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Coil combination using linear deconvolution in k-space for phase imaging
Background: The combination of multi-channel data is a critical step for the imaging of phase and susceptibility contrast in magnetic resonance imaging (MRI). Magnitude-weighted phase combination methods often produce noise and aliasing artifacts in the magnitude images at accelerated imaging sceneries. To address this issue, an optimal coil combination method through deconvolution in k-space is proposed in this paper.
Methods: The proposed method firstly employs the sum-of-squares and phase aligning method to yield a complex reference coil image which is then used to calculate the coil sensitivity and its Fourier transform. Then, the coil k-space combining weights is computed, taking into account the truncated frequency data of coil sensitivity and the acquired k-space data. Finally, combining the coil k-space data with the acquired weights generates the k-space data of proton distribution, with which both phase and magnitude information can be obtained straightforwardly. Both phantom and in vivo imaging experiments were conducted to evaluate the performance of the proposed method.
Results: Compared with magnitude-weighted method and MCPC-C, the proposed method can alleviate the phase cancellation in coil combination, resulting in a less wrapped phase.
Conclusions: The proposed method provides an effective and efficient approach to combine multiple coil image in parallel MRI reconstruction, and has potential to benefit routine clinical practice in the future
Electronic Tuning of Mixed Quinoidal‐Aromatic Conjugated Polyelectrolytes: Direct Ionic Substitution on Polymer Main‐Chains
The synthesis of conjugated polymers with ionic substituents directly bound to their main chain repeat units is a strategy for generating strongly electron-accepting conjugated polyelectrolytes, as demonstrated through the synthesis of a series of ionic azaquinodimethane (iAQM) compounds. The introduction of cationic substituents onto the quinoidal para-azaquinodimethane (AQM) core gives rise to a strongly electron-accepting building block, which can be employed in the synthesis of ionic small molecules and conjugated polyelectrolytes (CPEs). Electrochemical measurements alongside theoretical calculations indicate notably low-lying LUMO values for the iAQMs. The optical band gaps measured for these compounds are highly tunable based on structure, ranging from 2.30 eV in small molecules down to 1.22 eV in polymers. The iAQM small molecules and CPEs showcase the band gap reduction effects of combining the donor-acceptor strategy with the bond-length alternation reduction strategy. As a demonstration of their utility, the iAQM CPEs so generated were used as active agents in photothermal therapy
Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence
Many-body correlations can yield key insights into the nature of interacting
systems; however, detecting them is often very challenging in many-particle
physics, especially in nanoscale systems. Here, taking a phosphorus donor
electron spin in a natural-abundance 29Si nuclear spin bath as our model
system, we discover both theoretically and experimentally that many-body
correlations in nanoscale nuclear spin baths produce identifiable signatures in
the decoherence of the central spin under multiple-pulse dynamical decoupling
control. We find that when the number of decoupling -pulses is odd, central
spin decoherence is primarily driven by second-order nuclear spin correlations
(pairwise flip-flop processes). In contrast, when the number of -pulses is
even, fourth-order nuclear spin correlations (diagonal interaction renormalized
pairwise flip-flop processes) are principally responsible for the central spin
decoherence. Many-body correlations of different orders can thus be selectively
detected by central spin decoherence under different dynamical decoupling
controls, providing a useful approach to probing many-body processes in
nanoscale nuclear spin baths
Development of Competency Indexes to Assess Nursing Postgraduate's Tutor
The aim of this study was to develop competency indexes assessing nursingpostgraduate's tutor in China. Based on Iceberg competency theory, a Delphisurvey was carried out. 30 nursing experts in 16 provinces of China wereinvited to rate the importance of indexes and give some comments on thecontent. There were 22 experts taking part in two rounds Delphi study. AKendall's W test also demonstrated experts were well coordinated. Duringthe first round, overall mean scores were high, except for 1 tertiary index.We also added and moved some indexes building on the experts'suggestions. After two rounds, we developed competency indexesappropriate to assess tutots' competencies, consisting of 5 preliminaryindexes, 13 secondary indexes and 68 tertiary indexes. The competencyindexes were validated and scientific, it can be used to assess tutors in China
Next-to-leading-order corrections to exclusive processes in factorization
We calculate next-to-leading-order (NLO) corrections to exclusive processes
in factorization theorem, taking as an example.
Partons off-shell by are considered in both the quark diagrams from
full QCD and the effective diagrams for the pion wave function. The gauge
dependences in the above two sets of diagrams cancel, when deriving the
-dependent hard kernel as their difference. The gauge invariance of the
hard kernel is then proven to all orders by induction. The light-cone
singularities in the -dependent pion wave function are regularized by
rotating the Wilson lines away from the light cone. This regularization
introduces a factorization-scheme dependence into the hard kernel, which can be
minimized in the standard way. Both the large double logarithms and
, being a parton momentum fraction, arise from the loop correction
to the virtual photon vertex, the former being absorbed into the pion wave
function and organized by the resummation, and the latter absorbed into a
jet function and organized by the threshold resummation. The NLO corrections
are found to be only few-percent for , if setting the
factorization scale to the momentum transfer from the virtual photon.Comment: 13 pages; version to appear in Physical Review
Scaling in directed dynamical small-world networks with random responses
A dynamical model of small-world network, with directed links which describe
various correlations in social and natural phenomena, is presented. Random
responses of every site to the imput message are introduced to simulate real
systems. The interplay of these ingredients results in collective dynamical
evolution of a spin-like variable S(t) of the whole network. In the present
model, global average spreading length \langel L >_s and average spreading time
_s are found to scale as p^-\alpha ln N with different exponents.
Meanwhile, S behaves in a duple scaling form for N>>N^*: S ~ f(p^-\beta
q^\gamma t'_sc), where p and q are rewiring and external parameters, \alpha,
\beta, \gamma and f(t'_sc) are scaling exponents and universal functions,
respectively. Possible applications of the model are discussed.Comment: 4 pages, 6 Figure
Negotiating Agency and Control: Theorizing Human-Machine Communication from a Structurational Perspective
Intelligent technologies have the potential to transform organizations and organizing processes. In particular, they are unique from prior organizational technologies in that they reposition technology as agent rather than a tool or object of use. Scholars studying human-machine communication (HMC) have begun to theorize the dual role played by human and machine agency, but they have focused primarily on the individual level. Drawing on Structuration Theory (Giddens, 1984), we propose a theoretical framework to explain agency in HMC as a process involving the negotiation of control between human and machine agents. This article contributes to HMC scholarship by offering a framework and research agenda to guide future theory-building and research on the use of intelligent technologies in organizational contexts
Exoskeletons and the Future of Work: Envisioning Power and Control in a Workforce Without Limits
Exoskeletons are an emerging form of technology that combines the skills of both machines and humans to give wearers the ability to complete physically demanding tasks that would be too strenuous for most humans. Exoskeleton adoption has the potential to both enhance and disrupt many aspects of work, including power dynamics in the workplace and the human-machine interactions that take place. Dyadic Power Theory (DPT) is a useful theory for exploring the impacts of exoskeleton adoption. In this conceptual paper, we extend DPT to relationships between humans and machines in organizations, as well as human-human communication where use of an exoskeleton has resulted in shifts of power
Controlled tuning of whispering gallery modes of GaN/InGaN microdisk cavities
Controlled tuning of the whispering gallery modes of GaN/InGaN {\mu}-disk
cavities is demonstrated. The whispering gallery mode (WGM) tuning is achieved
at room temperature by immersing the {\mu}-disks in water and irradiating with
ultraviolet (UV) laser. The tuning rate can be controlled by varying the laser
excitation power, with a nanometer precision accessible at low excitation power
(~ several {\mu}W). The selective oxidation mechanism is proposed to explain
the results and supported by theoretical analysis. The tuning of WGMs in
GaN/InGaN {\mu}-disk cavities may have important implication in cavity quantum
electrodynamics and the development of efficient light emitting devices
A full free spectral range tuning of p-i-n doped Gallium Nitride microdisk cavity
Effective, permanent tuning of the whispering gallery modes (WGMs) of p-i-n
doped GaN microdisk cavity with embedded InGaN quantum dots over one free
spectral range is successfully demonstrated by irradiating the microdisks with
a ultraviolet laser (380nm) in DI water. For incident laser powers between 150
and 960 nW, the tuning rate varies linearly. Etching of the top surface of the
cavity is proposed as the driving force for the observed shift in WGMs, and is
supported by experiments. The tuning for GaN/InGaN microdisk cavities is an
important step for deterministically realizing novel nanophotonic devices for
studying cavity quantum electrodynamics
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