Effect of peanut stilbenoids, arachidin-1 and arachidin-3, on Streptococcus mutans growth and acid production

In this study we evaluated the effect of prenylated peanut stilbenoids on the growth, biofilm accumulation and acid production of the dental caries pathogen Streptococcus mutans. Prior research with the non-prenylated stilbenes, resveratrol and piceatannol, has shown that these molecules are active against S. mutans. Here we sought to determine if the addition of a prenyl group to the stilbene backbone increased anti-S. mutans activities. Two prenylated stilbenes, arachidin-1 and arachidin-3, were produced using a peanut hairy root production system. Compared to resveratrol and piceatannol, both arachidin-1 and arachidin-3 led to greater inhibition of S. mutans planktonic growth. This effect also led to reduced biofilm formation, by inhibiting growth, instead of a specific action against biofilm cells. Lastly, sub-MIC concentrations of arachidin-3 reduced the acid production of S. mutans above the 'critical pH' that leads to tooth enamel erosion. In summary, stilbenoids have anti-S. mutans activity, and prenylation enhances this activity.

Simultaneous Perception of Forces and Motions Using Bimanual Interactions

When teaching physical skills, experts or robotic assistants commonly move a novice through a task. However, this guiding motion is only partially effective at portraying the full experience because the guided person is only performing the task passively and the guidance and task forces can become ambiguously intertwined. The interaction evaluated in this paper separates the task and guidance forces by guiding one hand so the user can actively recreate the motion with their other hand that receives task-related forces. This method is based on the ability of humans to easily move their hands through similar paths, such as drawing circles, compared to the difficulty of simultaneously drawing a square with one hand and a circle with the other. Several experiments were first performed to characterize the reference frames, interaction stiffnesses, and trajectories that humans can recreate. Visual Symmetry and Joint-Space Symmetry proved to be easier than Point Mirror Symmetry and participants' recreated motions typically lagged by approximately 50-100 ms. Based on these results, participants used bimanual guidance to identify the orientation of a hard rod embedded in a soft material. The results show that participants could identify the orientation of the rod equally well when working independently compared to being bimanually guided through a desired motion.

Mechanics of Flexible Needles Robotically Steered through Soft Tissue

The tip asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. This enables robotic needle steering, which can be used in medical procedures to reach subsurface targets inaccessible by straight-line trajectories. However, accurate path planning and control of needle steering requires models of needle-tissue interaction. Previous kinematic models required empirical observations of each needle and tissue combination in order to fit model parameters. This study describes a mechanics-based model of robotic needle steering, which can be used to predict needle behavior and optimize system design based on fundamental mechanical and geometrical properties of the needle and tissue. We first present an analytical model for the loads developed at the tip, based on the geometry of the bevel edge and material properties of soft-tissue simulants (gels). We then present a mechanics-based model that calculates the deflection of a bevel-tipped needle inserted through a soft elastic medium. The model design is guided by microscopic observations of needle-gel interactions. The energy-based formulation incorporates tissue-specific parameters, and the geometry and material properties of the needle. Simulation results follow similar trends (deflection and radius of curvature) to those observed in experimental studies of robotic needle insertion.

Incidence of erythromelalgia: a population-based study in Olmsted County, Minnesota

OBJECTIVE

To estimate the population-based incidence of erythromelalgia. Background Only one report describing the incidence of erythromelalgia has been published previously.

STUDY DESIGN

A population-based analysis of data from the Rochester Epidemiology Project.

SETTING

Tertiary care medical centre in Olmsted County, Minnesota (a rural county in the south-eastern portion of the state).

PATIENTS

Thirty-three residents of Olmsted County with a diagnosis of erythromelalgia during the study period.

METHODS

Age- and sex-specific incidence rates of erythromelalgia were determined.

INTERVENTION

None.

MAIN OUTCOME

Population-based incidence rate.

RESULTS

The overall age- and sex-adjusted incidence rate (95% confidence interval, 95% CI) was 1.3 (0.8-1.7) per 100,000 people per year. The incidence of primary and secondary erythromelalgia was 1.1 (0.7-1.5) and 0.2 (0.02-0.4) per 100,000 people per year, respectively. The age-adjusted incidence rates (95% CI) were 2.0 (1.2-2.7) per 100,000 women and 0.6 (0.1-1.1) per 100,000 men. The study was limited by the small sample size and potential variability in recognition of erythromelalgia.

CONCLUSION

The population-based incidence of erythromelalgia has increased with each decade in Olmsted County over the past three decades; overall incidence was 1.3 per 100,000 people per year, approximately 5 times higher than previously reported.

Physical Collaboration of Human-Human and Human-Robot Teams

Human partners working on a target acquisition task perform faster than do individuals on the same task, even though the partners consider each other to be an impediment. We recorded the force profile of each partner during the task, revealing an emergent specialization of roles that could only have been negotiated through a haptic channel. With this understanding of human haptic communication we attempted a "haptic Turing test," replicating human behaviors in a robot partner. Human participants consciously and incorrectly believed their partner was human. However, force profiles did not show specialization of roles in the human partner, nor enhanced dyadic performance, suggesting that haptic interaction holds a greater subconscious subtlety. We further report observations of a non-zero dyadic steady state force perhaps analogous to co-contraction within the limb of an individual, where it contributes to limb stiffness and disturbance rejection. We present results on disturbance rejection in a dyad, showing lack of an effective dyadic strategy for brief events.