Al/Ge co-doped large mode area fiber with high SBS threshold.

We propose a novel approach of making large effective area laser fiber with higher threshold for the stimulated Brillouin scattering (SBS) using Al/Ge co-doping in the fiber core. The increased SBS threshold is achieved by reducing the acoustic-optic overlap integral while keeping the optical refractive index profile with a step structure. The manipulation of the overlap integral is done by adjusting the relative doping level between Al(2)O(3) and GeO(2) in the core. The mechanism is validated by detailed examples of numerical modeling. An Yb-doped double clad fiber with the core co-doped with Al(2)O(3) and GeO(2) was fabricated by the OVD process. Measured acoustic velocity profile using a scanning acoustic microscope verified that the acoustic velocity in the fiber core changes with the design. An amplifier utilizing the fiber demonstrated that the proposed fiber yielded 6 dB higher SBS threshold than a fiber without using the co-doping scheme.

Time reversal and object reconstruction with single-cycle pulses.

We demonstrate the reconstruction of one- and two-dimensional objects by numerically backpropagating measured scattered terahertz transients. The spatial resolution determined by the Sparrow criterion is found to correspond to approximately 30% of the peak wavelength and 85% of the mean wavelength of the power spectrum of the single-cycle waveform.

Powerful connections for public health: the National Library of Medicine and the National Network of Libraries of Medicine.

As incorporated in Healthy People 2010 objectives, data and information systems and a skilled workforce are 2 of the critical components of the public health infrastructure. The National Library of Medicine (NLM) and the National Network of Libraries of Medicine (NN/LM) are important resources for improving Internet access and providing related training to the public health workforce and to those in training for public health careers. The NLM and the NN/LM have joined forces with the Centers for Disease Control and Prevention, the Health Resources and Services Administration, the Association of State and Territorial Health Officials, the National Association of County and City Health Officials, and the Public Health Foundation. The goal of this collaboration is to improve electronic resources useful in public health practice and increase awareness of them, to train public health professionals to use electronic information services, and to help public health agencies obtain the equipment and Internet connections needed to use these services effectively. The databases, outreach programs, and connection grants available to public health professionals from the NLM, and the training and ongoing support available from the NN/LM for accessing these programs and services, are described.

White-light schlieren optics using bacteriorhodopsin as an adaptive image grid.

A schlieren apparatus using a bacteriorhodopsin film as an adaptive image grid with white-light illumination is demonstrated for the first time to our knowledge. Relevant spectral properties of the film are characterized. Potential applications include a single-ended schlieren system for gas-leak detection.