Drag Reduction in Turbulent Wall-Bounded Flows of Realistic Polymer Solutions

Suspensions of DNA macromolecules (0.8 wppm, 60 kbp), modeled as finitely extensible nonlinear elastic dumbbells coupled to the Newtonian fluid, show drag reduction up to 27% at friction Reynolds number 180, saturating at the previously unachieved Weissenberg number ≃10^{4}. At a large Weissenberg number, the drag reduction is entirely induced by the fully stretched polymers, as confirmed by the extensional viscosity field. The polymer extension is strongly non-Gaussian, in contrast to the assumptions of classical viscoelastic models.

Prevalence of exercise-induced arrhythmias in young athletes with fragmented QRS pattern in lead V1

Funding Acknowledgements

Type of funding sources: None.

Background

Resting 12-lead electrocardiogram (ECG) in apparently health athletes has specific pattern, typically associate to heart remodelling in response to regular exercise. (1,2) Moreover, these adaptations were correlated to typical ventricular arrhythmias, not associated with underlying cardiac abnormalities.(3) Recently, also fragmented QRS complex in lead V1 (fQRSV1), representing right ventricular (RV) activation, seems related to training-induced RV remodelling in athletes, where its prevalence is greater.(4)

Purpose

Evaluate presence of fQRSV1pattern at resting ECG in a population of young athletes and its relationship with training-associated structural heart adaptations and exercise-induced ventricular arrhythmias.

Methods

This study retrospectively enrolled subjects who consecutively undergo to annual pre-participation screening and also to transthoracic echocardiography assessment, from January 2015 to September 2020. For each participant, medical history, physical examination, resting ECG, maximal standardized exercise test and echocardiographic evaluation were collected. All ECG were reviewed by two independent physicians to evaluate fQRSV1 pattern.

Results

684 young athletes (mean age 14.87±1.96 years, 36% female) were included and the overall prevalence of fQRSV1was 27%. Figure 1 shows an example of fQRSV1 pattern. Principal subject characteristics and evaluations data are shown in Table 1. fQRSV1 subjects presented a significantly wider QRS interval (p=0.004) and lower heart rate at rest (p=0.001). Exercise workload expressed in METs and exercise duration were higher in subjects with fQRSV1 (p=0.002 and p=0.023, respectively). Echocardiographic data showed that subjects with fQRSV1differ in morphological and functional right ventricular (RV) characteristics, especially had a higher indexed RV end diastolic diameter (p=0.019) and higher TAPSE (p=0.013). Patients with fQRSV1did not show an increased occurrence of supraventricular or ventricular arrhythmias, regardless of morphology, neither for isolated nor for repetitive events.

Conclusion

Overall prevalence of fQRSV1 pattern in young athletes is comparable with the one studied in other population of adult athletes in previous studies. Adolescent athletes with fQRSV1 present structural heart characteristic that differ from subjects without this ECG pattern, especially in RV feature. No differences in prevalence of any type of exercise-induced arrhythmias was shown, especially in common ventricular arrhythmias consistent with origin from the right ventricular outflow tract, previously described in healthy athletes.

Analysis of the overshoot of the respiratory exchange ratio during recovery from maximal exercise testing in patients with heart failure with reduced ejection fraction

Funding Acknowledgements

Type of funding sources: None.

Background

Transient increases (overshoot) in respiratory gas analysis parameters have been observed during recovery after maximal cardiopulmonary exercise testing (CPET), but their clinical significance is not clearly understood.(1) Respiratory exchange ratio (RER) at peak exercise (RER peak) is an objective index to evaluate exercise effort.(2) Moreover, overshoot phenomenon of the RER is commonly observed during recovery from CPET.(3) On the other hand, the overshoot of some CPET parameters during recovery has been found reduced in magnitude in patients with heart failure with reduced ejection fraction (HFrEF).(4)

Purpose

We aimed to examine the clinical significance of RER behaviour after a maximal effort and to understand if this could help in the classification of specific subpopulations of patients.

Methods

In this cross-sectional study patients with HFrEF who underwent functional evaluation with CPET between 2017 and 2020 were included. A maximal CPET with at least two minute of recorded recovery was performed and always RER achieved at peak of exercise was higher than 1.10. RER behaviour during recovery has been evaluated, assessing its maximal value (RER max), the magnitude of the RER overshoot (RER mag), the time to reach RER max during recovery and the linear slope of increase of the RER from peak exercise to RER max (RER slope). Additionally, subgroup analyses were performed.

Results

80 patients with HFrEF were included. Figure 1 shows an example of analyzed RER overshoot parameters. Principal clinical characteristics, CPET parameters and recovery metrics are shown in Table I. Significant correlations between RER recovery parameters and prognostically relevant CPET indices of cardiorespiratory fitness and efficiency were found, especially between RER mag and VO2peak (r=0.333; p=0.03), and RER mag and VE/VCO2slope (r= - 0.494; p<0.01). At multiple linear regression, VE/VCO2slope was the only determinant of RER mag. Patients in a more severe disease state (Ventilatory class III/IV and Weber’s classes C/D) present RER overshoot parameters significantly reduced compared with those in a light/moderate disease state (Ventilatory class I/II and Weber’s classes A/B), (all p=0.01).

Conclusions

The overshoots phenomena of RER during recovery from maximal exercise were associated with patients’ cardiopulmonary function, and their magnitudes were less prominent in HFrEF patients with a lower cardiorespiratory efficiency. Thus, the evaluation of the overshoot during recovery from CPET might represent an interesting clinical and prognostic tool in patients with HFrEF.

Effect of bariatric surgery on blood pressure and workload-indexed pressure during submaximal and maximal exercise

Funding Acknowledgements

Type of funding sources: None.

Background

Obesity is a disease characterized by an increase of resting blood pressure and by an increased risk of developing hypertension and cardiovascular events. Exaggerated blood pressure during exercise increases risk of cardiovascular events independently from the baseline blood pressure levels.

Purpose

to evaluate the blood pressure response and the Workload-indexed blood pressure, during a cardio-pulmonary exercise test (CPET) before and after bariatric surgery (BS).

Methods

257 patients with severe obesity performed maximal incremental CPET one month before and six months after BS under the same experimental protocol. The systolic blood pressure was measured at rest (SBPrest), at the submaximal effort (SBPsubmax) at the same exercise intensity (3 METs), at the exercise peak (SBP max) and lastly in the recovery phase (SBPrec). The submaximal and maximal Workload-indexed Sistolic Blood Pressure (W-SBPsubmax and W-SBPmax, respectively) were calculated with the formula: ΔBP/ΔMETs. Diastolic blood pressure was analysed at rest (DBPrest) and during the recovery phase (DBPrec).

Results

Age was on average 45 ± 10.3 years, BMI before BS was equal to 43.9 ± 6.4 Kg/m2 and 73.5% were females. After BS, there was a significant weight loss (-25.9 ± 6.2%). SBPrest and DBPrest decrease significantly after BS (ΔSBP: -10.2 ± 15.8 and -5.2 ± 11.6 mmHg; p <0.001, respectively), also when considering percentage variation of pre BS values (ΔSBP%: -7.4 ±12.3% and -5.9 ± 15.9%; p< 0.001, respectively). Submaximal and maximal systolic blood pressure showed significant reduction after BS both as ΔSBP (-15.0 ± 19.7 mmHg and -10.3 ± 25.1mmHg; p < 0.001, respectively) and ΔSBP% (-9.6 ± 13.0% and -5.0 ± 14.0%; p < 0.001, respectively). Furthermore, W-SBP decreased significantly during submaximal exercise (-3.0 ± 12.2 mmHg/METs; p 0.001) and at peak of exercise (-2.1 ± 4.8 mmHg/METs; p < 0.001). Lastly, also systolic and diastolic blood pressure during the recovery phase showed a significant reduction (-7.5 ± 7.0 mmHg and -3.3 ± 6.0 mmHg; p < 0.001). A Spearman’s correlation analysis showed a significant but weak correlation between ΔSBP%submax and % of weight loss (rho = 0.138; p = 0.027).

Conclusions

After BS, a marked reduction of all blood pressure values was detectable in all phases of CPET. W-SBPsubmax and W-SBPmax, as expression of load independent pressure response, decreased significantly. The reduction in the submaximal blood pressure was significantly but only weakly correlated with changes in body weight, suggesting its substantial independence from weight loss. These findings also support a potential role of CPET in detecting, high risk patients and adequate treatment effectiveness in patients with severe obesity.

Abstract Figure. Exercise SBP before and after BS

Single-phase anaerobic digestion of the organic fraction of municipal solid waste without dilution: Reactor stability and process performance of small, decentralised plants

Currently, centralised plants are the most favoured approach for the anaerobic treatment of the organic fraction of municipal solid waste (OFMSW). However, centralised solutions imply certain environmental impacts, which prevent large-scale implementation of the anaerobic digestion (AD). As a result, we are digesting <5% of organic waste both in Europe and the USA even today. Pursuing the criteria for maximising the balance between profit and impacts, an innovative layout with the ultimate goal of promoting the use of small, decentralised AD plants is proposed. In this study, source-separated OFMSW (SS-OFMSW) was treated in a mesophilic plug flow reactor by applying an atypical combination of conditions such as high SS-OFMSW solid content (214.5 g·kg^-1), high organic loading rate (6.2 kg VS·m^-3·d^-1), and no dilution or co-substrate addition. A suitable and an efficient mixing system is essential to control the process. Accordingly, the process was stable in a single-stage reactor, in the absence of digestate recirculation, obtaining specific gas production of 0.67 m³·kg^-1 VS in terms of biogas and 0.41 m³·kg^-1 VS in terms of methane. High reactor volume exploitation and small plant construction were feasible, reaching a gas production rate of 4.5 m³·m^-3 d^-1. The estimated costs in terms of capital and operating expenditure are expected to realize gross economic sustainability of full-scale installation.

The Fluid-Dynamics of Endo Vascular Aneurysm Sealing (EVAS) System failure

Purpose

The main objective of this work is to investigate hemodynamics phenomena occurring in EVAS (Endo Vascular Aneurysm Sealing), to understand if and how they could lead to type 1a endoleaks and following re-intervention. To this aim, methods based on computational fluid mechanics are implemented as a tool for checking the behavior of a specific EVAS configuration, starting from the post-operative conditions. Pressure and velocity fields are detailed and compared, for two configurations of the Nellix, one as attained after correct implantation and the other in pathological conditions, as a consequence of migration or dislocation of endobags.

Methods

The computational fluid dynamics (CFD) approach is used to simulate the behavior of blood within a segment of the aorta, before and after the abdominal bifurcation. The adopted procedure allows reconstructing the detailed vascular geometry from high-resolution computerized tomography (CT scan) and generating the mesh on which the equations of fluid mechanics are discretized and solved, in order to derive pressure and velocity field during heartbeats.

Results

The main results are obtained in terms of local velocity fields and wall pressures. Within the endobags, velocities are usually quite regular during the whole cardiac cycle for the post-implanted condition, whereas they are more irregular for the migrated case. The largest differences among the two cases are observed in the shape and location of the recirculation region in the rear part of the aorta and the region between the endobags, with the formation of a gap due to the migration of one or both of the two. In this gap, the pressure fields are highly different among the two conditions, showing pressure peaks and pressure gradients at least four times larger for the migrated case in comparison to the post-implanted condition.

Conclusions

In this paper, the migration of one or both endobags is supposed to be related to the existing differential pressures acting in the gap formed between the two, which could go on pushing the two branches one away from the other, thus causing aneurysm re-activation and endoleaks. Regions of flow recirculation and low-pressure drops are revealed only in case of endobag migration and in presence of an aneurysm. These regions are supposed to lead to possible plaque formation and atherosclerosis.

Exact regularized point particle (ERPP) method for particle-laden wall-bounded flows in the two-way coupling regime

The Exact Regularized Point Particle (ERPP) method is extended to treat the interphase momentum coupling between particles and fluid in the presence of walls by accounting for the vorticity generation due to the particles close to solid boundaries. The ERPP method overcomes the limitations of other methods by allowing the simulation of an extensive parameter space (Stokes number, mass loading, particle-to-fluid density ratio and Reynolds number) and of particle spatial distributions that are uneven (few particles per computational cell). The enhanced ERPP method is explained in detail and validated by considering the global impulse balance. In conditions when particles are located close to the wall, a common scenario in wall-bounded turbulent flows, the main contribution to the total impulse arises from the particle-induced vorticity at the solid boundary. The method is applied to direct numerical simulations of particle-laden turbulent pipe flow in the two-way coupling regime to address the turbulence modulation. The effects of the mass loading, the Stokes number and the particle-to-fluid density ratio are investigated. The drag is either unaltered or increased by the particles with respect to the uncoupled case. No drag reduction is found in the parameter space considered. The momentum stress budget, which includes an extra stress contribution by the particles, provides the rationale behind the drag behaviour. The extra stress produces a momentum flux towards the wall that strongly modifies the viscous stress, the culprit of drag at solid boundaries.

The ESC ACCA EAPCI EORP acute coronary syndrome ST-elevation myocardial infarction registry

Aims 

The Acute Cardiac Care Association (ACCA)–European Association of Percutaneous Coronary Intervention (EAPCI) Registry on ST-elevation myocardial infarction (STEMI) of the EurObservational programme (EORP) of the European Society of Cardiology (ESC) registry aimed to determine the current state of the use of reperfusion therapy in ESC member and ESC affiliated countries and the adherence to ESC STEMI guidelines in patients with STEMI.

Methods and results 

Between 1 January 2015 and 31 March 2018, a total of 11 462 patients admitted with an initial diagnosis of STEMI according to the 2012 ESC STEMI guidelines were enrolled. Individual patient data were collected across 196 centres and 29 countries. Among the centres, there were 136 percutaneous coronary intervention centres and 91 with cardiac surgery on-site. The majority of centres (129/196) were part of a STEMI network. The main objective of this study was to describe the demographic, clinical, and angiographic characteristics of patients with STEMI. Other objectives include to assess management patterns and in particular the current use of reperfusion therapies and to evaluate how recommendations of most recent STEMI European guidelines regarding reperfusion therapies and adjunctive pharmacological and non-pharmacological treatments are adopted in clinical practice and how their application can impact on patients’ outcomes. Patients will be followed for 1 year after admission.

Conclusion 

The ESC ACCA-EAPCI EORP ACS STEMI registry is an international registry of care and outcomes of patients hospitalized with STEMI. It will provide insights into the contemporary patient profile, management patterns, and 1-year outcome of patients with STEMI.

Pericardial fat, insulin resistance, and left ventricular structure and function in morbid obesity

BACKGROUND AND AIM

Morbid obesity is often accompanied by insulin resistance and increased ectopic fat surrounding the heart. We evaluated the relation of epicardial and pericardial fat with insulin resistance and left ventricular (LV) structure and function.

METHODS AND RESULTS

Epicardial and pericardial fat thicknesses were determined at 2-dimensional echocardiography in 80 morbid obese subjects [age 42 ± 12 years, 31% men, body mass index (BMI) 44.4 ± 7 kg/m(2)]. LV hypertrophy (LV mass ≥51 g/m(2.7)), inappropriately high LV mass for a given cardiac workload (observed vs predicted LV mass >128%), and stress-adjusted LV mid-wall fractional shortening were determined. Pericardial and epicardial fat thicknesses had direct associations with BMI (r = 0.40 and 0.45, both p < 0.01) and waist circumference (r = 0.37 and 0.45, both p < 0.01). Pericardial (partial r = 0.35, p < 0.01), but not epicardial fat thickness (partial r = 0.05, p = n.s.), was correlated with homeostasis model assessment-insulin resistance after adjustment for BMI. Pericardial fat also had a strong negative correlation with mid-wall fractional shortening (p = 0.01) and a positive one with inappropriately high LV mass (p < 0.01), while no such relation was found for epicardial fat (both p = n.s.). Independently of age, male sex, BMI, and anti-hypertensive treatment, pericardial fat thickness had an independent positive association with inappropriately high LV mass (β = 0.29, p = 0.02), and a negative one with stress-adjusted mid-wall fractional shortening (β = -0.26, p = 0.04).

CONCLUSIONS

Pericardial fat thickness is associated with insulin resistance, inappropriately high LV mass, and LV systolic dysfunction in obese individuals. Findings from this study confirm the existence of a connection between insulin resistance, cardiac ectopic fat deposition and cardiac dysfunction in morbid obesity.

Quantum heat fluctuations of single-particle sources

Optimal single electron sources emit regular streams of particles, displaying no low-frequency charge current noise. Because of the wave packet nature of the emitted particles, the energy is, however, fluctuating, giving rise to heat current noise. We investigate theoretically this quantum source of heat noise for an emitter coupled to an electronic probe in the hot-electron regime. The distribution of temperature and potential fluctuations induced in the probe is shown to provide direct information on the single-particle wave function properties and display strong nonclassical features.

Environmental microbial contamination in dental setting: a local experience

INTRODUCTION

Patients and operators are exposed during dental practice to an infective risk, which derives especially from microorganisms suspended in aerosols. Environmental microbiological monitoring in dental settings represents a good instrument to detect critical situations.

METHODS

In order to investigate environmental microbial contamination level in a local reality, we analyzed water, air and surfaces samples of a community-based dental facility by using protocol and threshold values proposed in a recent multicenter study carried out by the Italian Society of Hygiene, Preventive Medicine and Public Health (S.It.I.) working group "Hygiene in Dentistry". Microbial contamination was assessed in the same room for 4 non-consecutive weeks during all the five working days, before and at the end of the daily activity. Air was sampled also during clinical activity, through both active and passive sampling systems.

RESULTS

Contamination of water showed a decrease during activities, while a decrease in air contamination was registered only at the end of the day. Passive sampling values resulted more often above threshold values adopted. At the same time, surfaces contamination increases at the end of the activity. It seems that in the dental clinic analyzed microbial buildup represents the higher critical element. No differences have been registered among the different days of the week.

DISCUSSION

Our study highlights the need to improve disinfection procedures and air treatment systems in the considered environment. Microbiological monitoring could represent an important element to detect the presence of risk factors and to adopt control measures.

[Stomatologic approach in patients with congenital coagulation deficit]

BACKGROUND

The purpose of the present paper was to resolve postoperative bleeding after oral surgery in patients with congenital coagulative defects, avoid transfusion of clotting factors and improve the patient's quality of life.

METHODS

Since 1988, 1598 oral surgery procedures have been performed on patients with congenital coagulative defects treated with a protocol including pre- and postoperative tranexamic acid rinses.

RESULTS

The use of tranexamic acid mouth washing has obtained effective hemostasis in 86% of cases and only 4% of surgical procedures required clotting factor transfusions.

CONCLUSIONS

The results suggest that mouth washing with tranexamic acid prevents excessive oral bleeding in patients with congenital deficit of the coagulation system. Furthermore, a total elimination of the granulation tissue, that reduces the possibility of activation of the fibrinolytic mechanism, is also important.

[A health education program for the prevention of heart diseases carried out in a population in Calabria]

BACKGROUND

To evaluate the behaviour and knowledge of students on cardiovascular risk factors and to programme a campaign for the prevention of cardiovascular diseases.

METHODS

All students attending the last year of the secondary school of this province answered a questionnaire. An educational campaign followed the analysis of the questionnaire.

RESULTS

The analysis of 3675 questionnaires shows that almost all students were between 18 and 20; 16% of males (m) and 7.4% of females (f) were overweight; 1.5% and 0.4% respectively were obese; 88.8% of m and 44% of were doing physical activity; 32.4% of m and 26.8% of f were cigarette smokers. Knowledge about cardiovascular risk factors were poor. Development of the prevention campaign. In the school districts four seminars were organized to discuss about cardiovascular prevention with science teachers of the province, using audiovisual materials. The same teachers devote 4-6 hours to the same matters during school lessons. In the next months conferences destined to the population of the province will be organized.

CONCLUSIONS

This program allows to promote health education in the whole population, through the students, with a low cost.

[Diltiazem in paroxysmal supraventricular tachycardia: electrocardiographic findings at termination]

The effects of diltiazem hydrochloride (0.3 mg/kg i.v. over 2 min.) was studied by continuous electrocardiographic monitoring in 60 patients. Conversion to sinus rhythm was achieved in 55 patients (91%). Electrocardiographic findings were: undisturbed sinus rhythm in 20 patients; A-V junctional rhythm in 4 patients; complex ventricular arrhythmias (ventricular tachycardia or complex VPCs) in 19 patients. Patients with complex ventricular arrhythmias were matched against patients with normal sinus rhythm, with respect to the following parameters: age, sex, heart disease, tachycardia duration, tachycardia cycle length, sinus cycle length, pre- and post-infusion blood pressure. No differences between the two groups of patients were found. Ventricular arrhythmias occurring at the termination of supraventricular tachycardia are difficult to explain. Nevertheless, these arrhythmias are not associated with organic heart disease. They could be the expression of triggered activity.

Toxic polyneuropathy of shoe workers in Italy. A clinical, neurophysiological and follow-up study

Cases of polyneuropathy due to exposure to industrial solvents have been studied at several shoe factories in the province of Siena. After the screening of 654 employees 98 verified cases were detected. Of these, 16 were rated as moderate to severe, 45 as mild, and 37 were minimally involved but with characteristic electrodiagnostic abnormalities. Follow-up study in 53 patients showed that neurological signs and symptoms as well as electrodiagnostic abnormalities continued for years in several patients. In addition, after a year's observation, some patients showed signs of central nervous system dysfunction such as spasticity of the lower limbs and increased deep tendon reflexes. High percentages of commercial n-hexane were found in all the samples of glues and solvents collected from home-workers and from factories where cases of polyneuropathy occurred.

[Protective effect against bacterial plaque accumulation of a mouthwash containing cetylpyridinium]

A mouthwash containing 0.05% cetylpyridium led to a marked reduction in the accumulation of bacterial plaque in a double-blind cross-over trial on 40 subjects. The preparation is thus a sound mean for the prevention of caries and periodontal disease. Its tolerance and subjective satisfaction were excellent.