bluuebunny/crossref_metadata_2025 huggingface dataset:
Meningioma selar gigante y síndrome frontal
Authors: Escudero Siosi Alexa José , Muñoz Ramírez Dalia Isadora , Chirveches Calvache María Alejandra
Published: December 2019

Los meningiomas representan los tumores meníngeos benignos más comunes, cuya expresión clínica se encuentra directamente relacionada con su dimensión, ubicación y subsecuente compresión del tejido neural contiguo. Generalmente, el diagnóstico es un hallazgo incidental. Las alternativas de tratamiento pueden variar de paciente a paciente y, en algunos casos, el manejo quirúrgico puede ser un desafío. El presente reporte de caso corresponde al de un paciente atendido en el servicio de urgencias del Hospital Universitario San Ignacio en el 2012, a quien se le descubrió un meningioma selar gigante asociado con un síndrome frontal florido secundario.
Síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) y su relación con complicaciones perioperatorias: revisión de la literatura
Authors: Ruiz Morales Álvaro , Hidalgo Martínez Patricia , Sánchez Mejía Sandra I. , Perea Bello Ana H. , Segura Salguero Juan Camilo , Chavarriaga Soto Julián , Valencia Peña Maury , Rodríguez Salazar Catalina , Ruiz Delgado Julio A. , Chaparro de Reyes Laura Catalina
Published: December 2019

El objetivo de este artículo es revisar la importancia del síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) en la población que va a ser llevada a cirugía y cómo detectar en el preoperatorio a pacientes con riesgo elevado de complicaciones en el perioperatorio mediante el cuestionario STOP-BANG. Para lo anterior, se realizó una búsqueda en las bases Pubmed, Science y SciELO. El SAHOS es un problema médico importante con prevalencia variable (hasta el 26 % en la población general dependiendo del centro donde se evalúe). Es una enfermedad de inicio insidioso y progresivo, en la que hay episodios recurrentes de apneas o hipopneas causadas por obstrucción de la vía aérea superior durante el sueño que produce un deterioro significativo de la calidad de vida. Se quiere evaluar si el cuestionario STOP-BANG es útil para identificar, en el preoperatorio, a pacientes que tengan complicaciones perioperatorias, probablemente porque identifica pacientes con SAHOS no diagnosticado.
Systematic Methodology for Reliability Analysis of Components in Axial Piston Units
Authors: Baus Ivan , Rahmfeld Robert , Schumacher Andreas , Pedersen Henrik C.
Published: December 2019

This paper covers a reliability analysis as a qualitative method, especially focused on axial piston units. The method is based on Fault Tree Analysis (FTA) and results in risk and reliability assessment at the components level. Especially, the development of the reliability assessment as a methodical tool is the core of the paper. Moreover, the FTA is combined with the industrial standard method known as Design Failure Mode Effects Analysis (DFMEA) which is typically used in the development phase of the design. The evaluation and the usability of the FTA methodology is analyzed in connection with field data. Thus, the deviation of the theoretical valuation from the field data was utilized as a success indicator of the method. The analysis of the fault spreading covers the assessment of component faults and links failure states with unit effects. The analysis of the axial piston unit as a system is made on idealized/theoretical design and functional behavior only. Hence, the failure rating and the effect is subsequently applied to determine the fault risk in form of the Risk Priority Number (RPN). The failure modes and effects are based on engineering experience of past decades, supported by existing DFMEAs of axial piston units. Thus, the assessment of the risk priority number is based on previous data, yielding the given severity, occurrence and detection quantification. This approach opens new opportunities of design assessment and the results show a good agreement to the damage accumulation seen in real field data. Furthermore, the connection between theoretical design assessment and field data do support the failure ranking improvement of the DFMEA.
A Hybrid Hydraulic-Electric Architecture (HHEA) for High Power Off-Road Mobile Machines
Authors: Li Perry Y. , Siefert Jacob , Bigelow David
Published: December 2019

Traditionally, off-road mobile machines such as excavators and wheel loaders are primarily powered by hydraulics and throttling valves are used to control their work circuits. In recent years, two general trends are towards more energy efficient systems and electrification. With electrification, both efficiency and control performance can be improved by the elimination of throttling losses and the use of high-bandwidth inverter control. Electrification is generally accomplished with Electro-hydraulic actuators (EHA) but they are limited to lower powered systems due to the high cost of electric machines capable of high power or high torque. This paper presents preliminary results of a new system architecture for off-road vehicles to improve efficiency and control performance. The architecture combines hydraulic power and electric power in such a way that the majority of power is provided hydraulically while electric drives are used to modulate this power. The hybrid hydraulic-electric architecture (HHEA) and its rationale are described. In addition, a case study is presented to illustrate its operation, its potential for energy saving, and its benefits of component downsizing. The case study indicates that compared to a baseline load sensing system, the HHEA has the potential to reduce energy consumption by more than 50%. Furthermore, the torque capability of the electrical components need only be ∼ 28% of what is required for the direct application of EHA.
Physically Motivated Simulation of Dynamic Hydraulic Seals
Authors: Angerhausen Julian , Murrenhoff Hubertus , Persson Bo N. J. , Schmitz Katharina
Published: December 2019

Seals are crucial machine elements, for example in hydraulic cylinders. However, especially in regard to dynamic seals, the theoretical understanding of the sealing mechanism is still insufficient. A physically motivated simulation can help to gain a more detailed understanding. In this contribution a elastohydrodynamic (EHD) seal simulation is presented. It is directly implemented in the commercial Software ABAQUS. The fluid film is considered by implementing the Reynolds equation. For a physically motivated simulation Persson’s theory of contact mechanics and rubber friction is used to calculate the solid contribution to the total friction of a hydraulic seal. Simulations for an oscillating motion of a cylinder rod, sealed by an O-ring seal, are carried out for different velocities and pressures. A qualitative comparison between measurement and simulation is provided. Hysteresis effects and the contributions from both, adhesive and viscoelastic friction to the total solid friction are investigated. The physical origin of these effects is discussed in order to provide a detailed understanding of the dynamic sealing mechanism.
Experimentally Validated Models for Switching Energy of Low Pressure Drop Digital Valves for Lightweight Portable Hydraulic Robots
Authors: Hashemi Saeed , Mitchell Hannah , Durfee William K.
Published: December 2019

The most critical factors for a switching valve in a lightweight, portable hydraulic systems are low pressure drop, low power consumption, fast response time, and small size and weight. In this paper, experimentally validated models are proposed for switching energy required by two valve architectures with minimum pressure drop (ball and butterfly valves). The orifice in a hydraulic valve creates a pressure drop across the valve that needs to be minimized especially for low-pressure passive applications. The ideal switching valve for a hydraulic device is one with an opening diameter that is the same as the hose diameter. Several valve architectures with low pressure drop can be motorized to be used as a digital valve. The valve operation mechanism determines the power consumption of the valve. In this paper, the energy to switch state was modeled for two rotary valve types: butterfly and ball. The model was being used to find the best valve configuration for low-pressure digital hydraulics. The model was validated through experiments on a low-pressure ball valve, a high-pressure ball valve, and a low-pressure butterfly valve. The butterfly valve has the lowest switching energy for the same geometry; however, this valve has a small pressure drop due to the presence of the disc in the open position. We conclude that either ball or butterfly valves are suitable for low-pressure, small-scale hydraulic applications.
Definition of Performance Requirements and Test Cases for Offshore/Subsea Winch Drive Systems With Digital Hydraulic Motors
Authors: Nordås Sondre , Ebbesen Morten K. , Andersen Torben O.
Published: December 2019

A subsea crane is normally mounted on a floating vessel and equipped with a winch system. The crane can operate in water down to 3000 m. The vessel tends to move up and down due to waves. This heave motion makes offshore lifting operations challenging. In order to ease the winch operation in rough sea, the winch can be equipped with additional systems like active heave compensation and constant tension. In active heave compensation and constant tension system, both motion and force control of the winch are important. This paper presents a digital displacement winch drive system and gives a description of challenges related to subsea lifting operations. The operation challenges are used to design a set of test cases for evaluating the performance of the digital displacement winch drive system.
Efficiency Optimized Pneumatic Pressure Booster
Authors: Reinertz Olivier , Schmitz Katharina
Published: December 2019

In the scope of this paper, a novel efficiency optimized supply pressure adaptive concept of pneumatic pressure boosters is presented. It is deduced from a profound analysis of state of the art components. The working cycle of the pump chambers can be divided into a filling, compression, pumping and decompression phase. A promising solution for efficiency improvements, which is further analyzed in the scope of this paper, is to adapt the required force of the compression chambers by nonlinear mechanics. Thus, a smaller force at the end of the stroke is required and a reduced air consumption of the driving chamber occurs. As the force demand of the compression chamber and therewith the load distribution over the stroke changes with the operational pressures, an adaptive concept needs to be implemented.

The novel device and its parameterization are deduced by means of an analytical description of state of the art pressure boosters. Subsequently, it is investigated by one-dimensional simulation in DSHplus. The results show broad applicability of the method in relevant applications and huge energy saving potentials compared to state of the art products.
Mechanical and Hydraulic Actuation Strategies for Mainstage Spool Valves in Hydraulic Motors
Authors: Boyce-Erickson Grey C. , Fulbright Nathaniel J. , Voth John A. F. , Chase Thomas R. , Li Perry Y. , Van de Ven James D.
Published: December 2019

A large variety of options for the internal valves of a hydraulic motor are available. Poppet valves, rotary valves, and port plates are common options, but each have drawbacks such as actuation force, complexity, leakage, or friction. An alternative type that is also common is spool valves. Spool valves require minimal actuation force and have low throttling losses if sized correctly. This paper compares two drive options for a mainstage spool valve: a hydraulic pilot from a rotary valve and mechanical actuation. Dynamic models of the two valve configurations are created to carry out design studies and evaluate the performance of the motor. Compressibility effects, viscous drag, and flow forces are included in the model. Simulations show that the rotary valve pilot operation causes an unacceptable lag in the motion of the spool that cannot be corrected without reducing performance when running in reverse. Furthermore, the rotary pilot stage drive results in the motor timing becoming retarded at higher operating speeds. For these reasons, mechanically actuated valves are preferred over pilot operated valves for hydraulic motors operated bi-directionally or across a wide speed range.
H
2-Optimal Low Order Transmission Line Models
Authors: Manhartsgruber Bernhard
Published: December 2019

Transmission line modeling has played a crucial role in understanding the dynamics of fluid power systems. A vast body of literature exists from simple lumped parameter approaches to fully coupled three-dimensional fluid structure interaction models. When it comes to computationally efficient, yet physically sound low order models needed for fast computations iteratively called by optimization codes or for the purpose of model based control design, there is still room for improvement. Modal approximations of the input-output behaviour of liquid transmission lines have been around for decades. The basic idea of tuning the parameters of a canonical linear time invariant state space model to fit the transfer functions of a transmission line model in the H2-optimal sense under passivity constraints has been published by the author of the present paper in the past. However, the method so far was barely usable due to numerical difficulties in the underlying optimization process. A new implementation of the method employing quadruple-precision floating point numbers has recently been found to resolve the convergence problems and is reported in the present paper. The new version of the method is based on analytic computation of the cost and constraint functions as well as their gradients in the computer algebra package Maple and automatic code generation for compilation in FORTRAN. Results are very promising because both the entire low frequency behaviour and the first three eigenmodes of a transmission line model can be accurately covered by a model of order eight only.
Series, Parallel, and Hybrid Series-Parallel Hydrostatic Transmission Architectures for Ground Locomotion
Authors: Martelli Massimo , Marani Pietro , Gessi Silvia
Published: December 2019

Ground locomotion of wheeled vehicles, in all-wheel drive configuration, is subject to unique, generally highly variable and not predictable, loading conditions on the driveline subsystem. Any sensible design must cope at least with the effects induced by slope changes, asymmetrical losses of adherence and cornering maneuvers.

When severe constraints on the driveline layout make the implementation of standard mechanical transmissions unfeasible, a typical option is given by compound hydrostatic transmission architectures, with multiple dedicated motor-wheels.

Requirements are then defined on two different levels: at vehicle level, traction functionality must never be lost; at hydraulic circuit level, all components must work within their nominal operating ranges and hydraulic stresses must be limited.

Common standard topologies for motor connection, viz. series and parallel, come with different strengths and weaknesses, often requiring the implementation of auxiliary highly dissipative compensation components and/or complex electronic control, while a hybrid series-parallel concept, derived from a patented application, based on three-port motors allows the implementation of an effective, purely hydraulic system.

In the present work, a general comparison of the above-mentioned architectures is provided, by means of numerical simulation, over a wide set of virtual experiments. Each architecture is analyzed: its specific features are described and the correlation between hydraulic performance/specifications and vehicle traction performance is pointed out.
Experimental Testing of a Variable Displacement Pump/Motor That Uses a Hydro-Mechanically Timed Digital Valving Mechanism to Achieve Partial-Stroke Piston Pressurization (PSPP)
Authors: Montzka Alissa , Epstein Nathan , Rannow Michael , Chase Thomas R. , Li Perry Y.
Published: December 2019

This work describes an efficient means to adjust the power level of an axial piston hydraulic pump/motor. Conventionally, the displacement of a piston pump is varied by changing the stroke length of each piston. Since the losses do not decrease proportionally to the displacement, the efficiency is low at low displacements. Here, with partial-stroke piston pressurization (PSPP), displacement is varied by changing the portion of the piston stroke over which the piston is subjected to high pressure. Since leakage and friction losses drop as the displacement is decreased, higher efficiency is achieved at low displacements with PSPP. While other systems have implemented PSPP with electric or cam-actuated valves, the pump described in this paper is unique in implementing PSPP by way of a simple, robust hydro-mechanical valve system. Experimental testing of a prototype PSPP pump/motor shows that the full load efficiency is maintained even at low displacements.
Designing an Improved Controller for a Pump Direct Driven Electro-Hydraulic System Using a Nonlinear Flow Mapping
Authors: Helian Bobo , Chen Zheng , Yao Bin , Yang Can
Published: December 2019

Pump control systems are widely used, because of their energy saving properties and their high efficiency. Nevertheless, pump control systems generally have a low accuracy, because of the nonlinear pump flow and other nonlinearities of hydraulic systems. Furthermore, due to the underlaying high order dynamics, pump control systems have low response times, which is one of the main drawbacks. Servo motor-pump direct driven systems are commonly used in today’s industry. The application of servo motor pumps allow a reliable performance with quick response times. For low speeds, however, servo motor pumps do not achieve a high accuracy due to the pump flow deviation. The goal of this paper is to present a controller for a servo motor-pump direct driven system, which improves the accuracy especially at low pump speeds. For that purpose, the controller uses a nonlinear flow mapping, which maps the desired pump flow and pump pressure to the voltage input for the motor-pump. Additionally, the controller uses a backstepping method, which tracks the position as a first step and regulates the pressure as a second step. Comparison experiments to a controller without nonlinear flow mapping show that the controller designed in this paper has improved performances and tracking accuracy.
2D CFD Analysis of Servovalve Main Stage Internal Leakage
Authors: Tamburrano Paolo , Plummer Andrew R. , Elliott Phil , Morris William , Page Sam , Distaso Elia , Amirante Riccardo , De Palma Pietro
Published: December 2019

This paper presents research aimed at understanding the effects of geometrical imperfections and tolerances upon the internal leakage occurring around null in the main stages of servovalves. Specifically, a two-dimensional (2D) computational fluid dynamic analysis was used to predict the direct leakage flow as a function of the overlap and clearance between the spool and bushing sleeve, as well as the roundness on the edges of the spool and bushing sleeve. Predictions of direct leakage flow against edge overlap, which have general validity, are provided in the paper for three selected values of the pressure drop. For different values of the pressure drop, analytical correlations can be applied using the data retrieved from these graphs. The analysis shows that the leakage flow is highly affected by the above-mentioned geometrical parameters. As expected, for given values of overlap and radial clearance, the greater the roundness of the edges caused by manufacturing processes or wear, the higher the leakage flow. For low leakage and hence low power loss requirement, the radii on the spool and bushing sleeve as well as the clearance must be maintained as low as possible. In addition, it is well-known that overlap between the spool and its bushing sleeve can help to reduce the leakage flow at null, and the effect of edge roundness on this reduction is now revealed.
Immersive 3D Vehicle Simulation for Hardware-in-the-Loop Testing of Mobile Hydraulic Controls
Authors: Liermann Matthias , Feller Christian , Lindinger Florian , Runge Dirk
Published: December 2019

The paper presents a HiL test setup for hydraulic propel systems that includes a multi-body dynamic simulation of a vehicle in a realistic 3D environment. It allows testing of driving scenarios under load conditions that would otherwise be very difficult to obtain. The hydraulic-mechanical part of the simulation is modeled in Simulink. An open-source C++ physics engine is used to model the vehicle multi-body mechanics and collision detection between the vehicle and the 3D environment. Despite the high complexity of the hydraulic drive train component models, the constraint of real-time execution of the simulation on a real-time target can be fulfilled.
A Control Algorithm for Active/Passive Hydraulic Winches Used in Active Heave Compensation
Authors: Moslått Geir-Arne , Padovani Damiano , Hansen Michael R.
Published: December 2019

The most common active heave compensated offshore cranes have hydraulic winch systems. This paper investigates an active/passive hydraulic winch system with variable-displacement motors and variable-displacement pumps. The paper addresses the challenges when the active motors are set with a low displacement. The active motor displacement is shown to have significant impact on the dynamics of the closed loop hydraulic system. The classical control strategy for this type of system do not address these challenges and will in certain situations have significantly reduced performance. Therefor, a new control method is presented that utilize the variable displacement of the pumps and motors for speed control and to improve dynamics characteristics. The new winch controller is tested in a high-fidelity simulation model and is shown to improve low speed performance, reduce winch speed limitations by up to 30%, reduce system peak pressure by approximately 20%, and reduce control error by approximately 30%.
The Effects of Stabilization Exercise on the Thickness of Lateral Abdominal Muscles During Standing Tasks in Women With Chronic Low Back Pain: A Randomized Triple-Blinded Clinical Trial Study
Authors: Ehsani Fatemeh , Hedayati Rozita , Bagheri Rasool , Jaberzadeh Shapour
Published: December 2019

Context: Chronic low back pain (CLBP) often presents with a dysfunction in deep abdominal muscles activity during standing tasks. Although some studies indicated that deep abdominal muscle activity improved during some functional tasks following stabilization exercise (SE), there is no study to evaluate the effect of SE on lateral abdominal muscles thickness during standing postural tasks. Objective: The purpose of this study was (1) to evaluate the lateral abdominal muscles thickness in the participants with CLBP while standing on a balance board and (2) to compare the effects of SE and a general exercise (GE) program on the lateral muscles thickness changes. Methods: This was a between-groups, triple-blinded randomized controlled trial design. In total, 40 females with CLBP were randomly assigned into 2 groups:  GE (control group) and supervised progressive SE (experimental group). Diagnostic ultrasound imaging was used before and after the intervention to measure lateral abdominal muscles thickness during standing on 2 different levels of platform in the Biodex Balance System. Visual analog scale and Roland–Morris Disability Questionnaire were used to evaluate changes in pain intensity and disability. Results: The results indicated significant increases in transverse abdominis muscle thickness during all standing tasks (P = .02) and significant decreases in pain intensity and disability following SE intervention (P < .001). However, the lateral abdominal muscle thicknesses were not changed after GE intervention while standing postural tasks (P > .05). The GE group revealed only significant decreases in pain intensity after intervention (P = .03). Conclusion: Supervised progressive SE improved the activity of deep abdominal muscles in standing postural tasks in the patients with CLBP.
Acute Muscular Responses to Practical Low-Load Blood Flow Restriction Exercise Versus Traditional Low-Load Blood Flow Restriction and High-/Low-Load Exercise
Authors: Thiebaud Robert S. , Abe Takashi , Loenneke Jeremy P. , Garcia Tyler , Shirazi Yohan , McArthur Ross
Published: December 2019

Context:Blood flow restriction (BFR) increases muscle size and strength when combined with low loads, but various methods are used to produce this stimulus. It is unclear how using elastic knee wraps can impact acute muscular responses compared with using nylon cuffs, where the pressure can be standardized.Objective:Investigate how elastic knee wraps compare with nylon cuffs and high-load (HL)/low-load (LL) resistance exercise.Design:A randomized cross-over experimental design using 6 conditions combined with unilateral knee extension.Setting:Human Performance Laboratory.Participants:A total of 9 healthy participants (males = 7 and females = 2) and had an average age of 22 (4) years.Intervention:LL (30% of 1-repetition maximum [1-RM]), HL (70% 1-RM), BFR at 40% of arterial occlusion pressure (BFR-LOW), BFR at 80% of arterial occlusion pressure (BFR-HIGH), elastic knee wraps stretched by 2 in (PRACTICAL-LOW), and elastic knee wraps stretched to a new length equivalent to 85% of thigh circumference (PRACTICAL-HIGH). BFR and practical conditions used 30% 1-RM.Main Outcome Measures:Muscle thickness, maximum voluntary isometric contraction, and electromyography amplitude. Bayesian statistics evaluated differences in changes between conditions using the Bayes factor (BF10), and median and 95% credible intervals were reported from the posterior distribution.Results:Total repetitions completed were greater for BFR-LOW versus PRACTICAL-HIGH (BF10 = 3.2, 48.6 vs 44 repetitions) and greater for PRACTICAL-LOW versus BFR-HIGH (BF10 = 717, 51.8 vs 36.3 repetitions). Greater decreases in changes in maximum voluntary isometric contraction were found in PRACTICAL-HIGH versus HL (BF10 = 1035, ∼103 N) and LL (BF10 = 45, ∼66 N). No differences in changes in muscle thickness were found between LL versus PRACTICAL-LOW/PRACTICAL-HIGH conditions (BF10 = 0.32). Greater changes in electromyography amplitude were also found for BFR-LOW versus PRACTICAL-HIGH condition (BF10 = 6.13, ∼12%), but no differences were noted between the other BFR conditions.Conclusions:Overall, elastic knee wraps produce a more fatiguing stimulus than LL or HL conditions and might be used as an alternative to pneumatic cuffs that are traditionally used for BFR exercise.
Impact of Candida auris Infection in a Neutropenic Murine Model
Authors: Torres Steven R. , Pichowicz Amber , Torres-Velez Fernando , Song Renjie , Singh Navjot , Lasek-Nesselquist Erica , De Jesus Magdia
Published: December 2019

Candida auris
has become a global public health threat due to its multidrug resistance and persistence. Currently, there are limited murine models to study
C. auris
infection. Those models use a combination of cyclophosphamide and cortisone acetate, suppressing both innate and adaptive immunity. Here, we compare
C. auris
infection in two neutrophil-depleted murine models in which innate immunity is targeted using the monoclonal antibodies 1A8 and RB6-8C5.
Soil Microbial Communities in Diverse Agroecosystems Exposed to the Herbicide Glyphosate
Authors: Kepler Ryan M. , Epp Schmidt Dietrich J. , Yarwood Stephanie A. , Cavigelli Michel A. , Reddy Krishna N. , Duke Stephen O. , Bradley Carl A. , Williams Martin M. , Buyer Jeffrey S. , Maul Jude E.
Published: December 2019

Increasing the efficiency of food production systems while reducing negative environmental effects remains a key societal challenge to successfully meet the needs of a growing global population. The herbicide glyphosate has become a nearly ubiquitous component of agricultural production across the globe, enabling an increasing adoption of no-till agriculture. Despite this widespread use, there remains considerable debate on the consequences of glyphosate exposure. In this paper, we examine the effect of glyphosate on soil microbial communities associated with the roots of glyphosate-resistant crops. Using metabarcoding techniques, we evaluated prokaryotic and fungal communities from agricultural soil samples (
n
 = 768). No effects of glyphosate were found on soil microbial communities associated with glyphosate-resistant corn and soybean varieties across diverse farming systems.
Quantifying Oxygen Management and Temperature and Light Dependencies of Nitrogen Fixation by Crocosphaera watsonii
Authors: Inomura Keisuke , Deutsch Curtis , Wilson Samuel T. , Masuda Takako , Lawrenz Evelyn , Bučinská Lenka , Sobotka Roman , Gauglitz Julia M. , Saito Mak A. , Prášil Ondřej , Follows Michael J.
Published: December 2019

Crocosphaera
is one of the major N
2
-fixing microorganisms in the open ocean. On a global scale, the process of N
2
fixation is important in balancing the N budget, but the factors governing the rate of N
2
fixation remain poorly resolved. Here, we combine a mechanistic model and both previous and present laboratory studies of
Crocosphaera
to quantify how chemical factors such as C, N, Fe, and O
2
and physical factors such as temperature and light affect N
2
fixation. Our study shows that
Crocosphaera
combines multiple mechanisms to reduce intracellular O
2
to protect the O
2
-sensitive N
2
-fixing enzyme. Our model, however, indicates that these protections are insufficient at low temperature due to reduced respiration and the rate of N
2
fixation becomes severely limited. This provides a physiological explanation for why the geographic distribution of
Crocosphaera
is confined to the warm low-latitude ocean.
The Modified Surface Killing Assay Distinguishes between Protective and Nonprotective Antibodies to PspA
Authors: Genschmer Kristopher R. , Vadesilho Cintia F. M. , McDaniel Larry S. , Park Sang-Sang , Hale Yvette , Miyaji Eliane N. , Briles David E.
Published: December 2019

The most important finding of this study is that the MSKA can be used as an
in vitro
functional assay. Such an assay will be critical for the development of PspA-containing vaccines. The other important findings relate to the locations and nature of the protection-eliciting epitopes of PspA. There are limited prior data on the locations of protection-eliciting PspA epitopes, but those data along with the data presented here make it clear that there is not a single epitope or domain of PspA that can elicit protective antibody and there exists at least one region of the αHD which seldom elicits protective antibody. Moreover, these data, in concert with prior data, strongly make the case that protective epitopes in the αHD are highly conformational (≥100-amino-acid fragments of the αHD are required), whereas at least some protection-eliciting epitopes in the proline-rich domain are encoded by ≤15-amino-acid sequences.
Gut Microbiomes of the Eastern Oyster (
Crassostrea virginica
) and the Blue Mussel (
Mytilus edulis
): Temporal Variation and the Influence of Marine Aggregate-Associated Microbial Communities
Authors: Pierce Melissa L. , Ward J. Evan
Published: December 2019

This work investigates the influence that extrinsic factors, diet, and the environment can have on the microbiomes of shellfish. Over the course of a year, the gut microbial communities of two species of bivalves, oysters and mussels, held under identical conditions in coastal marine waters were compared. While the mussels and oysters harbored gut microbial communities with similar composition, on a functional level, they exhibited species and temporal variation. These results indicate that intrinsic factors influence the bivalve microbiome, resulting in species variability, even when environmental conditions, feeding mechanism, and particle diet are constant. Seasonal and multispecies comparisons for bivalve-associated microbial communities are rare, and we believe this research represents an important contribution. The results presented here advance our understanding of the symbiotic interactions between marine invertebrates, the microbial communities they harbor, and the environment.
An abnormal finding in the third trimester
Authors: Marshall Hannah , Petrie Kyle
Published: December 2019

A healthy woman presented with an antepartum haemorrhage at 35/40 during a low-risk pregnancy with normal antenatal bloods and anomaly scan at 20/40 gestation. Following an abnormal ultrasound (USS), the baby was delivered by emergency C-section.

A male infant was born in good condition but admitted to the neonatal unit for monitoring. Examination revealed global hypotonia, a weak uncoordinated suck and absent Moro reflex. He had widened sagittal sutures and a large posterior fontanelle. The remainder of the examination was unremarkable. Abnormal bloods are shown in table 1 .

Table 1

Initial newborn blood results

TestValueNormal rangeWhite cell count3.23×109/L10.0–26.0×109/LNeutrophils0.52×109/L1.0–8.5×109/LBilirubin221 µmol/L0–20 µmol/LGamma glutamyl transferase828 IU/L20–183 IU/L

He was treated for suspected sepsis due to jaundice and temperature instability.

Cranial USS was performed immediately ( figure 1 ). Urgent MRI of the brain further characterised these abnormalities ( figures 2–3 ).

Figure 1

Coronal section of cranial ultrasound obtained on day 1 of life.

Figure 2

Coronal section from MRI performed on day 1 of life.

Figure 3

Sagittal section from MRI performed on day 1 of life.

Questions

What are the causes for the abnormalities seen in figures 1–3 ?

What investigations should be considered?

What is the diagnosis?

How do we manage this condition?

What are the likely outcomes?

Answers can be found on page 2
Kangaroo mother care: need of the day
Authors: Sohail Rubina , Rasul Noreen , Naeem Ammara , Khan Humayun Iqbal
Published: December 2019

Each year approximately 20 million low birthweight babies are born globally. Prematurity is a leading cause of neonatal mortality in developing countries and results in 60%–80% of neonatal deaths. Neonatal mortality is the major contributor to under-5 mortality. According to Pakistan Demographic and Health Survey 2017–2018, neonatal mortality in Pakistan is 42 per 1000 live births and under-5 mortality is 74 per 1000 live births. One out of every 22 newborns dies in Pakistan, which is an alarming figure. Majority of these deaths are preventable. They can be prevented by well-trained midwives, safe delivery, early initiation of breast feeding within an hour after birth and skin-to-skin contact. Pakistan is among the top 10 countries with the highest number of preterm births and with limited resources to manage the burden. Kangaroo mother care (KMC) is a safe and economical alternative to provide preterm care in developing countries. In babies at gestational age less than 37 weeks or with neonatal weight less than 2.5 kg, skin-to-skin contact prevents hypothermia and infection. Neonatal mortality and morbidity can be reduced by providing preterm care through KMC. This case report is of a preterm baby who was delivered at 33 weeks of gestation with a weight of 1.3 kg and was saved by KMC in the paediatric department of Services Hospital in Lahore.
Feasibility study for use of angiographic parametric imaging and deep neural networks for intracranial aneurysm occlusion prediction
Authors: Shiraz Bhurwani Mohammad Mahdi , Waqas Muhammad , Podgorsak Alexander R , Williams Kyle A , Davies Jason M , Snyder Kenneth , Levy Elad , Siddiqui Adnan , Ionita Ciprian N
Published: December 2019

Background

Angiographic parametric imaging (API), based on digital subtraction angiography (DSA), is a quantitative imaging tool that may be used to extract contrast flow parameters related to hemodynamic conditions in abnormal pathologies such as intracranial aneurysms (IAs).

Objective

To investigate the feasibility of using deep neural networks (DNNs) and API to predict IA occlusion using pre- and post-intervention DSAs.

Methods

We analyzed DSA images of IAs pre- and post-treatment to extract API parameters in the IA dome and the corresponding main artery (un-normalized data). We implemented a two-step correction to account for injection variability (normalized data) and projection foreshortening (relative data). A DNN was trained to predict a binary IA occlusion outcome: occluded/unoccluded. Network performance was assessed with area under the receiver operating characteristic curve (AUROC) and classification accuracy. To evaluate the effect of the proposed corrections, prediction accuracy analysis was performed after each normalization step.

Results

The study included 190 IAs. The mean and median duration between treatment and follow-up was 9.8 and 8.0 months, respectively. For the un-normalized, normalized, and relative subgroups, the DNN average prediction accuracies for IA occlusion were 62.5% (95% CI 60.5% to 64.4%), 70.8% (95% CI 68.2% to 73.4%), and 77.9% (95% CI 76.2% to 79.6%). The average AUROCs for the same subgroups were 0.48 (0.44–0.52), 0.67 (0.61–0.73), and 0.77 (0.74–0.80).

Conclusions

The study demonstrated the feasibility of using API and DNNs to predict IA occlusion using only pre- and post-intervention angiographic information.
Predicting the duration of sickness absence spells due to back pain: a population-based study from Sweden
Authors: Ropponen Annina , Gémes Katalin , Frumento Paolo , Almondo Gino , Bottai Matteo , Friberg Emilie , Alexanderson Kristina
Published: December 2019

Objectives

We aimed to develop and validate a prediction model for the duration of sickness absence (SA) spells due to back pain (International Statistical Classification of Diseases and Related Health Problems 10th Revision: M54), using Swedish nationwide register microdata.

Methods

Information on all new SA spells >14 days from 1 January 2010 to 30 June 2012 and on possible predictors were obtained. The duration of SA was predicted by using piecewise constant hazard models. Nine predictors were selected for the final model based on a priori decision and log-likelihood loss. The final model was estimated in a random sample of 70% of the SA spells and later validated in the remaining 30%.

Results

Overall, 64 048 SA spells due to back pain were identified during the 2.5 years; 74% lasted ≤90 days, and 9% >365 days. The predictors included in the final model were age, sex, geographical region, employment status, multimorbidity, SA extent at the start of the spell, initiation of SA spell in primary healthcare and number of SA days and specialised outpatient healthcare visits from the preceding year. The overall c-statistic (0.547, 95% CI 0.542 to 0.552) suggested a low discriminatory capacity at the individual level. The c-statistic was 0.643 (95% CI 0.634 to 0.652) to predict >90 days spells, 0.686 (95% CI 0.676 to 0.697) to predict >180 spells and 0.753 (95% CI 0.740 to 0.766) to predict >365 days spells.

Conclusions

The model discriminates SA spells >365 days from shorter SA spells with good discriminatory accuracy.
Study of the dilepton electromagnetic decays of $$\chi _{cJ}(1P)$$
Authors: Wang Xuan-He , Jiang Yue , Wang Tianhong , Tan Xiao-Ze , Li Geng , Wang Guo-Li
Published: December 2019

In this paper, the dilepton electromagnetic decays $$\chi _{cJ}(1P) \rightarrow J/\psi e^+e^-$$χcJ(1P)→J/ψe+e- and $$\chi _{cJ}(1P) \rightarrow J\psi \mu ^+\mu ^-$$χcJ(1P)→Jψμ+μ-, where $$\chi _{cJ}$$χcJ denotes $$\chi _{c0}$$χc0, $$\chi _{c1}$$χc1 and $$\chi _{c2}$$χc2, are calculated systematically in the improved Bethe–Salpeter method. The numerical results of decay widths and the invariant mass distributions of the final lepton pairs are given. The comparison is made with the recently measured experimental data of BESIII. It is shown that for the cases including $$e^+e^-$$e+e-, the gauge invariance is decisive and should be considered carefully. For the processes of $$\chi _{cJ}(1P) \rightarrow J/\psi e^+e^-$$χcJ(1P)→J/ψe+e-, the branching fraction are: $$\mathcal {B}[\chi _{c0}(1P) \rightarrow J/\psi e^+e^-]=1.06^{+0.16}_{-0.18} \times 10^{-4}$$B[χc0(1P)→J/ψe+e-]=1.06-0.18+0.16×10-4, $$\mathcal {B}[\chi _{c1}(1P) \rightarrow J/\psi e^+e^-]=2.88^{+0.50}_{-0.53} \times 10^{-3}$$B[χc1(1P)→J/ψe+e-]=2.88-0.53+0.50×10-3, and $$\mathcal {B}[\chi _{c2}(1P) \rightarrow J/\psi e^+e^-]=1.74^{+0.22}_{-0.21} \times 10^{-3}$$B[χc2(1P)→J/ψe+e-]=1.74-0.21+0.22×10-3. The calculated branching fractions of $$\chi _{cJ}(1P)\rightarrow J/\psi \mu ^+\mu ^-$$χcJ(1P)→J/ψμ+μ- channels are: $$\mathcal {B}[\chi _{c0}(1P) \rightarrow J/\psi \mu ^+\mu ^-]=3.80^{+0.59}_{-0.64} \times 10^{-6}$$B[χc0(1P)→J/ψμ+μ-]=3.80-0.64+0.59×10-6, $$\mathcal {B}[\chi _{c1}(1P) \rightarrow J/\psi \mu ^+\mu ^-]=2.04^{+0.36}_{-0.38} \times 10^{-4}$$B[χc1(1P)→J/ψμ+μ-]=2.04-0.38+0.36×10-4, and $$\mathcal {B}[\chi _{c2}(1P) \rightarrow J/\psi \mu ^+\mu ^-]=1.66^{+0.19}_{-0.19} \times 10^{-4}$$B[χc2(1P)→J/ψμ+μ-]=1.66-0.19+0.19×10-4.
Human Action Recognition Based on a Spatio-Temporal Video Autoencoder
Authors: Sousa e Santos Anderson Carlos , Pedrini Helio
Published: December 2019

Due to rapid advances in the development of surveillance cameras with high sampling rates, low cost, small size and high resolution, video-based action recognition systems have become more commonly used in various computer vision applications. Human operators can be supported with the aid of such systems to detect events of interest in video sequences, improving recognition results and reducing failure cases. In this work, we propose and evaluate a method to learn two-dimensional (2D) representations from video sequences based on an autoencoder framework. Spatial and temporal information is explored through a multi-stream convolutional neural network in the context of human action recognition. Experimental results on the challenging UCF101 and HMDB51 datasets demonstrate that our representation is capable of achieving competitive accuracy rates when compared to other approaches available in the literature.
Coincidence of Homeostasis and Bifurcation in Feedforward Networks
Authors: Duncan William , Golubitsky Martin
Published: December 2019

Homeostasis is an important and common biological phenomenon wherein an output variable does not change very much as an input parameter is varied over an interval. It can be studied by restricting attention to homeostasis points — points where the output variable has a vanishing derivative with respect to the input parameter. In a feedforward network, if a node has a homeostasis point then downstream nodes will inherit it. This is the case except when the downstream node has a bifurcation point coinciding with the homeostasis point. We apply singularity theory to study the behavior of the downstream node near these homeostasis-bifurcation points. The unfoldings of low codimension homeostasis-bifurcation points are found. In the case of steady-state bifurcation, the behavior includes multiple homeostatic plateaus separated by hysteretic switches. In the case of Hopf bifurcation, the downstream node may have limit cycles with a wide range of near-constant amplitudes and periods. Homeostasis-bifurcation is therefore a mechanism by which binary, switch-like responses or stable clock rhythms could arise in biological systems.
Transition Dynamics of Generalized Periodic Discharges Observed in EEG Waveforms
Authors: Zhang Honghui , Deng Zichen , Liu Shuang
Published: December 2019

Generalized periodic discharges (GPD) are generalized waveforms that recur with a relatively uniform morphology and duration observed in EEG recordings of many types of metabolic encephalopathy, which are often referred to as epileptiform. In this paper, we try to link these spatiotemporal electrocortical activities and significant attributes of cortex based on Liley’s mean field model, and seek possible generation mechanisms of GPD rhythms from several factors. To these ends, the dynamical properties of simulated EEG consistent with neurophysiological features of human cortex are investigated, among which GPD patterns are our focus. Firstly, with different value sets of model parameters, we reproduce some typical simulation waveforms which are analogous to mammalian normal or abnormal brain activities detected by EEG. Or in other words, we put more emphasis on brain waveforms of GPD states, normal states, and low firing rate states in our numerical simulations, and mode transitions among different firing states are our main interests. Secondly, through analysis of maximum Lyapunov exponents and frequency spectrum, we give several mode transitions by varying synaptic connections between excitatory and inhibitory populations, which support the conjecture that selective changes of synaptic connections can trigger GPD states, such as in excitatory (AMPA receptors) and inhibitory neurotransmitters (GABA receptors). Thirdly, we stress the importance of time delay on neural population connections and find that they are free to transfer among different firing modes with appropriate time delays. Furthermore, considering the effects of external inputs to cerebral cortex, we verify that stimulation can lead to good controls on GPD patterns, including facilitation and elimination. Finally, we show that more dynamical rhythms can be produced when taking into account the cortico-cortical connections. These modeling results are expected to shed light into the pathophysiological mechanisms of GPD modes from a theoretical viewpoint.
On Topological Entropy of Finite Representations of the Hénon Map
Authors: Galias Zbigniew
Published: December 2019

The topological entropy of finite representations of the Hénon map is studied. Efficient methods to compute the topological entropy of finite representations of maps are presented. Accurate finite representations of the Hénon map and its iterates are constructed and the topological entropy of these representations is calculated. The relation between the topological entropy of the Hénon map and the topological entropy of its finite representations is discussed.
A New Megastable Oscillator with Rational and Irrational Parameters
Authors: Wang Zhen , Hamarash Ibrahim Ismael , Shabestari Payam Sadeghi , Jafari Sajad
Published: December 2019

In this paper, a new two-dimensional nonlinear oscillator with an unusual sequence of rational and irrational parameters is introduced. This oscillator has endless coexisting limit cycles, which make it a megastable dynamical system. By periodically forcing this system, a new system is designed which is capable of exhibiting an infinite number of coexisting asymmetric torus and strange attractors. This system is implemented by an analog circuit, and its Hamiltonian energy is calculated.
Quadrature MC-DCSK Scheme for Chaos-Based Cognitive Radio
Authors: Quyen Nguyen Xuan
Published: December 2019

In this study, we investigate an enhanced architecture of multicarrier differential chaos-shift keying (MC-DCSK) scheme using quadrature modulation (QM), namely QMC-DCSK. The use of quadrature modulation aims at doubling the data rate over a defined bandwidth and hence improve bandwidth efficiency of the system. In the proposed scheme, the chaotic spreading sequence is transmitted on a predefined frequency while each of the remaining frequencies is phase-shifted at a [Formula: see text] angle in order to produce two quadrature subcarriers located at the same frequency. These subcarriers are modulated by the product of the chaotic spreading sequence and the corresponding bit substreams in parallel. Noncoherent demodulation is carried out in the receiver in order to recover the original data based on the sign of correlation values. Architecture and operation of the conventional and proposed schemes are described. The BER performance over a wireless channel is theoretically derived and then numerically verified. The bit rate, energy and bandwidth efficiencies are evaluated in comparison with those of MC-DCSK. In particular, the application of the proposed scheme to cognitive radio (CR) in the scenario of using multicarrier modulation and chaotic spread-spectrum is discussed and evaluated. The obtained results prove that QMC-DCSK is a fit technique for CR communications.