bluuebunny/crossref_metadata_2025 huggingface dataset:
Markers of cognitive reserve and dementia incidence in the English Longitudinal Study of Ageing
Authors: Almeida-Meza Pamela , Steptoe Andrew , Cadar Dorina
Published: March 2020

Background

In the current climate of an ageing population, it is imperative to identify preventive measures for dementia.

Aims

We implemented a multifaceted index of cognitive reserve markers and investigated dementia incidence over 15 years of follow-up in a representative sample of the English population.

Method

Data were 12 280 participants aged ≥50 years from the English Longitudinal Study of Ageing, free from dementia at their baseline assessments during wave 1 (2002–2003), 3 (2006–2007) or 4 (2008–2009), and followed up until wave 8 (2016–2017). The Cognitive Reserve Index was constructed as a composite measure of education, occupation and leisure activities, using a standardised questionnaire. Cox proportional hazards regression models were used to estimate the hazard ratios of dementia in relation to cognitive reserve levels (low, medium and high) and its components (education, occupation and leisure activities).

Results

During the follow-up period, 602 participants aged 56–99 years developed dementia. Higher levels of cognitive reserve (hazard ratio 0.65, 95% CI 0.48–0.89,P= 0.008) were associated with a lower risk of dementia. An individual analysis of its components showed that higher levels of education (hazard ratio 0.56, 95% CI 0.36–0.88,P= 0.012), occupation (hazard ratio 0.72, 95% CI 0.56–0.91,P= 0.008) and leisure activities (hazard ratio 0.74, 95% CI 0.56–0.99,P= 0.047) were predictive of a reduced dementia risk, with the first two components particularly protective in younger participants (<85 years).

Conclusions

This study showed a reduced risk of dementia for individuals with a higher level of cognitive reserve, represented by higher education, complex occupations and multifaceted level of leisure activities.
The Evolving Concept of Cryptogenic Stroke
Authors: Kamel Hooman
Published: March 2020

PURPOSE OF REVIEW

This article discusses cryptogenic stroke and the results of recent randomized trials that can inform its evaluation and management.

RECENT FINDINGS

Most cryptogenic strokes appear embolic, leading to the term embolic stroke of undetermined source. It was previously thought that embolic stroke of undetermined source was a single, therapeutically relevant entity, the underlying sources of which would respond to anticoagulant therapy; however, two large randomized trials found no benefit with anticoagulation compared to antiplatelet therapy for secondary stroke prevention after embolic stroke of undetermined source. A single antiplatelet drug remains the recommended long-term antithrombotic treatment for secondary stroke prevention in embolic stroke of undetermined source. However, three caveats should be considered with regard to cryptogenic stroke. First, those with minor stroke symptoms presenting early after onset should receive 3 weeks of dual antiplatelet therapy. Second, all patients with cryptogenic stroke should be monitored for atrial fibrillation. Third, patients 60 years of age or younger with a patent foramen ovale (PFO) should be carefully evaluated to determine whether the PFO may have caused the stroke and whether they might benefit from PFO closure.

More personalized strategies may soon be available to guide treatment of cryptogenic stroke. In the meantime, it is hoped that the application of recent findings from clinical trials will reduce stroke recurrence in this important population.
Legal Liability Associated With rtPA Administration and Surrogate Decision Makers
Authors: Kass Joseph S. , Rose Rachel V.
Published: March 2020

Stroke is one of the most common conditions neurologists treat in emergency situations. This article examines the issues of surrogate decision makers and the physician’s potential legal liability in the context of the administration or nonadministration of recombinant tissue plasminogen activator (rtPA) in a common emergency department scenario.
Update on Treatment of Acute Ischemic Stroke
Authors: Rabinstein Alejandro A.
Published: March 2020

EDITOR’S NOTE

The article “Update on Treatment of Acute Ischemic Stroke” by Dr Rabinstein was first published in the February 2017 Cerebrovascular Disease issue of Continuum: Lifelong Learning in Neurology as “Treatment of Acute Ischemic Stroke” and has been updated by Dr Rabinstein for this issue at the request of the Editor-in-Chief.

PURPOSE OF REVIEW

This article provides an update on the state of the art of the treatment of acute ischemic stroke with particular emphasis on the indications for reperfusion therapy.

RECENT FINDINGS

In addition to the previously established indications for intravenous (IV) thrombolysis with recombinant tissue plasminogen activator (rtPA) within 4.5 hours of stroke symptom onset and endovascular therapy with mechanical thrombectomy for patients with large artery occlusion who can be treated within 6 hours of symptom onset, recent randomized controlled trials have now established new indications for emergency reperfusion in patients with wake-up stroke or delayed presentation (up to 24 hours from last known well in the case of mechanical thrombectomy). Identification of patients who may benefit from acute reperfusion therapy within this extended time window requires screening with perfusion brain imaging or, in the case of IV thrombolysis for wake-up strokes, emergency brain MRI. Collateral status and time to reperfusion remain the primary determinants of outcome.

SUMMARY

Timely successful reperfusion is the most effective treatment for patients with acute ischemic stroke. Recent evidence supports the expansion of the time window for reperfusion treatment in carefully selected patients.
Evolutionary insights in Amazonian turtles (Testudines, Podocnemididae): co-location of 5S rDNA and U2 snRNA and wide distribution of Tc1/Mariner
Authors: Cavalcante Manoella Gemaque , Nagamachi Cleusa Yoshiko , Pieczarka Julio Cesar , Noronha Renata Coelho Rodrigues
Published: March 2020

Eukaryotic genomes exhibit substantial accumulation of repetitive DNAs. These sequences can participate in chromosomal reorganization events and undergo molecular cooption to interfere with the function and evolution of genomes. In turtles, repetitive DNA sequences appear to be accumulated at probable break points and may participate in events such as non-homologous recombination and chromosomal rearrangements. In this study, repeated sequences of 5S rDNA, U2 snRNA, and Tc1/Mariner transposons were amplified from the genomes of the turtles, Podocnemis expansa and Podocnemis unifilis, and mapped by fluorescence in situ hybridization. Our data confirm the 2n=28 chromosomes for these species (the second lowest 2n in the order Testudines). We observe high conservation of the co-located 5S rDNA and U2 snRNA genes on a small chromosome pair (pair 13), and surmise that this represents the ancestral condition. Our analysis reveals a wide distribution of the Tc1/Mariner transposons, and we discuss how the mobility of these transposons can act on karyotypic reorganization events (contributing to the 2n decrease of those species). Our data add new information for the order Testudines and provide important insights into the dynamics and organization of these sequences in the chelonian genomes.
Cytoplasmic dynein-2 at a glance
Authors: Vuolo Laura , Stevenson Nicola L. , Mukhopadhyay Aakash G. , Roberts Anthony J. , Stephens David J.
Published: March 2020

Cytoplasmic dynein-2 is a motor protein complex that drives the movement of cargoes along microtubules within cilia, facilitating the assembly of these organelles on the surface of nearly all mammalian cells. Dynein-2 is crucial for ciliary function, as evidenced by deleterious mutations in patients with skeletal abnormalities. Long-standing questions include how the dynein-2 complex is assembled, regulated, and switched between active and inactive states. A combination of model organisms, in vitro cell biology, live-cell imaging, structural biology and biochemistry has advanced our understanding of the dynein-2 motor. In this Cell Science at a Glance article and the accompanying poster, we discuss the current understanding of dynein-2 and its roles in ciliary assembly and function.
New Data-based Cutoffs for Maximal Exercise Criteria across the Lifespan
Authors: WAGNER JONATHAN , NIEMEYER MAX , INFANGER DENIS , HINRICHS TIMO , STREESE LUKAS , HANSSEN HENNER , MYERS JONATHAN , SCHMIDT-TRUCKSÄSS ARNO , KNAIER RAPHAEL
Published: March 2020

Purpose

To determine age-dependent cutoff values for secondary exhaustion criteria for a general population free of exercise limiting chronic conditions; to describe the percentage of participants reaching commonly used exhaustion criteria during a cardiopulmonary exercise test (CPET); and to analyze their oxygen uptake at the respective criteria to quantify the impact of a given criterion on the respective oxygen uptake (V˙O2) values.

Methods

Data from the COmPLETE-Health Study were analyzed involving participants from 20 to 91 yr of age. All underwent a CPET to maximal voluntary exertion using a cycle ergometer. To determine new exhaustion criteria, based on maximal respiratory exchange ratio (RERmax) and age-predicted maximal HR (APMHR), one-sided lower tolerance intervals for the tests confirming V˙O2 plateau status were calculated using a confidence level of 95% and a coverage of 90%.

Results

A total of 274 men and 252 women participated in the study. Participants were nearly equally distributed across age decades from 20 to >80 yr. A V˙O2 plateau was present in 32%. There were only minor differences in secondary exhaustion criteria between participants exhibiting a V˙O2 plateau and participants not showing a V˙O2 plateau. New exhaustion criteria according to the tolerance intervals for the age group of 20 to 39 yr were: RERmax ≥ 1.13, APMHR210 − age ≥ 96%, and APMHR208 × 0.7 age ≥ 93%; for the age group of 40 to 59 yr: RERmax ≥ 1.10, APMHR210 − age ≥ 99%, and APMHR208 × 0.7 age ≥ 92%; and, for the age group of 60 to 69 yr: RERmax ≥ 1.06, APMHR210 − age ≥ 99%, and APMHR208 × 0.7 age ≥ 89%.

Conclusions

The proposed cutoff values for secondary criteria reduce the risk of underestimating V˙O2max. Lower values would increase false-positive results, assuming participants are exhausted although, in fact, they are not.
Endogenous Infrastructure Development and Spatial Takeoff in the First Industrial Revolution
Authors: Trew Alex
Published: March 2020

This paper develops a model in which the evolution of the transport sector occurs alongside the growth in trade and output of agricultural and manufacturing firms. Simulation output captures aspects of the historical record of England and Wales over 1710–1881. A number of counterfactuals demonstrate the role that the timing and spatial distribution of infrastructure development play in determining the timing of takeoff. There can be a role for policy in accelerating takeoff through improving infrastructure, but the spatial distribution of that improvement matters. (JEL H54, N53, N63, N73, N93, R12, R42)
Deconstructing Monetary Policy Surprises— The Role of Information Shocks
Authors: Jarociński Marek , Karadi Peter
Published: March 2020

Central bank announcements simultaneously convey information about monetary policy and the central bank's assessment of the economic outlook. This paper disentangles these two components and studies their effect on the economy using a structural vector autoregression. It relies on the information inherent in high-frequency co-movement of interest rates and stock prices around policy announcements: a surprise policy tightening raises interest rates and reduces stock prices, while the complementary positive central bank information shock raises both. These two shocks have intuitive and very different effects on the economy. Ignoring the central bank information shocks biases the inference on monetary policy nonneutrality. (JEL D83, E43, E44, E52, E58, G14)
Host deficiency in ephrin-A1 inhibits breast cancer metastasis
Authors: Shiuan Eileen , Inala Ashwin , Wang Shan , Song Wenqiang , Youngblood Victoria , Chen Jin , Brantley-Sieders Dana M.
Published: March 2020

Background: The conventional dogma of treating cancer by focusing on the elimination of tumor cells has been recently refined to include consideration of the tumor microenvironment, which includes host stromal cells. Ephrin-A1, a cell surface protein involved in adhesion and migration, has been shown to be tumor suppressive in the context of the cancer cell. However, its role in the host has not been fully investigated. Here, we examine how ephrin-A1 host deficiency affects cancer growth and metastasis in a murine model of breast cancer.

Methods: 4T1 cells were orthotopically implanted into the mammary fat pads or injected into the tail veins of ephrin-A1 wild-type (Efna1+/+), heterozygous (Efna1+/-), or knockout (Efna1-/-) mice. Tumor growth, lung metastasis, and tumor recurrence after surgical resection were measured. Flow cytometry and immunohistochemistry (IHC) were used to analyze various cell populations in primary tumors and tumor-bearing lungs.

Results: While primary tumor growth did not differ between Efna1+/+, Efna1+/-, and Efna1-/- mice, lung metastasis and primary tumor recurrence were significantly decreased in knockout mice. Efna1-/- mice had reduced lung colonization of 4T1 cells compared to Efna1+/+ littermate controls as early as 24 hours after tail vein injection. Furthermore, established lung lesions in Efna1-/- mice had reduced proliferation compared to those in Efna1+/+ controls.

Conclusions: Our studies demonstrate that host deficiency of ephrin-A1 does not impact primary tumor growth but does affect metastasis by providing a less favorable metastatic niche for cancer cell colonization and growth. Elucidating the mechanisms by which host ephrin-A1 impacts cancer relapse and metastasis may shed new light on novel therapeutic strategies.
A review of open source ventilators for COVID-19 and future pandemics
Authors: Pearce Joshua M.
Published: March 2020

Coronavirus Disease 2019 (COVID-19) threatens to overwhelm our medical infrastructure at the regional level causing spikes in mortality rates because of shortages of critical equipment, like ventilators. Fortunately, with the recent development and widespread deployment of small-scale manufacturing technologies like RepRap-class 3-D printers and open source microcontrollers, mass distributed manufacturing of ventilators has the potential to overcome medical supply shortages. In this study, after providing a background on ventilators, the academic literature is reviewed to find the existing and already openly-published, vetted designs for ventilators systems. These articles are analyzed to determine if the designs are open source both in spirit (license) as well as practical details (e.g. possessing accessible design source files, bill of materials, assembly instructions, wiring diagrams, firmware and software as well as operation and calibration instructions). Next, the existing Internet and gray literature are reviewed for open source ventilator projects and designs. The results of this review found that the tested and peer-reviewed systems lacked complete documentation and the open systems that were documented were either at the very early stages of design (sometimes without even a prototype) and were essentially only basically tested (if at all). With the considerably larger motivation of an ongoing pandemic, it is assumed these projects will garner greater attention and resources to make significant progress to reach a functional and easily-replicated system. There is a large amount of future work needed to move open source ventilators up to the level considered scientific-grade equipment, and even further work needed to reach medical-grade hardware. Future work is needed to achieve the potential of this approach by developing policies, updating regulations, and securing funding mechanisms for the development and testing of open source ventilators for both the current COVID19 pandemic as well as for future pandemics and for everyday use in low-resource settings.
Features of distribution of seismic activity in different regions of Earth over phases of the 11-year solar cycle
Authors: Ruzhich Valeriy , Levina Elena
Published: March 2020

We discuss the relationship of solar activity with the seismicity of Earth and reasons for the differences in the results of studies of various authors. Using the epoch superposition method, we analyze the differences in seismic activity distribution over phases of the 11-year solar cycle for the whole world, hemispheres, sectors, latitudinal belts, and individual regions. The northeastern sector of Earth has been shown to make the main contribution to the planetary distribution of seismic activity over phases of the 11-year solar cycle. We have revealed a pattern in the distribution of seismic activity over latitudinal belts: the solar cycle phases, at which the main maximum of seismic activity occurs, increase with increasing latitude in both hemispheres. For some regions, the results may differ from the generalized results for Earth due to the influence of local geodynamic conditions during the destruction of the earth's crust. In middle latitudes, the maximum number of earthquakes is shifted to the later phases of the solar cycle from west to east, which was not found for the northern regions. We discuss possible reasons for various manifestations of solar-terrestrial relationships for different regions, taking into account their different structure and geodynamic development modes. The presence of pronounced maxima of the seismic activity distribution over the 11-year solar cycle phases allows us to use them for refining the “time” parameter in the medium-term prediction of dangerous earthquakes.
Relationships between parameters of uric acid exchange and immunity as well as microbiota in patients with neuroendocrine-immune complex dysfunction
Authors: Gozhenko Anatoliy , Smagliy Vadym , Korda Inna , Badiuk Nataliya , Zukow Walery , Kovbasnyuk Marta , Popovych Igor
Published: March 2020

Background. Previously, we found a wide range of uric acid exchange parameters and functional relationships of uricemia and uricosuria with the parameters of immunity in healthy rats analyzed. The purpose of this study is to clarify such relationships in patients with neuroendocrine-immune complex dysfunction on the background of chronic pyelonephritis combined with cholecystitis in remission. Material and Methods. The object of observation were 34 men and 10 women aged 24-70 years old, who came to the Truskavets’ spa for the rehabilitation treatment. The serum and daily urine levels of the uric acid by uricase method were determined. Immune status evaluated on a set of I and II levels recommended by the WHO. The condition of microbiota is evaluated on the results of sowing of feces and urine. Results. The canonical correlation analysis revealed that raw uricemia determines by 28% nine parameters of immunity (relative blood content of pan-lymphocytes and their CD4+-, CD56+-, 0-populations, relative content of polymorphonuclear neutrophils, intensity and completeness of their phagocytosis Staph. aureus and their bactericidal capacity, saliva content of IgG) as well as bacteriuria and content in E. coli feces. Uricemia, normalized by sex and age, determines by 25% another constellation of immunity parameters (relative CD8+ lymphocytes content, CIC, E. coli phagocytosis intensity and completeness, Staph. aureus phagocytosis activity and completeness) as well as content in E. coli feces with impaired enzymatic activity and Klebsiela&Proteus. Instead, uricosuria determines only four parameters of immunity and only by 11,5%. Conclusion. Endogenous uric acid has a modulating overall beneficial effect on a number of immune and microbiota parameters in both healthy rats and people with neuroendocrine-immune complex dysfunction.
Physiotherapeutic procedures used in patients after surgical treatment of maxillofacial and occlusal disorders
Authors: Gębska Magdalena , Weber-Nowakowska Katarzyna
Published: March 2020

The treatment of patients with craniofacial defects is interdisciplinary and long term. In order to restore the function of the stomatognathic system (chewing, swallowing, speech, breathing) and to improve the aesthetic appearance of the face, patients with malformations and acquired defects require combination therapy. It is necessary to cooperate with a surgeon, orthodontist, phoniatrist, speech therapist, prosthetist, psychologist and physiotherapist. The earlier treatment of facial cranial defects is started, the better final results can be obtained. The aims of rehabilitation are prevention of pulmonary complications, prevention of deep vein thrombosis, restoration of the efficiency of the stomatognathic system, removal of functional and organic consequences of surgery. The implementation of these goals begins on the first day after surgery and continues until the patient is discharged from the hospital. The next step is ambulatory rehabilitation.
Physical activity as one of the elements of a comprehensive obesity treatment
Authors: Kucharczuk Magda , Sikorska Hanna , Juraszek Karolina Małgorzata , Wyżgowski Przemysław , Leksowski Krzysztof
Published: March 2020

Obesity is nowadays a disease of civilization contributing to the increase in mortality worldwide, especially in developing and developed countries. There is a need to take action to normalise the weight of as many people as possible, bearing in mind disadvantageous to the health and the life, effects of exaggerated increasing the amount of the fatty tissue. In this connection, the need to shape patterns of pro-healthy behaviour should be particularly emphasised. The implementation of appropriate physical activity should be one of the basic elements of a comprehensive obesity treatment. Taking into account a wide range of exercises, it is important to choose the right activity for a given person, taking into account their abilities and performance, as well as indications and contraindications to a specific form of training. A key role in the weight reduction process is played by the determination to continue the recommendations made in a long-term and systematic manner. If attempts of the non-invasive treatment turn out to be ineffective, sick persons with the obesity can be qualified for the bariatric surgery. Implementing the physical activity in the period before and post-operative is bringing the sequence of beneficial changes in the body of the patient. It often improves the well-being of patients as well as results in the faster convalescence and lowering the risk of complications. Both the non-invasive and surgical treatment of obesity should be complemented by the introduction of appropriate physical activity.
Propiedades psicométricas del PERMA-Profiler para la medición del bienestar en una muestra de estudiantes universitarios chilenos
Authors: Cobo-Rendón Rubia , Pérez Villalobos María Victoria , Díaz Mujica Alejandro
Published: March 2020

Introducción: en términos científicos y sociales, los estudios sobre el bienestar han sido relevantes en los últimos años, lo que hace necesario investigar acerca de las propiedades psicométricas de los cuestionarios que se utilizan para su medición. El objetivo de este trabajo fue estimar las propiedades psicométricas del cuestionario PERMA-Profiler en una muestra de estudiantes universitarios chilenos. Materiales y métodos: se evaluaron las respuestas de 1462 estudiantes universitarios de una universidad tradicional ubicada al sur de Chile, con una edad media de 19.09 años (DE=1.72). Se realizó un análisis factorial confirmatorio, se evaluaron las correlaciones dimensión/total del cuestionario e índices de consistencia interna. Resultados: el análisis factorial reportó la presencia de cinco factores. Se presentaron niveles de correlación moderada, positiva y significativa entre las dimensiones del PERMA-Profiler. Los índices de consistencia de la escala total y de la mayoría de las dimensiones se ubicaron entre α=.65 a .91 y de ω=.66 a .92, a excepción de la dimensión de compromiso. Conclusión: se confirman los cinco factores propuestos en la teoría y un adecuado nivel de correlación entre sus dimensiones y de fiabilidad del cuestionario. El PERMA-Profiler puede ser empleado para la medición de la salud mental de los estudiantes y como una herramienta válida para la evaluación de intervenciones en este contexto.
Interseccionalidad en las desigualdades sociales para la realización de actividad física en Argentina
Authors: Ballesteros Matías Salvador , Freidin Betina , Wilner Agustín , Fernández Rendina Lucas
Published: March 2020

Introducción: el objetivo del artículo es analizar las desigualdades en cuanto a la realización de actividad física para mejorar la condición física o para hacer deporte, determinadas por distintos factores sociales, geográficos y demográficos, así como por algunas de las interacciones entre estos factores. Para ello, se recurrió a la estrategia de análisis cuantitativo de datos secundarios. La fuente utilizada es la Encuesta Nacional de Factores de Riesgo, realizada sobre una muestra probabilística de hogares urbanos de Argentina, en el 2009. Desarrollo: para examinar los datos, se realizó un análisis descriptivo bivariado y, luego, regresiones logísticas binarias, en las que se incorporaron interacciones, para poner a prueba diversas hipótesis sobre el efecto de las distintas variables independientes, así como de su interseccionalidad. Conclusiones: los resultados muestran la importancia de considerar un enfoque interseccional e incorporar interacciones en las regresiones logísticas binarias para comprender la naturaleza multiplicativa de las desigualdades en la práctica de actividad física, que los modelos multivariados aditivos no pueden captar.
The Impact of Using the LEGO Education Program on Mathematics Achievement of Different Levels of Elementary Students
Authors: Altakhayneh Bahjat
Published: March 2020

This study aims to investigate the impact of using a LEGO Education program, specifically the “MoreToMath” kit, on the achievement of Deferent Levels of Elementary Students. The quantitative research design was used in this research study, and the participants were comprised of 120 elementary school students in the 2nd grade, in Amman, Jordan. A quasi-experimental research method and the MANCOVA were used, and a study tool to measure achievement was developed by the researcher for which the validity and reliability of achievement were verified. The results of the study show that there was a statistically significant improvement (α ≤0.05) in the achievement of the experimental study group, that studied using LEGO education, over the control group. There is also a statistically significant difference (α ≤ 0.05) between the arithmetic means of the three sub-groups of students’ previous achievement levels— high, middle, and low— and by using the Least Significant Differences (LSD) test we notice that there are significant differences between the high and low sub-groups, as well as between the middle and low. However, that there are no significant differences between the high and middle level sub-groups; and there is also no statistically significant interaction between the groups (experimental, control) and the levels of pre-achievement seen in the post-achievement levels. The study results indicate that the use of new technological tools, like the “MoreToMath” kit, may be beneficial in teaching mathematics as they tend to motivate students, and can lead to higher achievement for elementary students of different mathematics aptitude levels.
The Effects of the ECIRR Learning Model on Mathematical Reasoning Ability in the Curriculum Perspective 2013: Integration on Student Learning Motivation
Authors: Pahrudin Agus , Ahid Nur , Huda Syamsul , Ardianti Nita , Putra Fredi Ganda , Anggoro Bambang Sri , Joemsittiprasert Watcharin
Published: March 2020

This study aims to determine the impact of the ECIRR(Elicit, Confront, Identify, Resolve, Reinforce) learning model on students' mathematical reasoning abilities in terms of student motivation. The research method used was a quasy-experimental method with a post-test only control design research design. The population of this study was all students in five classes XII Private School. The Samples were taken at class XII AP-2 and XII MM-1 as the experimental class, and class XII AP-1 and XII MM-2 as the control class. The data analysis technique used is hypothesis testing using ANAVA 2 paths. Based on the research results obtained that (a) There is an influence of the ECIRR (Elicit, Confront, Identify, Resolve, Reinforce) learning model on mathematical reasoning abilities. (b) There is an influence of student learning motivation on mathematical reasoning abilities. (c) There is no interaction between the treatment of learning models and categories of students' learning motivation towards mathematical reasoning abilities. So as a whole it can be concluded that the ECIRR (Elicit, Confront, Identify, Resolve, Reinforce) learning model influences the ability of mathematical reasoning and can increase students' learning motivation.
Developing MeMoRI on Newton’s Laws: For Identifying Students’ Mental Models
Authors: Fratiwi Nuzulira Janeusse , Samsudin Achmad , Ramalis Taufik Ramlan , Saregar Antomi , Diani Rahma , Irwandani Irwandani , Rasmitadila Rasmitadila , Ravanis Konstantinos
Published: March 2020

The identification of students’ mental models is crucial in understanding their knowledge of scientific concepts. This research aimed to develop a Mental Models Representation Instrument on Newton's Laws (MeMoRI-NL). The ADDIE (Analyzing, Designing, Developing, Implementing and Evaluating) model was used as a research method. The sample consisted of 30 students of 15-16 years-old at one of senior high school in Tatar Pasundan. The data was examined using Rasch analysis on validity, reliability, level of difficulty, and distributions of students’ mental models. Students’ mental models were classified as Scientific (SC), Synthetic (SY), Synthetic almost Misconception (SYM), and Initial (IN) model. Based on the evaluating stage, students’ mental models are mostly in the SYM and IN model. Consequently, it can be concluded that the Mental Models Representation Instrument on Newton's Laws (MeMoRI-NL) can be developed using the ADDIE model and most of the students' mental model has not been following scientific knowledge. Based on this research, teachers or educators should enhance students' mental models, especially for female students.
Orthogonal Procrustes and norm-dependent optimality
Authors: Cape Joshua
Published: March 2020

This note revisits the classical orthogonal Procrustes problem and investigates the norm-dependent geometric behavior underlying Procrustes alignment for subspaces. It presents generic, deterministic bounds quantifying the performance of a specified Procrustes-based choice of subspace alignment. Numerical examples illustrate the theoretical observations and offer additional, empirical findings which are discussed in detail. This note complements recent advances in statistics involving Procrustean matrix perturbation decompositions and eigenvector estimation.
Quantum theory of near-field optical imaging with rare-earth atomic clusters
Authors: Majorel Clément , Girard Christian , Cuche Aurélien , Arbouet Arnaud , Wiecha Peter R.
Published: March 2020

Scanning near-field optical microscopy (SNOM) using local active probes provides general images of the electric part of the photonic local density of states. However, certain atomic clusters can supply more information by simultaneously revealing both the magnetic and the electric local density of states in the optical range. For example, nanoparticles doped with rare-earth elements like europium or terbium provide both electric dipolar (ED) and magnetic dipolar (MD) transitions. In this theoretical paper, we develop a quantum description of active systems (rare-earth ions) coupled to a photonic nanostructure by solving the optical Bloch equations together with Maxwell’s equations. This approach allows us to access the population of the emitting energy levels for all atoms excited by the incident light, degenerated at the extremity of the tip of a near-field optical microscope. We show that it is possible to describe the collected light intensity due to ED and MD transitions in a scanning configuration. By carrying out simulations on different experimentally interesting systems, we demonstrate that our formalism can be of great value for the interpretation of experimental configurations, including various external parameters such as the laser intensity, the polarization and wavelength, the SNOM probe size, and the nature of the sample.
Perturbation-induced morphological transformations in vector-field singularities
Authors: Khan Saba N. , Deepa S. , Arora Gauri , Senthilkumaran P.
Published: March 2020

In this paper, we report the morphological transformations of vector-field singularities (V-points) under symmetric and asymmetric perturbation using a diamond-shaped diffracting aperture. The number of null intensity points in the diffraction pattern depicts the magnitude of the polarization singularity index. Also, under symmetric perturbation, a higher-order V-point singularity disintegrates into|η|number of unit-index singularities following the index conservation rule. Asymmetric perturbations, realized by laterally shifting the aperture, lead to the formation of pairs of generic elliptic-field singularities (C-points) that are more fundamental and stable. In this process, the helicity and polarization singularity index are both conserved. This may find application in the context of singularimetry, where weak fields are measured by considering them as perturbations of unstable optical beams [Phys. Rev. Lett.109,183903(2012)PRLTAO0031-900710.1103/PhysRevLett.105.053904].
Simulation of harmonic and supercontinuum generation in polycrystalline media
Authors: Gu Jiahui , Hastings Michael G. , Kolesik Miroslav
Published: March 2020

Highly efficient, broadband frequency conversion in polycrystalline
zinc-blende media receives increasing interest, motivated by both
applications and understanding of the underlying processes. However,
realistic simulations of the complex physics, in which random
quasi-phase-matching plays a major role, is challenging because of the
disorder. Here we present a family of models of increasing complexity,
including a (3 + 1)D model with full resolution in time and space.
Using ZnSe as the demonstration medium, we show that while a
small-beam, axially symmetric approximation is able to provide
qualitatively correct spectra at a low computation cost, the
computationally more demanding (3 + 1)D approach achieves
semi-quantitative agreement between the simulated supercontinuum
spectrum and experiment results. The fully resolved (3 + 1)D
simulations thus provide an accurate new tool for the characterization
and optimization of supercontinuum generation in transparent
polycrystals.
Nonlinear light mode dispersion and nonuniform mode comb by a Fabry-Perot with chirped fiber gratings
Authors: Bekker Alexander , Levit Boris , Weill Rafi , Fischer Baruch
Published: March 2020

We demonstrate a nonlinear light mode dispersion and a nonuniform frequency mode comb by a chirped fiber Bragg gratings (CFBG) Fabry-Perot (FP) at the 1550 nm wavelength regime. We give analytical expressions for the general chirp case, and an experimental demonstration with a linear chirp, showing a square-root dependence of the dispersion as a function of the FP mode number. Such sublinear dispersion is required, for example, for photon Bose-Einstein condensation (BEC) in a one-dimensional (1D) system like fiber cavities.
Photoelectronic memory based on nitride multiple quantum wells and the hybrid of graphene nanoflakes and a-IGZO film
Authors: Liou Yi-Rou , Lin Hsia-Yu , Cai Shu-Yi , Liao Yu-Ming , Lin Tai-Yuan , Chen Yang-Fang
Published: March 2020

Optical memories are vitally important for the future development of high speed and low cost information technologies. Current optical memory devices still suffer from difficulties such as scaling-down of size, short-life expectancy, and non-volatility without the control of a gate electrode. To resolve these obstacles, a robust photoelectronic memory device is designed and demonstrated based on the integration of amorphous InGaZnO (a-IGZO), GNSs, and nitride multiple-quantum-wells light-emitting diode (MQWs LED). Utilizing the inherent nature of the band alignment between a-IGZO and graphene nanosheets (GNSs), electrons can transfer from a-IGZO to GNSs causing a persistent photoconductivity (PPC). With the long-lasting lifetime of PPC, the signal can be written optically and the encoded signal can be read both electrically and optically. The read and write processes reveal little current degradation for more than 10,000 sec, even repeated for more than hundred times. The device can convert invisible information to visible signal, and the encoded information can be simply erased under a reversed bias without a gate electrode. In addition, the memory device possesses a simple vertically stacked structure for 3D integration, and it is compatible with established technologies.
Understanding the material loss of anti-resonant hollow-core fibers
Authors: Wu Dakun , Yu Fei , Liao Meisong
Published: March 2020

In this paper, the material loss of anti-resonant hollow-core fiber (AR-HCF) and its properties are studied. We revisit the formula of power attenuation coefficient for the index-guiding optical fiber described by Snyder and Love in the 1980s and derive the modal overlap factor that governs the material loss of hollow-core fibers (HCF). The modal overlap factor formula predicts the material loss of AR-HCF, which agrees with numerical simulations by the finite element method. The optimization of silica-based AR-HCF design for the lowest loss at 4 µm wavelength is numerically discussed where the silica absorption reaches over 800 dB/m. Our work would provide practical guidance to develop low-loss AR-HCF at highly absorptive wavelengths, e.g. in the vacuum UV and mid/far-infrared spectral regions.
High fill-factor miniaturized SPAD arrays with a guard-ring-sharing technique
Authors: Morimoto Kazuhiro , Charbon Edoardo
Published: March 2020

We present a novel guard-ring-sharing technique to push the limit of SPAD pixel miniaturization, and to demonstrate the operation of SPAD arrays with a 2.2 µm-pitch, the smallest ever reported. Device simulation and preliminary tests suggest that the optimized device design ensures the electrical isolation of SPADs with guard-ring sharing. 4×4 SPAD arrays with two parallel selective readout circuits are designed in 180 nm CMOS technology. SPAD characteristics for the pixel pitch of 2.2, 3, and 4 µm are systematically measured as a function of an active diameter, active-to-active distance, and excess bias. For a 4 µm-pitch, the fill factor is 42.4%, the maximum PDP 33.5%, the median DCR 2.5 cps, the timing jitter 88 ps, and the crosstalk probability is 3.57%, while the afterpulsing probability is 0.21%. Finally, we verified the feasibility of the proposed technique towards compact multi-megapixel 3D-stacked SPAD arrays.
Cs-Ar optical amplifier with a saturation intensity of 10 kW-cm−2 and single-pass extraction efficiency of 28% at 852.2 nm
Authors: Park S. , Mironov A. E. , Eden J. G.
Published: March 2020

Optical amplification by the stimulated emission of Cs(6p 2P3/2)-Ar atomic pairs, observed in pump-probe experiments over a ∼290 GHz-wide spectral region lying to the red of the Cs D2 line (852.1 nm), has been realized by photoexciting thermalized, ground state Cs-Ar atoms in the 834-849 nm wavelength interval. When the gain medium is pumped at the peak of the CsAr B2Σ1/2+←X2Σ1/2+ transition at 836.7 nm, maximum gain occurs between 852.2 nm and 852.3 nm and >28% of the energy stored in the upper laser level is extracted with 8 ns (FWHM) probe pulses in a single pass. From the measured rate of saturation of the extracted pulse energy with increasing probe intensity, the product of γ0L and Esat, the saturation pulse energy, is measured directly to be 400 ± 20 µJ and the lower limit for the saturation intensity (Isat) of this amplifier is estimated to be 10 kW-cm−2 at 852.2 nm. Circularly polarizing the optical pump beam increases the optical-to-optical conversion efficiency by 20%, and the storage lifetime of the upper laser level is observed from temporally-resolved gain spectra to be 5 ± 1 ns. Pump excitation spectra also reveal a significant contribution from Ar-Cs-Ar (3-body) photoassociation and suprathermal Ar atoms generated by the dissociation of the CsAr B2Σ1/2+ complex. Multipass-amplifier geometries with broad-bandwidth probe signals are expected to yield upper state energy extraction efficiencies above 50%. This alkali-rare gas amplifier demonstrates the efficiencies available with the storage of energy in, and optical extraction from, excited atomic collision pairs.
Graphene/WS2 heterostructure saturable absorbers for ultrashort pulse generation in L-band passively mode-locked fiber lasers
Authors: Du Wenxiong , Li Heping , Lan Changyong , Li Chun , Li Junwen , Wang Zhuang , Liu Yong
Published: March 2020

Graphene/WS2 (G/WS2) van der Waals (vdW) heterostructures are utilized as saturable absorbers (SAs) in compact mode-locked fiber lasers operating in the telecommunication L-band for the first time. The interlayer coupling is confirmed by Raman and photoluminescence spectra. In comparison with pure WS2, the heterostructure exhibits excellent nonlinear optical properties in terms of larger modulation depth and lower saturation intensity due to the strong interlayer coupling. By incorporating the G/WS2-based SA into an all-anomalous-dispersion fiber laser, stable conventional-soliton pulses with a pulse duration down to 660 fs can be realized at 1601.9 nm, manifesting better output performance compared to pure WS2. In addition, through shifting the cavity dispersion to the net-normal dispersion, the G/WS2 SA can also be applied for dissipative-soliton generation. Resultant output pulses feature the central wavelength of 1593.5 nm and the pulse duration of 55.6 ps. Our results indicate that the G/WS2 vdW heterostructure is a promising candidate as SA for pulsed laser applications, which pave the way for the development of novel ultrafast photonic devices with desirable performance.
What about computational super-resolution in fluorescence Fourier light field microscopy?
Authors: Stefanoiu Anca , Scrofani Gabriele , Saavedra Genaro , Martínez-Corral Manuel , Lasser Tobias
Published: March 2020

Recently, Fourier light field microscopy was proposed to overcome the limitations in conventional light field microscopy by placing a micro-lens array at the aperture stop of the microscope objective instead of the image plane. In this way, a collection of orthographic views from different perspectives are directly captured. When inspecting fluorescent samples, the sensitivity and noise of the sensors are a major concern and large sensor pixels are required to cope with low-light conditions, which implies under-sampling issues. In this context, we analyze the sampling patterns in Fourier light field microscopy to understand to what extent computational super-resolution can be triggered during deconvolution in order to improve the resolution of the 3D reconstruction of the imaged data.
Direct measurement of the frequency ratio for Hg and Yb optical lattice clocks and closure of the Hg/Yb/Sr loop
Authors: Ohmae Noriaki , Bregolin Filippo , Nemitz Nils , Katori Hidetoshi
Published: March 2020

We performed the first direct measurement of the frequency ratio between a mercury (199Hg) and an ytterbium (171Yb) optical lattice clock to find νHg/νYb = 2.177 473 194 134 565 07(19) with the fractional uncertainty of 8.8 × 10−17. The ratio is in excellent agreement with expectations from the ratios νHg/νSr and νYb/νSr obtained previously in comparisons against a strontium (87Sr) optical lattice clock. The completed closure (νHg/νYb)(νYb/νSr)(νSr/νHg) − 1 = 0.4(1.3) × 10−16 tests the frequency reproducibility of the optical lattice clocks beyond what is achievable in comparison against the current realization of the second in the International System of Units (SI).
Broadband mid-infrared coherent light source from fiber-laser-pumped difference frequency generators based on cascaded crystals
Authors: Feng Xi , Shi Jinqiao , Liu Pei , Zhang Zhaowei
Published: March 2020

We present difference frequency generators (DFGs) using cascaded PPLN crystals, each with a distinct poling-period, as the parametric gain medium. We show that the phase-matching bandwidth of cascaded crystals is the combination of that of each individual crystal. In the non-phase-matched section of cascaded crystals, there exists periodic backward and forward frequency-conversion processes. Nonetheless, we demonstrate that such a periodic back-conversion process would not compromise the parametric gain bandwidth of cascaded nonlinear crystals. By using two PPLN crystals with poling periods of 31 µm and 29 µm, we experimentally obtained mid-infrared light sources having instantaneous-bandwidth covering 2.8-3.9 µm, which was roughly twice as much as that from a system based on a single crystal. Moreover, our numerical results show that light sources with an instantaneous-bandwidth covering 2.5-5 µm could be obtained by cascading more crystals. This scheme represents a promising technical route to transform conventional DFGs into a device capable of generating spatially-coherent light emission with very broad instantaneous-bandwidth.
Chirp-free optical-signal generation using dual-and-direct current-voltage modulation of transistor lasers
Authors: Tung Chien-Ting , Chang Shu-Wei , Wu Chao-Hsin
Published: March 2020

Transistor lasers (TLs) can be current-modulated as a diode laser or voltage-modulated as a Franz-Keldysh electro-absorption modulator. These two modulation schemes result in opposite frequency shifts that can cancel each other. In this work, we present the principle of generating optical signals with minimal frequency chirps using TLs. With the proper setting of pulse shapes for the current and voltage inputs, optical signals that are robust against distortions can be directly output from TLs for the medium-distance or long-distance optical fiber communication.
Postcompression of picosecond pulses into the few-cycle regime
Authors: Balla Prannay , Bin Wahid Ammar , Sytcevich Ivan , Guo Chen , Viotti Anne-Lise , Silletti Laura , Cartella Andrea , Alisauskas Skirmantas , Tavakol Hamed , Grosse-Wortmann Uwe , Schönberg Arthur , Seidel Marcus , Trabattoni Andrea , Manschwetus Bastian , Lang Tino , Calegari Francesca , Couairon Arnaud , L’Huillier Anne , Arnold Cord L. , Hartl Ingmar , Heyl Christoph M.
Published: March 2020

In this work, we demonstrate postcompression of 1.2 ps laser pulses to
13 fs via gas-based multipass spectral broadening. Our results yield a
single-stage compression factor of about 40 at 200 W in-burst average
power and a total compression factor

>

90

at reduced power. The employed
scheme represents a route toward compact few-cycle
sources driven by industrial-grade Yb:YAG lasers at high
average power.