Effects of Preference for Attachment to Low-degree Nodes on the Degree Distributions of a Growing Directed Network and a Simple Food-Web Model

We study the growth of a directed network, in which the growth is constrained by the cost of adding links to the existing nodes. We propose a new preferential-attachment scheme, in which a new node attaches to an existing node i with probability proportional to 1/k_i, where k_i is the number of outgoing links at i. We calculate the degree distribution for the outgoing links in the asymptotic regime (t->infinity), both analytically and by Monte Carlo simulations. The distribution decays like k c^k/Gamma(k) for large k, where c is a constant. We investigate the effect of this preferential-attachment scheme, by comparing the results to an equivalent growth model with a degree-independent probability of attachment, which gives an exponential outdegree distribution. Also, we relate this mechanism to simple food-web models by implementing it in the cascade model. We show that the low-degree preferential-attachment mechanism breaks the symmetry between in- and outdegree distributions in the cascade model. It also causes a faster decay in the tails of the outdegree distributions for both our network growth model and the cascade model.Comment: 10 pages, 7 figures. A new figure added. Minor modifications made in the tex

Lomna žilavost trenjem zavarenih spojeva iz AlCu4SiMg aluminijske legure

The objective of paper was to determine the fracture toughness of friction stir welding (FSW) joints of EN AW-2014 AlCu4SiMg) aluminium alloy, and to compare the fracture toughness of FSW with that of conventional metal inert gas (MIG) process. FSW of aluminium alloy was performed on a conventional semiautomatic milling machine. Defect free FSW welds were produced on alloy plates at constant tool rotation and traverse speed of 1600 rpm and 200 mm/min, respectively. The results of Vickers hardness and Charpy impact tests were used to evaluate the fracture toughness of welded joints. Low heat input, absence of melting and filler metal resulted in better fracture toughness for FSW joints

Milli Eğitim Bakanlığı İlköğretim Müfettişleri Başkanlıkları Yönetmeliğinin Analizi

The legal organisation regulating Primary education inspectors working principles, and defining the operations and functions of the inspectorate is the Ministry of National Education and is based on regulations which came into effect in 13 August 1999. These new regulations have brought in many changes. This study explains the new changes brought in and to analyse them in view of inspectors comments from a sample of 300 Primary Education Inspectors was chosen from all over Turkey. The results have been analyzed by “SPSS for Windows”. It was found that Primary Education Inspectors only welcome some of the changes in the conditions in the regulation. It was determined that they agree moderately with Üıe articles concerning "training”, and they agree partially and strongly with the articles on “responsibility areas”. It was also determined that the new regulations have brought in many changes, particularly with regard to probationary periods for inspectors, proficiency exams, appointments, conditions of presidency, responsibility areas and service regions.İlköğretim müfettişlerinin çalışma usul ve esasları ile teftiş kurulunun yapısı, işleyişi ve işlevlerini düzenleyen yasal dayanak “MEB İlköğretim Müfettişleri Başkanlıkları Yönetmeliği” dir. 13 Ağustos 1999 tarihinde yürürlüğe giren bu yönetmelik, önceki yönetmeliğe göre birçok değişiklik getirmiştir. Bu araştırımda, MEB İlköğretim Müfettişleri Başkanlıkları Yönetmeliği’nin, yürürlükten kalkan 27 Ekim 1990 tarihli “MEB İlköğretim Müfettişleri Kumlu Yönetmeliği” ile bir karşılaştırmasını yaparak getirdiği değişiklikleri belirlemek, yeni yönetmelik hakkında müfettişlerin görüşleri ışığında bir değerlendirme yapmak amaçlanmıştır. Hazırlanan veri toplama aracı Türkiye genelinde görev yapan ve 2000 yılı Temmuz ve Ağustos aylarında Türkiye’nin her ilinden gelerek Isparta’da düzenlenen hizmetiçi eğitim kursuna katılan 300 ilköğretim müfetüşine uygulanmıştır. Veriler “SPSS for Windows” paket istatistik programı ile çözümlenmiştir. Araştırma bulgularından elde edilen sonuçlara göre, ilköğretim müfettişlerinin, yönetmeliğin “seçilme koşullan” ile ilgili getirdiği değişikliklerden bazılanm benimserken çoğunu benimsemedikleri, “yetiştirme” ile ilgili maddelere “orta” düzeyde, “görev alanları ile ilgili maddelere ise “kısmen” ve “çok” düzeylerinde katıldıktan saptanmıştır

Lomna žilavost trenjem zavarenih spojeva iz AlCu4SiMg aluminijske legure

The objective of paper was to determine the fracture toughness of friction stir welding (FSW) joints of EN AW-2014 AlCu4SiMg) aluminium alloy, and to compare the fracture toughness of FSW with that of conventional metal inert gas (MIG) process. FSW of aluminium alloy was performed on a conventional semiautomatic milling machine. Defect free FSW welds were produced on alloy plates at constant tool rotation and traverse speed of 1600 rpm and 200 mm/min, respectively. The results of Vickers hardness and Charpy impact tests were used to evaluate the fracture toughness of welded joints. Low heat input, absence of melting and filler metal resulted in better fracture toughness for FSW joints

A Systematic Review and Meta-analysis of the Relationships among Post-secondary Students’ Attitudes Toward Statistics and Statistics Achievement

Background: An understanding of statistics is essential in our data-driven world. Accordingly, successful completion of a statistics course is required for undergraduate and graduate students from many disciplines. Attitudes toward statistics is a multidimensional construct that expresses individuals’ positive or negative dispositions to statistics. A wide body of research indicates that there are statistically significant relationships among attitudes toward statistics and statistics achievement. However, the reported magnitudes of these relationships differ across studies.  Methods/Design: This review will examine the relationships among post-secondary students’ scores on the attitude components assessed by the Survey of Attitudes toward Statistics (SATS) and their statistics achievement assessed using a variety of measures. As the data allow, this review then will explore the impact of possible moderating research characteristics including, for example, those associated with research sources, institutions, courses, subjects, and the SATS and statistics achievement measures. Discussion: In the resulting journal article, this section will focus on the results and the strengths and limitations of the synthesized literature. We expect that the study will contribute to the literature on the relationship between attitudes toward statistics and achievement by synthesizing the individual research results. The availability of the required information and the quality of primary studies will be potential limitations for the current study

Effect of Aging Treatment on Surface Roughness, Mechanical Properties, and Fracture Behavior of 6xxx and 7xxx Aluminum Alloys

The effect of aging treatment on the surface roughness and mechanical properties of AA6061 and AA7075 alloys was studied. Microhardness and tensile tests were used to investigae the mechanical properties. X-ray diffraction analysis was used to investigate the surface of the specimens. Furthermore, after tensile tests fractured surfaces were examined with scanning electron microscopy. An atomic force microscope was employed for analysis of the effect of aging treatment on surface roughness. Higher surface roughness with an increase in the volume fraction of the precipitate was revealed.Исследовано влияние процесса старения на шероховатость поверхности и механические свойства алюминиевых сплавов AA6061 и AA7075. Механические свойства исследовали при испытаниях на микротвердость и растяжение. Поверхность образцов исследовали с помощью рентгеноструктурного анализа. После испытания на растяжение поверхность разрушения исследовали методом растровой электронной микроскопии. Влияние процесса старения на шероховатость поверхности изучали с помощью атомно-силового микроскопа. Показано, что с ростом шероховатости поверхности увеличивается количество выделившихся фаз.Досліджено вплив процесу старіння на шорсткість поверхні і механічні властивості алюмінієвих сплавів АА6061 та АА7075. Механічні властивості досліджували при випробуваннях на мікротвердість і розтяг. Поверхню зразків досліджували за допомогою рентгеноструктурного аналізу. Після випробувань на розтяг поверхню руйнування досліджували методом растрової електронної мікроскопії. Вплив процесу старіння на шорсткість поверхні вивчали за допомогою атомно-силового мікроскопа. Показано, що з ростом шорсткості поверхні збільшується кількість виділених фа

Magnetoelectric Effect in Hydrogen Harvesting: Magnetic Field as a Trigger of Catalytic Reactions (Adv. Mater. 19/2022)

Magnetic fields have been regarded as an additional stimulus for electro- and photocatalytic reactions, but not as a direct trigger for catalytic processes. Multiferroic/magnetoelectric materials, whose electrical polarization and surface charges can be magnetically altered, are especially suitable for triggering and control of catalytic reactions solely with magnetic fields. Here, we demonstrate that magnetic fields can be employed as an independent input energy source for hydrogen harvesting by means of the magnetoelectric effect. Composite multiferroic CoFe2O4-BiFeO3 core-shell nanoparticles act as catalysts for the hydrogen evolution reaction (HER) that is triggered when an alternating magnetic field is applied to an aqueous dispersion of the magnetoelectric nanocatalysts. Based on density functional calculations, we propose that the hydrogen evolution is driven by changes in the ferroelectric polarization direction of BiFeO3 caused by the magnetoelectric coupling. We believe our findings will open new avenues towards magnetically induced renewable energy harvesting

Self-optimization, community stability, and fluctuations in two individual-based models of biological coevolution

We compare and contrast the long-time dynamical properties of two individual-based models of biological coevolution. Selection occurs via multispecies, stochastic population dynamics with reproduction probabilities that depend nonlinearly on the population densities of all species resident in the community. New species are introduced through mutation. Both models are amenable to exact linear stability analysis, and we compare the analytic results with large-scale kinetic Monte Carlo simulations, obtaining the population size as a function of an average interspecies interaction strength. Over time, the models self-optimize through mutation and selection to approximately maximize a community fitness function, subject only to constraints internal to the particular model. If the interspecies interactions are randomly distributed on an interval including positive values, the system evolves toward self-sustaining, mutualistic communities. In contrast, for the predator-prey case the matrix of interactions is antisymmetric, and a nonzero population size must be sustained by an external resource. Time series of the diversity and population size for both models show approximate 1/f noise and power-law distributions for the lifetimes of communities and species. For the mutualistic model, these two lifetime distributions have the same exponent, while their exponents are different for the predator-prey model. The difference is probably due to greater resilience toward mass extinctions in the food-web like communities produced by the predator-prey model.Comment: 26 pages, 12 figures. Discussion of early-time dynamics added. J. Math. Biol., in pres

Pregnancy outcomes in antiphospholipid antibody positive patients: prospective results from the AntiPhospholipid Syndrome Alliance for Clinical Trials and InternatiOnal Networking (APS ACTION) Clinical Database and Repository ('Registry').

Objectives: To describe the outcomes of pregnancies in antiphospholipid antibody (aPL)-positive patients since the inception of the AntiPhospholipid Syndrome Alliance for Clinical Trials and InternatiOnal Networking Registry. Methods: We identified persistently aPL-positive patients recorded as 'pregnant' during prospective follow-up, and defined 'aPL-related outcome' as a composite of: (1) Preterm live delivery (PTLD) at or before 37th week due to pre-eclampsia (PEC), eclampsia, small-for-gestational age (SGA) and/or placental insufficiency (PI); or (2) Otherwise unexplained fetal death after the 10th week of gestation. The primary objective was to describe the characteristics of patients with and without aPL-related composite outcomes based on their first observed pregnancies following registry recruitment. Results: Of the 55 first pregnancies observed after registry recruitment among nulliparous and multiparous participants, 15 (27%) resulted in early pregnancy loss <10 weeks gestation. Of the remaining 40 pregnancies: (1) 26 (65%) resulted in term live delivery (TLD), 4 (10%) in PTLD between 34.0 weeks and 36.6 weeks, 5 (12.5%) in PTLD before 34th week, and 5 (12.5%) in fetal death (two associated with genetic anomalies); and (2) The aPL-related composite outcome occurred in 9 (23%). One of 26 (4%) pregnancies with TLD, 3/4 (75%) with PTLD between 34.0 weeks and 36.6 weeks, and 3/5 (60%) with PTLD before 34th week were complicated with PEC, SGA and/or PI. Fifty of 55 (91%) pregnancies were in lupus anticoagulant positive subjects, as well as all pregnancies with aPL-related composite outcome. Conclusion: In our multicentre, international, aPL-positive cohort, of 55 first pregnancies observed prospectively, 15 (27%) were complicated by early pregnancy loss. Of the remaining 40 pregnancies, composite pregnancy morbidity was observed in 9 (23%) pregnancies

Stochastic Delay Accelerates Signaling in Gene Networks

The creation of protein from DNA is a dynamic process consisting of numerous reactions, such as transcription, translation and protein folding. Each of these reactions is further comprised of hundreds or thousands of sub-steps that must be completed before a protein is fully mature. Consequently, the time it takes to create a single protein depends on the number of steps in the reaction chain and the nature of each step. One way to account for these reactions in models of gene regulatory networks is to incorporate dynamical delay. However, the stochastic nature of the reactions necessary to produce protein leads to a waiting time that is randomly distributed. Here, we use queueing theory to examine the effects of such distributed delay on the propagation of information through transcriptionally regulated genetic networks. In an analytically tractable model we find that increasing the randomness in protein production delay can increase signaling speed in transcriptional networks. The effect is confirmed in stochastic simulations, and we demonstrate its impact in several common transcriptional motifs. In particular, we show that in feedforward loops signaling time and magnitude are significantly affected by distributed delay. In addition, delay has previously been shown to cause stable oscillations in circuits with negative feedback. We show that the period and the amplitude of the oscillations monotonically decrease as the variability of the delay time increases