An algorithm to classify the asymptotic set associated to a polynomial mapping

We provide an algorithm to classify the asymptotic sets of the dominant polynomial mappings F: \C^3 \to \C^3 of degree 2, using the definition of the so-called "{\it fa\c{c}ons}" in \cite{Thuy}. We obtain a classification theorem for the asymptotic sets of dominant polynomial mappings F: \C^3 \to \C^3 of degree 2. This algorithm can be generalized for the dominant polynomial mappings F: \C^n \to \C^n of degree $d$, with any $(n, d) \in {(\N^*)}^2$

On a singular variety associated to a polynomial mapping from \C^n to \C^{n-1}

We construct a singular variety ${\mathcal{V}}_G$ associated to a polynomial mapping G : \C^{n} \to \C^{n - 1} where $n \geq 2$. We prove that in the case G : \C^{3} \to \C^{2}, if $G$ is a local submersion but is not a fibration, then the homology and the intersection homology with total perversity (with compact supports or closed supports) in dimension two of the variety ${\mathcal{V}}_G$ is not trivial. In the case of a local submersion G : \C^{n} \to \C^{n - 1} where $n \geq 4$, the result is still true with an additional condition

On a singular variety associated to a polynomial mapping

In the paper "Geometry of polynomial mapping at infinity via intersection homology" the second and third authors associated to a given polynomial mapping F : \C^2 \to \C^2 with nonvanishing jacobian a variety whose homology or intersection homology describes the geometry of singularities at infinity of the mapping. We generalize this result.Comment: 1 figur

THE EFFECTS OF QUESTION-ANSWER RELATIONSHIP STRATEGY ON EFL HIGH SCHOOL STUDENTS’ READING COMPREHENSION

This paper reports the effects of the question-answer relationship strategy (QARS) on English as a foreign language (EFL) high school students’ reading comprehension and their perceptions of implementing this reading strategy. An experimental study was conducted with 50 tenth-grade students in a district high school in Can Tho City. The data were collected from the pretest and posttest, questionnaire, and interviews. The findings show that the QARS had positive effects on students’ reading comprehension and that students had positive perceptions of implementing this reading strategy. The findings of this research add to the contemporary literature the value of using the QARS to promote student learning reading.  Article visualizations

O Teorema de Poincare-Hopf

The Poincare-Hopf Theorem is one of the most used in other areas of science. There are applications of the Poincare-Hopf Theorem in physics, chemistry, biology and even in economics, psychology, etc ... The Poincare-Hopf Theorem connects an invariant of combinatorial, the character of Euler-Poincare to an invariant of differential geometry, index of vector fields. The results that connect two very different areas of mathematics can be considered as the most beautiful, useful and fruitful.Comment: in Portugues

EFFECTS OF ADDITIVES, PIGMENT AND FILLER ON PHYSICO- MECHANICAL PROPERTIES AND WEATHER RESISTANCE OF POLYUREA COATINGS

Polyurea coatings are known to provide high hardness, stable color, excellent weather durability and good scratch resistance. Being cured, the coatings can also express heat resistance up to 150 oC, good resistance to acids, oils, as well as other chemicals, high flexibility and strain, excellent adhesion to various substrate materials such as concrete, steel, ceramic, glass and others. In this paper, a polyurea coating has been developed on basis of polyaspartic acid esters and polyisocyanate curing agent, using 3 % nanoclay additive. The physical, mechanical, and chemical properties of the coatings were examined by current technical specifications. The results for developed coating were recorded as follow: 76 in.lb impact strength, 7.5 mm elongation, and 0.7 relative hardness; no blistering was observed after 30 days of immersion in  5 % HCl and 5 % NaOH solutions. Weather resistance of the coatings was also evaluated with full absence of peeling, blistering and high gloss retention after 500 h accelerated UV testing

Genetic diversity of Afzelia xylocarpa (Kurz) Craib in Vietnam based on analyses of chloroplast markers and random amplified polymorphic DNA (RAPD)

Afzelia xylocarpa (Kurz) Craib is not only an endangered species in Vietnam, but also around the world. The wood of this tree species is very valuable as it is used to construct houses and high quality furniture. Habitat loss and exploitation of A. xylocarpa by man have threatened the population to such an extent that the number of mature trees of this species has dwindled to quite a low quantity. Declining numbers of A. xylocarpa in turn causes a constriction of the gene pool. Thus, it is very important to evaluate the genetic diversity of A. xylocarpa (Kurz) Craib in order to conserve and sustain the surviving population of these trees. 50 samples of A. xylocarpa (Kurz) Craib were collected from seven locations in four provinces (Gia Lai, Dac Lac, Dong Nai and Ninh Thuan) and used to evaluate the genetic diversity of these trees based on the analysis of chloroplast 16S rRNA, non-coding regions between trnH-trnK, trnD-trnT and psbC-trnS chloroplast genes using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and random amplified polymorphic DNA (RAPD) markers. The data obtained reveals that the 50 samples of A. xylocarpa (Kurz) Craib have low level of genetic diversity, as supported by the fact that the genetic similarity coefficients of the trees ranged from 49 to 100%. At the similarity level of 49%, the 50 samples were grouped into two main groups. There was no clear local specificities of the samples as the samples from same locality were not found in same group. Due to low level of genetic diversity, low numbers of trees and scattered occurrence, setting up suitable conservation strategies are urgently needed.Key words: Afzelia xylocarpa (Kurz) Craib, genetic diversity, non-coding sequences, random amplified polymorphic DNA (RAPD) markers

Musculoskeletal Pain and Work-related Risk Factors among Waste Collectors in Hanoi, Vietnam: A Cross-sectional Study

BACKGROUND: Musculoskeletal disorders (MSDs) are prevalent among waste collectors (WCs) in developing countries. AIM: This study aimed to investigate the prevalence of MSDs and the factors associated with the risk of persistent musculoskeletal pain among WCs in Hanoi, Vietnam. METHODS: A cross-sectional survey was utilized to study 468 WCs in 2017. The Örebro Musculoskeletal Pain Questionnaire and a questionnaire on demographic and work conditions were used to collect data. Descriptive and multivariate logistics regression analyzes were applied at a significance level of 0.05 to examine the factors related to the risk of persistent pain. FINDINGS: About 74.4% of the participants of this study experienced MSDs in at least one body region and 9.4% reported MSDs in all 10 body sites. The lower back was reported to be the most affected followed by the neck and shoulders. The risk of persistent musculoskeletal pain was significantly associated with age (odds ratio (OR) = 2.31, confidence interval (CI) = 1.05–5.09), gender (OR = 3.29, CI = 1.28–8.44), work hours (OR = 2.35, CI = 1.12–4.92), work shift (OR = 0.48, CI = 0.26–0.92), duration of poor postures of the neck (OR = 0.31, CI = 0.13–0.76), bent back (OR = 0.4 CI = 0.18–0.92) and for medial rotation (OR = 3.01, CI = 1.42–6.36), carrying heavy objects (OR = 2.94, CI = 1.15–7.48), and experience of work dissatisfaction (OR = 3.31, CI = 1.46-7.52), stress (OR = 7.14, CI = 3.14–16.24), or anxiety (OR = 6.37, CI = 3.07–13.21). CONCLUSIONS: High prevalence of MSDs among WCs and its association with self-assessed unfavorable work postures and work-related stress implies the need of mechanical and social support at work for WC to prevent the development of MSDs and persistent pain