Physical fitness normative values for 6–18-year-old Greek boys and girls,using the empirical distribution and the lambda,mu, and sigma statistical method

The aim of the this study was to establish age- and gender-specific physical fitness normative values and to compare percentiles and Z scores values in a large, nationwide sample of Greek children aged 6–18 years. From March 2014 to May 2014, a total of 424,328 boys and girls aged 6–18 years who attended school in Greece were enrolled. The studied sample was representative, in terms of age–sex distribution and geographical region. Physical fitness tests (i.e. 20?m shuttle run test (SRT), standing long jump, sit and reach, sit-ups, and 10?×?5?m SRT) were performed and used to calculate normative values, using the percentiles of the empirical distributions and the lambda, mu, and sigma statistical method. Normative values were presented as tabulated percentiles for five health-related fitness tests based on a large data set comprising 424,328 test performances. Boys typically scored higher than girls on cardiovascular endurance, muscular strength, muscular endurance, and speed/agility, but lower on flexibility (all p values <0.001). Older boys and girls had better performances than younger ones (p?相似文献   

Contradictions,dialectical oppositions and shifts in teaching mathematics

The study reported in this paper concerns the tensions and conflicts that teachers experience while they enact a new set of reform-oriented curricular materials into their classrooms. Our focus is οn the interactions developed in two groups of teachers in two schools for a period of a school year. We use Activity Theory to study emerging contradictions and we elaborate on the construct of dialectical opposition to understand the nature of these contradictions and their potential for teacher learning. We provide evidence that discussions about contradictions and their dialectical character in the two groups support teachers to engage differently in mathematics teaching and learning and carry potentials for shifts in the practices that evolve in their classrooms. Our study addresses empirically in the context of mathematics teaching the philosophical claim about the role of contradictions as a driving force for any dynamic system.     

Students’ achievement goals,emotion perception ability and affect and performance in the classroom: a multilevel examination

Performance at school is affected not only by students’ achievement goals but also by emotional exchanges among classmates and their teacher. In this study, we investigated relationships between students’ achievement goals and emotion perception ability and class affect and performance. Participants were 949 Greek adolescent students in 49 classes and their Greek language and mathematics teachers. Results from multilevel analyses indicated that students’ mastery-approach and performance-approach goals were positively related to positive affect whereas performance-avoidance goals were negatively related to positive affect. At class-level, relationships between achievement goals and affect were moderated by students’ emotion perception ability. These findings highlight the importance of emotion abilities and their role in motivational processes for class-level outcomes.     

The influence of water depth on kinematic and spatiotemporal gait parameters during aquatic treadmill walking

The purpose of this study was to investigate kinematic and spatiotemporal variables of aquatic treadmill walking at three different water depths. A total of 15 healthy individuals completed three two-minute walking trials at three different water depths. The aquatic treadmill walking was conducted at waist-depth, chest-depth and neck-depth, while a customised 3-D underwater motion analysis system captured their walking. Each participant’s self-selected walking speed at the waist level was used as a reference speed, which was applied to the remaining two test conditions. A repeated measures ANOVA showed statistically significant differences among the three walking conditions in stride length, cadence, peak hip extension, hip range of motion (ROM), peak ankle plantar flexion and ankle ROM (All p values < 0.05). The participants walked with increased stride length and decreased cadence during neck level as compared to waist and chest level. They also showed increased ankle ROM and decreased hip ROM as the water depth rose from waist and chest to the neck level. However, our study found no significant difference between waist and chest level water in all variables. Hydrodynamics, such as buoyancy and drag force, in response to changes in water depths, can affect gait patterns during aquatic treadmill walking.     

Study of the stability of a series of synthetic colorants applied with styrene-acrylic copolymer, widely used in contemporary paintings, concerning the effects of accelerated ageing

This study examines the materials of a contemporary pictorial artwork, belonging to the Macedonian Museum of Contemporary Art in Thessaloniki (Greece), and needing conservation. The combined use of micro-FTIR and micro-Raman spectroscopy allowed the identification of almost all painting materials. Moreover, the stability of a series of synthetic pigments towards accelerated ageing is investigated in applications using the contemporary binding medium styrene-acrylic copolymer. The pigments in question are: Hansa yellow PY3 and PY74, quinacridone PV19 and PR122, naphthol AS PR112, phthalocyanine green PG7 and blue PB15, dioxazine PV37, van Dyck brown PBk11, ivory black PBk9, and titanium dioxide PW6. The organic pigments were applied alone or mixed with titanium dioxide, in rutile form or as a mixture of rutile/anatase. The experimental swatches were subjected to ageing tests, and subsequently studied as to colour changes by means of colorimetric measurements, and as to the molecular structure differentiations by infrared spectroscopy in reflectance mode. The ageing tests included exposure to high temperature and humidity (90 °C, 60% RH) and to ultraviolet radiation (350 nm, 30 °C and 50% RH, with a substantial temperature increase at 90 °C for 3 days). The greater colour difference is caused by high temperature and humidity, whereas paint layers containing TiO₂, and especially the mixture of the forms rutile/anatase, prove very susceptible to ultraviolet radiation, demonstrating a significant colour difference and extended molecular changes.     

Training self-other distinction facilitates perspective taking in young children

People sometimes commit ‘egocentric errors’, failing to ignore their own perspective when interpreting others' communication. Training imitation-inhibition, when participants perform the opposite action from another person, facilitates subsequent perspective-taking in adults. This study tested whether imitation-inhibition training also facilitates perspective-taking in 3- to 6-year-olds, an age where egocentric perspective may be particularly influential. Children participated in a 10-min imitation-inhibition, imitation, or non-social-inhibition training (white, n = 25 per condition, 33 female, period: 2018–2021), then the communicative-perspective-taking Director task. Training had a significant effect (F(2, 71) = 3.316, p = .042, η² = .085): on critical trials, the imitation-inhibition-group selected the correct object more often than the other groups. Imitation-inhibition training specifically enhanced the perspective-taking process possibly by highlighting the distinction between self and other.     

Subspace design of low-rank estimators for higher-order statistics

Higher-order statistics (HOS) are well known for their robustness to additive Gaussian noise and ability to preserve phase. HOS estimates, on the other hand, have been criticized for high complexity and the need for long data in order to maintain small variance. Since rank reduction offers a general principle for reduction of estimator variance and complexity, we consider the problem of designing low-rank estimators for HOS. We propose three methods for choosing the transformation matrix that reduces the mean-square error (MSE) associated with the low-rank HOS estimates. We also demonstrate the advantages of using low-rank third-order moment estimates for blind system estimation. Results indicate that the full rank MSE corresponding to some data length N can be attained by a low-rank estimator corresponding to a length significantly smaller than N.     

ICTs and Internet adoption in China's tourism industry

The fast development of information communication technologies (ICTs) and the expansion of the Internet have changed industry structures around the world. New technologies have been adopted in the tourism industry in Europe and America for more than 30 years, and the trend is likely to continue into the future. China, as a fast-growing developing country in Asia, is gaining importance in the international tourism market for its historical and cultural attractiveness as a destination. It is also becoming a booming tourism source country as its population starts travelling overseas. This study examines how the ICT and Internet gradually change the tourism industry structure in China; how important such changes are, and to where such changes will lead China's tourism industry. This exploratory research is conducted based on information collected from several tourism organisations, such as airlines, hotels, tour operators, visitor attractions and the tourism authorities within China.     

Changes in school mathematics knowledge in Greece: a Bernsteinian analysis

The purpose of this paper is to critically examine the changes that took place in school mathematics knowledge for pupils aged six and seven (first grade of Greek elementary school) and its pedagogical approach, which took shape following the reforms of the mathematics curricula in 1982 and 2003. Our analysis is based on Bernstein’s theoretical framework on pedagogic discourse and Dowling’s theoretical framework on textual domains. The results showed that there are differences between the 1982 and 2003 reforms, in terms both of the content of mathematics knowledge, as well as of the forms of pedagogic interaction between the teacher and the pupil.     

Quadriceps muscle blood flow and oxygen availability during repetitive bouts of isometric exercise in simulated sailing

In this study, we wished to determine whether the observed reduction in quadriceps muscle oxygen availability, reported during repetitive bouts of isometric exercise in simulated sailing efforts (i.e. hiking), is because of restricted muscle blood flow. Six national-squad Laser sailors initially performed three successive 3-min hiking bouts followed by three successive 3-min cycling tests sustained at constant intensities reproducing the cardiac output recorded during each of the three hiking bouts. The blood flow index (BFI) was determined from assessment of the vastus lateralis using near-infrared spectroscopy in association with the light-absorbing tracer indocyanine green dye, while cardiac output was determined from impedance cardiography. At equivalent cardiac outputs (ranging from 10.3±0.5 to 14.8±0.86 L · min(-1)), the increase from baseline in vastus lateralis BFI across the three hiking bouts (from 1.1±0.2 to 3.1±0.6 nM · s(-1)) was lower (P = 0.036) than that seen during the three cycling bouts (from 1.1±0.2 to 7.2±1.4 nM · s(-1)) (Cohen's d: 3.80 nM · s(-1)), whereas the increase from baseline in deoxygenated haemoglobin (by ～17.0±2.9 μM) (an index of tissue oxygen extraction) was greater (P = 0.006) during hiking than cycling (by ～5.3±2.7 μM) (Cohen's d: 4.17 μM). The results suggest that reduced vastus lateralis muscle oxygen availability during hiking arises from restricted muscle blood flow in the isometrically acting quadriceps muscles.