Population ecology and foraging theory can be combined to simulate the population dynamics of hunter-gatherers and their prey resources. Such simulation study is important to issues of conservation because many of the population processes that link human foragers and their prey occur over time scales that elude both ethnographic and archaeological fieldwork. To demonstrate, we used the model to examine hunter-gatherer population dynamics. We focused on a prey characteristic that affects its susceptibility to over-exploitation: the intrinsic rate of increase. r. We found that forager-prey systems can stabilize without intentional conservation behavior and that prey 'switching,' fall-back foods, and in certain circumstances, a higher r contribute to resource species persistence. Furthermore, a prey's vulnerability to local depletion or extinction may depend on the demographic characteristics of the suite of resources harvested along with it. The model can serve as a 'null hypothesis' for examining intentional resource conservation and presents points in concordance with, as well as divergent from, tenets in conservation biology. In particular, we discuss the implications of these findings for indigenous resource conservation in Amazonia (e.g., the overhunting of large primates and avifauna and the adoption of new procurement technologies) as well as the 'Pleistocene Overkill Hypothesis'.

Risk-sensitive analysis of subsistence adaptations is warranted when (i) outcomes are to some degree unpredictable and (ii) they have nonlinear consequences for fitness and/or utility. Both conditions are likely to be common among peoples studied by ecological anthropologists and archaeologists. We develop a general conceptual model of risk. We then review and summarize the extensive empirical literatures from biology and anthropology for methodological insights and for their comparative potential. Risk-sensitive adaptive tactics are diverse and they are taxonomically widespread. However, the anthropological literature rarely makes use of formal models of risk-sensitive adaptation, while the biological literature lacks naturalistic observations of risk-sensitive behavior. Both anthropology and biology could benefit from greater interdisciplinary exchange. © 1999 Plenum Publishing Corporation.

The use of discrete-time stochastic parameterization to account for model error due to unresolved scales in ensemble Kalman filters is investigated by numerical experiments. The parameterization quantifies the model error and produces an improved non-Markovian forecast model, which generates high quality forecast ensembles and improves filter performance. Results are compared with the methods of dealing with model error through covariance inflation and localization (IL), using as an example the two-layer Lorenz-96 system. The numerical results show that when the ensemble size is sufficiently large, the parameterization is more effective in accounting for the model error than IL; if the ensemble size is small, IL is needed to reduce sampling error, but the parameterization further improves the performance of the filter. This suggests that in real applications where the ensemble size is relatively small, the filter can achieve better performance than pure IL if stochastic parameterization methods are combined with IL.

We compare two approaches to the predictive modeling of dynamical systems from partial observations at discrete times. The first is continuous in time, where one uses data to infer a model in the form of stochastic differential equations, which are then discretized for numerical solution. The second is discrete in time, where one directly infers a discrete-time model in the form of a nonlinear autoregression moving average model. The comparison is performed in a special case where the observations are known to have been obtained from a hypoelliptic stochastic differential equation. We show that the discrete-time approach has better predictive skills, especially when the data are relatively sparse in time. We discuss open questions as well as the broader significance of the results.

Importance sampling algorithms are discussed in detail, with an emphasis on implicit sampling, and applied to data assimilation via particle filters. Implicit sampling makes it possible to use the data to find high-probability samples at relatively low cost, making the assimilation more efficient. A new analysis of the feasibility of data assimilation is presented, showing in detail why feasibility depends on the Frobenius norm of the covariance matrix of the noise and not on the number of variables. A discussion of the convergence of particular particle filters follows. A major open problem in numerical data assimilation is the determination of appropriate priors; a progress report on recent work on this problem is given. The analysis highlights the need for a careful attention both to the data and to the physics in data assimilation problems.

Conventional on-chip electrostatic discharge (ESD) protection structures for integrated circuits (ICs) rely on in-Si p-n-junction-based devices, which have many inherent disadvantages unsuitable for ICs at nanonodes. This letter reports a novel above-IC graphene-based nanoelectromechanical system (gNEMS) transient switch ESD protection mechanism and structure. Transmission line pulse testing shows dual-polarity transient ESD switching effect with a response time down to 200 ps. This gNEMS switch is a potential ESD protection solution to realize the above-Si ESD protection designs through 3-D integration in IC back end of line.

We report systematic transient characterization of a graphene ribbon (GR) used as an interconnect for electrostatic discharge (ESD) protection of future integrated circuits. A large set of GR wires (around 6000) with varying and practical dimensions were fabricated using the chemical vapor deposition method and characterized by transmission line pulsing (TLP) and very fast TLP (VFTLP) measurements. Comprehensive TLP and VFTLP testing with varying pulse rise time (tr) and duration (td) was performed across a wide temperature range ( T = -30/+110°C). Measurement-based statistics reveal the relationship between ESD capability of GR wires and the wire length (L), width (W), and number of graphene layers, as well as ESD pulse shapes and operation temperature.

Using a sample of 3.8 M ψ(2S) events accumulated with the BES detector, the process ψ(2S) →π+π-J/ψ is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the J/ψ-(π+π-) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter κ, predicts that D wave pions should be present. We determine κ=0.183 ±0.002±0.003 based on the joint mππ-cos θπ* distribution. The fraction of D wave amplitude as a function of mππ is found to decrease with increasing mππ, in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions. ©2000 The American Physical Society.

Radiative decays of the radially excited charmonium resonance, (Formula presented) into (Formula presented) (Formula presented) and (Formula presented) final states have been measured in a sample of (Formula presented) (Formula presented) events collected by the BES Collaboration. The branching ratios (Formula presented) and (Formula presented) are obtained. When compared to the corresponding radiative (Formula presented) decays, the observed (Formula presented) radiative decay rates into (Formula presented) and (Formula presented) are consistent with the prediction of the “12%” rule. © 2003 The American Physical Society.

The first measurement of (Formula presented) and an upper limit for (Formula presented) are determined from 22.3 (Formula presented) of (Formula presented) annihilation data at a c.m. energy of 4.03 GeV. The data were recorded by the Beijing Spectrometer (BES) at BEPC. A recoil charge method is applied to charm threshold data to determine the charge of the D meson in the recoil from (Formula presented) reconstructed (Formula presented) (Formula presented) mesons. The branching fractions (Formula presented) and (Formula presented) are determined from 10 events with a reconstructed D and a recoiling (Formula presented) In addition, a 90% C.L. upper limit of (Formula presented) is determined from a search for semileptonic decays of the (Formula presented) © 2000 The American Physical Society.