Frequency limitation of GaAs transferred-electron devices: influence of operating d.c. and r.f. field values

The possibility of making use of the transferred-electron effect for power generation in the whole millimetre-wave range is shown for long and uniform-field GaAs samples. A great improvement in the upper frequency limit under large-signal operation is reported.     

Noise of hot carriers in the channel of n silicon junction gate field effect transistors

At 77 K the noise current spectral density of n type silicon channel junction gate field effect transistors is about 70 times higher than predicted by the theory. This discrepancy is explained by the authors taking into account the noise temperature of hot electrons which is measured for n Si at 77 K vs the electric field. The theory of noise in FETs is subsequently modified and gives results in reasonable agreement with the experiment. This theory can be applied to every one dimensional device.     

Modelling of ionospheric high-order errors for new generation GNSS

In dual frequency Global Positioning System receivers, the ionospheric propagation delays are commonly estimated and corrected using the “ionosphere free” combinations of pseudo-range observables. With this method, the ionospheric delay is estimated at the first-order proportional to the inverse of the frequency square. However, higher-order terms exist that may be taken into account when precise corrections are required. The second-order term results from the influence of the geomagnetic field on the ionospheric propagation of the signals. The third-order term includes the refractive effects due to the bending of the ray. Contributions of the second- and third-order terms typically amount to values in the centimetre and millimetre ranges, respectively. In a near future, triple-frequency Global Navigation Satellite Systems transmitting high-resolution codes will become available. These systems are expected to provide a noticeable improvement in accuracy. This paper focuses on the Galileo signals as Galileo In-Orbit Validation Element (GIOVE) signals are now available for acquisition. A solution relying on the triple-frequency characteristics of a signal-in-space is investigated with results based on first measurements of GIOVE-A signals. Eventually, a method is described that relies on precise dual-frequency phase measurements to evaluate the second-order ionospheric contribution for Galileo data.     

99Tc- and 239Pu-Doped Glass Leaching Experiments: Residual Alteration Rate and Radionuclide Behavior

The long-term behavior of high-level nuclear glass subjected to alpha/beta radiation by long-life radionuclides must be investigated with respect to geological disposal. This study focuses on the effects of alpha and beta radiations on the chemical reactivity of R7T7 glass with pure water, mainly on the residual alteration rate regime. Glass specimens doped with 0.85 wt% ²³⁹PuO₂ (α emitter) and 0.24 wt% ⁹⁹TcO₂ (β emitter) that simulate alpha and beta dose rate corresponding to long-term disposal conditions are leached under static conditions in argon atmosphere at 90°C, in initially pure water and at a high surface-area-to-volume ratio (S/V = 20/cm). The alteration rate is monitored by the release of glass alteration tracer elements (B, Na, and Li). Radiation effects on the leached glass and its gel network are characterized by SEM and TEM analyses. Plutonium and technetium releases are also measured by radiometry, and their chemical oxidation state is assessed by measuring the pH and reduction–oxidation potential of the leachates. The results do not highlight any significant effect of alpha/beta radiation on the residual alteration of these doped glasses. These observations are consistent with solid characterizations, which show that a protective layer can be formed under such irradiation fields. Under our experimental conditions (Eh~380 mV/SHE, pH_90°C = 8–8.6), very low concentrations of soluble plutonium are measured in the leachate, indicating strong plutonium retention, whereas technetium performs as a soluble element and is not retained in the altered layer.     

Group II innate lymphoid cells and microvascular dysfunction from pulmonary titanium dioxide nanoparticle exposure

Background

The cardiovascular effects of pulmonary exposure to engineered nanomaterials (ENM) are poorly understood, and the reproductive consequences are even less understood. Inflammation remains the most frequently explored mechanism of ENM toxicity. However, the key mediators and steps between lung exposure and uterine health remain to be fully defined. The purpose of this study was to determine the uterine inflammatory and vascular effects of pulmonary exposure to titanium dioxide nanoparticles (nano-TiO₂). We hypothesized that pulmonary nano-TiO₂ exposure initiates a Th2 inflammatory response mediated by Group II innate lymphoid cells (ILC2), which may be associated with an impairment in uterine microvascular reactivity.

Methods

Female, virgin, Sprague-Dawley rats (8–12 weeks) were exposed to 100 μg of nano-TiO₂ via intratracheal instillation 24 h prior to microvascular assessments. Serial blood samples were obtained at 0, 1, 2 and 4 h post-exposure for multiplex cytokine analysis. ILC2 numbers in the lungs were determined. ILC2s were isolated and phosphorylated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-?B) levels were measured. Pressure myography was used to assess vascular reactivity of isolated radial arterioles.

Results

Pulmonary nano-TiO₂ exposure was associated with an increase in IL-1ß, 4, 5 and 13 and TNF- α 4 h post-exposure, indicative of an innate Th2 inflammatory response. ILC2 numbers were significantly increased in lungs from exposed animals (1.66?±?0.19%) compared to controls (0.19?±?0.22%). Phosphorylation of the transactivation domain (Ser-468) of NF-κB in isolated ILC2 and IL-33 in lung epithelial cells were significantly increased (126.8?±?4.3% and 137?±?11% of controls respectively) by nano-TiO₂ exposure. Lastly, radial endothelium-dependent arteriolar reactivity was significantly impaired (27?±?12%), while endothelium-independent dilation (7?±?14%) and α-adrenergic sensitivity (8?±?2%) were not altered compared to control levels. Treatment with an anti- IL-33 antibody (1 mg/kg) 30 min prior to nano-TiO₂ exposure resulted in a significant improvement in endothelium-dependent dilation and a decreased level of IL-33 in both plasma and bronchoalveolar lavage fluid.

Conclusions

These results provide evidence that the uterine microvascular dysfunction that follows pulmonary ENM exposure may be initiated via activation of lung-resident ILC2 and subsequent systemic Th2-dependent inflammation.

     

Quorum Sensing and Quorum Quenching in the Phycosphere of Phytoplankton: a Case of Chemical Interactions in Ecology

The interactions between bacteria and phytoplankton regulate many important biogeochemical reactions in the marine environment, including those in the global carbon, nitrogen, and sulfur cycles. At the microscopic level, it is now well established that important consortia of bacteria colonize the phycosphere, the immediate environment of phytoplankton cells. In this microscale environment, abundant bacterial cells are organized in a structured biofilm, and exchange information through the diffusion of small molecules called semiochemicals. Among these processes, quorum sensing plays a particular role as, when a sufficient abundance of cells is reached, it allows bacteria to coordinate their gene expression and physiology at the population level. In contrast, quorum quenching mechanisms are employed by many different types of microorganisms that limit the coordination of antagonistic bacteria. This review synthesizes quorum sensing and quorum quenching mechanisms evidenced to date in the phycosphere, emphasizing the implications that these signaling systems have for the regulation of bacterial communities and their activities. The diversity of chemical compounds involved in these processes is examined. We further review the bacterial functions regulated in the phycosphere by quorum sensing, which include biofilm formation, nutrient acquisition, and emission of algaecides. We also discuss quorum quenching compounds as antagonists of quorum sensing, their function in the phycosphere, and their potential biotechnological applications. Overall, the current state of the art demonstrates that quorum sensing and quorum quenching regulate a balance between a symbiotic and a parasitic way of life between bacteria and their phytoplankton host.     

Starch Properties in Different Lines of an old Hungarian Wheat Variety,Bánkúti 1201

The old Hungarian wheat variety, Bánkúti 1201 was previously divided into lines on the basis of high molecular weight (HMW) glutenin subunit composition. In this work the starch properties of these lines were studied. The amylose contents of the lines ranged from 14.4% to 24.2%, which means a wide variation. The Rapid Visco Analyser (RVA) peak viscosity of the starch ranged from 232 to 372 Rapid Visco Units (RVU) and the enthalpy of gelatinisation (ΔH) measured by Differential Scanning Calorimetry (DSC) varied between 8.3 and 16.3 J/g. To study the relationship between the different lines on the basis of starch properties, Hierarchical Cluster Analysis was carried out based on RVA, DSC and HPLC results. Five groups of Bánkúti lines could be distinguished on the basis of these traits. According to the results, Bánkúti lines heterogeneous with respect to their HMW glutenin composition are also heterogeneous for their starch properties. Nevertheless, there was no correlation between the variability in protein composition and starch properties.