Predictors of ultrasound abnormalities among women treated for community-onset acute pyelonephritis: a prospective study.

OBJECTIVES: Acute pyelonephritis (AP) is a common but potentially severe infection. It may be complicated by pyelocaliceal dilatation which requires emergency urine drainage. In outpatient care, ultrasound (US) appears to be the easier way to diagnose pyelocaliceal dilatation, though most APs will not be complicated and do not require immediate ultrasound. We aimed to identify predictors of ultrasound abnormalities in an outpatient AP cohort. METHODS: A prospective study was conducted from April 2006 to September 2019 in an outpatient care network. Patients aged 15 and over treated for AP were included. Men, pregnant women, patients with solitary kidney, and patients without data on their management were excluded. A common algorithm ensured the same approach from diagnosis to treatment. Data were collected prospectively in an anonymized database. We described the characteristics of the patients. Univariate and then multivariate analyses were performed to identify predictors of ultrasound abnormalities. RESULTS: 2054 women were treated for AP. Among them, 32.5% (n = 667) had a history of urinary tract infections and 5.8% (n = 120) of uropathy. The most frequent uropathogen was E. coli (n = 1,432; 69.7%); Extended-Spectrum Beta-Lactamases (ESBLs) were found in 39 (1.9%) urine cultures. Ultrasound was abnormal in 7.3% (n = 149). Age over 55 years (OR = 2.23; 95% CI 1.58‒3.15; p < 0.0001) and uropathy (OR = 3.69; 95% CI 2.26‒6.01; p < 0.0001) were independently identified as predictors of ultrasound abnormalities. The risk increased by 1.8% (95% CI 1.0‒2.6) with each additional year of age. CONCLUSIONS: This study identified age and uropathy as independent predictors of abnormal ultrasound in women treated with community-onset AP.

PRISM, a Patient-Reported Outcome Instrument, Accurately Measures Symptom Change in Refractory Gastroesophageal Reflux Disease.

BACKGROUND: Most patients with gastroesophageal reflux disease (GERD) experience relief following treatment with proton pump inhibitors (PPIs) (Vakil et al. in Am J Gastroenterol 101:1900-1920, 2006; Everhart and Ruhl in Gastroenterology 136:376-386, 2009). As many as 17-44% of patients, however, exhibit only partial response to therapy. Most extant GERD patient-reported outcome (PRO) instruments fail to meet development best practices as described by the FDA (Talley and Wiklund in Qual Life Res 14:21-33, 2005; Van Pinxteren et al. in Cochrane Database Syst Rev 18:CD002095, 2004; El-Serag et al. in Aliment Pharmacol Ther 32:720-737, 2010). AIM: To develop and validate a PRO instrument for clinical trials involving patients with GERD who are PPI partial responders. METHODS: We prepared a systematic literature review, held patient focus groups, convened an expert panel, and conducted cognitive interviews to establish content validity. Eligible participants took PPI therapy for at least 8 weeks, had undergone an upper endoscopy, and scored at least 8 points on the GerdQ [6]. Qualitative data guided development of 26 draft items. Items were reviewed by expert panels and debriefed with patients. The resulting 21-item instrument underwent psychometric evaluation during a Phase IIB trial. RESULTS: During the trial, confirmatory factor analysis (n = 220) resulted in a four-factor model displaying the highest goodness of fit. All domains had a high inter-item correlation (Cronbach's α > 0.8). Test-retest reliability and convergent validity were strong, with highly significant (p < 0.01) correlations between average weekly PRISM scores and severity anchors and significant (p < 0.05) correlations with anchor subscales. Cumulative distribution functions revealed significant differences between responders and non-responders. CONCLUSIONS: Analysis in a clinical trial setting demonstrated strong psychometric properties suggesting validity of PRISM. Developed in line with FDA guidance on PROs, PRISM represents an important new outcome measure for patients with GERD with a partial response to PPI therapy.

The Weiss Functional Impairment Rating Scale-Parent Form for assessing ADHD: evaluating diagnostic accuracy and determining optimal thresholds using ROC analysis.

PURPOSE: The Weiss Functional Impairment Rating Scale-Parent Form (WFIRS-P) is a 50-item scale that assesses functional impairment on six clinically relevant domains typically affected in attention-deficit/hyperactivity disorder (ADHD). As functional impairment is central to ADHD, the WFIRS-P offers potential as a tool for assessing functional impairment in ADHD. These analyses were designed to examine the overall performance of WFIRS-P in differentiating ADHD and non-ADHD cases using receiver operating characteristics (ROC) analysis. This is the first attempt to empirically determine the level of functional impairment that differentiates ADHD children from normal controls. METHODS: This observational study comprised 5-19-year-olds with physician-diagnosed ADHD (n = 476) and non-ADHD controls (n = 202). ROC analysis evaluated the ability of WFIRS-P to discriminate between ADHD and non-ADHD, and identified a WFIRS-P cut-off score that optimises correct classification. Data were analysed for the complete sample, for males versus females and for participants in two age groups (5-12 versus 13-19 years). RESULTS: Area under the curve (AUC) was 0.91 (95% confidence interval 0.88-0.93) for the overall WFIRS-P score, suggesting highly accurate classification of ADHD distinct from non-ADHD. Sensitivity (0.83) and specificity (0.85) were maximal for a mean overall WFIRS-P score of 0.65, suggesting that this is an appropriate threshold for differentiation. DeLong's test found no significant differences in AUCs for males versus females or 5-12 versus 13-19 years, suggesting that WFIRS-P is an accurate classifier of ADHD across gender and age. CONCLUSIONS: When assessing function, WFIRS-P appears to provide a simple and effective basis for differentiating between individuals with/without ADHD in terms of functional impairment. CLASSIFICATION: Disease-specific applications of QOL research.

Comparative efficacy and safety of attention-deficit/hyperactivity disorder pharmacotherapies, including guanfacine extended release: a mixed treatment comparison.

This study compared the clinical efficacy and safety of attention-deficit/hyperactivity disorder (ADHD) pharmacotherapy in children and adolescents 6-17 years of age. A systematic literature review was conducted to identify randomized controlled trials (RCTs) of pharmacologic monotherapies among children and adolescents with ADHD. A Bayesian network meta-analysis was conducted to compare change in symptoms using the ADHD Rating Scale Version IV (ADHD-RS-IV), Clinical Global Impression-Improvement (CGI-I) response, all-cause discontinuation, and adverse event-related discontinuation. Thirty-six RCTs were included in the analysis. The mean (95% credible interval [CrI]) ADHD-RS-IV total score change from baseline (active minus placebo) was -14.98 (-17.14, -12.80) for lisdexamfetamine dimesylate (LDX), -9.33 (-11.63, -7.04) for methylphenidate (MPH) extended release, -8.68 (-10.63, -6.72) for guanfacine extended release (GXR), and -6.88 (-8.22, -5.49) for atomoxetine (ATX); data were unavailable for MPH immediate release. The relative risk (95% CrI) for CGI-I response (active versus placebo) was 2.56 (2.21, 2.91) for LDX, 2.13 (1.70, 2.54) for MPH extended release, 1.94 (1.59, 2.29) for GXR, 1.77 (1.31, 2.26) for ATX, and 1.62 (1.05, 2.17) for MPH immediate release. Among non-stimulant pharmacotherapies, GXR was more effective than ATX when comparing ADHD-RS-IV total score change (with a posterior probability of 93.91%) and CGI-I response (posterior probability 76.13%). This study found that LDX had greater efficacy than GXR, ATX, and MPH in the treatment of children and adolescents with ADHD. GXR had a high posterior probability of being more efficacious than ATX, although their CrIs overlapped.

Psychometric properties of PedsQL generic core scales for children with functional constipation in the Netherlands.

OBJECTIVES: The aim of the study was to evaluate the psychometric properties of the Dutch translation of the Pediatric Quality of Life Inventory version 4.0 Generic Core Scales (PedsQL) in children with functional constipation (FC). METHODS: The PedsQL was completed by children with FC ages 5 to 18 years and by the parents of children ages 2 to 18 years. To assess construct validity, all of the parents and children completed the PedsQL Gastrointestinal Symptoms Module (GI module) and children ages 8 to 18 years completed the defecation disorder list. Item response distributions, internal consistency reliability, patient-parent agreement, and discriminating ability were evaluated. RESULTS: Overall, 269 children were enrolled. The PedsQL showed minimal missing responses (self-report: 5.3% with >50% missing, parent report: 2.6% with >50% missing) and achieved satisfactory internal consistency for the total (self-report: α = 0.86, parent report: α = 0.88), physical health (self-report: α = 0.75, parent report α = 0.83), and psychosocial health (self-report: α = 0.80; parent report: α = 0.85) scores. Internal consistency was less convincing for those ages 5 to 7 years (α = 0.53-0.77) than for older individuals. Self-reported health-related quality of life was lower than parent reported, with the exception of children ages 5 to 7 years. Interrater reliability intraclass correlations were 0.52 to 0.61 for the overall population. Correlations among the PedsQL, GI module, and defecation disorder list were consistent with a priori hypotheses and generally supported construct validity. The PedsQL distinguished between a previously published healthy reference sample and children with FC, and between those with mild and severe symptoms (P < 0.05). CONCLUSIONS: The self-reported and proxy reported PedsQL demonstrated satisfactory measurement properties in Dutch children with FC ages 8 to 18 years. Further research is needed to establish internal consistency and validity in those ages 5 to 7 years.

Dispersible Conjugated Polymer Nanoparticles as Biointerface Materials for Label-Free Bacteria Detection.

Fast and efficient identification of bacterial pathogens in water and biological fluids is an important issue in medical, food safety, and public health concerns that requires low-cost and efficient sensing strategies. Impedimetric sensors are promising tools for monitoring bacteria detection because of their reliability and ease-of-use. We herein report a study on new biointerface-based amphiphilic poly(3-hexylthiophene)-b-poly(3-triethylene-glycol-thiophene), P3HT-b-P3TEGT, for label-free impedimetric detection of Escherichia coli (E. coli). This biointerface is fabricated by the self-assembly of P3HT-b-P3TEGT into core-shell nanoparticles, which was further decorated with mannose, leading to an easy-to-use solution-processable nanoparticle material for biosensing. The hydrophilic block P3TEGT promotes antifouling and prevents nonspecific interactions, while improving the ionic and electronic transport properties, thus enhancing the electrochemical-sensing capability in aqueous solution. Self-assembly and micelle formation of P3HT-b-P3TEGT were analyzed by 2D-NMR, Fourier transform infrared, dynamic light scattering, contact angle, and microscopy characterizations. Detection of E. coli was characterized and evaluated using electrochemical impedance spectroscopy and optical and scanning electron microscopy techniques. The sensing layer based on the mannose-functionalized P3HT-b-P3TEGT nanoparticles demonstrates targeting ability toward E. coli pili protein with a detection range from 103 to 107 cfu/mL, and its selectivity was studied with Gram(+) bacteria. Application to real samples was performed by detection of bacteria in tap and the Nile water. The approach developed here shows that water/alcohol-processable-functionalized conjugated polymer nanoparticles are suitable for use as electrode materials, which have potential application in fabrication of a low-cost, label-free impedimetric biosensor for the detection of bacteria in water.

Correlations Between Clinical Trial Outcomes Based on Symptoms, Functional Impairments, and Quality of Life in Children and Adolescents With ADHD.

OBJECTIVE: To assess relationships between treatment-associated changes in measures of ADHD symptoms, functional impairments, and health-related quality of life in children and adolescents with ADHD. METHOD: Pearson correlation coefficients were calculated post hoc for changes from baseline to endpoint in outcomes of one randomized, placebo- and active-controlled trial of lisdexamfetamine (osmotic-release methylphenidate reference) and one of guanfacine extended-release (atomoxetine reference). RESULTS: Changes in ADHD Rating Scale IV (ADHD-RS-IV) total score generally correlated moderately with changes in Child Health and Illness Profile-Child Edition: Parent Report Form (CHIP-CE:PRF) Achievement and Risk Avoidance ( r ≈ .4), but weakly with Resilience, Satisfaction, and Comfort ( r ≈ .2); and moderately with Weiss Functional Impairment Rating Scale-Parent (WFIRS-P) total score ( r ≈ .5). CHIP-CE: PRF Achievement and Risk Avoidance correlated moderately to strongly with WFIRS-P total score ( r ≈ .6). CONCLUSION: The ADHD-RS-IV, CHIP-CE:PRF, and WFIRS-P capture distinct but interconnected aspects of treatment response in individuals with ADHD.

Health-Related Quality of Life and Work Productivity of Adults With ADHD: A U.K. Web-Based Cross-Sectional Survey.

OBJECTIVE: The objective of this study was to assess health-related quality of life (HRQoL) in adult ADHD. METHOD: U.K. residents aged 18 to 55 years with ADHD and no major mental health comorbidities completed an online survey of disorder history, the EuroQoL 5-Dimensions 5-Level (EQ-5D-5L), and the Work Productivity and Activity Impairment Questionnaire: General Health (WPAI:GH). ADHD Rating Scale-IV (ADHD-RS-IV) score was assessed by telephone. RESULTS: In total, 233 participants completed the study (mean age 32.6 years; 65.2% women). Mean ( SD) ADHD-RS-IV total score, EQ-5D utility, and visual analog scale (VAS) scores were 43.5 (7.88), 0.74 (.21), and 69.8 (17.76), respectively. Mean ( SD) WPAI:GH scores indicated that health problems caused 45.7% (29.9) overall work impairment and 45.8% (28.9) impairment in regular daily activities. Greater work and activity impairment were both significantly independently associated with lower utility after adjusting for age, gender, and somatic comorbidities. CONCLUSION: Adult ADHD impairs HRQoL, work productivity, and regular daily activities.

Population-based cohort of 500 patients with Gaucher disease in Israel.

OBJECTIVE: To characterise a population-based cohort of patients with Gaucher disease (GD) in Israel relative to the general population and describe sociodemographic and clinical differences by disease severity (ie, enzyme replacement therapy [ERT] use). DESIGN: A cross-sectional study was conducted. SETTING: Data from the Clalit Health Services electronic health record (EHR) database were used. PARTICIPANTS: The study population included all patients in the Clalit EHR database identified as having GD as of 30 June 2014. RESULTS: A total of 500 patients with GD were identified and assessed. The majority were ≥18 years of age (90.6%), female (54.0%), Jewish (93.6%) and 34.8% had high socioeconomic status, compared with 19.0% in the general Clalit population. Over half of patients with GD with available data (51.0%) were overweight/obese and 63.5% had a Charlson Comorbidity Index ≥1, compared with 46.6% and 30.4%, respectively, in the general Clalit population. The majority of patients with GD had a history of anaemia (69.6%) or thrombocytopaenia (62.0%), 40.4% had a history of bone events and 22.2% had a history of cancer. Overall, 41.2% had received ERT. CONCLUSIONS: Establishing a population-based cohort of patients with GD is essential to understanding disease progression and management. In this study, we highlight the need for physicians to monitor patients with GD regardless of their ERT status.

A cost-effectiveness analysis of lisdexamfetamine dimesylate in the treatment of adults with attention-deficit/hyperactivity disorder in the UK.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is a chronic neurobehavioral disorder in children that may persist into adulthood. Lisdexamfetamine dimesylate (LDX) is approved in many countries for ADHD treatment in children, adolescents, and adults. OBJECTIVES: Estimate the cost-effectiveness of LDX as a first- or second-line treatment for adults with ADHD from the United Kingdom (UK) National Health Service (NHS) perspective compared with methylphenidate extended release (MPH-ER) and atomoxetine (ATX). METHODS: A 1-year decision-analytic model was developed. Health outcomes included response, non-response and inability to tolerate. Efficacy data were obtained from a mixed-treatment comparison (MTC). Response was a score of 1 or 2 on the Clinical Global Impression-Improvement scale. Tolerability was assessed by discontinuation rates due to adverse events. Utilities were identified via a systematic literature review. Health care resource use estimates were obtained via a survey of clinicians. Daily drug costs were estimated from mean doses reported in the trials used in the MTC. One-way and probabilistic sensitivity analyses (PSAs) were performed. RESULTS: LDX dominated MPH-ER and ATX; reducing mean per-patient annual cost by £5 and £200, and increasing mean quality-adjusted life years (QALYs) by 0.005 and 0.009, respectively. In the PSA, the probability of cost-effectiveness for LDX vs. MPH-ER and ATX at a threshold of £20,000 per QALY was 61% and 80%, respectively. CONCLUSIONS: From the perspective of the UK NHS, LDX is likely to provide a cost-effective treatment for adults with ADHD. This conclusion may be drawn with more certainty in comparison with ATX than with MPH-ER.

Treatment outcomes after methylphenidate in adults with attention-deficit/hyperactivity disorder treated with lisdexamfetamine dimesylate or atomoxetine.

PURPOSE: To compare treatment adherence, discontinuation, add-on, and daily average consumption (DACON) among adults with attention-deficit/hyperactivity disorder receiving second-line lisdexamfetamine dimesylate (LDX) or atomoxetine (ATX), following methylphenidate. PATIENTS AND METHODS: A retrospective cohort study using US commercial claims databases (Q2/2009-Q3/2013). RESULTS: At month 12, the LDX cohort (N=2,718) had a higher adherence level (proportion of days covered: 0.48 versus 0.30, P<0.001) and was less likely to discontinue (Kaplan-Meier estimate: 63% versus 85%, P<0.001) than the ATX cohort (N=674). There were no statistical differences in treatment add-on rates between cohorts (Kaplan-Meier estimate: 26% versus 25%, P=0.297). The LDX cohort had a lower DACON (1.10 versus 1.31, P<0.001) and was less likely to have a DACON >1 (adjusted odds ratio: 0.20, 95% confidence interval: 0.15-0.25, P<0.001) than the ATX cohort. CONCLUSION: Adults with attention-deficit/hyperactivity disorder treated with LDX following methylphenidate had a higher treatment adherence and lower discontinuation and DACON relative to those treated with ATX following methylphenidate.

Cost-effectiveness of prucalopride in the treatment of chronic constipation in the Netherlands.

OBJECTIVE: To assess the cost-effectiveness of prucalopride vs. continued laxative treatment for chronic constipation in patients in the Netherlands in whom laxatives have failed to provide adequate relief. METHODS: A Markov model was developed to estimate the cost-effectiveness of prucalopride in patients with chronic constipation receiving standard laxative treatment from the perspective of Dutch payers in 2011. Data sources included published prucalopride clinical trials, published Dutch price/tariff lists, and national population statistics. The model simulated the clinical and economic outcomes associated with prucalopride vs. standard treatment and had a cycle length of 1 month and a follow-up time of 1 year. Response to treatment was defined as the proportion of patients who achieved "normal bowel function". One-way and probabilistic sensitivity analyses were conducted to test the robustness of the base case. RESULTS: In the base case analysis, the cost of prucalopride relative to continued laxative treatment was € 9015 per quality-adjusted life-year (QALY). Extensive sensitivity analyses and scenario analyses confirmed that the base case cost-effectiveness estimate was robust. One-way sensitivity analyses showed that the model was most sensitive in response to prucalopride; incremental cost-effectiveness ratios ranged from € 6475 to 15,380 per QALY. Probabilistic sensitivity analyses indicated that there is a greater than 80% probability that prucalopride would be cost-effective compared with continued standard treatment, assuming a willingness-to-pay threshold of € 20,000 per QALY from a Dutch societal perspective. A scenario analysis was performed for women only, which resulted in a cost-effectiveness ratio of € 7773 per QALY. CONCLUSION: Prucalopride was cost-effective in a Dutch patient population, as well as in a women-only subgroup, who had chronic constipation and who obtained inadequate relief from laxatives.

Economic burden associated with chronic constipation in Sweden: a retrospective cohort study.

BACKGROUND: Chronic constipation is a common condition, but few studies have assessed its cost and impact on resource use. The purpose of this cohort study was to assess the health care utilization and costs of chronic constipation in a Swedish population using health care claims data. METHODS: Data were compiled on health care costs, drug costs, and mortality for Västra Götaland, Sweden (2005-2009). These data were used to identify patients aged 18 years or older with chronic constipation, defined as: at least two health care contacts with a primary diagnosis of constipation within 12 months or at least one care contact with a primary diagnosis of constipation and two dispatches of laxatives 6 months before and 12 months after the index date. Patients with irritable bowel syndrome or taking opioids, both of which can cause constipation, were excluded. Costs, resource use, comorbidities, and laxative use were assessed during a 12-month follow-up period. RESULTS: In total, 4,043 patients with chronic constipation were identified. They had a mean (SD) age of 67±18 years. Mortality was 7% during the 12-month follow-up period and the most common comorbidity was hypertension (22%). In the 12-month follow-up period, patients with chronic constipation had a mean (SD) of 2.3±7.5 constipation-related health care contacts and a mean (SD) of 15.2±19.5 other health care contacts. Annual costs, adjusted for sex, age group, mortality, and comorbidities, were €5,388, of which €951 were for constipation-related care. CONCLUSION: Patients with chronic constipation constituted an elderly population with a high disease burden in Sweden between 2005 and 2009. Mean annual constipation-related health care costs, adjusted for potentially confounding factors, were €951 per patient.

Constipation-related direct medical costs in 16 887 patients newly diagnosed with chronic constipation.

BACKGROUND: Chronic constipation is a common condition, but the exact impact on healthcare budgets in Western Europe is poorly documented. OBJECTIVES: The aim of this study was to (a) investigate chronic constipation-related direct medical costs in patients with newly diagnosed chronic constipation and (b) study differences in costs according to natural history. PATIENTS AND METHODS: We identified 16 887 patients newly diagnosed with chronic constipation in a Dutch health insurance database (∼1.3 million patients) in 2006-2009. Individuals with chronic constipation were selected on the basis of chronic laxative use (≥90 days/year) and diagnostic related groups for chronic constipation. On the basis of the episodes of laxative use and diagnostic related groups, individuals were categorized as having persistent, episodic, and nonrecurrent disease. Unadjusted costs for laxatives and hospital care for chronic constipation and constipation-related comorbidities were assessed and compared between patients with nonrecurrent, episodic, and persistent disease. Factors associated with costs were identified using Cox regression analyses. RESULTS: The mean total chronic constipation-related direct medical costs in the first year after diagnosis were &OV0556;310±845 and consisted of laxatives (45%) and hospital care for chronic constipation (26%) as well as constipation-related comorbidities (29%). Costs were highest in patients with persistent disease (&OV0556;367±882) compared with patients with episodic (&OV0556;292±808) and nonrecurrent (&OV0556;263±613) disease (P<0.01). Male sex was associated with higher costs, whereas increasing age, diabetes, and use of opioids were associated with lower costs. CONCLUSION: Pharmacy costs and hospital care costs for chronic constipation-related comorbidities were the largest cost drivers for total constipation-related direct medical costs in patients with newly diagnosed chronic constipation. Direct medical costs differed according to patient characteristics.

Value of Provoked or Spontaneous Flank Pain in Men with Febrile Urinary Tract Infections.

BACKGROUND: Our objective was to identify the clinical, laboratory and radiological characteristics of febrile urinary tract infections (UTI) in men and to focus on the value of flank pain in these men managed in an ambulatory care system. METHODS: A network was designed to manage men with febrile UTI without hospitalization according to an algorithm designed with different specialists. The patients' characteristics were prospectively recorded and each patient was followed up until completely cured. We artificially divided patients into two groups. Group 1: men without flank pain diagnosed as prostatitis and a second group (Group 2) of men with flank pain or provoked flank pain more likely to have a pyelonephritis. Groups were compared to find arguments to differentiate prostatitis to pyelonephritis. RESULTS: 350 men were included in the study, half of these men reported urinary symptoms (dysuria, urgency and burning urination). The negative predictive values of the nitrite and leukocytes test were poor alone or in combination. The renal ultrasound was never informative. None of the patients failed to respond to the treatment. No difference was found between groups. CONCLUSIONS: Laboratory test results and radiological features had a poor predictive value. Men with suspected pyelonephritis did not evolve differently from those with suspected prostatitis. Monitoring and treatment of men with febrile UTI does not seem to depend on the existence of a pyelonephritis suspected after the presence of a lumbar pain. Ambulatory management of febrile UTI is feasible and safe, requiring an efficient network for patient's surveillance.

Probing structure and dynamics of bulk and confined crude oils by multiscale NMR spectroscopy, diffusometry, and relaxometry.

We propose using a set of noninvasive multiscale NMR techniques for probing the structure and dynamics of bulk and confined crude oils with and without asphaltene. High-field 1D (1)H and (13)C NMR spectroscopies evidence the proton species and the amount of asphaltene and give an average chain length for the hydrocarbon aliphatic chains. Two-dimensional (1)H diffusion-ordered NMR spectroscopy (DOSY) spectra allow us to identify two populations of hydrocarbons characterized by two distributions of translational diffusion coefficients in the presence of asphaltene and a single one without asphaltene. A detailed analysis of the distributions of longitudinal, T1, relaxation times measured at different magnetic fields is proposed in terms of highly skewed bimodal (or monomodal) log-normal distributions, confirming the two environments in the presence of asphaltene and a single one without asphaltene. We show that these distributions are similar to the gas and gel permeation chromatography distributions, thus showing a connection of the hydrocarbon dynamics with their chain lengths. The remarkable observed features of the nuclear magnetic relaxation dispersion (NMRD) profiles of <1/T1> for bulk and confined crude oils with and without asphaltene are interpreted with an original relaxation model of intermittent surface dynamics of proton species at the proximity of asphaltene nanoaggregates and bulk dynamics in between clusters of these nanoaggregates. This allows us to probe the 2D translational diffusion correlation time and the time of residence of hydrocarbons in the proximity of the asphaltene nanoaggregates. Provided that the diffusion of the hydrocarbons close to the asphaltene nanoaggregates is three times smaller than the bulk diffusion, as the DOSY experiments show, this time of residence gives an average radius of exploration for the 2D hydrocarbon diffusion, r2D ≈ 3.9 nm, of the same order of magnitude as the aggregate sizes found by J. Eyssautier with SAXS and SANS in asphaltene solutions and by O. C. Mullins with the observation of gravitational gradients of asphaltenes in oilfield reservoirs.

Generating spin turbulence through nonlinear excitation in liquid-state NMR.

Chaotic dynamics of a water magnetization in a 600 MHz NMR spectrometer was generated by a radiation damping-based electronic feedback. Erratic induction signal was observed for several tens of seconds. The analysis of the data shows that this chaotic behaviour can be ascribed to spin turbulence in the sample and that a simpler model based on the three-dimensional Bloch equations modified to include a feedback field may not account for the experimental data.