First and subsequent return stroke properties of cloud-to-ground lightning

Lightning properties obtained by a network of magnetic direction finders and by electric field measurements for distances from 50 to 500 km are compared for three summer thunderstorms in Sweden. The data from direct field recordings indicate 31, 17, and 26 pcts. of negative subsequent return strokes with peak current (as inferred from the peak electric field) higher than the first. Electric fields from first strokes are compared with normalized amplitudes registered by the magnetic direction finding system. The efficiency of detection by the magnetic direction finding system is discussed in terms of the percentage of lightning flashes observed by electric field measurements that are not localized. Statistics of the number of strokes per flash and the interstroke time intervals are presented

Community-based Memory Screening Intervention and Memory Knowledge in Older Adults

As the United States’ population ages, there is a growing need for older adults to screen for age-related memory problems. Four theoretically-derived psychosocial factors are predictive of dementia screening intention: perceived benefits, perceived susceptibility, self-efficacy, and knowledge about aging memory. The current study preliminarily tested whether these factors could be increased with a community-based, educational memory screening intervention. Educational presentations were offered at community senior centers and data on psychosocial factors and willingness to screen were collected pre- and post-presentation from 32 older adult participants (age M = 78.69, SD = 7.12). Perceived benefits and self-efficacy significantly increased from pre- to post-presentation (Perceived benefits F(1,31) = 8.73, p \u3c .01, partial η2= .22; Self-efficacy F(1,30) = 7.52, p \u3c .01, partial η2= .20).. The majority of participants (75%) signed up for memory screens following the presentation. Participants had generally high satisfaction ratings and positive narrative responses about the presentation. Results provide information about how the presentation can be refined to address psychosocial factors and determine if these factors impact willingness to screen for memory. This feasibility and efficacy study represents a step to raising knowledge and awareness of memory and aging issues among older adults in the community

On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

Measurements of the various plasma configurations produced by a planar magnetized coaxial gun provide insight into the magnetic topology evolution resulting from magnetic helicity injection. Important features of the experiments are a very simple coaxial gun design so that all observed geometrical complexity is due to the intrinsic physical dynamics rather than the source shape and use of a fast multiple-frame digital camera which provides direct imaging of topologically complex shapes and dynamics. Three key experimental findings were obtained: (1) formation of an axial collimated jet [Hsu and Bellan, Mon. Not. R. Astron. Soc. 334, 257 (2002)] that is consistent with a magnetohydrodynamic description of astrophysical jets, (2) identification of the kink instability when this jet satisfies the Kruskal-Shafranov limit, and (3) the nonlinear properties of the kink instability providing a conversion of toroidal to poloidal flux as required for spheromak formation by a coaxial magnetized source [Hsu and Bellan, Phys. Rev. Lett. 90, 215002 (2003)]. A new interpretation is proposed for how the n=1 central column instability provides flux amplification during spheromak formation and sustainment, and it is shown that jet collimation can occur within one rotation of the background poloidal field.Comment: Physics of Plasmas (accepted

Possible geopotential improvement from satellite altimetry

Possible geopotential improvement from satellite altimetr

TOM-1/tomosyn acts with the UNC-6/netrin receptor UNC-5 to inhibit growth cone protrusion in Caenorhabditis elegans

In the polarity/protrusion model of growth cone repulsion from UNC-6/netrin, UNC-6 first polarizes the growth cone of the VD motor neuron axon via the UNC-5 receptor, and then regulates protrusion asymmetrically across the growth cone based on this polarity. UNC-6 stimulates protrusion dorsally through the UNC-40/DCC receptor, and inhibits protrusion ventrally through UNC-5, resulting in net dorsal growth. Previous studies showed that UNC-5 inhibits growth cone protrusion via the flavin monooxygenases and potential destabilization of F-actin, and via UNC-33/CRMP and restriction of microtubule plus-end entry into the growth cone. We show that UNC-5 inhibits protrusion through a third mechanism involving TOM-1/tomosyn. A short isoform of TOM-1 inhibited protrusion downstream of UNC-5, and a long isoform had a pro-protrusive role. TOM-1/tomosyn inhibits formation of the SNARE complex. We show that UNC-64/syntaxin is required for growth cone protrusion, consistent with a role of TOM-1 in inhibiting vesicle fusion. Our results are consistent with a model whereby UNC-5 utilizes TOM-1 to inhibit vesicle fusion, resulting in inhibited growth cone protrusion, possibly by preventing the growth cone plasma membrane addition required for protrusion

Ultraviolet television data from the Orbiting Astronomical Observatory. 1: Instrumentation and analysis techniques for the celescope experiment

The celescope instrumentation and data analysis system is described, the major problems encountered during orbital operation are summerized, and a few major problems that were anticipated but did not materialize are listed

Plasma Relaxation and Topological Aspects in Hall Magnetohydrodynamics

Parker's formulation of isotopological plasma relaxation process in magnetohydrodynamics (MHD) is extended to Hall MHD. The torsion coefficient alpha in the Hall MHD Beltrami condition turns out now to be proportional to the "potential vorticity." The Hall MHD Beltrami condition becomes equivalent to the "potential vorticity" conservation equation in two-dimensional (2D) hydrodynamics if the Hall MHD Lagrange multiplier beta is taken to be proportional to the "potential vorticity" as well. The winding pattern of the magnetic field lines in Hall MHD then appears to evolve in the same way as "potential vorticity" lines in 2D hydrodynamics

How Not to Overwater a Rheophyte

Many herbaceous plants native to Malesian perhumid tropical forests are difficult to cultivate long term in traditional (peat, coir and bark) compost mixes. As a result, many appear to be underrepresented in ex situ living plant collections. Under the leaf-litter, lowland rainforest soils are typically surprisingly low in organic content (< 2%) and many of the smaller forest-floor-dwelling plants exist mainly on steep slopes of bare mineral soils with limited leaf-litter cover. By adopting purely inorganic compost media and placing pots in trays of water the wet mineral soils of their natural habitats are replicated and the plants can be cultivated long term with notable ease. The use of wholly inorganic media reduces the incidence of root rot to such an extent that it is suggested that they should be used more often for the cultivation of slow-growing taxa from other regions which are often considered to be ‘difficult’

A Fresh Catch of Massive Binaries in the Cygnus OB2 Association

Massive binary stars may constitute a substantial fraction of progenitors to supernovae and gamma-ray bursts, and the distribution of their orbital characteristics holds clues to the formation process of massive stars. As a contribution to securing statistics on OB-type binaries, we report the discovery and orbital parameters for five new systems as part of the Cygnus OB2 Radial Velocity Survey. Four of the new systems (MT070, MT174, MT267, and MT734 (a.k.a. VI Cygni #11) are single-lined spectroscopic binaries while one (MT103) is a double-lined system (B1V+B2V). MT070 is noteworthy as the longest period system yet measured in Cyg OB2, with P=6.2 yr. The other four systems have periods ranging between 4 and 73 days. MT174 is noteworthy for having a probable mass ratio q<0.1, making it a candidate progenitor to a low-mass X-ray binary. These measurements bring the total number of massive binaries in Cyg OB2 to 25, the most currently known in any single cluster or association.Comment: Accepted for publication in the Astrophysical Journa