19,750 research outputs found
The Web of the Spider. Laura Barr Lougee. Bloomfield Hills, Michigan: Cranbrook Institute of Science, 1964. 44 pp. $3.50.
Excerpt: It is a relief to find such a straightforward and objective work as Lougee\u27s The Web of the Spider. Her brief but lucid descriptions of spider anatomy, silk production and web construction will induce appreciation and observation of these much-maligned animals
Ted Kaczynski: Evil or Insane?
Explores the life of the infamous Unabomber, and demonstrates why his manifesto on society and his extraordinary intelligence makes him the most unique and brilliant serial killer in United States history
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Orbital Frontal Cortex Projections to Secondary Motor Cortex Mediate Exploitation of Learned Rules.
Animals face the dilemma between exploiting known opportunities and exploring new ones, a decision-making process supported by cortical circuits. While different types of learning may bias exploration, the circumstances and the degree to which bias occurs is unclear. We used an instrumental lever press task in mice to examine whether learned rules generalize to exploratory situations and the cortical circuits involved. We first trained mice to press one lever for food and subsequently assessed how that learning influenced pressing of a second novel lever. Using outcome devaluation procedures we found that novel lever exploration was not dependent on the food value associated with the trained lever. Further, changes in the temporal uncertainty of when a lever press would produce food did not affect exploration. Instead, accrued experience with the instrumental contingency was strongly predictive of test lever pressing with a positive correlation between experience and trained lever exploitation, but not novel lever exploration. Chemogenetic attenuation of orbital frontal cortex (OFC) projection into secondary motor cortex (M2) biased novel lever exploration, suggesting that experience increases OFC-M2 dependent exploitation of learned associations but leaves exploration constant. Our data suggests exploitation and exploration are parallel decision-making systems that do not necessarily compete
Results and conjectures on simultaneous core partitions
An n-core partition is an integer partition whose Young diagram contains no
hook lengths equal to n. We consider partitions that are simultaneously a-core
and b-core for two relatively prime integers a and b. These are related to
abacus diagrams and the combinatorics of the affine symmetric group (type A).
We observe that self-conjugate simultaneous core partitions correspond to the
combinatorics of type C, and use abacus diagrams to unite the discussion of
these two sets of objects.
In particular, we prove that (2n)- and (2mn+1)-core partitions correspond
naturally to dominant alcoves in the m-Shi arrangement of type C_n,
generalizing a result of Fishel--Vazirani for type A. We also introduce a major
statistic on simultaneous n- and (n+1)-core partitions and on self-conjugate
simultaneous (2n)- and (2n+1)-core partitions that yield q-analogues of the
Coxeter-Catalan numbers of type A and type C.
We present related conjectures and open questions on the average size of a
simultaneous core partition, q-analogs of generalized Catalan numbers, and
generalizations to other Coxeter groups. We also discuss connections with the
cyclic sieving phenomenon and q,t-Catalan numbers.Comment: 17 pages; to appear in the European Journal of Combinatoric
On resonance line profiles predicted by radiation driven disk wind models
We report on resonance line profiles predicted by radiation driven disk wind
models which extend radially one order of magnitude farther out than our
previous models. Our main result is that the inclusion of a disk wind at larger
radii changes qualitatively and quantitatively the line profiles predicted by
the models. Our new models predict line absorption that is significantly
stronger than those predicted by old models. Some of the previous line profiles
exhibit a doubled-humped structure near the line center which is now replaced
by a more plausible single, blueshifted minimum. We emphasize that the
improvements in the shape as well as the strength of the absorption were
achieved without changing the gross properties of the wind. In particular, our
new models do not predict a higher mass-loss rate than the previous models. The
main changes in the line profiles are due to the fact that the ratio between
the rotational velocity and poloidal velocity of the wind decreases downstream.
The new line profiles reproduce well the line absorption of the nova-like
variable, IX~Vel, and promise to reproduce observations of other cataclysmic
variables. This success of the radiation driven disk wind model provides an
important link between outflows in OB stars and outflows in active galactic
nuclei.Comment: to appear in ApJ Lette
Dynamically Evolving Sectors for Convective Weather Impact
A new strategy for altering existing sector boundaries in response to blocking convective weather is presented. This method seeks to improve the reduced capacity of sectors directly affected by weather by moving boundaries in a direction that offers the greatest capacity improvement. The boundary deformations are shared by neighboring sectors within the region in a manner that preserves their shapes and sizes as much as possible. This reduces the controller workload involved with learning new sector designs. The algorithm that produces the altered sectors is based on a force-deflection mesh model that needs only nominal traffic patterns and the shape of the blocking weather for input. It does not require weather-affected traffic patterns that would have to be predicted by simulation. When compared to an existing optimal sector design method, the sectors produced by the new algorithm are more similar to the original sector shapes, resulting in sectors that may be more suitable for operational use because the change is not as drastic. Also, preliminary results show that this method produces sectors that can equitably distribute the workload of rerouted weather-affected traffic throughout the region where inclement weather is present. This is demonstrated by sector aircraft count distributions of simulated traffic in weather-affected regions
Evidence of a Role for G Protein Signaling Modulator 3 in Cell Division
Components of G protein-mediated signaling are associated with positioning and orienting the mitotic spindle in the process of cell division. However, a functional role for G protein signaling modulator 3 (GPSM3) in cell division has yet to be defined. The purpose of this study was to investigate a potential role for GPSM3 in cell division. Vascular smooth muscle cells (VSMCs) from Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats, that are known to express GPSM3, were used as a model system. Here I report that GPSM3 mRNA and protein levels varied during different stages of the cell cycle in SHR VSMCs. In HEK-293 cells, overexpressing GPSM3 resulted in an increased rate of proliferation. Finally, during metaphase, anaphase, and telophase, GPSM3 and β-tubulin co-localize at the mitotic spindle and midbody. Overall, this study provides evidence of a role for GPSM3 in cell division, likely via an interaction with the mitotic spindle
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