Crystal Rows Research Articles

Morphology, ultrastructure and molecular phylogeny of Johsia chumphonensis gen. et sp. nov. and Parvodinium parvulum comb. nov. (Peridiniopsidaceae, Dinophyceae)

ABSTRACT The family Peridiniopsidaceae encompasses mainly freshwater species of the genera Peridiniopsis, Palatinus and Parvodinium. Only one benthic, marine species ‘Scrippsiella’ hexapraecingula has been attributed to this family. Here we established five strains by isolating single Parvodinium-like cells from the marine Gulf of Thailand, Hainan Island waters (China), off Manado (Indonesia) and from a freshwater reservoir in Fuzhou (China). All strains were examined with light, scanning and transmission electron microscopy, and their SSU, ITS-5.8S and partial LSU rRNA regions were sequenced. Four marine strains share a plate formula of Po, cp, X, 4′, 2a, 6′′, 6C, 4S, 5′′′, 2′′′′ and are herein attributed to a new genus Johsia as J. chumphonensis gen. et sp. nov. Its theca is characterized by an epitheca 1.5 times as long as the hypotheca in dorsal view and a 2a plate about half the size of 1a. A type B eyespot was observed in J. chumphonensis comprising two rows of lipid globules within a chloroplast with a single row of crystals overlying the eyespot. Production of spherical cysts was observed in culture. The freshwater strain shows a plate pattern of Po, cp, X, 4′, 2a, 7′′, 6C, 5S, 5′′′, 2′′′′, characterized by two unequal antapical plates and a lack of antapical spines, fitting the description of Peridinium parvulum, which was transferred to Parvodinium as P. parvulum comb. nov. In this species, a type A eyespot was observed comprising four rows of lipid globules within a chloroplast. A molecular phylogeny was inferred based on concatenated data from SSU, ITS-5.8S and partial LSU rRNA gene sequences using maximum likelihood and Bayesian inference. Our results show that Johsia is nested within the Peridiniopsidaceae and is a sister clade to Peridiniopsis borgei and the strain UTEX1948 identified as ‘Scrippsiella’ hexapraecingula with three anterior intercalary plates.

Dynamics of Discrete Breathers in a Pt3Al Crystal

The discrete breathers in a Pt3Al crystal, which exhibit soft (DB1) and hard (DB2) nonlinearity, are shown to possess a number of principal differences. Unlike an immobile and stable DB1, a DB2 breather is mainly localized on four Al atoms and is stretched along one of the close-packed rows of crystals. On the other hand, DB2 can displace hundreds of nanometers along one of the directions of close packing. Having localized a considerable amount of energy, both DB1 and DB2 breathers slowly emit it during their lifetime. A collision of DB1 and DB2 results in part of their energy being released into the Al sublattice, the larger part lost by DB2 that is destroyed faster than DB1. The DB2 breather can effectively transport the energy throughout the crystal, and a collision of DBs results in its considerable localization in the crystal. A capability of transferring the energy can thus give rise to structural transformations far from the focus of excitation of such localized objects.

Revision and evaluation of the systematic affinity of the calcitarch genusPithonellabased on exquisitely preserved Turonian material from Tanzania

Extraordinarily well-preserved pithonellid microfossils (calcitarchs, “calcispheres”) from the Turonian (upper Cretaceous) of Tanzania reveal previously unknown morphological traits, crystallographic patterns, and chemical signatures, providing new insight to this enigmatic group of microfossils. Using combined transmitted-reflected light microscopy, scanning electron microscope imagery, electron microprobe elemental analysis and stable isotope geochemistry, the present study reveals four new aspects of the genusPithonella, notably, the following. An affinity with cyst-forming organisms, potentially the dinoflagellates, is indicated by the presence of a hatch opening and corresponding operculum. The pristine outer wall architecture consists of thin, smooth shingle-shaped plates with regular rows of slit-shaped pores and an apical sub-angular or circular pore. This primary surface pattern is significantly different from previous descriptions of an outer wall consisting of “parquet-shaped” prismatic crystal rows; this latter surface pattern is formed by secondary overgrowth. The crystallographic pattern of the inner wall is crypto-crystalline. Unaltered pithonellids reveal a calcite chemistry characterized by comparably high Mg-contents, relatively enriched stable carbon isotope values, and stable oxygen values indicating a surface water habitat. Based on these previously unseen traits, the diagnosis of the genusPithonellais emended. A new species,Pithonella diconica, is described from the lower-middle Turonian sediments of Tanzania.

Acoustic interference suppression of quartz crystal microbalance sensor arrays utilizing phononic crystals

Acoustic interference suppression of quartz crystal microbalance (QCM) sensor arrays utilizing phononic crystals is investigated in this paper. A square-lattice phononic crystal structure is designed to have a complete band gap covering the QCM's resonance frequency. The monolithic sensor array consisting of two QCMs separated by phononic crystals is fabricated by micromachining processes. As a result, 12 rows of phononic crystals with band gap boost insertion loss between the two QCMs by 20 dB and also reduce spurious modes. Accordingly, the phononic crystal is verified to be capable of suppressing the acoustic interference between adjacent QCMs in a sensor array.

Crystal-morphology and Evolution of Snow Cover: Empirical Modeling on the Base of Symmetry Theory

Snow cover is represented as a natural community of the shapes of growing crystals interacting with each other and exposed to environmental influences. It is worked out the empirical deterministic models describing the sublimation-metamorphic cycle of seasonal snow cover and the polymorphic variants of this cycle. The main driving force of processes yielding an evolutionary row of crystals are internal interactions within a snow pack. For all that the factor of time (the age of genetic player) plays a crucial role in sublimation metamorphism. Stadiality of the forms of crystal growth and self-development snow layers are revealed. They are a result of successive process of superposition of ice crystal-chemical symmetry and dissymmetry of the whole system soil–snow–atmosphere, according to the known P. Curie principle. Crystal-morphological classification for season snow is worked out by author on the base of the given an account evolutionary model. Two categories of crystal shapes have been picked out: classes and types of forms. The first category reflects the invariant aspect of snow sublimation metamorphism and the second one – the hydrothermal conditions of this process in each layer of the snow pack. Evolution of snow pack structure is conditioned to a marked degree by probabilistic conformity to natural laws, manifesting themselves in the processes of auto-regulation of metamorphism. These processes include the two types of regulation: the self-regulation of snow layers, on the one hand, and their regulation from outside – under the influence of atmospheric perturbations, on the other hand. An analysis of the processes of auto-regulation of metamorphism is capable of rendering a substantial service in the development of methods of short- and long-term forecasting of the avalanches. Crystal-morphological structure of snow cover may be considered also as a “quickly running” model of many evolutionary biosphere processes.

Compact interrogator for fiber optic Bragg sensors based on an acousto-optic filter formed by photonic crystal rows of air holes

Fiber optic sensors are typically used with expensive tunable lasers or optical spectrum analyzers for wavelength interrogation. We propose to replace the tunable laser by a broadband optical source incorporated with a novel thin linewidth acousto-optic tunable filter. It utilizes optical beam expanders constituted by photonic crystal rows of air holes in LiNbO(3) waveguide. A new design is numerically studied for a short structure (with 32 photonic crystal rows) by a two-dimensional finite-difference time-domain method. Extrapolation of these results to larger structure sizes (about 1 cm) demonstrates the possibility to develop compact interrogators with 0.4 pm wavelength resolution and 40 nm tunable range around 1550 nm.

Compact acousto-optic filter with beam expanders constituted by photonic crystal rows of airholes

A compact acousto-optic (AO) filter with multireflector (MR) beam expanders constituted by 32 photonic crystal rows of airholes in LiNbO(3) waveguide has been proposed and numerically studied by the two-dimensional finite-difference-time-domain method. The diameter and position of every row of holes are gradually varied along MR beam expanders in order to provide high efficiency and good sidelobe suppression. Device sizes are 70 μm × 150 μm, with an FWHM bandwidth of 4.4 nm, a tuning range of 110 nm, internal loss of -3 dB, and sidelobes of -20 dB, thus providing a unique value of 0.6 μm(2) for the product FWHM bandwidth by an AO length. It is intended for use in fiber optics telecommunications and sensing.

Volumetric image ultrasound transducer underfluid catheter system

An underfluid ultrasound imaging catheter system includes a catheter having a distal end inserted into an underfluid structure, an ultrasonic transducer array mounted proximate the distal end of the catheter wherein the array has a row of individual transducer crystals, a lens mounted on the array for defocusing ultrasound beams in a direction perpendicular to an axis of the array so as to provide a volumetric field of view within which the underfluid features are imaged. Alternatively, the single row of transducer crystals is replaced by multiple rows of transducer crystals so as to provide a volumetric field of view. This imaging catheter system helps an operator see 3-dimensional images of an underfluid environment, such as the 3-dimensional images of fluid-filled cavities of heart, blood vessel, urinary bladder, etc. Features in such wide volumetric field of view can be imaged, measured, or intervened by an underfluid therapeutic device with an aid of the real-time image.

Front-end electronics for PWO-based PHOS calorimeter of ALICE

The electromagnetic Photon Spectrometer (PHOS) of ALICE consists of five modules with 56×64 PWO crystals, operated at −25 °C. Glued to each crystal are APD diodes which amplify a lightyield of 4.4 photoelectrons/MeV, followed by charge-sensitive pre-amplifiers with a charge conversion gain of ca. 1 V/pC. We describe our new 32-channel shaper/digitizer and readout electronics for gain-programmable photodiodes. These Front-End Electronics (FEE) cards are installed below the crystals in an isolated warm volume in geometrical correspondence to 2×16 crystal rows per card. With a total detector capacitance of 100 pF and a noise level of 3 MeV, the FEEs cover a 14 bit dynamic range from 5 MeV to 80 GeV. The low noise level is achieved by operating the APDs and preamplifiers at low temperature and by applying a relatively long shaping time of 1 μs. The offline timing resolution, obtained via a Gamma-2 fit is less than 2 ns. The second-order, dual-gain shapers produce semi-Gaussian output for 10 bit ADCs with embedded multi-event buffers. A Readout Control Unit (RCU) masters data readout with address-mapped access to the event-buffers and controls registers via a custom bus which interconnects up to 14 FEE cards. Programmable bias voltage controllers on the FEE cards allow for very precise gain adjustment of each individual APD. Being co-designed with the TRU trigger cards, each FEE card generates eight fast signal sums (2×2 crystals) as input to the TRU. FPGA-based algorithms generate level-0 and level-1 trigger decisions at 40 MHz and allow PHOS also to operate in self-triggered mode. Inside each PHOS module there are 112 FEE and 8 TRU cards which dissipate ca. 1 kW heat which is extracted via a water cooling system.

Photonic Crystal Micro-Cavity Based Radiation Filter

In this paper, a band-stop radiation filter based upon a planar photonic crystal single-defect micro-cavity is studied. The micro-cavity is located within a photonic crystal region and fed by a ridge waveguide. Because the micro-cavity structure is bounded on one side by a limited number of crystal rows, there is strong radiation, at resonance, into the surrounding 2D slab (i.e., the region that is free from the photonic crystal). The antenna radiation pattern of this micro-cavity can be substantially directional and is strongly dependent upon the cavity resonant wavelength, giving the possibility for this device to act as a directional radiation filter.The theoretical analysis of this device is performed by using 2D Finite-Difference Time-Domain (FDTD) methods, while the device is fabricated in an InP epi-layered structure. Initial characterization results are also presented for this single-defect radiation filter.

Growth dynamics of isotactic polypropylene single crystals during isothermal crystallization from a miscible polymeric solvent.

The present article presents a spatiotemporal growth of isotactic polypropylene (iPP) single crystals, melt crystallized from a polymeric solvent, i.e., poly (ethylene octene) copolymer that is known to be miscible with iPP. Optical and atomic force microscopic investigations reveal that the melt grown single crystals of iPP develop in the form of two parallel rows of crystal lamellae, but these crystals merge at the tips. To elucidate the mechanism of these emerging parallel rows of iPP crystals, a phase field model pertaining to solidification phenomena has been employed that involves a nonconserved crystal order parameter and a chain-tilting angle. This phase field model is based on the free energy of crystallization, having an asymmetric double well, and a tensorial surface free energy of the crystal interface coupled with a curvature elastic free energy that is possessed by the solid-liquid interface. The spatiotemporal simulation of iPP single crystal growth has been carried out on a square lattice based on the finite difference method for spatial steps and an explicit method for temporal steps with a periodic boundary condition. The appearance of the seemingly twin crystal is captured in the simulation, which may be attributed to the sector demarcation that is taking place in the anisotropically growing single crystal of iPP.

Processing–structure–properties relationship of multilayer films. 1. Structure characterization

Low density polyethylene (LDPE)/poly(ethylene terephthalate) (PET) multilayer films with and without a reactive tie layer were prepared by blowing process. The layers contents were fixed and the parameters evaluated were blow-up ratio (BUR), draw-down ratio (DDR) and frost-line height (FL). Their effect on the structure was studied. No crystallinity for the PET layer was induced by the blowing process. The orientation of the multilayer films was characterized by birefringence and infrared spectroscopy (FTIR). The measured birefringence showed a negligible orientation for PET layer, and the LDPE layer oriented mainly along the machine direction. FTIR characterization also showed a negligible orientation for PET layer, and for LDPE layer, the crystalline a-axis tended toward machine direction, crystalline b-axis located in transverse–normal plane with no orientation for the amorphous phase. The lamellar arrangement of LDPE layer with respect to machine direction was obtained by dissolving the amorphous phase in solution of potassium permanganate in a mixture of equal volumes of orthophosphoric and sulfuric acid. The crystallization of oriented LDPE melts produced a morphology consisting of rows of lamellar crystals aligned parallel to the machine direction at higher draw-down ratio. It was not always of the row-nucleated type, the exact morphology patterns greatly depended on the distribution of the crystalline a-axis and b-axis orientation, which in turn was dependent on DDR, BUR and frost-line height.

Optical characterisation of 2D macroporous silicon photonic crystals with bandgaps around 3.5 and 1.3 μm

Transmission measurements were performed on thin 2D silicon photonic crystals (PCs) with 1–4 crystal rows in order to investigate the effect of a finite structure and to obtain an estimate of the crystal thickness necessary to minimize crosstalk between adjacent waveguides. For wavelengths deep within the H-bandgap a strong exponential decay revealing an attenuation constant of 10 dB per crystal row was measured. For opto-electronic applications, the lattice constant of macroporous Si was successfully downscaled from a pitch of 1.5 to 0.5 μm. Reflection measurements performed at these structures show good agreement with corresponding bandstructure calculations exhibiting a complete bandgap around λ=1.3μm.

Coupled guide and cavity in a two-dimensional photonic crystal

We demonstrate, in a planar two-dimensional (2D) configuration, in the optical regime a clear association of two photonic crystal elements and the ability to produce a low-loss coupled system. A channel waveguide is brought to between two and five crystal rows (450 to 1126 nm) from a 2D microcavity fabricated in a GaAs/AlGaAs waveguide. We probe these two elements individually and explore their interaction.

Atom Acceleration Caused by Screw Dislocation Slip in Crystals

The possibility of two-well potential build-up along crystal rows in the vicinity of a screw dislocation core under external mechanical stress is considered. It is shown that under such conditions the slip of dislocations can be accompanied by atom acceleration. The numerical modeling of atom collisions and atom acceleration at a dislocation slip is carried out. Russian text ignored.

Particle dynamics during electronic sputtering of solid krypton

We have modeled electronic sputtering of solid krypton by excimer production with molecular dynamics. Both excimer evolution in the solid and deexcitation processes have been incorporated in the simulation. The excimer dynamics in the lattice has been analyzed: the excimers formed near the surface shift upwards whereas those formed in the bulk contribute to long-range collision sequences directed along crystal rows. Singlet and triplet excitations showed considerable differences in their behavior. The defects introduced in the target strongly influenced the development of the phenomena. Good agreement of simulation results with experimental data has been achieved.

Interferences in resonant excitation of hydrogenic channeled ions.

We have observed selection rules for the resonant excitation of swift hydrogenlike ions (Z=6,7) axially channeled in the 〈111〉 direction of a diamond lattice (silicon). The resonant excitation arises from a coherent periodic perturbation by the atoms in the bounding crystal rows. We show that the selection rules are the consequence of destructive and constructive interference in the quantum mechanical transition amplitude for excitation.

Electrical activation of bismuth implanted into silicon by rapid thermal annealing and kinetics of defects

The rapid thermal annealing (RTA) of Si implanted with Bi+, to a dose of 5.0×1014 cm−2 at the energy of 150 keV, was investigated using sheet resistivity, Hall measurements, and channeling analysis. Approximately 95% of the Bi dose is found substitutional and 90% is electrically active after annealing is performed at 600 °C for times longer than 1 min. The electrical activation yield of Bi after RTA at temperatures ≥700 °C is observed to decrease when increasing the temperature and time of the annealing process. The data taken from electrical measurements and angular scan across the 〈100〉 axis are evidence that the electrically inactive concentration of the Bi correlates with the concentration of Bi atoms located slightly displaced from the crystal rows.

Voltage-dependent scanning tunneling microscopy images of liquid crystals on graphite

Voltage-dependent images of liquid crystals on graphite were observed in air by scanning tunneling microscopy (STM). Molecular rows of liquid crystals and the atomic pattern of the graphite substrate were imaged with high (above 1 V) and low (below 0.1 V) bias voltages, respectively. Patterns of molecules, grain boundaries, and distinguishable defects of the liquid crystal arrangement were reproduced even after imaging the substrate in the same area. This indicates that the graphite lattice can be seen by STM without touching or disturbing the adsorbed molecules on it. A resonant tunneling model is proposed to explain the phenomenon.

The Electronic Structure of Copper Oxide Crystalline Compounds. II. Chemical Bonding in Copper–Oxygen Crystals

AbstractThe crystalline structure of copper‐oxygen compounds with copper atom in the oxidation states I, II, and III is reviewed. A calculation is made of the electronic structure of the row of crystals with copper‐oxygen bonding. It is shown that the covalence effects are essential for copper oxide compounds containing copper atoms in oxydation states CuII and CuIII LUC‐CNDO calculations of La2CuO4 and YBa2Cu3Ox (x = 6,7) crystals are made. It is concluded that the higher copper valency is favourable for superconductivity.