COVARIANCE ANALYSIS WITH A COVARIATE INTERACTION: AN EXAMPLE OF A SIMPLE LINEAR REGRESSION COMPARISON TECHNIQUE

Many real data sets that would normally lend themselves to being analyzed by an analysis of covariance, have a covariate interaction present with one or more of the factors in the experiment. Because this violates the assumption of same-slope covariate effect across all treatments, an analysis of covariance should not be performed. The course normally taken when there is such an interaction is to derive regression equations for the dependent variable as a function of the covariate, at each level of the factor(s) being tested. A general linear model F-test can then be used to test whether there are any overall differences between the regression lines. A technique that uses two mathematical distance measures to detect regression line differences once a significant general linear model F-test is obtained is illustrated. Applying these distance measures enables us to perform modified multiple comparisons of the regressions without resorting to the use of multiple pairwise general linear model F-tests, which inflate the Type I error rate. with this method, we are able to incorporate both factor and covariate information into the analysis to overcome the covariate-factor interaction problem

DISTANCE MEASURES IN POST HOC COMPARISONS OF TEMPERATURE GERMINATION QUADRATIC RESPONSE SURFACES

Generalized quadratic response surface models are used to describe seed germination at diurnally alternating cold and warm incubation temperatures for three Great Basin exotic plant species. The method of the F-statistic SSdrop is applied to determine whether the response surface models are equal. Two proposed distance measures are used as modified multiple comparison techniques for determining differences between surfaces. These measures prove useful in distinguishing between the species showing the highest germination response and the one showing the lowest response to the incubation temperature ranges studied

Large thermoelectric figure of merit at high temperature in Czochralski-grown clathrate Ba8Ga16Ge30

The Czochralski method was used to grow a 46-mm-long crystal of the Ba8Ga16Ge30 clathrate, which was cut into disks that were evaluated for thermoelectric performance. The Seebeck coefficient and electrical and thermal conductivities all showed evidence of a transition from extrinsic to intrinsic behavior in the range of 600–900 K. The corresponding figure of merit (ZT) was found to be a record high of 1.35 at 900 K and with an extrapolated maximum of 1.63 at 1100 K. This makes the Ba8Ga16Ge30 clathrate an exceptionally strong candidate for medium and high-temperature thermoelectric applications

Contracting Agile Developments for Mission Critical Systems in the Public Sector

Although Agile is a well established software development paradigm, major concerns arise when it comes to contracting issues between a software consumer and a software producer. How to contractualize the Agile production of software, especially for security & mission critical organizations, which typically outsource software projects, has been a major concern since the beginning of the \u201cAgile Era.\u201d In literature, little has been done, from a foundational point of view regarding the formalization of such contracts. Indeed, when the development is outsourced, the management of the contractual life is non\u2013trivial. This happens because the interests of the two parties are typically not aligned. In these situations, software houses strive for the minimization of the effort, while the customer commonly expects high quality artifacts. This structural asymmetry can hardly be overcome with traditional \u201cWaterfall\u201d contracts. In this work, we propose a foundational approach to the Law & Economics of Agile contracts. Moreover, we explore the key elements of the Italian procurement law and outline a suitable solution to merge some basic legal constraints with Agile requirements. Finally, a case study is presented, describing how Agile contracting has been concretely implemented in the Italian Defense Acquisition Process. This work is intended to be a framework for Agile contracts for the Italian public sector of critical systems, according to the new contractual law (Codice degli Appalti)

Public Benefits of Undeveloped Lands on Urban Outskirts: Non-Market Valuation Studies and their Role in Land Use Plans

Over the past three decades, the economics profession has developed methods for estimating the public benefits of green spaces, providing an opportunity to incorporate such information into land-use planning. While federal regulations routinely require such estimates for major regulations, the extent to which they are used in local land use plans is not clear. This paper reviews the literature on public values for lands on urban outskirts, not just to survey their methods or empirical findings, but to evaluate the role they have played--or have the potential to play-- in actual land use plans. Based on interviews with authors and representatives of funding agencies and local land trusts, it appears that academic work has had a mixed reception in the policy world. Reasons for this include a lack of interest in making academic work accessible to policy makers, emphasizing revealed preference methods which are inconsistent with policy priorities related to nonuse values, and emphasis on benefit-cost analyses. Nevertheless, there are examples of success stories that illustrate how such information can play a vital role in the design of conservation policies. Working Paper 07-2

Episodic Occurrence of Favourable Weather Constrains Recovery of a Cold Desert Shrubland After Fire

Key to the long-term resilience of dryland ecosystems is the recovery of foundation plant species following disturbance. In ecosystems with high interannual weather variability, understanding the influence of short-term environmental conditions on establishment of foundation species is essential for identifying vulnerable landscapes and developing restoration strategies. We asked how annual environmental conditions affect post-fire establishment of Artemisia tridentata, a shrub species that dominates landscapes across much of the western United States, and evaluated the influence of episodic establishment on population recovery. We collected A. tridentata stem samples from 33 plots in 12 prescribed fire sites that burned 8–11 years before sampling. We determined individual establishment years using annual growth rings. We measured seasonal soil environmental conditions at the study sites and asked if these conditions predicted annual establishment density. We then evaluated whether establishment patterns could be predicted by site-level climate or dominant subspecies. Finally, we tested the effect of the magnitude and frequency of post-fire establishment episodes on long-term population recovery. Annual post-fire recruitment of A. tridentata was driven by the episodic availability of spring soil moisture. Annual establishment was highest with wetter spring soils (relative influence [RI] = 19.4%) and later seasonal dry-down (RI = 11.8%) in the year of establishment. Establishment density declined greatly 4 to 5 years after fire (RI = 17.1%). Post-fire establishment patterns were poorly predicted by site-level mean climate (marginal R2 ≤ 0.18) and dominant subspecies (marginal R2 ≤ 0.43). Population recovery reflected the magnitude, but not the frequency, of early post-fire establishment pulses. Post-fire A. tridentata density and cover (measured 8–11 years after fire) were more strongly related to the magnitude of the largest establishment pulse than to establishment frequency, suggesting that population recovery may occur with a single favourable establishment year. Synthesis and applications. This study demonstrates the importance of episodic periods of favourable weather for long-term plant population recovery following disturbance. Management strategies that increase opportunities for seed availability to coincide with favourable weather conditions, such as retaining unburned patches or repeated seeding treatments, can improve restoration outcomes in high-priority areas