Bin Yang on the Global History of Cowries

Bin Yang correctly states that cowrie shells (250 species) and cowrie monies (two species mostly) deserve far more attention in global histories than they have received. He provides the most comprehensive view of the global history of cowries and cowrie monies to date. Multiple shell monies proliferated worldwide, but they did not concentrate within China (except Yunnan) nor within Europe. Why did specific cowries accumulate only in certain specific geographical locations? Yang establishes a general answer: cultural preferences for holding specific objects, including specific monies, determined where the shells were concentrated. He offers global evidence that, I argue, contradicts mainstream economic theory, which is based upon conceptual aggregation of diverse monies into amorphous stocks of (national or regional) money (singular). Yang demonstrates repeatedly that distinct market locations and distinct market prices existed for specific cowrie and other shell monies (plural) throughout global history. His evidence starkly demonstrates inadequacies of mainstream monetary theory (although he does not say as much). The relentless evidence of the existence of monetary disaggregation, evidence highlighted throughout Yang’s volume, demonstrates an urgent need for alternative monetary theories that portray prices and stocks of individual monies in conformity with empirical evidence provided by archival historians.

Economic Diversification under Saudi Vision 2030

The last decade has brought a row of substantial changes that have profound implications for the traditional hydrocarbon resource-rich economies. Economic conditions may change radically either throughout a decade or within months. The question is whether there is no other option for a hydrocarbon resource-rich economy than to be held hostage to the fluctuations in global oil prices. The general answer to a changing environment is: Adapt! From the macroeconomic perspective, this means diversifying the economy to broaden the income base and significantly reduce the dependence on oil revenues. The Saudi Vision 2030 represents a complex plan for substantial socioeconomic adjustments that are about to move the economy toward a more diversified and sustainable one. This discussion paper examines the preferred diversification paths for the Saudi economy in more detail, with a focus on the foreseen adjustments in the sectoral composition of the economy along with broader macroeconomic shifts. The evaluation of the foreseen diversification impacts is based on the updated Vision 2030 Input-Output Table that maps the changing structure of the Saudi economy over the coming decade. We discuss the assumed expansion of the diversification frontrunners, their changing contribution to the overall economic activity and identify the preferred diversification paths for the Saudi economy. The advances in economic diversification are measured by applying the Shannon-Weaver index to sectoral GDP and household income. The expected sectoral changes are wide-reaching, so the basic macroeconomic relations are also subject to adjustments. We also conduct a sensitivity analysis to examine the effects of the foreseen diversification on the resilience of the Saudi economy to external shocks.

Predicting classifications in marine biomonitoring with supervised machine learning: how much data is required?

Marine coastal ecosystems offer numerous ecosystem services and are therefore subject to a variety of stressors from anthropogenic activities. Environmental biomonitoring programs for effective management and conservation of coastal marine ecosystems are therefore crucial. Traditional monitoring has been based on macrofauna indices which are laborious and require expert knowledge. Recently, eDNA metabarcoding has become increasingly popular as it does not involve macrofauna species identification and is therefore cost and time inexpensive. Studies have shown that ecosystem monitoring based on eDNA metabarcoding is feasible and random forest (RF) algorithms can predict various biological indices, and therefore ecosystem health. To propose adequate designs for future eDNA metabarcoding-based marine coastal monitoring surveys, the aim of the study is to find out (1) What is the lower limit of reads for accurate RF predictions in coastal marine monitoring using microbial communities? (2) Is this limit the same for different monitoring targets? To achieve this goal, we exploited four different Illumina amplicon datasets obtained from bacterial communities in different costal environments. From these datasets, we predicted different objectives relevant for biomonitoring. For each dataset, those corresponding prediction objectives (labels) were predicted using amplicon sequence variants (ASVs) as features. After construction of RF models using all available sequences of a dataset (full model, serving as benchmark for targeted prediction accuracy), we then successively down-sampled each dataset to lower sequence numbers. Prediction accuracies of the reduced models were then compared to the accuracies of the full models to assess the minimum number of features to obtain the targeted prediction accuracy. Our results show that there is no general answer to question (1) and that (2) the limit varies between different monitoring targets. We have identified the most informative criteria that are relevant to assess the sequencing depth required to predict a biomonitoring category using RF. This may guide future study designs and may help to estimate and control costs in applied routine DNA-based biomonitoring using RF to predict the biomonitoring target. In our contribution we will elucidate and discuss these criteria.

Mucoidy, a general mechanism for maintaining lytic phage in populations of bacteria

ABSTRACT We present evidence that phage resistance resulting from overproduction of exopolysaccharides, mucoidy, provides a general answer to the longstanding question of how lytic viruses are maintained in populations dominated by bacteria upon which they cannot replicate. In serial transfer culture, populations of mucoid Escherichia coli MG1655 that are resistant to lytic phages with different receptors, and thereby requiring independent mutations for surface resistance, are capable of maintaining these phages with little effect on their total density. Based on the results of our analysis of a mathematical model, we postulate that the maintenance of phage in populations dominated by mucoid cells can be attributed primarily to high rates of transition from the resistant mucoid states to susceptible non-mucoid states. Our tests with both population dynamic and single cell experiments as well as genomic analysis are consistent with this hypothesis. We discuss reasons for the generalized resistance of these mucoid E. coli, and the genetic and molecular mechanisms responsible for the high rate of transition from mucoid to sensitive states responsible for the maintenance of lytic phage in mucoid populations of E. coli.

COUNTERPARTY CREDIT RISK IN A CLEARING NETWORK

In this paper, we offer a network model that derives the expected counterparty risk of an arbitrary market after netting in a closed-form expression. Graph theory is used to represent market participants and their relationship among each other. We apply the powerful theory of characteristic functions (c.f.) and Hilbert transforms to determine the expected counterparty risk. The latter concept is used to express the c.f. of the random variable (r.v.) [Formula: see text] in terms of the c.f. of the r.v. [Formula: see text]. This paper applies this concept for the first time in mathematical finance in order to generalize results of Duffie & Zhu (2011), in several ways. The introduced network model is applied to study the features of an over-the-counter and a centrally cleared market. We also give a more general answer to the question of whether it is more advantageous for the overall counterparty risk to clear via a central counterparty or classically bilateral between the two involved counterparties.

Invariance in ecological pattern

Background: The abundance of different species in a community often follows the log series distribution. Other ecological patterns also have simple forms. Why does the complexity and variability of ecological systems reduce to such simplicity? Common answers include maximum entropy, neutrality, and convergent outcome from different underlying biological processes. Methods: This article proposes a more general answer based on the concept of invariance, the property by which a pattern remains the same after transformation. Invariance has a long tradition in physics. For example, general relativity emphasizes the need for the equations describing the laws of physics to have the same form in all frames of reference. Results: By bringing this unifying invariance approach into ecology, we show that the log series pattern dominates when the consequences of processes acting on abundance are invariant to the addition or multiplication of abundance by a constant. The lognormal pattern dominates when the processes acting on net species growth rate obey rotational invariance (symmetry) with respect to the summing up of the individual component processes. Conclusions: Recognizing how these invariances connect pattern to process leads to a synthesis of previous approaches. First, invariance provides a simpler and more fundamental maximum entropy derivation of the log series distribution. Second, invariance provides a simple derivation of the key result from neutral theory: the log series at the metacommunity scale and a clearer form of the skewed lognormal at the local community scale. The invariance expressions are easy to understand because they uniquely describe the basic underlying components that shape pattern.

Dissipation-induced topological insulators: A no-go theorem and a recipe

Nonequilibrium conditions are traditionally seen as detrimental to the appearance of quantum-coherent many-body phenomena, and much effort is often devoted to their elimination. Recently this approach has changed: It has been realized that driven-dissipative dynamics could be used as a resource. By proper engineering of the reservoirs and their couplings to a system, one may drive the system towards desired quantum-correlated steady states, even in the absence of internal Hamiltonian dynamics. An intriguing category of equilibrium many-particle phases are those which are distinguished by topology rather than by symmetry. A natural question thus arises: which of these topological states can be achieved as the result of dissipative Lindblad-type (Markovian) evolution? Beside its fundamental importance, it may offer novel routes to the realization of topologically-nontrivial states in quantum simulators, especially ultracold atomic gases. Here I give a general answer for Gaussian states and quadratic Lindblad evolution, mostly concentrating on the example of 2D Chern insulator states. I prove a no-go theorem stating that a finite-range Lindbladian cannot induce finite-rate exponential decay towards a unique topological pure state above 1D. I construct a recipe for creating such state by exponentially-local dynamics, or a mixed state arbitrarily close to the desired pure one via finite-range dynamics. I also address the cold-atom realization, classification, and detection of these states. Extensions to other types of topological insulators and superconductors are also discussed.

Mucoidy, a general mechanism for maintaining lytic phage in populations of bacteria

We present evidence that phage resistance resulting from overproduction of exopolysaccharides, mucoidy, provides a general answer to the longstanding question of how lytic viruses are maintained in populations dominated by bacteria upon which they cannot replicate. In serial transfer culture, populations of mucoid E. coli MG1655 that are resistant to lytic phages with different receptors, and thereby requiring independent mutations for surface resistance, are capable of maintaining these phages with little effect on their total density. Based on the results of our analysis of a mathematical model, we postulate that the maintenance of phage in populations dominated by mucoid cells can be attributed primarily to high rates of transition from the resistant mucoid states to susceptible non-mucoid states. Our tests with both population dynamic and single cell experiments as well as DNA sequence analysis are consistent with this hypothesis. We discuss reasons for the generalized resistance of these mucoid E. coli, and the genetic and molecular mechanisms responsible for the high rate of transition from mucoid to sensitive states responsible for the maintenance of lytic phage in mucoid populations of E. coli.