Otitis media at 6-monthly assessments of Australian First Nations children between ages 12-36 months: Findings from two randomised controlled trials of combined pneumococcal conjugate vaccines

OBJECTIVES

In remote communities of northern Australia, First Nations children with hearing loss are disproportionately at risk of poor school readiness and performance compared to their peers with no hearing loss. The aim of this trial is to prevent early childhood persisting otitis media (OM), associated hearing loss and developmental delay. To achieve this, we designed a mixed pneumococcal conjugate vaccine (PCV) schedule that could maximise immunogenicity and thereby prevent bacterial otitis media (OM) and a trajectory of educational and social disadvantage.

METHODS

In two sequential parallel, open-label, randomised controlled trials, eligible infants were first allocated 1:1:1 to standard or mixed PCV primary schedules at age 28-38 days, then at age 12 months to a booster dose (1:1) of 13-valent PCV, PCV13 (Prevenar13®, +P), or 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugated vaccine, PHiD-CV10 (Synflorix®, +S). Here we report findings of standardised ear assessments conducted six-monthly from age 12-36 months, by booster dose.

RESULTS

From March 2013 to September 2018, 261 children were allocated to booster + P (n = 131) or + S (n = 130). There were no significant differences in prevalence of any OM diagnosis by booster dose or when stratified by primary schedule. We found high, almost identical prevalence of OM in both boost groups at each age (for example 88% of 129 and 91% of 128 children seen, respectively, at primary endpoint age 18 months, difference -3% [95% Confidence Interval -11, 5]). At each age prevalence of bilateral OM was 52%-78%, and tympanic membrane perforation was 10%-18%.

CONCLUSION

Despite optimal pneumococcal immunisation, the high prevalence of OM persists throughout early childhood. Novel approaches to OM prevention are needed, along with improved early identification strategies and evaluation of expanded valency PCVs.

Dietary Tyrosine Intake (FFQ) Is Associated with Locus Coeruleus, Attention and Grey Matter Maintenance: An MRI Structural Study on 398 Healthy Individuals of the Berlin Aging Study-II

BACKGROUND AND OBJECTIVE

It is documented that low protein and amino-acid dietary intake is related to poorer cognitive health and increased risk of dementia. Degradation of the neuromodulatory pathways, (comprising the cholinergic, dopaminergic, serotoninergic and noradrenergic systems) is observed in neurodegenerative diseases and impairs the proper biosynthesis of key neuromodulators from micro-nutrients and amino acids. How these micro-nutrients are linked to neuromodulatory pathways in healthy adults is less studied. The Locus Coeruleus-Noradrenergic System (LC-NA) is the earliest subcortical structure affected in Alzheimer's disease, showing marked neurodegeneration, but is also sensitive for age-related changes. The LC-NA system is critical for supporting attention and cognitive control, functions that are enhanced both by tyrosine administration and chronic tyrosine intake. The purpose of this study was to 1) investigate whether the dietary intake of tyrosine, the key precursor for noradrenaline (NA), is related to LC signal intensity 2) whether LC mediates the reported association between tyrosine intake and higher cognitive performance (measured with Trail Making Test - TMT), and 3) whether LC signal intensity relates to an objective measure of brain maintenance (BrainPAD).

METHODS

The analyses included 398 3T MRIs of healthy participants from the Berlin Aging Study II to investigate the relationship between LC signal intensity and habitual dietary tyrosine intake-daily average (HD-Tyr-IDA - measured with Food Frequency Questionnaire - FFQ). As a control procedure, the same analyses were repeated on other main seeds of the neuromodulators' subcortical system (Dorsal and Medial Raphe, Ventral Tegmental Area and Nucleus Basalis of Meynert). In the same way, the relationships between the five nuclei and BrainPAD were tested.

RESULTS

Results show that HD-Tyr-IDA is positively associated with LC signal intensity. Similarly, LC disproportionally relates to better brain maintenance (BrainPAD). Mediation analyses reveal that only LC, relative to the other nuclei tested, mediates the relationship between HD-Tyr-IDA I and performance in the TMT and between HD-Tyr-IDA and BrainPAD.

CONCLUSIONS

These findings provide the first evidence linking tyrosine intake with LC-NA system signal intensity and its correlation with neuropsychological performance. This study strengthens the role of diet for maintaining brain and cognitive health and supports the noradrenergic theory of cognitive reserve. Within this framework, adequate tyrosine intake might increase the resilience of LC-NA system functioning, by preventing degeneration and supporting noradrenergic metabolism required for LC function and neuropsychological performance.

POS0346 THE THERAPEUTIC EFFECTS OF OMEGA-6 PUFA (PINOLENIC ACID) ON THE TRANSCRIPTOMIC PROFILE OF ACTIVATED PERIPHERAL BLOOD MONONUCLEAR CELLS ISOLATED FROM HEALTHY CONTROLS AND RHEUMATOID ARTHRITIS PATIENTS

Background:

Globally, Rheumatoid arthritis (RA) is the most common chronic inflammatory arthritis. EULAR recommends patient education and disease modifying anti-rheumatic drugs including advanced targeted therapies for management1 2. Many patients seek advice on a dietary intervention that may improve symptoms. Foods high in omega-3 polyunsaturated fatty acids (PUFAs) is one of the most common recommended based on their anti-inflammatory properties3 4. Previously we showed pinolenic acid (PNLA), an omega-6 (PUFAs) found in pine nuts, reduced lipid uptake, endocytosis and migration of monocyte in vitro. PNLA also reduced IL-6, TNF-α, IL-1β and PGE2 produced by lipopolysaccharide (LPS) activated PBMCs from patients with RA and healthy controls (HCs).

Objectives:

We hypothesis that PNLA inhibits key inflammatory processes in synovities as in diagram.1. We investigated the transcriptomic profile of PNLA treatment on LPS activated PBMCs isolated from HCs and RA patients.

Methods:

Adult RA patients (n=6) were recruited from the Rheumatology Department of University Hospital of Wales together with 6 HCs. Blood was collected after taking signed informed consent. PBMCs were isolated by Ficoll gradient centrifugation and pre-treated with 25 μM PNLA or vehicle and then activated with 100 ng/ml LPS. RNA was extracted followed by library construction and sequencing for whole genomic transcriptome. DEGs were analysed using DESeq2 and pathway analysis was performed using Ingenuity pathway analysis. The study was approved by the Research Ethics Committee for Wales (reference no. 12/WA/0045).

Results:

DEGs were selected with at least differential genes using at least 1.2* fold changes and adjusted p-value of <0.05. PNLA significantly upregulates the expression of PDK4, PAI-1 (SERPINE1), FBP1, and NDRG2. These genes have important roles in metabolic pathways. Pathway analysis predicted upstream activation of nuclear receptors peroxisome proliferator-activated receptor (PPARs) involved in the anti-inflammatory process, and inhibition of NF-κB and STAT1, the major transcription factors of the pro-inflammatory cytokines TNF-α, IL-1, IL-6 and IFN-γ.

Conclusion:

PNLA has significant effects on the regulation of metabolic and inflammatory pathways in PBMCs from RA patients and HCs. Based on these results we demonstrate that PNLA may have beneficial anti-inflammatory effects in patients with RA

References:

[1]Agca R, Heslinga SC, Rollefstad S, Heslinga M, McInnes. IB, Peters MJL, Kvien, TK., Dougados, M, Radner, H, Atzeni, F. and Primdahl, J. 2017. EULAR recommendations for cardiovascular disease risk management in patients with rheumatoid arthritis and other forms of inflammatory joint disorders: 2015/2016 update. Annals of the rheumatic diseases, 76(1), pp.17-28.

[2]Smolen JS, Landewé RBM, Bijlsma JWJ, et al. 2019. EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs: updateAnnals of the Rheumatic Diseases 2020; 79:685-699.

[3]Chehade L, Jaafar ZA, El Masri D, Zmerly H, Kreidieh D, Tannir H, Itani L, and El Ghoch, M. 2019. Lifestyle Modification in Rheumatoid Arthritis: Dietary and Physical Activity Recommendations Based on Evidence. Current rheumatology reviews, 15(3), pp.209-214.

[4]Marchand NE, Chiu Y-H, Yoshida K, Malspeis S, Sparks JA, Costenbader K, et al. Threshold Level for Long-term Healthy Diet Adherence to Reduce the Risk of Rheumatoid Arthritis Among Women in a Prospective Cohort Using a Marginal Structural Model Approach.:25.

Diagram 1.

Disclosure of Interests:

None declared

Improving understanding of type 2 diabetes remission: research recommendations from Diabetes UK's 2019 remission workshop

AIM

To describe the process and outputs of a workshop convened to identify key priorities for future research in the area of remission of type 2 diabetes, and provide recommendations to researchers and research funders on how best to address them. With the ultimate aim of enabling the remission of type 2 diabetes to become a possibility for more people.

METHODS

A 1-day research workshop was conducted, bringing together 31 researchers, people living with diabetes, healthcare professionals and members of staff from Diabetes UK to identify and prioritize recommendations for future research into remission of type 2 diabetes.

RESULTS

Workshop attendees identified 10 key themes for further research. Four of these themes were prioritized for further focus: (i) understanding how to personalize lifestyle approaches based on biology, patient choice and subtypes; (ii) understanding the biology of remission; (iii) understanding the most effective approaches to implementation of lifestyle interventions; and (iv) understanding the best approaches to combining therapies (gut hormones, other drugs, lifestyle approaches and bariatric surgery).

CONCLUSIONS

This paper outlines recommendations to address the current gaps in knowledge related to remission of type 2 diabetes.

Cancer and COVID-19: how understanding grief helps the pandemic frontlines

I first heard of Dr. Elisabeth Kübler-Ross in medical school, when learning how to deliver bad news. […]

Development of Azeliragon, an Oral Small Molecule Antagonist of the Receptor for Advanced Glycation Endproducts, for the Potential Slowing of Loss of Cognition in Mild Alzheimer's Disease

Increasing evidence supports the role of the Receptor for Advanced Glycation Endproducts (RAGE) in the pathology of Alzheimer's disease. Azeliragon (TTP488) is an orally bioavailable small molecule inhibitor of RAGE in Phase 3 development as a potential treatment to slow disease progression in patients mild AD. Preclinical studies in animal models of AD (tgAPPSwedish/London) have shown azeliragon to decrease Aβ plaque deposition; reduce total Aβ brain concentration while increasing plasma Aβ levels; decreases sAPPβ while increasing sAPPα; reduce levels of inflammatory cytokines; and slow cognitive decline and improve cerebral blood flow. In the Phase 2b study, 18-months treatment in patients with mild-to-moderate AD indicated a baseline to endpoint change in ADAS-cog of 3.1 points in favor of drug. A greater magnitude of effect was evident in the sub-group of patients with mild AD (MMSE 21-26) with a baseline to endpoint change of 4 points on the ADAS-cog in favor of azeliragon and a 1 point change in CDR-sb in favor of drug. Azeliragon 5 mg/day delayed time to cognitive deterioration (7-point change in ADAS-cog from baseline, logrank p=0.0149). Based on promising results from the Phase 2b study, a Phase 3 registration program (STEADFAST) is being conducted under a Special Protocol Assessment from FDA. The ongoing Phase 3 program, if successful may demonstrate azeliragon can slow cognitive decline in mild AD patients.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Large-scale discovery of novel genetic causes of developmental disorders

Despite three decades of successful, predominantly phenotype-driven discovery of the genetic causes of monogenic disorders, up to half of children with severe developmental disorders of probable genetic origin remain without a genetic diagnosis. Particularly challenging are those disorders rare enough to have eluded recognition as a discrete clinical entity, those with highly variable clinical manifestations, and those that are difficult to distinguish from other, very similar, disorders. Here we demonstrate the power of using an unbiased genotype-driven approach to identify subsets of patients with similar disorders. By studying 1,133 children with severe, undiagnosed developmental disorders, and their parents, using a combination of exome sequencing and array-based detection of chromosomal rearrangements, we discovered 12 novel genes associated with developmental disorders. These newly implicated genes increase by 10% (from 28% to 31%) the proportion of children that could be diagnosed. Clustering of missense mutations in six of these newly implicated genes suggests that normal development is being perturbed by an activating or dominant-negative mechanism. Our findings demonstrate the value of adopting a comprehensive strategy, both genome-wide and nationwide, to elucidate the underlying causes of rare genetic disorders.

What are the health benefits of physical activity in type 1 diabetes mellitus? A literature review

Physical activity improves well-being and reduces the risk of heart disease, cancer and type 2 diabetes mellitus in the general population. In individuals with established type 2 diabetes, physical activity improves glucose and lipid levels, reduces weight and improves insulin resistance. In type 1 diabetes mellitus, however, the benefits of physical activity are less clear. There is poor evidence for a beneficial effect of physical activity on glycaemic control and microvascular complications, and significant risk of harm through hypoglycaemia. Here we review the literature relating to physical activity and health in type 1 diabetes. We examine its effect on a number of outcomes, including glycaemic control, lipids, blood pressure, diabetic complications, well-being and overall mortality. We conclude that whilst there is sufficient evidence to recommend physical activity in the management of type 1 diabetes, it is still unclear as to what form, duration and intensity should be recommended and whether there is benefit for many of the outcomes examined.

Effect of the definition of type II diabetes remission in the evaluation of bariatric surgery for metabolic disorders

BACKGROUND

The American Diabetes Association recently defined remission of type II diabetes as a return to normal measures of glucose metabolism (haemoglobin (Hb) A1c below 6 per cent, fasting glucose less than 5·6 mmol/l) at least 1 year after bariatric surgery without hypoglycaemic medication. A previously used common definition was: being off diabetes medication with normal fasting blood glucose level or HbA1c below 6 per cent. This study evaluated the proportion of patients achieving complete remission of type II diabetes following bariatric surgery according to these definitions.

METHODS

This was a retrospective review of data collected prospectively in three bariatric centres on patients undergoing gastric bypass, sleeve gastrectomy and gastric banding.

RESULTS

Some 1006 patients underwent surgery, of whom 209 had type II diabetes. Median follow-up was 23 (range 12-75) months. HbA1c was reduced after operation in all three surgical groups (P < 0·001). A total of 72 (34·4 per cent) of 209 patients had complete remission of diabetes, according to the new definition; the remission rates were 40·6 per cent (65 of 160) after gastric bypass, 26 per cent (5 of 19) after sleeve gastrectomy and 7 per cent (2 of 30) after gastric banding (P < 0·001 between groups). The remission rate for gastric bypass was significantly lower with the new definition than with the previously used definition (40·6 versus 57·5 per cent; P = 0·003).

CONCLUSION

Expectations of patients and clinicians may have to be adjusted as regards remission of type II diabetes after bariatric surgery. Focusing on improved glycaemic control rather than remission may better reflect the benefit of this type of surgery and facilitate improved glycaemic control after surgery.

The truth will come to light: directions and challenges in extracting the knowledge embedded within trained artificial neural networks

To date, the preponderance of techniques for eliciting the knowledge embedded in trained artificial neural networks (ANN's) has focused primarily on extracting rule-based explanations from feedforward ANN's. The ADT taxonomy for categorizing such techniques was proposed in 1995 to provide a basis for the systematic comparison of the different approaches. This paper shows that not only is this taxonomy applicable to a cross section of current techniques for extracting rules from trained feedforward ANN's but also how the taxonomy can be adapted and extended to embrace a broader range of ANN types (e.g., recurrent neural networks) and explanation structures. In addition the paper identifies some of the key research questions in extracting the knowledge embedded within ANN's including the need for the formulation of a consistent theoretical basis for what has been, until recently, a disparate collection of empirical results.

The dynamic nature of group A streptococcal epidemiology in tropical communities with high rates of rheumatic heart disease

Prospective surveillance was conducted in three remote Aboriginal communities with high rates of rheumatic heart disease in order to investigate the epidemiology of group A beta-haemolytic streptococci (GAS). At each household visit, participants were asked about sore throat. Swabs were taken from all throats and any skin sores. GAS isolates were emm sequence and pattern-typed using standard laboratory methods. There were 531 household visits; 43 different emm types and subtypes (emmST) were recovered. Four epidemiological patterns were observed. Multiple emmST were present in the population at any one time and household acquisition rates were high. Household acquisition was most commonly via 5- to 9-year-olds. Following acquisition, there was a 1 in 5 chance of secondary detection in the household. Throat detection of emmST was brief, usually <2 months. The epidemiology of GAS in these remote Aboriginal communities is a highly dynamic process characterized by emmST diversity and turnover.

Clear not simple: An approach to community consultation for a maternal pneumococcal vaccine trial among Indigenous women in the Northern Territory of Australia

PneuMum is a randomised controlled maternal vaccination trial, using 23-valent Pneumococcal Polysaccharide Vaccine (23vPPV) during the third trimester or at delivery compared to vaccination at 7 months post delivery. The primary outcomes are infant middle ear disease and nasopharyngeal pneumococcal carriage at 7 months of age. PneuMum is the first vaccine trial to be conducted among Indigenous people in the Northern Territory. We describe the study design and the approach taken to develop the PneuMum message in collaboration with key Indigenous stakeholders and then to communicate the PneuMum message with Indigenous communities and potential participants. We hope that these methods will provide a model for future research involving Indigenous communities to ensure Indigenous involvement in research and ultimate improvements in Indigenous health.

Observation of muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam

This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current nu(mu) interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27 x 10(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336+/-14 events. The data are consistent with nu(mu) disappearance via oscillations with |Delta(m)2/32|=2.74 +0.44/-0.26 x10(-3)eV(2) and sin(2)(2theta(23))>0.87 (68% C.L.).

The role of mitochondrial haplogroups in primary open angle glaucoma

AIM

To investigate a possible association between mitochondrial haplogroups and primary open angle glaucoma (POAG).

METHODS

Genomic DNA was extracted from 140 POAG patients and 75 healthy individuals. Restriction enzyme digest analysis of polymerase chain reaction (PCR) amplified fragments was used to determine the mitochondrial haplogroup of each patient and control.

RESULTS

The median age was 73 years for the POAG patients (range 51-87, SD 8.01) and 78 years for the controls (range 68-90, SD 4.4). Mean IOP was 20.8 mm Hg for the patients (SD 2.6) and 16.2 mm Hg for the controls (SD 3.4). Median cup/disc ratio was 0.8 and 0.3 for patients and controls respectively. No statistically significant difference was found in the haplogroup distribution between the POAG patients and the healthy individuals (Fisher's exact test).

CONCLUSION

In this cohort, mitochondrial haplogroups do not appear to contribute to the pathogenesis of POAG.

Right ventricular infarction complicated by right to left shunting through an atrial septal defect: successful treatment with an Amplatzer septal occluder

A 68 year old woman presented with right ventricular myocardial infarction complicated by refractory hypoxaemia. She was found to have a significant right to left shunt at the atrial level through a previously undiagnosed ostium secundum atrial septal defect. Percutaneous closure of the atrial septal defect with an Amplatzer septal occluder resulted in prompt improvement in her oxygenation and clinical state. Such closure should be considered for patients with right ventricular infarction and refractory hypoxaemia caused by a right to left interatrial shunt.

Head lice prevalence in primary schools in Victoria, Australia

OBJECTIVES

To determine the prevalence of and assess risk factors associated with head lice infections (pediculosis) in children from government primary schools in Victoria, Australia.

METHODS

Between May and October 2001, children were selected by clustered random sampling of schools and classes, then examined for head lice using hair conditioner and a fine-toothed head lice comb. There were 1838 children screened from 16 primary schools. Risk factors evaluated included metropolitan or rural residence, school class, gender and hair length.

RESULTS

Thirteen percent of children (239/1838) had an active infection (95% CI, 10.9-15.1) and 3.3% (61/1838) had an inactive infection (95% CI, 2.0-4.6). Prevalence of active pediculosis varied between schools from 0 to 28%. Our screening identified no more than one case per class in the majority of classes screened (58.5%). Females were 2.2 times more likely to have active infection than males (95% CI [1.7,2.9]) and there was no significant difference for the other risk factors investigated.

CONCLUSIONS

Our study demonstrated the prevalence of head lice varied across Victoria and showed that risk factors commonly attributed to head lice infections did not hold true. Our findings support the premise that traditional ad hoc mass school-based screening may not be the best use of resources when controlling head lice. We suggest a more pragmatic community-based approach.

Predicting sudden death in patients with mild to moderate chronic heart failure

OBJECTIVES

To explore the relation between non-invasive measures of cardiac function and sudden cardiac death, as well as the development and utility of an index integrating these variables to identify patients at increased risk of this mode of death.

DESIGN

UK-HEART (United Kingdom-heart failure evaluation and assessment of risk trial) was a prospective study conducted between December 1993 and April 2000. The study was specifically designed to identify non-invasive markers of death and mode of death among patients with chronic heart failure.

SETTING

8 UK general hospitals.

MAIN OUTCOME MEASURES

Death and mode of death.

RESULTS

553 patients aged a mean (SD) of 63 (10) years, in New York Heart Association functional class 2.3 (0.02), recruited prospectively. After 2365 patient-years' follow up, 201 patients had died (67 suddenly). Predictors of sudden death were greater cardiothoracic ratio, QRS dispersion, QT dispersion corrected for rate (QTc) across leads V1-V6 on the 12 lead ECG, and the presence of non-sustained ventricular tachycardia. The hazard ratio and 95% confidence intervals (CI) of sudden death for a 10% increase in cardiothoracic ratio was 1.43 (95% CI 1.20 to 1.71), for a 10% increase in QRS dispersion 1.11 (95% CI 1.04 to 1.19), for the presence of non-sustained ventricular tachycardia 2.03 (95% CI 1.27 to 3.25), and for a 10% increase in QTc dispersion across leads V1-V6 1.03 (95% CI 1.00 to 1.07) (all p < 0.04). An index derived from these four factors performed well in identifying patients specifically at increased risk of sudden death.

CONCLUSIONS

Results show that an index derived from three widely available non-invasive investigations has the potential to identify ambulant patients with chronic heart failure at increased risk of sudden death. This predictive tool could be used to target more sophisticated investigations or interventions aimed at preventing sudden death.

Enhanced mechanical properties of polyacrylonitrile/multiwall carbon nanotube composite fibers

The use of multiwall carbon nanotubes (MWNTs) as a reinforcing phase in a polyacrylonitrile (PAN) fiber matrix was investigated with the goal of producing a PAN-derived carbon/MWNT composite fiber with enhanced physical properties. MWNTs were dispersed in a PAN/DMAc (dimethylacetamide) solution and spun into composite fibers containing up to 5 wt.% MWNTs, with the use of a lab-scale dry-jet wet spinline. The spinning process resulted in alignment of the MWNTs parallel with the fiber axis. Three types of chemical vapor deposition (CVD)-derived, high-purity MWNTs were used: as produced, graphitized (heat treated to 2800 degrees C), and NaCN-treated (chemically treated to attach CN groups to the nanotube surface). Tensile tests were performed to measure yield stress/strain, initial modulus, break stress/strain, and energy to yield and energy to break. Significant mechanical property increases were recorded for the composite fibers compared with the control samples with no MWNT reinforcement: break strength +31%, initial modulus +36%, yield strength +46%, energy to yield +80%, and energy to break +83%.