bluuebunny/crossref_metadata_2025 huggingface dataset:
Different Post Placement Strategies for the Restoration of Endodontically Treated Maxillary Premolars with Two Roots: Single Post vs Double Post
Authors: Grandini Simone , Ferrari Marco , Spicciarelli Valentina , Marruganti Crystal , Martignoni Marco , Andreatti Ludovica , Doldo Tiziana
Published: April 2021

Aim and objective

The present study compared the fracture strength and failure pattern of endodontically treated, bi-rooted, maxillary premolars with different number of coronal walls and postendodontic restoration (one vs double post).

Materials and methods

105 premolars were divided into 3 groups according to the number of residual walls: control group (intact teeth; n = 15), group 1 (3 residual walls; n = 45), group 2 (2 residual walls; n = 45). Each test group was then divided into 3 subgroups (n = 15 each) according to postendodontic restoration: no post (A), 1 post (B) or 2 posts (C). A load was applied parallel to the longitudinal axis of the teeth, thus simulating physiological occlusion. ANOVA and Tukey's tests were used to detect fracture strength differences among groups, while Chi-square test was used to check differences in fracture pattern.

Results

No significant differences were observed between control group (intact teeth) and groups A1 (p = 0.999), B1 (p = 0.997) and C1 (p = 1.000); statistically significant differences were detected between control group and groups A2 (p < 0.001), B2 (p < 0.001) and C2 (p < 0.05). Different post placement techniques were non-significantly associated with fracture pattern in both groups 1 (p = 0.666) and 2 (p = 0.143) while, irrespective of the number of posts, the presence of the post was significantly associated with the fracture pattern in teeth with two residual walls. The double-post technique did not further improve the fracture resistance of hardly damaged endodontically treated maxillary bi-rooted premolars compared to single-post technique. Therefore, the insertion of a single post in the palatal canal could be a safer and more conservative choice.

Clinical significance

The double-post technique did not further improve the fracture resistance of severely structurally compromised endodontically treated maxillary premolars with two roots compared to the single-post technique. Therefore, the safer and less invasive treatment is the placement of a single post in the palatal canal.

How to cite this article

Spicciarelli V, Marruganti C, Martignoni M, et al. Different Post Placement Strategies for the Restoration of Endodontically Treated Maxillary Premolars with Two Roots: Single Post vs Double Post. J Contemp Dent Pract 2020;21(12):1374–1378.
Analisa Studi Tundaan Waktu Kedatangan Pesawat pada Bandar Udara Hasanuddin Makassar
Authors: Rahman Qarnila Ridhaniah
Published: April 2021

Jaringan pelayanan angkutan udara adalah sejumlah jadwal penerbangan yang mengurus kegiatan angkutan udara dengan jadwal yang telah ditentukan. Berdasarkan wilayah, lokasi penerbangan dibagi menjadi penerbangan dalam negeri dan penerbangan luar negeri. Jaringan penerbangan dalam dan luar negeri merupakan satu kesatuan dan terintegrasi. Oleh karena itu, semakin banyak pengguna pesawat dari berbagai daerah sesuai dengan kebutuhan perjalanannya, karena pengaruh kemajuan teknologi akan semakin berpengaruh terhadap penerbangan untuk menyediakan fasilitas yang sesuai dengan kebutuhannya, namun fasilitas masing-masing pesawat yang memberikan layanan akan semakin banyak. tidak mempengaruhi waktu. perjalanannya. Dalam penelitian ini terdapat beberapa data adalah dari jadwal penerbangan yang menempuh perjalanan selama satu minggu. Data diambil dalam penelitian ini dari jadwal kedatangan masing-masing pesawat yang memasuki Bandara Hasanuddin.
Kata kunci: Jadwal Penerbangan, Waktu Tundaan
Flipped classroom como puente hacia nuevos retos en la educación primaria
Authors: Llanos García Gonzalo , Bravo-Agapito Javier
Published: April 2021

En los últimos años, el escenario educativo en España se ha caracterizado por una evidente transformación en cuanto a la metodología que se aplica en las aulas de las distintas etapas educativas.
La falta de motivación en gran parte del alumnado invita a reestructurar un sistema educativo anclado en el tiempo. Existe una necesidad de adaptar los contenidos y su transmisión, siguiendo la nueva realidad que rodea a los alumnos del presente. En este sentido, la tecnología de la información y las comunicaciones (TIC) es un instrumento de transmisión y motor de cambio hacia nuevos puentes de aprendizaje. En particular, el modelo flipped classroom consiste en invertir la manera de explicar los contenidos educativos trasformando la figura del docente y el discente.
Este trabajo propone una metodología para implementar el modelo flipped classroom en el ámbito de la educación primaria.
De este modo, la educación y la TIC se fusionan, transformando el aula en un ambiente que incita a la creatividad, al trabajo colaborativo, a la discusión y a la reflexión.
ERP Implementations and its Major Challenges in Auditing Security Issues for SMEâ€™s
Authors: Panda Gopikrishna , Jena Debasish , Samantaray Anup Kumar
Published: April 2021

Enterprise Resource planning helps S.M.E.'s to enjoy unimaginable benefits. Nevertheless the problems of ERP in S.M.E.'s remain unsolved. The troubles faced by S.M.E.'s with regards to ERP is quiet understandable. However there is always a scope for making things better and making ERP's more user friendly for Small and Medium Enterprises. In this paper the authors have extensively studied major implementation challenges and security issues pertaining to the implementation of ERP in various SMEâ€™s.
Study to Assess lifestyle Practices of Overweight and Normal Weight Children in Selected School of District Hoshiarpur, Punjab, India
Authors: Shukla Bhuvanesh , Kaur Amandeep
Published: April 2021

Lifestyle is considered to be an important determinant of health and sickness. It has also a great role in growth and development of children. Some of the health problems are rooted in childhood habits and lifestyle. A number of factors contribute to becoming overweight. Genetics, lifestyle habits, or a combination of both may be involved. Genes help to determine body type and how body stores and burns fat. Studies have shown that a child's risk of obesity greatly increases if one or more parent is overweight or obese. Daily schedules are so jam-packed that there's little time to prepare healthier meals or to squeeze in some exercise. Childrenâ€™ s dietary habits have been shifted away from healthy foods to much greater reliance on fast food, processed snack foods and sugary drinks. Now more than ever life is sedentary; children spend more time playing with electronic devices, from computers to handheld video game systems, than actively playing outside. Television is a major culprit. Children who watch more than 4 hours a day are more likely to be overweight compared with children who watch 2 hours or less.
Social Media Changing Inter-Personal Relationship Among Urban Couples
Authors: Virk Hasanbir
Published: April 2021

Social media is playing a vital role in urban life and with the young working students and married couples. As this medium has grown over a last few decades, most popular among youth. The social media once need for sharing views and short notes, chatting, initially through Facebook, Orkut, Yahoo and other mailing apps has grown up to the current stage over the period of last thirty years and plus. The trend of the social media started changing in the last more than a decade when its impacts on the social life become more vigilant.
Emotional Dynamics of Action and Core Involvement: A new theoretical perspective for designing development strategies in schools
Authors: Upadhayaya Venus
Published: April 2021

Emotional Dynamics of Action and Core Involvement are theortical perspectives that define an individual's life long scope of learning and progress.  An individualâ€™s life long Emotional Dynamics of Action (EDA) and his/her Core Involvement in what he/she aspires to do, in what he/she takes up, in whatever he/she achieves get immensely impacted in school. EDA and CI are not isolated patterns of emotional construct; they get constantly evolved and devolved, constantly learned and unlearned. An individual's EDA and CI constantly impact those around and also constantly get impacted by those around. Thus school becomes a space that defines the life-long capacity of an individual. Schools greatly make up a society and its behavioural and attitudinal construct. The aim of this paper is to on a fresh construct define how schools play a pivotal role in determining a childâ€™s consciousness. The psychological patterns determining communication between a childâ€™s internal and external settings and his level of self-awareness get shaped in school. And these psychological patterns define the EDA and CI of the individual. Researcher defines how positive EDA and CI can be cultivated and practised and how schools can become a major strageic point for development.
Első generációs hallgatók a campuson : Különös tekintettel az eredményesség kérdéskörére
Authors: Bocsi Veronika , Pusztai Gabriella , Fényes Zsuzsanna Hajnalka
Published: April 2021

A tanulmány célja, hogy az családjukból elsőként a felsőoktatásba lépők (a továbbiakban röviden: első generációs hallgatók) egyetemi pályafutásának egyik fontos területét, az eredményességet járja körül. Az elemzésbe olyan háttérváltozókat is bevonunk, amelyek a hallgatói lét fontos alapjait képezik: tanulmányuk motivációit, az egyetemi integráció különböző formáit és a szülők oktatáshoz való viszonyát. A nemzetközi szakirodalom ezeken a területeken – az eredményességet is ideértve – az első generációs hallgatók hátrányos helyzetére mutat rá. Kutatásunk során egy tudományegyetem karokra reprezentatív adatbázisát használtuk fel (N = 810). Az eredményesség fogalmát kétféleképpen mértük: egyrészt egy komplex, tudományos és munkaerőpiaci kimenetet magába foglaló kérdéssorral, amelyből indexet készítettünk, másrészt pedig az utolsó két szemeszter súlyozott tanulmányi átlagával. Az első generációs és a szülői iskolázottság tekintetében heterogén hátterű hallgatók alacsonyabb eredményességét komplex megközelítéssel tudtuk megragadni. A diplomás szülők gyermekeinek előnye a regressziós modellben is kimutatható volt, ugyanakkor a heterogén hátterű hallgatókhoz képest az első generációs hallgatók is kedvezőbb helyzetben voltak. Az eredményesség mind a két típusát alakították a szoros oktatói kapcsolatok, illetve a nemi hovatartozás. A tanulmányi átlag vizsgálata során a szülők végzettsége nem bírt magyarázó erővel.
The Use of Bedside Ultrasound for Gallstone Disease Care within a Community-based Emergency Department: A Confirmation Bias
Authors: Gunther Karin H , Smith Joshua , Boura Judith , Sherman Andrew , Siegel David
Published: April 2021

INTRODUCTION

Traditional evaluation for suspicion of gallstone or gallbladder-related disease includes evaluation with a formal technician-performed ultrasound. However, the use of point-of-care bedside ultrasounds (Bedside US) has been shown to be a viable alternative for the diagnosis of gallstones and gallbladder-related diseases. Purpose Statement: The purpose of this study was to evaluate the impact of Bedside US use in gallbladder evaluation on key patient care outcomes within our community-based emergency department setting.

METHODS

This retrospective study compared the use of no ultrasound (No US), a formal technician performed ultrasound (Tech US) and Bedside US for gallstone and gallbladder related diseases within a community hospital emergency department between January 1, 2015 and January 1, 2018. Initial vitals, lab work, patient socio-demographics, medical history, emergency department length of stay in hours and disposition were reviewed.

RESULTS

Of a total N = 449 patients included, patients who received a Bedside US had the fewest computerized tomography scans (No US 62% vs. Tech US 29% vs. Bedside US 16%; p < 0.0001), the shortest median emergency department length of stay (No US 4.5 days vs. Tech US 5.0 days vs. Bedside US 3.0 days; p < 0.0001), and were more likely to be discharged home (No US 41% vs. Tech US 55% vs. Bedside US 81%; p = 0.0006) compared to those that received no ultrasound or a formal ultrasound. Patients who received a Bedside US also had the statistically significant highest incidence of prior cholelithiasis (No US 29.4% vs Tech US 14.3% vs. Bedside US 31.3%; p = 0.001) and lowest total median bilirubin levels (No US 0.5 vs. Tech US 0.5 vs. Bedside US 0.3; p = 0.016) when compared to the other two groups.

CONCLUSIONS

Although there was a confirmation bias, these study results indicate that point-of-care bedside ultrasound could be a viable alternative for gallstones and gallbladder-related diseases with benefits of use in a community hospital setting.
Using Quantitative D-Dimer to Determine the Need for Pulmonary CT Angiography in COVID-19 Patients
Authors: Mikhjian Gary , Elghoroury Ahmad , Cronovich Keith , Brody Kevin , Jarski Robert
Published: April 2021

INTRODUCTION:

COVID-19 has been frequently cited as a condition causing a pro-inflammatory state leading to hypercoagulopathy and increased risk for venous thromboembolism. This condition has thus prompted prior studies and screening models that utilize D-dimer for pulmonary embolism (PE) into question. The limited research to date has failed to provide tools or guidance regarding what COVID-19 positive patients should receive pulmonary CT angiography screening. This knowledge gap has led to missed diagnoses, CT overutilization, and increased morbidity and mortality.

OBJECTIVE:

The purpose of this study was to examine the utility of the quantitative D-dimer lab marker in a convenience sample of 426 COVID-19 positive patients to assist providers in determining the utility of pulmonary CT angiography.

METHODS:

The authors conducted a retrospective analysis on all COVID-19 positive patients within the Henry Ford Medical System between March 1st, 2020 through April 30th, 2020 who received pulmonary CT angiography and had a quantitative D-dimer lab drawn within 24 hours of CT imaging.

RESULTS:

Our sampling criteria yielded a total of n = 426 patients, of whom 347 (81.5%) were negative for PE and 79 (18.5%) were positive for PE. The average D-dimer in the negative PE group was 2.95 μg./mL. (SD 4.26), significantly different than the 9.15 μg./mL. (SD 6.80) positive PE group (P < 0.05; 95% CI -7.8, -4.6). Theoretically, applying the traditional ≤ 0.5 μg./mL. D-dimer cut-off to our data would yield a sensitivity of 100% and specificity of 7.49% for exclusion of PE. Based on these results, the authors would be able to increase the D-dimer threshold to < 0.89 μg./mL. to maintain their sensitivity to 100% and raise the specificity to 27.95%. Observing a D-dimer cut-off value of ≤ 1.28 μg./mL. would reduce sensitivity to 97.47% but increase the specificity to 57.93%.

CONCLUSIONS:

These study results support the utilization of alternative D-dimer thresholds to exclude PE in COVID-19 patients. Based on these findings, providers may be able to observe increased D-dimer cut-off values to reduce unnecessary pulmonary CT angiography scans.
Common Problematic Scholarly Activity Project Planning Expectations of Project Novices
Authors: Wisniewski Samuel J. , Corser William D.
Published: April 2021

INTRODUCTION

Scholarly Activity (SA) projects, whether using methods more traditionally associated with research and or “quality improvement” projects, have been shown to confer value to resident physicians and other project novices in multiple ways. The inclusion of community and university-based residents and faculty in spearheading SA projects has led to improved understanding of medical literature and enhanced clinical practices, arguably producing more “well-rounded” physicians.

PURPOSE OF PAPER

The primary purpose of this paper is to provide a summary of problematic expectations frequently assumed by project novices when developing and conducting SA projects.

RESULTS

The authors will discuss a total of 26 problematic project-related novice expectations during five typical project phase categories.

CONCLUSIONS

Learning to navigate the complexities of training to become a practicing physician, while also planning high quality SA project designs has been and will continue to be a complex challenge. The authors hope that this article can be used by supervising faculty and other graduate medical education mentors to assist the SA project novice (SAPN) plan SA projects. By establishing realistic expectations during project planning phases, the SAPN can avoid potential missteps that typically impede SA project completion.
A Closer Look into the Association between the Sacroiliac Joint and Low Back Pain
Authors: Wieczorek Ashley , Campau Erin , Pionk Elizabeth , Gabriel-Champine Molly E. , Ríos-Bedoya Carlos F.
Published: April 2021

INTRODUCTION

Low back pain is the most common type of global disability and annually costs the United States over two billion dollars. Opioids have been used to reduce low back pain, although current evidence concerning efficacy is lacking. Sacroiliac joint dysfunction (SIJD) is estimated to be a primary pain source of low back pain in between 10 and 25% of affected patients. The primary objective of this study was to evaluate the rate of SIJD identified through osteopathic techniques in a convenience sample of patients seeking low back pain treatment. The secondary objective was to assess prevalence of low back pain and SIJD among different age groups, and genders.

METHODS

Retrospective chart reviews were completed the adult patients who had received osteopathic manipulative treatment for low back pain at Family Health and Wellness Center in Essexville, MI from January 2018 through June 2019. The prevalence of patients with SIJD was identified during reviews of osteopathic procedural documentation for patients seeking low back pain treatment. Data regarding patients’ age, sex, and treatment modalities were also extracted. Descriptive statistics consisting of frequencies and percentages were calculated.

RESULTS

A total of 84 patient records were reviewed. A total of 51 (60.7%) patients seeking low back pain treatment were diagnosed with SIJD identified by osteopathic providers. This included patients with both lumbar and sacral diagnoses simultaneously. SIJD alone accounted for 26 (31%) of patients seeking treatment. Female patients were more likely to have SIJD involvement than males. Forty one (48.8%) treated patients were between 45-64 years old. Muscle Energy Technique was documented to be the most used for 68 (81%) patients. In addition, techniques tended to move from direct to indirect for older patients.

DISCUSSION

Our study demonstrated that SIJD appeared to contribute to low back pain in 51 (60.7%) of low back pain cases identified using osteopathic techniques. This is much greater than the previously reported percentages of 10 to 25%. One possible confounding influence included varied resident screening and reporting of sacral dysfunction. Since multiple areas of the body can be treated at one time, our current procedure notes did not allow for distinguishing between which types of modalities were used on each region or capture residents’ preferred treatments.

CONCLUSIONS

Although further studies are needed, our results suggest that knowledge of SIJD’s impact on low back pain could lead to improved patient outcomes such as decreased medical costs and opioid use.
A Longitudinal Observation of the Influence of Michigan Sports Concussion Law on Parents’ Knowledge and Perception of Sport-Related Concussion
Authors: LaBond Virginia , Liebsch Karyn , West Brian , Caputo Dane , Barber Kimberly
Published: April 2021

INTRODUCTION

In 2013, Michigan enacted legislation requiring parents and athletes to receive educational material concerning sport-related concussion (SRC). The aim of this study was to examine trends in concussion knowledge of parents from one community following implementation of Michigan’s Sports Concussion Laws (MSCL).

METHODS

A convenience sample of parents of students from a suburban school district were surveyed via district email at one year and five years post MSCL implementation. Results were compared to an equivalent 33-item survey obtained prior to the law. Individual questions were compared between the three surveys using Chi-square analysis with statistical significance observed at p < 0.05.

RESULTS

A total of 381 responses were obtained from the one-year post-MSCL (1yMSCL) and 178 in the five-year post-MSCL (5yMSCL) survey. Awareness of district policy regarding concussion was significantly higher after implementation of the MSCL (i.e., 77% at 1yMSCL and 71% at 5yMSCL) compared to prior 18% pre-MSCL (p < 0.0001). Respondents to the 5yMSCL survey were also significantly more aware of medical guidelines surrounding “return to play” after SRC compared to 1yMSCL (84.8% v 78.7%, p = 0.01). At 5yMSCL, significantly more respondents agreed that head injuries could cause more brain damage to children than adults (86.5% v 78.7% at 1yMSCL, p = 0.03). Finally, most parents at both survey periods rated the concussion educational material as the most helpful information source regarding SRC.

CONCLUSIONS

Based on these results, parental knowledge awareness appears to have increased concerning awareness of medical guidelines for SRC and potential brain damage risks to children after enactment of the MSCL.
Estimation of the error covariance matrix for IASI radiances and its impact on the assimilation of ozone in a chemistry transport model
Authors: El Aabaribaoune Mohammad , Emili Emanuele , Guidard Vincent
Published: April 2021

Abstract. In atmospheric chemistry retrievals and data assimilation systems, observation errors associated with satellite radiances are chosen empirically and generally treated as uncorrelated. In this work, we estimate inter-channel error covariances for the Infrared Atmospheric Sounding Interferometer (IASI) and evaluate their impact on ozone assimilation with the chemistry transport model MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle). The method used to calculate observation errors is a diagnostic based on the observation and analysis residual statistics already adopted in many numerical weather prediction centres. We used a subset of 280 channels covering the spectral range between 980 and 1100 cm−1 to estimate the observation-error covariance matrix. This spectral range includes ozone-sensitive and atmospheric window channels. We computed hourly 3D-Var analyses and compared the resulting O3 fields against ozonesondes and the measurements provided by the Microwave Limb Sounder (MLS) and by the Ozone Monitoring Instrument (OMI). The results show significant differences between using the estimated error covariance matrix with respect to the empirical diagonal matrix employed in previous studies. The validation of the analyses against independent data reports a significant improvement, especially in the tropical stratosphere. The computational cost has also been reduced when the estimated covariance matrix is employed in the assimilation system, by reducing the number of iterations needed for the minimizer to converge.
Design and characterization of a new oxidation flow reactor for laboratory and long-term ambient studies
Authors: Xu Ningjin , Collins Don R.
Published: April 2021

Abstract. Oxidation flow reactors (OFRs) are frequently used to
study the formation and evolution of secondary aerosol (SA) in the
atmosphere and have become valuable tools for improving the accuracy of
model simulations and for depicting and accelerating realistic atmospheric
chemistry. Driven by rapid development of OFR techniques and the increasing
appreciation of their wide application, we designed a new all-Teflon
reactor, the Particle Formation Accelerator (PFA) OFR, and characterized it
in the laboratory and with ambient air. A series of simulations and
experiments were performed to characterize (1) flow profiles in the reactor
using computational fluid dynamics (CFD) simulations, (2) the UV intensity
distribution in the reactor and the influence of it and varying O3
concentration and relative humidity (RH) on the resulting equivalent OH
exposure (OHexp), (3) transmission efficiencies for gases and
particles, (4) residence time distributions (RTDs) for gases and particles
using both computational simulations and experimental verification, (5) the
production yield of secondary organic aerosol (SOA) from oxidation of
α-pinene and m-xylene, (6) the effect of seed particles on resulting
SA concentration, and (7) SA production from ambient air in Riverside, CA,
US. The reactor response and characteristics are compared with those of a
smog chamber (Caltech) and of other oxidation flow reactors: the Toronto
Photo-Oxidation Tube (TPOT), the Caltech Photooxidation Flow Tube (CPOT),
the TUT Secondary Aerosol Reactor (TSAR), quartz and aluminum versions of
Potential Aerosol Mass reactors (PAMs), and the Environment and Climate
Change Canada OFR (ECCC-OFR). Our studies show that (1) OHexp can be varied over a range comparable
to that of other OFRs; (2) particle transmission efficiency is over 75 %
in the size range from 50 to 200 nm, after minimizing static charge on the
Teflon surfaces; (3) the penetration efficiencies of CO2 and SO2
are 0.90 ± 0.02 and 0.76 ± 0.04, respectively, the latter of
which is comparable to estimates for LVOCs; (4) a near-laminar flow profile
is expected based on CFD simulations and suggested by the RTD experiment
results; (5) m-xylene SOA and α-pinene SOA yields were 0.22 and 0.37,
respectively, at about 3 × 1011 molec. cm−3 s OH
exposure; (6) the mass ratio of seed particles to precursor gas has a
significant effect on the amount of SOA formed; and (7) during measurements
of SA production when sampling ambient air in Riverside, the mass
concentration of SA formed in the reactor was an average of 1.8 times that
of the ambient aerosol at the same time.
The “Ideal Spectrograph” for Atmospheric Observations
Authors: Platt Ulrich , Wagner Thomas , Kuhn Jonas , Leisner Thomas
Published: April 2021

Abstract. Spectroscopy of scattered-sunlight in the near UV to near IR spectral ranges has proven to be an extremely useful tool for the analysis of atmospheric trace gas distributions. A central parameter for the achievable sensitivity and spatial resolution of spectroscopic instruments is the étendue (product of aperture angle and entrance area) of the spectrograph, which is at the heart of the instrument. The étendue of an instrument can be enhanced by (1) up-scaling all instrument dimensions or (2) by changing the instrument F-number, (3) by increasing the entrance area, or (4) by operating many instruments (of identical design) in parallel. The étendue can be enhanced by (in principle) arbitrary factors by options (1) and (4), the effect of options (2) and (3) is limited. We present some new ideas and considerations how instruments for the spectroscopic determination of atmospheric gases could be optimized by using new possibilities in spectrograph design and manufacturing. Particular emphasis is on arrays of massively parallel instruments for observations using scattered-sunlight. Such arrays can reduce size and weight of instruments by orders of magnitude, while preserving spectral resolution and light throughput. We also discuss the optimal size of individual spectrographs in a spectrograph array and give examples of spectrograph systems for use on a (low Earth orbit) satellite including one with sub-km ground pixel size.
Modern silicon dynamics of a small high-latitude subarctic lake
Authors: Zahajská Petra , Olid Carolina , Stadmark Johanna , Fritz Sherilyn C. , Opfergelt Sophie , Conley Daniel J.
Published: April 2021

Abstract. High biogenic silica (BSi) concentrations occur sporadically in lake sediments
throughout the world; however, the processes leading to high BSi concentrations
vary.
We explored the factors responsible for the high BSi concentration in sediments
of a small, high-latitude subarctic lake (Lake 850). The Si budget of this
lake had not been fully characterized before to establish the drivers
of BSi accumulation in this environment.
To do this, we combined
measurements of variations in stream discharge, dissolved silica (DSi) concentrations, and stable
Si isotopes in both lake and stream water with measurements of BSi content in
lake sediments. Water, radon, and Si mass balances revealed the importance
of groundwater discharge as a main source of DSi to the lake, with
groundwater-derived DSi inputs 3 times higher than those from ephemeral
stream inlets. After including all external DSi sources (i.e., inlets and groundwater
discharge) and estimating the total BSi accumulation in the sediment,
we show that diatom production consumes up to 79 % of total DSi input.
Additionally, low sediment accumulation rates were observed based on the
dated gravity core. Our findings thus demonstrate that groundwater discharge
and low mass accumulation rate can account for the high BSi accumulation
during the last 150 cal yr BP. Globally, lakes have been estimated to
retain one-fifth of the annual DSi terrestrial weathering flux that
would otherwise be delivered to the ocean. Well-constrained
lake mass balances, such as presented here, bring clarity to those estimates
of the terrestrial Si cycle sinks.
Subsurface iron accumulation and rapid aluminium removal in the Mediterranean following African dust deposition
Authors: Bressac Matthieu , Wagener Thibaut , Leblond Nathalie , Tovar-Sánchez Antonio , Ridame Céline , Albani Samuel , Guasco Sophie , Dufour Aurélie , Jacquet Stéphanie , Dulac François , Desboeufs Karine , Guieu Cécile
Published: April 2021

Abstract. Mineral dust deposition is an important supply mechanism for trace elements in the low-latitude ocean. Our understanding of the controls of such inputs has been mostly built onto laboratory and surface ocean studies. The lack of direct observations and the tendency to focus on near surface waters prevent a comprehensive evaluation of the role of dust in oceanic biogeochemical cycles. In the frame of the PEACETIME project (ProcEss studies at the Air-sEa Interface after dust deposition in the MEditerranean sea), the responses of the aluminium (Al) and iron (Fe) cycles to two dust wet deposition events over the central and western Mediterranean Sea were investigated at a timescale of hours to days using a comprehensive dataset gathering dissolved and suspended particulate concentrations, along with sinking fluxes. Dissolved Al (dAl) removal was dominant over dAl released from dust. Fe / Al ratio of suspended and sinking particles revealed that biogenic particles, and in particular diatoms, were key in accumulating and exporting Al relative to Fe. By combining these observations with published Al / Si ratios of diatoms, we show that adsorption onto biogenic particles, rather than active uptake, represents the main sink for dAl in Mediterranean waters. In contrast, systematic dissolved Fe (dFe) accumulation occurred in subsurface waters (~100–1000 m), while dFe input from dust was only transient in the surface mixed-layer. The rapid transfer of dust to depth (up to ~180 m d−1), the Fe-binding ligand pool in excess to dFe in subsurface (while nearly-saturated in surface), and low scavenging rates in this particle-poor depth horizon are all important drivers of this subsurface dFe enrichment. At the annual scale, this previously overlooked mechanism may represent an additional pathway of dFe supply for the surface ocean through diapycnal diffusion and vertical mixing. However, low subsurface dFe concentrations observed at the basin scale (< 0.5 nmol kg−1) questions the residence time for this dust-derived subsurface reservoir, and hence its role as a supply mechanism for the surface ocean, stressing the need for further studies. Finally, these contrasting responses indicate that dAl is a poor tracer of dFe input in the Mediterranean Sea.
Introducing electronic circuits and hydrological models to postsecondary physical geography and environmental science students: systems science, circuit theory, construction, and calibration
Authors: Kinar Nicholas J.
Published: April 2021

Abstract. A classroom activity involving the construction, calibration, and
testing of electronic circuits was introduced to an advanced hydrology class
at the postsecondary level. Two circuits were constructed by students: (1) a
water detection circuit and (2) a hybrid relative humidity (RH)/air
temperature sensor and pyranometer. The circuits motivated concepts of
systems science, modelling in hydrology, and model calibration. Students
used the circuits to collect data useful for providing inputs to
mathematical models of hydrological processes. Each student was given the
opportunity to create a custom hydrological model within the context of the
class. This is an example of constructivist teaching where students engage
in the creation of meaningful knowledge, and the instructor serves as a
facilitator to assist students in the achievement of a goal. Analysis of
student-provided feedback showed that the circuit activity motivated,
engaged, and facilitated learning. Students also found the activity to be a
novel and enjoyable experience. The theory of circuit operation and
calibration is provided along with a complete bill of materials (BOM) and
design files for replication of this activity in other postsecondary
classrooms. Student suggestions for improvement of the circuit activity are
presented along with additional applications.
Exchange interaction in short-lived flavine adenine dinucleotide biradical in aqueous solution revisited by CIDNP (chemically induced dynamic nuclear polarization) and nuclear magnetic relaxation dispersion
Authors: Zhukov Ivan V. , Kiryutin Alexey S. , Panov Mikhail S. , Fishman Natalya N. , Morozova Olga B. , Lukzen Nikita N. , Ivanov Konstantin L. , Vieth Hans-Martin , Sagdeev Renad Z. , Yurkovskaya Alexandra V.
Published: April 2021

Abstract. Flavin adenine dinucleotide (FAD) is an important
cofactor in many light-sensitive enzymes. The role of the adenine moiety of
FAD in light-induced electron transfer was obscured, because it involves an
adenine radical, which is short-lived with a weak chromophore. However, an
intramolecular electron transfer from adenine to flavin was revealed several
years ago by Robert Kaptein by using chemically induced dynamic nuclear
polarization (CIDNP). The question of whether one or two types of biradicals of
FAD in aqueous solution are formed stays unresolved so far. In the present
work, we revisited the CIDNP study of FAD using a robust mechanical sample
shuttling setup covering a wide magnetic field range with sample
illumination by a light-emitting diode. Also, a cost efficient fast field
cycling apparatus with high spectral resolution detection up to 16.4 T for
nuclear magnetic relaxation dispersion studies was built based on a 700 MHz
NMR spectrometer. Site-specific proton relaxation dispersion data for FAD
show a strong restriction of the relative motion of its isoalloxazine and
adenine rings with coincident correlation times for adenine, flavin, and
their ribityl phosphate linker. This finding is consistent with the
assumption that the molecular structure of FAD is rigid and compact. The
structure with close proximity of the isoalloxazine and purine moieties is
favorable for reversible light-induced intramolecular electron transfer from
adenine to triplet excited flavin with formation of a transient
spin-correlated triplet biradical F⚫−-A⚫+. Spin-selective recombination of the biradical leads to the formation of CIDNP
with a common emissive maximum at 4.0 mT detected for adenine and flavin
protons. Careful correction of the CIDNP data for relaxation losses during
sample shuttling shows that only a single maximum of CIDNP is formed in the
magnetic field range from 0.1 mT to 9 T; thus, only one type of FAD
biradical is detectable. Modeling of the CIDNP field dependence provides
good agreement with the experimental data for a normal distance distribution
between the two radical centers around 0.89 nm and an effective electron
exchange interaction of −2.0 mT.
Establishment and characteristics analysis of a crop–drought vulnerability curve: a case study of European winter wheat
Authors: Wu Yanshen , Guo Hao , Zhang Anyu , Wang Jing'ai
Published: April 2021

Abstract. As an essential component of drought risk, crop–drought
vulnerability refers to the degree of the adverse response of a crop to a
drought event. Different drought intensities and environments can cause
significant differences in crop yield losses. Therefore, quantifying drought
vulnerability and then identifying its spatial characteristics will help
understand vulnerability and develop risk-reduction strategies. We select
the European winter wheat growing area as the study area and 0.5∘ × 0.5∘ grids as the basic assessment units. Winter wheat
drought vulnerability curves are established based on the
erosion–productivity impact calculator model simulation. Their loss change
and loss extent characteristics are quantitatively analysed by the key
points and cumulative loss rate, respectively, and are then synthetically
identified via K-means clustering. The results show the following. (1) The
regional yield loss rate starts to rapidly increase from 0.13 when the
drought index reaches 0.18 and then converts to a relatively stable stage
with the value of 0.74 when the drought index reaches 0.66. (2) In contrast
to the Pod Plain, the stage transitions of the vulnerability curve lags
behind in the southern mountain area, indicating a stronger tolerance to
drought. (3) According to the loss characteristics during the initial,
development, and attenuation stages, the vulnerability curves can be divided
into five clusters, namely low-low-low, low-low-medium,
medium-medium-medium, high-high-high, and low-medium-high loss types,
corresponding to the spatial distribution from low latitude to high latitude
and from mountain to plain. The paper provides ideas for the study of the
impact of environment on vulnerability and for the possible application of
vulnerability curve in the context of climate change.
Pervasive diffusion of climate signals recorded in ice-vein ionic impurities
Authors: Ng Felix S. L.
Published: April 2021

Abstract. A theory of vein impurity transport conceived two decades
ago predicts that signals in the bulk concentration of soluble ions in ice
migrate under a temperature gradient. If valid, it would mean that some
palaeoclimatic signals deep in ice cores (signals from vein impurities as
opposed to matrix or grain-boundary impurities) suffer displacements that upset
their dating and alignment with other proxies. We revisit the vein physical
interactions to find that a strong diffusion acts on such signals. It arises
because the Gibbs–Thomson effect, which the original theory neglected,
perturbs the impurity concentration of the vein water wherever the bulk
impurity concentration carries a signal. Thus, any migrating vein signals
will not survive into deep ice where their displacement matters, and the
palaeoclimatic concern posed by the original theory no longer stands.
Simulations with signal peaks introduced in shallow ice at the GRIP and
EPICA Dome C ice-core sites, ignoring spatial fluctuations of the ice grain
size, confirm that rapid damping and broadening eradicates the peaks by
two-thirds way down the ice column. Artificially reducing the solute
diffusivity in water (to mimic partially connected veins) by 103 times
or more is necessary for signals to penetrate into the lowest several
hundred metres with minimal amplitude loss. Simulations incorporating
grain-size fluctuations on the decimetre scale show that these can cause the
formation of new, non-migrating solute peaks. The deep solute peaks observed
in ice cores can only be explained by widespread vein disconnection or a
dominance of matrix or grain-boundary impurities at depth (including their
recent transfer to veins) or signal formation induced by grain-size
fluctuations; in all cases, the deep peaks would not have displaced far.
Disentangling the different signal contributions – from veins, the ice
matrix, grain boundaries, and grain-size fluctuations – will aid robust
reconstruction from ion records.
Advances in altimetric snow depth estimates using bi-frequency SARAL/CryoSat-2 Ka/Ku measurements
Authors: Garnier Florent , Fleury Sara , Garric Gilles , Bouffard Jérôme , Tsamados Michel , Laforge Antoine , Bocquet Marion , Fredensborg Hansen Renée Mie , Rémy Frederique
Published: April 2021

Abstract. Although snow depth on sea ice is a key parameter for Sea Ice Thickness (SIT), there currently does not exist reliable estimations. In Arctic, nearly all SIT products use a snow depth climatology (the Warren-99 modified climatology, W99m) constructed from in-situ data obtained prior to the first significant impacts of climate change. In Antarctica, the lack of information on snow depth remains a major obstacle in the development of reliable SIT products. In this study, we present the latest version of the Altimetric Snow Depth (ASD) product computed over both hemispheres from the difference of the radar penetration into the snow pack between the CryoSat-2 Ku-band and the SARAL Ka-band frequency radars. The ASD solution is compared against a wide range of snow depth products including model data (Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS) or its equivalent in Antarctica the Global Ice-Ocean Modeling and Assimilation System (GIOMAS), the MERCATOR model and NASA's Eulerian Snow On Sea Ice Model (NESOSIM, only in Arctic)), the Advanced Microwave Scanning Radiometer 2 (AMSR-2) passive radiometer data, and the Dual-altimeter Snow Thickness (DuST) Ka-Ku product (only in Arctic). It is validated in the Arctic against in-situ and airborne validation data. These comparisons demonstrate that ASD provide a consistent snow depth solution, with space and time patterns comparable with those of the alternative Ka-Ku DuST product, but with a mean bias of about 6.5 cm. We also demonstrate that ASD is consistent with the validation data. Comparisons with Operation Ice Bridge's (OIB) airborne snow radar in Arctic during the period of 2014–2018 show a correlation of 0.66 and a RMSE of about 6 cm. Furthermore, a first-guess monthly climatology has been constructed in Arctic from the ASD product, which shows a good agreement with OIB during 2009–2012. This climatology is shown to provide a better solution than the W99m climatology when compared with validation data. Finally, we have characterised the SIT uncertainty due to the snow depth from an ensemble of SIT solutions computed for the Arctic by using the different snow depth products previously used in the comparison with the ASD product. During the period of 2013–2019, we found a spatially averaged SIT mean standard deviation of 20 cm. Deviations between SIT estimations due to different snow depths can reach up to 77 cm. Using the ASD data instead of W99m to estimate SIT over this time period leads to a reduction of the average SIT of about 30 cm.
Offshore wind farm global blockage measured with scanning lidar
Authors: Schneemann Jörge , Theuer Frauke , Rott Andreas , Dörenkämper Martin , Kühn Martin
Published: April 2021

Abstract. The objective of this paper was the experimental investigation of the accumulated induction effect of a large offshore wind farm as a whole,
i.e. the global-blockage effect, in relation to atmospheric-stability estimates and wind farm operational states. We measured the inflow of a
400 MW offshore wind farm in the German North Sea with a scanning long-range Doppler wind lidar. A methodology to reduce the statistical
variability of different lidar scans at comparable measurement conditions was introduced, and an extensive uncertainty assessment of the averaged
wind fields was performed to be able to identify the global-blockage effect, which is small compared to e.g. wind turbine wake effects and ambient
variations in the inflow. Our results showed a 4 % decrease in wind speed (accuracy range of 2 % to 6 %) at transition piece height
(24.6 m) upwind of the wind farm with the turbines operating at high thrust coefficients above 0.8 in a stably stratified atmosphere, which
we interpreted as global blockage. In contrast, at unstable stratification and similar operating conditions and for situations with low thrust
coefficients (i.e. approx. 0 for not operating turbines and ≤ 0.3 for turbines operating far above rated wind speed) we identified no wind
speed deficit. We discussed the significance of our measurements and possible sources of error in long-range scanning lidar campaigns and give
recommendations on how to measure small flow effects like global blockage with scanning Doppler lidar. In conclusion, we provide strong evidence for
the existence of global blockage in large offshore wind farms in stable stratification and the turbines operating at a high thrust coefficient by
planar lidar wind field measurements. We further conclude that global blockage is dependent on atmospheric stratification.
Las diversas interpretaciones de la teoría del conocimiento de Giordano Bruno y sus problemas. Hacia una elucidación de los conceptos de phantasia e imago
Authors: Fernández Fernández Juan Carlos
Published: April 2021

en este trabajo analizo las diversas interpretaciones que ha suscitado la teoría del conocimiento de Giordano Bruno a partir de la segunda mitad del siglo XX. El objetivo principal es destacar una serie de problemas fundamentales que han de ser superados si se quiere esclarecer adecuadamente el conjunto de la propuesta gnoseológica de Bruno, en concreto sus tesis relativas al estatuto y función de la facultad fantástica y sus productos, las imágenes. Son tres los problemas destacados: (1) la confusión terminológica que por parte de los intérpretes se observa en torno al concepto “imago”, en su doble sentido ontológico y gnoseológico; (2) la tesis de que los productos mentales carecen de rasgos lógicos, idea a su vez derivada de una interpretación en exceso idealista de la génesis del conocimiento y (3) la tesis de la “inmanencia fantásica”, consistente en reducir toda actividad gnoseológica al ámbito de la fantasía. Para justificar la problematicidad inherente a estas ideas acudiré tanto al texto bruniano como a la conocida distinción escolástica entre “concepto formal” y “concepto objetivo”.
Cyber-victimization Trends in Trinidad & Tobago: The Results of An Empirical Research
Authors:   University of Trinidad and Tobago, Trinidad and Tobago, Smith Troy , Stamatakis Nikolaos ,   United Arab Emirates University, United Arab Emirates
Published: April 2021

Cybertechnology has brought benefits to the Caribbean in the form of new regional economic and social growth. In the last years, Caribbean countries have also become attractive targets for cybercrime due to increased economic success and online presence with a low level of cyber resilience. This study examines the online-related activities that affect cybercrime victimization by using the Routine Activity Theory (RAT). The present study seeks to identify activities that contribute to different forms of cybercrime victimization and develop risk models for these crimes, particularly the understudied cyber-dependent crimes of Hacking and Malware. It also aims to explore if there are similarities or differences in factors leading to victimization, which correlate to the classification of crimes as either cyber-dependent or cyber-enabled. The data analysis suggests that there is significant applicability for RAT in explaining Online Harassment victimization, while the usability of the RAT for predicting Malware victimization proved to be minimal, with only two significant variables being identified, with both being associated with Capable Guardianship.
Educational leadership (II)
Authors:   ", Patraşcu Dumitru ,   Ion Creanga",   State Pedagogical University
Published: April 2021

The article reviews some conceptual delimitations, basic leadership skills, organizational culture of the school, leadership models, personal styles of leaders, exercise to determine the profile of the managerial / leadership style.