Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Mathematics (7)
- Phenomenology (5)
- Teacher education (5)
- Teacher training (5)
- Instructional technology (4)
-
- Mathematics education (4)
- Nature of science (4)
- Professional development (4)
- Critical race theory (3)
- Identity (3)
- Instructional design (3)
- Literacy (3)
- Metacognition (3)
- Science education (3)
- Adolescents (2)
- Calculus (2)
- Case study (2)
- Critical theory (2)
- Culture (2)
- Discourse (2)
- ESOL (2)
- Education (2)
- Ethnography (2)
- Faculty development (2)
- Gender (2)
- Inquiry (2)
- Language arts (2)
- Middle grades (2)
- Middle school (2)
- Multicultural education (2)
Articles 31 - 60 of 81
Full-Text Articles in Education
The Writing Experiences Of Urban Adolescents: A Multicase Study, Rebecca Covington Calder
The Writing Experiences Of Urban Adolescents: A Multicase Study, Rebecca Covington Calder
Middle-Secondary Education and Instructional Technology Dissertations
In the field of adolescent literacy studies, writing has been neglected in both research and instruction (Juzwik, Curcic, Wolbers, Moxley, Dimling, & Shankland, 2005; Graham & Perin, 2007; Scherff & Piazza, 2005; Troia, 2007), especially in urban settings. Given the importance of writing instruction in secondary education, this qualitative case study investigates the writing experiences of five urban adolescent writers in a high school in a major city in the Southeastern U.S. Research questions included: (1) What are the writing experiences of urban adolescents in and out of school? and (2) In what ways do urban adolescents make use of …
Considering Hans-Georg Gadamer's Philosophical Hermeneutics As A Referent For Student Understanding Of Nature-Of-Science Concepts, Jared Michael Rashford
Considering Hans-Georg Gadamer's Philosophical Hermeneutics As A Referent For Student Understanding Of Nature-Of-Science Concepts, Jared Michael Rashford
Middle-Secondary Education and Instructional Technology Dissertations
The purpose of this study is to examine philosophical hermeneutics as a referent for student understanding of Nature-of-Science (NOS) concepts. Rather than focus on a prescriptive set of canons used in addressing NOS pedagogy in K-12 schools, this study seeks to explicate a descriptive set of principles based on Hans Georg-Gadamer’s theory of interpretation that has the potential for developing dispositions necessary for understanding. Central among these are the concepts of fore-structure, prejudice, temporal distance, and history of effect, all of which constitute part of the whole of the hermeneutic circle as envisaged by Gadamer. As such, Gadamer’s hermeneutics is …
To Iron Or To Do Science: A Storied Life Of A Latina From Scientist To Science Teacher, Sarida Peguero Hoy
To Iron Or To Do Science: A Storied Life Of A Latina From Scientist To Science Teacher, Sarida Peguero Hoy
Middle-Secondary Education and Instructional Technology Dissertations
Reform initiatives such as Science for All Americans (AAA, 1989) and National Science Education Standards (NRC, 1996) argue for making science accessible to all children regardless of age, sex, cultural and/or ethic background, and disabilities. One of the most popular and prevailing phrases highlighting science education reform in the last decade has been science for all. In terms of making science accessible to all, science educators argue that one role of science teachers ought to be to embrace students’ experiences outside of the science classroom by becoming aware and inclusive of the cultural resources that student’s households contain. Moll, González …
An Exploratory Study Of Mathematics Engagement Of Secondary Students, Tracy Thomas Brown
An Exploratory Study Of Mathematics Engagement Of Secondary Students, Tracy Thomas Brown
Middle-Secondary Education and Instructional Technology Dissertations
An Exploratory Study of Mathematics Engagement of Secondary Students by Tracy Thomas Brown A large proportion of American students are not psychologically connected or engaged to what is occurring in their classes; in addition, they fail to take school seriously, have lost interest in school, and do not value or seek out success (Steinberg, Brown, & Dornbusch, 1996). In addition, the relationship in a mathematics classroom between schooling and engagement from the student’s perspective is not well known (Cothran & Ennis, 2000). The purpose of this study was to investigate engagement in order to describe students’ constructs of student engagement, …
To Stay And To Change: Beginning Social Justice Educators Creating Collaborative Third Space(S), Teresa Renae Fisher
To Stay And To Change: Beginning Social Justice Educators Creating Collaborative Third Space(S), Teresa Renae Fisher
Middle-Secondary Education and Instructional Technology Dissertations
Beginning teachers committed to social justice and emancipatory education often experience isolation and discouragement and need communities for intellectual, social, and emotional support as they learn to teach, and sustain their commitments to transformative pedagogy. This qualitative inquiry followed recent graduates who demonstrated personal commitments to a more just world through their lives and their studies and who began their first year as teachers in a variety of settings. Framed within a theory of transformational learning, third space, and Adler’s concepts of social interest and encouragement, the participants and the participant researcher co-created a virtual community to reflect upon and …
Factors Affecting Construction Of Science Discourse In The Context Of An Extracurricular Science And Technology Project, Horace P. Webb
Factors Affecting Construction Of Science Discourse In The Context Of An Extracurricular Science And Technology Project, Horace P. Webb
Middle-Secondary Education and Instructional Technology Dissertations
Doing and learning science are social activities that require certain language, activities, and values. Both constitute what Gee (2005) calls Discourses. The language of learning science varies with the learning context (Lemke, 2001,1990). Science for All Americans (AAAS, 1990) and Inquiry and the National Science Education Standards (NRC, 2000) endorse inquiry science learning. In the United States, most science learning is teacher-centered; inquiry science learning is rare (NRC, 2000). This study focused on 12 high school students from two suburban high schools, their three faculty mentors, and two engineering mentors during an extracurricular robotics activity with FIRST Robotics Competition (FRC). …
An Autoethnography:A Mathematics Teacher's Journey Of Identity Construction And Change, Anthony B. Stinson
An Autoethnography:A Mathematics Teacher's Journey Of Identity Construction And Change, Anthony B. Stinson
Middle-Secondary Education and Instructional Technology Dissertations
Despite some gains, improving secondary mathematics instruction remains an area of concern of the National Council of Teachers of Mathematics (NCTM). Recitation, also known as lecturing, prevails as the practice of choice of mathematics teachers in the United States. However, the report of the NCTM Research Advisory Committee 2000 indicates that the mathematical proficiency of students increases when the practice of choice includes more than recitation. Therefore, changes in instruction in the mathematics classroom should occur to improve student learning. The purpose of this dissertation is to provide a personalized account of one mathematics teacher’s use of reflective teaching as …
What Is Mathematics? An Exploration Of Teachers' Philosophies Of Mathematics During A Time Of Curriculum Reform, Kimberly White-Fredette
What Is Mathematics? An Exploration Of Teachers' Philosophies Of Mathematics During A Time Of Curriculum Reform, Kimberly White-Fredette
Middle-Secondary Education and Instructional Technology Dissertations
Current reform in mathematics teaching and learning is rooted in a changing vision of school mathematics, one that includes constructivist learning, student-centered pedagogy, and the use of worthwhile tasks (National Council of Teachers of Mathematics, 1989, 1991, 2000). This changing vision not only challenges teachers’ beliefs about mathematics instruction but their philosophies of mathematics as well (Dossey, 1992). This study investigates the processes that four teachers’ go through as they implement a new task-based mathematics curriculum while exploring their personal philosophies of mathematics. The participants were part of a graduate-level course that examined, through the writings of Davis and Hersh …
African American Men And College Mathematics: Gaining Access And Attaining Success, Christopher Charlie Jett
African American Men And College Mathematics: Gaining Access And Attaining Success, Christopher Charlie Jett
Middle-Secondary Education and Instructional Technology Dissertations
The research literature regarding African American male college students reports that they often experience difficulties with mathematics (Stage & Kloosterman, 1995; Treisman, 1992). It is also reported that many African American students enter college seeking to complete their degrees in mathematics and science, but few of these students successfully complete the core requirements (Hrabowski, Maton, & Greif, 1998; Treisman, 1992). In spite of these reported trends, there are some African American male students who, indeed, achieve in college mathematics. The purpose of this study was to analyze how being African American and male might play out in the college mathematics …
Orchestrating Student Discourse Opportunities And Listening For Conceptual Understandings In High School Science Classrooms, Melissa Grass Kinard
Orchestrating Student Discourse Opportunities And Listening For Conceptual Understandings In High School Science Classrooms, Melissa Grass Kinard
Middle-Secondary Education and Instructional Technology Dissertations
Scientific communities have established social mechanisms for proposing explanations, questioning evidence, and validating claims. Opportunities like these are often not a given in science classrooms (Vellom, Anderson, & Palincsar, 1993) even though the National Science Education Standards (NSES, 1996) state that a scientifically literate person should be able to “engage intelligently in public discourse and debate about important issues in science and technology” (National Research Council [NRC], 1996). Research further documents that students’ science conceptions undergo little modification with the traditional teaching experienced in many high school science classrooms (Duit, 2003, Dykstra, 2005). This case study is an examination of …
On The Border Of A New Culture: Spanish-Speaking Middle School Newcomers' Perceptions, Expectations And Attitudes, Margo H. Williams
On The Border Of A New Culture: Spanish-Speaking Middle School Newcomers' Perceptions, Expectations And Attitudes, Margo H. Williams
Middle-Secondary Education and Instructional Technology Dissertations
The purpose of this study was to examine the Spanish-speaking newcomer middle school students’ perceptions of school, expectations from school, and attitudes toward school. Of particular concern was how these students’ perceptions, expectations, and attitudes developed over a 5-month period. The theoretical framework for the study was derived from Vygotsky’s (1978) sociocultural theory; second language acquisition (SLA) theories (Dulay & Burt, 1973; Krashen, 1982; Johnson, 1996; Long, 1985; Schumann, 1978); and Norton’s (1997) theory of identity, investment, and imagined communities. The participants in this study were 4 Spanish-speaking middle school students enrolled in an Intensive English to Speakers of Other …
The Interplay Among Prospective Secondary Mathematics Teachers' Affect, Metacognition, And Mathematical Cognition In A Problem-Solving Context, Belinda Pickett Edwards
The Interplay Among Prospective Secondary Mathematics Teachers' Affect, Metacognition, And Mathematical Cognition In A Problem-Solving Context, Belinda Pickett Edwards
Middle-Secondary Education and Instructional Technology Dissertations
The purpose of this grounded theory study was to explore the interplay of prospective secondary mathematics teachers’ affect, metacognition, and mathematical cognition in a problem-solving context. From a social constructivist epistemological paradigm and using a constructivist grounded theory approach, the main research question guiding the study was: What is the characterization of the interplay among prospective teachers’ mathematical beliefs, mathematical behavior, and mathematical knowledge in the context of solving mathematics problems? I conducted four interviews with four prospective secondary mathematics teachers enrolled in an undergraduate mathematics course. Participant artifacts, observations, and researcher reflections were regularly recorded and included as part …
Examining The Effects Of Selected Computer-Based Scaffolds On Preservice Teachers' Levels Of Reflection As Evidenced In Their Online Journal Writing, Guolin Lai
Middle-Secondary Education and Instructional Technology Dissertations
This study used explanatory mixed methods to examine the effects of two computer-based reflection writing scaffolds, question prompts and writing process display, on preservice teachers’ levels of reflection in their online reflective journal writing. The scaffolds were embedded in a system simulating the Professional Accountability Support System Using a Portal Approach (PASS-PORT). The outcome measure was the level of reflection achieved in participants’ writing. The researcher collected data at the College of Education of a major southern university in the United States. Participants were undergraduate students enrolled in a technology integration course in fall 2007. Sixty-five preservice teachers participated in …
Effects Of An Advanced Mathematics Education Graduate Program On Teacher Practice, Mickey Newman Washburn, Jr.
Effects Of An Advanced Mathematics Education Graduate Program On Teacher Practice, Mickey Newman Washburn, Jr.
Middle-Secondary Education and Instructional Technology Dissertations
Public concern over the mathematical incompetence of students and adults is longstanding and justified. The No Child Left Behind act has affected the nation’s teachers, their school systems, and their communities. The act required all classrooms have a “highly-qualified teacher” by June, 2006 (United States Department of Education, 2002). Thus, the purpose of this evaluative case study was to understand if the unique National Board Certification (NBC) focused Educational Specialist (EdS) program was effective in creating change in teacher practice of six high school mathematics teachers in a suburban Georgia county. The learning outcomes of the program and perceptions of …
Social Studies Educators' Perceptions Of And Beliefs About The Inclusion Of Religion In Textbooks., Victor Keith Mccrory
Social Studies Educators' Perceptions Of And Beliefs About The Inclusion Of Religion In Textbooks., Victor Keith Mccrory
Middle-Secondary Education and Instructional Technology Dissertations
During the past two centuries, the inclusion of religious content in social studies textbooks has dramatically changed. In the late 1800s, the progressive education movement ushered in new forms of religious content in social studies textbooks (Nord, 1999). Contemporary researchers have addressed the inclusion of religious content in the United States through various textbook studies (Bellito, 1996; Sewall, 1995). Very few studies, however, have been conducted that gauge social studies teachers’ perceptions of and beliefs about the manner in which religion should be included in the textbooks (Stone & Zam, 2006). The purpose of this mixed method research study is …
Online Professional Development: An Analysis Of Instructor Beliefs And Instructional Strategies For The Facilitation Of Learning With Adult Educators, Kathi L. Vanderbilt
Online Professional Development: An Analysis Of Instructor Beliefs And Instructional Strategies For The Facilitation Of Learning With Adult Educators, Kathi L. Vanderbilt
Middle-Secondary Education and Instructional Technology Dissertations
The purpose of this qualitative case study was to examine the beliefs of 5 experienced instructors about the ways adults learn in online professional development (OPD) courses, beliefs about creating online learning environments, and beliefs about instructional strategies for facilitating adult learning. The following questions guided this study: 1. What are the instructor’s beliefs about the ways that adults learn in online professional development courses? 2. What are the instructor’s beliefs about creating an online learning environment for adult learners? 3. What are the instructor’s beliefs about the use of instructional strategies to facilitate online learning with adults? The setting …
Promoting Mathematical Understanding Through Open-Ended Tasks; Experiences Of An Eighth-Grade Gifted Geometry Class, Carol H. Taylor
Promoting Mathematical Understanding Through Open-Ended Tasks; Experiences Of An Eighth-Grade Gifted Geometry Class, Carol H. Taylor
Middle-Secondary Education and Instructional Technology Dissertations
Promoting Mathematical Understanding Through Open-Ended Tasks; Experiences of an Eighth-Grade Gifted Geometry Class by Carol H. Taylor Gifted students of mathematics served through acceleration often lack the opportunities to engage in challenging, complex investigations involving higher-level thinking. This purpose of this study was to examine the ways mathematically gifted students think about and do mathematics creatively as indicators of deep understanding through collaborative work on four open-ended tasks with high-level cognitive demand. The study focused on the mathematical thinking involved in students’ construction of mathematical understanding through the social interaction of group problem solving. This case study used ethnographic methodology …
Discovering The Voices Of The Segregated: Oral History Of The Educational Experiences Of The Turkish People Of Sumter County, South Carolina, Terri Ann Ognibene
Discovering The Voices Of The Segregated: Oral History Of The Educational Experiences Of The Turkish People Of Sumter County, South Carolina, Terri Ann Ognibene
Middle-Secondary Education and Instructional Technology Dissertations
This qualitative study is a narrative investigation that analyzes the educational experiences of the segregated Turkish people of Sumter County, South Carolina during the integration movement. Four participants share their stories of how attending an elementary school for Turkish students affected their integration into White high schools. Oral history is the specific research methodology that is used. The theoretical framework that guides this study is critical-narrative theory. Through critical research, the researcher analyzes how “the social institution of school is structured such that the interests of some members and classes of society are preserved and perpetuated at the expense of …
Investigating The Experience: A Case Study Of A Science Professional Development Program Based On Kolb's Experiential Learning Model, Brian Davis
Middle-Secondary Education and Instructional Technology Dissertations
Professional development for educators has been defined as the process or processes by which teachers achieve higher levels of professional competence and expand their understanding of self, role, context and career (Duke and Stiggins, 1990). Currently, there is limited research literature that examines the effect a professional development course, which uses David Kolb’s experiential learning model, has on the professional growth and teaching practice of middle school science teachers. The purpose of this interpretive case study is to investigate how three science teachers who participated in the Rivers to Reef professional development course interpreted the learning experience and integrated the …
Attitudinal Study: The Interaction Of Students Taking Calculus And Prerequisite Courses While Participating In Peer Tutorials, Deborah Coleman Hannah
Attitudinal Study: The Interaction Of Students Taking Calculus And Prerequisite Courses While Participating In Peer Tutorials, Deborah Coleman Hannah
Middle-Secondary Education and Instructional Technology Dissertations
Bridging the achievement gap while improving overall performance in high school mathematics is a primary concern in the educational arena. A peer tutoring strategy was implemented to examine its effects on the achievement and attitude of African American students in mathematics courses. Vygotsky’s theory of social interaction and the Zone of Proximal Development served as the guide for this investigation involving 138 high school students. Dyads were formed by pairing 46 Algebra and Geometry students with 46 Advanced Placement Calculus students for after- school tutorial sessions. Forty-six members of a control group received no tutoring intervention. Participants completed a 25-item …
Perspective On Multicultural Education: Case Studies Of A German And An American Female Minority Teacher, Yesim Ozbarlas
Perspective On Multicultural Education: Case Studies Of A German And An American Female Minority Teacher, Yesim Ozbarlas
Middle-Secondary Education and Instructional Technology Dissertations
American and German educational systems have both experienced an increase of ethnic groups in the classrooms; however, in both countries the increase in ethnic groups is not matched by increases in the numbers of minority teachers (NEA, 2005). Therefore, challenges such as interracial tensions and conflicts, an increasing percentage of second language learners, and continuous gaps in achievement suggest that an increase in the numbers of minority teachers is imperative as the twenty-first century begins (Gay, 2000; Luchtenberg, 2004). These increases suggest a need for a more thorough understanding of minority teachers’ viewpoints as they serve as role models, mentors, …
Equity Pedagogy In The Secondary Mathematics Classrooms Of Three Preservice Teachers, Pamela Annette Seda
Equity Pedagogy In The Secondary Mathematics Classrooms Of Three Preservice Teachers, Pamela Annette Seda
Middle-Secondary Education and Instructional Technology Dissertations
In the United States, diverse learners, defined by race, ethnicity, language, and socioeconomic status, do poorly in mathematics in disproportionate numbers. Research suggests that teachers who use instructional practices that build on the cultural strengths of racial and ethnic minorities can increase academic achievement for these students. Using culturally relevant pedagogy as a theoretical framework, this qualitative case study investigated the equity pedagogy of three secondary mathematics student interns in an alternative teacher preparation program during their student teaching experience. The following research questions were also investigated: What school factors do the interns perceive to influence their decisions in implementing …
Student Teaching In An Urban Context: Student Teachers' Views And Construction Of Identities, Desha L. Williams
Student Teaching In An Urban Context: Student Teachers' Views And Construction Of Identities, Desha L. Williams
Middle-Secondary Education and Instructional Technology Dissertations
There is a shortage of secondary mathematics teachers throughout the United States (Howard, 2003, Matus, 1999). This deficit is heightened in urban areas (Bracey, 2002; Howard, 2003). Understanding how urban teachers develop into highly qualified, motivated teachers of urban learners may provide guidance in decreasing the shortage of urban secondary mathematics teachers and provide direction for teacher education programs in preparing future teachers of urban learners. Thus, the purpose of this study was to examine the experiences pre-service teachers undergo during student teaching and how those experiences impact their views on teaching in an urban context, as well as how …
No Writer Left Behind: Examining The Reading-Writing Connection In The Reading First Classroom Through A Teacher Study Group, Kim Street Coady
No Writer Left Behind: Examining The Reading-Writing Connection In The Reading First Classroom Through A Teacher Study Group, Kim Street Coady
Middle-Secondary Education and Instructional Technology Dissertations
The goal of the federally-funded Reading First program is to ensure that all students read well by the end of third grade (Georgia Department of Education, 2006). However, Reading First makes few (if any) provisions for writing in its required 135-minute reading block for literacy instruction. Is it possible to teach reading effectively to young children without involving them in writing? The purpose of this naturalistic study was to investigate how the Reading First framework affected the teaching of writing in primary classrooms in one elementary school that received Reading First funding for three years. Using a social constructivist theoretical …
A Kaleidoscope Of Decisions: Using Cognitive Flexibility Theory To Advance A Novice Esol Teacher's Scaffolding Expertise, Donna Lester Taylor
A Kaleidoscope Of Decisions: Using Cognitive Flexibility Theory To Advance A Novice Esol Teacher's Scaffolding Expertise, Donna Lester Taylor
Middle-Secondary Education and Instructional Technology Dissertations
Instructional scaffolding is a powerful tool that many teachers utilize to meet the challenge of individualizing instruction for diverse learners. The concept of instructional scaffolding is complex (Meyer, 1993), in that teachers have to determine what, how much, and what kind of help to give to students in a moment’s notice (Rodgers, 2004/05). Gaining expertise with scaffolding can take years, which leads us to worry about the effectiveness of novice teachers. A scarcity of research examining how to support a teacher’s development of instructional decisions such as scaffolding is reported (Anders, Hoffman, & Duffy, 2000). The ability to make scaffolding …
Investigating Secondary School Students' Experience Of Learning Statistics, Kimberly D. Gardner
Investigating Secondary School Students' Experience Of Learning Statistics, Kimberly D. Gardner
Middle-Secondary Education and Instructional Technology Dissertations
Although more students are taking courses in statistics before leaving high school, the research base on teaching and learning statistics at the high school level has not accumulated as rapidly (Garfield & Chance, 2000). Very little is known about how secondary school students learn statistics, how the misconceptions they bring to the subject impede their learning, and what should be taught or assessed (Watson & Callingham, 2003). Studies that have investigated these issues tend to focus on the K-5, undergraduate, and graduate levels of education (Groth, 2003). Therefore, more research is needed at the secondary level (Garfield & Chance, 2000). …
Performing Identities As Literate Fourth Graders Via (D)Iscourse In A Testing-Driven Classroom, Meadow Sherrill Graham
Performing Identities As Literate Fourth Graders Via (D)Iscourse In A Testing-Driven Classroom, Meadow Sherrill Graham
Middle-Secondary Education and Instructional Technology Dissertations
Students in every classroom construct a (D)iscourse of literacy that reflects not only who they are but their environment as well. (D)iscourses are more than just dialogues, rather they integrate not only the cultural values and norms of that situation, but also the specific language needs (Gee, 2001). Additionally, (D)iscourses reveal the internal narratives of individuals as they present themselves within context to others (Bruner, 2002). The No Child Left Behind Act of 2001 (NCLB) introduced new influences on school and classroom environments. NCLB implemented standardized, high-stakes testing to measure student, teacher and school performance, attaching serious consequences to not …
Culturally Relevant Professional Development: An Examination Of Race, Practice, And Self Through An Africa-American Teacher Study Group, Charnita V. West
Culturally Relevant Professional Development: An Examination Of Race, Practice, And Self Through An Africa-American Teacher Study Group, Charnita V. West
Middle-Secondary Education and Instructional Technology Dissertations
This naturalistic investigation examined how the implementation of a teacher study group assisted African-American teachers in instituting culturally relevant pedagogy. Ladson-Billings (1994) coined the term culturally relevant pedagogy to address the need for developing and implementing authentic methods for teaching African-American students. However, teachers also need opportunities to be engaged in learning experiences that will facilitate their growth in this area. Although teacher study groups are a popular form of professional development (Birchak et al., 1998), research on teacher study groups designed exclusively for African-American teachers is absent from the literature. Informed by tenets of sociocultural theory (Lave & Wenger, …
Conceptual Change In Pre-Service Science Teachers' Views On Nature Of Science When Learning A Unit On The Physics Of Waves, Ehsan Habib Kattoula
Conceptual Change In Pre-Service Science Teachers' Views On Nature Of Science When Learning A Unit On The Physics Of Waves, Ehsan Habib Kattoula
Middle-Secondary Education and Instructional Technology Dissertations
Recent reform efforts in science education have culminated in National Science Education Standards (NSES), which include the nature of science and science inquiry themes across all grade levels. Consideration must be given to pre-service science teachers’ nature of science conceptions and their perceived roles in implementing the nature of science in the science classroom. This qualitative study investigates how pre-service science teachers’ views about the nature of science develop and change when learning a college physics unit on waves in an urban university. The study uses case study methodology with four pre-service science teachers as individual units of analysis. Data …
Teacher Inquiry In A Professional Development School Environment, Elizabeth Murray Pendergraft
Teacher Inquiry In A Professional Development School Environment, Elizabeth Murray Pendergraft
Middle-Secondary Education and Instructional Technology Dissertations
No abstract provided.