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Homogeneous lignin fractions coming from industrial ultrafiltration processes were subjected to a photocatalytic oxidation process in order to reduce their molecular weight and produce more accessible substrates for the following enzymatic treatment. Early results indicate that due to the effectiveness of the photocatalytic step which accounts for a reduction of the mean molecular weight of treated lignins, the enzymatic production of small degradation compounds is favoured.

Categorical risk factors with significant differences. Categorical risk factors with significant differences between case (BDV-seropositive) and control (seronegative) farms (Additional file 2: Table S2a) and, on the animal level, between case (BDV-seropositive) and control (seronegative) farms (Additional file 2 Table S2b). (DOCX 23 kb)

Continuous risk factors with significant differences between case (BDV-seropositive) and control (seronegative) farms. Within the continuous variables, differences between the number of cattle, sheep, goats, and loss of lambs between the case and control groups. (DOCX 21 kb)

Antibody titer of 10 sera against homologous and heterologous BDV and BVDV isolates. Cross-neutralisation titers of 10 sera against five, four, and one BVDV-I, BDV, and BVDV-II strain, respectively. (DOCX 19 kb)

We present the results of an experimental and theoretical investigation of monosubstituted ethyl-, vinyl-, and ethynyl-ferrocene (EtFC, VFC, and EFC) free molecules, obtained by means of synchrotron-radiation based C 1s photoabsorption (NEXAFS) and photoemission (C 1s XPS) spectroscopies, and density functional theory (DFT) calculations. Such a combined study is aimed at elucidating the role played by the C-C bond unsaturation degree of the substituent on the electronic structure of the ferrocene derivatives. Such substituents are required for molecular chemical anchoring onto relevant surfaces when ferrocenes are used for molecular electronics hybrid devices. The high resolution C 1s NEXAFS spectra exhibit distinctive features that depend on the degree of unsaturation of the hydrocarbon substituent. The theoretical approach to consider the NEXAFS spectrum made of three parts allowed to disentangle the specific contribution of the substituent group to the experimental spectrum as a function of its unsaturation degree. C 1s IEs were derived from the experimental data analysis based on the DFT calculated IE values for the different carbon atoms of the substituent and cyclopentadienyl (Cp) rings. Distinctive trends of chemical shifts were observed for the substituent carbon atoms and the substituted atom of the Cp ring along the series of ferrocenes. The calculated IE pattern was rationalized in terms of initial and final state effects influencing the IE value, with special regard to the different mechanism of electron conjugation between the Cp ring and the substituent, namely the σ/π hyperconjugation in EtFC and the π-conjugation in VFC and EFC.

We designed long-term in vivo experiments to study rabbit urethral regeneration and remodelling over a hyaluronan biodegradable prosthesis. Seven months after the resection of a 1.5-cm-long tract of the urethra and its substitution with the prosthesis, radiological analysis showed the disappearance of the implant and the re-establishment of urethral continuity along the transmural defect. The regenerated tissue remodelled around the implant and exhibited good distensibility under pressure. Histological evaluation showed that the neo-urethra was lined with transitional epithelium and the stroma contained abundant elastic fibres. An examination of the pattern of the major cytoskeletal and cytocontractile proteins of smooth muscle cells and fibroblasts was able to distinguish fibroblasts from smooth muscle cells and myofibroblasts in the neo-urethra. These experiments provide evidence for the potential, successful use of biocompatible/bioresorbable devices for reconstructive surgery of the urethra.

The causative agents of rabies are single-stranded, negative-sense RNA viruses in the genus Lyssavirus of Rhabdoviridae, consisting of twelve classified and three as yet unclassified species including classical rabies virus (RABV). Highly neurotropic RABV causes rapidly progressive encephalomyelitis with nearly invariable fatal outcome. Rapid and reliable diagnosis of rabies is highly relevant for public and veterinary health. Due to growing variety of the genus Lyssavirus observed, the development of suitable molecular assays for diagnosis and differentiation is challenging. This work focused on the establishment of a suitable real-time RT-PCR technique for rabies diagnosis as a complement to fluorescent antibody test and rabies tissue culture infection test as gold standard for diagnosis and confirmation. The real-time RT-PCR was adapted with the goal to detect the whole spectrum of lyssavirus species, for nine of which synthesized DNA fragments were used. For the detection of species, seven probes were developed. Serial dilutions of the rabies virus strain CVS-11 showed a 100-fold higher sensitivity of real-time PCR compared to heminested RT-PCR. Using a panel of thirty-one lyssaviruses representing four species, the suitability of the protocol could be shown. Phylogenetic analysis of the sequences obtained by heminested PCR allowed correct classification of all viruses used.

The optical and electronic properties of organic molecules suggest application in hybrid optical-electronic integrated circuits and thin film devices, but pure, high quality, organic solid films are difficult to make. A better approach is to trap organic molecules as guests at high concentration in a durable host-guest film. Polymer, plastic, and sol-gel films can serve as hosts,1–3but their properties are less than ideal, and the techniques for making them time consuming and involved. Here we describe our Jet Vapor Deposition (JVD) technology for trapping complex organic dyes in hard, adherent inorganic hosts. Jet vapor deposition is the only vapor deposition technique able to make organic-ceramic films, and it offers a number of advantages over other approaches. Individual organic guests can be trapped at high doping levels of several percent, and the possible combinations of guest and host are nearly unlimited. The properties of vapor deposited ceramic hosts are superior to those of polymer hosts. Deposition at high rate and room temperature enables reliable, high throughput, economic production, and renders JVD compatible with semiconductor vapor deposition technology. Here we review the principles of JVD, describe experimental applications to thin film waveguides, lasers, and chemical sensors, and discuss some of the properties of JVD host-guest materials.

The efficacy of monosialoganglioside GM1 treatment was evaluated in a model of experimental stroke. Cerebral ischemia was induced by permanent occlusion of left middle cerebral artery. GM1 was administered intravenously soon after the occlusion of the artery and then intramuscularly daily for 7 days. Results indicate that GM1 can reduce the extent of infarct volume and neurochemical deficits associated with the ischemic event. The protection was more evident in the cortex than in the caudate-putamen. These observations confirm and extend the evidence of the GM1 efficacy in experimental models of stroke and further support the usefulness of gangliosides in the treatment of these pathologies.

A large body of experimental data suggests that neurotrophic molecules and/or substances that facilitate their action could be pharmaceutical agents for neurodegenerative pathologies. In particular, it has been demonstrated that nerve growth factor (NGF) exerts a physiological role for forebrain cholinergic neurons, while brain-derived neurotrophic factor (BDNF) seems to play a relevant role in rescuing dopaminergic neurons following damage. In addition, gangliosides are reported to potentiate neurotrophic factor effects in vitro as well as in vivo. In this study we examined the effects of the monosialoganglioside GM1 in different experimental models. The responsiveness of forebrain cholinergic neurons following NGF +/- GM1 was evaluated by assessing choline acetyltransferase (ChAT) activity in hippocampus, septal area and striatum of behaviorally impaired 24-month-old rats. NGF was intracerebroventricularly (i.c.v.) infused for 2 weeks while GM1 was given systemically for 3 weeks, starting from the beginning of NGF infusion. Moreover, the possible protective effects of GM1 were assessed following exposure of cultured cerebellar granule cells and dopaminergic mesencephalic neurons to different doses of 6-OH-DOPA, a metabolite of the dopamine pathway which has excitotoxic properties and has been hypothesized to participate in the pathology of Parkinson's disease. GM1 treatment to aged rats was seen to potentiate the NGF-induced increase of ChAT activity in the striatum ipsilateral to the NGF infusion. Moreover, in the striatum contralateral to the NGF infusion, GM1 increased ChAT activity above the control values, whereas NGF treatment alone did not affect enzymatic activity. GM1 treatment of cerebellar granule cells and mesencephalic neurons counteracted the dose- and time-dependent neurotoxicity of 6-OH-DOPA. These data support the notion that GM1 might prove useful in treating those pathological conditions where trophic factor deficits and/or excitotoxin-related toxicity play an important role.

In the context of the ongoing eradication campaign for bovine viral diarrhea virus (BVDV) in cattle in Switzerland, the role of South American camelids (SAC) as a possible virus reservoir needed to be evaluated.To assess and characterize the prevalence of pestivirus infections in SAC in Switzerland.Serum samples collected from 348 animals (40 herds) in 2008 and from 248 animals (39 herds) in 2000 were examined for antibodies against pestiviruses and for the presence of BVDV viral RNA.Cross-sectional study using stratified, representative herd sampling. An indirect BVDV-ELISA was used to analyze serum samples for pestivirus antibodies, and positive samples underwent a serum neutralization test (SNT). Real-time RT-PCR to detect pestiviral RNA was carried out in all animals from herds with at least 1 seropositive animal.In 2008, the overall prevalence of animals positive for antibodies (ELISA) and pestiviral RNA or was 5.75 and 0%, respectively. In 2000, the corresponding prevalences were 3.63 and 0%, respectively. The seroprevalences (SNT) for BVDV, border disease virus or undetermined pestiviruses were estimated to be 0, 1.73, and 4.02% in 2008, and 0.40, 1.21, and 2.02% in 2000, respectively.At the present time, SAC appear to represent a negligible risk of re-infection for the BVDV eradication program in cattle in Switzerland.

Numerical studies of nonlinear prism coupling into thin-film organic material waveguides have been carried out. Results are presented showing that, for an undiluted, low absorption material, the electronic response dominates at pulse widths of tens of nanoseconds. The result of an increase in the absorption is that shorter pulses are necessary for access to the Kerr law nonlinearity alone. Guidelines are provided for distinguishing between electronic and thermal responses.

Poiché l'armatura di rinforzo contenuta nei sistemi a cappotto contribuisce a garantire la durabilità del sistema, è stata verificata la variazione delle caratteristiche meccaniche di questo componente in relazione alla durata dell'invecchiamento previsto nella guida ETAG 004 - "External thermal insulation composite systems with rendering"

Nonlinear optical properties of conjugated polymers can be measured using various techniques, including third-harmonic generation, two-photon absorption, nonlinear grating coupling and interferometry. These methods will be compared with regard to their suitability for obtaining specific parameters. We illustrate the application of these techniques to the study of π-conjugated polymeric systems, such as poly(4-BCMU), poly(3-decylthiophene) and 4-dialkylamino-4′-nitrostilbene (DANS) side-chain polymer, all of them regarded as candidates for the realization of all-optical switching devices, and outline relevance and limits of each technique.

Single-polarization interferometric measurements of intensity-induced refractive index changes using an intensity-modulated mode-locked laser are reported. The technique is used to determine the electronic and thermal intensity-dependent index changes in a polydiacetylene waveguide. Monte Carlo analysis shows that a sensitivity of at least 0.02 rad is expected from the configuration. >

We derive exact dispersion relations for transverse magnetic polarized guided waves at an interface between either a linear dielectric or a metal and a nonlinear dielectric. The nonlinearity is taken to be a Kerr-type nonlinearity. Numerical results are presented for the dielectric–metal case.

Since 1991, no cases of Equine Infectious Anemia (EIA) have been reported in Switzerland. Risk factors for introduction of the virus into Switzerland are still present or have even increased as frequent inapparent infections, large numbers of imported horses, (since 2003) absence of compulsory testing prior to importation, EIA cases in surrounding Europe, possible illegal importation of horses, frequent short-term stays, poor knowledge of the disease among horse owners and even veterinarians. The aim of this study was to provide evidence of freedom from EIA in imported and domestic horses in Switzerland. The serum samples from 434 horses imported since 2003 as well as from 232 domestic horses fifteen years of age or older (since older horses have naturally had a longer time of being exposed to the risk of infection) were analysed using a commercially available ELISA test. All samples were seronegative, indicating that the maximum possible prevalence that could have been missed with this sample was 0.5% (95% confidence).

This research was mainly devoted to characterise thin films of carbon nitride (CN) grown by Pulsed Laser Deposition in specific conditions. We introduced a Radio Frequency (RF) system to generate plasma of Nitrogen, in the close proximity of the Silicon substrate, crossing the carbon plume coming from the ablated graphite target, so as to increase the reactivity of the species and the probability of generating carbon nitride films. By XPS, Raman and OES (optical emission spectroscopy) we compared two samples grown by expanding the Carbon plume a) in pure Nitrogen and b) with the plasma activation of Nitrogen. We verified a sensible increase in activation and reactivity of nitrogen, resulting in CN formation, when using plasma confined near the substrate by a negative biased ring. We performed also some measurements of surface conductivity by the four point probe method and verified a different behaviour of the samples: an almost graphitic behaviour for the sample grown with N2 atmosphere and a more insulating nature for the sample grown with plasma, owing to an increased incorporation of nitrogen.

This article is an introduction to photoelectron spectroscopies (X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and synchrotron radiation-based techniques), and their use for the investigation of both fundamental aspects and relevant applications in the field of electrochemical power cells. By means of case studies, various methods are presented of how to extract, from photoemission spectra, information related to significant properties of all cell components, such a: solution-side (and, to some extent, bulk-side) composition of electrodes and membranes; their surface electronic structure and reactivity; formation of a solid electrolyte interface; capacity fading and problems associated with performance and safety of power cells; and localized chemical phenomena, which can be explored by spatial-resolved photoemission. Special emphasis is laid on the interpretation of photoemission studies of the basic phenomena related to power cells, notably intercalation reaction. Theoretical models are briefly recalled and compared with experimental results. The more recent technical developments are described, which can offer new perspective uses of these flexible and powerful spectroscopies.

Third Harmonic Generation (THG) in trans-β-carotene/polystyrene films is reported for fundamental wavelengths ranging from 0.95 μm to 1.9 μm. The results are analyzed with a four electronic level model which includes vibrational sub-structure. Our analysis indicates that the complex third order susceptibility deduced from the THG Maker fringe is strongly dominated by the presence of a two-photon state (an A g state) located above the first one-photon allowed B u state. Our results show little evidence for the presence of the 2A g state located at lower energy than the 1B u state. Two-photon absorption at 1.13 μm and 0.77 μm confirms our THG results.

The complex cubic susceptibility dispersion of side chain polymers containing 4‐dialkylamino‐4’‐nitro‐stilbene, 4‐alkoxy‐4’‐nitro‐stilbene as their side groups has been measured in the range of 0.953 μm to 1.904 μm with third harmonic generation. A two level model is compared to the experimental data in the three‐photon‐resonance spectral region. Microscopic local field cascading was found to give an important contribution to the third order susceptibility. Nonlinear susceptibilities comparable to those of fully conjugated backbone polymers are obtained.

The near infrared dispersion of the third order nonlinear optical susceptibility, χ (3) , of poly [5, 7-dodecadiyn-1, 12-diol-bis (n- butoxycarbonyl-methyl-urethane)], poly (4-BCMU), is investigated by third-harmonic-generation and two-photon-absorption. A four level model gives a good fit to the measured dispersions in the range of 0.770 μm to 1.904μm. The coupling between the first 1 B u state and the two 1 A g states, located above and below it, control the dispersion of χ (3) in the linear transparency region of poly (4-BCMU).

The prevalences of Cryptosporidium parvum, rotavirus, bovine coronavirus (BCV), and enterotoxigenic Escherichia coli (E coli K99) were determined in diarrhoeic dairy calves aged one to 21 days on 71 dairy farms in western Switzerland during the winter of 2005 to 2006. Faecal samples from 147 untreated calves suffering from acute diarrhoea were analysed by standardised diagnostic methods, and the immunoglobulin status of each calf was evaluated. The prevalences of C parvum, rotavirus, BCV and E coli k99 were 55.0 per cent, 58.7 per cent, 7.8 per cent and 5.5 per cent, respectively. The proportions of herds positive for the respective pathogens among the herds with diarrhoeic calves were 41.7 per cent, 52.1 per cent, 2.1 per cent and 2.1 per cent. The immunoglobulin concentration in the serum of 90.5 per cent of the diarrhoeic calves was below 8 g/l.

The aim of this paper was to examine the effect of eliminating persistently infected (PI) animals on BVDV infection during transhumance and to identify possible weak points in the prevention of new infection. An initial blood sample (A) was taken from all the animals until one week before the date of trans-humance (n = 190) and examined for virus by means of real-time RT-PCR or antigen-ELISA and for antibodies by means of ELISA. One PI animal was identified and eliminated. On the day of transhumance (B), serology was performed of the blood samples of all animals that had had a negative or unknown antibody status (n = 93) when blood sample A had been examined. At the end of the transhumance season (C) those animals that had tested seronegative in sample B were re-examined for antibodies (n = 65). The case incidence per animal year amounted to 37.1% up to sample A, 41.8% between sample A and sample B (4 seroconversions). Four cases of seroconversion were diagnosed during the transhumance season, which equalled a case incidence of 17.8% per animal year. A season of transhumance free of PI animals failed to completely prevent BVDV infection, but the new infection rate was significantly diminished. The most possible explanation for new infections are abortions of PI-animals.

Optical third harmonic generation at 1.904, 1.579 and 1.064 μm experiments have been performed on thin films fabricated from side chain polymers containing effectively 4-dialkylamino-nitro-benzene, 4-dialkylamino-4′-nitro-stilbene, 4-dialkylamino-4′-nitro-diphenylbutadiene, 4-dialkylamino-4′-nitro-diphenylhexatriene as the side groups. We have measured values of χ (3) (−3ω; ω, ω, ω) in the range of 0.54 × 10 −12 to 7.42 × 10 −12 esu, at 1.904 μm incident radiation, which are comparable to the nonresonant values found in fully conjugated back-bone polymers [1]. The values of χ (3) at both 1.904 and 1.579 μm change by a factor of 15 as the conjugation length is increased.

We evaluated the effects of treatment with the inner ester derivative of the monosialoganglioside GM1 on cortical electroencephalographic activity and hippocampal CA1 morphology after transitory, near-complete cerebral ischemia in rats. Ischemia was induced by the four-vessel occlusion method, and we studied only the 58 rats that showed flattening of the cortical electroencephalogram for the entire 30 minutes of occlusion. The ganglioside (n = 30) or saline (n = 28) was administered intravenously immediately after release of the carotid clips and then intramuscularly for 21 days of observation. Cortical electroencephalographic activity was monitored throughout the experiment. After 21 days of recirculation we assessed hippocampal CA1 damage by light microscopy. The results indicate that treatment with the ganglioside reduces postischemic secondary damage to the cortical circuitry (as indicated by significantly higher cortical electroencephalographic activity late after reperfusion) and limits neuronal loss in the CA1 region. Our results lend support to the possible therapeutic use of ganglioside in human pathologic conditions associated with cerebrovascular insufficiencies.

It is well known that, in Switzerland, communal grazing of livestock on alpine pastures plays an important role in the spread of BVD virus. Analogously, we might expect that the communal raising on farms specialising in raising heifers of animals born on different farms would also favour the spread of BVDV. This study investigated whether a persistently infected (PI) breeding heifer kept on this type of farm over a period of 26 months would put the other animals at risk of being infected. The PI-animal was in contact with 75 heifers (here defined as contact animals) on this farm. Thirty-two of the contact animals that were probably pregnant (animals at risk of giving birth to a PI-calf) were moved to 8 different breeding farms (here defined as farms at risk). On these 8 farms, 246 calves were found to be at risk of being infected with BVDV. We examined 78 calves and investigated whether the move of the pregnant animals from their original farm had permitted the virus to spread to these 8 other farms. The contact animals had a seroprevalence of 92% and the animals at risk a seroprevalence of 100%. Only one PI-animal was found on the farms at risk. This BVD infection, however, occurred independently of the PI-breeding animal. Seropositive calves were found only on 2 farms. This study did not provide any proof for a spread of BVDV with the PI-breeding animal as a source; likewise, no persistent infection was proven to exist on the farms at risk. This result is likely to be representative for the endemic situation of BVD in Switzerland. Thus, PI-animals present on heifer raising farms infect calves well before servicing. Hence, no new PI-animals are generated, and the infection becomes self-limiting. When we reconstructed the animal movements between the farms and determined the animals to be examined with the aid of the Swiss national animal traffic database (TVD) we found the data of 37% of the heifers to be incomplete and failed to successfully establish the whereabouts of 3 animals.

The adsorption of a bi-functional organic molecule like phenol on Si(1 00)2 · 1 has been investigated by synchrotron radiation-induced photoemission in the valence band, Si 2p, C 1s and O 1s core-level regions. Experiments have been carried out as a function of phenol exposure at room temperature. Phenol adsorbs on Si(1 00)2 · 1 through a dissociative mechanism at room temperature, interacting with the surface by its alcoholic functionality. The line-shape analysis of Si 2p spectra indicates the formation of Si-O and Si-H bonds, as a consequence of the cleavage of the C-O-H bond and the binding of the fragments (CO- group and H atom) to the Si(1 00)2 · 1 surface dimers. The progressive quenching of the silicon surface dimer atoms and the corresponding intensity increase of the Si-OC and Si-H components have been observed as a function of phenol exposure. The presence of the phenoxide (CO-) group on the silicon surface has been evidenced also by the C 1s spectrum, consisting of two components in a 1:5 intensity ratio, energy splitted by 1.5 eV, which can be assigned to carbon atom linked to oxygen (C-O group) and carbon atoms of the aromatic ring, respectively.

The major histocompatibility class II DQ molecules are dimeric glycoproteins involved in antigen presentation to CD4(+) T cells. In the current work, we have performed the molecular analysis of the goat Cahi-DQA1 gene. Sequencing of the Cahi-DQA1 cDNA revealed a single 768bp open reading frame. The alignment of this sequence with its bovine and ovine DQA1 counterparts revealed a remarkable degree of nucleotide identity (92-93% for the most similar bovine and ovine sequences). Moreover, we amplified a region including the 3'-end of intron 1, exon 2 and the 5'-end of intron 2. We identified seven Cahi-DQA1 alleles that likely correspond to four different allelic lineages. The alignment of these seven Cahi-DQA1 alleles revealed the existence of 23 amino acid polymorphic sites, seven of which (alpha(10), alpha(55), alpha(56), alpha(68), alpha(69), alpha(71) and alpha(76)) are highly polymorphic with at least three amino acid substitutions. Ten of the 23 polymorphic amino acid sites were included in the peptide binding region and consequently they might play a crucial role in immunological processes modulating disease pathogenesis.

In May 2003, an abandoned puppy of unknown origin

The pharmacokinetics and intramuscular (i.m.) bioavailability of cefoperazone and cefamandole (20mg/kg) were investigated in dogs and the findings related to minimal inhibitory concentrations (MICs) for 90 bacterial strains isolated clinically from dogs. The MICs of cefamandole for Staphylococcus intermedius (MIC(90) 0.125 microg/mL) were lower than those of cefoperazone (MIC(90) 0.5 micro/mL) although the latter was more effective against Escherichia coli strains (MIC(90) 2.0 microg/mL vs. 4.0 microg/mL). The pharmacokinetics of the drugs after intravenous administrations were similar: a rapid distribution phase was followed by a slower elimination phase (t((1/2)lambda2) 84.0+/-21.3 min for cefoperazone and 81.4+/-9.7 min for cefamandole). The apparent volume of distribution and body clearance were 0.233 L/kg and 1.96 mL/kg/min for cefoperazone, 0.190 L/kg and 1.76 mL/kg/min for cefamandole. After i.m. administration the bioavailability and peak serum concentration of cefamandole (85.1+/-13.5% and 35.9+/-5.4 microg/mL) were significantly higher than cefoperazone (41.4+/-7.1% and 24.5+/-3.0 micog/mL), but not the serum half-lives (t(1/2el) 134.3+/-12.6 min for cefoperazone and 145.4+/-12.3 min for cefamandole). The time above MIC(90) indicated that cefamandole can be administered once daily to dogs for the treatment of staphylococcal infections (T>MIC for S. intermedius 23.8+/-0.3 and for Staphylococcus aureus 21.6+/-0.6h).

High-channel capacity is demonstrated with a 36-nm gain-flattened erbium-doped fiber amplifier (EDFA) with over 28 dBm output power. Wavelength-multiplexed and Raman-based pump sources are used to achieve the high output maintaining telecom grade reliability.

The objective of this study is to propose a project management model which includes the unified process (UP) and UML language, for e-business software development in a physically distributed environment. The research is a qualitative study, aiming to develop methods and models. The main research method is the case study, according to Yin (1992). Initial results point towards a model, which includes the spiral life cycle type, the development process of object-oriented systems (using UML specification language and the unified process as proposed by RUP), and the incorporation of the procedural approach proposed by PMBOK (2000). The proposed model is divided into 6 phases, where each one of these phases contains a set of associated activities. In the future, the intention is to develop a support software for the model and apply this software into the environment in study. This extremely important study line demonstrates that the business world and business practices in the software development area are moving ahead of existent theories and conceptual models in this area. This study, yet in its initial phases, starts to bring significant results that contribute to meet market expectations nowadays.

Third‐harmonic generation has been used to measure the magnitude and phase of the nonlinear susceptibility χ(3)(3ω) of SiO2‐TiO2 sol‐gel thin films as a function of TiO2 concentration. Nonlinearities 20 times larger than those of fused silica were found, making such films useful for nonlinear optics in glass waveguides.

Nonlinear optical measurements in strip‐loaded channel waveguides of poly(4‐BCMU) at 1.319 μm are reported. Using a pulse‐modulated interferometry method, the intensity‐dependent refractive index is found to have an electronic contribution, n2=(4.8±2.7)×10−8 cm2/MW, and an estimated thermal contribution, n2=−(7.9±4.5)×10−11 cm2/MW, for 60 pS laser pulses at 76 MHz. The two‐photon absorption coefficient β is less than 0.25 cm/GW. Figures‐of‐merit suggest that poly(4‐BCMU) has properties desirable for all‐optical devices, but that fabrication losses and thermal effects due to absorption will limit device performance.

We present theoretical investigations of electrical and optical phenomena in the near breakdown regime of pseudomorphic HEMTs. The main effect of the drain current enhancement is found to be a parasitic bipolar effect due to holes, created by impact ionization, which accumulate in the substrate. Calculated electroluminescense spectra of holes, radiatively recombining with electrons in the source-sided channel, exhibit transitions which are allowed due to the bias-induced band bending of the channel. The calculated electroluminescence of the gate-source region agrees well with available experimental data. We predict that the hole accumulation in the source side of the channel region takes place on a time scale of ∼150 ps, thus allowing a direct time-resolved experimental observation.

Double-clad optical fibers are a robust, convenient medium for efficient optical amplification. Their compatibility with high-power semiconductor laser pump sources allows them to operate at saturated power levels of several watts, significantly higher than the level achievable with conventional diode-pumped fiber amplifiers. When coupled with a high-speed master oscillator, such an amplifier becomes an efficient high-speed, high-power optical transmitter. Such a source is of considerable interest for a high-speed space link. The transmitter consisted of a high-speed master laser diode, a high-gain fiber preamplifier, and a high-efficiency fiber power amplifier. The master oscillator was a Fabry-Perot laser diode centered at /spl lambda/=1072 nm, mounted in a high-speed, fiber-coupled package. The laser operated kink free to >50 mW and exhibited a 3-dB roll-off frequency of 11.1 GHz. Both the pre-amp and power amp were based on Yb-doped double-clad fibers pumped with /spl lambda/=915 nm fiber-coupled laser diodes. A polarization-independent optical isolator prevented feedback from the amplifier destabilizing the master oscillator. A free-space WDM module used to combine the signal and pump light into the core and cladding, respectively, of the pre-amp fiber, is shown.

The full range of physiological actions of melatonin is not completely known. In mammals, it modulates gonadal function and regulates biological rhythms. Furthermore, it has also been reported to have anxyolitic, sedative, and anticonvulsant properties, both in human and animals. Recently it has been shown that melatonin is a potent, endogenous hydroxyl radical scavenger suggesting that it might interfere with neurodegenerative processing involving free-radical formation and excitatory amino acid release. Using primary cultures of rat cerebellar neurons and in vivo models of brain injury in rats, we demonstrate that melatonin might be considered an endogenous neuroprotective factor useful for the pharmacological treatment of neurological disorders and neural degeneration produced by glutamate excitotoxicity and oxidative stress.

Summary A case of symptomless, solitary lipoma of the choroid plexus is described. The tumour was found in the left lateral ventricle of an adult female baboon ( Papio papio ) in the course of post-mortem examination. Routine histological investigation showed that the tumour was composed exclusively of characteristic adipose cells with scarce collagen septa and without other hamartoma-like constituents, such as glial cells, neurons, cartilage or muscle fibres. The tumour mass was lined by a typical single layer of cuboidal cells; no calcifications were observed either inside the tumour or in the adjacent periventricular regions. This case is reported in view of the rarity of such tumours of the choroid plexus in man and animals, and to throw light on their possible origin.