AUTHOREA
Log in Sign Up Browse Preprints
LOG IN SIGN UP

Preprints

Explore 66,105 preprints on the Authorea Preprint Repository

A preprint on Authorea can be a complete scientific manuscript submitted to a journal, an essay, a whitepaper, or a blog post. Preprints on Authorea can contain datasets, code, figures, interactive visualizations and computational notebooks.
Read more about preprints.

Frequency and risk factors of acute and permanent femoral arterial occlusion in neona...
Mahmut GOKDEMIR
Nimet CINDIK

Mahmut GOKDEMIR

and 1 more

October 24, 2021
Background: In neonates, securing femoral arterial access is challenging and time consuming even in experienced hands. Data on frequency and risk factors of ALAP and PFAO are scarce in neonates with CHD. We investigated frequency and risk factors of acute loss of the arterial pulse (ALAP) and permanent femoral arterial occlusion (PFAO) in neonates with congenital heart disease (CHD) underwent ultrasound˗guided femoral arterial access (US˗GFAA). Methods: We divided the patients into groups according to the presence of ALAP and PFAO. We obtained data related to patient characteristics and access variables of US˗GFAA from our database of pediatric cardiac catheterization between August 2017 and May 2021. We used an echocardiography˗S6, 12˗MHz linear probe, 21˗gauge needle, and a 0.018”guidewire for arterial access. A 4˗French sheath (7cm) was placed in all patients. Results: US˗GFAA was obtained in 323(98.8%) of the 327 neonates. We identified ALAP in 130(40.2%) patients and PFAO in 19(5.9%) patients. Median weight was 3.05(IQR: 2.80˗3.40) kg, first attempt success rate was 88.2% and median access time was 46 sec (IQR: 23˗94). Logistic regression analysis identified coarctation of the aorta (Odds ratio: 2.46; 95% CI: 1.30˗4.66; P=0.006) as independent risk factor for ALAP, but did not identify any independent risk factors for PFAO. Conclusion: This study showed that coarctation of the aorta is an independent risk factor for ALAP in neonates with CHD underwent US˗GFAA and placed a 4˗French sheath. Although most cases of ALAP resolve in the early period, the frequency of PFOA remains high despite effective treatment.
Late-onset panuveitis in a Chinese girl with sporadic Blau syndrome: a case report
Zicheng Ma

Zicheng Ma

October 24, 2021
The onset of ocular symptoms at age 18 is relatively rare in BS and the eye lesions are usually serious.We reported a case of a 18 year-old Chinese girl with late-onset mild panuveitis with sporadic Blau syndrome .
Oppression or Protection: Reflecting on Medicine and Justice Through Narrative Medici...
Haley Newman
Caroline Diorio

Haley Newman

and 7 more

October 24, 2021
Early in the Coronavirus Disease 2019 pandemic, our medical center, like many, halted in-person learning activities. The narrative medicine sessions we planned for the pediatric hematology/oncology fellows were no exception. At this time we also witnessed waves of civil unrest fueled by systemic racism toward Americans of color. Amidst the isolation, apprehension, and turmoil, we turned to narrative medicine. To keep our participants safe and work around novel constraints, we adapted the narrative medicine curriculum for virtual delivery.
A finite element method for the solution of singularly perturbed problems of mathemat...
Aditya Kaushik

Aditya Kaushik

January 20, 2022
 A singularly perturbed convection diffusion problem is solved numerically using finite element method based on higher order polynomials. More precisely, we introduce a modified graded mesh generated using some implicitly defined functions. Higher order parameter uniform convergence is obtained in -weighted energy norm. Moreover, the error estimates obtained are optimal in the sense that they are free from logarithmic factor. A number of test examples are taken into account and a rigorous comparative analysis is presented. Moreover, we compare the proposed method with others found in the literature.
Genital mycoplasma and preterm birth: a difficult puzzle to solve. Letter re: Genital...
Andrew Kotaska
Lesley Paulette

Andrew Kotaska

and 1 more

October 23, 2021
Genital mycoplasma and preterm birth: a difficult puzzle to solve. Letter re: Genital Mycoplasma infection and spontaneous preterm birth outcome: a prospective cohort studySir.In their recent paper, Cunha and colleagues analyzed data from a diverse group of 1349 Brazilian women who participated in a 2011 study evaluating etiological factors associated with preterm birth. 11Cunha GKP, Bastos LB, de Freitas SF, Cavalli RC, Quintana SM. Genital mycoplasma infection and spontaneous preterm birth outcome: a prospective cohort study. BJOG  https://doi-org.uml.idm.oclc.org/10.1111/1471-0528.16949 Women were interviewed and examined at 20-25 weeks’ gestation, and cervicovaginal cultures were taken for mycoplasma, ureaplasma, and bacterial vaginosis. Women were followed until delivery, and clinical associations with preterm birth were evaluated. Positive associations were found for shortened cervix and a history of prior preterm birth. No association was found for infection with mycoplasma, ureaplasma, or bacterial vaginosis. They concluded that “genital mycoplasma infection was not a risk of spontaneous preterm birth, even with other abnormal vaginal microbiota conditions.”There is a flaw in their methodology and conclusion. In the original study, women with a positive culture for ureaplasma or mycoplasma were treated with azithromycin, and those with bacterial vaginosis were treated with oral metronidazole. Treatment would have reduced the presence of these pathogens, limiting their ability to cause preterm birth. Accordingly, this study shows that women with treated mycoplasma, ureaplasma or bacterial vaginosis do not have an increased incidence of preterm birth; however, no comment can be made on whether untreated infection causes preterm birth.Presumably the original investigators who performed the study treated women with genital infection because they believed it might prevent preterm birth; and there lies the rub. An observational study using vaginal culture results unavailable until after birth has shown an association between untreated mycoplasma infection and preterm birth.22Foxman B, Wen A, Srinivasan U, et al. Mycoplasma, bacterial vaginosis, associated bacteria BVAB3, race, and risk of preterm birth in a high-risk cohort. Am J Obstet Gynecol 2014;210:226.e1-7. However, in order to determine whether mycoplasma causes preterm birth and whether treatment prevents it, a randomized trial of treatment or placebo in infected women at elevated risk of preterm birth is needed. This may not be easily feasible. Ethically, investigators may be able to demonstrate research equipoise: that we do not yet know whether treatment reduces preterm birth associated with mycoplasma infection. However, women found to have genital mycoplasma who are at increased risk of preterm birth would need to believe that the benefits and harms of treating or not treating are equal. Given the relative safety of antibiotics and the high morbidity of preterm birth, practically, equipoise may be hard to find.In Northern Canada, with high rates of sexually transmitted infections including mycoplasma, we suspect a causal relationship with preterm birth and late miscarriage. Based on observational studies and anecdotal evidence, our practice is to screen women with a history of prior preterm birth, late miscarriage, or short cervix for ureaplasma, mycoplasma, and bacterial vaginosis in the second trimester and treat those who are positive.2,33Taylor-Robinson D, Lamont R. Mycoplasmas in pregnancy. BJOG 2011;118:164–174.,44Morency AM, Bujold E. The Effect of Second-Trimester Antibiotic Therapy on the Rate of Preterm Birth. J Obstet Gynaecol Can 2007;29(1):35–44 We also test women with threatened preterm labour remote from term and treat those who are positive, sometimes with marked reduction in symptoms. In keeping with Taylor-Robinson’s paper, treatment failures with azithromycin used for Mycoplasma hominis have prompted a switch to Clindamycin, whose activity against both mycoplasma and bacterial vaginosis may explain its better performance than metronidazole in the prevention of preterm birth.3,4 We await better evidence, but are not holding our breath.
Dynamic of a two-strain COVID-19 model with vaccination
Stéphane Tchoumi
Herieth rwezaula

Stéphane Tchoumi

and 2 more

October 23, 2021
COVID-19 is a respiratory illness caused by an RNA virus prone to mutations. In December 2020, variants with different characteristics that could affect transmissibility emerged around the world. To address this new dynamic of the disease, we formulate and analyze a mathematical model of a two-strain COVID- 19 transmission dynamics with strain 1 vaccination. The model is theoretically analyzed and sufficient conditions for the stability of its equilibria are derived. In addition to the disease-free and endemic equilibria, the model also has single-strain 1 and strain 2 endemic equilibria. Using the center manifold theory, it is shown that the model does not exhibit the phenomenon of backward bifurcation, and global stability of the model equilibria when the basic reproduction number R 0 is either less or greater than unity as the case maybe are proved using various approaches. Simulations to support the model theoretical results are provided. We calculate the basic reproductive number for both strains R 1 and R 2 independently. Results indicate that - both strains will persist when R 1 > 1 and R 2 > 1 - Stain 2 could establish itself as the dominant strain if R 1 < 1 and R 2 > 1, or when R 2 is at least two times greater than R 1 . However, with the current knowledge of the epidemiology of the COVID-19 pandemic and the availability of treatment and an effective vaccine against strain 1, it is expected that eventually, strain 2 will likely be eradicated in the population due to de novo herd immunity provided the threshold parameter R 2 is controlled to remain below unity.
PARTICLE TRAJECTORIES AND THE PERCEPTION OF CLASSICAL MOTION IN THE FREE PROPAGATION...
John Briggs

John Briggs

October 25, 2021
The free propagation in time of a normalisable wave packet is the oldest problem of continuum quantum mechanics. Its motion from microscopic to macroscopic distance is the way in which most quantum systems are detected experimentally. Although much studied and analysed since 1927 and presented in many text books, here the problem is re-appraised from the standpoint of semi-classical mechanics. Particular aspects are the emergence of deterministic trajectories of particles emanating from a region of atomic dimensions and the interpretation of the wave function as describing a single particle or an ensemble of identical particles. Of possible wave packets, that of gaussian form is most studied due to the simple exact form of the time-dependent solution in real and in momentum space. Furthermore, this form is important in laser optics. Here the equivalence of the time-dependent Schroedinger equation to the paraxial equation for the propagation of light is demonstrated explicitly. This parallel helps to understand the relevance of trajectory concepts and the conditions necessary for the perception of motion as classical.
Comparison of traditional and molecular surveys of fish biodiversity in southern Te W...
Paul Czechowski

Paul Czechowski

and 7 more

February 07, 2024
A document by Paul Czechowski. Click on the document to view its contents.
Longitudinal evaluation of brain development in fetuses with congenital diaphragmatic...
Doaa Emam
Michael Aertsen

Doaa Emam

and 11 more

October 22, 2021
Objective To document longitudinal changes in brain development in fetuses with congenital diaphragmatic hernia (CDH). Design Retrospective cohort study Setting Single tertiary fetal surgery center Population Fetuses with isolated CDH and at least two MRI-examinations (n=42 fetuses). Fifty-six fetuses who underwent MRI for a condition not interfering with fetal brain development or fetuses from healthy volunteers served as controls. Methods Biometry included biparietal and fronto-occipital diameter, ventricular atrial width, transcerebellar diameter, head circumference and width of the extra-axial space. Cortical maturation was assessed using a qualitative and quantitative grading system. 3D volumes were segmented for white matter, intra-axial and extra-axial cerebrospinal fluid and cerebellum. Main outcome measures Brain development on MRI with subjective and objective assessment. Results The mean GA at first MRI was 28.0 ± 2.1 wks and at the second 33.2 ± 1.3 wks. The mean GA in controls was 30.7 ± 4.2 wks. At 28 weeks CDH fetuses displayed abnormal maturation grading (p<0.003) and fissure depth (p<0.05). By 33 wks, the brain grading indices were still abnormal (p<0.01), but fissure depth measurements were in the normal range (p>0.05). Also, the extra-axial fluid and the ventricular volume were increased (resp. p 0.0054 and p 0.0243). There was no difference in white matter or cerebellum volume (p>0.05). Conclusions Brain development in CDH fetuses around 28 weeks appears to be delayed. This is less prominent at 33 weeks. In addition, there was an increase in ventricular and extra-axial space volume in the third trimester.
Genomics of white-tailed eagle (Haliaeetus albicilla) in the North-Atlantic islands r...
Charles Christian Riis Hansen
Jacob  Rasmussen

Charles Christian Hansen

and 18 more

October 22, 2021
Using whole genome shotgun sequences from 92 white-tailed eagles (Haliaeetus albicilla) sampled from Greenland, Iceland, Norway, Denmark, Estonia, and Turkey between 1885-1950 and after 1990, we investigate the genomic variation within countries over time, and between countries. Clear genetic differentiation is observed between samples from the different countries, with the largest differences between the island and mainland populations, and indications that the island populations share the most recent ancestry with the Norwegian population. We find signs of strong inbreeding in the island populations. Further, temporal differences are observed in some populations, for example, replacement of the Danish gene pool following its population’s extinction in the early 20th century, as well as a change in the genetic diversity of the Icelandic population following a severe bottleneck during the last century, all of which could warrant a further conservation effort in Iceland. More generally, all populations show a decline in effective population size, which may have been shaped by I) distinct refugia during the last glacial period, II) population divergence following the colonization of the deglaciated areas ~10,000 years ago, III) human population expansion and e.g., settlement in Iceland ~1,100 years ago, and IV) human persecution and toxic pollutants during the last two centuries.
Prevention vs. Cure: is BioGlue priming the optimal strategy against E-Vita Neo graft...
Cian Tan
Professor Mohamad Bashir

Cian Tan

and 1 more

October 22, 2021
Background Since the introduction of the E-Vita Open NEO aortic prosthesis in 2020, several incidences of post-anastomotic oozing from the polyester portion of the graft have emerged. The use of BioGlue to prime E-Vita Open NEO to prevent this has been suggested as a way to mitigate this worrying complication. We investigate the extent of graft oozing in E-Vita Open NEO and evaluate the use of BioGlue in preventing oozing, both experimentally and in terms of potential clinical complications. Methods and materials E-Vita Open NEO (in straight and branched configurations) was implanted in a perfused model. The distal stent-graft and side branches were clamped, and the graft pressurised with blood to 120 mmHg. The volume of blood (ml) oozing from the graft within 60 seconds was measured. Non-pressurised grafts were coated with BioGlue up to a thickness 1-, 2-, and 3 mm, and the volume (mm3) of BioGlue required to do so was recorded. Results Within 60 seconds, 250.0 ml of blood oozed from the grafts tested. 43.694 mm3, 87.389 mm3, and 174.778 mm3 of BioGlue was required to coat the device with 1-, 2-, and 3 mm of BioGlue. Conclusion Graft oozing from E-Vita Open NEO represents an omnipresent and worrying risk. The use of BioGlue herein is likely associated with several adverse consequences, which are an additional risk on top of that posed by graft oozing. These risks call into question the suitability of E-Vita Open NEO, especially when compared to alternative devices not affected by oozing.
Climate Change and Global Health: A Call to more Research and more Action
Ioana Agache
Juan Aguilera

Ioana Agache

and 31 more

October 22, 2021
There is increasing understanding, globally, that climate change and increased pollution will have a profound and mostly harmful effect on human health. This review brings together international experts to describe both the direct (such as heat waves) and indirect (such as vector-borne disease incidence) impacts of climate change depending on their vulnerability (i.e., diseases) on an international, economic, political and environmental context. This unique review also expands on these issues to address a third category of potential longer-term impacts on global health: famine, population dislocation, and environmental justice and education. This scholarly resource explores these issues fully, linking them to global health in urban and rural settings in developed and developing countries. The review finishes with a practical discussion of action that health professionals around the world in our field can yet take.
Fixed-time projective synchronization of delayed memristive neural networks via aperi...
Hao Pu
Fenjun Li

Hao Pu

and 1 more

October 22, 2021
In this paper, the fixed-time projective synchronization issue for a class of delayed memristive neural networks is studied via aperiodically intermittent switching control. Firstly, according to the existing aperiodically intermittent switching strategy, a novel theorem for aperiodically intermittent switching fixed-time stability is proposed and proved through mathematical induction. Subsequently, an aperiodically intermittent switching controller is designed to reach fixed-time projective synchronization for drive-response systems. The power exponent is a function of error system state rather than one or two fixed constants. With the help of the extended differential inclusion framework, the inequality technique and the analysis method, some novel sufficient conditions are derived to ensure fixed-time projective synchronization for the considered systems. The settling time is closely related to the number of neurons and the maximum ratio of the rest width to the aperiodic time span, but independent of the initial value conditions. Furthermore, the fixed-time complete synchronization, fixed-time anti-synchronization and fixed-time stability obtained are special cases of the main theorem. Meanwhile, the conclusions of this paper improve some previous relevant works. Finally, a numerical example is given to verify the effectiveness and feasibility of the obtained results
A Rapidly Progressing Pleural Effusion within 24 Hours: A Case Report
Bassem  Alhariri
Ayisha  Ameen

Bassem Alhariri

and 2 more

October 22, 2021
Patients with pleural effusion are mostly presenting with shortness of breath and pleuritic chest pain. This report describes a case of PE who presented with left shoulder pain and was found to have rapidly accumulating massive effusion within 24 hours of presentation. Thoracocentesis was performed a showed an exudative picture
Robot-assisted Endoscopic Surgery: Removal of a Huge Tricuspid Valve Myxoma
Lun Wu Hung
Cheng Ya Lee

Lun Wu Hung

and 2 more

October 22, 2021
Cardiac myxoma is the most common benign cardiac tumor. Its tremendous size and fragile character severely bother the surgeons. Several minimal invasive approaches had been applied for radical tumor excision. The wound was forcibly enlarged for en-bloc specimen removal and prevention of debris sputtering. We reported a case of huge tricuspid valve (TV) myxoma managed by robot-assisted endoscopic tumor resection and TV repair. The tumor was downsized with a morcellator and removed through a keyhole wound (1.1 cm in diameter). The patient recovered uneventfully and was discharged after four days.
Comparison of Bleeding Profiles of Sugammadex and Neostigmine in Orthotopic Liver Tra...
Hong Liang
Launia White

Hong Liang

and 3 more

October 22, 2021
In the era of “fast-track’ liver transplantation (LT), neuromuscular blockade (NMB) antagonists such as neostigmine or sugammadex are used to achieve the restoration of neuromuscular function. While sugammadex reverses NMB faster than neostigmine, it has been shown to prolong prothrombin time (PT) and activated thromboplastin time (aPTT). However, this agent’s impact on coagulation during LT is not understood. We compare bleeding risk associated with sugammadex versus neostigmine during liver transplantation. This is a single-center, retrospective review of LT patients who received NMB antagonists intraoperatively between 01/01/2015 to 05/31/2018 at Mayo Clinic in Florida. The primary outcomes were postoperative day (POD) 0-1 bleeding events and POD 0 values of aPTT and INR. Total 241 patients were included, with 135 patients in the neostigmine group (NG) and 106 in the sugammadex group (SG). POD 0-1 postoperative bleeding requiring transfusion occurred in 20% of NG versus 10.4% in SG. POD 0-1 re-operation for bleeding occurred in 1.5% in NG vs. 0% in SG. POD 0 mean INR was 2.0±0.4 in both groups. POD 0 mean aPTT was 45.5±7.9 in NG vs. 49.3±9.0 in SG. Our retrospective study suggests that sugammadex is not associated with an increased risk of bleeding compared to neostigmine use.
Ground state solutions for a Kirchhoff type elliptic systems involving critical expon...
Shengbing Deng
Tingting Huang

Shengbing Deng

and 1 more

October 22, 2021
The aim of this paper is to study the ground state solution for a Kirchhoff type elliptic systems without the Ambrosetti-Rabinowitz condition.
Enhanced Language Model with Hybrid Knowledge Graph for Mathematical Topic Prediction
Minghui  Wu
Canghong Jin

Minghui Wu

and 3 more

October 22, 2021
Understanding mathematical topics is important for both educators and students to capture latent concepts of questions, evaluate study performance, and recommend content in online learning systems. Compared to traditional text classification, mathematical topic classification has several main challenges: (1) the length of mathematical questions is relatively short; (2) there are various representations of the same mathematical concept(i.e., calculations and application); (3) the content of question is complex including algebra, geometry, and calculus. In order to overcome these problems, we propose a framework that combines content tokens and mathematical knowledge concepts in whole procedures. We embed entities from mathematics knowledge graphs, integrate entities into tokens in a masked language model, set up semantic similarity-based tasks for next-sentence prediction, and fuse knowledge vectors and token vectors during the fine-tuning procedure. We also build a Chinese mathematical topic prediction dataset consisting of more than 70,000 mathematical questions with topics. Our experiments using real data demonstrate that our knowledge graph-based mathematical topic prediction model outperforms other state-of-the-art methods.
Existence and nonexistence of nontrivial solutions for a critical biharmonic equation...
duan tian
he han

duan tian

and 2 more

October 22, 2021
In this paper, we study the existence and nonexistence of nontrivial solutions to the following critical biharmonic problem with the Steklov boundary conditions Δ2=+Δ+||2**-2 in , =Δ+=0 on , where ,, ∈ , ⊂ N( ≥ 5) is a unit ball, 2** = 2/N-4 denotes the critical Sobolev exponent for the embedding 2() →2** () and is the outer normal derivative of on . Under some assumptions on , and , we prove the existence of nontrivial solutions to the above biharmonic problem by the Mountain pass theorem and show the nonexistence of nontrivial solutions to it by the Pohozaev identity.
Acoustic emission analysis for characterisation of damage mechanisms in glass fiber...
Samira Gholizadeh

Samira Gholizadeh

and 3 more

February 16, 2022
a Department of Mechanical and Manufacturing engineering, universiti Putra Malaysia, serdang, Malaysia; b school of engineering and technology (Mechanical engineering), university college of technology sarawak (ucts), sarawak, Malaysia ABSTRACT This study assesses the progression of damage occurring on glass fiber reinforced polyester composite specimens using acoustic emission (AE) parameters. Its aims are to improve understanding of the particular characteristics of AE signals; and also to determine the relationship between AE signals and the failure of the material. Time and frequency domain trends were analysed at four different applied loads (60.97, 67.75, 74.52 and 81.30 MPa) representing 45-60% of the ultimate tensile strength of material. The relevant AE parameters were analysed both in the early stages of the test and as the material neared the fracture zone. The results showed a high degree of correlation between the root mean square and number of hits AE values and the number of cycles to failure, of 92.99 and 92.19%, respectively. This correlation, as well as AE basic parameters, suggests that AE can be a valuable tool to predict the fatigue life and detect the onset of damage in such composite materials.
Estimation accuracy of species abundance based on environmental DNA with relation to...
Toshiaki Jo
Hiroki Yamanaka

Toshiaki Jo

and 1 more

October 22, 2021
Environmental DNA (eDNA) analysis is a promising tool for non-disruptive and cost-efficient estimation of species abundance. However, its practical applicability in natural environments is limited because it is unclear whether eDNA concentrations actually represent species abundance in the field. Although the importance of accounting for eDNA dynamics, such as transport and degradation, has been discussed, the influences of eDNA characteristics, including production source and state, and methodology, including collection and quantification strategy and abundance metrics, on the accuracy of eDNA-based abundance estimation were entirely overlooked. We conducted a meta-analysis using 56 previous eDNA literature and investigated the relationships between the accuracy (R2) of eDNA-based abundance estimation and eDNA characteristics and methodology. Our meta-regression analysis found that R2 values were significantly lower for crustaceans than fish, suggesting that less frequent eDNA production owing to their external morphology and physiology may impede accurate estimation of their abundance via eDNA. Moreover, R2 values were positively associated with filter pore size, indicating that selective collection of larger-sized eDNA, which is typically fresher, could improve the estimation accuracy of species abundance. Furthermore, R2 values were significantly lower for natural than laboratory conditions, while there was no difference in the estimation accuracy among natural environments. Our findings shed a new light on the importance of what characteristics of eDNA should be targeted for more accurate estimation of species abundance. Further empirical studies are required to validate our findings and fully elucidate the relationship between eDNA characteristics and eDNA-based abundance estimation.
The Crimean-Congo haemorrhagic fever tick vector Hyalomma marginatum in south of Fran...
Thierno Madiou Bah
Vladimir Grobois

Madiou Thierno Bah

and 15 more

October 22, 2021
For the first time we built a correlative model for predicting the distribution of H. marginatum, one of the main vector of Crimean-Congo Haemorrhagic fever virus (CCHFV), at high resolution in a recently colonized area, namely south of France. Field tick collections were conducted on horses from 2016 to 2021 in 14 French southern departments, which resulted in a first map of H. marginatum on the national territory. Such updated presence/absence data, as well as the mean number of H. marginatum per examined animal (mean parasitic load) as a proxy of the tick abundance, were correlated to multiple parameters that described the climate and habitats characterizing each collection site, as well as movements of horses as a possible source of tick diffusion and new establishment. Our model highlighted the importance of warm temperatures all along the year, as well as dry conditions during summer and moderate annual humidity for the establishment of H. marginatum. A predominance of open natural habitats in the environment was also identified as a supporting factor, in opposition to artificial and humid habitats that were determined as unsuitable. Based on this model, we predicted the current suitable areas for the establishment of the tick H. marginatum in South of France, with a relatively good accuracy using internal and external validation methods. Concerning tick abundance, some correlative relationships were similar than in the occurrence model but the type of horse movements were also pointed out as an important factor explaining the mean parasitic load, leading to differential exposure to ticks. The limitations of estimating and modelling H. marginatum abundance in a correlative model are discussed.
Experiment and Theory Elucidate the Pathways for H3+ Formation in the Ultrafast Doubl...
James Farrar

James Farrar

October 22, 2021
This Research Highlight provides context for the report of Gope et al. on experimental and computational probes of the decay of doubly-ionized methanol to H3+ and HCO+/COH+. The formation of the H3+ ionic product is shown to occur through the agency of a roaming H2 molecule generated from the carboxyl moiety that undergoes prompt proton transfer from the carbon atom, or, delayed proton transfer from the oxygen atom. This novel method for H3+ formation is contrasted with the conventional ion-molecule pathway, known for over a century, that forms the basis for interstellar molecule formation.
Deterministic Quantum Mechanics: Classical nuclear motion explains chemical reactions...
Erik Rohloff
Dominik Rudolph

Erik Rohloff

and 3 more

October 22, 2021
Is a classical description of nuclear motion sufficient when describing chemical reactions? The present paper investigates some phenomena that were previously attributed to nuclear quantum effects. The aim is to show that these phenomena can be modelled with traditional Car-Parrinello molecular dynamics, that is, with a method which treats nuclear motion classically. We find that no additional paradigm is needed for describing chemical reactions. The special reactivity observed for carbenes can be attributed to the special environment represented by a noble gas matrix. Also the infrared spectrum of porphycene is perfectly modelled by traditional Car-Parrinello molecular dynamics. If no more convincing examples are produced, one will stick to deterministic quantum mechanics, as it is the simpler theory which, in addition, is free of paradoxa.
← Previous 1 2 … 2029 2030 2031 2032 2033 2034 2035 2036 2037 … 2754 2755 Next →

| Powered by Authorea.com

  • Home