bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutritional Ketosis with Ketogenic Diets or Exogenous Ketones: Features, Convergence, and Divergence
Authors: Poff Angela M. , Koutnik Andrew P. , Egan Brendan
Published: July 2020

Athletes, clinicians, and practitioners are increasingly interested in the proposed performance and therapeutic benefits of nutritional ketosis (NK). NK is best operationally defined as a nutritionally induced metabolic state resulting in blood β-hydroxybutyrate concentrations of ≥0.5 mM. Most tissues readily metabolize ketone bodies (KBs), and KBs in turn regulate metabolism and signaling in both a systemic and tissue-specific manner. During fasting, starvation, or ketogenic diets, endogenous synthesis of KBs is amplified resulting in a state of NK. Orally administered exogenous ketone supplements rapidly elevate circulating KBs and produce a similar, but far from identical, metabolic state. NK results in a number of convergent features regardless of endogenous or exogenous induction; however, important differences also are observed. The implications of NK across health, disease, and performance is rapidly becoming more evident, thus acknowledging the convergent and divergent features of NK is critical for fully understanding the potential utility of this metabolic state.
Tratamento de fraturas ipsilaterais da diáfise e do colo do fêmur com implante único
Authors: Clazzer Renata , De Lima Diego Ariel , Viana Marcos Levy Machado Barbalho , Paiva Keilerte Renes Gurgel , De Lima Lana Lacerda
Published: July 2020

Objetivo: apresentar um caso de coxa vara após tratamento de fraturas ipsilaterais da diáfise e do colo do fêmur com implante único e revisar sistematicamente a literatura sobre o assunto. Metodologia: foi realizada pesquisa em maio de 2019 nas bases de dados do PubMed, Clinicalkey e Google Scholar, com limite de data nos últimos cinco anos. Os seguintes termos de indexação foram usados para a busca: “intertrochanteric and ipsilateral shaft fractures” e " femoral neck and ipsilateral shaft fractures”. Apenas estudos clínicos que apresentassem sugestões de manejo no tratamento de fratura do fêmur proximal e diafisário ipsilateral foram selecionados. Foram excluídos os estudos nos quais não apresentavam indicação da técnica de tratamento, assim como artigos de revisão e capítulos de livros ou periódicos não indexados. Resultados: finalizou-se a busca com número total de 21 artigos encontrados. Nenhum dos métodos de fixação disponíveis (implante único ou múltiplo) mostrou clara superioridade para abordar a associação de fraturas do fêmur proximal e diáfise do fêmur ipsilateral. No relato de caso, mesmo com a consolidação em varo do colo femoral, o quadro do paciente evoluiu bem. A fratura do colo era basocervical e, possivelmente, teve um comportamento mais próximo à fratura transtrocantérica, o que explica a evolução favorável, mesmo com desvio. Conclusão: nenhum método mostrou evidente superioridade ao outro. Deve-se atentar para a redução estável e a fixação rígida da fratura proximal, sobretudo do colo, embora a fixação da fratura diafisária não deva dificultar as ações sobre a fratura proximal.
Venezuelan migrant population in Colombia: health indicators in the context of the Sustainable Development Goals
Authors: Bonilla-Tinoco Laura Juliana , Aguirre-Lemus Melissa , Fernández-Niño Julián Alfredo
Published: July 2020

Background:The number of Venezuelan migrants in Colombia has dramatically increased over the past years, which poses great challenges to the Colombian health system. Therefore, the aim of this study was to compare some health indicators related to the Sustainable Development Goals between the Venezuelan migrant population and the Colombian population.

Methods:A longitudinal, descriptive analysis of the maternal mortality ratio; the neonatal, infant and under-five mortality; the proportionate mortality due to undernourishment; and the rates of alleged sexual felony, intimate partner violence and domestic violence in the Venezuelan migrant population in Colombia and in the Colombian population in the 2015-2019 period was conducted. Maternal and child health and undernourishment indicators were estimated for the 2015-18 period, while the gender-based violence indicators were obtained only for 2018-19, since those were the years with information available for each of these indicators. Data was extracted from official sources, such as the National Administrative Department of Statistics (DANE), National Institute of Legal Medicine and Forensic Sciences (INMLCF) and Migración Colombia. The categorical and numerical variables were described through percentages and rates, respectively.

Results:Venezuelan migrants in Colombia had higher rates of maternal, neonatal, infant and under-five mortality, as well as proportionate mortality due to undernourishment, than the Colombian population throughout the study years, although the difference between them decreased at the end of the period. As for the gender-based violence indicators, the Colombian population showed higher rates than the Venezuelan migrants, and both Colombian and Venezuelan female victims showed higher rates in these violence indicators than their male counterparts of the same nationality.

Conclusions:Some apparent inequalities still persist despite the efforts of the Colombian government to attend to the health needs of the Venezuelan migrant population. Colombia must keep and strengthen migratory inclusion in its public policies to impact on migrants’ health.
Testing the effect of PAR1 inhibitors on Plasmodium falciparum-induced loss of endothelial cell barrier function
Authors: Storm Janet , Wu Yang , Davies Jill , Moxon Christopher A. , Craig Alister G.
Published: July 2020

Background: Sequestration and cytoadherence of Plasmodium falciparum-infected erythrocytes (IE) to microvascular endothelium alters endothelial barrier function and plays a role in the pathogenesis of severe malaria. Binding of IE is mediated by P. falciparum erythrocyte membrane protein 1 (PfEMP1) and the PfEMP1 variants that binds to endothelial protein C receptor (EPCR) have, in particular, been associated with the dysregulation of the coagulation/inflammation pathways in endothelial cells. This has prompted speculation about the role of protease-activated receptor-1 (PAR1) activation and signalling in causing endothelial activation and loss of barrier function in cerebral malaria.

Methods: We used a co-culture of primary human brain microvascular endothelial cells (HBMEC) with P. falciparum material, recombinant PfEMP1 or lysates from IE, and measured barrier function by trans endothelial electrical resistance (TEER).  A selection of PAR1 inhibitors was tested for their ability to reverse the P. falciparum and thrombin induced decrease in barrier function.

Results: An initial screen in the presence of recombinant PfEMP1 identified a few inhibitors that were able to reduce the rapid thrombin-induced barrier disruption even when activated protein C (aPC) was unable to do so. However, PAR1 inhibitors did not rescue the barrier dysfunction after co-culture with IE lysate.

Conclusions: The selected PAR1 inhibitors were able to reverse the disruption of barrier function by thrombin but did not reverse the IE lysate induced disruption of barrier function, implicating a different PAR1-independent mechanism.  These findings have implications for the design of adjunct therapies to reduce brain swelling in cerebral malaria.
Maturidade empresarial impacta risco idiossincrático?
Authors: Damasceno Felipe Storch , Monte Mor Danilo Soares , Gonçalves Leilia Mara dos Santos , Francisco Alysson
Published: July 2020

Este estudo tem por objetivo averiguar se os estágios do ciclo de vida das empresas brasileiras influenciam a volatilidade idiossincrática das mesmas. Utilizam-se como estimadores o CAPM (Capital Asset Pricing Model) proposto por Assaf Neto, Lima e Araújo (2006) para a volatilidade idiossincrática, e Dickinson (2011) para as fases do ciclo de vida das empresas. Os resultados demonstram que a volatilidade idiossincrática é menor nas fases de crescimento e de maturidade, indicando que a identificação do ciclo de vida que determinada empresa pertence é importante para a manutenção de investimentos menos arriscados.
Intention to continue to use mobile productivity apps
Authors: Contreras Pinochet Luis Hernan , Tanaka Letícia Yoshimi , Azevedo Marcia Carvalho de , Lopes Evandro Luiz
Published: July 2020

The aim of this article is to understand the role of user value perspectives (perceived utility and perceived pleasure) in the intention to continue to use mobile productivity applications. The proposed model was developed based on data collected in a survey with 320 respondents. A Multivariate of Structural Equations Modeling was used. The results validate the model and confirm that the selected constructs have considerable explanatory power. It was understood that, in productivity apps, the hedonic characteristic should be observed carefully, and that this type of app has greater identification with perceived utility characteristics and confirmation of expectations, by its very nature.
Educação empreendedora: a prática docente estimulando a mente do estudante
Authors: Guimarães Jairo de Carvalho , Dos Santos Ildamara Ferreira
Published: July 2020

Empreendedorismo é um fenômeno que tem evoluído nas últimas décadas, levando ao desenvolvimento social e econômico regional. Neste sentido, surgiu a necessidade de analisar o tema sob a perspectiva da Educação Empreendedora. O estudo busca identificar se há influência do docente quanto à formação empreendedora discente, sendo o seu objetivo a descrição da influência do professor para a formação do espírito empreendedor. A pesquisa é descritiva e exploratória, orientada por meio do Survey, de abordagem quantitativa. Os dados foram analisados com o auxílio do Software Excel 2013™, cujos resultados confirmam a influência do docente quanto à intenção empreendedora dos discentes.
Ciudadanos organizados y derecho a la salud. Significados en la Venezuela del siglo XXI
Authors: Delgado Blanco Andy del Valle
Published: July 2020

Este artículo presenta los resultados de una investigación realizada en Venezuela, entre 2012 y 2013, bajo el paradigma cualitativo, con la forma de un estudio de caso y anclado teóricamente en el enfoque de las capacidades de Amartya Sen. A partir de una serie de entrevistas, se buscó descubrir los sentidos y significados que los ciudadanos organizados elaboran sobre el derecho a la salud. Los resultados muestran información de sus valoraciones sobre el sistema de derechos y los mecanismos que los respaldan; se evidencian cuestionamientos a la efectividad de las garantías previstas en la Constitución de 1999: la atención en salud no llega a todos los ciudadanos, la provisión de los bienes y servicios en salud es limitada y de baja calidad, con notorias dificultades para el acceso a tratamientos y medicamentos. En términos senianos, esto se traduce en restricciones a las oportunidades reales de llevar la vida que quieren y tienen razones para valorar, y, por ende, en una disminución de su libertad.
Aportes de los sistemas locales de justicia a la construcción de una cultura de paz. El caso de la localidad de Kennedy (Bogotá)
Authors: Guzmán Yesica Alejandra
Published: July 2020

Se presenta un análisis de los aportes de la implementación de los sistemas locales de justicia a la construcción de una cultura de paz, abordando el caso de la localidad de Kennedy (Bogotá). Se parte de la comprensión de los slj como herramienta para garantizar el derecho fundamental de acceso a la justicia y de su relación con la construcción de una cultura de paz. Entre los principales hallazgos se concluye que los slj han aportado en la formación de operadores de justicia y en la creación de rutas y espacios de articulación entre actores de la justicia formal y comunitaria, contribuyendo a combatir las barreras operativas y a fortalecer la democracia participativa. Así mismo, se identifican como principales retos para el éxito de la política garantizar su continuidad y sistematicidad en los procesos, lo que implica convertirla en una política de Estado, evitando que esté a merced de la voluntad política, la articulación institucional, la sensibilización y formación continua de los operadores de justicia y la inclusión de actores comunitarios, lo que supondría una democratización de la administración de justicia.
Improving Text Analysis Using Sentence Conjunctions and Punctuation
Authors: Büschken Joachim , Allenby Greg M.
Published: July 2020

User-generated content in the form of customer reviews, blogs, and tweets is an emerging and rich source of data for marketers. Topic models have been successfully applied to such data, demonstrating that empirical text analysis benefits greatly from a latent variable approach that summarizes high-level interactions among words. We propose a new topic model that allows for serial dependency of topics in text. That is, topics may carry over from word to word in a document, violating the bag-of-words assumption in traditional topic models. In the proposed model, topic carryover is informed by sentence conjunctions and punctuation. Typically, such observed information is eliminated prior to analyzing text data (i.e., preprocessing) because words such as “and” and “but” do not differentiate topics. We find that these elements of grammar contain information relevant to topic changes. We examine the performance of our models using multiple data sets and establish boundary conditions for when our model leads to improved inference about customer evaluations. Implications and opportunities for future research are discussed.
Diagnosis of Precocious Puberty in Girls
Authors: Gaudino Rossella , Calcaterra Valeria , Farello Giovanni , Gasparri Manuela , Monti Claudio Maria , Bozzola Elena , Villani Alberto , Bozzola Mauro
Published: July 2020

Puberty is one of the most astonishing periods of human life, when significant physical alterations occur along with psychosocial maturation. Precocious Puberty (PP) is defined as the appearance and progressive development of secondary sexual characteristics at a younger age than the general population, i.e. for Caucasian girls before 8 years of age. Untreated precocious puberty usually leads to short stature and can also cause significant emotional and behavioral issues. In recent years, an increased incidence of PP has been found in many countries although several studies now suggest that this trend has slowed down over the last decade in most industrialized countries, while persisting in other countries. Some girls with idiopathic precocious puberty may also have slowly progressive pubertal development without deterioration of their predicted height over a 2-year follow-up period. It is important to determine which girls to treat and the role of the clinician remains crucial. The clinician also needs to be familiar with the terminology of pubertal progression.
The aim of this review was to examine the diagnosis of central precocious puberty (CPP) taking in account clinical practice and international literature.
The effects of COVID-19 on perioperative morbidity and mortality in patients with hip fractures
Authors: Kayani Babar , Onochie Elliot , Patil Vijay , Begum Fahima , Cuthbert Rory , Ferguson David , Bhamra Jagmeet S. , Sharma Aadhar , Bates Peter , Haddad Fares S.
Published: July 2020

Aims

During the COVID-19 pandemic, many patients continue to require urgent surgery for hip fractures. However, the impact of COVID-19 on perioperative outcomes in these high-risk patients remains unknown. The objectives of this study were to establish the effects of COVID-19 on perioperative morbidity and mortality, and determine any risk factors for increased mortality in patients with COVID-19 undergoing hip fracture surgery.

Methods

This multicentre cohort study included 340 COVID-19-negative patients versus 82 COVID-19-positive patients undergoing surgical treatment for hip fractures across nine NHS hospitals in Greater London, UK. Patients in both treatment groups were comparable for age, sex, body mass index, fracture configuration, and type of surgery performed. Predefined perioperative outcomes were recorded within a 30-day postoperative period. Univariate and multivariate analysis were used to identify risk factors associated with increased risk of mortality.

Results

COVID-19-positive patients had increased postoperative mortality rates (30.5% (25/82) vs 10.3% (35/340) respectively, p < 0.001) compared to COVID-19-negative patients. Risk factors for increased mortality in patients with COVID-19 undergoing surgery included positive smoking status (hazard ratio (HR) 15.4 (95% confidence interval (CI) 4.55 to 52.2; p < 0.001) and greater than three comorbidities (HR 13.5 (95% CI 2.82 to 66.0, p < 0.001). COVID-19-positive patients had increased risk of postoperative complications (89.0% (73/82) vs 35.0% (119/340) respectively; p < 0.001), more critical care unit admissions (61.0% (50/82) vs 18.2% (62/340) respectively; p < 0.001), and increased length of hospital stay (mean 13.8 days (SD 4.6) vs 6.7 days (SD 2.5) respectively; p < 0.001), compared to COVID-19-negative patients.

Conclusion

Hip fracture surgery in COVID-19-positive patients was associated with increased length of hospital stay, more admissions to the critical care unit, higher risk of perioperative complications, and increased mortality rates compared to COVID-19-negative patients. Risk factors for increased mortality in patients with COVID-19 undergoing surgery included positive smoking status and multiple (greater than three) comorbidities. Cite this article: Bone Joint J 2020;102-B(9):1136–1145.
Advancing behavioural public policies: in pursuit of a more comprehensive concept
Authors: Ewert Benjamin , Loer Kathrin
Published: July 2020

Behavioural public policy is predominantly based on insights from behavioural economics and psychology in order to ‘nudge’ people to act in line with specific aims and to overcome the dilemma of behaviour that contradicts economic rationality. In contrast, we define behavioural public policy as a multi-disciplinary and multi-methodological concept that utilises insights from the whole range of behavioural research. Based on a scoping review and peer survey we see merit in behavioural insights from disciplines such as anthropology, geography and sociology as well as the application of qualitative methods. Our findings identify the need to advance behavioural public policy conceptually and methodologically. This article challenges our current understanding of behavioural policymaking by integrating ‘foreign’ views and approaches that do not (yet) belong to the core discipline. We argue that behavioural public policy should not be a synonym for a limited number of policy approaches (for example, nudges) based on specific research methods (for example, randomised control trials) to reach individual behaviour change. Instead, our findings suggest a redefinition of the scientific footing of behavioural public policy.
Relative time and life course research
Authors: Sánchez-Mira Núria , Bernardi Laura
Published: July 2020

Mainstream life course studies often draw on a conventional understanding of time as a unidirectional clock-based entity, which proceeds in a uniform and linear manner. This paper argues that, in order to understand the social, relational and psychological processes of change and continuity that characterise life course processes, we need to adopt a more comprehensive and explicit conceptualisation of time – a conceptualisation that goes beyond an absolute (linear, chronological, uniform) definition – to incorporate the notion of relative time. Drawing on insights from narrative and biographical research, discussions of the temporal embeddedness of human agency and multidisciplinary research on time perceptions and time perspectives, we propose a definition of relative time based on three main characteristics: its multidirectional, elastic and telescopic nature. The paper promotes the integration of absolute and relative time in the study of life course processes, and the important role of prospective qualitative research in this respect, and outlines future avenues for research in this direction.
Digital technology as a trigger for learning: promises and realities
Authors: Sancho -Gil Juana M.
Published: July 2020

In the last fitty years, the remarkable development of digital technology, that has permeated practically all social, economic and cultural, political and technological realms is producing several phenomena that have a direct impact in education. In this paper, I discuss first, the fact that more and more we refer to digital technology as just ‘technology”, as if the rest of the many organizational, symbolic, artefactual and biotechnological developments were something “natural”. Second, I refer to the rise and spread of technological solutionism in education and a growing discourse that sees every new digital technology as the arrival of the Promised Land, as the panacea to solve the problems of education. I go on analysing the collateral effects of this discourse in the educational practice, with an especial reference to persuasive technologies and Big Data. The article concludes with the request and the need for researchers, practitioners and education policy makers to avoid the temptation to solve a deeply "wicked" problem such as education with simple solutions.
Are primary education teachers from Catalonia (Spain) trained on the ICT and disability?
Authors: Fernández Batanero José María , Román Graván Pedro , Siles Rojas Carmen
Published: July 2020

In this work, we present the results of a study that had as an objective to understand the perception of key informants (directors, heads of studies and ICT coordinators from education centers, as well as well as directors and technology managers from teacher’s training centers), on the levels of technological training and knowledge possessed by the Primary Education teachers from the Autonomous Community of Catalonia, with respect to the use of the ICT with students with disabilities. For the methodology, a qualitative research design was used. The information was obtained from an analysis of 68 interviews conducted to professional from the education sector in Catalonia.  The results obtained showed that the professionals perceived a low level of training and knowledge of the teachers with respect to the use of the ICT with people with disabilities. The findings showed the need to design and implement didactic training that empowers the teachers.
Investigating Digital Distraction among Pre-service Science, Technology, and Mathematics Teachers in Nigeria
Authors: Awofala Adeneye Olarewaju , Olabiyi Oladiran Stephen , Okunuga Racheal O , Ojo Omolabake Temilade , Awofala Awoyemi Abayomi , Lawani Abisola O
Published: July 2020

Internationally, proliferation of digital technologies in classrooms has produced digital distractions among digital natives in this 21st century. Thus, it is highly imperative to develop a suitable instrument for assessing and measuring digital distraction among higher education students to enable continuing research and practice. While previous studies had treated and measured digital distraction as a sub-component of a multi-dimensional construct and as a test, the present study through instrumentation survey research, developed and authenticated a standalone digital distraction scale among pre-service science, technology and mathematics (STM) teachers in Nigeria. The instrument is constructed by adopting a multidimensional standpoint of digital distraction around a higher-order modelling method. The pre-service STM teachers were recruited from a culturally varied university student population in Nigeria. The results showed a high level of digital distraction among the pre-service STM teachers in Nigeria and the digital distraction is composed of several connected yet distinctive factors (emotional distraction, digital addiction, and distraction by procrastination), with proof backing up a higher-order structural archetypal. More so, empirical evidence confirmed the measurement invariance of the scale with regards to gender and the consistency of the psychometric properties of the digital distraction scale. Finally, a test-retest reliability of the digital distraction scale showed that the scores are not variable over time and that the scale is not sensitive to alterations in the learning milieu. Finally, it is hoped that this tool will be handy for educators interested in isolating pre-service STM teachers at risk of high digital distraction which may cause lack of respect and privation of courtesy for instructors and personal distraction in the classroom.
Digital technologies in support of students learning in Higher Education: literature review
Authors: Pinto Marta , Leite Carlinda
Published: July 2020

Digital technologies are an integral part of Higher Education teaching, revealing a set of technologies chosen to integrate formal learning contexts, and therefore being used by students in support of learning. This paper presents a literature review mapping the digital technologies set for higher education students to use in formal education contexts, over the last five years between 2012 and 2017. Results show a pattern of technologies reflecting teacher’s choice for methods combining face-to-face and at distance learning, frequently in relation to the adoption of flipped classroom methods. Mapping the digital technologies used by students, showed a pattern of three most used in a total of nine types identified. Institutional Learning Management Systems mainly support a wider access to information and learning materials, followed by technologies that promote publishing and sharing content related to class activities, and a broad range of technologies categorized under ICTs. The overall impact of use of technologies in students learning process and outcomes revealed to be positive, used with the intention to promote students’ active engagement and participation in the learning process inside and outside the classroom walls. The data also revealed digital technologies to support more transmissive ways of teaching, facilitating students individually to Access, share and publish information, and significantly lesser used to promote collaborative and cooperative learning.
Tunable asymmetric transmission across stretchable chiral metamaterial
Authors: Zhou Lei , Wang Yueke , Zhou Jiaxin , Ding Jian , Lu Mengjia , Sang Tian
Published: July 2020

A stretchable chiral metamaterial with L-shaped and T-shaped Au patterns (SCMM-LT) is proposed to generate asymmetric transmission (AT) for circularly polarized waves on the polydimethylsiloxane substrate in the mid-infrared region. The peak value of AT can reach 50.02% at the resonance wavelength of 19.1 µm, owing to the enantiomerically sensitive plasmons. With stretching along the

x

axis and the

y

axis. respectively, the band of AT shifts to a longer wavelength, which proves the SCMM-LT can be a candidate as the tunable chiral metamaterial. In the future, the proposed stretchable chiral metamaterial could potentially possess high applicability for wearable electronic devices in a variety of sensor fields.
Fast focus-shifter based on a unimorph deformable mirror
Authors: Verpoort Sven , Bittner Matthias , Wittrock Ulrich
Published: July 2020

On-the-fly remote laser processing plays an increasingly important role in modern fabrication techniques. These processes require guiding of the focus of a laser beam along the contours of the workpiece in three dimensions. State-of-the-art galvanometer scanners already provide highly dynamic and precise transverse

x

−

y

beam steering. However, longitudinal focus shifting (“z-shifting”) relying on conventional optics is restricted to a bandwidth of a few hundred Hz. We have developed and manufactured a fast piezo-based z-shifting mirror with diffraction-limited surface fidelity providing a focus shift of

Δ
z
>
60

m
m

with an actuation rate of 2 kHz.
Improving the visible light communication localization system using Kalman filtering with averaging
Authors: Shawky Eman , El-Shimy Mohamed , Mokhtar Amr , El-Badawy El-Sayed A. , Shalaby Hossam M. H.
Published: July 2020

Two techniques are proposed for improving the accuracy of localization estimation in indoor visible light communication systems, namely, averaging and Kalman filtering with averaging schemes. In the averaging technique, the receiver position is estimated using the received signal strength (RSS) indication method multiple times (e.g.,

N

 samples), and the acquired estimations are averaged over all samples. To further improve the localization, the Kalman filtering algorithm is adopted to estimate the received power over

N

samples, followed by applying the RSS technique on the average received power. The proposed techniques are analyzed mathematically, considering the effects of both line-of-sight (LOS) and first-reflection from non-LOS propagations. The performance of the proposed techniques is determined by evaluating the positioning errors in a typical room. The results are compared to that of the traditional RSS system. Simulation results reveal that an improvement of about 33.3% in the average positioning error is achievable when using the averaging scheme as compared to that of the traditional RSS scheme. This improvement increases to 72.2% when adopting the proposed Kalman filtering scheme.
Atoms in axially shifted tightly focused counter-propagating beams: the role of the Gouy and curvature phases
Authors: Koksal K. , Lembessis V. E. , Yuan J. , Babiker M.
Published: July 2020

We consider the interaction of atoms with two tightly focused and axially shifted counter-propagating optical beams. At sub-wavelength focusing, we find that the scattering force potential in the three-dimensional space between the shifted focal planes changes from a feature with a saddle-point to a three-dimensional trapping potential. Further analysis shows that due to the tight focusing, the trapping depends on significant contributions arising from the Gouy and curvature phase gradients of the interfering beams. The physics and its effects are illustrated with reference to the sub-wavelength trapping of sodium atoms.
Optical properties of water relaxing after intense laser exposure
Authors: Kononenko Vitali V. , Gololobov Viktor M. , Zavedeev Evgeny V. , Konov Vitaly I.
Published: July 2020

The dynamics of the optical properties of water bulk exposed to femtosecond radiation (Ti-sapphire laser, wavelength 800 nm, intensity

∼

10

13

W

/

c
m

2

) was studied in the time window of

≈
1.5

n
s

using a pump–probe technique. Both the refractive index and absorbance were measured by femtosecond interferometric microscopy, which allowed us to gather deconvoluting quantitative data about the induced processes: solvation of excess electrons, geminate recombination, and development of cavitation. We found that the number of electrons produced by a strong, near infrared (NIR) field in the cavitation regime (

<

10

19

c
m

−
3

) is much lower than was previously thought. The obtained data clarify the mechanisms of laser energy deposition in water and are of crucial importance to understand intensive light action on aqueous-based systems.
Adaptive terahertz image super-resolution with adjustable convolutional neural network
Authors: Li Yade , Hu Weidong , Zhang Xin , Xu Zhihao , Ni Jiaqi , Ligthart Leo P.
Published: July 2020

During the real-aperture-scanning imaging process, terahertz (THz) images are often plagued with the problem of low spatial resolution. Therefore, an accommodative super-resolution framework for THz images is proposed. Specifically, the 3D degradation model for the imaging system is firstly proposed by incorporating the focused THz beam distribution, which determines the relationship between the imaging range and the corresponding image restoration level. Secondly, an adjustable CNN is introduced to cope with this range dependent super-resolution problem. By simply tuning an interpolation parameter, the network can be adjusted to produce arbitrary restoration levels between the trained fixed levels without extra training. Finally, by selecting the appropriate interpolation coefficient according to the measured imaging range, each THz image can be coped with its matched network and reach the outstanding super-resolution effect. Both the simulated and real tested data, acquired by a 160 ∼ 220 GHz imager, have been used to demonstrate the superiority of our method.
Ptychography imaging by 1-D scanning with a diffuser
Authors: Wen Xiu , Geng Yong , Zhou Xuyang , Tan Jiubin , Liu Shutian , Tan Cuimei , Liu Zhengjun
Published: July 2020

It is beneficial to improve the resolution by a diffuser in imaging systems, because higher frequency information could be involved into the captured patterns via scattering effect. In this paper, a lensless imaging method is designed by 1-D scanning. A diffuser is placed upstream of the object, which is translated in a one-dimensional path and corresponding positions are corrected by cross-correlation. Our method requires a diffraction pattern of the object without a diffuser to speed up convergence and improve resolution. In field reconstruction, the amplitude constraint is added into the iterative phase retrieval algorithm. The high-quality complex-valued images can be obtained with ∼15 patterns. As a ptychography, the proposed method only needs a 1-D device, which could simplify the experimental equipment for reducing costs and measurement time.
Multifunctional reflective dielectric metasurface in the terahertz region
Authors: Li Jiu-Sheng , Zhou Chen
Published: July 2020

The recent emergence of digital coding metasurfaces has significantly simplified the design of functional devices and manipulated electromagnetic waves digitally. In this paper, we propose a dielectric coding metasurface with different functions, which is implemented by a metasurface with specific coding sequences. It is composed of a three-dimensional T-shaped dielectric block placed on a metal plate. Compared with traditional metal resonators, the all-dielectric metasurface has relatively low loss and the reflection amplitude maintains a high value. Here, we demonstrate five different functions of anomalous reflection, beam splitting, diffuse scattering, line focusing, and vortex beam generation achieved under normal incidence of the linearly polarized wave. Through full-wave numerical simulation, the far-field scattering patterns and near-field electric-field intensity distribution of the proposed metasurface under various reflection conditions are obtained, which is in good agreement with the theoretical prediction. It is verified that the multifunctional dielectric coding metasurface provides a new way to control the reflection of terahertz waves.
Enhanced emission of in-situ fabricated perovskite-polymer composite films on gold nanoparticle substrates
Authors: Perveen Abida , Deng Luogen , Muravitskaya Alina , Yang Di , Movsesyan Artur , Gaponenko Sergey , Chang Shuai , Zhong Haizheng
Published: July 2020

We compared the photoluminescence (PL) of perovskite-polymer composite films on gold nanoparticle (AuNPs) substrates without and with a buffer layer of polymethyl methacrylate (PMMA). It is found that a 1.8-fold PL enhancement can be experienced due to surface plasmons with solely AuNPs substrates. With PMMA placed between the emissive layer and AuNPs, the plasmonic effect is reduced while reflectance and interface enhanced emission is increased, which results in a final PL increase of 2-fold. Such enhancements provide potential strategies to enhance the light-emitting properties of in-situ fabricated perovskite quantum dots films for light conversion applications such as LCD backlights, silicon solar cells, and photodetectors.
Structure and morphology of low mechanical loss TiO2-doped Ta2O5
Authors: Fazio Mariana A. , Vajente Gabriele , Ananyeva Alena , Markosyan Ashot , Bassiri Riccardo , Fejer Martin M. , Menoni Carmen S.
Published: July 2020

The exceptional stability required from high finesse optical cavities and high precision interferometers is fundamentally limited by Brownian motion noise in the interference coatings of the cavity mirrors. In amorphous oxide coatings these thermally driven fluctuations are dominant in the high index layer compared to those in the low index SiO2 layer in the stack. We present a systematic study of the evolution of the structural and optical properties of ion beam sputtered TiO2-doped Ta2O5 films with annealing temperature. We show that low mechanical loss in TiO2-doped Ta2O5 with a Ti cation ratio = 0.27 is associated with a material that consists of a homogeneous titanium-tantalum-oxygen mixture containing a low density of nanometer sized Ar-filled voids. When the Ti cation ratio is 0.53, phase separation occurs leading to increased mechanical loss. These results suggest that amorphous mixed oxides with low mechanical loss could be identified by considering the thermodynamics of ternary phase formation.
High-resolution label-free imaging of tissue morphology with confocal phase microscopy
Authors: Schnell Martin , Gupta Shravan , Wrobel Tomasz P. , Drage Michael G. , Bhargava Rohit , Carney P. Scott
Published: July 2020

Label-free imaging approaches seek to simplify and augment histopathologic assessment by replacing the current practice of staining by dyes to visualize tissue morphology with quantitative optical measurements. Quantitative phase imaging (QPI) operates with visible/UV light and thus provides a resolution matched to current practice. Here we introduce and demonstrate confocal QPI for label-free imaging of tissue sections and assess its utility for manual histopathologic inspection. Imaging cancerous and normal adjacent human breast and prostate, we show that tissue structural organization can be resolved with high spatial detail comparable to conventional hematoxylin and eosin (H&E) stains. Our confocal QPI images are found to be free of halo, solving this common problem in QPI. We further describe a virtual imaging system based on finite-difference time-domain (FDTD) calculations and combine it with numerical tissue phantoms to quantitatively show the absence of halo and the improved clarity in resolving subcellular features with confocal QPI compared to wide-field QPI. Confocal QPI bears the potential to become a common tool for label-free disease diagnosis, while the presented FDTD method provides a flexible platform to evaluate the diagnostic potential of QPI methods.
All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers
Authors: Chantakit Teanchai , Schlickriede Christian , Sain Basudeb , Meyer Fabian , Weiss Thomas , Chattham Nattaporn , Zentgraf Thomas
Published: July 2020

Dynamic control of compact chip-scale contactless manipulation of particles for bioscience applications remains a challenging endeavor, which is restrained by the balance between trapping efficiency and scalable apparatus. Metasurfaces offer the implementation of feasible optical tweezers on a planar platform for shaping the exerted optical force by a microscale-integrated device. Here we design and experimentally demonstrate a highly efficient silicon-based metalens for two-dimensional optical trapping in the near-infrared. Our metalens concept is based on the Pancharatnam–Berry phase, which enables the device for polarization-sensitive particle manipulation. Our optical trapping setup is capable of adjusting the position of both the metasurface lens and the particle chamber freely in three directions, which offers great freedom for optical trap adjustment and alignment. Two-dimensional (2D) particle manipulation is done with a relatively low-numerical-aperture metalens (

NA

ML

=
0.6

). We experimentally demonstrate both 2D polarization-sensitive drag and drop manipulation of polystyrene particles suspended in water and transfer of angular orbital momentum to these particles with a single tailored beam. Our work may open new possibilities for lab-on-a-chip optical trapping for bioscience applications and microscale to nanoscale optical tweezers.
Synchronous nanoscale topographic and chemical mapping by differential-confocal controlled Raman microscopy
Authors: Cui Han , Wang Yun , Qiu Lirong , Li Shucheng , Cooper Jonathan M. , Zhao Weiqian
Published: July 2020

Confocal Raman microscopy is currently used for label-free optical sensing and imaging within the biological, engineering, and physical sciences as well as in industry. However, currently these methods have limitations, including their low spatial resolution and poor focus stability, that restrict the breadth of new applications. This paper now introduces differential-confocal controlled Raman microscopy as a technique that fuses differential confocal microscopy and Raman spectroscopy, enabling the point-to-point collection of three-dimensional nanoscale topographic information with the simultaneous reconstruction of corresponding chemical information. The microscope collects the scattered Raman light together with the Rayleigh light, both as Rayleigh scattered and reflected light (these are normally filtered out in conventional confocal Raman systems). Inherent in the design of the instrument is a significant improvement in the axial focusing resolution of topographical features in the image (to

∼
1
  
nm

), which, when coupled with super-resolution image restoration, gives a lateral resolution of 220 nm. By using differential confocal imaging for controlling the Raman imaging, the system presents a significant enhancement of the focusing and measurement accuracy, precision, and stability (with an antidrift capability), mitigating against both thermal and vibrational artefacts. We also demonstrate an improved scan speed, arising as a consequence of the nonaxial scanning mode.
Integrated dispersion compensated mode-locked quantum dot laser
Authors: Zhang Zeyu , Norman Justin C. , Liu Songtao , Malik Aditya , Bowers John E.
Published: July 2020

Quantum dot lasers are excellent on-chip light sources, offering high defect tolerance, low threshold, low temperature variation, and high feedback insensitivity. Yet a monolithic integration technique combining epitaxial quantum dot lasers with passive waveguides has not been demonstrated and is needed for complex photonic integrated circuits. We present here, for the first time to our knowledge, a monolithc offset quantum dot integration platform that permits formation of a laser cavity utilizing both the robust quantum dot active region and the versatility of passive GaAs waveguide structures. This platform is substrate agnostic and therefore compatible with the quantum dot lasers directly grown on Si. As an illustration of the potential of this platform, we designed and fabricated a 20 GHz mode-locked laser with a dispersion-engineered on-chip waveguide mirror. Due to the dispersion compensation effect of the waveguide mirror, the pulse width of the mode-locked laser is reduced by a factor of 2.8.
Influence of mixed organic cations on the nonlinear optical properties of lead tri-iodide perovskites
Authors: Zhang Xuanyu , Xiao Shuyu , Li Ruxue , He Tingchao , Xing Guichuan , Chen Rui
Published: July 2020

Metal halide perovskite materials have been widely studied recently due to their excellent optoelectronic properties. Among these materials, organic-inorganic hybrid perovskites have attracted much attention because of their relatively soft framework, which makes them more suitable for nonlinear optical (NLO) applications. However, there is rare physical mechanism study on the coexistence of two-photon absorption (TPA) and saturable absorption (SA) in organic-inorganic hybrid perovskite materials. To clarify this issue, the NLO properties of mixed cation perovskite

MA

1
−
x

FA

x

PbI

3

 
[
MA
=

CH

3

NH

3

,
FA
=
CH

(

NH

2

)

2

,

x
=
0

, 0.2, 0.4, 0.6, and 0.8] thin films are investigated in this paper. Based on the nonlinear transmittance and femtosecond-transient absorption spectrum measurements, it is found that the

MA

1
−
x

FA
x

PbI
3

materials exhibit NLO behavior dependent on excitation intensity. The TPA coefficient of

MA

1
−
x

FA

x

PbI

3

decreases with the increase of formamidinium (FA) content, while the relevant saturable intensity increases. In addition, it is revealed that the linear absorption process from valence band 2 to valance band 1 still exists even under a very low excitation intensity. With the increase of excitation intensity, the light transmittance at 1300 nm decreases first and then increases sharply, which also supports the explanation for the coexistence of TPA and SA. It is expected that our findings will promote the application of perovskite materials in nonlinear optoelectronic devices.
Mit Computer Vision zur automatisierten Qualitätssicherung in der industriellen Fertigung: Eine Fallstudie zur Klassifizierung von Fehlern in Solarzellen mittels Elektrolumineszenz-Bildern
Authors: Zschech Patrick , Sager Christoph , Siebers Philipp , Pertermann Maik
Published: July 2020

Die Qualitätssicherung bei der Produktion von Solarzellen ist ein entscheidender Faktor, um langfristige Leistungsgarantien auf Solarpanels gewähren zu können. Die vorliegende Arbeit leistet hierzu einen Beitrag zur automatisierten Fehlererkennung auf Wafern, indem Elektrolumineszenz-Bilder eines realen Herstellungsszenarios mithilfe von verschiedenen Computer-Vision-Modellen klassifiziert werden. Die Herausforderung besteht hierbei nicht nur darin, defekte Wafer von funktionsfähigen zu separieren, sondern gleichzeitig auch zwischen spezifischen Fehlerarten zu unterscheiden, während geringe Inferenzzeiten sicherzustellen sind. Zu diesem Zweck werden neben einfachen statistischen Modellen verschiedene Deep-Learning-Architekturen auf Basis von Convolutional Neural Networks (CNNs) verprobt und miteinander vergleichen. Ziel der Arbeit ist es, verschiedene Klassifizierungsansätze unterschiedlicher Komplexität zu testen und auf ihre praktische Einsatzfähigkeit unter realen Bedingungen zu untersuchen. Die Fallstudie zeigt, dass je nach Situation unterschiedliche Modelle ihre Existenzberechtigung haben und in Kombination sehr gute Ergebnisse erzielen. So lassen sich bereits mit statistischen Modellen und einfachen CNN-Varianten zuverlässige Aussagen mit Genauigkeiten von über 99 % bei Fehlertypen einfacher bis mittlerer Erkennbarkeit realisieren. Werden die Fehlerbilder demgegenüber diffuser und soll die Nachvollziehbarkeit der Ergebnisse durch positionsgenaue Lokalisierung von Fehlerobjekten gewährleistet werden, sind fortgeschrittenere Ansätze auf Basis sogenannter Region-Proposal-Netzwerke erforderlich, die allerdings auch mit einem erhöhten Labeling-Aufwand beim Annotieren der Fehlerobjekte einhergehen. Da die Umsetzung sämtlicher Modelle ausschließlich auf Open Source Tools wie zum Beispiel TensorFlow, Keras und OpenCV basiert, demonstriert die Fallstudie zudem, welche Möglichkeiten durch frei verfügbare Lösungen im Bereich von Computer Vision geboten werden.