2,907 research outputs found
Lightweight, broad-band spectrum analyzer
Spectrum analyzer, utilizing techniques similar to those used to classify energy levels of nuclear particles, is incorporated into electric field detector. Primary advantage is ability to perform qualitative broad-band frequency analysis over a large dynamic amplitude range with minimum weight and electrical power requirements
Spike frequency adaptation affects the synchronization properties of networks of cortical oscillators
Oscillations in many regions of the cortex have common temporal characteristics with dominant frequencies centered around the 40 Hz (gamma) frequency range and the 5–10 Hz (theta) frequency range. Experimental results also reveal spatially synchronous oscillations, which are stimulus dependent (Gray&Singer, 1987;Gray, König, Engel, & Singer, 1989; Engel, König, Kreiter, Schillen, & Singer, 1992). This rhythmic activity suggests that the coherence of neural populations is a crucial feature of cortical dynamics (Gray, 1994). Using both simulations and a theoretical coupled oscillator approach, we demonstrate that the spike frequency adaptation seen in many pyramidal cells plays a subtle but important role in the dynamics of cortical networks. Without adaptation, excitatory connections among model pyramidal cells are desynchronizing. However, the slow processes associated with adaptation encourage stable synchronous behavior
Survey of VLF electric fields in the magnetosphere with the polar orbiting spacecraft, 1964-45a
Very low frequency electric fields in magnetosphere sampled by polar orbiting satellit
Dynamically-Coupled Oscillators -- Cooperative Behavior via Dynamical Interaction --
We propose a theoretical framework to study the cooperative behavior of
dynamically coupled oscillators (DCOs) that possess dynamical interactions.
Then, to understand synchronization phenomena in networks of interneurons which
possess inhibitory interactions, we propose a DCO model with dynamics of
interactions that tend to cause 180-degree phase lags. Employing an approach
developed here, we demonstrate that although our model displays synchronization
at high frequencies, it does not exhibit synchronization at low frequencies
because this dynamical interaction does not cause a phase lag sufficiently
large to cancel the effect of the inhibition. We interpret the disappearance of
synchronization in our model with decreasing frequency as describing the
breakdown of synchronization in the interneuron network of the CA1 area below
the critical frequency of 20 Hz.Comment: 10 pages, 3 figure
Isolation and identification of a male-produced aggregation-sex pheromone for the velvet longhorned beetle, Trichoferus campestris.
The velvet longhorned beetle, Trichoferus campestris (Faldermann) ("VLB"; Coleoptera: Cerambycidae), is native to eastern Asia where it infests and damages a wide range of deciduous and coniferous tree species, including orchard and timber species. Immature stages of VLB are transported to new countries via international commerce, and populations have established outside the native range of the species. Here, we show that identification of pheromones of invasive pest species can be expedited by knowledge of the semiochemistry of related taxa. Histological sectioning revealed subcuticular, male-specific prothoracic glands connected to pits in the cuticle, which, in related species, are diagnostic for production of male-produced aggregation-sex pheromones, usually characterized by 2,3-alkanediol/hydroxyketone structural motifs. However, in preliminary field bioassays, beetles were not attracted by any known cerambycid pheromones. Subsequently, we identified a novel variant of the hydroxyketone motif ("trichoferone") from headspace volatiles of males. In field bioassays, synthetic trichoferone was more attractive to both sexes of VLB than previously developed high-release-rate ethanol lures, and attraction was strongly female biased. This study demonstrated the utility of the prothoracic gland trait for predicting pheromone use in cerambycid species in the subfamily Cerambycinae, and that identification of pheromones of novel species can be expedited by knowledge of pheromones of related species. Trichoferone should prove to be a valuable tool for detection of VLB in regions where the beetle is or may become established
Salvage Local Treatments After Focal Therapy for Prostate Cancer
CONTEXT: Whether focal therapy (FT) for prostate cancer (PC) jeopardizes outcomes from salvage treatments is a matter of debate still to be resolved. OBJECTIVE: To review the literature on oncological and functional outcomes and complications for available treatment options for recurrent or residual PC after primary FT. EVIDENCE ACQUISITION: We performed a nonsystematic search of PubMed for articles assessing relevant outcomes for salvage local treatment after FT failure using a manual search. When no evidence could be extracted for the FT domain, records dealing with recurrence after whole-gland ablation were considered. EVIDENCE SYNTHESIS: Four retrospective series assessed salvage treatments after FT failure evaluating cases of radical prostatectomy (RP) and repeat ablation (sample size from 12 to 22 patients). The quality of the studies was low, with a high risk of bias. Other options are radiation therapy (RT) and whole-gland or focal repeat ablations, although these have only been described after whole-gland ablation. With some exceptions, including sexual function for RP, overall complications and oncological and functional outcomes do seem to be acceptable and are not much worse than those in the primary setting. Important limitations include the low level of the evidence and the absence of standardized criteria for FT, salvage treatment, and FT failure. CONCLUSIONS: Current evidence shows acceptable outcomes for post-FT salvage options, although this is based on retrospective data. While it seems that FT has a minimal impact on salvage treatment results, prospective controlled studies are needed to confirm these preliminary data. PATIENT SUMMARY: We performed a literature search to determine the treatment options available for prostate cancer after failure of focal therapy and their outcomes. Options include radical prostatectomy, repeat whole-gland ablation, focal ablation, and radiotherapy. Overall cancer control, impacts on urinary and sexual function, and complications seem slightly worse but not markedly different compared to primary treatments, but high-quality studies are awaited to confirm these findings
Electron-beam propagation in a two-dimensional electron gas
A quantum mechanical model based on a Green's function approach has been used
to calculate the transmission probability of electrons traversing a
two-dimensional electron gas injected and detected via mode-selective quantum
point contacts. Two-dimensional scattering potentials, back-scattering, and
temperature effects were included in order to compare the calculated results
with experimentally observed interference patterns. The results yield detailed
information about the distribution, size, and the energetic height of the
scattering potentials.Comment: 7 pages, 6 figure
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