bluuebunny/crossref_metadata_2025 huggingface dataset:
presença das multinacionais brasileiras em território chinês
Authors: Leme Fleury Maria Tereza
Published: August 2021

Em um primeiro estágio, as empresas brasileiras percorreram trajetórias já conhecidas ao se internacionalizarem para a China, mas, em anos recentes, desbravaram novos caminhos.
riscos das doações não perenes
Authors: Gama Marina , Lana Jeferson
Published: August 2021

Para haver captura de valor, é necessário perenidade nas doações. para haver perenidade, é necessário estratégia.
Large-scale quality assessment of prokaryotic genomes with metashot/prok-quality
Authors: Albanese Davide , Donati Claudio
Published: August 2021

Metagenomic sequencing allows large-scale identification and genomic characterization. Binning is the process of recovering genomes from complex mixtures of sequence fragments (metagenome contigs) of unknown bacteria and archaeal species. Assessing the quality of genomes recovered from metagenomes requires the use of complex pipelines involving many independent steps, often difficult to reproduce and maintain. A comprehensive, automated and easy-to-use computational workflow for the quality assessment of draft prokaryotic genomes, based on container technology, would greatly improve reproducibility and reusability of published results. We present metashot/prok-quality, a container-enabled Nextflow pipeline for quality assessment and genome dereplication. The metashot/prok-quality tool produces genome quality reports that are compliant with the Minimum Information about a Metagenome-Assembled Genome (MIMAG) standard, and can run out-of-the-box on any platform that supports Nextflow, Docker or Singularity, including computing clusters or batch infrastructures in the cloud. metashot/prok-quality is part of the metashot collection of analysis pipelines. Workflow and documentation are available under GPL3 licence on GitHub.
Globalization of Tanka: How Twitter Contributes to Development of Traditional Japanese Poetry
Authors: Kensuke Koshida
Published: August 2021

Tanka poems are a representative type of classical Japanese poetry with a long history. Beginning as Waka, which were widely composed starting in the 7th century, today they continue to be produced by people of diverse backgrounds while retaining their ancient characteristics. In other words, tanka poems can be regarded as a valuable part of Japanese cultural heritage that are loved and enjoyed in contemporary Japan.

My paper focuses on the current state of modern tanka and the significance of tanka in contemporary society. In the processes of globalization, the Internet (for example, Twitter and other social media) is becoming the main platform for creating and reading modern tanka. Twitter, in particular, has become the largest such forum and features tanka from all over the world. And more, there are some poets who use Twitter as their main place of work. A similar phenomenon is seen in other social media, and it can be said that social media has had a great impact on modern tanka.

The main conclusion of my paper is that social media has become a global tool for tanka which has been passed as a tradition shaped over centuries from one generation to another. As a result, the traditional framework of social exclusiveness of this poetic genre from ancient times has been removed, leaving an environment where people of any social status can easily create and read tanka and join the tanka community. In other words, because of the impact of social media, the tanka community today has become a melting pot of a wide variety of people, with poets now coming from very different backgrounds.

This indicates that tanka’s character as an aspect of Japan’s cultural heritage is changing, especially among young generations who use social media in their daily life, while still retaining some of its traditional attributes. Tanka is an important genre in Japanese literature, itself a core element of Japanese culture, while possessing, at the same time, the potential to be shared all over the world. Therefore, research on tanka on a global scale offers a potentially significant contribution to Japanese studies.
Irena Krzywicka and Hiratsuka Raichō – Life, Activity, Work
Authors: Prażuch Zofia
Published: August 2021

The main aim of this article is to draw a comparison between two female figures – Hiratsuka Raichō from Japan and Irena Krzywicka from Poland. Despite the fact that these two women lived in different countries and came from totally different cultural backgrounds, they fought for a better future for women. Both Irena Krzywicka and Hiratsuka Raichō lived during a difficult time of war and were witnesses to dynamic political and social changes in their respective countries. As in historical terms, this was the very beginning of feminist movement, both in Poland and Japan, their lives and activities fall within the period of the first wave of feminism.
Welfare Implications of Congestion Pricing: Evidence from SFpark
Authors: Feldman Pnina , Li Jun , Tsai Hsin-Tien
Published: August 2021

Problem definition: Congestion pricing offers an appealing solution to urban parking problems—charging varying rates across time and space as a function of congestion may shift demand and improve allocation of limited resources. It aims to increase the accessibility of highly desired public goods and to reduce traffic caused by drivers who search for available parking spaces. At the same time, complex policies make it harder for consumers to make search-based decisions. We investigate the effect of congestion pricing on consumer and social welfare. Academic/practical relevance: This paper contributes to the theory and practice of the management of scarce resources in the public sector, where welfare is of particular interest. Methodologically, we contribute to the literature on structural estimation of dynamic spatial search models. Methodology: Using data from the City of San Francisco, both before and after the implementation of a congestion-pricing parking program, SFpark, we estimate the welfare implications of the policy. We use a dynamic spatial search model to structurally estimate consumers’ search costs, distance disutilities, price sensitivities, and trip valuations. Results: We find that congestion pricing increases consumer and social welfare by more than 4% and reduces search traffic by more than 10% in congested regions compared with fixed pricing. However, congestion pricing may hurt welfare in uncongested regions, in which the focus should be on increasing utilization. Moreover, an unnecessarily complex congestion-pricing scheme makes it difficult for consumers to make search-based decisions. We find that a simpler pricing policy may yield higher welfare than a complex one. Lastly, compared with a policy that imposes limits on parking durations, congestion pricing increases social welfare by allocating the scarce resource to consumers who value it most. Managerial implications: The insights from SFpark offer important implications for local governments that consider alternatives for managing parking and congestion and for public-sector managers who evaluate the tradeoffs between approaches to manage public resources.
From Arms to Trees: Opportunity Costs and Path Dependence and the Exploration-Exploitation Tradeoff
Authors: Levinthal Daniel A.
Published: August 2021

The literature on the exploration-exploitation tradeoff has anchored on the n-armed bandit problem as its canonical formal representation. This structure, however, omits a fundamental property of evolutionary dynamics. Contrary to a bandit formulation, foregoing an opportunity may negate the possibility of engaging in that opportunity in the future, not just modifying the beliefs about the attractiveness of engaging in that opportunity. Thus, the bandit structure only incorporates path dependence with respect to beliefs and not with regard to capabilities as our usual conceptions of dynamics of learning and capabilities would suggest. Furthermore, the consideration of opportunity cost is rather static and does not address the dynamic unfolding of opportunity structures. The nature of path dependence and opportunity costs are used to frame many of our existing conceptualizations of search processes and firm dynamics, including bandit models, real options, pivoting, the “secretary problem,” and “island” models of firm diversification. The discussion points to the need to develop canonical models of what evolutionary biologists’ term phylogenetic trees and opens up a set of new questions, such as what is the degree of parallelism of trajectories that is possible within an organization, what is the fecundity of different trajectories in terms of likelihood of branching possibilities arising, and how are these latent branching opportunities accessed?
The Heterogeneous Effects of P2P Ride-Hailing on Traffic: Evidence from Uber’s Entry in California
Authors: Dhanorkar Suvrat , Burtch Gordon
Published: August 2021

Despite their promise, popularity, and rapid growth, the transit implications of ride-hailing platforms (e.g., Uber, Lyft) are not altogether clear. On the one hand, ride-hailing services can provide pooling (i.e., traffic reductions) advantages by efficiently matching customer demand (i.e., trips) with resources (i.e., cars) or by facilitating car-sharing. On the other hand, ride-hailing may also induce extra travel because of increased convenience and travel mode substitution, which may create crowding (i.e., traffic increases). We seek to reconcile these divergent perspectives here, exploring the heterogeneous determinants of ride-hailing’s effects. Taking advantage of Uber’s staggered entry into various geographic markets in California, we execute a regression-based difference-in-differences analysis to estimate the impact of ride-hailing services on traffic volumes. Using monthly micro data from more than 9,000 vehicle detector station units deployed across California, we show that Uber’s effect (either pooling or crowding) on traffic depends on various contextual factors. We find some evidence of pooling effects on weekdays; however, Uber’s entry leads to significant crowding effects on weekends. Furthermore, the crowding effect is amplified on interior roads and in areas characterized by high population density. Although ride-hailing seems to have a substitution effect on public transportation, we find ride-hailing services may have a complementary effect for carpooling users. Finally, we show that premium ride-hailing services (e.g., Uber Black) almost exclusively lead to a crowding effect. We conduct a battery of robustness tests (e.g., propensity score matching, alternative treatment approaches, placebo tests) to ensure the consistency of our findings.
Young children's sleep difficulties: Are mainstream research findings supported by more recent evidence?
Authors: Sutton Carole
Published: August 2021

A substantial body of evidence about how to support parents with their child's sleep difficulties has been published and this can inform the practice of health visitors and others who work with the families concerned. However, does more recently published research in this field support or question the findings of mainstream studies? This article will examine how some recent studies do support and develop earlier evidence, while others open new fields of research, or challenge official guidance in new ways.
Hsa_circ_0066523 promotes the proliferation and osteogenic differentiation of bone mesenchymal stem cells by repressing PTEN
Authors: Xin Wei , Yuan Shuai , Wang Bo , Qian Qirong , Chen Yi
Published: August 2021

Aims

Circular RNAs (circRNAs) are a novel type of non-coding RNA that plays major roles in the development of diverse diseases including osteonecrosis of the femoral head (ONFH). Here, we explored the impact of hsa_circ_0066523 derived from forkhead box P1 (FOXP1) (also called circFOXP1) on bone mesenchymal stem cells (BMSCs), which is important for ONFH development.

Methods

RNA or protein expression in BMSCs was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot, respectively. Cell Counting Kit 8 (CCK8) and 5-ethynyl-2’-deoxyuridine (EdU) were used to analyze cell proliferation. Alkaline phosphatase (ALP) activity, ALP staining, and Alizarin Red S staining were employed to evaluate the osteoblastic differentiation. Chromatin immunoprecipitation (ChIP), luciferase reporter, RNA pull down, and RNA immunoprecipitation (RIP) assays were combined for exploring molecular associations.

Results

Circ_0066523 was upregulated in osteogenic induction process of BMSCs. Silencing circ_0066523 restrained the proliferation and osteogenic differentiation of BMSCs. Mechanistically, circ_0066523 activated phosphatidylinositol-4,5-bisphosphate 3-kinase / AKT serine/threonine kinase 1 (PI3K/AKT) pathway via recruiting lysine demethylase 5B (KDM5B) to epigenetically repress the transcription of phosphatase and tensin homolog (PTEN). Functionally, AKT signalling pathway agonist or PTEN knockdown counteracted the effects of silenced circ_0066523 on BMSC proliferation and differentiation.

Conclusion

Circ_0066523 promotes the proliferation and differentiation of BMSCs by epigenetically repressing PTEN and therefore activating AKT pathway. This finding might open new avenues for the identification of therapeutic targets for osteoblast differentiation related diseases such as ONFH. Cite this article: Bone Joint Res 2021;10(8):526–535.
Localized surface plasmon resonance-based biosensor on gold nanoparticles for Taenia solium detection
Authors: Arcas Ariadny S. , Jaramillo Lizeth , Costa Natália S. , Allil Regina Célia S. B. , Werneck Marcelo M.
Published: August 2021

This paper describes, for the first time to our knowledge, a fast-response and specific
biosensor for detection of Taenia solium, a parasite
responsible for neurocysticercosis disease that affects the central
nervous system. The biosensor is based on the localized surface
plasmon resonance (LSPR) technique on gold nanoparticles (AuNPs) in
colloidal suspension that were functionalized and activated with
antibodies to perform an immuno-capture effect. The AuNPs were
synthetized by Turkevich and seed-mediated growth methods. A variety
of concentrations of T. solium antigen
were added to test the detection and the dose-response profile. Small
antigen concentrations were detected indicating that the limit of
detection is lower than 0.1 µg/mL of antigen. The results demonstrate
the potential of the AuNPs LSPR biosensor as a clinical tool for
neurocysticercosis diagnostic.
Unsupervised learning polarimetric underwater image recovery under nonuniform optical fields
Authors: Yang Shilong , Qu Bowen , Liu Genshen , Deng Dingxuan , Liu Shiyuan , Chen Xiuguo
Published: August 2021

Turbid media will lead to a sharp decline in image quality. Polarization imaging is an effective method to obtain clear images in turbid media. In this paper, we propose an improved method that combines unsupervised learning and polarization imaging theory, which can be applied in a variety of nonuniform optical fields. We treat the background light as a spatially variable parameter, so we designed an end-to-end unsupervised generative network to inpaint the background light, which produces an adversarial loss with the discriminative network to improve the performance. And we use the angle of polarization to estimate the polarization parameters. The experimental results have demonstrated the effectiveness and generalization ability of our method. Compared with other works, our method shows a better real-time performance and has a lower cost in preparing the training dataset.
Efficient global stereo-matching method of general images under a long baseline based on baseline estimation
Authors: Li Jing , Li Zigang , Zhao Hong
Published: August 2021

For three-dimensional (3D) measurement of a large object, stereo matching needs to be done under a relatively long baseline in order to reduce the accumulated errors caused by the splicing process, but this brings new challenges to matching efficiency. The images under a short baseline have an advantage avoiding a very large disparity level that is usually presented in a large baseline to improve efficiency, whether the image pairs to be matched are of translation or rotation configuration. This paper mainly focuses on the general case existing for both, and the purpose is to efficiently execute a stereo matching in this scene based on short baseline estimation. A rectification method of three images used for baseline estimation is first studied to make the image planes become coplanar, which removes the vertical disparity. The three rectified images can form a stereo pair with a short baseline and the other one has a long baseline. Then the relationship that exists between disparities of a pixel on rectified stereo pairs with different baselines is deduced by considering the quantization error introduced in the projection and rectification. In this way, the disparity search range of a pixel on the rectified stereo pair with the long baseline is reduced from the usual hundreds of pixels to a few pixels predicted by its disparity with the short baseline, which greatly improves the calculation efficiency and makes it especially suitable for the 3D measurement of large objects. Experimental results are presented to demonstrate the efficiency and accuracy of the method.
Dual-logarithmic demodulation method application in a wide gas optical thickness range
Authors: Zhang Zhifeng , Chang Jun , Sun Jiachen , Zhang Qinduan , Fan Yongmei
Published: August 2021

Direct absorption spectroscopy (DAS) is an extremely practical and effective technology to detect gas concentration in site applications. Dual-beam subtraction is one of the most common demodulation methods in DAS, yet this method cannot solve the problem of absolute absorption curve nonlinearization in a wide optical thickness range. A real-time and practical dual-logarithmic demodulation method is proposed and proved to be robust when the optical thickness is much greater than linear region. Moreover, the error of optical thickness peak is only 1.18% between the dual-logarithmic demodulation system and simulation after correcting the dual-beam subtraction demodulation system under a 300 K, 1 atm, and 3 m absorption path. When the range of optical thickness peak of acetylene is from 0.0252 to 2.5335 at 1532.83 nm, the peak voltages always maintain satisfactory linearity (

R

-

s
q
u
a
r
e

=
0.9989

).
Compressive endoscopic imaging with complementary light modulation
Authors: Gao Weiwei , Mo Huixia , Wu Guohua , Yang Dongyue , Yin Longfei
Published: August 2021

We propose an effective endoscopic imaging method utilizing compressive sensing (CS) theory on the basis of complementary light modulation of a spatial light modulator. Both the simulated and the experimental results show that complementary compressive sensing (CCS) always needs less time to obtain better work than conventional CS with normal modulation at the same sampling rate. First, the speed of CCS is at least twice as fast as CS. Second, in comparison with CS, CCS can improve the signal-to-noise ratio of the reconstructed image by 49.7%, which indicates that this method is of great significance to endoscopic applications in terms of image fidelity and denoising performance.
Defect detection system for silicon solar panels under all-day irradiation
Authors: Wu Sheng , Zhang Yijun , Qian Yunsheng , Lang Yizheng , Yang Minjie , Sun Mohan
Published: August 2021

In terms of the shortcomings of defect detection based on the electroluminescence of conventional silicon solar panels, which can only be performed under darkroom conditions, a defect detection system that can work under the Sun with any irradiance in all weather is designed. The system electrifies solar panels through a modulated current source, uses high frame rate InGaAs area array detectors for image data acquisition, and transmits images via CameraLink. Using these image data as data sources, a defect display algorithm model is designed. Through experiments, it can effectively collect the defect information of solar panels within the range of 0.2 to

1300

W

/

m

2

of sunlight irradiance. Based on this, according to the relationship of the modulated phase difference between the defective points and the nondefective points found in the experiment, an enhancing algorithm for image saliency is proposed. The results show that this algorithm can reduce background interference in an effective way and improve the contrast of defects displayed under high irradiance.
Femtosecond laser-induced damage threshold of nematic liquid crystals at 1030  nm
Authors: Ramousse Loic , Chériaux Gilles , Claudet Cyrille , Jullien Aurélie
Published: August 2021

The laser-induced damage threshold (LIDT) of nematic liquid crystals is
investigated in the femtosecond regime at

≃
1030

n
m

. The thickness and breakdown of
freely suspended thin films (

≃
100

n
m

) of different mixtures (MLC2073,
MLC2132, and E7) is monitored in real time by spectral-domain
interferometry. The duration of laser pulses was varied from 180 fs to
1.8 ps for repetition rates ranging from single shot to 1 MHz. The
dependence of the LIDT with pulse duration suggests a damage mechanism
dominated by ionization mechanisms at low repetition rate and by
linear absorption at high repetition rate. In the single-shot regime,
LIDTs exceeding

1

J

/

c
m

2

are found for the three investigated
mixtures. The LIDT of polyvinyl alcohol is also investigated by the
same method.
Quantitative evaluation of the dynamic activity of HeLa cells in different viability states using dynamic full-field optical coherence microscopy
Authors: Park Soongho , Nguyen Thien , Benoit Emilie , Sackett Dan L. , Garmendia-Cedillos Marcial , Pursley Randall , Boccara Claude , Gandjbakhche Amir
Published: August 2021

Dynamic full-field optical coherence microscopy (DFFOCM) was used to characterize the intracellular dynamic activities and cytoskeleton of HeLa cells in different viability states. HeLa cell samples were continuously monitored for 24 hours and compared with histological examination to confirm the cell viability states. The averaged mean frequency and magnitude observed in healthy cells were 4.79±0.5 Hz and 2.44±1.06, respectively. In dead cells, the averaged mean frequency was shifted to 8.57±0.71 Hz, whereas the magnitude was significantly decreased to 0.53±0.25. This cell dynamic activity analysis using DFFOCM is expected to replace conventional time-consuming and biopsies-required histological or biochemical methods.
Deep-learning Augmented Reflectance Microscopy for Label-free Multiplexed Cytometry
Authors: Cheng Shiyi , Fu Sipei , Kim Yumi Mun , Song Weiye , Li Yunzhe , Xue Yujia , Yi Ji , Tian Lei
Published: August 2021

We develop a label-free multiplexed cytometry technique based on deep-learning-augmented virtual labeling. We demonstrate accurate single-cell structural phenotypes of cell cycles and multi-parametric single-cell profiling across a large cell population from the multiplexed readouts.
Ultrafast Cellular Automata Dynamics of Phase-change Optical Response
Authors: Zhang L. , Macdonald K. F. , Zheludev N. I.
Published: August 2021

We introduce a cellular automata methodology for studying photonics of light-induced phase transitions. Multiphysical complexity over disparate length/timescales is reduced to a simple, heuristic rule/parameter set in a model successfully describing several independent experimental datasets.
Femtosecond Time-Resolved Infrared-Resonant Third-Order Sum-Frequency Spectroscopy Towards Label-Free Imaging
Authors: Wang Jizhou , Wang Kai , Shen Yujie , Han Zehua , Li Fu , He Zhe , Wang Da-wei , Sokolov Alexei V. , Scully Marlan O.
Published: August 2021

We experimentally demonstrate a time-resolved infrared-resonant third-order sum-frequency spectroscopy. This technique provides a new way to measure the dynamics of the infrared active vibrational states. It can be combined with microscopes for label-free imaging.
Probing nonlinear plasmonic near-fields in crystalline atomically-thin films
Authors: Echarri A. Rodríguez , İyikanat F. , Cox Joel D. , de Abajo F. Javier García
Published: August 2021

Transdimensional materials as atomically thin-films of noble metals show promising optical properties for next-generation nanophotonic devices. We reveal their linear and nonlinear optical properties when combined with their plasmonic response.
Enhanced Luminescence of CdSe/ZnS Quantum Dots in Epsilon-near-zero Waveguide
Authors: So Jinkyu , Yuan Guang Hui , Soci Cesare , Zheludev Nikolay
Published: August 2021

We report a long awaited experimental observation of resonant enhancement of luminescence from an ensemble of quantum dots embedded in a photonic waveguide operating in the epsilon-near-zero cutoff regime.
Deeply Subwavelength Topological Microscopy
Authors: Pu Tanchao , Ou Jun-Yu , Yuan Guanghui , Rogers Edward , Papasimakis Nikitas , Smith P. J. , Zheludev Nikolay I.
Published: August 2021

We demonstrate experimentally imaging resolution exceeding λ/20 by a new far-field and label-free approach based on illumination with topologically structured light fields and artificial intelligence. Further improvements promise resolution beyond λ/100.
Engineering Nearest Neighbor Coupling in Huygens Metasurfaces
Authors: Oguntoye Isaac O. , Padmanabha Siddharth , Simone Brittany , Ollanik Adam , Escarra Matthew D.
Published: August 2021

Nearest neighbor coupling in antenna systems tends to reduce the overall optical efficiency of the system. Here, we compare arrays of disc and donut resonators that confine the impinging beam locally. Maximum optical efficiency of 70% for anomalous refraction is achieved.
Semiconductor optical amplifier (SOA) integrated electroabsorption modulator (EAM) for dispersion and amplitude compensation in long-distance optical fiber transmission
Authors: Chen Rih-You , Chen Cong-Long , Chen Yang-Jeng , Wei Chia-Chien , chiu Yi-Jen
Published: August 2021

A negative frequency chirp- and amplitude- compensation in long-distance optical fiber transmission by using SOA-integrated EAM have been demonstrated. Data transmission of 36Gb/s 16-QAM OFDM signal with 10.5GHz bandwidth over a 100km single mode fiber.
Design and Operation of Coherent Pulse Stacking Amplification as a Deep Recurrent Neural Network
Authors: Pei Hanzhang , Whittlesey Mathew , Du Qiang , Galvanauskas Almantas
Published: August 2021

We show equivalence of coherent pulse stacking system to a deep recurrent neural network, and experimentally demonstrate real-time learning on stacking cavities and input pulses, necessary for high fidelity coherent temporal combining with ∼102 pulses.
Wideband Acousto-Optical Modulation on Suspended Thin-Film Lithium Niobate
Authors: Hassanien Ahmed E. , Chow Edmond , Link Steffen , Yang Yansong , Goddard Lynford , Gong Songbin
Published: August 2021

We present a wideband acousto-optic modulator on a suspended thin-film lithium niobate where both light and acoustic waves are guided simultaneously. The modulator has a center frequency of 1.9 GHz and bandwidth of 70 MHz.
Continuous wave vertical emission from terahertz microcavity lasers with a dual injection scheme
Authors: Ottomaniello Andrea , Conte Gloria , Pitanti Alessandro , Vicarelli Leonardo , Profeti Alessandro , Beere Harvey E. , Ritchie David A. , Mattoli Virgilio , Bianco Federica , Tredicucci Alessandro
Published: August 2021

Quantum cascade lasers (QCLs) represent a most promising compact source at terahertz (THz) frequencies, but efficiency of their continuous wave (CW) operation still needs to be improved to achieve large-scale exploitation. Here, we demonstrate highly efficient operation of a subwavelength microcavity laser consisting of two evanescently coupled whispering gallery microdisk resonators. Exploiting a dual injection scheme for the laser cavity, single mode CW vertical emission at

3.3
 

THz

is obtained at

10
 

K

with

6.4
 

mA

threshold current and

145
 

mW/A

slope efficiency up to

320
 
μ

W

emitted power measured in quasi-CW mode. The tuning of the laser emission directionality is also obtained by independently varying the pumping strength between the microdisks. By connecting the resonators through a suspended gold bridge, the laser out-coupling efficiency in the vertical direction is strongly enhanced. Owing to the high brightness, low-power consumption and CW operation, the proposed microcavity laser design could allow the realization of high-performance CW THz QCLs ready for massive parallelization.
Ultra-broadband Bragg concave diffraction grating designs on 220-nm SOI for wavelength demultiplexing
Authors: Li Ke , Zhu Jingping , Duan Qihang , Sun Yuzhou , Hou Xun
Published: August 2021

The appropriate broadband design of a de/multiplexer can significantly increase the channel number and consequently the transmission capacity of a wavelength division multiplexing system. Herein, we present the first ultra-broadband Bragg concave diffraction grating (CDG) on a 220-nm silicon-on-insulator, covering most of the E, S, C, L, and U telecommunication wavebands spanning from 1.425 to 1.675 μm. A wide-band-gap Bragg mirror is employed to facilitate broadband reflection, with a low diffraction order of grating for a sufficient free spectral range. Numerical simulations show that the proposed approaching blazed concave diffraction grating (AB-CDG) for the two-material case exhibits a high integration, simple fabrication process, and promising spectral performance. We fabricate the grating for design verification with a low transmission loss of −0.6 dB and a crosstalk below −33.7 dB for the eight measured wavelength channels covering the spectral range from 1.5 to 1.61 μm that is limited by the bandwidth of the grating coupler. This design can be used for broadband wavelength demultiplexing, frontier astronomical observation, and spectroscopic imaging.
Improved comb and dual-comb operation of terahertz quantum cascade lasers utilizing a symmetric thermal dissipation
Authors: Wang Chenjie , Li Ziping , Liao Xiaoyu , Guan Wen , Ma Xuhong , Zhou Kang , Cao J. C. , Li Hua
Published: August 2021

In the terahertz frequency range, the quantum cascade laser (QCL) is a suitable platform for the frequency comb and dual-comb operation. Improved comb performances have been always much in demand. In this work, by employing a symmetric thermal dissipation scheme, we report an improved frequency comb and dual-comb operation of terahertz QCLs. Two configurations of cold fingers, i.e., type A and B with asymmetric and symmetric thermal dissipation schemes, respectively, are investigated here. A finite-element thermal analysis is carried out to study the parametric effects on the thermal management of the terahertz QCL. The modeling reveals that the symmetric thermal dissipation (type B) results in a more uniform thermal conduction and lower maximum temperature in the active region of the laser, compared to the traditional asymmetric thermal dissipation scheme (type A). To verify the simulation, experiments are further performed by measuring laser performance and comb characteristics of terahertz QCLs emitting around 4.2 THz mounted on type A and type B cold fingers. The experimental results show that the symmetric thermal dissipation approach (type B) is effective for improving the comb and dual-comb operation of terahertz QCLs, which can be further widely adopted for spectroscopy, imaging, and near-field applications.
Post-compression of long-wave infrared 2 picosecond sub-terawatt pulses in bulk materials
Authors: Polyanskiy Mikhail N. , Pogorelsky Igor V. , Babzien Marcus , Kupfer Rotem , Vodopyanov Konstantin L. , Palmer Mark A.
Published: August 2021

We have experimentally demonstrated the post-compression of a long-wave infrared (9.2 μm) 150 GW peak power pulse from 2 ps to less than 500 fs using a sequence of two bulk materials with negative group velocity dispersion (GVD). The compression resulted in up to 1.6-fold increase of the peak power and up to 2.8-fold increase of the intensity in the center of a quasi-Gaussian beam. The partial decoupling of the self-phase modulation and chirp compensation stages by using two materials with significantly different ratios of nonlinear refractive index to GVD provides accurate optimization of the compression mechanism and promises a viable path to scaling peak powers to supra-terawatt levels. During the preparatory study, we measured, for the first time to our knowledge, the nonlinear refractive indices of NaCl, KCl, and BaF2 for picosecond pulses in the long-wave infrared region.
Simple, efficient and reliable characterization of Laguerre-Gaussian beams with non-zero radial indices in diffraction from an amplitude parabolic-line linear grating
Authors: Rasouli Saifollah , Fathollazade Somaye , Amiri Pouria
Published: August 2021

In this work, we report the characterization of a Laguerre-Gaussian (LG) beam with given values of topological charge (TC) and radial index in a simple, efficient, and robust experimental diffraction scheme. The beam diffracts from an amplitude parabolic-line linear grating and the resulting diffraction patterns at zero- and first-order reveals the values of the TC, l, and radial index p of the incident LG beam using a simple analysis. The zero-order diffraction pattern consists of p + 1 concentric intensity rings and the first-order diffraction pattern contains an (l + p + 1) by (p + 1) two-dimensional array of intensity spots. The experimental scheme is robust since it is not sensitive to the relative locations of the impinging beam axis and the grating center, and is efficient since most of the energy of the output beam is in the diffraction order of interest for LG beam characterization. The measurement is also simple since the intensity spots of the array are placed exactly over straight and parallel lines. Both experimental and simulation results are presented and are consistent with each other.
Generation of annular femtosecond few-cycle pulses by self-compression and spatial filtering in solid thin plates
Authors: Gao Yitan , Su Yabei , Xu Siyuan , Zhu Xiaoxian , Zhao Kun , Fang Shaobo , Zhu Jiangfeng , Wei Zhiyi
Published: August 2021

Annular-shaped femtosecond few-cycle pulses are generated by 40fs laser pulses propagating through 6 solid thin plates in numerical simulations as well as in experiments. The generation of such pulses takes advantage of the conical emission caused by plasma effect, which introduces continuously varying off-axis plasma density along the radial direction of the propagating beam. The negative dispersion induced by the plasma causes the pulse at particular radial location to be self-compressed and to form an annular beam of short pulse, which can be extracted simply by spatial filtering. Meanwhile, by adjusting the input pulse energy and position of each thin plate relative to the laser focus, we control the plasma density in thin plates which changes the ratio between ionization and effects providing positive dispersion, and obtain a higher compression ratio indicating that the scheme of solid thin plates has the flexibility to regulate the laser intensity so as to plasma density, thus the negative dispersion the pulse experiences during propagation. Few-cycle pulses as short as 8.8 fs are generated in experiments, meanwhile the shortest pulse duration found in the simulations is 5.0 fs, which corresponds to two optical cycles at its central wavelength 761 nm. This method has great potential in high-power few-cycle pulse generation.
Electrically tunable polarization independent liquid crystal lenses based on orthogonally anisotropic orientations on adjacent micro-domains
Authors: Lin Yi-Hsin , Wang Yu-Jen , Hu Guo-Lin , Reshetnyak Victor
Published: August 2021

Polarization dependency is an intrinsic property of liquid crystals (LC) devices but major problem is optical efficiency. We demonstrated a polarization independent liquid crystal phase modulation based on the orthogonal nematic LC (OLC) mode wherein the optics axes of nematic liquid crystal molecules are set orthogonally to adjacent sub-domains for the first time. Such an OLC mode includes sub-domain with anisotropic orientations but collectively presents a capability of a polarizer-free optical phase modulation. An OLC mode cell provides a tunable optical phase of ∼3.35π radians for unpolarized light and different linearly polarized light. Among the polarizer-free LC mode, the proposed OLC mode is single-layered with large tunable optical phase. We also demonstrated a polarizer-free LC micro-lens. We expect this novel LC mode provide alternatives technology roadmap for upcoming optical applications, such as electrically tunable ophthalmic lenses and optical systems for augmented reality.
Widely tunable silicon-fiber laser at 2  µm
Authors: Vallée Jean-Michel , Jean Philippe , Guay Philippe , Fortin Vincent , Genest Jérôme , Bernier Martin , Shi Wei
Published: August 2021

Laser sources operating in the 2 µm spectral region play an important role for sensing and spectroscopy, and potentially for optical communication systems. In this work, we demonstrate a widely tunable hybrid silicon-fiber laser operating in the 2 µm band. By introducing a silicon-integrated Vernier filter in a fiber laser, we achieved continuous wavelength tuning over a range of 100 nm, from 1970 to 2070 nm. Fiber-coupled output power up to 28 mW was measured with a full-width-half-maximum linewidth smaller than 260 kHz and a side-mode-suppression ratio greater than 40 dB over the spectral range.
Particles 3D tracking with large axial depth by using the 2π-DH-PSF
Authors: Li Hangfeng , Wang Famin , Wei Tongda , Miao Xin , Cheng Yu , Pang Xinpei , Jiang Keming , Huang Wei , Zhang Yunhai
Published: August 2021

We propose a

2

π

-double-helix point spread function (

2

π

-DH-PSF) using the Fresnel zone approach that can rotate

2

π

rad. When 16 Fresnel zones are used, the particles can be tracked in the axial range of 10 µm in a

100

×

microscopy imaging system (

N
A

=

1.4

,

λ
=

514

n
m

). We measured the diffusion coefficient of nanospheres in different concentrations of glycerol with the

2

π

-DH-PSF, and the error between the measured results and theoretical value was within 10%, indicating the superior performance of

2

π

-DH-PSF in 3D localization imaging of nanoparticles. When combined with the defocus phase, the rotation angle can reach

4

π

rad, four times that of the conventional DH-PSF.
High-performance, compact optical standard
Authors: Newman Zachary L. , Maurice Vincent , Fredrick Connor , Fortier Tara , Leopardi Holly , Hollberg Leo , Diddams Scott A. , Kitching John , Hummon Matthew T.
Published: August 2021

We describe a high-performance, compact optical frequency standard
based on a microfabricated Rb vapor cell and a low-noise, external
cavity diode laser operating on the Rb two-photon transition at
778 nm. The optical standard achieves an instability of

1.8
×

10

−
13

τ

−
1

/

2

for times less than 100 s and a
flicker noise floor of

1
×

10

−
14

out to 6000 s. At long integration
times, the instability is limited by variations in optical probe power
and the ac Stark shift. The retrace was measured to

5.7
×

10

−
13

after 30 h of dormancy. Such a
simple, yet high-performance optical standard could be suitable as an
accurate realization of the meter or, if coupled with an optical
frequency comb, as a compact atomic clock comparable to a hydrogen
maser.
Photonic generation of high-performance microwave frequency combs using an optically injected semiconductor laser with dual-loop optoelectronic feedback
Authors: Zhang Renheng , Zhou Pei , Li Kunxi , Bao Hualong , Li Nianqiang
Published: August 2021

An approach to generating microwave frequency combs (MFCs) with superior performance is proposed and experimentally demonstrated based on an optically injected semiconductor laser (OISL). The OISL operates at the period-one (P1) oscillation state under proper injection conditions. A sinusoidal voltage signal is used to modulate the P1 state for the initial MFC generation, and then two optoelectronic feedback loops are introduced to enhance the performance of the MFC: a short-delay feedback loop is firstly applied to improve comb contrast based on Fourier domain mode locking (FDML), and a long-delay feedback loop is added to reduce the comb linewidth based on the self-injection-locking technique. In the proof-of-concept experiment, a K-band MFC (18–26 GHz) with a line spacing of 8.45 MHz is obtained, where a comb linewidth of approximately 500 Hz and a comb contrast over 45 dB are simultaneously achieved. Additionally, each comb component exhibits superior performance in terms of phase noise, all below

−

90

d
B
c

/

H
z

at 10 kHz offset, demonstrating an excellent coherence among these combs.
8.75  Gbps visible light communication link using an artificial neural network equalizer and a single-pixel blue micro-LED
Authors: Wei Zixian , Liu Zhongxu , Liu Xin , Wang Lei , Wang Lai , Yu Changyuan , Fu H. Y.
Published: August 2021

Visible light communication (VLC) beyond 10 Gbps is an important characteristic that can support the future 6 G high-capacity requirements. On the one hand, in order to break the electro-optics (E-O) bandwidth limitation of the light-emitting diodes (LEDs), we fabricated two high-bandwidth (

>

g
i
g
a
h
e
r
t
z

) single wetting layer micro-LEDs with 50 and 75 µm active regions. On the other hand, for mitigating the nonlinear effects of the VLC system, an artificial neural network equalizer is designed and implemented in offline digital signal processing. Both efforts lead to a breakthrough of data rates at a single VLC link. Using quadrature phase shift keying orthogonal frequency division multiplexing, the data rate of a 1.025 GHz VLC link based on a 75 µm micro-LED can reach 8.75 Gbps with a bit-error-ratio (BER) of

2.73
×

10

−
3

. In addition, the E-O characteristics and communication performances of micro-LED with two diameters are compared and discussed. To the best of our knowledge, the data rate of 8.75 Gbps is the highest record of the VLC link based on a single-pixel blue micro-LED with a BER within the forward error correction citation of

3.8
×

10

−
3

.
Tunable lens using dielectric elastomer sandwiched by transparent conductive liquid
Authors: Cheng Yang , Chen Chuanxun , Cao Jie , Bao Chun , Yang Ao , Hao Qun
Published: August 2021

We propose and demonstrate a compact tunable lens with high transmittance using a dielectric elastomer sandwiched by transparent conductive liquid. The transparent conductive liquid not only serves as the refractive material of the tunable lens but also works as the compliant electrode of the dielectric elastomer. The overall dimensions of the proposed tunable lens are 16 mm in diameter and 10 mm in height, and the optical transmittance is as high as 92.2% at 380–760 nm. The focal power variation of the tunable lens is

−

23.71

D

at an actuation voltage of 3.0 kV. The rise and fall times are 60 ms and 185 ms, respectively. The fabrication process of the tunable lens is free of the deposition of opaque compliant electrodes. Such a tunable lens promises a potential solution in various compact imaging systems.
Enhanced narrowband mid-IR thermal radiation enabled by plasmonic stacked gratings
Authors: Abubakar Yusuf , Gong Yongkang , Qiao Dun , Fan Yuanlong , Evered Christopher , Jones Adam , Saleh Hatef Dinparasti , Li Kang , Copner Nigel
Published: August 2021

We demonstrate tailored thermal radiation in the mid-infrared wavelength range with intriguing capabilities of high emissivity, narrowband spectra, and sharp angular response. The proposed thermal emitter consists of stacking a two-dimensional metallic grating on top of a one-dimensional dielectric Bragg grating (BG). It is interesting to find that the light interaction between the metallic grating and the BG gives rise to impedance matching at wavelengths located in the photonic bandgap of the BG, and allows enhanced polarization-dependent emissivity, selective resonance response, and high radiation directivity. We investigate the plasmonic resonance by exploring various properties and functions including tuning spectral selectivity and tailoring bandwidth at different light polarization and angle of incidence. The developed plasmonic stacked gratings could pave the way towards novel integrated infrared source platforms for various applications such as thermal analysis, imaging, security, biosensing, and medical diagnosis.
Ultrafast 2 × 2 green micro-LED array for optical wireless communication beyond 5  Gbit/s
Authors: Lin Gong-Ru , Kuo Hao-Chung , Cheng Chih-Hsien , Wu Yi-Chien , Huang Yu-Ming , Liou Fang-Jyun , Lee Yi-Che
Published: August 2021

A green

2
×
2

micro light-emitting diode (

μ
-
LED

) array with nanostructured grating patterns grown on a semipolar (20-21)-oriented gallium nitride (GaN) buffered layer on (22-43)-oriented sapphire substrate is specially transistor-outline can (TO-can) packaged with a sub-miniature-A (SMA) connector for high-speed data communication beyond 5 Gbit/s. Through a specific design for suppressing the quantum-confined Stark effect (QCSE) in the green

2
×
2
 
μ
-
LED

array with a low polarization-related electric field and flat quantum well band diagram, the green

2
×
2
 
μ
-
LED

array exhibits a turn-on voltage of 2.5 V and output power of 0.3 mW at

1
  
A
/

cm

2

. The green

2
×
2
 
μ
-
LED

array also reveals a wavelength shift from 543 nm to 537 nm smaller than that of conventional devices grown on

c

-plane buffered GaN substrate due to the inhibited QCSE. The 50 µm emission aperture of the green

2
×
2
 
μ
-
LED

array ensures a lower capacitance for a larger

−
3
  
dB

modulation bandwidth, which exhibits

−
1
  
dB

power compression at a larger bias under high-speed operation, as it is less affected by the high resistance of the single

μ
-
LED

element. With a specific TO-can+SMA package, the green

2
×
2
 
μ
-
LED

array exhibits maximal data rates exceeding 1.5 Gbit/s for the non-return-to-zero on–off keying format and beyond 5.02 Gbit/s for the bit-loaded discrete multitone (BL-DMT) format, which is very promising for optical wireless communication. As the sampling rate increases from 4 GSa/s to 16 GSa/s, the

μ
-
LED

array’s received signal-to-noise ratio (SNR) improves dramatically from 15.4 dB to 12.2 dB. The SNR remains about 15.4 dB, with a matching bit-error ratio (BER) of

2.7
×

10

−
3

, whereas the 10-fold oversampling of the eight-ray quadrature amplitude modulation orthogonal frequency-division multiplexing (8-QAM OFDM) data stream with 16 GSa/s appears to reduce the SNR by

−
3
  
dB

, resulting in a decoded BER of

3.3
×

10

−
3

. The green

2
×
2
 
μ
-
LED

array has demonstrated greater potential in data transmission beyond 5 Gbit/s using the BL-DMT algorithm for future applications in domains of visible light communication or optical wireless communication when packaged with handed mobile devices.
The evolutionary history of topological variations in the CPA/AT transporters
Authors: Sudha Govindarajan , Bassot Claudio , Lamb John , Shu Nanjiang , Huang Yan , Elofsson Arne
Published: August 2021

CPA/AT transporters are made up of scaffold and a core domain. The core domain contains two non-canonical helices (broken or reentrant) that mediate the transport of ions, amino acids or other charged compounds. During evolution, these transporters have undergone substantial changes in structure, topology and function. To shed light on these structural transitions, we create models for all families using an integrated topology annotation method. We find that the CPA/AT transporters can be classified into four fold-types based on their structure; (1) the CPA-broken fold-type, (2) the CPA-reentrant fold-type, (3) the BART fold-type, and (4) a previously not described fold-type, the Reentrant-Helix-Reentrant fold-type. Several topological transitions are identified, including the transition between a broken and reentrant helix, one transition between a loop and a reentrant helix, complete changes of orientation, and changes in the number of scaffold helices. These transitions are mainly caused by gene duplication and shuffling events. Structural models, topology information and other details are presented in a searchable database, CPAfold (cpafold.bioinfo.se).