Effect of Clarification System on the Conservation of Virgin Olive Oil during Its Storage

The results obtained in this work explain how clarification systems can affect the conservation of virgin olive oils (VOOs) during the storage step. The evolution of the quality and sensory properties during the storage of VOOs clarified by different systems, vertical centrifugal separator (VCS) with minimal water addition and conical bottom settling tank (CBST), is studied at industrial scale for two different crop years. In general, VCS oils show a slight higher moisture and solid impurities content at the end of the storage step due to a higher emulsion grade (because of the emulsion generated) caused by the rotating movement of this clarification system. For the studied clarification systems, no remarkable differences are observed between the oils during their storage for quality indexes. However, these systems show differences regarding oil sensory properties. The VOOs clarified by VCS are characterized by a higher presence of phenol components, higher positive sensory attributes intensity, and higher lipoxygenase (LOX) aldehydes content during their storage. VOOs from CBST show lower phenol content, a higher “non‐LOX” volatiles content, and the presence of sensory defects during storage. Practical Applications: The results obtained in this work are very important in order to provide specific recommendations and scientific support based on objective data to improve VOO quality. As described in this study, the VCS with a minimal water addition can be a better option to produce VOO of improved quality. This clarification system is an efficient and quick operation that reduces the contact between oil and the remaining water and impurities during the storage step. The minimal water addition used in this clarification system allows obtaining VOOs with higher phenol content and positive sensory notes. This leads to prolong VOO shelf‐life and conservation during the storage stage, due to preservation of the quality indexes and minor components with antioxidant activity. Besides, this clarification system reduces the water consumption during oil clarification and generates a lower wastewater volume regarding conventional vertical centrifugation, and therefore can be considered more environmentally friendly.     

Tumor necrosis factor-induced contraction of cultured rat mesangial cells: interaction with angiotensin II

The role of tumor necrosis factor alpha in the regulation of renal function, particularly glomerular filtration rate, has not been completely defined. This study was designed to assess the intrinsic role of this cytokine on glomerular filtration rate by analyzing its short-term effect on the degree of contraction in cultured rat mesangial cells, not only directly but also in the presence of angiotensin II. Contraction was evaluated both morphologically--by measuring planar cell surface area of cultured rat mesangial cells and glomerular cross-sectional area of isolated rat glomeruli--and biochemically--by analyzing myosin light-chain phosphorylation in cells. Tumor necrosis factor alpha significantly decreased planar cell surface area in a dose-dependent and time-dependent manner, an effect completely abolished by preincubation of the cells with platelet-activating factor receptor antagonists BN 52021 and alprazolam. This effect was also observed in the presence of angiotensin II, whether tumor necrosis factor alpha was added before or after angiotensin II, increasing the reduction in planar cell surface area induced by angiotensin II in both cases. Changes in planar cell surface area were evident not only when the absolute values of this parameter were considered but also when the percentage of contracted cells (cells with a planar cell surface area reduction > 10%) was analyzed. Tumor necrosis factor alpha also induced a significant reduction of glomerular cross-sectional area in isolated rat glomeruli. The results of the morphologic studies were supported by myosin light-chain phosphorylation experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Advantages and limitations of MgO as a dielectric for GaN

MgO and Sc₂O₃ were deposited by gas source molecular beam epitaxy on GaN. MgO was found to produce lower interface state densities than Sc₂O₃, 2–3 × 10¹¹ vs. 9–11 × 10¹¹ eV⁻¹ cm⁻². The good electrical quality of the interface is believed to be due to the presence of a single crystal epitaxial layer at the GaN surface. By contrast, the MgO was found to be more sensitive to environmental and thermal degradation than the Sc₂O₃. The environmental degradation is believed to be due to interaction with water vapor in the air and was suppressed by capping of the MgO. Annealing at the temperatures needed for implant activation in GaN produced significant roughening of the MgO/GaN interface and an order of magnitude increase in the interface state density. This sensitivity to thermal degradation will require changes in the processing sequence presently envisioned for e-mode devices in order to avoid damaging the interface and increasing the gate leakage in the device.     

Thermal Stability of Nitride-Based Diffusion Barriers for Ohmic Contacts to <Emphasis Type="Italic">n</Emphasis>-GaN

The use of TaN, TiN, and ZrN diffusion barriers for Ti/Al-based contacts on n-GaN (n ∼ 3 × 10¹⁷ cm⁻³) is reported. The annealing temperature (600–1,000°C) dependence of the Ohmic contact characteristics using a Ti/Al/X/Ti/Au metallization scheme, where X is TaN, TiN, or ZrN, deposited by sputtering was investigated by contact resistance measurements and Auger electron spectroscopy (AES). The as-deposited contacts were rectifying and transitioned to Ohmic behavior for annealing at ≥600°C. A minimum specific contact resistivity of ∼6 × 10⁻⁵ Ω-cm⁻² was obtained after annealing over a broad range of temperatures (600–900°C for 60 s), comparable to that achieved using a conventional Ti/Al/Pt/Au scheme on the same samples. The contact morphology became considerably rougher at the high end of the annealing range. The long-term reliability of the contacts at 350°C was examined; each contact structure showed an increase in contact resistance by a factor of three to four over 24 days at 350°C in air. AES profiling showed that the aging had little effect on the contact structure of the nitride stacks.     

Fabrication approaches to ZnO nanowire devices

To date, most of the work on ZnO nanostructures has focused on the synthesis methods and there have been only a few reports of the electrical characteristics. We report on fabrication methods for obtaining device functionality from single ZnO nanorods. A key aspect is the use of sonication to facilitate transfer of the nanorods from the initial substrate on which they are grown to another substrate for device fabrication. Examples of devices fabricated using this method are briefly described, including metal-oxide semiconductor field effect depletion-mode transistors with good saturation behavior, a threshold voltage of ∼−3 V, and a maximum transconductance of order 0.3 mS/mm and Pt Schottky diodes with excellent ideality factors of 1.1 at 25°C and very low (1.5×10⁻¹⁰ A, equivalent to 2.35 Acm⁻², at −10 V) reverse currents. The photoresponse showed only a minor component with long decay times (tens of seconds) thought to originate from surface states. These results show the ability to manipulate the electron transport in nanoscale ZnO devices.     

Two are Better than One: Combining ZnO and MgF2 Nanoparticles Reduces Streptococcus pneumoniae and Staphylococcus aureus Biofilm Formation on Cochlear Implants

Streptococcus pneumoniae (S. pneumoniae) and Staphylococcus aureus (S.aureus) are considered the most common colonizers of cochlear implants (CI), which have prompted the search for new ways to inhibit their growth and biofilm development. In the current study, CI‐based platforms are prepared and sonochemically coated with ZnO or MgF₂ nanoparticles (NPs), two agents previously shown to possess antibacterial properties. Additionally, a method is developed for coating both ZnO and MgF₂ on the same platform to achieve synergistic activity against both pathogens. Each surface is characterized, and the optimal conditions for the NP homogenous distribution on the surface are determined. The ZnO‐MgF₂ surface significantly reduces the S. pneumoniae and S. aureus biofilm compared with the surfaces coated with either ZnO or MgF₂, even though it contains smaller amounts of each NP type. Importantly, leaching assays show that the NPs remain anchored to the surface for at least 7 d. Finally, biocompatibility studies demonstrate that coating with low concentrations of ZnO‐MgF₂ results in no toxicity toward primary human fibroblasts from the auditory canal. Taken together, these findings underscore the potential of using NP combinations such as the one presented here to efficiently inhibit bacterial colonization and growth on medical devices such as CIs.     

Lateral schottky GaN rectifiers formed by Si<Superscript>+</Superscript> ion implantation

Type conversion of p-GaN by direct Si⁺ ion implantation and subsequent annealing was demonstrated by the fabrication of lateral Schottky diodes. The Si⁺ activation percentage was measured as a function of annealing time (30–300 sec) and temperature (1,000–1,200°C), reaching a maximum of ∼30% for 1,200°C, 2-min anneals. The resulting n-type carrier concentration was 1.1×10¹⁸ cm⁻³ for a moderate Si⁺ ion dose of ∼2×10¹⁴ cm⁻². The lateral Schottky diodes displayed a negative temperature coefficient of −0.15 V·K for reverse breakdown voltage.     

Demonstration of GaN MIS diodes by using AlN and Ga2O3(Gd2O3) as dielectrics

GaN MIS diodes were demonstrated utilizing AlN and Ga₂O₃(Gd₂O₃) as insulators. A 345 Å of AlN was grown on the MOCVD grown n-GaN in a MOMBE system using trimethylamine alane as Al precursor and nitrogen generated from a SVT RF N₂ plasma. For the Ga₂O₃(Gd₂O₃) growth, a multi-MBE chamber was used and a 195 Å oxide was E-beam evaporated from a single crystal source of Ga₅Gd₃O₁₂. The forward breakdown voltage of AlN and Ga₂O₃(Gd₂O₃) diodes are 5 and 6 V, respectively, which are significantly improved over 1.2 V from that of a Schottky contact. From the C–V measurements, both kinds of diodes showed good charge modulation from accumulation to depletion at different frequencies. The insulator/GaN interface roughness and the thickness of the insulator were measured with X-ray reflectivity.     

GaN, ZnO and InN nanowires and devices

A brief review is given of recent developments in wide bandgap semiconductor nanowire synthesis and devices fabricated on these nanostructures. There is strong interest in these devices for applications in UV detection, gas sensors and transparent electronics.