A radio-pulsing white dwarf binary star.

White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 107-year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they mainly originate from the cool star. AR Sco's broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.

Movement planning and attentional control of visuospatial working memory: evidence from a grasp-to-place task.

In this study, we have investigated the influence of available attentional resources on the dual-task costs of implementing a new action plan and the influence of movement planning on the transfer of information into visuospatial working memory. To approach these two questions, we have used a motor-memory dual-task design in which participants grasped a sphere and planned a placing movement toward a left or right target according to a directional arrow. Subsequently, they encoded a centrally presented memory stimulus (4 × 4 symbol matrix). While maintaining the information in working memory, a visual stay/change cue (presented on the left, center or right) either confirmed or reversed the planned movement direction. That is, participants had to execute either the prepared or the re-planned movement and finally reported the symbols at leisure. The results show that both, shifts of spatial attention required to process the incongruent stay/change cues and movement re-planning, constitute processing bottlenecks as they both reduced visuospatial working memory performance. Importantly, the spatial attention shifts and movement re-planning appeared to be independent of each other. Further, we found that the initial preparation of the placing movement influenced the report pattern of the central working memory stimulus. Preparing a leftward movement resulted in better memory performance for the left stimulus side, while the preparation of a rightward movement resulted in better memory performance for the right stimulus side. Hence, movement planning influenced the transfer of information into the capacity-limited working memory store. Therefore, our results suggest complex interactions in that the processes involved in movement planning, spatial attention and visuospatial working memory are functionally correlated but not linked in a mandatory fashion.

Evidence for water in the rocky debris of a disrupted extrasolar minor planet.

The existence of water in extrasolar planetary systems is of great interest because it constrains the potential for habitable planets and life. We have identified a circumstellar disk that resulted from the destruction of a water-rich and rocky extrasolar minor planet. The parent body formed and evolved around a star somewhat more massive than the Sun, and the debris now closely orbits the white dwarf remnant of the star. The stellar atmosphere is polluted with metals accreted from the disk, including oxygen in excess of that expected for oxide minerals, indicating that the parent body was originally composed of 26% water by mass. This finding demonstrates that water-bearing planetesimals exist around A- and F-type stars that end their lives as white dwarfs.

The functional role of working memory in the (re-)planning and execution of grasping movements.

Three experiments were conducted to dissociate movement planning costs and movement execution costs in working memory (WM). The aim of the study was to clarify what kind of WM processes (verbal, spatial, or both) are recruited during movement planning and movement execution. Therefore, a WM task (verbal and spatial versions) was combined with a high-precision manual action. Participants initially planned a placing movement toward 1 of 2 targets, subsequently encoded verbal or spatial information in WM, and then executed the movement during the retention phase. We tested the impact of movement execution on memory performance (Experiment 1), the role of WM task difficulty as a moderating variable in motor-memory interactions (Experiment 2), and the impact of implementing a new motor plan during memory retention (Experiment 3). Our results show that movement execution disrupted spatial more than verbal memory (Experiment 1) and that this domain-specific interference pattern was independent of WM task difficulty (Experiment 2). Hence, the results of Experiments 1 and 2 demonstrate that executing a prepared movement recruits domain-specific visuospatial memory resources. Experiment 3 involved trials that required the implementation of a new motor plan. The additional planning requirement during the retention phase reduced performance in both WM tasks in equal measure beyond the relative movement execution costs observed in Experiments 1 and 2. These results provide evidence for distinct roles of WM in manual actions, with action execution requiring principally modality-specific capacities and (re-)planning engaging modality-general WM resources.

The costs of changing an intended action: movement planning, but not execution, interferes with verbal working memory.

How much cognitive effort does it take to change a movement plan? In previous studies, it has been shown that humans plan and represent actions in advance, but it remains unclear whether or not action planning and verbal working memory share cognitive resources. Using a novel experimental paradigm, we combined in two experiments a grasp-to-place task with a verbal working memory task. Participants planned a placing movement toward one of two target positions and subsequently encoded and maintained visually presented letters. Both experiments revealed that re-planning the intended action reduced letter recall performance; execution time, however, was not influenced by action modifications. The results of Experiment 2 suggest that the action's interference with verbal working memory arose during the planning rather than the execution phase of the movement. Together, our results strongly suggest that movement planning and verbal working memory share common cognitive resources.

Two white dwarfs with oxygen-rich atmospheres.

Stars with masses ranging from 7 to 10 times the mass of the Sun end their lives either as massive white dwarfs or weak type II supernovae, but there are only limited observational constraints on either evolutionary channel. Here we report the detection of two white dwarfs with large photospheric oxygen abundances, implying that they are bare oxygen-neon cores and that they may have descended from the most massive progenitors that avoid core collapse.

Size and age estimates at sexual maturity for the little skate Leucoraja erinacea from the western Gulf of Maine, U.S.A.

Size and age estimates at sexual maturity were determined for 162 male and 273 female little skates Leucoraja erinacea collected from the western Gulf of Maine. Maturity ogives suggest that 50% maturity in females occurs at age 9.5 years and 480 mm total length (LT), whereas 50% maturity in males occurs at a slightly younger age of 7.7 years and smaller size of 460 mm LT. Age estimates were made from 389 L. erinacea ranging in size from 93 to 570 mm LT. The index of average per cent error and age-bias plots indicated that the ageing methods were precise and non-biased. Additionally, annual periodicity of band formation was validated with oxytetracycline in eight individuals (three males and five females) ranging in age from 3 to 12 years. In conclusion, results from this study indicate that L. erinacea exhibits characteristics that make other elasmobranch populations highly susceptible to overexploitation.

Rostral ventrolateral medullary opioid receptor activation modulates pressor response to muscle contraction.

The effects of an opioid agonist, [D-Ala2]methionine enkephalinamide (DAME), administered into the rostral ventrolateral medulla (rVLM) or caudal ventrolateral medulla (cVLM) on cardiovascular responses to isometric muscle contraction were determined in anesthetized rats. A 30-s contraction evoked by tibial nerve stimulation increased mean arterial pressure (MAP) and heart rate (HR) by 34 +/- 6 mmHg and 40 +/- 7 beats/min, respectively, with a developed tension of 322 +/- 30 g, after bilateral insertion of microdialysis probes into the rVLM. Thirty-minute dialysis of DAME (10 and 100 microM) attenuated the contraction-evoked cardiovascular changes dose dependently (10 microM: MAP = 25 +/- 4 mmHg, HR = 27 +/- 3 beats/min, tension = 333 +/- 25 g; 100 microM: MAP = 14 +/- 4 mmHg, HR = 16 +/- 5 beats/min, tension = 330 +/- 34 g). Preadministration of an opioid antagonist, naloxone (100 microM), augmented contraction-evoked MAP and HR responses and blocked effects of 100 microM DAME. Microdialysis of DAME into the cVLM produced no changes in the pressor response to contraction. At end of each experiment, tibial nerve stimulation after neuromuscular blockade evoked no MAP or HR change. Results demonstrate that opioid receptor activation within the rVLM modulates cardiovascular responses to isometric muscle contraction.

Central 5-HT1A modulation of cardiovascular responses to tibial nerve stimulation-evoked muscle contraction.

The effects of administering 8-hydroxy-2-(di-n-propylamine) tetralin [8-OH-DPAT, a serotonin 1A (5-HT1A) receptor agonist] into the rostral ventrolateral medulla (RVLM) on cardiovascular responses during tibial nerve stimulation-evoked muscle contraction were investigated using anesthetized rats. Stimulation of the tibial nerve (3 times motor threshold, 0.1 ms, 40 Hz) for 30 s increased mean arterial pressure (MAP), heart rate (HR), and muscle tension by 25 +/- 3 mmHg, 24 +/- 4 beats/min, and 299 +/- 35 g, respectively. Bilateral microdialysis of 8-OH-DPAT (10 mM) for 30 min attenuated the stimulation-evoked increases in MAP (8 +/- 2 mmHg) and HR (11 +/- 5 beats/min), without a change in muscle tension (292 +/- 30 g). However, administration of 1 mM 8-OH-DPAT had no effect on the cardiovascular responses. Thirty minutes of microdialysis of 8-OH-DPAT (10 mM) into the caudal ventrolateral medulla produced no effect on cardiovascular responses during muscle contraction. Prior administration of 10 mM 1-[2-methoxyphenyl]-4-[4-(2-phthalimido)-butyl]piperazine (NAN-190), a 5-HT1A receptor antagonist, for 30 min into the RVLM blocked the attenuating effects of subsequent microdialysis of 8-OH-DPAT (10 mM). Results suggest that activation of 5-HT1A receptors within the RVLM inhibit cardiovascular responses elicited during static muscle contraction.

Chair design affects how older adults rise from a chair.

OBJECTIVE: To determine how modifications of key chair design aspects, such as seat height, posterior seat tilt, backrest recline, seat compressibility, and armrest placement, affect how older adults rise from a chair and the seating comfort they experience. DESIGN: Cross-sectional comparison. SETTING: Congregate housing facility and university laboratory. SUBJECTS: Two groups of volunteers, Old (n = 29, mean age 84) and Young (n = 21, mean age 23). MEASUREMENTS: Analysis of time to rise, body motion (determined by use of digitized videotaping), and self-reported difficulty when subjects rose from a variety of controlled chair settings thought to represent important chair design specifications encountered by older adults. Subjects also reported their comfort while being seated in these settings. RESULTS: Lowered seat height, increased posterior seat tilt and backrest recline, and perhaps increased seat compressiblity cause increased time to rise, increased body motion, and increased self-reported ratings of rise difficulty in both Young and Old groups. Under the most challenging conditions, the effect appears to be stronger in the Old than in the Young: a few Old were unable to rise, and the Old took disproportionately longer to rise and used disproportionately greater neck motion (P generally < 0.001) compared with the Young. Arm rest placement did not alter rise performance or ratings significantly. The conditions in which rise difficulty increases or decreases do not correspond exactly to conditions in which comfort increases or decreases. Some aspects that increase rise difficulty, such as tilt/recline and seat compressiblity, may also increase comfort. CONCLUSIONS: Aspects of chair design such as lowered seat height, increased posterior seat tilt, increased back recline, and increased compressibility interfere with chair egress in older adults. While decreasing ease of egress, however, these same factors may increase seating comfort. Furniture designers and manufacturers must find a balance between degree of sitting comfort, ease of egress and the degree to which the seating device facilitates functional independence, particularly to meet the needs of disable older adults.

A difference between front-loaded streptokinase and standard-dose recombinant tissue-type plasminogen activator in preserving left ventricular function after acute myocardial infarction (the Central Illinois Thrombolytic Therapy Study).

A blinded, randomized trial compared the effects of front-loaded streptokinase with those of the conventional dose of intravenous recombinant tissue-type plasminogen activator (rt-PA) on left ventricular (LV) function after acute myocardial infarction (AMI). Thrombolytic therapy was administered in the emergency departments of 30 community hospitals in central Illinois, and subsequent studies were performed at 1 tertiary referral center. Patients aged < or = 75 years with a first AMI who could be treated within 4 hours of the onset of chest pain were randomly assigned to receive either streptokinase (375,000 IU bolus, followed by 1,125,000 IU over 1 hour) or rt-PA (10 mg bolus, followed by 50 mg in the first hour, and 20 mg/hour for the next 2 hours). All patients were treated with aspirin (325 mg) and intravenous heparin. Patients were transferred for angiography within 24 hours. During the 30-month study, 253 patients were treated with intravenous thrombolytic therapy 2.4 +/- 1.0 hour after the onset of AMI. In patients with anterior wall AMI (n = 90), global LV ejection fraction measured by angiography within 24 hours was 45 +/- 12% with rt-PA, and 39 +/- 13% with streptokinase (p < 0.03). Convalescent radionuclide angiography documented a persistent beneficial effect of rt-PA on LV regional wall contractility, but not global ejection fraction. There were no differences between rt-PA and streptokinase in preserving global or regional LV function in patients with inferior wall AMI.

Ectoparasites and endoparasites in sexually transmitted diseases.

A number of protozoan organisms, both ectoparasitic and endoparasitic, may be related to sexual activity. The broad range of clinical presentations makes this group of diseases challenging to diagnose. Patients may present with skin, genital, gastroenterologic, pulmonary, or neurologic symptoms, or may be asymptomatic. A careful history, including specific sexual history, with appropriate laboratory evaluation will aid the primary care physician in making the correct diagnosis and thus supply the correct treatment. Awareness that infection with multiple organisms is frequent in some populations is important. Prevention of reinfection or further transmission of the disease must be aggressively pursued by patient education about the means of transmission of the disease and avoidance of high-risk sexual practices.

The primary care physician and thrombolytic therapy for acute myocardial infarction: comparison of intravenous streptokinase in community hospitals and the tertiary referral center.

From September 1982 through December 1987, 1012 patients were treated with intravenous streptokinase within 6 hours of acute myocardial infarction. Most of them (816/1012, 81 percent) were treated in community hospitals by primary care physicians. The remaining 196 (19 percent) were treated in the referral center, usually by a cardiologist. Cardiac catheterization within 2 days showed an open infarct artery in 87 percent of the community hospital and 83 percent of the referral center patients (P = NS). Predischarge ejection fraction was similar for community hospital and referral center patients (49 percent +/- 14 percent versus 51 percent +/- 14 percent, respectively), and there was a similar rate of bleeding complications (10 percent versus 13 percent, respectively). We conclude that primary physicians can use intravenous streptokinase effectively and safely in the treatment of patients in community hospitals.

Independently activated talking tracheostomy systems for quadriplegic patients.

Patients who require mechanical ventilator support use cuffed tracheostomy tubes to facilitate prolonged, intermittent, positive-pressure ventilation. The air flow provided by these cuffed tracheostomy tubes bypasses the vocal cords, preventing verbal expression by the patient. Specially designed cuffed tracheostomy tubes are available that restore air flow across the vocal cords without compromising a patient's ventilation. These tracheostomy tubes require an air control port to be covered when air flow is needed by the patient to produce speech. Individuals with neuromuscular impairment usually require an attendant to activate the control port. Electromechanical systems have been developed to allow independent activation of the air flow by the patient. Both freestanding and wheelchair-based systems are described.

Primary afferent projections to the central octavus nuclei in the elasmobranch, Rhinobatos sp., as demonstrated by nerve degeneration.

Nerve degeneration studies were performed to determine the central projections of the octavus nerve in the guitarfish. Rhinobatos sp. Most first-order octavus nerve afferents are confined to the ventral longitudinal column of the medulla, which consists of four octavus nuclei: the nucleus octavus anterior (NOA), nucleus octavus magnocellularis (NOM), nucleus octavus descendens (NOD); and nucleus octavus posterior (NOP). Central projections of the octavus nerve outside of the ventral octavus nuclear column are to the vestibulolateral lobe of the cerebellum, the large multipolar cells that lie deep to the cerebellar crest of nucleus intermedius, the reticular formation, and the nucleus octavolateralis efferens. In addition, the cytoarchitectural features of the four octavus nuclei have been analyzed: the NOA consists of large spindle-shaped neurons and medium-sized multipolar neurons; the NOM is a small nucleus consisting of very large multipolar neurons; the NOD contains several types of neurons including large spindle-shaped neurons, large multipolar neurons, and polymorphic small and medium-sized neurons; and the NOP contains small spherical and small multipolar neurons evenly distributed throughout the nucleus. On the basis of the morphology of the neurons, the NOA and NOD appear to have subdivisions suggesting a more complex organization of the octavus nuclear column than previously recognized.

Emergency room practice among family physicians.

An attempt was made to determine the extent to which physicians trained and certified in family medicine are involved in emergency medicine. An 18-item, self-report questionnaire was mailed to 73 graduates of a family practice residency program to obtain information on their practices, their professional and emergency medicine experiences, and their attitudes toward the practice of emergency medicine by family practitioners. Ten percent of the 60 responding physicians were currently involved in full-time emergency medicine in either emergency rooms or minor emergency clinics. Twenty-eight percent of the respondents were currently practicing emergency medicine on either a part-time or sporadic basis. Supplemental income was cited the most often as a reason for becoming involved in emergency medicine. Only variables related to the physicians' attitudes discriminated between those who were practicing emergency medicine and those who were not.

Primary afferent projections of the octavus nerve to the inferior reticular formation and adjacent nuclei in the elasmobranch, Rhinobatos sp.

Projections of primary afferent fibers from the octavus nerve to the inferior reticular formation were determined by nerve degeneration and HRP labeling. Descending afferents from the horizontal ampullary nerve exit the ventral border of the nucleus octavus descendens via arcuate fiber tracts, and project to a group of neurons adjacent to the spinal lemniscus; to the inferior reticular formation; and to the nucleus funiculi lateralis. The possible influence of these afferent projections on directed swimming motion is discussed.

Central projections of the octavolateralis nerves of the clearnose skate, Raja eglanteria.

The central projections of first-order lateral line and octavus nerve afferents of the clearnose skate, Raja eglanteria, were determined by nerve degeneration and horseradish peroxidase techniques. The octavolateralis area of the medulla, which receives these afferents, is organized into dorsal, intermediate, and ventral longitudinal columns of cells and neuropil. Fibers that innervate the electroreceptive sense organs enter the dorsal longitudinal column via the dorsal root of the anterior lateral line nerve and terminate within the dorsal nucleus. Mechanoreceptive fibers from neuromasts of the head and trunk are carried by the ventral root of the anterior lateral line nerve and posterior lateral line nerve, respectively. Both nerves enter the intermediate longitudinal column and terminate throughout the rostrocaudal extent of the intermediate nucleus. Fibers of the ventral root of the anterior lateral line nerve are confined to the medial portion of the intermediate nucleus and posterior lateral line nerve fibers to the lateral portion. In addition, ascending mechanoreceptive fibers from both head and trunk neuromasts project to the vestibulolateral lobe of the cerebellum. Octavus nerve afferents enter the medulla and terminate primarily within the four octaval nuclei that comprise the ventral longitudinal column. Rostrocaudally, these nuclei are the anterior, magnocellular, descending, and posterior octaval nuclei. A few ascending axons continue beyond the anterior octaval nucleus and course to the vestibulolateral lobe of the cerebellum. Some descending axons emanate from the descending octaval nucleus and course to the reticular formation and intermediate nucleus. Therefore, electroreceptive lateral line, mechanoreceptive lateral line, and octavus nerve afferents project ipsilaterally and terminate predominantly within separate medullary nuclei. The significance of octavus nerve projections to the intermediate nucleus and overlap of mechanoreceptive and octavus afferents within the vestibulolateral lobe of the cerebellum cannot be determined until it is known which fibers of the inner ear sense organs project to these areas. Retrograde transport of horseradish peroxidase results in the labeling of large multipolar cells, both ipsilaterally and contralaterally, within a column of gray that lies dorsolateral to the reticular formation. These cells are interpreted as the cell of origin of the efferent components of the anterior and posterior lateral line nerves.