6,878 research outputs found
The Trichoptera of Panama XIV. New species of microcaddisflies (Trichoptera: Hydroptilidae) from Omar Torrijos Herrera National Park
Abstract. In 2017, a new project was begun to assess the biodiversity of national parks and forest reserves in the Republic of Panama. Designated “Proyecto Sistema de Producción Sostenible Conservación de la Biodiversidad (PSPSCB)”, this project is managed by Panama’s Ministerio de Ambiente. The first park sampled in 2017 was Omar Torrijos Herrera National Park (OTHNP). Trichoptera (Insecta) were collected at four locations using both Malaise traps and UV light traps. The rugged terrain and lack of access in this remote park limited the sampled area. Sampling included streams in both the Caribbean and Pacific drainages. Seven new species of microcaddisflies (Hydroptilidae: Alistotrichia coclensis Armitage and Harris, Cerasmatrichia akanthos Armitage and Harris, Metrichia corazones Armitage and Harris, Neotrichia espinosa Armitage and Harris, Neotrichia michaeli Armitage and Harris, Neotrichia pierpointorum Armitage and Harris, and Neotrichia yayas Armitage and Harris) and one new country record, Metrichia macrophallata Flint, were identified from this preliminary survey and are reported herein. Other recently described species are reported here for the first time outside of their type localities. Based on other areas more extensively sampled compared to this modest survey, many more new species and new country records await discovery in OTHNP as are reported herein. There are now 439 species distributed among 15 families and 55 genera known from Panama.
Resumen. En 2017, se inició un nuevo proyecto para evaluar la biodiversidad de parques nacionales y reservas forestales en la República de Panamá. Designado “Proyecto Sistema de Producción Sostenible Conservación de la Biodiversidad (PSPSCB)”, este proyecto es administrado por el Ministerio de Ambiente de Panamá. El primer parque muestreado en 2017 fue el Parque Nacional Omar Torrijos Herrera (OTHNP). Se recogieron Trichoptera en cuatro ubicaciones utilizando trampas Malaise y trampas de luz UV. El terreno accidentado y la falta de acceso en este parque remoto limitaron el área muestreada. El muestreo incluyó corrientes en los drenajes del Caribe y del Pacífico. Siete nuevas especies de micro-Trichoptera (Hydroptilidae: Alistotrichia coclensis Armitage and Harris, Cerasmatrichia akanthos Armitage and Harris, Metrichia corazones Armitage and Harris, Neotrichia espinosa Armitage and Harris, Neotrichia michaeli Armitage and Harris, Neotrichia pierpointorum Armitage and Harris, and Neotrichia yayas Armitage and Harris) y un nuevo registro de país, Metrichia macrophallata Flint, se identificaron a partir de esta encuesta preliminar y se informan aquí. Otras especies recientemente descritas se registran aquí por primera vez fuera de sus localidades tipo. Con base en otras áreas más extensamente muestreadas, en comparación con esta modesta investigación, muchas más especies nuevas y nuevos registros para el país esperan ser descubiertos en el OTHNP como se informa aquí. Ahora en Panamá, hay 439 especies conocidas de Trichoptera distribuidas entre 15 familias y 55 géneros
Accretion Disc Evolution in Single and Binary T Tauri Stars
We present theoretical models for the evolution of T Tauri stars surrounded
by circumstellar discs. The models include the effects of pre-main-sequence
stellar and time dependent disc evolution, and incorporate the effects of
stellar magnetic fields acting on the inner disc. For single stars, consistency
with observations in Taurus-Auriga demands that disc dispersal occurs rapidly,
on much less than the viscous timescale of the disc, at roughly the epoch when
heating by stellar radiation first dominates over internal viscous dissipation.
Applying the models to close binaries, we find that because the initial
conditions for discs in binaries are uncertain, studies of extreme mass ratio
systems are required to provide a stringent test of theoretical disc evolution
models. We also note that no correlation of the infra-red colours of T Tauri
stars with their rotation rate is observed, in apparent contradiction to the
predictions of simple magnetospheric accretion models.Comment: 11 pages, MNRAS in pres
How useful are the stages of change for targeting interventions? randomized test of a brief intervention to reduce smoking
Objectives. To see whether the stages of change are useful for targeting a brief intervention to reduce smoking based on implementation intentions. A second objective was to rule out demand characteristics as an alternative explanation for the findings of intervention studies based on the transtheoretical model and implementation intentions. Design. Participants (N = 350) were randomized to a passive control condition (questionnaire only), active control condition (questionnaire-plus-instruction to plan to quit) or experimental condition (questionnaire, plan to quit, form an implementation intention). Their behavior and psychosocial orientation to quit were measured at baseline and 2-month follow-up. Main Outcome Measures. Theory of planned behavior variables, nicotine dependence and quitting. Results. Significantly more people quit smoking in the experimental condition than in the control conditions, and the planning instructions changed intention to quit and perceived control over quitting, but not behavior. Stage of change moderated these effects such that implementation intentions worked best for individuals who were in the preparation stage at baseline. Conclusion. Harnessing both motivational and volitional processes seems to enhance the effectiveness of smoking cessation programs, although further work is required to clarify inconsistencies in the literature using the stages of change.</p
Quasi-Langmuir-Blodgett Thin Film Deposition of Carbon Nanotubes
The handling and manipulation of carbon nanotubes continues to be a challenge
to those interested in the application potential of these promising materials.
To this end, we have developed a method to deposit pure nanotube films over
large flat areas on substrates of arbitrary composition. The method bears some
resemblance to the Langmuir-Blodgett deposition method used to lay down thin
organic layers. We show that this redeposition technique causes no major
changes in the films' microstructure and that they retain the electronic
properties of as-deposited film laid down on an alumina membrane.Comment: 3 pages, 3 figures, submitted Journal of Applied Physic
Magnetically modulated accretion in T Tauri stars
We examine how accretion on to T Tauri stars may be modulated by a
time-dependent `magnetic gate' where the inner edge of the accretion disc is
disrupted by a varying stellar field. We show that magnetic field variations on
time-scales shorter than 10^5 yr can modulate the accretion flow, thus
providing a possible mechanism both for the marked photometric variability of T
Tauri stars and for the possible conversion of T Tauri stars between classical
and weak line status. We thus suggest that archival data relating to the
spectrophotometric variability of T Tauri stars may provide an indirect record
of magnetic activity cycles in low-mass pre-main-sequence stars.Comment: LaTeX file (requires mn.sty), 4 pages, no figures or tables. To
appear in MNRAS
MHD simulations of the collapsar model for GRBs
We present results from axisymmetric, time-dependent magnetohydrodynamic
(MHD) simulations of the collapsar model for gamma-ray bursts. Our main
conclusion is that, within the collapsar model, MHD effects alone are able to
launch, accelerate and sustain a strong polar outflow. We also find that the
outflow is Poynting flux-dominated, and note that this provides favorable
initial conditions for the subsequent production of a baryon-poor fireball.Comment: 4 pages, to appear in proceedings of "2003 GRB Conference" (Santa Fe,
NM, September 8-12, 2003), needs aipprocs LaTeX class, movies are available
at http://rocinante.colorado.edu/~proga
Thermal Expansion and Magnetostriction Studies of a Kondo Lattice Compound: Ceagsb2
We have investigated a single crystal of CeAgSb2 using low field
ac-susceptibility, thermal expansion and magnetostriction measurements in the
temperature range 1.5K to 90K. The ac-susceptibility exhibits a sharp peak at
9.7K for both B//c and B perp c due to the magnetic ordering of the Ce moment.
The thermal expansion coefficient alpha, exhibits highly anisotropic behaviour
between 3K and 80K : alpha is positive for dL/L perp c, but negative for dL/L
// c. Furthermore, alpha (for dL/L) perp c (i.e. in ab-plane) exhibits a sharp
peak at TN followed by a broad maximum at 20K, while a sharp negative peak at
TN followed by a minimum at 20K has been observed for (dL/L //) the c
direction. The observed maximum and minimum in alpha(T) at 20K have been
attributed to the crystalline field effect on the J=5/2 state of the Ce3+ ion.
The magnetostriction also exhibits anisotropic behaviour with a large
magnetostriction along the c-axis. The ab-plane magnetostriction exhibits a
peak at B=3.3T at 3K, which is consistent with the observed peak in the
magnetoresistance measurements.Comment: 4 Pages (B5), 3 figures, submitted to SCES200
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