Early adolescents' enjoyment experienced in learning situations and its relation to student achievement

While many studies confirm that positive emotions, including enjoyment, lead to better student achievement, less empirical evidence exists about possible mediator variables that link achievement to enjoyment. It is proposed that achievement and enjoyment form a circular dependency; enjoyment in learning leads to higher achievement but a degree of achievement is required to enjoy learning. This study provides insight into the reverse of the much studied enjoyment to achievement link and provides practical recommendations on how to use these findings. Founded in Control-value theory, which suggests that control and value cognitions are important variables that mediate the connection between enjoyment and achievement, this study explores the reciprocal achievement-cognition-enjoyment link. The reciprocal link was investigated by applying a one year longitudinal design to students of grade 6 and 7 (N = 356). This age group was chosen because early adolescence represents a critical period during which a strong decrease in positive learning emotions is observed. Part of the work involved identifying factors that might be responsible for this negative development. Results of cross-lagged path analysis identified reciprocal effects between student achievement and enjoyment with control and value cognitions functioning as partial mediators. High achievement goes with high control and value cognitions, which in turn positively affect enjoyment. However, cross-lagged correlations could only be partly confirmed. The results are discussed in terms of theoretical and practical implications.

Early adolescents’ enjoyment experienced in learning situations at school and its relation to student achievement

While many studies confirm that positive emotions, including enjoyment, lead to better student achievement, less empirical evidence exists about possible mediator variables that link achievement to enjoyment. It is proposed that achievement and enjoyment form a circular dependency; enjoyment in learning leads to higher achievement but a degree of achievement is required to enjoy learning. This study provides insight into the reverse of the much studied enjoyment to achievement link and provides practical recommendations on how to use these findings. Founded in Control-value theory, which suggests that control and value cognitions are important variables that mediate the connection between enjoyment and achievement, this study explores the reciprocal achievement-cognition-enjoyment link. The reciprocal link was investigated by applying a one year longitudinal design to students of grade 6 and 7 (N = 356). This age group was chosen because early adolescence represents a critical period during which a strong decrease in positive learning emotions is observed. Part of the work involved identifying factors that might be responsible for this negative development. Results of cross-lagged path analysis identified reciprocal effects between student achievement and enjoyment with control and value cognitions functioning as partial mediators. High achievement goes with high control and value cognitions, which in turn positively affect enjoyment. However, cross-lagged correlations could only be partly confirmed. The results are discussed in terms of theoretical and practical implications

Concentration- and time-dependent effects of the synthetic estrogen, 17alpha-ethinylestradiol, on reproductive capabilities of the zebrafish, Danio rerio

Partial or full life-cycle tests are needed to assess the potential of endocrine-disrupting compounds (EDCs) to adversely affect development and reproduction of fish. Small fish species such as zebrafish, Danio rerio, are under consideration as model organisms for appropriate test protocols. The present study examines how reproductive effects resulting from exposure of zebrafish to the synthetic estrogen 17alpha-ethinylestradiol (EE2) vary with concentration (0.05 to 10 ng EE2 L(-1), nominal), and with timing/duration of exposure (partial life-cycle, full life-cycle, and two-generation exposure). Partial life-cycle exposure of the parental (F1) generation until completion of gonad differentiation (0-75 d postfertilization, dpf) impaired juvenile growth, time to sexual maturity, adult fecundity (egg production/female/day), and adult fertilization success at 1.1 ng EE2 L(-1) and higher. Lifelong exposure of the F1 generation until 177 dpf resulted in lowest observed effect concentrations (LOECs) for time to sexual maturity, fecundity, and fertilization success identical to those of the developmental test (0-75 dpf), but the slope of the concentration-response curve was steeper. Reproduction of zebrafish was completely inhibited at 9.3 ng EE2 L(-1), and this was essentially irreversible as a 3-mo depuration restored fertilization success to only a very low rate. Accordingly, elevated endogenous vitellogenin (VTG) synthesis and degenerative changes in gonad morphology persisted in depurated zebrafish. Full life-cycle exposure of the filial (F2) generation until 162 dpf impaired growth, delayed onset of spawning and reduced fecundity and fertilization success at 2.0 ng EE2 L(-1). In conclusion, results show that the impact of estrogenic agents on zebrafish sexual development and reproductive functions as well as the reversibility of effects, varies with exposure concentration (reversibility at < or = 1.1 ng EE2 L(-1) and irreversibility at 9.3 ng EE2 L(-1)), and between partial and full life-cycle exposure (exposure to 10 ng EE2 L(-1) during critical period exerted no permanent effect on sexual differentiation, but life-cycle exposure did).

Sex determination and temperature-induced sex differentiation in three natural populations of Nile tilapia (Oreochromis niloticus) adapted to extreme temperature conditions

As a species of major interest for aquaculture, the sex determination system (SDS) of Nile tilapia, Oreochromis niloticus, has been widely investigated. In this species, sex determination is considered to be governed by the interactions between a complex system of genetic sex determination factors (GSD) and the influence of temperature (TSD) during a critical period. Previous studies were exclusively carried out on domestic stocks with the genetic and maintenance limitations associated. Given the wide distribution and adaptation potential of the Nile tilapia, we investigated under controlled conditions the sex determination system of natural populations adapted to three extreme thermal regimes: stable extreme environments in Ethiopia, either cold temperatures in a highland lake (Lake Koka), or warm temperatures in hydrothermal springs (Lake Metahara), and an environment with large seasonal variations in Ghana (Kpandu, Lake Volta). The sex ratio analysis was conducted on progenies reared under constant basal (27 degrees C) or high (36 degrees C) temperatures during the 30 days following yolk-sac resorption. Sex ratios of the progenies reared at standard temperature suggest that the three populations share a similar complex GSD system based on a predominant male heterogametic factor with additional influences of polymorphism at this locus and/or action of minor factors. The three populations presented a clear thermosensitivity of sex differentiation, with large variations in the intensity of response depending on the parents. This confirms the presence of genotype-environment interactions in TSD of Nile tilapia. Furthermore the existence of naturally sex-reversed individuals is strongly suggested in two populations (Kpandu and Koka). However, it was not possible here to infer if the sex-inversion resulted from minor genetic factors and/or environmental influences. The present study demonstrated for the first time the conservation of a complex SDS combining polymorphic GSD and TSD components in natural populations of Nile tilapia. We discuss the evolutionary implications of our findings and highlight the importance of field investigations of sex determination. (c) 2007 Elsevier B.V. All rights reserved.

Tracing glacier wastage in the Northern Tien Shan (Kyrgyzstan/Central Asia) over the last 40 years

The status and dynamics of glaciers are crucial for agriculture in semiarid parts of Central Asia, since river flow is characterized by major runoff in spring and summer, supplied by glacier- and snowmelt. Ideally, this coincides with the critical period of water demand for irrigation. The present study shows a clear trend in glacier retreat between 1963 and 2000 in the Sokoluk watershed, a catchment of the Northern Tien Shan mountain range in Kyrgyzstan. The overall area loss of 28% observed for the period 1963–2000, and a clear acceleration of wastage since the 1980s, correlate with the results of previous studies in other regions of the Tien Shan as well as the Alps. In particular, glaciers smaller than 0.5 km2 have exhibited this phenomenon most starkly. While they registered a medium decrease of only 9.1% for 1963–1986, they lost 41.5% of their surface area between 1986 and 2000. Furthermore, a general increase in the minimum glacier elevation of 78 m has been observed over the last three decades. This corresponds to about one-third of the entire retreat of the minimum glacier elevation in the Northern Tien Shan since the Little Ice Age maximum.

An economic assessment of drought effects on three grassland systems in Switzerland

This paper analyzes the economic impacts of summer drought on Swiss grassland production. We combine field trial data from drought experiments in three different grasslands in Switzerland with site-specific information on economic costs and benefits. The analysis focuses on the economic implications of drought effects on grassland yields as well as grassland composition. In agreement with earlier studies, we found rather heterogeneous yield effects of drought on Swiss grassland systems, with significantly reduced yields as a response to drought at the lowland and sub-alpine sites, but increased yields at the wetter pre-alpine site. Relative yield losses were highest at the sub-alpine site (with annual yield losses of up to 37 %). However, because income from grassland production at extensive sites relies to a large extent on ecological direct payments, even large yield losses had only limited implications in terms of relative profit reductions. In contrast, negative drought impacts at the most productive, intensively managed lowland site were dominant, with average annual drought-induced profit margin reductions of about 28 %. This is furthermore emphasized if analyzing the farm level perspective of drought impacts. Combining site-specific effects at the farm level, we found that in particular farms with high shares of lowland grassland sites suffer from summer droughts in terms of farm-level fodder production and profit margins. Moreover, our results showed that the higher competitiveness of weeds (broad-leaved dock) under drought conditions will require increasing attention on weed control measures in future grassland production systems. Taking into account that the risk of drought occurrence is expected to increase in the coming years, additional instruments to cope with drought risks in fodder production and finally farmers’ income have to be developed.

Influence of credibility, warnings, and source-monitoring questions on the misinformation effect.

Introduction. Erroneous answers in studies on the misinformation effect (ME) can be reduced in different ways. In some studies, ME was reduced by SM questions, warnings, or a low credibility of the source of post-event information (PEI). Results are inconsistent, however. Of course, a participant can deliberately decide to refrain from reporting a critical item only when the difference between the original event and the PEI is distinguishable in principle. We were interested in the question to what extent the influence of erroneous information on a central aspect of the original event can be reduced by different means applied singly or in combination. Method. With a 2 (credibility; high vs. low) x 2 (warning; present vs. absent) between subjects design and an additional control group that received neither misinformation nor a warning (N = 116), we examined the above-mentioned factors’ influence on the ME. Participants viewed a short video of a robbery. The critical item suggested in the PEI was that the victim was given a kick by the perpetrator (which he was actually not). The memory test consisted of a two-forced-choice recognition test followed by a SM test. Results. To our surprise, neither a main effect of erroneous PEI nor a main effect of credibility was found. The error rates for the critical item in the control group (50%) as well as in the high (65%) and low (52%) credibility condition without warning did not significantly differ. A warning about possible misleading information in the PEI significantly reduced the influence of misinformation in both credibility conditions by 32-37%. Using a SM question significantly reduced the error rate too, but only in the high credibility no warning condition. Conclusion and Future Research. Our results show that, contrary to a warning or the use of a SM question, low source credibility did not reduce the ME. The most striking finding was, however, the absence of a main effect of erroneous PEI. Due to the high error rate in the control group, we suspect that the wrong answers might have been caused either by the response format (recognition test) or by autosuggestion possibly promoted by the high schema-consistency of the critical item. First results of a post-study in which we used open-ended questions before the recognition test support the former assumption. Results of a replication of this study using open-ended questions prior to the recognition test will be available by June.

Cholesterol metabolism, transport, and hepatic regulation in dairy cows during transition and early lactation

The transition from the nonlactating to the lactating state represents a critical period for dairy cow lipid metabolism because body reserves have to be mobilized to meet the increasing energy requirements for the initiation of milk production. The purpose of this study was to provide a comprehensive overview on cholesterol homeostasis in transition dairy cows by assessing in parallel plasma, milk, and hepatic tissue for key factors of cholesterol metabolism, transport, and regulation. Blood samples and liver biopsies were taken from 50 multiparous Holstein dairy cows in wk 3 antepartum (a.p.), wk 1 postpartum (p.p.), wk 4 p.p., and wk 14 p.p. Milk sampling was performed in wk 1, 4, and 14 p.p. Blood and milk lipid concentrations [triglycerides (TG), cholesterol, and lipoproteins], enzyme activities (phospholipid transfer protein and lecithin:cholesterol acyltransferase) were analyzed using enzymatic assays. Hepatic gene expression patterns of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGC) synthase 1 (HMGCS1) and HMGC reductase (HMGCR), sterol regulatory element-binding factor (SREBF)-1 and -2, microsomal triglyceride transfer protein (MTTP), ATP-binding cassette transporter (ABC) A1 and ABCG1, liver X receptor (LXR) α and peroxisome proliferator activated receptor (PPAR) α and γ were measured using quantitative RT-PCR. Plasma TG, cholesterol, and lipoprotein concentrations decreased from wk 3 a.p. to a minimum in wk 1 p.p., and then gradually increased until wk 14 p.p. Compared with wk 4 p.p., phospholipid transfer protein activity was increased in wk 1 p.p., whereas lecithin:cholesterol acyltransferase activity was lowest at this period. Total cholesterol concentration and mass, and cholesterol concentration in the milk fat fraction decreased from wk 1 p.p. to wk 4 p.p. Both total and milk fat cholesterol concentration were decreased in wk 4 p.p. compared with wk 1 and 14 p.p. The mRNA abundance of genes involved in cholesterol synthesis (SREBF-2, HMGCS1, and HMGCR) markedly increased from wk 3 a.p. to wk 1 p.p., whereas SREBF-1 was downregulated. The expression of ABCA1 increased from wk 3 a.p. to wk 1 p.p., whereas ABCG1 was increased in wk 14 p.p. compared with other time points. In conclusion, hepatic expression of genes involved in the biosynthesis of cholesterol as well as the ABCA1 transporter were upregulated at the onset of lactation, whereas plasma concentrations of total cholesterol, phospholipids, lipoprotein-cholesterol, and TG were at a minimum. Thus, at the gene expression level, the liver seems to react to the increased demand for cholesterol after parturition. Whether the low plasma cholesterol and TG levels are due to impaired hepatic export mechanisms or reflect an enhanced transfer of these compounds into the milk to provide essential nutrients for the newborn remains to be elucidated.

The nature of syntactic impairment in autism

This paper presents a first exploration of the syntactic abilities of autistic children using the framework of truncation theory (Rizzi 1993-4, 2000). It is the first step of an ongoing research project aiming to (a) provide a complete map of syntax in autism, for such work has never been attempted from a sound linguistic perspective (b) develop a targeted remediation program to enhance syntactic abilities of autistic children. Recently, a growing body of work has emphasized the existence of a causal relation between the acquisition of complex syntax (embedding) and the development of a theory of mind (in normally-developing, deaf and autistic children). Early identification and remediation of syntactic deficits is therefore crucial not only to enhance cognitive abilites related to theory of mind, but also because of the critical period hypothesis for language acquisition.

Better conduct of clinical trials: the control group in critical care trials

OBJECTIVE: To review trial design issues related to control groups. DESIGN: Review of the literature with specific reference to critical care trials. MAIN RESULTS AND CONCLUSIONS: Performing randomized controlled trials in the critical care setting presents specific problems: studies include patients with rapidly lethal conditions, the majority of intensive care patients suffer from syndromes rather than from well-definable diseases, the severity of such syndromes cannot be precisely assessed, and the treatment consists of interacting therapies. Interactions between physiology, pathophysiology, and therapies are at best marginally understood and may have a major impact on study design and interpretation of results. Selection of the right control group is crucial for the interpretation and clinical implementation of results. Studies comparing new interventions with current ones or different levels of current treatments have the problem of the necessity of defining "usual care." Usual care controls without any constraints typically include substantial heterogeneity. Constraints in the usual therapy may help to reduce some variation. Inclusion of unrestricted usual care groups may help to enhance safety. Practice misalignment is a novel problem in which patients receive a treatment that is the direct opposite of usual care, and occurs when fixed-dose interventions are used in situations where care is normally titrated. Practice misalignment should be considered in the design and interpretation of studies on titrated therapies.