No abstract

The Florida Everglades Dry Deposition Study (FEDDS) was conducted to test newly developed measurement techniques used to quantify the dry-deposition of speciated mercury to the Florida Everglades ecosystem. One component of FEDDS employed micrometeorological and dynamic flux chamber techniques to study the air-surface exchange of gaseous elemental mercury over a mixed sawgrass/cattail marsh within Water Conservation Area 3. These measurements provided information related to the magnitudes of, and processes associated with, the bidirectional flux of gaseous elemental mercury within this ecosystem for use in the development of a canopy-scale mercury dry deposition model. During the 2000 FEDDS study period, on average elemental gaseous mercury was emitted from the ecosystem during the daytime (16 ( 30 ng m -2 h -1 ), with deposition observed at night (-1 ( 4 ng m -2 h -1 ). The measured fluxes followed a diurnal pattern and were positively correlated with ambient temperature, solar radiation, and water vapor fluxes and negatively correlated with carbon dioxide fluxes. Our study results suggest that while flux-gradient techniques currently used in many mercury air-surface exchange studies can provide useful information on the general nature of mercury fluxes and the environmental parameters that influence them, there is sufficient uncertainty in the measurement of vertical gradients of gaseous elemental mercury to warrant caution in the interpretation of such measurements, especially during periods typically characterized as having small gradients (day/night transition periods and wellmixed conditions).

Tissue engineering is replete with methods for inducing and mediating cell differentiation, which are crucial for ensuring proper regrowth of desired tissues. In this study, we developed a 3D-printed, non-positive Poisson's Ratio (NPPR) scaffold intended for future use in stretch-mediated cell differentiation applications, such as in muscle and tendon regeneration. We utilized dynamic optical projection stereolithography (DOPsL) to fabricate multi-layered, cell-laden NPPR scaffolds – these scaffolds can not only support aggregate cell growth, but can also be printed with locally-tunable force-displacement properties at length scales appropriate for tissue interaction. These NPPR multilayered mesh scaffolds can be embedded into highly elastic hydrogels in order to couple a reduced NPPR behavior to a normally Positive Poisson's Ratio (PPR) solid bulk material. This hybrid structure may potentially enable induced ‘auxetic’ behavior at the single-cell scale while tuning the Poisson's Ratio to a more isolated value. This would be uniquely suited for providing stretch-mediated effects for various cell-types within the tendon-to-muscle tissue transition.

No abstract

Bound and resonance states of HO 2 have been calculated quantum mechanically by the Lanczos homogeneous filter diagonalization method ͓Zhang and Smith, Phys. Chem. Chem. Phys. 3, 2282 ͑2001͒; J. Chem. Phys. 115, 5751 ͑2001͔͒ for nonzero total angular momentum Jϭ1,2,3. For lower bound states, agreement between the results in this paper and previous work is quite satisfactory; while for high lying bound states and resonances these are the first reported results. A helicity quantum number ⍀ assignment ͑within the helicity conserving approximation͒ is performed and the results indicate that for lower bound states it is possible to assign the ⍀ quantum numbers unambiguously, but for resonances it is impossible to assign the ⍀ helicity quantum numbers due to strong mixing. In fact, for the high-lying bound states, the mixing has already appeared. These results indicate that the helicity conserving approximation is not good for the resonance state calculations and exact quantum calculations are needed to accurately describe the reaction dynamics for HO 2 system. Analysis of the resonance widths shows that most of the resonances are overlapping and the interferences between them lead to large fluctuations from one resonance to another. In accord with the conclusions from earlier Jϭ0 calculations, this indicates that the dissociation of HO 2 is essentially irregular.