While the emergent field of quantum thermodynamics has the potential to impact energy science, the performance of thermal machines is often classical. We ask whether quantum effects can boost the ...performance of a thermal machine to reach quantum supremacy, i.e., surpassing both the efficiency and power achieved in classical thermodynamics. To this end, we introduce a nonadiabatic quantum heat engine operating an Otto cycle with a many-particle working medium, consisting of an interacting Bose gas confined in a time-dependent harmonic trap. It is shown that thanks to the interplay of nonadiabatic and many-particle quantum effects, this thermal machine can outperform an ensemble of single-particle heat engines with same resources, demonstrating the quantum supremacy of many-particle thermal machines.
One consequence of climate change is the alteration of global water fluxes, both in amount and seasonality. As a result, the seasonal difference between dry- (p < 100 mm/month) and wet-season (p > ...100 mm/month) precipitation (p) has increased over land during recent decades (1980-2005). However, our analysis expanding to a 60-year period (1950-2009) showed the opposite trend. This is, dry-season precipitation increased steadily, while wet-season precipitation remained constant, leading to reduced seasonality at a global scale. The decrease in seasonality was not due to a change in dry-season length, but in precipitation rate; thus, the dry season is on average becoming wetter without changes in length. Regionally, wet- and dry-season precipitations are of opposite sign, causing a decrease in the seasonal variation of the precipitation over 62% of the terrestrial ecosystems. Furthermore, we found a high correlation (r = 0.62) between the change in dry-season precipitation and the trend in modelled net primary productivity (NPP), which is explained based on different ecological mechanisms. This trend is not found with wet-season precipitation (r = 0.04), These results build on the argument that seasonal water availability has changed over the course of the last six decades and that the dry-season precipitation is a key driver of vegetation productivity at the global scale.
Due to their high productivity in both crops and algae, tropical countries are likely to be the future world suppliers of feedstocks as well as biofuels such as biodiesel. In this work five ...feedstocks: palm, jatropha, microalgae, tallow and waste cooking oil were analyzed and compared using techno-economic and environmental criteria. For each feedstock, technological configurations currently used in the industry were taken into account (acid catalysis, basic catalysis and cogeneration). In this work, it was found that productivities for the basic catalyzed process were comparatively higher (1.010 kg biodiesel/kg crude oil), than those catalyzed by acid (0.85–0.95 kg biodiesel/kg crude oil). After the simulation of the selected processes, the lowest production costs were obtained for jatropha (USD 0.15/L, basic catalysis) and for waste cooking oils (USD 0.23/L, acid catalysis). The PEI (Potential Environmental Impact) generated for basic catalyzed process ranged from −0.04 to −0.09, while the acid catalyzed case −0.020 and −0.06 PEI per kg of product. The jatropha and microalgae oil using basic catalyzed configuration with energy cogeneration were the best process alternative from the environmental and economical points of view.
•Five different feedstocks and three technologies for biodiesel production are analyzed.•Biodiesel from basic catalysis has a higher yield than basic catalysis, but also higher production costs.•Production costs can be effectively reduced using residue-based cogeneration schemes.
Extreme weather events represent a large risk to food production systems. In this study, we evaluated the impacts of the 2011–2012 drought in Mexico, the worst in the last 70 years, on free-ranged ...livestock populations to link extreme weather events and production. We also considered the potential prevalence of recurring droughts under two contrasting future climate scenarios to examine what could happen over this century. Our results showed that cattle and goat stocks decreased about 3% in response to the drought countrywide. Regionally, the changes in cattle and goat populations generally mimicked the precipitation anomaly, with the strongest reductions across the driest areas in central and northern Mexico. Our work showed that the biophysical and management components of livestock production interact depending on the regions and the type of livestock, leading to a mosaic of spatial responses. It seems that the management of large herds limits the economic viability of drought crisis management options such as the importation of fodder and water, or by moving the animals to other pastures. Sheep herds were much less affected since more than 50% of the total sheep stock is raised in wetter states, which showed a relatively small (~ − 10%) precipitation anomaly during the drought. Under the severe climate change scenario, a greater frequency of extremely dry years (once every 3 years) would have negative impacts on livestock production regionally. Climate change together with already existing trends in overgrazing and soil erosion could further increase the sensitivity of livestock production across the country.
Graphical abstract
High-intensity hurricane disturbances have severe consequences on forest structure and functioning. Through wind force and heavy rainfall, they cause extensive canopy removal and an input of fine ...litter and woody debris well above normal levels. We examined litterfall
N
and
P
concentrations and fluxes before and after Hurricane Patricia (category 4) landfall in October 2015 in the seasonally dry tropical forest of the Chamela region, Jalisco, Mexico. Additionally, we compared the forest response to Patricia with those to Hurricane Jova (2011), from the Eastern North Pacific basin and to Hurricane Dean (2007) from the Atlantic basin. Nutrient concentrations in hurricane-induced litterfall in October 2015 were 2.2 times higher in leaf litter than in the woody fraction. Both litterfall
N
and
P
concentrations during the period November–February following the hurricane were generally higher than in similar periods in years previous to and after Patricia. Nutrient fluxes in October 2015 (75.9 kgN/ha and 3.6 kgP/ha) represented 55% (
N
) and 52% (
P
) of the total fluxes that year, which were much higher than those in any of the three years following the hurricane. These results suggest that forest biogeochemical resilience has changed in the short term. The annual litterfall
N
and
P
fluxes during the year of Hurricane Dean were lower than in 2011 and 2015, but similar to non-hurricane years. After Patricia, the annual
N
flux was higher, but the annual
P
flux lower than after Jova, and the former represents the largest annual
N
flux in our more than 25 years record.
Cattle populations are one of the most important global ecological drivers. The global cattle population tripled during the past century, leading to large impacts on nutrient cycling, greenhouse gas ...emissions and biodiversity loss. Nonetheless, their populations have not increased uniformly through the last seven decades (1961–2018), with large unexplained variation between years. We hypothesized a main driver for such fluctuation was climate variability and thus examined global and national level relationships between cattle population growth and precipitation anomalies for the period 1961–2017. We showed that the variation in the global cattle population growth rate was related to precipitation anomalies following a distinctive parabolic relationship, where extreme wetness or dryness decreased population growth. When the analysis was downscaled to the national level, we found the strength of such relationship to be determined by the background climate and management intensity. Countries in drier climates and with less intensive cattle management showed the largest susceptibility to extreme annual precipitation. We propose a general model to explain the relationship between precipitation extremes and cattle populations at multiple scales, based on ecological processes applicable to grazing systems.
Display omitted
•Global cattle population and climate dynamics were evaluated.•Extreme precipitation decreased global cattle numbers.•Cattle in dry countries was more sensitive to extremes.•High-intensity cattle management was less sensitive to extremes.•A general multi-scalar process is proposed.
Transient slab flattening beneath Colombia Wagner, L. S.; Jaramillo, J. S.; Ramírez‐Hoyos, L. F. ...
Geophysical research letters,
16 July 2017, Letnik:
44, Številka:
13
Journal Article
Recenzirano
Subduction of the Nazca and Caribbean Plates beneath northwestern Colombia is seen in two distinct Wadati Benioff Zones, one associated with a flat slab to the north and one associated with normal ...subduction south of 5.5°N. The normal subduction region is characterized by an active arc, whereas the flat slab region has no known Holocene volcanism. We analyze volcanic patterns over the past 14 Ma to show that in the mid‐Miocene a continuous arc extended up to 7°N, indicating normal subduction of the Nazca Plate all along Colombia's Pacific margin. However, by ~6 Ma, we find a complete cessation of this arc north of 3°N, indicating the presence of a far more laterally extensive flat slab than at present. Volcanism did not resume between 3°N and 6°N until after 4 Ma, consistent with lateral tearing and resteepening of the southern portion of the Colombian flat slab at that time.
Key Points
The flat slab beneath Colombia originally extended much farther south than it does today
Volcanic ages suggest that flattening began at ~9 Ma, with full arc cessation by ~6 Ma
Modern arc in the south was reestablished after 4 Ma during slab tearing and resteepening
PDF
