Norms That Regulate the Theorem Construction Process in an Inquiry Classroom of 3D Geometry: Teacher's Management to Promote Them

This paper aims to illustrate how a teacher instilled norms that regulate the theorem construction process in a three-dimensional geometry course. The course was part of a preservice mathematics teacher program, and it was characterized by promoting inquiry and argumentation. We analyze class excerpts in which students address tasks that require formulating conjectures, that emerge as a solution to a problem and proving such conjectures, and the teacher leads whole-class activities where students' productions are exposed. For this, we used elements of the didactical analysis proposed by the onto-semiotic approach and Toulmin's model for argumentation. The teacher's professional actions that promoted reiterative actions in students' mathematical practices were identified; we illustrate how these professional actions impelled students' actions to become norms concerning issues about the legitimacy of different types of arguments (e.g., analogical and abductive) in the theorem construction process

Database partitioning strategies for social network data

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 64-66).In this thesis, I designed, prototyped and benchmarked two different data partitioning strategies for social network type workloads. The first strategy takes advantage of the heavy-tailed degree distributions of social networks to optimize the latency of vertex neighborhood queries. The second strategy takes advantage of the high temporal locality of workloads to improve latencies for vertex neighborhood intersection queries. Both techniques aim to shorten the tail of the latency distribution, while avoiding decreased write performance or reduced system throughput when compared to the default hash partitioning approach. The strategies presented were evaluated using synthetic workloads of my own design as well as real workloads provided by Twitter, and show promising improvements in latency at some cost in system complexity.by Oscar Ricardo Moll Thomae.M.Eng

SeeSaw: Interactive Ad-hoc Search Over Image Databases

As image datasets become ubiquitous, the problem of ad-hoc searches over image data is increasingly important. Many high-level data tasks in machine learning, such as constructing datasets for training and testing object detectors, imply finding ad-hoc objects or scenes within large image datasets as a key sub-problem. New foundational visual-semantic embeddings trained on massive web datasets such as Contrastive Language-Image Pre-Training (CLIP) can help users start searches on their own data, but we find there is a long tail of queries where these models fall short in practice. SeeSaw is a system for interactive ad-hoc searches on image datasets that integrates state-of-the-art embeddings like CLIP with user feedback in the form of box annotations to help users quickly locate images of interest in their data even in the long tail of harder queries. One key challenge for SeeSaw is that, in practice, many sensible approaches to incorporating feedback into future results, including state-of-the-art active-learning algorithms, can worsen results compared to introducing no feedback, partly due to CLIP's high-average performance. Therefore, SeeSaw includes several algorithms that empirically result in larger and also more consistent improvements. We compare SeeSaw's accuracy to both using CLIP alone and to a state-of-the-art active-learning baseline and find SeeSaw consistently helps improve results for users across four datasets and more than a thousand queries. SeeSaw increases Average Precision (AP) on search tasks by an average of .08 on a wide benchmark (from a base of .72), and by a .27 on a subset of more difficult queries where CLIP alone performs poorly.Comment: SIGMOD 2024 camera read

Export and modification of (poly)peptides in the lantibiotic way

The invention includes a method for harvesting a polypeptide produced by a host cell, wherein the polypeptide has not undergone intra-cellular post-translational modification, such as dehydration of a serine or a threonine, and/or thioether bridge formation. The invention also includes a method for producing thioether containing peptides and dehydroalanine/dehydrobutyrine-containing peptides, wherein extracellularly thioether rings may be formed

High-throughput screening for substrate specificity-adapted mutants of the nisin dehydratase NisB

Microbial lanthipeptides are formed by a two-step enzymatic introduction of (methyl)lanthionine rings. A dehydratase catalyzes the dehydration of serine and threonine residues, yielding dehydroalanine and dehydrobutyrine, respectively. Cyclase-catalyzed coupling of the formed dehydroresidues to cysteines forms (methyl)lanthionine rings in a peptide. Lanthipeptide biosynthetic systems allow discovery of target-specific, lanthionine-stabilized therapeutic peptides. However, the substrate specificity of existing modification enzymes impose limitations on installing lanthionines in non-natural substrates. The goal of the present study was to obtain a lanthipeptide dehydratase with the capacity to dehydrate substrates that are unsuitable for the nisin dehydratase NisB. We report high-throughput screening for tailored specificity of intracellular, genetically encoded NisB dehydratases. The principle is based on the screening of bacterially displayed lanthionine-constrained streptavidin ligands, which have a much higher affinity for streptavidin than linear ligands. The designed NisC-cyclizable high-affinity ligands can be formed via mutant NisB-catalyzed dehydration but less effectively via wild-type NisB activity. In Lactococcus lactis, a cell surface display precursor was designed comprising DSHPQFC. The Asp residue preceding the serine in this sequence disfavors its dehydration by wild-type NisB. The cell surface display vector was coexpressed with a mutant NisB library and NisTC. Subsequently, mutant NisB-containing bacteria that display cyclized strep ligands on the cell surface were selected via panning rounds with streptavidin-coupled magnetic beads. In this way, a NisB variant with a tailored capacity of dehydration was obtained, which was further evaluated with respect to its capacity to dehydrate nisin mutants. These results demonstrate a powerful method for selecting lanthipeptide modification enzymes with adapted substrate specificity

Estructura y dinámica de argumentos analógicos, abductivos y deductivos: un curso de geometría del espacio como contexto de reflexión

Se describen procesos de argumentación con énfasis en los argumentos analógicos, surgidos cuando un grupo de estudiantes aborda un problema que puede ser resuelto tanto en la geometría plana como en la del espacio. Para ello, en el marco de una metodología cualitativa basada en la realidad del aula, se emplea el modelo de Toulmin para tipificar los argumentos producidos y se realiza un análisis ontosemiótico para describir la actividad matemática asociada. Los resultados permiten legitimar el uso de argumentos abductivos o analógicos en procesos de resolución de problemas (particularmente, de geometría del espacio) precisando la forma en que estos articulan y dinamizan diversos objetos (conceptos, procedimientos, proposiciones) presentes en el proceso. Además, permiten detallar las fases de una argumentación por analogía mediante las configuraciones de los dominios que involucra

Bidirectional Associations between Fussy Eating and Functional Constipation in Preschool Children

ObjectiveTo examine bidirectional associations between a child's fussy eating behavior and functional constipation.Study designParticipants were 4823 children enrolled in a prospective cohort study from pregnancy onward. We assessed fussy eating at age 4 years with the Child Eating Behavior Questionnaire, and assessed functional constipation using ROME II and III criteria with parental questionnaires at age 2, 3, 4, and 6 years.ResultsHigher food fussiness at age 4 years was associated with a greater risk of functional constipation at both 4 years (OR, 1.30; 95% CI, 1.20-1.42; P < .001 per 1 SD increase) and 6 years (OR, 1.12; 95% CI, 1.03-1.23; P < .05 per 1 SD increase). The converse was also observed; previous constipation predicted a greater risk of being a fussy eater at age 4 years (constipation at 2 years: OR, 2.05; 95% CI 1.43-2.94; P < .001; constipation at 3 years: OR, 1.72; 95% CI, 1.26-2.35, P < .001). Path analyses confirmed that the association between fussy eating and functional constipation was indeed bidirectional, showing that functional constipation at age 3 years predicted fussy eater classification at age 4 years (β = 0.06; P < .001), which in turn predicted functional constipation at age 6 years (β = 0.08: P < .001) independent of each other.ConclusionA vicious cycle might develop in which children with functional constipation develop unhealthy eating behavior, which in turn increases the risk of functional gastrointestinal disease