The G protein-gated potassium current I(K,ACh) is constitutively active in patients with chronic atrial fibrillation

Background— The molecular mechanism of increased background inward rectifier current (IK1) in atrial fibrillation (AF) is not fully understood. We tested whether constitutively active acetylcholine (ACh)-activated IK,ACh contributes to enhanced basal conductance in chronic AF (cAF). Methods and Results— Whole-cell and single-channel currents were measured with standard voltage-clamp techniques in atrial myocytes from patients with sinus rhythm (SR) and cAF. The selective IK,ACh blocker tertiapin was used for inhibition of IK,ACh. Whole-cell basal current was larger in cAF than in SR, whereas carbachol (CCh)-activated IK,ACh was lower in cAF than in SR. Tertiapin (0.1 to 100 nmol/L) reduced IK,ACh in a concentration-dependent manner with greater potency in cAF than in SR (−logIC50: 9.1 versus 8.2; P<0.05). Basal current contained a tertiapin-sensitive component that was larger in cAF than in SR (tertiapin [10 nmol/L]-sensitive current at −100 mV: cAF, −6.7±1.2 pA/pF, n=16/5 [myocytes/patients] versus SR, −1.7±0.5 pA/pF, n=24/8), suggesting contribution of constitutively active IK,ACh to basal current. In single-channel recordings, constitutively active IK,ACh was prominent in cAF but not in SR (channel open probability: cAF, 5.4±0.7%, n=19/9 versus SR, 0.1±0.05%, n=16/9; P<0.05). Moreover, IK1 channel open probability was higher in cAF than in SR (13.4±0.4%, n=19/9 versus 11.4±0.7%, n=16/9; P<0.05) without changes in other channel characteristics. Conclusions— Our results demonstrate that larger basal inward rectifier K+ current in cAF consists of increased IK1 activity and constitutively active IK,ACh. Blockade of IK,ACh may represent a new therapeutic target in AF

Metabolic costs of bat echolocation in a non-foraging context support a role in communication

The exploitation of information is a key adaptive behavior of social animals, and many animals produce costly signals to communicate with conspecifics. In contrast, bats produce ultrasound for auto-communication, i.e., they emit ultrasound calls and behave in response to the received echo. However, ultrasound echolocation calls produced by non-flying bats looking for food are energetically costly. Thus, if they are produced in a non-foraging or navigational context this indicates an energetic investment, which must be motivated by something. We quantified the costs of the production of such calls, in stationary, non-foraging lesser bulldog bats (Noctilio albiventris) and found metabolic rates to increase by 0.021 ± 0.001 J/pulse (mean ± standard error). From this, we estimated the metabolic rates of N. albiventris when responding with ultrasound echolocation calls to playbacks of echolocation calls from familiar and unfamiliar conspecific as well as heterospecific bats. Lesser bulldog bats adjusted their energetic investment to the social information contained in the presented playback. Our results are consistent with the hypothesis that in addition to orientation and foraging, ultrasound calls in bats may also have function for active communication

Shear modulus of the hadron-quark mixed phase

Robust arguments predict that a hadron-quark mixed phase may exist in the cores of some "neutron" stars. Such a phase forms a crystalline lattice with a shear modulus higher than that of the crust due to the high density and charge separation, even allowing for the effects of charge screening. This may lead to strong continuous gravitational-wave emission from rapidly rotating neutron stars and gravitational-wave bursts associated with magnetar flares and pulsar glitches. We present the first detailed calculation of the shear modulus of the mixed phase. We describe the quark phase using the bag model plus first-order quantum chromodynamics corrections and the hadronic phase using relativistic mean-field models with parameters allowed by the most massive pulsar. Most of the calculation involves treating the "pasta phases" of the lattice via dimensional continuation, and we give a general method for computing dimensionally continued lattice sums including the Debye model of charge screening. We compute all the shear components of the elastic modulus tensor and angle average them to obtain the effective (scalar) shear modulus for the case where the mixed phase is a polycrystal. We include the contributions from changing the cell size, which are necessary for the stability of the lower-dimensional portions of the lattice. Stability also requires a minimum surface tension, generally tens of MeV/fm^2 depending on the equation of state. We find that the shear modulus can be a few times 10^33 erg/cm^3, two orders of magnitude higher than the first estimate, over a significant fraction of the maximum mass stable star for certain parameter choices.Comment: 22 pages, 12 figures, version accepted by Phys. Rev. D, with the corrections to the shear modulus computation and Table I given in the erratu

Sexual Dimorphism in the Attachment Ability of Leptinotarsa decemlineata Say (Coleoptera, Chrysomelidae) on Rough Substrata

Leptinotarsa decemlineata lebt oligophag ausschließlich auf Vertretern der Solanaceae, insbesondere Solanum spp. (Radcliffe 1982). Die herbivore Spezies ist fähig, erfolgreich auf den unbehaarten, behaarten und glandulär behaarten Blattoberflächen der Nachtschattengewächse zu haften, sich fortzubewegen und zu leben. Dazu verhelfen paarige Krallen und Hafthaarkissen an den Tarsen (Rivnay 1928). Das ausgesprochen gute Haftvermögen und die Substratanpassungsfähigkeit haariger Haftsysteme von Insekten sind für verschiedene Vertreter der Diptera und Coleoptera experimentell belegt (siehe Review von Gorb 2001). Stork (1980 a, b) beobachtete insbesondere bei Käfern der Familien Chrysomelidae und Coccinellidae einen ausgeprägten Sexualdimorphismus der tarsalen Hafthaare. Schanz (1953) beschreibt für L. decemlineata drei verschiedene Hafthaartypen: (1) Haare mit sich asymmetrisch verjüngenden Spitzen, (2) spatelförmige Gebilde und (3) Haare mit Haftsohlen, welche nur die Männchen besitzen. Hinsichtlich der geschlechterspezifischen Unterschiede der Haftkraft auf verschieden rauen Oberflächen existieren bislang wenige quantitative Nachweise. Pelletier & Smilowitz (1987) wiesen für Männchen von L. decemlineata in Inversionsexperimenten ein außerordentliches Haftvermögen auf Glas- und Kunststoffoberflächen nach, wobei sie dessen Gründe in den maskulin-spezifischen Hafthaaren mit scheibenförmig verbreiterten Enden vermuteten. Die Fähigkeit der Männchen, an glatten Oberflächen besonders gut zu haften, wurde als eine Anpassung an die Haftung auf den glatten Oberflächen der Weibchenelytren während der Kopulation erklärt. Die meisten natürlichen Oberflächen (insbesondere Pflanzenoberflächen) sind jedoch rau. Somit besteht die Frage, ob beide Geschlechter auch eine unterschiedliche Spezialisierung der Haftsysteme für die Haftung auf rauen Substraten besitzen. Um den Einfluss unterschiedlicher Oberflächenrauhigkeiten auf die Haftsystemfunktionalität der Weibchen und Männchen von L. decemlineata zu prüfen, wurden in der vorliegenden Studie Kraftmessungen mit einzelnen Individuen auf Oberflächen mit exakt definierter Rauheit durchgeführt.The remarkable attachment ability and the adaptability to different substrates of insects‘ hairy attachment systems have been experimentally demonstrated in representatives of Diptera and Coleoptera. Many representatives from the family Chrysomelidae exhibit a distinctive sexual dimorphism in the structure of adhesive tarsal hairs. Differences in attachment ability between sexes have been previously reported for smooth substrata. In L. decemlineata, a very strong attachment ability on smooth glass and plastic surfaces has been described in males, and explained by the action of specialised mushroom-like tarsal hairs. The present study demonstrates the influence of different surface roughnesses on the attachment forces of L. decemlineata males and females. The maximum attachment force of individual beetles was measured on epoxy resin surfaces (0-12 &#956;m surface roughness) using a centrifugal force tester. On the smooth surface, no considerable differences between males and females were found, whereas, on rough surfaces, adherence of females was significantly stronger, up to twice that of males. The results indicate that the main functional trait of the adhesive system of females is its stronger specialization to rough plant surfaces

Dynamic Problems of Evolution

Evolution and growth of natural and man-made processes have impressed human beings from the very beginning. What is evolution? Is it the passage from an initial to a higher stage? What does "higher" mean in a world of many objectives? Is "higher" bound to the existence of monotonous indicators like entropy, or is it "gambling" within a predetermined combinatoric multifold of possibilities? Questions of this kind arise from the phenomena in our environment, from the spring-off of new species, but also from processes in our man-made technological world. How is the transition of basic innovation to technology and use of the corresponding products by society, what forecast can be made from increasing CO2, in the atmosphere on the impact on climate, from features of seismologic waves on future events etc. That means there is a strong connection between evolution processes and the emphasis of systems analysis as a help for strategic actions. This paper deals with general considerations about possible growth mechanisms as a base for creating valid growth models. But the main goal is to show how the parameters in growth models can be estimated using on one hand a fuzzy approach together with vector optimization and on the other hand a Bayesian approach. It can be seen that both approaches are useful and applicable and we get informations from one approach which the other one cannot give us. We studied already the growth of cracks in materials, processes well described in [10]. Preliminary results are contained in [13]. Research will be continued to identify the superposition of driving forces and of coupled systems in which oscillations can arise because of time delays between their driving-force pulses

SARS-CoV-2 infection prevalence in healthcare workers and administrative and support staff: The first-wave experience at three academic hospitals in the Tshwane district of Gauteng Province, South Africa

Background. The availability of well and functional healthcare workers (HCWs) and support staff is pivotal to a country’s ability to manage the COVID-19 pandemic effectively. While HCWs have been identified as being at increased risk for acquisition of SARS-CoV-2 infection, there is a paucity of data pertaining to South African (SA) HCW-related infection rates. Global and provincial disparities in these numbers necessitate local data in order to mitigate risks.Objectives. To ascertain the overall SARS-CoV-2 infection rates and outcomes among all hospital staff at three hospitals in the Tshwane district of Gauteng Province, SA, and further determine associations with the development of severe COVID-19 disease.Methods. This retrospective audit was conducted across three academic hospitals in the Tshwane district for the period 1 June - 31 August 2020. Deidentified data from occupational health and safety departments at each hospital were used to calculate infection rates. A more detailed analysis at one of the three hospitals included evaluation of demographics, work description, possible source of SARS-CoV-2 exposure (community or hospital), comorbidities and outcomes.Results. The period prevalence of SARS-CoV-2 infections ranged from 6.1% to 15.4% between the three hospitals, with the average period prevalence being 11.1%. The highest incidence of SARS-CoV-2 infections was observed among administrative staff (2.8 cases per 1 000 staff days), followed by nursing staff (2.7 cases per 1 000 staff days). Medical doctors had the lowest incidence of 1.1 cases per 1 000 staff days. SARS-CoV-2 infections were categorised as either possibly community or possibly healthcare facility acquired for 26.6% and 73.4% of the infections, respectively. The administrative group had the highest proportion of possible community-acquired infections (41.8%), while doctors had the lowest (6.1%). The mean age of individuals with mild and severe disease was 41 years and 46.1 years, respectively (p=0.004). The presence of comorbidities was significantly associated with severity of disease (p=0.002).Conclusions. This study highlights that hospital staff, including administrative staff, are clearly at high risk for acquisition of SARS-CoV-2 infection during a surge.

Cost-Effectiveness Analysis of Needle Arthroscopy Versus Magnetic Resonance Imaging in the Diagnosis and Treatment of Meniscal Tears of the Knee

© 2019 The Authors Purpose: To determine whether needle arthroscopy (NA) compared with magnetic resonance imaging (MRI) in the diagnosis and treatment of meniscal tears is cost-effective when evaluated over a 2-year period via patient-reported outcomes. The hypothesis is that improved diagnostic accuracy with NA would lead to less costly care and similar outcomes. Methods: A Markov model/decision tree analysis was performed using TreeAge Pro 2017 software. Patients were evaluated for degenerative and traumatic damage to the lateral/medial meniscus. Assumed sensitivities and specificities were derived from the medical literature. The direct costs for care were derived from the 2017 Medicare fee schedule and from private payer reimbursement rates. Costs for care included procedures performed for false-positive findings and for care for false-negative findings. Effectiveness was examined using the global knee injury and osteoarthritis outcome score (KOOS). Patients were evaluated over 2 years for costs and outcomes, including complications. Dominance and incremental cost-effectiveness were evaluated, and 1- to 2-way sensitivity analysis was performed to determine those variables that had the greatest effect. The consolidated economics evaluation and reporting standards checklist for reporting economic evaluations was used. Results: NA was less costly and had similar KOOS versus MRI for both the medial/lateral meniscus with private pay. Costs were less for both Medicare and private pay for medial meniscus, $780 to$1,862, and lateral meniscus, $314 to$1,256, respectively. Conclusions: Based on the reported MRI incidence of false positives with the medial meniscus and false negatives with the lateral meniscus and based on assumed standards of care, more costly care is provided when using MRI compared with NA. Outcomes were similar with NA compared with MRI. Level of Evidence: Level II, economic and decision analysis

The J_1-J_2 antiferromagnet with Dzyaloshinskii-Moriya interaction on the square lattice: An exact diagonalization study

We examine the influence of an anisotropic interaction term of Dzyaloshinskii-Moriya (DM) type on the groundstate ordering of the J_1-J_2 spin-1/2-Heisenberg antiferromagnet on the square lattice. For the DM term we consider several symmetries corresponding to different crystal structures. For the pure J_1-J_2 model there are strong indications for a quantum spin liquid in the region of 0.4 < J_2/J_1 < 0.65. We find that a DM interaction influences the breakdown of the conventional antiferromagnetic order by i) shifting the spin liquid region, ii) changing the isotropic character of the groundstate towards anisotropic correlations and iii) creating for certain symmetries a net ferromagnetic moment.Comment: 7 pages, RevTeX, 6 ps-figures, to appear in J. Phys.: Cond. Ma