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This study evaluated the cross-cultural measurement invariance of the Pandemic Fatigue Scale (PFS) in five South American countries, Argentina, Bolivia, Paraguay, Peru, and Uruguay. A total of 1448 people selected through convenience sampling (295 Argentines, 294 Bolivians, 279 Uruguayans, 277 Peruvians, and 303 Paraguayans) participated. The two-dimensional structure of the PFS fitted well with the data from each country. Invariance analysis showed that PFS was completely invariant across countries, thus providing a solid basis for comparisons between groups. Adequate discrimination and difficulty were reported for all items. Adequate discrimination parameters would indicate that the PFS items would allow people to differentiate the choice of response alternatives based on the presence of PF. In addition, the difficulty parameters indicate that people require a greater presence of the latent trait to respond to the higher response alternatives of PFS. It was also observed that the boredom and neglect dimensions have a significant and negative impact on protective behaviors, providing evidence of validity based on their relationship with other constructs. In conclusion, the PFS presents evidence of validity and MI for the measurement of PF in the five South American countries included in this study. Thus, PFS can contribute to future empirical research that compares FP in different South American populations and cultures. [ABSTRACT FROM AUTHOR]

This article discusses the circulation of knowledge in sociology through a case study based on the transnational exchanges between North-American sociologist Irving L. Horowitz and Latin American sociologists and intellectuals in the sixties. We explore his letters with three figures who played pivotal roles in the institutionalization of sociology in Latin America: Gino Germani, an Italian born sociologist who became a pioneer figure for establishing scientific sociology in Argentina; the Mexican sociologist Pablo González Casanova, who performed a similar role in his country; and Arnaldo Orfila Reynal, a prestigious editor in the region, who headed two of the most powerful publishing houses in the Latin American market for the social sciences and humanities in the 1960s and 1970s - Fondo de Cultura Económica (FCE) and Siglo XXI. We argue that while these exchanges happened under unequal conditions produced by the structural inequalities of the global system of knowledge production that emerged after World War II, the works of Latin American intellectuals were relevant for Horowitz's project of critical sociology for two main reasons: they provided intellectual sources for radical theorization on development and modernization, and they represented strategic assets for Horowitz present himself as a mediator between Third World problems and North-American audiences. [ABSTRACT FROM AUTHOR]

Purpose: Major depressive disorder (MDD) and anxiety disorders (AD) are both highly prevalent among individuals with arrhythmia, ischemic heart disease, heart failure, hypertension, and dyslipidemia. There should be increased support for MDD and AD diagnosis and treatment in individuals with cardiac diseases, because treatment rates have been low. However, cardiac–psychiatric drug interaction can make pharmacologic treatment challenging. Methods: The objective of the present systematic review was to investigate cardiac–psychiatric drug interactions in three different widely used pharmacological databases (Micromedex, Up to Date, and ClinicalKey). Results: Among 4914 cardiac–psychiatric drug combinations, 293 significant interactions were found (6.0%). When a problematic interaction is detected, it may be easier to find an alternative cardiac medication (32.6% presented some interaction) than a psychiatric one (76.9%). Antiarrhythmics are the major class of concern. The most common problems produced by these interactions are related to cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest), increased exposure of cytochrome P450 2D6 (CYP2D6) substrates, or reduced renal clearance of organic cation transporter 2 (OCT2) substrates and include hypertensive crisis, increased risk of bleeding, myopathy, and/or rhabdomyolysis. Conclusion: Unfortunately, there is considerable inconsistency among the databases searched, such that a clinician's discretion and clinical experience remain invaluable tools for the management of patients with comorbidities present in psychiatric and cardiac disorders. The possibility of an interaction should be considered. With a multidisciplinary approach, particularly involving a pharmacist, the prescriber should be alerted to the possibility of an interaction. MDD and AD pharmacologic treatment in cardiac patients could be implemented safely both by cardiologists and psychiatrists. Trial Registration: PROSPERO Systematic Review Registration Number: CRD42018100424. [ABSTRACT FROM AUTHOR]

A monolithic lab-on-a-chip fabricated by femtosecond laser micromachining capable of label-free biosensing is reported. The device is entirely made of fused silica, and consists of a microdisk resonator integrated inside a microfluidic channel. Whispering gallery modes are excited by the evanescent field of a circular suspended waveguide, also incorporated within the channel. Thermal annealing is performed to decrease the surface roughness of the microstructures to a nanometric scale, thereby reducing intrinsic losses and maximizing the Q-factor. Further, thermally-induced morphing is used to position, with submicrometric precision, the suspended waveguide tangent to the microresonator to enhance the spatial overlap between the evanescent field of both optical modes. With this fabrication method and geometry, the alignment between the waveguide and the resonator is robust and guaranteed at all instances. A maximum sensitivity of 121.5 nm/RIU was obtained at a refractive index of 1.363, whereas near the refractive index range of water-based solutions the sensitivity is 40 nm/RIU. A high Q-factor of 105 is kept throughout the entire measurement range. [ABSTRACT FROM AUTHOR]

The correct determination of aortic annulus dimensions is a crucial step to avoid complications in Transcatheter Aortic Valve Replacement (TAVR). Currently, the gold standard method for the evaluation of the aortic annulus is Multidetector Computed Tomography (MDCT), which is limited by the risk of contrast-induced nephropathy. Three-dimensional transesophageal echocardiography automated software (3DTEEa) have been used as an alternative in patients with contra-indications to MDCT. We aimed to evaluate the accuracy of 3DTEEa-derived aortic annulus dimensions; to assess the influence of calcification in the agreement between 3DTEEa and MDCT; and to determine reclassification in prosthesis size choice if 3DTEEa was the only imaging method. One hundred and seven consecutive patients referred for TAVR were studied. Aortic annulus dimensions were determined using MDCT and 3DTEE manual (3DTEEm) and automated measurements. Valve calcification was assessed with MDCT. Limits of agreement (LOA) were narrower for 3DTEEa (minimum diameter: mean bias 0.60; LOA - 2.94 to 4.14; maximum diameter: mean bias 0.20; LOA - 3.82 to 4.22) as compared to 3DTEEm (minimum diameter: mean bias 0.22; LOA - 3.84 to 4.28; maximum diameter: mean bias - 1.25; LOA - 6.37; 3.86). Compared to MDCT, 3DTEEa overestimated while 3DTEEm underestimated most parameters. No differences were found in average bias between methods according to quartiles of valve calcification. Most patients would have received the same size valve (63.9%) if 3DTEEa was the only available method. Measurement of aortic annulus dimensions using a 3DTEE automatic software is feasible and not influenced by valve calcification. It may be an alternative for patients who cannot undergo MDCT. [ABSTRACT FROM AUTHOR]

Grapevine bacterial canker caused by Xanthomonas citri pv. viticola (X. campestris pv. viticola) (Xcv), was detected in Brazil in 1998 and is currently regarded as a quarantine disease with limited distribution in the country. To improve sensitivity and speed in the detection of Xcv in asymptomatic grapevines, two pairs of primers were designed, targeting sequences of a pathogenicity gene (hrpB) and the xanthomonadin coding cluster. Both pairs were tested in conventional PCR (cPCR) and real-time PCR (qPCR) formats. Primers targeting the hrpB gene showed cross reactions with other Xanthomonas spp. but were effective for use in both cPCR and qPCR, whereas primers for the xanthomonadin gene were highly specific for Xcv but showed low efficiency in qPCR. Enrichment of plant extracts in semi-selective medium before qPCR allowed a significant increase in sensitivity when compared to total DNA extraction, making it possible to detect as low as 101 CFU ml-1. Under natural infection conditions, symptomatic and asymptomatic grapevines were tested by qPCR with hrpB primers and cPCR with xanthomonadin primers. In both cases, plant extracts were enriched for 36-72h. Xcv was detected in all symptomatic samples by qPCR and the result was confirmed by cPCR. For the asymptomatic samples, Xcv was detected in 93.4% with qPCR and in 89.5% with cPCR. These two methods offer advantages in terms of sensitivity and specificity, and they could be useful in quarantine programs, certification of grapevine propagating material and detection of inoculum sources in alternative hosts, contributing to the prevention of pathogen spread to disease-free areas. [ABSTRACT FROM AUTHOR]

Background: About 30% of regular cannabis users report withdrawal symptoms on cessation of prolonged use, such as irritability, insomnia, decreased appetite, depressed mood, anxiety, and restlessness. However, among highly dependent and/or in-treatment users, the incidence of withdrawal can be even higher, reaching up to 50-95% of individuals. This syndrome was only recognized by the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) as a diagnosis with specific criteria in 2013. The treatment options are poor, with high rates of relapse and non-responders. In this scenario, agonist replacement therapy with cannabinoids has demonstrated potential as a promising therapeutic intervention, with a series of studies having been carried out in recent years.Objective: This review sought to summarize trials with cannabinoid agonist replacement therapy for cannabis withdrawal symptoms with the aim of evaluating the efficacy of this pharmacological intervention.Data Sources: We entered the following search terms on the PubMed, Web of Science and PsycINFO databases: (marijuana OR marihuana OR cannabis OR THC OR tetrahydrocannabinol OR hashish OR pot) AND (treatment OR medication) AND (withdrawal OR abstinence) AND (dronabinol OR nabilone OR nabiximols OR sativex OR cesamet OR synthetic cannabinoid). The date of the most recent search was September 2017.Study Eligibility Criteria, Participants, and Interventions: Original trials, published in English, performed on humans and dealing with cannabis users who were treated for cannabis withdrawal symptoms using synthetic cannabinoids were all included in the present systematic review. Quality and risk of bias across studies were assessed using a Cochrane tool.Study Appraisal and Synthesis Methods: The first, second, and last authors read the abstracts of all studies found in the search (n = 243). The inclusion and exclusion criteria were applied, and 233 articles were excluded. The first and second authors independently developed a data extraction sheet based on the included articles.Results: The present review included ten original articles. Despite the limited number of studies and methodological differences, our findings demonstrate that the use of dronabinol, nabilone, or nabiximols, either alone or in combination with other drugs, shows promise in reducing cannabis withdrawal symptoms, probably with a dose-dependent effect. This has also been considered a safe group of medications with good tolerability and few adverse effects.Limitations: No method of handling data and combining results of studies was carried out, representing a limitation of the review.Conclusions and Implication Of the Key Findings: Cannabinoids appear to be a promising group of drugs for the treatment of cannabis withdrawal symptoms. These medications may help decrease the rate of relapse in the treatment of cannabis dependence due to withdrawal symptoms occurring within the first few weeks of treatment.Systematic Review Registration: The protocol for this review has been registered in the PROSPERO International prospective register of systematic reviews (PROSPERO 2014:CRD42014014118). [ABSTRACT FROM AUTHOR]

Based on both unique morphological characteristics of the gamont, distinct changes caused to the host erythrocyte and analysis of partial 18S rRNA gene sequences, a new parasite of the genus Hepatozoon Miller, 1908 is described from the snake Philodryas nattereri Steindachner (Squamata: Dipsadidae) in northeastern Brazil. The new species, Hepatozoon musa n. sp., is characterized by large and curved mature gamonts (18.9 ± 0.9 μm in length and 3.8 ± 0.3 μm in width) that considerably engorge infected host erythrocytes and displace the nucleus laterally, which become longer and thinner. Phylogenetic estimates indicate the new species is more closely related to the recently described Hepatozoon cuestensis O'Dwyer, Moço, Paduan, Spenassatto, Silva & Ribolla, 2013, from Brazilian rattlesnakes. These recent findings highlight the need for further studies of Hepatozoon to better determine the biodiversity of this common but poorly-studied parasite group. [ABSTRACT FROM AUTHOR]

Shear step strain experiments with various strain amplitudes have been performed on poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) melts using both stress-controlled and strain-controlled rheometers. Firstly, the onset of the rheological nonlinearity, i.e., nonlinear stress damping behavior, occurring after a large step strain is found to be a phenomenological consequence of an abrupt stress decline within the transient period of strain actuation. Such a feature, analogous to the stress overshoot in a fast startup shear with sufficiently high rates, is interpreted based on theoretical frameworks concerning chain disentanglement/re-entanglement arising from chain retraction. Furthermore, this work infers that full technical considerations in step strain experiments are indispensable for acquisition of accurate stress relaxation data, as some common but easily overlooked technical problems are influential, probably introducing errors. For instance, a too long finite rise time and a stress overload enable to hinder the nonlinearity onset in the transient period, resulting in inaccurate experimental data. In this sense, the stress-controlled rheometer is advantageous relative to the strain-controlled one, although the inertia in the stress-controlled mode incurs a strain overshoot effect. Nevertheless, the amplitude-dependent strain overshoot offers a very subtle effect on the stress damping behavior. Moreover, transducer compliance problems need to be taken into account, especially for high stiffness polymers. Overall, the effects of such technical factors are dictated by their ability to influence the chain stretching/retraction and the disentanglement. A well-considered experimental methodology is necessary to achieve confidence windows in step strain experiments for analysis accuracy. [ABSTRACT FROM AUTHOR]

The efficiency of in vitro polyploidization depends on several variables associated to the plant, the antimicrotubule agent and the interactions between them. In the present work, we have used response-surface methodology to determine the best operating conditions for plant recovery in polyploidization assays for shoot apices and somatic embryos of two seedless grape cultivars, employing colchicine and oryzalin. Explant type, tubulin-interfering compound and concentration were the critical factors determining plant recovery. Linear reduction in viable plant regeneration via organogenesis and somatic embryogenesis was obtained by increasing oryzalin concentrations and treatment time, whereas the effects of colchicine were better described by a quadratic design for both explants types. The conditions promoting higher rates of plant recovery were used in chromosome doubling experiments with oryzalin and colchicine for shoot apices and somatic embryos of 'Crimson seedless' and 'BRS Clara'. The established protocols allowed the recovery of non-chimerical autotetraploid plants at rates higher than 30 % for both cultivars. Stomata size parameters statistically correlate to the ploidy level of the regenerants and were effective for preliminary polyploidy screening. Autotetraploid lines of seedless grapes were incorporated into the Vitis germplasm bank for further agronomical evaluations. To our knowledge, this is the first report of in vitro oryzalin induced polyploidization of grapevine and of the use of mathematical modeling to optimize chromosome doubling in plants. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to test whether the first use of an illicit drug increases the chance of first use of other illicit drugs. Method: The transitions from the first use of a drug to the first use of another drug were analyzed. Comparisons were made between first drug users and non-users. Survival analysis methods were used to compare the cumulative probability of second drug use after adjusting for socio-demographic covariates and the intermediate use of alcohol and/or tobacco. A total of 12,721 Brazilian university students participated in this study. Results: Inhalants and marijuana were used prior to the use of several other drugs, whereas the opposite pattern was not found. Ecstasy was used before other drugs in several instances. Other well-examined drugs, such as amphetamines, cocaine and hallucinogens, were used both before and after other illicit drugs without any marked predominance for either of the two roles. Conclusions: This study supports the role of the use of marijuana and inhalants almost exclusively before the use of other illicit drugs, whereas the use of ecstasy has an opposite role. These roles could be linked to the prevalence of lifetime use and whether individuals were at an earlier or later age during experimentation. [ABSTRACT FROM AUTHOR]

Species of Hepatozoon Miller, 1908 are blood parasites most commonly found in snakes but some have been described from all tetrapod groups and a wide variety of hematophagous invertebrates. Previous studies have suggested possible associations between Hepatozoon spp. found in predators and prey. Particularly, some saurophagous snakes from North Africa and the Mediterranean region have been found to be infected with Hepatozoon spp. similar to those of various sympatric lizard hosts. In this study, we have screened tissue samples of 111 North African and Mediterranean snakes, using specific primers for the 18S rRNA gene. In the phylogenetic analysis, the newly-generated Hepatozoon spp. sequences grouped separately into five main clusters. Three of these clusters were composed by Hepatozoon spp. also found in snakes and other reptiles from the Mediterranean Basin and North Africa. In the other two clusters, the new sequences were not closely related to geographically proximate known sequences. The phylogeny of Hepatozoon spp. inferred here was not associated with intermediate host taxonomy or geographical distribution. From the other factors that could explain these evolutionary patterns, the most likely seems series of intermediate hosts providing similar ribotypes of Hepatozoon and a high prevalence of host shifts for Hepatozoon spp. This is indicated by ribotypes of high similarity found in different reptile families, as well as by divergent ribotypes found in the same host species. This potentially low host specificity has profound implications for the systematics of Hepatozoon spp. [ABSTRACT FROM AUTHOR]

Water frogs, Pelophylax perezi, that are introduced in the Azores, were screened for parasites using PCR primers known to amplify Apicomplexa parasites, and using nematode-specific primers. With the former, three different organisms were detected: Hepatozoon, a trichodinid protozoan ciliate and a possible Stramenopile. Using the latter set of primers, a single unknown spirurid nematode was also detected. Phylogenetic analyses indicate that Hepatozoon detected within amphibian hosts appear to form a clade, although relationships of these parasites do not match the vertebrate intermediate host phylogeny. Regarding the possible Stramenopile, it is unclear whether this organism was actually present on the amphibian or in the water on the surface of the tissue sample. Our findings highlight that many different organisms can be detected with these primers and that they can be used to screen introduced host populations to detect parasites that have been brought with them. [ABSTRACT FROM AUTHOR]

Background: Nicotine dependence is difficult to treat, and the biological mechanisms that are involved are not entirely clear. There is an urgent need to develop better drugs and more effective treatments for clinical practice. A critical step towards accelerating progress in medication development is to understand the neurobehavioral effects of pharmacotherapies on clinical characteristics associated with nicotine dependence. Objectives: This review sought to summarize the functional magnetic resonance imaging (fMRI) literature on smoking cessation with the aim to better understand the neural processes underlying the effects of nicotinic and non-nicotinic pharmacological smoking cessation treatments on specific symptoms of nicotine dependence and withdrawal. Data Sources: We conducted a search in Pubmed, Web of Science and PsycINFO databases with the keywords 'fMRI' or 'functional magnetic resonance imaging' and 'tobacco' or 'nicotine' or 'smok*'. The date of the most recent search was May 2012. Study Eligibility Criteria, Participants and Interventions: The original studies that were included were those of smokers or nicotine-dependent individuals, published in the English language, with pharmacological treatment for nicotine dependence and use of fMRI with blood oxygen level-dependent (BOLD) imaging or continuous arterial spin labelling (CASL). No date limit was applied. Study Appraisal and Synthesis Methods: Two of the authors read the abstracts of all studies found in the search ( n = 1,260). The inclusion and exclusion criteria were applied, and 1,224 articles were excluded. In a second step, the same authors read the remaining 36 studies. Nineteen of the 36 articles were excluded. The results were tabulated by the number of individuals and their mean age, the main sample characteristics, smoking status, study type and methodology, and the main fMRI findings. Results: Seventeen original fMRI studies involving pharmacological treatment of smokers were selected. The anterior and posterior cingulate cortex, medial and lateral orbitofrontal cortex, ventral striatum, amygdala, thalamus and insula are heavily involved in the maintenance of smoking and nicotine withdrawal. The effects of varenicline and bupropion in alleviating withdrawal symptoms and decreasing smoking correlated with modulation of the activities of these areas. Nicotine replacement therapy seems to improve cognitive symptoms related to withdrawal especially by modulating activities of the default-network regions; however, nicotine replacement does not necessarily alter the activities of neural circuits, such as the cingulate cortices, that are associated with nicotine addiction. Limitations: The risk of bias in individual studies, and across studies, was not assessed, and no method of handling data and combining results of studies was carried out. Most importantly, positron emission tomography (PET) studies were not included in this review. Conclusions and Implication of Key Findings: fMRI studies delineate brain systems that contribute to cognitive deficits and reactivity to stimuli that generate the desire to smoke. Nicotinic and non-nicotinic pharmacotherapy may reduce smoking via distinct neural mechanisms of action. These findings should contribute to the development of new medications and discovery of early markers of the therapeutic response of cigarette smokers. [ABSTRACT FROM AUTHOR]

The most promising method capable of providing accurate measurements of the first and second normal-stress differences in shear flows at shear rates typical of polymer processing is the so-called hole-pressure method, but its use has not been as widespread as would be expected, namely due to the experimental difficulties associated with performing such experiments accurately. In this work, we use a small-scale modular slit die to assess the practical utility of the method for in-line monitoring of polymer melt flow. We provide a quantitative analysis of intrinsic error sources and use state-of-the-art data acquisition tools to minimize errors associated with pressure transducers. Our results demonstrate that the method can be used to accurately measure the viscosity and first normal-stress difference in melts but probably not the second normal-stress difference because the intrinsic errors are too high, even when the influence of all the potential error sources is minimized or eliminated. [ABSTRACT FROM AUTHOR]

In this work, we report on the sensitivity of rheometrical techniques to the nature and size of the interface/interphase in coextruded thermoplastic urethanes (TPUs). In particular, the interphases developed during coextrusion of an amorphous glass (hard) TPU (Isoplast ETPU 301) with one of two elastomeric (soft) TPUs (Estane TPU 58277 and Estane TPU X1175) were studied. Differences in the thickness and nature of the interphase of the two coextruded bilayer films were observed by atomic force microscopy. In one case, the interphase is thicker and rough, and in the other case, it is thinner and flat. Rheology was used in order to probe the type and characteristics of the interphases, with coextruded films having been tested in steady shear, small-amplitude oscillatory shear (SAOS), uniaxial extension, and stress relaxation after a step strain in shear. The results were compared with theoretical predictions assuming zero-thickness interfaces and no interfacial slip. For SAOS and stress relaxation experiments, expressions were deduced in order to enable such a prediction to be made. Of all four rheometrical tests, only stress relaxation after a step shear did not follow the theoretical predictions and, thus, was sensitive enough to detect the presence of the interphase. [ABSTRACT FROM AUTHOR]

Microscopy has traditionally been the most common method in parasitological studies, but in recent years molecular screening has become increasingly frequent to detect protozoan parasites in a wide range of vertebrate hosts and vectors. During routine molecular screening of apicomplexan parasites in reptiles using the 18S rRNA gene, we have amplified and sequenced Proteromonas parasites from three lizard hosts (less than 1% prevalence). We conducted phylogenetic analysis to confirm the taxonomic position and infer their relationships with other stramenopiles. Although our phylogeny is limited due to scarcity of molecular data on these protists, our results confirm they are closely related to Proteromonas lacertae. Our findings show that unexpected parasites can be amplified from host samples (blood and tissue) using general procedures to detect hemoparasites, and stress that positive PCR amplifications alone should not be considered as definitive proof of infection by particular parasites. Further validation by sequence confirmation and thorough phylogenetic assessment will not only avoid false positives and biased prevalence estimates but also provide valuable information on the biodiversity and phylogenetic relationships of other parasitic organisms. More generally, our results illustrate the perils of general diagnosis protocols in parasitological studies and the need of cross-validation procedures. [ABSTRACT FROM AUTHOR]

In a recent paper by T. Schweizer (Schweizer 2000) a large collection of experimental difficulties associated with the measurement of uniaxial extensional properties of polymer melts in the Rheometrics RME extensional rheometer is described. The work covers topics such as sample preparation for different types of polymers (sensitive or not to moisture) supplied in different shapes (pellets or powder), the necessary corrections to the tensile force, and the ever-present problem of determining the true strain rates of the experiments. The aim of the present paper is to complement and expand the work of Schweizer by pointing out other experimental problems that are the cause of errors in extensional rheometry of polymer melts. The present analysis, however, is not exclusively dedicated to the RME, unlike that of Schweizer, being directed instead to a general class of apparatus that work according to the principle of stretching a constant length sample between pairs of counter-rotating rollers; for example, all the data shown was obtained with our own extensional rheometer (Maia et al. 1999). This work will focus on the importance of the correct choice of the supporting media used for sample heating and support, the importance of end-effects, and the influence that the griping surfaces can have in such measurements. [ABSTRACT FROM AUTHOR]

Over the last decade several international programmes have been developed around different standard fluids, one of which is the so-called S1 fluid. This is a solution of polyisobutylene in a mixed solvent and the aim of the programme has been to study the rheology of polymer solutions from the dilute solution to the melt. The focus of this paper will be on the flow visualisation of contraction flows of S1 through orifice dies and on the estimation of some of its extensional properties. The contraction ratios range from 24.4:1 and 124.3:1. The measured entry pressure drops will be correlated with contraction ratio and apparent wall shear rate. Experimental evidence will show that, when regarded as a function of wall shear rate, the entry pressure drops are independent of the contraction ratios. The flow fields for different contraction ratios, at any constant apparent wall shear rate, however, differ substantially. The evolution of the flow fields is monitored and it is shown that an initial increase in vortex size is followed by a slower decrease, this happening at a constant Weissenberg number. At the same Weissenberg number, small scale instabilities start occurring near the office. As the shear rate is increased further, these instabilities grow in size until, eventually, the flow structure is destroyed. An extensional viscosity is evaluated using a modified form of the Binding analysis for contraction flows and we show that the results are not only in qualitative agreement with those from other groups, but also that the analysis is able to predict exactly the onset of the aforementioned flow instabilities. [ABSTRACT FROM AUTHOR]