Localized holographic recording in doubly doped lithium niobate

Persistent holograms are recorded locally with red light in a LiNbO>3 crystal doped with Mg and Fe. Selective erasure is realized by use of a focused UV sensitizing light. We demonstrate the recording of 50 localized images as well as selective erasure in a 4 mm × 4 mm × 4 mm crystal. A comparison of the total recording time for M holograms obtained with the conventional distributed-volume recording and the localized methods is presented

Diffraction efficiency of localized holograms in doubly doped LiNbO3 crystals

The diffraction efficiency of M holograms superimposed in the volume of the recording medium is proportional to 1/M^2. We present a method, based on nondestructive localized holograms in a doubly doped LiNbO3 crystal, that allows us to also record M holograms in the same volume without an exposure schedule or a diffraction efficiency that has 1/M dependence. We compare experimentally the final diffraction efficiency obtained with the localized and distributed recording methods

Localized holographic recording in doubly doped lithium niobate

In holographic data storage, pages of information are overlapped in the volume of the recording medium. Due to destructive read-out of holograms in photorefractive crystals such as LiNbO_3:Fe, holograms are recorded with an exposure schedule in order to equalize diffraction efficiency. This leads to a final diffraction efficiency proportional to 1/M^2, where M is the number of exposures. Coherent erasure of a particular page also erases all the other pages stored in the same volume. We believe to have found a technique that does not require an exposure schedule and that can record M holograms with diffraction efficiency following a 1/M dependence. Our technique is based on non-destructive read-out in doubly-doped LiNbO_3. The technique is based on the recording of localized holograms in thin layers across the volume of the crystal

Wie groß ist der Einfluss von deutschen Wirtschaftsforschungsinstituten? Ein Ranking anhand von RePEc-Daten

Bei dem vorliegenden Artikel handelt es sich um eine Analyse des wissenschaftlichen Einflusses der deutschsprachigen Wirtschaftsforschungsinstitute hinsichtlich ihrer Working Paper und Policy Papers Series. Dazu wurden Statistiken über die Anzahl der Zitierungen der Veröffentlichungsreihen zusammengetragen, Indikatoren berechnet und schlussendlich die Institute in einem Ranking verglichen. Im Ergebnis zeigt sich, dass das Deutsche Institut für Wirtschaftsforschung in Berlin sowohl bei den Working Paper als auch bei den Policy Paper den Rang 1 belegt

Wie groß ist der Einfluss von deutschen Wirtschaftsforschungsinstituten? Ein Ranking anhand von RePEc-Daten

Bei dem vorliegenden Artikel handelt es sich um eine Analyse des wissenschaftlichen Einflusses der deutschsprachigen Wirtschaftsforschungsinstitute hinsichtlich ihrer Working Paper und Policy Papers Series. Dazu wurden Statistiken über die Anzahl der Zitierungen der Veröffentlichungsreihen zusammengetragen, Indikatoren berechnet und schlussendlich die Institute in einem Ranking verglichen. Im Ergebnis zeigt sich, dass das Deutsche Institut für Wirtschaftsforschung in Berlin sowohl bei den Working Paper als auch bei den Policy Paper den Rang 1 belegt

Localized holographic recording in doubly doped lithium niobate

In holographic data storage, pages of information are overlapped in the volume of the recording medium. Due to destructive read-out of holograms in photorefractive crystals such as LiNbO_3:Fe, holograms are recorded with an exposure schedule in order to equalize diffraction efficiency. This leads to a final diffraction efficiency proportional to 1/M^2, where M is the number of exposures. Coherent erasure of a particular page also erases all the other pages stored in the same volume. We believe to have found a technique that does not require an exposure schedule and that can record M holograms with diffraction efficiency following a 1/M dependence. Our technique is based on non-destructive read-out in doubly-doped LiNbO_3. The technique is based on the recording of localized holograms in thin layers across the volume of the crystal

Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems

Current paradigm suggests that spatial and temporal competition for resources limit an exotic invader, cheatgrass (Bromus tectorum L.), which once established, alters fire regimes and can result in annual grass dominance in sagebrush steppe. Prescribed fire and fire surrogate treatments (mowing, tebuthiuron, and imazapic) are used to reduce woody fuels and increase resistance to exotic annuals, but may alter resource availability and inadvertently favor invasive species. We used four study sites within the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) to evaluate 1) how vegetation and soil resources were affected by treatment, and 2) how soil resources influenced native herbaceous perennial and exotic annual grass cover before and following treatment. Treatments increased resin exchangeable NH4+, NO3-, H2PO4-, and K+, with the largest increases caused by prescribed fire and prolonged by application of imazapic. Burning with imazapic application also increased the number of wet growing degree days. Tebuthiuron and imazapic reduced exotic annual grass cover, but imazapic also reduced herbaceous perennial cover when used with prescribed fire. Native perennial herbaceous species cover was higher where mean annual precipitation and soil water resources were relatively high. Exotic annual grass cover was higher where resin exchangeable H2PO4- was high and gaps between perennial plants were large. Prescribed fire, mowing, and tebuthiuron were successful at increasing perennial herbaceous cover, but the results were often ephemeral and inconsistent among sites. Locations with sandy soil, low mean annual precipitation, or low soil water holding capacity were more likely to experience increased exotic annual grass cover after treatment, and treatments that result in slow release of resources are needed on these sites. This is one of few studies that correlate abiotic variables to native and exotic species cover across a broad geographic setting, and that demonstrates how soil resources potentially influence the outcome of management treatments

A Synopsis of Short-Term Response to Alternative Restoration Treatments in Sagebrush-Steppe: The SageSTEP Project

AbstractThe Sagebrush Steppe Treatment Evaluation Project (SageSTEP) is an integrated long-term study that evaluates ecological effects of alternative treatments designed to reduce woody fuels and to stimulate the herbaceous understory of sagebrush steppe communities of the Intermountain West. This synopsis summarizes results through 3 yr posttreatment. Woody vegetation reduction by prescribed fire, mechanical treatments, or herbicides initiated a cascade of effects, beginning with increased availability of nitrogen and soil water, followed by increased growth of herbaceous vegetation. Response of butterflies and magnitudes of runoff and erosion closely followed herbaceous vegetation recovery. Effects on shrubs, biological soil crust, tree cover, surface woody fuel loads, and sagebrush-obligate bird communities will take longer to be fully expressed. In the short term, cool wet sites were more resilient than warm dry sites, and resistance was mostly dependent on pretreatment herbaceous cover. At least 10 yr of posttreatment time will likely be necessary to determine outcomes for most sites. Mechanical treatments did not serve as surrogates for prescribed fire in how each influenced the fuel bed, the soil, erosion, and sage-obligate bird communities. Woody vegetation reduction by any means resulted in increased availability of soil water, higher herbaceous cover, and greater butterfly numbers. We identified several trade-offs (desirable outcomes for some variables, undesirable for others), involving most components of the study system. Trade-offs are inevitable when managing complex natural systems, and they underline the importance of asking questions about the whole system when developing management objectives. Substantial spatial and temporal heterogeneity in sagebrush steppe ecosystems emphasizes the point that there will rarely be a “recipe” for choosing management actions on any specific area. Use of a consistent evaluation process linked to monitoring may be the best chance managers have for arresting woodland expansion and cheatgrass invasion that may accelerate in a future warming climate

A Synopsis of Short-Term Response to Alternative Restoration Treatments in Sagebrush-Steppe: The SageSTEP Project

The Sagebrush Steppe Treatment Evaluation Project (SageSTEP) is an integrated long-term study that evaluates ecological effects of alternative treatments designed to reduce woody fuels and to stimulate the herbaceous understory of sagebrush steppe communities of the Intermountain West. This synopsis summarizes results through 3 yr posttreatment. Woody vegetation reduction by prescribed fire, mechanical treatments, or herbicides initiated a cascade of effects, beginning with increased availability of nitrogen and soil water, followed by increased growth of herbaceous vegetation. Response of butterflies and magnitudes of runoff and erosion closely followed herbaceous vegetation recovery. Effects on shrubs, biological soil crust, tree cover, surface woody fuel loads, and sagebrush-obligate bird communities will take longer to be fully expressed. In the short term, cool wet sites were more resilient than warm dry sites, and resistance was mostly dependent on pretreatment herbaceous cover. At least 10 yr of posttreatment time will likely be necessary to determine outcomes for most sites. Mechanical treatments did not serve as surrogates for prescribed fire in how each influenced the fuel bed, the soil, erosion, and sage-obligate bird communities. Woody vegetation reduction by any means resulted in increased availability of soil water, higher herbaceous cover, and greater butterfly numbers. We identified several trade-offs (desirable outcomes for some variables, undesirable for others), involving most components of the study system. Trade-offs are inevitable when managing complex natural systems, and they underline the importance of asking questions about the whole system when developing management objectives. Substantial spatial and temporal heterogeneity in sagebrush steppe ecosystems emphasizes the point that there will rarely be a “recipe” for choosing management actions on any specific area. Use of a consistent evaluation process linked to monitoring may be the best chance managers have for arresting woodland expansion and cheatgrass invasion that may accelerate in a future warming climate

Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems

Current paradigm suggests that spatial and temporal competition for resources limit an exotic invader, cheatgrass (Bromus tectorum L.), which once established, alters fire regimes and can result in annual grass dominance in sagebrush steppe. Prescribed fire and fire surrogate treatments (mowing, tebuthiuron, and imazapic) are used to reduce woody fuels and increase resistance to exotic annuals, but may alter resource availability and inadvertently favor invasive species.We used four study sites within the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) to evaluate 1) how vegetation and soil resources were affected by treatment, and 2) how soil resources influenced native herbaceous perennial and exotic annual grass cover before and following treatment. Treatments increased resin exchangeable NH₄⁺, NO₃⁻, H₂PO₄⁻, and K⁺, with the largest increases caused by prescribed fire and prolonged by application of imazapic. Burning with imazapic application also increased the number of wet growing degree days. Tebuthiuron and imazapic reduced exotic annual grass cover, but imazapic also reduced herbaceous perennial cover when used with prescribed fire. Native perennial herbaceous species cover was higher where mean annual precipitation and soil water resources were relatively high. Exotic annual grass cover was higher where resin exchangeable H₂PO₄⁻ was high and gaps between perennial plants were large. Prescribed fire, mowing, and tebuthiuron were successful at increasing perennial herbaceous cover, but the results were often ephemeral and inconsistent among sites. Locations with sandy soil, low mean annual precipitation, or low soil water holding capacity were more likely to experience increased exotic annual grass cover after treatment, and treatments that result in slow release of resources are needed on these sites. This is one of few studies that correlate abiotic variables to native and exotic species cover across a broad geographic setting, and that demonstrates how soil resources potentially influence the outcome of management treatments.Keywords: prescribed fire, soil water, soil nutrients, herbicide, exotic annual grass, mowin