Although low density polyethylene (LDPE) has long been widely used in packaging applications, some limitations in its use still exist and are due to its relatively poor gas barrier properties and low mechanical strength which can restrict its extensive use for more advanced applications, such as electronic and pharmaceutical packaging. The purpose of this study was to investigate the possibility of using montmorillonite (MMT) nanoclay as a means to enhance the thermal, mechanical, and barrier properties of LDPE prepared via melt extrusion. The level of exfoliated dispersion of the MMT nanoclay in the prepared LDPE-MMT composite was confirmed using transmission electron microscopy (TEM). The relationship between the resulting morphology and the thermal, mechanical, and barrier properties as a function of the MMT content was evaluated. The results showed that incorporating >3 wt.% of MMT nanoclay produced significant changes in the morphology of the LDPE-MMT nanoclay composite in that the segregated matrix adopted an oriented arrangement of exfoliated clay platelets. Thermogravimetric analysis (TGA) showed that the thermal stability of LDPE improved significantly as a result of MMT nanoclay incorporation. Furthermore, differential scanning calorimetry (DSC) analysis indicated that increasing clay content above 3 wt.% effectively reduces the crystallinity of LDPE-MMT composites through the suppression effect. The tensile strength of LDPE increased gradually with an increased content of MMT nanoclay and the maximum value of 16.89 N/mm2 was obtained at 10 wt.% MMT content. This value represents a 40.87% increase relative to the tensile strength of the pristine LDPE. Barrier properties of LDPE and LDPE-MMT nanoclay composites were assessed by examining the permeability with respect to oxygen and water vapor. As the content of MMT nanoclay was increased to 10 wt.%, the permeability of the nanocomposite films to oxygen and water vapor notably decreased to 42.8% and 26.2%, respectively.

We report on enhanced mechanical, tribological, and surface-wettability characteristics of polymeric films dispersed with inorganic fullerene (IF)-type tungsten disulfide (WS2) nanoparticles derived through a two-step hydrothermal route. Imaging through transmission electron microscopy suggests the occurrence of polyhedral cage-like structures with a visibly nonspherical hollow ranging 55–75 nm. The mechanical stability of IF-type WS2 dispersed in polyvinyl alcohol (PVA) gets improved with increasing nano-inclusions, and upto 6 wt% loading. As compared with nanosheets, the IF-WS2 in PVA at the critical loading offers nearly 28.6, 33.6, and 42% respective improvements as regards, breaking stress, elongation at break, and toughness. Moreover, Stribeck curves in the mixed lubricating regime have revealed a nearly ∼80% reduction of coefficient of friction (COF) due to inclusion of IF-type WS2 in PVA. In the hydrodynamic region, the COF is drastically lowered from a typical value of 0.55 to 0.15 at the maximal sliding velocity with nanoparticle loading and despite the fact that the tribo feature gives a rising trend for a particular curve. Furthermore, exhibiting a progressive increase in water contact angle, a clear transition from the hydrophilic (∼64°) to hydrophobic (∼107°) surface of the nanocomposite films has been witnessed after inclusion of nano IF-WS2. An increased hydrophobicity and lowered surface adhesion and COF values along with marginal drop in surface energy are ensured in the investigated specimens. Investigation of responsive tribological and wetting–dewetting transition would find scope not only in coating and textile industry but also in smart miniaturized components.

Halloysite nanotubes (HNTs)/polytetrafluoroethylene (PTFE) nanocomposites were prepared by the cold compression moulding method. The effects of addition of HNTs (HNTs ‘filling’) on the performances of PTFE were explored using X-ray diffraction, Fourier Transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis which showed that HNTs were well dispersed in the PTFE matrix by means of physical mixing at lower contents of 2–5 wt.%; the introduction of HNTs into PTFE could improve the heat stability of the PTFE. Furthermore, the mechanical and tribological performances of the nanocomposites were measured to examine the filling effect. The tensile strength of the HNTs/PTFE nanocomposites at 2–5 wt.% HNTs content increased by ~3.5% while their wear rates decreased by 55–90% relative to pure PTFE, clear proof of the filling effect of HNTs with a high aspect ratio.

A brief evolutionary description is given of the development of the discipline of weed science in the United States. Topics discussed include public recognition of weed science, losses from weeds, allocation of resources, herbicide usage, and future predictions of the development of the discipline. Weed scientists have had a major impact during the past four decades in increasing crop yields and reducing labor requirements for controlling weeds in crop production systems. Weed scientists have been so effective that recognition of their contributions and impact have often been overlooked in academic institutions but not in private industries that have staffed for herbicide development.

The biomechanical response of tissues serves as a valuable marker in the prediction of disease and in understanding the related behavior of the body under various disease and age states. Alterations in the macroscopic biomechanical response of diseased tissues are well documented; however, a thorough understanding of the microstructural events that lead to these changes is poorly understood. In this article we introduce a novel microbiaxial optomechanical device that allows two-photon imaging techniques to be coupled with macromechanical stimulation in hydrated planar tissue specimens. This allows that the mechanical response of the microstructure can be quantified and related to the macroscopic response of the same tissue sample. This occurs without the need to fix tissue in strain states that could introduce a change in the microstructural configuration. We demonstrate the passive realignment of fibrous proteins under various types of loading, which demonstrates the ability of tissue microstructure to reinforce itself in periods of high stress. In addition, the collagen and elastin response of tissue during viscoelastic behavior is reported showing interstitial fluid movement and fiber realignment potentially responsible for the temporal behavior. We also demonstrate that nonhomogeneities in fiber strain exist over biaxial regions of assumed homogeneity.

By using very simple considerations related to the mechanical Lagrangian itself, one obtains a new general class of parameter adaptation algorithms for robot manipulators, which provides such approaches as PID adaptation schemes. These models could apply to random structural mechanical Systems, subject to the conditon that they are defined by Lagrangians.

By establishing an avascular, highly elastic, region within the fetal area of high acuity (AHA), the developing primate eye has created a unique substrate on which the mechanical forces of intraocular pressure (IOP) and growth-induced retinal stretch (stretch) can act. We proposed (Springer & Hendrickson, 2004b) that these forces generate both the pit and high cone density found in the adult AHA. In this paper, we use quantitative measures to determine the temporal relationships between nasal and temporal retinal elongation, changes in pit depth, cone packing, and cone morphology over M. nemestrina retinal development. Retinal length increased rapidly to about 105 days postconception (dpc; Phase 1) and then elongation virtually ceased (Phase 2) until just after birth (180 dpc). Retinal elongation due to stretch resumed during Phase 3 until approximately 315 dpc (4–5 months), after which time the retina appeared mature (Phase 4). The pit appeared during the quiescent Phase 2, suggesting that IOP acts, in conjunction with molecular changes in the inner retina, on the highly elastic, avascular, AHA to generate a deep, narrow pit and causes inner retinal cellular displacements. Subsequently (Phase 3), the pit widened, became 50% shallower and central inner retinal lamina thinned slightly due to a small amount of retinal stretch occurring in the AHA. Centripetal movement of cones was minimal until just after birth when the pit reached 88% of its maximal depth. Accelerated cone packing during Phase 3 was temporally correlated with increased stretch. A slight stretching of the central inner retina generates “lift” forces that cause the pit to become shallower and wider. In turn, these “lift” forces draw cones toward the center of the AHA (Springer, 1999). Localized changes in cone morphology associated with packing, included smaller cell body size, a change from a monolayer to a multilayered mound of cell bodies, elongation of inner segments and tilting of the apical portion toward the AHA. These changes began in cones overlying the edges of the pit, not its center. Henle cone axons formed initially in association with centrifugal displacement of the inner retina during pit formation, with an additional subsequent elongation due to cones moving centripetally. An integrated, two-factor model of AHA formation is presented. Initially, during the second half of gestation (Phase 2), IOP acts on the hyperelastic avascular zone of the AHA to generate a deep pit in the inner retina. In the first 4 months after birth (Phase 3), central retinal stretch generates tensile “lift” forces that remodel the pit and pack cones by drawing them toward the AHA center.

Mechanisms underlying the development of the primate area of high acuity (AHA) remain poorly understood. Finite-element models have identified retinal stretch and intraocular pressure (IOP) as possible mechanical forces that can form a pit (Springer & Hendrickson, 2004). A series of Macaca nemestrina monkey retinas between 68 days postconception (dpc) and adult were used to quantify growth and morphological changes. Retinal and pars plana length, optic disc diameter, disc-pit distance, and inner and outer retinal laminar thickness were measured over development to identify when and where IOP or stretch might operate. Horizontal optic disc diameter increased 500 μm between 115 dpc and 2 months after birth when it reached adult diameter. Disc growth mainly influences the immediate surrounding retina, presumably displacing retinal tissue centrifugally. Pars plana elongation also began at 115 dpc and continued steadily to 3–4 years postnatal, so its influence would be relatively constant over retinal development. Unexpectedly, horizontal retinal length showed nonlinear growth, divided into distinct phases. Retinal length increased rapidly until 115 dpc and then remained unchanged (quiescent phase) between 115–180 dpc. After birth, the retina grew rapidly for 3 months and then very slowly into adulthood. The onset of pit development overlapped the late fetal quiescent phase, suggesting that the major mechanical factor initiating pit formation is IOP, not retinal growth-induced stretch. Developmental changes in the thickness of retinal layers were different for inner and outer retina at many, but not all, of the ten eccentricities examined. Peripheral inner and outer retinal layers thinned appreciably with age, consistent with retinal stretch having a larger effect on the retinal periphery. Central inner retina around the area of high acuity (AHA) changed tri-phasically. It increased in thickness prenatally, thinned transiently after birth, and then resumed thickening. Transient postnatal inner retinal thinning around the pit coincided with the resumption of retinal growth and with cone packing providing evidence that a small amount of growth-induced central retinal stretch may account for cone packing as previously hypothesized (Springer, 1999). Central outer retina around the AHA progressively thickened over the fetal period. It reached asymptotic thickness at birth and continued to thicken into adulthood at some temporal, but not nasal, central eccentricities. These data indicate that peripheral outer and inner retina progressively thin with age because of eye growth-induced stretch, while central retina is minimally affected by stretch. Outer and inner retinal laminar thickness at the same locus can change in different directions, suggesting that they shear with respect to one another. This shearing induces the elongation of Henle axons, while their angle reflects the direction of shear.

Compelling anecdotal evidence exists for the potentially lifesaving benefits of mechanical external chest compression (MECC), but no published trials of the technique exist. The history and technique for MECC are discussed and illustrated by a case report. Although the technique is not discussed in the Resuscitation Guideline 2000, and the need for it within the intensive care unit has reduced, the use of MECC will have its greatest impact when initiated in the prehospital setting for patients suffering from severe, sudden-onset, asphyxic asthma.

The VersaMed 201 is a lightweight, computer-controlled, electrically driven ventilator, designed for transport, home-ventilation and field use. We have evaluated the device in human beings with healthy and pathological lungs. In the first part of the study, the VersaMed was substituted for a standard operating room ventilator for 15–30 min during elective surgery in 20 subjects. In the second stage of the study, 20 patients with lung pathology who were being ventilated in the critical care department were transferred to the VersaMed for a 30-min period. In all the patients studied, arterial blood gases, haemodynamic parameters and other respiratory variables were maintained at similar values seen with the standard ventilators used. We conclude that the VersaMed 201 is suitable for use in human beings with healthy and pathological lungs as a reliable, portable ventilator.

There is a risk of regurgitation if a laryngeal mask airway is used with intermittent positive pressure ventilation. The lower the pressure gradient between airway and stomach, the less will be the likelihood of stomach insufflation with gas and consequent regurgitation. A flow generator ventilator, such as the Penlon Nuffield 200 which achieves a peak pressure at the end of inspiration at any given tidal volume, is likely to produce a higher peak airway pressure than a pressure generator. Replacing the expiratory valve by a venturi gives a preferable flow pattern with an inspiratory pressure plateau. At equal tidal volumes, the venturi modification provided a 10% lower inflation pressure (standard deviation 6%, P < 0.01) and a 1.8% smaller leak (P < 0.05) past the laryngeal mask airway. The same comparison but using identical inflation pressures, gave 8% larger tidal volumes (standard deviation 5.1%, P < 0.01) and a 2% smaller leak (P < 0.01) past the laryngeal mask airway.

The concentrations of nitrous oxide, sevoflurane and oxygen in the circle system of a closed-circuit anaesthesia machine, the PhysioFlex™, were measured in seven patients. During anaesthesia, the settings for each gas were changed and their concentrations recorded. At the induction of anaesthesia, it took 80– 510s (median 190 s) for the end-tidal sevoflurane concentration to reach 2.0%, and 920–2640 s (median 1500 s) for the oxygen in the breathing circuit to reach 30%. At this time, the nitrous oxide concentration was 60±3% (mean±SD). During anaesthesia, it took 90–480 s (median 140 s) for the end-tidal sevoflurane concentration setting to decrease from 3.0 to 1.0%, and 90–400 s (median 110 s) to return from 1.0 to 3.0%. When the inspired oxygen was increased from 30 to 50%, circuit concentrations reached equilibrium in 40–60 s (median 40 s), and when decreased from 50% back to 30%, equilibrium took 310–470 s (median 450 s). During recovery from anaesthesia, inspiratory sevoflurane concentration took 40–70 s (median 50 s) to decrease to 0.2%. The PhysioFlex™ provided adequate control of sevoflurane and oxygen concentrations, but not of increasing nitrous oxide concentrations.