2,877 research outputs found
Does binding of synesthetic color to the evoking grapheme require attention?
The official published version can be accessed from the link below.The neural mechanisms involved in binding features such as shape and color are a matter of some debate. Does accurate binding rely on spatial attention functions of the parietal lobe or can it occur without attentional input? One extraordinary phenomenon that may shed light on this question is that of chromatic-graphemic synesthesia, a rare condition in which letter shapes evoke color perceptions. A popular suggestion is that synesthesia results from cross-activation between different functional regions (e.g., between shape and color areas of the ventral pathway). Under such conditions binding may not require parietal involvement and could occur preattentively. We tested this hypothesis in two synesthetes who perceived grayscale letters and digits in color. We found no evidence for preattentive binding using a visual search paradigm in which the target was a synesthetic inducer. In another experiment involving color judgments, we show that the congruency of target color and the synesthetic color of irrelevant digits modulates performance more when the digits are included within the attended region of space. We propose that the mechanisms giving rise to this type of synesthesia appear to follow at least some principles of normal binding, and even synesthetic binding seems to require attention.This work has been supported by a Veterans Administration Senior Research Career Scientist Award and NINDS grant #MH62331 to LCR and the Elizabeth Roboz Einstein fellowship in Neuroscience and Human Development to NS
Landau level spectroscopy of ultrathin graphite layers
Far infrared transmission experiments are performed on ultrathin epitaxial
graphite samples in a magnetic field. The observed cyclotron resonance-like and
electron-positron-like transitions are in excellent agreement with the
expectations of a single-particle model of Dirac fermions in graphene, with an
effective velocity of c* = 1.03 x 10^6 m/s.Comment: 4 pages 4 figures Slight revisions following referees' comments. One
figure modifie
In situ imaging of field emission from individual carbon nanotubes and their structural damage
©2002 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?APPLAB/80/856/1DOI:10.1063/1.1446994Field emission of individual carbon nanotubes was observed by in situ
transmission electron microscopy. A fluctuation in emission current was due to a
variation in distance between the nanotube tip and the counter electrode owing
to a "head-shaking" effect of the nanotube during field emission. Strong
field-induced structural damage of a nanotube occurs in two ways: a
piece-by-piece and segment-by-segment pilling process of the graphitic layers,
and a concentrical layer-by-layer stripping process. The former is believed
owing to a strong electrostatic force, and the latter is likely due to heating
produced by emission current that flowed through the most outer graphitic
layers
Plasmon assisted transport through disordered array of quantum wires
Phononless plasmon assisted thermally activated transport through a long
disordered array of finite length quantum wires is investigated analytically.
Generically strong electron plasmon interaction in quantum wires results in a
qualitative change of the temperature dependence of thermally activated
resistance in comparison to phonon assisted transport. At high temperatures,
the thermally activated resistance is determined by the Luttinger liquid
interaction parameter of the wires.Comment: 7 pages, 1 figure, final version as publishe
HIFs, angiogenesis, and metabolism:elusive enemies in breast cancer
Hypoxia-inducible factors (HIFs) and the HIF-dependent cancer hallmarks angiogenesis and metabolic rewiring are well-established drivers of breast cancer aggressiveness, therapy resistance, and poor prognosis. Targeting of HIF and its downstream targets in angiogenesis and metabolism has been unsuccessful so far in the breast cancer clinical setting, with major unresolved challenges residing in target selection, development of robust biomarkers for response prediction, and understanding and harnessing of escape mechanisms. This Review discusses the pathophysiological role of HIFs, angiogenesis, and metabolism in breast cancer and the challenges of targeting these features in patients with breast cancer. Rational therapeutic combinations, especially with immunotherapy and endocrine therapy, seem most promising in the clinical exploitation of the intricate interplay of HIFs, angiogenesis, and metabolism in breast cancer cells and the tumor microenvironment
Multi-shell gold nanowires under compression
Deformation properties of multi-wall gold nanowires under compressive loading
are studied. Nanowires are simulated using a realistic many-body potential.
Simulations start from cylindrical fcc(111) structures at T=0 K. After
annealing cycles axial compression is applied on multi-shell nanowires for a
number of radii and lengths at T=300 K. Several types of deformation are found,
such as large buckling distortions and progressive crushing. Compressed
nanowires are found to recover their initial lengths and radii even after
severe structural deformations. However, in contrast to carbon nanotubes
irreversible local atomic rearrangements occur even under small compressions.Comment: 1 gif figure, 5 ps figure
Dietary Acid Load and Bone Turnover During Long-Duration Spaceflight and Bed Rest
Background Bed rest studies document that a lower dietary acid load is associated with lower bone resorption. Objective We tested the effect of dietary acid load on bone metabolism during spaceflight. Design Controlled 4-d diets with a high or low animal proteinto-potassium (APro:K) ratio (High and Low diets, respectively) were given to 17 astronauts before and during spaceflight. Each astronaut had 1 High and 1 Low diet session before flight and 2 High and 2 Low sessions during flight, in addition to a 4-d session around flight day 30 (FD30), when crew members were to consume their typical in-flight intake. At the end of each session, blood and urine samples were collected. Calcium, total protein, energy, and sodium were maintained in each crew member's preflight and in-flight controlled diets. Results Relative to preflight values, N-telopeptide (NTX) and urinary calcium were higher during flight, and bone-specific alkaline phosphatase (BSAP) was higher toward the end of flight. The High and Low diets did not affect NTX, BSAP, or urinary calcium. Dietary sulfur and age were significantly associated with changes in NTX. Dietary sodium and flight day were significantly associated with urinary calcium during flight. The net endogenous acid production (NEAP) estimated from the typical dietary intake at FD30 was associated with loss of bone mineral content in the lumbar spine after the mission. The results were compared with data from a 70-d bed rest study, in which control (but not exercising) subjects APro:K was associated with higher NTX during bed rest. Conclusions Long-term lowering of NEAP by increasing vegetable and fruit intake may protect against changes in loss of bone mineral content during spaceflight when adequate calcium is consumed, particularly if resistive exercise is not being performed. This trial was registered at clinicaltrials.gov as NCT01713634
Magnetoplasmons in quasi-neutral epitaxial graphene nanoribbons
We present infrared transmission spectroscopy study of the inter-Landau-level
excitations in quasi-neutral epitaxial graphene nanoribbon arrays. We observed
a substantial deviation in energy of the transition
from the characteristic square root magnetic-field dependence of
two-dimensional graphene. This deviation arises from the formation of
upper-hybrid mode between the Landau level transition and the plasmon
resonance. In the quantum regime the hybrid mode exhibits a distinct dispersion
relation, markedly different from that expected for conventional
two-dimensional systems and highly doped graphene
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