Spring and latch dynamics can act as control pathways in ultrafast systems.

Ultrafast movements propelled by springs and released by latches are thought limited to energetic adjustments prior to movement, and seemingly cannot adjust once movement begins. Even so, across the tree of life, ultrafast organisms navigate dynamic environments and generate a range of movements, suggesting unrecognized capabilities for control. We develop a framework of control pathways leveraging the non-linear dynamics of spring-propelled, latch-released systems. We analytically model spring dynamics and develop reduced-parameter models of latch dynamics to quantify how they can be tuned internally or through changing external environments. Using Lagrangian mechanics, we test feedforward and feedback control implementation via spring and latch dynamics. We establish through empirically-informed modeling that ultrafast movement can be controllably varied during latch release and spring propulsion. A deeper understanding of the interconnection between multiple control pathways, and the tunability of each control pathway, in ultrafast biomechanical systems presented here has the potential to expand the capabilities of synthetic ultra-fast systems and provides a new framework to understand the behaviors of fast organisms subject to perturbations and environmental non-idealities.

Consensus exercise identifying priorities for research in the field of general surgery of childhood in the UK.

BACKGROUND: The evidence base underlying clinical practice in children's general surgery is poor and high-quality collaborative clinical research is required to address current treatment uncertainties. The aim of this study was, through a consensus process, to identify research priorities for clinical research in this field amongst surgeons who treat children. METHODS: Questions were invited in a scoping survey amongst general surgeons and specialist paediatric surgeons. These were refined by the study team and subsequently prioritized in a two-stage modified Delphi process. RESULTS: In the scoping survey, a total of 226 questions covering a broad scope of children's elective and emergency general surgery were submitted by 76 different clinicians. These were refined to 71 research questions for prioritization. A total of 168 clinicians took part in stage one of the prioritization process, and 157 in stage two. A 'top 10' list of priority research questions was generated for both elective and emergency general surgery of childhood. These cover a range of conditions and concepts, including inguinal hernia, undescended testis, appendicitis, abdominal trauma and enhanced recovery pathways. CONCLUSION: Through consensus amongst surgeons who treat children, 10 priority research questions for each of the elective and emergency fields have been identified. These should provide a basis for the development of high-quality multicentre research projects to address these questions, and ultimately improve outcomes for children requiring surgical care.

Thermal Desorption Analysis of Hydrogen in Non-hydrogen-Charged Rolling Contact Fatigue-Tested 100Cr6 Steel.

Hydrogen diffusion during rolling contact fatigue (RCF) is considered a potential root cause or accelerator of white etching cracks (WECs) in wind turbine gearbox bearing steels. Hydrogen entry into the bearing steel during operation is thought to occur either through the contact surface itself or through cracks that breach the contact surface, in both cases by the decomposition of lubricant through catalytic reactions and/or tribochemical reactions of water. Thermal desorption analysis (TDA) using two experimental set-ups has been used to measure the hydrogen concentration in non-hydrogen-charged bearings over increasing RCF test durations for the first time. TDA on both instruments revealed that hydrogen diffused into the rolling elements, increasing concentrations being measured for longer test durations, with numerous WECs having formed. On the other hand, across all test durations, negligible concentrations of hydrogen were measured in the raceways, and correspondingly no WECs formed. Evidence for a relationship between hydrogen concentration and either the formation or the acceleration of WECs is shown in the rollers, as WECs increased in number and severity with increasing test duration. It is assumed that hydrogen diffusion occurred at wear-induced nascent surfaces or areas of heterogeneous/patchy tribofilm, since most WECs did not breach the contact surface, and those that did only had very small crack volumes for entry of lubricant to have occurred.

The Evolution of White Etching Cracks (WECs) in Rolling Contact Fatigue-Tested 100Cr6 Steel.

The formation of white etching cracks (WECs) in steel rolling element bearings can lead to the premature rolling contact fatigue (RCF) failure mode called white structure flaking. Driving mechanisms are still debated but are proposed to be combinations of mechanical, tribochemical and electrical effects. A number of studies have been conducted to record and map WECs in RCF-tested samples and bearings failed from the field. For the first time, this study uses serial sectioning metallography techniques on non-hydrogen charged test samples over a range of test durations to capture the evolution of WEC formation from their initiation to final flaking. Clear evidence for subsurface initiation at non-metallic inclusions was observed at the early stages of WEC formation, and with increasing test duration the propagation of these cracks from the subsurface region to the contact surface eventually causing flaking. In addition, an increase in the amount of associated microstructural changes adjacent to the cracks is observed, this being indicative of the crack being a prerequisite of the microstructural alteration.

Segmental colonic dilation is associated with premature termination of high-amplitude propagating contractions in children with intractable functional constipation.

BACKGROUND: Colonic dilation is common in children with intractable functional constipation (FC). Our aim was to describe the association between segmental colonic dilation and colonic dysmotility in children with FC. METHODS: We performed a retrospective study on 30 children with intractable FC (according to the Rome III criteria) who had undergone colonic manometry and contrast enema within a 12-month time period. Colonic diameter was measured at 5 cm intervals from the anal verge up to the splenic flexure. Moreover, the distance between the lateral margins of the pedicles of vertebra L2 was measured to provide a ratio (colonic diameter or length/distance between the lateral margins; "standardized colon size" [SCS]). All manometry recordings were visually inspected for the presence of high-amplitude propagating contractions (HAPCs); a parameter for colonic motility integrity. The intracolonic location of the manometry catheter sensors was assessed using an abdominal X-ray. KEY RESULTS: Colonic segments with HAPCs had a significantly smaller median diameter than colonic segments without HAPCs (4.08 cm vs 5.48 cm, P<.001; SCS 1.14 vs 1.66, P=.001). Children with prematurely terminating HAPCs had significantly larger SCS ratios for colonic diameter than children with fully propagating HAPCs (P=.008). SCS ratios for the length of the rectosigmoid and the descending colon and the SCS ratio for sigmoid colon diameter were significantly larger in children with FC compared to a previously described normative population (P<.0001, P<.0001 and P=.0007 respectively). CONCLUSIONS & INFERENCES: Segmental colonic dilation was associated with prematurely terminating HAPCs and may be a useful indicator of colonic dysmotility.

Perching and takeoff of a robotic insect on overhangs using switchable electrostatic adhesion.

For aerial robots, maintaining a high vantage point for an extended time is crucial in many applications. However, available on-board power and mechanical fatigue constrain their flight time, especially for smaller, battery-powered aircraft. Perching on elevated structures is a biologically inspired approach to overcome these limitations. Previous perching robots have required specific material properties for the landing sites, such as surface asperities for spines, or ferromagnetism. We describe a switchable electroadhesive that enables controlled perching and detachment on nearly any material while requiring approximately three orders of magnitude less power than required to sustain flight. These electroadhesives are designed, characterized, and used to demonstrate a flying robotic insect able to robustly perch on a wide range of materials, including glass, wood, and a natural leaf.

Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix.

Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the 'drop-cast' method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young's modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young's modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

Rectal atresia and anal stenosis: the difference in the operative technique for these two distinct congenital anorectal malformations.

Rectal atresia and anal stenosis are rare forms of anorectal malformations. The aim of the definitive surgical repair in such cases is to preserve the anal canal, the dentate line, and the sphincter complex. We present a case of rectal atresia and anal stenosis to demonstrate the differences in the operative repair. The techniques described leave the anterior wall of the very distal anal canal untouched in both rectal stenosis and anal atresia; however, the dissection of the rectum differs. The atretic rectum in rectal atresia is mobilized and sutured to the anal canal circumferentially. In anal stenosis, the posterior rectum is mobilized in the form of rectal advancement, and the posterior 180° is anastomosed directly to the skin (as in a standard PSARP) with preservation of the anal canal as the anterior 180° of the final anoplasty. These patients have an excellent prognosis for bowel control and fecal continence, and therefore, complete mobilization and resection of the anal canal must be avoided.

No change in calcium absorption in adult Pakistani population before and after vitamin D administration using strontium as surrogate.

UNLABELLED: Vitamin D, parathyroid hormone levels and calcium absorption was assessed before and after cholecalciferol using Strontium as a surrogate. Increase in 25OHD, lowering of iPTH with no effect on Sr absorption was seen, suggesting the possibility that maximal Ca absorption had already been achieved in these volunteers. INTRODUCTION: This paper discusses the determination of calcium (Ca) absorption, using strontium (Sr) as a surrogate, before and after a single IM injection of vitamin D(3) (600,000 IU). METHODS: Baseline serum 25-hydroxyvitamin D (25OHD), Sr, Ca, P, and intact parathyroid hormone (iPTH) were determined in 53 fasting volunteers, followed by administrating (PO) 0.03 mM (4.8 mg/kg) SrCl(2) and collecting blood at 0.5, 1 and 4 h to determine the absorption (AUC(0 → t )) of Sr. Following the initial absorption test, volunteers received a single IM injection of 600,000 IU vitamin D(3). Two months later, the fasting serum and the Sr absorption test were repeated, as described above. RESULTS: The IM injection of vitamin D(3) caused a significant increase in fasting 25OHD (from 43.5 ± 19 to 66.1 ± 19.1 nmol/L (p < 0.001)) and a trend toward lower serum iPTH (from 59.8 ± 27.8 to 53 ± 31 ng/L). Fasting serum Ca and P remained unchanged. A higher 25OHD level failed (p = 0.32) to translate into a higher rate of Sr absorption. AUC(0 → 4 h) were almost identical before and after the IM injection of vitamin D(3). CONCLUSION: A single vitamin D(3) injection of 600,000 IU significantly increase mean 25OHD concentration and tended to lower iPTH concentrations in volunteers with initially low 25OHD status, suggesting to utilize this simple form of treatment to improve vitamin D status and to have a possible biological effect on Ca homeostasis. However, we found no obvious effect on Sr absorption, suggesting the possibility that maximal vitamin D-dependent Ca absorption had already been achieved in these volunteers at a lower vitamin D status.

Constipation in Children

Constipation in children is a universal problem; occurring in 0.7-28 of the population. The exact aetiology is unknown; but the majority of children have a functional; rather than organic; aetiology. Symptoms associated with constipation include abdominal pain; a poor appetite and faecal incontinence; all of which interfere with the quality of life of the child and his or her family. Early intervention with appropriate management is necessary to prevent ongoing sequelae. Once an organic cause has been excluded; a programme of intervention should be implemented; namely evacuation of any faecal mass present; followed by regular maintenance therapy to encourage evacuation of a daily soft stool for at least 2-3 months; prior to gradual withdrawal. Emotional support; exercise and dietary modification are linked to the therapy and will ensure a successful outcome. Failure to implement the protocol may result in ongoing problems in up to 50 of children as they enter adulthood

Conceptual design of flapping-wing micro air vehicles.

Traditional micro air vehicles (MAVs) are miniature versions of full-scale aircraft from which their design principles closely follow. The first step in aircraft design is the development of a conceptual design, where basic specifications and vehicle size are established. Conceptual design methods do not rely on specific knowledge of the propulsion system, vehicle layout and subsystems; these details are addressed later in the design process. Non-traditional MAV designs based on birds or insects are less common and without well-established conceptual design methods. This paper presents a conceptual design process for hovering flapping-wing vehicles. An energy-based accounting of propulsion and aerodynamics is combined with a one degree-of-freedom dynamic flapping model. Important results include simple analytical expressions for flight endurance and range, predictions for maximum feasible wing size and body mass, and critical design space restrictions resulting from finite wing inertia. A new figure-of-merit for wing structural-inertial efficiency is proposed and used to quantify the performance of real and artificial insect wings. The impact of these results on future flapping-wing MAV designs is discussed in detail.

A review of experimental techniques to produce a nacre-like structure.

The performance of man-made materials can be improved by exploring new structures inspired by the architecture of biological materials. Natural materials, such as nacre (mother-of-pearl), can have outstanding mechanical properties due to their complicated architecture and hierarchical structure at the nano-, micro- and meso-levels which have evolved over millions of years. This review describes the numerous experimental methods explored to date to produce composites with structures and mechanical properties similar to those of natural nacre. The materials produced have sizes ranging from nanometres to centimetres, processing times varying from a few minutes to several months and a different range of mechanical properties that render them suitable for various applications. For the first time, these techniques have been divided into those producing bulk materials, coatings and free-standing films. This is due to the fact that the material's application strongly depends on its dimensions and different results have been reported by applying the same technique to produce materials with different sizes. The limitations and capabilities of these methodologies have been also described.

Anaesthesia for 1131 patients undergoing proximal femoral fracture repair: a retrospective, observational study of effects on blood pressure, fluid administration and perioperative anaemia.

Intra-operative hypotension is a frequent occurrence during anaesthesia for hip fracture surgery in older patients with co-morbidities. We analysed retrospective data from the Brighton Hip Fracture Database to determine the intra-operative fall in systolic blood pressure, and the incidence of absolute (lowest systolic blood pressure < 90 mmHg) and relative (> 20% fall in systolic blood pressure from baseline) hypotension during general or spinal anaesthesia among 1131 non-consecutive patients with hip fracture. General anaesthesia for 489 patients (43.2%) produced a greater mean (SD) fall in systolic blood pressure than spinal anaesthesia for 578 patients (51.1%): 34.2% (13.0%) vs 29.7% (10.8%), respectively (p < 0.0001), mean difference 4.5% (95% CI 3.1-5.9%), and was associated with greater mean (SD) intra-operative fluid administration (1555 (801) ml vs 1375 (621) ml, respectively, p < 0.0001). We observed a correlation between the volume of subarachnoid hyperbaric bupivacaine 0.5% and fall in systolic blood pressure (p = 0.004): compared with patients receiving > 1.5 ml (n = 463), fewer patients receiving ≤ 1.5 ml bupivacaine 0.5% (n = 97) experienced episodes of absolute (31.1% vs 11.3%, p < 0.0001) or relative (83.9% vs 26.8%, p < 0.0001) hypotension. Both mean (SD) intravenous fluid administration (1097 ml (439) vs 1431 ml (638), p < 0.0001) and mean peri-operative fall in haemoglobin concentration (2.1 (1.8) g.dl(-1) vs 2.6 (1.7) g.dl(-1), p = 0.009) were lower in the low-dose spinal group. If these data are confirmed by other researchers, intra-operative hypotension (and consequent haemodilution secondary to reactive fluid administration) in this patient group may be reduced by the simple expedient of administering more cautious general anaesthesia, or reduced volumes of subarachnoid local anaesthetic.

The tribological behaviour of different clearance MOM hip joints with lubricants of physiological viscosities.

Clearance is one of the most influential parameters on the tribological performance of metal-on-metal (MOM) hip joints and its selection is a subject of considerable debate. The objective of this paper is to study the lubrication behaviour of different clearances for MOM hip joints within the range of human physiological and pathological fluid viscosities. The frictional torques developed by MOM hip joints with a 50 mm diameter were measured for both virgin surfaces and during a wear simulator test. Joints were manufactured with three different diametral clearances: 20, 100, and 200 microm. The fluid used for the friction measurements which contained different ratios of 25 percent newborn calf serum and carboxymethyl cellulose (CMC) with the obtained viscosities values ranging from 0.001 to 0.71 Pa s. The obtained results indicate that the frictional torque for the 20 microm clearance joint remains high over the whole range of the viscosity values. The frictional torque of the 100 microm clearance joint was low for the very low viscosity (0.001 Pa s) lubricant, but increased with increasing viscosity value. The frictional torque of the 200 microm clearance joint was high at very low viscosity levels, however, it reduced with increasing viscosity. It is concluded that a smaller clearance level can enhance the formation of an elastohydrodynamic lubrication (EHL) film, but this is at the cost of preventing fluid recovery between the bearing surfaces during the unloaded phase of walking. Larger clearance bearings allow a better recovery of lubricant during the unloaded phase, which is necessary for higher viscosity lubricants. The selection of the clearance value should therefore consider both the formation of the EHL film and the fluid recovery as a function of the physiological viscosity in order to get an optimal tribological performance for MOM hip joints. The application of either 25 per cent bovine serum or water in existing in vitro tribological study should also be revised to consider the relevance of clinic synovial fluid viscosities and to avoid possible misleading results.

Programmable matter by folding.

Programmable matter is a material whose properties can be programmed to achieve specific shapes or stiffnesses upon command. This concept requires constituent elements to interact and rearrange intelligently in order to meet the goal. This paper considers achieving programmable sheets that can form themselves in different shapes autonomously by folding. Past approaches to creating transforming machines have been limited by the small feature sizes, the large number of components, and the associated complexity of communication among the units. We seek to mitigate these difficulties through the unique concept of self-folding origami with universal crease patterns. This approach exploits a single sheet composed of interconnected triangular sections. The sheet is able to fold into a set of predetermined shapes using embedded actuation. To implement this self-folding origami concept, we have developed a scalable end-to-end planning and fabrication process. Given a set of desired objects, the system computes an optimized design for a single sheet and multiple controllers to achieve each of the desired objects. The material, called programmable matter by folding, is an example of a system capable of achieving multiple shapes for multiple functions.

Artificial insect wings of diverse morphology for flapping-wing micro air vehicles.

The development of flapping-wing micro air vehicles (MAVs) demands a systematic exploration of the available design space to identify ways in which the unsteady mechanisms governing flapping-wing flight can best be utilized for producing optimal thrust or maneuverability. Mimicking the wing kinematics of biological flight requires examining the potential effects of wing morphology on flight performance, as wings may be specially adapted for flapping flight. For example, insect wings passively deform during flight, leading to instantaneous and potentially unpredictable changes in aerodynamic behavior. Previous studies have postulated various explanations for insect wing complexity, but there lacks a systematic approach for experimentally examining the functional significance of components of wing morphology, and for determining whether or not natural design principles can or should be used for MAVs. In this work, a novel fabrication process to create centimeter-scale wings of great complexity is introduced; via this process, a wing can be fabricated with a large range of desired mechanical and geometric characteristics. We demonstrate the versatility of the process through the creation of planar, insect-like wings with biomimetic venation patterns that approximate the mechanical properties of their natural counterparts under static loads. This process will provide a platform for studies investigating the effects of wing morphology on flight dynamics, which may lead to the design of highly maneuverable and efficient MAVs and insight into the functional morphology of natural wings.

Meiotic drive by the Y-linked D gene in Aedes aegypti (L.) (Diptera: Culicidae) is associated with disruption of spermiogenesis, leading to premature senescence of spermatozoa.

Y chromosome meiotic drive in the mosquito Aedes aegypti, due to the gene D (Distorter) in coupling with M (male determination) [the MD haplotype], is associated with spermiogenic disruption, leading to senescence, at a rate proportionate to male excess. Spermiogenesis was compared between 'Enhanced Mutant' males with a strongly female-depleted sex ratio (8.9% females), 'Mutant' males showing a lesser degree of distortion (38.3% females), and two controls with normal sex ratios (51.2% and 49.2% females). Sections of testes dissected from mature pupae and adults aged 0, 4, 8, 12 and 16 days were examined by transmission electron microscopy. A difference between Mutant and control spermiogenesis was apparent as early as the pupal stage when some Mutant spermatids showed extra tail elements (axonemes and/or mitochondrial derivatives). The same was true of Enhanced Mutant males but to a more extreme degree. Sperm senescence was evident in Enhanced Mutant testes from day 0 of adult life but in Mutant testes not until day 4. Progressive disorganisation was associated with many loose organelles, and disturbance of the anterior-posterior axis of gamete differentiation within the testis. Degenerative changes of a similar kind in the controls did not become apparent until day 8. These findings are discussed with respect to other characteristics of this meiotic drive system, in terms of a theory of inhibition of reduction division in spermatogenesis associated with fragmentation of the X chromosome, leading to the formation of a restitution nucleus as early as metaphase 1.

Male biased sex ratio in the Mediterranean fruit fly Ceratitis capitata, an example of Y-chromosome meiotic drive.

A case of Y-chromosome meiotic drive is reported in the Mediterranean fruit fly Ceratitis capitata. It arose in an irradiated male and results in excess of males. Male excess is inherited strictly from father to son. A Y-linked factor MP (male producer) is proposed. Higher drive can be selected, but distortion declines rapidly in the absence of selection. Hybrid males from crosses between driving males and nondriving females also show drive but to a reduced extent, suggesting the action of suppressors. Sex ratio distortion is independent of postzygotic mortality, and is not associated with an obvious chromosome arrangement. Spermiogenesis in driving males is characterised by abnormalities in sperm tails and reduced numbers in some sperm cysts, whereas neighbouring cysts of the same MP testis are essentially wild type. The average number of missing sperms plus deformed sperms approximates to the average depression in female recovery among the progenies of siblings, suggesting that most of the missing or abnormal sperms would have given rise to females, that is, they would have been X-bearing. To explain the heterogeneity between neighbouring cysts, a theory is proposed that links it to variation in X-chromosome sensitivity to MP, arising by random suppression of the genetic basis of sensitivity during the six mitotic divisions in the origin of the cyst from its stem cell before meiosis.