Analyzing imbalance among homogeneous index servers in a web search system

The performance of parallel query processing in a cluster of index servers is crucial for modern web search systems. In such a scenario, the response time basically depends on the execution time of the slowest server to generate a partial ranked answer. Previous approaches investigate performance issues in this context using simulation, analytical modeling, experimentation, or a combination of them. Nevertheless, these approaches simply assume balanced execution times among homogeneous servers (by uniformly distributing the document collection among them, for instance)—a scenario that we did not observe in our experimentation. On the contrary, we found that even with a balanced distribution of the document collection among index servers, correlations between the frequency of a term in the query log and the size of its corresponding inverted list lead to imbalances in query execution times at these same servers, because these correlations affect disk caching behavior. Further, the relative sizes of the main memory at each server (with regard to disk space usage) and the number of servers participating in the parallel query processing also affect imbalance of local query execution times. These are relevant findings that have not been reported before and that, we understand, are of interest to the research community.     

临床医学期刊在健康科普中的作用

随着泛在网络时代的到来,新媒体已成为人们获取健康知识的首要途径;但当前网络健康知识来源芜杂,各种夸大甚至歪曲医学事实的报道层出不穷,健康科普的“含金量”亟须提高。临床医学期刊是权威医学成果发布和交流的重要平台,拥有由作者、审者和编者等众多优秀医学专业工作者组成的专家团队,具有天然的健康科普优势和媒体属性。《协和医学杂志》通过将医学论文科普化、捕捉新闻热点、培养科普人才、充分利用新媒体平台等途径,证明临床医学期刊有责任更有能力在健康科普中发挥重要作用。     

Emotional eavesdropping: infants selectively respond to indirect emotional signals

Two experiments examined whether 18-month-olds learn from emotions directed to a third party. Infants watched an adult perform actions on objects, and an Emoter expressed Anger or Neutral affect toward the adult in response to her actions. The Emoter then became neutral and infants were given access to the objects. Infants' actions were influenced by their memory of the Emoter's affect. Moreover, infants' actions varied as a function of whether they were currently in the Emoter's visual field. If the previously angry Emoter was absent (Experiment 1) or turned her back (Experiment 2), infants did not use the prior emotion to regulate their behavior. Infants learn from emotional eavesdropping, and their subsequent behavior depends on the Emoter's orientation toward them.     

The role of gender constancy in early gender development

Kohlberg's (1966) hypothesis that the attainment of gender constancy motivates children to attend to gender norms was reevaluated by examining these links in relation to age. Ninety-four 3- to 7-year-old children were interviewed to assess whether and how constancy mediates age-related changes in gender-related beliefs. As expected, results indicated a general pattern of an increase in stereotype knowledge, the importance and positive evaluation of one's own gender category, and rigidity of beliefs between the ages of 3 and 5. Moreover, the stability phase, rather than full constancy, mediated some of these relations. After age 5, rigidity generally decreased with age, with relations primarily mediated by consistency.     

Getting sloshed in outer space

We document some basic facts about how liquids behave in the low gravity of outer space and how this poses challenges to space scientists and engineers who need to design and test systems that handle fluids in outer space while working in the 1-g environment on Earth. N Ananthkrishnan is Director, Coral Digital Technologies (P) Ltd, a Bangalore-based company working in the area of multidisciplinary simulation and system integration of aerospace, naval and surface vehicles, and in the design and development of autonomous unmanned/micro air vehicles.     

An Autonomist Biopolitics of Education: Reproduction,Resistance, and the Specter of Constituent Bíos

In considering the enigmatic relationships between philosophy, politics, and pedagogy, this essay attempts to map some of the currents in educational scholarship, particularly those running between reproduction theories and resistance theories. While these two theoretical frameworks have been at odds with one another, Gregory Bourassa suggests that both share orthodox commitments that prevent them from appreciating the constituent dimensions of revolutionary subjectivity. In seeking an alternative orientation, Bourassa proposes an autonomist biopolitics of education. This framework inverts the traditional circuits of resistance and suggests that schools follow behind and resist the constituent life forms (constituent bíos) of students. If resistance theory only attempts to identify the ways in which students resist school practices, it risks obscuring the potentiality of constituent bíos as a social ontology that is primary, always already present, and subject to the resistant practices of the school. Therefore, a key contribution of this essay is its development of an autonomist biopolitics of education. Within this framework, constituent bíos is recognized as the foundational and constitutive motor to which schools are constantly reacting. The adoption of this perspective, alongside more conventional understandings of resistance, offers a more nuanced conception of the relation between forms of life and schools.     

Interventions supporting baccalaureate achievement of Latinx STEM students matriculating at 2-year institutions: A systematic review

Numerous national reports have identified the importance of significantly improving pathways that begin with Latinx students enrolling in 2-year institutions and ultimately completing baccalaureate degrees in STEM fields at 4-year institutions. Many programs using multiple interventions have been designed, implemented, and studied to achieve this goal. To synthesize what has been learned from studies of these programs, this article presents a systematic review of published studies of programs designed to support Latinx student success in 2-year institutions and successful transfer to 4-year institutions, particularly for STEM majors. A total of 49 quantitative, 9 qualitative, and 16 mixed-methods studies published as reports, articles, or dissertations since 1980 were identified that met the criteria for the review. Studies covered a wide range of interventions, including mentoring, counseling, advising, study groups, tutoring, scholarships, orientations, career services, undergraduate research, articulation agreements, and transfer programs. Individually, these studies report positive influences on student success outcomes, including 2- and 4-year graduation, transfer to a 4-year institution, retention, and success in individual courses. However, the number of qualifying studies was surprisingly small, considering the importance of improving success of Latinx students and the length of time during which the problem has been repeatedly emphasized. Few interventions have been undertaken from explicitly assets-based perspectives or theoretical frameworks. The lack of explicit frameworks underlying interventions—combined with a sole/primary focus on students—suggests many interventions were approached from a deficit-based perspective. Further, the study found no pattern of replication studies that might confirm effectiveness of potentially promising interventions. Based on our analysis of evaluations presented in the studies, it does not appear that the research community has developed agreed-upon methods to evaluate commonly agreed-upon outcomes. Finally, no intervention has been sufficiently supported that widespread implementation could be recommended.     

Gender differences in mathematics and science competitions: A systematic review

Gendered patterns in mathematics and science interest emerge in early childhood, develop over time, and ultimately reflect advanced course selection in secondary education. During the crucial time adolescents become aware of their strengths and interests and specialize accordingly, they get the opportunity to participate in out-of-school learning programs such as mathematics and science competitions. This raises the question whether mathematics and science competitions contribute to gender equity by equally promoting female and male interests. In this article, we present a systematic review on gender differences and the mechanisms explaining success and failure in mathematics and science competitions. On an international level, we found large gender differences regarding participation in all Olympiads with the exception of the biology Olympiad. In fairs and national Olympiads, overall participation rates were not gendered as such, but females preferred biology topics whereas males preferred physics related topics. Male and female achievement in fairs was comparable, but males clearly outperformed female participants at the Olympiads, with the smallest differences in the biology Olympiad. Variables and theoretical frameworks explaining participation and achievement and the role of gender in mathematics and science competitions are discussed. We suggest that gender stereotypes, through their influence on self-concept and interest, play an important role in the mechanisms resulting in low female participation rates in and beyond mathematics and science competitions (especially in physics and chemistry). The mechanisms we found explaining female representation during a national selection competition might be considered as reflecting those in female mathematics or science careers and could thus serve as food for thought on countering the gender gap in mathematics and science.     

Teachers’ role and attitudes concerning ADHD medication: A qualitative analysis

The increased use of Attention Deficit/Hyperactivity Disorder (ADHD) medication by children has led to growing concerns. In a previous study, we found that many of the teachers that were interviewed about ADHD spontaneously associated ADHD with medication. The present study is a qualitative reanalysis of what precisely these 30 primary school teachers had spontaneously said about medication in our previous semi‐structured interviews on ADHD. Almost all respondents had experience with pupils taking ADHD medication. The majority of spontaneously mentions medication as the treatment of ADHD. Attitudes towards ADHD medication use by pupils are mainly ambivalent, but more positive than negative effects of medication are reported. However, what teachers say about ADHD medication is often not based on sound information; their attitudes tend to be formed by personal experiences rather than founded on professional and scientific sources. We conclude from our analysis that it will be in the interest of reducing the number of children on ADHD medication that teachers have good access to verified and up‐to‐date information on ADHD and medication so that they are better supported in making evidence‐based pedagogical judgments.     

Agency and Structure: Principals’ Ability to Bring about Sustainable Improvement in Underperforming Schools in South Africa

This article reports on a study of which the purpose was to understand the role of principals in changing underperforming schools towards sustainable improvement in one circuit area of North-West, South Africa. School principals play a crucial role in guiding schools towards sustainable improvement by shaping a vision of academic success for all learners. Managing teaching is one of the core modules in South Africa’s new national qualification for school principals, and that being the case, principals should play a central role in effecting the educational transformation of all learners. The quality of principals’ leadership is the key factor driving the transformational turnaround and improvement required in schools. They perform a highly complex and dynamic role in enhancing and sustaining school improvement. It was the goal of this qualitative study to explore cultural, structural, and agential challenges faced by principals in their effort to provide for change and improvement in their schools. Six schools were purposefully selected to participate in the study and semi-structured interviews were used to gather data from the principals. The study established that paying attention to cultural, structural and agential factors in schools increases their ability to sustain learner improvement.