Extracellular carbohydrate polymers from five desert soil algae with different cohesion in the stabilization of fine sand grain

Extracellular polymeric substances (EPS) from four filamentous cyanobacteria Microcoleus vaginatus, Scytonema javanicum, Phormidium tenue and Nostoc sp. and a coccoid single-cell green alga Desmococcus olivaceus that had been separated from desert algal crusts of Tegger desert of China, were investigated for their chemical composition, structure,and physical properties. The EPS contained 7.5-50.3% protein (in polymers ranging from 14 to more than 200 kD, SDS-PAGE) and 16.2-46.5% carbohydrate (110-460 kD, GFC). 6-12 kinds of monosaccharides, including 2-O-methyl rhamnose, 2-O-methyl glucose, and N-acetyl glucosamine were found. The main carbohydrate chains from M. vaginatus and S. javanicum consisted mainly of equal proportion of Man, Gal and Glc, that from P. tenue consisted mainly of arabinose, glucose and rhamnose. Arabinose was present in pyranose form, mainly alpha-L 1 --> 3 linked, with branches on C4 of almost half of the units. Glucose was responsible for the terminal units, in addition of having some units as beta1 --> 3 and some as beta1 --> 4 linked. Rhamnose was mainly 1 --> 3 linked with branches on C2 on half of the units. The carbohydrate polymer from D. olivaceus was composed mainly of beta1 --> 4 linked xylose, galactose and glucose. The galactose part was present both in beta-pyranose and -furanose forms. Arabinose in alpha-L-furanose form was mainly present as 1 --> 2 and 1 --> 2, 5 linked units, rhamnose only as alpha 1 --> 3 and xylose as beta 1 --> 4. The backbone of the polysaccharide from Nostoc sp. was composed of beta-1 --> 4 linked xylose, galactose and glucose. Most of the glucose was branched on position C6, terminal glucose and 2-O-methyl glucose units are also present. The relationship between structure, physical properties and potential biological function is discussed. (C) 2003 Elsevier Ltd. All rights reserved.

Moisture content in Dall's porpoise (Phocoenoides dalli) tissues: a reference base for conversion factors between dry and wet weight trace element concentrations in cetaceans

Concentration of trace elements measured by dry weight basis has become more commonly used in recent studies on cetaceans than wet weight basis, which was used more in earlier studies. Because few authors present moisture content data in their papers, it is difficult to compare the concentrations of trace elements between various studies. Therefore, we felt that it would be useful if a reference conversion factor (CF) for tissue types could be found to convert between wet weight and dry weight data on trace element concentrations. We determined the moisture contents of 14 tissues of Dall's porpoise (Phocoenoides dalli), and then, calculated the CF values for those tissues. Because the moisture content of each tissue differs from other tissues, it is necessary to use a specific CIF for each tissue rather than a general CF for several tissues. We have also found that CIF values for Dall's porpoise tissues are similar to the same tissues in other cetaceans. Therefore CF values from Dall's porpoise can be reliably used to convert between wet and dry weight concentrations for other cetacean tissues as reference data. (C) 2002 Elsevier Science Ltd. All rights reserved.

Effect of desert soil algae on the stabilization of fine sands

Four filamentous cyanobacteria, Microcoleus vaginatus, Phormidium tenue, Scytonema javanicum (Kutz.) and Nostoc sp., and a single-celled green alga, Desmococcus olivaceus, all isolated from Shapotou (Ningxia Hui Autonomous Region of China), were batch cultured and inoculated onto unconsolidated sand in greenhouse and field experiments. Their ability to reduce wind erosion in sands was quantified by using a wind tunnel laboratory. The major factors related to cohesion of algal crusts, such as biomass, species, species combinations, bioactivity, niche, growth phase of algae, moisture, thickness of the crusts, dust accretion (including dust content and manner of dust added) and other cryptogams (lichens, fungi and mosses) were studied. The best of the five species were M. vaginatus and P. tenue, while the best mix was a blend of 80% M. vaginatus and 5% each of P. tenue, S. javanicum, Nostoc sp. and D. olivaceus. The threshold friction velocity was significantly increased by the presence of all of the cyanobacterial species, while the threshold impact velocity was notably increased only by the filamentous species. Thick crusts were less easily eroded than thin crusts, while biomass was more effective than thickness. Dust was incorporated best into Microcoleus crust when added in small amounts over time, and appeared to increase growth of the cyanobacterium as well as strengthen the cohesion of the crust. Microbial crust cohesion was mainly attributed to algal aggregation, while lichens, fungi and mosses affected more the soil structure and physico-chemical properties.

Finite element beam propagation method for analysis of plasmonic waveguide

The basic idea of the finite element beam propagation method (FE-BPM) is described. It is applied to calculate the fundamental mode of a channel plasmonic polariton (CPP) waveguide to confirm its validity. Both the field distribution and the effective index of the, fundamental mode are given by the method. The convergence speed shows the advantage and stability of this method. Then a plasmonic waveguide with a dielectric strip deposited on a metal substrate is investigated, and the group velocity is negative for the fundamental mode of this kind of waveguide. The numerical result shows that the power flow direction is reverse to that of phase velocity.

Passive stabilization of a passively mode-locked Nd : GdVO4 laser by inverse saturable absorption

A diode-pumped Nd:GdVO4 laser mode-locked by a semiconductor saturable absorber and output coupler (SESAOC) is passively stabilized to suppress Q-switched mode-locking. A phase mismatched 131130 second-harmonic generation (SHG) crystal is used for passive stabilization. The continuous wave mode-locking (CWML) threshold is reduced and the pulse width is compressed. The pulse width is 6.5 ps as measured at the repetition rate of 128 MHz. (c) 2007 Elsevier B.V. All rights reserved.

Finite element analysis of stress and strain distributions in InAs/GaAs quantum dots

In this paper, we perform systematic calculations of the stress and strain distributions in InAs/GaAs truncated pyramidal quantum dots (QDs) with different wetting layer (WL) thickness, using the finite element method (FEM). The stresses and strains are concentrated at the boundaries of the WL and QDs, are reduced gradually from the boundaries to the interior, and tend to a uniform state for the positions away from the boundaries. The maximal strain energy density occurs at the vicinity of the interface between the WL and the substrate. The stresses, strains and released strain energy are reduced gradually with increasing WL thickness. The above results show that a critical WL thickness may exist, and the stress and strain distributions can make the growth of QDs a growth of strained three-dimensional island when the WL thickness is above the critical value, and FEM can be applied to investigate such nanosystems, QDs, and the relevant results are supported by the experiments.

Monostable-Bistable Transition Logic Element (MOBILE) Model for Single-Electron Transistors

The traditional monostable-bistable transition logic element (MOBILE) structure is usually composed of resonant tunneling diodes (RTD). This letter describes a new type MOBILE structure consisting of single-electron transistors (i.e. SET-MOBILE). The analytical model of single-electron transistors ( SET) has been considered three states (including an excited state) of the discrete quantum energy levels. The simulation results show negative differential conductance (NDC) characteristics in I-DS-V-DS curve. The SET-MOBILE utilizing NDC characteristics can successfully realize the basic logic functions as the RTD-MOBILE.

An ambient proof and wide tuning range LC VCO with automatic amplitude control for tuner applications

This paper represents a LC VCO with AAC (Auto Amplitude Control), in which PMOS FETs are used as active components, and the varactors are directly connected to ground to widen Kvco linear range. The AAC circuitry adds little noise to the VCO and provides it with robust performance over a wide temperature and carrier frequency range. The VCO is fabricated in 50-GHz 0.35-mu m SiGe BiCMOS process. The measurement results show that it has -127.27-dBc/Hz phase noise at 1-MHz offset and a linear gain of 32.4-MHz/V between 990-MHz and 1.14-GHz. The whole circuit draws 6.6-mA current from 5.0-V supply.

Interaction of linear waves with infinitely long horizontal cylinders studied by boundary element method

The two-dimensional problems concerning the interaction of linear water waves with cylinders of arbitrary shape in two-layer deep water are investigated by use of the Boundary Integral Equation method (BIEM). Simpler new expressions for the Green functions are derived, and verified by comparison of results obtained by BIEM with these by an analytical method. Examined are the radiation and scattering of linear waves by two typical configurations of cylinders in two-layer deep water. Hydrodynamic behaviors including hydrodynamic coefficients, wave forces, reflection and transmission coefficients and energies are analyzed in detail, and some interesting physical phenomena are observed.

Response amplitude and hydrodynamic force for a buoy over a convex

A buoy as an offshore structure is often placed over a convex such as a caisson or a submerged island. The hydrodynamic fluid/solid interaction becomes more complex due to the convex compared with that on the flat. Both the buoy and the convex are idealized as vertical cylinders. Linear potential theory is used to investigate the response amplitude and the hydrodynamic force for a buoy over a convex due to diffraction and radiation in water of finite depth. These are derived from the total velocity potential. A set of theoretical added mass, damping coefficient, and exciting force expressions have been proposed. Analytical results of the response amplitude and hydrodynamic force are given. Finally, the numerical results show that the effect of the convex on the response amplitude and hydrodynamic force for the buoy is ignored if the size of the convex is relatively smaller.

Phase and amplitude reconstruction from a single carrier-frequency interferogram without phase unwrapping

A rapid algorithm for phase and amplitude reconstruction from a single spatial-carrier interferogram is proposed by bringing a phase-shifting mechanism into reconstruction of a carrier-frequency interferogram. The algorithm reconstructs phase through directly obtaining and integrating its real-value derivatives, avoiding a phase unwrapping process. The proposed method is rapid and easy to implement and is made insensitive to the profile of the interferogram boundaries by choosing a suitable integrating path. Moreover, the algorithm can also be used to reconstruct the amplitude of the object wave expediently without retrieving the phase profile in advance. The feasibility of this algorithm is demonstrated by both numerical simulation and experiment. (c) 2008 Optical Society of America.