7,776 research outputs found
Interactive Music Generation with Positional Constraints using Anticipation-RNNs
Recurrent Neural Networks (RNNS) are now widely used on sequence generation
tasks due to their ability to learn long-range dependencies and to generate
sequences of arbitrary length. However, their left-to-right generation
procedure only allows a limited control from a potential user which makes them
unsuitable for interactive and creative usages such as interactive music
generation. This paper introduces a novel architecture called Anticipation-RNN
which possesses the assets of the RNN-based generative models while allowing to
enforce user-defined positional constraints. We demonstrate its efficiency on
the task of generating melodies satisfying positional constraints in the style
of the soprano parts of the J.S. Bach chorale harmonizations. Sampling using
the Anticipation-RNN is of the same order of complexity than sampling from the
traditional RNN model. This fast and interactive generation of musical
sequences opens ways to devise real-time systems that could be used for
creative purposes.Comment: 9 pages, 7 figure
Electron-electron and spin-orbit interactions in armchair graphene ribbons
The effects of intrinsic spin-orbit and Coulomb interactions on low-energy
properties of finite width graphene armchair ribbons are studied by means of a
Dirac Hamiltonian. It is shown that metallic states subsist in the presence of
intrinsic spin-orbit interactions as spin-filtered edge states, in contrast
with the insulating behavior predicted for graphene planes. A charge-gap opens
due to Coulomb interactions in neutral ribbons, that vanishes as , with a gapless spin sector. Weak intrinsic spin-orbit interactions do
not change the insulating behavior. Explicit expressions for the
width-dependent gap and various correlation functions are presented.Comment: Will appear in PR
Graphene zigzag ribbons, square lattice models and quantum spin chains
We present an extended study of finite-width zigzag graphene ribbons (ZGRs)
based on a tight-binding model with hard-wall boundary conditions. We provide
an exact analytic solution that clarifies the origin of the predicted width
dependence on the conductance through junctions of ribbons with different
widths. An analysis of the obtained solutions suggests a new description of
ZGRs in terms of coupled chains. We pursue these ideas further by introducing a
mapping between the ZGR model and the Hamiltonian for N-coupled quantum chains
as described in terms of 2N Majorana fermions. The proposed mapping preserves
the dependence of ribbon properties on its width thus rendering metallic
ribbons for N odd and zero-gap semiconductor ribbons for N even. Furthermore,
it reveals a close connection between the low-energy properties of the ZGR
model and a continuous family of square lattice model Hamiltonians with similar
width-dependent properties that includes the flux and the trivial square
lattice models. As a further extension, we show that this new description makes
it possible to identify various aspects of the physics of graphene ribbons with
those predicted by models of quantum spin chains (QSCs)
Currents and pseudomagnetic fields in strained graphene rings
We study the effects of strain on the electronic properties and persistent
current characteristics of a graphene ring using the Dirac representation. For
a slightly deformed graphene ring flake, one obtains sizable pseudomagnetic
(gauge) fields that may effectively reduce or enhance locally the applied
magnetic flux through the ring. Flux-induced persistent currents in a flat ring
have full rotational symmetry throughout the structure; in contrast, we show
that currents in the presence of a circularly symmetric deformation are
strongly inhomogeneous, due to the underlying symmetries of graphene. This
result illustrates the inherent competition between the `real' magnetic field
and the `pseudo' field arising from strains, and suggest an alternative way to
probe the strength and symmetries of pseudomagnetic fields on graphene systems
Seismocardiographic Signal Timing with Myocardial Strain
Speckle Tracking Echocardiography (STE) is a relatively new method for
cardiac function evaluation. In the current study, STE was used to investigate
the timing of heart-induced mostly subaudible (i.e., below the frequency limit
of human hearing) chest-wall vibrations in relation to the longitudinal
myocardial strain. Such an approach may help elucidate the genesis of these
vibrations, thereby improving their diagnostic value
Adjuvant vs. salvage radiation therapy in men with high-risk features after radical prostatectomy: Survey of North American genitourinary expert radiation oncologists
INTRODUCTION:
The management of patients with high-risk features after radical prostatectomy (RP) is controversial. Level 1 evidence demonstrates that adjuvant radiation therapy (RT) improves survival compared to no treatment; however, it may overtreat up to 30% of patients, as randomized clinical trials (RCTs) using salvage RT on observation arms failed to reveal a survival advantage of adjuvant RT. We, therefore, sought to determine the current view of adjuvant vs. salvage RT among North American genitourinary (GU) radiation oncology experts.
METHODS:
A survey was distributed to 88 practicing North American GU physicians serving on decision-making committees of cooperative group research organizations. Questions pertained to opinions regarding adjuvant vs. salvage RT for this patient population. Treatment recommendations were correlated with practice patterns using Fisher's exact test.
RESULTS:
Forty-two of 88 radiation oncologists completed the survey; 23 (54.8%) recommended adjuvant RT and 19 (45.2%) recommended salvage RT. Recommendation of active surveillance for Gleason 3+4 disease was a significant predictor of salvage RT recommendation (p=0.034), and monthly patient volume approached significance for recommendation of adjuvant over salvage RT; those seeing <15 patients/month trended towards recommending adjuvant over salvage RT (p=0.062). No other demographic factors approached significance.
CONCLUSIONS:
There is dramatic polarization among North American GU experts regarding optimal management of patients with high-risk features after RP. Ongoing RCTs will determine whether adjuvant RT improves survival over salvage RT. Until then, the almost 50/50 division seen from this analysis should encourage practicing clinicians to discuss the ambiguity with their patients
Heart Rate Monitoring During Different Lung Volume Phases Using Seismocardiography
Seismocardiography (SCG) is a non-invasive method that can be used for
cardiac activity monitoring. This paper presents a new electrocardiogram (ECG)
independent approach for estimating heart rate (HR) during low and high lung
volume (LLV and HLV, respectively) phases using SCG signals. In this study,
SCG, ECG, and respiratory flow rate (RFR) signals were measured simultaneously
in 7 healthy subjects. The lung volume information was calculated from the RFR
and was used to group the SCG events into low and high lung-volume groups. LLV
and HLV SCG events were then used to estimate the subjects HR as well as the HR
during LLV and HLV in 3 different postural positions, namely supine, 45 degree
heads-up, and sitting. The performance of the proposed algorithm was tested
against the standard ECG measurements. Results showed that the HR estimations
from the SCG and ECG signals were in a good agreement (bias of 0.08 bpm). All
subjects were found to have a higher HR during HLV (HR) compared
to LLV (HR) at all postural positions. The
HR/HR ratio was 1.110.07, 1.080.05,
1.090.04, and 1.090.04 (meanSD) for supine, 45 degree-first
trial, 45 degree-second trial, and sitting positions, respectively. This heart
rate variability may be due, at least in part, to the well-known respiratory
sinus arrhythmia. HR monitoring from SCG signals might be used in different
clinical applications including wearable cardiac monitoring systems
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