Stochastic niche-based models for the evolution of species

There have been many studies to examine whether one trait is correlated with another trait across a group of present-day species (for example, do species with larger brains tend to have longer gestation times. Since the introduction of the phylogenetic comparative method some authors have argued that it is necessary to have a biologically realistic model to generate evolutionary trees that incorporates information about the ecological niche occupied by species. Price presented a simple model along these lines in 1997. He defined a two-dimensional niche space formed by two continuous-valued traits, in which new niches arise with trait values drawn from a bivariate normal distribution. When a new niche arises, it is occupied by a descendant species of whichever current species is closest in ecological niche space. In sequence, more species are then evolved from already-existing species to which they are ecologically closest. Here we explore ways of extending Price's adaptive radiation model. One extension is to increase the dimensionality of the niche space by considering more than two continuous traits. A second extension is to allow both extinction of species (which may leave unoccupied niches) and removal of niches (which causes species occupying them to go extinct). To model this problem, we consider a continuous-time stochastic process which implicitly defines a phylogeny. To explore if trees generated under such a model (or under different parametrizations of the model) are realistic we can compute a variety of summary statistics that can be compared to those of empirically observed phylogenies. For example, there are existing statistics that aim to measure: tree balance, the relative rate of diversification, and phylogenetic signal of traits.Comment: The Eleventh International Conference on Matrix-Analytic Methods in Stochastic Models (MAM11), 2022, Seoul, Republic of Kore

Factorizing twists and R-matrices for representations of the quantum affine algebra U_q(\hat sl_2)

We calculate factorizing twists in evaluation representations of the quantum affine algebra U_q(\hat sl_2). From the factorizing twists we derive a representation independent expression of the R-matrices of U_q(\hat sl_2). Comparing with the corresponding quantities for the Yangian Y(sl_2), it is shown that the U_q(\hat sl_2) results can be obtained by `replacing numbers by q-numbers'. Conversely, the limit q -> 1 exists in representations of U_q(\hat sl_2) and both the factorizing twists and the R-matrices of the Yangian Y(sl_2) are recovered in this limit.Comment: 19 pages, LaTe

SENSORIMOTOR ASPECTS OF THE SPINE IN ATHLETES AND NON-ATHLETES

Deficits in proprioceptive capabilities are often associated with the occurrence of low back pain as seen in tests involving exact position reproduction. The degree to which athletic activity can improve kinesthetic sensibility of the spine has not been satisfactorily determined previously. Twenty-seven volunteers (30.4 ±4.4 years) were divided into two groups: athletes (n=18; training 5.7 ±3.8 h/week) and non-athletes (n=9). During an active reproduction test, subjects performed the following trunk positions in random order: flexion [A(10°-20°), B(40°-60°), C(80°-90°)], lateral flexion [A(0°-20°), B(20°-45°)], and axial rotation [A(0°-20°), B(20°-45°)].Using a 3D-ultrasound motion analysis system the variability of the given angle was recorded for each trial. A large variation was generally demonstrated in the measured values. Regarding the accurate reproduction of a given angle, the athlete group showed less discrepancy with a smaller standard deviation than the non-athlete group. The results point to superior kinesthetic abilities in the athlete group and the possibility of improving proprioceptive functions with training

Estimasi Produktifitas Ikan Tuna Melalui Frame Survey Nelayan Pancing Tonda di Negeri Laha Pulau Ambon

Frame survey adalah metode pengambilan data dengan pendekatan sensus dan sudah banyak diaplikasi untuk mengestimasi konteks atau strata. Estimasi produktifitas hasil tangkapan pancing tonda pada strata waktu atau periode yang berbeda belum banyak dipublikasikan. Dengan menggunakan metode frame survey melalui wawancara, 5 nelayan pancing tonda di Dusun Kamiri Desa Laha menghasilkan tangkapan beberapa jenis ikan tuna seperti cakalang (Katsuwonus pelamis), putilai (Euthynnus affinis), tatihu atau madidihang (Thunnus albacares) dan tongkol (Auxis thazard). Ikan putilai memiliki produktifitas tertinggi 40 ton pada periode 2015. Semua jenis ikan tertangkap didominasi ukuran sedang (50-75cm). Dapat disimpulkan bahwa rpoduktifitas ikan tuna hasil tangkapan pancing tonda didominasi ikan berukuran sedang atau dewasa muda. Hal ini harus menjadi perhatian serius dalam pengelolaan perikanan tuna untuk menjaga kesinambungan populasinya

Turnover and activity-dependent transcriptional control of NompC in the Drosophila ear.

Across their lives, biological sensors maintain near-constant functional outputs despite countless exogenous and endogenous perturbations. This sensory homeostasis is the product of multiple dynamic equilibria, the breakdown of which contributes to age-related decline. The mechanisms of homeostatic maintenance, however, are still poorly understood. The ears of vertebrates and insects are characterized by exquisite sensitivities but also by marked functional vulnerabilities. Being under the permanent load of thermal and acoustic noise, auditory transducer channels exemplify the homeostatic challenge. We show that (1) NompC-dependent mechanotransducers in the ear of the fruit fly Drosophila melanogaster undergo continual replacement with estimated turnover times of 9.1 hr; (2) a de novo synthesis of NompC can restore transducer function in the adult ears of congenitally hearing-impaired flies; (3) key components of the auditory transduction chain, including NompC, are under activity-dependent transcriptional control, likely forming a transducer-operated mechanosensory gain control system that extends beyond hearing organs

Topics in Quantum Computers

I provide an introduction to quantum computers, describing how they might be realized using language accessible to a solid state physicist. A listing of the minimal requirements for creating a quantum computer is given. I also discuss several recent developments in the area of quantum error correction, a subject of importance not only to quantum computation, but also to some aspects of the foundations of quantum theory.Comment: 22 pages, Latex, 1 eps figure, Paper to be published in "Mesoscopic Electron Transport", edited by L. Kowenhoven, G. Schoen and L. Sohn, NATO ASI Series E, Kluwer Ac. Publ., Dordrecht. v2: typos in refrences fixe

Distribution of echocardiographic parameters and their associations with cardiovascular risk factors in the Rotterdam Study

Insight into echocardiographic parameters in the general population may facilitate early recognition of ventricular dysfunction, reducing the population morbidity and mortality of heart failure. We examined the distribution of structural, systolic and diastolic echocardiographic parameters and their associations with cardiovascular risk factors in the Rotterdam Study, a population-based cohort study in men and women aged ≥55 years. Participants with prevalent heart failure, myocardial infarction and atrial fibrillation and flutter were excluded. Echocardiographic parameters were assessed using two-dimensional, M-mode and Doppler echocardiography. Echocardiograms were available in 4,425 participants. Structural parameters were generally larger in men, and most consistently associated with age, body mass index and blood pressure in both sexes. Prevalence of moderate or poor left ventricular systolic function was 3.9% in men and 2.1% in women. Age, body mass index and blood pressure were most consistently associated with systolic function. E/A ratio was lower in women than in men. Age and diastolic blood pressure were most consistently associated with E/A ratio in both sexes. In conclusion, ventricular systolic and diastolic dysfunction is present in asymptomatic individuals. Selected established cardiovascular risk factors are associated with structural, systolic and diastolic parameters

Stability of surfaces in the chalcopyrite system

It has been observed previously that the stable surfaces in chalcopyrites are the polar 112 surfaces. We present an electron microscopy study of epitaxial films of different compositions. It is shown that for both CuGaSe2 and CuInSe2 the 001 surfaces form 112 facets. With increasing Cu excess the faceting is suppressed, indicating a lower surface energy of the 001 surface than the energy of the 112 surface in the Cu rich regime, but the 001 surface is higher in energy than the 112 surface in the Cu poor regime. As both surfaces are polar the stabilization is attributed to defect formatio