Internal Cycling Research Articles

Plasticity in nitrogen conservation strategy under C gain variation in annual and perennial Physaria (Brassicaceae)

Perennial plants have a greater reliance on internal cycling of nitrogen and are less influenced by external fluctuations of soil fertility than annuals. Despite their importance, the major mechanisms in which annuals and perennials differ in the way they couple nitrogen conservation strategies to imbalances in carbon economy are not fully understood. We characterized the functional mechanism by which Physaria (Brassicaceae) species differing in life cycle adjust nitrogen use efficiency and productivity, in response to variations in carbon gain (CO2 assimilation rate). We set up a field experiment with a split-plot design with two factors: species (2 annuals and 2 perennials) and incident radiation IR (100 % of IR – control, and 35 % of IR). Reduced photosynthesis (brought about by artificial shading) resulted in lower total biomass accumulation in all species. This reduction was linked to a differential plasticity in leaf traits (specific leaf area – SLA – and nitrogen pool) between annuals and perennials, and had different consequences for nitrogen conservation. Annuals showed a decrease in Nitrogen Use Efficiency (NUEleaf), and nitrogen conservation was dependent on carbon economy. Annuals also had higher nitrogen loss due to higher proportion of senescent leaves, and a decrease in resorption efficiency and proficiency, relative to control plants. Perennials kept NUEleaf stable, but the strategy was species-specific: on one hand shaded P. mendocina plants had conservative leaves (non-plastic and low SLA), lower leaf senescence and higher residence time in relation to control. On the other hand, Physaria pinetorum, a short-lived perennial, combined both strategies: greater nitrogen loss due to lower resorption and proficiency, low SLA, and lower leaf senescence under lower IR. These differences in quantity and quality of leaf litter may have consequences beyond the plant’s C and N economy, providing differences in functions such as soil N cycling and thus in ecosystem services.

Universal relation between thermodynamic driving force and one-way fluxes in a nonequilibrium chemical reaction with complex mechanism

In nonequilibrium chemical reaction systems, a fundamental relationship between unbalanced kinetic one-way fluxes and thermodynamic chemical driving forces is believed to exists. However this relation has been rigorously demonstrated only in a few cases in which one-way fluxes are well defined. In terms of its stochastic kinetic representation, we formulate the one-way fluxes for a general chemical reaction far from equilibrium, with arbitrary complex mechanisms, multiple intermediates, and internal kinetic cycles. For each kinetic cycle, the logarithm of the ratio of the steady-state forward and backward one-way fluxes is equal to the free energy difference between the reactants and products along the cycle. This fundamental relation is further established for general chemical reaction networks with multiple input and output complexes. Our result not only provides an equivalent definition of free energy difference in nonequilibrium chemical reaction networks, it also unifies the stochastic and macroscopic nonequilibrium chemical thermodynamics in a very broad sense.

Design, Installation, and Operation of a Heat-Integrated Distilled Water Pilot Plant with Internal Cooling Water Circulation Cycle

For hundreds of years, distilled water has been used in numerous important applications ranging from medicinal to steam ironing, but its production on pilot scale is still under research and development. Conventionally, pilot-scale water distillation units receive tap water and boil it to form vapors and then condensed the vapors to get distilled water. The cooling water to the condenser absorbs heat from condensing vapors and rejected as a hot water to drain. Thus, the amount of cooling water wasted at high temperature is significant. The design of a distilled water pilot plant that could minimize water wastage together with heat recovery is therefore needed. In this study, a pilot plant producing around 30 l/h of distilled water has been constructed so that part of hot tap water coming out from the condenser is sent to the boiler chamber. The other portion is cooled in a direct contact cooling tower with ambient air. A water makeup line is used to compensate water losses in the cooling tower. Process design calculations of major equipment were conducted, and the installation was carried out at our facility. The performance of individual equipment was carried out and found satisfactory. The quality of distilled water was checked and found meeting the international standards. The amount of tap water intake per kg of steam produced reduced significantly with a production efficiency of 92%. It is reported that the amount of water saved by using internal circulation line is significant.

AAIM Recommendations for the 2020-2021 Internal Medicine Residency Application Cycle in Response to the COVID-19 Pandemic

This statement was released in June 2020 by the Alliance for Academic Internal Medicine to provide guidance for the 2020-2021 residency application cycle in light of the COVID-19 pandemic. While many of the recommendations are specific to this cycle, others, such as the Department Summary Letter of Evaluation, are meant to be an enduring change to the internal medicine residency application process. AAIM realizes that some schools may not yet have the tools or resources to implement the template fully this cycle and look toward collaboration within the internal medicine education community to facilitate adoption in the cycles to come.

Future acidification of the Baltic Sea – A sensitivity study

Abstract Future acidification of coastal seas will depend not only on the development of atmospheric CO2 partial pressure (pCO2), but also on changes in the catchment areas, exchange with the adjacent ocean, and internal cycling of carbon and nutrients. Here we use a coupled physical-biogeochemical Baltic Sea model to quantify the sensitivity of pH to changes both in external forcing and internal processes. The experiments include changes in runoff, supply of dissolved inorganic carbon (DIC) and total alkalinity (AT), nutrient loads, exchange between the Baltic and North Seas, and atmospheric pCO2. We furthermore address the potential different future developments of runoff and river loads in boreal and continental catchments, respectively. Changes in atmospheric pCO2 exert the strongest control on future pH according to our calculations. This CO2-induced acidification could be further enhanced in the case of desalination of the Baltic Sea, although increased concentrations of AT in the river runoff due to increased weathering to some extent could counteract acidification. Reduced nutrient loads and productivity would reduce the average annual surface water pH but at the same time slightly increase wintertime surface water pH (the annual pH minimum). The response time of surface water pH to sudden changes in atmospheric pCO2 is approximately one month, whereas response times to changes in e.g. runoff and AT/DIC loads are more related to residence times of water and salt (>30 years). It seems unlikely that the projected future increase in atmospheric pCO2 and associated pH reduction could be fully counteracted by any of the other processes addressed in our experiments.

Temporal variability of dissolved trace metals at the DYFAMED time-series station, Northwestern Mediterranean

We present here results of an 18-month survey (July 2007–March 2009) of a suite of selected trace metals (TM: Co, Ni, Cu, Pb) in a 2350 m-deep offshore water column in the Ligurian Sea (Northwestern Mediterranean Sea). This low-nutrient low-chlorophyll region is characterised by a long stratification period (May–November) during which surface waters are depleted of macronutrients. Trace metals exhibit a range of biogeochemical behaviours from surface-enriched (scavenged-type) to surface-depleted (nutrient-like) with Co and Ni as representative cases. Cobalt (28–172 pM) distributions are governed by external inputs of aeolian dust deposition and removal by adsorption onto particles in surface, intermediate and deep waters as well. Nickel (3.57–5.52 nM) distributions are governed by internal biogeochemical cycles, together with physical mixing and circulation patterns. Nickel is primarily removed from surface waters with biogenic particles and then remineralised at depth. Copper (1.39–2.89 nM) distributions illustrate a mixture of the two typical behaviours mentioned above. Distributions of typically anthropogenic and particle-reactive Pb (82–235 pM) are in agreement with a Mediterranean flow source of Pb for the adjacent North Atlantic Ocean. The mechanisms controlling the biogeochemical cycling of TMs, such as atmospheric inputs, physical forcing, and interactions with primary production, are discussed according to the TM physico-chemical properties and biological importance.

Recognizing Allogenic Controls on the Stratigraphic Architecture of Ancient Alluvial Fans in the Western US

Alluvial fans are a significant part of the sediment routing system, forming distinctive steep, fan-shaped deposits of coarse-grained detritus where rivers lose flow velocity after exiting confined mountain drainages. Processes on the fan are influenced by both internal (autogenic) feedback cycles like channel avulsion and by external (allogenic) conditions such as climate and tectonics. These conditions in turn influence the stratigraphic architecture (i.e., the pattern of channel stacking and sizes) within the fan. Studying stratigraphic architecture of alluvial fans can, therefore, provide insight into controls on fan deposition. We employ UAV-based photogrammetric models to analyze the stratigraphic architecture of two well-exposed ancient alluvial fans in the western US – the Eocene Richards Mountain Conglomerate and the Cretaceous Echo Canyon Conglomerate. Both fans were deposited under relatively warm, wet climates and compressional tectonic regimes. We use a seven-fold hierarchy of bounding surfaces and associated lithosomes to describe alluvial fan architecture. First- through fourth-order surfaces and lithosomes represent bedform to channel-scale features influenced primarily by autogenic processes on the fan. Controls on fifth-order surfaces/lithosomes have historically been poorly understood, but probably represent fanhead trench migration and lobe construction. Sixth-order surfaces bound individual alluvial fans and seventh-order surfaces correspond to formation boundaries. These are controlled primarily by tectonics. The fifth-order architectural style of the deposits in our two study areas is significantly different and we use this difference to try to isolate a primary control on fifth-order alluvial architecture. Average width:height ratios of fifth-order lithosomes are nearly twice as high for Echo Canyon (112:1) than for Richards Mountain (64:1). This indicates that active channels on the Echo Canyon fan were more mobile than those on the Richards Mountain fan. We attribute this to a more seasonal climate and less vegetation during the deposition of the Echo Canyon Conglomerate. This would have increased lateral migration by destabilizing channels through increased sediment flux and flood events. Our results imply that fifth-order stratigraphic architecture of ancient alluvial fans may provide insight into allogenic processes related to paleoclimate. They also indicate risk of increased geologic hazards on alluvial fans where anthropogenic climate change increases future climate variability.

Bulk and Export Production Fluxes in the Gulf of Aqaba, Northern Red Sea

Marine particulate fluxes were studied between 2014 and 2017 in the oligotrophic Gulf of Aqaba (GOA), northern Red Sea. A bottom tethered mooring mounted with 5 sediment trap stations (KC Denmark Inc.) at approximately equal depth intervals between 120 and 570 m (water depth of ∼610 m) was rotated monthly. The bulk particulate fluxes were determined for the entire period, with organic C and N, CaCO3, and lithogenic fluxes determined for the first two and half years of the deployment. The results are evaluated in the context of monthly resolved records of seawater temperature, chlorophyll-a concentrations, and macro-nutrient concentrations, as well as hourly to weekly dust load records and rare fluvial events. The results are further compared to core-tops collected from varying water depths and are combined to produce a basin source-to-sink mass balance of particulate fluxes. The GOA undergoes strong seasonal changes expressed by surface water temperatures and water column stratification and mixing, which control the vertical and temporal distribution of nutrients and primary and export production. Accordingly, the seasonal variability in particulate fluxes varies over a wide range, typically displaying peak bulk fluxes in bottom waters during the winter (∼5–7 g m–2 d–1) and minimum values in shallow waters during summer (<0.5 g m–2 d–1). Organic C and N fluxes are the highest in shallow waters and display strong vertical attenuation that varies seasonally, a-priori reflecting enhanced remineralization in the warm shallow waters during summer. In contrast, particulate organic carbon and nitrogen fluxes are enhanced in bottom waters during winter, due to the combined effect of the increased presence of mineral ballasts and vertical water column mixing. The quantification of particulate fluxes in the GOA suggests that, while most of the bulk particulates are introduced into the basin via episodic fluvial events, with direct dust inputs contributing approximately an order of magnitude less material, the internal cycling of terrigenous material is complex, with a lag between the initial deposition of influxing material along shallow margins and seasonal reworking and transport of sediments to the deep seafloor. Nevertheless, the fluxes of terrigenous and organic particulates are largely independent of each other, with export production fluxes driven by water column mixing and nutrient availability in the photic zone. In addition to being the first quantitative report of bulk and export production fluxes in the region, our results provide an improved understanding of the interplay between export production and terrigenous fluxes as well as an interpretation of the paleo-record in the GOA and in comparable environments. On a wider scale, the findings reported here relate to the role of dust deposition and hemipelagic sedimentation in the oceans and their impact on export production and particle cycling in coastal regions. Combined, these findings illuminate the factors impacting marine habitats and ecosystems, the cycling and sequestration of trace elements and anthropogenic components in the oceans, and facilitate better understanding of the interplay between solid and dissolved phases in the oceans and reconstructing past oceanographic and climatic conditions from marine sediment cores.

Power generation as a useful option for flare gas recovery: Enviro-economic evaluation of different scenarios

Flaring of associated gas from oil wells and excess gas from gas processing units and oil refineries is one of the most critical resources of greenhouse gas emissions to the atmosphere. In addition to environmental impacts, burning flare gases having high heating value results in considerable economic losses. Considering the significant amount of gas flaring in Iran, much more attention should be given to flare gas recovery processes. In the current study, four power generation scenarios, including Gas Turbine Cycle, Combined Gas Turbine Cycle, Reciprocating Internal Combustion Engine Cycle, and Solid Oxide Fuel Cell/Gas Turbine Cycle are investigated in terms of economic and environmental performance, for flare gas recovery purposes. The performance evaluation of the mentioned scenarios was carried out using eight different flare gas samples from different resources in Iran, including four associated gas samples, two samples from the gas refinery, and two samples from the oil refinery plants. The results indicate that among the studied scenarios, RICE and SOFC/GT cycles have the best and worst economic performance, respectively. Samples having higher flowrates showed better economic performance compared to the others. In addition to flowrate, gas composition, i.e., the amount of H2S and H2 existing in flare gas could be determinative factors in the economic profitability of the scenarios. In terms of emission of the pollutants to the atmosphere, RICE showed the best performance among the evaluated scenarios.

Role of energy in technological dynamics

• Role of energy in economic transformations • Energy resources and their availability • Fossil fuels egemony • Quality of energy sources • Energy budget of the planet • Steady state economy • Efficiency in energy management • Renewable sources and their applications • Biofuels and synthetic biology • The nuclear dilemma Our planet is an open system, subject to an energy flux that favours the emergence of some complex structures, thanks to the support of internal cycles involving energy and matter transformations. The description of their alternance can be pursued through the narrative of their evolution, starting from simple activities, and then moving towards large scale systems, more complex and more connected. The interchanges occur through deep technological transformations, whose dynamics affected the economic development and different aspects of human history. In this framework the warning on the perils of climate changes due to the accumulation of carbon dioxide in the atmosphere, is evidencing the necessity of limiting their use, despite the implied enormous infrastructural changements.

Emerging role of dissolved organic nitrogen in supporting algal bloom persistence in Lake Taihu, China: Emphasis on internal transformations

Dissolved organic nitrogen (DON) accounts for a significant fraction of the dissolved nitrogen (N) pool in eutrophic lakes, and substantial components of DON are available for phytoplankton. However, long-term changes in DON concentrations in eutrophic lakes have been poorly documented, and the particulate-related internal cycling of DON at the molecular level remains unclear. In this study, changes in the concentration of DON during the past 14 years of Lake Taihu, China were analyzed. Algae and sediment suspensions were incubated under summer sunlight to examine transformations of DON (e.g., photodissolution) at the bulk concentration and molecular level. Concentrations of DON in Lake Taihu ranged from 0 to 4.59 mg L−1, with a mean of 0.82 ± 0.60 mg L−1 (n = 3360). Although annual averages of the concentration of DON (n = 240) showed no significant linear variation from 2005 to 2018, the percentage of DON in total dissolved nitrogen (TDN) increased linearly (p < .05) and was maintained at >50% after 2015. Seasonally, DON concentrations were highest in spring (1.10 ± 0.56 mg L−1), followed by winter (0.87 ± 0.58 mg L−1) and summer (0.54 ± 0.37 mg L−1) concentrations, and lowest in autumn (0.44 ± 0.38 mg L−1). Outdoor incubation experiments suggest that both algae and sediment suspensions contribute to significant increases of DON concentrations but contribute to decreases of inorganic N concentrations at the end of incubations. Moreover, the production of DON by algae suspensions differed from that of sediment suspensions, with more labile components released from algae (e.g., proteins and amino acids), while more refractory components were released from sediment suspensions (e.g., lignin with low H/C and O/C). Taken together, these results emphasize the increasing percentage of DON in TDN during 2009–2018 and the different patterns of algae- and sediment-dominated internal DON transformations in Lake Taihu.

Atmospheric deposition of elements and its relevance for nutrient budgets of tropical forests

Atmospheric deposition is an important component of the nutrient cycles of terrestrial ecosystems, but field measurements are especially scarce in tropical regions. In this study we analysed 15 months of precipitation chemistry collected in an old growth tropical forest located in French Guiana. We measured nutrient inputs via bulk precipitation and throughfall and used the canopy budget model to estimate nutrient fluxes via canopy exchange and dry deposition. Based on this method we quantified net fluxes of macronutrients and compared their contribution to internal cycling rates via litterfall. Our results suggest that while atmospheric deposition of nitrogen was relatively high (13 kg ha−1 year−1), and mainly in organic forms, the N inputs via litterfall were an order of magnitude higher. In contrast to nitrogen, we found that atmospheric deposition of phosphorus (0.5 kg ha−1 year−1) supplied up to one third of the annual litterfall input to the forest floor. Most strikingly, combined annual inputs of potassium via atmospheric deposition (14 kg ha−1 year−1) and canopy leaching (22 kg ha−1 year−1) were three times larger than internal nutrient recycling via litterfall (11 kg ha−1 year−1). We conclude that atmospheric deposition of phosphorus and especially potassium may play an important role in sustaining the productivity of this old-growth tropical rainforest.

Comparative study on the series, parallel and cascade cycles of a multi-mode room temperature magnetic refrigeration system

Abstract Magnetic refrigeration has been investigated as an appropriate alternative for vapor-compression refrigeration to reduce the greenhouse effect. However, the commercialization process of MR is obstructed by the inadequate cooling condition. In this paper, a multi-mode MR system with series, parallel and cascade cycle modes is constructed. The optimal utilization factors, internal cycle mechanisms and refrigeration characteristics of three modes are compared. The magnetocaloric material used is 277.4 g of gadolinium, and two NbFeB permanent magnets are assembled to provide a maximum magnetic field intensity of 1.5 T. The results show that different modes affect the MR system performance. The series mode increases the temperature span by increasing the length of the regeneration zone. The parallel mode improves the cooling power owing to the simultaneous output of double regenerators. The novel cascade cycle constructs the higher- and lower- temperature regeneration stages, which are effectively utilized to provide a large temperature span and suitable cooling power. The obtained no-load temperature spans are 5.66 K, 4.16 K and 7.35 K in the series, parallel and cascade cycles, respectively, and the corresponding maximum specific cooling powers are 29.02, 39.47 and 34.79 W/kg. Compared with the parallel mode, the cycle characteristics of the series and cascade modes receive a greater degree of investigation. The series mode shows a larger potential for large-temperature-span output system, and the cascade cycle is most likely to meet both the temperature span and cooling power output requirements simultaneously. The results provide some guidelines for the design of magnetic refrigeration prototypes.

Drivers of Oyster Reef Ecosystem Metabolism Measured Across Multiple Timescales

Oxygen flux measurements between oyster reefs and the overlying water column approximate total ecosystem metabolism, representing a potentially valuable reef monitoring tool. In this study, seasonal oxygen flux measurements were made over an intertidal Crassostrea virginica oyster reef on the Virginia (USA) coast using the non-invasive aquatic eddy covariance (AEC) technique. Reef respiration (R) ranged from − 276 mmol m−2 day−1 in the summer to − 55 mmol m−2 day−1 in the winter, likely due to temperature effects on oyster filtering and sediment microbial activity. Reef gross primary production (GPP) varied less seasonally, resulting in net ecosystem metabolism (NEM) that was highly heterotrophic in the summer (− 141 mmol m−2 day−1) and nearly balanced in the winter (− 11 mmol m−2 day−1). Measurements of reef sediment chl a indicated higher concentrations of benthic microalgae than surrounding bare mudflat, while photosynthesis-irradiance curves utilizing 15-min flux averages confirmed light as a dominant short-term driver of microalgal production. Metabolic values were compared with past AEC results from this reef, creating a 4-year record that included a significant oyster die-off. Over this time span, R was closely coupled to GPP, indicating rapid internal cycling of carbon, while reef primary production was primarily attributed to sediment, rather than epiphytic, microalgae. Both R and GPP substantially decreased following the oyster die-off. These results illustrate that oyster reefs are highly dynamic environments, with complex processes that act on numerous time scales ranging from minutes to years. Consequently, AEC metabolism measurements can aid in oyster reef monitoring.

Grazing regulation of phosphorus cycling in grassland ecosystems: Advances and prospects

Grassland ecosystems, which cover a total area of 52.5 million square kilometers and account for 40.5% of the global land surface, are the largest biomes in the world. Grazing is the most dominant and direct land use type in grasslands and a predominant driver regulating multiple ecosystem functions and services, such as primary production, nitrogen (N) and phosphorus (P) cycling, carbon sequestration, forage and food production, and water and soil erosion control etc. Many studies have demonstrated that primary production of grasslands is often limited by water, N and P availability, which interact with grazing to influence the maintenance of ecosystem functions and services. However, compared with numerous studies on the effects of grazing on N cycling and plant water use, fewer studies have explored how grazing influence P cycling of grasslands, particularly the internal cycling of P among main pools within ecosystems. Here we reviewed the advances in grazing effects on soil and plant P pools and biological processes of P cycling. Our review is mainly focused on: (1) Grazing effects on internal and external cycles of P in grassland ecosystems; (2) grazing effects on soil P vertical distribution, and P inputs and outputs mediated by soil erosion and spatial heterogeneity; and (3) mechanisms underlying grazing-induced changes in plant P content and P pools across different levels of organization (individual, species, functional group and community). Finally, we proposed a unified framework synthesizing the influence of grazing on P pools and key biological processes of P cycling in grassland ecosystems. We also proposed eight key questions that need to be addressed in future studies: (1) How do the dominant P forms (e.g., nucleic acids, phospholipids, cytoplasmic inorganic P, cytoplasmic organic P, and polyphosphate) and concentration within soil microbial biomass vary with grazing intensity? How does the role of microorganisms as sink and source of P change with increasing grazing intensity? (2) How does grazing affect enzyme activities, including phosphomonoesterases, phosphodiesterases, triphosphoric monoester hydrolases, and enzymes acting on phosphoryl-containing anhydrides and on P–N bonds, and thereby P mineralization in soil? (3) How does grazing regulate the biological processes of P transformation in plant-soil-microbial P cycle? (4) To what degree molecular approaches and omics analyses can improve our understanding of the important role of plants and rhizosphere microorganisms in P cycling? (5) How does grazing affect the relationship between plant diversity and arbuscular mycorrhizal fungi (AMF) diversity, and thereby plant P uptake and utilization? (6) How do grazing animals differ in their effects on the pools and pathways of P cycling due to the interspecific differences in diet and foraging preference? (7) How do other herbivores in terms of grasshoppers, rodents, earthworms, and plant feeding nematodes influence the biological processes of P cycling? (8) How does grazing affect the N:P stoichiometry of key ecosystem compartments, and hence the coupled N and P cycles.

Viabilidade econômica para a geração de energia elétrica a partir do biogás produzido em estação de tratamento de esgoto

Objetivo do estudo: apresentar a análise dos dados coletados referentes às características de esgoto afluente da Estação de Tratamento de Esgoto Serraria, em Porto Alegre/RS.Metodologia / abordagem: pesquisa descritiva com abordagem quantitativa e centralizada no estudo de caso da exploração de biogás gerada para produção de energia elétrica.Originalidade/relevância: este estudo concentra-se na viabilidade técnica e econômica para a geração de eletricidade a partir de efluente de biogás para uso na própria estação, atendendo a maioria das cargas locais, e também, da tecnologia de conversão de energia empregada a partir do ciclo de combustão interna Otto, com seus acessórios.Principais resultados: os custos de instalação, operação e manutenção por cinco anos estão estimados em torno de R$ 4.500.000,00. Além disso, o retorno sobre o capital investido ocorre, no máximo, em 4 anos e 7 meses.Contribuições teóricas / metodológicas: há uma tendência de aumento da eletricidade a partir da tarifa da rede e do fluxo de insumos nos UASBs, tornando a autogeração ainda mais viável. Atualmente, o biogás é queimado e o lodo gerado é depositado em aterros sanitários, o que possibilita a produção de energia elétrica e fornecimento à rede de distribuição.Conclusão: as usinas de estação de tratamento de esgoto constituídas de depósito de lodo anaeróbio de fluxo ascendente seguida de lodos ativos têm como objetivo o tratamento de efluentes, isto é, promover a separação dos gases, sólidos e líquidos como forma de tratamento sustentável e, além disso, proporcionar benefícios e recursos sustentáveis para a sociedade.

Mathematical Representation of Clausius’ and Kelvin’s Statements of the Second Law and Irreversibility

We provide a stochastic mathematical representation for Clausius' and Kelvin-Planck's statements of the Second Law of Thermodynamics in terms of the entropy productions of a finite, compact driven Markov system and its lift. A surjective map is rigorously established through the lift when the state space is either a discrete graph or a continuous n-dimensional torus T^n. The corresponding lifted processes have detailed balance thus a natural potential function but no stationary probability. We show that in the long-time limit the entropy production of the finite driven system precisely equals the potential energy decrease in the lifted system. This theorem provides a dynamic foundation for the two equivalent statements of Second Law of Thermodynamics, a la Kelvin's and Clausius'. It suggests a modernized, combined statement: "A mesoscopic engine that works in completing irreversible internal cycles statistically has necessarily an external effect that lowering a weight accompanied by passing heat from a warmer to a colder body."

Method for calculating material balance of complex process flowcharts

When developing, analyzing, and optimizing chemical production technologies, one should first calculate the material and heat balances in order to quantify the products and wastes produced, the reagents and energy consumed, as well as to determine characteristics of equipment required. Thus, balance calculation helps to perform primary analysis of technology feasibility and to obtain initial data for estimation of capital and operational costs. Calculating material balance for the series-connected apparatus working in a steady-state mode is a trivial problem. For the process flowcharts with branching and recycled flows, however, calculations get more complicated. Iterative method of calculation with termination of iterations when convergence condition is met is frequently used to calculate the material balance of flowcharts with recycled flows. This method has several limitations, namely the increase in computational time, iterative accumulation of errors, possible oscillations of solution, etc. In complex flowcharts, branching and recycled flows often lead to internal cycles. For this reason, the more complex is the flowchart, the stronger is the influence of iterative method limitations that are mentioned above. This work is aimed to validate and improve material balance calculation for complex chemical process flowcharts with branching and recycled flows. We introduce the analytical solution instead of iterative algorithm used to perform such calculations and propose methods for convolution of straight, branched, and cycled segments of these flowcharts.

The C:N:P Stoichiometry of Planted and Natural Larix principis-rupprechtii Stands along Altitudinal Gradients on the Loess Plateau, China

Carbon:nitrogen:phosphorus (C:N:P) stoichiometry plays a critical role in nutrient cycling, biodiversity, and ecosystem functionality. However, our understanding of the responses of C:N:P stoichiometry to elevation and forest management remains elusive. Here we sampled 18 Larix principis-rupprechtii sites along altitudinal gradients (1700-2300 m) on Guandishan Mountain in the Loess Plateau, China. We determined the leaf, litter, and soil C N P contents and C:N:P stoichiometric ratios, as well as nutrient resorption efficiency (NuRE), and diameter at breast height (DBH) increments in both planted and natural stands, and then tested the impacts of elevation and stand origin on these parameters’ management. We found different C:N:P stoichiometry between natural and planted forests. The results revealed that: soil C, N, and N:P ratios, litter C:P and N:P ratios, leaf C:N and N:P ratios increased significantly; however, soil C:N ratios, litter P, leaf N and P, nitrogen resorption efficiency (NRE), and DBH increments decreased significantly with elevation in the planted forests. Soil C,N and N:P ratios, litter C, as well as C:N and C:P ratios increased significantly with elevation in natural forests. The soil N, P and N:P ratios, litter C:P and N:P ratios, leaf C, C:P and N:P ratios, nitrogen resorption efficiency (NRE), phosphorus resorption efficiency (PRE), and DBH increments were, on average, higher in the planted, rather than natural forests. Our results indicated that there was an enhancing P-limitation in both the planted and natural forests, and the plantations were more restricted by P. Moreover, compared to natural forests, plantations converged toward a higher conservative N- and P-use strategy by enhancing resorption efficiencies of internal nutrient cycling and a higher annual growth rate.

Flash/distillation for separating 2-pentanone/4-heptanone/water azeotropic mixture based equilibrium data and process design

4-heptanone and 2-Pentanone are promising organic solvents due to their high thermal stability. Due to the lack of binary interaction parameters between 4-heptanone and 2-Pentanone, the vapour-liquid equilibrium experiment is measured for 4-heptanone and 2-Pentanone in this work. The binary interaction parameters are obtained by UNIQUAC model, Wilson model and NRTL model regression. Based on the heterogeneous characteristics of the system, two kinds of steady-state processes are designed. Based on the minimum annual cost, TAC, carbon emissions and thermodynamic efficiency of the corresponding steady-state process were calculated, and for different feeding ways were compared. In addition, the internal cycle dynamic control (basic control structure and dual temperature control structure) are explored. The anti-disturbance performance of the system is detected by introducing 5% the feed disturbance. The result shows that the dual temperature control structure has a good anti-disturbance ability in the face of feed and composition disturbance. The interaction parameters obtained by experimental regression provide a theoretical basis for the design of steady-state process. Flash/distillation technology provides guidance for industrial purification of 2-pentanone/4-heptanone.