Genetic Structure in Native Populations of Grape Phylloxera (Homoptera: Phylloxeridae)

Random amplified polymorphic DNA (RAPD) markers were used to study genetic structure and diversity in native grape phylloxera populations growing on Vitis arizonica Englemann in central Arizona and on V. riparia Michaux in New York. RAPD data from the Arizona collections were clustered into 3 subpopulations, whereas data from the New York collections were not clustered, which reflected topographic features and the distribution of the sampled vines. Similarity coefficients of the 2 collection areas had similar ranges (0.89-1.0). The similarity coefficient between the Arizona and New York collections was 0.62. Analyses of molecular variance were used to partition the variance in genetic distances, and confirmed the results of the dendrogram clustering. The clustering of the Arizona populations is likely the result of gene flow restriction caused by geographic isolation. Greater diversity was expected among the Arizona populations. That diversity levels were similar suggests that other factors, such as inbreeding or past population history, must play a role in the relatively low level of diversity found in Arizon

Strategies for Maintaining Large Robot Communities

The confluence of progress in micro-actuators, power sources, and mixed-signal microelectronics have recently moved swarm robotics and robot communities from simulation to reality. Swarms of 20 to 100 robots are in use already, implementations with several hundred robots are practicable, and communities exceeding a thousand robots are certainly conceivable. Such large robotic communities provide platforms for numerous exciting research directions including collaborative swarms and self-reconfiguring structures. Maintaining hundreds of robots, however, poses significant practical challenges. The literature on strategies for maintaining software and hardware in large robot communities is sparse, even if applicable concepts from wireless sensor-networks are included. Crucial for the viability of any such strategy is its impact on cost per robot. To provide a realistic setting we introduce a robot platform designed to be fabricated in full on standard printed circuit board (PCB) assembly lines. In this context we introduce a framework for on-line testing and calibration based on code pieces, termed plasmids, that migrate among the micro-controllers of the robots. The proposed approach allows the robots access to a larger library of code then what could be stored locally. The robot consists of a single PCB that doubles as chassis and contains no custom mechanical components. Inexpensive motors (mass produced to vibrate mobile phones) are directly soldered to the circuit board and used in direct drive. Our prototypes use a 200 mAh rechargeable lithium polymer battery giving the robot over an hour of autonomy while moving at a speedy 1 m/s. An MSP430F2131 microcontroller controls the robot and communicates with neighbouring robots via infrared light. The simplicity of the design allows the entire robot to be assembled with low-cost PCB manufacturing techniques and is well suited for small-scale mass production of several hundred robots. While this design significantly reduces the current cost barrier to obtaining a robot swarm, it also shifts the attention to the practical problem of maintaining hundreds of robots. Recharging batteries, sieving out robots with worn tyres or accidental damage is one aspect. A second aspect is testing and calibration. It can not be performed in the PCB assembly process and cost considerations prevent proprioceptive sensor. Collaboration among robots to verify performance and provide feedback (e.g., drift direction during a run and return) provide a scalable alternative. A third aspect is the maintenance of software in the robot community. Our plasmid framework addresses all three aspects with a design that is lightweight enough to run on the microcontrollers. Pieces of code and associated attributes (version, target number for redistribution, lifetime, conditions for transmission) are propagated among robots that meet. For example, the code may perform a test on the robot and require to be forwarded to four other robots that have not encountered this test, before it is deleted. Such test plasmids traverse the robot community which, in its collective memory,contains and executes more code than would fit within the program memory of a single device

Multiple aneurysms in childhood

AbstractArterial aneurysms in children are rare. When present, they are often associated with connective tissue disorders or arteritidies. Idiopathic aneurysms occurring at multiple sites throughout the arterial tree are rare, with only ten cases reported. This report describes a case of multiple arterial aneurysms of uncertain origin involving upper-extremity, extracranial cerebrovascular, aortoiliac, and renal arteries in a 14-year-old boy. The clinical presentation, vascular reconstruction, pathologic findings, and a brief review of the literature are described

Effects of Reduced Strength on Self-Selected Pacing for Long-Duration Activities

Strength and aerobic capacity are predictors of astronaut performance for extravehicular activities (EVA) during exploration missions. It is expected that astronauts will selfselect a pace below their ventilatory threshold (VT). PURPOSE: To determine the percentage of VT that subjects selfselect for prolonged occupational tasks. METHODS: Maximal aerobic capacity and a variety of lowerbody strength and power variables were assessed in 17 subjects who climbed 480 rungs on a ladder ergometer and then completed 10 km on a treadmill as quickly as possible using a selfselected pace. The tasks were performed on 4 days, with a weighted suit providing 0% (suit fabric only), 40%, 60%, and 80% of additional bodyweight (BW), thereby altering the strength to BW ratio. Oxygen consumption and heart rate were continuously measured. Repeated measures ANOVA and posthoc comparisons were performed on the percent of VT values under each suited condition. RESULTS: Subjects consistently selfpaced at or below VT for both tasks and the pace was related to suit weight. At the midpoint for the ladder climb the 80% BW condition elicited the lowest metabolic cost (19+/-14% below VT), significantly different than the 0% BW (3+/-16%, P=0.002) and the 40% BW conditions (5+/-22%, P=0.023). The 60% BW condition (13+/-19%) was different than the 40% BW condition (P=0.034). Upon completion of the ladder task there were no differences among the conditions (0%BW: 3+/-18%; 40%BW: 3+/-21%; 60%BW: 8+/-25%; 80%BW: 10+/-18%). All subjects failed to complete 5km at 80%BW. At the midpoint of the treadmill test the three remaining conditions were all significantly different (0%BW: 20+/-15%; 40%BW: 33+/-15%; 60%BW: 41+/-19%). Upon completion of the treadmill test the 60% BW condition (38+/-12%) was significantly different than the 40% BW (28+/-15%, P=0.024). CONCLUSIONS: Decreasing relative strength results in progressive and disproportionate decreases (relative to VT) in selfselected pacing during longduration activities. Thus, during prolonged, endurancetype activities, large reductions in strength cause notable performance decrements despite no changes in aerobic capacity. These data highlight the importance of both aerobic capacity and muscle strength to the performance of prolonged EVA in exploration mission scenarios

Heart Rate Responses to Unaided Orion Side Hatch Egress in the Neutral Buoyancy Laboratory

NASA is developing the Orion capsule as a vehicle for transporting crewmembers to and from the International Space Station (ISS) and for future human space exploration missions. Orion and other commercial vehicles are designed to splash down in the ocean where nominally support personnel will assist crewmembers in egressing the vehicle. However, off-nominal scenarios will require crewmembers to egress the vehicle unaided, deploy survival equipment, and ingress a life raft. PURPOSE: To determine the heart rate (HR) responses to unaided Orion side hatch egress and raft ingress as a part of the NASA Crew Survival Engineering Team's evaluation of the PORT Orion mockup in the Neutral Buoyancy Laboratory (NBL). METHODS: Nineteen test subjects, including four astronauts (N=19, 14 males/5 females, 38.6+/-8.4 y, 174.4+/-9.6 cm, 75.7+/-13.1 kg), completed a graded maximal test on a cycle ergometer to determine VO2peak and HRpeak and were divided into five crews of four members each; one subject served on two crews. Each crew was required to deploy a life raft, egress the Orion vehicle from the side hatch, and ingress the life raft with two 8 kg emergency packs per crew. Each crew performed this activity one to three times; a total of ten full egresses were completed. Subjects wore a suit that was similar in form, mass, and function to the Modified Advanced Crew Escape Suit (MACES) including helmet, gloves, boots, supplemental O2 bottles, and a CO2-inflated life preserver (approx.18 kg); subjects began each trial seated supine in the PORT Orion mockup with seat belts and mockup O2 and communication connections and ended each trial with all four crewmembers inside the life raft. RESULTS: VO2peak was 40.8+/-6.8 mL/kg/min (3.1+/-0.7 L/min); HRpeak was 181+/-10 bpm. Total egress time across trials was 5.0+/-1.6 min (range: 2.8-8.0 min); all subjects were able to successfully complete all trials. Average maximum HR at activity start, at the hatch opening, in the water, and in the raft, was 108, 137, 147, and 153 bpm, respectively; these values corresponded to 59+/-10%, 73+/-8%, 82+/-3%, and 84+/-6% of HRpeak, respectively. The highest HRs were seen after raft ingress and ranged from 72-99% HRpeak. Across all trials, cumulative averages of 5.4, 3.0, 1.1, and 0.2 min were spent at HRs >60%, >70%, >80%, and >90% HRpeak, respectively. CONCLUSION: Unaided Orion side hatch egress in the NBL is a relatively short-duration activity that elicits a high HR response for several min. Although all crewmembers successfully completed this activity, additional factors such as high seas, poor visibility, an incapacitated crewmember, neurovestibular perturbation, and neuromuscular deconditioning characteristic of a true operational environment may increase the physiologic demand (or decrease crewmembers' physiologic capacity) of unaided Orion side hatch egress. Additionally, landing conditions may require the crewmembers to egress from the top hatch, which is expected to be even more physiologically demanding; this condition will be evaluated in subsequent collaborative testing with the NASA Crew Survival Engineering Team

Mesenteric artery disease in the elderly

AbstractPurposeThe purpose of this study was to estimate the population-based prevalence of mesenteric artery stenosis (MAS) and occlusion among independent elderly Americans.MethodAs part of an ancillary investigation to the Cardiovascular Health Study (CHS), participants in the Forsyth County, NC cohort had visceral duplex sonography of the celiac arteries and superior mesenteric arteries (SMAs). Critical MAS was defined by celiac peak systolic velocity ≥2.0 m/s and/or SMA peak systolic velocity ≥2.7 m/s. Occlusion of either vessel was defined by lack of a Doppler-shifted signal within the imaged artery. Demographic data, blood pressures, and blood lipid levels were collected as part of the baseline CHS examination. Participants' weights were measured at baseline and before the duplex exam. Univariate tests of association were performed with two-way contingency tables, Student t tests, and Fisher exact tests. Multivariate associations were examined with logistic regression analysis.ResultsA total of 553 CHS participants had visceral duplex sonography technically adequate to define the presence or absence of MAS. The study group had a mean age of 77.2 ± 4.9 years and comprised 63% women and 37% men. Participant race was 76% white and 23% African-American. Ninety-seven participants (17.5%) had MAS. There was no significant difference in age, race, gender, body mass index, blood pressure, cholesterol, or low-density lipoproteins for participants with or without MAS. Forward stepwise variable selection found renal artery stenosis (P = .008; odds ratio [OR], 2.85; 95% confidence interval [CI], 1.31, 6.21) and high-density lipoprotein >40 (P = .02; OR, 3.03; 95% CI, 1.17, 7.81) significantly associated with MAS in a multivariate logistic regression model. Eighty-three of the 97 participants with MAS (15.0% of the cohort) had isolated celiac stenosis. Seven participants (1.3% of the cohort) had combined celiac and SMA stenosis. Five participants (0.9% of the cohort) had isolated SMA stenosis. Two participants (0.4% of the cohort) had celiac occlusion. Considering all participants with MAS, there was no association with weight change. However, SMA stenosis and celiac occlusion demonstrated an independent association with annualized weight loss (P = .028; OR, 1.54; 95% CI, 1.05, 2.26) and with renal artery stenosis (P =.001; OR, 9.48; 95% CI, 2.62, 34.47).ConclusionThis investigation provides the first population-based estimate of the prevalence of MAS among independent elderly Americans. MAS existed in 17.5% of the study cohort. The majority had isolated celiac disease. SMA stenosis and celiac artery occlusion demonstrated a significant and independent association with weight loss and concurrent renal artery disease

An allometric scaling relationship in the brain of preterm infants

Allometry has been used to demonstrate a power–law scaling relationship in the brain of premature born infants. Forty-nine preterm infants underwent neonatal MRI scans and neurodevelopmental testing at age 2. Measures of cortical surface area and total cerebral volume demonstrated a power–law scaling relationship (α = 1.27). No associations were identified between these measures and investigated clinical variables. Term equivalent cortical surface area and total cerebral volume measures and scaling exponents were not related to outcome. These findings confirm a previously reported allometric scaling relationship in the preterm brain, and suggest that scaling is not a sensitive indicator of aberrant cortical maturation