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It has been demonstrated that persistent organic pollutants (POPs) can affect the immune system of mammals and birds. In this study, the concentration of different POPs and leukocytes in blood samples from three chinstrap penguin (Pygoscelis antarctica) populations was analysed in order to assess the impact on haematological parameters. Using blood sample smears, basophils, eosinophils, heterophils, lymphocytes and monocytes were quantified. Mature and immature red blood cells were counted and cell alterations in both white and red blood cells were analysed. At the same time, whole blood was analysed for POPs. The results showed that contaminants, such as dichlorodiphenyltrichloroethane and its metabolites (ΣDDT), as well as polychlorinated biphenyls (ΣPCB), had significant correlations to eosinophils, lymphocytes and heterophils. This indicates possible immunohaematological alterations derived from exposure to such contaminants. Cytological alterations were also observed, such as cytotoxic granules, toxic heterophils, and atypical and granulated lymphocytes, which would demonstrate that these seabirds are being exposed to stress agents that could be producing some alterations at a leukocytary cellular level.
An overview of recently obtained authors’ results on traveling wave solutions of some
classes of PDEs is presented. The main aim is to describe all possible travelling wave
solutions of the equations. The analysis was conducted using the methods of qualitative
and bifurcation analysis in order to study the phase-parameter space of the corresponding
wave systems of ODEs. In the first part we analyze the wave dynamic modes of populations
described by the “growth - taxis - diffusion" polynomial models. It is shown that
“suitable" nonlinear taxis can affect the wave front sets and generate non-monotone waves,
such as trains and pulses, which represent the exact solutions of the model system.
Parametric critical points whose neighborhood displays the full spectrum of possible model
wave regimes are identified; the wave mode systematization is given in the form of
bifurcation diagrams. In the second part we study a modified version of the
FitzHugh-Nagumo equations, which model the spatial propagation of neuron firing. We assume
that this propagation is (at least, partially) caused by the cross-diffusion connection
between the potential and recovery variables. We show that the cross-diffusion version of
the model, besides giving rise to the typical fast travelling wave solution exhibited in
the original “diffusion" FitzHugh-Nagumo equations, additionally gives rise to a slow
traveling wave solution. We analyze all possible traveling wave solutions of the model and
show that there exists a threshold of the cross-diffusion coefficient (for a given speed
of propagation), which bounds the area where “normal" impulse propagation is possible. In
the third part we describe all possible wave solutions for a class of PDEs with
cross-diffusion, which fall in a general class of the classical Keller-Segel models
describing chemotaxis. Conditions for existence of front-impulse, impulse-front, and
front-front traveling wave solutions are formulated. In particular, we show that a
non-isolated singular point in the ODE wave system implies existence of free-boundary
Traveling waves for the nonlocal Fisher Equation can exhibit much more complex behaviour
than for the usual Fisher equation. A striking numerical observation is that a traveling
wave with minimal speed can connect a dynamically unstable steady state 0 to a Turing
unstable steady state 1, see . This is proved
in [1, 6] in
the case where the speed is far from minimal, where we expect the wave to be monotone.
Here we introduce a simplified nonlocal Fisher equation for which we can build simple
analytical traveling wave solutions that exhibit various behaviours. These traveling
waves, with minimal speed or not, can (i) connect monotonically 0 and 1, (ii) connect
these two states non-monotonically, and (iii) connect 0 to a wavetrain around 1. The
latter exist in a regime where time dynamics converges to another object observed in
[3, 8]: a
wave that connects 0 to a pulsating wave around 1.
Transport number measurements and impedance spectroscopy in controlled temperature and atmosphere were used to investigate the electrical properties of La2Mo2O9 sintered samples. These samples were prepared from nanocrystalline La2Mo2O9 powders as obtained from a new soft chemistry route involving the polymerisation of acrylamide. By means of the electromotive force method measurements, the sintered compound was found mainly oxygen conductor in the range of 400 °C-800 °C with oxide-ion transport number greater than 0.99. The effect of the oxygen partial pressure on the electrical conductivity of La2Mo2O9 was investigated by impedance spectroscopy from 1 to 10−22 atm, showing a highly stable conduction properties up to 10−17 atm at 800 °C.
Polymer/TiO2 composite solar cells (CSCs) are currently being investigated by academic research groups and industrial companies due to the prospect of achieving good power conversion efficiencies and lifetime stability at a low production cost. We present data of the initial period of operation (up to several hours) of such devices, which show that during this period the CSCs operate in a non-steady state regime. The transient behaviour is accounted for using an equivalent circuit model (ECM) of the photovoltaic device with time-dependent resistors.
Golden time of thrombolysis therapy in acute ischemic stroke is only three hours. Emergency medical services transport and hospital prenotification were not been strengthened in Taiwan.
In order to elevate the medical quality of acute ischemic stroke, we developed a Quality Control Circle (QCC) focused on a comprehensive thrombolysis service for patients with acute ischemic stroke administered pre-hospital and in an emergency department.
QCC activities contained early recognition of acute stroke by EMT, hospital prenotification, early emergency management, activate the stroke team, shorten the time to CT scan and report, and early thromobolytic therapy. There were three policy groups via quality method analysis which these methods aimed to improve the efficiency and quality of management process focused on acute ischemic stroke.
Group 1: After the implementation of QCC, the number of times of pre-hospital notification was six in Mar. 2010, achieve the expected standard. Group 2: Responses were received from 160 people for the pretest and 145 people for the posttest. In the pretest and posttest analysis, significant improvement in the attitudes of the physician group (p < 0.001) and general behavior (p < 0.001) were disclosed. The case-based educational module of acute stroke was better than the traditional oral lecture especially in the nursing group (p < 0.001). Group 3: The rate of administering thrombolytic therapy/total ischemic stroke increased from 3.1% to 10.5 % (from Mar to Apr, 2010) after running the organized service. These activities reached the goal of expected standard (5%). All above groups were set up into standardization. The thrombolytic rate in effect maintainence was still around 5% eight months later.
Setting up and running a organized thrombolysis service for patients with acute ischemic stroke prehospital and in the emergency department can be a good method to increase the rate of administration of thrombolytic therapy.
Self-assembled hexagonal networks with discrete Au particles on Al2O3 (00.1) and Si (111) have been synthesized. SiOx nanowires were grown on individual Au particles using a vapor transport deposition process. The growth of SiOx nanowires was found to cover completely the surface of Au particles on Al2O3 (00.1). On the other hand, the SiOx nanowires were grown selectively on Au particles on Si (111). Interaction of Au and Si substrate is invoked to explain the difference.
In the present work, the screen printing technique has been used to deposit thick films of Zr0.84Y016O1.92 (8YSZ). In order to control the final porosity in view of a specific application (SOFCs or gas sensor), an experimental design based on analysis of variances (ANOVA) has been carried out. From this, we were able to determine the influence of several technological parameters on films porosity and grain size. The films obtained have been analysed with both Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) combined with SEM. We show that only the combination of experimental design and advanced observation technique such as Focused Ion Beam allowed us to extract significant information for the improvement of the deposition process.
Ion beam synthesis of a buried SiO2 layer is an attractive silicon-on-insulator technology for high speed CMOS circuits and radiation hardened devices. We demonstrate here a new annealing procedure at 1405°C that produces silicon films of excellent quality, essentially free of oxygen precipitates and with sharp interfaces between the Si and the SiO2.
Excimer laser annealing at 248 nm has resulted in the recrystallization of a-GaAs on (100) silicon. An AlAs encapsulation layer was found to be necessary to prevent the loss of arsenic during laser annealing. An energy density of 105 mJ/cm2 was the critical energy density which gave optimum results. Field effect transistors were fabricated on the regrown (100) GaAs utilizing ion implantation for the n-type channel, and resulted in a transconductance of 70–80 mS/mm.
A formidable obstacle to develop the optimal conditions for growing dislocation—free crystals has been the lack of a direct technique to monitor the perfection of the solid/liquid (S/L) interface during growth. Recently we have developed a technique which detects, in—situ, the emergence of dislocation(s) at the crystallization front. This novel technique is based on the thermoelectric principles, and utilizesthe dependence of the Seebeck emf generated across the S/L interface upon the interface temperature, crystal orientation, and dopant concentration. The technique was used to directly measure the S/L interface temperature during growth of Ga and In—doped Ga. For the latter, the technique also shows the breakdown (instability) of the faceted interface, which leads to the entrapment of the In—rich bands. The applicability of the technique to monitor defect formation during crystal growth processes such as thin film zone, Czochralski, or liquid phase epitaxy will be discussed.
The formation of a silicon-on-insulator (SOI) structure by implanting a high dose of N+ ions to form a buried Si3N4 layer is studied by transmission electron microscopy (TEM) and by secondary ion mass spectroscopy (SIMS). The SOI structure is formed by implanting silicon wafers with 7.5x1017 N+ ions/cm2 at 160 keV and at wafer temperatures of 400, 500, or 600°C. The implanted wafers are subsequently annealed at 1200°C for times ranging from 10 minutes to 2 hours. The microstructures and nitrogen distributions of the asimplanted and post-annealed wafers are examined in order to elucidate the development of the final microstructure.
It has been previously reported that intense illumination on a-Si:H induces luminescence fatigue. The effect of light soaking on the photoconductivity of this material is also known. In this work, studies of photoluminescence (PL) at 10°K shows that the intensity of the main peak at 1.3eV can be correlated with the decrease in the photoconductivity (PC) of the sample. Similar to the PC, the effects of light soaking on the PL spectrum are reversible; annealing at 200°C fully restore the PL spectrum. Our results indicate that the light-induced radiative defects are also involved in the carrier recombination mechanism. By measuring the PL spectrum at temperatures in the range from 10 to 120°K, the activation energy for the non-radiative process has been determined in both light-soaked and heat-dried states.
A process sequence for polycrystalline silicon NMOS logic circuitry is presented here. The fabrication sequence eliminates ion implantation steps and requires a maximum process temperature of 900°C. Low process temperature and diffusion doping may allow use of high temperature glass as substrates. Diffusion doping of large substrates eliminates expensive modification of an ion implanter. Initial Work utilized ion implantation to dope device channels before oxidation. Phosphorus channel doping is effective in the control of device threshold, based on the observation that both enhancement and depletion mode device behavior can be obtained. Boron doping is not effective because segregation of the boron into SiO2 occurs during subsequent oxidation. The results obtained from ion implantation doping show that functioning NMOS gates can be fabricated. In fact, it was discovered that undoped polycrystalline silicon channels provide suitable enhancement mode devices, while lightly phosphorus doped channels yield depletion mode devices. A process sequence based solely on phosphorus diffusion is then demonstrated.
To prepare silicon-on-insulator (SOI) films by graphite-strip-heater zone-melting recrystallization (ZMR), a capping technique must be used to insure wetting by the molten Si zone. We have demonstrated two new capping techniques that result in reproducible wetting without degrading the crystallographic texture of the recrystallized film: annealing SiO2- capped Si films in NH3 and depositing two SiNx layers with carefully controlled compositions on the SiO2 capping layer. Wetting is promoted by the incorporation of trace amounts of nitrogen at the Si-SiO2 interface. Both N implantation experiments and Auger spectroscopy studies establish that the presence of less than a monolayer of nitrogen at this interface is sufficient to insure wetting.
We studied the selective epitaxial deposition of silicon in patterned oxide-free regions over silicon dioxide in a RF-heated, commercial, reduced-pressure epitaxial reactor, using SiH2Cl2/HCl/H2 gas system. We found that etching into silicon occurs at the high end of HCl content, and nucleation on the silicon dioxide at the low end of HCl content. The selective epitaxial growth of silicon islands is obtained in between.
The formation of silicon-on-insulator structures, by recrystallising polycrystalline silicon films with a dual electron beam technique, has been studied over a wide range of conditions. The quality of the layers has been assessed by examining cross-sections in the SEM and optical microscopy of the surface after a Secco etch. The range of line powers which gives device-worthy single crystal material becomes greater as the sweep speed increases and as the background temperature is reduced. The extent of melting into the substrate in the seed windows and below the isolating oxide was determined from the movement of an arsenic implant. The experimental results are compared to the predictions from a one dimensional model for the heat flow.
Latchup free CMOS devices have been fabricated by forming PMOS transistors in a 0.5μm thick laser recrystallized silicon layer. This recrystallized layer is isolated fram the bulk wafer by a lμm thick oxide layer. The NMOS transistors were fabricated both in the bulk wafer in the region which was used as the recrystallization seeds, as well as in the recrystallized silicon layer itself. Ring oscillators fabricated with 3μm channel length using a bi-layer lateral CMOS structure show a naninal delay of 1.7ns/stage. The MOS devices fabricated in the recrystallized silicon show low subthreshold leakage current, and surface electron and hole mobilities of 580cm2/V.s and 210cm2/V.s respectively.