Kris Baert

Characterization and optimization of infrared poly SiGe bolometers

In this paper, we present a complete characterization of poly SiGe bolometers. Devices having different dimensions and different geometry have been fabricated. The dependence of the low-frequency noise and of the temperature coefficient of resistance (TCR) on resistivity in poly SiGe has been measured and modeled. The impact of resistivity, bias voltage, thermal conductance, thickness, and dimensions of the active element on the device performance has been investigated. It has been demonstrated that, by using the appropriate absorber and by optimizing the device parameters, poly SiGe bolometers are suitable for realizing high-performance focal plane arrays (FPAs).

Nanoscaled interdigitated titanium electrodes for impedimetric biosensing

Nanoscaled interdigitated electrodes (IDEs) are developed for the purpose of being used as miniature and sensitive affinity biosensors. Because of the ease to derivatise its surface, oxidized Ti is chosen as an electrode material on a SiO2 substrate. For proof of principle, oxidized and non-oxidized Ti IDEs are characterised in salt solutions and the immobilisation of glucose oxidase is monitored using impedance spectroscopy. Beside transducer development and demonstration, tailored bio interfaces are a prerequisite for the development of sensitive affinity biosensors. Therefore, a characterisation of immobilisations (based on silanisations) on TiO2 and SiO2 is conducted. For this study, different analytical techniques are identified and evaluated. The use of these techniques will enable a thorough characterisation of immobilisation processes, ultimately leading to miniature and sensitive affinity biosensors.

Comparative pharmacokinetics of three non-steroidal anti-inflammatory drugs in five bird species

Information on the pharmacokinetics and pharmacodynamics of anti-inflammatory drugs in birds is scarce. Choice of drug and of dosage is usually empirical, since studies of anti-inflammatory drugs are lacking. In this study, three common veterinary non-steroidal anti-inflammatory drugs (NSAIDs) were administered intravenously to five different bird species. Sodium salicylate, flunixin and meloxicam were selected as anti-inflammatory drugs. These NSAIDs were administered intravenously to chickens (Gallus gallus), ostriches (Struthio camelus), ducks (Anas platyrhynchos), turkeys (Meleagris gallopavo) and pigeons (Columba livia). Plasma concentrations of the drugs were determined by validated high-performance liquid chromatography methods and pharmacokinetic parameters were calculated. Most bird species exhibited rapid elimination of these drugs. Ostriches had the fastest elimination rate for all three NSAIDs, but there were some interesting species differences. Chickens had a half-life that was approximately 10-fold as long as the other bird species for flunixin. The half-life of chickens and pigeons was three-fold as long as the other bird species for meloxicam, and, for salicylic acid, the half-life in pigeons was at least three-five-fold longer than in the other bird species.

Experimental determination of the maximum post-process annealing temperature for standard CMOS wafers

This paper reports on the experimental determination of the maximum post-process annealing temperature for standard 0.35 /spl mu/m CMOS wafers with aluminum based interconnections and tungsten plugs, without introducing significant modifications to their standard characteristics. The impact of increasing the post-processing temperature from 475/spl deg/C to 575/spl deg/C, for periods varying between 30 and 90 min, on both the front and back end is analyzed. 0.35 /spl mu/m CMOS technologies with different Al alloys, Al-1wt%Si-0.5wt%Cu (AlSiCu) or Al-0.5wt%Cu (AlCu), and different back end structures are considered. It is illustrated that the maximum annealing temperature is a function of the structure and composition of the interconnection layers and their maximum allowable resistance increase. It is also demonstrated that the transistor characteristics, the silicide quality and the leakage currents are as good as unaffected by annealing for 90 min at temperatures up to 525/spl deg/C.

Developing a safe antifungal treatment protocol to eliminate Batrachochytrium dendrobatidis from amphibians

Batrachochytrium dendrobatidis is one of the most pathogenic microorganisms affecting amphibians in both captivity and in nature. The establishment of B. dendrobatidis free, stable, amphibian captive breeding colonies is one of the emergency measures that is being taken to save threatened amphibian species from extinction. For this purpose, in vitro antifungal susceptibility testing and the development of efficient and safe treatment protocols are required. In this study, we evaluated the use of amphotericin B and voriconazole to treat chytridiomycosis in amphibians. The concentration at which the growth of five tested B. dendrobatidis strains was inhibited was 0.8 μg/ml for amphotericin B and 0.0125 μg/ml for voriconazole. To completely eliminate a mixture of sporangia and zoospores of strain IA042 required 48 h of exposure to 8 μg/ml of amphotericin B or 10 days to 1.25 μg/ml of voriconazole. Zoospores were killed within 0.5 h by 0.8 μg/ml of amphotericin B, but even after 24 h exposure to 1.25 μg/ml of voriconazole they remained viable. Amphotericin B was acutely toxic for Alytes muletensis tadpoles at 8 μg/ml, whereas toxic side effects were not noticed during a seven-day exposure to voriconazole at concentrations as high as 12.5 μg/ml. The voriconazole concentrations remained stable in water during this exposure period. On the basis of this data, experimentally inoculated postmetamorphic Alytes cisternasii were sprayed once daily for 7 days with a 1.25 μg/ml solution of voriconazole in water which eliminated the B. dendrobatidis infection from all treated animals. Finally, treatment of a naturally infected colony of poison dart frogs (Dendrobatidae) using this protocol, combined with environmental disinfection, cleared the infection from the colony.

Structural and mechanical properties of polycrystalline silicon germanium for micromachining applications

In this paper, we propose polycrystalline silicon germanium (poly SiGe) as a material suitable for MEMS applications. Films are prepared by chemical vapor deposition (CVD) at atmospheric pressure (AP) or reduced pressure (RP). The structure of the films is investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) for different deposition and annealing conditions. The stress in the as-grown and annealed layers is measured, and the correlation between stress and structural properties is discussed. It is demonstrated that by adjusting the deposition conditions, the stress of the as-grown material can be varied from -145 to 60 MPa. Examples of poly SiGe micromachined devices, prepared at 650/spl deg/C, are presented. It is shown that by using as-grown poly SiGe, it is possible to realize surface-micromachined suspended membranes having 0.6-/spl mu/m-wide and 50-/spl mu/m-long supports. The effect of the average stress and stress gradient on the mechanical stability of surface-micromachined structures is illustrated. Finally, the strain in poly SiGe is measured, and it is found to vary, according to the deposition conditions from -6.88/spl times/10/sup -4/ to 3.6/spl times/10/sup -1/ These values are compared to those measured for APCVD poly Si.

Pharmacokinetics of Acyclovir after Intravenous Infusion of Acyclovir and after Oral Administration of Acyclovir and Its Prodrug Valacyclovir in Healthy Adult Horses

ABSTRACT The purpose of this study was twofold. The first aim was to evaluate the oral bioavailability and pharmacokinetics (PKs) of acyclovir in horses after intravenous (i.v.) administration and after oral administration of acyclovir and its prodrug, valacyclovir. Second, we aimed to combine these PK data with pharmacodynamic (PD) information, i.e., 50% effective concentrations (EC50 values) from in vitro studies, to design an optimal dosage schedule. Three treatments were administered to healthy adult horses: 10 mg of acyclovir/kg of body weight delivered as an i.v. infusion over 1 h, 20 mg of acyclovir/kg administered as tablets by nasogastric intubation, and 20 mg of valacyclovir/kg administered as tablets by nasogastric intubation. Total plasma concentrations were measured by a high-performance liquid chromatography method combined with fluorescence detection, while unbound plasma concentrations were determined by liquid chromatography-tandem mass spectrometry. The peak concentration of i.v. acyclovir was approximately 10 μg/ml for both the total and the unbound plasma concentrations. The mean half-life of elimination was between 5.05 h (total concentration) and 11.9 h (unbound concentration). Oral administration of acyclovir resulted in low maximum concentration in plasma (Cmax) and poor bioavailability. A 10-times-higher Cmax and an 8-times-higher bioavailability were achieved with oral administration of valacyclovir. The i.v. administration of 10 mg/kg acyclovir and the oral administration of 20 mg/kg valacyclovir achieved concentrations within the sensitivity range of equine herpesvirus type 1 (EHV-1). The higher bioavailability of valacyclovir makes it an attractive candidate for the prophylactic and/or therapeutic treatment of horses infected with EHV-1. The results from the PK/PD modeling showed that a dosage of 40 mg/kg valacyclovir, administered three times daily, would be sufficient to reach plasma concentrations above the EC50 values.

Scavenging energy from human body: design of a piezoelectric transducer

The present work concerns the concept and the modeling of a device for transforming a part of the mechanical energy originating from human limb motion into electrical energy. The device is formed by a frame containing a free moving mass. Useful electrical power is generated by the impact of this mass on piezoelectric cantilevers positioned at the end of the frame. In order to evaluate device performances a detailed analysis of the dynamics of the system is coupled to a model of the piezoelectric transducer. It is found that an optimized device, when mounted on the human wrist, can theoretically generate up to 40 /spl mu/W/cm/sup 3/.

Voriconazole, a safe alternative for treating infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii in bearded dragons (Pogona vitticeps)

Dermal and systemic infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii (CANV) are highly prevalent in reptiles and may result in severe disease and high mortality. Due to the high incidence of therapeutic failures, optimizing treatment is required. We first determined in this study the minimal inhibitory concentrations (MIC) of itraconazole, voriconazole, amphotericin B and terbinafine against 32 CANV isolates. For voriconazole, amphotericin B and terbinafine a monomodal MIC distribution was seen, whereas a bimodal MIC distribution was present for itraconazole, indicating acquired resistance in one isolate. Fourteen naturally-infected bearded dragons (Pogona vitticeps), from the same owner, were treated orally with either itraconazole (5 mg/kg q24h) or voriconazole (10 mg/kg q24h). The clinical condition, drug plasma concentrations and the presence of CANV in skin samples were followed. The animals were treated until complete clearance of the fungus. The plasma concentrations of voriconazole and itraconazole exceeded the minimal inhibitory concentrations of the CANV isolates. Elimination of CANV was achieved on average after 27 and 47 days of treatment with itraconazole and voriconazole, respectively. Whereas only 2 out of 7 survived after itraconazole treatment, only a single animal died in the voriconazole treated group. In conclusion, based on a limited number of animals, voriconazole applied at a regimen of 10 mg/kg bodyweight (BW) q24h seems to be a safe and effective antimycotic drug to eliminate CANV infections in bearded dragons.

Designing voriconazole treatment for racing pigeons: balancing between hepatic enzyme auto induction and toxicity

Aspergillosis is a major cause of mortality in captive birds and its prognosis is often poor due to treatment failure. Voriconazole is a novel triazole antifungal agent that may be useful for the treatment of this infection in birds as it has shown promise in other animal models of the disease. We examined the pharmacokinetic behaviour of voriconazole in racing pigeons (Columbia livia forma domestica). Intravenous, oral and aerosol administration were investigated in single (10 mg/kg BW PO; 10, 5, 2.5 mg/kg BW IV), multiple dose (10, 20 mg/kg BW PO q12h, q24h) and nebulization (15 min, 10 mg/ml NaCl 0.9%) experiments. Quantitative measurements of voriconazole in plasma, as well as in lung tissue, collected at several time points, were done with a validated high performance liquid chromatography method using ultraviolet detection. Designing a treatment schedule with voriconazole is complicated by dose-dependent pharmacokinetics and induction of its biotransformation. Moreover, hepatic changes were seen in the oral multiple dose regimen at 10 and 20 mg/kg BW twice a day. Taking all features into account our study suggests that the oral dosage schedules of 10 mg/kg BW twice a day or 20 mg/kg BW once a day could be most appropriate in treating pigeons with aspergillosis.