684 research outputs found
Bilaterally Combined Electric and Acoustic Hearing in Mandarin-Speaking Listeners: The Population With Poor Residual Hearing
The hearing loss criterion for cochlear implant candidacy in mainland China is extremely stringent (bilateral severe to
profound hearing loss), resulting in few patients with substantial residual hearing in the nonimplanted ear. The main objective
of the current study was to examine the benefit of bimodal hearing in typical Mandarin-speaking implant users who have
poorer residual hearing in the nonimplanted ear relative to those used in the English-speaking studies. Seventeen Mandarinspeaking bimodal users with pure-tone averages of 80 dB HL participated in the study. Sentence recognition in quiet and in
noise as well as tone and word recognition in quiet were measured in monaural and bilateral conditions. There was no
significant bimodal effect for word and sentence recognition in quiet. Small bimodal effects were observed for sentence
recognition in noise (6%) and tone recognition (4%). The magnitude of both effects was correlated with unaided thresholds at
frequencies near voice fundamental frequencies (F0s). A weak correlation between the bimodal effect for word recognition
and unaided thresholds at frequencies higher than F0s was identified. These results were consistent with previous findings
that showed more robust bimodal benefits for speech recognition tasks that require higher spectral resolution than speech
recognition in quiet. The significant but small F0-related bimodal benefit was also consistent with the limited acoustic hearing
in the nonimplanted ear of the current subject sample, who are representative of the bimodal users in mainland China.
These results advocate for a more relaxed implant candidacy criterion to be used in mainland China
Numerical approximations for the tempered fractional Laplacian: Error analysis and applications
In this paper, we propose an accurate finite difference method to discretize
the -dimensional (for ) tempered integral fractional Laplacian and
apply it to study the tempered effects on the solution of problems arising in
various applications. Compared to other existing methods, our method has higher
accuracy and simpler implementation. Our numerical method has an accuracy of
, for if (or if ) with
, suggesting the minimum consistency conditions. The accuracy can
be improved to , for if
(or if ). Numerical experiments confirm our analytical results and provide
insights in solving the tempered fractional Poisson problem. It suggests that
to achieve the second order of accuracy, our method only requires the solution
for any . Moreover, if the solution
of tempered fractional Poisson problems satisfies for and , our method has the accuracy
of . Since our method yields a (multilevel) Toeplitz stiffness
matrix, one can design fast algorithms via the fast Fourier transform for
efficient simulations. Finally, we apply it together with fast algorithms to
study the tempered effects on the solutions of various tempered fractional
PDEs, including the Allen-Cahn equation and Gray-Scott equations.Comment: 21 pages, 11 figures, 3 table
Enhancement of shot noise due to the fluctuation of Coulomb interaction
We have developed a theoretical formalism to investigate the contribution of
fluctuation of Coulomb interaction to the shot noise based on Keldysh
non-equilibrium Green's function method. We have applied our theory to study
the behavior of dc shot noise of atomic junctions using the method of
nonequilibrium Green's function combined with the density functional theory
(NEGF-DFT). In particular, for atomic carbon wire consisting 4 carbon atoms in
contact with two Al(100) electrodes, first principles calculation within
NEGF-DFT formalism shows a negative differential resistance (NDR) region in I-V
curve at finite bias due to the effective band bottom of the Al lead. We have
calculated the shot noise spectrum using the conventional gauge invariant
transport theory with Coulomb interaction considered explicitly on the Hartree
level along with exchange and correlation effect. Although the Fano factor is
enhanced from 0.6 to 0.8 in the NDR region, the expected super-Poissonian
behavior in the NDR regionis not observed. When the fluctuation of Coulomb
interaction is included in the shot noise, our numerical results show that the
Fano factor is greater than one in the NDR region indicating a super-Poissonian
behavior
Bulk Cr tips for scanning tunneling microscopy and spin-polarized scanning tunneling microscopy
A simple, reliable method for preparation of bulk Cr tips for Scanning
Tunneling Microscopy (STM) is proposed and its potentialities in performing
high-quality and high-resolution STM and Spin Polarized-STM (SP-STM) are
investigated. Cr tips show atomic resolution on ordered surfaces. Contrary to
what happens with conventional W tips, rest atoms of the Si(111)-7x7
reconstruction can be routinely observed, probably due to a different
electronic structure of the tip apex. SP-STM measurements of the Cr(001)
surface showing magnetic contrast are reported. Our results reveal that the
peculiar properties of these tips can be suited in a number of STM experimental
situations
A Census of Outflow to Magnetic Field Orientations in Nearby Molecular Clouds
We define a sample of 200 protostellar outflows showing blue and redshifted
CO emission in the nearby molecular clouds Ophiuchus, Taurus, Perseus and Orion
to investigate the correlation between outflow orientations and local, but
relatively large-scale, magnetic field directions traced by Planck 353 GHz dust
polarization. At high significance (p~1e-4), we exclude a random distribution
of relative orientations and find that there is a preference for alignment of
projected plane of sky outflow axes with magnetic field directions. The
distribution of relative position angles peaks at ~30deg and exhibits a broad
dispersion of ~50deg. These results indicate that magnetic fields have
dynamical influence in regulating the launching and/or propagation directions
of outflows. However, the significant dispersion around perfect alignment
orientation implies that there are large measurement uncertainties and/or a
high degree of intrinsic variation caused by other physical processes, such as
turbulence or strong stellar dynamical interactions. Outflow to magnetic field
alignment is expected to lead to a correlation in the directions of nearby
outflow pairs, depending on the degree of order of the field. Analyzing this
effect we find limited correlation, except on relatively small scales < 0.5 pc.
Furthermore, we train a convolutional neural network to infer the inclination
angle of outflows with respect to the line of sight and apply it to our outflow
sample to estimate their full 3D orientations. We find that the angles between
outflow pairs in 3D space also show evidence of small-scale alignment.Comment: ApJ Accepte
Direct Covalent Chemical Functionalization of Unmodified Two-Dimensional Molybdenum Disulfide
Two-dimensional semiconducting transition metal dichalcogenides (TMDCs) like
molybdenum disulfide (MoS2) are generating significant excitement due to their
unique electronic, chemical, and optical properties. Covalent chemical
functionalization represents a critical tool for tuning the properties of TMDCs
for use in many applications. However, the chemical inertness of semiconducting
TMDCs has thus far hindered the robust chemical functionalization of these
materials. Previous reports have required harsh chemical treatments or
converting TMDCs into metallic phases prior to covalent attachment. Here, we
demonstrate the direct covalent functionalization of the basal planes of
unmodified semiconducting MoS2 using aryl diazonium salts without any
pretreatments. Our approach preserves the semiconducting properties of MoS2,
results in covalent C-S bonds, is applicable to MoS2 derived from a range of
different synthesis methods, and enables a range of different functional groups
to be tethered directly to the MoS2 surface. Using density functional theory
calculations including van der Waals interactions and atomic-scale scanning
probe microscopy studies, we demonstrate a novel reaction mechanism in which
cooperative interactions enable the functionalization to propagate along the
MoS2 basal plane. The flexibility of this covalent chemistry employing the
diverse aryl diazonium salt family is further exploited to tether active
proteins to MoS2, suggesting future biological applications and demonstrating
its use as a versatile and powerful chemical platform for enhancing the utility
of semiconducting TMDCsComment: To appear in Chemistry Materials (In press
CMR exploration I -- filament structure with synthetic observations
In this paper, we carry out a pilot parameter exploration for the
collision-induced magnetic reconnection (CMR) mechanism that forms filamentary
molecular clouds. Following Kong et al. (2021), we utilize Athena++ to model
CMR in the context of resistive magnetohydrodynamics (MHD), considering the
effect from seven physical conditions, including the Ohmic resistivity
(), the magnetic field (), the cloud density (), the cloud
radius , the isothermal temperature , the collision velocity , and
the shear velocity . Compared to their fiducial model, we consider a
higher and a lower value for each one of the seven parameters. We quantify the
exploration results with five metrics, including the density probability
distribution function (-PDF), the filament morphology (250 m dust
emission), the - relation, the dominant fiber width, and the ringiness
that describes the significance of the ring-like sub-structures. The
exploration forms straight and curved CMR-filaments with rich sub-structures
that are highly variable in space and time. The variation translates to
fluctuation in all the five metrics, reflecting the chaotic nature of magnetic
reconnection in CMR. A temporary relation is noticeable during
the first 0.6 Myr. Overall, the exploration provides useful initial insights to
the CMR mechanism.Comment: 31 pages, 20 figures, 1 tabl
- …