bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicon single-electron random number generator based on random telegraph signals at room temperature
Authors: Ibukuro Kouta , Liu Fayong , Husain Muhammad Khaled , Sotto Moïse , Hillier Joseph , Li Zuo , Tomita Isao , Tsuchiya Yoshishige , Rutt Harvey , Saito Shinichi
Published: November 2020

The need for hardware random number generators (HRNGs) that can be integrated in a silicon (Si) complementary-metal–oxide–semiconductor (CMOS) platform has become increasingly important in the era of the Internet-of-Things (IoT). Si MOSFETs exhibiting random telegraph signals (RTSs) have been considered as such a candidate for HRNG, though its application has been hindered by RTS’s variability and uncontrollable, unpredictable characteristics. In this paper, we report the generation and randomness evaluation of random numbers from RTSs in a Si single electron pump (SEP) device at room temperature. SEP devices are known to consistently produce RTSs due to a quantum dot electrically defined by multi-layer polycrystalline Si gates. Using RTSs observed in our devices, random numbers were extracted by a classifier supported by supervised learning, where part of data was used to train the classifier before it is applied to the rest to generate random numbers. The random numbers generated from RTSs were used as inputs for the Monte Carlo method to calculate the values of π, and the distribution was compared against the result obtained from the Mersenne Twister, a representative pseudo-random number generator (PRNG), under the same condition. π was estimated more than 80 000 times, and the distribution of the estimated values has a central value of 3.14 with a variance of 0.273, which is only twice as large as the result from PRNG. Our result paves a way to fully electronic CMOS compatible HRNGs that can be integrated in a modern system-on-a-chip in IoT devices.
Stability analysis of flow of active extensile fibers in confined domains
Authors: Zhao Longhua , Yao Lingxing , Golovaty Dmitry , Ignés-Mullol Jordi , Sagués Francesc , Carme Calderer M.
Published: November 2020

In this article, we study shear flow of active extensile filaments confined in a narrow channel. They behave as nematic liquid crystals that we assumed are governed by the Ericksen–Leslie equations of balance of linear and angular momentum. The addition of an activity source term in the Leslie stress captures the role of the biofuel prompting the dynamics. The dimensionless form of the governing system includes the Ericksen, activity, and Reynolds numbers together with the aspect ratio of the channel as the main driving parameters affecting the stability of the system. The active system that guides our analysis is composed of microtubules concentrated in bundles, hundreds of microns long, placed in a narrow channel domain, of aspect ratios in the range between 10−2 and 10−3 dimensionless units, which are able to align due to the combination of adenosine triphosphate-supplied energy and confinement effects. Specifically, this work aims at studying the role of confinement on the behavior of active matter. It is experimentally observed that, at an appropriately low activity and channel width, the active flow is laminar, with the linear velocity profile and the angle of alignment analogous to those in passive shear, developing defects and becoming chaotic, at a large activity and a channel aspect ratio. The present work addresses the laminar regime, where defect formation does not play a role. We perform a normal mode stability analysis of the base shear flow. A comprehensive description of the stability properties is obtained in terms of the driving parameters of the system. Our main finding, in addition to the geometry and magnitude of the flow profiles, and also consistent with the experimental observations, is that the transition to instability of the uniformly aligned shear flow occurs at a threshold value of the activity parameter, with the transition also being affected by the channel aspect ratio. The role of the parameters on the vorticity and angular profiles of the perturbing flow is also analyzed and found to agree with the experimentally observed transition to turbulent regimes. A spectral method based on Chebyshev polynomials is used to solve the generalized eigenvalue problems arising in the stability analysis.
Extension of the LDA-1/2 method to the material class of bismuth containing III–V semiconductors
Authors: Liebscher Sven C. , Bannow Lars C. , Hader Jörg , Moloney Jerome V. , Koch Stephan W.
Published: November 2020

The local density approximation-1/2 method is employed in density functional theory calculations for the electronic structure of III–V dilute bismide systems. For the representative example of Ga(SbBi) with Bi concentrations below 10%, it is shown that this method works very efficiently, especially due to its reasonably low demand on computer memory. The resulting band structure and wavefunctions are used to compute the interaction matrix elements that serve as input to the microscopic calculations of the optical properties and intrinsic losses relevant for the optoelectronic applications of dilute bismides.
The performance of CIPSI on the ground state electronic energy of benzene
Authors: Loos Pierre-François , Damour Yann , Scemama Anthony
Published: November 2020

Following the recent work of Eriksen et al. [J. Phys. Chem. Lett. 11, 8922 (2020)], we report the performance of the configuration interaction using a perturbative selection made iteratively method on the non-relativistic frozen-core correlation energy of the benzene molecule in the cc-pVDZ basis. Following our usual protocol, we obtain a correlation energy of −863.4 mEh, which agrees with the theoretical estimate of −863 mEh proposed by Eriksen et al. [J. Phys. Chem. Lett. 11, 8922 (2020)] using an extensive array of highly accurate new electronic structure methods.
Turbulent boundary layer flow over two side-by-side wall-mounted cylinders: Wake characteristics and aerodynamic loads
Authors: Bhamitipadi Suresh Dhanush , Aju Emmanuvel Joseph , Jin Yaqing
Published: November 2020

The distinctive wake characteristics and aerodynamic loads of two side-by-side wall-mounted cylinders were experimentally studied under turbulent boundary layer flows with various gaps. Time-resolved particle image velocimetry was used to analyze the mean and unsteady wake features, whereas a high-resolution load cell was applied to measure the characteristics of lift and drag forces. The results show that the decrease in gap between two cylinders can effectively delay the wake recovery and suppress both the downwash and upwash flows near the top and bottom ends. Overall, with smaller gaps, the turbulence intensity near the top end becomes higher due to the stronger local velocity shear. The distribution of integral time scales indicates that the velocity fluctuations in the near wake region along the middle cylinder span are highly influenced by the local recirculation flows, whereas those near the top end are dominated by the mixing of boundary layer flows. By accounting the equivalent incoming velocity along the cylinder span, both lift and drag coefficient present a similar trend compared to the “infinite length” cylinder cases from previous works. Interestingly, different from cylinders with “infinite length,” no clear intermittency of aerodynamic loads was observed in the current work. This can be attributed to the suppression of two-dimensional vortex shedding due to the three-dimensional flow effects and strong background turbulence. The joint distribution of the lift and drag forces reveals that the lift fluctuations increase significantly with the growth of cylinder gaps, whereas that of drag force remains nearly constant.
The sound of silence in association football: Home advantage and referee bias decrease in matches played without spectators
Authors: Sors Fabrizio , Grassi Michele , Agostini Tiziano , Murgia Mauro
Published: November 2020

The home advantage and unconscious referee bias are two well‐documented phenomena in professional sports, especially in association football. Among the various factors determining them, the crowd noise is considered as one of the most relevant; yet, the majority of previous studies could not isolate its contribution. The possibility to study the effects of crowd noise – or, better, of its absence – in an ecological context was given by the matches played behind closed doors due to the COVID‐19 pandemic. The aim of the present study was to investigate whether home advantage and referee bias still occur (and to what extent) during matches played in absence of spectators. In particular, the focus was on the first and second divisions of the top four countries in the UEFA ranking, for a total of 841 matches behind closed doors. The hypothesis was that, if these phenomena are largely due to the effect of crowd noise, the absence of spectators should reduce their occurrence. Various parameters for each of the two phenomena were considered, and the analyses revealed a reduction of home advantage and the absence of referee bias. The results bring further support to the claim that, among all the factors contributing to home advantage and referee bias, crowd noise has a relevant role. Thus, spectators can significantly contribute to determine the dynamics and the outcomes of professional football matches.
On the classical and quantum Geroch group
Authors: Peraza Javier , Paternain Miguel , Reisenberger Michael
Published: November 2020

The Geroch group is an infinite dimensional transitive group of symmetries of classical cylindrically symmetric gravitational waves which acts by non-canonical transformations on the phase space of these waves. Here this symmetry is re derived and the unique Poisson bracket on the Geroch group which makes its action on the gravitational phase space Lie–Poisson is obtained. Two possible notions of asymptotic flatness are proposed that are compatible with the Poisson bracket on the phase space, and corresponding asymptotic flatness preserving subgroups of the Geroch group are defined which turn out to be compatible with the Poisson bracket on the group. A quantization of the Geroch group is proposed that is similar to, but distinct from, the

s
l

2

Yangian, and a certain action of this quantum Geroch group on gravitational observables is shown to preserve the commutation relations of Korotkin and Samtleben’s quantization of asymptotically flat cylindrically symmetric gravitational waves. The action also preserves three of the additional conditions that define their quantization. It is conjectured that the action preserves the remaining two conditions (asymptotic flatness and a unit determinant condition on a certain basic field) as well and is, in fact, a symmetry of their model. Our results on the quantum theory are formal, but a fairly detailed outline of how these results might be formulated rigorously within the framework of algebraic quantum theory is provided.
Non-oscillating power spectra in loop quantum cosmology
Authors: Navascués Beatriz Elizaga , Mena Marugán Guillermo A , Prado Santiago
Published: November 2020

We characterize in an analytical way the general conditions that a choice of vacuum state for the cosmological perturbations must satisfy to lead to a power spectrum with no scale-dependent oscillations over time. In particular, we pay special attention to the case of cosmological backgrounds governed by effective loop quantum cosmology and in which the Einsteinian branch after the bounce suffers a pre-inflationary period of decelerated expansion. This is the case more often studied in the literature because of the physical interest of the resulting predictions. In this context, we argue that non-oscillating power spectra are optimal to gain observational access to those regimes near the bounce where loop quantum cosmology effects are non-negligible. In addition, we show that non-oscillatory spectra can indeed be consistently obtained when the evolution of the perturbations is ruled by the hyperbolic equations derived in the hybrid loop quantization approach. Moreover, in the ultraviolet regime of short wavelength scales we prove that there exists a unique asymptotic expansion of the power spectrum that displays no scale-dependent oscillations over time. This expansion would pick out the natural Poincaré and Bunch–Davies vacua in Minkowski and de Sitter spacetimes, respectively, and provides an appealing candidate for the choice of a vacuum for the perturbations in loop quantum cosmology based on physical motivations.
The European master of science in nuclear fusion and engineering physics (FUSION-EP): 15 years of experience
Authors: Van Oost Guido , Beyer Peter , Devitre Alexis , Guirlet Rémy , Noterdaeme Jean-Marie , Thienpondt Hanne
Published: November 2020

The aim of the Erasmus Mundus Joint Master Degree (EMJMD) FUSION-EP is to provide a high-level research-oriented education and a well-integrated cultural experience within an international consortium of institutions leading the interdisciplinary field of magnetic fusion. The combined and harmonized teaching and research activities coordinated among eight partner universities in Belgium, Czech Republic, France, Germany and Spain offer a variety of competences in a field of crucial importance to the problem of world energy supply. Besides the ITER International Organization, there are 24 EU and non-EU academic and research associate partners. As the fusion community makes pace towards commercialization, the balance in research will shift from an academic-and-fundamental direction to a technology-and-industry-driven orientation. For this purpose, the programme offers two tracks: fusion science and fusion engineering. In addition, an advisory board keeps the curriculum in line with the research activities carried out by the associate and industrial partners. Internationalization, multidisciplinarity, and student mobility are inherent parts of the programme structure and philosophy. There exist several student and alumni initiatives leveraging meaningful connections within a global network. As a first step towards long-term sustainability, the consortium decided to transfer the programme coordination from Ghent University to Aix-Marseille University in 2019; the geographical, topical and professional proximity of ITER is expected to allow an optimal alignment of the programme with the professional needs of the emerging nuclear fusion industry.
Imaging multiphoton ionization dynamics of CH3I at a high repetition rate XUV free-electron laser
Authors: Cheng Yu-Chen , Oostenrijk Bart , Lahl Jan , Maclot Sylvain , Augustin Sven , Schmid Georg , Schnorr Kirsten , Meister Severin , Rompotis Dimitrios , Manschwetus Bastian , Redlin Harald , Bomme Cédric , Erk Benjamin , Rolles Daniel , Boll Rebecca , Olshin Pavel , Rudenko Artem , Meyer Michael , Johnsson Per , Moshammer Robert , Gisselbrecht Mathieu
Published: November 2020

XUV multiphoton ionization of molecules is commonly used in free-electron laser experiments to study charge transfer dynamics. However, molecular dissociation and electron dynamics, such as multiple photon absorption, Auger decay, and charge transfer, often happen on competing time scales, and the contributions of individual processes can be difficult to unravel. We experimentally investigate the Coulomb explosion dynamics of methyl iodide upon core–hole ionization of the shallow inner-shell of iodine (4d) and classically simulate the fragmentation by phenomenologically introducing ionization dynamics and charge transfer. Under our experimental conditions with medium fluence and relatively long XUV pulses (∼75 fs), we find that fast Auger decay prior to charge transfer significantly contributes to the charging mechanism, leading to a yield enhancement of higher carbon charge states upon molecular dissociation. Furthermore, we argue for the existence of another charging mechanism for the weak fragmentation channels leading to triply charged carbon atoms. This study shows that classical simulations can be a useful tool to guide the quantum mechanical description of the femtosecond dynamics upon multiphoton absorption in molecular systems.
From synchrotrons for XFELs: the soft x-ray near-edge spectrum of the ESCA molecule
Authors: Sorensen S L , Zheng X , Southworth S H , Patanen M , Kokkonen E , Oostenrijk B , Travnikova O , Marchenko T , Simon M , Bostedt C , Doumy G , Cheng L , Young L
Published: November 2020

A predictive understanding of soft x-ray near-edge absorption spectra of small molecules is an enduring theoretical challenge and of current interest for x-ray probes of molecular dynamics. We report the experimental absorption spectrum for the electron spectroscopy for chemical analysis (ESCA) molecule (ethyl trifluoroacetate) near the carbon 1s absorption edge between 285–300 eV. The ESCA molecule with four chemically distinct carbon sites has previously served as a theoretical benchmark for photoelectron spectra and now for photoabsorption spectra. We report a simple edge-specific approach for systematically expanding standard basis sets to properly describe diffuse Rydberg orbitals and the importance of triple excitations in equation-of-motion coupled-cluster calculations of the energy interval between valence and Rydberg excitations.
A comparative study of cold atmospheric plasma treatment, chemical versus physical strategy
Authors: Wang Qihui , Malyavko Alisa , Yan Dayun , Lamanna Olivia K , Hsieh Michael H , Sherman Jonathan H , Keidar Michael
Published: November 2020

To date, reactive oxygen species and reactive nitrogen species have been regarded as the key factors causing the observable cellular death of cold atmospheric plasma (CAP)-treated cancer cells. The chemical basis of the conventional CAP treatment highlights apoptosis as the main CAP-triggered cell death mechanism. However, we recently demonstrated a strong anti-melanoma effect based on physically-based CAP treatment. In this study, we compared the anti-cancer effect of chemically-based versus physically-based CAP treatment on four typical cancer cell lines in vitro. Three of these cancer cell lines were more sensitive to the physical factors in CAP than the chemical factors in CAP, while the fourth cell line followed the original trend of being more sensitive to chemical factors. This study demonstrated that the physically-based CAP treatment could be an effective anti-cancer approach, which might have a deep impact on the future application of CAP in medicine.
Tuning the optical response of a plasmonic T-shaped dimer with nanowire loads for improved SERS and sensing applications
Authors: Ren Mengke , Li Ran , Wang Junqiao , Fan Chunzhen , Ding Pei , Li Yan , He Jinna
Published: November 2020

Plasmonic nanostructures have important applications for surface-enhanced Raman chips, optical sensors, perfect absorbers, and so on. In this paper, we theoretically investigate the optical properties of a T-shaped dimer (TD) nanostructure and a TD with nanowire loads (TD/NL) nanostructure. By depositing the NLs around the TD, the optical property of the TD is significantly modified, and the extinction spectrum of composite TD/NL appears the splitting resonance peak and shows the asymmetric characteristic of Fano resonance due to the plasmon hybridization. Besides, a stronger electric field enhancement can be obtained in the composite TD/NL nanostructure, and the calculated results show the field enhancement effect of the dark mode in designed TD/NL nanostructure is three times than that in the TD nanostructure. Furthermore, the Fano resonance in TD/NL nanostructure reveals the narrow spectral linewidth and high quality factor, which is advantageous to optical refractive index sensors, and the corresponding sensing sensitivity is as high as 1083 nm RIU−1.
Density-dependent quark mass model revisited: thermodynamic consistency, stability windows and stellar properties
Authors: Backes Betânia C , Hafemann Eduardo , Marzola Isabella , Menezes Débora P
Published: November 2020

In this work a density-dependent quark model is revisited, its thermodynamic consistency checked and the stability window for absolutely stable quark matter obtained. The hypotheses of both pure quark matter with equal quark chemical potentials and stellar matter subject to chemical stability and charge neutrality are investigated. The parameters that appear in the density-dependent mass and satisfy the Bodmer–Witten conjecture are then used to compute the masses and radii of strange stars. We show that the obtained values are compatible with the recently observed massive stars.
Investigating the kinetics of the formation of a C Cottrell atmosphere around a screw dislocation in bcc iron: a mixed-lattice atomistic kinetic Monte-Carlo analysis
Authors: Candela R , Gelin S , Mousseau N , Veiga R G A , Domain C , Perez M , Becquart C S
Published: November 2020

We present a mixed-lattice atomistic kinetic Monte-Carlo algorithm (MLKMC) that integrates a rigid-lattice AKMC approach with the kinetic activation-relaxation technique (k-ART), an off-lattice/self-learning AKMC. This approach opens the door to study large and complex systems adapting the cost of identification and evaluation of transition states to the local environment. To demonstrate its capacity, MLKMC is applied to the problem of the formation of a C Cottrell atmosphere decorating a screw dislocation in α-Fe. For this system, transitions that occur near the dislocation core are searched by k-ART, while transitions occurring far from the dislocation are computed before the simulation starts using the rigid-lattice AKMC. This combination of the precision of k-ART and the speed of the rigid-lattice makes it possible to follow the onset of the C Cottrell atmosphere and to identify interesting mechanisms associated with its formation.
Antiferromagnetism, charge ordering and stretched Ni–O bond in Ln4Ni3O8 (Ln = La, Nd)
Authors: Fan Xinwei , Wen Hai-Hu
Published: November 2020

Superconductivity was recently observed in Sr-doped NdNiO2 film after a long pursuit, which inspires us to investigate another Ruddlesden–Popper-based nickelate Nd4Ni3O8 which may hold an antiferromagnetic order and a charge stripe order. Through ab initio calculations, we find that the obtained results turn out to be similar to those of La4Ni3O8. However, we propose that Ni1+ ions in the charge stripe order observed in La4Ni3O8 are in fact antiferromagnetically coupled through a twofold double-exchange mediated by the intermediate Ni2+ ion and the stretched Ni1+–O bond. Under high pressure, the extension of the stretched Ni1+–O bond is not favored and the system will be pushed into a meta-stable insulating state. Our picture can successfully explain the temperature dependence of resistivity under high pressure of La4Ni3O8, and shows also consistency with the insulating behavior of Nd4Ni3O8 observed in recent experiment. Considering a +1.33 average valence of Ni in Nd4Ni3O8, which is very close to that of the Sr-doped NdNiO2, our results support the earlier proposal that a possible way leading to metallicity and even superconductivity is to suppress the existing antiferromagnetism and charge ordering.
Singular self-energy for itinerant electrons in a dilute Ising spin bath
Authors: Fortin Jean-Yves
Published: November 2020

We consider itinerant spinless electrons moving as defects in a dilute two-dimensional Ising spin system, leading to an effective interaction mediated by spin fluctuations. Coupled self-consistent equations are analyzed after expressing the spin and fermion operators in terms of Grassmann variables. The effective mass, density of states, and specific heat are evaluated. We found that at low temperature and low electron density the effective mass is reduced, whereas in the critical region it sharply diverges. At higher temperature, the fermions behave like a Fermi liquid with a small enhanced mass.
Staphylococcus aureus biofilm eradication by the synergistic effect exerted by PEG-coated silicon dots immobilized in silica films and light irradiation
Authors: Gonik Eduardo , Rodríguez Sartori Damián , David Gara Pedro , Miñán Alejandro , Fernández Lorenzo de Mele Mónica , Gonzalez Mónica C
Published: November 2020

Immobilization of PEG-covered silicon dots, PEGSiDs, on glass substrates was performed following a simple strategy involving particle embedding by a sol-gel process forming a silica film on glass slides. The obtained films, denoted as fSiO
x
-PEGSiD, constitute a water-wettable, strongly supported, photoluminescent glass coating. The films showed high capacity for photosensitizing singlet oxygen (1O2) in the UVA when immersed in water. Staphylococcus aureus colonies formed on fSiO
x
-PEGSiDs modified glasses revealed the inhibition of bacterial adhesion and bacterial growth leading to the formation of loosely-packed and smaller S. aureus colonies. Upon 350 nm light irradiation of the biofilmed fSiO
x
-PEGSiDs -modified glasses, S. aureus growth was inhibited and bacteria killed reducing the number of living bacteria by three orders of magnitude. Eradication of attached bacteria was achieved by the synergistic effect exerted by a less adherent fSiO
x
-PEGSiDs surface that inhibits biofilm formation and the ability of the surface to photosensitize 1O2 to kill bacteria.
Tuning the electronic properties of highly anisotropic 2D dangling-bond-free sheets from 1D V2Se9 chain structures
Authors: Lee Weon-Gyu , Sung Dongchul , Lee Junho , Chung You Kyoung , Kim Bum Jun , Choi Kyung Hwan , Lee Sang Hoon , Jeong Byung Joo , Choi Jae-Young , Huh Joonsuk
Published: November 2020

True one-dimensional (1D) van der Waals materials can form two-dimensional (2D) dangling-bond-free anisotropic surfaces. Dangling bonds on surfaces act as defects for transporting charge carriers. In this study, we consider true 1D materials to be V2Se9 chains, and then the electronic structures of 2D sheets composed of true 1D V2Se9 chains are calculated. The (010) plane has indirect bandgap with 0.757 eV (1.768 eV), while the (111̅) plane shows a nearly direct bandgap of 1.047 eV (2.118 eV) for DFT-D3 (HSE06) correction, respectively. The (111̅) plane of V2Se9 is expected to be used in optoelectronic devices because it contains a nearly direct bandgap. Partial charge analysis indicates that the (010) plane exhibits interchain interaction is stronger than the (111̅) plane. To investigate the strain effect, we increased the interchain distance of planes until an indirect-to-direct bandgap transition occurred. The (010) plane then demonstrated a direct bandgap when interchain distance increased by 30%, while the (111̅) plane demonstrated a direct bandgap when the interchain distance increased by 10%. In mechanical sensors, this change in the bandgap was induced by the interchain distance.
Hollow and mesoporous lipstick-like nitrogen-doped carbon with incremented catalytic activity for oxygen reduction reaction
Authors: Zhang Ge , Zhou Jia , Liu Jiang , Ma Tian , Chen Yu , Xu Chunli
Published: November 2020

Hollow structure and pore size are considered to be crucial to the performance of nitrogen-doped carbon materials. In this paper, a lipstick-like hollow and mesoporous nitrogen-doped carbon (HNC-1000) material is prepared using a bottom-up template participation strategy. The images by scanning electron microscopy and transmission electron microscopy show that the precursor ZnO particles, the intermediate ZnO@ZIF-8 core–shell particles, and the target HNC-1000 particles all maintain a lipstick-like morphology, and HNC-1000 is a hollow nitrogen-doped carbon material. The specific surface area and pore size analyses show that the synthesized HNC-1000 has a very rich mesoporous structure with Vmeso+macro/Vtotal of 94.8% and mean mesopore size at 13.67 nm. X-ray photoelectron spectroscopy results show that the nitrogen in the catalyst HNC-1000 is mainly pyridine nitrogen and graphite nitrogen. The prepared HNC-1000 has excellent ORR catalytic activity with onset potential (0.98 V versus RHE), half-wave potential (0.85 V versus RHE), and limiting current density (5.51 mA cm−2), which is comparable to that of commercial Pt/C (20 wt%) and superior to NC-1000 derived from pristine ZIF-8. HNC-1000 also has good stability and strong methanol tolerance, which is superior to commercial Pt/C catalyst. The improved performance of HNC-1000 is attributed to its hollow and mesoporous morphology. These findings demonstrate a stratage for the rational design and synthesis of practical electrocatalysts.
Segmentation and classification of thyroid follicular neoplasm using cascaded convolutional neural network
Authors: Yang Bailin , Yan Meiying , Yan Zaoming , Zhu Changrui , Xu Dong , Dong Fangfang
Published: November 2020

In this paper, we present a segmentation and classification method for thyroid follicular neoplasms based on a combination of the prior-based level set method and deep convolutional neural network. The proposed method aims to discriminate thyroid follicular adenoma (TFA) and follicular thyroid carcinoma (FTC) in ultrasound images. In their appearance, these two kinds of tumours have similar shapes, sizes and contrasts. Therefore, it is difficult for even ultrasound specialists to distinguish them. Because of the complex background in thyroid ultrasound images, before distinguishing TFA and FTC, we need to segment the lesions from the whole image for each patient. The main challenge of segmentation is that the images often have weak edges and heterogeneous regions. The main issue of classification is that the accuracy depends on the features extracted from the segmentation results. To solve these problems, we conduct the two tasks, i.e. segmentation and classification, by a cascaded learning architecture. For segmentation, to obtain more accurate results, we exploit the Res-U-net framework and the prior-based level set method to enhance their respective abilities. Then, the classification network is trained by sharing shallow layers of the segmentation network. Testing the proposed method on real patient data shows that it is able to segment the lesion areas in thyroid ultrasound images with a Dice score of 92.65% and to distinguish TFA and FTC with a classification accuracy of 96.00%.
Dense feature-based motion estimation in MV fluoroscopy during dynamic tumor tracking treatment: preliminary study on reduced aperture and partial occlusion handling
Authors: Serpa Marco , Bert Christoph
Published: November 2020

Quality assurance solutions to complement available motion compensation technologies are central for their safe routine implementation and success of treatment. This work presents a dense feature-based method for soft-tissue tumor motion estimation in megavoltage (MV) beam’s-eye-view (BEV) projections for potential intra-treatment monitoring during dynamic tumor tracking (DTT). Dense sampling and matching principles were employed to track a gridded set of features landmarks (FLs) in MV-BEV projections and estimate tumor motion, capable to overcome reduced field aperture and partial occlusion challenges. The algorithm’s performance was evaluated by retrospectively applying it to fluoroscopic sequences acquired at ∼2 frames s−1 (fps) for a dynamic phantom and two lung stereotactic body radiation therapy (SBRT) patients treated with DTT on the Vero SBRT system. First, a field-specific train image is initialized by sampling the tumor region at, S, pixel intervals on a grid using a representative frame from a stream of query frames. Sampled FLs are locally characterized in the form of descriptor vectors and geometric attributes representing the target. For motion tracking, subsequent query frames are likewise sampled, corresponding feature descriptors determined, and then patch-wise matched to the training set based on their descriptors and geometric relationships. FLs with high correspondence are pruned and used to estimate tumor displacement. In scenarios of partial occlusions, position is estimated from the set of correctly (visible) FLs on past observations. Reconstructed trajectories were benchmarked against ground-truth manual tracking using the root-mean-square (RMS) as a metric of positional accuracy. A total of 19 fluoroscopy sequences were analyzed. This included scenarios of field aperture obstruction during three-dimensional conformal, as well as step-and-shoot intensity modulated radiotherapy (IMRT) delivery assisted with DTT. The algorithm resolved target motion satisfactorily. The RMS was <1.2 mm and <1.8 mm for the phantom and the clinical dataset, respectively. Dense tracking showed promising results to overcome localization challenges at the field penumbra and partial obstruction by multi-leaf collimator (MLC). Motion retrieval was possible in ∼66% of the control points studied. In addition to MLC obstruction, changes in the external/internal breathing dynamics and baseline drifts were a major source of estimation bias. Dense feature-based tracking is a viable alternative. The algorithm is rotation-/scale-invariant and robust to photometric changes. Tracking multiple features may help overcome partial occlusion challenges by the MLC. This in turn opens up new possibilities for motion detection and intra-treatment monitoring during IMRT and potentially VMAT.
Pulse length selection for optimizing the accelerated ion flux fraction of a bipolar HiPIMS discharge
Authors: Viloan Rommel Paulo B. , Zanáška Michal , Lundin Daniel , Helmersson Ulf
Published: November 2020

The effect on the energy distributions of metal and gas ions in a bipolar high-power impulse magnetron sputtering (HiPIMS) discharge as the negative and positive pulse lengths are altered are reported. The results presented demonstrate that the selection of the pulse lengths in a HiPIMS discharge is important in optimizing the amount of accelerated ions. A short enough negative pulse is needed so that ions do not escape to the substrate before being accelerated by the positive pulse that follows the main negative HiPIMS pulse. The length of the positive pulse should also be long enough to accelerate the majority of the ions, but a too long positive pulse depletes the process chamber of electrons so much that it makes it difficult to initiate the next HiPIMS pulse. When pulse lengths of negative and positive pulses are properly selected, the fraction of ions, both metal and gas, accelerated by the positive pulse voltage is close to 100%.
Recent trends in piezoelectric actuators for precision motion and their applications: a review
Authors: Mohith S , Upadhya Adithya R , Navin Karanth P , Kulkarni S M , Rao Muralidhara
Published: November 2020

The need for precision positioning applications has enormously influenced the research and development towards the growth of precision actuators. Over the years, piezoelectric actuators have significantly satisfied the requirement of precision positioning to a greater extent with the capability of broad working stroke, high-accuracy, and resolution (micro/nano range) coupled with the advantage of faster response, higher stiffness, and actuation force. The present review intends to bring out the latest advancement in the field of piezoelectric actuator technology. This review brings out the specifics associated with the development of materials/actuators, the working principles with different actuation modes, and classifications of the piezoelectric actuators and their applications. The present article throws light on the design, geometrical features, and the performance parameters of various piezoelectric actuators right from unimorph, bimorph, and multilayer to the large displacement range actuators such as amplified actuators, stepping actuators with relevant schematic representations and the quantitative data. A comparative study has been presented to evaluate the pros and cons of different piezoelectric actuators along with quantitative graphical comparisons. An attempt is also made to highlight the application domains, commercial and future prospects of technology development towards piezoelectric actuators for precision motion applications. The organization of the paper also assists in understanding the piezoelectric materials applicable to precision actuators. Furthermore, this paper is of great assistance for determining the appropriate design, application domains and future directions of piezoelectric actuator technology.
A new generalized θ-conformable calculus and its applications in mathematical physics
Authors: Hyder Abd-Allah , Soliman Ahmed H
Published: November 2020

In this work, a new generalized concept of conformable derivative is given and named generalized θ–conformable derivative (GTCD). Several properties are studied such as the chain rule, the quotient rule, the product rule, the Rolle’s theorem, the mean value theorem and the fundamental theorems of calculus. Also, the geometrical and physical interpretations of the GTCD are presented. It is very easy to see that the GTCD is comprehensive and includes many past derivatives as special cases. An application of the generalized θ–conformable derivatives (GTCDs) is presented along with the

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′

/

G
,
1

/

G

–approach to construct a novel gathering of exact solutions for the nonlinear (2+1)-dimensional biological population model (BPM) involving GTCDs. Moreover, some comparisons and graphical interpretations are given to support our results related to the (2+1)-dimensional BPM. All acquired results regarding the GTCD show its validity to applying in many problems in mathematical physics, engineering, biology and others.
Bio-inspired compact swarms of unmanned aerial vehicles without communication and external localization
Authors: Petráček Pavel , Walter Viktor , Báča Tomáš , Saska Martin
Published: November 2020

This article presents a unique framework for deploying decentralized and infrastructure-independent swarms of homogeneous aerial vehicles in the real world without explicit communication. This is a requirement in swarm research, which anticipates that global knowledge and communication will not scale well with the number of robots. The system architecture proposed in this article employs the ultraviolet direction and ranging technique to directly perceive the local neighborhood for direct mutual localization of swarm members. The technique allows for decentralization and high scalability of swarm systems, such as can be observed in fish schools, bird flocks, or cattle herds. The bio-inspired swarming model that has been developed is suited for real-world deployment of large particle groups in outdoor and indoor environments with obstacles. The collective behavior of the model emerges from a set of local rules based on direct observation of the neighborhood using onboard sensors only. The model is scalable, requires only local perception of agents and the environment, and requires no communication among the agents. Apart from simulated scenarios, the performance and usability of the entire framework is analyzed in several real-world experiments with a fully-decentralized swarm of unmanned aerial vehicles (UAVs) deployed in outdoor conditions. To the best of our knowledge, these experiments are the first deployment of decentralized bio-inspired compact swarms of UAVs without the use of a communication network or shared absolute localization. The entire system is available as open-source at https://github.com/ctu-mrs.
Flow turning effect and laminar control by the 3D curvature of leading edge serrations from owl wing
Authors: Muthuramalingam Muthukumar , Talboys Edward , Wagner Hermann , Bruecker Christoph
Published: November 2020

This work describes a novel mechanism of laminar flow control of straight and backward swept wings with a comb-like leading edge (LE) device. It is inspired by the LE comb on owl feathers and the special design of its barbs, resembling a cascade of complex 3D-curved thin finlets. The details of the geometry of the barbs from an owl feather were used to design a generic model of the comb for experimental and numerical flow studies with the comb attached to the LE of a flat plate. Due to the owls demonstrating a backward sweep of the wing during gliding and flapping from live recordings, our examinations have also been carried out at differing sweep angles. The results demonstrate a flow turning effect in the boundary layer inboards, which extends downstream in the chordwise direction over distances of multiples of the barb lengths. The inboard flow-turning effect described here, counter-acts the outboard directed cross-span flow typically appearing for backward swept wings. This flow turning behaviour is also shown on SD7003 airfoil using precursory LES investigations. From recent theoretical studies on a swept wing, such a way of turning the flow in the boundary layer is known to attenuate crossflow instabilities and delay transition. A comparison of the comb-induced cross-span velocity profiles with those proven to delay laminar to turbulent transition in theory shows excellent agreement, which supports the laminar flow control hypothesis. Thus, the observed effect is expected to delay transition in owl flight, contributing to a more silent flight.
A new estimate for oceanic precipitation amount and distribution using complementary precipitation observations from space and comparison with GPCP
Authors: Behrangi Ali , Song Yang
Published: November 2020

This study produces near global (81°S/N) spatial and seasonal maps of oceanic precipitation rate using complementary information from advanced precipitation measuring sensors and provides an independent reference that can be used to assess current precipitation products. The Merged CloudSat, Tropical Rainfall Measuring Mission (TRMM), and Global Precipitation Measurement (GPM) (MCTG) estimate uses light rainfall and snowfall estimates from CloudSat and merges them with the combined radar-radiometer products available from the TRMM and the GPM mission. The merging process is performed at grid level and for each season, so maps of the merged products can be constructed. MCTG was then compared with the most recent Global Precipitation Climatology Project (GPCP) product (V2.3) to identify regional, seasonal, and annual differences between the two products. Several areas of major differences were highlighted, among those are regions near 5°N/S, 20°N/S, 40°N/S and 60°N/S. These regions also show seasonal variations in the magnitude and exact location of the differences. The largest differences between GPCP and MCTG occur around 40°S and 60°S, showing an under- and overestimation of MCTG, respectively. Overall, MCTG suggests that GPCP underestimates the annual oceanic precipitation rate by 9.03%, while seasonal rates are underestimated by 7.14%, 9.71%, 9.96%, and 9.73% for winter, spring, summer, and fall, respectively. Such differences in global oceanic precipitation rates need to be considered in the future updates in water and energy budget calculations and in future updates of GPCP.
Caspian Sea is eutrophying: the alarming message of satellite data
Authors: Modabberi Anahita , Noori Roohollah , Madani Kaveh , Ehsani Amir Houshang , Danandeh Mehr Ali , Hooshyaripor Farhad , Kløve Bjørn
Published: November 2020

The competition over extracting the energy resources of the Caspian Sea together with the major anthropogenic changes in the coastal zones have resulted in increased pollution and environmental degradation of the sea. We provide the first evaluation of the spatiotemporal variation of chlorophyll-a (Chl-a) across the Caspian Sea. Using remotely sensed data from 2003 to 2017, we found that the Caspian Sea has suffered from a growing increase in Chl-a, especially in warmer months. The shallow parts of the sea, near Russia and Kazakhstan, especially where the Volga and Terek rivers discharge large nutrient loads (nitrogen- and phosphorus-rich compounds) into the sea, have experienced the highest variations in Chl-a. The Carlson’s trophic state index showed that during the study period, on average, about 12%, 26%, and 62% of the Caspian Sea’s area was eutrophic, mesotrophic, and oligotrophic, respectively. The identified trends reflect an increasing rate of environmental degradation in the Caspian Sea, which has been the subject of conflict among its littoral states that since the collapse of the Soviet Union have remained unable to agree on a legal regime for governing the sea and its resources.
Experimental investigation of Kramers–Kronig relations in chiral metasurfaces with reduced rotational symmetry
Authors: Singh Leeju , David Epstein Eliav , Cheskis Dima , Sternklar Shmuel , Gorodetski Yuri
Published: November 2020

We examine the Kramers–Kronig relations between the circular dichroism and the optical rotation dispersion in the k-space obtained from a chiral metasurface with a reduced rotational symmetry. We operate a leakage-radiation microscopy system to probe the near-field plasmonic modes and measure the polarization effects of the grating. By using our system we were able to capture and analyze the plasmonic modes at both air/gold and gold/glass interfaces. The k-space mapping of the chirality parameters allows us to fully analyze the optical activity of the metasurface. We experimentally find that the reduction in rotational symmetry affects the locality condition which unavoidably leads to the deviation from the Kramers–Kronig relation.
Phase transformation of a vortex beam in a liquid-based inferior mirage
Authors: Cisowski Claire M , Correia Ricardo R B
Published: November 2020

We study how a liquid-based inferior mirage, obtained by layering distilled water and ethanol, transforms the phase structure of a light beam possessing a helical wave front. An inferior mirage amounts for one total internal reflection, which effectively reverses the handedness of the wave front. We show that this transformation is accompanied by smooth unidirectional astigmatic changes and variations of the non-canonical strength of the phase singularity nested in the beam. A skew in the beam intensity distribution is observed where the phase singularity is inverted and allows the direct measurement of the topological charge of the beam. Freely propagating, partially inverted beams possessing spatially varying orbital fluxes can be obtained at the exit plane of the solution by adjusting the incidence conditions of the beam. This work lays the foundations for phase engineering of light beams in liquid-based optical mirages.
Two-dimensional materials applied for room-temperature thermoelectric photodetectors
Authors: Wang Jiaqi , Xie Zhemiao , Yeow John T W
Published: November 2020

Due to the practical demand in many fields, room-temperature photodetectors in mid/long-wavelength and terahertz ranges have attracted much attention. Photothermoelectric (PTE) detectors based on photothermal conversion and thermoelectric effect can realize ultra-broadband detection of a photon without external bias. In recent years, two-dimensional (2D) materials open up revolutionary opportunities in rapid and sensitive photodetection by virtue of their remarkable electronic and optical properties. Here, we provide a brief review of state-of-the-art photodetectors based on PTE effect and 2D materials. It is worth noting that emerging PTE detectors based on 2D materials, including graphene, transition metal dichalcogenides (TMDCs), black phosphorus (BP) and MXenes, are proposed systematically. Next, we will discuss the existing challenges and prospects in PTE detectors, followed by a conclusion of this review.
Fukushima spread plutonium far and wide
Authors: Cartlidge Edwin
Published: November 2020

Caesium was involved with carrying plutonium hundreds of kilometres away from the Fukushima Daiichi nuclear reactor, which could have implications for decommissioning, as Edwin Cartlidge reports
Bonds beyond the bounds of Earth
Authors: Glester Andrew
Published: November 2020

Proxima, the latest film by French screenwriter and director Alice Winocour, follows the final weeks on Earth for Sarah (Eva Green), an astronaut preparing for a 12-month stay on the International Space Station. Stunningly shot in part on location in Star City – the cosmonaut training centre in Russia – and in collaboration with the European Space Agency (ESA), the story transpires to be far more firmly rooted on Earth than it is about space.