Reflection high-energy electron diffraction analysis of polycrystalline films with grain size and orientation distributions

We report a computationally efficient algorithm to calculate reflection high-energy electron diffraction (RHEED) intensities from well-textured, small-grained polycrystalline films in the kinematic limit. We also show how the intensity maps of the spots in a RHEED pattern from such a film can be quantitatively analyzed to determine the film's average grain size, as well as its in-plane orientation and texture distributions. We find that the in-plane orientation and texture distribution widths of these films can be determined to within 1 degree and that the average lateral grain size can be measured to within a fraction of a nanometer after suitable calibration of our technique

Dependence of inner-shell vacancy production upon distance in hard Li-Al collisions

We match the predictions of molecular-dynamics simulations of 1.2 keV and 2.0 keV 7Li+ scattered from Al(100) to observed total Li atom spectra measured by time-of-flight spectroscopy. In doing so we determine the relevant parameters in a simple distance of closest approach model for the probability of production of single and double vacancies in the Li 1s shell during hard Li-Al collisions. In the standard Fano-Lichten model of vacancy production, vacancies are produced with unit probability if the collision is hard enough to force the collision partners past some critical distance of closest approach. We find that such an assumption is insufficient to fit our simulations to experimental observations, and that we must allow for a gradual turning on of the vacancy production probability as the distance of closest approach decreases. The resulting model may be useful in modeling atomic excitation effects in simulations of other ion-impact processes

Local Property Tax Limitations vs. School District Employee Pension Costs in Pennsylvania

In Pennsylvania as in many other states, employee pension costs are a significant source of financial pressure for school districts. In order to gain greater insight into the nature of Pennsylvania school districts’ financial burden related to pension commitments, this article presents the findings of two scenarios, one which compared the maximum amount of local property tax revenue Pennsylvania school districts could raise under a 2010 state property tax limitation statute, Act 120, to their pension obligations; and a second scenario which incorporated a 1% annual salary increase into the analysis. The article is divided into three sections

Beyond IT interoperability assessment: Complexity analysis of the project context

IT people do best what they are trained to do: examine interoperability issues through a technical lens. It may be unfair to ask of them to systematically and comprehensively analyze non-IT concerns of an interoperability project such as business strategy, constraints and governance. Yet to fully understand the feasibility of an interoperability project, IT people need to examine non-IT factors that can make or break these complex, expensive and time consuming projects. This paper is about a model that emerged from a research project about understanding the nature of IT projects. The Complexity-Based Project Classification Framework can be used to assess the feasibility of a business interoperability project. A three-round international Delphi project with a sample of 23 acknowledged experts identified and prioritized the non-technical project attributes that need to be analyzed when assessing IT project feasibility. The Complexity-Based Project Classification Framework emerged. The Complexity-Based Project Classification Framework is composed of three parts: preconditions, contextual complexity attributes and project effort attributes. Once preconditions are in place (e.g. the organization needs to support using this model for assessing the feasibility of business interoperability) then the project team can assess the interoperability project by considering its project effort attributes (e.g. technology) and project contextual attributes (e.g. relative project size). It is suggested that practitioners who use this Framework will have an improved understanding of the IT interoperability project feasibility

Property Tax Restrictions on School Board Fiscal Taxing Authority in Pennsylvania

Historically, in Pennsylvania, the property tax has been the only significant local revenue source over which school boards have had authority, and their authority to raise property tax rates was unrestricted. This flexibility has proved helpful especially when the state has enacted unfunded mandates

The Progression Towards Project Management Competence

The purpose of this research was to investigate the soft competencies by project phase that IT project managers, hybrid and technical team members require for project success. The authors conducted qualitative interviews to collect data from a sample of 22 IT project managers and business leaders located in Calgary, Canada. They identified the key competencies for the three types of job roles. The research participants offered their opinions of what are the most important competencies from the following competence categories: Personal Attributes (e.g. eye for details), Communication (e.g. effective questioning), Leadership (e.g. create an effective project environment), Negotiations (e.g. consensus building), Professionalism (e.g. life long learning), Social Skills (e.g. charisma) and Project Management Competencies (e.g. manage expectations). The authors discuss the progression of competence through these job roles. They identified and discuss the interplay between a change in job role and the required competencies necessary for IT project success from a neuro-science perspective

On the CFT duals for near-extremal black holes

We consider Kerr-Newman-AdS-dS black holes near extremality and work out the near-horizon geometry of these near-extremal black holes. We identify the exact U(1)_L x U(1)_R isometries of the near-horizon geometry and provide boundary conditions enhancing them to a pair of commuting Virasoro algebras. The conserved charges of the corresponding asymptotic symmetries are found to be well defined and non-vanishing and to yield central charges c_L\neq0 and c_R=0. The Cardy formula subsequently reproduces the Bekenstein-Hawking entropy of the black hole. This suggests that the near-extremal Kerr-Newman-AdS-dS black hole is holographically dual to a non-chiral two-dimensional conformal field theory.Comment: 11 page

A near-NHEK/CFT correspondence

We consider excitations around the recently introduced near-NHEK metric describing the near-horizon geometry of the near-extremal four-dimensional Kerr black hole. This geometry has a U(1)_L x U(1)_R isometry group which can be enhanced to a pair of commuting Virasoro algebras. We present boundary conditions for which the conserved charges of the corresponding asymptotic symmetries are well defined and non-vanishing and find the central charges c_L=12J/hbar and c_R=0 where J is the angular momentum of the black hole. Applying the Cardy formula reproduces the Bekenstein-Hawking entropy of the black hole. This suggests that the near-extremal Kerr black hole is holographically dual to a non-chiral two-dimensional conformal field theory.Comment: 11 pages, v2: references updated, adde

Searching Gravitational Waves from Pulsars, Using Laser Beam Interferometers

We use recent population synthesis results to investigate the distribution of pulsars in the frequency space, having a gravitational strain high enough to be detected by the future generations of laser beam interferometers. We find that until detectors become able to recover the entire population, the frequency distribution of the 'detectable' population will be very dependent on the detector noise curve. Assuming a mean equatorial deformation $\epsilon =10^{-6}$, the optimal frequency is around 450 Hz for interferometers of the first generation (LIGO or VIRGO) and shifts toward 85 Hz for advanced detectors. An interesting result for future detection stategies is the significant narrowing of the distribution when improving the sensitivity: with an advanced detector, it is possible to have 90% of detection probability while exploring less than 20% of the parameter space (7.5% in the case of $\epsilon =10^{-5}$). In addition, we show that in most cases the spindown of 'detectable' pulsars represents a period shift of less than a tens of nanoseconds after one year of observation, making them easier to follow in the frequency space.Comment: 5 pages, 3 figures accepted for publication in Astronomy & Astrophysic