A Universal Stellar Initial Mass Function? A Critical Look at Variations

Few topics in astronomy initiate such vigorous discussion as whether or not the initial mass function (IMF) of stars is universal, or instead sensitive to the initial conditions of star formation. The distinction is of critical importance: the IMF influences most of the observable properties of stellar populations and galaxies, and detecting variations in the IMF could provide deep insights into the process by which stars form. In this review, we take a critical look at the case for IMF variations, with a view towards whether other explanations are sufficient given the evidence. Studies of the field, local young clusters and associations, and old globular clusters suggest that the vast majority were drawn from a "universal" IMF: a power-law of Salpeter index ($\Gamma=1.35$) above a few solar masses, and a log normal or shallower power-law ($\Gamma \sim 0-0.25$) between a few tenths and a few solar masses (ignoring the effects of unresolved binaries). The shape and universality of the IMF at the stellar-substellar boundary is still under investigation and uncertainties remain large, but most observations are consistent with a IMF that declines ($\Gamma < -0.5$) well below the hydrogen burning limit. Observations of resolved stellar populations and the integrated properties of most galaxies are also consistent with a "universal IMF", suggesting no gross variations in the IMF over much of cosmic time. There are indications of "non-standard" IMFs in specific local and extragalactic environments, which clearly warrant further study. Nonetheless, there is no clear evidence that the IMF varies strongly and systematically as a function of initial conditions after the first few generations of stars.Comment: 49 pages, 5 figures, to appear in Annual Reviews of Astronomy and Astrophysics (2010, volume 48

KEMAMPUAN KONEKSI MATEMATIKA SISWA SMP DALAM PENYELESAIAN SOAL MATEMATIKA

Abstract. Mathematics is a study that is useful for human life such as becoming a basic of modern technology development, having an important role in many sciences and increasing human thoughts. Mathematic connection is inspired because it is not partitioned in many separated topics, but it is a unity. Besides, mathematics also can not separate from the other sciences and problems in human life. Without mathematic connection, the&nbsp; tudents must study and memorize too many concepts and mathemathics' procedure that is separated away from the others. Keywords: Mathematics Connection,Mathematics &nbsp;Problem Solving,Connection &nbsp

Selecting and Preparing Teachers and School Leaders to Improve Educational Outcomes

In the following three studies we explore ways to improve the quality of school-based personnel by identifying characteristics and training of effective teachers and principals. First, to enhance the selection and hiring of teachers into preparation programs and/or school districts, we examine whether teachers' non-cognitive characteristics predict teacher value-added and evaluation ratings. This work builds upon research in psychology and economics which shows the impact of individuals' non-cognitive attributes on outcomes of interest. Here, evidence indicates that teachers' non-cognitive characteristics significantly influence student achievement gains and predict higher evaluation ratings. Due to the select sample of teachers examined in this analysis--Teach For America corps members--this work represents a proof of concept and calls for continued research on a more representative sample of teachers. Second, to better inform the choices made by states and districts in staffing schools, we question whether effectiveness differences exist between teachers traditionally prepared in-state versus out-of-state, and if so, we test three research-based hypotheses to explain differences. Overall, the findings indicate that out-of-state prepared teachers are significantly less effective than in-state prepared and alternative entry teachers in North Carolina elementary schools. Further, out-of-state prepared teachers' lack of familiarity with the state's educational environment and attrition patterns--high rates of turnover coupled with the attrition of less effective teachers--help explain their performance. This suggests policy mechanisms to increase the in-state prepared teaching population and improve the quality of out-of-state prepared teachers. Finally, to contribute to the nascent principal quality research agenda, we detail the characteristics of first-time principals and the schools that hire them. Further, we question whether individual principal characteristics or those of the environments in which they previously worked are associated with student achievement gains. Descriptively, we find that a majority of first-time principals are homegrown--promoted from within the district--and evidence that first-time principals sort into schools based on observed characteristics. Our strongest value-added results indicate that early-career principals who served in high value-added schools as assistant principals promote greater student achievement gains. This suggests that principals learn key aspects of effective school leadership during their assistant principal experience.Doctor of Philosoph

Analisis Perbandingan Protokol Keamanan MiniSec dan Sensor Network Encryption Protocol (SNEP) Pada Jaringan Sensorik Nirkabel

Sensor Jaringan Nirkabel adalah jaringan nirkab el yang b erisikan sekumpulan sensor untuk menganalisa kondisi suatu lingkungan sep erti tingkat kelembapan, suhu udara dan tingkat kebisingan akan tetapi pesan yang dikirimkan mempunyai p engamanan yang rendah terhadap serangan yang dapat diberikan oleh attacker. Protokol keamanan pada jaringan sensorik nirkabel mempunyai pengaruh yang besar untuk menjaga integritas, kerahasiaan data serta kemampuan pengiriman data untuk menghadapi kendala yang sering ditemukan pada pengiriman data di jaringan sensorik nirkabel yang dapat menyebabkan sensor tidak dapat diakses oleh user dan hilangnya kemampuan untuk mengirimkan informasi lingkungan yang dianalisa oleh sensor pada suatu lingkungan. Analisis protokol ini dilakukan untuk menentukan protokol manakah yang mempunyai performa yang lebih baik dalam penanganan serangan pada jaringan sensorik nirkabel dengan membandingkan protokol keamanan MiniSec dan Sensor Network Encryption Protocol (SNEP). Simulasi protokol dilakukan dengan menggunakan aplikasi NS-3 dan perbandingan protokol keamanan menggunakan metoda studi literatur. Pada akhir penelitian ditemukan pada aspek confidentiality, integrity dan authentication MiniSec mempunyai kinerja yang lebih fleksibel daripada SNEP pada tahapan autentikasi enkripsi dan MiniSec menggunakan energi lebih rendah dari pada SNEP dikarenakan MiniSec melakukan enkripsi serta autentikasi pada tahapan yang sama tidak seperti SNEP dengan dua tahapan yang terpisah untuk autentikasi dan enkripsi

DATA SHARING TO DRIVE THE IMPROVEMENT OF TEACHER PREPARATION PROGRAMS

Background/Context: Teacher preparation programs (TPPs) face increasing pressure from the federal government, states, and accreditation agencies to improve the quality of their practices and graduates, yet they often do not possess enough data to make evidence-based reforms. Purpose/Objective: This manuscript has four objectives: (a) to present the strengths and shortcomings of accountability-based TPP evaluation systems; (b) to detail the individual-level data being shared with TPPs at public universities in North Carolina; (c) to describe how data sharing can lead to TPP improvement and the challenges that programs will need to overcome; and (d) to detail how three TPPs are using the data for program improvement. Setting: North Carolina public schools and schools of education at public universities in North Carolina. Importantly, this individual-level data sharing system can be instituted among TPPs in other states. Population/Participants/Subjects: Teachers initially-prepared b

The credit matter and the myth ten yearly of crisis: the case of Indonesia / Batara Maju Simatupang and Kevin Bastian Sirait

This article investigates the behavior of bank groups based on total credit during the 1997/1998 Asian financial crisis, the 2008 financial crisis and ten years after the crisis. The objects of this study are groups of state-owned banks, national private banks regional development banks, foreign banks, and joint venture banks in Indonesia. The approach taken to analyze the relationship and behavior of the bank is a correlation matrix analysis and stepwise regression. Estimates of total loans use an auto-regressive integrated moving average (ARIMA) and compare them with actual total loans from 1998, 2008, until 2018. During the crisis, there are three categories of lending, namely credit crunch, credit rationing, and credit. From the results of the analysis, it appears that the impact of the financial crisis is not as severe as the Asian financial crisis. From the stepwise regression analysis, the inflation rate in 2008 was not statistically significant in describing Indonesia's economic growth during the period of the Asian financial crisis and the 2008 financial crisis. Moreover, in fact, the myth of the ten-year crisis did not occur, because during the 2008 world financial crisis and afterward, the absorption of credit significantly reflected the sustained movement of Indonesia's economic growth