Energy benefits and emergent space use patterns of an empirically parameterized model of memory-based patch selection

Many species frequently return to previously visited foraging sites. This bias towards familiar areas suggests that remembering information from past experience is beneficial. Such a memory-based foraging strategy has also been hypothesized to give rise to restricted space use (i.e. a home range). Nonetheless, the benefits of empirically derived memory-based foraging tactics and the extent to which they give rise to restricted space use patterns are still relatively unknown. Using a combination of stochastic agent-based simulations and deterministic integro-difference equations, we developed an adaptive link (based on energy gains as a foraging currency) between memory-based patch selection and its resulting spatial distribution. We used a memory-based foraging model developed and parameterized with patch selection data of free-ranging bison Bison bison in Prince Albert National Park, Canada. Relative to random use of food patches, simulated foragers using both spatial and attribute memory are more efficient, particularly in landscapes with clumped resources. However, a certain amount of random patch use is necessary to avoid frequent returns to relatively poor-quality patches, or avoid being caught in a relatively poor quality area of the landscape. Notably, in landscapes with clumped resources, simulated foragers that kept a reference point of the quality of recently visited patches, and returned to previously visited patches when local patch quality was poorer than the reference point, experienced higher energy gains compared to random patch use. Furthermore, the model of memory-based foraging resulted in restricted space use in simulated landscapes and replicated the restricted space use observed in free-ranging bison reasonably well. Our work demonstrates the adaptive value of spatial and attribute memory in heterogeneous landscapes, and how home ranges can be a byproduct of non-omniscient foragers using past experience to minimize temporal variation in energy gains

Teams between Neo-Taylorism and Anti-Taylorism

The concept of teamworking is the product of two distinct developments. One: a neo- Tayloristic form of organization of work, of which Toyota has shown that it can be very profitable, was packaged and reframed to make it acceptable to the Western public. Two: anti-Tayloristic ways of organizing work, inspired by ideals of organizational democracy, were relabeled to make these acceptable to profit-oriented managers. Drawing on empirical research in Scandinavia, Germany, The Netherlands and the UK, as well as on published case studies of Japanese companies, the paper develops a neo-Tayloristic and an anti-Tayloristic model of teamworking. Key concerns in the teamworking literature are intensification of work and the use of shop floor autonomy as a cosmetic or manipulative device. Indeed, all the features of neo-Tayloristic teamworking are geared towards the intensification of work. However, one of the intensification mechanisms, the removal of Tayloristic rigidities in the division of labor, applies to anti-Tayloristic teamworking as well. This poses a dilemma for employee representatives. In terms of autonomy, on the other hand, the difference between neo-Tayloristic and anti-Tayloristic teamworking is real. In anti-Tayloristic teamworking, there is no supervisor inside the team. The function of spokesperson rotates. All team members can participate in decision-making. Standardization is not relentlessly pursued; management accepts some measure of worker control. There is a tendency to alleviate technical discipline, e.g. to find alternatives for the assembly line. Buffers are used. Remuneration is based on proven skill level; there are no group bonuses. In contrast, in neo-Tayloristic teamworking, a permanent supervisor is present in the team as team leader. At most, only the team leader can participate in decision-making. Standardization is relentlessly pursued. Management prerogatives are nearly unlimited. Job designers treat technical discipline, e.g. short-cycled work on the assembly line, as unproblematic. There are no buffers. A substantial part of wages consists of individual bonuses based on assessments by supervisors on how deeply workers cooperate in the system. Group bonuses are also given. The instability and vulnerability of anti-Tayloristic teamworking imply that it can only develop and flourish when managers and employee representatives put determined effort into it. The opportunity structure for this contains both economic and political elements. In mass production, the economic success of Toyota, through skillful mediation by management gurus, makes the opportunity structure for anti-Tayloristic teamworking relatively unfavorable

Food System Resilience: Concepts, Issues, and Challenges

Food system resilience has multiple dimensions. We draw on food system and resilience concepts and review resilience framings of different communities. We present four questions to frame food system resilience (Resilience of what? Resilience to what? Resilience from whose perspective? Resilience for how long?) and three approaches to enhancing resilience (robustness, recovery, and reorientation—the three “Rs”). We focus on enhancing resilience of food system outcomes and argue this will require food system actors adapting their activities, noting that activities do not change spontaneously but in response to a change in drivers: an opportunity or a threat. However, operationalizing resilience enhancement involves normative choices and will result in decisions having to be negotiated about trade-offs among food system outcomes for different stakeholders. New approaches to including different food system actors’ perceptions and goals are needed to build food systems that are better positioned to address challenges of the future. Expected final online publication date for the Annual Review of Environment and Resources, Volume 47 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates

Upconversion and energy transfer modeling in Er, Yb : CaYAlO4

This paper models the mechanism of upconversion and energy transfer between Er and Yb ions in diode-pumped Er, Yb : CaYAlO4 crystal. Rate equations are used for modeling and are solved numerically for the populations of different levels as a function of time. Many input parameters are measured experimentally and the rest of the parameters are predicted from the model. Population inversion is studied for these transitions in Er : [MATH

Second Preimages on n-Bit Hash Functions for Much Less than 2n Work

Abstract. We expand a previous result of Dean [Dea99] to provide a second preimage attack on all n-bit iterated hash functions with Damg˚ard-Merkle strengthening and n-bit intermediate states, allowing a second preimage to be found for a 2 k-message-block message with about k × 2 n/2+1 +2 n−k+1 work. Using RIPEMD-160 as an example, our attack can find a second preimage for a 2 60 byte message in about 2 106 work, rather than the previously expected 2 160 work. We also provide slightly cheaper ways to find multicollisions than the method of Joux [Jou04]. Both of these results are based on expandable messages–patterns for producing messages of varying length, which all collide on the intermediate hash result immediately after processing the message. We provide an algorithm for finding expandable messages for any n-bit hash function built using the Damg˚ard-Merkle construction, which requires only a small multiple of the work done to find a single collision in the hash function.

Conservation planning in spatially and temporally dynamic marine environments

Pelagic ecosystems provide a significant and vital component of the ocean’s productivity and biodiversity. They are also heavily exploited and are currently the focus of numerous ecosystem-based management exercises. Over the past ten years there has been increasing enthusiasm for marine protected areas (MPAs) as a tool for pelagic conservation. However, there remains almost a complete absence of systematic conservation planning in the pelagic realm, both within exclusive economic zones and the high seas. Here we demonstrate the use of a decision support system to guide the implementation of MPAs that consider the physical and biological dynamics typical of the pelagic realm, and propose a method for integrative planning for pelagic and benthic conservation in the Southern Benguela ecosystem. Our approach was to maximize the representation of threatened species and key fisheries species within MPAs closed to fishing. In addition to representation, we consider MPA design to address the dynamics of the system using time series data of key oceanographic characteristics and abundance of small pelagic fish. We also discuss problems associated with offshore conservation, where the features of interest are ephemeral and dynamic. Our approach explicitly involves stakeholders and we incorporate socio-economic data into decision support tools

XMSS -- A practical forward secure signature scheme based on minimal security assumptions

We present the hash-based signature scheme XMSS. It is the first provably (forward) secure and practical signature scheme with minimal security requirements: a pseudorandom and a second preimage resistant (hash) function family. Its signature size is reduced to less than 25 % compared to the best provably secure hash based signature scheme

New proofs for NMAC and HMAC: Security without collision-resistance

HMAC was proved in [3] to be a PRF assuming that (1) the underlying compression function is a PRF, and (2) the iterated hash function is weakly collision-resistant. However, recent attacks show that assumption (2) is false for MD5 and SHA-1, removing the proof-based support for HMAC in these cases. This paper proves that HMAC is a PRF under the sole assumption that the compression function is a PRF. This recovers a proof based guarantee since no known attacks compromise the pseudorandomness of the compression function, and it also helps explain the resistance-to-attack that HMAC has shown even when implemented with hash functions whose (weak) collision resistance is compromised. We also show that an even weaker-than-PRF condition on the compression function, namely that it is a privacy-preserving MAC, suffices to establish HMAC is a secure MAC as long as the hash function meets the very weak requirement of being computationally almost universal, where again the value lies in the fact that know