202 research outputs found
Variable Weighted Ordered Subset Image Reconstruction Algorithm
We propose two variable weighted iterative reconstruction algorithms (VW-ART and VW-OS-SART) to improve the algebraic reconstruction technique (ART) and simultaneous algebraic reconstruction technique (SART) and establish their convergence. In the two algorithms, the weighting varies with the geometrical direction of the ray. Experimental results with both numerical simulation and real CT data demonstrate that the VW-ART has a significant improvement in the quality of reconstructed images over ART and OS-SART. Moreover, both VW-ART and VW-OS-SART are more promising in convergence speed than the ART and SART, respectively
Tamoxifen retards glycosphingolipid metabolism in human cancer cells
AbstractIn this study we provide evidence that tamoxifen, the widely used breast cancer drug, is a potent antagonist of glycolipid metabolism. When added to the medium of cultured multidrug resistant (MDR) KB-V-1 carcinoma cells, tamoxifen, at 5.0 ÎĽM, drastically lowered the levels of glucosylceramide (glc-cer), as evidenced by a reduction in glc-cer mass. In a similar fashion, in cultured human melanoma cells grown with [3H]galactose, tamoxifen inhibited formation of glc-cer by 44%, and retarded lactosylceramide and ganglioside formation by 50 and 35%, respectively. When glc-cer synthase of melanoma was assayed in cell-free incubations, the inclusion of tamoxifen, at a 1:10 molar ratio with ceramide, inhibited glc-cer synthesis by 50%. These results clearly reveal a new action of tamoxifen and thereby pose intriguing questions regarding mechanisms of action in the realm of estrogen receptor-independent modalities, including effects on MDR
Identification and expression profiling analysis of calmodulin-binding transcription activator genes in maize (Zea mays L.) under abiotic and biotic stresses
Study on reversal and lateral vibration in the stepped well
The reversal and lateral vibration of the drill string are very complex motion and can affect the normal operation of the drill string. The movement of the drill string in the stepped well is different from the movement of the drill string in the regular well. The vibration of the drill string in the stepped well varies with the size of the wellbore and can be visually reflected by the phase speed. To find out the relationship between reversal and lateral vibration, the natural frequency of lateral vibration of the drill string was solved by using the method of energy conservation. The analysis shows that the phase speed of flexural wave in the stepped well is faster in small size wellbore than in large size wellbore. The reversal and lateral resonance is easy to happen in small size wellbore, and the reversal will excite lateral vibration. When the sum of reversal and rotational angular frequencies approaches the natural angular frequency of lateral vibration, the lateral resonance will occur
Long-Short-Range Message-Passing: A Physics-Informed Framework to Capture Non-Local Interaction for Scalable Molecular Dynamics Simulation
Computational simulation of chemical and biological systems using ab initio
molecular dynamics has been a challenge over decades. Researchers have
attempted to address the problem with machine learning and fragmentation-based
methods, however the two approaches fail to give a satisfactory description of
long-range and many-body interactions, respectively. Inspired by
fragmentation-based methods, we propose the Long-Short-Range Message-Passing
(LSR-MP) framework as a generalization of the existing equivariant graph neural
networks (EGNNs) with the intent to incorporate long-range interactions
efficiently and effectively. We apply the LSR-MP framework to the recently
proposed ViSNet and demonstrate the state-of-the-art results with up to
error reduction for molecules in MD22 and Chignolin datasets. Consistent
improvements to various EGNNs will also be discussed to illustrate the general
applicability and robustness of our LSR-MP framework
On Channel Reciprocity in Reconfigurable Intelligent Surface Assisted Wireless Network
Channel reciprocity greatly facilitates downlink precoding in time-division
duplexing (TDD) multiple-input multiple-output (MIMO) communications without
the need for channel state information (CSI) feedback. Recently, reconfigurable
intelligent surfaces (RISs) emerge as a promising technology to enhance the
performance of future wireless networks. However, since the artificial
electromagnetic characteristics of RISs are not from the nature, it brings up a
question: does the channel reciprocity hold in RIS-assisted TDD wireless
networks? After briefly reviewing the reciprocity theorem, in this article, we
show that there still exists channel reciprocity for RIS-assisted wireless
networks satisfying certain conditions. We also experimentally demonstrate the
reciprocity at the sub-6 GHz and the millimeter-wave frequency bands by using
two fabricated RISs. Furthermore, we introduce several RIS-assisted approaches
to realizing nonreciprocal channels. Finally, potential opportunities brought
by reciprocal/nonreciprocal RISs and future research directions are outlined.Comment: In general, when the control signals applied to the unit cells remain
unchanged, commonly designed and fabricated RISs inherently obey the
reciprocity theorem. Nevertheless, there are several RIS-assisted approaches
to realizing nonreciprocal channels. Potential opportunities brought by
reciprocal/nonreciprocal RISs and future research directions are outline
Path Loss Modeling and Measurements for Reconfigurable Intelligent Surfaces in the Millimeter-Wave Frequency Band
Reconfigurable intelligent surfaces (RISs) provide an interface between the
electromagnetic world of wireless propagation environments and the digital
world of information science. Simple yet sufficiently accurate path loss models
for RISs are an important basis for theoretical analysis and optimization of
RIS-assisted wireless communication systems. In this paper, we refine our
previously proposed free-space path loss model for RISs to make it simpler,
more applicable, and easier to use. The impact of the antenna's directivity of
the transmitter, receiver, and the unit cells of the RIS on the path loss is
explicitly formulated as an angle-dependent loss factor. The refined model
gives more accurate estimates of the path loss of RISs comprised of unit cells
with a deep sub-wavelength size. Based on the proposed model, the properties of
a single unit cell are evaluated in terms of scattering performance, power
consumption, and area, which allows us to unveil fundamental considerations for
deploying RISs in high frequency bands. Two fabricated RISs operating in the
millimeter-wave (mmWave) band are utilized to carry out a measurement campaign.
The measurement results are shown to be in good agreement with the proposed
path loss model. In addition, the experimental results suggest an effective
form to characterize the power radiation pattern of the unit cell for path loss
modeling.Comment: Model refinements are introduced to previously proposed free-space
path loss model for RISs in order to make it simpler and easier to use. The
properties of a single unit cell are evaluated in terms of scattering
performance, power, and area, as it is the basic element of an RIS. We report
the world's first measurement campaign in the mmWave frequency band to
validate the path loss model for RIS
Activation of Dopamine 4 Receptor Subtype Enhances Gamma Oscillations in Hippocampal Slices of Aged Mice
Aim: Neural network oscillation at gamma frequency band (γ oscillation, 30–80 Hz) is synchronized synaptic potentials important for higher brain processes and altered in normal aging. Recent studies indicate that activation of dopamine 4 receptor (DR4) enhanced hippocampal γ oscillation of young mice and fully recovered the impaired hippocampal synaptic plasticity of aged mice, we determined whether this receptor is involved in aging-related modulation of hippocampal γ oscillation.
Methods: We recorded Îł oscillations in the hippocampal CA3 region from young and aged C57bl6 mice and investigated the effects of dopamine and the selective dopamine receptor (DR) agonists on Îł oscillation.
Results: We first found that Îł oscillation power (Îł power) was reduced in aged mice compared to young mice, which was restored by exogenous application of dopamine (DA). Second, the selective agonists for different D1- and D2-type dopamine receptors increased Îł power in young mice but had little or small effect in aged mice. Third, the D4 receptor (D4R) agonist PD168077 caused a large increase of Îł power in aged mice but a small increase in young mice, and its effect is blocked by the highly specific D4R antagonist L-745,870 or largely reduced by a NMDAR antagonist. Fourth, D3R agonist had no effect on Îł power of either young or aged mice.
Conclusion: This study reveals DR subtype-mediated hippocampal Îł oscillations is aging-related and DR4 activation restores the impaired Îł oscillations in aged brain, and suggests that D4R is the potential target for the improvement of cognitive deficits related to the aging and aging-related diseases
Comparison of Double Kissing Crush Versus Culotte Stenting for Unprotected Distal Left Main Bifurcation Lesions Results From a Multicenter, Randomized, Prospective DKCRUSH-III Study
ObjectivesThe study aimed to investigate the difference in major adverse cardiac event (MACE) at 1-year after double kissing (DK) crush versus Culotte stenting for unprotected left main coronary artery (UPLMCA) distal bifurcation lesions.BackgroundDK crush and Culotte stenting were reported to be effective for treatment of coronary bifurcation lesions. However, their comparative performance in UPLMCA bifurcation lesions is not known.MethodsA total of 419 patients with UPLMCA bifurcation lesions were randomly assigned to DK (n = 210) or Culotte (n = 209) treatment. The primary endpoint was the occurrence of a MACE at 1 year, including cardiac death, myocardial infarction, and target vessel revascularization (TVR). In-stent restenosis (ISR) at 8 months was secondary endpoint, and stent thrombosis (ST) served as a safety endpoint. Patients were stratified by SYNTAX (Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery) and NERS (New Risk Stratification) scores.ResultsPatients in the Culotte group had significant higher 1-year MACE rate (16.3%), mainly driven by increased TVR (11.0%), compared with the DK group (6.2% and 4.3%, respectively; all p < 0.05). ISR rate in side branch was 12.6% in the Culotte group and 6.8% in the DK group (p = 0.037). Definite ST rate was 1.0% in the Culotte group and 0% in the DK group (p = 0.248). Among patients with bifurcation angle ≥70°, NERS score ≥20, and SYNTAX score ≥23, the 1-year MACE rate in the DK group (3.8%, 9.2%, and 7.1%, respectively) was significantly different to those in the Culotte group(16.5%, 20.4%, and 18.9%, respectively; all p < 0.05).ConclusionsCulotte stenting for UPLMCA bifurcation lesions was associated with significantly increased MACEs, mainly due to the increased TVR. (Double Kissing [DK] Crush Versus Culotte Stenting for the Treatment of Unprotected Distal Left Main Bifurcation Lesions: DKCRUSH-III, a Multicenter Randomized Study Comparing Double-Stent Techniques; ChiCTR-TRC-00000151
Yersinia pestis Interacts With SIGNR1 (CD209b) for Promoting Host Dissemination and Infection
Yersinia pestis, a Gram-negative bacterium and the etiologic agent of plague, has evolved from Yersinia pseudotuberculosis, a cause of a mild enteric disease. However, the molecular and biological mechanisms of how Y pseudotuberculosis evolved to such a remarkably virulent pathogen, Y pestis, are not clear. The ability to initiate a rapid bacterial dissemination is a characteristic hallmark of Y pestis infection. A distinguishing characteristic between the two Yersinia species is that Y pseudotuberculosis strains possess an O-antigen of lipopolysaccharide (LPS) while Y pestis has lost the O-antigen during evolution and therefore exposes its core LPS. In this study, we showed that Y pestis utilizes its core LPS to interact with SIGNR1 (CD209b), a C-type lectin receptor on antigen presenting cells (APCs), leading to bacterial dissemination to lymph nodes, spleen and liver, and the initiation of a systemic infection. We therefore propose that the loss of O-antigen represents a critical step in the evolution of Y pseudotuberculosis into Y pestis in terms of hijacking APCs, promoting bacterial dissemination and causing the plague.Peer reviewe
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