bluuebunny/crossref_metadata_2025 huggingface dataset:
Lightning-fast and privacy-preserving outsourced computation in the cloud
Authors: Liu Ximeng , Deng Robert H. , Wu Pengfei , Yang Yang
Published: September 2020

In this paper, we propose a framework for lightning-fast privacy-preserving outsourced computation framework in the cloud, which we refer to as LightCom. Using LightCom, a user can securely achieve the outsource data storage and fast, secure data processing in a single cloud server different from the existing multi-server outsourced computation model. Specifically, we first present a general secure computation framework for LightCom under the cloud server equipped with multiple Trusted Processing Units (TPUs), which face the side-channel attack. Under the LightCom, we design two specified fast processing toolkits, which allow the user to achieve the commonly-used secure integer computation and secure floating-point computation against the side-channel information leakage of TPUs, respectively. Furthermore, our LightCom can also guarantee access pattern protection during the data processing and achieve private user information retrieve after the computation. We prove that the proposed LightCom can successfully achieve the goal of single cloud outsourced data processing to avoid the extra computation server and trusted computation server, and demonstrate the utility and the efficiency of LightCom using simulations.
Anesthetic Management of Reversible Cerebral Vasoconstriction Syndrome During Vaginal Delivery: A Case Report
Authors: Peace Jack M. , Bhat Adithya D. , Peralta Feyce M.
Published: September 2020

Reversible cerebral vasoconstriction syndrome (RCVS) is a rare group of vascular disorders characterized by severe headache with or without other neurologic symptoms. Pregnancy is known to precipitate RCVS, typically in the postpartum period. With improved recognition of this condition, RCVS is now increasingly identified in the antepartum period. Labor and vaginal delivery are characterized by fluctuations in hemodynamic and intracerebral pressures and present challenges for intrapartum anesthetic management. We report our experience with a patient with RCVS admitted for external cephalic version and subsequent vaginal delivery.
Cardiac hypertrophy in a dish: A human stem cell based model
Authors: Johansson Markus , Ulfenborg Benjamin , Andersson Christian X. , Heydarkhan-Hagvall Sepideh , Jeppsson Anders , Sartipy Peter , Synnergren Jane
Published: September 2020

Cardiac hypertrophy is an important and independent risk factor for the development of heart failure. To better understand the mechanisms and regulatory pathways involved in cardiac hypertrophy, there is a need for improved in vitro models. In this study, we investigated how hypertrophic stimulation affected human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs). The cells were stimulated with endothelin-1 (ET-1) for 8, 24, 48, 72, or 96h. Parameters including cell size, ANP-, proBNP-, and lactate concentration were analyzed. Moreover, transcriptional profiling using RNA-sequencing was performed to identify differentially expressed genes following ET-1 stimulation. The results show that the CMs increase in size by approximately 13% when exposed to ET-1 in parallel to increases in ANP and proBNP protein and mRNA levels. Furthermore, the lactate concentration in the media was increased indicating that the CMs consume more glucose, a hallmark of cardiac hypertrophy. Using RNA-seq, a hypertrophic gene expression pattern was also observed in the stimulated CMs. Taken together, these results show that hiPSC-derived CMs stimulated with ET-1 display a hypertrophic response. The results from this study also provide new molecular insights about the underlying mechanisms of cardiac hypertrophy and may help accelerate the development of new drugs against this condition.
Cell to cell communication mediates glioblastoma progression in Drosophila
Authors: Portela Marta , Mitchell Teresa , Casas-Tintó Sergio
Published: September 2020

Glioblastoma (GB) is the most aggressive and lethal tumour of the central nervous system (CNS). GB cells grow rapidly and display a network of projections (ultra-long tumour microtubes (TMs)), that mediate cell to cell communication. GB-TMs infiltrate throughout the brain, enwrap neurons and facilitate the depletion of the signalling molecule wingless (Wg)/WNT from the neighbouring healthy neurons. GB cells establish a positive feedback loop including Wg signalling upregulation that activates cJun N-terminal kinase (JNK) pathway and matrix metalloproteases (MMPs) production, which in turn promote further TMs infiltration, GB progression and neurodegeneration. Thus, cellular and molecular signals other than primary mutations emerge as central players of GB. Using a Drosophila model of GB, we describe the temporal organization of the main cellular events that occur in GB, including cell to cell interactions, neurodegeneration and TMs expansion. We define the progressive activation of JNK pathway signalling in GB mediated by the receptor Grindelwald (Grnd) and activated by the ligand Eiger (Egr)/TNFα produced by surrounding healthy brain tissue. We propose that cellular interactions of GB with the healthy brain tissue precede TM expansion and conclude that non-autonomous signals facilitate GB progression. These results contribute to deciphering the complexity and versatility of these incurable tumours.
Denovo designing, retrosynthetic analysis, and combinatorial synthesis of a hybrid antiviral (VTAR-01) to inhibit the interaction of SARS-CoV2 spike glycoprotein with human angiotensin-converting enzyme 2
Authors: Tiwari Vishvanath
Published: September 2020

SARS-like coronavirus (SARS-CoV2) has emerged as a global threat to humankind and is rapidly spreading. The infectivity, pathogenesis, and infection of this virus are dependent on the interaction of SARS-CoV2 spike protein with human ACE2 (hACE2). Spike protein contains a receptor-binding domain (RBD) that recognizes hACE-2. In the present study, we are reporting a denovo designed novel hybrid antiviral ‘VT-AR-01’ molecule that binds at the interface of RBD-hACE2 interaction. A series of antiviral molecules were tested for binding at the interface of RBD-hACE2 interaction. In-silico screening, molecular mechanics, molecular dynamics simulation (MDS) analysis suggest ribavirin, ascorbate, lopinavir, and hydroxychloroquine have strong interaction at RBD-hACE2 interface. These four molecules were used for denovo fragment-based antiviral design. Denovo designing, docking, and MDS analysis identified a ‘VTAR’ hybrid molecule that has better interaction with this interface as compared to all antiviral used to design it. We have further used retrosynthetic analysis and combinatorial synthesis to design 100 variants of VT-AR molecules. Retrosynthetic analysis and combinatorial synthesis, along with docking and MDS, identified VT-AR-01 that interact with the interface of the RBD-ACE2 complex. MDS analysis confirmed its interaction with the RBD-ACE2 interface by involving Glu35 and Lys353 of ACE2, as well as Gln493 and Ser494 of RBD. Interaction of spike protein with ACE2 is essential for pathogenesis and infection of this virus; hence, this in-silico designed hybrid antiviral molecule (VT-AR-01) that binds at the interface of RBD-hACE2 may be further developed to control the infection of SARS-CoV2.
Neuronal changes and cognitive deficits in a multi-hit rat model following cumulative impact of early life stressors
Authors: Sarkar Tiyasha , Patro Nisha , Patro Ishan Kumar
Published: September 2020

Perinatal protein malnourishment is a leading cause for mental and physical retardation in children with poor socioeconomic conditions. Such malnourished children are vulnerable to additional stressors that may synergistically act to cause neurological disorders at adulthood. In this study, the above mentioned condition was mimicked via a multi-hit rat model in which pups born to protein malnourished mothers (LP) were co-injected with polyinosinic:polycytidylic acid (Poly I:C; viral mimetic) at Postnatal day (PND) 3 and lipopolysaccharide (LPS; bacterial mimetic) at PND 9. Individual exposure of Poly I:C and LPS was also given to LP pups to correlate chronicity of stress. Similar treatments were also given to control pups. Hippocampal cellular apoptosis, β III tubulin catastrophe, altered neuronal profiling and spatial memory impairments were assessed at PND 180, using specific immunohistochemical markers (active caspase 3, β III tubulin, doublecortin), Golgi studies and cognitive mazes (Morris Water Maze and T maze). Increase in cellular apoptosis, loss of dendritic arborization and spatial memory impairments were higher in multi-hit group, than the single-hit groups. Such impairments observed due to multi-hit stress, mimicked conditions similar to many neurological disorders and hence it is hypothesized that later life neurological disorders might be an outcome of multiple early life hits.
Inhibition of ER stress improves progressive motor deficits in a REEP1-null mouse model of hereditary spastic paraplegia
Authors: Wang Bingjie , Yu You , Wei Lai , Zhang Yan
Published: September 2020

Hereditary spastic paraplegias (HSPs) are genetic neurodegenerative diseases. HSPs are characterized by lower-extremity weakness and spasticity. However, there is no specific clinical treatment strategy to prevent or reverse nerve degeneration in HSPs. Mutations in receptor expression-enhancing protein 1 (REEP1) are well-recognized and relatively common causes of autosomal dominant HSPs. REEP1 modifies the endoplasmic reticulum (ER) shape, and is implicated in the ER stress response. Defects in the ER stress response seem to be crucial mechanisms underlying HSP neurodegeneration. Here, we report that REEP1−/− mice exhibit progressive motor deficits, along with denervation of neuromuscular junctions and increased ER stress. Moreover, marked axonal degeneration and morphological abnormalities are observed. In this study, we treated both REEP1−/− and wild-type (WT) mice with salubrinal, which is a specific inhibitor of ER stress, and we observed increased nerve-muscle connections and enhanced motor functions. Our data highlight the importance of ER homeostasis in HSPs, providing new opportunities for HSP treatment.
Alpha synuclein aggresomes inhibit ciliogenesis and multiple functions of the centrosome
Authors: Iqbal Anila , Baldrighi Marta , Murdoch Jennifer N. , Fleming Angeleen , Wilkinson Christopher J.
Published: September 2020

Protein aggregates are the pathogenic hallmarks of many different neurodegenerative diseases and include the accumulation of α-synuclein, the main component of Lewy bodies found in Parkinson's disease. Aggresomes are closely-related, cellular accumulations of misfolded proteins. They develop in a juxtanuclear position, adjacent to the centrosome, the microtubule organizing centre of the cell, and share some protein components. Despite the long-standing observation that aggresomes/Lewy bodies and the centrosome sit side-by-side in the cell, no studies have been done to see whether these protein accumulations impede organelle function. We investigated whether the formation of aggresomes affected key centrosome functions: its ability to organize the microtubule network and to promote cilia formation. We find that when aggresomes are present, neuronal cells are unable to organise their microtubule network. New microtubules are not nucleated and extended, and the cells fail to respond to polarity cues. Since neurons are polarised, ensuring correct localisation of organelles and the effective intracellular transport of neurotransmitter vesicles, loss of centrosome activity could contribute to functional deficits and neuronal cell death in Parkinson's disease. In addition, we provide evidence that many cell types, including dopaminergic neurons, cannot form cilia when aggresomes are present, which would affect their ability to receive extracellular signals.
The pulse of morphogenesis: actomyosin dynamics and regulation in epithelia
Authors: Miao Hui , Blankenship J. Todd
Published: September 2020

Actomyosin networks are some of the most crucial force-generating components present in developing tissues. The contractile forces generated by these networks are harnessed during morphogenesis to drive various cell and tissue reshaping events. Recent studies of these processes have advanced rapidly, providing us with insights into how these networks are initiated, positioned and regulated, and how they act via individual contractile pulses and/or the formation of supracellular cables. Here, we review these studies and discuss the mechanisms that underlie the construction and turnover of such networks and structures. Furthermore, we provide an overview of how ratcheted processivity emerges from pulsed events, and how tissue-level mechanics are the coordinated output of many individual cellular behaviors.
Pou2f1 and Pou2f2 cooperate to control the timing of cone photoreceptor production in the developing mouse retina
Authors: Javed Awais , Mattar Pierre , Lu Suying , Kruczek Kamil , Kloc Magdalena , Gonzalez-Cordero Anai , Bremner Rod , Ali Robin R. , Cayouette Michel
Published: September 2020

Multipotent retinal progenitor cells (RPCs) generate various cell types in a precise chronological order, but how exactly cone photoreceptor production is restricted to early stages remains unclear. Here, we show that the POU-homeodomain factors Pou2f1/Pou2f2, the homologs of Drosophila temporal identity factors nub/pdm2, regulate the timely production of cones in mice. Forcing sustained expression of Pou2f1 or Pou2f2 in RPCs expands the period of cone production, whereas misexpression in late-stage RPCs triggers ectopic cone production at the expense of late-born fates. Mechanistically, we report that Pou2f1 induces Pou2f2 expression, which binds to a POU motif in the promoter of the rod-inducing factor Nrl to repress its expression. Conversely, conditional inactivation of Pou2f2 in RPCs increases Nrl expression and reduces cone production. Finally, we provide evidence that Pou2f1 is part of a cross-regulatory cascade with the other temporal identity factors Ikzf1 and Casz1. These results uncover Pou2f1/2 as regulators of the temporal window for cone genesis and, given their widespread expression in the nervous system, raise the possibility of a general role in temporal patterning.
A discrete interface in matrix stiffness creates an oscillatory pattern of endothelial monolayer disruption
Authors: VanderBurgh Jacob A. , Potharazu Archit V. , Schwager Samantha C. , Reinhart-King Cynthia A.
Published: September 2020

Intimal stiffening upregulates endothelial cell contractility, disrupting barrier integrity; however, intimal stiffening is non-uniform. The impact of local changes in intimal stiffness on proximal and distal cell–cell interactions is unknown. To investigate the range at which matrix stiffness heterogeneities impact neighboring endothelial cells within a monolayer, we built a micropillar system with adjacent regions of stiff and compliant matrix. The stiffness interface results in an oscillatory pattern of neutrophil transendothelial migration, symmetrical about the interface and well-fit by a sinusoid function. ‘Peaks’ of the sinusoid were found to have increased cellular contractility and decreased barrier function relative to ‘troughs’ of the sinusoid. Pharmacological modulation of contractility was observed to break symmetry, altering the amplitude and wavelength of the sinusoid, indicating that contractility may regulate this effect. This work illuminates a novel biophysical phenomenon of the role of stiffness-mediated cell–matrix interactions on cell–cell interactions at a distance. Additionally, it provides insight into the range at which intimal matrix stiffness heterogeneities will impact endothelial barrier function and potentially contribute to atherogenesis.
The Long-Term Impacts of Grants on Poverty: Nine-Year Evidence from Uganda’s Youth Opportunities Program
Authors: Blattman Christopher , Fiala Nathan , Martinez Sebastian
Published: September 2020

In 2008, Uganda gave $400 per person to thousands of young people to help them start skilled trades, work more, and raise incomes. Four years on, an experimental evaluation found grants raised work by 17 percent and earnings by 38 percent (Blattman, Fiala, Martinez 2014). After nine years, we find these gains have dissipated. Grantees’ investment leveled off; controls eventually increased their incomes through business and casual labor; and so both groups converged in employment, earnings, and consumption levels. We see little effect on mortality, fertility, or family health and education. However, grants had lasting impacts on durable asset stocks and skilled work. (JEL H53, I32, I38, O15, O22)
Nonlinear Pricing with Average-Price Bias
Authors: Martimort David , Stole Lars A.
Published: September 2020

Empirical evidence suggests that consumers facing complex nonlinear prices often make choices based on average (not marginal) prices. Given such behavior, we characterize a monopolist’s optimal nonlinear price schedule. In contrast to the textbook setting, nonlinear prices designed for “ average-price bias” distort consumption downward for consumers with the highest marginal utility and typically feature quantity premia rather than quantity discounts. These properties arise because the bias replaces consumer information rents with “curvature rents.” Whether or not a monopolist prefers consumers with average-price bias depends upon underlying preferences and costs. (JEL D11, D21, D42, L12)
The DNA of New Exporters: Spin-offs and FDI at the Extensive Margin of Trade
Authors: Blum Bernardo S. , Claro Sebastian , Horstmann Ignatius , Tombe Trevor
Published: September 2020

Other than that new exporters account for a large part of aggregate export growth, we know little else. We document that aggregate export growth in Chile is driven by only a few new exporters. These exporters are new business entities, operate new plants, and behave much like experienced exporters: they start large and have high survival rates. Moreover, 70 percent of these new firms are owned by existing businesses and are likely the by-product of either domestic spin-offs or foreign direct investment (24 percent). By focusing on the average new exporter, the existing models of new exporter dynamics miss these key features of export growth. (JEL F14, F23, L22, L60, M13, O14, O19)
Rage against the Machines: Labor-Saving Technology and Unrest in Industrializing England
Authors: Caprettini Bruno , Voth Hans-Joachim
Published: September 2020

Can new technology cause social instability and unrest? We examine the famous “Captain Swing” riots in 1830s England. Newly collected data on threshing machine diffusion shows that labor-saving technology was associated with more riots. We instrument technology adoption with the share of heavy soils in a parish: IV estimates demonstrate that threshing machines were an important cause of unrest. Where alternative employment opportunities softened the blow of new technology, there was less rioting. Conversely, where enclosures had impoverished workers, the effect of threshing machines on rioting was amplified. (JEL J24, L16, N13, N33, N53, O33, Q16)
Pretreatment structural and arterial spin labeling MRI is predictive for p53 mutation in high-grade gliomas
Authors: Mao Jiaji , Deng Dabiao , Yang Zehong , Wang Wensheng , Cao Minghui , Huang Yun , Shen Jun
Published: September 2020

Objectives:

To determine the performance of pretreatment structural and arterial spin labelling (ASL) MRI in predicting p53 mutation in patients with high-grade gliomas (HGGs).

Methods:

Pre-treatment structural and ASL MRI were performed in 57 patients with histologically confirmed HGGs and information of p53 status. Whole-lesion histogram analysis of cerebral blood flow (CBF) images of the enhancing tumour and the peritumoral oedema in the HGGs were performed. Visually AcceSAble Rembrandt Images features were used as qualitative analysis. The differences of ASL histogram parameters and Visually AcceSAble Rembrandt Images features between HGGs with or without p53 mutation were analyzed with post hoc correction for multiple comparisons. LASSO regression was performed to select the optimal features that could predict p53 mutation, followed by receiver operating characteristic analysis to determine the predictive efficacy.

Results:

A total of 33 HGGs with p53 mutation and 24 without p53 mutation were included. HGGs with mutant p53 showed lower CBFpercentile5and CBFuniformityof the enhancing tumour (p < 0.05) and higher prevalence of the qualitative MRI feature of enhancing tumour crossing midline (ETCM) (p < 0.05) as compared with HGGs with wild-type p53. LASSO regression showed that the CBFuniformityof the enhancing tumour and ETCM were predictive features for p53 mutation. CBFuniformityshowed an acceptable performance in predicting p53 mutation (area under the curve = 0.721), when combined with the feature of ETCM, its predictive efficacy was significantly improved (area under the curve = 0.814, p = 0.012).

Conclusion:

An integrated pre-treatment structural and ASL MRI can help to predict p53 mutation in HGGs.
The pursuit of radiology training in times of a pandemic
Authors: Pervez Anum , McCurdie Fiona , Poon Daniel
Published: September 2020

The Coronavirus-19 (COVID-19) pandemic has been the greatest challenge faced by the National Health Service (NHS) in its lifetime. The crisis has seen the disruption of many long-held institutions, most critically of which is specialty training. In this article, we discuss the impact of the pandemic on Radiology training in the UK. We explore the methods that have been used to combat these difficulties and suggest workable solutions. As technology platforms become ever more integral to our daily clinical routines, we discuss how these offer a new approach to training. We argue that, of all the medical disciplines, radiologists are best placed to design and implement technology-based training, and lead other specialties in doing so. Whilst the upheaval of traditional approaches to education is a challenge, we propose that this departure from the norm offers exciting opportunities for improvement.
CARACTERIZAÇÃO E AVALIAÇÃO DA EFICIÊNCIA DOS TERMINAIS INTERMODAIS BRASILEIROS
Authors: Santos Alexandre Borges , Sproesser Renato Luiz
Published: September 2020

O presente estudo teve como objetivo caracterizar e avaliar a eficiência dos terminais intermodais brasileiros. Os objetivos propostos nesta pesquisa foram alcançados por meio de um estudo quali-quantitativo. Com a utilização de três insumos e um único produto, a mensuração da eficiência dos terminais foi realizada por meio do modelo Variable Return to Scale orientado a produto da técnica Análise Envoltória de Dados. Dos 24 terminais analisados, 8 foram considerados 100% eficientes, dezesseis ineficientes, sendo que quinze terminais apresentaram nível de eficiência abaixo de 51,7%, que foi a média do setor encontrada. Cabe ressaltar que o trabalho limitou-se à mensuração da eficiência operacional, não levando em consideração aspectos financeiros. Os resultados da pesquisa apontam potencial de aumento de transbordo nos terminais intermodais brasileiros, mantendo insumos inalterados. Os resultados da pesquisa podem, portanto, servir como apoio à decisão para gestores, visando ao aumento da eficiência dos terminais e do transporte intermodal no país.
Thermal lensing effects and nonlinear refractive indices of fluoride crystals induced by high-power ultrafast lasers
Authors: Andrus Liam , Ben-Yakar Adela
Published: September 2020

Thermo-optical and nonlinear property characterization of refractive
optical components is essential for endoscopic instrumentation that
utilizes high-power, high-repetition-rate ultrafast lasers. For
example, ytterbium-doped fiber lasers are well suited for ultrafast
laser microsurgery applications; however, the thermo-optical responses
of many common lens substrates are not well understood at 1035 nm
wavelength. Using a

z

-scan technique, we first measured the
nonlinear refractive indices of

C
a
F

2

,

M
g
F

2

, and

B
a
F

2

at 1035 nm and found values that
match well with those from the literature at 1064 nm. To elucidate
effects of thermal lensing, we performed

z

-scans at multiple laser repetition
rates and multiple average powers. The results showed negligible
thermal effects up to an average power of 1 W and at 10 W
material-specific thermal lensing significantly altered

z

-scan measurements. Using a 2D
temperature model, we could determine the source of the observed
thermal lensing effects. Linear absorption was determined as the main
source of heating in these crystals. On the other hand, inclusion of
nonlinear absorption as an additional heat source in the simulations
showed that thermal lensing in borosilicate glass was strongly
influenced by nonlinear absorption. This method can potentially
provide a sensitive method to measure small nonlinear absorption
coefficients of transparent optical materials. These results can guide
design of miniaturized optical systems for ultrafast laser surgery and
deep-tissue imaging probes.
Few-layer GaSe nanosheet-based broadband saturable absorber for passively Q-switched solid-state bulk lasers
Authors: Shi Bingnan , He Guanbai , Yang Kejian , Zhang Baitao , He Jingliang
Published: September 2020

In this paper, few-layer two-dimensional (2D) GaSe nanosheets were fabricated and utilized as broadband saturable absorbers (SAs) for passively

Q

-switched (PQS) solid-state bulk lasers operating at 1.06 and 1.99 µm. For 1.06 µm laser operation, the maximum average output power, the shortest pulse width, and the largest single pulse energy were determined to be 438 mW, 285 ns, and 2.31 µJ, respectively, while for 1.99 µm PQS laser operation, they were 937 mW, 383 ns, and 9.56 µJ. Our results identified the great potential applications of few-layer 2D GaSe nanosheets for practical optical modulators such as SAs for pulsed laser generation.
Analysis of material concentration in step-index fibers with alumina cores produced by means of the powder-in-tube technique
Authors: Meng Lingqiang , Ji Jingxian , Röhrer Christian , Kleem Götz , Graf Thomas , Ahmed Marwan Abdou
Published: September 2020

Step-index fibers (SIFs) with alumina cores were fabricated employing the powder-in-tube technique. The fabricated SIFs have alumina concentrations of up to 32 mol%, which is the highest value reported so far for fibers with core diameters smaller than 25 μm. The mixing mechanisms between alumina and silica during fiber drawing were revealed by energy dispersive X-ray analysis of the neck-down area of the preform. The results of the measurements and simulations indicate that besides diffusion, fluid dynamics between softened silica and alumina powder also play an important role in the resulting alumina and silica concentrations in the fiber. The influence of different drawing parameters on the alumina and silica concentrations of the fibers is also presented.
Spectrometric detection of weak forces in cavity optomechanics
Authors: Zhou Yue-Hui , Tan Qing-Shou , Fang Xi-Ming , Huang Jin-Feng , Liao Jie-Qiao
Published: September 2020

We propose a spectrometric method to detect a classical weak force acting upon the moving end mirror in a cavity optomechanical system. The force changes the equilibrium position of the end mirror, and thus the resonance frequency of the cavity field depends on the force to be detected. As a result, the magnitude of the force can be inferred by analyzing the single-photon emission and scattering spectra of the optomechanical cavity. Since the emission and scattering processes are much faster than the characteristic mechanical dissipation, the influence of the mechanical thermal noise is negligible in this spectrometric detection scheme. We also extent this spectrometric method to detect a monochromatic oscillating force by utilizing an optomechanical coupling modulated at the same frequency as the force.
Hybrid topological guiding mechanisms for photonic crystal fibers
Authors: Makwana Mehul , Wiltshaw Richard , Guenneau Sébastien , Craster Richard
Published: September 2020

We create hybrid topological-photonic localisation of light by introducing concepts from the field of topological matter to that of photonic crystal fiber arrays. S-polarized obliquely propagating electromagnetic waves are guided by hexagonal, and square, lattice topological systems along an array of infinitely conducting fibers. The theory utilises perfectly periodic arrays that, in frequency space, have gapped Dirac cones producing band gaps demarcated by pronounced valleys locally imbued with a nonzero local topological quantity. These broken symmetry-induced stop-bands allow for localised guidance of electromagnetic edge-waves along the crystal fiber axis. Finite element simulations, complemented by asymptotic techniques, demonstrate the effectiveness of the proposed designs for localising energy in finite arrays in a robust manner.
Photonic generation of pulsed microwave signals in the X-, Ku- and K-band
Authors: Peng Yiwei , Sun Keye , Shen Yang , Beling Andreas , Campbell Joe C.
Published: September 2020

Photonic microwave generation of high-power pulsed signals in the X-, Ku- and K-band using charge-compensated MUTC photodiodes is demonstrated. The impulse photoresponse without modulation showed a maximum peak voltage of 38.3 V and full-width at half-maximum of 30 ps. High power pulsed microwave signals at 10, 17 and 22 GHz with peak power up to 44.2 dBm (26.3 W), 41.6 dBm (14.5 W) and 40.6 dBm (11.5 W) were achieved, respectively.
Spontaneous phase locking of mechanical multimodes in anti-parity-time optomechanics
Authors: Chen Bing , Guo Yanqiang , Shen Heng
Published: September 2020

We propose a system for observing the spontaneous phase locking of two frequency separate mechanical modes in an anti-parity-time symmetric optomechanical system. In our approach, a common optical cavity mode mediates the coupling between two phonon modes, leading to the phase locking of the coupled mechanical modes to a common frequency in the symmetry unbroken regime. We furthermore observe the change of quantum correlation near the exceptional point. Our results are also directly relevant to numerous other physical platforms, such as atomic ensembles in cavity quantum electrodynamics (QED) systems and spin interaction mediated by collective motional mode in trapped ions.
Reference-free THz-TDS conductivity analysis of thin conducting films
Authors: Whelan Patrick R. , Shen Qian , Luo Da , Wang Meihui , Ruoff Rodney S. , Jepsen Peter U. , Bøggild Peter , Zhou Binbin
Published: September 2020

We present a reference-free method to determine electrical parameters of thin conducting films by steady state transmission-mode terahertz time-domain spectroscopy (THz-TDS). We demonstrate that the frequency-dependent AC conductivity of graphene can be acquired by comparing the directly transmitted THz pulse with a transient internal reflection within the substrate which avoids the need for a standard reference scan. The DC sheet conductivity, scattering time, carrier density, mobility, and Fermi velocity of graphene are retrieved subsequently by fitting the AC conductivity with the Drude model. This reference-free method was investigated with two complementary THz setups: one commercial fibre-coupled THz spectrometer with fast scanning rate (0.2-1.5 THz) and one air-plasma based ultra-broadband THz spectrometer for greatly extended frequency range (2-10 THz). Certain propagation correction terms for more accurate retrieval of electrical parameters are discussed.
A hyperspectral projector for simultaneous 3D spatial and hyperspectral imaging via structured illumination
Authors: Xu Yibo , Giljum Anthony , Kelly Kevin F.
Published: September 2020

Both 3D imaging and hyperspectral imaging provide important information of the scene and combining them is beneficial in helping us perceive and understand real-world structures. Previous hyperspectral 3D imaging systems typically require a hyperspectral imaging system as the detector suffers from complicated hardware design, high cost, and high acquisition and reconstruction time. Here, we report a low-cost, high-frame rate, simple-design, and compact hyperspectral stripe projector (HSP) system based on a single digital micro-mirror device, capable of producing hyperspectral patterns where each row of pixels has an independently programmable spectrum. We demonstrate two example applications using the HSP via hyperspectral structured illumination: hyperspectral 3D surface imaging and spectrum-dependent hyperspectral compressive imaging of volume density of participating medium. The hyperspectral patterns simultaneously encode the 3D spatial and spectral information of the target, requiring only a grayscale sensor as the detector. The reported HSP and its applications provide a solution for combining structured illumination techniques with hyperspectral imaging in a simple, efficient, and low-cost manner. The work presented here represents a novel structured illumination technique that provides the basis and inspiration of future variations of hardware systems and software encoding schemes.
Three fiber designs for mitigating thermal mode instability in high-power fiber amplifiers
Authors: Leidner Jordan P. , Marciante John R.
Published: September 2020

An improved fiber amplifier model for simulating thermal mode instability (TMI) in high-power fiber amplifiers is developed. The model is applied to reveal new physics regarding the thermal physics that is critical to the TMI process, which are not the glass volume or the cooling method, but rather the transit path length of the quantum-defect-defined thermal peak in the fiber amplifier. The new physics and model analysis are applied to create a set of design rules to guide the development of new fiber types specifically for intrinsically mitigating TMI. These rules and the improved model are applied to three new fiber concepts for mitigating TMI in high-power fiber amplifiers. All three fiber types are shown to substantially increase the TMI threshold, up to a factor of 2 in some cases. In addition, all three new fiber classes offer ways to simultaneously increase the core diameter and the TMI threshold.
Three-dimensional real-time darkfield imaging through Fourier lightfield microscopy
Authors: Scrofani Gabriele , Saavedra Genaro , Martínez-Corral Manuel , Sánchez-Ortiga Emilio
Published: September 2020

We report a protocol that takes advantage of the Fourier lightfield microscopy concept for providing 3D darkfield images of volumetric samples in a single-shot. This microscope takes advantage of the Fourier lightfield configuration, in which a lens array is placed at the Fourier plane of the microscope objective, providing a direct multiplexing of the spatio-angular information of the sample. Using the proper illumination beam, the system collects the light scattered by the sample while the background light is blocked out. This produces a set of orthographic perspective images with shifted spatial-frequency components that can be recombined to produce a 3D darkfield image. Applying the adequate reconstruction algorithm high-contrast darkfield optical sections are calculated in real time. The presented method is applied for fast volumetric reconstructions of unstained 3D samples.
Automated reconstruction of multiple objects with individual movement based on PSP
Authors: Lu Lei , Jia Zhaoyi , Pan Wei , Zhang Qinghui , Zhang Mengya , Xi Jiangtao
Published: September 2020

Many methods have been proposed to reconstruct the moving object based on phase shifting profilometry. Quality reconstruction results can be achieved when a single moving object or multiple objects with same movement are measured. However, errors will be introduced when multiple objects with individual movements are reconstructed. This paper proposes an automated method to track and reconstruct the multiple objects with individual movement. First, the objects are identified automatically and their bounding boxes are obtained. Second, with the identified objects’ images before movement, the objects are tracked by the KCF algorithm in the successive fringe pattern after movement. Third, the SIFT method is applied on the tracked object images and the objects’ movement is described individually by the rotation matrix and translation vector. Finally, the multiple objects are reconstructed based on the different movement information. Experiments are presented to verify the effectiveness.
Exploiting redundancy in color-polarization filter array images for dynamic range enhancement
Authors: Lapray Pierre-Jean
Published: September 2020

Color-polarization filter array (CPFA) sensors are able to capture linear polarization and color information in a single shot. For a scene that contains a high dynamic range of irradiance and polarization signatures, some pixel values approach the saturation and noise levels of the sensor. The most common CPFA configuration is overdetermined, and contains four different linear polarization analyzers. Assuming that not all pixel responses are equally reliable in CPFA channels, one can therefore apply the high dynamic range imaging scheme to improve the Stokes estimation from a single CPFA image. Here I present this alternative methodology and show qualitative and quantitative results on real data.
Picosecond stimulated Raman scattering at 3000 and 3430  cm−1 OH vibrations without optical breakdown
Authors: Pershin Sergey M. , Vodchits Alexander I. , Khodasevich Inna A. , Grishin Mikhail Ya. , Lednev Vasily N. , Orlovich Valentin A. , Chizhov Pavel A.
Published: September 2020

For the first time, to the best of our knowledge, stimulated Raman scattering (SRS) of picosecond laser pulses without optical breakdown has been detected simultaneously (as the first Stokes and anti-Stokes paired components) at

∼

3430

and

∼

3000

c
m

−
1

vibrations of water OH band. These components were generated coaxially to the pump beam in the forward direction as axial and conical ring beams, respectively, when the pump beam was focused at the water-air interface. We suggest an explanation of these new SRS phenomena by non-collinear four-wave parametric interaction.
Intensity-noise suppression in 1950-nm single-frequency fiber laser by bidirectional amplifier configuration
Authors: Guan Xianchao , Yang Changsheng , Lin Wei , Zhao Qilai , Tan Tianyi , Gu Quan , Zhou Kaijun , Wei Xiaoming , Yang Zhongmin , Xu Shanhui
Published: September 2020

In this Letter, a bidirectional amplifier configuration suppressing the relative intensity noise in a 1950-nm linearly polarized single-frequency fiber laser (SFFL) is proposed. The scheme to amplify the signal in a nonlinear saturated amplification regime with low gain distribution for suppressing the RIN is theoretically analyzed. By optimizing the input power level and reflectivity of the bidirectional power-amplifier, the RIN is decreased maximally by

>

24

d
B

within the frequency range of 200 kHz. A stable output power of over 5.16 W with a polarization extinction ratio of 21.2 dB is obtained. Additionally, the amplified signal maintains a linewidth of 7.1 kHz nearly identical with that of the seed, both with a signal-to-noise ratio of more than 60 dB. This all-optical technique on noise suppression applied to the fiber amplifier paves the way to realize low-noise SFFL with power improvement.
Tailored nanocomposites for 3D printed micro-optics
Authors: Weber Ksenia , Werdehausen Daniel , König Peter , Thiele Simon , Schmid Michael , Decker Manuel , De Oliveira Peter William , Herkommer Alois , Giessen Harald
Published: September 2020

Optical polymers cover only a rather narrow range of optical properties. This is a limiting factor for the design of polymer-based optical systems such as smartphone cameras. Moreover, it also poses a problem for femtosecond two-photon lithography, which is a state-of-the-art technology to 3D print high-quality optics from photopolymers. To overcome the limitations of conventional polymers, we introduce nano-inks based on the commonly used photopolymers IP-DIP and IP-S as polymer matrix and zirconium dioxide (ZrO2) nanoparticles. We show that the refractive index and dispersion of these nano-inks can be purposefully tailored by varying the constituent materials and the volume fraction of the nanoparticles. Furthermore, we demonstrate the suitability of our nano-inks for optical applications by 3D printing single micro-lenses and a multi-material achromatic Fraunhofer doublet. Our findings confirm that nanocomposites expand the range of optical properties that are accessible for polymer-based systems and allow for the design of tailored optical materials.
Auger electron spectroscopy for surface ferroelectric domain differentiation in selectively poled MgO:LiNbO3
Authors: McLoughlin Torrey , Randall Babbitt Wm. , Himmer Phillip A. , Nakagawa Wataru
Published: September 2020

Auger electron spectroscopy (AES) as a method to characterize the ferroelectric polarization domains in magnesium-doped lithium niobate crystals is demonstrated. Preliminary measurements on a test sample show a clearly identifiable relative shift in the energy of the Auger oxygen KLL transition peak between poled (inverted) and un-poled domains. Auger electrons detected from the negative polarization domains (-Z) have a higher energy than those from the positive domains indicating a lower ionization energy at the -Z domain surface. The degree of electron energy separation between the −Z and +Z domains was found to be dependent on proximity to the domain boundary and was potentially diminished by the accumulated charge under the incident primary beam. Polarization domain resolution is demonstrated on both the micron and millimeter scale, suggesting potential applicability of this technique to surface investigation and domain structure characterization of nonlinear optical devices such as periodically poled lithium niobate.
Temperature dependence of initial deformation and cracks of indium tin oxide film by quasi-continuous-wave laser irradiations
Authors: Peng Liping , Zhao Yuan’an , Liu Xiaofeng , Cao Zhaoliang , Li Dawei , Lian Yafei , Ma Hao , Hong Ruijin , Tao Chunxian , Zhang Dawei , Shao Jianda
Published: September 2020

In this study, we investigated the temperature dependence of the initial deformation and cracks of indium tin oxide (ITO) thin films deposited on a fused silica substrate using a 1064-nm quasi-continuous-wave laser. We observed that the laser-induced morphology threshold of the film shows a dramatic thickness effect. The laser-induced morphology threshold of a 100-nm ITO film is four times that of a 300-nm ITO film. Initial laser-induced surface morphologies of the initial deformation and cracks will occur as long as temperature rises to about 520 K and 1250 K, respectively, irrespective of the thickness of a film. Experimental results indicate that a thin ITO film is more likely to tolerate laser irradiation because of lower absorptivity than a thicker ITO film. Studying the temperature effect helps clarify more about the laser annealing process, which is a promising process in improving the performance of the ITO films.
On-chip optical parametric oscillation into the visible: generating red, orange, yellow, and green from a near-infrared pump
Authors: Lu Xiyuan , Moille Gregory , Rao Ashutosh , Westly Daron A. , Srinivasan Kartik
Published: September 2020

The on-chip generation of coherent, single-frequency laser light that
can be tuned across the visible spectrum would help enable a variety
of applications in spectroscopy, metrology, and quantum science.
Recently, third-order optical parametric oscillation (OPO) in a
microresonator has shown great promise as an efficient and scalable
approach toward this end. However, considering visible light
generation, so far only red light at

<

420

T
H
z

(near the edge of the visible band)
has been reported. In this work, we overcome strong material
dispersion at visible wavelengths and demonstrate on-chip OPO in a

S
i

3

N

4

microresonator covering

>

130

T
H
z

of the visible spectrum, including
red, orange, yellow, and green wavelengths. In particular, using an
input pump laser that is scanned 5 THz in the near-infrared from
386 THz to 391 THz, the OPO output signal is tuned from the
near-infrared at 395 THz to the visible at 528 THz, while the OPO
output idler is tuned from the near-infrared at 378 THz to the
infrared at 254 THz. The widest signal-idler separation of 274 THz is
more than an octave in span and is the widest demonstrated for a
nanophotonic OPO to date. More generally, our work shows how nonlinear
nanophotonics can transform light from readily accessible compact
near-infrared lasers to targeted visible wavelengths of interest.
Advances in on-chip photonic devices based on lithium niobate on insulator
Authors: Lin Jintian , Bo Fang , Cheng Ya , Xu Jingjun
Published: September 2020

Crystalline lithium niobate (LN) is an important optical material because of its broad transmission window that spans from ultraviolet to mid-infrared and its large nonlinear and electro-optic coefficients. Furthermore, the recent development and commercialization of LN-on-insulator (LNOI) technology has opened an avenue for the realization of integrated on-chip photonic devices with unprecedented performances in terms of propagation loss, optical nonlinearity, and electro-optic tunability. This review begins with a brief introduction of the history and current status of LNOI photonics. We then discuss the fabrication techniques of LNOI-based photonic structures and devices. The recent revolution in the LN photonic industry has been sparked and is still being powered by innovations of the nanofabrication technology of LNOI, which enables the production of building block structures, such as optical microresonators and waveguides of unprecedented optical qualities. The following sections present various on-chip LNOI devices categorized into nonlinear photonic and electro-optic tunable devices and photonic-integrated circuits. Some conclusions and future perspectives are provided.
Phase segregation in inorganic mixed-halide perovskites: from phenomena to mechanisms
Authors: Wang Yutao , Quintana Xavier , Kim Jiyun , Guan Xinwei , Hu Long , Lin Chun-Ho , Jones Brendon Tyler , Chen Weijian , Wen Xiaoming , Gao Hanwei , Wu Tom
Published: September 2020

Halide perovskites, such as methylammonium lead halide perovskites (

MAPbX

3

,

X
=
I

, Br, and Cl), are emerging as promising candidates for a wide range of optoelectronic applications, including solar cells, light-emitting diodes, and photodetectors, due to their superior optoelectronic properties. All-inorganic lead halide perovskites

CsPbX

3

are attracting a lot of attention because replacing the organic cations with

Cs

+

enhances the stability, and its halide-mixing derivatives offer broad bandgap tunability covering nearly the entire visible spectrum. However, there is evidence suggesting that the optical properties of mixed-halide perovskites are influenced by phase segregation under external stimuli, especially illumination, which may negatively impact the performance of optoelectronic devices. It is reported that the mixed-halide perovskites in forms of thin films and nanocrystals are segregated into a low-bandgap I-rich phase and a high-bandgap Br-rich phase. Herein, we present a critical review on the synthesis and basic properties of all-inorganic perovskites, phase-segregation phenomena, plausible mechanisms, and methods to mitigate phase segregation, providing insights on advancing mixed-halide perovskite optoelectronics with reliable performance.