Forgoing Preoperative Manometry for Minimally Invasive Hiatal Hernia Repair.

INTRODUCTION: Hiatal hernia commonly occurs in adults. Although most patients are asymptomatic, some experience reflux symptoms or dysphagia. These patients are frequently managed with acid suppression and lifestyle changes. However, medical management does not provide durable relief for some patients; therefore, surgical repair is considered. Routine preoperative investigations include esophagoscopy, esophagography, and manometry. We investigated the role of preoperative motility studies for the management of these patients when partial fundoplication is planned. METHODS: We performed a retrospective review of 185 patients who underwent elective minimally invasive hiatal hernia repair with partial fundoplication between 2014 and 2018. Patients were divided into two groups based on whether a preoperative motility study was performed. The primary outcomes were postoperative dysphagia, complications, postoperative interventions, and use of proton pump inhibitors. RESULTS: Ninety-nine patients underwent preoperative manometry and 86 did not. The lack of preoperative manometry was not associated with increased postoperative morbidity, including leak rate, readmission, and 30-d mortality. The postoperative dysphagia rates of the manometry and nonmanometry groups were 5% (5/99 patients) and 7% (6/86 patients) (P = 0.80), respectively. Furthermore, seven of 99 (7%) patients in the manometry group and 10 of 86 (12%) (P = 0.42) patients in the nonmanometry group underwent interventions, mainly endoscopic dilation, postoperatively owing to symptom recurrence. CONCLUSIONS: Forgoing preoperative manometry was not associated with significant adverse outcomes after minimally invasive hiatal hernia repair. Although manometry is reasonable to perform, it should not be considered a mandatory part of the preoperative assessment when partial fundoplication is planned.

Orb2 enables rare-codon-enriched mRNA expression during Drosophila neuron differentiation.

Regulation of codon optimality is an increasingly appreciated layer of cell- and tissue-specific protein expression control. Here, we use codon-modified reporters to show that differentiation of Drosophila neural stem cells into neurons enables protein expression from rare-codon-enriched genes. From a candidate screen, we identify the cytoplasmic polyadenylation element binding (CPEB) protein Orb2 as a positive regulator of rare-codon-dependent mRNA stability in neurons. Using RNA sequencing, we reveal that Orb2-upregulated mRNAs in the brain with abundant Orb2 binding sites have a rare-codon bias. From these Orb2-regulated mRNAs, we demonstrate that rare-codon enrichment is important for mRNA stability and social behavior function of the metabotropic glutamate receptor (mGluR). Our findings reveal a molecular mechanism by which neural stem cell differentiation shifts genetic code regulation to enable critical mRNA stability and protein expression.

Long-term safety of dietary salt: A 5-year ProspEctive rAndomized bliNded and controlled stUdy in healThy aged cats (PEANUT study).

BACKGROUND: High-salt diets promote urine dilution and decrease urolithiasis risk. OBJECTIVE: Prospectively evaluate the safety of chronic high dietary salt intake (randomized controlled trial). ANIMALS: Twenty research colony neutered, healthy aged cats (11.5 years [10.0-11.6], median [interquartile range]). METHODS: Healthy cats were randomized to control or high-salt dry diets (sodium: 1.02 ± 0.16 [mean, SD] and 3.26 ± 0.30 g/Mcal metabolizable energy [ME], respectively; chloride: 2.26 ± 0.33 and 5.71 ± 0.28 g/Mcal ME, respectively), fed for up to 60 months. Assessments included CBC, plasma biochemistry, urinalysis, glomerular filtration rate (GFR), blood pressure, renal and cardiac (conventional Doppler and 2-dimensional color tissue Doppler) imaging, annually. Cats that died or were euthanized underwent necropsy. Diet effects over time were evaluated with linear mixed models. RESULTS: Follow-up duration (median [Interquartile range]) was similar between the control (38.7 months [28.6-48.2]) and high-salt group (51.4 months [45.7-59.0]). Diet had no significant effect on changes in GFR, blood pressure, plasma creatinine concentration, end-diastolic left ventricular (LV) wall thicknesses, LV internal diameters, LV systolic function, left atrial size, or systolic and diastolic Doppler variables. One control cat developed hypertension. One high-salt group cat developed persistent azotemia. Serial plasma biochemistry and urine specific gravity suggested early chronic kidney disease in 4 nonazotemic cats (2 per group), consistent with necropsy findings. CONCLUSIONS AND CLINICAL IMPORTANCE: In healthy aged cats, a commercial veterinary diet containing 3.26 ± 0.30 g/Mcal ME sodium was safe with regard to renal and cardiac function for up to 5 years.

Efficacy and Safety of Risperidone in Patients With Delirium: The RIDDLE Pilot Study.

BACKGROUND: The cornerstone treatment of delirium is to assess and treat its underlying causes and prevent further complications. Drug therapy may be necessary to control agitation and behavioral symptoms associated with delirium. The aim of this pilot study was to evaluate the feasibility of a randomized placebo controlled trial to evaluate the efficacy and safety of risperidone in the treatment of delirium. METHODS: This was a randomized double-blinded placebo-controlled trial. Patients were enrolled in the study if they were hospitalized and 65 years or older and had a diagnosis of delirium. Delirium Rating Scale revised 98 was used to determine delirium and motor agitation. RESULTS: A total of 14 participants with 57% being men and having a mean age of 86 years were included. There were no statistically significant differences between the risperidone and placebo group for the Delirium Rating Scale revised 98 score. There were no severe adverse reactions reported in the study, and no patients discontinued the study for adverse reactions. CONCLUSIONS: Risperidone at low doses (1 mg daily or less) was well tolerated for the treatment of delirium. Future large-scale trials are needed to evaluate the safety and efficacy of risperidone in the treatment of delirium. This pilot study taught us that the phase 2 RIsperDone DELirium trial will need a multicenter design with more research personnel to increase the number of participants enrolled.

Orb2 enables rare-codon-enriched mRNA expression during Drosophila neuron differentiation.

Regulation of codon optimality is an increasingly appreciated layer of cell- and tissue-specific protein expression control. Here, we use codon-modified reporters to show that differentiation of Drosophila neural stem cells into neurons enables protein expression from rare-codon-enriched genes. From a candidate screen, we identify the cytoplasmic polyadenylation element binding (CPEB) protein Orb2 as a positive regulator of rare-codon-dependent expression in neurons. Using RNA sequencing, we reveal that Orb2-upregulated mRNAs in the brain with abundant Orb2 binding sites have a rare-codon bias. From these Orb2-regulated mRNAs, we demonstrate that rare-codon enrichment is important for expression control and social behavior function of the metabotropic glutamate receptor (mGluR). Our findings reveal a molecular mechanism by which neural stem cell differentiation shifts genetic code regulation to enable critical mRNA and protein expression.

Effectiveness of prescribing codes in reducing inappropriate proton pump inhibitors in ambulatory care.

BACKGROUND: Health care deciders are aware of the inappropriate use of proton pump inhibitors (PPIs). To reduce inappropriate prescriptions, the Conseil du Médicament (CdM) issued a practice guideline and the Régie de l'Assurance Maladie du Quebec (RAMQ) asked prescribers to justify its use by writing a specific indication code for their patients to obtain drug coverage. OBJECTIVES: This study aimed to evaluate the effectiveness of the intervention by the RAMQ to reduce inappropriate PPI prescription. METHODS: A cross-sectional quasi-experimental prospective study was performed in an emergency department. Patients aged 18 years or older were included in 2016 to 2017 and 2019 to 2021 in the pre- and postintervention group, respectively. The proportion of patients on PPI without an appropriate indication were identified from patient interviews and chart review. RESULTS: A total of 871 and 1475 patients were recruited in the pre- and postintervention groups. According to the CdM guideline, the proportion of inappropriate PPI prescription was 30.7% (n = 267) in the preintervention group and 49.1% (n = 724) in the postintervention group (P < 0.001). According to the RAMQ criteria, the proportion of inappropriate PPI prescription was of 76.1% (n = 663) and 81.4% (n = 1200) in the pre- and postintervention group, respectively (P < 0.001). CONCLUSION: This study highlights the ineffectiveness of the codes for PPI prescriptions in reducing inappropriate prescriptions. It seems that the obligation to write a code does not lead to a reassessment of PPI indication.

Common Conditions II: Acute Appendicitis, Intussusception, and Gastrointestinal Bleeding.

Perforated appendicitis continues to be a significant cause of morbidity for children. In most centers, ultrasound has replaced computed tomography as the initial imaging modality for this condition. Controversies surrounding optimal medical and surgical management of appendicitis are discussed. Management of intussusception begins with clinical assessment and ultrasound, followed by image-guided air or saline reduction enema. When surgery is required, laparoscopy is typically utilized unless bowel resection is required. The differential diagnosis for pediatric gastrointestinal bleeding is broad but often made with age, history, and physical examination. Endoscopy or laparoscopy is sometimes needed to confirm a diagnosis or for treatment.

Safety And Efficacy of Clonidine for Acute Hypertensive Urgency in an Older and Hospitalized Population.

Objective To describe the use of clonidine in hospitalized older people for acute management of hypertension. Methods This was an observational retrospective cross-sectional chart review study. Older people hospitalized between November 2017 and November 2018, with a one-time or as-needed clonidine order were eligible, and a random sample of these patients were included. Hospitalized patients could be admitted for hypertensive urgency or emergency, or for other reasons. Results During the 12-month study period, 546 charts were identified as having at least one clonidine prescription, 248 were screened and 205 were included. The mean age was 75 years of age ± 8 years of age and men made up 53% (n = 109) of the group. One hundred fifty-one patients (74%) received at least one dose of clonidine and the remaining patients has a clonidine prescription but did not reach the blood pressure threshold for clonidine administration. The mean number of doses per patient was 1.8 ± 2.0. Twenty-nine percent of clonidine doses were given when systolic and diastolic blood pressure was below 180 mmHg and 120 mmHg respectively. A total of 25 patients (17%) had a potential adverse reaction following clonidine administration. One patient had a stroke and two patients fell. Sixty-eight patients had evidence of target organ dysfunction related to hypertension prior to clonidine administration. Conclusions Clonidine remains widely prescribed in hospitalized older people. It is possibly due to its rapid onset and little need for dosing adjustment. Clinical interventions should be designed and implanted to reduce its prescription.

Differences in Metabolic Profiles of Healthy Dogs Fed a High-Fat vs. a High-Starch Diet.

Obesity is a common problem in dogs and overconsumption of energy-rich foods is a key factor. This study compared the inflammatory response and fecal metabolome of dogs fed a high-fat vs. a high-starch diet. Ten healthy lean adult beagles were equally allocated into two groups in a cross-over design. Each group received two diets in which fat (horse fat) and starch (pregelatinized corn starch) were exchanged in an isocaloric way to compare high fat vs. high starch. There was a tendency to increase the glucose and glycine concentrations and the glucose/insulin ratio in the blood in dogs fed with the high-fat diet, whereas there was a decrease in the level of Non-esterified fatty acids and a tendency to decrease the alanine level in dogs fed with the high-starch diet. Untargeted analysis of the fecal metabolome revealed 10 annotated metabolites of interest, including L-methionine, which showed a higher abundance in dogs fed the high-starch diet. Five other metabolites were upregulated in dogs fed the high-fat diet, but could not be annotated. The obtained results indicate that a high-starch diet, compared to a high-fat diet, may promote lipid metabolism, anti-oxidative effects, protein biosynthesis and catabolism, mucosal barrier function, and immunomodulation in healthy lean dogs.

Beneficial effects of a prescription home-prepared diet and of zucchini on urine calcium oxalate supersaturation and urinary parameters in adult cats.

OBJECTIVES: From the authors' experience, the consumption of a balanced prescription home-prepared diet that includes zucchini (courgette) benefits cats with recurrent urolithiasis, but there is no published evidence to support this. The aim was to study the effects on urinary parameters of (1) a balanced prescription home-prepared diet containing zucchini, and (2) the addition of zucchini to a dry food, compared with two commercial therapeutic diets. METHODS: Eight healthy cats were included in a Latin-square designed protocol. Five diets were evaluated: two commercial diets, designed for cats with urinary disorders, one high-moisture (U-WET) and one high-sodium dry (U-DRY); one home-prepared diet (HOME); one commercial dry food for adult maintenance (DRY); and DRY given together with 10 g of zucchini per kg body weight (DRY-Zuc). After a 7-day adaptation period, urine was collected and daily food and water intakes were assessed for 12 days. Urinary parameters, and relative supersaturation (RSS) for calcium oxalate (CaOx) and struvite, were determined. Data underwent repeated measures ANOVA analysis. RESULTS: The digestibility of energy, dry matter, protein and fat was highest with the HOME diet. CaOx RSS was lowest in cats eating the HOME diet, but not significantly different from the U-WET or U-DRY diets. CaOx RSS was lower in cats eating the DRY-Zuc diet than in cats eating the DRY diet. Struvite RSS did not differ significantly among groups. CONCLUSIONS AND RELEVANCE: This study shows that a balanced prescription home-prepared diet was safe and allowed a very low urinary CaOx RSS. It also showed that adding zucchini to dry food lowered the urine CaOx RSS.

Factors associated with late-life psychosis in primary care older adults without a diagnosis of dementia.

PURPOSE: The epidemiology of late-life psychosis (LLP) remains unclear comparatively to early-onset psychosis. The study aims to estimate the prevalence and incidence of LLP over a 3-year period and examine the correlates of LLP in community-living older adults aged ≥ 65 years recruited in primary care. METHODS: Study sample included N = 1481 primary care older adults participating in the Étude sur la Santé des Aînés (ESA)-Services study. Diagnoses were obtained from health administrative and self-reported data in the 3 years prior and following baseline interview. The prevalence and incidence of LLP (number of cases) were identified in the 3-year period following interview. Participants with dementia or psychosis related to dementia were excluded. Logistic regressions were used to ascertain the correlates of LLP as function of various individual and health system factors. RESULTS: The 3-year prevalence and incidence of LLP was 4.7% (95% CI = 3.64-5.81) and 2.8% (95% CI = 1.99-3.68), respectively. Factors associated with both prevalent and incident LLP included functional status, number of physical diseases, hospitalizations, continuity of care and physical activity. Older age and the presence of suicidal ideation were associated with incident LLP, while higher education, a depressive disorder and a history of sexual assault were associated with persistent cases. CONCLUSIONS: Results highlight the importance of LLP in primary care older adult patients without dementia. Health system factors were consistent determinants of prevalent and incident LLP, suggesting the need for better continuity of care in at-risk primary care older adults.

Enhancing the Natural Biological Control in the Thyroid Hormone Homeostasis As a First-Order Control System.

This study explores the natural control system that exists within the pituitary gland. More specifically, this study investigates the regulation of the thyroid stimulating hormone (TSH), released by the anterior pituitary, with regards to the thyroid releasing hormone (TRH), which is released by the hypothalamus. Using appropriate assumptions on the behavior of the hormones, along with relevant boundary conditions, we modeled an output of TSH using constant TRH input over the course of a six-hour period. Other relevant hormones such as thyroxine (T4), triiodothyronine (T3), and their relevant intermediaries were also modeled as a means to complete the natural feedback found physiologically. Due to our boundary conditions, we do not consider the consumption or final function of these hormones since they leave the pituitary gland, our control system; instead, we consider a constant TRH since it is produced by the hypothalamus. Finally, we explore the results of reducing the TRH input while observing the TSH response. We append a short loop controller feedback that uses the TSH output to regulate a TRH input to remedy the reduction of TRH. The open-loop transfer function derived presented three poles at the clearance exponents for T4, TSH, and central T3, with a phase margin of 74.1°, characterizing a stable but slow system that can be improved with a simple proportional control.

Medication appropriateness on an acute geriatric care unit: the impact of the removal of a clinical pharmacist.

BACKGROUND: evidence is largely available indicating benefits to adding a pharmacist on acute care wards. The benefits of maintaining pharmacotherapeutic consultant services on a geriatric ward remain unexplored. OBJECTIVES: to determine the impact of the removal of a clinical pharmacist from an acute geriatric ward on patients' Medication Appropriateness Index (MAI) scores, admission-related outcomes and drug burdens. METHODS: researchers consulted the archives for records of patients admitted to the geriatric care unit before and after the pharmacist's withdrawal. The primary outcome of differential MAI scores and secondary outcomes of rehospitalisations, emergency department visits, durations of hospitalisation and differential drug count were compared pre- and post-intervention. An interrupted time series analysis regression model was used for the primary outcome. RESULTS: a total of 305 patients admitted before (n = 208) and after (n = 97) the pharmacist's withdrawal were included in the study. The intervention had a significant impact on the primary outcome, increasing the relative differential MAI score (adjusted mean) by 9.3 points (95% confidence interval 3.9-14.6). As for the secondary outcomes, differences in admission-related outcomes were non-significant but the mean differential drug count significantly increased post-intervention from 0.02 to 1.36 (P < 0.001). CONCLUSION: the removal of the pharmacist led to an increase in inappropriate drug prescription. Careful consideration should be given to decisions regarding the removal of the pharmacist from acute geriatric care teams.

Effects of High-Fat Diet at Two Energetic Levels on Fecal Microbiota, Colonic Barrier, and Metabolic Parameters in Dogs.

Increased consumption of energy-rich foods is a key factor in overweight, obesity, and associated metabolic disorders. This would be, at least in part, related to microbiota disturbance. In rodent models of obesity, microbiota disruption has been associated with alteration of the intestinal barrier, endotoxemia, inflammation grade, and insulin sensitivity. The aim of the present study was to assess the effects of a high-fat diet (HFD), fed at two energetic levels, on microbiota, intestinal barrier, and inflammatory and metabolic parameters in dogs. A HFD (33% fat as fed, 4,830 kcal/kg) was given to 24 healthy Beagle dogs at 100% (HF-100; n = 8) and at 150% (HF-150; n = 16) of their maintenance energy requirements for 8 weeks. Analysis of similarity revealed a significant difference in gut microbiota ß-diversity following the diet compared to week 0 in both groups while α-diversity was lower only in the HF-150 group. Firmicutes/Bacteroidetes ratio was higher in the HF-150 group compared to the HF-100 group at weeks 2 and 8. A reduction in insulin sensitivity was observed over time in the HF150 group. Neither endotoxemia nor inflammation was observed in either group, did not find supporting data for the hypothesis that the microbiota is involved in the decline of insulin sensitivity through metabolic endotoxemia and low-grade inflammation. Colonic permeability was increased at week 4 in both groups and returned to initial levels at week 8, and was associated with modifications to the expression of genes involved in colonic barrier function. The increase in intestinal permeability may have been caused by the altered intestinal microbiota and increased expression of genes encoding tight junction proteins might indicate a compensatory mechanism to restore normal permeability. Although simultaneous changes to the microbiota, barrier permeability, inflammatory, and metabolic status have not been observed, such a causal link cannot be excluded in dogs overfed on a HFD. Further studies are necessary to better understand the link between HFD, intestinal microbiota and the host.

Impact of Pharmacist Interventions in an Ambulatory Geriatric Care Clinic: The IMPACC Study.

OBJECTIVE: To compare the impact of a pharmacist's presence for the detection of drug-related problems (DRP) in an interdisciplinary geriatric-ambulatory clinic with a control group without a pharmacist.
DESIGN: Retrospective quasi-experimental study.
SETTING: A geriatric ambulatory-care clinic of a 772-bed tertiary-care teaching hospital in Montreal, Canada.
PARTICIPANTS: A total of 227 ambulatory patients 65 years of age and older presenting to their appointment at the geriatric ambulatory clinic between May 1, 2018, and April 30, 2019.
MAIN OUTCOME MEASURE(S): DRP detected by the interdisciplinary team during the patient evaluation process. Data were collected from clinical notes written by the health care professionals in the electronic medical chart.
RESULTS: The mean age was 80.8 years, and 60.8% of the population were female. Patients were prescribed a mean of 11.3 medications at home. Overall, 636 DRP were detected in the study population. In the adjusted analysis, the difference between the two groups was 2.7 (95% confidence interval 2.0-3.3) DRP detected favoring the group with a pharmacist.
CONCLUSION: The inclusion of a pharmacist in an interdisciplinary team in an ambulatory geriatric-care clinic was associated to a positive impact on care by substantially increasing the number of DRP detected in older patients.

Effect of Aqueous Extract and Polyphenol Fraction Derived from Thymus atlanticus Leaves on Acute Hyperlipidemia in the Syrian Golden Hamsters.

Thymus atlanticus, an endemic plant of Morocco, is traditionally used as a liniment or a drink to treat various diseases. However, there are few available scientific data regarding its biological effects. In this connection, the present study aimed to investigate the hypolipidemic and antioxidant effects of aqueous extract and polyphenol fraction of Thymus atlanticus in Syrian golden hamsters treated with Triton WR-1339 (triton, 20 mg/100 g body weight). The hamsters orally received the extracts (400 mg/kg), and blood samples were collected after 24 h of treatment to determine plasma lipid, insulin, and fasting blood glucose levels. Plasma malondialdehyde level and plasma total antioxidant (TAS) were also evaluated. The T. atlanticus extracts significantly decreased triglycerides, total cholesterol, VLDL-C, and LDL-C and increased HDL-C when compared with the hyperlipidemic group. Both extracts suppressed the effect of the triton injection on TAS and reduced the level of plasma malondialdehyde. The extracts produced no significant change in the blood glucose level but effectively prevented the mild hyperinsulinemia induced by triton. These findings suggest that T. atlanticus may be a useful alternative treatment for the control of hyperlipidemia and its related diseases.

Weight-gain induced changes in renal perfusion assessed by contrast-enhanced ultrasound precede increases in urinary protein excretion suggestive of glomerular and tubular injury and normalize after weight-loss in dogs.

Early detection of obesity-related glomerulopathy in humans is challenging as it might not be detected by routine biomarkers of kidney function. This study's aim was to use novel kidney biomarkers and contrast-enhanced ultrasound (CEUS) to evaluate the effect of obesity development and weight-loss on kidney function, perfusion, and injury in dogs. Sixteen healthy lean adult beagles were assigned randomly but age-matched to a control group (CG) (n = 8) fed to maintain a lean body weight (BW) for 83 weeks; or to a weight-change group (WCG) (n = 8) fed the same diet to induce obesity (week 0-47), to maintain stable obese weight (week 47-56) and to lose BW (week 56-83). At 8 time points, values of systolic blood pressure (sBP); serum creatinine (sCr); blood urea nitrogen (BUN); serum cystatin C (sCysC); urine protein-to-creatinine ratio (UPC); and urinary biomarkers of glomerular and tubular injury were measured. Glomerular filtration rate (GFR) and renal perfusion using CEUS were assayed (except for week 68). For CEUS, intensity- and time-related parameters representing blood volume and velocity were derived from imaging data, respectively. At 12-22% weight-gain, cortical time-to-peak, representing blood velocity, was shorter in the WCG vs. the CG. After 37% weight-gain, sCysC, UPC, glomerular and tubular biomarkers of injury, urinary immunoglobulin G and urinary neutrophil gelatinase-associated lipocalin, respectively, were higher in the WCG. sBP, sCr, BUN and GFR were not significantly different. After 23% weight-loss, all alterations were attenuated. Early weight-gain in dogs induced renal perfusion changes measured with CEUS, without hyperfiltration, preceding increased urinary protein excretion with potential glomerular and tubular injury. The combined use of routine biomarkers of kidney function, CEUS and site-specific urinary biomarkers might be valuable in assessing kidney health of individuals at risk for obesity-related glomerulopathy in a non-invasive manner.

Plasma homocysteine concentration in privately owned healthy adult cats: assessment of biological determinants and establishment of a reference interval.

OBJECTIVES: The assessment of homocysteine status in diseased cats has indicated high plasma concentrations in chronic kidney disease and yielded conflicting results with respect to cardiovascular disorders. Previous investigations in small populations of normal cats revealed greater-than-expected variability in plasma homocysteine concentration. The purpose of this study was to determine biological determinants and the reference interval (RI) of plasma homocysteine concentration in the feline species, under strict pre-analytical conditions. METHODS: In this prospective observational study, privately owned healthy adult cats underwent a complete physical examination, urinalysis and blood testing, in order to rule out any signs of disease. Plasma homocysteine concentration was measured using high-performance liquid chromatography-tandem mass spectrometry. RESULTS: Of 151 cats recruited, 30 cats were not included owing to abnormal physical examination or fractious behaviour, and 30 cats were excluded based on abnormalities on blood work or urinalysis. Plasma homocysteine concentrations >28 µmol/l were associated with a dietary protein content >9.3 g/100 kcal metabolisable energy. The RI for plasma homocysteine concentration was determined to be 6.2-52.3 µmol/l. CONCLUSIONS AND RELEVANCE: Normal values for plasma homocysteine concentration in cats have a wide RI, suggesting high inter-individual variability. Whether some healthy cats exhibit impaired homocysteine metabolism remains to be elucidated.

PFG-NMR as a Tool for Determining Self-Diffusivities of Various Probe Molecules through H-ZSM-5 Zeolites.

The understanding of major zeolite applications is partially based on diffusion of molecules inside or outside microporous networks. However, it is still a challenge to measure such phenomena. The diffusion ordered nuclear magnetic resonance spectroscopy (DOSY) technique has been reported to measure a probe molecule's diffusion inside porous solids. Pulsed-field gradient (PFG)-NMR has been used herein to measure the self-diffusivity of different probe molecules, such as neopentane, benzene, toluene and 1-dodecene with increasing dynamic diameter, respectively, on a series of H-ZSM-5 zeolites. The latter materials exhibit different crystal sizes, Si/Al ratios and the presence (or absence) of crystalline defects. In addition, shaped zeolite bodies representing industrial catalysts were compared with the afore-mentioned samples.