The stability of different phases of the three-dimensional nonrelativistic electron gas is analyzed using stochastic methods. With decreasing density, we observe a continuous transition from the paramagnetic to the ferromagnetic fluid, with an intermediate stability range (20 6 5 # r s # 40 6 5) for the partially spin-polarized liquid. The freezing transition into a ferromagnetic Wigner crystal occurs at r s 65 6 10. We discuss the relative stability of different magnetic structures in the solid phase. [ S0031-9007(99) PACS numbers: 71.10. Ca, 05.30.Fk, 75.10.Lp Ever since the pioneering work of Wigner and Seitz [1] on the cohesive energy of metals, the calculation of the ground state energy of the interacting electron gas became the object of considerable theoretical interest [2]. Indeed, the electron gas provides the simplest model in which nontrivial magnetic structures and electron localization can be realized by varying a single parameter, namely, the average electron density r.In the present paper we investigate the relative stability of various broken symmetry phases of the nonrelativistic three-dimensional electron gas, both fluid and solid, using stochastic methods. We find that the paramagnetic to ferromagnetic (full spin polarization) transition is not first order, but a continuous one, involving partial spin polarization states (weak ferromagnetism) [3]. Moreover we find that the transition to a Wigner crystal occurs at a significantly larger density than the value commonly accepted [3,4] and that near the quantum freezing transition the fcc and bcc crystal phases are nearly degenerate.The jellium model consists of N electrons enclosed in a box of volume V (periodically repeated in space) in the presence of a neutralizing background of positive charge. Two parameters characterize its zero temperature phase diagram, namely, the particle density r N͞V and the spin polarization z jN " 2 N # j͞N, where N "͑#͒ is the number of spin-up(down) electrons (N N " 1 N # ). The system is governed by the Hamiltonian (Hartree a.u.)where r i and p i are the position and linear momentum of particle i, and L is a constant representing the effect of the background. Since we are interested in the macroscopic properties of this model system, the thermodynamic limit (N, V !`, keeping r constant) is to be performed in the end by finite size extrapolation. [4,5] and semianalytic methods [6]. Not surprisingly, the least known regime is the strongly correlated one, for which an early quantum Monte Carlo calculation [4] is still the most authoritative study.To delve into the strong coupling regime we employ the variational (VMC) and diffusion (DMC) quantum Monte Carlo methods. The starting point is provided by a variational wave function of the Jastrow type:where det "͑#͒ ͓w͔ is a spin-up(down) Slater determinant of one-electron orbitals w that are either plane waves (fluid phases) or localized functions (crystal phases). In the equation above, R ͑r 1 , . . . , r N ͒ and S ͑s 1 , . . . , s N ͒ represent the full set of po...

PurposeThis paper aims to examine the entrepreneurial attitudes of undergraduate students enrolled in the Small Business Institute® (SBI) program at multiple universities in the USA. Research has encouraged a continuous study and refinement of the entrepreneurial profile, particularly for young adults. Past studies have linked certain personality constructs and entrepreneurship, and shown a connection between entrepreneurial intentions and past business experience.Design/methodology/approachA total of 216 students completed the entrepreneurial attitudes orientation (EAO) survey. The EAO provides a composite score based on four attitude subscales: achievement in business; innovation in business; perceived personal control of business outcomes; and perceived self‐esteem in business. In addition, participants were asked to provide demographic information and past entrepreneurial experience.FindingsResults indicated that the majority of students possessed entrepreneurial attitudes. Furthermore, both student characteristics and entrepreneurial experience were found to be associated with certain entrepreneurial attitudes. Specifically, male students scored higher on both personal control and innovation, and students with family business experience had more developed entrepreneurial attitudes.Practical implicationsThe SBI and other similar training/education programs provide the opportunity for direct entrepreneurial exposure. Their ability to impact attitudes toward entrepreneurship provides a venue for career opportunities. Further discussion centers on the relationship between entrepreneurial attitudes and degree of past experience.Originality/valueThe paper provides an examination of entrepreneurial attitudes that focuses on both demographics and past experiences for a unique educational program that helps promote entrepreneurship as a viable career option.

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This manuscript reports on the results of 2 experiments dealing with behavioral and adrenocortical responses to separation among 9-month-old human infants. In both experiments the social context of separation was manipulated. The results of Experiment 1 yielded evidence of a statistically significant adrenocortical response to 30 min of separation under conditions in which the substitute caregiver responded sensitivity to infant distress, but was busy and relatively noninteractive when babies were not distressed during the separation period. Altering the behavior of the substitute caregiver such that she was warm, responsive, and interactive throughout the separation produced a significant reduction in adrenocortical activity and in negative affect. In fact, these measures were not significantly different than those obtained when the mother and infant remained together in the playroom (No Separation). In Experiment 2, the effects of group versus singleton care were examined using the less stressful mode of substitute caregiving as described above. No significant condition differences in behavioral distress or cortisol were found. Furthermore, neither condition elicited a significant increase in cortisol over basal levels. Finally, these data provide evidence that maternal reports of infant Distress to Limits temperament, using Rothbart's Infant Behavior Questionnaire, predict adrenocortical responses to separation, while reports of Fear of Novelty do not.

When should software development teams have the flexibility to modify their directions and how do we balance that flexibility with controls essential to produce acceptable outcomes? We use dynamic capabilities theory and an extension of control theory to understand these questions. This work is examined in a case study. Our results demonstrate that flexibility may be needed when the starting conditions are uncertain and that effective control in these situations requires use of traditional controls plus a new type of control we term emergent outcome control.

Limited Print and Electronic Distribution RightsThis document and trademark(s) contained herein are protected by law. This representation of RAND intellectual property is provided for noncommercial use only. Unauthorized posting of this publication online is prohibited. Permission is given to duplicate this document for personal use only, as long as it is unaltered and complete. Permission is required from RAND to reproduce, or reuse in another form, any of its research documents for commercial use. For information on reprint and linking permissions, please visit www.rand.org/pubs/permissions.html.The RAND Corporation is a research organization that develops solutions to public policy challenges to help make communities throughout the world safer and more secure, healthier and more prosperous. RAND is nonprofit, nonpartisan, and committed to the public interest.RAND's publications do not necessarily reflect the opinions of its research clients and sponsors.Support RAND Make a tax-deductible charitable contribution at www.rand.org/giving/contribute www.rand.org For more information on this publication, visit www.rand.org/t/RR2133Published by the RAND Corporation, Santa Monica, Calif. © Copyright 2017 RAND CorporationR® is a registered trademark.iii PrefaceThe reauthorization of the U.S. Elementary and Secondary Education Act, referred to as the Every Student Succeeds Act (ESSA), emphasizes evidence-based interventions while giving states and districts new flexibility on the use of federal funds, including funds that could be used to support social and emotional learning (SEL).The RAND Corporation reviewed recent evidence on U.S.-based SEL interventions for K-12 students to better inform the use of SEL interventions under ESSA. This report discusses the opportunities for supporting SEL under ESSA, the standards of evidence under ESSA, and SEL interventions that should be eligible for federal funds through ESSA. Federal, state, and district education policymakers can use this report to identify relevant, evidence-based SEL interventions that meet their local needs.This research was conducted in RAND Education (a division of the RAND Corporation) and commissioned by The Wallace Foundation. The Wallace Foundation is committed to supporting programs and practices that help children and young people develop the social and emotional skills they need for success, and to commissioning research that contributes credible, useful evidence to the field. SummaryAmong educators and researchers, there is growing acknowledgement that student success depends not only on achievement in core academic subjects but also on learning a broader range of intrapersonal and interpersonal competencies. Efforts to develop these competencies are often described using the phrase social and emotional learning (SEL). Although the federal Every Student Succeeds Act (ESSA) legislation does not explicitly mention SEL, educators and policymakers can leverage funding offered under ESSA to support evidence-based programming that is related to SEL and ...

Purpose – This paper's purpose is to identify and accentuate the dilemma faced by small- to medium-sized enterprises (SMEs) who use mobile devices as part of their mobility business strategy. While large enterprises have the resources to implement emerging security recommendations for mobile devices, such as smartphones and tablets, SMEs often lack the IT resources and capabilities needed. The SME mobile device business dilemma is to invest in more expensive maximum security technologies, invest in less expensive minimum security technologies with increased risk, or postpone the business mobility strategy in order to protect enterprise and customer data and information. This paper investigates mobile device security and the implications of security recommendations for SMEs. Design/methodology/approach – This conceptual paper reviews mobile device security research, identifies increased security risks, and recommends security practices for SMEs. Findings – This paper identifies emerging mobile device security risks and provides a set of minimum mobile device security recommendations practical for SMEs. However, SMEs would still have increased security risks versus large enterprises who can implement maximum mobile device security recommendations. SMEs are faced with a dilemma: embrace the mobility business strategy and adopt and invest in the necessary security technology, implement minimum precautions with increased risk, or give up their mobility business strategy. Practical implications – This paper develops a practical list of minimum mobile device security recommendations for SMEs. It also increases the awareness of potential security risks for SMEs from mobile devices. Originality/value – This paper expands previous research investigating SME adoption of computers, broadband internet-based services, and Wi-Fi by adding mobile devices. It describes the SME competitive advantages from adopting mobile devices for enterprise business mobility, while accentuating the increased business risks and implications for SMEs.