Primary and methyl aliphatic halides and tosylates undergo substitution reactions with nucleophiles in one step by the classic S N 2 mechanism, which is characterized by second-order kinetics and inversion of configuration at the reaction center. Tertiary aliphatic halides and tosylates undergo substitution reactions with nucleophiles in two (or more) steps by the classic S N 1 mechanism, which is characterized by first-order kinetics and incomplete inversion of configuration at the reaction center due to the presence of ion pairs. When (...) the nucleophile is also the solvent, the substitution reaction is called a solvolysis, and both the S N 2 and S N 1 reactions now obey first-order kinetics. Schleyer and Bentley have provided solid, but not conclusive, evidence that secondary substrates undergo solvolysis by a merged mechanism, one that blends characteristics of both the S N 2 and S N 1 mechanisms. The following paper presents the history of their sustained pursuit of a merged mechanism and subsequent rebuttals to this claim. Several issues related to the philosophy and sociology of science are also discussed. (shrink)

The mechanistic significance of a kinetic isotope effect on a cytochrome P‐450catalyzed reaction depends, fundamentally, on the nature of the interaction of the substrate with the active site of the enzyme as well as on the nature of the chemistry of the reaction catalyzed. Consequently, kinetic isotope effects can be used to extract information on the topology of the enzyme and the mechanism of substrate oxidation. Kinetic isotope effect studies are sometimes accompanied by ‘metabolic switching’ or (...) a change in metabolic pathway, catalyzed either by the same enzyme or by a different enzyme. For the specific case where ‘metabolic switching’ gives rise to a change in regional specificity for the cytochrome P‐450 catalyzed metabolism of a compound, this change can be explained in terms of the topological constraints on substrate binding imposed by the active site of the enzyme. (shrink)

The precise position of a spectral line emitted by an atomic system depends on the mass of the atomic nucleus and is therefore different for isotopes belonging to the same element. The possible presence of an isotope effect followed from Bohr's atomic theory of 1913, but it took several years before it was confirmed experimentally. Its early history involves the childhood not only of the quantum atom, but also of the concept of isotopy. Bohr's prediction of the isotope (...) effect was apparently at odds with early attempts to distinguish between isotopes by means of their optical spectra. However, in 1920 the effect was discovered in HCl molecules, which gave rise to a fruitful development in molecular spectroscopy. The first detection of an atomic isotope effect was no less important, as it was by this means that the heavy hydrogen isotope deuterium was discovered in 1932. The early development of isotope spectroscopy led to successes as well as problems. At the end of the paper I briefly comment on the relationship between theory, experiment and prediction in this area of spectral physics. (shrink)

Mechanisms occurring at the atomic level are now known to drive processes essential for life, as revealed by quantum effects on biochemical reactions. Some macroscopic characteristics of organisms may thus show an atomic imprint, which may be transferred across organisms and affect their evolution. This possibility is considered here for the first time, with the aim of elucidating the appearance of an animal innovation with an unclear evolutionary origin: migratory behaviour. This trait may be mediated by a radical pair (...) (RP) mechanism in the retinal flavoprotein cryptochrome, providing essential magnetic orientation for migration. Isotopes may affect the performance of quantum processes through their nuclear spin. Here, we consider a simple model and then apply the standard open quantum system approach to the spin dynamics of cryptochrome RP. We changed the spin quantum number (I) and g‐factor of hydrogen and nitrogen isotopes to investigate their effect on RP's yield and magnetic sensitivity. Strong differences arose between isotopes with I = 1 and I = 1/2 in their contribution to cryptochrome magnetic sensitivity, particularly regarding Earth's magnetic field strengths (25–65 µT). In most cases, isotopic substitution improved RP's magnetic sensitivity. Migratory behaviour may thus have been favoured in animals with certain isotopic compositions of cryptochrome. (shrink)

Reading difficulties that are not addressed at the primary level continue to exist at the secondary level with serious consequences. Thus, it is important to provide struggling students with specific reading support. In particular, many students with learning disabilities and emotional behavioral disorders demonstrate reading obstacles and are at risk for motivation loss. A multiple baseline design was used to evaluate the effects of a motivational reading racetrack as peer-tutoring on the word reading skills of secondary students (...) with LD with and without EBD. The intervention was conducted through 4–5 baseline and 16–18 reading units three times a week for 15 min over 8 weeks. The results showed positive effects indicating a highly effective treatment. In addition, follow-up results were also promising. Our findings indicate that this multicomponent intervention has a positive effect on the word fluidity of low-achieving students in secondary education with LD and/or EBD. (shrink)

Osteoporosis (OP) is a bone disease which affects a number of post‐menopausal females and puts many at risk for fractures. A large number of patients are taking bisphosphonates (BPs) to treat their OP and a rare complication is the development of atypical femoral fractures (AFF). No real explanations for the mechanisms underlying the basis for development of where AFF develop while on BPs has emerged. The present hypothesis will discuss the possibility that part of the risk for an AFF is (...) a secondary effect of BPs on a subset of vascular cells in a genetically at‐risk population, leading to localized deregulation of the endothelial cell (EC)‐bone cell‐matrix units in nutrient channels/canals of the femur and increased risk for AFF. This concept of targeting ECs is consistent with location of AFF in the femur, the bilateral risk for occurrence of AFF, and the requirement for long term exposure to the drugs. (shrink)

This paper reports the findings of a predominantly qualitative study that explored the effects of the practice of Philosophy for Children on pupils’ affective engagement.[1] From its conception, the practice of P4C has been linked to the development of caring and collaborative thinking and the study aimed to closely consider that relationship. An appropriate self-designed P4C program was implemented with 75 Year 9 pupils of Religious Education at an independent secondary school in the United Kingdom. An interpretive research (...) approach was taken and thematic analysis was appropriated to analyse the data. Findings supported the claims of previous research that P4C can foster affective engagement in many pupils, particularly those pupils who find emotional expression and interpersonal interactions challenging. A tentative conclusion reached supposes that P4C has the potential to contribute to the affective engagement of pupils, but with the recommendation that implementing a P4C program must be executed carefully and with the mindfulness that it may not have the same potential or usefulness for all pupils universally. (shrink)

Physical activities are generally accepted as promoting important psychological benefits. However, studies examining martial arts as a form of physical activity and mental health have exhibited many methodological limitations in the past. Additionally, recent philosophical discussion has debated whether martial arts training promotes psychological wellbeing or illness. Self-efficacy has an important relationship with mental health and may be an important mechanism underpinning the potential of martial arts training to promote mental health. This study examined the effect of martial arts training (...) on the psychological construct of self-efficacy. A total of 283 secondary school students with a mean age of 12.76 (SD = 0.68) years were recruited to complete a time-limited (10-session) martial arts intervention, which was examined using a randomised controlled trial. Univariate ANOVAs found that the intervention improved the experimental group’s self-efficacy compared to the control group, which was sustained at follow-up. Regression analysis indicated that socio-educational status moderated this outcome. These findings support the martial arts-based intervention’s potential to improve self-efficacy and promote wellbeing through physical activity. Martial arts training may be an efficacious psychosocial treatment that can be used as a complementary approach to promote mental health. (shrink)

Although many studies have revealed the importance of study skills for students' first?year performance and college retention, the extent of the impact of study skills preparation on students' academic achievement is less clear. This paper explores the impact of pre?university study skills preparation on students' first?year study experiences, academic achievement and persistence. The setting for this study is a large law school in the Netherlands which attracts students from more than 100 schools for secondary education. The results show that (...) the perceived study skills preparation concerning time management and learning skills does have a positive impact on college students' first?year study behaviour and academic achievement. However, the study also shows that the impact of perceived college preparation is far less important for college retention than other factors such as satisfaction about the chosen degree programme and tutorial attendance. (shrink)

Central sensitization refers to the increased responsiveness of nociceptive neurons in the central nervous system after repeated or sustained peripheral nociceptor activation. It is hypothesized to play a key role in the development of chronic pain. A hallmark of central sensitization is an increased sensitivity to noxious mechanical stimuli extending beyond the injured location, known as secondary hyperalgesia. For its ability to modulate the transmission and the processing of nociceptive inputs, attention could constitute a promising target to prevent central (...) sensitization and the development of chronic pain. It was recently shown that the experimental induction of central sensitization at both forearms of healthy volunteers using bilateral high-frequency electrocutaneous stimulation (HFS), can be modulated by encouraging participants to selectively focus their attention to one arm, to the detriment of the other arm, resulting in a greater secondary hyperalgesia on the attended arm as compared to the unattended one. Given the potential value of the question being addressed, we conducted a preregistered replication study in a well-powered independent sample to assess the robustness of the effect, i.e., the modulatory role of spatial attention on the induction of central sensitization. This hypothesis was tested using a double-blind, within-subject design. Sixty-seven healthy volunteers performed a task that required focusing attention toward one forearm to discriminate innocuous vibrotactile stimuli while HFS was applied on both forearms simultaneously. Our results showed a significant increase in mechanical sensitivity directly and 20 min after HFS. However, in contrast to the previous study, we did not find a significant difference in the development of secondary hyperalgesia between the attended vs. unattended arms. Our results question whether spatial selective attention affects the development of secondary hyperalgesia. Alternatively, the non-replication could be because the bottom-up capture of attention caused by the HFS-mediated sensation was too strong in comparison to the top-down modulation exerted by the attentional task. In other words, the task was not engaging enough and the HFS pulses, including those on the unattended arm, were too salient to allow a selective focus on one arm and modulate nociceptive processing. (shrink)

Stable heavy isotopes co‐exist with their lighter counterparts in all elements commonly found in biology. These heavy isotopes represent a low natural abundance in isotopic composition but impose great retardation effects in chemical reactions because of kinetic isotopic effects (KIEs). Previous isotope analyses have recorded pervasive enrichment or depletion of heavy isotopes in various organisms, strongly supporting the capability of biological systems to distinguish different isotopes. This capability has recently been found to lead to general decline of (...) heavy isotopes in metabolites during yeast aging. Conversely, supplementing heavy isotopes in growth medium promotes longevity. Whether this observation prevails in other organisms is not known, but it potentially bears promise in promoting human longevity. (shrink)

The study examined the impact of students’ absolute age-position at the time of testing by grade level and gender on their achieved level of mathematics, reading and science performance. An analysis was conducted based on a sample of 11,500 15-year-old pupils in the United Arab Emirates who participated in the OECD’s Programme for International Student Assessment 2012 study. In support of an absolute age-position effect it was found that the youngest age-at-test student grouping demonstrated significantly lower levels of mathematics, reading (...) and science performance than their older peers. It was also shown that grade level had a significant influence on the demonstration of functional knowledge by same-aged students. Lastly, the female students attained significantly higher levels of mathematics, reading and science performance than their male counterparts. (shrink)

The purpose of this study was to examine student perceptions of teaching behavior. Additionally the aim was to examine if teacher characteristics (educational level, gender, and teaching experience) could explain differences in student perceptions of their teachers. Teaching behavior was studied from the research on teaching and teacher effectiveness perspective. Secondary students (N = 7,114), taught by 410 teachers in Spain, participated in the study. Survey data were analyzed using non-parametric tests, Kruskal-Wallis, U Mann-Whitney with Bonferroni correction, and the (...) analysis of effect sizes. Furthermore, a regression model was applied. Results showed that teaching behavior was perceived as sufficient to good, depending on the teaching behavior domain. Results indicated interesting differences between lower secondary education, upper secondary education and vocational education and training teachers. The effect size values (rU statistic) ranged between 0.43 and 0.63, highlighting the significant effect of teachers’ teaching experience on the six teaching skills domains: learning climate, efficient classroom management, clarity of instruction, activating teaching, differentiation, and teaching learning strategies. Those teachers with less teaching experience were the ones who showed higher scores. Findings from the regression model showed that educational level had a significant predictive effect on the six teaching skills domains, mainly for male teachers. However, in several domains female teachers were perceived by students to outperform their male counterparts. (shrink)

This paper argues that two principles held by many metaphysicians and philosophers of mind are inconsistent: there is no systematic overdetermination, and some causal effects are also determined by their metaphysical grounds. Call this “The Problem of Secondary Effects.” After introducing the problem and noting philosophical theories that face it, the paper offers further clarification by considering three potential strategies for solving it. All fail. An approach that sacrifices ‘secondary effects’ is briefly sketched as a (...) solution. (shrink)

This study investigated new avenues for understanding the association between parental autonomy support and academic engagement among Chinese secondary vocational students based on Self-Determination Theory and Career Construction Theory. We highlighted the mediator role of career adaptability and career decision-making self-efficacy in the relationship between parental autonomy support and academic engagement. Using self-reported data from 1,930 secondary vocational students in a city in Central China, we performed correlation analysis and mediation analysis by using SPSS and Mplus. The results (...) revealed that parental autonomy support was positively associated with students’ academic engagement. Moreover, as an adaptability resource and adapting response, career adaptability and career decision-making self-efficacy played mediating roles between parental autonomy support and academic engagement. These findings offered crucial empirical evidence for understanding the association between parental support and academic engagement among Chinese secondary vocational students. Meanwhile, it also validated the application of Career Construction Theory in a sample of secondary vocational students in China and provided constructive insights for implementing diverse support measures to boost their academic and career development. (shrink)