Beat Neuenschwander

Study of the dog population and the rabies control activities in the Mirigama area of Sri Lanka

The national health authorities of Sri Lanka have adopted a combined strategy of rabies vaccination and stray dog removal to control endemic dog rabies. Despite the control efforts, an increase of animal and human rabies cases has occurred since 1994. As a consequence, a project to evaluate the national rabies control program has been started and a study focussing on the dog population and rabies control activities in a limited area of Mirigama was conducted. Information on canine abundance and the accessibility of dogs for rabies vaccination was obtained by a household survey, vaccination of dogs against rabies at several vaccination points, collar-marking, and transect line recapture. The number of unvaccinated dogs was estimated by using Bayesian methodology. The estimated number of dogs per square kilometre was 87 (95% credibility interval: 80, 93) for owned dogs and 108 (100, 116) for owned and ownerless dogs. Coverage after the immunisation campaign was 57.6% (53.3, 61.9%) if vaccination at the vaccination points was considered and 66% (60.4, 72.0%) if recently provided vaccination by private veterinarians was also taken into account. The proportion of households with at least one dog vaccinated varied between 59.1 and 94.2% within the catchment area of the different vaccination points. Unvaccinated dogs were puppies (12%), ownerless dogs (57%), and owned dogs, which were not presented for vaccination (31%). In order to improve the rabies immunisation coverage among dogs and to achieve complete elimination of rabies it was recommended that the 95% catchment area of each vaccination point be assessed, the distribution of vaccination points in the vaccination area be redefined if necessary, a system for the vaccination of dogs missing the vaccination campaign for dog owner-specific reasons be established, and an inexpensive marking system be used for vaccinated dogs.

Optimization of the volume ablation rate for metals at different laser pulse-durations from ps to fs

Ultra short laser pulses in the ps or fs regime are used, when high requirements concerning machining quality are demanded. However, beside the quality also the process efficiency denotes a key factor for the successful transfer of this technology into real industrial applications. Based on the ablation law, holding for ultra short pulses with moderate fluences, it has been shown that the volume ablation rate can be maximized with an optimum setting of the laser parameters. The value of this maximum depends on the threshold fluence and the energy penetration depth. Both measures themselves depend on the pulse duration. For metals the dependence of the threshold fluence is well known, it stays almost constant for pulse durations up to about 10 ps and begin then to slightly increase with the pulse duration. The contrary behavior is observed for the energy penetration depth, it decreases over the whole range when the pulse duration is raised from 500 fs to 50 ps. In this paper we will show that the maximum ablation rate can therefore be increased by a factor of 1.5 to 2 when the pulse duration is reduced from 10 ps down to 500 fs.

Processing of metals and dielectric materials with ps-laserpulses: results, strategies, limitations and needs

Ultra short (ps, fs) laser pulses are used, when high requirements concerning accuracy, surface roughness, heat affected zone etc. are demanded for surface structuring. Ps-laser systems that are suited to be operated in industrial environments are of great interest for many practical applications. Here results in the field of 3-d structuring (metals and transparent materials), induced processes and structuring of flexible solar cells will be presented. Beside the pulse duration, which is given by the laser system, the user has a wide variety of optimization parameters such as fluence, repetition rate and wavelength. Based on a simple model it will be shown, that there exist optimum laser parameters to achieve maximum volume ablation rates at a given average power. To take benefit of these optimum parameters and to prevent harmful effects like plasma shielding and surface melting, adapted structuring strategies, depending on the requirements, have to be used. Todays ultra short pulsed systems have average powers from a few W up to a few 10W at high repetition rates. The actual available beam guiding systems are limited and can often not fulfill the requirements needed for high throughput structuring with optimized parameters. Based on the achieved results, the needs for future beam guiding systems will be discussed.

Field evaluation of two bait delivery systems for the oral immunization of dogs against rabies in Tunisia

Two bait delivery systems for the oral immunization of dogs against rabies were tested in small scale field trials in a semi-rural area in Tunisia: bait delivery to owned dogs during door to door visits of households (door to door baiting) and distribution of baits on transect lines (transect line baiting). A prototype bait (DBL2) configured for industrial production and containing either sulfadimethoxine (SDM) as a systemic marker or Rhodamine B as a topical marker was used. The overall proportion of dogs which took a bait and presented topical marker staining after door to door baiting was 59.1%. The total time and costs spent per bait accepting dog averaged 34 person minutes and US

Processing of dielectric materials and metals with PS laserpulses

4, respectively. Unconsummated baits were readily recovered. No unprotected human contacts with baits were recorded. Door to door baiting is a very specific but time-consuming method that enables a safe administration of vaccine baits to owned dogs. For transect line baiting, baits were distributed at a density of ca 3000 baits per km2 along double transect lines. Baits were recovered after 20 h. According to the proportion of SDM positive serum samples, 24.1% of owned dogs in the baiting area had consumed baits. Of all owned and ownerless dogs, presumably free-roaming during transect line baiting, > 40% had consumed baits. The total time and costs spent per bait accepting dog averaged 48 person minutes and ca US

Ultra-high-precision surface structuring by synchronizing a galvo scanner with an ultra-short-pulsed laser system in MOPA arrangement

20, respectively. The household census revealed 32 direct human contacts with the bait matrix which corresponds to 1.4% of inhabitants. Placing baits on transect lines gives the possibility to vaccinate dogs not accessible by vaccination systems which base on dog owner participation. However, the method is not specific, less safe than other systems, not easily accepted by the human population, and costly.

Factors controlling the incubation in the application of ps laser pulses on copper and iron surfaces

Ever since industrially applicable ps laser systems have been available, cold ablation with ultra short laser pulses is of huge interest when high requirements concerning accuracy, defined surface roughness and small heat affected zone are demanded. Interesting applications are in the fields of surface and 3-d structuring with direct and induced processes. For a profitable industrial use of this technology high process efficiency is required, which is enabled by the development of systems with high average power of more than 100 W. The process efficiency directly scales with the average power when the repetition rate of the system is properly chosen. But aside from process efficiency often a high surface quality (low surface roughness, minimized surface melting and no oxidation processes) is desired. These measures are not only strongly affected by the laser parameters but also by the strategy of structuring. Especially for surface structuring the corresponding requirements for the equipment of the beam guiding system are often not accomplishable and therefore there is a strong demand for new technologies which have to be developed.Ever since industrially applicable ps laser systems have been available, cold ablation with ultra short laser pulses is of huge interest when high requirements concerning accuracy, defined surface roughness and small heat affected zone are demanded. Interesting applications are in the fields of surface and 3-d structuring with direct and induced processes. For a profitable industrial use of this technology high process efficiency is required, which is enabled by the development of systems with high average power of more than 100 W. The process efficiency directly scales with the average power when the repetition rate of the system is properly chosen. But aside from process efficiency often a high surface quality (low surface roughness, minimized surface melting and no oxidation processes) is desired. These measures are not only strongly affected by the laser parameters but also by the strategy of structuring. Especially for surface structuring the corresponding requirements for the equipment of the beam g...

Simultaneous diagonalization algorithms with applications in multivariate statistics

For surface and 3D structuring the ultra short pulsed laser systems are mostly used in combination with galvo scanners. This work reports on the synchronization of the scanner mirror motion with the clock of the laser pulses, which is usually in the range of 100 kHz and higher, by a modification of the electronic scanner control. This synchronization facilitates the placement of the small ablation craters from single pulses with the precision of about 1 μm relative to each other. The precise control of the crater positions offers the possibility to test and optimize new structuring strategies. Results of this optimization process with respect to minimum surface roughness, steepness of wall, accuracy to shape and efficiency will be presented.

High Throughput and High Precision Laser Micromachining with ps-Pulses in Synchronized Mode with a fast Polygon Line Scanner

For laser micro processing with short and ultra-short pulses the threshold fluence is affected by the incubation and changes with the number of pulses applied. In general the incubation effect is described by a power function including the incubation coefficient S. Beside the threshold fluence also the energy penetration depth is subject to the incubation effect; moreover it is a main cause for the change of the threshold fluence with increasing pulse number. The behavior of the threshold fluence can be explained by varying absorption (due to changes in the surface reflectivity), chemical changes of the surface (e.g. due to oxidation) or changes in the microstructure of the material whereas the behavior of the energy penetration depth could be explained by the latter two effects but should not be affected by a change in the absorption. To try to distinguish between these three effects a systematic ablation study with 10 ps pulses at 1064nm wavelength on copper and iron under different gases atmospheres and pressures was done. The results show on the one hand the change of the energy penetration depth is the main cause of the incubation and that on the other hand an adapted model better fits the trend of the threshold fluence and the penetration depth as a function of the number of pulses applied. The influence of the gas (air, oxygen, nitrogen and argon) is only marginal whereas a reduction of the pressure from normal atmosphere down to 50 mbar results in a 25% increase of the maximum removal rate. Induced changes in the microstructure were detected by a high resolution X-ray diffraction analysis on single crystal (111-orientation) copper and iron samples.

Processing of metals with ps-laser pulses in the range between 10ps and 100ps

The following problem arises from multivariate statistical models in principal component and canonical correlation analysis. Let