Nuclear Quasi-Elastic Electron Scattering Limits Nucleon Off-Mass Shell Properties

The use of quasi-elastic electron nucleus scattering is shown to provide significant constraints on models of the proton electromagnetic form factor of off-shell nucleons. Such models can be constructed to be consistent with constraints from current conservation and low-energy theorems, while also providing a contribution to the Lamb shift that might potentially resolve the proton radius puzzle in muonic hydrogen. However, observations of quasi-elastic scattering limit the overall strength of the off-shell form factors to values that correspond to small contributions to the Lamb shift.Comment: 11 pages, 2 figures. Resubmission to improve the clarity, and correct possible misconception

Development of a Sonic Sensor for Aircraft Applications

The field of aeroacoustics has been an area of constant research over the past six decades. Acoustic waves have some special characteristics that allow for heating, cooling, and even active flow control over airfoil shapes using synthetic jets and other methods. They can also be used to measure properties of the flow over an aircraft, including the free-stream pressure ratio, density ratio, and total temperature. The current measurement techniques to obtain these parameters applied to aircraft require a specific probe. It is desired to apply knowledge of acoustics to develop an aircraft sensor that can measure multiple flow properties with minimal impact to the flow field. Adding a sensor that can read total temperature, static temperature, airspeed, and angle of attack will have the added benefit of reducing the number of sensors sticking into the flow and may result in a reduction in failure mode analysis due to the minimization of the number of sensors on the aircraft. This work explores the applicability of sonic anemometry to aircraft for high subsonic and sonic speeds. A computational simulation is developed as a validation of the concept and low speed experiments are shown to validate the theory. This effort identifies the underlying issues associated with applying sonic anemometry to high-speed flows and provides methods to overcome them. This work investigates the use of phased array technology to increase the accuracy and applicability at the higher speeds and smaller footprints (lighter and fewer systems). Phased arrays use the constructive and destructive interference to boost and direct the desired signal, in this case, acoustic waves. These acoustic waves have been shown to provide haptic feedback and levitate small particles utilizing a relatively inexpensive ultrasonic phased array system. It is shown that the ultrasonic phased array overcomes the hydrodynamic noise to produce a strong signal for use in the calculation of the flow parameters up to the maximum speed tested. It is also shown that the signal is strong enough to produce consistent time delay estimations, via cross-correlation, with a 0.05 second sample time to integrate into modern air data systems.Ph.D

R-matrix calculation of electron collisions with electronically excited O2 molecules

Low-energy electron collisions with O$_2$ molecules are studied using the fixed-bond R-matrix method. In addition to the O$_2$ ${X}^3\Sigma_{g}^-$ ground state, integrated cross sections are calculated for elecron collisions with the ${a}^1\Delta_{g}$ and ${b}^1\Sigma_{g}^+$ excited states of O$_2$ molecules. 13 target electronic states of O$_2$ are included in the model within a valence configuration interaction representations of the target states. Elastic cross sections for the ${a}^1\Delta_{g}$ and ${b}^1\Sigma_{g}^+$ excited states are similar to the cross sections for the ${X}^3\Sigma_{g}^-$ ground state. As in case of excitation from the ${X}^3\Sigma_{g}^-$ state, the O$_2^-$ $\Pi_u$ resonance makes the dominant contribution to excitation cross sections from the ${a}^1\Delta_{g}$ and ${b}^1\Sigma_{g}^+$ states. The magnitude of excitation cross sections from the ${a}^1\Delta_{g}$ state to the ${b}^1\Sigma_{g}^+$ state is about 10 time larger than the corresponding cross sections from the ${X}^3\Sigma_{g}^-$ to the ${b}^1\Sigma_{g}^+$ state. For this ${a}^1\Delta_{g}$ $\to$ ${b}^1\Sigma_{g}^+$ transition, our cross section at 4.5 eV agrees well with the available experimental value. These results should be important for models of plasma discharge chemistry which often requires cross sections between the excited electronic states of O$_2$.Comment: 26 pages, 10 figure

Effect of silver content on the structure and antibacterial activity of silver-doped phosphate-based glasses

Staphylococcus aureus can cause a range of diseases, such as osteomyelitis, as well as colonize implanted medical devices. In most instances the organism forms biofilms that not only are resistant to the body's defense mechanisms but also display decreased susceptibilities to antibiotics. In the present study, we have examined the effect of increasing silver contents in phosphate-based glasses to prevent the formation of S. aureus biofilms. Silver was found to be an effective bactericidal agent against S. aureus biofilms, and the rate of silver ion release (0.42 to 1.22 µg·mm–2·h–1) from phosphate-based glass was found to account for the variation in its bactericidal effect. Analysis of biofilms by confocal microscopy indicated that they consisted of an upper layer of viable bacteria together with a layer (20 µm) of nonviable cells on the glass surface. Our results showed that regardless of the silver contents in these glasses (10, 15, or 20 mol%) the silver exists in its +1 oxidation state, which is known to be a highly effective bactericidal agent compared to that of silver in other oxidation states (+2 or +3). Analysis of the glasses by 31P nuclear magnetic resonance imaging and high-energy X-ray diffraction showed that it is the structural rearrangement of the phosphate network that is responsible for the variation in silver ion release and the associated bactericidal effectiveness. Thus, an understanding of the glass structure is important in interpreting the in vitro data and also has important clinical implications for the potential use of the phosphate-based glasses in orthopedic applications to deliver silver ions to combat S. aureus biofilm infections

Neutral pion decay into ννˉ\nu\bar{\nu} in dense skyrmion matter

We study the weak decay of the neutral pion to a neutrino-antineutrino pair, $\pi^0\to \nu \bar{\nu}$, in the Skyrme model. In baryon free-space the process is forbidden by helicity while in a dense baryonic medium, the process becomes possible already to leading order in $G_F$ due to the break-down of Lorentz symmetry in the background medium.Comment: 7 pages, RevTeX, 4 figures. Expanded discussion in light of referee comment

Fight or Flight: Parental Decisions about Predators at Nests of Northern Bobwhites (Colinus virginianus)

Patterns of nest defense against predators by ground-nesting bird species in the wild are poorly understood, largely because of a historical inability to directly monitor nests. Most nest-defense studies have observed responses elicited from artificial predators or human observers presented to nesting birds, and few have attempted to present these events in the context of predator—prey relationships found in the wild. We hypothesized that predator threat level (e.g., the threat posed to the clutch or to the clutch and the attending adult), parental characteristics, clutch investment, and future reproductive opportunities would influence avian nest-defense decisions. During 1999–2006, we examined predation events (n = 242) from 790 video-monitored Northern Bobwhite (Colinus virginianus) nests. We evaluated parental, predator, daily, and seasonal correlates that potentially contributed to patterns of nest defense by Northern Bobwhites using a model selection approach. The top model showed that nest defense was strongest at nests with larger predators that posed a threat to both adults and the clutch. This model also contained clutch size, but parameter estimates suggest that predator type was the only significant factor determining rates of nest defense. Our results suggest that Northern Bobwhites use the threat posed to the nest and the attending adult by the approaching predator as the primary cue in decisions to engage in nest defense

Patterns of Incubation Behavior in Northern Bobwhites (\u3ci\u3eColinus virginianus\u3c/i\u3e)

Patterns of incubation and nesting behavior for many species of birds, especially those with cryptic nests, have been difficult to obtain due to logistical and technological limitations. As a result, little is known about the daily attendance rhythms and behavioral patterns of many species, including the Northern Bobwhite (Colinus virginianus), despite this species being one of the most studied birds in the world. Incubation represents parental investment in offspring, and a multitude of factors may affect investment behaviors, including reproductive ecology, sex and age of parent, habitat quality, clutch age, and timing in the nesting season. Most Northern Bobwhite nests are incubated by a single adult, most often by females, but also by some males. We assessed the nest attendance patterns and parental investment in bob-white clutches (n 118) using continuous near-infrared video of nests being incubated by male or female bobwhites. We found that incubating parents took 0 –3 recesses per day. A single recess was most common for 87% of nest-days, and most of these were during mid-day to late afternoon (12:00 19:00). Mean total daily recess time was 182 min (95% CI: 98–264) for nests that hatched and 224 min (95% CI: 140–308) for nests that failed. We observed no difference between sexes in the number or length of recesses taken, but females initiated recess later in the day (median start time 15:00) than males (median start time 14:00). We found that nest recess length decreased as the clutch got older and increased as the nesting season progressed. Video surveillance systems proved to be a use-ful tool for observing and quantifying patterns of incubation behavior in a ground-nesting species with cryptic nests

Patterns of Incubation Behavior in Northern Bobwhites (\u3ci\u3eColinus virginianus\u3c/i\u3e)

Patterns of incubation and nesting behavior for many species of birds, especially those with cryptic nests, have been difficult to obtain due to logistical and technological limitations. As a result, little is known about the daily attendance rhythms and behavioral patterns of many species, including the Northern Bobwhite (Colinus virginianus), despite this species being one of the most studied birds in the world. Incubation represents parental investment in offspring, and a multitude of factors may affect investment behaviors, including reproductive ecology, sex and age of parent, habitat quality, clutch age, and timing in the nesting season. Most Northern Bobwhite nests are incubated by a single adult, most often by females, but also by some males. We assessed the nest attendance patterns and parental investment in bob-white clutches (n 118) using continuous near-infrared video of nests being incubated by male or female bobwhites. We found that incubating parents took 0 –3 recesses per day. A single recess was most common for 87% of nest-days, and most of these were during mid-day to late afternoon (12:00 19:00). Mean total daily recess time was 182 min (95% CI: 98–264) for nests that hatched and 224 min (95% CI: 140–308) for nests that failed. We observed no difference between sexes in the number or length of recesses taken, but females initiated recess later in the day (median start time 15:00) than males (median start time 14:00). We found that nest recess length decreased as the clutch got older and increased as the nesting season progressed. Video surveillance systems proved to be a use-ful tool for observing and quantifying patterns of incubation behavior in a ground-nesting species with cryptic nests