bluuebunny/crossref_metadata_2025 huggingface dataset:
Length scales and alloys of iron
Authors: Bhadeshia H K D H
Published: December 2019

Many of the structures common within steels are not geometrically smooth, which means that their stereological parameters, such as the amount of interfacial area per unit volume, are resolution dependent. The tendency of brittle phases to crack is size dependent, as is the strength. The ability of steel to resist cleavage can be influenced by the size and distribution of coherent domains within the structure. A different diffusion theory applies when dealing with steep concentration gradients. All of these aspects are of importance in the design, characterisation and theory of steels, illustrated here with a few examples, where the neglect of length scales is improper.
Thermochemical surface engineering: a playground for science and innovation
Authors: Christiansen T L , Somers M A J
Published: December 2019

This article illustrates the plethora of different possibilities in thermochemical surface engineering (TSE) and the close interlink between science and innovation. Three widely different examples of gaseous TSE are presented: surface engineering of austenitic stainless steel by high- and low- temperature surface treatment, surface hardening of titanium by incorporation of nitrogen, oxygen and carbon, and direct synthesis of magnetic iron-nitride α”-Fe16N2. It is shown how 3D printed materials made of stainless steel and titanium can benefit from TSE.
Using synchrotron radiation to improve understanding of deformation of polycrystalline metals by measuring, modelling and publishing 4D information
Authors: Greeley D , Yaghoobi M , Pagan D , Sundararaghavan V , Allison J
Published: December 2019

The evolution of deformation in a Mg-Nd alloy has been investigated using 3D HEDM and crystal plasticity simulation using the PRISMS-Plasticity CPFE Code. Using a simplified representative volume element (RVE), the average stress-strain response is well predicted by the PRISMS-Plasticity simulation. The distribution of the resolved shear stresses corresponding to the basal mode for all grains is obtained using both HEDM and the CPFE. simulation. The results show that the CPFE predicted substantially narrower distributions, thus indicating the need for improved digital representation of the RVE. The results of these HEDM experiments and PRISMS-Plasticity simulations have been stored in the Materials Commons in a straight-forward manner and are being made available as a published dataset. Both PRISMS-Plasticity and the Materials Commons are open-source and available for use by the global materials community.
Comparison of the Elastic-Plastic Transition in Nanocrystalline Nickel Pillars Fabricated by Electron Beam Lithography and Focused Ion Beam Methods
Authors: Sedore Matthew , Diak Bradley J. , Murray Andrew , Riel Bruno
Published: December 2019

The elastic-plastic transition or yield behaviour was observed during compression of nanocrystalline nickel pillars fabricated by electroplating into electron beam lithography (EBL) forms or by focused ion beam (FIB) milling of the same electroplated structure. The experimental methodology allowed structures with different surface defect source/obstacles and similar bulk defects to be compared. Pillars with 1 to 2 um diameter cross-sections were made with height to diameter aspect ratios from 2:1 to 6:1, grain size of 91 ± 23 nm, and <110>, <111>, <100> textures in the growth direction. The pillars were compressed under a flat punch at constant loading rates from 1.5 to 30 μΝ/s using an instrumented indenter. EBL pillars generally showed a gradual elastic-plastic transition similar to yielding in bulk nickel followed by strain bursts. In contrast, FIB-milled pillars consistently showed stochastic yielding. The Young’s modulus was 55 to 350 GPa for all pillars, agreeing with values in the literature. The yield stress at 0.2% offset strain for EBL pillars ranged from 480 to 1800 MPa, and 320 to 700 MPa for FIB-milled pillars that was narrowed to 550 to 650 MPa after subsequent annealing, with initial deformation localized near the tops of FIB-milled pillars due to geometrical tapering. EBL pillar shear yield strengths exceed the literature reported for Ni and appear to lose their size dependence.
Load transfer and strain gradients in pearlite investigated by means of in-situ neutron diffraction
Authors: Tacq Jeroen , Verlinden Bert , Seefeldt Marc
Published: December 2019

In-situ neutron diffraction experiments have been performed during tensile testing of undeformed and cold rolled pearlite. The microstructure of the samples varied from spheroidised cementite to randomly oriented lamellae to lamellae aligned with the loading direction. Both the ferrite lattice strain and diffraction peak width have been analysed. Conclusions were drawn regarding the influence of cementite morphology on load transfer from ferrite to cementite. The ferrite lattice strain was found to decrease after yielding in a sample with aligned lamellae, whereas an increasing ferrite lattice strain would be expected. This might be explained based on the non-ideal nature of the lamellar microstructure. Upon unloading of the material, the diffraction peak width decreases, which may be attributed to strain gradients in the deformed pearlite.
3D microstructural analysis in the steel industry
Authors: Taniyama Akira
Published: December 2019

Since steel products have complex microstructures and chemical composition to achieve high strength and high functionality, it is important to characterize the internal structure with analytic techniques and to be able to predict their properties using simulation techniques. It is now possible to characterize and analyze the structural arrangements in raw steel materials and steel products, including the shapes of defects such as voids and cracks, as well as the crystallographic grain structure, by use of powerful new 3D characterization and analysis techniques, which can provide information on the internal structure on the micron or even submicron scale. It is expected, therefore, that application of new methods and results should lead to improvements in the mechanical properties of steel products. In this article, 3D analysis of the internal structure in a duplex stainless steel, and of strain propagation in pure nickel are presented as examples of the industrial application of 3D microstructural analysis.
Comparing local deformation measurements to predictions from crystal plasticity during reverse loading of an aerospace alloy
Authors: Atkinson M D , Lebensohn R A , da Fonseca J Quinta
Published: December 2019

Cyclic loading is of great importance in aerospace applications but the origins of the change in flow stress with load path are poorly understood and difficult to predict. Many crystal plasticity models are capable of modelling macroscopic flow behaviour during non-monotonic load paths, such as the Bauschinger effect often seen when reverse loading. Although these models represent the microstructure explicitly, it remains unclear whether they capture reversibility at the local microstructural scale, or simply fit the macroscopic hardening response better by using more fitting parameters. Here we present experimental surface deformation data acquired using high resolution digital image correlation (HR-DIC) during a reverse load cycle. With resolution greater than 200nm, these experiments reveal the discrete nature of deformation in the form of localised crystallographic slip bands. These results are then compared statistically, over many hundreds of grains, to crystal plasticity simulations of reverse loading. Simulation results are taken from both finite element method (CPFEM) and fast Fourier transform (CPFFT) encompassing the two popular numerical techniques for full-field crystal plasticity models.
Recovery kinetics in Al-0.3%Cu after heavy rolling
Authors: Shuai L F , Huang T L , Wu G L , Hansen N , Huang X , Yu T
Published: December 2019

The recovery kinetics of a nanoscale lamellar structure Al-0.3%Cu alloy, which was produced by 98% cold rolling, during annealing at temperatures from 100 to 200 °C have been analyzed in this study. Microstructural characterization using electron channelling contrast in the scanning electron microscope shows a uniform coarsening of the lamellar structure and gradual precipitation of second phase particles (Al2Cu) during annealing at these temperatures. Fitting of the microhardness values for samples annealed for between 4 and 4096 minutes at different temperatures with a recovery model reveals a change, in the apparent activation energy from 79 kJ/mol at the beginning to 105 kJ/mol at the end of recovery annealing, which leads to a discussion of the recovery mechanisms.
Exploring high strength metallic materials: a lesson from pearlitic steel wire
Authors: Zhang X
Published: December 2019

In human history, the development of stronger materials through the ages is reflected with names of eras illustrating our progress. Besides phase transformations, plastic deformation is one of the major methods to produce products with reliable and predictable mechanical properties such as strength. Pearlitic steel wire, the strongest mass-produced steel, shows an excellent combination of formability and strength. The present overview summarizes the investigation of cold-drawn pearlitic steel wires over the last 150 years, covering the pearlite phase transformation, chemical composition design for wires with high strength, microstructure evolution during wire drawing, strengthening mechanisms and structure-strength relationships. By focusing on the structure, challenges and future strategy are outlined to further improve the strength and performance of pearlitic steel wire, where these routes may also applicable to other metals.
Adaptive unknown input observer for nonlinear systems with application to fault diagnosis
Authors: Mondal Sharifuddin
Published: December 2019

An adaptive unknown input observer for nonlinear systems whose nonlinear functions satisfy Lipschitz condition is presented. The main advantage of the proposed observer is that it is sufficient to satisfy the standard existence conditions of normal unknown input observer design. Another advantage is that it estimates both states and parameters simultaneously. So it can be very much useful for robust control and fault diagnosis. As a possible application, an actuator fault diagnosis scheme is developed for single link robot arm. Finally, numerical simulation is performed to validate the effectiveness of the proposed observer in estimating the parameter along with states.
The in-plane dynamic crushing of quadrilateral chiral honeycomb coatings
Authors: Jun-Jie Li , Yue Wu , Shi-Peng Wang , Meng Tao
Published: December 2019

For the anti-impact performance of hyperelastic coatings covered on the ship hull, the in-plane dynamic crushing behaviors of quadrilateral chiral honeycomb coatings (including chiral and anti-chiral) were numerically studied by explicit dynamic finite element simulations. The deformation mode, energy absorption and supporting reaction force under different impact speeds have been analyzed. The results show that: (1) If the impact speed is low, the chiral honeycomb coatings display the rotational deformation; (2) With the increase of impact speed, the deformation at the top of coating is remarkable; (3) The response of energy absorption and supporting reaction force corresponds to the macroscopic deformation mode of chiral honeycomb coatings.
Novel test scenarios needed to validate outdoor stability of perovskite solar cells
Authors: Song Wenya , Aernouts Tom
Published: December 2019

Perovskite solar cells (PSCs) will eventually operate outdoors, subjected to diurnal cycles with varying irradiance and cell temperature throughout 24 h periods. Hereby, we show the PSC stability results from laboratory accelerated stress tests can not obviously suggest their stability in outdoor-like situations. Thus, to validate PSC outdoor stability, it is necessary to emulate outdoor conditions, for which we propose possible test scenarios.
Home-Based Contingency Management Delivered by Community Health Workers to Improve Alcohol Abstinence: A Randomized Control Trial
Authors: Jirapramukpitak Tawanchai , Pattanaseri Keerati , Chua Kia-Chong , Takizawa Patcharapim
Published: December 2019

Aim

To evaluate the effectiveness of home-based contingency management (CM) in improving abstinence in an incentive-dependent manner among alcoholic individuals.

Methods

A 12-week, home-visit (HV) only controlled, randomized incentive-ranging trial of 161 adults with current alcohol dependence was recruited using social network theory techniques. Participants randomly received HV, low- (CM-L) or higher-magnitude CM (CM-H). Community health workers made regular home visits, monitored drinking behavior and delivered CM as appropriate. Two follow-up visits at weeks 13 and 16 were conducted to assess whether abstinence would still be maintained after the interventions discontinued. Rates of continuous reported abstinence (primary), numbers of positive breath samples (secondary) over the intervention period and rates of prolonged reported abstinence (secondary) were evaluated.

Results

CM did not significantly improve the rates of continuous reported abstinence across the 12-week intervention period (odds ratio (OR) for trend 1.2, 95% confidence interval (CI) 0.7–2.1, P = 0.601). There was a significant reduction, however, in the average number of positive breath samples submitted by the CM-H group (generalized linear model, β −0.5, 95% CI −0.9 to −0.2, P = 0.005). The CM-H arm also had a significantly higher abstinence rate during the follow-up period (OR 3.4, 95% CI 1.3–8.8, P = 0.013). Event history model suggested that the CM-H condition had significantly higher chances of achieving renewed abstinence across the study period (OR 2.0, 95% CI 1.3–3.2, P = 0.003).

Conclusions

Home-based CM with sufficient incentive is promising in reducing alcohol use and in improving rates of abstinence over time. Allowing for a certain grace period may better capture the delayed treatment effect of home-based CM.
Environmental determinants of total evaporative water loss in birds at multiple temperatures
Authors: Song Soorim , Beissinger Steven R
Published: December 2019

Endotherms dissipate heat to the environment to maintain a stable body temperature at high ambient temperatures, which requires them to maintain a balance between heat dissipation and water conservation. Birds are relatively small, contain a large amount of metabolically expensive tissue, and are mostly diurnal, making them susceptible to physiological challenges related to water balance and heat dissipation. We compiled total evaporative water loss (TEWL) measurements for 174 species of birds exposed to different temperatures and used comparative methods to examine their relationships with body size, ambient temperature, precipitation, diet, and diel activity cycle. TEWL in the thermoneutral zone (TNZ) was associated primarily with body mass and activity phase. Larger and more active-phase birds, with their higher metabolic rates, lost more water through evaporation than smaller, resting-phase birds, particularly at higher thermal exposures. However, maximum temperature of the natural habitat became an important determinant of TEWL when birds were exposed to temperatures exceeding the TNZ. Species from hotter climates exhibited higher TEWL. Adaptation to arid climates did not restrict evaporative water loss at thermal conditions within the TNZ, but promoted evaporative water loss at exposures above the TNZ. The TEWL of granivores, which ingest food with low water content, differed little from species with other food habitats under all thermal conditions. The effects of environmental covariates of TEWL were dissimilar across thermal exposures, suggesting no evidence for a tradeoff between water conservation in the TNZ and heat dissipation at exposure to higher temperatures. Thus, birds may be able to acclimate when climate change results in the need to increase heat dissipation due to warming, except perhaps in hot, arid environments where species will need to depend heavily upon evaporative cooling to maintain homeothermy.
Sociality and tattoo skin disease among bottlenose dolphins in Shark Bay, Australia
Authors: Powell Sarah N , Wallen Megan M , Miketa Madison L , Krzyszczyk Ewa , Foroughirad Vivienne , Bansal Shweta , Mann Janet
Published: December 2019

Social behavior is an important driver of infection dynamics, though identifying the social interactions that foster infectious disease transmission is challenging. Here we examine how social behavior impacts disease transmission in Indo-Pacific bottlenose dolphins (Tursiops aduncus) using an easily identifiable skin disease and social network data. We analyzed tattoo skin disease (TSD) lesions based on photographs collected as part of a 34-year longitudinal study in relation to the sociality of T. aduncus using three metrics (degree, time spent socializing, and time in groups) and network structure, using the k-test. We show that calves with TSD in the second year of life associated more with TSD-positive individuals in the first year of life compared with calves that did not have TSD. Additionally, the network k-test showed that the social network links are epidemiologically relevant for transmission. However, degree, time spent in groups, and time spent socializing were not significantly different between infected and uninfected groups. Our findings indicate that association with infected individuals is predictive of an individual’s risk for TSD and that the social association network can serve as a proxy for studying the epidemiology of skin diseases in bottlenose dolphins.
Impact of vitamin D on cardiac structure and function in chronic kidney disease patients with hypovitaminosis D: a randomized controlled trial and meta-analysis
Authors: Banerjee Debasish , Chitalia Nihil , Ster Irina Chis , Appelbaum Evan , Thadhani Ravi , Kaski Juan Carlos , Goldsmith David
Published: December 2019

Aims

Vitamin D deficiency is associated with cardiovascular events in chronic kidney disease (CKD) yet the impact of supplementation is controversial. Previous active vitamin D supplementation studies did not show improvement in cardiac structure or function but the effect of native vitamin D supplementation in CKD patients with low vitamin D levels is unknown. We have addressed this question via both a randomized double-blind prospective study and a meta-analysis of three randomized placebo-controlled studies.

Methods and results

We conducted a randomized double-blind, placebo-controlled trial of vitamin D supplementation in stable, non-diabetic, CKD three to four patients with circulating vitamin D <75nmol/L, who were receiving treatment with ACEi or ARB and had high-normal left ventricular (LV) mass. Patients were randomized to receive six directly observed doses of 100 000 IU cholecalciferol (n = 25) or matched placebo (n = 23). The primary endpoint was changed in LV mass index (LVMI) over 52 weeks, as assessed by cardiac magnetic resonance imaging. Secondary endpoints included changes in LV ejection fraction (LVEF); LV and right ventricular volumes and left and right atrial area. Vitamin D concentration increased with the administration of cholecalciferol. The change in LVMI with cholecalciferol [median (inter-quartile range), −0.25 g (−7.20 to 5.30)] was no different from placebo [−4.30 g (9.70 to 2.60)]. There was no difference in changes of LVEF; LV and right ventricular volumes and left and right atrial area. The meta-analysis of three 52-week, randomized placebo-controlled studies using active/native vitamin D supplementation showed no differences in LVMI measurements.

Conclusion

Vitamin D supplementation does not have beneficial effects on LV mass in CKD patients.
No increased extracellular volume fraction or conduction time after childhood septal myectomy
Authors: Schleihauf Julia , Cleuziou Julie , Meierhofer Christian , Klingel Karin , Jesinghaus Moritz , Kaltenecker Emanuel , Ewert Peter , Wolf Cordula M
Published: December 2019

OBJECTIVES

The aim of this study was to assess the effect of surgical septal myectomy performed during early childhood for severe, drug-refractory hypertrophic cardiomyopathy with left ventricular outflow tract obstruction on the extent of septal myocardial extracellular volume fraction and the potential risk of developing atrioventricular cardiac conduction system disease.

METHODS

In this retrospective study, data from 30 patients with a confirmed diagnosis of childhood-onset hypertrophic cardiomyopathy were reviewed including cardiovascular magnetic resonance (CMR) with myocardial T1 mapping and late gadolinium enhancement, histopathology of myocardial specimens, transthoracic echocardiography, electrocardiography, 24-h Holter and cardiopulmonary exercise testing. Eighteen patients without were compared to 12 patients with prior septal myectomy performed during childhood (non-operated versus myectomy patients).

RESULTS

Late gadolinium enhancement on CMR as a correlate for focal myocardial fibrosis was found in 53% of patients, predominantly located in the septal region, with no difference between groups. As compared to non-operated patients, those after myectomy showed a similar amount of total and septal extracellular volume fraction, as calculated from pre- and post-contrast CMR T1 mapping, which is a correlate for diffuse interstitial myocardial fibrosis. PQ-intervals or the occurrence of higher degree conduction system disease were equal between the 2 groups.

CONCLUSIONS

Data from CMR and electrocardiography suggest that surgical septal myectomy performed during early childhood for severe obstructive hypertrophic cardiomyopathy does not cause an increased septal extracellular volume fraction or delayed atrioventricular conduction time on long-term follow-up.
ENGAGING RURAL VETERANS’ PERCEPTIONS OF SURVIVORSHIP CARE FOR HEAD AND NECK CANCER
Authors: Seaman Aaron T , Friberg Julia , Adamowicz Jenna L , Kendell Nicholas , Pagedar Nitin A , Howren M Bryant , Christensen Alan J
Published: December 2019

The purpose of this study was to investigate 1) rural patients’ perceptions of their own rurality and its effects on experience of head and neck cancer survivorship, and 2) potential barriers and facilitators to survivorship care within an integrated health care delivery system of the Veterans Health Administration (VHA). Data from qualitative interviews with Veterans who have a history of head and neck cancer are presented to understand the complex ways that rurality impacts cancer survivorship. Head and neck cancer survivors must contend with specific challenges resulting from their risk factors and treatment, including access to complex medical follow up, long-term physical and psychological effects of treatment, and tobacco- and alcohol-related comorbidities. While integration within the VHA facilitates coordination of specialty and primary care and the transfer of medical information, the use of community care in rural areas presents coordination challenges, especially for survivors with comorbidities.
Kuwabara-Kono numerical dissipation: a new method to simulate granular matter
Authors: James Guillaume , Vorotnikov Kirill , Brogliato Bernard
Published: December 2019

A new method is introduced for the simulation of multiple impacts in granular media using the Kuwabara-Kono (KK) contact model, a nonsmooth (not Lipschitz continuous) extension of Hertz contact that accounts for viscoelastic damping. We use the technique of modified equations to construct time-discretizations of the nondissipative Hertz law matching numerical dissipation with KK dissipation at different consistency orders. This allows us to simulate dissipative impacts with good accuracy without including the nonsmooth KK viscoelastic component in the contact force. This tailored numerical dissipation is developed in a general framework, for Newtonian dynamical systems subject to dissipative forces proportional to the time-derivative of conservative forces. Numerical tests are performed for the simulation of impacts in Newton’s cradle and on alignments of alternating large and small balls. Resulting wave phenomena (oscillator synchronization, propagation of dissipative solitary waves, oscillatory tails) are accurately captured by implicit schemes with tailored numerical dissipation, even for relatively large time steps.
On an Example of Quiver Donaldson–Thomas/Relative Gromov–Witten Correspondence
Authors: Bousseau Pierrick
Published: December 2019

We explain and generalize a recent example of quiver Donaldson–Thomas/relative Gromov–Witten correspondence due to Reineke–Weist by showing how to reduce it to the Gromov–Witten/Kronecker correspondence by a degeneration and blow-up. We also refine the result by working with all genera on the Gromov–Witten side and with refined Donaldson–Thomas invariants on the quiver side.
Constitutive expression of the cryptic vanGCd operon promotes vancomycin resistance in Clostridioides difficile clinical isolates
Authors: Shen Wan-Jou , Deshpande Aditi , Hevener Kirk E , Endres Bradley T , Garey Kevin W , Palmer Kelli L , Hurdle Julian G
Published: December 2019

Objectives

To describe, for the first time (to the best of our knowledge), the genetic mechanisms of vancomycin resistance in clinical isolates of Clostridioides difficile ribotype 027.

Methods

Clinical isolates and laboratory mutants were analysed: genomically to identify resistance mutations; by transcriptional analysis of vanGCd, the vancomycin resistance operon encoding lipid II d-alanine-d-serine that is less bound by vancomycin than native lipid II d-alanine-d-alanine; by imaging of vancomycin binding to cell walls; and for changes in vancomycin bactericidal activity and autolysis.

Results

Vancomycin-resistant laboratory mutants and clinical isolates acquired mutations to the vanSR two-component system that regulates vanGCd. The substitutions impaired VanSR’s function, resulting in constitutive transcription of vanGCd. Resistance was reversed by silencing vanG, encoding d-alanine-d-serine ligase in the vanGCd operon. In resistant cells, vancomycin was less bound to the cell wall septum, the site where vancomycin interacts with lipid II. Vancomycin’s bactericidal activity was reduced against clinical isolates and laboratory mutants (64 and ≥1024 mg/L, respectively) compared with WT strains (4 mg/L). Truncation of the potassium transporter TrkA occurred in laboratory mutants, which were refractory to autolysis, accounting for their survival in high drug concentrations.

Conclusions

Ribotype 027 evolved first-step resistance to vancomycin by constitutively expressing vanGCd, which is otherwise silent. Experimental evolutions and bactericidal assays show that ribotype 027 can acquire mutations to drastically enhance its tolerance to vancomycin. Thus, further epidemiological studies are warranted to examine the extent to which vancomycin resistance impacts clinical outcomes and the potential for these strains to evolve higher-level resistance, which would be devastating.
Absence of the type I-E CRISPR-Cas system in Klebsiella pneumoniae clonal complex 258 is associated with dissemination of IncF epidemic resistance plasmids in this clonal complex
Authors: Tang Yu , Fu Pan , Zhou Ying , Xie Yingzhou , Jin Jialin , Wang Bei , Yu Lianhua , Huang Yunkun , Li Gang , Li Meng , Liang Wei , Ou Hong-Yu , Jiang Xiaofei
Published: December 2019

Background

The pandemics caused by MDR Klebsiella pneumoniae are mostly due to the global dissemination of high-risk clonal complex 258 (CC258) and related IncF epidemic plasmids. However, the factors leading to the epidemiological advantages of CC258–IncF linkage remain obscure. The Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) and CRISPR-associated protein (CRISPR-Cas) systems, providing adaptive immunity against invading DNA, play an important role in the interactions between plasmids and hosts.

Objectives

To investigate the relationship between CRISPR-Cas systems and the high-risk linkage CC258–IncF.

Methods

CRISPR-Cas loci were detected among 381 collected K. pneumoniae clinical isolates and 207 K. pneumoniae complete genomes available in GenBank. MLST was used to determine the genetic relatedness of these isolates. Nucleotide BLAST was used to search for protospacers on K. pneumoniae plasmids.

Results

We observed an epidemic correlation between CRISPR-Cas loci, CC258 and IncF plasmids. Interestingly, most type I-E CRISPR-Cas systems identified carried spacers matching the backbone regions of IncF plasmids.

Conclusions

Our results suggest that the absence of type I-E CRISPR-Cas systems in K. pneumoniae CC258 is strongly associated with the dissemination of IncF epidemic plasmids, contributing to the global success of the international high-risk linkage CC258–IncF. Our findings provide new information regarding the dissemination and evolution of the high-risk linkage of K. pneumoniae CC258–IncF and pave the way for new strategies to address the problem of antibiotic resistance.
Geographical Distribution of Aedes aegypti aegypti and Aedes aegypti formosus (Diptera: Culicidae) in Kenya and Environmental Factors Related to Their Relative Abundance
Authors: Futami K , Iwashita H , Higa Y , Lutiali P A , Sonye G O , Mwatele C , Njenga S M , Minakawa N
Published: December 2019

The mosquito Aedes aegypti (L.) is the primary vector of various infectious viruses and is typified by a polymorphic color and abundance of white scales on the body. It has been conventionally separated into two subspecies, Ae. aeg. formosus (Walker) (Aaf) and Ae. aeg. aegypti (L.) (Aaa), with Aaf considered a ‘sylvan’ form and Aaa a ‘domestic’ form. Because the two subspecies show different susceptibilities to dengue viruses it is important to understand their distribution. In this study, we collected larvae from artificial and natural habitats in southern Kenya and reared them to adults to morphologically identify subspecies. We describe the geographical distribution and relative abundance of Aaa and Aaf in Kenya, and estimate the environmental factors associated with their distributions by GIS using climate and environment data. A total of 5,243 Ae. aegypti adults were collected from 249 sites, with Aaa accounting for 22% of the specimens. The relative abundance of Aaa was higher in coastal areas versus sites in western Kenya. Aaa abundance was also higher in urbanized than forested areas, which is consistent with known ecology. In contrast and inconsistent with previous studies, both Aaa and Aaf were sympatric in artificial and natural habitats. The high relative abundance of Aaa in coastal areas might derive from old populated cities, climate, and/or introduction from abroad.
Diagnosing pulsar winds in black-widow, redback, and other binary millisecond pulsar systems
Authors: Zilles Anne , Kotera Kumiko , Rohrmann Rene , Althaus Leandro
Published: December 2019

Binary systems composed of a recycled millisecond pulsar and a stellar companion in close orbit could be excellent sites to diagnose pulsar winds. In such systems, the pulsar outflow irradiates and heats up the companion atmosphere, which can lead to the observation of strong day/night modulations in temperature. We demonstrate with particle shower simulations that the particle energy of the wind affects the heating depth in the atmosphere: the wind heat can be deposited above or below the photosphere, leading to different signatures in the observed spectra. We apply our method to four specific systems: We find that systems with cool night-side companions showing strong temperature variations can give interesting lower limits on the particle energy in the winds. In particular, if the companion night side of PSR B1957+20 were to be suddenly irradiated, deep heating would only take place if particles with energy >100 TeV were present. Observational evidence of deep heating in this system thus suggests that (i) such particles exist in the pulsar wind and/or (ii) binary evolution non-trivially takes the companion to the observed temperature asymmetry. Besides, the observed temperature difference can be maintained only with particle energies of the order of 100 MeV.
Spectroscopic QUasar Extractor and redshift (z) Estimator squeze – I. Methodology
Authors: Pérez-Ràfols Ignasi , Pieri Matthew M , Blomqvist Michael , Morrison Sean , Som Debopam
Published: December 2019

We present Spectroscopic QUasar Extractor and redshift (z) Estimator squeze, a software package to classify quasar spectra and estimate their redshifts. squeze is a random forest classifier operating on the parameters of candidate emission peaks identified in the spectra. We test the performance of the algorithm using visually inspected data from BOSS as a truth table. Only 4 per cent of the sample (∼6800 quasars and ∼11 520 contaminants) is needed for converged training in recommended choices of the confidence threshold (0.2 < pmin < 0.7). For an operational mode that balances purity and completeness (pmin = 0.32), we recover a purity of $97.40\pm 0.47{{\ \rm per\ cent}}$ ($99.59\pm 0.06{{\ \rm per\ cent}}$ for quasars with z ≥ 2.1) and a completeness of $97.46\pm 0.33{{\ \rm per\ cent}}$ ($98.81\pm 0.13{{\ \rm per\ cent}}$ for quasars with z ≥ 2.1). squeze can be used to obtain an ≈100 per cent pure sample of z ≥ 2.1 quasars (with ≈97 per cent completeness) by using a confidence threshold of pmin = 0.7. The estimated redshift error is $1500{\rm \, km\,s^{ -1}}$ and we recommend that squeze be used in conjunction with an additional step of redshift tuning to achieve maximum precision. We find that squeze achieves the necessary performance to replace visual inspection in BOSS-like spectroscopic surveys of quasars with subsequent publications in this series exploring expectations for future surveys and alternative methods.
Modelling X-ray RMS spectra I: intrinsically variable AGNs
Authors: Parker M L , Alston W N , Igo Z , Fabian A C
Published: December 2019

We present simple xspec models for fitting excess variance spectra of active galactic nuclei. Using a simple Monte Carlo approach, we simulate a range of spectra corresponding to physical parameters varying, then calculate the resulting variance spectra. Starting from a variable power law, we build up a set of models corresponding to the different physical processes that can affect the final excess variance spectrum. We show that the complex excess variance spectrum of IRAS 13224−3809 can be well described by such an intrinsic variability model, where the power-law variability is damped by relativistic reflection and enhanced by an ultra-fast outflow. The reflection flux is correlated with that of the power law, but not perfectly. We argue that this correlation is stronger at high frequencies, where reverberation lags are detected, while excess variance spectra are typically dominated by low-frequency variability.
Hot gas flows on a parsec scale in the low-luminosity active galactic nucleus NGC 3115
Authors: Yao Zhiyuan , Gan Zhaoming
Published: December 2019

NGC 3115 is known as the low-luminosity active galactic nucleus that hosts the nearest (z ∼ 0.002) billion-solar-mass supermassive black hole (∼1.5 × 109 M⊙). Its Bondi radius rB (∼3.6 arcsec) can be readily resolved with Chandra, which provides an excellent opportunity to investigate the accretion flow on to a supermassive black hole. In this paper, we perform two-dimensional hydrodynamical numerical simulations, tailored for NGC 3115, on the mass flow across the Bondi radius. Our best fittings for the density and temperature agree well with the observations of the hot interstellar medium in the centre of NGC 3115. We find that the flow properties are determined solely by the local galaxy properties in the galaxy centre: (1) stellar winds (including supernova ejecta) supply the mass and energy sources for the accreting gas; (2) similar to in the one-dimensional calculations, a stagnation radius rst ∼ 0.1 rB is also found in the two-dimensional simulations, which divides the mass flow into an inflow–outflow structure; (3) the radiatively inefficient accretion flow theory applies well inside the stagnation radius, where the gravity is dominated by the supermassive black hole and the gas is supported by rotation; (4) beyond the stagnation radius, the stellar gravity dominates the spherical-like fluid dynamics and causes the transition from a steep density profile outside to a flat density profile inside the Bondi radius.
A record of the final phase of giant planet migration fossilized in the asteroid belt’s orbital structure
Authors: Clement Matthew S , Morbidelli A , Raymond S N , Kaib N A
Published: December 2019

The asteroid belt is characterized by an extreme low total mass of material on dynamically excited orbits. The Nice model explains many peculiar qualities of the Solar system, including the belt’s excited state, by invoking an orbital instability between the outer planets. However, previous studies of the Nice model’s effect on the belt’s structure struggle to reproduce the innermost asteroids’ orbital inclination distribution. Here, we show how the final phase of giant planet migration sculpts the asteroid belt, in particular its inclination distribution. As interactions with leftover planetesimals cause Saturn to move away from Jupiter, its rate of orbital precession slows as the two planets’ mutual interactions weaken. When the planets approach their modern separation, where Jupiter completes just short of five orbits for every two of Saturn’s, Jupiter’s eccentric forcing on Saturn strengthens. We use numerical simulations to show that the absence of asteroids with orbits that precess between 24 and 28 arcsec yr−1 is related to the inclination problem. As Saturn’s precession speeds back up, high-inclination asteroids are excited on to planet crossing orbits and removed from the inner main belt. Through this process, the asteroid belt’s orbital structure is reshaped, leading to markedly improved simulation outcomes.
Functional independence, access to kidney transplantation and waitlist mortality
Authors: Chu Nadia M , Sison Stephanie , Muzaale Abimereki D , Haugen Christine E , Garonzik-Wang Jacqueline M , Brennan Daniel C , Norman Silas P , Segev Dorry L , McAdams-DeMarco Mara
Published: December 2019

Background

Approximately half of the patients who progress to end-stage kidney disease (ESKD) and undergo dialysis develop difficulties carrying out essential self-care activities, leading to institutionalization and mortality. It is unclear what percentage of kidney transplant (KT) candidates, a group of ESKD patients selected to be healthy enough to withstand transplantation, are functionally independent and whether independence is associated with better access to KT and reduced waitlist mortality.

Methods

We studied a prospective cohort of 3168 ESKD participants (January 2009 to June 2018) who self-reported functional independence in more basic self-care Activities of Daily Living (ADL) (needing help with eating, dressing, walking, grooming, toileting and bathing) and more complex instrumental ADL (IADL) (needing help using a phone, shopping, cooking, housework, washing, using transportation, managing medications and managing money). We estimated adjusted associations between functional independence (separately) and listing (Cox), waitlist mortality (competing risks) and transplant rates (Poisson).

Results

At KT evaluation, 92.4% were independent in ADLs, but only 68.5% were independent in IADLs. Functionally independent participants had a higher chance of listing for KT [ADL: adjusted hazard ratio (aHR) = 1.55, 95% confidence interval (CI) 1.30–1.87; IADL: aHR = 1.39, 95% CI 1.26–1.52]. Among KT candidates, ADL independence was associated with lower waitlist mortality risk [adjusted subdistribution HR (aSHR) = 0.66, 95% CI 0.44–0.98] and higher rate of KT [adjusted incidence rate ratio (aIRR) = 1.58, 95% CI 1.12–2.22]; the same was not observed for IADL independence (aSHR = 0.86, 95% CI 0.65–1.12; aIRR = 1.01, 95% CI 0.97–1.19).

Conclusions

Functional independence in more basic self-care ADL was associated with better KT access and lower waitlist mortality. Nephrologists, geriatricians and transplant surgeons should screen KT candidates for ADLs, and identify interventions to promote independence and improve waitlist outcomes.
Association of all-cause mortality with pre-dialysis systolic blood pressure and its peridialytic change in chronic hemodialysis patients
Authors: Zhang Hanjie , Preciado Priscila , Wang Yuedong , Meyring-Wosten Anna , Raimann Jochen G , Kooman Jeroen P , van der Sande Frank M , Usvyat Len A , Maddux Dugan , Maddux Franklin W , Kotanko Peter
Published: December 2019

Background

Pre-dialysis systolic blood pressure (pre-HD SBP) and peridialytic SBP change have been associated with morbidity and mortality among hemodialysis (HD) patients in previous studies, but the nature of their interaction is not well understood.

Methods

We analyzed pre-HD SBP and peridialytic SBP change (calculated as post-HD SBP minus pre-HD SBP) between January 2001 and December 2012 in HD patients treated in US Fresenius Medical Care facilities. The baseline period was defined as Months 4–6 after HD initiation, and all-cause mortality was noted during follow-up. Only patients who survived baseline and had no missing covariates were included. Censoring events were renal transplantation, modality change or study end. We fitted a Cox proportional hazard model with a bivariate spline functions for the primary predictors (pre-HD SBP and peridialytic SBP change) with adjustment for age, gender, race, diabetes, access-type, relative interdialytic weight gain, body mass index, albumin, equilibrated normalized protein catabolic rate and ultrafiltration rate.

Results

A total of 172 199 patients were included. Mean age was 62.1 years, 61.6% were white and 55% were male. During a median follow-up of 25.0 months, 73 529 patients (42.7%) died. We found that a peridialytic SBP rise combined with high pre-HD SBP was associated with higher mortality. In contrast, when concurrent with low pre-HD SBP, a peridialytic SBP rise was associated with better survival.

Conclusion

The association of pre-HD and peridialytic SBP change with mortality is complex. Our findings call for a joint, not isolated, interpretation of pre-HD SBP and peridialytic SBP change.
Endoscopic Endonasal Surgery for Resection of Giant Craniopharyngioma in a Toddler—Multimodal Presurgical Planning, Surgical Technique, and Management of Complications: 2-Dimensional Operative Video
Authors: Fernandez-Miranda Juan C , Hwang Peter , Grant Gerald
Published: December 2019

A 2-yr-old patient with a giant craniopharyngioma presented with seizures and panhypopituitarism. The lesion was initially approached at an outside institution with a transfrontal cyst fenestration, but progressive growth occurred later. Multiple management options were considered; we recommended an endoscopic endonasal approach with the goal of maximal safe resection.

Virtual reality simulation and 3-dimensional printing were employed to evaluate whether the absence of pneumatization of the sinuses and the overall size of the nasal cavity could preclude effective surgical access. Our lab results suggested the binostril approach was feasible.

A wide surgical exposure was performed from planum sphenoidale to clivus and from orbit to orbit. After removing the large calcified tumor portion, we found an accurate plane of dissection between tumor capsule, hypothalami, and visual pathways. By the end of resection, arterial bleeding was encountered secondary to an avulsion of the posterior communicating artery from the posterior cerebral artery. An angled aneurysm clip was placed with a single-shaft applier to secure the site of injury without narrowing the parent artery. Immediate and delayed magnetic resonance imaging and computed tomography angiography studies showed gross total resection, no stroke, and no pseudoaneurysm formation.

On postoperative day 9, patient developed neurological decline and pneumocephalus secondary to necrotic nasoseptal flap. Two endonasal repairs with a lateral nasal wall flap were attempted with no success. A temporoparietal fascia flap was then harvested and transposed from the temporal to the pterygopalatine fossa to successfully repair the skull base defect. The patient has made an extraordinary recovery with no neurological sequalae.

The patient's parents provided consent for the procedure and use of intraoperative photos and videos for academic purposes. Institutional Review Board approval was not required.
The screening and management of newborns at risk for low blood glucose
Authors: Narvey Michael R , Marks Seth D
Published: December 2019

Hypoglycemia in the first hours to days after birth remains one of the most common conditions facing practitioners across Canada who care for newborns. Many cases represent normal physiologic transition to extrauterine life, but another group experiences hypoglycemia of longer duration. This statement addresses key issues for providers of neonatal care, including the definition of hypoglycemia, risk factors, screening protocols, blood glucose levels requiring intervention, and managing care for this condition. Screening, monitoring, and intervention protocols have been revised to better identify, manage, and treat infants who are at risk for persistent, recurrent, or severe hypoglycemia. The role of dextrose gels in raising glucose levels or preventing more persistent hypoglycemia, and precautions to reduce risk for recurrence after leaving hospital, are also addressed. This statement differentiates between approaches to care for hypoglycemia during the ‘transitional’ phase—the first 72 hours post-birth—and persistent hypoglycemia, which occurs or presents for the first time past that point.
Les besoins en fer jusqu’à l’âge de deux ans
Authors: Unger Sharon L , Fenton Tanis R , Jetty Radha , Critch Jeff N , O’connor Deborah L
Published: December 2019

Le fer est un micronutriment essentiel à la synthèse de l’hémoglobine, au développement du système nerveux central et à la protection contre les infections. La petite enfance est une période de vulnérabilité au cours de laquelle la carence en fer est liée à une perturbation du développement neurologique. Une situation socioéconomique défavorisée, une naissance prématurée et un régime alimentaire sous-optimal sont des facteurs de risque de carence en fer. Une surcharge de fer attribuable à une insuffisance du mécanisme d’excrétion du fer peut également se manifester. Il est capital d’offrir un apport en fer suffisant aux nourrissons jusqu’à l’âge de deux ans.