Probing the Magnetosheath Boundaries Using Interstellar Boundary Explorer (IBEX) Orbital Encounters.

Inside the magnetosheath, the IBEX-Hi energetic neutral atom (ENA) imager measures a distinct background count rate that is more than 10 times the typical heliospheric ENA emissions observed when IBEX is outside the magnetosheath. The source of this enhancement is magnetosheath ions of solar wind (SW) origin that deflect around the Earth's magnetopause (MP), scatter and neutralize from the anti-sunward part of the IBEX-Hi sunshade, and continue into the instrument as neutral atoms, behaving indistinguishably from ENAs emitted from distant plasma sources. While this background pollutes observations of outer heliospheric ENAs, it provides a clear signature of IBEX crossings over the magnetospheric boundaries. In this study, we investigate IBEX encounters with the magnetosheath boundaries using ∼8 yr of orbital data, and we determine the MP and bow shock (BS) locations derived from this background signal. We find 280 BS crossings from X GSE ∼ 11 Re to X GSE âˆ¼ -36 Re and 241 MP crossings from X GSE ∼ 6 Re to X GSE âˆ¼ -48 Re. We compare IBEX BS and MP crossing locations to those from IMP-8, Geotail, Cluster, Magion-4, ISEE, and Magnetospheric Multiscale Mission, and we find that IBEX crossing locations overlap with the BS and MP locations inferred from these other data sets. In this paper, we demonstrate how IBEX can be used to identify magnetosheath crossings, and extend boundary observations well past the terminator, thus further constraining future models of magnetosheath boundaries. Furthermore, we use the IBEX data set to show observational evidence of near-Earth magnetotail squeezing during periods of strong interplanetary magnetic field B y.

Structures and spectral variations of the outer heliosphere in IBEX energetic neutral atom maps.

The Interstellar Boundary Explorer (IBEX) has obtained all-sky images of energetic neutral atoms emitted from the heliosheath, located between the solar wind termination shock and the local interstellar medium (LISM). These flux maps reveal distinct nonthermal (0.2 to 6 kilo-electron volts) heliosheath proton populations with spectral signatures ordered predominantly by ecliptic latitude. The maps show a globally distributed population of termination-shock-heated protons and a superimposed ribbonlike feature that forms a circular arc in the sky centered on ecliptic coordinate (longitude lambda, latitude beta) = (221 degrees, 39 degrees), probably near the direction of the LISM magnetic field. Over the IBEX energy range, the ribbon's nonthermal ion pressure multiplied by its radial thickness is in the range of 70 to 100 picodynes per square centimeter AU (AU, astronomical unit), which is significantly larger than the 30 to 60 picodynes per square centimeter AU of the globally distributed population.

Global observations of the interstellar interaction from the Interstellar Boundary Explorer (IBEX).

The Sun moves through the local interstellar medium, continuously emitting ionized, supersonic solar wind plasma and carving out a cavity in interstellar space called the heliosphere. The recently launched Interstellar Boundary Explorer (IBEX) spacecraft has completed its first all-sky maps of the interstellar interaction at the edge of the heliosphere by imaging energetic neutral atoms (ENAs) emanating from this region. We found a bright ribbon of ENA emission, unpredicted by prior models or theories, that may be ordered by the local interstellar magnetic field interacting with the heliosphere. This ribbon is superposed on globally distributed flux variations ordered by both the solar wind structure and the direction of motion through the interstellar medium. Our results indicate that the external galactic environment strongly imprints the heliosphere.

A comparison of 1% prilocaine with 0.5% ropivacaine for outpatient-based surgery under axillary brachial plexus block.

UNLABELLED: We compared the use of 1% prilocaine with 0.5% ropivacaine for axillary brachial plexus anesthesia in a double-blinded manner in day-stay patients to determine the better of the two local anesthetics in terms of onset time and duration of motor block. Sixty patients scheduled for outpatient upper-limb surgery were allocated randomly to receive either prilocaine (28 patients) or ropivacaine (32 patients) at a volume of 0.7 mL/kg. The brachial plexus was located with a plexus needle and nerve stimulator. By 20 min after injection of prilocaine or ropivacaine, there was no difference in analgesic effect. By this time, it was apparent whether or not a block was going to be adequate for surgery. Pain returned after a mean of 278 min (SD 111 min; range, 160-630 min) with prilocaine as compared with 636 min (SD 284 min; range, 210-1440 min) with ropivacaine. Analgesia use was similar in both groups. Duration of motor block with prilocaine was a mean of 254 min (SD 62 min; range, 130-385 min), as compared with 642 min (SD 199 min; range, 350-1080 min) with ropivacaine. We conclude that there is no clinically important difference between 1% prilocaine and 0.5% ropivacaine in time to onset of axillary brachial plexus block when they are injected in equal volumes. There is a significantly longer duration of action with ropivacaine, which may make it less suitable for day-stay upper-limb surgery because of the handicap from reduced muscle power. IMPLICATIONS: This study compares two local anesthetics to determine which is most suitable for day-stay upper-limb surgery under axillary brachial plexus block. Prilocaine 1% is more suitable than ropivacaine 0.5% because of a more prolonged duration of action of ropivacaine, although this could be useful in other circumstances.

Setting targets for sedation with a target-controlled propofol infusion.

We studied 30 unpremedicated patients undergoing muscle biopsy under femoral nerve block to determine sedation levels reached with a Diprifusor target-controlled propofol infusion, in order to establish the equivalent of the ED50 for different levels of depth of sedation. Infusion was started at 0.8 microg x ml(-1) and altered by increments of 0.1 microg x ml(-1) after equilibrium between target and calculated concentrations, until the desired level of sedation was reached. The ED50 target propofol concentrations for sedation at sedation levels 2 (drowsy), 3 (drowsy, responds to verbal stimulation) and 4 (responsive to physical stimulation only) were 1.0 microg x ml(-1), 1.6 microg x ml(-1) and 2.1 microg x ml(-1), respectively. At sedation level 3, several patients exhibited spontaneous movement, hindering surgery. Oxygen supplementation is recommended for sedation at level 4.

Patient-controlled sedation using propofol in elderly patients in day-case cataract surgery.

Patient-controlled sedation (PCS) with propofol has been used successfully as an adjunct to local anaesthetic procedures. We studied a group of elderly patients (mean age 75.4 yr) undergoing cataract surgery and attempted to increase patient acceptability and comfort of local anaesthesia. Propofol was self-administered in a dose of 0.25 mg kg-1 for patients more than 60 yr of age, with a lockout period of 3 min. A total of 14 of 20 patients used PCS; eight of 20 used the PCS only once and another six had three tries or less. Despite this, 18 of 20 patients claimed they found the PCS useful. However, while it is possible to administer PCS successfully to elderly patients undergoing cataract surgery and produce a decrease in the level of anxiety, we found it unacceptable because of head movement in two patients. These patients received only two and three divided doses, to a maximum of 29 and 30 mg, respectively. There were no other adverse events.

TNO stereopsis test as an aid to the prevention of amblyopia.

In this investigation, carried out under a Youth Health Care postgraduate course in Nijmegen, the stereopsis of a school population of 730 children, aged 4-18 years, was recorded and clinically evaluated. Stereopsis was measured using the TNO test, a random-dot stereo test especially designed for the early detection of amblyopia. The main aims of this study were to establish the validity of the TNO test as a screening test for amblyopia, obtain information about the variability and age dependence of stereopsis, and to evaluate the efficacy of amblyopia prevention. The most important findings can be summarized as follows: 1. All amblyopes are detected by the TNO test's recommended referral criterion of 240 sec arc (binocular threshold parallax in sec arc). 2. The red-green anaglyphs used in the test do not pose problems for individuals with a colour vision deficiency. 3. The ability to discriminate depth improves by a factor of two over the age interval 4-12 years. 4. A stereoacuity of < or = 120 sec arc is a good predictor of normal or correctable normal vision, and may therefore help in evaluating the often incomplete results of eye tests of young children. 5. Where there is an increased perinatal risk, there is a greater chance of disturbed binocular vision. 6. It is estimated that 75% of amblyopes remain amblyopic, possibly because of delayed detection; 60% of the amblyopes in the population examined were not identified before the age of 5 years.