bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance comparison of a dedicated total breast PET system with a clinical whole-body PET system: a simulation study
Authors: Samanta Suranjana , Jiang Jianyong , Hamdi Mahdjoub , Register Alan Z , Majewski Stanislaw , Williams Mark B , Turkington Timothy G , Tornai Martin P , Laforest Richard , O’Sullivan Joseph A , Tai Yuan-Chuan 
Published: April 2021

Abstract
This paper presents a novel PET geometry for breast cancer imaging. The scanner consists of a ‘stadium’ (a rectangle with two semi-circles on opposite sides) shaped ring, along with anterior and posterior panels to provide high sensitivity and high spatial resolution for an imaging field-of-view (FOV) that include both breasts, mediastinum and axilla. We simulated this total-breast PET system using GATE and reconstructed the coincidence events using a GPU-based list-mode image reconstruction implementing maximum likelihood expectation-maximization (ML-EM) algorithm. The rear-panel is made up of a single layer of LSO crystals (3.2 × 3.2 × 20 mm3 each), while the ‘stadium’-shaped elongated ring and the anterior panel are made with dual-layered LSO crystals (1.6 × 1.6 × 6 mm3 each). The energy resolution and coincidence resolving time of all detectors are assumed to be 12% and 250 ps full-width-at-half-maximum, respectively. Various sized simulated lesions (4, 5, 6 mm) having 4:1, 5:1, and 6:1 lesion-to-background radioactivity concentration ratios, mimicking different biological uptakes, were strategically located throughout a volumetric torso phantom. We compared system sensitivity and lesion detectability of the dedicated total-breast PET system to a state-of-the-art clinical whole-body PET scanner. The mean sensitivity of the total-breast PET system is 3.21 times greater than that of a whole-body PET scanner in the breast regions. The total-breast PET system also provides better contrast-recovery coefficients for lesions of all sizes and lesion-to-background ratios in the breast when compared to a reference clinical whole-body PET scanner. Receiver operating characteristics (ROC) study shows the area under the ROC curve is 0.948 and 0.924 for the total-breast system and the whole-body PET scanner, respectively, in the detection of 4 mm diameter lesions with 4:1 lesion-to-background ratio. This study demonstrates our novel geometry can provide an imaging FOV larger than conventional PEM systems to simultaneously image both breasts, chest wall and axillae with significantly improved lesion detectability in the breasts when compared to a whole-body PET scanner.
PET image reconstruction with deep progressive learning
Authors: Lv Yang , Xi Chen 
Published: April 2021

Abstract
Convolutional neural networks (CNNs) have recently achieved state-of-the-art results for positron emission tomography (PET) imaging problems. However direct learning from input image to target image is challenging if the gap is large between two images. Previous studies have shown that CNN can reduce image noise, but it can also degrade contrast recovery for small lesions. In this work, a deep progressive learning (DPL) method for PET image reconstruction is proposed to reduce background noise and improve image contrast. DPL bridges the gap between low quality image and high quality image through two learning steps. In the iterative reconstruction process, two pre-trained neural networks are introduced to control the image noise and contrast in turn. The feedback structure is adopted in the network design, which greatly reduces the parameters. The training data come from uEXPLORER, the world’s first total-body PET scanner, in which the PET images show high contrast and very low image noise. We conducted extensive phantom and patient studies to test the algorithm for PET image quality improvement. The experimental results show that DPL is promising for reducing noise and improving contrast of PET images. Moreover, the proposed method has sufficient versatility to solve various imaging and image processing problems.
Investigating the role of pericytes in cerebral autoregulation: a modeling study
Authors: Milanovic Selena , Shaw Kira , Hall Catherine , Payne Stephen 
Published: April 2021

Abstract
The brain’s inability to store nutrients for more than a few seconds makes it one of the most tightly regulated systems in the body. Driven by metabolic demand, cerebral autoregulation (CA) ensures a constant cerebral blood flow (CBF) over a ±50% change in arterial blood pressure (ABP) from baseline. Recent evidence suggests that pericytes, contractile cells in the capillary bed, play a previously-ignored regulatory role. To elucidate the CA phenomenon, the role of oxygen metabolism, pericyte activity and neural signaling in CBF modulation were quantified. Driven by nutrient metabolism in the tissue and pressure sensitivity in the vasculature, the model introduced here successfully replicates CA. To highlight the role of different vessel sizes, vessels with a diameter above 1 mm were represented using a lumped parameter model while the microvasculature was illustrated as a branching tree network model. This novel approach elucidated the relationship between the microvasculature’s nutrient supply and arterial regulation. Capillary responses to local increases in neuronal activity were experimentally determined, showing that pericytes can increase the diameter of the adjacent vessel by 2.5% in approximately 1 s. Their response was quantified and included in the computational model as an active component of the capillary bed. To compare the efficacy model presented here to existing ones, four feedback mechanisms were tested. To simulate dynamic CBF regulation a 10% increase in ABP was imposed. This resulted in a 23.79%–34.33% peak increase in CBF, depending on the nature of the feedback mechanism of the model. The four feedback mechanisms that were studied significantly differ in the response time, ultimately highlighting that capillaries play a fundamental role in the rapid regulation of CBF. Conclusively, this study indicates that while pericytes do not greatly alter the peak CBF change, they play a fundamental role in the speed of regulation.
Radiation hardness studies of thin and low bulk resistivity LGADs
Authors: Jain Geetika , Jain Chakresh , Saumya Saumya , Agrawal Namrata , Bhardwaj Ashutosh , Ranjan Kirti 
Published: April 2021

Abstract
The low gain avalanche detector (LGAD), having a unique feature of built-in charge multiplication, is more efficient in terms of charge collection (CC) than the traditional silicon detector even after irradiation. However, a dramatic decrease in the charge multiplication beyond a fluence of 3 × 1014

n

eq

⋅

cm−2 is observed in the measurements. In the reported work, TCAD CC simulations are carried out on various physical and geometrical LGAD design parameters with the aim to understand and extend the radiation hardness capabilities. It is observed that a thin LGAD with low bulk resistivity may survive up to a fluence of 3 × 1015

n

eq

⋅

cm−2 for an optimal choice of p-well design. A detailed investigation including CC and leakage current validation with experimental data and 1D electric field profile, in support of optimizations performed, is also provided.
A cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion
Authors: Kan Junwu , Zhang Min , Wang Shuyun , Zhang Zhonghua , Zhu Yana , Wang Jin 
Published: April 2021

Abstract
Harvesting energy from the rotary environment to replace the conventional electrochemical batteries has gained considerable interest. Different from the existing rotation-induced energy harvesters based on the bidirectional deformation of piezoelectric vibrators, a novel cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion was presented and fabricated in this paper. The new piezoelectric rotary energy harvester (PREH) was characterized by the simultaneous realization of unidirectional deformation and limited amplitude for piezoelectric vibrators. To verify the feasibility of the proposed principle and design, a theoretical model was established based on Fourier series as well as superposition principle. Meanwhile, the influence of the system parameters on the response characteristic of the presented PREH were obtained by simulation. And then, the experiments of rotating speed response were performed to evaluate the energy harvesting performance in terms of the deformation and open-circuit voltage. Both simulation and experimental results showed that the amplitude of the piezo-cantilever could be limited by using the cam mechanism and there were obvious resonance peaks on the amplitude-rotary speeds curves. Thus, the relatively stable output voltage could be maintained over a broad rotating speed range. Also, the stable voltage increased with the increasing of cam lift, but the effective rotating speed range became narrow. With the increasing of the cam angle, the effective rotating speed bandwidth could be increased, whereas the self-locking phenomenon of the piezo-cantilever would occur when the angle was increased to some extent. Besides, the bandwidth could be adjusted by changing the number of exciting magnets and stiffness of cam system. Under the optimum matching parameters, the maximum power 10.88 mW was reached for the presented PREH.
A novel chiral metamaterial with multistability and programmable stiffness
Authors: Wang Jia-Xin , Yang Qing-Sheng , Wei Yu-Ling , Tao Ran 
Published: April 2021

Abstract
Chiral metamaterials are widely studied for their unique mechanical properties, but still have problems such as low stiffness and few available scenarios. Based on the tetra-chiral metamaterial, a type of metamaterial with programmable stiffness and multistability is designed in this paper. The stiffness of two-dimensional (2D) metamaterial can be adjusted programmatically by changing its geometric parameters. The equivalent elastic modulus and Poisson’s ratio were obtained by using an analytical solution and finite element method. Then the 2D metamaterials were extended to cylindrical tubes with multistability. The deformation patterns of the 2D metamaterials and cylindrical tubes with different geometric parameters were investigated. It is found that the cylindrical tubes can exhibit compression–torsion coupling and multistability deformation characteristics. This work can provide a valuable reference for designs of novel metamaterials with coupled deformation, as well as further expanding the field of application.
An approach for the design and validation of high frequency vibration energy harvesting devices
Authors: Munk David J , Ellul Ethan J G , Moss Scott D 
Published: April 2021

AbstractThe aim of this work is to explore a topology optimisation approach for the design of high frequency vibration energy harvesting devices capable of operating in the range of 1800–2600 Hz. The main objective of the approach is to develop an optimisation algorithm for tailoring the resonant behaviour of the cantilever energy harvesters to the dominant frequencies of the available vibrations present in a Bell 206B-1 Kiowa helicopter main rotor gearbox. Hence, the devices designed are to be operated in the high frequency, highly loaded, extreme environments commonly found on aircraft structures. A multi-physics model capable of predicting the performance of the developed cantilever energy harvesters is presented and the design optimisation problem is formulated and then solved with the bi-directional evolutionary structural optimisation method. Two designs were experimentally validated; one that is sensitive to a single mode in the range 1800–2600 Hz equipped with a single transducer having a 6.35 mm diameter and 0.5 mm thickness and the other sensitive to three modes in the same range equipped with two transducers. Output powers of 0.3–3.1 mW were measured, demonstrating the approach’s potential to design harvesters capable of powering many useful sensor types.
Microwave single-tone optomechanics in the classical regime
Authors: Golokolenov Ilya , Cattiaux Dylan , Kumar Sumit , Sillanpää Mika , Mercier de Lépinay Laure , Fefferman Andrew , Collin Eddy 
Published: April 2021

Abstract
We report on the quantitative experimental illustration of elementary optomechanics within the classical regime. All measurements are performed in a commercial dilution refrigerator on a mesoscopic drumhead aluminium resonator strongly coupled to a microwave cavity, using only strict single-tone schemes. Sideband asymmetry is reported using in-cavity microwave pumping, along with noise squashing and back-action effects. Results presented in this paper are analysed within the simple classical electric circuit theory, emphasizing the analogous nature of classical features with respect to their usual quantum description. The agreement with theory is obtained with no fitting parameters. Besides, based on those results a simple method is proposed for the accurate measurement of the ratio between microwave internal losses and external coupling.
Uniaxial strain induced symmetry lowering and valleys drift in MoS2
Authors: Jiang Cunyuan , Xiong Wen , Li Chong , Niu Chunyao , Wang Fei 
Published: April 2021

Abstract
The uniaxial strain is an effective way to change the symmetry of a crystal and thus tuning their electronic properties. In the present work, we elucidate the physical mechanism of the symmetry-broken-induced energy valleys drift in monolayer molybdenum disulfide. When the uniaxial strain reduces the rotational symmetry of valleys from C

3
to C

1
and an in-plane electric field breaks the balance of electron distribution of valleys, the valley dipole can survive readily and quantum nonlinear Hall effect might be realized. Our work offers key insights for understanding the uniaxial strain induced valleys drift in monolayer MoS2, which is critical to precisely control the valleytronics properties of two-dimensional materials.
Uncovering double-stripe and plaquette antiferromagnetic states in the one-band Hubbard model on a frustrated square lattice
Authors: Ruan Ze , Jiang Xiu-Cai , Song Ze-Yi , Zhang Yu-Zhong 
Published: April 2021

Abstract
Groundstate magnetism of the one-band Hubbard model on the frustrated square lattice where both nearest-neighbour t
1 and next-nearest-neighbour t
2 hoppings are considered at half-filling are revisited within mean field approximation. Two new magnetic phases are detected at intermediate strength of Hubbard U and relative strong frustration of t
2/t
1, named double-stripe and plaquette antiferromagnetic states, both of which are metallic and stable even at finite temperature and electron doping. The nature of the phase transitions between different phases and the properties of the two new states are analyzed in detail. Our results of various magnetic states emerging from geometric frustration in the minimal model suggests that distinct antiferromagnetism observed experimentally in the parent states of two high-T
c superconducting families, i.e. cuprates and iron-based superconductors, may be understood from a unified microscopic origin, irrespective of orbital degrees of freedom, or hoppings further than next-nearest neighbor, etc.
Improved ammonia vapor sensing properties of Al-doped ZnO nanoparticles prepared by sol-gel process
Authors: Poul Raj I Loyola , Gobalakrishnan S , Praseetha P K , Chidhambaram N , Saravanakumar S , Ganesh V , AlFaify S , Algarni H , Yahia I S 
Published: April 2021

Abstract
Aluminium-doped ZnO nanoparticles were synthesized using the simple and cost-effective sol-gel route. Their structural, morphological, optical, and ammonia vapor sensing properties were compared with the pristine ZnO sample. The x-ray diffraction results showed that the pristine and Al-doped ZnO samples exhibit a hexagonal structure with the P63mc space group. A detailed structural investigation was carried through the Rietveld refinement technique. The decrease in crystallite size and the increasing nature of the sample’s microstrain were observed through the Williamson-Hall (W-H) analysis. 1-D, 2-D, and 3-D electron density distribution in a single unit cell of ZnO nanoparticles were studied with the maximum entropy method and it is confirmed that the ionic nature of the Zn-O bond increases by Al doping. The surface morphology of the samples was altered significantly after the addition of aluminum with ZnO. Aluminium doping causes a notable bandgap broadening in the ZnO nanostructures. A momentous enhancement of ammonia detection sensitivity of 129% at 25 ppm was observed for the ZnO:Al(3%) sample and its response time is greater than the other tested samples. Further, ZnO:Al(3%) sample exhibits the best response and recovery time of 28 and 8 s, respectively. It has also shown a stable ammonia vapor sensing ability for five consecutive cycles.
Investigation of new waves in chemical engineering
Authors: Abdelrahman Mahmoud A E , Refaey H A , Alharthi Mathkar A 
Published: April 2021

Abstract
Modelling of wave motion and propagation characteristics of waves is of great significant in chemical engineering. Waves are the major source of chemical actions in various real life applications. We apply an efficacious solver to give exact traveling wave solutions of the Hirota-maccari model. This solver introduces closed-form wave structures of the solutions. The traveling wave solutions are expressed by hyperbolic function solutions. These solutions may be applicable for some real life problems in chemical engineering, biological engineering, plasma physics and etc. Some two and three dimensional graphics are plotted for certain parameter values to describe the propagation of traveling wave solutions. Finally, it is pondered that the proposed approach can also be applied to another sort of complex models.
Phase structures and transitions of quintessence surrounding RN black holes in a grand canonical ensemble *
Authors: Huang Yuchen , Jing Hongmei , Tao Jun , Yao Feiyu 
Published: April 2021

Abstract
Considering a grand canonical ensemble, we study the phase structures and transitions of RN black holes surrounded by quintessence dark energy on two different boundary conditions, namely AdS space and a Dirichlet wall. For AdS space, under the condition of fixed temperature and potential, as the temperature increases for lower potential, the black hole undergoes a first-order phase transition, while for higher potential, no phase transition occurs. There are two different regions in the parameter space. For the Dirichlet wall, on which the temperature and potential are fixed, the state parameter of quintessence

is analyzed in detail. Then, three different physically allowed regions in the parameter space of the black hole are well studied. As the temperature rises, first-order and second-order phase transitions may occur. In this case, there are nine regions in the parameter space, which is evidently distinct from the case of AdS space.
Coexistence of isospin I = 0 and I = 1 pairings in asymmetric nuclear matter *
Authors: Yan Yi-Jun , Shang Xin-Le , Dong Jian-Min , Zuo Wei 
Published: April 2021

Abstract
The coexistence of neutron-neutron (n-n), proton-proton (p-p), and neutron-proton (n-p) pairings is investigated by adopting an effective density-dependent contact pairing potential. These three types of pairings can coexist only if the n-p pairing is stronger than the n-n and p-p pairings for the isospin asymmetric nuclear matter. In addition, the existence of n-n and p-p pairs might enhance n-p pairings in asymmetric nuclear matter when the n-p pairing strength is significantly stronger than the n-n and p-p ones. Conversely, the n-p pairing is reduced by the n-n and p-p pairs when the n-p pairing interaction approaches n-n and p-p pairings.
Transcranial photobiomodulation changes topology, synchronizability, and complexity of resting state brain networks
Authors: Ghaderi Amir Hossein , Jahan Ali , Akrami Fatemeh , Moghadam Salimi Maryam 
Published: April 2021

Abstract

Objective. Transcranial photobiomodulation (tPBM) is a recently proposed non-invasive brain stimulation approach with various effects on the nervous system from the cells to the whole brain networks. Specially in the neural network level, tPBM can alter the topology and synchronizability of functional brain networks. However, the functional properties of the neural networks after tPBM are still poorly clarified. Approach. Here, we employed electroencephalography and different methods (conventional and spectral) in the graph theory analysis to track the significant effects of tPBM on the resting state brain networks. The non-parametric statistical analysis showed that just one short-term tPBM session over right medial frontal pole can significantly change both topological (i.e. clustering coefficient, global efficiency, local efficiency, eigenvector centrality) and dynamical (i.e. energy, largest eigenvalue, and entropy) features of resting state brain networks. Main results. The topological results revealed that tPBM can reduce local processing, centrality, and laterality. Furthermore, the increased centrality of central electrode was observed. Significance. These results suggested that tPBM can alter topology of resting state brain network to facilitate the neural information processing. On the other hand, the dynamical results showed that tPBM reduced stability of synchronizability and increased complexity in the resting state brain networks. These effects can be considered in association with the increased complexity of connectivity patterns among brain regions and the enhanced information propagation in the resting state brain networks. Overall, both topological and dynamical features of brain networks suggest that although tPBM decreases local processing (especially in the right hemisphere) and disrupts synchronizability of network, but it can increase the level of information transferring and processing in the brain network.
Benchmark of quasi-linear models against gyrokinetic single scale simulations in deuterium and tritium plasmas for a JET high beta hybrid discharge
Authors: Mariani A. , Mantica P. , Casiraghi I. , Citrin J. , Görler T. , Staebler G.M. , JET1 contributors EUROfusion 
Published: April 2021

Abstract
A benchmark of the reduced quasi-linear models QuaLiKiz and TGLF with GENE gyrokinetic simulations has been performed for parameters corresponding to a JET high performance hybrid pulse in deuterium. Given the importance of the study of such advanced scenarios in view of ITER and DEMO operations, the dependence of the transport on the ion isotope mass has also been assessed, by repeating the benchmark changing the ion isotope to tritium. TGLF agrees better with GENE on the linear spectra and the flux levels. However, concerning the isotope dependence, only QuaLiKiz reproduces the GENE radial trend of a basically gyro-Bohm (gB) scaling at inner radii and instead anti-gB at outer radii. The physics effects which are responsible of the antigB effect in GENE simulations have been singled out.