4,518 research outputs found
Photoacoustic microscopy of myocardial sheet architecture in unfixed and unstained mammalian hearts
The laminar myocardial sheet architecture and its dynamic change play a key role in myocardial wall thickening. Histology, confocal optical microscopy (COM), and diffusion tensor MRI (DTI) have been used to unveil the structures and functions of the myocardial sheets. However, histology and COM require fixation, sectioning, and staining processes, which dehydrate and deform the sheet architecture. Although DTI can delineate sheet architecture nondestructively in viable hearts, it cannot provide cellular-level resolution. Here we show that photoacoustic microscopy (PAM), with high resolution (~1 μm) and label-free detection, is appropriate for imaging 3D myocardial architecture. Perfused half-split mouse hearts were also imaged by PAM in vitro without fixation, dehydration, nor staining. The laminar myocardial sheet architecture was clearly visualized within a 0.15 mm depth range. Two populations of oppositely signed sheet angles were observed. Therefore, PAM promises to access dynamic changes of myocardial architectures in ex vivo perfused-viable hearts
Photoacoustic microscopy of myocardial sheet architecture in unfixed and unstained mammalian hearts
The laminar myocardial sheet architecture and its dynamic change play a key role in myocardial wall thickening. Histology, confocal optical microscopy (COM), and diffusion tensor MRI (DTI) have been used to unveil the structures and functions of the myocardial sheets. However, histology and COM require fixation, sectioning, and staining processes, which dehydrate and deform the sheet architecture. Although DTI can delineate sheet architecture nondestructively in viable hearts, it cannot provide cellular-level resolution. Here we show that photoacoustic microscopy (PAM), with high resolution (~1 μm) and label-free detection, is appropriate for imaging 3D myocardial architecture. Perfused half-split mouse hearts were also imaged by PAM in vitro without fixation, dehydration, nor staining. The laminar myocardial sheet architecture was clearly visualized within a 0.15 mm depth range. Two populations of oppositely signed sheet angles were observed. Therefore, PAM promises to access dynamic changes of myocardial architectures in ex vivo perfused-viable hearts
Assessment of density functional approximations for the hemibonded structure of water dimer radical cation
Due to the severe self-interaction errors associated with some density
functional approximations, conventional density functionals often fail to
dissociate the hemibonded structure of water dimer radical cation (H2O)2+ into
the correct fragments: H2O and H2O+. Consequently, the binding energy of the
hemibonded structure (H2O)2+ is not well-defined. For a comprehensive
comparison of different functionals for this system, we propose three criteria:
(i) The binding energies, (ii) the relative energies between the conformers of
the water dimer radical cation, and (iii) the dissociation curves predicted by
different functionals. The long-range corrected (LC) double-hybrid functional,
omegaB97X-2(LP) [J.-D. Chai and M. Head-Gordon, J. Chem. Phys., 2009, 131,
174105.], is shown to perform reasonably well based on these three criteria.
Reasons that LC hybrid functionals generally work better than conventional
density functionals for hemibonded systems are also explained in this work.Comment: 10 pages, 5 figures, 4 table
Effects of Moderate Exercise on Relieving Mental Load of Elementary School Teachers
Long-term endurance exercise could increase activity of parasympathetic nervous and decrease activity of sympathetic nervous at rest. However, previous studies all focused on the effect of endurance training on heart rate variability (HRV) for athletes or sedentary subjects. In Taiwan, elementary school teachers teaching and processing the children’s and administrative problems always stand and walk. They will sit down only when they review and correct the students’ home work. Thus, the goal of this study was to elucidate the beneficial effect of moderate intensity exercise on relieving mental load of elementary school teachers. There were 20 participants in the exercise group and another 20 participants in the nonexercise group. The exercising teachers performed 12 weeks of moderate intensity exercise training for an average of 30 minutes per day, 3 times per week. HRV was measured before and after the 4th, 6th, and 12th weeks. The time and frequency domain parameters of HRV all had significant increases between the beginning and after 12 weeks of training. However, the time and frequency domain parameters of HRV in the nonexercise group had significant decreases between the beginning and after 12 weeks of training. The long-term moderate exercises can relieve mental load of elementary school teachers. Moreover, age was the considerable factor affecting HRV in this study
Green functions for generalized point interactions in 1D: A scattering approach
Recently, general point interactions in one dimension has been used to model
a large number of different phenomena in quantum mechanics. Such potentials,
however, requires some sort of regularization to lead to meaningful results.
The usual ways to do so rely on technicalities which may hide important
physical aspects of the problem. In this work we present a new method to
calculate the exact Green functions for general point interactions in 1D. Our
approach differs from previous ones because it is based only on physical
quantities, namely, the scattering coefficients, and , to construct .
Renormalization or particular mathematical prescriptions are not invoked. The
simple formulation of the method makes it easy to extend to more general
contexts, such as for lattices of general point interactions; on a line; on
a half-line; under periodic boundary conditions; and confined in a box.Comment: Revtex, 9 pages, 3 EPS figures. To be published in PR
Endoscopic Therapy of Colonic Liver Flexure Mucocele
Colorectal mucoceles usually arise in the appendix, and colonic disease is very rare. We report the first case of a mucocele of the colonic liver flexure that was treated successfully with endoscopy. A 36-year-old man was admitted to our hospital because of abdominal distension persisting for 3 days. Colonoscopic examination revealed a round polyp in the hepatic flexure, and we performed hot snare polypectomy with argon plasma coagulation. Histologically, the polypectomy specimen was confirmed to be a mucocele, with no neoplastic changes. Follow-up examinations at 6 and 12 months showed no evidence of recurrence
Anomalous excitonic phase diagram in band-gap-tuned Ta2Ni(Se,S)5
During a band-gap-tuned semimetal-to-semiconductor transition, Coulomb
attraction between electrons and holes can cause spontaneously formed excitons
near the zero-band-gap point, or the Lifshitz transition point. This has become
an important route to realize bulk excitonic insulators -- an insulating ground
state distinct from single-particle band insulators. How this route manifests
from weak to strong coupling is not clear. In this work, using angle-resolved
photoemission spectroscopy (ARPES) and high-resolution synchrotron x-ray
diffraction (XRD), we investigate the broken symmetry state across the
semimetal-to-semiconductor transition in a leading bulk excitonic insulator
candidate system Ta2Ni(Se,S)5. A broken symmetry phase is found to be
continuously suppressed from the semimetal side to the semiconductor side,
contradicting the anticipated maximal excitonic instability around the Lifshitz
transition. Bolstered by first-principles and model calculations, we find
strong interband electron-phonon coupling to play a crucial role in the
enhanced symmetry breaking on the semimetal side of the phase diagram. Our
results not only provide insight into the longstanding debate of the nature of
intertwined orders in Ta2NiSe5, but also establish a basis for exploring
band-gap-tuned structural and electronic instabilities in strongly coupled
systems.Comment: 27 pages, 4 + 9 figure
Structure of hadron resonances with a nearby zero of the amplitude
We discuss the relation between the analytic structure of the scattering
amplitude and the origin of an eigenstate represented by a pole of the
amplitude.If the eigenstate is not dynamically generated by the interaction in
the channel of interest, the residue of the pole vanishes in the zero coupling
limit. Based on the topological nature of the phase of the scattering
amplitude, we show that the pole must encounter with the
Castillejo-Dalitz-Dyson (CDD) zero in this limit. It is concluded that the
dynamical component of the eigenstate is small if a CDD zero exists near the
eigenstate pole. We show that the line shape of the resonance is distorted from
the Breit-Wigner form as an observable consequence of the nearby CDD zero.
Finally, studying the positions of poles and CDD zeros of the KbarN-piSigma
amplitude, we discuss the origin of the eigenstates in the Lambda(1405) region.Comment: 7 pages, 3 figures, v2: published versio
Molecular Dynamics Simulations of the Roller Nanoimprint Process: Adhesion and Other Mechanical Characteristics
Molecular dynamics simulations using tight-binding many body potential are carried out to study the roller imprint process of a gold single crystal. The effect of the roller tooth’s taper angle, imprint depth, imprint temperature, and imprint direction on the imprint force, adhesion, stress distribution, and strain are investigated. A two-stage roller imprint process was obtained from an imprint force curve. The two-stage imprint process included the imprint forming with a rapid increase of imprint force and the unloading stage combined with the adhesion stage. The results show that the imprint force and adhesion rapidly increase with decreasing taper angle and increasing imprint depth. The magnitude of the maximum imprint force and the time at which this maximum occurs are proportional to the imprint depth, but independent of the taper angle. In a comparison of the imprint mechanisms with a vertical imprint case, while high stress and strain regions are concentrated below the mold for vertical imprint, they also occur around the mold in the case of roller imprint. The regions were only concentrated on the substrate atoms underneath the mold in vertical imprint. Plastic flow increased with increasing imprint temperature
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