David W. Blodgett

Applying risk perception theory to public health workforce preparedness training.

Since 9/11, public health has seen a progressive culture change toward a 24/7 emergency response organizational model. This transition entails new expectations for public health workers, including (1) a readiness and willingness to report to duty in emergencies and (2) an ability to effectively communicate risk to an anxious public about terrorism or naturally occurring disasters. To date, however, research on readiness education for health department workers has focused little attention upon the risk perceptions that may influence their willingness to report to duty during disasters, as well as their ability to provide effective emergency risk communication to the public. Here, we apply risk perception factors to explore the potential barriers and remedies to effective public health workforce emergency response.

Modeling of the frequency- and temperature-dependent absorption coefficient of long-wave-infrared (2–25 µm) transmitting materials

A semiempirical multiphonon model based on quantum-mechanical oscillators under a Morse potential is applied to the absorption coefficient of far-infrared transmitting materials. Known material properties are combined with absorption coefficient data to fit the empirical parameters of the model. This provides an accurate means of predicting the intrinsic absorption of the materials in their multiphonon regions. Extinction data are obtained by measuring material transmittances with a Fourier-transform spectrometer and comparing them with the lossless transmittances predicted by Sellmeier models. Where appropriate, scatter models are used to separate the extinction into loss due to scatter and absorption. Data and model parameters are presented for GaAs, GaP, ZnS, and ZnSe.

Analysis and representation of BSDF and BRDF measurements

BSDF and BRDF measurements of randomly rough surfaces are often limited to the plane of incidence. For a surface with no change in optical properties upon rotation in the plane of the sample, this is sufficient to completely represent the BRDF or BSDF of a material at a specific frequency. We apply a simple empirical model that accurately represents the full bi-directional dependence of the scatterance or reflectance based on this limited experimental data set. From these models the total integrated reflectance, total integrated scatterance, and emittance can be obtained. Example measurements of opaque painted flat surfaces, transparent samples, and fibers are presented.

Neutron irradiation of sapphire for compressive strengthening. II. Physical properties changes

Abstract Irradiation of sapphire with fast neutrons (0.8–10 MeV) at a fluence of 1022/m2 increased the c-axis compressive strength and the c-plane biaxial flexure strength at 600 °C by a factor of ∼2.5. Both effects are attributed to inhibition of r-plane twin propagation by damage clusters resulting from neutron impact. The a-plane biaxial flexure strength and four-point flexure strength in the c- and m-directions decreased by 10–23% at 600 °C after neutron irradiation. Neutron irradiation had little or no effect on thermal conductivity, infrared absorption, elastic constants, hardness, and fracture toughness. A featureless electron paramagnetic resonance signal at g=2.02 was correlated with the strength increase: This signal grew in amplitude with increasing neutron irradiation, which also increased the compressive strength. Annealing conditions that reversed the strengthening also annihilated the g=2.02 signal. A signal associated with a paramagnetic center containing two Al nuclei was not correlated with strength. Ultraviolet and visible color centers also were not correlated with strength in that they could be removed by annealing at temperatures that were too low to reverse the compressive strengthening effect of neutron irradiation.

Detection of ultrasound using an apertureless near-field scanning optical microscope

A method for the detection of ultrasonic vibrations using the apertureless near-field scanning optical microscope (ANSOM) is presented. Due to the changes in tip-sample separation, ultrasonic vibrations are seen as perturbations on the near-field signal. Both contact transducer (5 MHz) and laser-generated ultrasound have been successfully transduced. The linear dependence of the near-field signal on tip-sample separation makes the interpretation of these wave forms similar to that for conventional ultrasonic techniques.

Longwave infrared absorption and scatter properties of ZnS and ZnSe

ZnS and ZnSe are two of the most extensively used longwave infrared optical window materials. Standard grade ZnS exhibits excellent transmittance properties from the 7-12 micrometer region. Post-deposition hot-isostatic pressing converts the standard grade ZnS to multispectral ZnS. Multispectral ZnS is transparent from the ultraviolet to the longwave region. ZnSe is optically superior to any grade of ZnS, but significantly weaker. In this paper, the experimental characterization of the multiphoton absorption edge in standard and multispectral grade ZnS and ZnSe as a function of temperature and frequency is presented. A broadband FTIR transmissometer is used to acquire data at temperatures ranging from 10 to 800 K for both materials. The frequency range is from 600 to 5000 cm-1 for ZnS and 400 to 5000 cm-1 for ZnSe. Using this experimental data set a multiphonon absorption model is developed that represents the experimental data over all temperatures and frequencies.

Characterization and modeling of the infrared properties of GaP and GaAs

The experimental characterization of multiphonon absorption in polycrystalline GaP and GaAs as a function of temperature and frequency is presented. Becaues GaP and GaAs have moderate bandgaps, free carrier absorption is examined at high temperature as well. The longwave transparency and excellent thermal and mechanical properties of GaP make it a candidate for future high-stress environment applications. In this paper, a broadband FTIR transmissometer is used with a frequency range from 500 to 5000 cm-1 for GaP and 400 to 5000 cm-1 for GaAs. Spectral measurements were performed from 10 to 800 K for GaP and 10 to 295 K for GaAs. In addition, high temperature laser transmittance measurements using HeNe lasers (632.8 nm and 3.39 μm) and a CO2 (10.6 μm) laser were conducted up to 1100 K. Using this experimental data set, an updated multiphonon and free carrier absorption model is developed that represents the experimental data over all temperatures and frequencies.

Characterization and modeling of the infrared properties of diamond and SiC

Diamond and Silicon Carbide (SiC) are two of the most durable infrared transmitting window materials available today. Diamond is transparent from 0.25 - 3 μm, exhibits weak absorption in the mid-infrared, and is again transparent from 8 μm well into the microwave range. Silicon Carbide has a single infrared transmission window from a 0.4 - 6 μm. In this paper, experimental characterization of the multiphonon absorption in CVD diamond and various grades of SiC as a function of temperature and frequency is presented. A broadband FTIR transmissometer is used. The temperature range is from 10 to 800 K and the frequency range is from 500 to 5000 cm-1. Using this experimental data set up updated multiphonon absorption model is developed that represents the experimental data over all temperatures and frequencies.

Ultrasonic assessment of tooth structure

A means of assessing the internal structure of teeth based upon use of high frequency, highly localized ultrasound (acoustic waves) generated by a short laser pulse is discussed. Some key advantages of laser-generated ultrasound over more traditional contact transducer methods are that it is noncontact and nondestructive in nature and requires no special surface preparation. Optical interferometric detection of ultrasound provides a complementary nondestructive, noncontact technique with a very small detection footprint. This combination of techniques, termed laser-based ultrasonics, holds promise for future in-vivo diagnostics of tooth health. In this paper, initial results using laser-based ultrasound for assessment of dental structures are presented on an extracted human incisor. Results show the technique to be sensitive to the enamel/dentin, dentin/pulp, and dentin/cementum junctions as well as a region of dead tracts in the dentin.

Laser ultrasonic techniques for assessment of tooth structure

Dental health care and research workers require a means of imaging the structures within teeth in vivo. For example, there is a need to image the margins of a restoration for the detection of poor bonding or voids between the restorative material and the dentin. With conventional x-ray techniques, it is difficult to detect cracks and to visualize interfaces between hard media. This due to the x-ray providing only a 2 dimensional projection of the internal structure (i.e. a silhouette). In addition, a high resolution imaging modality is needed to detect tooth decay in its early stages. If decay can be detected early enough, the process can be monitored and interventional procedures, such as fluoride washes and controlled diet, can be initiated which can help the tooth to re-mineralize itself. Currently employed x-ray imaging is incapable of detecting decay at a stage early enough to avoid invasive cavity preparation followed by a restoration with a synthetic material. Other clinical applications include the visualization of periodontal defects, the localization of intraosseous lesions, and determining the degree of osseointegration between a dental implant and the surrounding bone. A means of assessing the internal structure of the tooth based upon use of high frequency, highly localized ultrasound (acoustic waves) generated by a laser pulse is discussed. Optical interferometric detection of ultrasound provides a complementary technique with a very small detection footprint. Initial results using laser-based ultrasound for assessment of dental structures are presented. Discussion will center on the adaptability of this technique to clinical applications.