1,124 research outputs found
Birational automorphism groups of projective varieties of Picard number two
We slightly extend a result of Oguiso on birational or automorphism groups
(resp. of Lazi\'c - Peternell on Morrison-Kawamata cone conjecture) from
Calabi-Yau manifolds of Picard number two to arbitrary singular varieties X
(resp. to klt Calabi-Yau pairs in broad sense) of Picard number two. When X has
only klt singularities and is not a complex torus, we show that either Aut(X)
is almost cyclic, or it has only finitely many connected components.Comment: title slightly changed to this; some proof simplified; submitted to
the Proceedings of Groups of Automorphisms in Birational and Affine Geometry,
28 October - 3 November 2012, C.I.R.M., Trento, Ital
Business Faculty and Undergraduate Students\u27 Perceptions of Online Learning: A Comparative Study
In this paper, the authors compare business faculty and undergraduate students\u27 perceptions of online learning. Specifically, a survey was given to a convenience sample of 893 undergraduate students (of which 890 were usable) at two regional universities in the southern United States; a modified version of the survey was mailed to a random sample of 1,175 business faculty members throughout the United States. Comparison of the results from each group showed that a number of differences in perception exist, due, perhaps, to the heterogeneous points of view and motivations for online learning between faculty and students. Since many universities are still deciding the extent of their offerings of such courses, this information may be helpful to university administrators in deciding which types of courses at their universities might be offered online. Faculty who are considering teaching one or more online courses may find the results of this study helpful in structuring these online offerings. The results of this study should assist students in gaining a realistic expectation of what to anticipate from online learning courses based on information we have found and studies we have done. It is important that students have a realistic perception of the online learning experience
Student Perceptions Of The Online Classroom: An Update
In this paper, the authors compare perceptions of 2001-2002 undergraduate students toward online courses, with the attitudes of undergraduate students matriculating in 2005. Specifically, a questionnaire developed and used in a study during the period 2001-2002, in which there were eight hundred ninety-six (896) undergraduate students at two medium-sized southern universities, was again given to six hundred twenty-six (626) undergraduate students at these same two universities in 2005. The results suggest that students continue to have questions about the overall appeal of online courses, despite the fact that three to four years have elapsed. The results of this study should be of interest to university administrators, faculty members, and students who plan to offer, teach, or take online courses in the future. This information may be helpful to university administrators in deciding which types of courses at their universities might be offered online. Faculty who are considering teaching one or more online courses may find the results of this study helpful in structuring these online offerings. This research is also intended to give students a realistic expectation of what to anticipate from online courses, based upon information we have found and studies we have done
Local collaborations for physical activity promotion: a network analysis.
This study aims to describe a local network for physical activity promotion and identify factors associated to collaboration or partnership ties between its actors. The study was carried out in a district of São Paulo, Brazil. Thirty-two actors responsible for policies, programs, and initiatives to promote physical activity within the district were interviewed from June to December 2012. Interviews included information about the actors' attributes and their relationships with the other actors. Network analysis techniques were used to describe and analyze the structure of the network. Thirty-two actors maintained 179 relationships among themselves (density = 0.18), of which 46% were reciprocal. Four in 10 relationships did not extend beyond information exchange. Forty-six relationships were classified as collaborations or partnerships (density = 0.09), of which 40% were concentrated on one actor of the public sector. To perceive institutional structure and bureaucracy as limiting factors to networking has been positively associated with new collaboration or partnership ties (OR = 2.37; 95%CI: 1.2-5.50). Understanding the structure of the network may empower the actors and foster self-management, facilitating the identification and decision, in a collaborative way, in which new relationships may have greater impact in the physical activity promotion within the district
Curve classes on irreducible holomorphic symplectic varieties
We prove that the integral Hodge conjecture holds for 1-cycles on irreducible
holomorphic symplectic varieties of K3 type and of Generalized Kummer type. As
an application, we give a new proof of the integral Hodge conjecture for cubic
fourfolds.Comment: 15 page
Impact of comprehensive pulmonary rehabilitation on anxiety and depression in hospitalized COPD patients.
To prospectively evaluate the effect of inpatient pulmonary rehabilitation (iPR) on anxiety and depression as outcome measures in patients with COPD, we studied 149 consecutive adults COPD referred to our iPR after an exacerbation. Patients were divided according to the GOLD staging into: Group 1 (stage 2a, n = 48, FEV1 63 +/- 9% pred.), Group 2 (stage 2b, n = 53, FEV1 42 +/- 6% pred.) and Group 3 (stage 3, n = 48, FEV1 25 +/- 7% pred.). The iPR consisted of twelve 3-hours daily sessions. Hospital Anxiety Depression (HAD) Scale as well as 6-minute walk (6MWD) with evaluation of dyspnea (D) and leg fatigue (F) at rest and end of effort, and health related quality of life by means of St. George Respiratory Questionnaire (SGRQ) were assessed before (T0) and after (T1) the iPR. 6MWD, D and F at end of effort and SGRQ total score similarly improved (p < 0.001) in all groups after iPR. The mean level of HAD-anxiety (from 9.1 +/- 4.0 to 7.7 +/- 3.5, from 9.0 +/- 4.6 to 7.2 +/- 4.6 and from 8.1 +/- 4.1 to 6.7 +/- 4.3 in group 1,2 and 3 respectively) and HAD-depression (from 9.4 +/- 3.5 to 8.2 +/- 3.5, from 9.1 +/- 4.2 to 8.2 +/- 4.5 and from 9.0 +/- 4.0 to 7.4 +/- 4.5 respectively) similarly changed (p < 0.0001) over time in all groups. The total percentage of patients with abnormal score (> 10) of HAD-anxiety (from 31% to 21%) and HAD-depression (from 30% to 22%) significantly decreased (p < 0.05) after the iPR. Inpatient pulmonary rehabilitation may improve levels of anxiety and depression as well as symptoms, exercise capacity and health related quality of life in moderate to severe COPD patients after an acute exacerbation
The Relationship between Gut Microbiota and Respiratory Tract Infections in Childhood: A Narrative Review
Respiratory tract infections (RTIs) are common in childhood and represent one of the main causes of hospitalization in this population. In recent years, many studies have described the association between gut microbiota (GM) composition and RTIs in animal models. In particular, the “inter-talk” between GM and the immune system has recently been unveiled. However, the role of GM in human, and especially infantile, RTIs has not yet been fully established. In this narrative review we provide an up-to-date overview of the physiological pathways that explain how the GM shapes the immune system, potentially influencing the response to common childhood respiratory viral infections and compare studies analysing the relationship between GM composition and RTIs in children. Most studies provide evidence of GM dysbiosis, but it is not yet possible to identify a distinct bacterial signature associated with RTI predisposition. A better understanding of GM involvement in RTIs could lead to innovative integrated GM-based strategies for the prevention and treatment of RTIs in the paediatric population
Valorization of wheat bran agro-industrial byproduct as an upgrading filler for mycelium-based composite materials
When considered by a biorefinery approach, an agroindustrial byproduct such as wheat bran can find a new standing in the field of fabrication of mycelium-based materials. The present work reports on a systematic study on the effect of wheat bran as an upgrading feedstock for the growth and development of fully biobased and biodegradable composites. Two families of materials based on bran/cotton and bran/hemp mixtures were fabricated on an industrial scale. The natural materials thus obtained were fully characterized and their end-life was assessed in composting conditions. The research focusses on two main aspects: the nutritional contribution of bran for the fungal growth and its effect on the mechanical properties as a filler in the final composites. It must be noted that the valorization and exploitation of a byproduct such as bran can have a considerable impact on the industrial production of mycelium-based composite materials, by reducing the time of production while increasing their mechanical performances
Natural deep eutectic solvents as thermostabilizer for Humicola insolens cutinase
As a new generation of green solvents, deep eutectic solvents (DESs) are considered a promising alternative to current harsh organic solvents and find application in many chemical processing methods such as extraction and synthesis. DESs, normally formed by two or more components via various hydrogen bond interactions, offer high potential as medium for biocatalysis reactions where they can improve efficiency by enhancing substrate solubility and the activity and stability of the enzymes. In the current study, the stabilization of Humicola insolens cutinase (HiC) in natural deep eutectic solvents (NADESs) was assessed. The best hydrogen bond donor among sorbitol, xylitol, erythritol, glycerol and ethylene glycol, and the best acceptor among betaine, choline chloride, choline acetate, choline dihydrogen citrate and tetramethylammonium chloride, were selected, evaluating binding energies and molecular orientations through molecular docking simulations, and finally used to prepare NADES aqueous solutions. The effects of component ratio and NADES concentration on HiC thermostability at 90 degrees C were also investigated. The choline dihydrogen citrate:xylitol, in a 1:1 ratio with a 20 wt% concentration, was selected as the best combination in stabilizing HiC, increasing its half-life three-fold
From food waste to eco-friendly functionalized polymer composites: Investigation of orange peels as active filler
: The development of eco-friendly polymer composites with multifunctional properties aligns with the goals of the circular economy agenda, which aims to minimize waste and promote the sustainable use of resources by closing the loop of product life cycles. Eco-friendly polymer composites play a crucial role in achieving these objectives. The present work focuses on the preparation of fully biobased blends obtained by melt mixing a bio-polyester, poly(butylene succinate-co-adipate) (PBSA), with orange peels up to 20 wt%, to yield active polymer composites. Orange peels, employed here as natural filler, are largely available from food wastes, they are rich in phenolic compounds and possess antioxidant activity as shown by the experimental tests carried out. The thermal stability of the formulated composites is almost unchanged by the filler addition, showing only a slight decrease of the crystallization temperatures and crystalline fraction within the composites. The mechanical properties of the compounds evidence an increase in the elastic modulus together with a decrease in the tensile strength, while the elongation at break remains almost constant. The incorporation of the natural filler enabled the integration of antioxidant and antibacterial properties, which were absent in the original pristine polymer
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