Experimentally Determined Hansen Solubility Parameters of Biobased and Biodegradable Polyesters.

Hansen solubility parameters (HSP) of 15 commercially relevant biobased and biodegradable polyesters were experimentally determined by applying a novel approach to the classic solubility study method. In this approach, the extent of swelling in polymer films was determined using a simple equation based on the mass difference between swollen and nonswollen film samples to obtain normalized solvent uptake (N). Using N and HSPiP software, highly accurate HSP values were obtained for all 15 polyesters. Qualitative evaluation of the HSP values was conducted by predicting the miscibility of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-co-HHx, 7 mol % HHx) and poly(lactic acid) (PLA) with a novel lignin-based plasticizer (ethyl 3-(4-ethoxy-3-methoxyphenyl)propanoate, EP) with a relative energy difference (RED) less than 0.4. Additionally, an HSP-predicted plasticizer (di(2-ethylhexyl) adipate, DA) with a larger RED (>0.7) was used to demonstrate the effects of less-miscible additives. Plasticized samples were analyzed by differential scanning calorimetry and polarized optical microscopy (POM) to determine the Tg depression, with EP showing linear Tg depression up to 50% plasticizer loading, whereas DA shows minimal Tg depression past 10% loading. Further analysis by POM reveals that the DA phase separates from both polymers at loadings as low as 2.5% (PHB-co-HHx, 7 mol % HHx) and 5% (PLA), while the EP phase separates at a much higher loading of 50% (PHB-co-HHx, 7 mol% HHx) and 30% (PLA).

A Biologically Degradable and BioseniaticTM Feedstock for the High-Quality 3D Printing of Anatomical Models.

A Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) -based filament was evaluated as an alternative feedstock for Fused Deposition Modeling (FDM) of instructional and clinical medical specimens. PHBHHx-based prints of domestic cat vertebrae, skull bone, and an aortic arch cast were found comparable to conventional materials. PHBHHx-based filament and extrudate samples were evaluated for biological degradability, to meet the BioseniaticTM standard, defined by the University of Georgia New Materials Institute. Both samples achieved more than 90% mineralization within 32 days in industrial composting conditions.

Review of appendicectomies over a decade in a tertiary hospital in New Zealand.

BACKGROUND: Acute appendicectomy is the most common emergency operation for patients with abdominal pain. In the last decade, computed tomography (CT) scans have increasingly been used to aid in the diagnosis in order to reduce the negative appendicectomy rate. The aim of this study was to evaluate our institution's negative appendicectomy rate and the use of pre-operative imaging. METHODS: A retrospective review was undertaken for all adult patients (>16 years), who underwent an appendicectomy on emergency basis in the years 2004, 2009 and 2014. Cases were identified from the hospital electronic theatre record system. Data were also obtained from the patients records and laboratory reports. RESULTS: A total of 874 patients were included, 227 in 2004, 308 in 2009 and 339 in 2014. The negative appendicectomy rate was 29.1% in 2004, 20.1% in 2009 and 19.5% in 2014 (P = 0.014). Negative appendicectomies were more common in women (P = <0.001), patients between the ages of 16-30 years (P = <0.001) and were associated with low inflammatory markers (median white cell count of 10.2, C-reactive protein of 8, P = <0.001). The use of CT scan prior to operation increased between 2009 and 2014 (34 (11.0%) versus 64 (18.9%), P = <0.001). CONCLUSION: Though the number of appendicectomies being performed in our institution has increased over the last decade, the negative appendicectomy rate remains fairly static and the increased use of CT scans did not further decrease the proportion of negative appendicectomies between 2009 and 2014.