Abundance anomalies of carbon and nitrogen in the IUE spectra of Algol-type interacting binaries

There are two primary ways in which the products of nucleosynthesis in stellar interiors may appear at the surface of a star. These are mixing and/or loss of the original unburned stellar envelope. In interacting binaries, overflow can contribute dramatically to envelope loss. The simplest abundance anomalies to be expected from nuclear burning of hydrogen, helium, or carbon would be under or over abundances H, He, C, O, Ne, and Mg. In addition, it is expected that carbon is initially severely depleted, while nitrogen is enhanced during hydrogen burning via the CNO cycle in stars above two solar masses. Other, more subtle anomalies are also expected, and elements heavier than magnesium can be created during very late evolution by nuclear burning in massive stars. Consequently, it is expected that abundance anomalies of various kinds should occur in interacting binaries where one or both stars have lost significant amounts of mass

Mass flow in the interacting binary TX Ursae Majoris

Twenty-two far-ultraviolet and 23 near-ultraviolet high resolution IUE spectra of the interactive Algol-type binary TX Ursae Majoris (B8 V + F-K III-IV) were analyzed in order to determine the nature of the mass flow occurring in this system. Absorption features due to high-temperature ions of Si IV, C IV, and N V are always present. The resonance lines of Al III, Fe II, Mg II and Si IV show strong phase and secular variations indicative of gas streaming and circumstellar/circumbinary material. Radial velocities as high as 500 to 600 km/sec are present. The gas flow is particularly prominent in 1985 between phases 0.7 and 0.0. The system is more active than U Sagittae and as active as U Cephei

Stability Implications of Bendixson’s Criterion

This note presents a proof that the omega limit set of a solution to a planar system satisfying the Bendixson criterion is either empty or is a single equilibrium. The proof involves elementary techniques which should be accessible to senior undergraduates and graduate students

Leave Like a Champion: Teacher Embeddedness and Turnover at an Urban “No-Excuses” Charter Management Organization

Teacher turnover remains considerably higher at Charter Management Organizations (CMOs), despite initially high perceptions of fit at the time of hire. Grounded in an emerging branch-off of job embeddedness theory—teacher embeddedness—this multi-site case study of one urban CMO used interviews of departed teachers and principals and focus groups of new and veteran teachers to determine the predominating factors of reduced feelings of embeddedness and, ultimately, turnover. Findings indicate that teacher embeddedness is threatened by methods the CMO has proliferated as “best practice” and factors researchers have empirically correlated with turnover

Exploring the Drugs-Homicide Connection

Although research generally assumes a close relationship between drugs and violence, very little is known about the many different roles drugs can play in criminal events. Drug related as an event classification scheme is relatively common in homicide research, as well as other areas of inquiry, and is usually understood to be an important component in the causal processes of criminal events. Yet such classification schemes often suggest a simple, unidimensional construct. In reality, drug-related crimes are com-plex events. The purpose of this researchwas first to disaggregate the concept of drug-related homicide by providing an event classification scheme that conceptualizes the diverse roles drugs play in drug-related events.Acategorical coding scheme is presented that is similar to that proposed by Goldstein (1995) and later tested by Brownstein and colleagues (Brownstein & Goldstein, 1990; Brownstein, Baxi, Goldstein, & Ryan, 1992) that specifies three distinct types of homicide events. Included among these are (a) events that involved no evidence of illicit drugs associated with the homicide event, (b) those that involved the presence of drugs or drug use at the scene as well as events where either the victim and/or offender were buying or selling drugs (we term this peripherally drug-related homicides), and (c) events where the sale or use of drugswas the motivating feature of the homicide event. In some situations, there may be overlap between categories b and c; however, category c is distinct in that it includes features of motivation. The second purpose was to determine the relative importance of various situational and contextual characteristics of homicide events in understanding different types of drug-related events. Delineating these features will be an important step in filling in the gaps of knowledge about the assumed relationship between drugs and violence

Mass loss in the interacting semi-detached binary delta librae

The interacting Algol-type binary Delta Librae (AOV + G: V) has been observed with the International Ultraviolet Explorer (IUE) satellite. More than fifty high resolution spectra in the far-ultraviolet and mid-ultraviolet spectrum have been analyzed in order to model the mass flow in the Delta Librae system. The resonance lines of Si IV and C IV are present in absorption and vary in strength both secularly and with phase. The radial velocities of the Si IV and C IV absorption lines generally follow the orbital motion of the primary star but deviate by typically a few tens of kilometers per second in the direction of the observer. The presence of Si IV and C IV features indicates the existence of a region considerably hotter than the normal AOV photosphere and, since these lines are present at all phases, this region must be fairly extensive. These results are interpreted in terms of a 'pseudo-photosphere' around the equatorial region of the AOV star, created by matter being accreted from the G-type companion. The widths of the Si IV and C IV absorption features imply that some of the matter lost by the G-star leaves the system entirely

Evaluation of a Comprehensive Approach to Reducing Gun Violence in Detroit

Increasingly criminal justice agencies are integrating “data based” approaches into their operational strategies. This “new” model of criminal justice suggests that analysis of data on recent crime and violence incidents can lead to a more focused and targeted effort than previous enforcement efforts. Through such efforts, individuals, groups, and locations that exhibit a high level of gun violence within a limited geographic area are identified and a variety of intervention are then implemented. These interventions typically include both enforcement as well as offender focused interventions. These efforts differ from prior enforcement strategies in that they emphasize the integration of a problem analysis component in which data analysis is used to identify the patterns of gun violence in a small target area and enforcement resources are concentrated in this area. However, this approach also differs from previous “crackdown” enforcement strategies in that there are also community and offender intervention components that are integral to this model. The community component seeks to identify ways in which the community can be involved in working with law enforcement to reduce gun violence in this area. This is often through increased community meetings, and establishing more frequent and effective means of communication between the community and local law enforcement. In addition, the enforcement strategies used in this model are data and intelligence driven. As such they are focused on identifying the most problematic locations, groups and individuals that are most responsible for gun violence in this community. This report documents the implementation and outcomes of the implementation of Project Safe Neighborhoods in one of the jurisdictions in which this model was first implemented

OCL Plus: Processes and Events in Object-Centred Planning

An important area in AI Planning is the expressiveness of planning domain specification languages such as PDDL, and their aptitude for modelling real applications. This paper presents OCLplus, an extension of a hierarchical object centred planning domain definition language, intended to support the representation of domains with continuous change. The main extension in OCLplus provides the capability of interconnection between the planners and the changes that are caused by other objects of the world. To this extent, the concept of event and process are introduced in the Hierarchical Task Network (HTN), object centred planning framework in which a process is responsible for either continuous or discrete changes, and an event is triggered if its precondition is met. We evaluate the use of OCLplus and compare it with a similar language, PDDL+