Manual control theory applied to air traffic controller-pilot cooperation

Reduced runway separation standards are among the means which have been proposed for increasing airport capacity. The probability of a blunder will dominate the calculation of safe separation standards. Then the determinant of safe system performance will be the system reaction time comprised of the air traffic controller's detection, decision and communication delays, and the response times of the pilot and aircraft in executing a collision avoidance manuever. Estimates of these times, based on existing data, show that the delays ascribable to the human portions of the man-machine system are comparatively unimportant. New developments in radar, computers, and data links will be required to provide any substantial improvement of the existing system, and the goal of 2500 ft of separation may not be achievable

A Universe Without Weak Interactions

A universe without weak interactions is constructed that undergoes big-bang nucleosynthesis, matter domination, structure formation, and star formation. The stars in this universe are able to burn for billions of years, synthesize elements up to iron, and undergo supernova explosions, dispersing heavy elements into the interstellar medium. These definitive claims are supported by a detailed analysis where this hypothetical "Weakless Universe" is matched to our Universe by simultaneously adjusting Standard Model and cosmological parameters. For instance, chemistry and nuclear physics are essentially unchanged. The apparent habitability of the Weakless Universe suggests that the anthropic principle does not determine the scale of electroweak breaking, or even require that it be smaller than the Planck scale, so long as technically natural parameters may be suitably adjusted. Whether the multi-parameter adjustment is realized or probable is dependent on the ultraviolet completion, such as the string landscape. Considering a similar analysis for the cosmological constant, however, we argue that no adjustments of other parameters are able to allow the cosmological constant to raise up even remotely close to the Planck scale while obtaining macroscopic structure. The fine-tuning problems associated with the electroweak breaking scale and the cosmological constant therefore appear to be qualitatively different from the perspective of obtaining a habitable universe.Comment: 27 pages; 4 figure

The level and duration of RSV-specific maternal IgG in infants in Kilifi Kenya

Background Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infection in infants. The rate of decay of RSV-specific maternal antibodies (RSV-matAb), the factors affecting cord blood levels, and the relationship between these levels and protection from infection are poorly defined. Methods A birth cohort (n = 635) in rural Kenya, was studied intensively to monitor infections and describe age-related serological characteristics. RSV specific IgG antibody (Ab) in serum was measured by the enzyme linked immunosorbent assay (ELISA) in cord blood, consecutive samples taken 3 monthly, and in paired acute and convalescent samples. A linear regression model was used to calculate the rate of RSV-matAb decline. The effect of risk factors on cord blood titres was investigated. Results The half-life of matAb in the Kenyan cohort was calculated to be 79 days (95% confidence limits (CL): 76–81 days). Ninety seven percent of infants were born with RSV-matAb. Infants who subsequently experienced an infection in early life had significantly lower cord titres of anti-RSV Ab in comparison to infants who did not have any incident infection in the first 6 months (P = 0.011). RSV infections were shown to have no effect on the rate of decay of RSV-matAb. Conclusion Maternal-specific RSV Ab decline rapidly following birth. However, we provide evidence of protection against severe disease by RSV-matAb during the first 6–7 months. This suggests that boosting maternal-specific Ab by RSV vaccination may be a useful strategy to consider

Electrophoretic Analyses of Serum Proteins of the Albino Rat

Author Institution: Department of Biology, Bowling Green State University, Bowling Green, Ohio 43403Study of the leukemias and polycythemia has been complicated by the inability to isolate pure preparations of suspected "control factors" of hemopoiesis. The presence in rat serum of a factor controlling granulocyte maturation in rat bone-marrow has been demonstrated, but precise analysis has not been possible because of the lack of clear identification of rat-serum proteins. This study analyzes serum proteins of the albino rat through relative electrophoretic mobilities and specific staining. Pooled rat- and human-serum samples were fractionated by gel nitration on Sephadex G-200. The resulting fractions were further separated by vertical discontinuous polyacrylamide gel electrophoresis. Identification of proteins was based on relative mobility and on reactions with general portein, glycoprotein, lipoprotein, and haptoglobin stains. The low-molecular-weight fraction (MW 5,000-150,000) of rat serum contained prealbumin, albumin, three alpha-1, five alpha-2, and two beta globulins, and two alpha lipoproteins. The three alpha-1 globulins were implicated as a possible maturation factor. The slowest alpha-2 globulin was shown to be a haptoglobin. The intermediate-molecularweight fraction (MW 150,000-300,000) was composed of two gamma globulins, a benzidinepositive alpha-2 globulin, two alpha-1 globulins, and an alpha lipoprotein component. The high-molecular-weight fraction (MW 300,000+) contained a beta-lipoprotein, two gamma macroglobulins, and two alpha-1 macroglobulins. Further diffuse staining was present in the gamma region. All of the non-lipoproteins in these two fractions were glycoproteins. Mobilities of the major identifiable human-serum proteins (prealbumin, albumin, gamma globulin, haptoglobin) were similar to the same proteins in the rat, although many differences were apparent. Human albumin and prealbumin formed a separate fourth fraction which was not found in the rat

Global stability analysis of birhythmicity in a self-sustained oscillator

We analyze global stability properties of birhythmicity in a self-sustained system with random excitations. The model is a multi-limit cycles variation of the van der Pol oscillatorintroduced to analyze enzymatic substrate reactions in brain waves. We show that the two frequencies are strongly influenced by the nonlinear coefficients $\alpha$ and $\beta$. With a random excitation, such as a Gaussian white noise, the attractor's global stability is measured by the mean escape time $\tau$ from one limit-cycle. An effective activation energy barrier is obtained by the slope of the linear part of the variation of the escape time $\tau$ versus the inverse noise-intensity 1/D. We find that the trapping barriers of the two frequencies can be very different, thus leaving the system on the same attractor for an overwhelming time. However, we also find that the system is nearly symmetric in a narrow range of the parameters.Comment: 17 pages, 8 figures, to appear on Choas, 201

Empirical investigation of the relationship between use and impacts of collaborative information technologies

Collaborative information technologies (CIT) to support groups working together or collaborating to accomplish tasks is becoming increasingly popular. Practitioner reports suggest that collaboration can have a significant influence on business performance and can lead to a sustained competitive advantage in a turbulent global environment (Frost and Sullivan, 2006). However, despite the large investments that organizations have been making in CIT (Hansen and Nohria, 2004), recent empirical evidence suggests that the utilization of CIT in organizations across five global regions is surprisingly limited and it generally does not meet the expectations of the practitioner and academic communities, in spite of substantial efforts of organizations to make such technologies available/accessible to their end-users (Bajwa et al., 2008). Is it plausible that CIT use may not have substantial impacts or lead to impacts that are not desirable to organizations? Our research focuses on addressing this research question through a large-scale macro-level investigation

A universal ionization threshold for strongly driven Rydberg states

We observe a universal ionization threshold for microwave driven one-electron Rydberg states of H, Li, Na, and Rb, in an {\em ab initio} numerical treatment without adjustable parameters. This sheds new light on old experimental data, and widens the scene for Anderson localization in light matter interaction.Comment: 4 pages, 1 figur

Organizational impacts of collaborative information technologies: Case studies and empirical evidence

Our research focuses on information technology (IT) enabled collaboration systems. We refer to these systems as Collaborative Information Technologies (CITs). Traditional collaboration systems were designed to improve performance of group members or teams by supporting communications and the flow of information. However, modern day CITs have the capabilities to support not only communication and information flow, but also the computing needs of teams/groups engaged in accomplishing tasks/projects. There are many CIT options that organizations can deploy to support team work with varying degrees of virtuality. While some of these technologies have been around for decades (for example, audio conferencing, video conferencing, proprietary groupware, group support systems etc.), others became popular more with the commercialization of the Internet (email, intranets, extranets, web conferencing, data conferencing etc.). Although most CITs support limited functionality for collaboration, integrated e-collaboration tools are beginning to emerge to support a range of functionality required in collaborative efforts [Munkvold and Zigurs 2005]. In recent years, the increasing popularity of CITs has triggered a large number of research investigations and the trend continues to grow. Much of this research has focused on groups as the unit of analysis. There have been only a few large scale organizational level studies exploring CITs. Moreover, for the most part, these studies have investigated specific/individual CITs despite the notion that most collaborative efforts should typically be supported by multiple tools. Some studies exploring adoption of multiple CITs have been undertaken [see Bayo-Moriones and Lera-Lopez 2007; Bajwa et al. 2008]. However, to our knowledge there are no large scale organizational level empirical studies exploring CIT impacts. Here we describe our efforts to explore post adoption impacts of CITs at the organization level