Simple Quantitative Rules Research Articles

Predictability of the community-function landscape in wine yeast ecosystems.

Predictively linking taxonomic composition and quantitative ecosystem functions is a major aspiration in microbial ecology, which must be resolved if we wish to engineer microbial consortia. Here, we have addressed this open question for an ecological function of major biotechnological relevance: alcoholic fermentation in wine yeast communities. By exhaustively phenotyping an extensive collection of naturally occurring wine yeast strains, we find that most ecologically and industrially relevant traits exhibit phylogenetic signal, allowing functional traits in wine yeast communities to be predicted from taxonomy. Furthermore, we demonstrate that the quantitative contributions of individual wine yeast strains to the function of complex communities followed simple quantitative rules. These regularities can be integrated to quantitatively predict the function of newly assembled consortia. Besides addressing theoretical questions in functional ecology, our results and methodologies can provide a blueprint for rationally managing microbial processes of biotechnological relevance.

Winners Repeat, Losers Repeat

I present a tactical asset allocation proof-of-concept portfolio. It is intended to harvest the non-IID statistical attributes of stocks, bonds, commodities, and currencies, both domestic and international. It has as its objective to benefit from markets’ propensity to trend from month to month and during both bull and bear market environments. The proof-of-concept portfolio relies on a simple quantitative rule that allows for rigorous evaluation over the past 102.1 years. The results presented herein suggest that Tactical Asset Allocation (TAA) is an approach worthy of consideration. Moreover, the article suggests that a necessary condition for TAA success lies in correctly specifying its rather differentiated investment objective—one that may be unrelated to comparisons with popular fixed-weight index benchmarks. Such fixed-weight benchmarks have correlations with TAA strategies that are so low as to make commonly used statistical comparisons irrelevant (i.e., not statistically significant). This article attempts to correct our industry’s mischaracterization and overpromising of all things TAA by focusing on the time required for success.

Analyzing the Proposed Reconfiguration of Accident‐and‐Emergency Facilities in England

The Keogh Report of 2013 proposed a major reconfiguration of the accident and emergency (A&E) system under National Health Service (NHS) England to improve service. The proposed reconfiguration includes centralized facilities with multiple specialties as well as small local minor‐injury facilities. We use stylized queuing models to analyze cost and service implications of the proposed reconfiguration. We find that increasing numbers of specialty patients that require admission to hospital makes splitting off specialty A&Es from general ones more attractive. The same applies for patients with minor injuries. Our work generally supports the reconfiguration recommended in the Keogh report but with some fine‐tuning: For instance, a merger of A&Es (pooling) does not always make sense even though it increases patient numbers when the patients in the two A&Es are of different types. We provide simple quantitative rules to indicate whether the proposed reconfiguration could lower costs in any particular region of the country. The results here are consistent with some NHS England providers attempting specialty A&Es for geriatric patients and mobile drunkenness treatment centers on weekends. Our rules and approach can be useful for identifying candidate reconfiguration opportunities not only for NHS England but also for any other context where pooling and arrival heterogeneity are important considerations.

Improvement of terahertz field effect transistor detectors by substrate thinning and radiation losses reduction.

Phenomena of the radiation coupling to the field effect transistors based terahertz (THz) detectors are studied. We show that in the case of planar metal antennas a significant portion of incoming radiation, instead of being coupled to the transistors, is coupled to an antenna substrate leading to responsivity losses and/or cross-talk effects in the field effect based THz detector arrays. Experimental and theoretical investigations of the responsivity versus substrate thickness are performed. They clearly show how to minimize the losses by the detector/ array substrate thinning. In conclusion simple quantitative rules of losses minimization by choosing a proper substrate thickness of field effect transistor THz detectors are presented for common materials (Si, GaAs, InP, GaN) used in semiconductor technologies.

Research on Energy Value of Dynamic Energy Budget

Dynamic Energy Budget software aims to identify simple quantitative rules for the organization of metabolism of individual organisms. It is always used to delineate reserves, as separate from structure. The energy density of Eriocheir sinensis was studied through DEB software in this paper. The results showed that Hepatopancreas energy density (32.17±3.77 KJ/g) was higher than gonad (23.19±2.86KJ/g), muscle (24.41±1.41 KJ/g) and carapace energy density (14.42±1.76 KJ/g). The difference between gonad (23.19±2.86KJ/g) and muscle energy density (4.41±1.41 KJ/g) of females and males was significant (P < 0.01), but not between muscle and carapace energy density (P > 0.05), and no difference between female and male individual in total energy (P = 0.887) at the stable stage. The linear relation between volume and weight of Eriocheir sinensis was gained by using regression analysis, V=6.104+1.117WW (R2=0.973, n=98), and the linear relation between total energy and dry weight was also gained, E=18.12DW-28.05 (R2=0.962 ,n=24).

Optimal Corporate Investment and Financing Policies: A Simple Quantitative Rule in a Novel General Setting

We aim at obtaining a simple quantitative rule for the joint determining of optimal corporate investment and financing policies in an intertemporal setting. A novel general continuous-time framework, inspired by the optimal portfolio design literature, is first built. We derive the optimal assets-to-equity and debt-to-equity ratios. Novel principles - driven by speculation and hedging motives - for the corporate decision-making process are exposed. The rule is then simplified to offer an easily obtainable quantitative benchmark for the firm’s manager. We eventually show how the proposed behavior can be applied in practice.

Genetic structure of a foundation species: scaling community phenotypes from the individual to the region

Understanding the local and regional patterns of species distributions has been a major goal of ecological and evolutionary research. The notion that these patterns can be understood through simple quantitative rules is attractive, but while numerous scaling laws exist (e.g., metabolic, fractals), we are aware of no studies that have placed individual traits and community structure together within a genetics based scaling framework. We document the potential for a genetic basis to the scaling of ecological communities, largely based upon our long-term studies of poplars (Populus spp.). The genetic structure and diversity of these foundation species affects riparian ecosystems and determines a much larger community of dependent organisms. Three examples illustrate these ideas. First, there is a strong genetic basis to phytochemistry and tree architecture (both above- and belowground), which can affect diverse organisms and ecosystem processes. Second, empirical studies in the wild show that the local patterns of genetics based community structure scale up to western North America. At multiple spatial scales the arthropod community phenotype is related to the genetic distance among plants that these arthropods depend upon for survival. Third, we suggest that the familiar species-area curve, in which species richness is a function of area, is also a function of genetic diversity. We find that arthropod species richness is closely correlated with the genetic marker diversity and trait variance suggesting a genetic component to these curves. Finally, we discuss how genetic variation can interact with environmental variation to affect community attributes across geographic scales along with conservation implications.

A Note on the Local Current Associated with the Rising Phase of a Propagating Impulse in Nonmyelinated Nerve Fibers

To extend our recent paper dealing with the cable properties and the conduction velocity of nonmyelinated nerve fibers (Bull. Math. Biol. 64, 1069; 2002), the behavior of the local current associated with the rising phase of a propagating action potential is discussed. It is shown that the process of charging the membrane capacity by means of the local current plays a crucial role in determining the velocity of nerve conduction. The symmetry of the local current with respect to the boundary between the resting and active regions of the nerve fiber is emphasized. It is noted that there are several simple quantitative rules governing the intensities of the capacitive, resistive and total membrane currents observed during the rising phase of an action potential.

The receptor concept: pharmacology's big idea.

Chemical signalling is the main mechanism by which biological function is controlled at all levels, from the single cell to the whole organism. Chemical recognition is the function of receptors, which, in addition to recognising endogenous chemical signals, are also the target of many important experimental and therapeutic drugs. Receptors, therefore, lie at the heart of pharmacology. This article describes the way in which the receptor concept originated early in the 20th century, and evolved through a highly innovative stage of quantitative theory based on chemical kinetics, to the point where receptors were first isolated and later cloned, until we now have a virtually complete catalogue of all the receptors present in the genome. Studies on signal transduction are revealing great complexity in the events linking ligand binding to the physiological or therapeutic response. Though some simple quantitative rules of 'receptor theory' are still useful, the current emphasis is on unravelling the pathways that link receptors to responses, and it will be some time before we know enough about them to embark on the next phase of 'receptor theory'.

Fe clusters on Ni and Cu: size and shape dependence of the spin moment

We present ab-initio calculations of the electronic structure of small Fe clusters (1–9 atoms) on Ni(001), Ni(111), Cu(001) and Cu(111) surfaces. Our focus is on the spin moments and their dependence on cluster size and shape. We derive a simple quantitative rule that relates the moment of each Fe atom linearly to its coordination number. Thus, for an arbitrary Fe cluster the spin moment of the cluster and of the individual Fe atoms can be readily found if the positions of the atoms are known.

Quantitative aspects of metabolic organization: a discussion of concepts.

Metabolic organization of individual organisms follows simple quantitative rules that can be understood from basic physical chemical principles. Dynamic energy budget (DEB) theory identifies these rules, which quantify how individuals acquire and use energy and nutrients. The theory provides constraints on the metabolic organization of subcellular processes. Together with rules for interaction between individuals, it also provides a basis to understand population and ecosystem dynamics. The theory, therefore, links various levels of biological organization. It applies to all species of organisms and offers explanations for body-size scaling relationships of natural history parameters that are otherwise difficult to understand. A considerable number of popular empirical models turn out to be special cases of the DEB model, or very close numerical approximations. Strong and weak homeostasis and the partitionability of reserve kinetics are cornerstones of the theory and essential for understanding the evolution of metabolic organization.

The Nature of the Liquid State

IN his recent lecture to the Chemical Society on “The Significance of Crystal Structure,” Sir William Bragg has described and discussed the extremely important results obtained in his laboratory by the X-ray analysis of various carbon compounds, notably those belonging to the aromatic series. The special feature brought to light by the investigations is that the ultimate unit of crystal structure or elementary parallelepiped is not the chemical molecule, but, generally speaking, is a complex formed by the union of two, three, or four molecules. Further, the symmetry of the crystal tends to increase with the number of molecules in the unit, and also with the symmetry of the molecule itself. In fact, there are simple quantitative rules, first stated by Shearer, connecting these quantities.