Phase morphology, thermomechanical, and crystallization behavior of uncompatibilized and PP-g-MAH compatibilized polypropylene/polystyrene blends

In this article, we discuss the phase morphology, thermal, mechanical, and crystallization properties of uncompatibilized and compatibilized polypropylene/polystyrene (PP/PS) blends. It is observed that the Young's modulus increases, but other mechanical properties such as tensile strength, flexural strength, elongation at break, and impact strength decrease by blending PS to PP. The tensile strength and Young's modulus of PP/PS blends were compared with various theoretical models. The thermal stability, melting, and crystallization temperatures and percentage crystallinity of semicrystalline PP in the blends were marginally decreased by the addition of amorphous PS. The presence of maleic anhydride-grafted polypropylene (compatibilizer) increases the phase stability of 90/10 and 80/20 blends by preventing the coalescence. Hence, finer and more uniform droplets of PS dispersed phases are observed. The compatibilizer induced some improvement in impact strength for the blends with PP matrix phase, however fluctuations in modulus, strength and ductility were observed with respect to the uncompatibilized blend. The thermal stability was not much affected by the addition of the compatibilizer for the PP rich blends but shows some decrease in the thermal stability of the blends, where PS forms the matrix. On the other hand, the % crystallinity was increased by the addition of compatibilizer, irrespective of the blend concentration.

Muscle atrophy and changes in spinal morphology: is the lumbar spine vulnerable after prolonged bed-rest?

STUDY DESIGN: prospective longitudinal study. OBJECTIVE: to evaluate the effect of bed-rest on the lumbar musculature and soft-tissues. SUMMARY OF BACKGROUND DATA: earlier work has suggested that the risk of low back injury is higher after overnight bed-rest or spaceflight. Changes in spinal morphology and atrophy in musculature important in stabilizing the spine could be responsible for this, but there are limited data on how the lumbar musculature and vertebral structures are affected during bed-rest. METHODS: nine male subjects underwent 60-days head-down tilt bed-rest as part of the second Berlin Bed-Rest Study. Disc volume, intervertebral spinal length, intervertebral lordosis angle, and disc height were measured on sagittal plane magnetic resonance images. Axial magnetic resonance images were used to measure cross-sectional areas (CSAs) of the multifidus (MF), erector spinae, quadratus lumborum, and psoas from L1 to L5. Subjects completed low back pain (LBP) questionnaires for the first 7-days after bed-rest. RESULTS: increases in disc volume, spinal length (greatest at lower lumbar spine), loss of the lower lumbar lordosis, and move to a more lordotic position at the upper lumbar spine (P < 0.0097) were seen. The CSAs of all muscles changed (P < 0.002), with the rate of atrophy greatest at L4 and L5 in MF (P < 0.002) and at L1 and L2 in the erector spinae (P = 0.0006). Atrophy of the quadratus lumborum was consistent throughout the muscle (P = 0.15), but CSA of psoas muscle increased (P < 0.0001). Subjects who reported LBP after bed-rest showed, before reambulation, greater increases in posterior disc height, and greater losses of MF CSA at L4 and L5 than subjects who did not report pain (all P < 0.085). CONCLUSION: these results provide evidence that changes in the lumbar discs during bed-rest and selective atrophy of the MF muscle may be important factors in the occurrence of LBP after prolonged bed-rest.

Changes in intervertebral disc morphology persist 5 mo after 21-day bed rest

As part of the nutrition-countermeasures (NUC) study in Cologne, Germany in 2010, seven healthy male subjects underwent 21 days of head-down tilt bed rest and returned 153 days later to undergo a second bout of 21-day bed rest. As part of this model, we aimed to examine the recovery of the lumbar intervertebral discs and muscle cross-sectional area (CSA) after bed rest using magnetic resonance imaging and conduct a pilot study on the effects of bed rest in lumbar muscle activation, as measured by signal intensity changes in T(2)-weighted images after a standardized isometric spinal extension loading task. The changes in intervertebral disc volume, anterior and posterior disc height, and intervertebral length seen after bed rest did not return to prebed-rest values 153 days later. While recovery of muscle CSA occurred after bed rest, increases (P ≤ 0.016) in multifidus, psoas, and quadratus lumborum muscle CSA were seen 153 days after bed rest. A trend was seen for greater activation of the erector spinae and multifidus muscles in the standardized loading task after bed rest. Greater reductions of multifidus and psoas CSA muscle and greater increases in multifidus signal intensity with loading were associated with incidence of low back pain in the first 28 days after bed rest (P ≤ 0.044). The current study contributes to our understanding of the recovery of the lumbar spine after 21-day bed rest, and the main finding was that a decrease in spinal extensor muscle CSA recovers within 5 mo after bed rest but that changes in the intervertebral discs persist.

Evaluation of lumbar disc and spine morphology: long-term repeatability and comparison of methods

Establishing the long-term repeatability of quantitative measures of lumbar intervertebral disc and spinal morphology is important for planning interventional studies. We aimed to examine this issue and to determine to what extent a smaller number of measurements per disc or vertebral level could be used to save operator time without compromising measurement precision. Twenty-one healthy male subjects were scanned at baseline and 1.5 years later. On sagittal MR-scans intervertebral disc cross-sectional area, anterior disc height, posterior disc height, intervertebral angle and intervertebral length were measured. The repeatability of the average value from all sagittal images or from 1, 3, 5 or 7 images centred at the spinous process was evaluated. Bland-Altman analysis showed all measurements to be repeatable between testing days. Intervertebral length was the most precise measurement (coefficients of variation [CVs] between 1.2% and 1.5%), followed by disc cross-sectional area (CVs between 2.9% and 3.6%). Variance component analysis showed that using 7 images, but not 1, 3 or 5 images, resulted in a similar level of measurement error as when measurements from all images were included.

Electrospun poly(vinyl alcohol)/phase change material fibers: morphology, heat properties, and stability

A phase change material (PCM) from a mixture of plant oils was incorporated into electrospun poly(vinyl alcohol) (PVA) nanofibers using an emulsion electrospinning technique. Effects of PCM and PVA content in the emulsions on nanofiber morphology, heat properties, and phase change stability were examined. Higher PCM loadings in the nanofibers led to increased fiber diameter, gouged fiber surfaces, and higher heat enthalpies. The fibers maintained their morphological integrity even if the PCM melted. They showed reliable heat-regulating performance which can undergo at least 100 cycles of phase change. Such PCM fibers may be used for the development of thermoregulating fabrics or in passive heat storage devices.

Climate-related spatial and temporal variation in bill morphology over the past century in Australian parrots

Aim: Allen's rule posits that the appendages of endothermic organisms will be larger in warmer climates to allow for dumping of heat loads. Given a link between appendage size and climate, we tested the prediction that climate change has driven the evolution of larger bills in birds, resulting in measurable changes over the recent past. Location: Australia. Methods: We explored geographical and temporal variation in bill surface area of five Australian parrot species to determine whether individuals from warmer climates have larger bills, and whether there have been increases in bill surface area over time, consistent with climatic warming. Measurements were obtained from museum specimens dating from 1871 to 2008. These data were then related to geographical location, collection date and locality-specific climate data, in order to construct and compare models of spatio-temporal and climate-related variation in bill morphology. Results: There have been increases in bill surface area in mulga parrots (Psephotus varius), gang-gang cockatoos (Callocephalon fimbriatum), red-rumped parrots (Psephotus haematonotus) and male crimson rosellas (Platycercus elegans), equating to a c. 4-10% increase in bill surface area since 1871. Average maximum summer temperature in the 5 years prior to specimen collection also positively predicted bill surface area in mulga parrots, red-rumped parrots and crimson rosellas, consistent with Allen's rule. With the exception of red-rumped parrots, however, models with geographical location and year of collection were still better predictors of bill surface area than local climate at the date of collection. Main conclusions: Our analysis provides evidence that four species of parrot have exhibited adaptive change in bills over the past century potentially mitigating the thermal stress caused by climatic warming. Although consistent with the predicted effects of climate change, the temporal patterns we observe may have additional causes, however, such as changes in primary productivity, habitat or food availability.

A facile synthesis of mesoporous silica nanoparticle and its morphology manipulation by varying pH value

 Mesoporous silica nanoparticles (MSNs) with particle size of20 nm have been synthesised through the template directed method at low temperature. The pH value of the reaction solution was found to have a great impact on the morphology of the final products. The morphology of resultant MSNs were investigated through transmission electron microscope. The mesoporous structure was examined by Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods. The results suggested that the high pH value had a great effect on the morphology of the final MSNs. Higher pH value intensified the interaction between particles. The pH value less than 10 is good for the formation of nanoparticles, while at pH 12, a silica framework with heterogeneous mesopore structure can be obtained.