Mathematically gifted elementary students\u27 revisiting of Euler\u27s polyhedron theorem

This paper explores how the constructions of mathematically gifted fifth and sixth grade students using Euler’s polyhedron theorem compare to those of mathematicians as discussed by Lakatos (1976). Eleven mathematically gifted elementary school students were asked to justify the theorem, find counterexamples, and resolve conflicts between the theorem and counterexamples. The students provided two types of justification of the theorem. The solid figures suggested as counterexamples were categorized as 1) solids with curved surfaces, 2) solids made of multiple polyhedra sharing points, lines, or faces, 3) polyhedra with holes, and 4) polyhedra containing polyhedra. In addition to using the monster-barring method, the students suggested two new types of conjectures to resolve the conflicts between counterexamples and the theorem, the exception-baring method and the monster-adjustment method. The students’ constructions resembled those presented by mathematicians as discussed by Lakatos

Impacts of dietary nitrate on endothelial function, arterial stiffness, and systemic vascular pressure in peripheral arterial disease

Peripheral arterial disease (PAD) is the manifestation of atherosclerotic plaque in the larger arteries of the legs, which results in impaired blood flow to the lower extremities. Markers of vascular health, including endothelial function and arterial stiffness, have been shown to be attenuated in PAD. Purpose: We sought to examine the effects of a nitrate supplement (body mass-normalized dosage of beetroot juice) on vascular function measurements such as endothelial function, arterial stiffness, and central and peripheral blood pressure in patients with PAD. We hypothesized that acute intake of a nitrate supplement would improve vascular function. Methods: PAD patients (stage II-III, n=2, age around 73) had vascular measurements taken pre and post-beetroot juice ingestion including heart rate (HR), blood pressure (BP), endothelial function, arterial stiffness, and central pressure analysis. Results: Following nitrate ingestion, HR increased (Δ0.5 bpm) along with decreases in peripheral BP (Δ-9/-10 mmHg) and central BP (Δ-18/-4 mmHg). Endothelial function increased (Δ3.75%), carotid-to-radial pulse wave velocity decreased (Δ0.25 m/s), and augmentation index increased (Δ30.1%) after nitrate intake. Measurements of deceleration time increased (Δ49.5ms) and augmented pressure decreased (Δ-5 mmHg) after nitrate ingestion. Conclusion: Acute intake of a nitrate supplement may potentially be a useful therapeutic treatment to improve both central and peripheral vascular function which may be explained by increased endothelial dependent and independent vasodilatory mechanisms. However, this is a pilot study with two patients; therefore, future study is warranted with a bigger sample size to examine impacts of nitrate ingestion on vascular function and to further extrapolate our findings to patients with PAD

Acute mitochondrial antioxidant intake improves endothelial function, antioxidant enzyme activity, and exercise tolerance in patients with peripheral artery disease

Peripheral artery disease (PAD) is a manifestation of atherosclerosis in the leg arteries, which causes claudication. This may be in part due to vascular mitochondrial dysfunction and excessive reactive oxygen species (ROS) production. A mitochondrial-targeted antioxidant (MitoQ) has been shown to improve vascular mitochondrial function that, in turn, led to improved vascular function in older adults and animal models. However, the roles of vascular mitochondria in vascular function including endothelial function and arterial stiffness in patients with PAD are unknown; therefore, with the use of acute MitoQ intake, this study examined the roles of vascular mitochondria in endothelial function, arterial stiffness, exercise tolerance, and skeletal muscle function in patients with PAD. Eleven patients with PAD received either MitoQ or placebo in a randomized crossover design. At each visit, blood samples, brachial and popliteal artery flow-mediated dilation (FMD), peripheral and central pulse-wave velocity (PWV), blood pressure (BP), maximal walking capacity, time to claudication (COT), and oxygen utility capacity were measured pre- and-post-MitoQ and placebo. There were significant group by time interactions (P \u3c 0.05) for brachial and popliteal FMD that both increased by Δ2.6 and Δ3.3%, respectively, and increases superoxide dismutase (Δ0.03 U/mL), maximal walking time (Δ73.8 s), maximal walking distance (Δ49.3 m), and COT (Δ44.2 s). There were no changes in resting heart rate, BP, malondialdehyde, total antioxidant capacity, PWV, or oxygen utility capacity (P \u3e 0.05). MitoQ intake may be an effective strategy for targeting the vascular mitochondrial environment, which may be useful for restoring endothelial function, leg pain, and walking time in patients with PAD

Assessing Environmentally Sensitive Land to Desertification Using MEDALUS Method in Mongolia

Desertification is a global phenomenon caused by various processes, including climate change, vegetation processes, and human activities. The need to combat desertification is increasing in many countries. A reasonable assessment of the vulnerability or sensitivity of land cover to desertification at national scales is crucial to formulate appropriate strategies or policies for combating it. The main purpose of this work was to quantitatively assess the sensitivity of land cover to desertification in Mongolia using the MEDALUS approach. The MEDALUS method is a widely known technique for assessing desertification in the Mediterranean area. In this study, the method was adjusted to be applied to Mongolia, while the numerical methods of the MEDALUS remained the same. The modified MEDALUS method used nine factors from 2003 and 2008 to quantify the sensitivity of land to desertification. As a result, our study resulted in the calculation and spatial distribution of the Environmental Sensitive Area Index (ESAI), produced throughout Mongolia. In 2003, the middle region of the southern Mongolia had the highest sensitivity to desertification, while sensitivity in 2008 increased in the western area. Mongolia’s area with the highest ESAI range increased approximately five times, indicating rapid desertification occurring throughout Mongolia from 2003 to 2008

Presence of plasmid-mediated quinolone resistance (PMQR) genes in non-typhoidal Salmonella strains with reduced susceptibility to fluoroquinolones isolated from human salmonellosis in Gyeonggi-do, South Korea from 2016 to 2019

Non-typhoidal salmonellosis remains a pressing public health problem worldwide. Quinolones, particularly fluoroquinolones, are widely used to treat various infections, including non-typhoidal salmonellosis, which can be a serious illness. The emergence of fluoroquinolone-resistant Salmonella has resulted in treatment failure and high mortality rates. In this study, we estimated the presence of plasmid-mediated quinolone resistance (PMQR) genes in Salmonella enterica isolated from human salmonellosis patients in South Korea from 2016 to 2019. We evaluated the association of these genes with fluoroquinolone susceptibility. Antimicrobial susceptibility tests for Salmonella isolates were performed using the Vitek II system, and the minimum inhibitory concentrations (MIC) of ciprofloxacin and levofloxacin were determined using the E-test method. Plasmid-mediated quinolone resistance (PMQR) genes were detected by PCR amplification and quinolone resistance-determining regions (QRDRs) of the gyrA and parC genes were analyzed following Sanger sequencing of the PCR products. Thirty-four Salmonella strains with reduced susceptibility to fluoroquinolones (ciprofloxacin MIC ≥ 0.125 µg/mL and levofloxacin MIC ≥ 0.25 µg/mL) were selected from 208 human clinical Salmonella isolates. Among them, 22 Salmonella strains harbored one PMQR gene (qnrA, qnrB, or qnrS), and three Salmonella strains carried two PMQR genes (qnrS and aac(6′)-Ib-cr or qnrA and qnrB). qnrS was the most common PMQR gene. Serotyping revealed that Salmonella 4,[5]12:i:- (32.4%, 11/34) and Salmonella Typhimurium (29.4%, 10/34) were the two most predominant serovars, and Multi-locus sequence typing (MLST) showed that ST19 and ST34 were the most frequent sequence types. In conclusion, qnr gene-positive Salmonella 4,[5],12:i:- and Salmonella Typhimurium were the main serovars responsible for reduced susceptibility to fluoroquinolones. Therefore, our findings suggest that PMQR-positive Salmonella strains, which can be isolated from various samples including human, food, and the environment, should be carefully monitored.This research was supported by a Grant (19162MFDS037) from the Ministry of Food and Drug Safety in 2020

A Case of Familial Comedonal Darier's Disease

Darier's disease is a genetic disorder of keratinization with autosomal dominant inheritance. Its appearance is usually in the form of greasy, crusted, keratotic yellow-brown papules and plaques found particularly on seborrheic areas of the body. However, there are some clinical variants showing atypical skin lesions. Here we report an unusual case of Darier's disease, which mainly showed prominent comedonal papules over the face