Sideways maneuvers enable narrow aperture negotiation by free-flying hummingbirds

Many birds routinely fly fast through dense vegetation characterized by variably sized structures and voids. Successfully negotiating these cluttered environments requires maneuvering through narrow constrictions between obstacles. We show that Anna's hummingbirds (Calypte anna) can negotiate apertures less than one wingspan in diameter using a novel sideways maneuver that incorporates continuous, bilaterally asymmetric wing motions. Crucially, this maneuver allows hummingbirds to continue flapping as they negotiate the constriction. Even smaller openings are negotiated via a faster ballistic trajectory characterized by tucked and thus non-flapping wings, which reduces force production and increases descent rate relative to the asymmetric technique. Hummingbirds progressively shift to the swept method as they perform hundreds of consecutive transits, suggesting increased locomotor performance with task familiarity. Initial use of the slower asymmetric transit technique may allow birds to better assess upcoming obstacles and voids, thereby reducing the likelihood of subsequent collisions. Repeated disruptions of normal wing kinematics as birds negotiate tight apertures may determine the limits of flight performance in structurally complex environments. These strategies for aperture transit and associated flight trajectories can inform designs and algorithms for small aerial vehicles flying within cluttered environments.

Hummingbird blood traits track oxygen availability across space and time

Predictable trait variation across environments suggests shared adaptive responses via repeated genetic evolution, phenotypic plasticity or both. Matching of trait-environment associations at phylogenetic and individual scales implies consistency between these processes. Alternatively, mismatch implies that evolutionary divergence has changed the rules of trait-environment covariation. Here we tested whether species adaptation alters elevational variation in blood traits. We measured blood for 1217 Andean hummingbirds of 77 species across a 4600-m elevational gradient. Unexpectedly, elevational variation in haemoglobin concentration ([Hb]) was scale independent, suggesting that physics of gas exchange, rather than species differences, determines responses to changing oxygen pressure. However, mechanisms of [Hb] adjustment did show signals of species adaptation: Species at either low or high elevations adjusted cell size, whereas species at mid-elevations adjusted cell number. This elevational variation in red blood cell number versus size suggests that genetic adaptation to high altitude has changed how these traits respond to shifts in oxygen availability.

Electrostatic Charge on Flying Hummingbirds and Its Potential Role in Pollination

Electrostatic phenomena are known to enhance both wind- and insect-mediated pollination, but have not yet been described for nectar-feeding vertebrates. Here we demonstrate that wild Anna's Hummingbirds (Calypte anna) can carry positive charges up to 800 pC while in flight (mean ± s.d.: 66 ± 129 pC). Triboelectric charging obtained by rubbing an isolated hummingbird wing against various plant structures generated charges up to 700 pC. A metal hummingbird model charged to 400 pC induced bending of floral stamens in four plants (Nicotiana, Hemerocallis, Penstemon, and Aloe spp.), and also attracted falling Lycopodium spores at distances of < 2 mm. Electrostatic forces may therefore influence pollen transfer onto nectar-feeding birds.

Outcome of adult onset systemic lupus erythematosus in Iran

AIM

The aim of this study was to determine systemic lupus erythematosus (SLE) survival in adult patients and its predictors in Iran.

METHODS

The adult patients diagnosed with SLE and admitted to our referral general hospital from 1992 to 2011 were studied. Demographic, clinical and laboratory data at the time of diagnosis were obtained retrospectively and analyzed. Survival rates were calculated by the Kaplan-Meier method. Predictors of mortality were assessed by Cox regression analysis.

RESULTS

In total, 417 were enrolled in the study; 23 were lost to follow-up. Mean (SD) age of SLE onset was 30 (9.7) years. During the study period 35 patients (8.9%) died. The most common causes of death were active SLE (43%), infections (28.6%) and circulatory diseases (20%). Overall survival rates after 5, 10, 15 and 20 years were 93%, 90%, 90% and 80%, respectively. Poor survival predictors in univariate analysis were pericarditis, seizure and hematuria. With multivariate Cox regression analysis, no pericarditis (p = 0.007, HR = 0.22, 95%CI: 0.075-0.657) and no seizure (p = 0.019, HR = 0.35, 95%CI: 0.149-0.846) at the time of SLE diagnosis were found as protective factors in patients' survival.

CONCLUSION

Our study revealed that the survival rate of SLE is comparable with the acceptable worldwide trend. Presenting with pericarditis and seizure at the time of SLE diagnosis prominently decreased the survival rate. Prospective and multicenter studies are needed to better identify the behavior of SLE in Iran.

Sleep apnea & automobile crashes

BACKGROUND

As a group, patients with obstructive sleep apnea (OSA) are at increased risk of having automobile accidents. Previous studies using actual accident data have used only small numbers of subjects.

OBJECTIVE

To determine the rate of automobile accidents in a large population of OSA patients using objective data from the Ministry of Transportation of Ontario (MTO).

DESIGN

Retrospective study

SETTING

Academic sleep disorders clinic and laboratory.

PARTICIPANTS

All cases of OSA polygraphically confirmed between June 1990 and June 1994.

INTERVENTIONS

Cases of OSA were a priori divided into groups based on apnea-hypopnea index (AHI): (OSA1 - AHI 10-25, OSA2 - AHI 26-40, OSA3 - AHI>40) and driving records were obtained from the MTO. Age and sex matched controls were selected at random from drivers in the MTO driver database who hold passenger vehicle licences. Analysis was restricted to drivers with the same licence class.

MAIN OUTCOME MEASURES

Primary outcome measure was accidents in the five years preceding diagnosis. Secondary outcome was citations during the same period.

RESULTS

There were 155 of 460 OSA patients with one or more accidents compared with 150 of 581 Controls for the same time period (x2=7.7,p<0.01). The rate of accidents/year, for the preceding five years, was 0.07+/-0.14 for Controls versus 0.09+/-0.14 for OSA (p <0.05). This difference could all be accounted for by increased accident rate in OSA patients with the highest AHI (OSA3) (MVA/yr: 0.11+/-0.15, 0.08+/-0.12, 0.06+/-0.14 for OSA groups 3,2,1 respectively) as there was no differences among Control, OSA1 and OSA2 accident rates. OSA patients had twice as many citations as Controls (1.74+/-2.13 vs 0.86+/-1.43 p<0.001) although the types of citation were the same.

CONCLUSIONS

Increased automobile accidents in OSA may be restricted to cases with more severe apnea (AHI >40). Despite the large sample size (an order of magnitude greater than previous reports using accident data) further study is needed with even larger numbers, including more measures of disease severity and rigorously controlling for driving exposure.

Effects of nasal CPAP on simulated driving performance in patients with obstructive sleep apnoea

BACKGROUND

Many patients with obstructive sleep apnoea (OSA) have difficulty in driving and experience increased automobile accidents. It has previously been shown that patients with OSA perform poorly on a laboratory based divided attention driving test (DADT).

METHODS

Seventeen men with OSA of mean (SD) age 49.7 (11.2) years and an initial apnoea/hypopnoea index (AHI) of 73.0 (28.9) were restudied from one to 12 (mean (SD) 9.2 (4.2)) months after initiating treatment with nasal continuous positive airway pressure (CPAP) to examine the effects of treatment on DADT performance. Eighteen age and sex matched controls were also retested 8.4 (3.4) months after their initial tests. Following a practice session, all subjects were given the DADT for 20 minutes before each daytime nap of the standard multiple sleep latency test (MSLT).

RESULTS

Untreated patients with OSA, who performed much worse than controls in all measures, improved significantly on all measures of performance, particularly in tracking error which returned to the level of controls in all but one patient. Changes in performance were much greater for patients with OSA than for controls in tracking error (mean difference 106 (95% CI 75 to 135) cm), sleep latency/ MSLT (5.3 (95% CI 2.7 to 8.0) min), number of correct responses (1.2 (95% CI 0.4 to 1.9)), number of missed responses (1.7 (95% CI 0.9 to 2.3)), and number out of bounds (10.0 (95% CI 7.9 to 13.6)), but not for response time (0.1 (95% CI -0.3 to 0.2) s). Improvement in tracking error was highly correlated with improvement in sleepiness (r = 0.65).

CONCLUSIONS

Impairment in laboratory driving performance skills in patients with OSA is reversed by successful treatment with nasal CPAP. Changes in daytime sleepiness account for some but not all of the improvement.

Comparison of simulated driving performance in narcolepsy and sleep apnea patients

Many patients with obstructive sleep apnea (OSA) or narcolepsy have difficulty driving and increased automobile accidents. Previously we have shown that OSA patients perform poorly on a laboratory-based divided-attention driving test (DADT). Patients with narcolepsy may be as sleepy as OSA patients, so we compared performance on the DADT of OSA patients with that of narcolepsy patients. Twenty-one male OSA patients [age 49.3 +/- 12.7 (SD) years; apnea-hypopnea index (AHI) 73 +/- 29] 21 age- and sex-matched controls, and 16 narcoleptics (12 males, four females; age 39.6 +/- 15.2 years) underwent polysomnography followed by daytime sleep latency testing (MSLT). Following a practice session, all subjects were given the DADT for 20 minute prior to each daytime nap of the MSLT. Narcolepsy patients were younger than OSA or controls and more sleepy than OSA patients. Tracking error was much worse in patients than controls (228 +/- 145 cm for OSA vs. 196 +/- 146 for narcolepsy vs. 71 +/- 31 for controls; p < 0.001), although half of either patient group performed as well as controls. There was only a weak relationship between MSLT and tracking in either patient group. We conclude that impairment in laboratory driving performance skills is seen in both groups of sleepy patients but the degree of impairment is difficult to predict from sleepiness alone.

Simulated driving performance in patients with obstructive sleep apnea

To assist in determining ability to drive in patients with obstructive sleep apnea (OSA), we developed a divided attention driving test (DADT) based on the work of Moskowitz and Burns (6). We first examined its ability to detect impaired performance by testing normal subjects both sober and impaired by alcohol (mean blood alcohol level, 95 +/- 25 mg/dl). Subsequently, 21 male patients with OSA (age 49.3 +/- 12.7 [SD] yr; apnea hypopnea index [AHI] 73 +/- 29) and 21 age- and sex-matched control subjects underwent polysomnography followed by daytime sleep latency testing (MSLT). Before each day-time nap, subjects were given the DADT for 20 min. Patients who performed much worse than control subjects in all measures, with the largest difference noted in tracking error (OSA, 228 +/- 145 cm versus control 71 +/- 31 cm, p < 1 x 10(-9)). Half of the patients were worse than any control subject, with some showing performance worse than control subjects impaired by alcohol. However, MSLT and AHI explained less than 25% of the variance in tracking error, making individual prediction problematic. We concluded that in laboratory driving performance skills are markedly impaired in over half our group with sleep apnea. Further testing and comparing on-road performance should aid in predicting ability to drive.

Effects of minor tranquilizers and antidepressants on psychomotor performance

Results of laboratory and epidemiologic studies have raised concern that psychotropic drugs may contribute to accidents. This article reviews studies of the effects of minor tranquilizer and antidepressant drugs on psychomotor performance. Data clearly demonstrate that the most commonly prescribed tranquilizer, diazepam, impairs many aspects of psychomotor performance for several hours after dosing, and there is no evidence that behavioral tolerance develops with continued drug use or that patients are differently affected than nonpatients. Lorazepam similarly impairs psychomotor performance. Other frequently prescribed benzodiazepine drugs have not been sufficiently examined to warrant conclusions about their psychomotor effects. A newly marketed nonbenzodiazepine anxiolytic, buspirone, has been shown to have few effects on performance skills. Only one antidepressant, amitriptyline, has been studied thoroughly enough to conclude that it impairs psychomotor performance. The few studies of other, newer antidepressants suggest they may cause less impairment; however, more research is needed to confirm this.

Effects of flurazepam and zopiclone on the performance of chronic insomniac patients: a study of ethanol-drug interaction

Three groups of ten middle-aged insomniac patients were treated with placebo, flurazepam, or zopiclone for 12 consecutive days in a study designed to compare the residual daytime effects of long-acting flurazepam and short-acting zopiclone on a variety of cognitive and motor tasks. These effects were examined independently and in combination with ethanol effects. The effects of the drugs on sleep parameters were also subjectively assessed by means of questionnaires during treatment and withdrawal. The study demonstrated persistent performance effects with flurazepam. Testing at the end of the treatment period showed that movement time was impaired in the flurazepam treated group. Flurazepam also enhanced the increment of movement time produced by ethanol. One subject became severely confused when given ethanol after using flurazepam for 12 days. None of these effects were found with zopiclone. The rapid elimination of zopiclone may account for these findings.

Effects of long-term administration of buspirone and diazepam on driver steering control

The effects of buspirone, diazepam, and placebo on tracking control were investigated over a nine-day period, using three groups of subjects, each with eight females and eight males. Subjects were tested using an interactive, computer-based driving simulator on days one, eight, and nine of the treatment period. On day nine, subjects received alcohol with their drug treatment. Measures of steering control were derived from car-driver transfer functions. Tracking performance was also measured. Diazepam was found to adversely affect steering control measures in comparison with placebo. This was true both after doses on the first as well as the eighth day of treatment. Thus, there was no evidence of behavioral tolerance to diazepam. In contrast, buspirone was not found to have any adverse effects on steering control; in fact, some evidence of improved tracking control was found. When alcohol was added to each treatment on the ninth day, differences between the drug treatment groups were less pronounced but in the same direction as on the first and eighth days.

Learning disabled boys' performance and self-assessments on physical fitness tests

30 learning disabled boys drawn from a segregated private school for learning disabled children and 22 from a public school mainstream program and 22 nondisabled boys performed two physical fitness tests, sit-ups and shuttle run in one of two conditions. While normal achievers performed significantly better on one of the tests, there were no differences between the two samples of learning disabled youngsters. However, students' comparisons of their performance with classmates' indicated that learning disabled youngsters in the private school ranked themselves more favorably than those in mainstream classrooms.

Effects of chronically administered buspirone and diazepam on driving-related skills performance

The effects on driving skills of buspirone and diazepam, singly and in combination with alcohol, were examined. Three groups of 16 subjects each (8 men and 8 women) received either 20 mg of buspirone, 15 mg of diazepam, or placebo daily for 9 days. On day 9, they also received alcohol (men, 0.85 g/kg; women, 0.72 g/kg). On days 1, 8, and 9, subjects were tested on a driving simulator and given four sessions of divided attention tasks examining tracking and visual search performance. Extensive evidence of performance impairment associated with diazepam contrasted with improved performance under chronic buspirone treatment. Alcohol effects were additive.