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Presentation of results of non-stenting treatment versus endoscopic stenting placement in gastric staple leaks after laparoscopic sleeve gastrectomy (LSG).Between January 2007 and August 2020, 1371 eligible patients underwent LSG. After gastric leak detection, patients were classified into treatment groups A (endoscopic stent placement) and B (non-stenting management). Overall hospital stay, the time to complete gastric leak resolution and the incidence of further operative management constituted the main outcome measures. Statistical analysis included descriptive statistics and linear regression tests as needed.A total of 27 patients (19 F/8 M, median age: 44.8 years (range: 36-58) with median preoperative BMI: 43.5 kg/mConservative, non-stenting treatment of staple line leaks after LSG is feasible and is associated with superior results in terms of hospital say and leak resolution in comparison to endoscopic stenting.

This paper concentrates on the fundamental concepts of entropy, information and divergence to the case where the distribution function and the respective survival function play the central role in their definition. The main aim is to provide an overview of these three categories of measures of information and their cumulative and survival counterparts. It also aims to introduce and discuss Csiszár's type cumulative and survival divergences and the analogous Fisher's type information on the basis of cumulative and survival functions.

This report aims to present a rare case of a common carotid artery (CCA) pseudoaneurysm with a concomitant internal carotid artery (ICA) stenosis that were treated with a hybrid technique. This strategy included the retrograde placement of a CCA covered stent under ICA clamping followed by standardized carotid endarterectomy. The technique will be discussed and compared with other possible treatments.

Background Optimization of treatment with biologics is currently an unmet need for patients with ulcerative colitis (UC). Real-world studies provide neutral estimates of drug efficacy and safety within unselected patient populations and allow for the recognition of specific characteristics that affect response to therapy. Aims We aimed to depict the efficacy of vedolizumab in patients with UC in a real-world setting and identify prognosticators of improved outcomes. Methods Patients with active UC who commenced treatment with vedolizumab were prospectively followed up. Patient-reported outcomes (PROs) and clinical/endoscopic-reported outcomes were recorded at baseline and at weeks 14 and 54. Predefined endpoints of early and persistent efficacy were analyzed against clinical characteristics to identify prognostic factors for response. Results We included 96 patients (anti-TNF-exposed = 38.5%). At week 14, 73 patients (76%) had clinical response and 54 (56.3%) clinical remission. At week 54, the primary endpoint of vedolizumab persistence was met by 72 patients (75%), whereas steroid-free clinical remission by 59.4%. Among patients who had endoscopy, rates for mucosal healing (Mayo endoscopic score of 0) were 29.8% at week 14 and 44.6% at week 54, respectively. Vedolizumab treatment led to significant improvements in quality of life. Corticosteroid-refractory or anti-TNF-refractory disease, articular manifestations, and high baseline UC-PRO2 were associated with decreased efficacy of vedolizumab in the primary and secondary outcomes. Conclusions Vedolizumab is characterized by high efficacy and long-term treatment persistence in UC. More aggressive disease, as indicated by refractoriness to steroids or anti-TNFs and elevated baseline PROs, may predict suboptimal response and help pre-treatment prognostic stratification of patients. Supplementary Information The online version contains supplementary material available at 10.1007/s10620-021-06907-5.

Background The continuously increasing survivorship of female breast cancer makes the monitoring and improvement of patients’ quality of life ever so important. While globally there is a growing body of research on health-related quality of life 1 year after surgical treatment for non-metastatic breast cancer, up-to-date information regarding Greek patients is scarce. Objective To measure the level of QoL of non-metastatic BC survivors in Greece 1 year after surgery. Methods A sample of 200 female breast cancer survivors aged 18 to 75, who followed up as outpatients in five public hospitals were included in this cross-sectional study. All recruited patients agreed to participate in the study (100% response rate). Quality of life data were collected through the EORTC QLQ-C30 as well as BR23 questionnaires. Results Cronbach’s alpha for all scales of the two questionnaires was from 0.551 to 0.936 indicating very good reliability. According to the Multiple Linear Regression, older patients showed a lower future perspective (p = .031), with those living in rural areas, which was associated with more financial difficulties (p = .001). Women with tertiary education and those who had been hospitalized in a university hospital recorded better on global health status (p = .003 and .000 respectively). Patients who underwent chemotherapy reported better scores in the emotional function sub-scale (p = .025). Women with reconstruction and at least one complication appeared to have significantly better scores in future perspective and social function (p = .005, .002 respectively). Conclusions Breast cancer survivors were found to have an overall good quality of life, functioning/symptoms scores and were satisfied with the provided care.

BACKGROUND AND AIMS: There is a need to evaluate the benefit-risk ratio of current therapies in inflammatory bowel disease (IBD) patients to provide the best quality of care. The primary objective of I-CARE (IBD Cancer and serious infections in Europe) was to assess prospectively safety concerns in IBD, with specific focus on the risk of cancer/lymphoma and serious infections in patients treated with anti-tumor necrosis factor and other biologic monotherapy as well as in combination with immunomodulators.METHODS: I-CARE was designed as a European prospective longitudinal observational multicenter cohort study to include patients with a diagnosis of Crohn's disease, ulcerative colitis, or IBD unclassified established at least 3 months prior to enrollment.RESULTS: A total of 10,206 patients were enrolled between March 2016 and April 2019, including 6169 (60.4%) patients with Crohn's disease, 3853 (37.8%) with ulcerative colitis, and 184 (1.8%) with a diagnosis of IBD unclassified. Thirty-two percent of patients were receiving azathioprine/thiopurines, 4.6% 6-mercaptopurine, and 3.2% methotrexate at study entry. At inclusion, 47.3% of patients were treated with an anti-tumor necrosis factor agent, 8.8% with vedolizumab, and 3.4% with ustekinumab. Roughly one-quarter of patients (26.8%) underwent prior IBD-related surgery. Sixty-six percent of patients had been previously treated with systemic steroids. Three percent of patients had a medical history of cancer prior to inclusion and 1.1% had a history of colonic, esophageal, or uterine cervix high-grade dysplasia.CONCLUSIONS: I-CARE is an ongoing investigator-initiated observational European prospective cohort study that will provide unique information on the long-term benefits and risks of biological therapies in IBD patients. (EudraCT, Number: 2014-004728-23; ClinicalTrials.gov, Number: NCT02377258).

This paper is aimed to present a robust extension of the classical Rao test statistic, in the context of composite likelihood ideas and methods. The Rao-type test statistics are defined on the basis of the composite minimum power divergence estimators instead of the composite maximum likelihood estimator. These Rao-type test statistics are used to test simple and composite null hypotheses. Their performance is evaluated in terms of a simulation study which concentrates to the robustness and the comparison of the Rao-type tests with the respective Wald-type tests considered in Castilla et al. (Entropy 20:18, 2018). The proposed here procedures are developed on the basis of the restricted composite minimum density power divergence estimators which are also discussed for the sake of completeness.

In this paper we employ the closed-form of the Adaptive Length Scale Model (ALS-C) [Ghosh et al., "A new model for dilute polymer solutions in flows with strong extensional components", J. Rheol. 46, 1057–1089 (2002)] and we investigate its characteristics and potential to more accurately capture pressure-drop in contraction flows of viscoelastic fluids. The ALS-C model was originally derived based on purely homogeneous elongational flows in order to model coil-stretch hysteresis. However, in its originally proposed form we reveal a number of numerical issues which have not been analysed previously and are reported here considering both standard rheological flows, simple channel flows and complex flows within a 4:1 contraction. We demonstrate a new approach for evaluating the instantaneous change in the adaptive length scale as a result of instantaneous changes in the flow field, overcoming the need to employ other root-finding approaches. Guidelines are provided for the correct use of the employed local Weissenberg number and a modified approach is considered for the evolution equation of the actual extensibility, allowing its efficient use in complex numerical simulations. We illustrate that a suitable combination of the model parameters can produce behaviours that are found experimentally in viscoelastic fluids and we find that pressure-drop enhancements in flows within 4:1 contractions observed experimentally are achievable.

We numerically investigate inertial flows of viscoelastic fluids within a three-dimensional cross-slot geometry of square cross-section. Our study focuses on the inertial instability that occurs above a critical Reynolds number (Re) resulting in a transition to a steady flow asymmetry. We investigate numerically the effects of elasticity upon its characteristics by employing the upper-convected Maxwell (UCM), the Oldroyd-B and the modified Chilcott–Rallison finitely extensible nonlinear elastic (FENE–MCR) models. In so doing, we show that the UCM and the Oldroyd-B model results are restricted to very low nominal Weissenberg numbers at non-negligible Reynolds numbers, due to a significant increase in the strain rate at the stagnation point caused by inertia. The resulting steady-asymmetric flow at these critical conditions gives rise to the formation of a single axially-aligned spiral vortex, which is formed along the outlet channels of the geometry in good agreement with experimental observations. Below these critical conditions the flow remains steady-symmetric, varying from a nearly two-dimensional flow at very low Re to a more complex three-dimensional flow at higher Re. In a recent publication [Burshtein et al. [Phys. Rev. X, 7, 041039, (2017)]], we demonstrated experimentally, accompanied by limited complementary numerical simulations, the impact of elasticity upon the critical conditions for which the instability develops and the behaviour of the subsequent growth of vorticity of the single spiral vortex. Our results here show how different viscoelastic models influence the instability in a 3D cross-slot and demonstrate an interesting behaviour of the first normal-stress difference, providing an additional insight on the potential mechanisms which are responsible for the suppression of the spiral-vortex. We also elucidate the role played by solvent-to-total viscosity ratio and the extensibility parameter in the FENE–MCR model on the instability.

Angiogenesis is a biological process that involves the formation of new blood vessels from the existing vasculature, and it plays a fundamental role in the development and progression of several types of cancer, including lung cancer. The angiopoietin/Tie2 ligand/receptor system orchestrates vascular integrity. In particular, Angiopoietin-1 activates the endothelial cell (EC)-specific receptor tyrosine kinase, Tie2, which is essential for preserving endothelial quiescence. On the other hand, Angiopoietin-2 acts as an inhibitor of the Angiopoietin-1/Tie2 signaling pathways, thus facilitating the destabilization of quiescent endothelium in cases of inflammation and cancer. Clinical studies have proven that high levels of Angiopoietin-2 indicate the development of non-small-cell lung carcinomas (NSCLC), while high levels of Angiopoietin-2 are strongly related to tumor angiogenesis, lymphangiogenesis, metastasis, and poor prognosis. Interestingly, the association of Angiopoietin-2 levels with the type of surgical approach makes Angiopoietin-2 a valuable factor in selecting the most suitable therapeutic strategy for lung cancer patients. The role of the Angiopoietin-1 and Angiopoietin-4 levels in NSCLC development requires further investigation. The present review focuses on the clinical impact of the Angiopoietin-1, Angiopoietin-2, and Angiopoietin-4 levels in patients diagnosed with NSCLC, emphasizing the interaction between them, and how they affect the development, progression, and metastasis of lung disease. Finally, it estimates the role of angiopoietins levels in the effective therapy of lung cancer patients.

Epithelioid hemangioendothelioma (EHE) is a rare vascular tumor, affecting the liver, the lungs and the bones most frequently. It has a heterogenous clinical presentation and there is no consensus on optimal treatment. This report aims to present a rare case of a retroperitoneal EHE and to discuss on proper management.

In this paper, we develop a new procedure for estimating the parameters of a model by combining Zhang’s (2019) recent Gaussian estimator and the minimum density power divergence estimators of Basu et al. (1998). The proposed estimator is called the Minimum Density Power Divergence Gaussian Estimator (MDPDGE). The consistency and asymptotic normality of the MDPDGE are proved. The MDPDGE is applied to some classical univariate distributions and it is also investigated for the family of elliptically contoured distributions. A numerical study illustrates the robustness of the proposed estimator.

Objectives In transplantation surgery, the ischaemic organ and reperfusion impairment after cold storage remains a considerable risk factor for impaired function and potential failure of the grafted organ. Substantial logistical efforts have been undertaken to reduce the cold ischaemic time because the demand for available transplant organs and the periods of cold ischaemia are increasing. Methods Four molecules were investigated (erythropoietin, sildenafil, lazaroid [U74389G], octreotide) in individual intravenous infusions 1 hour before the organ was harvested. This study was performed in 30 healthy landrace/large-white pigs (male; >10 weeks old; average weight, 22 ± 2 kg) in groups of six. The organs were studied at harvest, and at 8 and 24 hours post-harvest. Results The lazaroid molecule increased malondialdehyde (MDA) levels in the liver and pancreas at 8 hours. Hepatic lazaroid molecules improved liver histology at 8 and 24 hours. For kidneys, erythropoietin had a positive effect at 24 hours post-harvest. For the pancreas, octreotide showed better performance. In the lungs, there was less interstitial oedema with erythropoietin and lazaroid compared with the control group at 8 hours post-harvest. Conclusion All molecules had a positive effect and decreased ischaemia/reperfusion graft injury. Thus, pretreatment before organ harvest has a beneficial role.

Microfluidic contraction devices have been proposed for extensional rheometry measurements, in particular as a useful method for determining the extensional viscosity of low elasticity solutions. The first commercially avail- able “Extensional Viscometer-Rheometer-On-a-Chip ”(e-VROC TM ), developed by Rheosense, is a hyperbolically- shaped contraction/expansion geometry which incorporates pressure-drop measurement capabilities. To better understand the underlying flow kinematics within this geometry we have conducted a numerical study perform- ing three-dimensional numerical simulations for both Newtonian and viscoelastic fluids. For the viscoelastic fluids the simplified Phan-Thien and Tanner (sPTT) and the Finitely Extensible Nonlinear Elastic models (FENE-P) are employed, in order to investigate the efficiency of this configuration in terms of increasing Weissenberg numbers and to understand the effects of various model parameters on the flow field. Our Newtonian fluid results suggest that the e-VROC TM geometry produces only a small region of extensional flow and is mainly shear-dominated, po- tentially suggesting any pressure-drop measurements from this device may be related to viscoelastic first normal- stress differences developed via a combination of shear and extension, rather than solely pure extension. By a careful selection of the sPTT and FENE-P model parameters, such that steady-state viscometric properties in ho- mogeneous flows are matched, we are able to show that a small enhanced pressure-drop is seen for both models, which is larger for the FENE-P model.

In this paper, we introduce a class of local divergences between two probability distributions and illustrate its usefulness in model selection. Explicit expressions of the proposed local divergences are derived when the underlying distributions are members of the exponential family of distributions or they are described by multivariate normal models. In addition, a local model selection criterion, termed the local divergence information criterion (LDiv.IC), is proposed. Simulations and applications are presented in order to study and exemplify the performance of the proposed criterion.

Some properties of the general families of bivariate distributions generated by beta dependent random variables are derived and discussed here. Some classic measures of dependence and information a...

It is well-known that in some situations it is not easy to compute the likelihood function as the datasets might be large or the model is too complex. In that contexts composite likelihood, derived by multiplying the likelihoods of subjects of the variables, may be useful. The extension of the classical likelihood ratio test statistics to the framework of composite likelihoods is used as a procedure to solve the problem of testing in the context of composite likelihood. In this paper we introduce and study a new family of test statistics for composite likelihood: Composite $$\phi $$ -divergence test statistics for solving the problem of testing a simple null hypothesis or a composite null hypothesis. To do that we introduce and study the asymptotic distribution of the restricted maximum composite likelihood estimate.

Aim First choice for restoration of the gastrointestinal tract after esophagectomy is gastric conduit, however when stomach is unavailable as in history of gastrectomy, concurrent gastric disease or gastric cancer, colon or subsequently jejenum can be used as an esophageal substitute. The aim of this study is to discuss safety, technique and feasibility of colonic interposition, in the era of minimally invasive surgery in a tertiary esophageal centre. Background & Methods From 01/09/2018 to 01/06/19, two patients with esophageal cancer underwent Hybrid 3-stage esophagectomy, using the left colon as an esophageal conduit, in our department. Both patients were objected to thoracoscopic esophageal mobilization, in prone position. The patients were then turned to supine position and laparotomy was performed. Colonic conduit was prepared, transferred to the left neck in a posterior mediastinal position and a handsewn oesophagocolonic anastomosis was performed. Clinicopathological outcomes were studied. Results Mean operative time was 420 minutes and mean blood loss was 160cc. No intraoperative complications were reported. The mean time of Intensive care unit stay of our patients was 6 days and mean duration of hospital stay was 25 days. Postoperative complications observed was 1 contralateral pneumothorax and 1 ipsilateral pneumonia. R0 resection was achieved in both patients. Mean lymph nodes harvested were 45. Both patients were discharged in good clinical condition. Conclusion Hybrid 3-stage esophagectomy with colonic interposition may be a safe and feasible technique when performed in an experienced Upper Gastrointestinal Surgical Department Unit.

Aim Lymphadenectomy in minimally-invasive esophageal cancer surgery still remains challenging and standardization of surgical procedures is of extreme importance. The aim of this study is to present our safe and reproducible technique in thoracoscopic superior lymphadenectomy during esophagectomy for cancer. Background & Methods In esophageal cancer surgery, dissection of the superior mediastinal lymph-nodes is of high importance. For adequate mediastinal lymph-node dissection, an extensive operating field is required along with appropriate equipment and experience. Thoracoscopy in prone position provides excellent visualization of the operative field comparing to thoracotomic phase. A step-by-step explanation of our surgical technique during thoracoscopic superior lymphadenectomy is provided. Results All patients were placed in prone position. The entire posterior mediastinal pleura was incised; azygos arch was divided with clips, facilitating dissection of the left side of the posterior mediastinum. The descending thoracic aorta was freed anteriorly, separating the esophagus; the thoracic duct was dissected and divided with vascular clips. Esophageal hiatus was dissected circumferentially and the esophageal wall was freed from the pericardiumanteriorly. Subcarinal lymph-nodes were dissected en bloc. Upper thoracic esophagus was separated from the membranous part of the trachea. The right recurrent laryngeal nerve lymph nodes were dissected at the level of the right subclavian artery, with extreme caution to avoid nerveinjury. Left recurrent laryngeal nerve was identified by posterior traction of the esophagus using a full thickness transluminal suture;by pulling it through a separate skin incision, the relative lymph nodes were dissected. Conclusion It is interesting that, higher number of lymph-nodes are harvested with this procedure which may be the result of better visualization/access. Overall, our technique has been standardized, is safe and reproducible and could be adopted by specialized Upper GI Units.

Aim Esophageal perforation is a serious injury associated with high morbidity and mortality. The management ranges from observation to operative treatment. The aim of this study was to evaluate safety and efficacy of different treatment strategies in patients with esophageal perforation depending on the severity and time from diagnosis to treatment. Background & Methods We performed a retrospective review of a prospective esophageal perforation database from two Upper GI Units between 01/01/2014 and 31/12/2018. Patients admitted for esophageal perforation were identified and reason of perforation, perforation site, time of diagnosis, management, length of stay (LOS) and outcomes were recorded. Results Sixteen patients were identified. Reason of perforation was Boerhaave's syndrome in n=9 (56.2%), iatrogenic in n=4 (25%) and foreign body in n=2 (12.5%) patients. Perforation site was distal esophagus in n=11 (68.7%) mid- esophagus in n=3 (18.7%) and Upper esophagus in n=2 (12.5%) patients. Time from perforation to diagnosis was 24h in n=12 (75%) and 48h in n=4 (25%) patients. Treatment in patients diagnosed the first 24h was esophagectomy in n=5 (41.6%), primary closure in n=2 (16.6%) and feeding tube along with thoracotomy and washout in n=2 (16.6%). Conservative management was offered in n=2 (16.6%). Patients diagnosed after 24h were managed with chest drains (50%) and stent insertion (50%). Mean LOS in patients that required surgical intervention was 18.2 days (Range: 6-60), while mean LOS in those who did not required was 11.1 days (Range: 1-37) Eleven (68.7%) patients were discharged in good clinical condition. Consclusion Esophageal perforations should be treated in specialized Upper GI Units due to the severity of the injury. Treatment plan should be individualized.

Background: Stress associated with learning of a psychomotor task can influence the trainees learning ability. Surgical simulation is a validated training milieu designed to replicate real-life situations, prevent biases and provide objective metrics. However, the complexity of stress mechanisms and the absence of a reliable detection method make stress estimation difficult to quantify and to interpret. Aim: a) To assess the feasibility of a new watch-sized device to noninvasively measure stress parameters in novices during a simulation task and b) to compare its derived cardiac stress parameters to those of an ambulatory Holter monitor. Materials and methods: Twenty-one novices were trained on a basic skills module. During base line, exercise, and recovery phases, all subjects wore a wearable device and data regarding blood volume pressure, heart rate, inter beat interval, electrodermal activity, and skin temperature were recorded. Additionally, Holter Monitoring was used to concomitantly capture heart rate, R-R intervals and heart rate variability. Before and after each experiment, all subjects completed the short, six-item STAI scale. Results: Data analysis showed: a) when compared to STAI, electrodermal activity exhibited the best correlation, sensitivity and specificity and b) the device derived cardiac parameters highly correlated with the reciprocal Holter values during all experiment phases. Conclusion: This wearable device is an easy to use and well accepted by the participants noninvasive tool, which can provide accurate stress estimation in our simulation setting. Additionally, it can replicate Holter derived stress related heart parameters, thus eliminating the need to wear a rather cumbersome device.

In the proximity of stagnation points, flow instabilities tend to arise at relatively low Reynolds numbers (Re). These instabilities often manifest as vortices that can evolve time-periodic patterns as Re is increased. These types of flows are well studied in cases for which the stagnation point is fixed on an obstacle and the resulting vortices are in the spanwise direction (e.g., the von Karman vortex street). However, they are less understood in intersecting flows, where the stagnation point is not wall-attached and the resulting vortices are stretched by the flow in the streamwise direction. In this study, quantitative flow velocimetry measurements and three-dimensional numerical simulations are used to characterize two types of steady vortical flow fields in rectangular, intersecting microfluidic geometries with different aspect ratios, α, of the intersecting channels. We show that by changing α, it is possible to precisely tune the features of the steady-state vortical flow field, including the number of vortices, their relative rotation direction, nearby circulation areas, and even vortex core structure. The unique steady-state features determine the onset parameters, dynamics, and frequency of time-periodic fluctuations that develop at higher Re. Our results can be directly applied for enhancing the control over the vortical motion of transported fluids in inertial microfluidics and lab-on-a-chip devices. Additionally, these findings contribute to the fundamental knowledge on vortical motion with the potential to improve the control over vortex-induced vibrations on obstacles in both terrestrial and marine environments.

The aim of this paper is to propose procedures that test statistical hypotheses locally, that is, assess the validity of a model in a specific domain of the data. In this context, the one and two sample problems will be discussed. The proposed tests are based on local divergences which are defined in such a way as to quantify the divergence between probability distributions locally, in a specific area of the joint domain of the underlined models. The theoretical results are exemplified using simulations and two real datasets.

In this work we discuss the implementation and the performance of an in-house viscoelastic two-phase solver, based on a diffuse interface approach. The Phase-Field method is considered and the Cahn-Hilliard equation is employed for describing the transport of a binary fluid system. The interface between the two fluids utilises a continuum approach, which is responsible for smoothing the inherent discontinuities of sharp interface models, facilitating studies that are related to morphological changes of the interface, such as droplet breakup and coalescence. The two-phase solver manages to predict the expected dynamics for all the cases investigated, and exhibits an overall good performance. The numerical implementation is able to predict the expected physical response of the oscillating drop case, while the performance is also validated by examining the droplet deformation case. The corresponding history of the deformation is predicted for several systems considering Newtonian fluids, viscoelastic fluids and combinations of both. Finally, we demonstrate the ability of the solver to capture the complex interfacial patterns of the Rayleigh-Taylor instability for different Atwood numbers when Newtonian fluids are considered. In the two regimes identified, the system is modified to consider viscoelastic fluids and the influence of elasticity is investigated.

This paper presents a model selection criterion in a composite likelihood framework based on density power divergence measures and in the composite minimum density power divergence estimators, which depends on an tuning parameter &alpha, After introducing such a criterion, some asymptotic properties are established. We present a simulation study and two numerical examples in order to point out the robustness properties of the introduced model selection criterion.

This note is concerned with a broad family of univariate distributions, namely the class of the beta-generated distributions which is created on the basis of the beta distribution by incorporating on this classic model a parent distribution function F with respective density f. The class of beta-generated distributions have received a great attention in the recent literature on distribution theory. The aim of this note is to provide with some properties and characterizations of the beta-generated distributions which are already known from the theory of order statistics.

A number of important industrial applications exploit the ability of small quantities of high molecular weight polymer to suppress instabilities that arise in the equivalent flow of Newtonian fluids, a particular example being turbulent drag reduction. However, it can be extremely difficult to probe exactly how the polymer acts to, e.g., modify the streamwise near-wall eddies in a fully turbulent flow. Using a novel cross-slot flow configuration, we exploit a flow instability in order to create and study a single steady-state streamwise vortex. By quantitative experiment, we show how the addition of small quantities (parts per million) of a flexible polymer to a Newtonian solvent dramatically affects both the onset conditions for this instability and the subsequent growth of the axial vorticity. Complementary numerical simulations with a finitely extensible nonlinear elastic dumbbell model show that these modifications are due to the growth of polymeric stress within specific regions of the flow domain. Our data fill a significant gap in the literature between the previously reported purely inertial and purely elastic flow regimes and provide a link between the two by showing how the instability mode is transformed as the fluid elasticity is varied. Our results and novel methods are relevant to understanding the mechanisms underlying industrial uses of weakly elastic fluids and also to understanding inertioelastic instabilities in more confined flows through channels with intersections and stagnation points.

A broad class of local divergences between two probability measures or between the respective probability distributions is proposed in this paper. The introduced local divergences are based on the classic Csiszar $$\phi $$ -divergence and they provide with a pseudo-distance between two distributions on a specific area of their common domain. The range of values of the introduced class of local divergences is derived and explicit expressions of the proposed local divergences are also derived when the underlined distributions are members of the exponential family of distributions or they are described by multivariate normal models. An application is presented to illustrate the behavior of local divergences.

Understanding the effect of varying shear stresses on individual polymer dynamics is important for applications such as polymer flooding, polymer induced drag reduction, or the design of DNA separation devices. In all cases, the individual polymer response to varying shear flows needs to be understood. A biomimetic design rule was recently proposed for bifurcating networks of rectangular channels of constant depth. These customised microfluidic geometries represent an elegant option to investigate, in a single device, multiple well-controlled shear stresses. Here, we present the first experimental realisation of such customised microfluidic networks, consisting of a series of rectangular microchannels with varying cross-sections, and we demonstrate their potential for testing polymer dynamics. We used microfluidic geometries optimised for both Newtonian and power-law fluids of constant or increasing average wall shear stress. The experimental model systems were tested using particle tracking velocimetry to confirm the theoretically predicted flow fields for shear-thinning xanthan gum solutions and a Newtonian fluid. Then, λ-DNA molecules were used as an example of shear sensitive polymers to test the effect of distinct shear stress distributions on their extension. By observing the conformation of individual molecules in consecutive channels, we demonstrate the effect of the varying imposed stresses. The results obtained are in good agreement with previous studies of λ-DNA extension under shear flow, validating the bifurcating network design. The customised microfluidic networks can thus be used as platforms for the investigation of individual polymer dynamics, in a large range of well-controlled local and cumulative shear stresses, using a single experiment.

20 σ. In this paper, a robust version of the Wald test statistic for composite likelihood is considered by using the composite minimum density power divergence estimator instead of the composite maximum likelihood estimator. This new family of test statistics will be called Wald-type test statistics. The problem of testing a simple and a composite null hypothesis is considered, and the robustness is studied on the basis of a simulation study. The composite minimum density power divergence estimator is also introduced, and its asymptotic properties are studied. Entropy; vol. 20 (2018)

This paper studies the change point problem for a general parametric, univariate or multivariate family of distributions. An information theoretic procedure is developed which is based on general divergence measures for testing the hypothesis of the existence of a change. For comparing the accuracy of the new test-statistic a simulation study is performed for the special case of a univariate discrete model. Finally, the procedure proposed in this paper is illustrated through a classical change-point example.

In this study, we optimise two types of multi-stream configurations (a T-junction and a flow-focusing design) to generate a homogeneous extensional flow within a well-defined region. The former is used to generate a stagnation point flow allowing molecules to accumulate significant strain, which has been found very useful for performing elongational studies. The latter relies on the presence of opposing lateral streams to shape a main stream and generate a strong region of extension in which the shearing effects of fluid–wall interactions are reduced near the region of interest. The optimisations are performed in two (2D) and three dimensions (3D) under creeping flow conditions for Newtonian fluid flow. It is demonstrated that in contrast with the classical-shaped geometries, the optimised designs are able to generate a well-defined region of homogeneous extension. The operational limits of the obtained 3D optimised configurations are investigated in terms of Weissenberg number for both constant viscosity and shear-thinning viscoelastic fluids. Additionally, for the 3D optimised flow-focusing device, the operational limits are investigated in terms of increasing Reynolds number and for a range of velocity ratios between the opposing lateral streams and the main stream. For all obtained 3D optimised multi-stream configurations, we perform the experimental validation considering a Newtonian fluid flow. Our results show good agreement with the numerical study, reproducing the desired kinematics for which the designs are optimised.

In a recent paper, Zografos [K. Zografos, On Mardia's and Song's measures of kurtosis in elliptical distributions, J. Multivariate Anal. 99 (2008) 858-879] has obtained general formulas for Song's measure for the elliptic family of distributions, and he introduced and studied its sample analogue. In this paper, based on the empirical estimator of this measure, we present a test to verify if the data are distributed according to a specific elliptical (spherical) distribution. In this context, the asymptotic distribution of the proposed statistic under the null hypothesis of specific spherical distributions is obtained. The proposed statistic also provides us with a procedure for testing multivariate normality. In order to evaluate the convergence of the proposed statistic to its limiting distribution, under the null hypothesis, a simulation study is performed to analyze the behavior of the percentiles of the proposed statistic in some special cases of spherical distributions. Moreover, a Monte Carlo study is carried out on the performance of the test statistic as a necessary test of fit of specific spherical distributions. In this framework, the type I error rates as well as the power of the test are studied. Finally, a well-known data set is used to illustrate the method developed in this paper. (C) 2011 Elsevier Inc. All rights reserved. Journal of Multivariate Analysis

In this work, we optimise microfluidic converging/diverging geometries in order to produce constant strain-rates along the centreline of the flow, for performing studies under homogeneous extension. The design is examined for both two-dimensional and three-dimensional flows where the effects of aspect ratio and dimensionless contraction length are investigated. Initially, pressure driven flows of Newtonian fluids under creeping flow conditions are considered, which is a reasonable approximation in microfluidics, and the limits of the applicability of the design in terms of Reynolds numbers are investigated. The optimised geometry is then used for studying the flow of viscoelastic fluids and the practical limitations in terms of Weissenberg number are reported. Furthermore, the optimisation strategy is also applied for electro-osmotic driven flows, where the development of a plug-like velocity profile allows for a wider region of homogeneous extensional deformation in the flow field.

Sonar is a popular sensor for robotic guidance, particularly for obstacle avoidance and for mapping. It has been used too for classifying objects and different surfaces. In this paper, we investigate further its use for surface classification. We discuss the characteristics of ultrasound reflection from surfaces and describe features which can extract from the sonar signature (a range-intensity plot) to distinguish between them. We show that a small set of features taken from the backscattering profile can be used to distinguish between several surfaces typical of those encountered by mobile robots with success rates approaching 100%. We demonstrate the methods using a data set acquired from a moving platform. © 2005 Elsevier B.V. All rights reserved.

Background: Acute coronary syndromes (ACS) represent the final step in the chronic process of atherothrombotic coronary disease which begins early in life as thickening of intima layer and progresses to fibroatheroma and fibrocalcific lesions with vulnerable characteristics. Methods: As abrupt occlusion in the settings of ACS happens due to platelet aggregation and mobilization antiplatelet treatment has gained significant interest especially in the settings of primary percutaneous intervention and the aim of this review article is to understand the current evidence justifying the use and combination of different antiplatelet agents. Results: Beyond aspirin, several antiplatelet agents (ADP receptor inhibitors, Glycoprotein IIb/IIIa inhibitors and varopaxar) are used in combination to effectively inhibit platelet activity. However the best choice, initiation, combination and duration of anti-thrombotic treatment, in order to maximize the effectiveness of therapy and reduce the hazard of bleeding, depends on the clinical setting and patient specific characteristics and is an issue of intense scientific interest. Conclusion: Early and potent platelet inhibition with safety reassurance can be achieved by a combination of antiplatelet agents and is essential for the management of ACS. Therefore in this review article we focus on the current evidence regarding rational, safety and effectiveness of current antiplatelet approaches in acute coronary syndromes.

The problem of classification of dimensional coherent elliptic random field observations into one of two populations specified by different regression mean models and common stationary scale matrix is considered, under the further assumption that the observations to be classified are dependent on the training samples. In this statistical frame, the behaviour of linear discriminant function is studied and an asymptotic expression for the distribution function of the probabilities of misclassification is derived.