Experimental characterisation on the behaviour of PLLA for stretch blowing moulding of bioresorbable vascular scaffolds

Processing tubes from poly (l-lactic acid) (PLLA) by stretch blow moulding (SBM) is used in the manufacture of bioresorbable vascular scaffolds (BVS) to improve their mechanical performance. To better understand this processing technique, a novel experimental setup by free stretch blow inside a water bath was developed to visualise the tube forming process and analyse the deformation behaviour. PLLA tubes were heated, stretched and blown with no mould present inside a temperature-controlled water bath whilst recording the processing parameters (axial force, inflation pressure). The onset of pressure activation relative to the axial stretch was controlled deliberately to produce a simultaneous (SIM) or sequential (SEQ) mode of deformation. Real-time images of the tube during forming were captured using high speed cameras and the surface strain of the patterned tube was extracted using digital image correlation (DIC). The deformation characteristics of PLLA tubes in SBM was quantified by analysis of shape evolution, strain history and stress-strain relationship

Laparoscopic Resection of a Left Upper Quadrant Mass Leading to a Surprise Diagnosis

Background. Resplenectomy is most commonly done for the treatment of recurrent idiopathic thrombocytopenic purpura (ITP) refractory to medical management due to the regrowth of a missed accessory spleen. Case Report. A 66-year-old male had undergone open splenectomy for traumatic rupture 40 years ago. He presented with a leiomyosarcoma of his leg, which was surgically removed. When he developed metastatic disease, chemotherapy was started. He developed left upper quadrant pain, and on CT scan, a 5 cm mass compatible with a sarcoma was found between the tail of the pancreas and the left adrenal gland. During laparoscopy, dense adhesion of the omentum to the abdominal wall and the stomach from his previous splenectomy was divided. The lesser sac was opened through the gastrocolic ligament, and the splenic flexure was taken down. Superior and dorsal to the tail of the pancreas next to the left adrenal gland, the mass was identified and carefully dissected out. The vascular pedicle, which originated from a side branch of the splenic vessels at the tail of the pancreas, was stapled. The gastric fundus showed multiple nodules, and therefore, a modified sleeve gastrectomy was done; also, a 2 cm nodule in segment 5 of the liver and an omental nodule were removed. The tumors and gastrectomy specimen were placed in an endobag and removed through a periumbilical mini-incision. The patient recovered without any complications from the procedure and his LUQ pain resolved. Pathology revealed no sarcoma metastases but accessory spleens in all specimens. Discussion. Splenosis with multiple implants within the abdomen after splenectomy for trauma is a rare condition. In our patient, this seems to have been triggered by chemotherapy for his sarcoma resulting in extramedullary hemopoiesis. Laparoscopic removal of accessory spleens can be safely done

Measured removal rates of chrysotile asbestos fibers from air and comparison with theoretical estimates based on gravitational settling and dilution ventilation

<p><i>Context</i>: Industrial hygiene assessments often focus on activity-based airborne asbestos concentration measurements, but few empirical data exist regarding the fiber removal rate from air after activities cease.</p> <p><i>Objective</i>: Grade 7T chrysotile indoor fiber settling (FS) rates were characterized using air sampling (NIOSH Method 7402).</p> <p><i>Materials and methods</i>: Six replicate events were conducted in a 58 m³ study chamber (ventilation 3.5 ACH), in which chrysotile-contaminated work clothing was manipulated for 15 min followed by 30 min of no activity. The fiber concentration decay constant and removal rate were characterized using an exponential decay model based on the measurements.</p> <p><i>Results</i>: Breathing zone airborne chrysotile concentrations decreased by 86% within 15–30 min after fiber disturbance, compared to concentrations during active disturbance (<i>p</i> < 0.05). Estimated mean time required for 99% of the phase contrast microscopy-equivalent (PCME) fibers to be removed from air was approximately 30 min (95% CI: 22–57 min). The observed effective FS velocity was 0.0034 m/s. This settling velocity was between 4.5-fold and 180-fold faster than predicted by two different particulate gravitational settling models. Additionally, PCME concentrations decreased approximately 2.5-fold faster than predicted due to air exchange alone (32 versus 79 min to 99% decrease in concentration).</p> <p><i>Discussion</i>: Other measurement studies have reported similar airborne fiber removal rates, supporting the finding that factors other than gravitational settling and dilution ventilation contribute measurably to PCM fiber removal from air (e.g. impaction, agglomeration).</p> <p><i>Conclusion</i>: Overall, the scientific weight of evidence indicates that the time necessary for removal of 99% of fibers greater than 5 μm in length (with aspect ratios greater than 3:1) is approximately 20–80 min.</p

Analysis of finite dose dermal absorption data:Implications for dermal exposure assessment

Peer reviewedPublisher PD