Robert S.; Fried, Daniel

2004-05-01

It is necessary to minimize peripheral thermal damage during laser irradiation, since thermal damage to collagen and mineral compromises the bond strength to restorative materials in dentin and inhibits healing and osteointegration in bone. The overall objective of this study was to test the hypothesis that lasers resonant to the specific absorption of water, collagen, and hydroxyapatite with pulse durations less than the thermal relaxation times at each respective laser wavelength will efficiently remove dentin with minimal peripheral thermal damage. Precise incisions were produced in 3 x 3 mm2 blocks of human dentin using CO2 (9.6 μm), Er:YSGG (2.79 μm), and Nd:YAG (355 nm) lasers with and without a computer controlled water spray. Polarization-sensitive optical coherence tomography was used to obtain optical cross-sections of each incision to determine the rate and efficiency of ablation. The peripheral thermal damage zone around each incision was analyzed using polarized light microscopy (PLM) and Synchrotron-Radiation Fourier Transform Infrared Spectro-microscopy (SR-FTIR). Thermally induced chemical changes to both mineral and the collagen matrix was observed with SR-FTIR with a 10-μm spatial resolution and those changes were correlated with optical changes observed with PLM. Minimal (alveolar bone.

An optical investigation of dentinal discoloration due to commonly endodontic sealers, using the transmitted light polarizing microscopy and spectrophotometry.

Science.gov (United States)

Suciu, Ioana; Ionescu, Ecaterina; Dimitriu, Bogdan Alexandru; Bartok, Ruxandra Ioana; Moldoveanu, Georgiana Florentina; Gheorghiu, Irina Maria; Suciu, Ileana; Ciocîrdel, Mihai

2016-01-01

The aim of this study was to establish the degree of tooth crown staining by commonly used endodontic sealers. Crown discolorations by tooth canal sealers [AH Plus (Dentsply DeTrey Gmbh, Konstanz, Germany); Endofill (Produits Dentaires SA, Vevey, Switzerland); Apexit (Dentsply DeTrey Gmbh, Konstanz, Germany); and MTA Fillapex (Angelus, Londrina, Brazil)] were tested on extracted human premolars. The samples were divided into five groups of five samples each, after root canal sealing. Five teeth were used as control groups. The spectrophotometric method was performed in order to quantify in terms of color change of the coronal part (it was also recorded a track on how the color changes over time). For the microscopic study of the extracted dental specimens subjected to this study, polarized transmitted light microscopy was used. This method involves the development of special microscopic preparations, called "thin sections". In our case, the thin section was performed on 20 prepared and obturated recently extracted teeth. The degree of discoloration was determined after one week and three months using spectrophotometry and polarized light microscopy. All sealers usually cause some degree of discoloration on the cervical aspect of the crowns that increases in time. AH Plus and Endofill caused the greatest discoloration, followed by Apexit and MTA Fillapex.

Polar silica-based stationary phases. Part II- Neutral silica stationary phases with surface bound maltose and sorbitol for hydrophilic interaction liquid chromatography.

Science.gov (United States)

Rathnasekara, Renuka; El Rassi, Ziad

2017-07-28

Two neutral polyhydroxylated silica bonded stationary phases, namely maltose-silica (MALT-silica) and sorbitol-silica (SOR-silica), have been introduced and chromatographically characterized in hydrophilic interaction liquid chromatography (HILIC) for a wide range of polar compounds. The bonding of the maltose and sorbitol to the silica surface was brought about by first converting bare silica to an epoxy-activated silica surface via reaction with γ-glycidoxypropyltrimethoxysilane (GPTMS) followed by attaching maltose and sorbitol to the epoxy surface in the presence of the Lewis acid catalyst BF 3 .ethereate. Both silica based columns offered the expected retention characteristics usually encountered for neutral polar surface. The retention mechanism is majorly based on solute' differential partitioning between an organic rich hydro-organic mobile phase (e.g., ACN rich mobile phase) and an adsorbed water layer on the surface of the stationary phase although additional hydrogen bonding was also responsible in some cases for solute retention. The MALT-silica column proved to be more hydrophilic and offered higher retention, separation efficiency and resolution than the SOR-silica column among the tested polar solutes such as derivatized mono- and oligosaccharides, weak phenolic acids, cyclic nucleotide monophosphate and nucleotide-5'-monophosphates, and weak bases, e.g., nucleobases and nucleosides. Copyright © 2017 Elsevier B.V. All rights reserved.

Phase microscopy using light-field reconstruction method for cell observation.

Science.gov (United States)

Xiu, Peng; Zhou, Xin; Kuang, Cuifang; Xu, Yingke; Liu, Xu

2015-08-01

The refractive index (RI) distribution can serve as a natural label for undyed cell imaging. However, the majority of images obtained through quantitative phase microscopy is integrated along the illumination angle and cannot reflect additional information about the refractive map on a certain plane. Herein, a light-field reconstruction method to image the RI map within a depth of 0.2 μm is proposed. It records quantitative phase-delay images using a four-step phase shifting method in different directions and then reconstructs a similar scattered light field for the refractive sample on the focus plane. It can image the RI of samples, transparent cell samples in particular, in a manner similar to the observation of scattering characteristics. The light-field reconstruction method is therefore a powerful tool for use in cytobiology studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Control of magnetic vortex polarity by the phase difference between voltage signals

Science.gov (United States)

Cui, Huanqing; Cai, Li; Yang, Xiaokuo; Wang, Sen; Zhang, Mingliang; Li, Cheng; Feng, Chaowen

2018-02-01

Using micromagnetic simulations, we investigate the voltage control of magnetic vortex polarity based on a designed multiferroic heterostructure that contains two separate piezoelectric films beneath a magnetostrictive nanodisk. The results show that controllable switching of vortex polarity can be achieved by proper modulation of the phase difference between two sinusoidal voltage pulses V1 and V2, which are applied to the two separate piezoelectric films, respectively. The frequencies of V1 and V2 are set at the gyrotropic eigenfrequency fG of the nanodisk, and the vortex polarity switching is completed via the nucleation-annihilation process of the vortex-antivortex pair. Our findings provide an additional effective means for ultralow power switching of the magnetic vortex, which lays the foundation for voltage-controlled vortex random access memory.

Reversible Decomposition of Secondary Phases in BaO Infiltrated LSM Electrodes-Polarization Effects

DEFF Research Database (Denmark)

Traulsen, Marie Lund; McIntyre, Melissa D.; Norrman, Kion

2016-01-01

and Raman spectroscopy reveal the formation of a secondary phase, Ba3Mn2O8, on the electrode. During the in operando Raman investigation of the BaO-infiltrated La0.85Sr0.15MnO3±δ electrodes, experiments are performed at 300 and 500 °C with oxygen partial pressure 0.1 atm and with −1 or +1 V Applied...... for the reduced polarization resistance observed at open Circuit voltage (OCV) in an oxygen containing atmosphere. Furthermore, the results illustrate the dramatic differences between the electrode surface composition at OCV and during cathodic polarization. Overall, the results highlight the dynamic interactions...... between minor secondary phases and applied potential, a general effect that may be important for the high-performance frequently observed with ceramic electrodes prepared by infiltration....

Quantitative phase-digital holographic microscopy: a new imaging modality to identify original cellular biomarkers of diseases

KAUST Repository

Marquet, P.

2016-05-03

Quantitative phase microscopy (QPM) has recently emerged as a powerful label-free technique in the field of living cell imaging allowing to non-invasively measure with a nanometric axial sensitivity cell structure and dynamics. Since the phase retardation of a light wave when transmitted through the observed cells, namely the quantitative phase signal (QPS), is sensitive to both cellular thickness and intracellular refractive index related to the cellular content, its accurate analysis allows to derive various cell parameters and monitor specific cell processes, which are very likely to identify new cell biomarkers. Specifically, quantitative phase-digital holographic microscopy (QP-DHM), thanks to its numerical flexibility facilitating parallelization and automation processes, represents an appealing imaging modality to both identify original cellular biomarkers of diseases as well to explore the underlying pathophysiological processes.

Dual-Polarized Planar Phased Array Analysis for Meteorological Applications

Directory of Open Access Journals (Sweden)

Chen Pang

2015-01-01

Full Text Available This paper presents a theoretical analysis for the accuracy requirements of the planar polarimetric phased array radar (PPPAR in meteorological applications. Among many factors that contribute to the polarimetric biases, four factors are considered and analyzed in this study, namely, the polarization distortion due to the intrinsic limitation of a dual-polarized antenna element, the antenna pattern measurement error, the entire array patterns, and the imperfect horizontal and vertical channels. Two operation modes, the alternately transmitting and simultaneously receiving (ATSR mode and the simultaneously transmitting and simultaneously receiving (STSR mode, are discussed. For each mode, the polarimetric biases are formulated. As the STSR mode with orthogonal waveforms is similar to the ATSR mode, the analysis is mainly focused on the ATSR mode and the impacts of the bias sources on the measurement of polarimetric variables are investigated through Monte Carlo simulations. Some insights of the accuracy requirements are obtained and summarized.

Spin-polarized scanning tunneling microscopy with quantitative insights into magnetic probes.

Science.gov (United States)

Phark, Soo-Hyon; Sander, Dirk

2017-01-01

Spin-polarized scanning tunneling microscopy and spectroscopy (spin-STM/S) have been successfully applied to magnetic characterizations of individual nanostructures. Spin-STM/S is often performed in magnetic fields of up to some Tesla, which may strongly influence the tip state. In spite of the pivotal role of the tip in spin-STM/S, the contribution of the tip to the differential conductance d I /d V signal in an external field has rarely been investigated in detail. In this review, an advanced analysis of spin-STM/S data measured on magnetic nanoislands, which relies on a quantitative magnetic characterization of tips, is discussed. Taking advantage of the uniaxial out-of-plane magnetic anisotropy of Co bilayer nanoisland on Cu(111), in-field spin-STM on this system has enabled a quantitative determination, and thereby, a categorization of the magnetic states of the tips. The resulting in-depth and conclusive analysis of magnetic characterization of the tip opens new venues for a clear-cut sub-nanometer scale spin ordering and spin-dependent electronic structure of the non-collinear magnetic state in bilayer high Fe nanoislands on Cu(111).

Atomic scale imaging of competing polar states in a Ruddlesden–Popper layered oxide

Science.gov (United States)

Stone, Greg; Ophus, Colin; Birol, Turan; Ciston, Jim; Lee, Che-Hui; Wang, Ke; Fennie, Craig J.; Schlom, Darrell G.; Alem, Nasim; Gopalan, Venkatraman

2016-01-01

Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden–Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure. PMID:27578622

Atomic scale imaging of competing polar states in a Ruddlesden-Popper layered oxide.

Science.gov (United States)

Stone, Greg; Ophus, Colin; Birol, Turan; Ciston, Jim; Lee, Che-Hui; Wang, Ke; Fennie, Craig J; Schlom, Darrell G; Alem, Nasim; Gopalan, Venkatraman

2016-08-31

Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden-Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure.

Proposals for the solution of the phase problem in electron microscopy

International Nuclear Information System (INIS)

Toorn, P. van.

1979-01-01

This thesis discusses the phase problem in electron microscopy, i.e. the determination of the unknown complex wave function in the image plane or in the exit pupil from the measured intensity distributions in both planes. The calculation of the wave function is the first problem to be solved for the determination of the object structure from electron micrographs. (Auth.)

Polarity dependent photoisomerization of ether substituted azodyes: Synthesis and photoswitching behavior.

Science.gov (United States)

Gan, Siew Mei; Pearl, Zynia Fernandes; Yuvaraj, A R; Lutfor, M R; Gurumurthy, Hegde

2015-10-05

Two new ether substituted azodyes were synthesized and characterized by different spectral analysis such as (1)H NMR, (13)C NMR, FTIR and UV/Vis. Synthesized compounds were used to study the photoisomerization phenomenon by using UV-Vis spectro-photometer. Interesting polarity dependent effect is observed for the first time on these materials. Trans-cis (E-Z) and cis-trans (Z-E) conversion occurred within 41 s and 445 min, respectively for both the compounds in solutions. Polarizing optical microscopy studies revealed that there is no liquid crystal phase for both the compounds. The dramatic variation in the optical property is speculated to be the polarity of the chemical species. These derivatives are useful to fabricate optical data storage devices. Copyright © 2015 Elsevier B.V. All rights reserved.

Suppression of metastable-phase inclusion in N-polar (0001¯) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

International Nuclear Information System (INIS)

Shojiki, Kanako; Iwabuchi, Takuya; Kuboya, Shigeyuki; Choi, Jung-Hun; Tanikawa, Tomoyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi; Usami, Noritaka

2015-01-01

The metastable zincblende (ZB) phase in N-polar (0001 ¯ ) (−c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the −c-plane and Ga-polar (0001) (+c-plane), the −c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the −c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated

Hard-x-ray phase-imaging microscopy using the self-imaging phenomenon of a transmission grating

International Nuclear Information System (INIS)

Yashiro, Wataru; Harasse, Sebastien; Momose, Atsushi; Takeuchi, Akihisa; Suzuki, Yoshio

2010-01-01

We report on a hard-x-ray imaging microscope consisting of a lens, a sample, and a transmission grating. After the theoretical framework of self-imaging phenomenon by the grating in the system is presented, equations for the electric field on the image plane are derived for ideal and real lenses and an equation for the intensity on the image plane for partially coherent illumination is derived. The equations are simple and similar to those applying to a projection microscope consisting of a transmission grating except that there is no defocusing effect, regardless of whether the grating is in front of or behind the lens. This means that x-ray phase-imaging microscopy can be done without the defocusing effect. It is also shown that, by resolving the self-image on the image plane, high-sensitive x-ray phase-imaging microscopy can be attained without degradation in the spatial resolution due to diffraction by the grating. Experimental results obtained using partially coherent illumination from a synchrotron x-ray source confirm that hard-x-ray phase-imaging microscopy can be quantitatively performed with high sensitivity and without the spatial resolution degradation.

Edge states and phase diagram for graphene under polarized light

Energy Technology Data Exchange (ETDEWEB)

Wang, Yi-Xiang, E-mail: wangyixiang@jiangnan.edu.cn [School of Science, Jiangnan University, Wuxi 214122 (China); Li, Fuxiang [Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2016-07-01

In this work, we investigate the topological phase transitions in graphene under the modulation of circularly polarized light, by analyzing the changes of edge states and its topological structures. A full phase diagram, with several different topological phases, is presented in the parameter space spanned by the driving frequency and light strength. We find that the high-Chern number behavior is very common in the driven system. While the one-photon resonance can create the chiral edge states in the π-gap, the two-photon resonance will induce the counter-propagating edge modes in the zero-energy gap. When the driving light strength is strong, the number and even the chirality of the edge states may change in the π-gap. The robustness of the edge states to disorder potential is also examined. We close by discussing the feasibility of experimental proposals.

Polarization controlled deep sub-wavelength periodic features written by femtosecond laser on nanodiamond thin film surface

Energy Technology Data Exchange (ETDEWEB)

Kumar Kuntumalla, Mohan; Srikanth, Vadali V. S. S., E-mail: vvsssse@uohyd.ernet.in [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); Rajamudili, Kuladeep; Rao Desai, Narayana [School of Physics, University of Hyderabad, Hyderabad 500046 (India)

2014-04-21

Deep sub-wavelength (Λ/λ = ∼0.22) periodic features are induced uniformly on a nanodiamond (ND) thin film surface using femtosecond (fs) laser irradiation (pulse duration = ∼110 fs and central wavelength of ∼800 nm). The topography of the surface features is controlled by the laser polarization. Orientation of features is perpendicular to laser polarization. Periodicity (spatial periodicity of < λ/4) of the surface features is less than the laser wavelength. This work gives an experimental proof of polarization controlled surface plasmon-fs laser coupling mechanism prompting the interaction between fs laser and solid matter (here ND thin film) which in turn is resulting in the periodic surface features. Scanning electron microscopy in conjunction with micro Raman scattering, X-ray diffraction, and atomic force microscopy are carried out to extract surface morphology and phase information of the laser irradiated regions. This work demonstrates an easy and efficient surface fabrication technique.

Direct observation of dopant distribution in GaAs compound semiconductors using phase-shifting electron holography and Lorentz microscopy.

Science.gov (United States)

Sasaki, Hirokazu; Otomo, Shinya; Minato, Ryuichiro; Yamamoto, Kazuo; Hirayama, Tsukasa

2014-06-01

Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in GaAs compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p-n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10(19) cm(-3) and 1 × 10(18) cm(-3) regions were clearly observed by using phase-shifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Design and simulation of a novel circularly polarized antenna with polarization reconfigurable characteristics

Directory of Open Access Journals (Sweden)

Zhang Hai

2016-01-01

Full Text Available A novel circularly polarized antenna with polarization reconfigurable characteristics was designed using co-simulation of Ansoft HFSS and Designer software. It consists of a dual-polarized antenna and phase switching network which act as the feed network for the dual-polarized antenna. The phase switching network was designed based on a Wilkinson power divider, where the output port was connected with SPDT to form a switching network. By controlling the SPDT state-off / on, the phase difference of the two ports could be alternated, which generated the orthogonal modes between the two ports of dual-polarized antenna. So that Left-hand circular polarization (LHCP and Right-hand circular polarization (RHCP could be achieved. The simulation shown that reflection coefficient was less than -12 dB and the axial ratio was below 3 dB between 1.8 GHz and 2.4 GHz with polarization reconfigurable characteristics.

Polarity-based fractionation in proteomics: hydrophilic interaction vs reversed-phase liquid chromatography.

Science.gov (United States)

Jafari, M; Mirzaie, M; Khodabandeh, M; Rezadoost, H; Ghassempour, A; Aboul-Enein, H Y

2016-07-01

During recent decades, hydrophilic interaction liquid chromatography (HILIC) ahs been introduced to fractionate or purify especially polar solutes such as peptides and proteins while reversed-phase liquid chromatography (RPLC) is also a common strategy. RPLC is also a common dimension in multidimensional chromatography. In this study, the potential of HILIC vs RPLC chromatography was compared for proteome mapping of human peripheral blood mononuclear cell extract. In HILIC a silica-based stationary phase and for RPLC a C18 column were applied. Then separated proteins were eluted to an ion trap mass spectrometry system. Our results showed that the HILIC leads to more proteins being identified in comparison to RPLC. Among the total 181 identified proteins, 56 and 38 proteins were fractionated specifically by HILIC and RPLC, respectively. In order to demonstrate this, the physicochemical properties of identified proteins such as polarity and hydrophobicity were considered. This analysis indicated that polarity may play a major role in the HILIC separation of proteins vs RPLC. Using gene ontology enrichment analysis, it was also observed that differences in physicochemical properties conform to the cellular compartment and biological features. Finally, this study highlighted the potential of HILIC and the great orthogonality of RPLC in gel-free proteomic studies. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Scanning tunneling microscopy and spectroscopy on GaN and InGaN surfaces

International Nuclear Information System (INIS)

Krueger, David

2009-01-01

Optelectronic devices based on gallium nitride (GaN) and indium gallium nitride (InGaN) are in the focus of research since more than 20 years and still have great potential for optical applications. In the first part of this work non-polar surfaces of GaN are investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). In SEM and AFM, the (1 anti 100)- and especially the (anti 2110)-plane are quite corrugated. For the first time, the (anti 2110)-plane of GaN is atomically resolved in STM. In the second part InGaN quantum dot layers are investigated by X-ray photoelectron spectroscopy (XPS), scanning tunneling spectroscopy (STS) and STM. The STMmeasurements show the dependency of surface morphology on growth conditions in the metalorganic vapour phase epitaxy (MOVPE). Nucleation, a new MOVPE-strategy, is based on phase separations on surfaces. It is shown that locally varying density of states and bandgaps can be detected by STS, that means bandgap histograms and 2D-bandgap-mapping. (orig.)

Joint compensation scheme of polarization crosstalk, intersymbol interference, frequency offset, and phase noise based on cascaded Kalman filter

Science.gov (United States)

Zhang, Qun; Yang, Yanfu; Xiang, Qian; Zhou, Zhongqing; Yao, Yong

2018-02-01

A joint compensation scheme based on cascaded Kalman filter is proposed, which can implement polarization tracking, channel equalization, frequency offset, and phase noise compensation simultaneously. The experimental results show that the proposed algorithm can not only compensate multiple channel impairments simultaneously but also improve the polarization tracking capacity and accelerate the convergence speed. The scheme has up to eight times faster convergence speed compared with radius-directed equalizer (RDE) + Max-FFT (maximum fast Fourier transform) + BPS (blind phase search) and can track up polarization rotation 60 times and 15 times faster than that of RDE + Max-FFT + BPS and CMMA (cascaded multimodulus algorithm) + Max-FFT + BPS, respectively.

Interference electron microscopy of one-dimensional electron-optical phase objects

International Nuclear Information System (INIS)

Fazzini, P.F.; Ortolani, L.; Pozzi, G.; Ubaldi, F.

2006-01-01

The application of interference electron microscopy to the investigation of electron optical one-dimensional phase objects like reverse biased p-n junctions and ferromagnetic domain walls is considered. In particular the influence of diffraction from the biprism edges on the interference images is analyzed and the range of applicability of the geometric optical equation for the interpretation of the interference fringe shifts assessed by comparing geometric optical images with full wave-optical simulations. Finally, the inclusion of partial spatial coherence effects are discussed

Solid Phase Characterization Of Heel Samples From Tank 241-C-110

International Nuclear Information System (INIS)

Page, J.S.; Cooke, G.A.; Pestovich, J.A.; Huber, H.J.

2011-01-01

During sluicing operations of tank 241-C-110, a significant amount of solids were unable to be retrieved. These solids (often referred to as the tank 'heel') were sampled in 2010 and chemically and mineralogically analyzed in the 222-S Laboratory. Additionally, dissolution tests were performed to identify the amount of undissolvable material after using multiple water contacts. This report covers the solid phase characterization of six samples from these tests using scanning electron microscopy, polarized light microscopy, and X-ray diffraction. The chemical analyses, particle size distribution analysis, and dissolution test results are reported separately. Two of the samples were from composites created from as-received material - Composite A and Composite B. The main phase in these samples was sodium-fluoride-phosphate hydrate (natrophosphate) - in the X-ray diffraction spectra, this phase was the only phase identifiable. Polarized light microscopy showed the presence of minor amounts of gibbsite and other phases. These phases were identified by scanning electron microscopy - energy dispersive X-ray spectroscopy as sodium aluminosilicates, sodium diuranate, and sodium strontium phosphate hydrate (nastrophite) crystals. The natrophosphate crystals in the scanning electron microscopy analysis showed a variety of erosive and dissolution features from perfectly shaped octahedral to well-rounded appearance. Two samples were from water-washed Composites A and B, with no change in mineralogy compared to the as-received samples. This is not surprising, since the water wash had only a short period of water contact with the material as opposed to the water dissolution tests. The last two samples were residual solids from the water dissolution tests. These tests included multiple additions of water at 15 C and 45 C. The samples were sieved to separate a coarser fraction of > 710 μm and a finer fraction of < 710 μm. These two fractions were analyzed separately. The coarser

Effect of a spiral phase on a vector optical field with hybrid polarization states

International Nuclear Information System (INIS)

Chen, Rui-Pin; Zhao, Tingyu; Zhong, Li-Xin; Chew, Khian-Hooi; Gu, Bing; Zhou, Guoquan

2015-01-01

The propagation dynamics of a vector field with inhomogeneous states of polarization (SoP) imposed a vortex is studied using the angular spectrum method. The evolution of SoP in the cross section of the field during propagation is analyzed numerically by the Stokes polarization parameters. The results indicate that SoP in the field cross section rotate along the propagation axis during propagation due to the existence of a vortex. In addition, the interaction between the phase singularity and the polarization singularity leads to the creation or annihilation of the optical field in the central region. In particular, the distributions of the transverse energy flow and both spin and orbital optical angular momentum fluxes in the cross section of the vortex vector optical field depend sensitively on both the vortex and polarization topology charges. (paper)

Polarity and microstructure in InN thin layers grown by MOVPE

International Nuclear Information System (INIS)

Kuwano, N.; Nakahara, Y.; Amano, H.

2006-01-01

Microstructures in InN grown on sapphire (0001) and yttria-stabilized zirconia (YSZ) (111) by metal-organic vapor phase epitaxy (MOVPE) were analyzed by means of transmission electron microscopy (TEM) in order to clarify the growth process. Special attention was paid to the selectivity of the crystal polarity of InN. The InN thin films grown on sapphire after nitridation has a flat surface while those grown on YSZ has hillocks on the surface. The crystal polarity was determined by comparing the experimentally observed intensity distribution in convergent beam electron diffraction (CBED) disks with those simulated by the Broch-wave method. It was found that the InN grown on the sapphire has a nitrogen-polarity and the one on YSZ has a mixture of In- and N-polarities. The effect of surface-nitridation of sapphire on the growth process is also discussed (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Advantages of intermediate X-ray energies in Zernike phase contrast X-ray microscopy.

Science.gov (United States)

Wang, Zhili; Gao, Kun; Chen, Jian; Hong, Youli; Ge, Xin; Wang, Dajiang; Pan, Zhiyun; Zhu, Peiping; Yun, Wenbing; Jacobsen, Chris; Wu, Ziyu

2013-01-01

Understanding the hierarchical organizations of molecules and organelles within the interior of large eukaryotic cells is a challenge of fundamental interest in cell biology. Light microscopy is a powerful tool for observations of the dynamics of live cells, its resolution attainable is limited and insufficient. While electron microscopy can produce images with astonishing resolution and clarity of ultra-thin (3D images of cryo-preserved cells. The relatively low X-ray energy (3D imaging (e.g., ~1 μm DoF for 20 nm resolution). An X-ray microscope operating at intermediate energy around 2.5 keV using Zernike phase contrast can overcome the above limitations and reduces radiation dose to the specimen. Using a hydrated model cell with an average chemical composition reported in literature, we calculated the image contrast and the radiation dose for absorption and Zernike phase contrast, respectively. The results show that an X-ray microscope operating at ~2.5 keV using Zernike phase contrast offers substantial advantages in terms of specimen size, radiation dose and depth-of-focus. Copyright © 2012 Elsevier Inc. All rights reserved.

Correction of phase-shifting error in wavelength scanning digital holographic microscopy

Science.gov (United States)

Zhang, Xiaolei; Wang, Jie; Zhang, Xiangchao; Xu, Min; Zhang, Hao; Jiang, Xiangqian

2018-05-01

Digital holographic microscopy is a promising method for measuring complex micro-structures with high slopes. A quasi-common path interferometric apparatus is adopted to overcome environmental disturbances, and an acousto-optic tunable filter is used to obtain multi-wavelength holograms. However, the phase shifting error caused by the acousto-optic tunable filter reduces the measurement accuracy and, in turn, the reconstructed topographies are erroneous. In this paper, an accurate reconstruction approach is proposed. It corrects the phase-shifting errors by minimizing the difference between the ideal interferograms and the recorded ones. The restriction on the step number and uniformity of the phase shifting is relaxed in the interferometry, and the measurement accuracy for complex surfaces can also be improved. The universality and superiority of the proposed method are demonstrated by practical experiments and comparison to other measurement methods.

Ultrastructural organization of premature condensed chromosomes at S-phase as observed by atomic force microscopy

International Nuclear Information System (INIS)

Fan Yihui; Zhang Xiaohong; Bai Jing; Mao Renfang; Zhang Chunyu; Lei Qingquan; Fu Songbin

2007-01-01

In this study, we used calyculin A to induce premature condensed chromosomes (PCC). S-phase PCC is as 'pulverized' appearance when viewed by light microscopy. Then, we applied atomic force microscopy (AFM) to investigate the ultrastructual organization of S-phase PCC. S-phase PCC shows ridges and grooves as observed by AFM. After trypsin treatment, chromosome surface roughness is increased and chromosome thickness is decreased. At high magnification, the ridges are composed of densely packed 30 nm chromatin fibers which form chromosome axis. Around the ridges, many 30 nm chromatin fibers radiate from center. Some of the 30 nm chromatin fibers are free ends. The grooves are not real 'gap', but several 30 nm chromatin fibers which connect two ridges and form 'grid' structure. There are four chromatin fibers detached from chromosome: two free straight 30 nm chromatin fibers, one loop chromatin fiber and one straight combining with loop chromatin fiber. These results suggested that the S-phase PCC was high-order organization of 30 nm chromatin fibers and the 30 nm chromatin fibers could exist as loops and free ends

Digital Holographic Microscopy: Quantitative Phase Imaging and Applications in Live Cell Analysis

Science.gov (United States)

Kemper, Björn; Langehanenberg, Patrik; Kosmeier, Sebastian; Schlichthaber, Frank; Remmersmann, Christian; von Bally, Gert; Rommel, Christina; Dierker, Christian; Schnekenburger, Jürgen

The analysis of complex processes in living cells creates a high demand for fast and label-free methods for online monitoring. Widely used fluorescence methods require specific labeling and are often restricted to chemically fixated samples. Thus, methods that offer label-free and minimally invasive detection of live cell processes and cell state alterations are of particular interest. In combination with light microscopy, digital holography provides label-free, multi-focus quantitative phase imaging of living cells. In overview, several methods for digital holographic microscopy (DHM) are presented. First, different experimental setups for the recording of digital holograms and the modular integration of DHM into common microscopes are described. Then the numerical processing of digitally captured holograms is explained. This includes the description of spatial and temporal phase shifting techniques, spatial filtering based reconstruction, holographic autofocusing, and the evaluation of self-interference holograms. Furthermore, the usage of partial coherent light and multi-wavelength approaches is discussed. Finally, potentials of digital holographic microscopy for quantitative cell imaging are illustrated by results from selected applications. It is shown that DHM can be used for automated tracking of migrating cells and cell thickness monitoring as well as for refractive index determination of cells and particles. Moreover, the use of DHM for label-free analysis in fluidics and micro-injection monitoring is demonstrated. The results show that DHM is a highly relevant method that allows novel insights in dynamic cell biology, with applications in cancer research and for drugs and toxicity testing.

Sparsity-based multi-height phase recovery in holographic microscopy

KAUST Repository

Rivenson, Yair

2016-11-30

High-resolution imaging of densely connected samples such as pathology slides using digital in-line holographic microscopy requires the acquisition of several holograms, e.g., at >6–8 different sample-to-sensor distances, to achieve robust phase recovery and coherent imaging of specimen. Reducing the number of these holographic measurements would normally result in reconstruction artifacts and loss of image quality, which would be detrimental especially for biomedical and diagnostics-related applications. Inspired by the fact that most natural images are sparse in some domain, here we introduce a sparsity-based phase reconstruction technique implemented in wavelet domain to achieve at least 2-fold reduction in the number of holographic measurements for coherent imaging of densely connected samples with minimal impact on the reconstructed image quality, quantified using a structural similarity index. We demonstrated the success of this approach by imaging Papanicolaou smears and breast cancer tissue slides over a large field-of-view of ~20 mm2 using 2 in-line holograms that are acquired at different sample-to-sensor distances and processed using sparsity-based multi-height phase recovery. This new phase recovery approach that makes use of sparsity can also be extended to other coherent imaging schemes, involving e.g., multiple illumination angles or wavelengths to increase the throughput and speed of coherent imaging.

Sparsity-based multi-height phase recovery in holographic microscopy

Science.gov (United States)

Rivenson, Yair; Wu, Yichen; Wang, Hongda; Zhang, Yibo; Feizi, Alborz; Ozcan, Aydogan

2016-11-01

High-resolution imaging of densely connected samples such as pathology slides using digital in-line holographic microscopy requires the acquisition of several holograms, e.g., at >6-8 different sample-to-sensor distances, to achieve robust phase recovery and coherent imaging of specimen. Reducing the number of these holographic measurements would normally result in reconstruction artifacts and loss of image quality, which would be detrimental especially for biomedical and diagnostics-related applications. Inspired by the fact that most natural images are sparse in some domain, here we introduce a sparsity-based phase reconstruction technique implemented in wavelet domain to achieve at least 2-fold reduction in the number of holographic measurements for coherent imaging of densely connected samples with minimal impact on the reconstructed image quality, quantified using a structural similarity index. We demonstrated the success of this approach by imaging Papanicolaou smears and breast cancer tissue slides over a large field-of-view of ~20 mm2 using 2 in-line holograms that are acquired at different sample-to-sensor distances and processed using sparsity-based multi-height phase recovery. This new phase recovery approach that makes use of sparsity can also be extended to other coherent imaging schemes, involving e.g., multiple illumination angles or wavelengths to increase the throughput and speed of coherent imaging.

Experimental verification of the rotational type of chiral spin spiral structures by spin-polarized scanning tunneling microscopy.

Science.gov (United States)

Haze, Masahiro; Yoshida, Yasuo; Hasegawa, Yukio

2017-10-16

We report on experimental verification of the rotational type of chiral spin spirals in Mn thin films on a W(110) substrate using spin-polarized scanning tunneling microscopy (SP-STM) with a double-axis superconducting vector magnet. From SP-STM images using Fe-coated W tips magnetized to the out-of-plane and [001] directions, we found that both Mn mono- and double-layers exhibit cycloidal rotation whose spins rotate in the planes normal to the propagating directions. Our results agree with the theoretical prediction based on the symmetry of the system, supporting that the magnetic structures are driven by the interfacial Dzyaloshinskii-Moriya interaction.

Strain-induced phase transition and electron spin-polarization in graphene spirals.

Science.gov (United States)

Zhang, Xiaoming; Zhao, Mingwen

2014-07-16

Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices.

Contrast Enhanced Microscopy Digital Image Correlation: A General Method to Contact-Free Coefficient of Thermal Expansion Measurement of Polymer Films

Science.gov (United States)

Jairo A. Diaz; Robert J. Moon; Jeffrey P. Youngblood

2014-01-01

Thermal expansion represents a vital indicator of the processing history and dimensional stability of materials. Solvent-sensitive, thin, and compliant samples are particularly challenging to test. Here we describe how textures highlighted by contrast enhanced optical microscopy modes (i.e., polarized light (PL), phase contrast (PC)) and bright field (BF) can be used...

A study on high NA and evanescent imaging with polarized illumination

Science.gov (United States)

Yang, Seung-Hune

Simulation techniques are developed for high NA polarized microscopy with Babinet's principle, partial coherence and vector diffraction for non-periodic geometries. A mathematical model for the Babinet approach is developed and interpreted. Simulation results of the Babinet's principle approach are compared with those of Rigorous Coupled Wave Theory (RCWT) for periodic structures to investigate the accuracy of this approach and its limitations. A microscope system using a special solid immersion lens (SIL) is introduced to image Blu-Ray (BD) optical disc samples without removing the protective cover layer. Aberration caused by the cover layer is minimized with a truncated SIL. Sub-surface imaging simulation is achieved by RCWT, partial coherence, vector diffraction and Babinet's Principle. Simulated results are compared with experimental images and atomic force microscopy (AFM) measurement. A technique for obtaining native and induced using a significant amount of evanescent energy is described for a solid immersion lens (SIL) microscope. Characteristics of native and induced polarization images for different object structures and materials are studied in detail. Experiments are conducted with a NA = 1.48 at lambda = 550nm microscope. Near-field images are simulated and analyzed with an RCWT approach. Contrast curve versus object spatial frequency calculations are compared with experimental measurements. Dependencies of contrast versus source polarization angles and air gap for native and induced polarization image profiles are evaluated. By using the relationship between induced polarization and topographical structure, an induced polarization image of an alternating phase shift mask (PSM) is converted into a topographical image, which shows very good agreement with AFM measurement. Images of other material structures include a dielectric grating, chrome-on-glass grating, silicon CPU structure, BD-R and BD-ROM.

Combined multi-plane phase retrieval and super-resolution optical fluctuation imaging for 4D cell microscopy

Science.gov (United States)

Descloux, A.; Grußmayer, K. S.; Bostan, E.; Lukes, T.; Bouwens, A.; Sharipov, A.; Geissbuehler, S.; Mahul-Mellier, A.-L.; Lashuel, H. A.; Leutenegger, M.; Lasser, T.

2018-03-01

Super-resolution fluorescence microscopy provides unprecedented insight into cellular and subcellular structures. However, going `beyond the diffraction barrier' comes at a price, since most far-field super-resolution imaging techniques trade temporal for spatial super-resolution. We propose the combination of a novel label-free white light quantitative phase imaging with fluorescence to provide high-speed imaging and spatial super-resolution. The non-iterative phase retrieval relies on the acquisition of single images at each z-location and thus enables straightforward 3D phase imaging using a classical microscope. We realized multi-plane imaging using a customized prism for the simultaneous acquisition of eight planes. This allowed us to not only image live cells in 3D at up to 200 Hz, but also to integrate fluorescence super-resolution optical fluctuation imaging within the same optical instrument. The 4D microscope platform unifies the sensitivity and high temporal resolution of phase imaging with the specificity and high spatial resolution of fluorescence microscopy.

Dipole-Oriented Molecular Solids Can Undergo a Phase Change and Still Maintain Electrical Polarization

Energy Technology Data Exchange (ETDEWEB)

Glavic, Artur G [ORNL; Cassidy, Andrew M [ORNL; Jorgensen, Mads Ry Ry [University of Aarhus, Denmark; Lauter, Valeria [ORNL; Rosu-Finsen, Alexander [Heriot-Watt University, Edinburgh, UK; Lasne, Jérôme [Heriot-Watt University, Edinburgh, UK; Jorgensen, Jakob [Aarhus University, Denmark; Iversen, Bo [ORNL; McCoustra, Martin [Heriot-Watt University, Edinburgh, UK; Field, David [University of Aarhus, Denmark

2016-10-02

It has recently been demonstrated that nanoscale molecular films can spontaneously assemble to self-generate intrinsic electric fields that can exceed 10⁸ V/m. These electric fields originate from polarization charges in the material that arise because the films self-assemble to orient molecular dipole moments. This has been called the spontelectric effect. Such growth of spontaneously polarized layers of molecular solids has implications for our understanding of how intermolecular interactions dictate the structure of molecular materials used in a range of applications, for example, molecular semiconductors, sensors, and catalysts. In this paper, we present the first in situ structural characterization of a representative spontelectric solid, nitrous oxide. Infrared spectroscopy, temperature-programmed desorption, and neutron reflectivity measurements demonstrate that polarized films of nitrous oxide undergo a structural phase transformation upon heating above 48 K. A mean-field model can be used to describe quantitatively the magnitude of the spontaneously generated field as a function of film-growth temperature, and this model also recreates the phase change. Finally, this reinforces the spontelectric model as a means of describing long-range dipole–dipole interactions and points to a new type of ordering in molecular thin films.

Polarity-dependent reversible resistance switching in Ge-Sb-Te phase-change thin films

NARCIS (Netherlands)

Pandian, Ramanathaswamy; Kooi, Bart J.; Palasantzas, George; De Hosson, Jeff T. M.; Pauza, Andrew

2007-01-01

In this paper, we demonstrate reversible resistance switching in a capacitorlike cell using a Ge-Sb-Te film that does not rely on amorphous-crystalline phase change. The polarity of the applied electric field switches the cell resistance between lower- and higher-resistance states, as was observed

Gas-phase synthesis of magnesium nanoparticles : A high-resolution transmission electron microscopy study

NARCIS (Netherlands)

Kooi, B.J.; Palasantzas, G.; de Hosson, J.T.M.

2006-01-01

Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg{1010} facets. Oxidation of Mg yields a MgO shell (similar to 3 nm

Dependence of Polarization of the near-Earth Asteroids (1036) Ganymed and (5143) Heracles on Wavelength and Phase Angle

Science.gov (United States)

Maleszewski, C.; McMillan, R.; Smith, P.

2012-12-01

We are measuring the polarization of asteroids with the SPOL polarimeter of Steward Observatory. With monthly access to the instrument, we can obtain many observations throughout phase angle. This is in contrast to other recent work that had to rely on aggregate properties of targets of similar taxonomic type. Comparing individual objects to these aggregate results may reveal differences of regolith properties from object to object. Both the phase angle and spectral dependence of polarization are being measured. SPOL provides simultaneous coverage from 0.40-0.75 microns, equivalent to BVR filters. Three phase curves thus reveal differences of phase angle dependences with respect to wavelength. The spectral dependence of the linear polarization is determined according to a linear trend previously used to describe the dependence for Main Belt Asteroids (MBAs) in various taxonomic classes (Belskaya et al. 2009). The slopes of these linear trends vs. phase angle are also investigated as was also done in the Belskaya analysis for MBAs in the C-, M-, and S-types. Two initial objects of interest are the NEAs (1036) Ganymed and (5143) Heracles. The taxonomic types of Ganymed and Heracles are S-type and Q-type respectively (DeMeo et al. 2009). For Ganymed, twelve observations were made between 2011 September and 2012 March. These include observations below ten degrees phase angle, which are currently lacking in the polarimetric databases. The positive branch of Ganymed's polarization phase curve behaved similarly across SPOL's wavelength range. But for wavelengths associated with a typical B-filter, the negative branch is more shallow and narrow. The negative phase branch of Ganymed is smaller compared to the aggregate phase curve of S-types determined by Gil-Hutton and Cañada-Assandri (2011). The linear polarization decreases with increasing wavelength at all observed phase angles. As the phase angle increases, the slope of the wavelength dependence of polarization

Polarization-independent broadband meta-holograms via polarization-dependent nanoholes.

Science.gov (United States)

Zhang, Xiaohu; Li, Xiong; Jin, Jinjin; Pu, Mingbo; Ma, Xiaoliang; Luo, Jun; Guo, Yinghui; Wang, Changtao; Luo, Xiangang

2018-05-17

Composed of ultrathin metal or dielectric nanostructures, metasurfaces can manipulate the phase, amplitude and polarization of electromagnetic waves at a subwavelength scale, which is promising for flat optical devices. In general, metasurfaces composed of space-variant anisotropic units are sensitive to the incident polarization due to the inherent polarization dependent geometric phase. Here, we implement polarization-independent broadband metasurface holograms constructed by polarization-dependent anisotropic elliptical nanoholes by elaborate design of complex amplitude holograms. The fabricated meta-hologram exhibits a polarization insensitive feature with an acceptable image quality. We verify the feasibility of the design algorithm for three-dimensional (3D) meta-holograms with simulation and the feasibility for two-dimensional (2D) meta-holograms is experimentally demonstrated at a broadband wavelength range from 405 nm to 632.8 nm. The effective polarization-independent broadband complex wavefront control with anisotropic elliptical nanoholes proposed in this paper greatly promotes the practical applications of the metasurface in technologies associated with wavefront manipulation, such as flat lens, colorful holographic displays and optical storage.

Deleterious phases precipitation on superduplex stainless steel UNS S32750: characterization by light optical and scanning electron microscopy

Directory of Open Access Journals (Sweden)

Juan Manuel Pardal

2010-09-01

Full Text Available Deleterious phases precipitation in superduplex stainless steels is the main concern in fabrication by welding and hot forming of this class of material. Sigma, chi and secondary austenite phases are considered deleterious phases because they produce negative effects on corrosion resistance. Besides, sigma and chi phases also promote strong decrease of toughness. In the present work, the precipitations of sigma, chi and secondary austenite under aging in the 800-950 °C interval were studied in two UNS S32750 steels with different grain sizes. The deleterious phases could be quantified by light optical microscopy, with no distinction between them. Scanning electron microscopy was used to distinguish the individual phases in various aging conditions. The results elucidate the influence of the aging temperature and grain size on the kinetics precipitation and morphology of deleterious phases. The kinetics of deleterious phases is higher in the fine grained material in the initial stage of aging, but the maximum amount of deleterious phases is higher in the coarse grained steel.

Circularly polarized light emission in scanning tunneling microscopy of magnetic systems

International Nuclear Information System (INIS)

Apell, S.P.; Penn, D.R.; Johansson, P.

2000-01-01

Light is produced when a scanning tunneling microscope is used to probe a metal surface. Recent experiments on cobalt utilizing a tungsten tip found that the light is circularly polarized; the sense of circular polarization depends on the direction of the sample magnetization, and the degree of polarization is of order 10%. This raises the possibility of constructing a magnetic microscope with very good spatial resolution. We present a theory of this effect for iron and cobalt and find a degree of polarization of order 0.1%. This is in disagreement with the experiments on cobalt as well as previous theoretical work which found order of magnitude agreement with the experimental results. However, a recent experiment on iron showed 0.0±2%. We predict that the use of a silver tip would increase the degree of circular polarization for a range of photon energies

Spatiotemporal polarization gradients in phase-bearing light

International Nuclear Information System (INIS)

Lembessis, V. E.; Babiker, M.

2010-01-01

It is shown how the interference of two circularly polarized laser beams endowed with orbital angular momentum can give rise to spatial and temporal polarization gradients, displaying axial as well as angular symmetry properties. Illustrations are given with reference to circularly polarized Laguerre-Gaussian beams as typical light beams carrying orbital angular momentum.

Photon-counting-based diffraction phase microscopy combined with single-pixel imaging

Science.gov (United States)

Shibuya, Kyuki; Araki, Hiroyuki; Iwata, Tetsuo

2018-04-01

We propose a photon-counting (PC)-based quantitative-phase imaging (QPI) method for use in diffraction phase microscopy (DPM) that is combined with a single-pixel imaging (SPI) scheme (PC-SPI-DPM). This combination of DPM with the SPI scheme overcomes a low optical throughput problem that has occasionally prevented us from obtaining quantitative-phase images in DPM through use of a high-sensitivity single-channel photodetector such as a photomultiplier tube (PMT). The introduction of a PMT allowed us to perform PC with ease and thus solved a dynamic range problem that was inherent to SPI. As a proof-of-principle experiment, we performed a comparison study of analogue-based SPI-DPM and PC-SPI-DPM for a 125-nm-thick indium tin oxide (ITO) layer coated on a silica glass substrate. We discuss the basic performance of the method and potential future modifications of the proposed system.

Transmission electron microscopy studies on nanometer-sized ω phase produced in Gum Metal

International Nuclear Information System (INIS)

Yano, Takaaki; Murakami, Yasukazu; Shindo, Daisuke; Hayasaka, Yuichiro; Kuramoto, Shigeru

2010-01-01

The morphology, numerical density and average spacing of the ω phase formed in Gum Metal, a Ti-based alloy showing unique mechanical properties, were studied by transmission electron microscopy. Based on dark-field image observations and precise thickness measurements using a thin-foil specimen, the average spacing of the nanometer-sized ω phase was determined to be 6 nm. This spacing appeared to be sufficiently small for trapping dislocations. The results are discussed in conjunction with the dislocation-free deformation mechanism proposed for Gum Metal.

Microstructure influence on corrosion behavior of a Fe–Cr–V–N tool alloy studied by SEM/EDS, scanning Kelvin force microscopy and electrochemical measurement

International Nuclear Information System (INIS)

Sababi, Majid; Ejnermark, Sebastian; Andersson, Jörgen; Claesson, Per M.; Pan, Jinshan

2013-01-01

Highlights: ► Localized corrosion of a new N-based tool alloy (Fe–Cr–V–N) has been studied. ► One-pass mode of scanning Kelvin force microscopy (KFM) was used in the study. ► The focus was on correlation between microstructure and localized corrosion. - Abstract: Microstructure influence on corrosion behavior of an N-based tool alloy (Fe–Cr–V–N) has been studied. Electron microscopy analysis showed two types of hard phases in the alloy. One-pass mode scanning Kelvin force microscopy (KFM) was used to investigate relative nobility of the hard phases. Volta potential mapping indicates higher nobility for the hard phases than the alloy matrix, and, the V- and N-rich particles exhibit the highest Volta potential. Post-polarization analysis by SEM revealed localized dissolution initiated in matrix regions adjacent to hard phase particles, and the boundary region surrounding the Cr- and Mo-rich particles is more prone to localized corrosion.

Theoretical investigation of confocal microscopy using an elliptically polarized cylindrical vector laser beam: Visualization of quantum emitters near interfaces

Science.gov (United States)

Boichenko, Stepan

2018-04-01

We theoretically study laser-scanning confocal fluorescence microscopy using elliptically polarized cylindrical vector excitation light as a tool for visualization of arbitrarily oriented single quantum dipole emitters located (1) near planar surfaces enhancing fluorescence, (2) in a thin supported polymer film, (3) in a freestanding polymer film, and (4) in a dielectric planar microcavity. It is shown analytically that by using a tightly focused azimuthally polarized beam, it is possible to exclude completely the orientational dependence of the image intensity maximum of a quantum emitter that absorbs light as a pair of incoherent independent linear dipoles. For linear dipole quantum emitters, the orientational independence degree higher than 0.9 can normally be achieved (this quantity equal to 1 corresponds to completely excluded orientational dependence) if the collection efficiency of the microscope objective and the emitter's total quantum yield are not strongly orientationally dependent. Thus, the visualization of arbitrarily oriented single quantum emitters by means of the studied technique can be performed quite efficiently.

Digital holographic microscopy of phase separation in multicomponent lipid membranes

Science.gov (United States)

Farzam Rad, Vahideh; Moradi, Ali-Reza; Darudi, Ahmad; Tayebi, Lobat

2016-12-01

Lateral in-homogeneities in lipid compositions cause microdomains formation and change in the physical properties of biological membranes. With the presence of cholesterol and mixed species of lipids, phospholipid membranes segregate into lateral domains of liquid-ordered and liquid-disordered phases. Coupling of two-dimensional intralayer phase separations and interlayer liquid-crystalline ordering in multicomponent membranes has been previously demonstrated. By the use of digital holographic microscopy (DHMicroscopy), we quantitatively analyzed the volumetric dynamical behavior of such membranes. The specimens are lipid mixtures composed of sphingomyelin, cholesterol, and unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine. DHMicroscopy in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes, three-dimensional information on the morphology variation of lipid stacks at arbitrary time scales is obtained. Moreover, the thickness distribution of the object at demanded axial planes can be obtained by numerical focusing. Our results show that the volume evolution of lipid domains follows approximately the same universal growth law of previously reported area evolution. However, the thickness of the domains does not alter significantly by time; therefore, the volume evolution is mostly attributed to the changes in area dynamics. These results might be useful in the field of membrane-based functional materials.

submitter Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

CERN Document Server

Nichman, Leonid; Järvinen, Emma; Ignatius, Karoliina; Höppel, Niko Florian; Dias, Antonio; Heinritzi, Martin; Simon, Mario; Tröstl, Jasmin; Wagner, Andrea Christine; Wagner, Robert; Williamson, Christina; Yan, Chao; Connolly, Paul James; Dorsey, James Robert; Duplissy, Jonathan; Ehrhart, Sebastian; Frege, Carla; Gordon, Hamish; Hoyle, Christopher Robert; Kristensen, Thomas Bjerring; Steiner, Gerhard; McPherson Donahue, Neil; Flagan, Richard; Gallagher, Martin William; Kirkby, Jasper; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Stratmann, Frank; Tomé, António

2016-01-01

Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary ...

Macroscopic Ensembles of Aligned Carbon Nanotubes in Bubble Imprints Studied by Polarized Raman Microscopy

Directory of Open Access Journals (Sweden)

Shota Ushiba

2014-01-01

Full Text Available We study the alignment of single-wall carbon nanotubes (SWCNTs in bubble imprints through polarized Raman microscopy. A hemispherical bubble containing SWCNTs is pressed against a glass substrate, resulting in an imprint of the bubble membrane with a coffee ring on the substrate. We find that macroscopic ensembles of aligned SWCNTs are obtained in the imprints, in which there are three patterns of orientations: (i azimuthal alignment on the coffee ring, (ii radial alignment at the edge of the membrane, and (iii random orientation at the center of the membrane. We also find that the alignment of SWCNTs in the imprints can be manipulated by spinning bubbles. The orientation of SWCNTs on the coffee ring is directed radially, which is orthogonal to the case of unspun bubbles. This approach enables one to align SWCNTs in large quantities and in a short time, potentially opening up a wide range of CNT-based electronic and optical applications.

Mobile phase effects on the retention on polar columns with special attention to the dual hydrophilic interaction-reversed-phase liquid chromatography mechanism, a review.

Science.gov (United States)

Jandera, Pavel; Hájek, Tomáš

2018-01-01

Hydrophilic interaction liquid chromatography on polar columns in aqueous-organic mobile phases has become increasingly popular for the separation of many biologically important compounds in chemical, environmental, food, toxicological, and other samples. In spite of many new applications appearing in literature, the retention mechanism is still controversial. This review addresses recent progress in understanding of the retention models in hydrophilic interaction liquid chromatography. The main attention is focused on the role of water, both adsorbed by the column and contained in the bulk mobile phase. Further, the theoretical retention models in the isocratic and gradient elution modes are discussed. The dual hydrophilic interaction liquid chromatography reversed-phase retention mechanism on polar columns is treated in detail, especially with respect to the practical use in one- and two-dimensional liquid chromatography separations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Visualizing the phenomena of wave interference, phase-shifting and polarization by interactive computer simulations

Science.gov (United States)

Rivera-Ortega, Uriel; Dirckx, Joris

2015-09-01

In this manuscript a computer based simulation is proposed for teaching concepts of interference of light (under the scheme of a Michelson interferometer), phase-shifting and polarization states. The user can change some parameters of the interfering waves, such as their amplitude and phase difference in order to graphically represent the polarization state of a simulated travelling wave. Regarding to the interference simulation, the user is able to change the wavelength and type of the interfering waves by selecting combinations between planar and Gaussian profiles, as well as the optical path difference by translating or tilting one of the two mirrors in the interferometer setup, all of this via a graphical user interface (GUI) designed in MATLAB. A theoretical introduction and simulation results for each phenomenon will be shown. Due to the simulation characteristics, this GUI can be a very good non-formal learning resource.

INFLUENCE OF POLARIZATION MODE DISPERSION ON THE EFFECT OF CROSS-PHASE MODULATION IN INTENSITY MODULATION-DIRECT DETECTION WDM TRANSMISSION SYSTEM

Directory of Open Access Journals (Sweden)

M S Islam

2010-03-01

Full Text Available Cross-phase modulation (XPM changes the state-of-polarization (SOP of the channels through nonlinear polarization rotation and induces nonlinear time dependent phase shift for polarization components that leads to amplitude modulation of the propagating waves in a wavelength division multiplexing (WDM system. Due to the presence of birefringence, the angle between the SOP changes randomly and as a result polarization mode dispersion (PMD causes XPM modulation amplitude fluctuation random in the perturbed channel. In this paper we analytically determine the probability density function of the random angle between the SOP of pump and probe, and evaluate the impact of polarization mode dispersion on XPM in terms of bit error rate, channel spacing etc for a two channel intensity modulation-direct detection WDM system at 10 Gb/s. It is found that the XPM induced crosstalk is polarization independent for channel spacing greater than 3 nm or PMD coefficient larger than 2 ps/√km. We also investigate the dependence of SOP variance on PMD coefficient and channel spacing.

Polarization Sensitive Coherent Raman Measurements of DCVJ

Science.gov (United States)

Anderson, Josiah; Cooper, Nathan; Lawhead, Carlos; Shiver, Tegan; Ujj, Laszlo

2014-03-01

Coherent Raman spectroscopy which recently developed into coherent Raman microscopy has been used to produce label free imaging of thin layers of material and find the spatial distributions of certain chemicals within samples, e.g. cancer cells.(1) Not all aspects of coherent scattering have been used for imaging. Among those for example are special polarization sensitive measurements. Therefore we have investigated the properties of polarization sensitive CARS spectra of a highly fluorescent molecule, DCVJ.(2) Spectra has been recorded by using parallel polarized and perpendicular polarized excitations. A special polarization arrangement was developed to suppress the non-resonant background scattering from the sample. These results can be used to improve the imaging properties of a coherent Raman microscope in the future. This is the first time coherent Raman polarization sensitive measurements have been used to characterize the vibrational modes of DCVJ. 1: K. I. Gutkowski, et al., ``Fluorescence of dicyanovinyl julolidine in a room temperature ionic liquid '' Chemical Physics Letters 426 (2006) 329 - 333 2: Fouad El-Diasty, ``Coherent anti-Stokes Raman scattering: Spectroscopy and microscopy'' Vibrational Spectroscopy 55 (2011) 1-37

Effect of Beam Scanning on Target Polarization Scattering Matrix Observed by Fully Polarimetric Phased-array Radar

Directory of Open Access Journals (Sweden)

Li Mianquan

2016-04-01

Full Text Available The polarization feature of a fully Polarimetric Phased-Array Radar (PPAR antenna varies according to the beam-scanning angle, thereby introducing two problems on the target Polarization Scattering Matrix (PSM measurement. First, the antenna polarization basis is defined within the vertical cross-section of an electromagnetic wave propagation direction, and the polarization basis of each beam direction angle is not identical, resulting in the PSM of a fixed-posture target observed by PPAR being not identical for different beam-scanning angles. Second, the cross polarization of the PPAR antenna increases with increasing beamscanning angle, resulting in a crosstalk among the elements of PSM observed by PPAR. This study focuses on the analysis of the abovementioned two aspects of the effect of beam scanning on target PSM observed by PPAR. The results will establish a more accurate observation of the equation for the precision PSM measurement of PPAR.

Organic high ionic strength aqueous two-phase solvent system series for separation of ultra-polar compounds by spiral high-speed counter-current chromatography

Science.gov (United States)

Zeng, Yun; Liu, Gang; Ma, Ying; Chen, Xiaoyuan; Ito, Yoichiro

2011-01-01

Existing two-phase solvent systems for high-speed countercurrent chromatography cover the separation of hydrophobic to moderately polar compounds, but often fail to provide suitable partition coefficient values for highly polar compounds such as sulfonic acids, catecholamines and zwitter ions. The present paper introduces a new solvent series which can be applied for the separation of these polar compounds. It is composed of 1-butanol, ethanol, saturated ammonium sulfate and water at various volume ratios and consists of a series of 10 steps which are arranged according to the polarity of the solvent system so that the two-phase solvent system with suitable K values for the target compound(s) can be found in a few steps. Each solvent system gives proper volume ratio and high density difference between the two phases to provide a satisfactory level of retention of the stationary phase in the spiral column assembly. The method is validated by partition coefficient measurement of four typical polar compounds including methyl green (basic dye), tartrazine (sulfonic acid), tyrosine (zwitter ion) and epinephrine (a catecholamine), all of which show low partition coefficient values in the polar 1-butanol-water system. The capability of the method is demonstrated by separation of three catecholamines. PMID:22033108

Sequential processing of quantitative phase images for the study of cell behaviour in real-time digital holographic microscopy.

Science.gov (United States)

Zikmund, T; Kvasnica, L; Týč, M; Křížová, A; Colláková, J; Chmelík, R

2014-11-01

Transmitted light holographic microscopy is particularly used for quantitative phase imaging of transparent microscopic objects such as living cells. The study of the cell is based on extraction of the dynamic data on cell behaviour from the time-lapse sequence of the phase images. However, the phase images are affected by the phase aberrations that make the analysis particularly difficult. This is because the phase deformation is prone to change during long-term experiments. Here, we present a novel algorithm for sequential processing of living cells phase images in a time-lapse sequence. The algorithm compensates for the deformation of a phase image using weighted least-squares surface fitting. Moreover, it identifies and segments the individual cells in the phase image. All these procedures are performed automatically and applied immediately after obtaining every single phase image. This property of the algorithm is important for real-time cell quantitative phase imaging and instantaneous control of the course of the experiment by playback of the recorded sequence up to actual time. Such operator's intervention is a forerunner of process automation derived from image analysis. The efficiency of the propounded algorithm is demonstrated on images of rat fibrosarcoma cells using an off-axis holographic microscope. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

Electron microscopy and phase analysis of fly ash from pressurized fluidized bed combustion

International Nuclear Information System (INIS)

Maenami, Hiroki; Isu, Norifumi; Ishida, Emile H.; Mitsuda, Takeshi

2004-01-01

The characterization of the typical fly ashes from pressurized fluidized bed combustion system (PFBC) in Japan and Europe was carried out by electron microscopy and phase analysis using energy-dispersive X-ray spectroscopy (EDX). The purity of limestone as in-bed sulfur removal sorbent influences the desulfurization reaction. The high-purity limestone yielded both hydroxyl ellestadite and anhydrite in Japanese PFBC ashes, while dolomite-rich limestone yielded anhydrite in European PFBC ashes. When the high-purity limestone was used, hydroxyl ellestadite particles were observed as the independent particles or the rim around limestone particles. The Al 2 O 3 content in the glassy phase was inversely proportional to the CaO content in the glassy phase, suggesting that the glassy phases were formed from metakaoline and calcite as end members. Since hydroxyl ellestadite, glassy phase and metakaoline are reactive under hydrothermal conditions, PFBC ashes are expected to be used as raw materials for autoclaved products

Electron microscopy analyses and electrical properties of the layered Bi2WO6 phase

International Nuclear Information System (INIS)

Taoufyq, A.; Ait Ahsaine, H.; Patout, L.; Benlhachemi, A.; Ezahri, M.

2013-01-01

The bismuth tungstate Bi 2 WO 6 was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2 1 non centrosymmetric space group previously proposed for this phase. The layers Bi 2 O 2 2+ and WO 4 2− have been directly evidenced from the HRTEM images. The electrical properties of Bi 2 WO 6 compacted pellets systems were determined from electrical impedance spectrometry (EIS) and direct current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi 2 WO 6 phase, with a representation of the cell dimensions (b and c vectors). The Bi 2 O 2 2+ and WO 4 2− sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi 2 WO 6 . • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification

Crystallography and Molecular Arrangement of Polymorphic Monolayer J-Aggregates of a Cyanine Dye: Multiangle Polarized Light Fluorescence Optical Microscopy Study.

Science.gov (United States)

Prokhorov, Valery V; Pozin, Sergey I; Perelygina, Olga M; Mal'tsev, Eugene I

2018-04-24

The molecular orientation in monolayer J-aggregates of 3,3-di(γ-sulfopropyl)-5,5-dichlorotiamonomethinecyanine dye has been precisely estimated using improved linear polarization measurements in the fluorescence microscope in which a multiangle set of polarization data is obtained using sample rotation. The estimated molecular orientation supplemented with the previously established crystallographic constraints based on the analysis of the well-developed two-dimensional J-aggregate shapes unambiguously indicate the staircase type of molecular arrangement for striplike J-aggregates with the staircases oriented along strips. The molecular transition dipoles are inclined at an angle of ∼25° to the strip direction, whereas the characteristic strip vertex angle ∼45° is formed by the [100] and [1-10] directions of the monoclinic unit cell. Measurements of the geometry of partially unwound tubes and their polarization properties support the model of tube formation by close-packed helical winding of flexible monolayer strips. In the tubes, the long molecular axes are oriented at a small angle in the range of 5-15° to the normal to the tube axis providing low bending energy. At a nanoscale, high-resolution atomic force microscopy imaging of J-aggregate monolayers reveals a complex quasi-one-dimensional organization.

NMR study of hyper-polarized 129Xe and applications to liquid-phase NMR experiments

International Nuclear Information System (INIS)

Marion, D.

2008-07-01

In liquid samples where both nuclear polarization and spin density are strong, the magnetization dynamics, which can be analysed by NMR (nuclear magnetic resonance) methods, is deeply influenced by the internal couplings induced by local dipolar fields. The present thesis describes some of the many consequences associated to the presence in the sample of concentrated xenon hyper-polarized by an optical pumping process. First, we deal with the induced modifications in frequency and line width of the proton and xenon spectra, then we present the results of SPIDER, a coherent polarization transfer experiment designed to enhance the polarization of protons, in order to increase their NMR signal level. A third part is dedicated to the description of the apparition of repeated chaotic maser emissions by un unstable xenon magnetization coupled to the detection coil tuned at the xenon Larmor frequency (here 138 MHz). In the last part, we present a new method allowing a better tuning of any NMR detection probe and resulting in sensible gains in terms of sensitivity and signal shaping. Finally, we conclude with a partial questioning of the classical relaxation theory in the specific field of highly polarized and concentrated spin systems in a liquid phase. (author)

Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy

NARCIS (Netherlands)

Prins, M.W.J.; Jansen, R.; Kempen, van H.

1996-01-01

We describe a model as well as experiments on spin-polarized tunneling with the aid of optical spin orientation. This involves tunnel junctions between a magnetic material and gallium arsenide (GaAs), where the latter is optically excited with circularly polarized light in order to generate

Cryogenic scanning laser microscopy. Investigation of large BSCCO mesas and development of a polarizing microscope

International Nuclear Information System (INIS)

Guenon, Stefan Alexander

2011-01-01

confirmed that the frequency of the emitted radiation and the bias voltage is determined by the Josephson relation for a wide range of different base temperatures. This way other mechanisms, causing THz radiation, rather than the Josephson effect can be excluded. Concerning the second part: Originally it was planned to extend the low-temperature scanning laser microscope with the facility of polarizing microscopy. The idea was to combine the LTSLM voltage imaging with the possibility of magneto-optical imaging. But it soon turned out that a new design would be necessary. A laser scanning polarizing microscope has certain advantages in comparison with a conventional polarizing microscope: Very high illumination intensities can be reached easily, the resolution can be improved by the factor 1.4 if a confocal optical design is used, and the serial signal processing facilitates the optimization of the signal-to-noise ratio. In addition, it is usually not necessary to remove the contrast of non-magnetic origin by subtracting an image of the uniform magnetized sample from the image of interest. In this thesis a design for a cryogenic scanning polarizing microscope (CSPM) is discussed in detail, tests and first results of the system are presented, and an outlook is given how two proceed with this project.

Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles

Science.gov (United States)

Kazemzadeh, Farnoud; Wong, Alexander

2016-12-01

Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

Characterisation of phases in nanostructured, multilayered titanium alloys by analytical and high-resolution electron microscopy.

Science.gov (United States)

Czyrska-Filemonowicz, A; Buffat, P A

2009-01-01

Surface processing of a Ti-6Al-4V alloy led to a complex multilayered microstructure containing several phases of the Ni-Ti-P-Al-O system, which improves the mechanical and tribological surface properties. The microstructure, chemical and phase compositions of the hard layer formed on the surface were investigated by LM, XRD, SEM as well as analytical/high-resolution TEM, STEM, EDS, electron diffraction and FIB. Phase identification based on electron diffraction, HRTEM and EDS microanalysis revealed the presence of several binary and ternary phases in the system Ti-Ni-P, sometimes with partial substitution of Ti by Al. However some phases, mainly nanoparticles, still remain not identified satisfactorily. Electron microscopy techniques used for identification of phases present in surface multilayers and some practical limits to their routine application are reminded here.

Field-induced magnetic phases and electric polarization in LiNiPO4

DEFF Research Database (Denmark)

Jensen, Thomas Bagger Stibius; Christensen, Niels Bech; Kenzelmann, M.

2009-01-01

Neutron diffraction is used to probe the (H,T) phase diagram of magnetoelectric (ME) LiNiPO4 for magnetic fields along the c axis. At zero field the Ni spins order in two antiferromagnetic phases. One has commensurate (C) structures and general ordering vectors k(C)=(0,0,0); the other one...... is incommensurate (IC) with k(IC)=(0,q,0). At low temperatures the C order collapses above mu H-0=12 T and adopts an IC structure with modulation vector parallel to k(IC). We show that C order is required for the ME effect and establish how electric polarization results from a field-induced reduction in the total...

Self-interference fluorescence microscopy with three-phase detection for depth-resolved confocal epi-fluorescence imaging.

Science.gov (United States)

Braaf, Boy; de Boer, Johannes F

2017-03-20

Three-dimensional confocal fluorescence imaging of in vivo tissues is challenging due to sample motion and limited imaging speeds. In this paper a novel method is therefore presented for scanning confocal epi-fluorescence microscopy with instantaneous depth-sensing based on self-interference fluorescence microscopy (SIFM). A tabletop epi-fluorescence SIFM setup was constructed with an annular phase plate in the emission path to create a spectral self-interference signal that is phase-dependent on the axial position of a fluorescent sample. A Mach-Zehnder interferometer based on a 3 × 3 fiber-coupler was developed for a sensitive phase analysis of the SIFM signal with three photon-counter detectors instead of a spectrometer. The Mach-Zehnder interferometer created three intensity signals that alternately oscillated as a function of the SIFM spectral phase and therefore encoded directly for the axial sample position. Controlled axial translation of fluorescent microsphere layers showed a linear dependence of the SIFM spectral phase with sample depth over axial image ranges of 500 µm and 80 µm (3.9 × Rayleigh range) for 4 × and 10 × microscope objectives respectively. In addition, SIFM was in good agreement with optical coherence tomography depth measurements on a sample with indocyanine green dye filled capillaries placed at multiple depths. High-resolution SIFM imaging applications are demonstrated for fluorescence angiography on a dye-filled capillary blood vessel phantom and for autofluorescence imaging on an ex vivo fly eye.

Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

International Nuclear Information System (INIS)

Wang, Y.P.; Zhou, L.; Zhang, M.F.; Chen, X.Y.; Liu, J.-M.; Liu, Z.G.

2004-01-01

Single-phased ferroelectromagnet BiFeO 3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 deg. C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm 2 , 4.0 μC/cm 2 , and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe 2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials

Coherent Raman Imaging of Live Muscle Sarcomeres Assisted by SFG Microscopy.

Science.gov (United States)

Kim, Hyunmin; Kim, Do-Young; Joo, Kyung-Il; Kim, Jung-Hye; Jeong, Soon Moon; Lee, Eun Seong; Hahm, Jeong-Hoon; Kim, Kyuhyung; Moon, Dae Woon

2017-08-23

In this study, we used spectrally focused coherent anti-Stokes Raman scattering (spCARS) microscopy assisted by sum-frequency generation (SFG) to monitor the variations in the structural morphology and molecular vibrations of a live muscle of Caenorhabditis elegans. The subunits of the muscle sarcomeres, such as the M-line, myosin, dense body, and α-actinin, were alternatively observed using spCARS microscopy for different sample orientations, with the guidance of a myosin positional marker captured by SFG microscopy. Interestingly enough, the beam polarization dependence of the spCARS contrasts for two parallel subunits (dense body and myosin) showed a ~90° phase difference. The chemically sensitive spCARS spectra induced by the time-varying overlap of two pulses allowed (after a robust subtraction of the non-resonant background using a modified Kramers-Krönig transformation method) high-fidelity detection of various genetically modified muscle sarcomeres tuned to the C-H vibration (2800-3100 cm -1 ). Conversely, SFG image mapping assisted by phase-retrieved spCARS spectra also facilitated label-free monitoring of the changes in the muscle content of C. elegans that are associated with aging, based on the hypothesis that the C-H vibrational modes could serve as qualitative chemical markers sensitive to the amount and/or structural modulation of the muscle.

Ultra-thin, single-layer polarization rotator

Directory of Open Access Journals (Sweden)

T. V. Son

2016-08-01

Full Text Available We demonstrate light polarization control over a broad spectral range by a uniform layer of vanadium dioxide as it undergoes a phase transition from insulator to metal. Changes in refractive indices create unequal phase shifts on s- and p-polarization components of incident light, and rotation of linear polarization shows intensity modulation by a factor of 103 when transmitted through polarizers. This makes possible polarization rotation devices as thin as 50 nm that would be activated thermally, optically or electrically.

Spin-polarized scanning tunneling microscopy and spectroscopy study of chromium on a Cr(001) surface.

Science.gov (United States)

Lagoute, J; Kawahara, S L; Chacon, C; Repain, V; Girard, Y; Rousset, S

2011-02-02

Several tens of chromium layers were deposited at 250 °C on a Cr(001) surface and investigated by spin-polarized scanning tunneling microscopy (SP-STM), Auger electron spectroscopy (AES) and scanning tunneling spectroscopy (STS). Chromium is found to grow with a mound-like morphology resulting from the stacking of several monolayers which do not uniformly cover the whole surface of the substrate. The terminal plane consists of an irregular array of Cr islands with lateral sizes smaller than 20 × 20 nm(2). Combined AES and STS measurements reveal the presence of a significant amount of segregants prior to and after deposition. A detailed investigation of the surface shows that it consists of two types of patches. Thanks to STS measurements, the two types of area have been identified as being either chromium pure or segregant rich. SP-STM experiments have evidenced that the antiferromagnetic layer coupling remains in the chromium mounds after deposition and is not significantly affected by the presence of the segregants.

Solid Phase Characterization of Tank 241-AY-102 Annulus Space Particulate

Energy Technology Data Exchange (ETDEWEB)

Cooke, G. A.

2013-01-30

The Special Analytical Studies Group at the 222-S Laboratory (222-S) examined the particulate recovered from a series of samples from the annular space of tank 241-AY-102 (AY-102) using solid phase characterization (SPC) methods. These include scanning electron microscopy (SEM) using the ASPEX®1 scanning electron microscope, X-ray diffraction (XRD) using the Rigaku®2 MiniFlex X-ray diffractometer, and polarized light microscopy (PLM) using the Nikon®3 Eclipse Pol optical microscope. The SEM is equipped with an energy dispersive X-ray spectrometer (EDS) to provide chemical information.

Phase-shifting Real-time Holographic Microscopy applied in micro-structures surface analysis

International Nuclear Information System (INIS)

Brito, I V; Gesualdi, M R R; Muramatsu, M; Ricardo, J

2011-01-01

The microscopic real-time analysis of micro structured materials is of great importance in various domains of science and technology. For other hand, the holographic interferometry comprises a group of powerful optical methods for non-destructive testing in surface analysis. The holographic microscopy uses the holographic interferometric techniques to obtain quantitative intensity and phase information of the optical waves by microscopic systems. With the development of CCD cameras, computers (hardware and software), and new materials for holographic recording, these techniques can be used to replace the classical form of registration and became promising tools in surface analysis. In this work, we developed a prototype of Photorefractive and Digital Holographic Microscope for real-time analysis of micro-structured systems based on the phase-shifting real-time holographic interferometry techniques. Using this apparatus, we are made analysis of shapes and surfaces to obtain the phase maps and the 3D profiles of some samples.

Phase dispersion of Raman and Rayleigh-enhanced four-wave mixings in femtosecond polarization beats

International Nuclear Information System (INIS)

Yan, Zhao; Zhi-Qiang, Nie; Chang-Biao, Li; Yan-Peng, Zhang; Chen-Li, Gan; Huai-Bin, Zheng; Yuan-Yuan, Li; Ke-Qing, Lu

2009-01-01

Based on color-locking noisy field correlation in three Markovian stochastic models, phase dispersions of the Raman- and Rayleigh-enhanced four-wave mixing (FWM) have been investigated. The phase dispersions are modified by both linewidth and time delay for negative time delay, but only by linewidth for positive time delay. Moreover, the results under narrowband condition are close to the nonmodified nonlinear dispersion and absorption of the material. Homodyne and heterodyne detections of the Raman, the Rayleigh and the mixing femtosecond difference-frequency polarization beats have also been investigated, separately

Direct characterization of phase transformations and morphologies in moving reaction zones in Al/Ni nanolaminates using dynamic transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Kim, J.S., E-mail: judy.kim@materials.ox.ac.uk [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Chemical Engineering and Materials Science/Molecular and Cellular Biology, University of California-Davis, 1 Shields Avenue, Davis, CA 95616 (United States); LaGrange, T.; Reed, B.W. [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Knepper, R.; Weihs, T.P. [Department of Materials Science and Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Browning, N.D. [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Chemical Engineering and Materials Science/Molecular and Cellular Biology, University of California-Davis, 1 Shields Avenue, Davis, CA 95616 (United States); Campbell, G.H. [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States)

2011-05-15

Highlights: > Fast phase transformations are examined in Al/Ni reactive nanolaminates. > Results visible only by dynamic transmission electron microscopy at ns resolution. > NiAl forms under 15 ns after reaction front in all three stoichiometries studied. > DTEM imaging reveals a transient cellular morphology in nonequiatomic films. - Abstract: Phase transformations and transient morphologies are examined as exothermic formation reactions self-propagate across Al/Ni nanolaminate films. The rapid evolution of these phases and sub-micrometer morphological features requires nanoscale temporal and spatial resolution that is not available with traditional in situ electron microscopy. This work uses dynamic transmission electron microscopy to identify intermetallic products and phase morphologies, as exothermic formation reactions self-propagate in nanolaminate films grown with 3:2, 2:3 and 1:1 Al/Ni atomic ratios. Single-shot diffraction patterns with 15 ns temporal resolution reveal that the NiAl intermetallic forms within {approx}15 ns of the reaction front's arrival in all three types of films and is the only intermetallic phase to form, as the reactions self-propagate and quench very rapidly. Time-resolved imaging reveals a transient cellular morphology in the Al-rich and Ni-rich foils, but not in the equiatomic films. The cellular features in the Al-rich and Ni-rich films are attributed to a cooling trajectory through a two-phase field of liquid + NiAl.

Rapid liquid phase sintered Mn doped BiFeO3 ceramics with enhanced polarization and weak magnetization

Science.gov (United States)

Kumar, Manoj; Yadav, K. L.

2007-12-01

Single-phase BiFe1-xMnxO3 multiferroic ceramics have been synthesized by rapid liquid phase sintering method to study the influence of Mn substitution on their crystal structure, dielectric, magnetic, and ferroelectric behaviors. From XRD analysis it is seen that Mn substitution does not affect the crystal structure of the BiFe1-xMnxO3 system. An enhancement in magnetization was observed for BiFe1-xMnxO3 ceramics. However, the ferooelectric hysteresis loops were not really saturated, we observed a spontaneous polarization of 10.23μC /cm2 under the applied field of 42kV/cm and remanent polarization of 3.99μC/cm2 for x =0.3 ceramic.

Label-free investigation of the effects of lithium niobate polarization on cell adhesion

Science.gov (United States)

Mandracchia, B.; Gennari, O.; Paturzo, M.; Grilli, S.; Ferraro, P.

2017-06-01

The determination of contact area is pivotal to understand how biomaterials properties influence cell adhesion. In particular, the influence of surface charges is well-known but still controversial, especially when new functional materials and methods are introduced. Here, we use for the first time Holographic Total Internal Reflection Microscopy (HoloTIRM) to study the influence of the spontaneous polarization of ferroelectric lithium niobate (LN) on the adhesion properties of fibroblast cells. The selective illumination of a very thin region directly above the substrate, achieved by Total Internal Reflection, provides high-contrast images of the contact regions. Holographic recording, on the other hand, allows for label-free quantitative phase imaging of the contact areas between cells and LN. Phase signal is more sensitive in the first 100nm and, thus more reliable in order to locate focal contacts. This work shows that cells adhering on negatively polarized LN present a significant increase of the contact area in comparison with cells adhering on the positively polarized LN substrate, as well as an intensification of contact vicinity. This confirms the potential of LN as a platform for investigating the role of charges on cellular processes. The similarity of cell adhesion behavior on negatively polarized LN and glass control also confirms the possibility to use LN as an active substrate without impairing cell behavior.

Polarization recovery through scattering media.

Science.gov (United States)

de Aguiar, Hilton B; Gigan, Sylvain; Brasselet, Sophie

2017-09-01

The control and use of light polarization in optical sciences and engineering are widespread. Despite remarkable developments in polarization-resolved imaging for life sciences, their transposition to strongly scattering media is currently not possible, because of the inherent depolarization effects arising from multiple scattering. We show an unprecedented phenomenon that opens new possibilities for polarization-resolved microscopy in strongly scattering media: polarization recovery via broadband wavefront shaping. We demonstrate focusing and recovery of the original injected polarization state without using any polarizing optics at the detection. To enable molecular-level structural imaging, an arbitrary rotation of the input polarization does not degrade the quality of the focus. We further exploit the robustness of polarization recovery for structural imaging of biological tissues through scattering media. We retrieve molecular-level organization information of collagen fibers by polarization-resolved second harmonic generation, a topic of wide interest for diagnosis in biomedical optics. Ultimately, the observation of this new phenomenon paves the way for extending current polarization-based methods to strongly scattering environments.

Collagen films with stabilized liquid crystalline phases and concerns on osteoblast behaviors

Energy Technology Data Exchange (ETDEWEB)

Tang, Minjian; Ding, Shan; Min, Xiang; Jiao, Yanpeng, E-mail: tjiaoyp@jnu.edu.cn; Li, Lihua; Li, Hong; Zhou, Changren, E-mail: tcrz9@jnu.edu.cn

2016-01-01

To duplicate collagen's in vivo liquid crystalline (LC) phase and investigate the relationship between the morphology of LC collagen and osteoblast behavior, a self-assembly method was introduced for preparing collagen films with a stabilized LC phase. The LC texture and topological structure of the films before and after stabilization were observed with polarizing optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The relationship between the collagen films and osteoblast behavior was studied with the 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide method, proliferation index detection, alkaline phosphatase measurements, osteocalcin assay, inverted microscopy, SEM observation, AFM observation, and cytoskeleton fluorescence staining. The results showed that the LC collagen film had continuously twisting orientations in the cholesteric phase with a typical series of arced patterns. The collagen fibers assembled in a well-organized orientation in the LC film. Compared to the non-LC film, the LC collagen film can promote cell proliferation, and increase ALP and osteocalcin expression, revealing a contact guide effect on osteoblasts. - Highlights: • Collagen film with liquid crystalline (LC) phase was observed by POM, SEM and AFM. • The effect of LC collagen film on osteoblasts behaviors was studied in detail. • LC collagen film promoted osteoblast proliferation and osteogenesis activity.

Improving the On-Line Extraction of Polar Compounds by IT-SPME with Silica Nanoparticles Modified Phases

Directory of Open Access Journals (Sweden)

Pascual Serra-Mora

2018-02-01

Full Text Available In the present work the extraction efficiency of in-tube solid-phase microextraction (IT-SPME for polar herbicides has been evaluated using extractive capillaries coated with different polymeric sorbents. For this purpose, aqueous solutions of herbicides with a wide range of polarities, including some highly polar compounds (log Kow < 1, have been directly processed by IT-SPME coupled on-line to capillary liquid chromatography with UV-diode array detection. For extraction, commercially available capillary columns coated with polydimethylsiloxane (PDMS and polyetilenglicol (PEG-based phases have been used, and the results have been compared with those obtained with a synthesized tetraethyl orthosilicate (TEOS-trimethoxyethylsilane (MTEOS polymer, as well as the same polymer reinforced with silica nanoparticles (SiO2 NPs. The SiO2 NPs functionalized TEOS-MTEOS coating provided the best results for most herbicides, especially for the most polar compounds. On the basis of the results obtained, conditions for the quantification of the herbicides tested are described using a SiO2 NPs reinforced TEOS-MTEOS coated capillary. The proposed method provided satisfactory linearity up to concentrations of 200 μg/L. The precision was also suitable, with relative standard deviations (RSDs values ≤9% (n = 3, and the limits of detection (LODs were within the 0.5–7.5 µg/L range. The method has been applied to different water samples and the extract obtained from an agricultural soil.

Nonlinear Polarimetric Microscopy for Biomedical Imaging

Science.gov (United States)

Samim, Masood

A framework for the nonlinear optical polarimetry and polarimetric microscopy is developed. Mathematical equations are derived in terms of linear and nonlinear Stokes Mueller formalism, which comprehensively characterize the polarization properties of the incoming and outgoing radiations, and provide structural information about the organization of the investigated materials. The algebraic formalism developed in this thesis simplifies many predictions for a nonlinear polarimetry study and provides an intuitive understanding of various polarization properties for radiations and the intervening medium. For polarimetric microscopy experiments, a custom fast-scanning differential polarization microscope is developed, which is also capable of real-time three-dimensional imaging. The setup is equipped with a pair of high-speed resonant and galvanometric scanning mirrors, and supplemented by advanced adaptive optics and data acquisition modules. The scanning mirrors when combined with the adaptive optics deformable mirror enable fast 3D imaging. Deformable membrane mirrors and genetic algorithm optimization routines are employed to improve the imaging conditions including correcting the optical aberrations, maximizing signal intensities, and minimizing point-spread-functions of the focal volume. A field-programmable-gate array (FPGA) chip is exploited to rapidly acquire and process the multidimensional data. Using the nonlinear optical polarimetry framework and the home-built polarization microscope, a few biologically important tissues are measured and analyzed to gain insight as to their structure and dynamics. The structure and distribution of muscle sarcomere myosins, connective tissue collagen, carbohydrate-rich starch, and fruit fly eye retinal molecules are characterized with revealing polarization studies. In each case, using the theoretical framework, polarization sensitive data are analyzed to decipher the molecular orientations and nonlinear optical

Complementary analyses on the local polarity in lateral polarity-inverted GaN heterostructure on sapphire (0001) substrate

International Nuclear Information System (INIS)

Katayama, Ryuji; Kuge, Yoshihiro; Onabe, Kentaro; Matsushita, Tomonori; Kondo, Takashi

2006-01-01

The fabrication of the lateral polarity-inverted GaN heterostructure on sapphire (0001) using a radio-frequency-plasma-enhanced molecular beam epitaxy is demonstrated. Its microscopic properties such as surface potentials, piezoelectric polarizations, and residual carrier densities were investigated by Kelvin force microscopy and micro-Raman scattering. The inversion from Ga polarity to N polarity in a specific domain and its higher crystal perfection had been unambiguously confirmed by these complementary analyses. The results were also fairly consistent with that of KOH etching, which suggests the applicability of these processes to the fabrication of photonic nanostructures

Deciphering complex, functional structures with synchrotron-based absorption and phase contrast tomographic microscopy

Science.gov (United States)

Stampanoni, M.; Reichold, J.; Weber, B.; Haberthür, D.; Schittny, J.; Eller, J.; Büchi, F. N.; Marone, F.

2010-09-01

Nowadays, thanks to the high brilliance available at modern, third generation synchrotron facilities and recent developments in detector technology, it is possible to record volumetric information at the micrometer scale within few minutes. High signal-to-noise ratio, quantitative information on very complex structures like the brain micro vessel architecture, lung airways or fuel cells can be obtained thanks to the combination of dedicated sample preparation protocols, in-situ acquisition schemes and cutting-edge imaging analysis instruments. In this work we report on recent experiments carried out at the TOMCAT beamline of the Swiss Light Source [1] where synchrotron-based tomographic microscopy has been successfully used to obtain fundamental information on preliminary models for cerebral fluid flow [2], to provide an accurate mesh for 3D finite-element simulation of the alveolar structure of the pulmonary acinus [3] and to investigate the complex functional mechanism of fuel cells [4]. Further, we introduce preliminary results on the combination of absorption and phase contrast microscopy for the visualization of high-Z nanoparticles in soft tissues, a fundamental information when designing modern drug delivery systems [5]. As an outlook we briefly discuss the new possibilities offered by high sensitivity, high resolution grating interferomtery as well as Zernike Phase contrast nanotomography [6].

Digital polarization holography advancing geometrical phase optics.

Science.gov (United States)

De Sio, Luciano; Roberts, David E; Liao, Zhi; Nersisyan, Sarik; Uskova, Olena; Wickboldt, Lloyd; Tabiryan, Nelson; Steeves, Diane M; Kimball, Brian R

2016-08-08

Geometrical phase or the fourth generation (4G) optics enables realization of optical components (lenses, prisms, gratings, spiral phase plates, etc.) by patterning the optical axis orientation in the plane of thin anisotropic films. Such components exhibit near 100% diffraction efficiency over a broadband of wavelengths. The films are obtained by coating liquid crystalline (LC) materials over substrates with patterned alignment conditions. Photo-anisotropic materials are used for producing desired alignment conditions at the substrate surface. We present and discuss here an opportunity of producing the widest variety of "free-form" 4G optical components with arbitrary spatial patterns of the optical anisotropy axis orientation with the aid of a digital spatial light polarization converter (DSLPC). The DSLPC is based on a reflective, high resolution spatial light modulator (SLM) combined with an "ad hoc" optical setup. The most attractive feature of the use of a DSLPC for photoalignment of nanometer thin photo-anisotropic coatings is that the orientation of the alignment layer, and therefore of the fabricated LC or LC polymer (LCP) components can be specified on a pixel-by-pixel basis with high spatial resolution. By varying the optical magnification or de-magnification the spatial resolution of the photoaligned layer can be adjusted to an optimum for each application. With a simple "click" it is possible to record different optical components as well as arbitrary patterns ranging from lenses to invisible labels and other transparent labels that reveal different images depending on the side from which they are viewed.

The atomic structure of polar and non-polar InGaN quantum wells and the green gap problem

Energy Technology Data Exchange (ETDEWEB)

Humphreys, C.J., E-mail: colin.humphreys@msm.cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Griffiths, J.T., E-mail: jg641@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Tang, F., E-mail: ft274@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Oehler, F., E-mail: fabrice.oehler@lpn.cnrs.fr [CNRS/C2N, Paris Sud University, Route de Nozay, 91460 Marcoussis (France); Findlay, S.D., E-mail: scott.findlay@monash.edu [School of Physics and Astronomy, Monash University, Victoria 3800 (Australia); Zheng, C., E-mail: changlin.zheng@monash.edu [Monash Centre for Electron Microscopy, Monash University, Victoria 3800 (Australia); Etheridge, J., E-mail: joanne.etheridge@mcem.monash.edu [Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Martin, T.L., E-mail: tomas.martin@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Bagot, P.A.J., E-mail: paul.bagot@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Moody, M.P., E-mail: michael.moody@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Sutherland, D., E-mail: danny.sutherland@manchester.ac.uk [School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Dawson, P., E-mail: philip.dawson@manchester.ac.uk [School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Schulz, S., E-mail: stefan.schulz@tyndall.ie [Tyndall National Institute, Lee Maltings Complex, Dyke Parade, Cork (Ireland); and others

2017-05-15

Highlights: • We have studied the atomic structure of polar and non-polar InGaN quantum wells. • The non-polar (11-20) InGaN quantum wells contain indium-rich clusters, unlike the polar (0001) quantum wells. • The electrons and holes in the quantum wells are localised by different mechanisms. - Abstract: We have used high resolution transmission electron microscopy (HRTEM), aberration-corrected quantitative scanning transmission electron microscopy (Q-STEM), atom probe tomography (APT) and X-ray diffraction (XRD) to study the atomic structure of (0001) polar and (11-20) non-polar InGaN quantum wells (QWs). This paper provides an overview of the results. Polar (0001) InGaN in QWs is a random alloy, with In replacing Ga randomly. The InGaN QWs have atomic height interface steps, resulting in QW width fluctuations. The electrons are localised at the top QW interface by the built-in electric field and the well-width fluctuations, with a localisation energy of typically 20 meV. The holes are localised near the bottom QW interface, by indium fluctuations in the random alloy, with a localisation energy of typically 60 meV. On the other hand, the non-polar (11-20) InGaN QWs contain nanometre-scale indium-rich clusters which we suggest localise the carriers and produce longer wavelength (lower energy) emission than from random alloy non-polar InGaN QWs of the same average composition. The reason for the indium-rich clusters in non-polar (11-20) InGaN QWs is not yet clear, but may be connected to the lower QW growth temperature for the (11-20) InGaN QWs compared to the (0001) polar InGaN QWs.

Cross polarization with phase and amplitude modulation of radio frequency fields in NMR-experiments with sample rotation at magic angle

International Nuclear Information System (INIS)

Dvinskij, S.V.; Chizhik, V.I.

2006-01-01

One analyzes cross polarization of nuclei within a rotating system of coordinates as applied to the NMR-experiments with a specimen rotation under the magic angle. One worded a concept of simultaneous phase and amplitude modulation according to which the Hamiltonian form of the restored dipole interaction persisted if inversion of difference of radiofrequency field amplitudes occurred simultaneously with phase inversion. One presents a theoretical substantiation in terms of the average Hamiltonian theory. The concept is demonstrated both experimentally and by means of numerical analysis for a number of special cases. Phase periodic inversion in cross polarized experiments is shown to result into practically important advantage of suppression of interactions of chemical shift and influence of effects of coarse adjustment of radiofrequency field parameters [ru

Polarized light microscopy for 3-dimensional mapping of collagen fiber architecture in ocular tissues.

Science.gov (United States)

Yang, Bin; Jan, Ning-Jiun; Brazile, Bryn; Voorhees, Andrew; Lathrop, Kira L; Sigal, Ian A

2018-04-06

Collagen fibers play a central role in normal eye mechanics and pathology. In ocular tissues, collagen fibers exhibit a complex 3-dimensional (3D) fiber orientation, with both in-plane (IP) and out-of-plane (OP) orientations. Imaging techniques traditionally applied to the study of ocular tissues only quantify IP fiber orientation, providing little information on OP fiber orientation. Accurate description of the complex 3D fiber microstructures of the eye requires quantifying full 3D fiber orientation. Herein, we present 3dPLM, a technique based on polarized light microscopy developed to quantify both IP and OP collagen fiber orientations of ocular tissues. The performance of 3dPLM was examined by simulation and experimental verification and validation. The experiments demonstrated an excellent agreement between extracted and true 3D fiber orientation. Both IP and OP fiber orientations can be extracted from the sclera and the cornea, providing previously unavailable quantitative 3D measures and insight into the tissue microarchitecture. Together, the results demonstrate that 3dPLM is a powerful imaging technique for the analysis of ocular tissues. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solid Phase Characterization of Tank 241-AY-102 Annulus Space Particulate

International Nuclear Information System (INIS)

Cooke, G. A.

2013-01-01

The Special Analytical Studies Group at the 222-S Laboratory (222-S) examined the particulate recovered from a series of samples from the annular space of tank 241-AY-102 (AY-102) using solid phase characterization (SPC) methods. These include scanning electron microscopy (SEM) using the ASPEX(R)1 scanning electron microscope, X-ray diffraction (XRD) using the Rigaku(R)2 MiniFlex X-ray diffractometer, and polarized light microscopy (PLM) using the Nikon(R)3 Eclipse Pol optical microscope. The SEM is equipped with an energy dispersive X-ray spectrometer (EDS) to provide chemical information

Mathematical imaging methods for mitosis analysis in live-cell phase contrast microscopy.

Science.gov (United States)

Grah, Joana Sarah; Harrington, Jennifer Alison; Koh, Siang Boon; Pike, Jeremy Andrew; Schreiner, Alexander; Burger, Martin; Schönlieb, Carola-Bibiane; Reichelt, Stefanie

2017-02-15

In this paper we propose a workflow to detect and track mitotic cells in time-lapse microscopy image sequences. In order to avoid the requirement for cell lines expressing fluorescent markers and the associated phototoxicity, phase contrast microscopy is often preferred over fluorescence microscopy in live-cell imaging. However, common specific image characteristics complicate image processing and impede use of standard methods. Nevertheless, automated analysis is desirable due to manual analysis being subjective, biased and extremely time-consuming for large data sets. Here, we present the following workflow based on mathematical imaging methods. In the first step, mitosis detection is performed by means of the circular Hough transform. The obtained circular contour subsequently serves as an initialisation for the tracking algorithm based on variational methods. It is sub-divided into two parts: in order to determine the beginning of the whole mitosis cycle, a backwards tracking procedure is performed. After that, the cell is tracked forwards in time until the end of mitosis. As a result, the average of mitosis duration and ratios of different cell fates (cell death, no division, division into two or more daughter cells) can be measured and statistics on cell morphologies can be obtained. All of the tools are featured in the user-friendly MATLAB®Graphical User Interface MitosisAnalyser. Copyright © 2017. Published by Elsevier Inc.

Quantum mechanical systems interacting with different polarizations of gravitational waves in noncommutative phase space

Science.gov (United States)

Saha, Anirban; Gangopadhyay, Sunandan; Saha, Swarup

2018-02-01

Owing to the extreme smallness of any noncommutative scale that may exist in nature, both in the spatial and momentum sector of the quantum phase space, a credible possibility of their detection lies in the gravitational wave (GW) detection scenario, where one effectively probes the relative length-scale variations ˜O [10-20-10-23] . With this motivation, we have theoretically constructed how a free particle and a harmonic oscillator will respond to linearly and circularly polarized gravitational waves if their quantum mechanical phase space has a noncommutative structure. We critically analyze the formal solutions which show resonance behavior in the responses of both free particle and HO systems to GW with both kind of polarizations. We discuss the possible implications of these solutions in detecting noncommutativity in a GW detection experiment. We use the currently available upper-bound estimates on various noncommutative parameters to anticipate the relative importance of various terms in the solutions. We also argue how the quantum harmonic oscillator system we considered here can be very relevant in the context of the resonant bar detectors of GW which are already operational.

Review of quantitative phase-digital holographic microscopy: promising novel imaging technique to resolve neuronal network activity and identify cellular biomarkers of psychiatric disorders

KAUST Repository

Marquet, Pierre

2014-09-22

Quantitative phase microscopy (QPM) has recently emerged as a new powerful quantitative imaging technique well suited to noninvasively explore a transparent specimen with a nanometric axial sensitivity. In this review, we expose the recent developments of quantitative phase-digital holographic microscopy (QP-DHM). Quantitative phase-digital holographic microscopy (QP-DHM) represents an important and efficient quantitative phase method to explore cell structure and dynamics. In a second part, the most relevant QPM applications in the field of cell biology are summarized. A particular emphasis is placed on the original biological information, which can be derived from the quantitative phase signal. In a third part, recent applications obtained, with QP-DHM in the field of cellular neuroscience, namely the possibility to optically resolve neuronal network activity and spine dynamics, are presented. Furthermore, potential applications of QPM related to psychiatry through the identification of new and original cell biomarkers that, when combined with a range of other biomarkers, could significantly contribute to the determination of high risk developmental trajectories for psychiatric disorders, are discussed.

Basal-plane stacking faults in non-polar GaN studied by off-axis electron holography

Energy Technology Data Exchange (ETDEWEB)

Liu, Lewis Z-Y; Rao, D V Sridhara; Kappers, M J; Humphreys, C J [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Geiger, D, E-mail: ZL249@cam.ac.u [Triebenberg Laboratory, Institute for Structure Physics, Technische Universitaet Dresden, D-01062 Dresden (Germany)

2010-02-01

We have studied basal-plane stacking faults in a non-polar (11-20) GaN epilayer using high-resolution electron microscopy and off-axis electron holography. The microstructure of the basal-plane stacking faults (BSFs) has been determined to be I{sub 1} type from high-resolution TEM images. High-resolution holograms along the [11-20] zone axis were obtained by off-axis electron holography on a Cs-corrected TEM, providing {approx}2 A spatial resolution in the reconstructed amplitude and phase images. Phase fluctuations across the stacking faults were detected, suggesting the presence of a built-in electric field. The uncertainties in the experiments and their interpretation are discussed.

Myosin helical pitch angle as a quantitative imaging biomarker for characterization of cardiac programming in fetal growth restriction measured by polarization second harmonic microscopy

Science.gov (United States)

Amat-Roldan, I.; Psilodimitrakopoulos, S.,; Eixarch, E.,; Torre, I.; Wotjas, B.; Crispi, F.; Figueras, F.; Artigas, D.,; Loza-Alvarez, P.; Gratacos, E.,

2009-07-01

Fetal growth restriction (FGR) has recently shown a strong association with cardiac programming which predisposes to cardiovascular mortality in adulthood. Polarization Second Harmonic Microscopy can quantify molecular architecture changes with high sensitivity in cardiac myofibrils. In this work, we use myosin helical pitch angle as an example to quantify such alterations related to this high risk population. Importantly, this shows a potential use of the technique as an early diagnostic tool and an alternative method to understand pathophysiological processes.

Full-angle tomographic phase microscopy of flowing quasi-spherical cells.

Science.gov (United States)

Villone, Massimiliano M; Memmolo, Pasquale; Merola, Francesco; Mugnano, Martina; Miccio, Lisa; Maffettone, Pier Luca; Ferraro, Pietro

2017-12-19

We report a reliable full-angle tomographic phase microscopy (FA-TPM) method for flowing quasi-spherical cells along microfluidic channels. This method lies in a completely passive optical system, i.e. mechanical scanning or multi-direction probing of the sample is avoided. It exploits the engineered rolling of cells while they are flowing along a microfluidic channel. Here we demonstrate significant progress with respect to the state of the art of in-flow TPM by showing a general extension to cells having almost spherical shapes while they are flowing in suspension. In fact, the adopted strategy allows the accurate retrieval of rotation angles through a theoretical model of the cells' rotation in a dynamic microfluidic flow by matching it with phase-contrast images resulting from holographic reconstructions. So far, the proposed method is the first and the only one that permits to get in-flow TPM by probing the cells with full-angle, achieving accurate 3D refractive index mapping and the simplest optical setup, simultaneously. Proof of concept experiments were performed successfully on human breast adenocarcinoma MCF-7 cells, opening the way for the full characterization of circulating tumor cells (CTCs) in the new paradigm of liquid biopsy.

High-efficiency resonant rf spin rotator with broad phase space acceptance for pulsed polarized cold neutron beams

Directory of Open Access Journals (Sweden)

P.-N. Seo

2008-08-01

Full Text Available High precision fundamental neutron physics experiments have been proposed for the intense pulsed spallation neutron beams at JSNS, LANSCE, and SNS to test the standard model and search for new physics. Certain systematic effects in some of these experiments have to be controlled at the few ppb level. The NPDGamma experiment, a search for the small parity-violating γ-ray asymmetry A_{γ} in polarized cold neutron capture on parahydrogen, is one example. For the NPDGamma experiment we developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5  cm×9.5  cm pulsed cold neutron beam with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to rf neutron spin flippers based on adiabatic fast passage. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically polarized ^{3}He neutron spin filters. The efficiency of the spin rotator was measured at LANSCE to be 98.8±0.5% for neutron energies from 3 to 20 meV over the full phase space of the beam. Systematic effects that the rf spin rotator introduces to the NPDGamma experiment are considered.

Direct Probing of Polarization Charge at Nanoscale Level

Energy Technology Data Exchange (ETDEWEB)

Kwon, Owoong [Sungkyunkwan Univ., Suwon (Republic of Korea). School of Advanced Materials and Engineering; Seol, Daehee [Sungkyunkwan Univ., Suwon (Republic of Korea). School of Advanced Materials and Engineering; Lee, Dongkyu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Han, Hee [Korea Research Inst. of Standards and Science (KRISS), Daejeon (South Korea); Lindfors-Vrejoiu, Ionela [Univ. of Cologne (Germany). Physics Inst.; Lee, Woo [Korea Research Inst. of Standards and Science (KRISS), Daejeon (South Korea); Jesse, Stephen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences; Lee, Ho Nyung [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Kalinin, Sergei V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences; Alexe, Marin [Univ. of Warwick, Coventry (United Kingdom). Dept. of Physics; Kim, Yunseok [Sungkyunkwan Univ., Suwon (Republic of Korea). School of Advanced Materials and Engineering

2017-11-14

Ferroelectric materials possess spontaneous polarization that can be used for multiple applications. Owing to a long-term development of reducing the sizes of devices, the preparation of ferroelectric materials and devices is entering the nanometer-scale regime. In order to evaluate the ferroelectricity, there is a need to investigate the polarization charge at the nanoscale. Nonetheless, it is generally accepted that the detection of polarization charges using a conventional conductive atomic force microscopy (CAFM) without a top electrode is not feasible because the nanometer-scale radius of an atomic force microscopy (AFM) tip yields a very low signal-to-noise ratio. But, the detection is unrelated to the radius of an AFM tip and, in fact, a matter of the switched area. In this work, the direct probing of the polarization charge at the nanoscale is demonstrated using the positive-up-negative-down method based on the conventional CAFM approach without additional corrections or circuits to reduce the parasitic capacitance. The polarization charge densities of 73.7 and 119.0 µC cm^-2 are successfully probed in ferroelectric nanocapacitors and thin films, respectively. The results we obtained show the feasibility of the evaluation of polarization charge at the nanoscale and provide a new guideline for evaluating the ferroelectricity at the nanoscale.

Unravelling the effects of mobile phase additives in supercritical fluid chromatography. Part I: Polarity and acidity of the mobile phase.

Science.gov (United States)

West, Caroline; Melin, Jodie; Ansouri, Hassna; Mengue Metogo, Maïly

2017-04-07

The mobile phases employed in current supercritical fluid chromatography (SFC) are usually composed of a mixture of pressurized carbon dioxide and a co-solvent. The co-solvent is most often an alcohol and may contain a third component in small proportions, called an additive (acid, base or salt). The polarity of such mobile phase compositions is here re-evaluated with a solvatochromic dye (Nile Red), particularly to assess the contribution of additives. It appears that additives, when employed in usual concentration range (0.1% or 20mM) do not modify the polarity in the immediate environment of the probe. In addition, the combination of carbon dioxide and an alcohol is known to form alkoxylcarbonic acid, supposedly conferring some acidic character to SFC mobile phases. Direct measurements of the apparent pH are impossible, but colour indicators of pH can be used to define the range of apparent pH provided by carbon dioxide-alcohol mixtures, with or without additives. Five colour indicators (Thymol Blue, Bromocresol Green, Methyl Red, Bromocresol Purple, and Bromothymol Blue) were selected to provide a wide range of aqueous pK a values (from 1.7 to 8.9). UV-vis absorption spectra measured in liquid phases of controlled pH were compared to those measured with a diode-array detector employed in SFC, with the help of chemometric methods. Based on these observations, it is concluded that the apparent pH range in carbon dioxide-methanol mobile phases is close to 5. Increasing the proportion of methanol (in the course of a gradient elution for instance) causes decreasing apparent pH. Strong acids can further decrease the apparent pH below 1.7; strong bases have little influence on the apparent pH, probably because, in this range of concentrations, they are titrated by alkoxylcarbonic acid or form ion pairs with alkoxycarbonate. However, bases and salts could stabilize the acidity in the course of gradient runs. Copyright © 2017 Elsevier B.V. All rights reserved.

Valley polarized quantum Hall effect and topological insulator phase transitions in silicene

KAUST Repository

Tahir, M.

2013-01-25

The electronic properties of silicene are distinct from both the conventional two dimensional electron gas and the famous graphene due to strong spin orbit interaction and the buckled structure. Silicene has the potential to overcome limitations encountered for graphene, in particular the zero band gap and weak spin orbit interaction. We demonstrate a valley polarized quantum Hall effect and topological insulator phase transitions. We use the Kubo formalism to discuss the Hall conductivity and address the longitudinal conductivity for elastic impurity scattering in the first Born approximation. We show that the combination of an electric field with intrinsic spin orbit interaction leads to quantum phase transitions at the charge neutrality point, providing a tool to experimentally tune the topological state. Silicene constitutes a model system for exploring the spin and valley physics not accessible in graphene due to the small spin orbit interaction.

Comparison of the layer structure of vapor phase and leached SRL glass by use of AEM [analytical electron microscopy

International Nuclear Information System (INIS)

Biwer, B.M.; Bates, J.K.; Abrajano, T.A. Jr.; Bradley, J.P.

1989-01-01

Test samples of 131 type glass that have been reacted for extended time periods in water vapor atmospheres of different relative humidities and in static leaching solution have been examined to characterize the reaction products. Analytical electron microscopy (AEM) was used to characterize the leached samples, and a complicated layer structure was revealed, consisting of phases that precipitate from solution and also form within the residual glass layer. The precipitated phases include birnes-site, saponite, and an iron species, while the intralayer phases include the U-Ti containing phase brannerite distributed within a matrix consisting of bands of an Fe rich montmorillonite clay. Comparison is made between samples leached at 40 degrees C for 4 years with those leached at 90 degrees C for 3-1/2 years. The samples reacted in water vapor were examined with scanning electron microscopy and show increasing reaction as both the relative humidity and time of reaction increases. These samples also contain a layered structure with reaction products on the glass surface. 15 refs., 5 figs

Kelvin probe force microscopy in liquid using electrochemical force microscopy

Directory of Open Access Journals (Sweden)

Liam Collins

2015-01-01

Full Text Available Conventional closed loop-Kelvin probe force microscopy (KPFM has emerged as a powerful technique for probing electric and transport phenomena at the solid–gas interface. The extension of KPFM capabilities to probe electrostatic and electrochemical phenomena at the solid–liquid interface is of interest for a broad range of applications from energy storage to biological systems. However, the operation of KPFM implicitly relies on the presence of a linear lossless dielectric in the probe–sample gap, a condition which is violated for ionically-active liquids (e.g., when diffuse charge dynamics are present. Here, electrostatic and electrochemical measurements are demonstrated in ionically-active (polar isopropanol, milli-Q water and aqueous NaCl and ionically-inactive (non-polar decane liquids by electrochemical force microscopy (EcFM, a multidimensional (i.e., bias- and time-resolved spectroscopy method. In the absence of mobile charges (ambient and non-polar liquids, KPFM and EcFM are both feasible, yielding comparable contact potential difference (CPD values. In ionically-active liquids, KPFM is not possible and EcFM can be used to measure the dynamic CPD and a rich spectrum of information pertaining to charge screening, ion diffusion, and electrochemical processes (e.g., Faradaic reactions. EcFM measurements conducted in isopropanol and milli-Q water over Au and highly ordered pyrolytic graphite electrodes demonstrate both sample- and solvent-dependent features. Finally, the feasibility of using EcFM as a local force-based mapping technique of material-dependent electrostatic and electrochemical response is investigated. The resultant high dimensional dataset is visualized using a purely statistical approach that does not require a priori physical models, allowing for qualitative mapping of electrostatic and electrochemical material properties at the solid–liquid interface.

Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite Polarization Sensitivity Analysis

Science.gov (United States)

Sun, Junqiang; Xiong, Xiaoxiong; Waluschka, Eugene; Wang, Menghua

2016-01-01

The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of five instruments onboard the Suomi National Polar-Orbiting Partnership (SNPP) satellite that launched from Vandenberg Air Force Base, California, on October 28, 2011. It is a whiskbroom radiometer that provides +/-56.28deg scans of the Earth view. It has 22 bands, among which 14 are reflective solar bands (RSBs). The RSBs cover a wavelength range from 410 to 2250 nm. The RSBs of a remote sensor are usually sensitive to the polarization of incident light. For VIIRS, it is specified that the polarization factor should be smaller than 3% for 410 and 862 nm bands and 2.5% for other RSBs for the scan angle within +/-45deg. Several polarization sensitivity tests were performed prelaunch for SNPP VIIRS. The first few tests either had large uncertainty or were less reliable, while the last one was believed to provide the more accurate information about the polarization property of the instrument. In this paper, the measured data in the last polarization sensitivity test are analyzed, and the polarization factors and phase angles are derived from the measurements for all the RSBs. The derived polarization factors and phase angles are band, detector, and scan angle dependent. For near-infrared bands, they also depend on the half-angle mirror side. Nevertheless, the derived polarization factors are all within the specification, although the strong detector dependence of the polarization parameters was not expected. Compared to the Moderate Resolution Imaging Spectroradiometer on both Aqua and Terra satellites, the polarization effect on VIIRS RSB is much smaller.

Electrical characterization of Ge–Sb–Te phase change nano-pillars using conductive atomic force microscopy

International Nuclear Information System (INIS)

Bae, Byeong-Ju; Hong, Sung-Hoon; Hwang, Seon-Yong; Hwang, Jae-Yeon; Yang, Ki-Yeon; Lee, Heon

2009-01-01

The electrical characteristic of phase change material was studied in nano-scale using nanoimprint lithography and a conducting atomic force microscopy measurement system. Nanoimprint lithography was used to fabricate the nano-scale phase change material pattern. A Pt-coated AFM tip was used as a top electrode to measure the electrical characteristics of the GST nano-pillar. The GST nano-pillar, which is 200 nm in diameter, was amorphized by 2 V and 5 ns reset pulse and was then brought back to the crystalline phase by applying 1.3 V and 150 ns set pulse. Using this measurement system, the GST nano-pillar was switched between the amorphous and crystalline phases more than five times. The results of the reset and the set current measurement with the GST nano-pillar sizes show that the reset and the set currents also decreased with the decrease of the GST pillar size

Distinction of heterogeneity on Au nanostructured surface based on phase contrast imaging of atomic force microscopy

International Nuclear Information System (INIS)

Jung, Mi; Choi, Jeong-Woo

2010-01-01

The discrimination of the heterogeneity of different materials on nanostructured surfaces has attracted a great deal of interest in biotechnology as well as nanotechnology. Phase imaging through tapping mode of atomic force microscopy (TMAFM) can be used to distinguish the heterogeneity on a nanostructured surface. Nanostructures were fabricated using anodic aluminum oxide (AAO). An 11-mercaptoundecanoic acid (11-MUA) layer adsorbed onto the Au nanodots through self-assembly to improve the bio-compatibility. The Au nanostructures that were modified with 11-MUA and the concave surfaces were investigated using the TMAFM phase images to compare the heterogeneous and homogeneous nanostructured surfaces. Although the topography and phase images were taken simultaneously, the images were different. Therefore, the contrast in the TMAFM phase images revealed the different compositional materials on the heterogeneous nanostructure surface.

Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam.

Science.gov (United States)

Boruah, B R; Neil, M A A

2009-01-01

We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

Electron microscopy analyses and electrical properties of the layered Bi{sub 2}WO{sub 6} phase

Energy Technology Data Exchange (ETDEWEB)

Taoufyq, A. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université du Sud Toulon-Var, BP 20132, 83957, La Garde Cedex (France); Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); Département d‘Études des Réacteurs, Laboratoire Dosimétrie Capteurs Instrumentation, CEA Cadarache (France); Société CESIGMA—Signals and Systems, 1576 Chemin de La Planquette, F 83 130 LA GARDE (France); Ait Ahsaine, H. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); Patout, L. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université du Sud Toulon-Var, BP 20132, 83957, La Garde Cedex (France); Benlhachemi, A.; Ezahri, M. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); and others

2013-07-15

The bismuth tungstate Bi{sub 2}WO{sub 6} was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2{sub 1} non centrosymmetric space group previously proposed for this phase. The layers Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} have been directly evidenced from the HRTEM images. The electrical properties of Bi{sub 2}WO{sub 6} compacted pellets systems were determined from electrical impedance spectrometry (EIS) and direct current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi{sub 2}WO{sub 6} phase, with a representation of the cell dimensions (b and c vectors). The Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi{sub 2}WO{sub 6}. • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification.

Phase Analysis of the Cellulose Triacetate-Nitromethane System

Directory of Open Access Journals (Sweden)

Anna B. Shipovskaya

2012-01-01

Full Text Available A comprehensive study was made on the cellulose triacetate-nitromethane system to explore its phase separation within ranges 2–25 wt.% and −5÷+80°C by means of polarization light and electron microscopy, the turbidity spectrum method, differential thermal and X-ray analyses, and rheological techniques. The physical state of the polymer was identified within the phase coexistence boundaries on the phase diagram which included three types of phase separation (amorphous (with a UCST at Tcr=57∘C and ccr=7.3 wt.%, crystal, and liquid crystal. The boundaries of the regions determining the coexistence of the liquid crystal (LC and the partly crystal phase were found to be inside the region of amorphous liquid-liquid phase separation. For cellulose ester-solvent systems, this state diagram is the first experimental evidence for the possibility of coexistence of several phases with amorphous, LC, and crystal polymer ordering.

A study of phase separation in peptide-loaded HPMC films using T(zero)-modulated temperature DSC, atomic force microscopy, and scanning electron microscopy.

Science.gov (United States)

Hussain, Samana; Grandy, David B; Reading, Mike; Craig, Duncan Q M

2004-07-01

Despite the widespread use of drug-loaded polymeric systems, there is still considerable uncertainty with regard to the nature of the distribution of the drug within the polymer matrix. The aim of this investigation was to develop thermal and microscopic techniques whereby the miscibility and spatial distribution of a model peptide, cyclosporin A (CyA), in hydroxypropyl methylcellulose (HPMC) films may be studied. The new technique of T(zero)-modulated temperature differential scanning calorimetry (T(zero) MTDSC), scanning electron microscopy (SEM), and pulse force mode atomic force microscopy (PFM-AFM) were used in conjunction to study films prepared using a solvent evaporation process, with a solvent extraction study performed to elucidate the nature of the observed phases. T(zero) MTDSC studies showed glass transitions for both the HPMC and CycA, with the T(g) for the HPMC and CycA seen for the mixed systems. SEM showed two spherical phases of differing electron density. PFM-AFM also showed spheres of differing adhesion that increased in size on addition of drug. Pixel intensity analysis indicated that the smaller spheres corresponded to CycA. Exposure of the films to dichloromethane, in which CycA is soluble but HPMC is not, resulted in the presence of voids that corresponded well to the spheres suggested to correspond to the drug. It was concluded that the system had undergone extensive or complete phase separation, and that the thermal and microscopic techniques outlined above are an effective means by which this issue may be studied. Copyright 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1672-1681, 2004

Fresnel zone-plate based X-ray microscopy in Zernike phase contrast with sub-50 nm resolution at NSRL

International Nuclear Information System (INIS)

Chen Jie; Li Wenjie; Tian Jinping; Liu Longhua; Xiong Ying; Liu Gang; Wu Ziyu; Tian Yangchao; Liu Yijin; Yue Zhengbo; Yu Hanqing; Wang Chunru

2009-01-01

A transmission X-ray microscope using Fresnel zone-plates (FZPs) has been installed at U7A beamline of National Synchrotron Radiation Laboratory (NSRL). The objective FZP with 45 nm outermost zone width delivers a sub-50 nm resolution. A gold phase ring with 2.5 μm thickness and 4 μm width was placed at the focal plane of the objective FZP at 8 keV to produce a negative Zernike phase contrast. A series of samples were used to test the performance of the Zernike phase contrast X-ray microscopy.

Fresnel zone-plate based X-ray microscopy in Zernike phase contrast with sub-50 nm resolution at NSRL

Energy Technology Data Exchange (ETDEWEB)

Chen Jie; Li Wenjie; Tian Jinping; Liu Longhua; Xiong Ying; Liu Gang; Wu Ziyu; Tian Yangchao [National Synchrotron Radiation Laboratory (China); Liu Yijin [School of Physics (China); Yue Zhengbo; Yu Hanqing [Laboratory of Environmental Engineering, School of Chemistry, University of Science and Technology of China, Hefei Anhui 230029 (China); Wang Chunru, E-mail: ychtian@ustc.edu.c [Institute of Chemistry, Chinese Academy of Sciences, Beijing 10060 (China)

2009-09-01

A transmission X-ray microscope using Fresnel zone-plates (FZPs) has been installed at U7A beamline of National Synchrotron Radiation Laboratory (NSRL). The objective FZP with 45 nm outermost zone width delivers a sub-50 nm resolution. A gold phase ring with 2.5 {mu}m thickness and 4 {mu}m width was placed at the focal plane of the objective FZP at 8 keV to produce a negative Zernike phase contrast. A series of samples were used to test the performance of the Zernike phase contrast X-ray microscopy.

Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor

Science.gov (United States)

Kinoshita, Yuto; Kida, Noriaki; Miyamoto, Tatsuya; Kanou, Manabu; Sasagawa, Takao; Okamoto, Hiroshi

2018-04-01

The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate the spin-polarized electrons on the subpicosecond timescale. Here, we report one such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after the resonant excitation of the interband transition between the Rashba-type spin-splitting energy bands with a femtosecond laser pulse circularly polarized. The phase of the emitted terahertz waves is reversed by switching the circular polarization. This suggests that the observed terahertz radiation originates from the subpicosecond spin-polarized photocurrents, which are generated by the asymmetric depopulation of the Dirac state. Our result provides a way for the current-induced terahertz radiation and its phase control by the circular polarization of incident light without external electric fields.

A Wideband and Polarization-Independent Metasurface Based on Phase Optimization for Monostatic and Bistatic Radar Cross Section Reduction

Directory of Open Access Journals (Sweden)

Jianxun Su

2016-01-01

Full Text Available A broadband and polarization-independent metasurface is analyzed and designed for both monostatic and bistatic radar cross section (RCS reduction in this paper. Metasurfaces are composed of two types of electromagnetic band-gap (EBG lattice, which is a subarray with “0” or “π” phase responses, arranged in periodic and aperiodic fashions. A new mechanism is proposed for manipulating electromagnetic (EM scattering and realizing the best reduction of monostatic and bistatic RCS by redirecting EM energy to more directions through controlling the wavefront of EM wave reflected from the metasurface. Scattering characteristics of two kinds of metasurfaces, periodic arrangement and optimized phase layout, are studied in detail. Optimizing phase layout through particle swarm optimization (PSO together with far field pattern prediction can produce a lot of scattering lobes, leading to a great reduction of bistatic RCS. For the designed metasurface based on optimal phase layout, a bandwidth of more than 80% is achieved at the normal incidence for the −9.5 dB RCS reduction for both monostatic and bistatic. Bistatic RCS reduction at frequency points with exactly 180° phase difference reaches 17.6 dB. Both TE and TM polarizations for oblique incidence are considered. The measured results are in good agreement with the corresponding simulations.

Transmission electron microscopy investigation of interfaces in a two-phase TiAl alloy

Science.gov (United States)

Mahon, G. J.; Howe, J. M.

1990-06-01

The atomic structures of the γ/α2 and γ/γT interfaces in a TiAl alloy were investigated using conventional and high-resolution transmission electron microscopy (TEM) in order to understand the growth mechanisms and deformation behavior of the two-phase alloy. The results show that the α2 plates grow from the γ phase by the migration of a/6 partial dislocation ledges across the faces and that the γ/α2 interface usually contains closely spaced arrays of interfacial dislocations. Deformation twins cut through both γ twin boundaries and α2 plates during deformation, although slip of twinning c slocations through α2 appears to be a difficult process. Both the γ/α2 and γ/γT interfaces can be imaged and modeled at the atomic level, although slight crystal and/or beam tilt can complicate image interpretation.

Natural enamel caries in polarized light microscopy: differences in histopathological features derived from a qualitative versus a quantitative approach to interpret enamel birefringence.

Science.gov (United States)

De Medeiros, R C G; Soares, J D; De Sousa, F B

2012-05-01

Lesion area measurement of enamel caries using polarized light microscopy (PLM) is currently performed in a large number of studies, but measurements are based mainly on a mislead qualitative interpretation of enamel birefringence in a single immersion medium. Here, five natural enamel caries lesions are analysed by microradiography and in PLM, and the differences in their histopathological features derived from a qualitative versus a quantitative interpretation of enamel birefringence are described. Enamel birefringence in different immersion media (air, water and quinoline) is interpreted by both qualitative and quantitative approaches, the former leading to an underestimation of the depth of enamel caries mainly when the criterion of validating sound enamel as a negatively birefringent area in immersion in water is used (a current common practice in dental research). Procedures to avoid the shortcomings of a qualitative interpretation of enamel birefringence are presented and discussed. © 2012 The Authors Journal of Microscopy © 2012 Royal Microscopical Society.

Water-induced phase separation of miconazole-poly (vinylpyrrolidone-co-vinyl acetate) amorphous solid dispersions: Insights with confocal fluorescence microscopy.

Science.gov (United States)

Saboo, Sugandha; Taylor, Lynne S

2017-08-30

The aim of this study was to evaluate the utility of confocal fluorescence microscopy (CFM) to study the water-induced phase separation of miconazole-poly (vinylpyrrolidone-co-vinyl acetate) (mico-PVPVA) amorphous solid dispersions (ASDs), induced during preparation, upon storage at high relative humidity (RH) and during dissolution. Different fluorescent dyes were added to drug-polymer films and the location of the dyes was evaluated using CFM. Orthogonal techniques, in particular atomic force microscopy (AFM) coupled with nanoscale infrared spectroscopy (AFM-nanoIR), were used to provide additional analysis of the drug-polymer blends. The initial miscibility of mico-PVPVA ASDs prepared under low humidity conditions was confirmed by AFM-nanoIR. CFM enabled rapid identification of drug-rich and polymer-rich phases in phase separated films prepared under high humidity conditions. The identity of drug- and polymer-rich domains was confirmed using AFM-nanoIR imaging and localized IR spectroscopy, together with Lorentz contact resonance (LCR) measurements. The CFM technique was then utilized successfully to further investigate phase separation in mico-PVPVA films exposed to high RH storage and to visualize phase separation dynamics following film immersion in buffer. CFM is thus a promising new approach to study the phase behavior of ASDs, utilizing drug and polymer specific dyes to visualize the evolution of heterogeneity in films exposed to water. Copyright © 2017 Elsevier B.V. All rights reserved.

Solving structure in the CP29 light harvesting complex with polarization-phased 2D electronic spectroscopy

Science.gov (United States)

Ginsberg, Naomi S.; Davis, Jeffrey A.; Ballottari, Matteo; Cheng, Yuan-Chung; Bassi, Roberto; Fleming, Graham R.

2011-01-01

The CP29 light harvesting complex from green plants is a pigment-protein complex believed to collect, conduct, and quench electronic excitation energy in photosynthesis. We have spectroscopically determined the relative angle between electronic transition dipole moments of its chlorophyll excitation energy transfer pairs in their local protein environments without relying on simulations or an X-ray crystal structure. To do so, we measure a basis set of polarized 2D electronic spectra and isolate their absorptive components on account of the tensor relation between the light polarization sequences used to obtain them. This broadly applicable advance further enhances the acuity of polarized 2D electronic spectroscopy and provides a general means to initiate or feed back on the structural modeling of electronically-coupled chromophores in condensed phase systems, tightening the inferred relations between the spatial and electronic landscapes of ultrafast energy flow. We also discuss the pigment composition of CP29 in the context of light harvesting, energy channeling, and photoprotection within photosystem II. PMID:21321222

Multi-layer solid-phase extraction and evaporation-enrichment methods for polar organic chemicals from aqueous matrices.

Science.gov (United States)

Köke, Niklas; Zahn, Daniel; Knepper, Thomas P; Frömel, Tobias

2018-03-01

Analysis of polar organic chemicals in the aquatic environment is exacerbated by the lack of suitable and widely applicable enrichment methods. In this work, we assessed the suitability of a novel combination of well-known solid-phase extraction (SPE) materials in one cartridge as well as an evaporation method and for the enrichment of 26 polar model substances (predominantly log D evaporation method were investigated for the recovery and matrix effects of the model substances and analyzed with hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS). In total, 65% of the model substances were amenable (> 10% recovery) to the mlSPE method with a mean recovery of 76% while 73% of the model substances were enriched with the evaporation method achieving a mean recovery of 78%. Target and non-target screening comparison of both methods with a frequently used reversed-phase SPE method utilizing "hydrophilic and lipophilic balanced" (HLB) material was performed. Target analysis showed that the mlSPE and evaporation method have pronounced advantages over the HLB method since the HLB material retained only 30% of the model substances. Non-target screening of a ground water sample with the investigated enrichment methods showed that the median retention time of all detected features on a HILIC system decreased in the order mlSPE (3641 features, median t R 9.7 min), evaporation (1391, 9.3 min), HLB (4414, 7.2 min), indicating a higher potential of the described methods to enrich polar analytes from water compared with HLB-SPE. Graphical abstract Schematic of the method evaluation (recovery and matrix effects) and method comparison (target and non-target analysis) of the two investigated enrichment methods for very polar chemicals in aqueousmatrices.

Towards non-invasive 3D hepatotoxicity assays with optical coherence phase microscopy

Science.gov (United States)

Nelson, Leonard J.; Koulovasilopoulos, Andreas; Treskes, Philipp; Hayes, Peter C.; Plevris, John N.; Bagnaninchi, Pierre O.

2015-03-01

Three-dimensional tissue-engineered models are increasingly recognised as more physiologically-relevant than standard 2D cell culture for pre-clinical drug toxicity testing. However, many types of conventional toxicity assays are incompatible with dense 3D tissues. This study investigated the use of optical coherence phase microscopy (OCPM) as a novel approach to assess cell death in 3D tissue culture. For 3D micro-spheroid formation Human hepatic C3A cells were encapsulated in hyaluronic acid gels and cultured in 100μl MEME/10%FBS in 96-well plates. After spheroid formation the 3D liver constructs were exposed to acetaminophen on culture day 8. Acetaminophen hepatotoxicity in 3D cultures was evaluated using standard biochemical assays. An inverted OCPM in common path configuration was developed with a Callisto OCT engine (Thorlabs), centred at 930nm and a custom scanning head. Intensity data were used to perform in-depth microstructural imaging. In addition, phase fluctuations were measured by collecting several successive B scans at the same location, and statistics on the first time derivative of the phase, i.e. time fluctuations, were analysed over the acquisition time interval to retrieve overall cell viability. OCPM intensity (cell cluster size) and phase fluctuation statistics were directly compared with biochemical assays. In this study, we investigated optical coherence phase tomography to assess cell death in a 3d liver model after exposure to a prototypical hepatotoxin, acetaminophen. We showed that OCPM has the potential to assess noninvasively and label-free drug toxicity in 3D tissue models.

Radiochromic film and polarization effects

International Nuclear Information System (INIS)

Yu, P.K.N.; Cheung, T.; Butson, M.J.; Cancer Services, Wollongong, NSW; Inwood, D.

2004-01-01

Full text: A new high sensitivity radiochromic film has been tested for its polarization properties. Gafchromic HS film has been shown to produce a relatively small (less than 3%) variation in measured optical density measured at 660nm wavelength when the light source is fully linear polarized and the film is rotated through 360 deg angle. Similar variations are seen when the detector is linearly polarized. If both light source and detector is linearly polarised variations in measured optical density can reach 15% when the film is rotated through 360 deg angle. This seems to be due to a phase shift in polarised light caused by the radiochromic film resulting in the polarised light source becoming out of phase with the polarised detector. Gafchromic HS radiochromic film produces a minimal polarization response with varying angle of rotation however we recommend that a polarization test be performed on a densitometry system to establish the extent of its polarization properties before accuracy dosimetry is performed with radiochromic HS film. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

Spontaneous spin polarization in quantum wires

Energy Technology Data Exchange (ETDEWEB)

Vasilchenko, A.A., E-mail: a_vas2002@mail.ru

2015-12-04

The total energy of a quasi-one-dimensional electron system was calculated using the density functional theory. In the absence of a magnetic field, we have found that ferromagnetic state occurs in the quantum wires. The phase diagram of the transition into the spin-polarized state is constructed. The critical electron density below which electrons are in spin-polarized state is estimated analytically. - Highlights: • Density functional theory used to study a spin-polarized state in quantum wires. • The Kohn–Sham equation for quasi-one-dimensional electrons solved numerically. • The phase diagram of the transition into the spin-polarized state is constructed. • The electron density below which electrons are in a spin-polarized state was found. • The critical density of electrons was estimated analytically.

Spontaneous spin polarization in quantum wires

International Nuclear Information System (INIS)

Vasilchenko, A.A.

2015-01-01

The total energy of a quasi-one-dimensional electron system was calculated using the density functional theory. In the absence of a magnetic field, we have found that ferromagnetic state occurs in the quantum wires. The phase diagram of the transition into the spin-polarized state is constructed. The critical electron density below which electrons are in spin-polarized state is estimated analytically. - Highlights: • Density functional theory used to study a spin-polarized state in quantum wires. • The Kohn–Sham equation for quasi-one-dimensional electrons solved numerically. • The phase diagram of the transition into the spin-polarized state is constructed. • The electron density below which electrons are in a spin-polarized state was found. • The critical density of electrons was estimated analytically.

Dynamic contrast enhancement in widefield microscopy using projector-generated illumination patterns

International Nuclear Information System (INIS)

Samson, Edward Carlo; Blanca, Carlo Mar

2007-01-01

We present a simple and cost-effective optical protocol to realize contrast-enhancement imaging (such as dark-field, optical-staining and oblique illumination microscopy) of transparent samples on a conventional widefield microscope using commercial multimedia projectors. The projector functions as both light source and mask generator implemented by creating slideshows of the filters projected along the illumination planes of the microscope. The projected optical masks spatially modulate the distribution of the incident light to selectively enhance structures within the sample according to spatial frequency thereby increasing the image contrast of translucent biological specimens. Any amplitude filter can be customized and dynamically controlled so that switching from one imaging modality to another involves a simple slide transition and can be executed at a keystroke with no physical filters and no moving optical parts. The method yields an image contrast of 89-96% comparable with standard enhancement techniques. The polarization properties of the projector are then utilized to discriminate birefringent and non-birefringent sites on the sample using single-shot, simultaneous polarization and optical-staining microscopy. In addition to dynamic pattern generation and polarization, the projector also provides high illumination power and spectral excitation selectivity through its red-green-blue (RGB) channels. We exploit this last property to explore the feasibility of using video projectors to selectively excite stained samples and perform fluorescence imaging in tandem with reflectance and polarization reflectance microscopy

An approach to spin-resolved molecular gas microscopy

Science.gov (United States)

Covey, Jacob P.; De Marco, Luigi; Acevedo, Óscar L.; Rey, Ana Maria; Ye, Jun

2018-04-01

Ultracold polar molecules are an ideal platform for studying many-body physics with long-range dipolar interactions. Experiments in this field have progressed enormously, and several groups are pursuing advanced apparatus for manipulation of molecules with electric fields as well as single-atom-resolved in situ detection. Such detection has become ubiquitous for atoms in optical lattices and tweezer arrays, but has yet to be demonstrated for ultracold polar molecules. Here we present a proposal for the implementation of site-resolved microscopy for polar molecules, and specifically discuss a technique for spin-resolved molecular detection. We use numerical simulation of spin dynamics of lattice-confined polar molecules to show how such a scheme would be of utility in a spin-diffusion experiment.

The effect of phase assemblages, grain boundaries and domain structure on the local switching behavior of rare-earth modified bismuth ferrite ceramics

International Nuclear Information System (INIS)

Alikin, Denis O.; Turygin, Anton P.; Walker, Julian; Bencan, Andreja; Malic, Barbara; Rojac, Tadej; Shur, Vladimir Ya.; Kholkin, Andrei L.

2017-01-01

Piezoelectric properties and ferroelectric/ferroelastic domain switching behavior of polycrystalline ceramics are strongly influenced by local scale (i.e. <100 nm) phenomena, such as, the phase assemblages, domain structure, and defects. The method of ceramic synthesis strongly effects the local properties and thus plays a critical role in determining the macroscopic ferroelectric and piezoelectric performance. The link between synthesis and local scale properties of ferroelectrics is, however, rarely reported, especially for the emerging lead-free materials systems. In this work, we focus on samarium modified bismuth ferrite ceramics (Bi_0_._8_8Sm_0_._1_2FeO_3, BSFO) prepared by two methods: standard solid state reaction (SSR) and mechanochemi≿ally assisted synthesis (MAS). Each ceramic possesses different properties at the local scale and we used the piezoresponse force microscopy (PFM) complemented by transmission electron microscopy (TEM) to evaluate phase distribution, domain structure and polarization switching to show that an increase in the anti-polar phase assemblages within the polar matrix leads to notable changes in the local polarization switching. SSR ceramics exhibit larger internal bias fields relative to the MAS ceramics, and the grain boundaries produce a stronger effect on the local switching response. MAS ceramics were able to nucleate domains at lower electric-fields and grow them at faster rates, reaching larger final domain sizes than the SSR ceramics. Local evidence of the electric-field induced phase transition from the anti-ferroelectric Pbam to ferroelectric R3c phase was observed together with likely evidence of the existence of head-to-head/tail-to-tail charged domain walls and domain vortex core structures. By comparing the domain structure and local switching behavior of ceramics prepared by two different methods this work brings new insights the synthesis-structure-property relationship in lead-free piezoceramics.

Thermally tunable broadband omnidirectional and polarization-independent super absorber using phase change material VO2

Directory of Open Access Journals (Sweden)

Zhejun Liu

Full Text Available In this letter, we numerically demonstrate a thermally tunable super absorber by using phase change material VO2 as absorbing layer in metal-insulator-metal structure. An omnidirectional super absorption at λ=2.56μm can be realized by heating the patterned grating VO2 film due to magnetic resonance mechanism. Furthermore, a broadband super absorption higher than 0.8 in the entire 1.6μm–4μm region is achieved when VO2 film is patterned chessboard structure and transformed to metal phase beyond transition temperature. This broadband super absorption can be fulfilled in a wide range of incident angle (0°–70° and under all polarization conditions. Keywords: Phase change material, Metal-insulator-metal, Super absorption, Magnetic resonance

Correlative STED and Atomic Force Microscopy on Live Astrocytes Reveals Plasticity of Cytoskeletal Structure and Membrane Physical Properties during Polarized Migration

Directory of Open Access Journals (Sweden)

Nathalie Rouach

2017-04-01

Full Text Available The plasticity of the cytoskeleton architecture and membrane properties is important for the establishment of cell polarity, adhesion and migration. Here, we present a method which combines stimulated emission depletion (STED super-resolution imaging and atomic force microscopy (AFM to correlate cytoskeletal structural information with membrane physical properties in live astrocytes. Using STED compatible dyes for live cell imaging of the cytoskeleton, and simultaneously mapping the cell surface topology with AFM, we obtain unprecedented detail of highly organized networks of actin and microtubules in astrocytes. Combining mechanical data from AFM with optical imaging of actin and tubulin further reveals links between cytoskeleton organization and membrane properties. Using this methodology we illustrate that scratch-induced migration induces cytoskeleton remodeling. The latter is caused by a polarization of actin and microtubule elements within astroglial cell processes, which correlates strongly with changes in cell stiffness. The method opens new avenues for the dynamic probing of the membrane structural and functional plasticity of living brain cells. It is a powerful tool for providing new insights into mechanisms of cell structural remodeling during physiological or pathological processes, such as brain development or tumorigenesis.

The magnetic domain structures of Fe thin films on rectangular land-and-groove substrates studied by spin-polarized secondary electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Ueda, S. [Photodynamics Research Center, RIKEN, Aoba-ku, Sendai 980-0845 (Japan)]. E-mail: uedas@postman.riken.go.jp; Iwasaki, Y. [Photodynamics Research Center, RIKEN, Aoba-ku, Sendai 980-0845 (Japan); Micro Systems Network Company, Sony Corporation, Tagajo, Miyagi 985-0842 (Japan); Ushioda, S. [Photodynamics Research Center, RIKEN, Aoba-ku, Sendai 980-0845 (Japan); Research Institute of Electrical Communication, Tohoku University, Aoba-ku, Sendai 980-8577 (Japan)

2004-10-01

The magnetic domain structures of Fe thin films on rectangular land-and-groove structures have been studied by spin-polarized secondary electron microscopy (SP-SEM) under an applied dc field. The coercive force on the land area was found to be higher than that on the groove area in the magnetization reversal due to the difference in surface roughness between land and groove areas. The magnetic domain structure and domain wall pinning behavior during the reversal process depended on the direction of the magnetic field relative to the rectangles. These results show that the anisotropy induced by film geometry also contributes to the magnetization reversal process of thin magnetic films on land{sub a}nd{sub g}roove substrates.

Influence of the grain size on deleterious phase precipitation in superduplex stainless steel UNS S32750

International Nuclear Information System (INIS)

Pardal, J.M.; Tavares, S.S.M.; Fonseca, M. Cindra; Souza, J.A. de; Corte, R.R.A.; Abreu, H.F.G. de

2009-01-01

In the present work, the effect of grain size on deleterious phase precipitation in a superduplex stainless steel was investigated. The materials studied were heat treated isothermally at 800 deg. C, 850 deg. C and 900 deg. C for times up to 120 min. Hardness tests, light optical microscopy, scanning electron microscopy and X-ray diffraction were carried out to detect sigma and other harmful precipitate phases. The ferritic and austenitic grain sizes in the solution treated condition of the two steels analyzed were measured by electron backscattered diffraction (EBSD). Cyclic polarization corrosion tests were performed to evaluate the effect of grain size on the corrosion resistance. The results presented show that the precipitation of deleterious phases such as χ, σ and γ 2 , which can occur during welding and forming operations, is retarded by grain growth

Highly stable polarization independent Mach-Zehnder interferometer

Energy Technology Data Exchange (ETDEWEB)

Mičuda, Michal, E-mail: micuda@optics.upol.cz; Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav, E-mail: jezek@optics.upol.cz [Department of Optics, Faculty of Science, Palacký University, 17. listopadu 1192/12, 77146 Olomouc (Czech Republic)

2014-08-15

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27×40 cm offers individually accessible paths and shows phase deviation less than 0.4° during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3° or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually.

Biological applications of near-field scanning optical microscopy

NARCIS (Netherlands)

Moers, M.H.P.; Moers, Marco H.P.; Ruiter, A.G.T.; Jalocha, A.; Jalocha, Alain; van Hulst, N.F.

1995-01-01

Near-field Scanning Optical Microscopy (NSOM) is a true optical microscopic technique allowing fluorescence, absorption, reflection and polarization contrast with the additional advantage of nanometer lateral resolution, unlimited by diffraction and operation at ambient conditions. NSOM based on

Evaluation of corrosion behaviour of tantalum coating obtained by low pressure chemical vapor deposition using electrochemical polarization

Science.gov (United States)

Levesque, A.; Bouteville, A.; de Baynast, H.; Laveissière, B.

2002-06-01

antalum coatings are elaborated on titanium substrates through Low Pressure Chemical Vapor Deposition from tantalum pentachloride-hydrogen gaseous phase at a deposition temperature of 800 °C and a total pressure of 3.3 mbar. The aim of this paper is to evaluate the effectiveness of this tantalum coating in corrosive solution. Optical Microscopy and Scanning Electron Microscopy observations reveal that deposits are of 1.7 μm in thickness and conformal. The corrosion resistance of tantalum coated titanium substrates is quantified through standard potentiodynamic polarization method. Even for tantalum coatings exhibiting some defects as pores, the corrosion current density is as low as 0.25 mA/cm^2.in very agressive solutions like kroll reagent (HN03/HF).

New approaches for the analysis of confluent cell layers with quantitative phase digital holographic microscopy

Science.gov (United States)

Pohl, L.; Kaiser, M.; Ketelhut, S.; Pereira, S.; Goycoolea, F.; Kemper, Björn

2016-03-01

Digital holographic microscopy (DHM) enables high resolution non-destructive inspection of technical surfaces and minimally-invasive label-free live cell imaging. However, the analysis of confluent cell layers represents a challenge as quantitative DHM phase images in this case do not provide sufficient information for image segmentation, determination of the cellular dry mass or calculation of the cell thickness. We present novel strategies for the analysis of confluent cell layers with quantitative DHM phase contrast utilizing a histogram based-evaluation procedure. The applicability of our approach is illustrated by quantification of drug induced cell morphology changes and it is shown that the method is capable to quantify reliable global morphology changes of confluent cell layers.

Phase-selective staining of metal salt for scanning electron microscopy imaging of block copolymer film

Energy Technology Data Exchange (ETDEWEB)

Li, Jing Ze, E-mail: Lijinge@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Microelectronic and Solid-state Electronic, University of Electronic Science and Technology of China, Chengdu 610054 (China); State Key Laboratory of Polymer Materials Engineering (Sichuan University), Chengdu 610054 (China); Xinjiang Key Laboratory of Electronic Information Materials and Devices, Urumuqi 830011 (China); Wang, Ying; Hong Wang, Zhi; Mei, Di; Zou, Wei [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Microelectronic and Solid-state Electronic, University of Electronic Science and Technology of China, Chengdu 610054 (China); Min Chang, Ai [State Key Laboratory of Polymer Materials Engineering (Sichuan University), Chengdu 610054 (China); Wang, Qi [Xinjiang Key Laboratory of Electronic Information Materials and Devices, Urumuqi 830011 (China); Komura, Motonori; Ito, Kaori [Division of Integrated Molecular Engineering, Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Iyoda, Tomokazu, E-mail: Iyoda.t.aa@m.titech.ac.jp [Division of Integrated Molecular Engineering, Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan)

2010-09-15

Three metal salts, i.e., AgNO{sub 3}, HAuCl{sub 4}, and KCl, were proposed as novel staining reagents instead of traditional RuO{sub 4} and OsO{sub 4} labeled with expensive price and extreme toxicity for scanning electron microscopy (SEM) imaging of microphase separated block copolymer film. A simple and costless aqueous solution immersion procedure could ensure selective staining of the metal slat in specific phase of the nanostructured copolymer film, leading to a clear phase contrasted SEM image. The heavy metal salt has better staining effect, demonstrating stable and high signal-to-noise SEM image even at an acceleration voltage as high as 30 kV and magnification up to 250,000 times.

Electronically tunable femtosecond all-fiber optical parametric oscillator for multi-photon microscopy

Science.gov (United States)

Hellwig, Tim; Brinkmann, Maximilian; Fallnich, Carsten

2018-02-01

We present a femtosecond fiber-based optical parametric oscillator (FOPO) for multiphoton microscopy with wavelength tuning by electronic repetition rate tuning in combination with a dispersive filter in the FOPO cavity. The all-spliced, all-fiber FOPO cavity is based on polarization-maintaining fibers and a broadband output coupler, allowing to get access to the resonant signal pulses as well as the idler pulses simultaneously. The system was pumped by a gain-switched fiber-coupled laser diode emitting pulses at a central wavelength of 1030 nm and an electronically tunable repetition frequency of about 2 MHz. The pump pulses were amplified in an Ytterbium fiber amplifier system with a pulse duration after amplification of 13 ps. Tuning of the idler (1140 nm - 1300 nm) and signal wavelengths (850 nm - 940 nm) was achieved by changing the repetition frequency of the pump laser by about 4 kHz. The generated signal pulses reached a pulse energy of up to 9.2 nJ at 920 nm and were spectrally broadened to about 6 nm in the FOPO by a combination of self-phase and cross-phase modulation. We showed external compression of the idler pulses at 920 nm to about 430 fs and appleid them to two-photon excitation microscopy with green fluorescent dyes. The presented system constitutes an important step towards a fully fiber-integrated all-electronically tunable and, thereby, programmable light source and already embodies a versatile and flexible light source for applications, e.g., for smart microscopy.

Automatic phase aberration compensation for digital holographic microscopy based on deep learning background detection.

Science.gov (United States)

Nguyen, Thanh; Bui, Vy; Lam, Van; Raub, Christopher B; Chang, Lin-Ching; Nehmetallah, George

2017-06-26

We propose a fully automatic technique to obtain aberration free quantitative phase imaging in digital holographic microscopy (DHM) based on deep learning. The traditional DHM solves the phase aberration compensation problem by manually detecting the background for quantitative measurement. This would be a drawback in real time implementation and for dynamic processes such as cell migration phenomena. A recent automatic aberration compensation approach using principle component analysis (PCA) in DHM avoids human intervention regardless of the cells' motion. However, it corrects spherical/elliptical aberration only and disregards the higher order aberrations. Traditional image segmentation techniques can be employed to spatially detect cell locations. Ideally, automatic image segmentation techniques make real time measurement possible. However, existing automatic unsupervised segmentation techniques have poor performance when applied to DHM phase images because of aberrations and speckle noise. In this paper, we propose a novel method that combines a supervised deep learning technique with convolutional neural network (CNN) and Zernike polynomial fitting (ZPF). The deep learning CNN is implemented to perform automatic background region detection that allows for ZPF to compute the self-conjugated phase to compensate for most aberrations.

High resolution electron microscopy of the triply incommensurate phase of 2H-TaSe2

Science.gov (United States)

Onozuka, Takashi; Otsuka, Nobuo; Sato, Hiroshi

1986-09-01

The triply incommensurate phase of 2H-TaSe2 obtained by cooling from the normal phase was investigated by transmission electron microscopy between 87 and 113 K with the resolution of 3 Å, one order of magnitude better than earlier experiments. Moirélike patterns observed in this phase were confirmed to be interference fringes due to the first- and second-order diffraction beams (with small separation and possibly with higher-order diffraction beams) from the incommensurate structure and were not due to the dark-field diffraction contrast of domains of the commensurate structure as interpreted earlier. Lattice fringes (~9 Å) of this modulated phase do not show any discontinuity across the boundaries of regions of different contrasts of the moirélike fringes which is expected from domain boundaries. Instead, a periodic change in the spacing of the lattice fringes (phase-slip region) expected from the superposition of split superlattice spots in forming the lattice image is observed. This is what is believed to be the first direct observation of the existence of the phase-slip region which is also expected from the discommensuration theory. A series of observations presented here thus shows that the triply incommensurate phase is intrinsically incommensurate and suggests the need for a modification of interpretations of this phase in terms of the double honeycomb discommensuration model.

Polarized-neutron-scattering study of the spin-wave excitations in the 3-k ordered phase of uranium antimonide.

Science.gov (United States)

Magnani, N; Caciuffo, R; Lander, G H; Hiess, A; Regnault, L-P

2010-03-24

The anisotropy of magnetic fluctuations propagating along the [1 1 0] direction in the ordered phase of uranium antimonide has been studied using polarized inelastic neutron scattering. The observed polarization behavior of the spin waves is a natural consequence of the longitudinal 3-k magnetic structure; together with recent results on the 3-k-transverse uranium dioxide, these findings establish this technique as an important tool to study complex magnetic arrangements. Selected details of the magnon excitation spectra of USb have also been reinvestigated, indicating the need to revise the currently accepted theoretical picture for this material.

Imaging bacterial spores by soft-x-ray microscopy

International Nuclear Information System (INIS)

Stead, A.D.; Ford, T.W.; Judge, J.

1997-01-01

Bacterial spores are able to survive dehydration, but neither the physiological nor structural basis of this have been fully elucidated. Furthermore, once hydrated, spores often require activation before they will germinate. Several treatments can be used to activate spores, but in the case of Bacillus subtlis the most effective is heat treatment. The physiological mechanism associated with activation is also not understood, but some workers suggest that the loss of calcium from the spores may be critical. However, just prior to germination, the spores change from being phase bright to phase dark when viewed by light microscopy. Imaging spores by soft x-ray microscopy is possible without fixation. Thus, in contrast to electron microscopy, it is possible to compare the structure of dehydrated and hydrated spores in a manner not possible previously. A further advantage is that it is possible to monitor individual spores by phase contrast light microscopy immediately prior to imaging with soft x-rays; whereas, with both electron microscopy and biochemical studies, it is a population of spores being studied without knowledge of the phase characteristics of individual spores. This study has therefore tried to compare dehydrated and hydrated spores and to determine if there is a mass loss from individual spores as they pass the transition from being phase bright to phase dark

Imaging bacterial spores by soft-x-ray microscopy

Energy Technology Data Exchange (ETDEWEB)

Stead, A.D.; Ford, T.W. [Univ. of London, Surrey (United Kingdom); Judge, J. [Unilever plc, Sharnbrook (United Kingdom)] [and others

1997-04-01

Bacterial spores are able to survive dehydration, but neither the physiological nor structural basis of this have been fully elucidated. Furthermore, once hydrated, spores often require activation before they will germinate. Several treatments can be used to activate spores, but in the case of Bacillus subtlis the most effective is heat treatment. The physiological mechanism associated with activation is also not understood, but some workers suggest that the loss of calcium from the spores may be critical. However, just prior to germination, the spores change from being phase bright to phase dark when viewed by light microscopy. Imaging spores by soft x-ray microscopy is possible without fixation. Thus, in contrast to electron microscopy, it is possible to compare the structure of dehydrated and hydrated spores in a manner not possible previously. A further advantage is that it is possible to monitor individual spores by phase contrast light microscopy immediately prior to imaging with soft x-rays; whereas, with both electron microscopy and biochemical studies, it is a population of spores being studied without knowledge of the phase characteristics of individual spores. This study has therefore tried to compare dehydrated and hydrated spores and to determine if there is a mass loss from individual spores as they pass the transition from being phase bright to phase dark.

Scanning tunneling microscopy and spectroscopy on GaN and InGaN surfaces; Rastertunnelmikroskopie und -spektroskopie an GaN- und InGaN-Oberflaechen

Energy Technology Data Exchange (ETDEWEB)

Krueger, David

2009-12-02

Optelectronic devices based on gallium nitride (GaN) and indium gallium nitride (InGaN) are in the focus of research since more than 20 years and still have great potential for optical applications. In the first part of this work non-polar surfaces of GaN are investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). In SEM and AFM, the (1 anti 100)- and especially the (anti 2110)-plane are quite corrugated. For the first time, the (anti 2110)-plane of GaN is atomically resolved in STM. In the second part InGaN quantum dot layers are investigated by X-ray photoelectron spectroscopy (XPS), scanning tunneling spectroscopy (STS) and STM. The STMmeasurements show the dependency of surface morphology on growth conditions in the metalorganic vapour phase epitaxy (MOVPE). Nucleation, a new MOVPE-strategy, is based on phase separations on surfaces. It is shown that locally varying density of states and bandgaps can be detected by STS, that means bandgap histograms and 2D-bandgap-mapping. (orig.)

Polarization contrast in reflection near-field optical microscopy with uncoated fibre tips

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Langbein, Wolfgang; Hvam, Jørn Märcher

1999-01-01

Using cross-hatched, patterned semiconductor surfaces and round 20-nm-thick gold pads on semiconductor wafers, we investigate the imaging characteristics of a reflection near-field optical microscope with an uncoated fibre tip for different polarization configurations and light wavelengths....... Is is shown that cross-polarized detection allows one to effectively suppress far-field components in the detected signal and to realise imaging of optical contrast on the sub-wavelength scale. The sensitivity window of our microscope, i.e. the scale on which near-field optical images represent mainly optical...

Multiwavelength Polarization of Rotation-powered Pulsars

Energy Technology Data Exchange (ETDEWEB)

Harding, Alice K.; Kalapotharakos, Constantinos [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2017-05-10

Polarization measurements provide strong constraints on models for emission from rotation-powered pulsars. We present multiwavelength polarization predictions showing that measurements over a range of frequencies can be particularly important for constraining the emission location, radiation mechanisms, and system geometry. The results assume a generic model for emission from the outer magnetosphere and current sheet in which optical to hard X-ray emission is produced by synchrotron radiation (SR) from electron–positron pairs and γ -ray emission is produced by curvature radiation (CR) or SR from accelerating primary electrons. The magnetic field structure of a force-free magnetosphere is assumed and the phase-resolved and phase-averaged polarization is calculated in the frame of an inertial observer. We find that large position angle (PA) swings and deep depolarization dips occur during the light-curve peaks in all energy bands. For synchrotron emission, the polarization characteristics are strongly dependent on photon emission radius with larger, nearly 180°, PA swings for emission outside the light cylinder (LC) as the line of sight crosses the current sheet. The phase-averaged polarization degree for SR is less that 10% and around 20% for emission starting inside and outside the LC, respectively, while the polarization degree for CR is much larger, up to 40%–60%. Observing a sharp increase in polarization degree and a change in PA at the transition between X-ray and γ -ray spectral components would indicate that CR is the γ -ray emission mechanism.

Optical-wireless-optical full link for polarization multiplexing quadrature amplitude/phase modulation signal transmission.

Science.gov (United States)

Li, Xinying; Yu, Jianjun; Chi, Nan; Zhang, Junwen

2013-11-15

We propose and experimentally demonstrate an optical wireless integration system at the Q-band, in which up to 40 Gb/s polarization multiplexing multilevel quadrature amplitude/phase modulation (PM-QAM) signal can be first transmitted over 20 km single-mode fiber-28 (SMF-28), then delivered over a 2 m 2 × 2 multiple-input multiple-output wireless link, and finally transmitted over another 20 km SMF-28. The PM-QAM modulated wireless millimeter-wave (mm-wave) signal at 40 GHz is generated based on the remote heterodyning technique, and demodulated by the radio-frequency transparent photonic technique based on homodyne coherent detection and baseband digital signal processing. The classic constant modulus algorithm equalization is used at the receiver to realize polarization demultiplexing of the PM-QAM signal. For the first time, to the best of our knowledge, we realize the conversion of the PM-QAM modulated wireless mm-wave signal to the optical signal as well as 20 km fiber transmission of the converted optical signal.

Trace-level determination of polar flavour compounds in butter by solid-phase extraction and gas chromatography-mass spectrometry.

Science.gov (United States)

Adahchour, M; Vreuls, R J; van der Heijden, A; Brinkman, U A

1999-06-04

Volatile compounds are responsible for the aromas of butter. A simple technique for the determination of these components is described which is based on solid-phase extraction (SPE) after melting of the butter and separation of the aqueous phase from the fat. Volatile flavours present in the water fraction are collected by off-line SPE on cartidges packed with a copolymer sorbent. After desorption with 500 microliters of methyl acetate, 1-microliter aliquots are quantified and/or identified by gas chromatography-mass spectrometry. The procedure was tested with respect to recovery, linearity and limit of detection in real-life samples using five polar model analytes. It allows the characterisation of polar flavour compounds in butter prior to and after heat treatment at 170 degrees C. From the five model compounds, vanillin, traces of diacetyl and maltol were found to be present in the butter samples. After heat treatment 500-1000-fold increased concentration of maltol, and substantial amounts of furaneol were detected.

Spin Polarization Inversion at Benzene-Absorbed Fe4N Surface

KAUST Repository

Zhang, Qian; Mi, Wenbo; Wang, Xiaocha; Wang, Xuhui

2015-01-01

We report a first-principle study on electronic structure and simulation of the spin-polarized scanning tunneling microscopy graphic of a benzene/Fe4N interface. Fe4N is a compound ferromagnet suitable for many spintronic applications. We found that, depending on the particular termination schemes and interface configurations, the spin polarization on the benzene surface shows a rich variety of properties ranging from cosine-type oscillation to polarization inversion. Spin-polarization inversion above benzene is resulting from the hybridizations between C pz and the out-of-plane d orbitals of Fe atom.

Spin Polarization Inversion at Benzene-Absorbed Fe4N Surface

KAUST Repository

Zhang, Qian

2015-05-27

We report a first-principle study on electronic structure and simulation of the spin-polarized scanning tunneling microscopy graphic of a benzene/Fe4N interface. Fe4N is a compound ferromagnet suitable for many spintronic applications. We found that, depending on the particular termination schemes and interface configurations, the spin polarization on the benzene surface shows a rich variety of properties ranging from cosine-type oscillation to polarization inversion. Spin-polarization inversion above benzene is resulting from the hybridizations between C pz and the out-of-plane d orbitals of Fe atom.

Label-free imaging of developing vasculature in zebrafish with phase variance optical coherence microscopy

Science.gov (United States)

Chen, Yu; Fingler, Jeff; Trinh, Le A.; Fraser, Scott E.

2016-03-01

A phase variance optical coherence microscope (pvOCM) has been created to visualize blood flow in the vasculature of zebrafish embryos, without using exogenous labels. The pvOCM imaging system has axial and lateral resolutions of 2 μm in tissue, and imaging depth of more than 100 μm. Imaging of 2-5 days post-fertilization zebrafish embryos identified the detailed structures of somites, spinal cord, gut and notochord based on intensity contrast. Visualization of the blood flow in the aorta, veins and intersegmental vessels was achieved with phase variance contrast. The pvOCM vasculature images were confirmed with corresponding fluorescence microscopy of a zebrafish transgene that labels the vasculature with green fluorescent protein. The pvOCM images also revealed functional information of the blood flow activities that is crucial for the study of vascular development.

Generation of 1.024-Tb/s Nyquist-WDM phase-conjugated twin vector waves by a polarization-insensitive optical parametric amplifier for fiber-nonlinearity-tolerant transmission

DEFF Research Database (Denmark)

Liu, Xiang; Hu, Hao; Chandrasekhar, S.

2014-01-01

We experimentally demonstrate the generation of 1.024-Tb/s Nyquist-WDM phase-conjugated vector twin waves (PCTWs), consisting of eight 128-Gb/s polarization-division-multiplexed QPSK signals and their idlers, by a broadband polarization-insensitive fiber optic parametric amplifier. This novel all...

Sorption behavior of charged and neutral polar organic compounds on solid phase extraction materials: which functional group governs sorption?

NARCIS (Netherlands)

Bäuerlein, P.S.; Mansell, J.E.; ter Laak, T.L.; de Voogt, P.

2012-01-01

Numerous polar anthropogenic organic chemicals have been found in the aqueous environment. Solid phase extraction (SPE) has been applied for the isolation of these from aqueous matrices, employing various materials. Nevertheless, little is known about the influence of functional groups on the

Polarization-dependent single-beam laser-induced grating-like effects on titanium films

International Nuclear Information System (INIS)

Camacho-Lopez, Santiago; Evans, Rodger; Escobar-Alarcon, Luis; Camacho-Lopez, Miguel A.; Camacho-Lopez, Marco A.

2008-01-01

In this paper we present results on polarization-dependent laser-induced effects on titanium (Ti) thin films. We irradiated the titanium films, in ambient air, using a nanosecond Nd:YAG laser (532 nm, 9 ns pulse duration, 10 Hz). Using a series of pulses of fluence well below the ablation threshold, it was possible to form grating-like structures, whose grooves run parallel to the linear polarization of the incident beam. No grating-like structures were obtained when circularly polarized light was used. Our results revealed the remarkable formation of tiny (100 nm and even smaller diameter) craters, which self-arrange quasi-periodically along the ridges (never on the valleys) of the grating-like structure. Optical and scanning electron microscopy were used to study the laser-induced changes on the surface of the titanium films. Micro-Raman spectroscopy was used to analyze the irradiated areas on the titanium films. The Raman analysis demonstrated that the grooves in the grating-like structure, build up from the laser-induced oxidation of titanium. This is the first time, to the best of our knowledge, that periodic surface structures are reported to be induced below the ablation threshold regime, with the grooves made of crystalline metal oxide, in this case TiO 2 in the well-known Rutile phase. The laser irradiated areas on the film acquired selective (upon recording polarization) holographic reflectance

Polarization-dependent single-beam laser-induced grating-like effects on titanium films

Energy Technology Data Exchange (ETDEWEB)

Camacho-Lopez, Santiago [Departamento de Optica, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Km 107 Carretera Tijuana-Ensenada, Ensenada, Baja California 22860 (Mexico)], E-mail: camachol@cicese.mx; Evans, Rodger [Departamento de Optica, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Km 107 Carretera Tijuana-Ensenada, Ensenada, Baja California 22860 (Mexico); Escobar-Alarcon, Luis [Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, Apdo. Postal 18-1027, Mexico DF 11801 (Mexico); Camacho-Lopez, Miguel A. [Facultad de Medicina, Universidad Autonoma del Estado de Mexico, Paseo Tollocan s/n, esq. Jesus Carranza, Toluca, Estado de Mexico 50120 (Mexico); Camacho-Lopez, Marco A. [Facultad de Quimica, Universidad Autonoma del Estado de Mexico, Tollocan s/n, esq. Paseo Colon, Toluca, Estado de Mexico, 50110 (Mexico)

2008-12-30

In this paper we present results on polarization-dependent laser-induced effects on titanium (Ti) thin films. We irradiated the titanium films, in ambient air, using a nanosecond Nd:YAG laser (532 nm, 9 ns pulse duration, 10 Hz). Using a series of pulses of fluence well below the ablation threshold, it was possible to form grating-like structures, whose grooves run parallel to the linear polarization of the incident beam. No grating-like structures were obtained when circularly polarized light was used. Our results revealed the remarkable formation of tiny (100 nm and even smaller diameter) craters, which self-arrange quasi-periodically along the ridges (never on the valleys) of the grating-like structure. Optical and scanning electron microscopy were used to study the laser-induced changes on the surface of the titanium films. Micro-Raman spectroscopy was used to analyze the irradiated areas on the titanium films. The Raman analysis demonstrated that the grooves in the grating-like structure, build up from the laser-induced oxidation of titanium. This is the first time, to the best of our knowledge, that periodic surface structures are reported to be induced below the ablation threshold regime, with the grooves made of crystalline metal oxide, in this case TiO{sub 2} in the well-known Rutile phase. The laser irradiated areas on the film acquired selective (upon recording polarization) holographic reflectance.

Live Cell Refractometry Using Hilbert Phase Microscopy and Confocal Reflectance Microscopy†

Science.gov (United States)

Lue, Niyom; Choi, Wonshik; Popescu, Gabriel; Yaqoob, Zahid; Badizadegan, Kamran; Dasari, Ramachandra R.; Feld, Michael S.

2010-01-01

Quantitative chemical analysis has served as a useful tool for understanding cellular metabolisms in biology. Among many physical properties used in chemical analysis, refractive index in particular has provided molecular concentration that is an important indicator for biological activities. In this report, we present a method of extracting full-field refractive index maps of live cells in their native states. We first record full-field optical thickness maps of living cells by Hilbert phase microscopy and then acquire physical thickness maps of the same cells using a custom-built confocal reflectance microscope. Full-field and axially averaged refractive index maps are acquired from the ratio of optical thickness to physical thickness. The accuracy of the axially averaged index measurement is 0.002. This approach can provide novel biological assays of label-free living cells in situ. PMID:19803506

Linear polarization of BY Draconis

International Nuclear Information System (INIS)

Koch, R.H.; Pfeiffer, R.J.

1976-01-01

Linear polarization measurements are reported in four bandpasses for the flare star BY Dra. The red polarization is intrinsically variable at a confidence level greater than 99 percent. On a time scale of many months, the variability is not phase-locked to either a rotational or a Keplerian ephemeris. The observations of the three other bandpasses are useful principally to indicate a polarization spectrum rising toward shorter wavelengths

Reversible Resistance Switching Effect in Amorphous Ge1Sb4Te7 Thin Films without Phase Transformation

International Nuclear Information System (INIS)

Hua-Jun, Sun; Li-Song, Hou; Yi-Qun, Wu; Xiao-Dong, Tang

2009-01-01

We demonstrate a reversible resistance switching effect that does not rely on amorphous-crystalline phase transformation in a nanoscale capacitor-like cell using Ge 1 Sb 4 Te 7 films as the working material. The polarity and amplitude of the applied electric voltage switches the cell resistance between low- and high-resistance states, as revealed in the current-voltage characteristics of the film by conductive atomic force microscopy (CAFM). This reversible SET/RESET switching effect is induced by voltage pulses and their polarity. The change of electrical resistance due to the switching effect is approximately two orders of magnitude

Morphologies of laser-induced damage in hafnia-silica multilayer mirror and polarizer coatings

International Nuclear Information System (INIS)

Genin, F.Y.; Stolz, C.J.

1996-08-01

Hafnium-silica multilayer mirrors and polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The mirrors and polarizers were coated for operation at 1053 nm at 45 degree and at Brewster's angle (56 degree), respectively. They were tested with a single 3-ns laser pulse. Morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies were found: pits, flatbottom pits, scalds, and delaminates. The pits and flat bottom pits ( 2 ). The pits seemed to result from ejection of nodular defects by causing local enhancement of the electric field. Scalds and delaminates could be observed at higher fluences (above 13 J/cm 2 ) and seemed to result from the formation of plasmas on the surface. These damage types often originated at pits and were less than 300 μm diameter; their size increased almost linearly with fluence. Finally, effects of the damage on the beam (reflectivity degradation and phase modulations) were measured

Interrelation between domain structures and polarization switching in hybrid improper ferroelectric Ca3(Mn,Ti)2O7

Science.gov (United States)

Gao, Bin; Huang, Fei-Ting; Wang, Yazhong; Kim, Jae-Wook; Wang, Lihai; Lim, Seong-Joon; Cheong, Sang-Wook

2017-05-01

Ca3Mn2O7 and Ca3Ti2O7 have been proposed as the prototypical hybrid improper ferroelectrics (HIFs), and a significant magnetoelectric (ME) coupling in magnetic Ca3Mn2O7 is, in fact, reported theoretically and experimentally. Although the switchability of polarization is confirmed in Ca3Ti2O7 and other non-magnetic HIFs, there is no report of switchable polarization in the isostructural Ca3Mn2O7. We constructed the phase diagram of Ca3Mn2-xTixO7 through our systematic study of a series of single crystalline Ca3Mn2-xTixO7 (x = 0, 0.1, 1, 1.5, and 2). Using transmission electron microscopy, we have unveiled the unique domain structure of Ca3Mn2O7: the high-density 90° stacking of a- and b-domains along the c-axis due to the phase transition through an intermediate Acca phase and the in-plane irregular wavy ferroelastic twin domains. The interrelation between domain structures and physical properties is unprecedented: the stacking along the c-axis prevents the switching of polarization and causes the irregular in-plane ferroelastic domain pattern. In addition, we have determined the magnetic phase diagram and found complex magnetism of Ca3Mn2O7 with isotropic canted moments. These results lead to negligible observable ME coupling in Ca3Mn2O7 and guide us to explore multiferroics with large ME coupling.

Manipulating the ferroelectric polarization state of BaTiO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Datta, S.; Rioult, M.; Stanescu, D.; Magnan, H.; Barbier, A., E-mail: antoine.barbier@cea.fr

2016-05-31

Controlling the ferroelectric polarization at macroscopic or microscopic levels is crucial in the framework of the development of ferroelectric materials used in yet challenging photo-electrochemical (PEC) cells and spintronic applications. We report here on polarization methods allowing to electrically polarize prototypical samples of BaTiO{sub 3} (001) films. Epitaxial single crystalline layers were grown up to a thickness of 25 nm by atomic oxygen assisted molecular beam epitaxy on 1 at.% Nb doped SrTiO{sub 3} (001) single crystals. The samples were both microscopically and macroscopically polarized using Piezoresponse Force Microscopy and electrochemical poling in an electrolyte respectively. In addition we demonstrate the possibility to retrieve a quasi-native mixed ferroelectric polarization state after annealing. These polarization methods may be applied to many other ferroelectric thin films. - Highlights: • Ferroelectricity of BaTiO{sub 3} layers can be micro- and macroscopically controlled. • Microscopic ferroelectric domains are defined with piezoresponse force microscopy. • Poling in a LiClO{sub 4} electrolyte is a macroscopic poling method. • Air annealing above the Curie temperature “resets” the polarization state.

Surface structure of YBa2Cu3O7-x probed by reversed-bias scanning tunneling microscopy

International Nuclear Information System (INIS)

Edwards, H.L.; Markert, J.T.; Lozanne, A.L.d.

1994-01-01

We report the results of scanning tunneling microscopy studies on high-quality single crystals of YBa 2 Cu 3 O 7-x (YBCO) which were cleaved along a basal plane in situ at 20 K prior to measurement. The initial results of a systematic study of the YBCO surface are presented. Reversed-bias images of the CuO chain layer reveal modulations 3.3±0.3|b|=1.3±0.1 nm in wavelength which change phase by 180 degree under bias polarity reversal along solid chains, and are invariant under bias polarity reversal at a point defect. Regions of sharp unit-cell-sized square corrugations with disordered islands are also observed. We interpret these new results in terms of our previous model [H. L. Edwards, J. T. Markert, and A. L. de Lozanne, Phys. Rev. Lett. 69, 2967 (1992)] of the cleaved YBCO surface

Formation and stability of Pb-, Zn- and Cu-PO4 phases at low temperatures: Implications for heavy metal fixation in polar environments

International Nuclear Information System (INIS)

White, Duanne A.; Hafsteinsdóttir, Erla G.; Gore, Damian B.; Thorogood, Gordon; Stark, Scott C.

2012-01-01

Low temperatures and frequent soil freeze–thaw in polar environments present challenges for the immobilisation of metals. To address these challenges we investigated the chemical forms of Pb, Zn and Cu in an Antarctic landfill, examined in vitro reaction kinetics of these metals and orthophosphate at 2 and 22 °C for up to 185 days, and subjected the products to freeze–thaw. Reaction products at both temperatures were similar, but the rate of production varied, with Cu-PO 4 phases forming faster, and the Zn- and Pb-PO 4 phases slower at 2 °C. All metal-orthophosphate phases produced were stable during a 2.5 h freeze–thaw cycle to −30 °C. Metal immobilisation using orthophosphate can be successful in polar regions, but treatments will need to consider differing mineral stabilities and reaction rates at low temperatures. - Highlights: ► We identify Cu, Pb and Zn species in an Antarctic Landfill. ► We identify the products and rates of reactions between metals and PO 4 3− at 2 and 22 °C. ► We test the stability of metal-orthophosphate species during freeze–thaw. ► We conclude that orthophosphate may immobilize metals in freezing ground. - Pb, Cu and Zn react with PO 4 3− at low temperatures (2 °C) to form low solubility metal-PO 4 phases at rates that may enable the in-situ remediation of metal contaminated soils in polar areas.

Multifocus microscopy with precise color multi-phase diffractive optics applied in functional neuronal imaging.

Science.gov (United States)

Abrahamsson, Sara; Ilic, Rob; Wisniewski, Jan; Mehl, Brian; Yu, Liya; Chen, Lei; Davanco, Marcelo; Oudjedi, Laura; Fiche, Jean-Bernard; Hajj, Bassam; Jin, Xin; Pulupa, Joan; Cho, Christine; Mir, Mustafa; El Beheiry, Mohamed; Darzacq, Xavier; Nollmann, Marcelo; Dahan, Maxime; Wu, Carl; Lionnet, Timothée; Liddle, J Alexander; Bargmann, Cornelia I

2016-03-01

Multifocus microscopy (MFM) allows high-resolution instantaneous three-dimensional (3D) imaging and has been applied to study biological specimens ranging from single molecules inside cells nuclei to entire embryos. We here describe pattern designs and nanofabrication methods for diffractive optics that optimize the light-efficiency of the central optical component of MFM: the diffractive multifocus grating (MFG). We also implement a "precise color" MFM layout with MFGs tailored to individual fluorophores in separate optical arms. The reported advancements enable faster and brighter volumetric time-lapse imaging of biological samples. In live microscopy applications, photon budget is a critical parameter and light-efficiency must be optimized to obtain the fastest possible frame rate while minimizing photodamage. We provide comprehensive descriptions and code for designing diffractive optical devices, and a detailed methods description for nanofabrication of devices. Theoretical efficiencies of reported designs is ≈90% and we have obtained efficiencies of > 80% in MFGs of our own manufacture. We demonstrate the performance of a multi-phase MFG in 3D functional neuronal imaging in living C. elegans.

PF2fit: Polar Fast Fourier Matched Alignment of Atomistic Structures with 3D Electron Microscopy Maps.

Directory of Open Access Journals (Sweden)

Radhakrishna Bettadapura

2015-10-01

Full Text Available There continue to be increasing occurrences of both atomistic structure models in the PDB (possibly reconstructed from X-ray diffraction or NMR data, and 3D reconstructed cryo-electron microscopy (3D EM maps (albeit at coarser resolution of the same or homologous molecule or molecular assembly, deposited in the EMDB. To obtain the best possible structural model of the molecule at the best achievable resolution, and without any missing gaps, one typically aligns (match and fits the atomistic structure model with the 3D EM map. We discuss a new algorithm and generalized framework, named PF(2 fit (Polar Fast Fourier Fitting for the best possible structural alignment of atomistic structures with 3D EM. While PF(2 fit enables only a rigid, six dimensional (6D alignment method, it augments prior work on 6D X-ray structure and 3D EM alignment in multiple ways: Scoring. PF(2 fit includes a new scoring scheme that, in addition to rewarding overlaps between the volumes occupied by the atomistic structure and 3D EM map, rewards overlaps between the volumes complementary to them. We quantitatively demonstrate how this new complementary scoring scheme improves upon existing approaches. PF(2 fit also includes two scoring functions, the non-uniform exterior penalty and the skeleton-secondary structure score, and implements the scattering potential score as an alternative to traditional Gaussian blurring. Search. PF(2 fit utilizes a fast polar Fourier search scheme, whose main advantage is the ability to search over uniformly and adaptively sampled subsets of the space of rigid-body motions. PF(2 fit also implements a new reranking search and scoring methodology that considerably improves alignment metrics in results obtained from the initial search.

Phase diagram of tetradecyltrimethylammonium bromide (TTAB) + water + octanol system with application of mechanical deformation

Science.gov (United States)

Yavuz, Aykut Evren; Masalci, Özgür; Kazanci, Nadide

2014-11-01

Morphological properties of tetradecyltrimethylammonium bromide (TTAB) + water + octanol system in different concentrations have been studied. In the process, isotropic phase (L1) and nematic calamitic (NC), nematic discotic (ND), hexagonal E and lamellar D anizotropic mesophases have been determined by polarizing microscopy method and partial ternary phase diagram of the system set up. Textural properties of the anisotropic mesophases of the system have been discussed and their birefringence values measured. Mechanical deformation has been applied to the mesophases. The textural properties and the birefringence values have been observed to be changed by the deformation, after and before which changes have been compared.

Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

Science.gov (United States)

Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

2016-02-01

Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

Performance study of the gamma-ray bursts polarimeter POLAR

Science.gov (United States)

Sun, J. C.; Wu, B. B.; Bao, T. W.; Batsch, T.; Bernasconi, T.; Britvitch, I.; Cadoux, F.; Cernuda, I.; Chai, J. Y.; Dong, Y. W.; Gauvin, N.; Hajdas, W.; He, J. J.; Kole, M.; Kong, M. N.; Kong, S. W.; Lechanoine-Leluc, C.; Li, Lu; Liu, J. T.; Liu, X.; Marcinkowski, R.; Orsi, S.; Pohl, M.; Produit, N.; Rapin, D.; Rutczynska, A.; Rybka, D.; Shi, H. L.; Song, L. M.; Szabelski, J.; Wang, R. J.; Wen, X.; Xiao, H. L.; Xiong, S. L.; Xu, H. H.; Xu, M.; Zhang, L.; Zhang, L. Y.; Zhang, S. N.; Zhang, X. F.; Zhang, Y. J.; Zwolinska, A.

2016-07-01

The Gamma-ray Burst Polarimeter-POLAR is a highly sensitive detector which is dedicated to the measurement of GRB's polarization with a large effective detection area and a large field of view (FOV). The optimized performance of POLAR will contribute to the capture and measurement of the transient sources like GRBs and Solar Flares. The detection energy range of POLAR is 50 keV 500 keV, and mainly dominated by the Compton scattering effect. POLAR consists of 25 detector modular units (DMUs), and each DMU is composed of low Z material Plastic Scintillators (PS), multi-anode photomultipliers (MAPMT) and multi-channel ASIC Front-end Electronics (FEE). POLAR experiment is an international collaboration project involving China, Switzerland and Poland, and is expected to be launched in September in 2016 onboard the Chinese space laboratory "Tiangong-2 (TG-2)". With the efforts from the collaborations, POLAR has experienced the Demonstration Model (DM) phase, Engineering and Qualification Model (EQM) phase, Qualification Model (QM) phase, and now a full Flight Model (FM) of POLAR has been constructed. The FM of POLAR has passed the environmental acceptance tests (thermal cycling, vibration, shock and thermal vacuum tests) and experienced the calibration tests with both radioactive sources and 100% polarized Gamma-Ray beam at ESRF after its construction. The design of POLAR, Monte-Carlo simulation analysis, as well as the performance test results will all be introduced in this paper.

Solid-phase extraction element based on epoxy polymer monolith for determination of polar organic compounds in aqueous media.

Science.gov (United States)

Takahashi, Tadashi; Odagiri, Kayo; Watanabe, Atsushi; Watanabe, Chuichi; Kubo, Takuya; Hosoya, Ken

2011-10-01

A solid-phase extraction element based on epoxy polymer monolith was fabricated for sorptive enrichment of polar compounds from liquid and gaseous samples. After ultrasonication of the element in an aqueous solution for a given period of time, the thermal desorption (TD) using a pyrolyzer with gas chromatography/mass spectrometry (GC/MS), in which TD temperature was programmed from 50 to 250 °C for the analytes absorbed in the element, was used to evaluate the element for basic extraction performance using the aqueous standard mixtures consisting of compounds having varied polarities such as hexanol, isoamyl acetate, linalool, furfural and decanoic acid, in concentrations ranging from 10 μg/L to 1 mg/L. Excellent linear relationships were observed for all compounds in the standard mixture, except decanoic acid. In the extraction of beverages such as red wine, the extraction element showed stronger adsorption characteristics for polar compounds such as alcohols and acids than a non-polar polydimethylsiloxane-based element. This feature is derived from the main polymer structure along with hydroxyl and amino groups present in the epoxy-based monolith polymer matrix. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Silicon photonic integrated circuit swept-source optical coherence tomography receiver with dual polarization, dual balanced, in-phase and quadrature detection.

Science.gov (United States)

Wang, Zhao; Lee, Hsiang-Chieh; Vermeulen, Diedrik; Chen, Long; Nielsen, Torben; Park, Seo Yeon; Ghaemi, Allan; Swanson, Eric; Doerr, Chris; Fujimoto, James

2015-07-01

Optical coherence tomography (OCT) is a widely used three-dimensional (3D) optical imaging method with many biomedical and non-medical applications. Miniaturization, cost reduction, and increased functionality of OCT systems will be critical for future emerging clinical applications. We present a silicon photonic integrated circuit swept-source OCT (SS-OCT) coherent receiver with dual polarization, dual balanced, in-phase and quadrature (IQ) detection. We demonstrate multiple functional capabilities of IQ polarization resolved detection including: complex-conjugate suppressed full-range OCT, polarization diversity detection, and polarization-sensitive OCT. To our knowledge, this is the first demonstration of a silicon photonic integrated receiver for OCT. The integrated coherent receiver provides a miniaturized, low-cost solution for SS-OCT, and is also a key step towards a fully integrated high speed SS-OCT system with good performance and multi-functional capabilities. With further performance improvement and cost reduction, photonic integrated technology promises to greatly increase penetration of OCT systems in existing applications and enable new applications.

Polarization Imaging Apparatus with Auto-Calibration

Science.gov (United States)

Zou, Yingyin Kevin (Inventor); Zhao, Hongzhi (Inventor); Chen, Qiushui (Inventor)

2013-01-01

A polarization imaging apparatus measures the Stokes image of a sample. The apparatus consists of an optical lens set, a first variable phase retarder (VPR) with its optical axis aligned 22.5 deg, a second variable phase retarder with its optical axis aligned 45 deg, a linear polarizer, a imaging sensor for sensing the intensity images of the sample, a controller and a computer. Two variable phase retarders were controlled independently by a computer through a controller unit which generates a sequential of voltages to control the phase retardations of the first and second variable phase retarders. A auto-calibration procedure was incorporated into the polarization imaging apparatus to correct the misalignment of first and second VPRs, as well as the half-wave voltage of the VPRs. A set of four intensity images, I(sub 0), I(sub 1), I(sub 2) and I(sub 3) of the sample were captured by imaging sensor when the phase retardations of VPRs were set at (0,0), (pi,0), (pi,pi) and (pi/2,pi), respectively. Then four Stokes components of a Stokes image, S(sub 0), S(sub 1), S(sub 2) and S(sub 3) were calculated using the four intensity images.

Characterisation of 3D-GaN/InGaN core-shell nanostructures by transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Griffiths, Ian; Cherns, David [School of Physics, H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL (United Kingdom); Wang, Xue; Wehman, Hergo-Heinrich; Waag, Andreas [Institute of Semiconductor Technology, Braunschweig University of Technology, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Mandl, Martin; Strassburg, Martin [Osram Opto Semiconductors GmbH, Leibnizstrasse 4, 93055 Regensburg (Germany)

2014-04-15

Transmission and scanning electron microscopy have been used to characterise GaN/InGaN 3D nanostructures grown on patterned GaN/sapphire substrates by metal organic vapour phase epitaxy (MOVPE). It has been found that the growth of well ordered arrays of such nanostructures, containing multiple quantum wells on non-polar side-facets, can be achieved with a low density of defects. Growth changes and surface morphology play a major role in the nucleation of any defects present. The nanostructure morphology has been investigated and differing growth rates on adjacent facets studied. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Nanoscale nuclear architecture for cancer diagnosis by spatial-domain low-coherence quantitative phase microscopy

Science.gov (United States)

Wang, Pin; Bista, Rajan K.; Khalbuss, Walid E.; Qiu, Wei; Staton, Kevin D.; Zhang, Lin; Brentnall, Teresa A.; Brand, Randall E.; Liu, Yang

2011-03-01

Alterations in nuclear architecture are the hallmark diagnostic characteristic of cancer cells. In this work, we show that the nuclear architectural characteristics quantified by spatial-domain low-coherence quantitative phase microscopy (SL-QPM), is more sensitive for the identification of cancer cells than conventional cytopathology. We demonstrated the importance of nuclear architectural characteristics in both an animal model of intestinal carcinogenesis - APC/Min mouse model and human cytology specimens with colorectal cancer by identifying cancer from cytologically noncancerous appearing cells. The determination of nanoscale nuclear architecture using this simple and practical optical instrument is a significant advance towards cancer diagnosis.

Surface polarization, rumpling, and domain ordering of strained ultrathin BaTiO_3(001) films with in-plane and out-of-plane polarization

International Nuclear Information System (INIS)

Dionot, Jelle; Mathieu, Claire; Barrett, Nick; Geneste, Gregory

2014-01-01

BaTiO_3 ultrathin films (thickness ≅1.6 nm) with in- and out-of-plane polarization are studied by first-principles calculations. Out-of-plane polarization is simulated using the method proposed by Shimada et al. [Phys. Rev. B 81, 144116 (2010)], which consists in building a supercell containing small domains with alternating up and down polarization. This allows one to investigate the properties of defect free BaTiO_3 ultrathin films with polarization perpendicular to the surface, as a function of in-plane lattice constant, i.e., epitaxial strain. The configurations with polarization perpendicular to the surface (c phase) are found stable under compressive strain, while under tensile strain, the polarization tends to lie in-plane (aa phase), along [110]. In the c phase, the most stable domain width is predicted to be 1 to 2 lattice constants, and the magnitude of the surface rumpling varies according to the direction of the polarization (upwards versus downwards), though its sign is unchanged, the oxygen anions pointing in all cases outwards. Finally, all the surfaces studied are found to be insulating. Analysis of the atom-projected electronic density of states gives insight into the surface contributions to the electronic structure. An important reduction of the Kohn-Sham band gap is predicted at TiO_2 terminations in the c phase (≅1 eV with respect to the aa phase). The Madelung potential at the surface plays the dominant role in modifications of the surface electronic structure. (authors)

Generation of Bright Phase-matched Circularly-polarized Extreme Ultraviolet High Harmonics

Science.gov (United States)

2014-12-08

1995). 42. Eichmann , H. et al. Polarization-dependent high-order two-color mixing. Phys. Rev. A 51, R3414–R3417 (1995). 43. Fleischer, A., Kfir, O...calculations of polarization-dependent two- color high-harmonic generation. Phys. Rev. A 52, 2262–2278 (1995). 10. Eichmann , H. et al. polarization

Real-space observation of a right-rotating inhomogeneous cycloidal spin spiral by spin-polarized scanning tunneling microscopy in a triple axes vector magnet.

Science.gov (United States)

Meckler, S; Mikuszeit, N; Pressler, A; Vedmedenko, E Y; Pietzsch, O; Wiesendanger, R

2009-10-09

Using spin-polarized scanning tunneling microscopy performed in a triple axes vector magnet, we show that the magnetic structure of the Fe double layer on W(110) is an inhomogeneous right-rotating cycloidal spin spiral. The magnitude of the Dzyaloshinskii-Moriya vector is extracted from the experimental data using micromagnetic calculations. The result is confirmed by comparison of the measured saturation field along the easy axis to the respective value as obtained from Monte Carlo simulations. We find that the Dzyaloshinskii-Moriya interaction is too weak to destabilize the single domain state. However, it can define the sense of rotation and the cycloidal spiral type once the single domain state is destabilized by dipolar interaction.

Evaluation of chromatographic conditions in reversed phase liquid chromatography-mass spectrometry systems for fingerprinting of polar and amphiphilic plant metabolites

DEFF Research Database (Denmark)

Nielsen, Nikoline Juul; Tomasi, Giorgio; Christensen, Jan H.

2016-01-01

Metabolic fingerprinting is a relatively young scientific discipline requiring robust, yet flexible and fit-for-purpose analytical methods. Here, we introduce a simple approach to select reversed phase LC systems with electrospray MS detection for fingerprinting of polar and amphiphilic plant met...

Interferometric polarization control

International Nuclear Information System (INIS)

Chuss, David T.; Wollack, Edward J.; Moseley, S. Harvey; Novak, Giles

2006-01-01

We develop the Jones and Mueller matrices for structures that allow control of the path length difference between two linear orthogonal polarizations and consider the effect of placing multiple devices in series. Specifically, we find that full polarization modulation (measurement of Stokes Q, U, and V) can be achieved by placing two such modulators in series if the relative angles of the beam-splitting grids with respect to the analyzer orientation are appropriately chosen. Such a device has several potential advantages over a spinning wave plate modulator for measuring astronomical polarization in the far infrared through millimeter: (i) The use of small, linear motions eliminates the need for cryogenic rotational bearings; (ii) the phase flexibility allows measurement of circular as well as linear polarization; and (iii) this architecture allows for both multiwavelength and broadband modulation. We also present initial laboratory results

The effects of Nitinol phases on corrosion and fatigue behavior

Science.gov (United States)

Denton, Melissa

The purpose of these studies was to provide a detailed understanding of Nitinol phases and their effects on corrosion and fatigue life. The two primary phases, austenite and martensite, were carefully evaluated with respect to material geometry, corrosion behavior, wear, and fatigue life. Material characterization was performed using several techniques that include metallography, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray photoelectron spectrum (XPS), and Auger electron spectroscopy (AES). Uniaxial tensile tests were conducted to determine the mechanical properties such as elongation, ultimate tensile strength, modulus, transformation strain, and plateau stress. In addition, accelerated wear testing and four point bend fatigue testing were completed to study the fatigue life and durability of the material. The corrosion of Nitinol was found to be dependent on various surface conditions. Electrochemical corrosion behavior of each phase was investigated using cyclic potentiodyamic polarization testing. The corrosion response of electropolished Nitinol was found to be acceptable, even after durability testing. Stress-induced martensite had a lower breakdown potential due to a rougher surface morphology, while thermally induced martensite and austenite performed similarly well. The surface conditioning also had a significant effect on Nitinol mechanical properties. Electropolishing provided a smooth mirror finish that reduced localized texture and enhanced the ductility of the material. Quasi-static mechanical properties can be good indicators of fatigue life, but further fatigue testing revealed that phase transformations had an important role as well. The governing mechanisms for the fatigue life of Nitinol were determined to be both martesitic phase transformations and surface defects. A new ultimate dislocation strain model was proposed based on specific accelerated step-strain testing.

Nonlinear Gyrokinetic Theory With Polarization Drift

International Nuclear Information System (INIS)

Wang, L.; Hahm, T.S.

2010-01-01

A set of the electrostatic toroidal gyrokinetic Vlasov equation and the Poisson equation, which explicitly includes the polarization drift, is derived systematically by using Lie-transform method. The polarization drift is introduced in the gyrocenter equations of motion, and the corresponding polarization density is derived. Contrary to the wide-spread expectation, the inclusion of the polarization drift in the gyrocenter equations of motion does not affect the expression for the polarization density significantly. This is due to modification of the gyrocenter phase-space volume caused by the electrostatic potential [T. S. Hahm, Phys. Plasmas 3, 4658 (1996)].

Sensing Noncollinear Magnetism at the Atomic Scale Combining Magnetic Exchange and Spin-Polarized Imaging.

Science.gov (United States)

Hauptmann, Nadine; Gerritsen, Jan W; Wegner, Daniel; Khajetoorians, Alexander A

2017-09-13

Storing and accessing information in atomic-scale magnets requires magnetic imaging techniques with single-atom resolution. Here, we show simultaneous detection of the spin-polarization and exchange force with or without the flow of current with a new method, which combines scanning tunneling microscopy and noncontact atomic force microscopy. To demonstrate the application of this new method, we characterize the prototypical nanoskyrmion lattice formed on a monolayer of Fe/Ir(111). We resolve the square magnetic lattice by employing magnetic exchange force microscopy, demonstrating its applicability to noncollinear magnetic structures for the first time. Utilizing distance-dependent force and current spectroscopy, we quantify the exchange forces in comparison to the spin-polarization. For strongly spin-polarized tips, we distinguish different signs of the exchange force that we suggest arises from a change in exchange mechanisms between the probe and a skyrmion. This new approach may enable both nonperturbative readout combined with writing by current-driven reversal of atomic-scale magnets.

Simple and fast spectral domain algorithm for quantitative phase imaging of living cells with digital holographic microscopy

Science.gov (United States)

Min, Junwei; Yao, Baoli; Ketelhut, Steffi; Kemper, Björn

2017-02-01

The modular combination of optical microscopes with digital holographic microscopy (DHM) has been proven to be a powerful tool for quantitative live cell imaging. The introduction of condenser and different microscope objectives (MO) simplifies the usage of the technique and makes it easier to measure different kinds of specimens with different magnifications. However, the high flexibility of illumination and imaging also causes variable phase aberrations that need to be eliminated for high resolution quantitative phase imaging. The existent phase aberrations compensation methods either require add additional elements into the reference arm or need specimen free reference areas or separate reference holograms to build up suitable digital phase masks. These inherent requirements make them unpractical for usage with highly variable illumination and imaging systems and prevent on-line monitoring of living cells. In this paper, we present a simple numerical method for phase aberration compensation based on the analysis of holograms in spatial frequency domain with capabilities for on-line quantitative phase imaging. From a single shot off-axis hologram, the whole phase aberration can be eliminated automatically without numerical fitting or pre-knowledge of the setup. The capabilities and robustness for quantitative phase imaging of living cancer cells are demonstrated.

Giant thermally-enhanced electrostriction and polar surface phase in L a2M o2O9 oxygen ion conductors

Science.gov (United States)

Li, Qian; Lu, Teng; Schiemer, Jason; Laanait, Nouamane; Balke, Nina; Zhang, Zhan; Ren, Yang; Carpenter, Michael A.; Wen, Haidan; Li, Jiangyu; Kalinin, Sergei V.; Liu, Yun

2018-04-01

Ferroelectrics possess spontaneous electric polarization at macroscopic scales which nonetheless imposes strict limitations on the material classes. Recent discoveries of untraditional symmetry-breaking phenomena in reduced material dimensions have indicated feasibilities to extend polar properties to broader types of materials, potentially opening up the freedom for designing materials with hybrid functionalities. Here, we report the unusual electromechanical properties of L a2M o2O9 (LAMOX) oxygen ion conductors, systematically investigated at both bulk and surface length levels. We first observed giant electrostriction effects in L a2M o2O9 bulk ceramics that are thermally enhanced in concert with their low-energy oxygen-vacancy hopping dynamics. Moreover, while no clear bulk polarization was detected, the surface phases of LAMOX were found to be manifestly polar, likely originating from the coupling between the intrinsic structural flexibilities with strain gradients (i.e., flexoelectricity) and/or chemical heterogeneities present in the materials. These findings identify L a2M o2O9 as a promising electromechanical material system and suggest that the flexible structural and chemical configurations in ionically active materials could enable fundamentally different venues to accommodate electric polarization.

Instrumentation with polarized neutrons

International Nuclear Information System (INIS)

Boeni, P.; Muenzer, W.; Ostermann, A.

2009-01-01

Neutron scattering with polarization analysis is an indispensable tool for the investigation of novel materials exhibiting electronic, magnetic, and orbital degrees of freedom. In addition, polarized neutrons are necessary for neutron spin precession techniques that path the way to obtain extremely high resolution in space and time. Last but not least, polarized neutrons are being used for fundamental studies as well as very recently for neutron imaging. Many years ago, neutron beam lines were simply adapted for polarized beam applications by adding polarizing elements leading usually to unacceptable losses in neutron intensity. Recently, an increasing number of beam lines are designed such that an optimum use of polarized neutrons is facilitated. In addition, marked progress has been obtained in the technology of 3 He polarizers and the reflectivity of large-m supermirrors. Therefore, if properly designed, only factors of approximately 2-3 in neutron intensity are lost. It is shown that S-benders provide neutron beams with an almost wavelength independent polarization. Using twin cavities, polarized beams with a homogeneous phase space and P>0.99 can be produced without significantly sacrificing intensity. It is argued that elliptic guides, which are coated with large m polarizing supermirrors, provide the highest flux.

Polarization-sensitive color in butterfly scales: polarization conversion from ridges with reflecting elements.

Science.gov (United States)

Zhang, Ke; Tang, Yiwen; Meng, Jinsong; Wang, Ge; Zhou, Han; Fan, Tongxiang; Zhang, Di

2014-11-03

Polarization-sensitive color originates from polarization-dependent reflection or transmission, exhibiting abundant light information, including intensity, spectral distribution, and polarization. A wide range of butterflies are physiologically sensitive to polarized light, but the origins of polarized signal have not been fully understood. Here we systematically investigate the colorful scales of six species of butterfly to reveal the physical origins of polarization-sensitive color. Microscopic optical images under crossed polarizers exhibit their polarization-sensitive characteristic, and micro-structural characterizations clarify their structural commonality. In the case of the structural scales that have deep ridges, the polarization-sensitive color related with scale azimuth is remarkable. Periodic ridges lead to the anisotropic effective refractive indices in the parallel and perpendicular grating orientations, which achieves form-birefringence, resulting in the phase difference of two different component polarized lights. Simulated results show that ridge structures with reflecting elements reflect and rotate the incident p-polarized light into s-polarized light. The dimensional parameters and shapes of grating greatly affect the polarization conversion process, and the triangular deep grating extends the outstanding polarization conversion effect from the sub-wavelength period to the period comparable to visible light wavelength. The parameters of ridge structures in butterfly scales have been optimized to fulfill the polarization-dependent reflection for secret communication. The structural and physical origin of polarization conversion provides a more comprehensive perspective on the creation of polarization-sensitive color in butterfly wing scales. These findings show great potential in anti-counterfeiting technology and advanced optical material design.

Imaging of polarity during zygotic and somatic embryogenesis of carrot (Daucus carota L.)

NARCIS (Netherlands)

Timmers, A.C.J.

1993-01-01

In this thesis a study of the regulation of coordinated growth and the development of polarity during embryogenesis of carrot, Daucus carota L., is described. To this end, several microscopical techniques were used, such as light microscopy, fluorescence microscopy,

Depth-variant blind restoration with pupil-phase constraints for 3D confocal microscopy

International Nuclear Information System (INIS)

Hadj, Saima Ben; Blanc-Féraud, Laure; Engler, Gilbert

2013-01-01

Three-dimensional images of confocal laser scanning microscopy suffer from a depth-variant blur, due to refractive index mismatch between the different mediums composing the system as well as the specimen, leading to optical aberrations. Our goal is to develop an image restoration method for 3D confocal microscopy taking into account the blur variation with depth. The difficulty is that optical aberrations depend on the refractive index of the biological specimen. The depth-variant blur function or the Point Spread Function (PSF) is thus different for each observation. A blind or semi-blind restoration method needs to be developed for this system. For that purpose, we use a previously developed algorithm for the joint estimation of the specimen function (original image) and the 3D PSF, the continuously depth-variant PSF is approximated by a convex combination of a set of space-invariant PSFs taken at different depths. We propose to add to that algorithm a pupil-phase constraint for the PSF estimation, given by the the optical instrument geometry. We thus define a blind estimation algorithm by minimizing a regularized criterion in which we integrate the Gerchberg-Saxton algorithm allowing to include these physical constraints. We show the efficiency of this method relying on some numerical tests

Experimental Evidence on the Dependence of the Standard GPS Phase Scintillation Index on the Ionospheric Plasma Drift Around Noon Sector of the Polar Ionosphere

Science.gov (United States)

Wang, Y.; Zhang, Q.-H.; Jayachandran, P. T.; Moen, J.; Xing, Z.-Y.; Chadwick, R.; Ma, Y.-Z.; Ruohoniemi, J. M.; Lester, M.

2018-03-01

First experimental proof of a clear and strong dependence of the standard phase scintillation index (σφ) derived using Global Positioning System measurements on the ionospheric plasma flow around the noon sector of polar ionosphere is presented. σφ shows a strong linear dependence on the plasma drift speed measured by the Super Dual Auroral Radar Network radars, whereas the amplitude scintillation index (S4) does not. This observed dependence can be explained as a consequence of Fresnel frequency dependence of the relative drift and the used constant cutoff frequency (0.1 Hz) to detrend the data for obtaining standard σφ. The lack of dependence of S4 on the drift speed possibly eliminates the plasma instability mechanism(s) involved as a cause of the dependence. These observations further confirm that the standard phase scintillation index is much more sensitive to plasma flow; therefore, utmost care must be taken when identifying phase scintillation (diffractive phase variations) from refractive (deterministic) phase variations, especially in the polar region where the ionospheric plasma drift is much larger than in equatorial and midlatitude regions.

Advances in polarization sensitive multiphoton nano-bio-imaging

Directory of Open Access Journals (Sweden)

Zyss J.

2010-06-01

Full Text Available In this talk, we shall shortly review four main directions of ongoing research in our laboratories, directed at the conception and demonstration of a variety of innovative configurations in nanoscale multiphoton imaging. A common feature to all of these directions appears to be the central role played by the involvement of polarization features, both in- and outgoing, moreover so in view of the tensorial aspects inherent to nonlinear schemes such second-harmonic generation, electro-optic modulation or two-photon fluorescence which will ne emphasized. These advances relate to the new domain of nonlinear ellipsometry in multiphoton imaging [1], of high relevance to fundamental aspects of nanophotonics and nanomaterial engineering as well as towards basic life science issues. The four domains to be shortly reported are: a polarization resolved second-harmonic generation in semiconductor QD’s with record small sizes in the 10-12 nm range [2] b original use of two-photon confocal polarization resolved microscopy in DNA stained by two photon fluorescent dyes in different LC phases arrangements so as to characterize these as well as ascertain the respective DNA-dye orientation (intercalant or groves [3] c elaboration and demonstration of an electrooptic confocal microscope in a highly sensitive interferometric and homodyne detection configuration allowing to map weak electric potentials such as in artificial functionalized membranes, the dynamical investigation of firing and propagation aspects of action potentials in neurones being currently the next step [4] d original plasmon based enhanced nanoscale confocal imaging involving a dual detection scheme (fluorescence imaging and ATR plasmon coupling in reflection whereby adequate preparation and switching of the incoming polarization state between radial, linear and azimuthal configurations, entail different images and plasmon enhancement levels [5].

Selective sensitivity in Kerr microscopy.

Science.gov (United States)

Soldatov, I V; Schäfer, R

2017-07-01

A new technique for contrast separation in wide-field magneto-optical Kerr microscopy is introduced. Utilizing the light from eight light emitting diodes, guided to the microscope by glass fibers and being switched synchronously with the camera exposure, domain images with orthogonal in-plane sensitivity can be displayed simultaneously at real-time, and images with pure in-plane or polar contrast can be obtained. The benefit of this new method of contrast separation is demonstrated for Permalloy films, a NdFeB sinter magnet, and a cobalt crystal. Moreover, the new technique is shown to strongly enhance the sensitivity of Kerr microscopy by eliminating parasitic contrast contributions occurring in conventional setups. A doubling of the in-plane domain contrast and a sensitivity to Kerr rotations as low as 0.6 mdeg is demonstrated.

Selective sensitivity in Kerr microscopy

Science.gov (United States)

Soldatov, I. V.; Schäfer, R.

2017-07-01

A new technique for contrast separation in wide-field magneto-optical Kerr microscopy is introduced. Utilizing the light from eight light emitting diodes, guided to the microscope by glass fibers and being switched synchronously with the camera exposure, domain images with orthogonal in-plane sensitivity can be displayed simultaneously at real-time, and images with pure in-plane or polar contrast can be obtained. The benefit of this new method of contrast separation is demonstrated for Permalloy films, a NdFeB sinter magnet, and a cobalt crystal. Moreover, the new technique is shown to strongly enhance the sensitivity of Kerr microscopy by eliminating parasitic contrast contributions occurring in conventional setups. A doubling of the in-plane domain contrast and a sensitivity to Kerr rotations as low as 0.6 mdeg is demonstrated.

High spatial precision nano-imaging of polarization-sensitive plasmonic particles

Science.gov (United States)

Liu, Yunbo; Wang, Yipei; Lee, Somin Eunice

2018-02-01

Precise polarimetric imaging of polarization-sensitive nanoparticles is essential for resolving their accurate spatial positions beyond the diffraction limit. However, conventional technologies currently suffer from beam deviation errors which cannot be corrected beyond the diffraction limit. To overcome this issue, we experimentally demonstrate a spatially stable nano-imaging system for polarization-sensitive nanoparticles. In this study, we show that by integrating a voltage-tunable imaging variable polarizer with optical microscopy, we are able to suppress beam deviation errors. We expect that this nano-imaging system should allow for acquisition of accurate positional and polarization information from individual nanoparticles in applications where real-time, high precision spatial information is required.

Dysprosium disilicide nanostructures on silicon(001) studied by scanning tunneling microscopy and transmission electron microscopy

International Nuclear Information System (INIS)

Ye Gangfeng; Nogami, Jun; Crimp, Martin A.

2006-01-01

The microstructure of self-assembled dysprosium silicide nanostructures on silicon(001) has been studied by scanning tunneling microscopy and transmission electron microscopy. The studies focused on nanostructures that involve multiple atomic layers of the silicide. Cross-sectional high resolution transmission electron microscopy images and fast Fourier transform analysis showed that both hexagonal and orthorhombic/tetragonal silicide phases were present. Both the magnitude and the anisotropy of lattice mismatch between the silicide and the substrate play roles in the morphology and epitaxial growth of the nanostructures formed

A four-phase strategy for the implementation of reflectance confocal microscopy in dermatology.

Science.gov (United States)

Hoogedoorn, L; Gerritsen, M J P; Wolberink, E A W; Peppelman, M; van de Kerkhof, P C M; van Erp, P E J

2016-08-01

Reflectance confocal microscopy (RCM) is gradually implemented in dermatology. Strategies for further implementation and practical 'hands on' guidelines are lacking. The primary outcome was to conduct a general strategy for further implementation of RCM. The secondary outcome was the diagnosis of psoriasis and differentiation of stable from unstable psoriatic plaques by means of the 'hands on' protocol, derived from the strategy. We used a four-phased model; an exploring phase, a systematic literature search, a clinical approach and, finally, an integration phase to develop a clinical guideline for RCM in psoriasis. Receiver operating characteristic curve statistics was applied to define the accuracy for the diagnosis of unstable psoriasis. A general strategy for further implementation of RCM and practical approach was developed to examine psoriasis by RCM and to distinguish stable from unstable psoriasis. Unstable psoriasis was diagnosed by epidermal inflammatory cell counts with a sensitivity and specificity of 91.7% and 98.3%, respectively, and with an accuracy of 0.92 (area under the curve). In addition, a monitoring model was proposed. This is the first study that shows a method for implementation of RCM in dermatology. The strategy and hands on protocol for psoriasis may serve as a model for other dermatological entities and additionally may lead to specialized ready-to-use RCM protocols for clinical dermatological practice. © 2016 European Academy of Dermatology and Venereology.

Single phase semipolar (11 anti 22) GaN on (10 anti 10) sapphire

Energy Technology Data Exchange (ETDEWEB)

Ploch, S.; Stellmach, J.; Schwaner, T.; Frentrup, M.; Wernicke, T.; Pristovsek, M.; Kneissl, M. [Institute of Solid States Physics, (Germany); Park, J.B.; Niermann, T.; Lehmann, M. [Institute of Optics and Atomic Physics, TU Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

2011-07-01

InGaN quantum well based light emitters grown on (0001) GaN suffer from poor quantum efficiencies with increasing indium mole fraction due to strong polarization fields along the polar crystal orientation. This effect can be greatly reduced by growing on semi- and non-polar GaN orientations. Semipolar (11 anti 22) GaN layers were deposited by metalorganic vapour phase epitaxy on (10 anti 10) sapphire. After sapphire substrate nitridation at 1000 C, a GaN nucleation layer was deposited at high temperature, followed by the deposition of 1.5 nm thick GaN buffer layers. The samples show predominantly (11 anti 22) orientation with a small fraction of (10 anti 13) oriented domains. With increasing nitridation layer thickness the (10 anti 13) phase is suppressed leading to a very smooth surface morphology (rms roughness < 4nm). PL measurements show dominant basel plane stacking fault (BSF) I{sub 1} luminescence without any other defects. Transmission electron microscopy measurements reveal a high BSF density. The FWHM of the X-ray diffraction rocking curve measurements of the (1122) reflection decreases to 1193 arcsec and 739 arcsec along [1 anti 100] and [11 anti 23] respectively with increasing nucleation temperature. Using high temperature nucleation smooth and homogeneous (11 anti 22) phase GaN layers have been obtained.

Measurement and Modelling of Phase Equilibrium of Oil - Water - Polar Chemicals

DEFF Research Database (Denmark)

Frost, Michael Grynnerup

in the temperature range of 303-323 K at atmospheric pressure. In the second part of this work, the CPA EoS has been used for modeling hydrocarbon systemcontaining polar chemicals, such as water and gas hydrate inhibitor MEG or methanol. All the experimental data measured in this work have been investigated using...... with the measurement of newexperimental data, but through the development of new experimental equipment for the study ofmulti-phase equilibrium. In addition to measurement of well-defined systems, LLE have beenmeasured for North Sea oils with MEG and water. The work can be split up into two parts: Experimental: VLE...... systems presented, confirming the quality of theequipment. The equipment is used for measurement of VLE for several systems of interest; methane+ water, methane + methanol, methane + methanol + water and methane + MEG. Details dealing with the design, assembling and testing of new experimental equipment...

A new method for generating axially-symmetric and radially-polarized beams

International Nuclear Information System (INIS)

Niu Chunhui; Gu Benyuan; Dong Bizhen; Zhang Yan

2005-01-01

A scheme for generating axially-symmetric and radially-polarized beams is proposed by using two diffractive phase elements (DPEs) made of birefringent materials. The design of these two DPEs is based on the general theory of phase-retrieval of optical system in combination with an iterative algorithm. The first DPE is used for demultiplexing two orthogonally linearly-polarized light beams to produce diffractive patterns, and the second DPE is used for compensating the phase difference to obtain the desired radially-polarized beam

Optically stimulated slowing of polar heavy-atom molecules with a constant beat phase

Science.gov (United States)

Yin, Yanning; Xu, Supeng; Xia, Meng; Xia, Yong; Yin, Jianping

2018-04-01

Polar heavy-atom molecules have been well recognized as promising candidates for precision measurements and tests of fundamental physics. A much slower molecular beam to increase the interaction time should lead to a more sensitive measurement. Here we theoretically demonstrate the possibility of the stimulated longitudinal slowing of heavy-atom molecules by the coherent optical bichromatic force with a constant beat phase. Taking the YbF meolecule as an example, we show that a rapid and short-distance deceleration of heavy molecules by a phase-compensation method is feasible with moderate conditions. A molecular beam of YbF with a forward velocity of 120 m/s can be decelerated below 10 m/s within a distance of 3.5 cm and with a laser irradiance for each traveling wave of 107.2 W/cm 2 . Our proposed slowing method could be a promising approach to break through the space constraint or the limited capture efficiency of molecules loadable into a magneto-optical trap in traditional deceleration schemes, opening the possibility for a significant improvement of the precision measurement sensitivity.

Context based mixture model for cell phase identification in automated fluorescence microscopy

Directory of Open Access Journals (Sweden)

Zhou Xiaobo

2007-01-01

Full Text Available Abstract Background Automated identification of cell cycle phases of individual live cells in a large population captured via automated fluorescence microscopy technique is important for cancer drug discovery and cell cycle studies. Time-lapse fluorescence microscopy images provide an important method to study the cell cycle process under different conditions of perturbation. Existing methods are limited in dealing with such time-lapse data sets while manual analysis is not feasible. This paper presents statistical data analysis and statistical pattern recognition to perform this task. Results The data is generated from Hela H2B GFP cells imaged during a 2-day period with images acquired 15 minutes apart using an automated time-lapse fluorescence microscopy. The patterns are described with four kinds of features, including twelve general features, Haralick texture features, Zernike moment features, and wavelet features. To generate a new set of features with more discriminate power, the commonly used feature reduction techniques are used, which include Principle Component Analysis (PCA, Linear Discriminant Analysis (LDA, Maximum Margin Criterion (MMC, Stepwise Discriminate Analysis based Feature Selection (SDAFS, and Genetic Algorithm based Feature Selection (GAFS. Then, we propose a Context Based Mixture Model (CBMM for dealing with the time-series cell sequence information and compare it to other traditional classifiers: Support Vector Machine (SVM, Neural Network (NN, and K-Nearest Neighbor (KNN. Being a standard practice in machine learning, we systematically compare the performance of a number of common feature reduction techniques and classifiers to select an optimal combination of a feature reduction technique and a classifier. A cellular database containing 100 manually labelled subsequence is built for evaluating the performance of the classifiers. The generalization error is estimated using the cross validation technique. The

Phasing of the Triatoma virus diffraction data using a cryo-electron microscopy reconstruction

International Nuclear Information System (INIS)

Estrozi, L.F.; Neumann, E.; Squires, G.; Rozas-Dennis, G.; Costabel, M.; Rey, F.A.; Guerin, D.M.A.; Navaza, J.

2008-01-01

The blood-sucking reduviid bug Triatoma infestans, one of the most important vector of American human trypanosomiasis (Chagas disease) is infected by the Triatoma virus (TrV). TrV has been classified as a member of the Cripavirus genus (type cricket paralysis virus) in the Dicistroviridae family. This work presents the three-dimensional cryo-electron microscopy (cryo-EM) reconstruction of the TrV capsid at about 25 A resolution and its use as a template for phasing the available crystallographic data by the molecular replacement method. The main structural differences between the cryo-EM reconstruction of TrV and other two viruses, one from the same family, the cricket paralysis virus (CrPV) and the human rhinovirus 16 from the Picornaviridae family are presented and discussed

Investigation of the polarization state of dual APPLE-II undulators.

Science.gov (United States)

Hand, Matthew; Wang, Hongchang; Dhesi, Sarnjeet S; Sawhney, Kawal

2016-01-01

The use of an APPLE II undulator is extremely important for providing a high-brilliance X-ray beam with the capability to switch between various photon beam polarization states. A high-precision soft X-ray polarimeter has been used to systematically investigate the polarization characteristics of the two helical APPLE II undulators installed on beamline I06 at Diamond Light Source. A simple data acquisition and processing procedure has been developed to determine the Stokes polarization parameters for light polarized at arbitrary linear angles emitted from a single undulator, and for circularly polarized light emitted from both undulators in conjunction with a single-period undulator phasing unit. The purity of linear polarization is found to deteriorate as the polarization angle moves away from the horizontal and vertical modes. Importantly, a negative correlation between the degree of circular polarization and the photon flux has been found when the phasing unit is used.

Erosion Potential of Tooth Whitening Regimens as Evaluated with Polarized Light Microscopy.

Science.gov (United States)

Brambert, Patrick; Qian, Fang; Kwon, So Ran

2015-11-01

Tooth whitening is a widely utilized esthetic treatment in dentistry. With increased access to over-the-counter (OTC) systems concerns have been raised as to potential adverse effects associated with overuse of whitening materials. Therefore, this study aimed to evaluate enamel erosion due to different whitening regimens when used in excess of recommended guidelines. Extracted human teeth (n = 66) were randomly divided into 11 groups (n = 6/group). Specimens were exposed to OTC products: Crest Whitestrips and 5-minute natural white and a do-it-yourself (DIY) strawberry whitening recipe. Within each regimen, groups were further divided per exposure time: specimens receiving the recommended product dosage; 5 times the recommended dosage; and 10 times the recommended dosage. Negative and positive controls were treated with grade 3 water and 1.0% citric acid, respectively. Specimens were nail-varnished to limit application to a 1 × 4 mm window. Following treatment, specimens were sectioned and erosion (drop in μm) measured using polarized light microscopy. Two-sample t-test was used to detect difference in amount of enamel erosion between negative and positive groups, while one-way analysis of variance (ANOVA), followed by post hoc Dunnett's test was used to detect difference between set of treatment groups and negative control groups or among all experimental groups. There was significant difference in mean amount of enamel erosion (p enamel erosion for positive control group was significantly greater than that for negative control group (23.50 vs 2.65 μm). There was significant effect for type of treatments on enamel erosion [F(9,50) = 25.19; p 0.05 for all instances), except for Natural White_10 times treatment group (p enamel erosion. Enamel erosion due to the overuse of whitening products varies for different modalities and products. Therefore, caution is advised when using certain over-the-counter products beyond recommended guidelines, as there is potential

Experimental evaluation of the ‘transport-of-intensity’ equation for magnetic phase reconstruction in Lorentz transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Kohn, Amit, E-mail: akohn@post.tau.ac.il [Department of Materials Science and Engineering, Faculty of Engineering, Tel Aviv University, 69978 Tel Aviv (Israel); Habibi, Avihay; Mayo, Martin [Department of Materials Engineering, Ben-Gurion University of the Negev, 84105 Beer Sheva (Israel)

2016-01-15

The ‘transport-of-intensity’ equation (TIE) is a general phase reconstruction methodology that can be applied to Lorentz transmission electron microscopy (TEM) through the use of Fresnel-contrast (defocused) images. We present an experimental study to test the application of the TIE for quantitative magnetic mapping in Lorentz TEM without aberration correction by examining sub-micrometer sized Ni{sub 80}Fe{sub 20} (Permalloy) elements. For a JEOL JEM 2100F adapted for Lorentz microscopy, we find that quantitative magnetic phase reconstructions are possible for defoci distances ranging between approximately 200 μm and 800 μm. The lower limit originates from competing sources of image intensity variations in Fresnel-contrast images, namely structural defects and diffraction contrast. The upper defocus limit is due to a numerical error in the estimation of the intensity derivative based on three images. For magnetic domains, we show quantitative reconstructions of the product of the magnetic induction vector and thickness in element sizes down to approximately 100 nm in lateral size and 5 nm thick resulting in a minimal detection of 5 T nm. Three types of magnetic structures are tested in terms of phase reconstruction: vortex cores, domain walls, and element edges. We quantify vortex core structures at a diameter of 12 nm while the structures of domain walls and element edges are characterized qualitatively. Finally, we show by image simulations that the conclusions of this experimental study are relevant to other Lorentz TEM in which spherical aberration and defocus are dominant aberrations. - Highlights: • Testing TIE for quantitative magnetic phase reconstruction in Lorentz TEM. • Quantitative magnetic phase reconstructions for defoci distances in 200–800 μm range. • Minimal detection of the product of the magnetic induction and thickness is 5 T nm. • Quantitative phase reconstruction for vortex core structures at 12 nm diameter. • Observations

The development of optical microscopy techniques for the advancement of single-particle studies

Science.gov (United States)

Marchuk, Kyle

Single particle orientation and rotational tracking (SPORT) has recently become a powerful optical microscopy tool that can expose many molecular motions. Unfortunately, there is not yet a single microscopy technique that can decipher all particle motions in all environmental conditions, thus there are limitations to current technologies. Within, the two powerful microscopy tools of total internal reflection and interferometry are advanced to determine the position, orientation, and optical properties of metallic nanoparticles in a variety of environments. Total internal reflection is an optical phenomenon that has been applied to microscopy to produce either fluorescent or scattered light. The non-invasive far-field imaging technique is coupled with a near-field illumination scheme that allows for better axial resolution than confocal microscopy and epi-fluorescence microscopy. By controlling the incident illumination angle using total internal reflection fluorescence (TIRF) microscopy, a new type of imaging probe called "non-blinking" quantum dots (NBQDs) were super-localized in the axial direction to sub-10-nm precision. These particles were also used to study the rotational motion of microtubules being propelled by the motor protein kinesin across the substrate surface. The same instrument was modified to function under total internal reflection scattering (TIRS) microscopy to study metallic anisotropic nanoparticles and their dynamic interactions with synthetic lipid bilayers. Utilizing two illumination lasers with opposite polarization directions at wavelengths corresponding to the short and long axis surface plasmon resonance (SPR) of the nanoparticles, both the in-plane and out-of-plane movements of many particles could be tracked simultaneously. When combined with Gaussian point spread function (PSF) fitting for particle super-localization, the binding status and rotational movement could be resolved without degeneracy. TIRS microscopy was also used to

The development of optical microscopy techniques for the advancement of single-particle studies

Energy Technology Data Exchange (ETDEWEB)

Marchuk, Kyle [Iowa State Univ., Ames, IA (United States)

2013-05-15

Single particle orientation and rotational tracking (SPORT) has recently become a powerful optical microscopy tool that can expose many molecular motions. Unfortunately, there is not yet a single microscopy technique that can decipher all particle motions in all environmental conditions, thus there are limitations to current technologies. Within, the two powerful microscopy tools of total internal reflection and interferometry are advanced to determine the position, orientation, and optical properties of metallic nanoparticles in a variety of environments. Total internal reflection is an optical phenomenon that has been applied to microscopy to produce either fluorescent or scattered light. The non-invasive far-field imaging technique is coupled with a near-field illumination scheme that allows for better axial resolution than confocal microscopy and epi-fluorescence microscopy. By controlling the incident illumination angle using total internal reflection fluorescence (TIRF) microscopy, a new type of imaging probe called “non-blinking” quantum dots (NBQDs) were super-localized in the axial direction to sub-10-nm precision. These particles were also used to study the rotational motion of microtubules being propelled by the motor protein kinesin across the substrate surface. The same instrument was modified to function under total internal reflection scattering (TIRS) microscopy to study metallic anisotropic nanoparticles and their dynamic interactions with synthetic lipid bilayers. Utilizing two illumination lasers with opposite polarization directions at wavelengths corresponding to the short and long axis surface plasmon resonance (SPR) of the nanoparticles, both the in-plane and out-of-plane movements of many particles could be tracked simultaneously. When combined with Gaussian point spread function (PSF) fitting for particle super-localization, the binding status and rotational movement could be resolved without degeneracy. TIRS microscopy was also used to

Introduction to the IEEE International Symposium on Applications of Ferroelectrics and International Symposium on Piezoresponse Force Microscopy and Nanoscale Phenomena in Polar Materials.

Science.gov (United States)

Ye, Zuo-Guang; Tan, Xiaoli; Bokov, Alexei A

2012-09-01

The 20th IEEE International Symposium on Applications of Ferroelectrics (ISAF) was held on July 24-27, 2011, in Vancouver, British Columbia, Canada, jointly with the International Symposium on Piezoresponse Force Microscopy and Nanoscale Phenomena in Polar Materials (PFM). Over a period of four days, approximately 400 scientists, engineers, and students from around the world presented their work and discussed the latest developments in the field of ferroelectrics, related materials, and their applications. It is particularly encouraging to see that a large number of students (115) were attracted to the joint conference and presented high-quality research works. This trend is not only important to this conference series, but more importantly, it is vital to the future of the ferroelectrics field.

Determination of the polarization states of an arbitrary polarized terahertz beam: vectorial vortex analysis.

Science.gov (United States)

Wakayama, Toshitaka; Higashiguchi, Takeshi; Oikawa, Hiroki; Sakaue, Kazuyuki; Washio, Masakazu; Yonemura, Motoki; Yoshizawa, Toru; Tyo, J Scott; Otani, Yukitoshi

2015-03-24

Vectorial vortex analysis is used to determine the polarization states of an arbitrarily polarized terahertz (0.1-1.6 THz) beam using THz achromatic axially symmetric wave (TAS) plates, which have a phase retardance of Δ = 163° and are made of polytetrafluorethylene. Polarized THz beams are converted into THz vectorial vortex beams with no spatial or wavelength dispersion, and the unknown polarization states of the incident THz beams are reconstructed. The polarization determination is also demonstrated at frequencies of 0.16 and 0.36 THz. The results obtained by solving the inverse source problem agree with the values used in the experiments. This vectorial vortex analysis enables a determination of the polarization states of the incident THz beam from the THz image. The polarization states of the beams are estimated after they pass through the TAS plates. The results validate this new approach to polarization detection for intense THz sources. It could find application in such cutting edge areas of physics as nonlinear THz photonics and plasmon excitation, because TAS plates not only instantaneously elucidate the polarization of an enclosed THz beam but can also passively control THz vectorial vortex beams.

Application of circular polarized synchrotron radiation

International Nuclear Information System (INIS)

Miyahara, Tsuneaki; Kawata, Hiroshi

1988-03-01

The idea of using the polarizing property of light for physical experiment by controlling it variously has been known from old time, and the Faraday effect and the research by polarizing microscopy are its examples. The light emitted from the electron orbit of an accelerator has the different polarizing characteristics from those of the light of a laboratory light source, and as far as observing it within the electron orbit plane, it becomes linearly polarized light. By utilizing this property well, research is carried out at present in synchrotron experimental facilities. Recently, the technology related to the insert type light cources using permanent magnets has advanced remarkably, and circular polarized light has become to be producible. If the light like this can be obtained with the energy not only in far ultraviolet region but also to x-ray region at high luminance, new possibility should open. At the stage that the design of an insert type light source was finished, and its manufacture was started, the research on the method of evaluating the degree of circular polarization and the research on the utilization of circular polarized synchrotron radiation are earnestly carried out. In this report, the results of researches presented at the study meeting are summarized. Moreover, the design and manufacture of the beam lines for exclusive use will be carried out. (Kako, I.)

Geometric phase from dielectric matrix

International Nuclear Information System (INIS)

Banerjee, D.

2005-10-01

The dielectric property of the anisotropic optical medium is found by considering the polarized photon as two component spinor of spherical harmonics. The Geometric Phase of a polarized photon has been evaluated in two ways: the phase two-form of the dielectric matrix through a twist and the Pancharatnam phase (GP) by changing the angular momentum of the incident polarized photon over a closed triangular path on the extended Poincare sphere. The helicity in connection with the spin angular momentum of the chiral photon plays the key role in developing these phase holonomies. (author)

Spin polarized electron tunneling and magnetoresistance in molecular junctions.

Science.gov (United States)

Szulczewski, Greg

2012-01-01

This chapter reviews tunneling of spin-polarized electrons through molecules positioned between ferromagnetic electrodes, which gives rise to tunneling magnetoresistance. Such measurements yield important insight into the factors governing spin-polarized electron injection into organic semiconductors, thereby offering the possibility to manipulate the quantum-mechanical spin degrees of freedom for charge carriers in optical/electrical devices. In the first section of the chapter a brief description of the Jullière model of spin-dependent electron tunneling is reviewed. Next, a brief description of device fabrication and characterization is presented. The bulk of the review highlights experimental studies on spin-polarized electron tunneling and magnetoresistance in molecular junctions. In addition, some experiments describing spin-polarized scanning tunneling microscopy/spectroscopy on single molecules are mentioned. Finally, some general conclusions and prospectus on the impact of spin-polarized tunneling in molecular junctions are offered.

Solid-phase characterization in flammable-gas-tank sludges by electron microscopy

International Nuclear Information System (INIS)

Liu, J.; Pederson, L.R.; Qang, L.Q.

1995-09-01

The crystallinity, morphology, chemical composition, and crystalline phases of several Tank 241-SY-101 (hereinafter referred to as SY-101) and Tank 241-SY-103 (hereinafter referred to as SY-103) solid samples were studied by transmission electron microscopy (TEM), electron energy dispersive spectroscopy (EDS), and electron diffraction. The main focus is on the identification of aluminum hydroxide thought to be present in these tank samples. Aluminum hydroxide was found in SY-103, but not in SY-101. This difference can be explained by the different OH/Al ratios found in the two tank samples: a high OH/Al ratio in SY-101 favors the formation of sodium aluminate, but a low OH/Al ratio in SY-103 favors aluminum hydroxide. These results were confirmed by a magnetic resonance study on SY-101 and SY-103 simulant. The transition from aluminum hydroxide to sodium aluminate occurs at an OH/Al molar ratio of 3.6. It is believed that the study of Al(OH) 3 was not affected by sample preparation because all Al(OH) 3 is in the solid form according to the NMR experiments. There is no Al(OH) 3 in the liquid. It is, therefore, most likely that the observation of Al(OH) 3 is representative of the real sludge sample, and is not affected by drying. Similar conclusions also apply to other insoluble phases such as iron and chromium

Investigation of shape memory of red blood cells using optical tweezers and quantitative phase microscopy

Science.gov (United States)

Cardenas, Nelson; Mohanty, Samarendra K.

2012-03-01

RBC has been shown to possess shape memory subsequent to shear-induced shape transformation. However, this property of RBC may not be generalized to all kinds of stresses. Here, we report our observation on the action of radiation pressure forces on RBC's shape memory using optical manipulation and quantitative phase microscopy (OMQPM). QPM, based on Mach-Zehnder interferrometry, allowed measurement of dynamic changes of shape of RBC in optical tweezers at different trapping laser powers. In high power near-infrared optical tweezers (>200mW), the RBC was found to deform significantly due to optical forces. Upon removal of the tweezers, hysteresis in recovering its original resting shape was observed. In very high power tweezers or long-term stretching events, shape memory was almost erased. This irreversibility of the deformation may be due to temperature rise or stress-induced phase transformation of lipids in RBC membrane.

Multiterminal semiconductor/ferromagnet probes for spin-filter scanning tunneling microscopy

NARCIS (Netherlands)

Vera Marun, I.J.; Jansen, R.

2009-01-01

We describe the fabrication of multiterminal semiconductor/ferromagnet probes for a new technique to study magnetic nanostructures: spin-filter scanning tunneling microscopy. We describe the principle of the technique, which is based on spin-polarized tunneling and subsequent analysis of the spin

Terahertz broadband polarization converter based on metamaterials

Science.gov (United States)

Li, Yonghua; Zhao, Guozhong

2018-01-01

Based on the metamaterial composed of symmetrical split resonant ring, a broadband reflective terahertz polarization converter is proposed. The numerical simulation shows that it can rotate the polarization direction of linear polarized wave 90° in the range of 0.7-1.8THz and the polarization conversion ratio is over 90%. The reflection coefficient of the two electric field components in the diagonal direction is the same and the phase difference is 180° ,which leads to the cross-polarization rotation.In order to further study the physical mechanism of high polarization conversion, we analyze the surface current distribution of the resonant ring. The polarization converter has potential applications in terahertz wave plate and metamaterial antenna design.

Investigation of non-collinear spin states with scanning tunneling microscopy.

Science.gov (United States)

Wulfhekel, W; Gao, C L

2010-03-05

Most ferromagnetic and antiferromagnetic substances show a simple collinear arrangement of the local spins. Under certain circumstances, however, the spin configuration is non-collinear. Scanning tunneling microscopy with its potential atomic resolution is an ideal tool for investigating these complex spin structures. Non-collinearity can be due to topological frustration of the exchange interaction, due to relativistic spin-orbit coupling or can be found in excited states. Examples for all three cases are given, illustrating the capabilities of spin-polarized scanning tunneling microscopy.

Study of Jupiter polarization properties

International Nuclear Information System (INIS)

Bolkvadze, O.R.

1980-01-01

Investigations into polarization properties of the Jupiter reflected light were carried on at the Abastumani astrophysical observatory in 1967, 1968 and 1969 in the four spectral ranges: 4000, 4800, 5400 and 6600 A deg. Data on light polarization in different parts of the Jupiter visible disk are given. Curves of dependence of the planet light polarization degree on a phase angle are plotted. It is shown that in the central part of the visible planet disk the polarization degree is low. Atmosphere is in a stable state in this part of Jupiter. Mean radius of particles of a cloud layer is equal to 0.26μ, and optical thickness of overcloud atmosphere tau=0.05. Height of transition boundary of the cloud layer into overcloud gas atmosphere changes from year to year at the edges of the equatorial zone. Optical thickness of overcloud atmosphere changes also with changing height of a transient layer. The polar Jupiter regions possess a high degree of polarization which depends on a latitude. Polarization increases monotonously with the latitude and over polar regions accepts a maximum value [ru

Polarization-dependent Imaging Contrast (PIC) mapping reveals nanocrystal orientation patterns in carbonate biominerals

Energy Technology Data Exchange (ETDEWEB)

Gilbert, Pupa U.P.A., E-mail: pupa@physics.wisc.edu [University of Wisconsin-Madison, Departments of Physics and Chemistry, Madison, WI 53706 (United States)

2012-10-15

Highlights: Black-Right-Pointing-Pointer Nanocrystal orientation shown by Polarization-dependent Imaging Contrast (PIC) maps. Black-Right-Pointing-Pointer PIC-mapping of carbonate biominerals reveals their ultrastructure at the nanoscale. Black-Right-Pointing-Pointer The formation mechanisms of biominerals is discovered by PIC-mapping using PEEM. -- Abstract: Carbonate biominerals are one of the most interesting systems a physicist can study. They play a major role in the CO{sub 2} cycle, they master templation, self-assembly, nanofabrication, phase transitions, space filling, crystal nucleation and growth mechanisms. A new imaging modality was introduced in the last 5 years that enables direct observation of the orientation of carbonate single crystals, at the nano- and micro-scale. This is Polarization-dependent Imaging Contrast (PIC) mapping, which is based on X-ray linear dichroism, and uses PhotoElectron Emission spectroMicroscopy (PEEM). Here we present PIC-mapping results from biominerals, including the nacre and prismatic layers of mollusk shells, and sea urchin teeth. We describe various PIC-mapping approaches, and show that these lead to fundamental discoveries on the formation mechanisms of biominerals.

Effect of asymmetrical transfer coefficients of a non-polarizing beam splitter on the nonlinear error of the polarization interferometer

Science.gov (United States)

Zhao, Chen-Guang; Tan, Jiu-Bin; Liu, Tao

2010-09-01

The mechanism of a non-polarizing beam splitter (NPBS) with asymmetrical transfer coefficients causing the rotation of polarization direction is explained in principle, and the measurement nonlinear error caused by NPBS is analyzed based on Jones matrix theory. Theoretical calculations show that the nonlinear error changes periodically, and the error period and peak values increase with the deviation between transmissivities of p-polarization and s-polarization states. When the transmissivity of p-polarization is 53% and that of s-polarization is 48%, the maximum error reaches 2.7 nm. The imperfection of NPBS is one of the main error sources in simultaneous phase-shifting polarization interferometer, and its influence can not be neglected in the nanoscale ultra-precision measurement.

Spin-polarized photoemission

International Nuclear Information System (INIS)

Johnson, Peter D.

1997-01-01

Spin-polarized photoemission has developed into a versatile tool for the study of surface and thin film magnetism. In this review, we examine the methodology of the technique and its application to a number of different problems, including both valence band and core level studies. After a detailed review of spin-polarization measurement techniques and the related experimental requirements we consider in detail studies of the bulk properties both above and below the Curie temperature. This section also includes a discussion of observations relating to unique metastable phases obtained via epitaxial growth. The application of the technique to the study of surfaces, both clean and adsorbate covered, is reviewed. The report then examines, in detail, studies of the spin-polarized electronic structure of thin films and the related interfacial magnetism. Finally, observations of spin-polarized quantum well states in non-magnetic thin films are discussed with particular reference to their mediation of the oscillatory exchange coupling in related magnetic multilayers. (author)

Spatially resolved quantitative mapping of thermomechanical properties and phase transition temperatures using scanning probe microscopy

Science.gov (United States)

Jesse, Stephen; Kalinin, Sergei V; Nikiforov, Maxim P

2013-07-09

An approach for the thermomechanical characterization of phase transitions in polymeric materials (polyethyleneterephthalate) by band excitation acoustic force microscopy is developed. This methodology allows the independent measurement of resonance frequency, Q factor, and oscillation amplitude of a tip-surface contact area as a function of tip temperature, from which the thermal evolution of tip-surface spring constant and mechanical dissipation can be extracted. A heating protocol maintained a constant tip-surface contact area and constant contact force, thereby allowing for reproducible measurements and quantitative extraction of material properties including temperature dependence of indentation-based elastic and loss moduli.

Assessment of occupational exposure to asbestos fibers: Contribution of analytical transmission electron microscopy analysis and comparison with phase-contrast microscopy.

Science.gov (United States)

Eypert-Blaison, Céline; Romero-Hariot, Anita; Clerc, Frédéric; Vincent, Raymond

2018-03-01

From November 2009 to October 2010, the French general directorate for labor organized a large field-study using analytical transmission electron microscopy (ATEM) to characterize occupational exposure to asbestos fibers during work on asbestos containing materials (ACM). The primary objective of this study was to establish a method and to validate the feasibility of using ATEM for the analysis of airborne asbestos of individual filters sampled in various occupational environments. For each sampling event, ATEM data were compared to those obtained by phase-contrast optical microscopy (PCOM), the WHO-recommended reference technique. A total of 265 results were obtained from 29 construction sites where workers were in contact with ACM. Data were sorted depending on the combination of the ACM type and the removal technique. For each "ACM-removal technique" combination, ATEM data were used to compute statistical indicators on short, fine and WHO asbestos fibers. Moreover, exposure was assessed taking into account the use of respiratory protective devices (RPD). As in previous studies, no simple relationship was found between results by PCOM and ATEM counting methods. Some ACM, such as asbestos-containing plasters, generated very high dust levels, and some techniques generated considerable levels of dust whatever the ACM treated. On the basis of these observations, recommendations were made to measure and control the occupational exposure limit. General prevention measures to be taken during work with ACM are also suggested. Finally, it is necessary to continue acquiring knowledge, in particular regarding RPD and the dust levels measured by ATEM for the activities not evaluated during this study.

DMFC anode polarization: Experimental analysis and model validation

Energy Technology Data Exchange (ETDEWEB)

Casalegno, A.; Marchesi, R. [Dipartimento di Energetica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

2008-01-03

Anode two-phase flow has an important influence on DMFC performance and methanol crossover. In order to elucidate two-phase flow influence on anode performance, in this work, anode polarization is investigated combining experimental and modelling approach. A systematic experimental analysis of operating conditions influence on anode polarization is presented. Hysteresis due to operating condition is observed; experimental results suggest that it arises from methanol accumulation and has to be considered in evaluating DMFC performances and measurements reproducibility. A model of DMFC anode polarization is presented and utilised as tool to investigate anode two-phase flow. The proposed analysis permits one to produce a confident interpretation of the main involved phenomena. In particular, it confirms that methanol electro-oxidation kinetics is weakly dependent on methanol concentration and that methanol transport in gas phase produces an important contribution in anode feeding. Moreover, it emphasises the possibility to optimise anode flow rate in order to improve DMFC performance and reduce methanol crossover. (author)

Three-dimensional polarization marked multiple-QR code encryption by optimizing a single vectorial beam

Science.gov (United States)

Lin, Chao; Shen, Xueju; Hua, Binbin; Wang, Zhisong

2015-10-01

We demonstrate the feasibility of three dimensional (3D) polarization multiplexing by optimizing a single vectorial beam using a multiple-signal window multiple-plane (MSW-MP) phase retrieval algorithm. Original messages represented with multiple quick response (QR) codes are first partitioned into a series of subblocks. Then, each subblock is marked with a specific polarization state and randomly distributed in 3D space with both longitudinal and transversal adjustable freedoms. A generalized 3D polarization mapping protocol is established to generate a 3D polarization key. Finally, multiple-QR code is encrypted into one phase only mask and one polarization only mask based on the modified Gerchberg-Saxton (GS) algorithm. We take the polarization mask as the cyphertext and the phase only mask as additional dimension of key. Only when both the phase key and 3D polarization key are correct, original messages can be recovered. We verify our proposal with both simulation and experiment evidences.

Linear polarizers based on oriented polymer blends

NARCIS (Netherlands)

Jagt, H.J.B.; Dirix, Y.J.L.; Hikmet, R.A.M.; Bastiaansen, C.W.M.

1998-01-01

Linear sheet polarizers based on the anisotropic scattering of light by drawn polymer blends are introduced here. The proper selection of materials and processing conditions for the production of large-area, flexible films of phase-segregated polymer blends suitable for polarization applications are

Polarization phenomena in few-body systems

International Nuclear Information System (INIS)

Conzett, H.E.

1975-12-01

Recent polarization studies in N--N scattering at and below 50 MeV have provided specific and significant improvements in the phase-shift parameters. High energy investigations with both polarized proton beams and targets have shown unexpectedly large spin effects, and this provides a challenge for theoretical effort to explain these results. Experimental and theoretical work on the three-nucleon problem continues to yield new and interesting results, with the emphasis now shifting to polarization studies in the breakup reaction. On-going work on several-nucleon systems continues to provide polarization data for general analyses, nuclear structure information, or specific resonance effects. Finally, the basic interaction symmetries continue to have unique and important consequences for polarization observables. 17 figures

Atomic-scale compensation phenomena at polar interfaces.

Science.gov (United States)

Chisholm, Matthew F; Luo, Weidong; Oxley, Mark P; Pantelides, Sokrates T; Lee, Ho Nyung

2010-11-05

The interfacial screening charge that arises to compensate electric fields of dielectric or ferroelectric thin films is now recognized as the most important factor in determining the capacitance or polarization of ultrathin ferroelectrics. Here we investigate using aberration-corrected electron microscopy and density-functional theory to show how interfaces cope with the need to terminate ferroelectric polarization. In one case, we show evidence for ionic screening, which has been predicted by theory but never observed. For a ferroelectric film on an insulating substrate, we found that compensation can be mediated by an interfacial charge generated, for example, by oxygen vacancies.

Lyotropic liquid crystalline phase behaviour in amphiphile-protic ionic liquid systems.

Science.gov (United States)

Chen, Zhengfei; Greaves, Tamar L; Fong, Celesta; Caruso, Rachel A; Drummond, Calum J

2012-03-21

Approximate partial phase diagrams for nine amphiphile-protic ionic liquid (PIL) systems have been determined by synchrotron source small angle X-ray scattering, differential scanning calorimetry and cross polarised optical microscopy. The binary phase diagrams of some common cationic (hexadecyltrimethyl ammonium chloride, CTAC, and hexadecylpyridinium bromide, HDPB) and nonionic (polyoxyethylene (10) oleyl ether, Brij 97, and Pluronic block copolymer, P123) amphiphiles with the PILs, ethylammonium nitrate (EAN), ethanolammonium nitrate (EOAN) and diethanolammonium formate (DEOAF), have been studied. The phase diagrams were constructed for concentrations from 10 wt% to 80 wt% amphiphile, in the temperature range 25 °C to >100 °C. Lyotropic liquid crystalline phases (hexagonal, cubic and lamellar) were formed at high surfactant concentrations (typically >50 wt%), whereas at thermal stability of the phases formed by these surfactants persisted to temperatures above 100 °C. The phase behaviour of amphiphile-PIL systems was interpreted by considering the PIL cohesive energy, liquid nanoscale order, polarity and ionicity. For comparison the phase behaviour of the four amphiphiles was also studied in water.

Short-coherence in-line phase-shifting infrared digital holographic microscopy for measurement of internal structure in silicon

Science.gov (United States)

Xi, Teli; Dou, Jiazhen; Di, Jianglei; Li, Ying; Zhang, Jiwei; Ma, Chaojie; Zhao, Jianlin

2017-06-01

Short-coherence in-line phase-shifting digital holographic microscopy based on Michelson interferometer is proposed to measure internal structure in silicon. In the configuration, a short-coherence infrared laser is used as the light source in order to avoid the interference formed by the reference wave and the reflected wave from the front surface of specimen. At the same time, in-line phase-shifting configuration is introduced to overcome the problem of poor resolution and large pixel size of the infrared camera and improve the space bandwidth product of the system. A specimen with staircase structure is measured by using the proposed configuration and the 3D shape distribution are given to verify the effectiveness and accuracy of the method.

Polar and chemical domain structures of lead scandium tantalate (PST)

International Nuclear Information System (INIS)

Peng, J.L.; Bursill, L.A.

1993-01-01

The local structure of chemical and polar domains and domain walls is determined directly by atomic resolution high-resolution electron microscopy. Thus the Pb, Ta and Sc atomic positions may be located in the images of very thin crystals. Furthermore the Pb cation displacements away from the ideal perovskite A-site have been measured directly for the first time. Local variations in polarization direction may be mapped directly off the images, provided certain electron optical conditions are met. The results are relevant to recent theories of polar-glass behaviour in relaxor-type complex oxide functional ceramics. 17 refs., 9 figs

Mechanosensation Dynamically Coordinates Polar Growth and Cell Wall Assembly to Promote Cell Survival.

Science.gov (United States)

Davì, Valeria; Tanimoto, Hirokazu; Ershov, Dmitry; Haupt, Armin; De Belly, Henry; Le Borgne, Rémi; Couturier, Etienne; Boudaoud, Arezki; Minc, Nicolas

2018-04-23

How growing cells cope with size expansion while ensuring mechanical integrity is not known. In walled cells, such as those of microbes and plants, growth and viability are both supported by a thin and rigid encasing cell wall (CW). We deciphered the dynamic mechanisms controlling wall surface assembly during cell growth, using a sub-resolution microscopy approach to monitor CW thickness in live rod-shaped fission yeast cells. We found that polar cell growth yielded wall thinning and that thickness negatively influenced growth. Thickness at growing tips exhibited a fluctuating behavior with thickening phases followed by thinning phases, indicative of a delayed feedback promoting thickness homeostasis. This feedback was mediated by mechanosensing through the CW integrity pathway, which probes strain in the wall to adjust synthase localization and activity to surface growth. Mutants defective in thickness homeostasis lysed by rupturing the wall, demonstrating its pivotal role for walled cell survival. Copyright © 2018 Elsevier Inc. All rights reserved.

4D profile of phase objects through the use of a simultaneous phase shifting quasi-common path interferometer

International Nuclear Information System (INIS)

Toto-Arellano, Noel-Ivan; Zurita, Gustavo Rodríguez; Montes-Pérez, Areli; Serrano-García, David Ignacio; García, Amalia Martínez

2011-01-01

Modulation of polarization is commonly employed in optical interferometry through the use of polarizers and quarter-wave retarders. Phase shifts between interfering beams can be easily controlled with such techniques. This communication describes some details of modulation of polarization which are useful in phase shifting interferometry applied to the study of phase objects. As an application, the case of a two-beam phase grating interferometer is discussed on the grounds of polarization analysis as an example. The configuration presented does not require micro-polarizer arrays or additional software to eliminate noise caused by vibration. This system does not use a double window, and generates two beams, the separation of which can be varied according to the characteristics of the grid used. Experimental results are also given

Investigation of the polarization state of dual APPLE-II undulators

International Nuclear Information System (INIS)

Hand, Matthew; Wang, Hongchang; Dhesi, Sarnjeet S.; Sawhney, Kawal

2016-01-01

Complete polarization analysis of the photon beam produced by a dual APPLE-II undulator configuration using a multilayer-based soft X-ray polarimeter is given. The use of an APPLE II undulator is extremely important for providing a high-brilliance X-ray beam with the capability to switch between various photon beam polarization states. A high-precision soft X-ray polarimeter has been used to systematically investigate the polarization characteristics of the two helical APPLE II undulators installed on beamline I06 at Diamond Light Source. A simple data acquisition and processing procedure has been developed to determine the Stokes polarization parameters for light polarized at arbitrary linear angles emitted from a single undulator, and for circularly polarized light emitted from both undulators in conjunction with a single-period undulator phasing unit. The purity of linear polarization is found to deteriorate as the polarization angle moves away from the horizontal and vertical modes. Importantly, a negative correlation between the degree of circular polarization and the photon flux has been found when the phasing unit is used

Investigation of the polarization state of dual APPLE-II undulators

Energy Technology Data Exchange (ETDEWEB)

Hand, Matthew; Wang, Hongchang, E-mail: hongchang.wang@diamond.ac.uk; Dhesi, Sarnjeet S.; Sawhney, Kawal [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom)

2016-01-01

Complete polarization analysis of the photon beam produced by a dual APPLE-II undulator configuration using a multilayer-based soft X-ray polarimeter is given. The use of an APPLE II undulator is extremely important for providing a high-brilliance X-ray beam with the capability to switch between various photon beam polarization states. A high-precision soft X-ray polarimeter has been used to systematically investigate the polarization characteristics of the two helical APPLE II undulators installed on beamline I06 at Diamond Light Source. A simple data acquisition and processing procedure has been developed to determine the Stokes polarization parameters for light polarized at arbitrary linear angles emitted from a single undulator, and for circularly polarized light emitted from both undulators in conjunction with a single-period undulator phasing unit. The purity of linear polarization is found to deteriorate as the polarization angle moves away from the horizontal and vertical modes. Importantly, a negative correlation between the degree of circular polarization and the photon flux has been found when the phasing unit is used.

Correlation of ''twins'' observed by optical microscopy and transmission electron microscopy in YBa2Cu3O7/sub -//sub x/ superconductors

International Nuclear Information System (INIS)

Hoff, H.A.; Singh, A.K.; Pande, C.S.

1988-01-01

By using transmission electron microscopy and optical microscopy on the same specimens, the patterns of light- and dark-contrast lines seen in reflected polarized light were shown to be an interference pattern due to the variable spacing of suboptical microtwins. These microtwins are mostly [110] reflection twins. The [110] twinning was observed to be cyclic and occasionally pseudotetragonal because of the progressive cycling of contact twin domains. Within a domain, and occasionally in a whole grain, the [110] reflection twins occurred as polysynthetic lamellae. The morphology of the domain structure can be explained from the theory of martensitic transformation

Study of polarization properties of fiber-optics probes with use of a binary phase plate.

Science.gov (United States)

Alferov, S V; Khonina, S N; Karpeev, S V

2014-04-01

We conduct a theoretical and experimental study of the distribution of the electric field components in the sharp focal domain when rotating a zone plate with a π-phase jump placed in the focused beam. Comparing the theoretical and experimental results for several kinds of near-field probes, an analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and an increase of the probe's energy throughput.

Anomalous Surface Wave Launching by Handedness Phase Control

KAUST Repository

Zhang, Xueqian

2015-10-09

Anomalous launch of a surface wave with different handedness phase control is achieved in a terahertz metasurface based on phase discontinuities. The polarity of the phase profile of the surface waves is found to be strongly correlated to the polarization handedness, promising polarization-controllable wavefront shaping, polarization sensing, and environmental refractive-index sensing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anomalous Surface Wave Launching by Handedness Phase Control

KAUST Repository

Zhang, Xueqian; Xu, Yuehong; Yue, Weisheng; Tian, Zhen; Gu, Jianqiang; Li, Yanfeng; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

2015-01-01

Anomalous launch of a surface wave with different handedness phase control is achieved in a terahertz metasurface based on phase discontinuities. The polarity of the phase profile of the surface waves is found to be strongly correlated to the polarization handedness, promising polarization-controllable wavefront shaping, polarization sensing, and environmental refractive-index sensing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Choosing the polarity of the phase-encoding direction in diffusion MRI: Does it matter for group analysis?

OpenAIRE

Kennis, M.; van Rooij, S.J.H.; Kahn, R.S.; Geuze, E.; Leemans, A.

2016-01-01

Notorious for degrading diffusion MRI data quality are so-called susceptibility-induced off-resonance fields, which cause non-linear geometric image deformations. While acquiring additional data to correct for these distortions alleviates the adverse effects of this artifact drastically – e.g., by reversing the polarity of the phase-encoding (PE) direction – this strategy is often not an option due to scan time constraints. Especially in a clinical context, where patient comfort and safety ar...

Interferometric characterization of the structured polarized light beam produced by the conical refraction phenomenon.

Science.gov (United States)

Peinado, Alba; Turpin, Alex; Iemmi, Claudio; Márquez, Andrés; Kalkandjiev, Todor K; Mompart, Jordi; Campos, Juan

2015-07-13

The interest on the conical refraction (CR) phenomenon in biaxial crystals has revived in the last years due to its prospective for generating structured polarized light beams, i.e. vector beams. While the intensity and the polarization structure of the CR beams are well known, an accurate experimental study of their phase structure has not been yet carried out. We investigate the phase structure of the CR rings by means of a Mach-Zehnder interferometer while applying the phase-shifting interferometric technique to measure the phase at the focal plane. In general the two beams interfering correspond to different states of polarization (SOP) which locally vary. To distinguish if there is an additional phase added to the geometrical one we have derived the appropriate theoretical expressions using the Jones matrix formalism. We demonstrate that the phase of the CR rings is equivalent to that one introduced by an azimuthally segmented polarizer with CR-like polarization distribution. Additionally, we obtain direct evidence that the Poggendorff dark ring is an annular singularity, with a π phase change between the inner and outer bright rings.

Review of quantitative phase-digital holographic microscopy: promising novel imaging technique to resolve neuronal network activity and identify cellular biomarkers of psychiatric disorders

KAUST Repository

Marquet, Pierre; Depeursinge, Christian; Magistretti, Pierre J.

2014-01-01

Quantitative phase microscopy (QPM) has recently emerged as a new powerful quantitative imaging technique well suited to noninvasively explore a transparent specimen with a nanometric axial sensitivity. In this review, we expose the recent

Generalized Expression for Polarization Density

International Nuclear Information System (INIS)

Wang, Lu; Hahm, T.S.

2009-01-01

A general polarization density which consists of classical and neoclassical parts is systematically derived via modern gyrokinetics and bounce-kinetics by employing a phase-space Lagrangian Lie-transform perturbation method. The origins of polarization density are further elucidated. Extending the work on neoclassical polarization for long wavelength compared to ion banana width [M. N. Rosenbluth and F. L. Hinton, Phys. Rev. Lett. 80, 724 (1998)], an analytical formula for the generalized neoclassical polarization including both finite-banana-width (FBW) and finite-Larmor-radius (FLR) effects for arbitrary radial wavelength in comparison to banana width and gyroradius is derived. In additional to the contribution from trapped particles, the contribution of passing particles to the neoclassical polarization is also explicitly calculated. Our analytic expression agrees very well with the previous numerical results for a wide range of radial wavelength.

Polar cap contraction and expansion during a period of substorms

Science.gov (United States)

Aikio, Anita; Pitkänen, Timo; Honkonen, Ilja; Palmroth, Minna; Amm, Olaf

We have studied the variations in the polar cap area and related parameters during a period of four substorms on February 18, 2004, following an extended quiet period. The measurements were obtained by the EISCAT incoherent scatter radars, MIRACLE magnetometers, Geotail and solar wind satellites. In addition, the event is modeled by the GUMICS-4 MHD simulation. By using the measured and modeled data, the dayside and nightside reconnection voltages are calculated. The results show a good general agreement in the polar cap boundary (PCB) location as estimated by the EISCAT radars and the GUMICS simulation. Deviations are found, too, like shorter durations of expansion phases in the simulation. Geotail measurements of the inclination angle of the magnetic field in the tail (Xgsm= -22 Re) agree with the PCB latitude variations measured by EISCAT at a different MLT. We conclude that a large polar cap corresponds to a stretched tail configuration in the near-Earth tail and a small polar cap to a more dipolar configuration. The substorm onsets took place during southward IMF. A specific feature is that the substorm expansion phases were not associated with significant contractions of the polar cap. Even though nightside reconnection voltages started to increase during expansion phases, maximum closure of open flux took place in the recovery phases. We shortly discuss implications of the observation to the definition of the recovery phase.

Marine target detection in quad-pol synthetic aperture radar imagery based on the relative phase of cross-polarized channels

Science.gov (United States)

Wang, Yunhua; Li, Huimin; Zhang, Yanmin; Guo, Lixin

2015-01-01

A focus on marine target detection in noise corrupted fully polarimetric synthetic aperture radar (SAR) is presented. The property of the relative phase between two cross-polarized channels reveals that the relative phases evaluated within sea surface area or noise corrupted area are widely spread phase angle region [-π,π] due to decorrelation effect; however, the relative phases are concentrated to zero and ±π for real target and its first-order azimuth ambiguities (FOAAs), respectively. Exploiting this physical behavior, the reciprocal of the mean square value of the relative phase (RMSRP) is defined as a new parameter for target detection, and the experiments based on fully polarimetric Radarsat-2 SAR images show that the strong noise and the FOAAs can be effectively suppressed in RMSRP image. Meanwhile, validity of the new parameter for target detection is also verified by two typical Radarsat-2 SAR images, in which targets' ambiguities and strong noise are present.

Effect of rubber polarity on selective wetting of carbon nanotubes in ternary blends

OpenAIRE

Le, H.H.; Parsaker, M.; Sriharish, M.N.; Henning, S.; Menzel, M.; Wiessner, S.; Das, A.; Do, Q.K.; Heinrich, G.; Radusch, H.J.

2015-01-01

Based on atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) analysis of the rubber-filler gel (wetting concept) the kinetics of selective wetting of carbon nanotubes (CNTs) in ternary styrene butadiene rubber (SBR)/butadiene rubber (BR)/natural rubber (NR) blends was qualitatively and quantitatively characterized. Almost all CNTs are found to be wetted by the non-polar NR but not by the other non-polar rubber like BR or weakly polar SBR. It was proposed that phos...

High resolution transmission electron microscopy studies of {sigma} phase in Ni-based single crystal superalloys

Energy Technology Data Exchange (ETDEWEB)

Sun Fei [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Zhang Jianxin, E-mail: jianxin@sdu.edu.cn [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Liu Pan [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Feng Qiang [National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Han Xiaodong; Mao Shengcheng [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)

2012-09-25

Graphical abstract: (a) TEM micrograph of {sigma} phase; (b) HRTEM image of {sigma}/{gamma} interface corresponding to the area of the white frame in (a); (c) an enlarged image of area from the white frame in (b). The combination of {sigma}/{gamma} interface appears very well, and a two-atomic-layer step is shown on the {sigma}/{gamma} interface. In addition, {sigma} phase has the orientation relationship of [0 0 1]{sub {gamma}}//[1 1 2{sup Macron }]{sub {sigma}}, (2{sup Macron} 2 0){sub {gamma}}//(1{sup Macron} 1 0){sub {sigma}}, (2{sup Macron }2{sup Macron} 0){sub {gamma}}//(1 1 1){sub {sigma}}; [0 1 1]{sub {gamma}}//[1 1 0]{sub {sigma}}, (1 1{sup Macron} 1){sub {gamma}}//(0 0 1{sup Macron }){sub {sigma}} with the {gamma} phase. Highlights: Black-Right-Pointing-Pointer Elemental characteristic of {sigma} phase is studied by HAADF techniques and EDS analysis. Black-Right-Pointing-Pointer Interfacial characteristics of {sigma}/{gamma} interface are revealed by HRTEM. Black-Right-Pointing-Pointer An atomic structural {sigma}/{gamma} interface with a two-atomic-layer step has been proposed. - Abstract: By means of high resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field image technique (HAADF), morphological of plate-shaped {sigma} phase and interfacial characteristics between plate-shaped {sigma} phase and {gamma} phase in Ni-based single crystal superalloys have been studied. On the basis of HRTEM observations, an atomic structural interface between {sigma} phase and {gamma} phase with a step has been proposed. {sigma} Phase has the relationship of [0 0 1]{sub {gamma}}//[1 1 2{sup Macron }]{sub {sigma}}, (2{sup Macron} 2 0){sub {gamma}}//(1{sup Macron} 1 0){sub {sigma},} (2{sup Macron }2{sup Macron} 0){sub {gamma}}//(1 1 1){sub {sigma}}; [0 1 1]{sub {gamma}}//[1 1 0]{sub {sigma}}, (1 1{sup Macron} 1){sub {gamma}}//(0 0 1{sup Macron }){sub {sigma}} with the {gamma} phase. The compositional characteristics of the {sigma} phase which

Near-field circular polarization probed by chiral polyfluorene

NARCIS (Netherlands)

Savoini, M.; Biagioni, P.; Lakhwani, G.; Meskers, S.C.J.; Duò, L.; Finazzi, M.

2009-01-01

We demonstrate that a high degree of circular polarization can be delivered to the near field (NF) of an aperture at the apex of hollow-pyramid probes for scanning optical microscopy. This result is achieved by analyzing the dichroic properties of an annealed thin polymer film containing a chiral

Leakage radiation interference microscopy.

Science.gov (United States)

Descrovi, Emiliano; Barakat, Elsie; Angelini, Angelo; Munzert, Peter; De Leo, Natascia; Boarino, Luca; Giorgis, Fabrizio; Herzig, Hans Peter

2013-09-01

We present a proof of principle for a new imaging technique combining leakage radiation microscopy with high-resolution interference microscopy. By using oil immersion optics it is demonstrated that amplitude and phase can be retrieved from optical fields, which are evanescent in air. This technique is illustratively applied for mapping a surface mode propagating onto a planar dielectric multilayer on a thin glass substrate. The surface mode propagation constant estimated after Fourier transformation of the measured complex field is well matched with an independent measurement based on back focal plane imaging.

Ferroelectric InMnO{sub 3}: Growth of single crystals, structure and high-temperature phase transitions

Energy Technology Data Exchange (ETDEWEB)

Bekheet, Maged F., E-mail: maged.bekheet@ceramics.tu-berlin.de [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany); Svoboda, Ingrid; Liu, Na [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Bayarjargal, Lkhamsuren [Institut für Geowissenschaften, Goethe-Universität, Altenhöferallee 1, d-60438 Frankfurt a.M. (Germany); Irran, Elisabeth [Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin (Germany); Dietz, Christian; Stark, Robert W.; Riedel, Ralf [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Gurlo, Aleksander [Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany)

2016-09-15

To understand the origin of the ferroelectricity in InMnO{sub 3}, single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. The results of single crystal X-ray diffraction, second harmonic generation and piezoresponse force microscopy studies of high-quality InMnO{sub 3} single crystals reveal that the room-temperature state in this material is ferroelectric with P6{sub 3}cm symmetry. The polar InMnO{sub 3} specimen undergoes a reversible phase transition from non-centrosymmetric P6{sub 3}cm structure to a centrosymmetric P6{sub 3}/mmc structure at 700 °C as confirmed by the in situ high-temperature Raman spectroscopic and synchrotron X-ray diffraction experiments. - Graphical abstract: Piezoresponse fore microscopy (PFM) studies of high quality InMnO{sub 3} single crystal revealed that the room-temperature state of this material is ferroelectric with a clear cloverleaf pattern corresponding to six antiphase ferroelectric domains with alternating polarization ±P{sub z}. Display Omitted - Highlights: • InMnO{sub 3} single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. • The room-temperature state of InMnO{sub 3} is ferroelectric with polar P6{sub 3}cm structure. • PolarInMnO{sub 3} reversibly transforms to a centrosymmetric P6{sub 3}/mmc structure above 700 °C.

Polarization effects on the electric properties of urea and thiourea molecules in solid phase

International Nuclear Information System (INIS)

Santos, O. L.; Fonseca, T. L.; Sabino, J. R.; Georg, H. C.; Castro, M. A.

2015-01-01

We present theoretical results for the dipole moment, linear polarizability, and first hyperpolarizability of the urea and thiourea molecules in solid phase. The in-crystal electric properties were determined by applying a supermolecule approach in combination with an iterative electrostatic scheme, in which the surrounding molecules are represented by point charges. It is found for both urea and thiourea molecules that the influence of the polarization effects is mild for the linear polarizability, but it is marked for the dipole moment and first hyperpolarizability. The replacement of oxygen atoms by sulfur atoms increases, in general, the electric responses. Our second-order Møller–Plesset perturbation theory based iterative scheme predicts for the in-crystal dipole moment of urea and thiourea the values of 7.54 and 9.19 D which are, respectively, increased by 61% and 58%, in comparison with the corresponding isolated values. The result for urea is in agreement with the available experimental result of 6.56 D. In addition, we present an estimate of macroscopic quantities considering explicit unit cells of urea and thiourea crystals including environment polarization effects. These supermolecule calculations take into account partially the exchange and dispersion effects. The results illustrate the role played by the electrostatic interactions on the static second-order nonlinear susceptibility of the urea crystal

Simulation and Verification of Tip-Induced Polarization During Kelvin Probe Force Microscopy Measurements on Film Capacitors

DEFF Research Database (Denmark)

Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

2017-01-01

have developed a physics-based finite element model of KPFM measurements on dielectrics in order to investigate the impact of tip-induced polarization. The model is compared with experiments on film capacitors, where it is found that tip-induced polarization is a significant contributor...

Effect of intermetallic phases on the anodic oxidation and corrosion of 5A06 aluminum alloy

Science.gov (United States)

Li, Song-mei; Li, Ying-dong; Zhang, You; Liu, Jian-hua; Yu, Mei

2015-02-01

Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered intermetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaCl solution. The results show that the size of Al-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the anodic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.

Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble

International Nuclear Information System (INIS)

Herzog, B. E.; Cadeddu, D.; Xue, F.; Peddibhotla, P.; Poggio, M.

2014-01-01

As the number of spins in an ensemble is reduced, the statistical fluctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer-scale ensembles of nuclear spins in a KPF 6 sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble.

Evidence of sharp and diffuse domain walls in BiFeO3 by means of unit-cell-wise strain and polarization maps obtained with high resolution scanning transmission electron microscopy.

Science.gov (United States)

Lubk, A; Rossell, M D; Seidel, J; He, Q; Yang, S Y; Chu, Y H; Ramesh, R; Hÿtch, M J; Snoeck, E

2012-07-27

Domain walls (DWs) substantially influence a large number of applications involving ferroelectric materials due to their limited mobility when shifted during polarization switching. The discovery of greatly enhanced conduction at BiFeO(3) DWs has highlighted yet another role of DWs as a local material state with unique properties. However, the lack of precise information on the local atomic structure is still hampering microscopical understanding of DW properties. Here, we examine the atomic structure of BiFeO(3) 109° DWs with pm precision by a combination of high-angle annular dark-field scanning transmission electron microscopy and a dedicated structural analysis. By measuring simultaneously local polarization and strain, we provide direct experimental proof for the straight DW structure predicted by ab initio calculations as well as the recently proposed theory of diffuse DWs, thus resolving a long-standing discrepancy between experimentally measured and theoretically predicted DW mobilities.

Gate-tunable polarized phase of two-dimensional electrons at the LaAlO3/SrTiO3 interface.

Science.gov (United States)

Joshua, Arjun; Ruhman, Jonathan; Pecker, Sharon; Altman, Ehud; Ilani, Shahal

2013-06-11

Controlling the coupling between localized spins and itinerant electrons can lead to exotic magnetic states. A novel system featuring local magnetic moments and extended 2D electrons is the interface between LaAlO3 and SrTiO3. The magnetism of the interface, however, was observed to be insensitive to the presence of these electrons and is believed to arise solely from extrinsic sources like oxygen vacancies and strain. Here we show the existence of unconventional electronic phases in the LaAlO3/SrTiO3 system pointing to an underlying tunable coupling between itinerant electrons and localized moments. Using anisotropic magnetoresistance and anomalous Hall effect measurements in a unique in-plane configuration, we identify two distinct phases in the space of carrier density and magnetic field. At high densities and fields, the electronic system is strongly polarized and shows a response, which is highly anisotropic along the crystalline directions. Surprisingly, below a density-dependent critical field, the polarization and anisotropy vanish whereas the resistivity sharply rises. The unprecedented vanishing of the easy axes below a critical field is in sharp contrast with other coupled magnetic systems and indicates strong coupling with the moments that depends on the symmetry of the itinerant electrons. The observed interplay between the two phases indicates the nature of magnetism at the LaAlO3/SrTiO3 interface as both having an intrinsic origin and being tunable.

Development of high-polarization Fe/Ge neutron polarizing supermirror: Possibility of fine-tuning of scattering length density in ion beam sputtering

Science.gov (United States)

Maruyama, R.; Yamazaki, D.; Akutsu, K.; Hanashima, T.; Miyata, N.; Aoki, H.; Takeda, M.; Soyama, K.

2018-04-01

The multilayer structure of Fe/Si and Fe/Ge systems fabricated by ion beam sputtering (IBS) was investigated using X-ray and polarized neutron reflectivity measurements and scanning transmission electron microscopy with energy-dispersive X-ray analysis. The obtained result revealed that the incorporation of sputtering gas particles (Ar) in the Ge layer gives rise to a marked reduction in the neutron scattering length density (SLD) and contributes to the SLD contrast between the Fe and Ge layers almost vanishing for spin-down neutrons. Bundesmann et al. (2015) have shown that the implantation of primary Ar ions backscattered at the target is responsible for the incorporation of Ar particles and that the fraction increases with increasing ion incidence angle and increasing polar emission angle. This leads to a possibility of fine-tuning of the SLD for the IBS, which is required to realize a high polarization efficiency of a neutron polarizing supermirror. Fe/Ge polarizing supermirror with m = 5 fabricated under the same condition showed a spin-up reflectivity of 0.70 at the critical momentum transfer. The polarization was higher than 0.985 for the qz range where the correction for the polarization inefficiencies of the beamline works properly. The result of the polarized neutron reflectivity measurement suggests that the "magnetically-dead" layers formed at both sides of the Fe layer, together with the SLD contrast, play a critical role in determining the polarization performance of a polarizing supermirror.

Interfacial B-site atomic configuration in polar (111) and non-polar (001) SrIrO3/SrTiO3 heterostructures

Science.gov (United States)

Anderson, T. J.; Zhou, H.; Xie, L.; Podkaminer, J. P.; Patzner, J. J.; Ryu, S.; Pan, X. Q.; Eom, C. B.

2017-09-01

The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111) and non-polar (001) SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111) interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001) interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111) perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

Interfacial B-site atomic configuration in polar (111 and non-polar (001 SrIrO3/SrTiO3 heterostructures

Directory of Open Access Journals (Sweden)

T. J. Anderson

2017-09-01

Full Text Available The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111 and non-polar (001 SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111 interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001 interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111 perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

Spin-polarized fuel in ICF pellets

International Nuclear Information System (INIS)

Wakuta, Yoshihisa; Emoto, Nobuya; Nakao, Yasuyuki; Honda, Takuro; Honda, Yoshinori; Nakashima, Hideki.

1990-01-01

The use of parallel spin-polarized DT or D 3 He fuel increases the fusion cross-section by 50%. By implosion-burn simulation for inertially confined fusion (ICF) pellets of the spin-polarized fuels, we found that the input energy requirement could be reduced by nearly a fact of two. These pellets taken up here include large-high-aspect-ratio DT target proposed in ILE Osaka University and DT ignitor/D 3 He fuel pellet proposed by our group. We also found that the polarized state could survive during the implosion-burn phase. (author)

Polarization Characteristics Inferred From the Radio Receiver Instrument on the Enhanced Polar Outflow Probe

Science.gov (United States)

Danskin, Donald W.; Hussey, Glenn C.; Gillies, Robert G.; James, H. Gordon; Fairbairn, David T.; Yau, Andrew W.

2018-02-01

The Radio Receiver Instrument (RRI) on the CAScade, Smallsat, and Ionospheric Polar Explorer/enhanced Polar Outflow Probe (CASSIOPE/e-POP) satellite was used to receive continuous wave and binary phase shift keyed transmissions from a high-frequency transmitter located in Ottawa, ON, Canada during April 2016 to investigate how the ionosphere affects the polarization characteristics of transionospheric high-frequency radio waves. The spacecraft orientation was continuously slewed to maintain the dipole orientation in a plane perpendicular to the direction toward the transmitter, enabling the first in situ planar polarization determination for continuous wave and binary phase shift keyed modulated radio waves from space at times when the wave frequency is at least 1.58 times the plasma frequency. The Stokes parameters and polarization characteristics were derived from the measured data and interpreted using an existing ray tracing model. For the southern part of the passes, the power was observed to oscillate between the two dipoles of RRI, which was attributed to Faraday rotation of the radio waves. For the first time, a reversal in the rate of change of orientation angle was observed where the minimum in modeled Faraday rotation occurred. The reversal point was poleward of the point of closest approach between the satellite and transmitter; this was explained by the variations of total electron content and component of magnetic field along the direction of propagation. The received signals show both quasi-longitudinal (QL) and quasi-transverse characteristics. South of the transmitter the QL regime is dominant. Around the reversal point, a combination of QL and quasi-transverse nature was observed.

Novel Microstrip Patch Antennas with Frequency Agility, Polarization Reconfigurability, Dual Null Steering Capability and Phased Array Antenna with Beam Steering Performance

Science.gov (United States)

Babakhani, Behrouz

Nowadays the wireless communication technology is playing an important role in our daily life. People use wireless devices not only as a conventional communication device but also as tracking and navigation tool, web browsing tool, data storage and transfer tool and so for many other reasons. Based on the user demand, wireless communication engineers try to accommodate as many as possible wireless systems and applications in a single device and therefore, creates a multifunctional device. Antenna, as an integral part of any wireless communication systems, should also be evolved and adjusted with development of wireless transceiver systems. Therefore multifunctional antennas have been introduced to support and enhance the functionality on modern wireless systems. The main focus and contribution of this thesis is design of novel multifunctional microstrip antennas with frequency agility, polarization reconfigurablity, dual null steering capability and phased array antenna with beam steering performance. In this thesis, first, a wide bandwidth(1.10 GHz to 1.60 GHz) right-handed circularly polarized (RHCP) directional antenna for global positioning system (GPS) satellite receive application has been introduced which covers all the GPS bands starting from L1 to L5. This design consists of two crossed bow-tie dipole antennas fed with sequentially phase rotated feed network backed with an artificial high impedance surface (HIS) structure to generate high gain directional radiation patterns. This design shows good CP gain and axial ratio (AR) and wide beamwidth performance. Although this design has good radiation quality, the size and the weight can be reduced as future study. In the second design, a frequency agile antenna was developed which also covers the L-band (L1 to L5) satellite communication frequencies. This frequency agile antenna was designed and realized by new implementation of varactor diodes in the geometry of a circular patch antenna. Beside wide frequency

Piezoelectric properties of PbTiO(3) thin films characterized with piezoresponse force and high resolution transmission electron microscopy

NARCIS (Netherlands)

Morelli, A.; Venkatesan, Sriram; Kooi, B. J.; Palasantzas, G.; De Hosson, J. Th. M.

2009-01-01

In this paper we investigate the piezoelectric properties of PbTiO(3) thin films grown by pulsed laser deposition with piezoresponse force microscopy and transmission electron microscopy. The as-grown films exhibit an upward polarization, inhomogeneous distribution of piezoelectric characteristics

Using Polarized Spectroscopy to Investigate Order in Thin-Films of Ionic Self-Assembled Materials Based on Azo-Dyes

Science.gov (United States)

Ahmad, Mariam; Andersen, Frederik; Brend Bech, Ári; Bendixen, H. Krestian L.; Nawrocki, Patrick R.; Bloch, Anders J.; Bora, Ilkay; Bukhari, Tahreem A.; Bærentsen, Nicolai V.; Carstensen, Jens; Chima, Smeeah; Colberg, Helene; Dahm, Rasmus T.; Daniels, Joshua A.; Dinckan, Nermin; El Idrissi, Mohamed; Erlandsen, Ricci; Førster, Marc; Ghauri, Yasmin; Gold, Mikkel; Hansen, Andreas; Hansen, Kenn; Helmsøe-Zinck, Mathias; Henriksen, Mathias; Hoffmann, Sophus V.; Hyllested, Louise O. H.; Jensen, Casper; Kallenbach, Amalie S.; Kaur, Kirandip; Khan, Suheb R.; Kjær, Emil T. S.; Kristiansen, Bjørn; Langvad, Sylvester; Lund, Philip M.; Munk, Chastine F.; Møller, Theis; Nehme, Ola M. Z.; Nejrup, Mathilde Rove; Nexø, Louise; Nielsen, Simon Skødt Holm; Niemeier, Nicolai; Nikolajsen, Lasse V.; Nøhr, Peter C. T.; Skaarup Ovesen, Jacob; Paustian, Lucas; Pedersen, Adam S.; Petersen, Mathias K.; Poulsen, Camilla M.; Praeger-Jahnsen, Louis; Qureshi, L. Sonia; Schiermacher, Louise S.; Simris, Martin B.; Smith, Gorm; Smith, Heidi N.; Sonne, Alexander K.; Zenulovic, Marko R.; Winther Sørensen, Alma; Vogt, Emil; Væring, Andreas; Westermann, Jonas; Özcan, Sevin B.

2018-01-01

Three series of ionic self-assembled materials based on anionic azo-dyes and cationic benzalkonium surfactants were synthesized and thin films were prepared by spin-casting. These thin films appear isotropic when investigated with polarized optical microscopy, although they are highly anisotropic. Here, three series of homologous materials were studied to rationalize this observation. Investigating thin films of ordered molecular materials relies to a large extent on advanced experimental methods and large research infrastructure. A statement that in particular is true for thin films with nanoscopic order, where X-ray reflectometry, X-ray and neutron scattering, electron microscopy and atom force microscopy (AFM) has to be used to elucidate film morphology and the underlying molecular structure. Here, the thin films were investigated using AFM, optical microscopy and polarized absorption spectroscopy. It was shown that by using numerical method for treating the polarized absorption spectroscopy data, the molecular structure can be elucidated. Further, it was shown that polarized optical spectroscopy is a general tool that allows determination of the molecular order in thin films. Finally, it was found that full control of thermal history and rigorous control of the ionic self-assembly conditions are required to reproducibly make these materials of high nanoscopic order. Similarly, the conditions for spin-casting are shown to be determining for the overall thin film morphology, while molecular order is maintained. PMID:29462883

Using Polarized Spectroscopy to Investigate Order in Thin-Films of Ionic Self-Assembled Materials Based on Azo-Dyes

Directory of Open Access Journals (Sweden)

Miguel R. Carro-Temboury Martin Kühnel

2018-02-01

Full Text Available Three series of ionic self-assembled materials based on anionic azo-dyes and cationic benzalkonium surfactants were synthesized and thin films were prepared by spin-casting. These thin films appear isotropic when investigated with polarized optical microscopy, although they are highly anisotropic. Here, three series of homologous materials were studied to rationalize this observation. Investigating thin films of ordered molecular materials relies to a large extent on advanced experimental methods and large research infrastructure. A statement that in particular is true for thin films with nanoscopic order, where X-ray reflectometry, X-ray and neutron scattering, electron microscopy and atom force microscopy (AFM has to be used to elucidate film morphology and the underlying molecular structure. Here, the thin films were investigated using AFM, optical microscopy and polarized absorption spectroscopy. It was shown that by using numerical method for treating the polarized absorption spectroscopy data, the molecular structure can be elucidated. Further, it was shown that polarized optical spectroscopy is a general tool that allows determination of the molecular order in thin films. Finally, it was found that full control of thermal history and rigorous control of the ionic self-assembly conditions are required to reproducibly make these materials of high nanoscopic order. Similarly, the conditions for spin-casting are shown to be determining for the overall thin film morphology, while molecular order is maintained.

Using Polarized Spectroscopy to Investigate Order in Thin-Films of Ionic Self-Assembled Materials Based on Azo-Dyes.

Science.gov (United States)

Kühnel, Miguel R Carro-Temboury Martin; Ahmad, Mariam; Andersen, Frederik; Bech, Ári Brend; Bendixen, H Krestian L; Nawrocki, Patrick R; Bloch, Anders J; Bora, Ilkay; Bukhari, Tahreem A; Bærentsen, Nicolai V; Carstensen, Jens; Chima, Smeeah; Colberg, Helene; Dahm, Rasmus T; Daniels, Joshua A; Dinckan, Nermin; Idrissi, Mohamed El; Erlandsen, Ricci; Førster, Marc; Ghauri, Yasmin; Gold, Mikkel; Hansen, Andreas; Hansen, Kenn; Helmsøe-Zinck, Mathias; Henriksen, Mathias; Hoffmann, Sophus V; Hyllested, Louise O H; Jensen, Casper; Kallenbach, Amalie S; Kaur, Kirandip; Khan, Suheb R; Kjær, Emil T S; Kristiansen, Bjørn; Langvad, Sylvester; Lund, Philip M; Munk, Chastine F; Møller, Theis; Nehme, Ola M Z; Nejrup, Mathilde Rove; Nexø, Louise; Nielsen, Simon Skødt Holm; Niemeier, Nicolai; Nikolajsen, Lasse V; Nøhr, Peter C T; Orlowski, Dominik B; Overgaard, Marc; Ovesen, Jacob Skaarup; Paustian, Lucas; Pedersen, Adam S; Petersen, Mathias K; Poulsen, Camilla M; Praeger-Jahnsen, Louis; Qureshi, L Sonia; Ree, Nicolai; Schiermacher, Louise S; Simris, Martin B; Smith, Gorm; Smith, Heidi N; Sonne, Alexander K; Zenulovic, Marko R; Sørensen, Alma Winther; Sørensen, Karina; Vogt, Emil; Væring, Andreas; Westermann, Jonas; Özcan, Sevin B; Sørensen, Thomas Just

2018-02-15

Three series of ionic self-assembled materials based on anionic azo-dyes and cationic benzalkonium surfactants were synthesized and thin films were prepared by spin-casting. These thin films appear isotropic when investigated with polarized optical microscopy, although they are highly anisotropic. Here, three series of homologous materials were studied to rationalize this observation. Investigating thin films of ordered molecular materials relies to a large extent on advanced experimental methods and large research infrastructure. A statement that in particular is true for thin films with nanoscopic order, where X-ray reflectometry, X-ray and neutron scattering, electron microscopy and atom force microscopy (AFM) has to be used to elucidate film morphology and the underlying molecular structure. Here, the thin films were investigated using AFM, optical microscopy and polarized absorption spectroscopy. It was shown that by using numerical method for treating the polarized absorption spectroscopy data, the molecular structure can be elucidated. Further, it was shown that polarized optical spectroscopy is a general tool that allows determination of the molecular order in thin films. Finally, it was found that full control of thermal history and rigorous control of the ionic self-assembly conditions are required to reproducibly make these materials of high nanoscopic order. Similarly, the conditions for spin-casting are shown to be determining for the overall thin film morphology, while molecular order is maintained.

Solid-Phase Microextraction Coupled to Capillary Atmospheric Pressure Photoionization-Mass Spectrometry for Direct Analysis of Polar and Nonpolar Compounds.

Science.gov (United States)

Mirabelli, Mario F; Zenobi, Renato

2018-04-17

A novel capillary ionization source based on atmospheric pressure photoionization (cAPPI) was developed and used for the direct interfacing between solid-phase microextraction (SPME) and mass spectrometry (MS). The efficiency of the source was evaluated for direct and dopant-assisted photoionization, analyzing both polar (e.g., triazines and organophosphorus pesticides) and nonpolar (polycyclic aromatic hydrocarbons, PAHs) compounds. The results show that the range of compound polarity, which can be addressed by direct SPME-MS can be substantially extended by using cAPPI, compared to other sensitive techniques like direct analysis in real time (DART) and dielectric barrier discharge ionization (DBDI). The new source delivers a very high sensitivity, down to sub parts-per-trillion (ppt), making it a viable alternative when compared to previously reported and less comprehensive direct approaches.

Third phase formation in organic solutions in the extraction of mono-acids by tertiary trialcoyl-amines diluted in very slightly polar organic solvents

International Nuclear Information System (INIS)

Robaglia, Michele

1973-01-01

The phenomena of third phase formation which can occur during the extraction of an acid with a tertiary amine diluted in a low polarity diluent are studied. In the first part a system including water (TnOA - C 6 H 12 - HCl - H 2 O) is compared with an anhydrous system (TnOA - C 6 H 12 - HCl - N 2 ). There are two kinds of gaps. One during amine salification, another one during the extraction of excess acid. The important part of the water content of the organic phase is demonstrated. The presence of water enhances the gaps. The polar water molecules are dissolved inside the tri-octylamine salt micelles. The heavy phase is formed by aggregates, the light phase represents the solubility of the non soluble species in the medium. In the second part are studied the influence of some parameters (like nature of diluent, acid, amine and temperature) on the gaps formation and on the extraction of excess acid and water. In every cases the part played by water remains the same. Finally some comparisons are made between tertiary systems and binary systems which formed them. The binary systems were studied by the mean of crystallization curves. (author) [fr

Electrically tunable spin polarization in silicene: A multi-terminal spin density matrix approach

International Nuclear Information System (INIS)

Chen, Son-Hsien

2016-01-01

Recent realized silicene field-effect transistor yields promising electronic applications. Using a multi-terminal spin density matrix approach, this paper presents an analysis of the spin polarizations in a silicene structure of the spin field-effect transistor by considering the intertwined intrinsic and Rashba spin–orbit couplings, gate voltage, Zeeman splitting, as well as disorder. Coexistence of the stagger potential and intrinsic spin–orbit coupling results in spin precession, making any in-plane polarization directions reachable by the gate voltage; specifically, the intrinsic coupling allows one to electrically adjust the in-plane components of the polarizations, while the Rashba coupling to adjust the out-of-plan polarizations. Larger electrically tunable ranges of in-plan polarizations are found in oppositely gated silicene than in the uniformly gated silicene. Polarizations in different phases behave distinguishably in weak disorder regime, while independent of the phases, stronger disorder leads to a saturation value. - Highlights: • Density matrix with spin rotations enables multi-terminal arbitrary spin injections. • Gate-voltage tunable in-plane polarizations require intrinsic SO coupling. • Gate-voltage tunable out-of-plane polarizations require Rashba SO coupling. • Oppositely gated silicene yields a large tunable range of in-plan polarizations. • Polarizations in different phases behave distinguishably only in weak disorder.

Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy

Energy Technology Data Exchange (ETDEWEB)

Miao, Hongchen; Sun, Yao; Zhou, Xilong; Li, Yingwei [LTCS and Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); Li, Faxin, E-mail: lifaxin@pku.edu.cn [LTCS and Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); HEDPS and Center for Applied Physics and Technology, Peking University, Beijing (China)

2014-08-14

Cellular electrets polymer is a new ferroelectret material exhibiting large piezoelectricity and has attracted considerable attentions in researches and industries. Property characterization is very important for this material and current investigations are mostly on macroscopic properties. In this work, we conduct nanoscale piezoelectric and ferroelectric characterizations of cellular polypropylene (PP) films using piezoresponse force microscopy (PFM). First, both the single-frequency PFM and dual-frequency resonance-tracking PFM testings were conducted on the cellular PP film. The localized piezoelectric constant d{sub 33} is estimated to be 7–11pC/N by correcting the resonance magnification with quality factor and it is about one order lower than the macroscopic value. Next, using the switching spectroscopy PFM (SS-PFM), we studied polarization switching behavior of the cellular PP films. Results show that it exhibits the typical ferroelectric-like phase hysteresis loops and butterfly-shaped amplitude loops, which is similar to that of a poly(vinylidene fluoride) (PVDF) ferroelectric polymer film. However, both the phase and amplitude loops of the PP film are intensively asymmetric, which is thought to be caused by the nonzero remnant polarization after poling. Then, the D-E hysteresis loops of both the cellular PP film and PVDF film were measured by using the same wave form as that used in the SS-PFM, and the results show significant differences. Finally, we suggest that the ferroelectric-like behavior of cellular electrets films should be distinguished from that of typical ferroelectrics, both macroscopically and microscopically.

Compact three-dimensional super-resolution system based on fluorescence emission difference microscopy

Science.gov (United States)

Zhu, Dazhao; Chen, Youhua; Fang, Yue; Hussain, Anwar; Kuang, Cuifang; Zhou, Xiaoxu; Xu, Yingke; Liu, Xu

2017-12-01

A compact microscope system for three-dimensional (3-D) super-resolution imaging is presented. The super-resolution capability of the system is based on a size-reduced effective 3-D point spread function generated through the fluorescence emission difference (FED) method. The appropriate polarization direction distribution and manipulation allows the panel active area of the spatial light modulator to be fully utilized. This allows simultaneous modulation of the incident light by two kinds of phase masks to be performed with a single spatial light modulator in order to generate a 3-D negative spot. The system is more compact than standard 3-D FED systems while maintaining all the advantages of 3-D FED microscopy. The experimental results demonstrated the improvement in 3-D resolution by nearly 1.7 times and 1.6 times compared to the classic confocal resolution in the lateral and axial directions, respectively.

Analysis of elliptically polarized maximally entangled states for bell inequality tests

Science.gov (United States)

Martin, A.; Smirr, J.-L.; Kaiser, F.; Diamanti, E.; Issautier, A.; Alibart, O.; Frey, R.; Zaquine, I.; Tanzilli, S.

2012-06-01

When elliptically polarized maximally entangled states are considered, i.e., states having a non random phase factor between the two bipartite polarization components, the standard settings used for optimal violation of Bell inequalities are no longer adapted. One way to retrieve the maximal amount of violation is to compensate for this phase while keeping the standard Bell inequality analysis settings. We propose in this paper a general theoretical approach that allows determining and adjusting the phase of elliptically polarized maximally entangled states in order to optimize the violation of Bell inequalities. The formalism is also applied to several suggested experimental phase compensation schemes. In order to emphasize the simplicity and relevance of our approach, we also describe an experimental implementation using a standard Soleil-Babinet phase compensator. This device is employed to correct the phase that appears in the maximally entangled state generated from a type-II nonlinear photon-pair source after the photons are created and distributed over fiber channels.

Spontaneous spin-polarization and phase transition in the relativistic approach

International Nuclear Information System (INIS)

Maruyama, Tomoyuki; Tatsumi, Toshitaka

2001-01-01

We study the spin-polarization mechanism in the highly dense nuclear matter with the relativistic mean-field approach. In the relativistic Hartree-Fock framework we find that there are two kinds of spin-spin interaction channels, which are the axial-vector and tensor exchange ones. If each interaction is strong and different sign, the system loses the spherical symmetry and holds the spin-polarization in the high-density region. When the axial-vector interaction is negative enough, the system holds ferromagnetism. (author)

Storm-enhanced plasma density and polar tongue of ionization development during the 15 May 2005 superstorm

Science.gov (United States)

Horvath, Ildiko; Lovell, Brian C.

2015-06-01

We investigate the ionosphere's global response to the 15 May 2005 superstorm in terms of storm evolution and ionospheric electrodynamics. Our aim is to study the global distribution of plasma and the resultant large-scale ionospheric features including the equatorial ionization anomaly (EIA), storm-enhanced density (SED), and polar tongue of ionization (TOI). We have combined multi-instrument ionospheric data, solar and terrestrial magnetic data, and polar convection maps. Results reveal the prompt penetration of the interplanetary electric field to the polar region and then to the equator with a dusk-to-dawn polarity during the initial phase and with a dawn-to-dusk polarity during the main phase. This drove during the initial phase a weak eastward equatorial electrojet (EEJ) in the American sector at nighttime and a weak westward EEJ in the Indian-Australian sector at daytime. During the main phase, these EEJs intensified and changed polarities. SED and polar TOI development was observed prior to and during the initial phase at evening-premidnight hours over North America and during the main phase in the south at afternoon-evening hours in the Australian sector. During the main phase and early in the recovery phase, the EIA-SED structure was well formed in the Asian longitude sector. Then, polar TOI development was absent in the north because of the long distance from the magnetic pole but was supported in the south because of the closeness of daytime cusp and magnetic pole. Thus, the EIA-SED-TOI structure developed twice but each time in a different longitude sector and with different characteristics.

On the solid–liquid phase diagrams of binary mixtures of even saturated fatty alcohols: Systems exhibiting peritectic reaction

Energy Technology Data Exchange (ETDEWEB)

Carareto, Natália D.D. [EXTRAE, Department of Food Engineering, Food Engineering Faculty, University of Campinas, UNICAMP, CEP 13083-862 Campinas, SP (Brazil); Santos, Adenílson O. dos [Social Sciences, Health and Technology Center, University of Maranhão, UFMA, CEP 65900-410 Imperatriz, MA (Brazil); Rolemberg, Marlus P. [Institute of Science and Technology, University of Alfenas, UNIFAL, Rodovia José AurélioVilela, CEP 37715400 Poços de Caldas, MG (Brazil); Cardoso, Lisandro P. [Institute of Physics GlebWataghin, University of Campinas, UNICAMP, C.P. 6165, CEP 13083-970 Campinas, SP (Brazil); Costa, Mariana C. [School of Applied Science, University of Campinas, UNICAMP, CEP 13484-350 Limeira, SP (Brazil); Meirelles, Antonio J.A., E-mail: tomze@fea.unicamp.br [EXTRAE, Department of Food Engineering, Food Engineering Faculty, University of Campinas, UNICAMP, CEP 13083-862 Campinas, SP (Brazil)

2014-08-10

Highlights: • SLE of binary mixtures of saturated fatty alcohols was studied. • Experimental data were obtained using DSC and stepscan DSC. • Microscopy and X-ray diffraction used as complementary techniques. • Systems presented eutectic, peritectic and metatectic points. - Abstract: The solid–liquid phase diagrams of the following binary mixtures of even saturated fatty alcohols are reported in the literature for the first time: 1-octanol (C8OH) + 1-decanol (C10OH), 1-decanol + 1-dodecanol (C12OH), 1-dodecanol + 1-hexadecanol (C16OH) and 1-tetradecanol (C14OH) + 1-octadecanol (C18OH). The phase diagrams were obtained by differential scanning calorimetry (DSC) using a linear heating rate of 1 K min{sup −1} and further investigated by using a stepscan DSC method. X-ray diffraction (XRD) and polarized light microscopy were also used to complement the characterization of the phase diagrams which have shown a complex global behavior, presenting not only peritectic and eutectic reactions, but also the metatectic reaction and partial immiscibility on solid state.

On the solid–liquid phase diagrams of binary mixtures of even saturated fatty alcohols: Systems exhibiting peritectic reaction

International Nuclear Information System (INIS)

Carareto, Natália D.D.; Santos, Adenílson O. dos; Rolemberg, Marlus P.; Cardoso, Lisandro P.; Costa, Mariana C.; Meirelles, Antonio J.A.

2014-01-01

Highlights: • SLE of binary mixtures of saturated fatty alcohols was studied. • Experimental data were obtained using DSC and stepscan DSC. • Microscopy and X-ray diffraction used as complementary techniques. • Systems presented eutectic, peritectic and metatectic points. - Abstract: The solid–liquid phase diagrams of the following binary mixtures of even saturated fatty alcohols are reported in the literature for the first time: 1-octanol (C8OH) + 1-decanol (C10OH), 1-decanol + 1-dodecanol (C12OH), 1-dodecanol + 1-hexadecanol (C16OH) and 1-tetradecanol (C14OH) + 1-octadecanol (C18OH). The phase diagrams were obtained by differential scanning calorimetry (DSC) using a linear heating rate of 1 K min −1 and further investigated by using a stepscan DSC method. X-ray diffraction (XRD) and polarized light microscopy were also used to complement the characterization of the phase diagrams which have shown a complex global behavior, presenting not only peritectic and eutectic reactions, but also the metatectic reaction and partial immiscibility on solid state

Characterization of muscle contraction with second harmonic generation microscopy

Science.gov (United States)

Prent, Nicole

Muscle cells have the ability to change length and generate force due to orchestrated action of myosin nanomotors that cause sliding of actin filaments along myosin filaments in the sarcomeres, the fundamental contractile units, of myocytes. The correlated action of hundreds of sarcomeres is needed to produce the myocyte contractions. This study probes the molecular structure of the myofilaments and investigates the movement correlations between sarcomeres during contraction. In this study, second harmonic generation (SHG) microscopy is employed for imaging striated myocytes. Myosin filaments in striated myocytes inherently have a nonzero second-order susceptibility, [special characters omitted] and therefore generate efficient SHG. Employing polarization-in polarization-out (PIPO) SHG microscopy allows for the accurate determination of the characteristic ratio, [special characters omitted] in birefringent myocytes, which describes the structure of the myosin filament. Analysis shows that the b value at the centre of the myosin filament, where the nonlinear dipoles are better aligned, is slightly lower than the value at the edges of the filament, where there is more disorder in orientation of the nonlinear dipoles from the myosin heads. Forced stretching of myocytes resulted in an SHG intensity increase with the elongation of the sarcomere. SHG microscopy captured individual sarcomeres during contraction, allowing for the measurement of sarcomere length (SL) and SHG intensity (SI) fluctuations. The fluctuations also revealed higher SHG intensity in elongated sarcomeres. The sarcomere synchronization model (SSM) for contracting and quiescent myocytes was developed, and experimentally verified for three cases (isolated cardiomyocyte, embryonic chicken cardiomyocyte, and larva myocyte). During contraction, the action of SLs and SIs between neighbouring sarcomeres partially correlated, whereas in quiescent myocytes the SLs show an anti-correlation and the SIs have no

Quantitative phase microscopy using deep neural networks

Science.gov (United States)

Li, Shuai; Sinha, Ayan; Lee, Justin; Barbastathis, George

2018-02-01

Deep learning has been proven to achieve ground-breaking accuracy in various tasks. In this paper, we implemented a deep neural network (DNN) to achieve phase retrieval in a wide-field microscope. Our DNN utilized the residual neural network (ResNet) architecture and was trained using the data generated by a phase SLM. The results showed that our DNN was able to reconstruct the profile of the phase target qualitatively. In the meantime, large error still existed, which indicated that our approach still need to be improved.

A beginner's guide to the modern theory of polarization

International Nuclear Information System (INIS)

Spaldin, Nicola A.

2012-01-01

The so-called Modern Theory of Polarization, which rigorously defines the spontaneous polarization of a periodic solid and provides a route for its computation in electronic structure codes through the Berry phase, is introduced in a simple qualitative discussion. - Graphical abstract: Cartoon of Wannier functions in a covalent solid shifting to contribute to the ferroelectric polarization.

Anisotropic chemical etching of semipolar {101-bar 1-bar}/{101-bar +1} ZnO crystallographic planes: polarity versus dangling bonds

International Nuclear Information System (INIS)

Palacios-Lidon, E; Perez-GarcIa, B; Colchero, J; Vennegues, P; Zuniga-Perez, J; Munoz-Sanjose, V

2009-01-01

ZnO thin films grown by metal-organic vapor phase epitaxy along the nonpolar [112-bar] direction and exhibiting semipolar {101-bar 1-bar}/{101-bar +1} facets have been chemically etched with HCl. In order to get an insight into the influence of the ZnO wurtzite structure in the chemical reactivity of the material, Kelvin probe microscopy and convergent beam electron diffraction have been employed to unambiguously determine the absolute polarity of the facets, showing that {101-bar +1} facets are unstable upon etching in an HCl solution and transform into (000+1)/{101-bar 1-bar} planes. In contrast, {101-bar 1-bar} undergo homogeneous chemical etching perpendicular to the initial crystallographic plane. The observed etching behavior has been explained in terms of surface oxygen dangling bond density, suggesting that the macroscopic polarity plays a secondary role in the etching process.

The Polarization of Achernar

Science.gov (United States)