The Role of Phase Migration of Carbon Nanotubes in Melt-Mixed PVDF/PE Polymer Blends for High Conductivity and EMI Shielding Applications.

In this work, the effects of blend ratio and mixing time on the migration of multi-walled carbon nanotubes (MWCNTs) within poly(vinylidene fluoride) (PVDF)/polyethylene (PE) blends are studied. A novel two-step mixing approach was used to pre-localize MWCNTs within the PE phase, and subsequently allow them to migrate into the thermodynamically favored PVDF phase. Light microscopy images confirm that MWCNTs migrate from PE to PVDF, and transmission electron microscopy (TEM) images show individual MWCNTs migrating fully into PVDF, while agglomerates remained trapped at the PVDF/PE interface. PVDF:PE 50:50 and 20:80 polymer blend nanocomposites with 2 vol% MWCNTs exhibit exceptional electromagnetic interference shielding effectiveness (EMI SE) at 10 min of mixing (13 and 16 dB, respectively-at a thickness of 0.45 mm), when compared to 30 s of mixing (11 and 12 dB, respectively), suggesting the formation of more interconnected MWCNT networks over time. TEM images show that these improved microstructures are concentrated on the PE side of the PVDF/PE interface. A modified version of the "Slim-Fast-Mechanism" is proposed to explain the migration behavior of MWCNTs within the PVDF/PE blend. In this theory, MWCNTs approaching perpendicular to the interface penetrate the PVDF/PE interface, while those approaching in parallel or as MWCNT agglomerates remain trapped. Trapped MWCNTs act as barriers to additional MWCNTs, regardless of geometry. This mechanism is verified via TEM and scanning electron microscopy and suggests the feasibility of localizing MWCNTs at the interface of PVDF/PE blends.

Evaluation of Clinical Prognostic Factors and Further Delineation of the Effect of Mesenteric Fibrosis on Survival in Advanced Midgut Neuroendocrine Tumours.

BACKGROUND: Small intestinal neuroendocrine tumours (SI NETs) represent 30-50% of small bowel neoplasms and often present at an advanced stage. To date, there is relatively limited literature regarding prognostic factors affecting overall survival (OS) in stage IV disease. In addition, the prevalence of mesenteric fibrosis (MF) in SI NETs and its effect on OS have not been sufficiently explored in the literature. AIM: The primary aim of this study was to perform a large-scale survival analysis in an institutional cohort of 387 patients with metastatic (stage IV) SI NETs. The secondary aim was to provide epidemiological information regarding the prevalence of MF and to evaluate its effect on OS. RESULTS: The median OS was 101 months (95% CI 84, 118). Age > 65 years, mesenteric metastases with and without desmoplasia, liver metastases, carcinoid heart disease (CHD) and bone metastases were associated with a significantly shorter OS, while primary tumour resection was predictive of a longer OS. The benefit of surgical resection was limited to symptomatic patients. MF was present in approximately 50% of patients with mesenteric lymphadenopathy. Elevated urinary 5-HIAA levels correlated strongly with the presence of CHD (p < 0.001) and to a lesser extent (p = 0.02) with MF. MF and CHD did not usually co-exist, suggesting that different mechanisms are likely to be involved in the development of these fibrotic complications. CONCLUSIONS: This study has identified specific prognostic factors in a large cohort of 387 patients with advanced SI NETs and has provided useful epidemiological data regarding carcinoid-related fibrotic complications.

Carbon Nanotube Migration in Melt-Compounded PEO/PE Blends and Its Impact on Electrical and Rheological Properties.

In this work, the effects of MWCNT concentration and mixing time on the migration of multi-walled carbon nanotubes (MWCNTs) within polyethylene oxide (PEO)/polyethylene (PE) blends are studied. Two-step mixing used to pre-localize MWCNTs within the PE phase and subsequently to observe their migration into the thermodynamically favored PEO phase. SEM micrographs show that many MWCNTs migrated into PEO. PEO/PE 40:60 polymer blend nanocomposites with 3 vol% MWCNTs mixed for short durations exhibited exceptional electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity (14.1 dB and 22.1 S/m, respectively), with properties dropping significantly at higher mixing times, suggesting the disruption of percolated MWCNT networks within the PE phase. PE grafted with maleic anhydride (PEMA) was introduced as a compatibilizer to arrest the migration of MWCNTs by creating a barrier at the PEO/PE interface. For the compatibilized system, EMI SE and electrical conductivity measurements showed a peak in electrical properties at 5 min of mixing (15.6 dB and 68.7 S/m), higher than those found for uncompatibilized systems. These improvements suggest that compatibilization can be effective at halting MWCNT migration. Although utilizing differences in thermodynamic affinity to draw MWCNTs toward the polymer/polymer interface of polymer blend systems can be an effective way to achieve interfacial localization, an excessively low viscosity of the destination phase may play a major role in reducing the entrapment of MWCNTs at the interface.

Characterization of a Subset of Patients With Rheumatoid Arthritis for Whom Current Management Strategies are Inadequate.

OBJECTIVE: A subset of patients with seropositive rheumatoid arthritis (RA) do not mount a C-reactive protein (CRP) response during flares. We hypothesize that these patients are more likely to experience poor clinical care and less likely to respond to traditional therapy. This study questioned whether this presentation was associated with worse disease outcome and distinct immunological features. METHODS: Using Power Doppler ultrasound, 48 RA patients with active synovitis were recruited; 30 had normal (n)CRP (5 mg/L or less) and 18 had high (h)CRP (more than 5 mg/L) levels. All had equivalent disease burden assessed by other clinical and laboratory parameters. RESULTS: Time to diagnosis and time to first disease-modifying antirheumatic drug were significantly longer in nCRP compared with hCRP patients (P < 0.05). Significantly more nCRP patients needed escalation to biologics after 2-year follow-up (P = 0.01). The inflammatory milieu was also different between the two subgroups. Synergy between inflammatory cytokines observed in hCRP patients was lost in nCRP patients, and nCRP patients had significantly increased regulatory T-cell (Treg) frequencies that correlated positively with predictors of poor disease outcome. Conversely, hCRP but not nCRP patients demonstrated a significant upregulation of alternative complement pathway factors that correlated negatively with Treg frequency. CONCLUSION: Patients with nCRP during flares of RA had an altered immunological profile compared with hCRP patients and experienced diagnostic delays and responded less favorably to conventional treatment.