Di-tert-butyl N,N′-(octa­hydro­penta­lene-2,5-di­yl)dicarbamate

In the molecule of the title compound, C18H32N2O4, the central bicyclo­[3.3.0]octane (octa­hydro­penta­lene) has a rigid ring junction. Both rings of the bicyclo­[3.3.0]octane unit adopt an envelope conformation, and the flexible tert-butyl­carbamoyl side chains each have an extended conformation. Such a constrained bicyclo­[3.3.0]octane aliphatic template is of inter­est with respect to the design of novel self-assembling motifs. Mol­ecules related by c-glide symmetry are linked via inter­molecular N—H⋯O hydrogen bonds, forming a two-dimensional layer structure. Neighboring layers are weakly associated along the a axis due to the close approach of the tert-butyl­carbamoyl groups (2.55 Å)

Variable Blue Straggler Stars in Open Cluster NGC 6819 Observed in the Kepler 'Superstamp' Field

NGC 6819 is an open cluster of age 2.4 Gyr that was in the NASA Kepler spacecraft field of view from 2009 to 2013. The central part of the cluster was observed in a 200 x 200 pixel `superstamp' during these four years in 30-minute cadence photometry, providing a unique long time-series high-precision data set. The cluster contains 'blue straggler' stars, i.e., stars on the main sequence above the cluster turnoff that should have left the main sequence to become red giants. We present light curves and pulsation frequency analyses derived from custom photometric reductions for five confirmed cluster members--four blue stragglers and one star near the main-sequence turnoff. Two of these stars show a rich spectrum of $\delta$ Scuti pulsation modes, with 236 and 124 significant frequencies identified, respectively, while two stars show mainly low-frequency modes, characteristic of $\gamma$ Doradus variable stars. The fifth star, a known active x-ray binary, shows only several harmonics of two main frequencies. For the two $\delta$ Scuti stars, we use a frequency separation--mean-density relation to estimate mean density, and then use this value along with effective temperature to derive stellar mass and radius. For the two stars showing low frequencies, we searched for period-spacing sequences that may be representative of gravity-mode or Rossby-mode sequences, but found no clear sequences. The common age for the cluster members, considered along with the frequencies, will provide valuable constraints for asteroseismic analyses, and may shed light on the origin of the blue stragglers.Comment: Accepted for publication in The Astronomical Journal February 23, 2023. 36 pages, 14 figures, 4 tables in text, 5 in Appendi

Effect of Polypropylene fibres on the Workability parameters of Extrudable Cementitious Material

Additive manufacturing in construction industry has been introduced as an aspiration for a more sustainable built environment and currently evolving with high demand amongst researches. This study is an investigation of the influence of polypropylene (PP) fibre addition on the workability parameters of a new extrudable concrete mixture. As the quality of final printed structure prominently depends on the fresh state properties of concrete, this investigation mainly focused on the rheological properties such as workability (flow), setting time, extrudability and buildability. These parameters were systematically investigated through a small scale experimental process with time after mixing. The selected control mix with Ground granulated blast furnace slag (GGBS) and Silica Fume (SF) was used in this analysis. The Control cementitious specimens without fibre inclusion and with fibre addition in different volume fraction of binder, ranging from 0.5% to 3% were printed. The results showed that the fibre addition of 0, 0.5 and 1.0% have the better flowability and extrudability compared to 1.5, 2 and 3%. Also, reduction in the print quality was assessed visually with increasing fibre percentage. However, results indicated that the initial setting time is comparatively low for those mixes with higher fibre inclusion which is required for better bond strength between layers. Moreover, higher fibre content caused better buildability and shape retention in the extruded samples

Collapse of the world's largest herbivores

Large wild herbivores are crucial to ecosystems and human societies. We highlight the 74 largest terrestrial herbivore species on Earth (body mass ≥100 kg), the threats they face, their important and often overlooked ecosystem effects, and the conservation efforts needed to save them and their predators from extinction. Large herbivores are generally facing dramatic population declines and range contractions, such that ~60% are threatened with extinction. Nearly all threatened species are in developing countries, where major threats include hunting, land-use change, and resource depression by livestock. Loss of large herbivores can have cascading effects on other species including large carnivores, scavengers, mesoherbivores, small mammals, and ecological processes involving vegetation, hydrology, nutrient cycling, and fire regimes. The rate of large herbivore decline suggests that ever-larger swaths of the world will soon lack many of the vital ecological services these animals provide, resulting in enormous ecological and social costs

Measuring the Impacts of Community-based Grasslands Management in Mongolia's Gobi

We assessed a donor-funded grassland management project designed to create both conservation and livelihood benefits in the rangelands of Mongolia's Gobi desert. The project ran from 1995 to 2006, and we used remote sensing Normalized Differential Vegetation Index data from 1982 to 2009 to compare project grazing sites to matched control sites before and after the project's implementation. We found that the productivity of project grazing sites was on average within 1% of control sites for the 20 years before the project but generated 11% more biomass on average than the control areas from 2000 to 2009. To better understand the benefits of the improved grasslands to local people, we conducted 280 household interviews, 8 focus group discussions, and 31 key informant interviews across 6 districts. We found a 12% greater median annual income as well as a range of other socioeconomic benefits for project households compared to control households in the same areas. Overall, the project generated measurable benefits to both nature and people. The key factors underlying project achievements that may be replicable by other conservation projects include the community-driven approach of the project, knowledge exchanges within and between communities inside and outside the country, a project-supported local community organizer in each district, and strong community leadership

Striking a Balance: Socioeconomic Development and Conservation in Grassland through Community-Based Zoning

The goal of preserving nature is often in conflict with economic development and the aspirations of the rural poor. Nowhere is this more striking than in native grasslands, which have been extensively converted until a mere fraction of their original extent remains. This is not surprising; grasslands flourish in places coveted by humans, primed for agriculture, plantations, and settlements that nearly always trump conservation efforts. The Umgano grassland conservation and poverty reduction project in KwaZulu-Natal Province, South Africa uses community-based spatial planning to balance the conversion of its lower-conservation value grasslands to a timber plantation, while conserving higher-value grasslands for heritage purposes and managed livestock grazing. Ten years after project launch, we measured the ecological and socioeconomic impacts of the project using Normalized Differential Vegetation Index remote sensing data and over 500 household interviews, as compared with similar non-conserved areas. Zoned management of the Umgano area had resulted in between 9% and 17% greater average peak production in the grassland areas compared to control sites. There was also a 21% gain in incomes for the roughly one hundred people employed by the forestry efforts, when compared to others in their village. Community-based spatial zoning is an overlooked tool for balancing conservation and development but may require, as we found in Umgano, certain critical factors including strong local leadership, an accountable financial management mechanism to distribute income, outside technical expertise for the zoning design, and community support