bluuebunny/crossref_metadata_2025 huggingface dataset:
Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers: potential allies in the COVID-19 pandemic instead of a threat?
Authors: Simko Fedor , Baka Tomas
Published: April 2021

Angiotensin-converting enzyme 2 (ACE2) is the leading player of the protective renin–angiotensin system (RAS) pathway but also the entry receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). RAS inhibitors seemed to interfere with the ACE2 receptor, and their safety was addressed in COVID-19 patients. Pedrosa et al. (Clin. Sci. (Lond.) (2021), 135, 465–481) showed in rats that captopril and candesartan up-regulated ACE2 expression and the protective RAS pathway in lung tissue. In culture of pneumocytes, the captopril/candesartan-induced ACE2 up-regulation was associated with inhibition of ADAM17 activity, counterbalancing increased ACE2 expression, which was associated with reduced SARS-CoV-2 spike protein entry. If confirmed in humans, these results could become the pathophysiological background for justifying RAS inhibitors as cornerstone cardiovascular protectives even during COVID-19 pandemic.
Host galaxy and orientation differences between different AGN types
Authors: Gkini Anamaria , Plionis Manolis , Chira Maria , Koulouridis Elias
Published: April 2021

Aims. The main purpose of this study is to investigate aspects regarding the validity of the active galactic nucleus (AGN) unification paradigm (UP). In particular, we focus on the AGN host galaxies, which according to the UP should show no systematic differences depending on the AGN classification.

Methods. For the purpose of this study, we used (a) the spectroscopic Sloan Digital Sky Survey (SDSS) Data Release 14 catalogue, in order to select and classify AGNs using emission line diagnostics, up to a redshift of z = 0.2, and (b) the Galaxy Zoo Project catalogue, which classifies SDSS galaxies in two broad Hubble types: spirals and ellipticals.

Results. We find that the fraction of type 1 Seyfert nuclei (Sy1) hosted in elliptical galaxies is significantly larger than the corresponding fraction of any other AGN type, while there is a gradient of increasing spiral-hosts from Sy1 to LINER, type 2 Seyferts (Sy2) and composite nuclei. These findings cannot be interpreted within the simple unified model, but possibly by a co-evolution scheme for supermassive black holes and galactic bulges. Furthermore, for the case of spiral host galaxies we find the Sy1 population to be strongly skewed towards face-on configurations, while the corresponding Sy2 population range in all host galaxy orientation configurations has a similar, but not identical, orientation distribution to star-forming galaxies. These results also cannot be interpreted by the standard unification paradigm, but point towards a significant contribution of the galactic disc to the obscuration of the nuclear region. This is also consistent with the observed preference of Sy1 nuclei to be hosted by ellipticals, that is, the dusty disc of spiral hosts contributes to the obscuration of the broad-line region, and thus relatively more ellipticals are expected to appear hosting Sy1 nuclei.
Asymptotic behavior of 2D stably stratified fluids with a damping term in the velocity equation
Authors: Bianchini Roberta , Natalini Roberto
Published: April 2021

This article deals with the asymptotic behavior of the two-dimensional inviscid Boussinesq equations with a damping term in the velocity equation. Precisely, we provide the time-decay rates of the smooth solutions to that system. The key ingredient is a careful analysis of the Green kernel of the linearized problem in Fourier space, combined with bilinear estimates and interpolation inequalities for handling the nonlinearity.
A procedure to estimate the lateral force in clay-pipe interaction after breakout
Authors: Trejo Pablo Cesar , Oliveira Jose Renato M.S. , Almeida Márcio S.S. , Almeida Maria C.F. , Vignoles Mario A.
Published: April 2021

The development of new offshore oil and gas fields is continuously expanding to ultra-deep waters. This tendency and the necessity of reducing project costs have been stimulating the development of new technologies as well as the enhancement of floating production systems. In this regard, pipelines and flexible riser systems have been getting more attention due to its low cost of installation and operation. In order to project a pipeline system, it is important to understand the pipe-soil interaction mechanisms and quantify the influence of soil behaviour on pipe response caused by lateral movement such as thermal buckling. The loads that a pipeline is subjected have been a topic of many experimental studies that aim to reproduce those loads in a realistic manner. This present study concerns the analysis of lateral clay-pipe interaction associated with large deformations and berm formation process at the leading edge of the pipe during movement at given burial depths. A series of centrifuge tests was conducted to assess the relationship between horizontal force and lateral pipe displacement. The breakout force experimental results were compared with different literature proposals, showing a good agreement. A procedure was also proposed to evaluate the normalized lateral force through the combination of two different approaches. The results showed a good comparison with the centrifuge experimental data.
Welche Pflanzen können bei Leber-/Galleleiden helfen?
Authors: Zündorf Ilse , Fürst Robert
Published: April 2021

Verdauungsprobleme gehören zu den Indikationen, bei denen die Betroffenen gerne zu pflanzlichen Arzneimitteln greifen. Das spiegelt sich auch in den Verkaufszahlen wider: Magen- und verdauungsfördernde Mittel standen im Jahr 2018 mit einem Umsatz von 148 Millionen Euro an vierter Stelle der 10 umsatzstärksten Indikationsgruppen bei Phytopharmaka. Dieser Beitrag beleuchtet die Frage, welche Rationale dahintersteckt und was man genau von den pflanzlichen Präparaten erwarten kann.
Neue Aspekte zur Fournierschen Gangrän – Ein Rapid Review
Authors: Kranz Jennifer , Dräger Desiree L. , Schneidewind Laila
Published: April 2021

Die Fourniersche Gangrän (FG) ist eine sporadische, lebensbedrohliche, nekrotisierende Infektion des Perineums, der Perinealregion und des äußeren Genitales. Aus der Literatur gibt es einige Hinweise darauf, dass die Prognose der Erkrankung in den letzten Jahren nicht wesentlich verbessert werden konnte. Daher wurde eine schnelle Evidenzanalyse mittels Literaturrecherche in MEDLINE aus den aktuellen Publikationen des Jahres 2020 durchgeführt, um mittels neuer Aspekte zu ermöglichen, die Versorgungssituation der betroffenen Patienten zu verbessern und weitere Forschungsvorhaben ideal zu planen. Insgesamt konnten für dieses Review 18 Publikationen berücksichtigt werden. Bei 15 dieser Arbeiten handelt es sich um Orginalarbeiten sowie 3 systematische Reviews. Bez. der Orginalarbeiten handelt es sich um 12 retrospektive Fallserien, 2 epidemiologische und eine prospektive Studie. 2 der systematischen Reviews inkludieren ebenfalls eine Metaanalyse. Die Mehrzahl der Autoren dieser Publikationen kommt unter anderem zu der Schlussfolgerung, dass die FG weiterhin eine ernsthafte Erkrankung mit teils inakzeptablen Mortalitätsraten für die moderne Medizin ist und es in der Therapie weiterhin Optimierungsbedarf gibt. Weiterhin wurden neue Risikofaktoren identifiziert, die mit einer erhöhten Mortalität bei FG Patienten assoziiert sind. Es handelt sich um eine Dyslipoproteinämie, Diabetes mellitus, Herzerkrankungen und akutes sowie chronisches Nierenversagen. 4 der inkludierten Arbeiten untersuchten den Zusammenhang des Auftretens von FG und der Einnahme oraler Antidiabetika, SGLT2- sowie DPP4-Hemmern. Keine Studie konnte dabei einen signifikanten Zusammenhang nachweisen, insbesondere eine Metaanalyse mit 84 Studien nicht. Vielversprechende Konzepte für die Wundbehandlung sind die hyperbare Oxygenierung (HBO), der vakuum-assistierte Wundverschluss und Wundkonditionierung mittels Larven. Zusammenfassend ist die FG ein seltenes, aber immer noch potenziell vital bedrohliches Krankheitsbild. Die Prognose konnte in den letzten Jahren nicht verbessert werden. Daher ist eine weitere Therapieoptimierung dringend erforderlich. Dies kann nur durch weitere Studien erreicht werden. Aufgrund der Seltenheit der Erkrankung sehen wir die Möglichkeit dies mit einer nationalen Registerstudie zu erreichen. Zusätzlich können aus dem Register Risikostratefizierungen erarbeitet werden, welche Patienten z. B. von einer Therapie in einem Zentrum oder bestimmten Wundkonditionierungen profitieren.
The Effect of Prandial Insulin Applied for Fat Protein Units on
Postprandial Glucose Excursions in Type 1 Diabetes Patients with Insulin Pump
Therapy: Results of a Randomized, Controlled, Cross-Over Study
Authors: Herrmann Ekaterina , Haak Thomas , Lippmann-Grob Bernhard , Tombek Astrid , Hermanns Norbert , Krichbaum Michael
Published: April 2021

Objective This randomized cross-over study aimed to compare different
algorithms for calculating prandial insulin considering the fat and protein
content of a standardized meal in type 1 diabetes patients using insulin pump
therapy (CSII).

Methods Twenty-six patients received a standardized evening meal for three
consecutive days using different algorithms for insulin dose adjustment: A)
exclusive consideration of carbohydrate content without considering fat-protein
content, B) high-dose algorithm considering additional insulin for fat protein
units (FPUs) with the same factor as for carbohydrates, and C) low-dose
algorithm considering additional insulin for FPUs with half the factor as for
carbohydrates. The primary outcome was the proportion of interstitial glucose
values in the target range (≥ 70 to ≤ 180 mg/dl) during
the post-prandial 12-hour follow-up period. Secondary outcomes were the
occurrence of hypo- and hyperglycemic episodes and the coverage with
carbohydrates for treatment of hypoglycemia.

Results The percentage of glucose values in the target range was
significantly higher when fat-protein content was not considered, whereas, in
the hyperglycemic range, it did not differ significantly among the three groups.
The percentage of hypoglycemic glucose values were the highest in the groups
considering fat-protein content and lowest in the group not considering FPUs
with no significant difference between the two groups in terms of FPUs.

Conclusions In adult type 1 diabetes patients using CSII, it is not
recommended to consider a high fat and protein content in the diet when
calculating prandial insulin dosage with the selected algorithms, as this
increases the risk of hypoglycemia disproportionately.
Plant Subclass and Superclass—The Next Level in Homoeopathy
Authors: Sankaran Rajan , Chunawala Aafreen
Published: April 2021

In recent years, the knowledge based on the individual ‘Sensation’ of families in Plants, Rows and Columns in Minerals and Sub-kingdoms in Animals has been explored and systematised. Recent research in the plant kingdom has taken this idea one step further. In the plants, we have the kingdom, class, subclass, order, family, remedy and the source. Each of these levels have a certain quality. The main idea behind this research work is to understand the ‘common sensation’ in each of the plant subclasses. As the research into the subclasses further evolved, the concept of superclasses came forth. This knowledge enables the physician to look beyond what he currently knows.
Fibrinolysis and Remote Ischemic Conditioning: Mechanisms and Treatment Perspectives in Stroke
Authors: Krag Andreas Engel , Blauenfeldt Rolf Ankerlund
Published: April 2021

Stroke is a leading cause of death and disability. Intravenous thrombolysis and mechanical thrombectomy have greatly improved outcomes in acute ischemic stroke (AIS). However, only a minority of patients receive reperfusion therapies, highlighting the need for novel neuroprotective therapies. Remote ischemic conditioning (RIC), consisting of brief, intermittent extremity occlusion and reperfusion induced with an inflatable cuff, is a potential neuroprotective therapy in acute stroke. The objective of this narrative review is to describe the effect of RIC on endogenous fibrinolysis and, from this perspective, investigate the potential of RIC in the prevention and treatment of stroke. A systematic literature search was performed in PubMed, and human studies in English were included. Seven studies had investigated the effect of RIC on fibrinolysis in humans. Long-term daily administration of RIC increased endogenous fibrinolysis, whereas a single RIC treatment did not acutely influence endogenous fibrinolysis. Fifteen studies had investigated the effect of RIC as a neuroprotective therapy in the prevention and treatment of stroke. Long-term RIC administration proved effective in reducing new cerebral vascular lesions in patients with established cerebrovascular disease. In patients with acute stroke, RIC was safe and feasible, though its clinical efficacy as a neuroprotectant is yet unproven. In conclusion, a single RIC treatment does not affect fibrinolysis in the acute phase, whereas long-term RIC administration may increase endogenous fibrinolysis. Increased endogenous fibrinolysis is unlikely to be the mediator of the acute neuroprotective effect of RIC in stroke patients, whereas it may partly explain the reduced stroke recurrence associated with long-term RIC treatment.
Tranexamic Acid Treatment for Trauma Victims
Authors: Roberts Ian , Brenner Amy , Shakur-Still Haleema
Published: April 2021

Worldwide, traumatic injury is responsible for over 5 million deaths per year, the majority due to exsanguination and head injury. The antifibrinolytic drug tranexamic acid is the only drug proven to reduce deaths after traumatic injury. Several large randomized controlled trials have provided high-quality evidence of its effectiveness and safety in trauma patients. Early tranexamic acid reduces deaths on the day of the injury in polytrauma patients and patients with isolated traumatic brain injury by around 20%. Treatment is time critical; for patients to benefit, tranexamic acid must be given as soon as possible after injury. Intramuscular administration is well tolerated and rapidly absorbed, with the potential to reduce time to treatment. Because the proportional reduction in bleeding death with tranexamic acid does not vary by baseline risk, a wide range of trauma patients stands to benefit. There are far more low-risk trauma patients than high-risk patients, with a substantial proportion of bleeding deaths in the low-risk group. As such, treatment should not be limited to patients with severe traumatic hemorrhage. We must give paramedics and physicians the confidence to treat a far wider range of trauma patients while emphasizing the importance of early treatment.
Impaired Fibrinolysis in the Antiphospholipid Syndrome
Authors: Antovic Aleksandra , Bruzelius Maria
Published: April 2021

The pathogenesis of the antiphospholipid syndrome (APS) is complex and involves the persistent presence of antiphospholipid antibodies (aPL) in the bloodstream causing a prothrombotic condition. aPL induce excessive activation of the endothelium, monocytes, and platelets in consort with aberrations in hemostasis/clotting, fibrinolytic system, and complement activation. Impaired fibrinolysis has been found in APS patients with thrombotic as well as obstetric manifestations. Increased levels of plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor, together with the presence of aPL against annexin-2, tissue-type plasminogen activator, and plasminogen contribute to the compromised fibrinolytic activity in these patients. Furthermore, unfavorably altered fibrin morphology, less amenable to fibrinolysis, has been proposed as a novel prothrombotic mechanism in APS. This review aims to summarize the present knowledge of the mechanisms involved in impaired fibrinolysis in APS patients. We also present a case from clinical practice as an illustration of fibrinolysis impairment in APS patients from a real-life setting.
Extraventricular Neurocytoma in Parietal Lobe
Authors: Gallego-Henao Katherine , Ramos-Delgado José M. , Moreno-Blanco Angelica , Placido-Méndez Aureliano , Zarate-Mendez Antonio
Published: April 2021

Extraventricular neurocytoma (EVN) was classified as a World Health Organization (WHO) grade II tumor; however, EVN is not fully understood; it presents a variable histological feature that included oligodendroglioma-like, neuropil-like matrix, ganglion or gangloid cells, perivascular pseudorosettes, vessel hyalinization, calcifications, and myxoid degeneration. In some very rare cases, atypical histological features such as increased mitotic figures, focal necrosis, endothelial cell proliferation, and Ki-67 index of >2% made this tumor more aggressive and more susceptible to recur. We present the case of a young patient who presents with a 2-year history of seizure without other symptoms. Magnetic resonance imaging reveals a parietal lobe and well-circumscribed lesion treated by gross total resection and adjuvant radiotherapy. Clear guidelines to treat this kind of lesions are not well established and there is not a consensus of correct treatment in these tumors.
Changemanagement: 2. ZUKE DIGITAL Kongress
Authors: Bannwarth Ralf
Published: April 2021

Nach dem Motto „Wie können wir besser für unseren Patienten einkaufen? Datenmanagement, Value-based Procurement und Krankenhauszukunftsgesetz unter der Lupe“ fand am 3. März 2021 der 2. ZUKE DIGITAL Kongress der Organisation „Zukunft Krankenhaus Einkauf“ statt.
Theory of topological corner state laser in Kagome waveguide arrays
Authors: Zhong Hua , Kartashov Yaroslav V. , Szameit Alexander , Li Yongdong , Liu Chunliang , Zhang Yiqi
Published: April 2021

In comparison with conventional lasers, topological lasers are more robust and can be immune to disorder or defects if lasing occurs in topologically protected states. Previously reported topological lasers were almost exclusively based on the first-order photonic topological insulators. Here, we show that lasing can be achieved in the zero-dimensional corner state in a second-order photonic topological insulator, which is based on the Kagome waveguide array with a rhombic configuration. If gain is present in the corner of the structure, where the topological corner state resides, stable lasing in this state is achieved, with the lowest possible threshold, in the presence of uniform losses and two-photon absorption. When gain acts in other corners of the structure, lasing may occur in edge or bulk states, but it requires substantially larger thresholds, and transition to stable lasing occurs over much larger propagation distances, sometimes due to instabilities, which are absent for lasing in corner states. We find that increasing two-photon absorption generally plays strong stabilizing action for nonlinear lasing states. The transition to stable lasing stimulated by noisy inputs is illustrated. Our work demonstrates the realistic setting for corner state lasers based on higher-order topological insulators realized with waveguide arrays.
On the gum arabic to improve the thermal properties of Fe3O4 nanoparticles
Authors: Elbeshir E. I. A.
Published: April 2021

In this study, the thermal properties of the powder sample of Fe3O4 magnetic nanoparticles prepared by the co-precipitation method and characterized by x-ray diffraction and transmission electron microscopy have been reported. An induction heater was used to determine the thermal properties of the sample coated with gum arabic (GA) in various concentrations, viz., X = 0, 20, 40, 60, and 80 mg/ml. The results show that the thermal properties of the sample depend on the concentration of GA. Furthermore, it was found that the specific heat capacity (CG) of the GA solution decreased with the increase in the concentration of GA.
Enhanced performance of white organic light-emitting devices based on ambipolar white organic single crystals
Authors: Zhu Qin-Cheng , Liu Yu , An Ming-Hui , Ding Ran , Ye Gao-Da , Gai Xi , Wang Hai , Du Ming-Xu , Chen Shuo-Nan , Feng Jing , Sun Hong-Bo
Published: April 2021

Organic single crystals are highly promising for applications in optoelectronic devices because of their higher mobility and thermal stability than amorphous thin films. Although white organic single crystals have been fabricated by the double-doped method and applied to realize white organic light-emitting devices (WOLEDs), the unbalanced carrier transport properties of the unipolar crystals severely limit the device performance. Here, ambipolar white organic single crystals are obtained by using mixed p- and n-type molecules as an ambipolar host for the red and green dopants. The white crystal with balanced carrier transport and balanced blue, green, and red emission intensity was applied to the single-crystal WOLEDs. The highest brightness of 1956 cd m−2 and the current efficiency of 1.31 cd A−1 are achieved, which are the best performance of the single-crystal WOLEDs reported to date. A high color rendering index is obtained, which varies between 82 and 87 with increasing driving current. It is expectable that this strategy would support the practical applications of organic single crystal-based OLEDs.
Microscopic metallic air-bridge arrays for connecting quantum devices
Authors: Jin Y. , Moreno M. , T. Vianez P. M. , Tan W. K. , Griffiths J. P. , Farrer I. , Ritchie D. A. , Ford C. J. B.
Published: April 2021

We present a single-exposure fabrication technique for a very large array of microscopic air-bridges using a tri-layer resist process with electron-beam lithography. The technique is capable of forming air-bridges with strong metal-metal or metal-substrate connections. This was demonstrated by its application in an electron tunneling device consisting of 400 identical surface gates for defining quantum wires, where the air-bridges are used as suspended connections for the surface gates. This technique enables us to create a large array of uniform one-dimensional channels that are open at both ends. In this article, we outline the details of the fabrication process, together with a study and the solution of the challenges present in the development of the technique, which includes the use of water-IPA (isopropyl alcohol) developer, calibration of the resist thickness, and numerical simulation of the development.
Can Minkowski tensors of a simply connected porous microstructure characterize its permeability?
Authors: Nair Prapanch , Mühlbauer Sebastian , Roy Shantanu , Pöschel Thorsten
Published: April 2021

We show that the permeability of periodic simply connected porous media can be reliably predicted from the Minkowski tensors (MTs) describing the pore microstructure geometry. To this end, we consider a large number of two-dimensional simulations of flow through periodic unit cells containing complex-shaped obstacles. The prediction is achieved by training a deep neural network using the simulation data with the MT elements as attributes. The obtained predictions allow for the conclusion that MTs of the pore microstructure contain sufficient information to characterize the permeability, although the functional relation between the MTs and the permeability could be complex to determine.
Distinguishing chaotic from stochastic dynamics via the complexity of ordinal patterns
Authors: Zhang Zelin , Zhang Mingbo , Chen Yufeng , Xiang Zhengtao , Xu Jinyu , Zhou Xiao
Published: April 2021

Distinguishing between chaotic and stochastic dynamics given an input series is a widely studied topic within the time series analysis due to high demand from the practitioners in various fields. Due to one of the fundamental properties of chaotic systems, namely, being sensitive to parameters and initial conditions, chaotic time series exhibit features also observed in randomly generated signals. In this paper, we introduce distance as a measure of similarity between segments based on the ordinal structure. Furthermore, we introduce a new fuzzy entropy, Fuzzy Permutation Entropy (FPE), which can be used to detect determinism in time series. FPE immunes from repeated equal values in signals to some extent, especially for chaotic series. With specific embedding dimensions, it can be employed to distinguish chaotic signals from noise. We show an example for white Gaussian noise, autoregressive moving-average, continuous or discrete chaotic time series, and test FPE’s performance with additive observational noise. We show an application of FPE on rolling bearings’ fault diagnosis.
Implementation of a hybrid Lagrangian filtered density function–large eddy simulation methodology in a dynamic adaptive mesh refinement environment
Authors: Castro Laura Pereira de , Pinheiro Abgail Paula , Vilela Vitor , Magalhães Gabriel Marcos , Serfaty Ricardo , Vedovotto João Marcelo
Published: April 2021

Multispecies mixing processes play an important role in many engineering, biological, and environmental applications. Since simulating mixing flows can be useful to understand its physics and to study industrial issues, this work aims to develop the basis of a methodology able to simulate the physics of multiple-species mixing flows, using a hybrid large eddy simulation/Lagrangian filtered density function (FDF) method on an adaptive, block-structured mesh. A computational model of notional particles transport on a distributed processing environment is built using a parallel Lagrangian map. This map connects the Lagrangian information with the Eulerian framework of the in-house code MFSim, in which transport equations are solved. The Lagrangian composition FDF method, through the Monte Carlo technique, performs algebraic calculations over an ensemble of notional particles and provides composition fields statistically equivalent to those obtained by finite volume numerical solution of partial differential equations. Finally, to maintain high accuracy in the system of stochastic differential equations solver when an adaptive mesh refinement environment is used, a methodology for ensuring mass conservation is developed to preserve at least the statistical moments up to order two, even in the case of annihilation or cloning of a large number of notional particles in one time step, ensuring the applicability of Lagrangian FDF methods in dynamically adaptive grid refinement.
Effect of wall slip on vertical film drainage in presence of soluble surfactants
Authors: Li Chunxi , Xiao Han , Jiang Rui , Ye Xuemin
Published: April 2021

A mathematical model is established to investigate a vertical gravity-driven drainage flow containing a soluble surfactant when considering the effect of wall slip. The lubrication theory is employed to obtain the evolution equations describing film thickness, surface velocity, surfactant concentrations at the air–liquid, solid–liquid interface, and in the bulk. The influence of constant slip length bc and variable slip length bs varying with surfactant concentration on the drainage dynamics is investigated compared with the case of no-slip bo, and the mechanism of the film thinning and the backflow caused by wall slip is examined. Simulated results show that the wall slip has a significant impact on the dynamics of the film drainage compared with the no-slip case. For the case of constant slip length, the wall slip accelerates the film thinning in the early stage. At the middle stage, the wall slip enhances the Marangoni effect and surface velocity rapidly decreases, causing a surface backflow phenomenon at the film bottom; the higher the slip length, the more obvious surface backflow. In the late stage, surface backflow weakens, and the film thickness is less than that of bo. For the case of variable slip length, in the early stage, the film thickness and surface velocity are between those of bo and bc; at the middle stage, a weak surface backflow is evolved at the film bottom; in the late stage, the film thickness is close to that of bc, and the surfactant concentration is lower than those of bo and bc.
Identification of traveling crossflow waves under real hypersonic flight conditions
Authors: Wan Bingbing , Tu Guohua , Yuan Xianxu , Chen Jianqiang , Zhang Yifeng
Published: April 2021

Understanding crossflow instabilities in three-dimensional boundary layers triggered by either traveling crossflow waves or stationary crossflow vortices is of great importance for modeling, predicting, and controlling hypersonic laminar-turbulent transition. However, due to very limited available flight experiment data, the crossflow instability under real flight conditions is still far from fully understood. To gain further insight, the raw data of a recent model flight experiment conducted by China Aerodynamics Research and Development Center have been thoroughly analyzed in the present study. The instrumented model is an inclined blunt cone mounted with several pressure sensors. Distinct low-frequency signals detected by these pressure sensors are peaked at about 10 kHz, which are in good agreement with the traveling-crossflow-wave frequencies with the largest N factors predicted by the eN method. Moreover, propagation velocities and wave angles of these signals obtained from correlation analysis also agree with the results from linear stability theory. The present study confirms that the detected low-frequency signals are traveling crossflow waves and provides the first evidence of traveling crossflow waves under real flight conditions.
Evaluating flow-field and expelled droplets in the mockup dental clinic during the COVID-19 pandemic
Authors: Li Xiujie , Mak Cheuk Ming , Ma Kuen Wai , Wong Hai Ming
Published: April 2021

In the setting of widespread severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) community transmission, reducing the exposure risk on dental professionals and the next patients is the key to reopening dental services in this pandemic environment. The study is motivated by the lack of understanding of the flow-field characteristics and droplet distribution during aerosol-generating procedures. The particle image velocimetry measurements with high temporal and spatial resolutions were performed under ultrasonic scaling in the mockup experimental dental clinic. Compared with other methods focusing on the settled droplet particles, the study focused on the visualization of suspended droplets. From the results of the velocity vector and trajectory map, the high-level contaminated area will be within 1 m from the oral cavity. The vortex structures were identified by the vorticity index. In the surface near the patient's head, a counterclockwise vortex would carry some droplets and contaminate this region. The small droplets circulated in the turbulence cloud and the droplet nuclei generated by dehydration are the two primary sources of suspended particles, which may cause airborne transmission in the dental clinic. About 65%–74% of the droplets in ultrasonic scaling were in the range of 50–180 μm. The research will provide references to the development of the precaution measures to reduce the SARS-CoV-2 exposure risk of dental professionals.
An active body in a Phan-Thien and Tanner fluid: The effect of the third polar squirming mode
Authors: Housiadas Kostas D.
Published: April 2021

An active, self-propelled, spherical microbody in a weakly viscoelastic matrix fluid is investigated theoretically using analytical techniques. The Upper-Convected Maxwell (UCM), Oldroyd-B, and exponential Phan-Thien and Tanner (ePTT) constitutive equations, along with the spherical squirmer model, are utilized. The contribution of the elastic stress in the governing equations give rise to three dimensionless numbers: the viscosity ratio, β, the Weissenberg number, Wi, and the ePTT rheological parameter, ε. Moreover, the squirmer model is characterized by three dimensionless parameters related to the fluid velocity on the surface of the body: the primary and secondary slip parameters ξ and μ, respectively, and the swirl parameter ζ. It is shown that the viscoelastic stress for the UCM and Oldroyd-B models becomes singular at a critical Weissenberg number, which depends only on the slip parameters, generalizing the findings previously reported for μ = 0 by Housiadas et al. [“Squirmers with swirl at low Weissenberg number,” J. Fluid Mech. 911, A16 (2021)]. When the ePTT model is utilized, the singularity is removed. The mechanism behind the speed and rotation rate enhancement associated with the secondary slip and swirl parameters is also investigated. It is demonstrated that, regardless of the values of the slip parameters, the swimming velocity of the body is enhanced by swirl, and for a sufficiently large ζ, its speed becomes larger than its speed in a Newtonian fluid with the same viscosity. Emphasis on the role of the secondary slip parameter is also given. It is shown that it affects substantially the force contributions on the body leading to a great variety of swimming behaviors. Its effect is quite complicated and sometimes similar to, or even more important than, the effect caused by the choice of the constitutive model.
Spectral analysis of internal solitary waves propagating over a stepped bottom topography via the Koopman operator
Authors: Zhang Jiuming , Sun Tiezhi , Zou Li , Wen Zehua , Yu Zongbing
Published: April 2021

In this paper, we present a study about the frequency characteristics of the process of internal solitary waves (ISWs) interacting with a stepped bottom topography. We perform experimental measurements of the waveforms and flow fields under various wave-making conditions by considering the degree of subsequent breaking. The piecewise dynamic mode decomposition (PDMD) method, which we have proposed, is introduced to construct the Koopman operator, linearize the process, and extract spectral information of the interaction. Furthermore, the universality of this method and the physical meaning of segmentation points are discussed for the ISW problem. The innovative part of this study lies in that to suit the precondition of PDMD, the energy formula of a Koopman mode is modified with emphasis on the damping rate. The spectra calculated by the modified modal energy are more in line with the physical phenomenon of the evolution. Through the spectral analysis, we infer that the occurrence of breaking may limit the main energy part of waveforms into a relatively low-frequency range, instead of generating high-frequency rapid oscillations. In contrast, the flow fields will contain more high-frequency information during the breaking process. The specific performance is that the spectra of vorticity fields have high-frequency sidebands that are clearly separated from the main energy part. Finally, to understand the flow behavior of ISWs, we extract and analyze the spatial information of the decomposed modes at dominant or distinctive frequencies. The modes corresponding to the oscillations of trailing edges and the early breaking phenomenon of vorticity fields are observed.
Role of bacterial RNA polymerase gate opening dynamics in DNA loading and antibiotics inhibition elucidated by quasi-Markov State Model
Authors: Unarta Ilona Christy , Cao Siqin , Kubo Shintaroh , Wang Wei , Cheung Peter Pak-Hang , Gao Xin , Takada Shoji , Huang Xuhui
Published: April 2021

Significance

The initiation of bacterial transcription requires DNA loading via flexible loading gate of the RNA polymerase complex, consisting of the clamp and β-lobe domain. While the clamp is important in transcription initiation, the role of β-lobe remains unclear. Using quasi-Markov State Models (qMSMs) constructed from molecular dynamics simulations, we showed that the opening of β-lobe is orders of magnitude faster than that of the clamp, which depends on the structure of Switch 2. Strikingly, opening of the β-lobe is sufficient geometrically to accommodate DNA loading even when the clamp is partially closed. These two observations highlight β-lobe’s critical role allowing DNA loading during initiation. Thus, β-lobe is a promising target for antibiotics. qMSM also provides a promising tool investigating biomolecular dynamics.
A case study of GK Aqua Farms in Chikwawa district, Malawi.
Authors: Longwe Priscilla M , Kang'ombe Jeremiah , Kaunda Emmanuel K. W.
Published: April 2021

This study was carried out to record the experiences of Gopi Krishna (GK) Aqua Farms, with special reference to feeding/fertilization methods, the production cycle and the farm's marketing/distribution strategy. GK Aqua Farms is situated in Chikwawa District, which is in the southern region of Malawi. 19 ha (47 acres) of its land is under water, about 12 ha (30 acres) of which is in an enclosed, fenced area, and the remaining 7 ha (17 acres) in an open, unfenced area. Since GK Aqua Farms started practicing on a commercial scale in November 2004, the business has promoted aquaculture within Malawi and has demonstrated its potential profitability by attaining gross margins of over K3 million (approximately US $21,430) after just one year. The farm raises three species of fish in a polyculture system; common carp (Cyprinus carpio), Tilapia rendalli and Oreochromis siranus. The fish are sold in Chikwawa District as well as in the neighbouring city of Blantyre. The fish are fed artificial diets and are stocked in ponds that are mainly fertilized with livestock manure. Partial harvests are carried out throughout the year, depending on consumer demand, with a complete harvest once a year. The fish are sold at a farm gate price of K400/kg (US $3/kg) for common carp and K250/kg (US $1.8/kg) for tilapia species and at a wholesale price of K500 (US $3.6/kg) for common carp and K300 (US $2.1/kg) for both tilapia species. Since it took over the farm in 2004, GK Aqua Farms has had a continuous rise in production from 4.2 tonnes per year in 2004 to 29.5 tonnes per year in 2008 with an expectation of similar increases over the next few years. The farm faces several problems including pests, inefficient feed supply and low sales during summer. The farm, however, does not operate any integrated aquaculture-agriculture systems.
Sustainability and income opportunities of farming milkfish (Chanos chanos) to local communities in Kenya: assessment of initial trials of earthen ponds.
Authors: Mirera David Oersted , Ngugi Charles C
Published: April 2021

This case study documents the development of earthen pond mariculture from the late 1980s to 2009 in Kenya and prospects of community milkfish (Chanos chanos) culture using satellite farmers along the coast of Kenya, as well as challenges to this kind of farming and approaches towards sustainability. Pond mariculture was started in the 1980s by the Kenyan Fisheries Department through the onset of prawn farming (Penaeus indicus and P. monodon) in large scale demonstration ponds at Ngomeni under funding from FAO. The total culture area was estimated at 60 ha and milkfish occurred as a by-product of the prawn culture operations with indications of good growth. Similar observations were made for the milkfish in the artisanal Kwetu prawn culture pond (0.8 ha) that was started in the late 1990s, and one individual middle-scale farmer in Mtwapa creek (Wampare) who had interest in prawn culture at the time and constructed ponds covering an area of 3 ha. The initial recommendations for the potential to culture milkfish in Kenya were made through a research project (Mwaluma, 2002) whose objectives were to assess the potential of mud crab (Scylla serrata) pen culture in natural mangrove channels at Mtwapa creek. Intense participatory research into potential for milkfish culture coupled with extension was initiated at the Kwetu Training Centre along the Kenya coast with satellite groups in 2004. Consequently, improvements have since been achieved with wild seed collection in mangrove pools, use of chicken manure as organic pond fertilizer, and dependency of tidal water exchange, which has led to a maximum growth rate of 1.2 g/day. The demand for milkfish production has increased greatly among the coastal poor (Mirera, 2009b) and presently (Sept 2009) five communities have constructed more than 25 milkfish production ponds with a maximum production capacity of more than 70 kg per crop. These farmers have appreciated the contribution of milkfish culture to achieving food security and income generation for their families. The first harvest of milkfish in the community ponds were bought by the research/extension officer, and were fried and eaten together by all members of the community (including none group members) to demonstrate that milkfish can grow under local culture conditions. In subsequent harvests, the whole community is informed a day before the harvest, whereby they come to the farms during harvesting and buy the fish in quotas at two dollars per kg.
Challenges and lessons learned in the culture of Indian shrimp, Penaeus indicus (H. Milne Edwards, 1837) in Hapas inside fertilized ponds in Mtwapa Creek, Kenya, 2009.
Authors: Wanjiru Caroline
Published: April 2021

World capture fisheries are declining while demand for fish is increasing due to population increase and an upward trend in diet preference where fish is preferred over white meat. It is hoped that aquaculture will help meet this deficit. In Kenya, coastal aquaculture remains under-developed even though over 3900 hectares of land have been designated as suitable for aquaculture. This case study is based on a study where Indian shrimp (Penaeus indicus) were cultured for 106 days, in hapas, inside fertilized ponds at Majaoni in Mtwapa creek, Mombasa district, Kenya. The manures used for pond fertilization were chicken, urea and cow dung. No manure was added in the control treatment. Physical, chemical and biological water parameters were taken weekly, fortnightly and monthly, respectively. Growth performance of the shrimp in terms of weight (g) and length (mm) was monitored fortnightly. The mean growth rates ranged between 1.13 and 2.34% day-1 in the control and chicken manure treated ponds, respectively. The highest net yield (NFY Kg ha-1) and annual production (AP Kg ha-1 yr-1) achieved was 18.87 Kg ha-1 and 64 Kg ha-1 yr-1, respectively, in the cow dung-treated ponds. The data collected from this study formed part of the author's MSc thesis in Aquaculture at the University of Nairobi. A major part of the study was funded by Alcoa Foundation's Conservation and Sustainability Fellowship Program which supported the author as a Practitioner Fellow in 2008. Additional support was provided through the Western Indian Ocean Marine Science Association (WIOMSA) small grant programme.
Commercial-scale aquaculture of tilapia species in Zambia.
Authors: Flynn Douglas
Published: April 2021

This case study describes the piloting and subsequent commercialization of an integrated pig and fish operation in Zambia. The initial scheme began in October 1981 using indigenous Zambian species including Oreochromis andersonii, Oreochromis macrochir and Tilapia rendalli. Different fertilization techniques were trialled, including organic (chicken manure) and inorganic (compound) fertilisers, and different integration systems were tested; ducks over fish and pigs over fish. Over the 29 years the project has been running, the variety of methods originally trialled have been refined to the extremely productive system in place today. Oreochromis niloticus is the dominant fish species produced, and members of the Clarias genus used as the main predator. The hatchery has been intensified (and now incorporates mono-sexing), aeration systems have been implemented in grow-out ponds and a green-water floating fish pellet has been developed. Yields have increased from an initial average of 2.5 to 3 tons/ha to present yields of over 11 tons/ha. The initial five hectare project has grown to over 45 ha of water producing over 600 tons of fish a year, and a stable herd of 200 sows producing in excess of 4100 slaughter stock per annum.
Comparison trials between Oreochromis andersonii (Kafue Bream) and O. niloticus (imported species) under farm conditions in Zambia.
Authors: Cayron-Thomas Emmanuéle
Published: April 2021

There has been much discussion for many years over the most suitable tilapia species to use in aquaculture. It has been thought for many years that Nile tilapia (Oreochromis niloticus) was the most productive, especially after it had been developed using the genetically improved farmed tilapia (GIFT) protocols, but no trials have taken place under standard farming conditions nor was there ever any consideration taken of the possible ecological side effects of the introduction of alien species into river systems. With the help of a small grant from the Food and Agricultural Organization of United Nations, Kalimba Farm, Zambia, undertook to carry out a direct comparison between the suitability of both O. niloticus and O. andersonii for fish culture under normal farm conditions. These trials took place over three years from 2004 to 2007. The overall results concluded that there were definite advantages for both species in different areas, but considering a genetically improved species was being compared with stock that had been genetically isolated for 25 years, the overall results were encouraging for the indigenous O. andersonii. In addition, taking into account the assumed damage to fragile river systems from the introduction of invasive O. niloticus it was felt that efforts should be made in future to encourage the use of O. andersonii as the preferred fish for aquaculture in areas of Zambia that are not already polluted with O. niloticus and, furthermore, an effort should be made to improve O. andersonii through an on-farm selective breeding programme using the GIFT protocols.
Role of the private sector in fry and fingerling production in Uganda.
Authors: Aulanier Félicie , Desprez Damien , Napuru Abudala , Mikolasek Olivier
Published: April 2021

In Uganda, fingerlings are only produced by private sector enterprises. A rapid appraisal approach of fry producers was used to collect quantitative and qualitative information about farm production. Sixty-one hatcheries of catfish, tilapia or mirror carp were identified. Visits were made to 31 farms located in 18 districts and the National Fisheries Resource Research Institute (NaFFIRI) contributed by providing information about five other farms in Buganda Region. Three types of hatcheries were identified without taking one large-scale farm into account. The number of workers was the first variable used to discriminate the farms: six or more workers (Medium Enterprise) against less than six workers (including family workers). Farms with less than six workers are composed of two types as characterized by the destination market of the fingerlings. The first type 'Associative Farm' belongs to a local group of farmers and sells the fingerlings mainly inside the group. The second type, 'Intermediate Enterprise', can be part of an association, but the fingerling production is destined for a wider market. Farms included in this Intermediate Enterprise group also have larger facilities. This type tends to move towards becoming a Medium Enterprise. A fourth type of farm, represented by Source of the Nile (SON) Fish Farm, which was not included in the previous categories, can be considered a 'Large-scale Enterprise'. It was demonstrated that, in Uganda, the Commercial Farms (Medium- and Large-scale Enterprises) also contribute to the development of the aquaculture sector by providing training and innovation. Only SON Fish Farm has established a fish selected breeding programme (tilapia).