Mesh Sleeve Research Articles

Simulation design of reliability improvement of metal hose for rocket engine

Abstract Facing the new challenges of high-density space launches in the later period, this paper studies the numerical simulation of the metal hose used in the new generation of launch vehicle models to improve the reliability of the metal hose. Through the calculation of bellows with different elements, it is found that the calculation results of shell element and solid element are similar, and the calculation efficiency of shell element is much higher than that of solid element. Finally, it is established that the SHELL181 is used for the finite element calculation of the bellows. Based on the stiffness equivalent theory, an equivalent model of the net sleeve with strands as the unit is established. Through the verification of finite element and experiment, this equivalent model can better simulate the linear stage of metal mesh sleeve under tension. Finally, the modeling method of metal hose simulation design is established.

Effect of density on pupal colour plasticity in the butterfly Mycalesis mineus (Lepidoptera, Nymphalidae)

AbstractWe tested the effect of larval density on pupal colour plasticity in the butterfly Mycalesis mineus. Pupal colour of this species is known to be a plastic phenotype, being either brown or green. Colour is correlated with pupation substrate: pupae on leaves are almost exclusively green, whereas off‐leaf substrates (stem, soil, etc.) include both green and brown pupae. We hypothesised that brown pupae are more frequent at high larval densities and tested this hypothesis using two experiments. In the first experiment, we reared larvae at different densities in plastic containers, which provided a restricted choice of pupation substrates. There was no influence of density on pupal colour. In the second experiment, we simulated more natural conditions, wherein larvae were reared in nylon mesh sleeves and had a greater choice of pupation substrates. Here, there was a strong correlation between larval density and the proportion of brown pupae. We discuss why results from the two experiments may have differed and what can be concluded about factors influencing pupal colour. We also discuss the importance of choice of experimental protocols, especially in relation to how realism trades off with practicality and control.

Mitigation of Deer Herbivory in Temperate Hardwood Forest Regeneration: A Meta-Analysis of Research Literature

Ungulate herbivory poses global challenges to forest regeneration. Deer, in combination with other biotic and abiotic factors, threaten to shift forest composition away from palatable hardwoods, such as oaks (Quercus spp.), and cause regeneration failure in some cases. Many studies have assessed methods to reduce or manage browse, but comprehensive analyses of the relative effectiveness of these techniques among published experiments are lacking. We synthesized the literature describing the results of methods to reduce deer browsing impacts, and assessed the effectiveness of deer browse management methods in controlling damage to hardwood forest regeneration. Specifically, we systematically analyzed results from 99 studies that used repellents, physical barriers, lethal population control, timber harvests, facilitation by neighboring plants, or fertilizer to affect browse, survival, or height growth of hardwood seedlings. Across studies, browse was reduced (mean effect size and confidence intervals) with the following: Fencing −3.17 (CI: −4.00–−1.31), shelters −1.28 (CI: −2.02–−0.67), cages −1.48 (CI: −3.14–−0.62), facilitation from neighboring plants −0.58 (CI: −1.11–−0.13), repellents −0.45 (CI: −0.56–−0.21), hunting −0.99 (CI: −1.51–−0.26). These methods each had positive effects on seedling height growth (except for repellents), and cages, timber harvests, fences, and mesh sleeves had positive effects on survival. Logging slash had no effect on browse incidence (−0.05, CI: −0.97–0.19). Fertilizer applied during seedling establishment increased browse (0.13, CI: 0.11–0.21), and did not affect height growth. We conclude that fences or other physical barriers best control for the effects of deer, but facilitation by surrounding vegetation, logging slash, hunting, habitat management through timber harvest, and certain repellents may also be moderately effective. Discrepancies between browse effectiveness and relative costs suggest that economic analyses should be developed to help to guide prescriptions for management.

Modeling and analysis of an electro-pneumatic braided muscle actuator

The present study deals with static modeling and analysis of a novel electro-pneumatic braided muscle (EPBM) actuator. The EPBM actuator is a hybrid McKibben-type actuator, made of a dielectric polymeric bladder enclosed in a braided mesh sleeve. A continuum mechanics-based electromechanical model is developed to predict the response of the actuator for a combined pressure and voltage loading. The model also incorporates braid-to-braid frictional effects. The model agrees well with existing experimental results for the special case of zero input voltage. Parametric studies are subsequently performed for varying braid angle, input pressure, and voltage. Finally, the model is utilized to study the impact of fiber-reinforcement in the bladder on the actuator performance.

Diversity and distribution of microbial communities in floral nectar of two night-blooming plants of the Sonoran Desert.

Nectar-inhabiting microbes are increasingly appreciated as important components of plant-pollinator interactions. We quantified the incidence, abundance, diversity, and composition of bacterial and fungal communities in floral nectar of two night-blooming plants of the Sonoran Desert over the course of a flowering season: Datura wrightii (Solanaceae), which is pollinated by hawkmoths, and Agave palmeri (Agavaceae), which is pollinated by bats but visited by hawkmoths that forage for nectar. We examined the relevance of growing environment (greenhouse vs. field), time (before and after anthesis), season (from early to late in the flowering season), and flower visitors (excluded via mesh sleeves or allowed to visit flowers naturally) in shaping microbial assemblages in nectar. We isolated and identified bacteria and fungi from >300 nectar samples to estimate richness and taxonomic composition. Our results show that microbes were common in D. wrightii and A. palmeri nectar in the greenhouse but more so in field environments, both before and especially after anthesis. Bacteria were isolated more frequently than fungi. The abundance of microbes in nectar of D. wrightii peaked near the middle of the flowering season. Microbes generally were more abundant as time for floral visitation increased. The composition of bacterial and especially fungal communities differed significantly between nectars of D. wrightii and A. palmeri, opening the door to future studies examining their functional roles in shaping nectar chemistry, attractiveness, and pollinator specialization.

Aortic root surgery in Marfan syndrome.

Marfan syndrome (MFS) is an autosomal dominant connective disease etiologically related with FBN-1 gene mutation. The altered microfibril protein structure result in characteristic cardiovascular abnormalities including aortic root dilatation, aortic root aneurysms, and aortic dissections. Aortic root aneurysms and subsequent dissection are the major causes of reduced life expectancy in MFS patients. Prophylactic aortic root replacement has improved the survival of patients with MFS. Elective root replacement carries very low mortality and morbidity. Emergency root replacement for dissection is accompanied with higher early mortality and late deaths/interventions. Both the techniques of aortic root replacement, total root replacement (TRR) with a prosthetic valved conduit, and valve-sparing root replacement (VSRR) yield excellent early and late results. Considering the low risk of prosthetic valve-related events, the improved long-term survival, and event-free survival, TRR continues to be a very effective surgical option. VSSR also seems to be a good option for the first 10 to 15years following surgery in MFS patients. The choice of procedure depends upon available expertise, patients' choice, feasibility of anticoagulation, possibility of pregnancy, and lifestyle of the patient. Aortic root morphology and state of valve cusps also affect the decision making. In recent times, personalized external aortic root support (PEARS) with a macroporous mesh sleeve has also emerged as a promising alternative to aortic root replacement. All these patients need close monitoring for whole life after surgical intervention.

External Aortic Root Support to Prevent Aortic Dilatation in Patients With Marfan Syndrome

BackgroundPersonalized external aortic root support (PEARS) was introduced in 2004 for prevention of aortic root dilatation in Marfan patients. The individual's aortic root is replicated by 3-dimensional printing. A polymer mesh sleeve is manufactured, which is implanted with the aim to support and stabilize the aortic wall. ObjectivesThe aim of this study was to assess effectiveness of PEARS for prevention of aortic root dilatation in Marfan patients. MethodsA total of 24 consecutive Marfan patients operated 2004 to 2012 were prospectively monitored with magnetic resonance imaging. Following a pre-defined protocol, baseline and follow-up aorta measurements were made in a blinded random sequence. ResultsThe mean age of the patients was 33 ± 13.3 years (range: 16 to 58 years), and the mean aortic root diameter was 45 ± 2.8 mm (range: 41 to 52 mm). Follow-up was 6.3 ± 2.6 years. There was no increase in the aortic root and ascending aorta diameters, but there was a tendency toward reduction: annulus diameter 28.9 ± 2.3 mm to 28.5 ± 2.4 mm (change −0.39 mm, 95% confidence interval [CI]: −1.05 to 0.27 mm), sinus of Valsalva diameter 44.9 ± 2.9 mm to 44.5 ± 3.0 mm (change −0.37 mm, 95% CI: −1.23 to 0.51 mm), and ascending aorta diameter 32.4 ± 3.6 mm to 32.3 ± 3.7 mm (change −0.10 mm, 95% CI: −0.92 to 0.74 mm). In the same period, the descending aorta diameter increased from 22.9 ± 2.4 mm to 24.2 ± 3.0 mm (change 1.32 mm, 95% CI: 0.70 to 1.94 mm; p < 0.001) with a tendency toward increase in aortic arch diameter 24.1 ± 2.0 mm to 24.5 ± 2.8 mm (change 0.41 mm, 95% CI: −0.56 to 1.37 mm). ConclusionsPEARS is effective in stabilizing the aortic root and preventing its dilatation. It is a viable alternative for prevention of aortic root dissection in Marfan patients.

Growth of planted seedlings inside protective sleeves under strip openings of different widths in a post-agricultural forest

Many second growth forests have poor regeneration and in some spatial and economic context, such as post-agricultural forests, it may be beneficial to increase tree diversity. We planted seedlings of yellow birch (Betula alleghaniensis) and bur oak (Quercus macrocarpa) in strip openings of 3, 6 and 9 m width to control light. Individual mesh sleeves were used to reduce browsing pressure but they also reduced available light for seedlings: a large mesh and a small mesh sleeves were tested in each opening. Available light for seedlings ranged from 5 to 46% of full sunlight. First year growth was almost non-responsive to all treatments for both species, but birch showed strong responses during second year. Birches in the large mesh sleeve and the 9 m opening had the largest height and diameter increments, while those in the small mesh sleeve and the 3 m opening had the smallest increments. Small mesh sleeves increased the height over stem diameter ratio for both species. Treatments affected several other morphometric variables of birch but none of the oak. More time is needed to assert if bur oak can be a candidate species for enrichment planting. We recommend strip openings of 9 m width and large mesh sleeves, for protection against deer browsing, while controlling neighbouring competition, to promote artificial regeneration of hardwood species.

Pull-Out Behavior of Adhesive Connections in Unreinforced Masonry Walls

The connections between walls of unreinforced masonry (URM) buildings and flexible timber diaphragms are critical building components that must perform adequately before desirable earthquake response of URM buildings may be achieved. Field observations made during the initial reconnaissance and the subsequent damage surveys of clay brick URM buildings following the 2010/2011 Canterbury, New Zealand, earthquakes revealed numerous cases where anchor connections joining masonry walls or parapets with roof or floor diaphragms appeared to have failed prematurely. These observations were more frequent for adhesive anchor connections than for through-bolt connections (i.e., anchorages having plates on the exterior facade of the masonry walls). Subsequently, an in-field test program was undertaken in an attempt to evaluate the performance of adhesive anchor connections between unreinforced clay brick URM walls and roof or floor diaphragm. The study consisted of a total of almost 400 anchor tests conducted in eleven existing URM buildings located in Christchurch, Whanganui and Auckland. Specific objectives of the study included the identification of failure modes of adhesive anchors in existing URM walls and the influence of the following variables on anchor load-displacement response: adhesive type, strength of the masonry materials (brick and mortar), anchor embedment depth, anchor rod diameter, overburden level, anchor rod type, quality of installation, and the use of metal mesh sleeves. In addition, the comparative performance of bent anchors (installed at an angle of minimum 22.5° to the perpendicular projection from the wall surface) and anchors positioned horizontally was investigated. Observations on the performance of wall-to-diaphragm connections in the 2010/2011 Canterbury earthquakes, a summary of the performed experimental program and test results, and a proposed pull-out capacity relationship for adhesive anchors installed into multi-leaf clay brick masonry are presented herein.

New concept and fundamental experiments of a smart pneumatic artificial muscle with a conductive fiber

A McKibben artificial muscle consisting of a rubber tube and a mesh sleeve made from fibers is a promising actuator as an artificial muscle because of its high power, low weight, and flexibility. However, an external pressure sensor or an expensive electro/pneumatic regulator is generally required to control the pneumatic pressure to drive the actuator.A novel smart McKibben-type artificial muscle with a pressure-sensing function has been proposed and developed in this study. One fiber on the sleeve of the actuator is converted from a normal to a conductive material. The applied pressure is estimated by observing the electrical resistance of the conductive fiber. Therefore, the fiber works as both a sensor and an actuator element.The fabrication process of the smart artificial muscle is established in this report, and the basic characteristics are clarified. Moreover, a compact driving control system of the smart artificial muscle, which uses a small rotary pump without external sensors, electro/pneumatic regulator, or valves, is proposed.

Self-reported occupational injuries among industrial beef slaughterhouse workers in the Midwestern United States

ABSTRACTAlthough workers in meatpacking facilities in the U.S. experience high rates of occupational injury, their injury experiences have received limited research attention. Prior research indicates underreporting in injury rates in this industry as well significant variation in injury rates among facilities. To add detail to the rates and circumstances surrounding occupational injury among meatpacking workers, we conducted a cross-sectional study of workers employed at an industrial beefpacking plant in Nebraska (n = 137) and interviewed workers about recent injury experiences. We assessed frequency, cause and nature of self-reported injury. We estimated annual incidence rates of self-reported injuries using the OSHA formula and compared these rates to industry-wide data. We also evaluated psychological distress in this workforce as measured by the Kessler-6 scale to assess whether distress was associated with recent occupational injury. In this study, 15.1% of workers experienced occupational injuries that required time off work, job transfer, or restriction during the past three months. The estimated annual incidence rate was 15.2 injuries per 100 full-time workers for these injuries at this plant. Rushing was identified as the cause of nearly 50% of injuries, and repetitive work as the cause of an additional 20% of injuries. Use of metal mesh sleeves (POR: 0.10 (p = 0.008)) and metal mesh gloves (POR: 0.41 (p = 0.05) were associated with reduced risk of injury. Use of a carbon steel for knife sharpening (POR: 5.2 (p = 0.02)) was associated with elevated risk of moderate and severe injury. There were no associations between self-reported occupational injury and overall measures of psychological distress. Self-reported incidence rate of severe injury in this plant was more than twice official industry estimates. Worker self-reports may illustrate key areas for injury prevention.

EVALUATING EFFICACY OF CONCEPTUAL SEDIMENT BARRIER MATRIX TOWARDS ECOSYSTEM RESTORATION ATTRIBUTES

The rationale behind the study was to estimate effectiveness of Eichhornia leaf filter sleeves as a sediment barrier matrix towards soil erosion and sediment control practice to curtail adverse impacts associated with sedimentation at the lake waters. The study had an objective to implement the development to fit the site under study to stabilize exposed soils as soon as practicable. The prime objective was to estimate the sediment captured by the sleeve to control and manage on-site by protecting the areas and retain sediment on-site. Primarily Eichhornia leaf filter sleeves (Sun dried premature Eichhornia leaf fills ) crammed in an IS 16008 (2012)tubular mesh sleeve as a linear land based treatment filter to primarily study the efficacy of filtration ability of sediments and soluble pollutants a further contemplation. It is found that besides sediments some of the pollutants can be trapped in sediments downstream. The efficacy of the model was analyzed to be successful in preventing sediment inflows at the lake waters. Effectively percent reduction of sand 89%, TSS 68%, silt 56%, turbidity 51%, and clay by 18% was recorded. This describes the effectual exploitation of the notorious weed Eichhornia biomass sleeve towards reducing sediments and turbidity of runoff waters entering the lake waters enhancing the ecological status of the lakes. The studies portray the application of the Eichhornia sleeve in high reduction in total suspended solids and sand.

Effects observation of protection sleeve of venous indwelling needle applied for patients with limb trauma

Objective To explore the influences of protection sleeve of venous indwelling needle on patients with limb trauma and its impact on anxiety. Methods A total of 152 patients with limb trauma were divided into control group (fixed by 3M transparent dressing and tape after successful puncture) and observation group (routine nursing care of indwelling needle + fixed by nylon elastic mesh sleeve) according to admission sequence. One week after intravenous transfusion, patients were evaluated by self-rating anxiety scale (SAS) developed by William W. K.Zung. Patients′ satisfaction was investigated by questionnaires during hospitalization. We also compared the score of SAS, sleep quality, indwelling needle drop-off, phlebitis, condition of tube blocking as well as patients′ satisfaction during hospitalization between two groups. Results Cases with anxiety in observation group (11 cases) were less than that in the control group (23 cases) with a significant difference (P 0.05). Conclusions The use of nylon elastic mesh sleeve based on routine nursing care of indwelling needle can effectively prevent the indwelling needle from dropping off. It also obviously alleviates the anxiety of patients with trauma, improves sleep quality, makes patients safe and comfortable and improves satisfactions with nursing. Key words: Innovation and promotion; Detaining needle; Anxiety; Elastic mesh sleeve; Limb trauma

MGuard Dacron mesh-covered stent implantation in patients with ST-elevation myocardial infarction and high thrombotic burden: in-hospital and long-term outcome in a single high-volume center

The MGuard (MG) is a stainless-steel closed cell stent covered with an ultra-thin polymer mesh sleeve, which has the purpose of ensuring reduced distal embolization of thrombotic material, thus lowering the risk of no-reflow/slow-flow phenomena. Only few data are available that evaluated the usefulness of the MG stent in patients with ST-elevation myocardial infarction (STEMI) with a high thrombotic burden. We prospectively collected data of patients presenting with STEMI and high thrombotic burden (thrombus burden grade 4 or 5 according to the TIMI score) who underwent primary percutaneous coronary intervention (PCI) with MG stent implantation in our center. Lesions involving a bifurcation or very calcified and tortuous vessels were not included. Final TIMI 3 flow, normal myocardial blush grade (MBG), and complete ST-segment resolution were defined as short-term endpoints, whereas major adverse cardiovascular events were evaluated during follow-up. From August 2008 to June 2013, the MG stent was implanted in 104 (9.3%) of 1108 patients who underwent primary PCI. Cardiogenic shock on admission was present in 4 patients (3.8%). Final TIMI 3 flow was achieved in 97.1% of patients, MBG 3 in 56.7%, and regression of ST-segment elevation ≥70% within 90 min was recorded in 64.4% of patients. In-hospital mortality was 2.9% (n=3), and at a mean follow-up of 455±430 days overall major adverse cardiovascular events were 11 (10.6%). Cardiac death occurred in 5 patients (4.9%) and stent thrombosis in 2 (1.9%). In selected patients with STEMI undergoing primary PCI, the use of the mesh-covered MG stent in vessels with high thrombotic burden despite thrombus aspiration was effective and safe both immediately and at mid-term follow-up.

Intracoronary mesenchymal stem cell transplantation in patients with ischemic cardiomyopathy

overcome during the implantation of this stent. Passage of the MGS through tortuous, calcified or small diameter vessels is very challenging, if not impossible. The few cases, where we failed to advance the stent through the lesion, were shepherds crook type of RCA anatomy. Another important issue is the compromising of side branches by the presence of polymer mesh sleeve on its external surface. In addition, there are no data about its behavior in high-thrombotic volume, especially when no other EPD were used. In our study, there were a few cases with thrombus load grade five, where M-Guard was used with the aspiration catheter and the effectiveness of their combination was impressive, resulting in TIMI 3 flow with satisfactory blush score. The limitations of our study concern the relatively small number of patients, taking mostly into consideration the subgroup of patients from theMGS group that TAwas not performed. Another aspect is also the lack of a randomized design. In conclusion, in the setting of pPCI, MGS proved to be effective and safe with low TVR and low thrombosis rates at 1 and 12 months, considering the high risk group of STEMI patients. In addition, final TIMI flow and MBG are higher and the incidence of no-reflow is less. That benefit from its use is independent from the performance of TA in pPCI. The authors report no relationships that could be construed as a conflict of interest.

Non-linear quasi-static model of pneumatic artificial muscle actuators

Pneumatic artificial muscles are a class of pneumatically driven actuators that are remarkable for their simplicity, lightweight, high stroke, and high force. The McKibben artificial muscle, which is a type of pneumatic artificial muscle, is composed of an elastomeric bladder, a braided mesh sleeve, and two end fittings. Gaylord first developed an analysis of the McKibben artificial muscle based on the conservation of energy principle. The Gaylord model predicts block force but fails to accurately capture actuation force versus contraction ratio behavior. To address this lack, a non-linear quasi-static model is developed based on finite strain theory. The internal stresses in the bladder are determined by treating it as a cylinder subjected to applied internal pressure and a prescribed kinematic constraint of the outer surface. Subsequently, the force balance approach is applied to derive the equilibrium equations in both the axial and circumferential directions. Finally, the closed-form pneumatic artificial muscle quasi-static actuator force is obtained. The analysis was experimentally validated using actuation force versus contraction ratio test data at a series of discrete inflation pressures for two different pneumatic artificial muscles: a large pneumatic artificial muscle ( L = 128.5 mm, B = 7.85 mm, with a latex bladder) and a miniature pneumatic artificial muscle ( L = 43.9 mm, B = 2.3 mm, with a V330 elastomeric bladder).

Long-term follow-up of mesh-covered stent implantation in patients with ST-segment elevation myocardial infarction

The MGuard stent (a bare-metal stent wrapped externally in a polymer mesh sleeve) was introduced to reduce the risk of distal embolisation and no-reflow phenomenon during percutaneous coronary intervention (PCI) in thrombus containing lesions, including ST-segment elevation myocardial infarction (STEMI). However, data on the long-term performance of the MGuard stent is limited. To assess the long-term safety and efficacy of MGuard stent implantation during primary PCI for STEMI. In this multicentre study, a total of 60 patients with STEMI ≤12 h treated with the MGuard stent were enrolled. Angiographic success of PCI was achieved in 96.7%, with the final TIMI grade 3 flow in 90.0% of patients. At six months, the overall rate of major adverse cardiac and cerebrovascular events (MACCE; composite of cardiac death, nonfatal target vessel reinfarction, target lesion revascularisation, and stroke) was 1.7%. A long-term follow-up of the study was successfully performed in 57 patients (mean follow-up of 38.7 ± 3.1 months). The long-term cardiac mortality was 7.0%, with a MACCE rate of 8.8%. There was no decrease in the left ventricular ejection fraction and no enlargement of the left ventriclebetween index and long-term follow-up echocardiogram. The early safety and efficacy of the MGuard stent was maintained during the long-term follow-up. However, comparative data from ongoing randomised clinical trials are still required to confirm the long-term efficacy of MGuard stent implantation in patients with STEMI.

Contractile Pneumatic Artificial Muscle Configured to Generate Extension

Pneumatic artificial muscles (PAMs) are comprised of an elastomeric bladder surrounded by a braided mesh sleeve. When the bladder is inflated, the actuator may either contract or extend axially, with the direction of motion dependent on the orientation of the fibers in the braided sleeve. Contractile PAMs have excellent actuation characteristics, including high specific power, specific work, and power density. Unfortunately, extensile PAMs exhibit much reduced blocked force, and are prone to buckling under axial compressive loading. For applications in which extensile motion and compressive force are desired, the push-PAM actuator introduced here exploits the operational characteristics of a contractile PAM, but changes the direction of motion and force by employing a simple internal mechanism using no gears or pulleys. Quasi-static behavior of the push-PAM was compared to a contractile PAM for a range of operating pressures. Based on these data, the push-PAM actuator can achieve force and stroke comparable to a contractile PAM tested under the same conditions.

LIGHT ENVIRONMENT GENERATES ECOLOGICAL TRADE‐OFFS IN HERBIVORES

All photographs by Teresa M. Stoepler White oak (Quercus alba) saplings were grown in (A) full sun or (B) full shade (under 90% light reduction shade cloth) on the roof of Bell Hall, a four-story building located at George Washington University in Washington, D.C. Saplings were kept under these light conditions for three months (30 March–30 June 2010), which encompassed the entire developmental process from pre-bud break through full leaf expansion and hardening, to induce saplings to produce (C) sun and (D) shade leaves, respectively. White oak shade-grown saplings produced fewer leaves than sun-grown saplings, but individual shade leaves were 78% larger, resulting in greater total leaf area compared to sun-grown saplings. Shade leaves were 27% lower in toughness, 14% lower in carbon:nitrogen ratio, 42% and 77% lower in hydrolyzable and condensed tannins, respectively, 12% higher in nitrogen, and 8% higher in water content relative to sun leaves. After leaves were fully hardened, the sun- and shade-grown white oak saplings (indicated by arrows) were (A, B) transported to the field site, Little Bennett Regional Park in Clarksburg, Maryland, and (C) placed in light gaps (foreground) and shaded forest understory habitats (background) in a full factorial design. Pictured in A: Arjun Awasthi; B: Patrick Lill and Margaret Rosati. Panel C modified from Fig. 1 in T. M. Stoepler, and B. Rehill. 2012. Forest habitat, not leaf phenotype, predicts late-season folivory of Quercus alba saplings. Functional Ecology 26:1205–1213; reproduced with permission from John Wiley and Sons. Sentinel lab-reared larvae of Euclea delphinii and Acharia stimulea (Limacodidae, Lepidoptera) were (A) reared in mesh sleeve cages (protected from enemies) or (B) exposed to parasitism on the saplings to measure the direct and indirect effects of light environment on caterpillar performance and parasitism (only A. stimulea is shown). The extent to which bottom-up factors affect higher trophic levels and the relative importance of direct and indirect effects on tritrophic interactions are poorly understood. We tested how light environment (direct; light gap vs. understory habitats) and leaf type (indirect; sun vs. shade leaves) affected the performance and parasitism of forest caterpillars reared on experimental white oak saplings. By manipulating light environment independent of leaf phenotype, we showed that caterpillar performance was maximized in the shade habitat/sun leaf treatment, revealing inherent ecological trade-offs for herbivores choosing between sunny (high leaf quality, harsh environment, high parasitism) and shaded (reduced leaf quality, less harsh environment, low parasitism) habitats. These photographs illustrate the article “Direct and indirect effects of light environment generate ecological trade-offs in herbivore performance and parasitism,” by Teresa M. Stoepler and John T. Lill, tentatively scheduled for publication in Ecology 94(10), October 2013. doi: http://dx.doi.org/10.1890/12-2068.1

External aortic root support: a histological and mechanical study in sheep†

Personalized external aortic root support has completed initial evaluation and has technology appraisal in the UK for patients with Marfan syndrome for use as an alternative to root replacement. Its long-term success in preventing aortic dissection remains uncertain. Here, we report a study in sheep to establish whether the externally supporting mesh, as used clinically, is biologically incorporated. The strength of the resulting mesh/artery composite has been tested. The carotid artery of growing sheep (n=6) was enclosed in a mesh sleeve made of a polymer, polyethylene terephthalate. After a predefined interval of 4-6 months, a length of the artery was excised, including the sleeved and unsleeved portions, and was stress tested and examined histologically. One animal died of pneumonia 7 days after implantation. Comparing sleeved with normal segments, the overall thickness was increased and there was a fibrotic sheet in the periarterial space. The overall vessel wall architecture was preserved in all specimens. Although media thickness of ensleeved arteries was smaller and in one animal mild oedema was found in one quadrant of the outer part of the media. There was a significant increase in stiffness and maximum tensile strength of the supported segments compared with normal arterial tissue. Polyethylene terephthalate mesh, as used for the external support of the dilated aortic root in Marfan syndrome, becomes incorporated in the periadventitial tissue of the carotid artery of sheep. Limited thinning of the media, without any signs of inflammation or medial necrosis, was visible. There was a significantly greater tensile strength in the carotid artery/mesh composite compared with the unsleeved carotid artery.