Science & Mathematics

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

This thesis explores the relation between module categories over small differential graded (abbreviated DG) categories on the one hand, and well generated triangulated categories on the other. In the first part, we construct the $\alpha$-continuous derived category D_\alpha A of a homotopically $\alpha$-cocomplete small DG category A, where $\alpha$ is a regular cardinal. This construction enjoys a useful and beautiful property which is the key technical result for proving the main theorem of the thesis. The categories D_\alpha A turn out to be the prototypes of the $\alpha$-compactly generated algebraic triangulated categories. Here algebraic means triangle equivalent to the stable category of a Frobenius category. The main result says that algebraic well generated categories are precisely those which are localizations of the derived category of some small DG category. This result is strongly reminiscent of a 1964 theorem of Gabriel and Popescu, which characterized the Grothendieck abelian categories as localizations of categories of modules over rings. It also gives a positive answer to Drinfeld?s question whether all well generated categories arise as localizations of compactly generated ones, for the class of algebraic triangulated categories. In the second part, we study the categories DA and D_\alpha A using the projective Quillen?s model category structure present on the category of DG modules. We introduce the subcategory of homotopically $\alpha$-compact cofibrant DG modules and we show that its homotopy category is precisely the $\alpha$-continuous derived category D_\alpha A. This enables us to give a second, completely different proof of the key technical result of the first part.

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

The adsorption of ammonia–borane (AB) over the (001) surface of TiC and ZrC, has been studied systematically by means of periodic-boundary density functional calculations using slab models. We present evidence that a surface with an appreciable degree of polarity such as those used in this research, can simultaneously activate the N-H and B-H bonds of the AB molecule and its dimer AB-AB. The molecule is highly activated by both supports, and the N-H and B-H bonds are stretched long enough to release one or two hydrogens. Additionally, the bond distance B-N is shortened by 0.04 and 0.06 Å by TiC and ZrC supports respectively, which results in the strengthening of the bond, what seems convenient to avoid unwanted by-products (NH3, BH3, etc.). A systematic study for the adsorption of BH2NH2, which is isoelectronic with ethylene, was also done. The adsorption leads to a major elongation of the B-N bond with respect to the calculated value in the gas phase (0.17 and 0.18 Å for TiC and ZrC respectively). Both supports can activate the molecule, with the biggest impact being on the BH2 fragment. On the other hand, the migration of hydrogen atoms on both supports is a thermodynamically favorable process. On the surface H prefers bonding to a C, which is in agreement with other studies for dissociative adsorption of H2 on metallic carbides. Nevertheless, we show that the hydrogen molecule readily forms when both atoms sit on the transition metal of the surface. On the basis of this theoretical study, both supports are proposed as potential catalysts for the dehydrogenation of ammonia–borane.

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

This paper explores decision-making processes in experience goods markets, emphasizing how agents learn to choose in situations where value is uncertain until after consumption.The study examines agents employing individual and social learning strategies within a multidimensional reinforcement learning framework, particularly in scenarios of repeated choices.Agents in our model gather insights from personal experiences and through recommendations within their social networks. The simulation results highlight the benefits of combining individual and social learning. While social learning yields consistent outcomes across agents, individual learning offers the possibility of higher rewards but also greater risks.A notable finding of this research is the development of asymmetrical influence patterns in social networks. This phenomenon refers to a tendency where certain agents become disproportionately influential in guiding others' choices, leading to a centralization in how advice is sought and followed within the network. This aspect of the model sheds light on the nuances of social dynamics in decision-making processes. The study enhances our understanding of consumer behavior in markets for experience goods, providing insights into the complex interplay of individual experiences and social influences in shaping economic decisions.

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

Granular materials are collections of solid particles of various shapes, materials and sizes, making their behavior complex. In the past, effective understanding was mainly derived from experiments, which were limited by the equipment available at the time. Numerical approaches based on the Discrete Element Method were then developed. These are powerful, reliable and widely used as efficient tools for studying granular media. In comparison, experimentation was not as widespread due to difficulties of preparation and instrumentation. In recent decades, non-contact full-field measurement techniques based on cameras have become increasingly familiar and attractive in the experimental mechanics community. This is due to rapid advances in equipment. Some of these were used to study two-dimensional (2D) granular media under mechanical loading: particle image velocimetry (PIV) to measure strain patterns; digital image correlation (DIC) to measure strains within deformable particles; photoelasticimetry to measure shear stresses in particles made of birefringent material; and thermoelastic stress analysis (TSA) based on infrared thermography (IRT) to measure hydrostatic stresses in particles. Some of these techniques enabled identifying the interparticle forces using appropriate image processing. However, there are certain limitations due to the specifications of each technique. Besides, soft granular materials have rarely been studied with these techniques. In this context, the aim of the thesis is to develop other full-field techniques for two purposes: 1) to identify contact forces using the virtual fields method (VFM) from knowledge of the strain distribution obtained by localized spectrum analysis (LSA); 2) to identify thermomechanical couplings in soft particles using IRT. Synthetic strain data provided by a finite element model were first used for the first objective. It was shown that if the mechanical response of the constitutive material is known, the contact forces applied to a particle can be identified since they are proportional to an integral of the measured strains weighted by their virtual counterparts. Various strategies were tested to propose kinematically admissible fields for the virtual displacements. Identification robustness was studied with respect to various sources of error. Measurements by LSA, providing a relevant compromise between strain resolution and spatial resolution, were then performed on a three-particle system and bigger systems made of PA66 cylindrical particles. In addition to the VFM equations, particle equilibrium and Newton's third law of motion were considered to propose a relevant strategy for processing the experimental data. The statistical analysis for bidisperse and tridisperse systems allowed to characterize the exponential and power laws for the strong and weak force networks, respectively, that are usually found in polydisperse dry systems.For the second objective, granular media made of thermoplastic polyurethane (TPU) cylinders with ellipsoidal cross-section were subjected to cyclic confined compression while being observed by an IRT camera. TPU was chosen because it features entropic elasticity, which gives a higher thermal signature than the materials used for TSA. This material also lends a soft character to the granular systems produced. Based on considerations of adiabaticity and thermodynamic cycle completion, strong thermoelastic coupling (TEC) was revealed in the contact areas between all particles due to stress concentrations. Strong mechanical dissipation (MD) was found at specific contacts and within some particles due to damage, viscosity and friction. TEC data was processed for a granular system comprised of about 600 interparticle contacts, providing statistical information. It is demonstrated that IRT provides valuable information to open prospects for building thermodynamically relevant models suitable for soft granular materials.

The binary Goldbach conjecture asserts that every even integer greater than $4$ is the sum of two primes. In order to prove this statement, we begin by introducing a kind of double sieve of Eratosthenes as follows. Given a positive even integer $x > 4$, we sift out from $[1, x]$ all those elements that are congruents to $0$ modulo $p$, or congruents to $x$ modulo $p$, where $p$ is a prime less than $\sqrt{x}$. So, any integer in the interval $[\sqrt{x}, x]$ that remains unsifted is a prime $q$ for which either $x-q = 1$ or $x-q$ is also a prime. Then, we introduce a new way of formulating a sieve, which we call the sequence of $k$-tuples of remainders. Using this tool, we prove that there exists an integer $K_\alpha > 5$ such that $p_k / 2$ is a lower bound for the sifting function of this sieve, for every even number $x$ that satisfies $p_k^2 < x < p_{k+1}^2$, where $k > K_\alpha$. This result implies that every even integer $x > p_k^2 \; (k > K_\alpha)$ can be expressed as the sum of two primes. Furthermore we provide the upper estimation $K_\alpha < 89$.

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

Abstract Background Most intervention areas for improving cancer screening uptake are in deprived neighbourhoods. However, in recent years, determinants and attitudes to screening have evolved, and new perspectives are needed in understanding cancer screening practices. It is therefore necessary to develop simple, effective and reproducible strategies for identifying intervention areas. Using one map, the aim is to investigate spatially and temporally breast and colorectal cancer screening in France from 2015-2016 to 2021-2022. Methods Uptake in breast (BS) and colorectal (CS) cancer screening at the census block level was generated by the regional cancer screening centre for women aged 50 to 74, residing in the Rhône department (mostly rural but including the urban Lyon metropolitan area). We used spatial analysis to create a map highlighting groups of hotspots, identifying their direction of propagation between 2015-2019 and 2020-2022. Results The results reveal interesting areas for intervention with differences and similarities in uptake of the two screenings. For CS, there was a 5-pt increase in uptake between the two periods (2015-2019: 33% and 2020-2022: 38%), whereas for BS the uptake remained stagnant around 49% on average in the metropolitan area. The map highlights 49 urban census blocks with consistently lower uptake rates in both screenings (39.2% for BS, 23.7% for CS) than the overall average. Conversely, some census blocks have consistently lower uptake rates on one screening but not on the other (CS or BS). Conclusions This work may inform the breast and colorectal locally screening trend and inform policymakers to develop tailored prevention strategies. These analyses are easily reproducible at different times and spaces, and they have the potential for evaluation and comparison of screening uptake. Key messages • Maps may inform policymakers to develop tailored prevention strategies. • Investigate spatially and temporally breast and colorectal cancer screening reveal interesting areas for interventions.

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.