The psychogenesis of peptic ulcer

Thesis (M.D.)--Boston Universit

Saltation threshold detection in a wind tunnel by the measurement of the net electrostatic charge

The Mars surface wind tunnel (MARSWIT) is an open circuit wind tunnel used for aeolian studies and is located inside a large vacuum chamber allowing testing at Martian surface atmospheric pressure. Since direct access is not available to the tunnel during operation at low pressure, a remote method of saltation detection is needed. The bed is observed by means of closed circuit video, but it is often difficult to determine the initiation of threshold. The measurement by means of an electrometer of the net electric charge produced by the saltating particles has provided a reliable means of saltation threshold detection. Saltating particles become charged several ways, both in wind tunnels and in a natural environment. The most significant of these methods are tribo-charging and contact charging, which always occur. Fracture charging may also occur under the high velocities associated with particle transport on Mars or under simulated Martian conditions. Detection in MARSWIT is achieved by allowing the saltating particles to impinge on a planar conducting surface normal to the flow that is connected to ground through a Keithly electrometer. The signal from the electrometer is connected to a strip chart recorder along with the analog signal from the pitot tube transducer that is used to determine the wind velocity in the tunnel. Thus, a record of wind velocity and the initiation of particle saltation is conveniently displayed together. While both positive and negative charges are produced during saltation, this method measures only the net charge; thus the charge may be either positive or negative depending upon the particles being tested, the size and size distribution of the test material, and the wind velocity. This has proven to be a very trustworthy and sensitive method of saltation threshold detection, being especially useful with the smaller sized particles which are the most difficult to observe visually

Growth and mortality of Ozark bass (Ambloplites constellatus) in streams of the Ozark Highlands

The Ozark bass (Ambloplites constellatus) is endemic to the Upper White River Basin, and a limited amount of information exists on the Ozark bass population, including growth and mortality characteristics. The purpose of this study was to determine growth and mortality of Ozark bass in the Upper White River Basin, compare growth of Ozark bass to other Ambloplites species, and compare growth and mortality of Ozark bass between sample sites. Sampling occurred in Crooked Creek and in the Lower Wilderness Area (LWA) of the Buffalo River, with multiple collections from each body of water. Sampling occurred during summer 2013 via electroshocking from a boat. Length and weight data were recorded while sampling, and fish ages were determined through otolith retrieval. Ozark bass exhibited similar growth patterns to Shadow bass (Ambloplites ariommus); however, Rock bass (Ambloplites rupestris) grew faster and larger. Growth of Ozark bass appeared to be similar between Crooked Creek and the LWA of the Buffalo River until 5 years of age. After age 5, the growth of fish collected from the LWA of the Buffalo River slowed compared to 5 and older fish collected from Crooked Creek. Ozark bass of the LWA of the Buffalo River had an overall greater mortality rate than those in Crooked Creek; however, one of two sites sampled on Crooked Creek had a comparable fish mortality rate to that measured in the LWA of the Buffalo River. Results indicated that size-selected mortality may have occurred in the LWA of the Buffalo River and at least one location sampled in Crooked Creek, possibly due to fishing mortality and angler popularity at the sites. Data collected in this study were part of a long-term attempt by the Arkansas Game and Fish Commission to gather baseline data on the Ozark bass population and to determine the efficacy of current harvest regulations for that species in the Upper White River Basin. Baseline data will be used in the future to determine whether local fish populations respond to climate change or other impacts to the watershed

Ensuring Professionalism of the External Evaluation Commission: The Slovenian Case Study

In 2006–2007, the Slovenian higher education (HE) system took the first steps toward building a national model of institutional external evaluation (IEE), which would be comparable with other European models. In the first part of the article, the authors discuss the main tendencies within the European he area. This is followed by an outline of the developments in the field of quality assurance within Slovenian he, stressing the years 2006 and 2007. The scientific contribution of the article lies in the evaluation outcomes of the national pilot IEES, with focus on the professional competences of the External evaluation commission (EEC) members. Observation results stress the importance of the proper training of EEC members. The authors propose that a systematic follow-up on the EEC work needs to be established and a code of ethics drawn up, highlighting the preferred values and principles of EEC members.quality assurance, higher education, external evaluation, institutional evaluation, external evaluation commission

Saltation threshold reduction due to the electrostatic agglomeration of fine particles

Particles between 80 and 110 microns in diameter are the most easily moved by the wind. As the particle size decreases below 60 microns, they are increasingly more difficult to move by surface winds, and a number of experiments were performed in an attempt to reduce the required wind velocity. These include: (1) the bombardment of a bed of fine particles by particles near the optimum size, the larger particles kicking the fine particles into the windstream where they are entrained; and (2) the electrostatic agglomeration of fine particles into sizes more easily saltated. The results of these experiments are discussed