Carbon and nutrient losses during manure storage under traditional and improved practices in smallholder crop-livestock systems - evidence from Kenya

In the absence of mineral fertiliser, animal manure may be the only nutrient resource available to smallholder farmers in Africa, and manure is often the main input of C to the soil when crop residues are removed from the fields. Assessments of C and nutrient balances and cycling within agroecosystems or of greenhouse gas emissions often assume average C and nutrient mass fractions in manure, disregarding the impact that manure storage may have on C and nutrient losses from the system. To quantify such losses, in order to refine our models of C and nutrient cycling in smallholder (crop-livestock) farming systems, an experiment was conducted reproducing farmers’ practices: heaps vs. pits of a mix of cattle manure and maize stover (2:3 v/v) stored in the open air during 6 months. Heaps stored under a simple roof were also evaluated as an affordable improvement of the storage conditions. The results were used to derive empirical models and graphs for the estimation of C and nutrient losses. Heaps and pits were turned every month, weighed, and sampled to determine organic matter, total and mineral N, P and K mass fractions. Soils beneath heaps/pits were sampled to measure mineral N to a depth of 1 m, and leaching tube tests in the laboratory were used to estimate P leaching from manure. After 6 months, ca. 70% remained of the initial dry mass of manure stored in pits, but only half of or less of the manure stored in heaps. The stored manure lost 45% of its C in the open air and 69% under roof. The efficiencies of nutrient retention during storage varied between 24–38% for total N, 34–38% for P and 18–34% for K, with the heaps under a roof having greater efficiencies of retention of N and K. Laboratory tests indicated that up to 25% of the P contained in fresh manure could be lost by leaching. Results suggest that reducing the period of storage by, for example, more frequent application and incorporation of manure into the soil may have a larger impact on retaining C and nutrient within the farm system than improving storage condition

Going where the Ad leads you: On High Advertised Prices and Search where to buy

The search literature assumes that consumers know which firms sell products they are looking for, but are unaware of the particular variety and the prices at which each firm sells. In this paper, we consider the situation where consumers are uncertain whether a firm carries the product at all by proposing a model where in the first stage firms decide on whether or not to carry the product. Firms may advertise, informing consumers not only of the price they charge, but also of the basic fact that they sell the product. In this way, advertising lowers the expected search cost. We show that this role of advertising can lead to a situation where advertised prices are higher than non—advertised prices in equilibrium

Advertising and Consumer Search in a Duopoly Model

We consider a duopoly in a homogenous goods market where part of the consumers are ex ante uninformed about prices. Information can come through two different channels: advertising and sequential consumer search. The model is similar to that of Robert and Stahl (1993) with two major (and some minor) modifications: (i) a (small) percentage of consumers is fully informed and (ii) less informed consumers do not have to pay a search cost for buying at a firm from which they have received an ad. We derive the symmetric Nash equilibria and show that price dispersion is an essential ingredient of any equilibrium. Despite the similarities in the models, our results differ substantially from those obtained by Robert and Stahl (1993). First, advertising and search are "substitutes" for a large range of parameters. Second, there is no monotone relationship between prices and the degree of advertising. In particular, it is possible that high prices are advertised, while low prices are not. Third, when the cost of either one of the information channels (search or advertising) vanishes, the competitive outcome arises. Finally, both expected advertised and non-advertised prices are non-monotonic in search cost. One of the implications is that firms actually may benefit from consumers having low (rather than high) search costs

Autonomy in nursing homes:Viewpoints of residents with physical impairments and staff

Introduction: Although the importance of maintaining autonomy for nursing home residents is recognised, little is known about this process in daily practice. Aim: The aim was to explore how residents maintain autonomy and how staff acts in relation to the autonomy of residents. Method: Shadowing, a non-participative observational method, including a short interview at the end, was used. Seventeen residents with physical impairments living in two different nursing homes were shadowed in their own environment during daily activities. Moreover, fifteen staff members, working in the same nursing homes, were shadowed. Field notes of the shadowing were typed out and the recorded interviews were transcribed verbatim resulting in a report per respondent. These were coded and thematically analysed. Results: Residents maintained autonomy by; ‘being able to decide and/or execute decisions’, ‘active involvement’, ‘transferring autonomy to others’, ‘using preferred spaces’, ‘choosing how to spend time in daily life’ and ‘deciding about important subjects’. Four activities of staff were identified; ‚getting to know each older adult as a person and responding to her/his needs‘, ‚encouraging an older adult to self-care‘, ‚stimulating an older adult to make choices‘ and ‚being aware of interactions‘. Discussion and Conclusion: Maintaining autonomy requires effort from both residents and staff. Although most residents with physical impairments experience restrictions in their autonomy because of the care-environment they live in, residents seemed to maintain autonomy in daily life. Moreover, staff consider it important to strengthen the autonomy of residents and use different activities to enhance autonomy. Relevance for research and practice: These insights help to improve autonomy of nursing home residents because the perspectives of both residents and staff are included. Therefore, the next step is to transfer these insights towards nursing home practice in such a way that it enhances staff and older adults to better maintain autonom

Random Resistor-Diode Networks and the Crossover from Isotropic to Directed Percolation

By employing the methods of renormalized field theory we show that the percolation behavior of random resistor-diode networks near the multicritical line belongs to the universality class of isotropic percolation. We construct a mesoscopic model from the general epidemic process by including a relevant isotropy-breaking perturbation. We present a two-loop calculation of the crossover exponent $\phi$. Upon blending the $\epsilon$-expansion result with the exact value $\phi =1$ for one dimension by a rational approximation, we obtain for two dimensions $\phi = 1.29\pm 0.05$. This value is in agreement with the recent simulations of a two-dimensional random diode network by Inui, Kakuno, Tretyakov, Komatsu, and Kameoka, who found an order parameter exponent $\beta$ different from those of isotropic and directed percolation. Furthermore, we reconsider the theory of the full crossover from isotropic to directed percolation by Frey, T\"{a}uber, and Schwabl and clear up some minor shortcomings.Comment: 24 pages, 2 figure

Emergent structural correlations in dense liquids

The complete quantitative description of the structure of dense and supercooled liquids remains a notoriously difficult problem in statistical physics. Most studies to date focus solely on two-body structural correlations, and only a handful of papers have sought to consider additional three-body correlations. Here, we go beyond the state of the art by extracting many-body static structure factors from molecular dynamics simulations and by deriving accurate approximations up to the six-body structure factor via density functional theory. We find that supercooling manifestly increases four-body correlations, akin to the two- and three-body case. However, at small wave numbers, we observe that the four-point structure of a liquid drastically changes upon supercooling, both qualitatively and quantitatively, which is not the case in two-point structural correlations. This indicates that theories of the structure or dynamics of dense liquids should incorporate many-body correlations beyond the two-particle level to fully capture their intricate behavior.</p

Generalized mode-coupling theory for mixtures of Brownian particles

Generalized mode-coupling theory (GMCT) has recently emerged as a promising first-principles theory to study the poorly understood dynamics of glass-forming materials. Formulated as a hierarchical extension of standard mode-coupling theory (MCT), it is able to systematically improve its predictions by including the exact dynamics of higher-order correlation functions into its hierarchy. However, in contrast to Newtonian dynamics, a fully generalized version of the theory based on Brownian dynamics is still lacking. To close this gap, we provide a detailed derivation of GMCT for colloidal mixtures obeying a many-body Smoluchowski equation. We demonstrate that a hierarchy of coupled equations can again be established and show that these, consistent with standard MCT, are identical to the ones obtained from Newtonian GMCT when taking the overdamped limit. Consequently, the nontrivial similarity between Brownian and Newtonian MCT is maintained for our multicomponent GMCT. As a proof of principle, we also solve the generalized mode-coupling equations for the binary Kob-Andersen Lennard-Jones mixture undergoing Brownian dynamics and confirm the improved predictive power of the theory upon using more levels of the GMCT hierarchy of equations. </p

Cage Length Controls the Nonmonotonic Dynamics of Active Glassy Matter

Dense active matter is gaining widespread interest due to its remarkable similarity with conventional glass-forming materials. However, active matter is inherently out of equilibrium and even simple models such as active Brownian particles (ABPs) and active Ornstein-Uhlenbeck particles (AOUPs) behave markedly differently from their passive counterparts. Controversially, this difference has been shown to manifest itself via either a speedup, slowdown, or nonmonotonic change of the glassy relaxation dynamics. Here we rationalize these seemingly contrasting views on the departure from equilibrium by identifying the ratio of the short-time length scale to the cage length, i.e., the length scale of local particle caging, as a vital and unifying control parameter for active glassy matter. In particular, we explore the glassy dynamics of both thermal and athermal ABPs and AOUPs upon increasing the persistence time. We find that for all studied systems there is an optimum of the dynamics; this optimum occurs when the cage length coincides with the corresponding short-time length scale of the system, which is either the persistence length for athermal systems or a combination of the persistence length and a diffusive length scale for thermal systems. This new insight, for which we also provide a simple physical argument, allows us to reconcile and explain the manifestly disparate departures from equilibrium reported in many previous studies of dense active materials.</p

Corrigendum: The quest for EEG power band correlation with ICA derived fMRI resting state networks

Contains fulltext : 136233.pdf (publisher's version ) (Open Access)[This corrects the article on p. 315 in vol. 7, PMID: 23805098.].2 p