Beehavior and Beyond: Realizations in Research

Most people would mistake the small carpenter bee Ceratina calcarata and its relatives for ants with wings,and I won’t pretend that I could tell the difference before I spent a summer researching this particular bee species. We are conditioned to associate bees with three things: black and yellow coloration, honey, and stinging pain. The small carpenter bee species that I studied, however, did not exhibit a single characteristic from that list, which I found shocking, given that they are native to North America and locally abundant. Was I asleep during the lecture on the North American native insect ecosystems in biology class? Even if I reviewed every lecture since kindergarten, I doubt that information would have popped up. This was the first of many realizations stimulated by my initial experiences with research as an undergraduate

Comparison of Cuticular Hydrocarbons in Three Populations of the Carpenter Bee “Ceratina calcarata” to help Understand their Role in Social Evolution

For the second summer in a row I analysed the composition of cuticular hydrocarbons (CHCs) on carpenter bees Ceratina calcarata, this time in populations from Missouri and Georgia as well as from New Hampshire. My goal was to find out if the CHC compositions differed significantly among these three populations. My results affirmed our prediction that the CHC composition varies by population, though there does appear to be some overlap across populations. The CHC variation observed suggests that chemical composition changes with latitude. CHCs are thought to have initially evolved to prevent water loss and then became part of chemical communication among individuals. Communication among insects plays a large role in their behavior and is critical to the development of complex social systems

Job Satisfaction Among Staff Nurses in Mental Health Units in a VA facility

Studies have indicated that work environment in mental health is stressful, however, few studies have focused on staff working in acute mental health settings (Jenkins & Elliott, 2004). The purpose of this study was to describe job satisfaction among a sample of mental health staff nurses who were caring for patients with acute psychiatric disorders in a federal hospital. The second purpose was to determine if there were relationships between global job satisfaction and ethnicity, years in the organization, current unit, field of nursing, working with patients with mental disorders and age of staff nurses. An anonymous survey was distributed to a convenience sample of 69 registered nurses who worked on the four mental health units using the McCloskey/Mueller Satisfaction Scale (MMSS). The scale is a 31-item questionnaire that identifies eight types of satisfaction. Thirty two responses were received out of 69 surveys distributed, a response rate of 46%. The findings revealed that mental health staff nurses were neither satisfied nor dissatisfied with the current jobs (mean score 3.4). Nurses were most happy about flexibility in work schedules and were most unhappy with balance and work. The demographic findings indicated that over 70% of the nurses were concerned about their personal safety while on duty. A Pearson correlations test revealed that there is no significant relationship between global job satisfaction and the seven variables mentioned. A chi-square test found no correlation between ethnicity and global job satisfaction. The study used a small, convenience non random sample, therefore findings cannot be generalized to all nurses at the VA or general nursing population. To determine the levels of nurses\u27 job satisfaction with a larger random sample, a repeat study is recommended to include mental health nurses in different facilities in California and other states. This research may guide future research in examining job satisfaction as a measure to the delivery of quality patient care and patient outcomes

The Explicit Simplified Interface Method for compressible multicomponent flows

This paper concerns the numerical approximation of the Euler equations for multicomponent flows. A numerical method is proposed to reduce spurious oscillations that classically occur around material interfaces. It is based on the "Explicit Simplified Interface Method" (ESIM), previously developed in the linear case of acoustics with stationary interfaces (2001, J. Comput. Phys. 168, pp.~227-248). This technique amounts to a higher order extension of the "Ghost Fluid Method" introduced in Euler multicomponent flows (1999, J. Comput. Phys. 152, pp. 457-492). The ESIM is coupled to sophisticated shock-capturing schemes for time-marching, and to level-sets for tracking material interfaces. Jump conditions satisfied by the exact solution and by its spatial derivative are incorporated in numerical schemes, ensuring a subcell resolution of material interfaces inside the meshing. Numerical experiments show the efficiency of the method for rich-structured flows.Comment: to be published in SIAM Journal of Scientific Computing (2005

Modeling 1-D elastic P-waves in a fractured rock with hyperbolic jump conditions

The propagation of elastic waves in a fractured rock is investigated, both theoretically and numerically. Outside the fractures, the propagation of compressional waves is described in the simple framework of one-dimensional linear elastodynamics. The focus here is on the interactions between the waves and fractures: for this purpose, the mechanical behavior of the fractures is modeled using nonlinear jump conditions deduced from the Bandis-Barton model classicaly used in geomechanics. Well-posedness of the initial-boundary value problem thus obtained is proved. Numerical modeling is performed by coupling a time-domain finite-difference scheme with an interface method accounting for the jump conditions. The numerical experiments show the effects of contact nonlinearities. The harmonics generated may provide a non-destructive means of evaluating the mechanical properties of fractures.Comment: accepted and to be published in the Journal of Computational and Applied Mathematic

Numerical modeling of elastic waves across imperfect contacts

A numerical method is described for studying how elastic waves interact with imperfect contacts such as fractures or glue layers existing between elastic solids. These contacts have been classicaly modeled by interfaces, using a simple rheological model consisting of a combination of normal and tangential linear springs and masses. The jump conditions satisfied by the elastic fields along the interfaces are called the "spring-mass conditions". By tuning the stiffness and mass values, it is possible to model various degrees of contact, from perfect bonding to stress-free surfaces. The conservation laws satisfied outside the interfaces are integrated using classical finite-difference schemes. The key problem arising here is how to discretize the spring-mass conditions, and how to insert them into a finite-difference scheme: this was the aim of the present paper. For this purpose, we adapted an interface method previously developed for use with perfect contacts [J. Comput. Phys. 195 (2004) 90-116]. This numerical method also describes closely the geometry of arbitrarily-shaped interfaces on a uniform Cartesian grid, at negligible extra computational cost. Comparisons with original analytical solutions show the efficiency of this approach.Comment: to be published in SIAM Journal of Scientific Computing (2006

Diffusive approximation of a time-fractional Burger's equation in nonlinear acoustics

A fractional time derivative is introduced into the Burger's equation to model losses of nonlinear waves. This term amounts to a time convolution product, which greatly penalizes the numerical modeling. A diffusive representation of the fractional derivative is adopted here, replacing this nonlocal operator by a continuum of memory variables that satisfy local-in-time ordinary differential equations. Then a quadrature formula yields a system of local partial differential equations, well-suited to numerical integration. The determination of the quadrature coefficients is crucial to ensure both the well-posedness of the system and the computational efficiency of the diffusive approximation. For this purpose, optimization with constraint is shown to be a very efficient strategy. Strang splitting is used to solve successively the hyperbolic part by a shock-capturing scheme, and the diffusive part exactly. Numerical experiments are proposed to assess the efficiency of the numerical modeling, and to illustrate the effect of the fractional attenuation on the wave propagation.Comment: submitted to Siam SIA