Behavioral Recognition: Computer Algorithms Alerting Law Enforcement to Suspicious Activity

Abstrac

Action Potential Gating of Calcium Channels and Transmitter Release

The regulation of transmitter release at the neuromuscular junction is tightly regulated by the influx of calcium in the presynaptic nerve terminal. Interestingly, the probability that release sites at the neuromuscular junction will liberate transmitter during each action potential is very low. The reasons for this low probability of release are not well understood. To test the hypothesis that individual N-type calcium channels open with a low probability, single channel recordings of N-type voltage-gated calcium channels were performed. Using this approach I determined the conductance of these channels, their probability of gating during an action potential waveform, and the magnitude of calcium flux during a single channel opening. I conclude from these studies that N-type voltage-gated calcium channels have a very low probability of opening (< 5%) during an action potential and the characteristics of calcium entry during single channel openings can help to explain the low probability of transmitter release at release sites in the neuromuscular junction. To understand how calcium current is activated physiologically, the activation and resulting current from N-type calcium channels elicited by different action potential waveforms were studied. This work was carried out at both room temperature and 37°C to provide a physiological context. Using the whole-cell patch clamp techniques, I studied the activation of current during various action potential shapes and conditions, and the kinetics of N- and L-type current activation. Using this approach I determined that N-type channels activate more slowly than L-type. Furthermore, depending on the action potential shape used and the temperature, action potentials can activate varying proportions (I/Imax) of N-type calcium current (ranging from 10-100%). Under physiological conditions using a frog motoneuron action potential waveform I determined that there was a very low proportion of calcium current activated by a natural action potential (~32%). Adenosine 5´-triphosphate (ATP) is co-released with acetylcholine (ACh) at the neuromuscular junction, and has been found to inhibit transmission. I used the cutaneous pectoris muscle of the Rana pipiens to study ATP-mediated modulation of ACh release. Intracellular postsynaptic recordings were used as a measure of ACh release, and agents that perturb the ATP signaling were examined

The correlates of computer use and academic achievement among college students from low income backgrounds

The following is a mixed method research study that explores the correlates between computer use and academic achievement among low-income college students at James Madison University. A sample of 42 sophomore, junior and senior students served as participants in this study. All participants were members of the university’s Centennial Scholars Program, an initiative created by the university in 2004 to give high school students from low-income backgrounds the opportunity to go to college on full-tuition scholarship. Using a theoretical framework that incorporated situated cognition theory (Brown, Duguid & Collins, 1989), communities of practice (Wenger, 1998) and the digital divide (Attewell, 2001) the research conducted explored how students from low-income backgrounds engaged with computers for academic and non-academic purposes and how this engagement relates to academic achievement (GPA). Quantitative research returned evidence that a correlation exists between academic achievement and social networking for academic purposes among this population, while qualitative research further explored how this population engaged with computer for academic and non-academic purposes

Influence of Adhesion at Steel/Mortar Interface on Corrosion Characteristics of Reinforcing Steel

The mechanism of corrosion of reinforcing steel in concrete is discussed based on electrochemical and electron microscopy observations. The importance of calcium hydroxide precipitation on the steel surf ace in the steel/mortar interface is evaluated by placing filter paper around reinforcing steel bar specimens prior to casting in mortar, thus preventing direct contact between steel and mortar. The voids created presumably prevent calcium hydroxide crystals from forming on the steel surface. Specimens with filter paper are compared to specimens with good steel/mortar adhesion using rapid macrocell and corrosion potential tests and a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The study included 21 macrocell and 16 corrosion potential tests run for periods of 25 to 89 days. Seven specimens were subjected to SEM/EDS analysis. Electrochemical results are mixed due to the influence of crevice corrosion. but it is generally shown that better protection is provided for steel with good steel/mortar adhesion than with filter paper. The filter paper, indeed, prevents calcium hydroxide crystals from forming on the steel surface. Corrosion products on active specimens with good mortar cover are shown to grow preferentially in voids created by air bubbles trapped in the mortar. The protective mechanism of calcium hydroxide crystals is proposed to be due to pH buffering by the hydroxyl ions released when the crystals are dissolved, a fact that cannot be proven easily, since many other factors may contribute to the protection of steel in concrete. This report is based on research by Henrik J. Axelsson in partial fulfillment of the requirements of the M.Sc. degree in Engineering Physics at Chalmers University of Technology, Gothenburg. Sweden. The research was sponsored by the Department of Civil and Envirorunental Engineering at the University of Kansas and by Structural Metals, Inc

Stray Current Corrosion Due to Utility Cathodic Protection

The conditions in which stray currents contribute to the corrosion damage of highway structures, the tests to determine if these conditions exist, and the methods recommended to alleviate either the conditions or the damage caused by stray current corrosion are investigated. An extensive review of the literature concerning the fundamentals of stray current corrosion and the practices of utility cathodic protection is presented, including a comprehensive study of the history of stray current corrosion, from its conception with the direct current trolley systems of the late 1880's to its present day problems in the cathodic protection industry. Federal, state, and Kansas Department of Transportation rules and policy are reviewed as they pertain to utility cathodic protection and the damage it may cause to adjacent underground highway structures. Based on the research covered within this report, procedural changes for the prevention of stray current corrosion damage to highway structures and additions to the KDOT Utility Accommodation Policy (1994) are recommended. The research herein concludes that: (1) that all construction close to cathodically protected utilities should be reported to the utility owners so that stray current interference can be assessed, (2) any utility pipeline found uncovered should be reported to its owner so that it can be inspected for corrosion damage, and (3) no underground highway structure should be located within the area of influence of a cathodic protection groundbed. Additionally, its recommended that the KDOT Utility Accommodation Policy (1994) be modified to: (I) directly state the policy on stray current interference from utility cathodic protection systems, (2) require utilities installing cathodic protection systems to submit the design plans as part of the process necessary to obtain a permit agreement for operating in a highway right-of-way, and (3) state that KDOT may require additional inspections along pipelines where interference could jeopardize the structural integrity of an underground highway structure

Evaluation of Corrosion-Resistant Steel Reinforcing Bars

The corrosion performance of a new reinforcing steel is compared with that of conventional steeL The effects of both microalloying and a special heat treatment are evaluated. The microalloying includes small increases in the percentages of copper, phosphorus, and chromium compared to conventional reinforcing steel (less than 1.5 percent total), and the heat treatment involves quenching and tempering after hot rolling. The increase in the phosphorus content exceeds the amount allowed in the ASTM specifications for reinforcing steeL The steels are evaluated using the Southern Exposure and Cracked Beam tests, which are generally accepted in United States practice, plus rapid corrosion potential and macrocell tests developed at the University of Kansas. Corrosion potential, macrocell corrosion rate, and macrocell mat-to-mat resistance are measured. Mechanical properties are compared with the requirements of ASTM A 615 to measure the affects of microalloying and heat treatment on the ductility and strength of the steel. The results indicate that the corrosion resistant steel has a macrocell corrosion rate equal to half that of conventional steel. The corrosion resisting mechanisms exhibited by the microalloying appear to involve the deposition of protective corrosion products at both the anode and the cathode. The epoxy coated corrosion resistant steel had a greater time-tocorrosion than epoxy-coated conventional steel. The microalloyed steel met the mechanical requirements of ASTM A 615 for reinforcement

Evaluation of Corrosion Protection Methods for Reinforced Concrete Highway Structures

Since the 1970s, research projects and field studies have been conducted on different methods for protecting reinforced concrete bridges from corrosion damage. The methods include alternative reinforcement and slab design, barrier methods, electrochemical methods, and corrosion inhibitors. Each method and its underlying principles are described, performance results of laboratory and/or field trials are reviewed, and systems are evaluated based on the results of the trials. Using performance results from the studies and costs obtained from transportation agencies, an economic analysis is used to estimate the cost of each system over a 75 year economic life using discount rates of 2, 4, and 6%. Epoxy-coated reinforcing steel is the most common corrosion protection method used in the United States today. Although controversial in many areas, epoxy-coated reinforcement has performed well in many states, including Kansas, since it was introduced in the early 1970s and is a low-cost backup to many other corrosion protection options. Research on stainless steel reinforcement indicates that it may remain free of corrosion in chloride contaminated concrete for more than 75 years. At a low discount rate (2%), solid stainless steel reinforcement is a cost-effective option compared to other options, but at higher discount rates (4%+), the present value cost of a deck with solid stainless steel is significantly higher than that of an unprotected deck. Stainless steel clad reinforcement is much less expensive than solid stainless steel reinforcement. The performance of stainless steel-clad reinforcement will be similar to that of solid stainless steel bars if the stainless steel coating is continuous and if the black steel core, exposed at the bar ends, is protected so that it does not come into contact with concrete pore solution. The present value of the cost of a bridge deck built with stainless steel-clad reinforcement is significantly lower than the present value for the cost of any other corrosion protection system. This method should be considered for experimental use. Solid stainless steel should be considered, as well, if a low discount rate (around 2%) is used. Hot rubberized asphalt membranes are the least expensive option, other than stainless steel-clad reinforcement. Hot rubberized asphalt and spray-applied liquid membranes should be considered for use on future projects. In laboratory tests, corrosion inhibitors have been shown to provide protection to steel in chloride contaminated concrete, but information on their performance in the field is limited. Both calcium nitrite and organic corrosion inhibitors have the potential to be cost-effective, if they perform as well in the field as they have in the laboratory, and should be considered for experimental use

Rapid Evaluation of Corrosion-Resistant Concrete Reinforcing Steel in the Presence of Deicers

Research to evaluate the properties of a corrosion resistant concrete reinforcing steel is reported. The steel is microalloyed (using copper, chromium, and phosphorous), and subjected to a special heat treatment, to provide corrosion resistance superior to conventional reinforcing steel. Rapid tests, developed at the University of Kansas, are modified and used to evaluate the corrosion properties of four types of steel representing combinations of alloying elements and heat treatment. The steels include two conventional steels, one hot-rolled and one subjected to a quenching and tempering heat treatment, and two corrosion-resistant steels, one hot-rolled and one heat-treated. The steels are evaluated in the presence of three deicing chemicals: sodium chloride, calcium chloride, and calcium magnesium acetate. The results indicate that the corrosion resistant steels exhibit a corrosion rate equal to about one half that of the conventional steels. At low concentrations, calcium chloride and calcium magnesium acetate appear to have a corrosive effect similar to sodium chloride. Calcium magnesium acetate appears to be less corrosive than calcium chloride and sodium chloride at intermediate concentrations. High concentrations of CaCl, and CMA appear to cause instability in the macrocell test, causing alternating patterns of active corrosion and passivation of the anode specimens

Corrosion-Resistant Steel Reinforcing Bars Initial Test

The initial portion of the first phase of a five phase research effort to evaluate a corrosionresistant steel for reinforcing bars is descnoed. Rapid corrosion potential and time-to-corrosion (macrocell) tests are used. The test specimen consists of a No. 5 reinforcing bar embedded in a 30 mm diameter, 102 nnn long cylinder of mortar. The mortar is made using portland cement, graded Ottawa sand, and deionized water. Four different steel types are evaluated: hot-rolled regular steel, Thermex treated (quenched and tempered) regular steel, hot-rolled corrosion resistant steel, and Thermex treated corrosion resistant steeL Corrosion potential tests are perlbrmed to determine the tendency of a steel to corrode. The results for these tests are fuirly consistent, with little scatter. There is no significant difference in potentials for the four steels. The use of different test solutions did not influence the potential of the four steels. The macrocell tests are perlbrmed to determine the time-to-corrosion and the corrosion rates. The results for some of these tests are not consistent and show considerable scatter. The macrocell test is sensitive to the quality in the specimen fabrication. Because the initial tests in Phase I did not perform as intended, it is difficult to determine for certain which steel has the best corrosion resistance based on the resUlts reported here. However, the hot rolled regular steel specimens consistently exluoit the highest corrosion rate. The test solutions used at the anode and cathode in the macrocell tests appear to influence the corrosion rate and the difference in rates between the four steels. When the difference in pH of the anode and cathode solutions is decreased, the corrosion rates are reduced and the difference between the rates for the four steels is more pronounced. Based on the results of the Phase I initial tests, some modifications to the specimen fabrication procedure are reconnnended. The epoxy band should be applied in two coats. The reinforcing bar lengths should be heated after cleaning and after applying each coat in order to improve the bond between the reinforcing bar and the first epoxy coat as well as between the two coats of epoxy. Special care should be exercised when applying the epoxy band. Addition work in Phase I includes an evaluation of the effects of changing the ratio of the number of cathode to anode specimens from 3:3 to 2:1. Special care should also be exercised in the oversight of the corrosion potential and macrocell tests

Finite Element Analysis of Concrete Fracture Specimens

The effects of the descending branch of the tensile stress-strain curve, fracture energy, grid refinement, and load-step size on the response of finite element models of notched concrete beams are studied. The width of the process zone and constraint of crack angles are investigated. Nonlinearity is 1 imited to cracking of the concrete. A limiting tensile stress criterion governs crack initiation. Concrete is represented as linear elastic prior to cracking. Cracks are modeled using a smeared representaion. The post-cracking behavior is controlled by the shape of the descending branch, fracture energy, crack angle, and element size. Unloading occurs at a slope equal to the i nitia 1 modulus of the material. load deflection curves and cracking patterns are used to evaluate the beam's response. Comparisons of the process zone size are made. All analyses are performed on a 200 x 200 x GOO mm concrete beam, with an initial notch length of 80 mm. The fracture energy, tensile strength, and shape of the descending branch interact to determine the stiffness and general behavior of the specimen. The width of the process zone has a negligible influence on the beam's response. The importance of proper crack orientation is demonstrated. The model is demonstrated to be objective with respect to grid refinement and load-step size