186 research outputs found
Environmental Considerations in Public Lands Mineral Leasing and Development II
62 pages.
Contains 6 attachments
Stimulated radiative laser cooling
Building a refrigerator based on the conversion of heat into optical energy
is an ongoing engineering challenge. Under well-defined conditions, spontaneous
anti-Stokes fluorescence of a dopant material in a host matrix is capable of
lowering the host temperature. The fluorescence is conveying away a part of the
thermal energy stored in the vibrational oscillations of the host lattice. In
particular, applying this principle to the cooling of (solid-state) lasers
opens up many potential device applications, especially in the domain of
high-power lasers. In this paper, an alternative optical cooling scheme is
outlined, leading to radiative cooling of solid-state lasers. It is based on
converting the thermal energy stored in the host, into optical energy by means
of a stimulated nonlinear process, rather than a spontaneous process. This
should lead to better cooling efficiencies and a higher potential of applying
the principle for device applications
Green deserts, but not always: a global synthesis of native woody species regeneration under tropical tree monocultures.
Abstract: Tree monocultures constitute an increasing fraction of the global tree cover and are the dominant tree- growing strategy of forest landscape restoration commitments. Their advantages to produce timber are well known, but their value for biodiversity is highly controversial and context dependent. Therefore, understanding whether, and in which conditions, they can harbor native species regeneration is crucial. Here, we conducted meta-analyses based on a global survey of the literature and on a database created with local, unpublished studies throughout Brazil to evaluate the regeneration potential of native species under tree monocultures and the way management influ-ences this regeneration. Native woody species regeneration under tree monoculturesharbors a substantial fraction of the diversity (on average 40% and 68% in the global and Brazilian surveys, respectively) and abundance (on average 25% and 60% in the global and Brazilian surveys, respectively) of regeneration observed in natural forests. Plantations with longer rotation lengths, composed of native tree species, and located adjacent to forest remnants harbor more species. Pine plantations harbor more na-tive individuals than eucalypt plantations, and the abundance of regenerating trees is higher in sites with higher mean temperatures. Species–area curves revealed that the number of woody species under pine and eucalypt plantations in Brazil is 606 and 598 species, respectively, over an aggregated sampled area of ca. 12 ha. We highlight that the understory of tree monocultures can harbor a considerable diversity of regener-ating native species at the landscape and regional scales, but this diversity strongly depends on management. Long- rotation length and favorable location are key factors for woody regeneration success under tropical tree monocultures. Therefore, tree monocultures can play a role in forest landscape restoration and conservation, but only if they are planned and managed for achieving this purpose
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