1,642 research outputs found
The hippocampus and visual perception
In this review, we will discuss the idea that the hippocampus may be involved in both memory and perception, contrary to theories that posit functional and neuroanatomical segregation of these processes. This suggestion is based on a number of recent neuropsychological and functional neuroimaging studies that have demonstrated that the hippocampus is involved in the visual discrimination of complex spatial scene stimuli. We argue that these findings cannot be explained by long-term memory or working memory processing or, in the case of patient findings, dysfunction beyond the medial temporal lobe (MTL). Instead, these studies point toward a role for the hippocampus in higher-order spatial perception. We suggest that the hippocampus processes complex conjunctions of spatial features, and that it may be more appropriate to consider the representations for which this structure is critical, rather than the cognitive processes that it mediates
Sustained response after a 2-year course of lamivudine treatment of hepatitis B e antigen-negative chronic hepatitis B
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72882/1/j.1365-2893.2004.00556.x.pd
Living IoT: A Flying Wireless Platform on Live Insects
Sensor networks with devices capable of moving could enable applications
ranging from precision irrigation to environmental sensing. Using mechanical
drones to move sensors, however, severely limits operation time since flight
time is limited by the energy density of current battery technology. We explore
an alternative, biology-based solution: integrate sensing, computing and
communication functionalities onto live flying insects to create a mobile IoT
platform.
Such an approach takes advantage of these tiny, highly efficient biological
insects which are ubiquitous in many outdoor ecosystems, to essentially provide
mobility for free. Doing so however requires addressing key technical
challenges of power, size, weight and self-localization in order for the
insects to perform location-dependent sensing operations as they carry our IoT
payload through the environment. We develop and deploy our platform on
bumblebees which includes backscatter communication, low-power
self-localization hardware, sensors, and a power source. We show that our
platform is capable of sensing, backscattering data at 1 kbps when the insects
are back at the hive, and localizing itself up to distances of 80 m from the
access points, all within a total weight budget of 102 mg.Comment: Co-primary authors: Vikram Iyer, Rajalakshmi Nandakumar, Anran Wang,
In Proceedings of Mobicom. ACM, New York, NY, USA, 15 pages, 201
Light, alertness, and alerting effects of white light:A literature overview
Light is known to elicit non-image-forming responses, such as effects on alertness. This has been reported especially during light exposure at night. Nighttime results might not be translatable to the day. This article aims to provide an overview of (1) neural mechanisms regulating alertness, (2) ways of measuring and quantifying alertness, and (3) the current literature specifically regarding effects of different intensities of white light on various measures and correlates of alertness during the daytime. In general, the present literature provides inconclusive results on alerting effects of the intensity of white light during daytime, particularly for objective measures and correlates of alertness. However, the various research paradigms employed in earlier studies differed substantially, and most studies tested only a limited set of lighting conditions. Therefore, the alerting potential of exposure to more intense white light should be investigated in a systematic, dose-dependent manner with multiple correlates of alertness and within one experimental paradigm over the course of day
Semiclassical theory of electron drag in strong magnetic fields
We present a semiclassical theory for electron drag between two parallel
two-dimensional electron systems in a strong magnetic field, which provides a
transparent picture of the most salient qualitative features of anomalous drag
phenomena observed in recent experiments, especially the striking sign reversal
of drag at mismatched densities. The sign of the drag is determined by the
curvature of the effective dispersion relation obeyed by the drift motion of
the electrons in a smooth disorder potential. Localization plays a role in
explaining activated low temperature behavior, but is not crucial for anomalous
drag per se.Comment: 10 page
Influences of dynamical disruptions on the evolution of pulsars in globular clusters
By comparing the physical properties of pulsars hosted by core-collapsed
(CCed) and non-core-collapsed (Non-CCed) globular clusters (GCs), we find that
pulsars in CCed GCs rotate significantly slower than their counterparts in
Non-CCed GCs. Additionally, radio luminosities at 1.4 GHz in CCed GCs are
higher. These findings are consistent with the scenario that dynamical
interactions in GCs can interrupt angular momentum transfer processes and
surface magnetic field decay during the recycling phase. Our results suggest
that such effects in CCed GCs are stronger due to more frequent disruptions of
compact binaries. This is further supported by the observation that both
estimated disruption rates and the fraction of isolated pulsars are
predominantly higher in CCed GCs.Comment: 9 pages, 8 figures, 3 tables, Accepted in MNRA
Scanning-probe spectroscopy of semiconductor donor molecules
Semiconductor devices continue to press into the nanoscale regime, and new
applications have emerged for which the quantum properties of dopant atoms act
as the functional part of the device, underscoring the necessity to probe the
quantum structure of small numbers of dopant atoms in semiconductors[1-3].
Although dopant properties are well-understood with respect to bulk
semiconductors, new questions arise in nanosystems. For example, the quantum
energy levels of dopants will be affected by the proximity of nanometer-scale
electrodes. Moreover, because shallow donors and acceptors are analogous to
hydrogen atoms, experiments on small numbers of dopants have the potential to
be a testing ground for fundamental questions of atomic and molecular physics,
such as the maximum negative ionization of a molecule with a given number of
positive ions[4,5]. Electron tunneling spectroscopy through isolated dopants
has been observed in transport studies[6,7]. In addition, Geim and coworkers
identified resonances due to two closely spaced donors, effectively forming
donor molecules[8]. Here we present capacitance spectroscopy measurements of
silicon donors in a gallium-arsenide heterostructure using a scanning probe
technique[9,10]. In contrast to the work of Geim et al., our data show
discernible peaks attributed to successive electrons entering the molecules.
Hence this work represents the first addition spectrum measurement of dopant
molecules. More generally, to the best of our knowledge, this study is the
first example of single-electron capacitance spectroscopy performed directly
with a scanning probe tip[9].Comment: In press, Nature Physics. Original manuscript posted here; 16 pages,
3 figures, 5 supplementary figure
Sign-reversal of drag in bilayer systems with in-plane periodic potential modulation
We develop a theory for describing frictional drag in bilayer systems with
in-plane periodic potential modulations, and use it to investigate the drag
between bilayer systems in which one of the layers is modulated in one
direction. At low temperatures, as the density of carriers in the modulated
layer is changed, we show that the transresistivity component in the direction
of modulation can change its sign. We also give a physical explanation for this
behavior.Comment: 4 pages, 4 figure
Multi-Wavelength Observations Of A New Redback Millisecond Pulsar 4FGL J1910.7-5320
We present the study of multi-wavelength observations of an unidentified
Fermi Large Area Telescope (LAT) source, 4FGL J1910.7-5320, a new candidate
redback millisecond pulsar binary. In the 4FGL 95% error region of 4FGL
J1910.7-5320, we find a possible binary with a 8.36-hr orbital period from the
Catalina Real-Time Transient Survey (CRTS), confirmed by optical spectroscopy
using the SOAR telescope. This optical source was recently independently
discovered as a redback pulsar by the TRAPUM project, confirming our
prediction. We fit the optical spectral energy distributions of 4FGL
J1910.7-5320 with a blackbody model, inferring a maximum distance of 4.1 kpc by
assuming that the companion fills its Roche-lobe with a radius of R = 0.7R_sun.
Using a 12.6 ks Chandra X-ray observation, we identified an X-ray counterpart
for 4FGL J1910.7-5320, with a spectrum that can be described by an absorbed
power-law with a photon index of 1.0+/-0.4. The spectrally hard X-ray emission
shows tentative evidence for orbital variability. Using more than 12 years of
Fermi-LAT data, we refined the position of the {\gamma}-ray source, and the
optical candidate still lies within the 68% positional error circle. In
addition to 4FGL J1910.7-5320, we find a variable optical source with a
periodic signal of 4.28-hr inside the 4FGL catalog 95% error region of another
unidentified Fermi source, 4FGL J2029.5-4237. However, the {\gamma}-ray source
does not have a significant X-ray counterpart in a 11.7 ks Chandra observation,
with a 3-{\sigma} flux upper limit of 2.4*10^-14 erg cm^-2 s^-1 (0.3-7 keV).
Moreover, the optical source is outside our updated Fermi-LAT 95% error circle.
These observational facts all suggest that this new redback millisecond pulsar
powers the {\gamma}-ray source 4FGL J1910.7-5320 while 4FGL J2029.5-4237 is
unlikely the {\gamma}-ray counterpart to the 4.28-hr variable.Comment: Accepted for publication in Ap
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