Poisson-like effect for flexural waves in periodically perforated thin plates

[EN] The Poisson-like effect, describing the redirection of waves by 90 degrees, is shown to be feasible for flexural waves propagating in perforated thin plates. It is demonstrated that the lowest order symmetric leaky guided mode (S0 mode) is responsible for the splitting of wave motion in two orthogonal directions. The S0 mode shows a feature of stationary waves containing standing wave modes in one and two orthogonal directions for smaller and larger holes, respectively. The former case is well understood thanks to the phenomenon of Wood's anomaly, which was first observed in optical gratings supposed to be transparent. On the contrary, the strong scattering caused by the larger holes leads to a mixed mode occurring when the incident wave is totally transmitted. The mixed mode easily couples with the incoming waves and, therefore, the Poisson-like effect activated under this mechanism is much stronger. Using the Poisson-like effect, a device is proposed in which about 82% of the incident mechanical energy is redirected to the perpendicular direction. Results obtained with arrays of free holes also apply to inclusions with parameters properly chosen. The findings may provide applications in beam splitting and waveguiding. (C) 2018 Acoustical Society of America.Work supported by the Ministerio de Economia y Competitividad of Spain and the EU Fondo Europeo de Desarrollo Regional under Project No. TEC2014-53088-C3-1-R, and the National Natural Science Foundation of China under Grants Nos. 11432004 and 11421091. P.G. acknowledges a scholarship with No. 201606120070 provided by China Scholarship Council.Gao, P.; Sánchez-Dehesa Moreno-Cid, J.; Wu, L. (2018). Poisson-like effect for flexural waves in periodically perforated thin plates. The Journal of the Acoustical Society of America. 144(2):1053-1058. https://doi.org/10.1121/1.5051648S10531058144

Single-phase metamaterial plates for broadband vibration suppression at low frequencies

[EN] By studying platonic crystals based on lattices of cavities containing N-beam resonators, we conclude that crystals made of 1-beam resonators easily produce low-frequency omnidirectional bandgaps. Based on this favorable property, hardly obtained for resonant cavities containing a higher number of beams N >= 2, we have designed single-phase metamaterial plates for the suppression of low frequency flexural waves in a broad range of frequencies. These metamaterials are obtained by using resonant cavities containing a multiple number M of identical 1-beam resonators uniformly distributed in the cavity. Square lattices of this type of resonators have been studied by using the impedance matrix approach and the multiple scattering method. This semi-analytical method has been employed to show the existence of complete bandgaps whose width can be optimized by increasing M. For the case M = 4, the largest number of resonators studied here, three complete bandgaps separated by two narrow passbands appear in the band structure. The formation of these complete bandgaps originates from the dynamic interaction between different local resonators as well as their interaction with the propagating waves in the host plate. By using composite structures consisting of platonic crystal slabs with complementary bandgaps, these separated bandgaps easily merge into a broadband wave attenuation region. The normalized width, defined as the percentage of the bandwidth to its central frequency, reaches 95.3%, representing an enhancement of about one order of magnitude compared with the absolute bandwidth obtained for the case of a single 1-beam resonator in the cavity. It is shown that the gaps can be easily tuned to lower frequencies by changing the geometrical parameters, such as the length of the beam, the radius and thickness of the smaller circular plate. Since the metamaterial is made of a single-phase material without attaching heavy masses, the work reported here provides a simple approach to construct low-cost structures with potential applications in aeronautic and astronautic industries for broadband vibration suppression at low frequencies. (C) 2018 Published by Elsevier Ltd.This work was supported by the Ministerio de Economia y Competitividad of the Spanish government and the European Union Fondo Europeo de Desarrollo Regional (FEDER) [Grant No. TEC2014-53088-C3-1-R], and the National Natural Science Foundation of China [Grant Nos. 11432004 and 11421091]. Penglin Gao acknowledges a scholarship provided by China Scholarship Council [Grant No. 201606120070].Gao, P.; Climente Alarcón, A.; Sánchez-Dehesa Moreno-Cid, J.; Wu, L. (2019). Single-phase metamaterial plates for broadband vibration suppression at low frequencies. Journal of Sound and Vibration. 444:108-126. https://doi.org/10.1016/j.jsv.2018.12.022S10812644

Theoretical study of platonic crystals with periodically structured N-beam resonators

[EN] A multiple scattering theory is applied to study the properties of flexural waves propagating in a plate with periodically structured N-beam resonators. Each resonator consists of a circular hole containing an inner disk connected to background plate with N rectangular beams. The Bloch theorem is employed to obtain the band structure of a two-dimensional lattice containing a single resonator per unit cell. Also, a numerical algorithm has been developed to get the transmittance through resonator slabs infinitely long in the direction perpendicular to the incident wave. For the numerical validation, a square lattice of 2-beam resonators has been comprehensively analyzed. Its band structure exhibits several flat bands, indicating the existence of local resonances embedded in the structure. Particularly, the one featured as the fundamental mode of the inner disk opens a bandgap at low frequencies. This mode has been fully described in terms of a simple spring-mass model. As a practical application of the results obtained, a homogenization approach has been employed to design a focusing lens for flexural waves, where the index gradient is obtained by adjusting the orientation of the resonators beams. Numerical experiments performed within the framework of a three-dimensional finite element method have been employed to discuss the accuracy of the models described here. Published by AIP Publishing.This work was supported by the Ministerio de Economia y Competitividad of the Spanish government and the European Union Fondo Europeo de Desarrollo Regional (FEDER) through Project No. TEC2014-53088-C3-1-R, and the National Science Foundation of China under Grant No. 11432004. Penglin Gao acknowledges a scholarship with No. 201606120070 provided by China Scholarship Council.Gao, P.; Climente Alarcón, A.; Sánchez-Dehesa Moreno-Cid, J.; Wu, L. (2018). Theoretical study of platonic crystals with periodically structured N-beam resonators. Journal of Applied Physics. 123(9). https://doi.org/10.1063/1.5009170S123

The ectonucleotidases CD39 and CD73 on T cells: The new pillar of hematological malignancy

Hematological malignancy develops and applies various mechanisms to induce immune escape, in part through an immunosuppressive microenvironment. Adenosine is an immunosuppressive metabolite produced at high levels within the tumor microenvironment (TME). Adenosine signaling through the A2A receptor expressed on immune cells, such as T cells, potently dampens immune responses. Extracellular adenosine generated by ectonucleoside triphosphate diphosphohydrolase-1 (CD39) and ecto-5’-nucleotidase (CD73) molecules is a newly recognized ‘immune checkpoint mediator’ and leads to the identification of immunosuppressive adenosine as an essential regulator in hematological malignancies. In this Review, we provide an overview of the detailed distribution and function of CD39 and CD73 ectoenzymes in the TME and the effects of CD39 and CD73 inhibition on preclinical hematological malignancy data, which provides insights into the potential clinical applications for immunotherapy

Rewiring carbon flow in Synechocystis PCC 6803 for a high rate of CO2-to-ethanol under an atmospheric environment

Cyanobacteria are an excellent microbial photosynthetic platform for sustainable carbon dioxide fixation. One bottleneck to limit its application is that the natural carbon flow pathway almost transfers CO2 to glycogen/biomass other than designed biofuels such as ethanol. Here, we used engineered Synechocystis sp. PCC 6803 to explore CO2-to-ethanol potential under atmospheric environment. First, we investigated the effects of two heterologous genes (pyruvate decarboxylase and alcohol dehydrogenase) on ethanol biosynthesis and optimized their promoter. Furthermore, the main carbon flow of the ethanol pathway was strengthened by blocking glycogen storage and pyruvate-to-phosphoenolpyruvate backflow. To recycle carbon atoms that escaped from the tricarboxylic acid cycle, malate was artificially guided back into pyruvate, which also created NADPH balance and promoted acetaldehyde conversion into ethanol. Impressively, we achieved high-rate ethanol production (248 mg/L/day at early 4 days) by fixing atmospheric CO2. Thus, this study exhibits the proof-of-concept that rewiring carbon flow strategies could provide an efficient cyanobacterial platform for sustainable biofuel production from atmospheric CO2

Numerical Study on the Dynamic Fracture Energy of Concrete Based on a Rate-Dependent Cohesive Model

As an important parameter for concrete, fracture energy is difficult to accurately measure in high loading rate tests due to the limitations of experimental devices and methods. Therefore, the utilization of numerical methods to study the dynamic fracture energy of concrete is a simple and promising choice. This paper presents a numerical investigation on the influence of loading rate on concrete fracture energy and cracking behaviors. A novel rate-dependent cohesive model, which was programmed as a user subroutine in the commercial explicit finite element solver LS-DYNA, is first proposed. After conducting mesh sensitivity analysis, the proposed model is calibrated against representative experimental data. Then, the underlying mechanisms of the increase in fracture energy due to a high strain rate are determined. The results illustrate that the higher fracture energy during dynamic tension loading is caused by the wider region of the damage zone and the increase in real fracture energy. As the loading rate increases, the wider region of the damage zone plays a leading role in increasing fracture energy. In addition, as the strain rate increases, the number of microcracks whose fracture mode is mixed mode increases, which has an obvious effect on the change in real fracture energy

Safety and Efficacy of Irreversible Electroporation in Locally Advanced Pancreatic Cancer: An Evaluation from a Surgeon’s Perspective

Irreversible electroporation (IRE) has emerged as a promising treatment for patients with locally advanced pancreatic cancer (LAPC). Therefore, in this study, we evaluate the safety and efficacy of IRE against LAPC, as well as exploring its impact on anti-tumor immunity. A retrospective analysis was conducted in consecutive patients at a single institution. Eligible patients were assigned to IRE, palliative surgery (PS), or vascular resection (VR) groups, according to their respective treatments. The IRE group consisted of LAPC patients. One-to-one propensity score matching was performed, in order to compare the incidence of complications and median overall survival (mOS). Serum and intratumoral cytokines, as well as intratumoral immune cells, were analyzed in order to identify changes in immunity after IRE. A total of 210 patients were included. After matching, the rate of major complications (Clavien–Dindo III–V), intra-abdominal hemorrhage, and re-intervention in the IRE group were similar to those in the VR group (p > 0.05). The mOS of the IRE group (13.0 months) was shorter than that of the VR group (15.0 months), but longer than that of the PS group (8.0 months) (p < 0.05). Patients in the IRE group had elevated serum levels of immunogenic cytokines, including IL-2, IL-6, and TNF-α, which were related to anti-tumor immunity. The survival advantage in IRE-treated patients was attributed to tumor ablation and immune modulation effects. Overall, IRE can be considered a feasible treatment for patients with LAPC