90 research outputs found
Meta-symplectic geometry of 3rd order Monge-Ampère equations and their characteristics
No full textThis paper is a natural companion of [Alekseevsky D.V., Alonso Blanco R., Manno G., Pugliese F., Ann. Inst. Fourier (Grenoble) 62 (2012), 497-524, arXiv:1003.5177], generalising its perspectives and results to the context of third-order (2D) Monge-Ampère equations, by using the so-called ''meta-symplectic structure'' associated with the 8D prolongation M⁽¹⁾ of a 5D contact manifold M. We write down a geometric definition of a third-order Monge-Ampère equation in terms of a (class of) differential two-form on M⁽¹⁾. In particular, the equations corresponding to decomposable forms admit a simple description in terms of certain three-dimensional distributions, which are made from the characteristics of the original equations. We conclude the paper with a study of the intermediate integrals of these special Monge-Ampère equations, herewith called of Goursat type.This paper is a contribution to the Special Issue on Analytical Mechanics and Dif ferential Geometry in honour
of Sergio Benenti. The full collection is available at http://www.emis.de/journals/SIGMA/Benenti.html.
The authors wish to express their gratitude towards the anonymous referees whose comments
contributed to shape the paper into its final form. The authors thank C. Ciliberto, E. Ferapontov
and F. Russo for stimulating discussions. The research of the first author has been partially
supported by the project “Finanziamento giovani studiosi – Metriche proiettivamente equivalenti,
equazioni di Monge–Amp`ere e sistemi integrabili”, University of Padova 2013–2015, by
the project “FIR (Futuro in Ricerca) 2013 – Geometria delle equazioni dif ferenziali”. The
research of the second author has been partially supported by the Marie Sk lodowska–Curie
Action No 654721 “GEOGRAL”, by the University of Salerno, and by the project P201/12/G028
of the Czech Republic Grant Agency (GA CR). Both the authors are members of G.N.S.A.G.A. ˇ
of I.N.d.A.M
X-ray diffraction and high-resolution NMR spectroscopic analysis of 2,4,7,8-tetra-O-acetyl-3-deoxy-α-d-manno-2-octulopyranosono-1,5-lactone
No full textCarbohydrate Research, 330, 145-147Note : if this item contains full text it may be a preprint, author manuscript, or a Gold OA copy that permits redistribution with a license such as CC BY. The final version is available through the publisher’s platform.The X-ray diffraction and high-resolution 1H and 13C NMR spectral data are reported for 2,4,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosono-1,5-lactone.https://login.libproxy.rpi.edu/login?url=https://doi.org/10.1016/s0008-6215(00)00264-
Rileggendo Bruner
No full textThe essay is dedicated to one of most eminent Italian scholar of pedagogy, Leonardo Trisci-uzzi and the author reflects about the different manners to study pedagogy today. The classical authors, as Bruner, Piaget or Dewey, would to be central for young students of education for their human and professional growth. We want thinking peoples – says the author – and to obtain this result it’s necessary to return to classic literature
Deciphering the nature of cell state transitions in single cells using quantitative modeling of temporal dynamics
No full textCells are the smallest operational units of living systems. Through synthesis of various biomolecules and exchange of signals with the environment, cells tightly regulate their composition to realize a specific functional state. The transformation of a cell by internal and external stimuli that alter its biomolecular composition is conceptualized as a cell state transition and plays a critical role in dynamic biological processes, including differentiation, development, and proliferation. Recent advances in technologies that can scrutinize cell states at a single-cell resolution, particularly single-cell RNA sequencing (scRNA-seq), offer the opportunity to assess how underlying molecular properties influence the conversion between states. However, the design of suitable computational methods to aid with interpretation of these data is an active and incomplete area of research. Here, I decode the intricate properties of cell state transitions through quantitative analyses and modeling, tackling three distinct research questions that explore the path, pace, and rules of temporal dynamics in single cells.
First, I examine cell state transitions at the population level, asking which transitions occur in a differentiation protocol where a homogeneous pool of progenitor cells is directed towards a mature cell type. I explore this question in the practical setting of an embryonic stem cell differentiation protocol to generate retinal pigmented epithelium (RPE) for treating age- related macular degeneration. Using scRNA-seq, I conclude that our protocol, rather than progressing along a linear route from stem cells to RPE, can be better explained by a divergence-convergence model of differentiation that largely recapitulates development.
Second, I investigate the pace at which cell state transitions occur, asking how the rate of the cell cycle varies across different tissues and environmental contexts and whether it can be inferred by the gene expression of an ensemble of cells. To this end, I reformulate the RNA velocity algorithm, which extrapolates future cell states from scRNA-seq data, into a unified framework with gene manifold estimation, implementing a Bayesian model for velocity inference of periodic processes. I observe variations in cell cycle speed among diverse samples and in response to chemical or genetic perturbations. I also propose an inferential framework for statistical significance testing and discover that cell cycle velocities can be approximated in real time and validated experimentally.
Third, I consider the maintenance of a steady-state biological system, asking whether the rules that govern transition probabilities among cell states can be defined using non- transcriptional modalities. To explore this, I formulate a Markov model and infer a cell transition matrix using maximum likelihood estimation from reconstructed cell lineage information in a setting where endpoint states are known but past cell states are latent. I apply the method to characterize lipid-state switches in dermal human fibroblasts, finding a remarkable stability of states, termed lipotypes, across cell generations.
In summary, this work advances our understanding of cell state transitions for retinal progenitor differentiation, cell cycle modulations, and fibroblast plasticity, introducing new modeling strategies to tackle these dynamics with modern single-cell omics techniquesUPLAMANN
The Financial, Legal, and Political Context of Private Education
No full textFive principles underlie the changing policy architecture of American K-12 education. The author discusses these principles; how they are blurring the traditional demarcation of public and private schools; and the implications of this discussion for a private education research agenda
Progress in Kdo-glycoside chemistry
No full textAbstractGlycosylation chemistry of 3-deoxy-d-manno-oct-2-ulosonic acid units has been considerably developed within the last decade. This review covers major achievements with respect to improved yields and anomeric selectivity as well as suppression of the elimination side reaction via selection of dedicated protecting groups and appropriate activation of the anomeric center
Production of mannanase from Bacillus Subtilis LBF-005 and its potential for manno-oligosaccharides production
No full text
Agent-based modeling automated : data-driven generation of innovation diffusion models
No full textSimulation modeling is useful to gain insights into driving mechanisms of diffusion of innovations. This study aims to introduce automation to make identification of such mechanisms with agent-based simulation modeling less costly in time and labor. We present a novel automation procedure in which the generation of diffusion models is automated. It comprises three phases: (1) preprocessing of empirical data on the diffusion of a specific innovation, taken out be the user; (2) automated inverse modeling of decision models from a decision model library for their capability of explaining these data; (3) policy simulation automatically assesses user-chosen policy interventions in their potential of influencing the spreading of the innovation. We present a working software implementation of this procedure. We applied this tool to data-analysis on the diffusion of a sustainable innovation, water-saving showerheads. The proposed procedure successfully generated simulation models that explained available diffusion data. This provided a proof of concept. Further, it progresses agent-based modeling by providing model validation by design and by enabling detailed bottom-down modeling at the lower complexity of top-down modeling. We believe the proposed approach can widen the circle of persons that can use simulation modeling and better understand and shape innovation
External validation of anti-Müllerian hormone based prediction of live birth in assisted conception
No full text<p>Background - Chronological age and oocyte yield are independent determinants of live birth in assisted conception. Anti-Müllerian hormone (AMH) is strongly associated with oocyte yield after controlled ovarian stimulation. We have previously assessed the ability of AMH and age to independently predict live birth in an Italian assisted conception cohort. Herein we report the external validation of the nomogram in 822 UK first in vitro fertilization (IVF) cycles.</p>
<p>Methods - Retrospective cohort consisting of 822 patients undergoing their first IVF treatment cycle at Glasgow Centre for Reproductive Medicine. Analyses were restricted to women aged between 25 and 42 years of age. All women had an AMH measured prior to commencing their first IVF cycle. The performance of the model was assessed; discrimination by the area under the receiver operator curve (ROCAUC) and model calibration by the predicted probability versus observed probability.</p>
<p>Results - Live births occurred in 29.4% of the cohort. The observed and predicted outcomes showed no evidence of miscalibration (p = 0.188). The ROCAUC was 0.64 (95% CI: 0.60, 0.68), suggesting moderate and similar discrimination to the original model. The ROCAUC for a continuous model of age and AMH was 0.65 (95% CI 0.61, 0.69), suggesting that the original categories of AMH were appropriate.</p>
<p>Conclusions - We confirm by external validation that AMH and age are independent predictors of live birth. Although the confidence intervals for each category are wide, our results support the assessment of AMH in larger cohorts with detailed baseline phenotyping for live birth prediction.</p>
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