Femtosecond optical vortices in air

We examine the robustness of ultrashort optical vortices propagating freely in the atmosphere. We first approximate the stability regions of femtosecond spinning pulses as a function of their topological charge. Next, we numerically demonstrate that atmospheric optical vortices are capable of conveying high power levels in air over hundreds of meters before they break up into filaments.     

Parallel processing of remotely sensed data: Application to the ATSR-2 instrument

Massively parallel computational paradigms can mitigate many issues associated with the analysis of large and complex remotely sensed data sets. Recently, the Beowulf cluster has emerged as the most attractive, massively parallel architecture due to its low cost and high performance. Whereas most Beowulf designs have emphasized numerical modeling applications, the Parallel Image Processing Environment (PIPE) specifically addresses the unique requirements of remote sensing applications. Automated, parallelization of user-defined analyses is fully supported. A neural network application, applied to Along Track Scanning Radiometer-2 (ATSR-2) data shows the advantages and performance characteristics of PIPE.     

Voice Therapy Improves Quality of Life in Age-Related Dysphonia: A Case-Control Study

The objective of the study is to determine the efficacy of voice therapy in the treatment of age-related dysphonia. The study was conducted using a retrospective case-control chart review. The medical records of 54 patients older than 60 years diagnosed with age-related dysphonia without complicating diagnoses were reviewed. Patients who chose to undergo voice therapy were grouped as cases. Patients who chose not to undergo voice therapy were grouped as controls. The voice-related quality of life (VRQOL) measure was used to measure outcomes before and after treatment in cases and at a minimum 2-month follow-up in controls. Of the 54 patients, 19 (10 female, 9 male; mean age 73 years) chose to undergo voice therapy and filled in >1 VRQOL questionnaire. Six patients (3 female, 3 male; mean age 66 years) chose not to undergo voice therapy and filled in >1 VRQOL questionnaire. The 19 cases experienced a mean improvement in VRQOL score of 19.21 (2-tailed matched pairs t test P=0.00038) after a mean of 4.1 voice therapy sessions and 5.1 months. The six controls experienced a mean change in VRQOL score of 0.42 (2-tailed matched pairs t test P=0.96) after a mean of 3.3 months. Voice therapy leads to statistically significant improvement in the VRQOL life in elderly patients with age-related dysphonia. It is an efficacious noninvasive therapy for this disease.     

Estimating the spatial distribution of artificial groundwater recharge using multiple tracers

Stable isotopes of water, organic micropollutants and hydrochemistry data are powerful tools for identifying different water types in areas where knowledge of the spatial distribution of different groundwater is critical for water resource management. An important question is how the assessments change if only one or a subset of these tracers is used. In this study, we estimate spatial artificial infiltration along an infiltration system with stage–discharge relationships and classify different water types based on the mentioned hydrochemistry data for a drinking water production area in Switzerland. Managed aquifer recharge via surface water that feeds into the aquifer creates a hydraulic barrier between contaminated groundwater and drinking water wells. We systematically compare the information from the aforementioned tracers and illustrate differences in distribution and mixing ratios. Despite uncertainties in the mixing ratios, we found that the overall spatial distribution of artificial infiltration is very similar for all the tracers. The highest infiltration occurred in the eastern part of the infiltration system, whereas infiltration in the western part was the lowest. More balanced infiltration within the infiltration system could cause the elevated groundwater mound to be distributed more evenly, preventing the natural inflow of contaminated groundwater.

Dedicated to Professor Peter Fritz on the occasion of his 80th birthday     

Effect of an entrained air bubble on the acoustics of an ink channel

Piezo-driven inkjet systems are very sensitive to air entrapment. The entrapped air bubbles grow by rectified diffusion in the ink channel and finally result in nozzle failure. Experimental results on the dynamics of fully grown air bubbles are presented. It is found that the bubble counteracts the pressure buildup necessary for the droplet formation. The channel acoustics and the air bubble dynamics are modeled. For good agreement with the experimental data it is crucial to include the confined geometry into the model: The air bubble acts back on the acoustic field in the channel and thus on its own dynamics. This two-way coupling limits further bubble growth and thus determines the saturation size of the bubble.