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In the last years, there has been an increasing interest in bioinspired approaches for different applications, including the spinning of high performance silk fibers. Bioinspired spinning is based on the natural spinning system of spiders and worms and requires combining changes in the chemical environment of the proteins with the application of mechanical stresses. Here we present the novel straining flow spinning (SFS) process and prove its ability to produce high performance fibers under mild, environmentally friendly conditions, from aqueous protein dopes. SFS is shown to be an extremely versatile technique which allows controlling a large number of processing parameters. This ample set of parameters allows fine-tuning the microstructure and mechanical behavior of the fibers, which opens the possibility of adapting the fibers to their intended uses.

Herein we present a chimeric recombinant spider silk protein (spidroin) whose aqueous solubility equals that of native spider silk dope and a spinning device that is based solely on aqueous buffers, shear forces and lowered pH. The process recapitulates the complex molecular mechanisms that dictate native spider silk spinning and is highly efficient; spidroin from one liter of bacterial shake-flask culture is enough to spin a kilometer of the hitherto toughest as-spun artificial spider silk fiber.

Mechanical deformability of cells is an important property for their function and development, as well as a useful marker of cell state. The classical technique of micropipette aspiration allows single-cell studies and we provide here a method to measure the two basic mechanical parameters, elastic modulus and Poisson’s ratio. The proposed method, developed from finite-element analysis of micropipette aspiration experiments, may be implemented in future technologies for the automated measurement of mechanical properties of cells, based on the micropipette aspiration technique or on the cell transit through flow constrictions. We applied this method to measure the elastic parameters of lymphocytes, in which the mechanical properties depend on their activation state. Additionally, we discuss in this work the accuracy of previous models to estimate the elastic modulus of cells, in particular the analytical model by Theret et al., widely used in the field. We show the necessity of using an improved model, taking into account the finite size of the cells, to obtain new insights that may remain hidden otherwise.

Regenerated silkworm fibers spun through a wet-spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk.

Objective:The new 2013/59 EURATOM Directive (ED) demands dosimetric optimisation procedures without undue delay. The aim of this study was to optimise paediatric conventional radiology examinations applying the ED without compromising the clinical diagnosis.Methods:Automatic dose management software (ADMS) was used to analyse 2678 studies of children from birth to 5 years of age, obtaining local diagnostic reference levels (DRLs) in terms of entrance surface air kerma. Given local DRL for infants and chest examinations exceeded the European Commission (EC) DRL, an optimisation was performed decreasing the kVp and applying the automatic control exposure. To assess the image quality, an analysis of high-contrast resolution (HCSR), signal-to-noise ratio (SNR) and figure of merit (FOM) was performed, as well as a blind test based on the generalised estimating equations method.Results:For newborns and chest examinations, the local DRL exceeded the EC DRL by 113%. After the optimisation, a reduction of 54% was obtained. No significant differences were found in the image quality blind test. A decrease in SNR (−37%) and HCSR (−68%), and an increase in FOM (42%), was observed.Conclusion:ADMS allows the fast calculation of local DRLs and the performance of optimisation procedures in babies without delay. However, physical and clinical analyses of image quality remain to be needed to ensure the diagnostic integrity after the optimisation process.Advances in knowledge:ADMS are useful to detect radiation protection problems and to perform optimisation procedures in paediatric conventional imaging without undue delay, as ED requires.

The development of a reliable procedure for removing the viscous coating of viscid silk has allowed the accurate characterization of the tensile behavior of clean flagelliform silk (i.e., silk of the flagelliform gland without the viscous coating synthetised in the aggregate gland). For comparison, tensile tests on native viscid silk (with the viscous coating) fibers were also performed. It was found that viscid silk, either native or clean, has an elastomeric behavior when kept wet, either by immersion in water (clean fibers) or by the effect of the viscid coating (native fibers). When tested in dry environments (35% RH, relative humidity, for clean fibers and 10% RH for native fibers), their mechanical behavior was no longer elastomeric, with it being more similar to other silk fibers. Furthermore, it was noticed that flagelliform silk fibers show a ground state to which they can return independent of the previous loading history.

When treating the degenerative arthritis that follows scapholunate instability or scaphoid pseudarthrosis, excision of the scaphoid must be combined with a stabilisation of the midcarpal joint. Two alternatives have been proposed for that purpose: fusing the lunate, triquetrum, capitate and hamate (four corner fusion), 4CF; or limiting the arthrodesis to the lunate and capitate, preserving or excising the triquetrum. Previous reports have attributed a high level of complications to lunocapitate arthrodesis, mainly in respect of nonunion. We have reviewed 17 patients who had been treated with a lunocapitate fusion, after an 8 to 12-year follow-up period, and found similar results compared with 4CF, even with a major degree of motion in ulnar-radial deviation. Recent work on the innervation of the radiotriquetral ligaments has given relevance to the preservation of lunotriquetral motion in maintaining proprioception. Also if the triquetrum is excised to gain more motion, the proprioceptive role of the radiotriquetral ligaments is compromised.

La artrosis trapeciometacarpiana es una patologia frecuente, de la que existen gran numero de tecnicas quirurgicas para su tratamiento. En los casos avanzados se han utilizado las artroplastias de reseccion y la artrodesis, pero son agresivas y no parecen una buena opcion para los pacientes jovenes, que tienen una gran demanda de la articulacion. Por otro lado, para una correcta indicacion quirurgica ademas del tipo de paciente debe considerarse el estadio de la enfermedad. Con la cirugia artroscopica de la zona es posible su evaluacion, desbridamiento, sinovectomia y otros gestos quirurgicos, teniendo quizas su mayor utilidad en los casos poco avanzados y con un trapecio conservado. Por ello, es deseable disponer de una adecuada clasificacion artroscopica de la enfermedad que oriente en el diagnostico y tratamiento, por lo que se propone un nuevo estadiaje. Estadio artroscopico I se caracteriza por sinovitis difusa, pero con minima o nula perdida de cartilago articular. Es frecuente la laxitud ligamentaria. Estos pacientes son candidatos a una sinovectomia, tanto mecanica como por radiofrecuencia, y si existe alguna laxitud ligamentaria se puede realizar una capsulorrafia de retensado. Estadio artroscopico II presencia de un desgaste limitado en la superficie articular de la zona central a la dorsal del trapecio. Representa una situacion irreversible que precisara de algun tipo de tecnica que modifique la articulacion para alterar los vectores de fuerza que actuan sobre la misma. Tras la sinovectomia, desbridamiento, ocasional exeresis de cuerpos intraarticulares y en muchos casos capsulorrafia termica asociada frecuentemente a una condroplastia de los margenes; despues se practicara la osteotomia de cierre dorsorradial del metacarpiano para mantener el pulgar en una posicion mas extendida y abducida, minimizando asi la tendencia que tiene el metacarpiano a subluxarse. Estadio artroscopico III se caracteriza por una perdida mas difusa de la superficie articular del trapecio. La base del metacarpiano puede presentar lesiones cartilaginosas de distinto grado. Su tratamiento va a ser mas complejo, resultando insuficientes el desbridamiento y las osteotomias de correccion. Es necesario realizar una hemitrapecectomia fresando los restos de cartilago y profundizando a traves del hueso subcondral hasta llegar a un plano sangrante, para aumentar el espacio articular y producir un trombo sanguineo organizado en el que pueda adherirse un injerto de interposicion tendinoso autologo o sintetico. El estadio III tambien podria tratarse mediante una clasica artroplastia de reseccion abierta, artrodesis o protetizacion, dependiendo de las preferencias del cirujano.

Trapeziometacarpal arthritis is a common pathology and there are a large number of surgical techniques to treat it. In the last few years, resection arthroplasty and arthrodesis have been used, but they are too aggressive and do not seem a good option for young patients, who make great demands upon the joint. On the other hand, for a correct surgical indication, in addition to the type of patient the stage the disease is at should be considered. Arthroscopic surgery of the area makes it possible to assess the condition as well as to perform a debridement, synovectomy and other surgical maneuvers, although it is most useful for the least advanced cases with a well-preserved trapezium. For that reason, it is best to perform a thorough classification of the disease that can guide diagnosis and treatment; therefore a new staging is proposed. Arthroscopic stage I : it is characterized by diffuse synovitis with little or no loss of articular cartilage. Ligament laxity is common. These patients are candidates for either mechanical or RF synovectomy and, if ligament laxity is present, then a retensioning capsulorrhaphy can be performed. Arthroscopic stage II: there is limited erosion of the joint surface of the central and dorsal areas of the trapezium. This is an irreversible situation that requires some type of technique that can modify the joint by altering the force vectors acting upon it. After synovectomy, a debridement is performed, followed by the occasional excision of intraarticular bodies and, in many cases, a thermal capsulorrhaphy often associated to a chondroplasty of the margins. Subsequently, a dorsoradial closing-wedge metacarpal osteotomy is performed to keep the thumb in a more extended and abducted position, thus minimizing the metacarpal's tend to subluxate. Arthroscopic stage III: characterized by a more diffuse loss of the trapezial joint surface. The base of the metacarpal can present with different types of chondral injuries. Their treatment tends to be complex and debridement and corrective osteotomy are often insufficient. In these cases a hemitrapezectomy is necessary; the remaining cartilage must be removed, reaming through the subchondral bone until a bleeding plane is reached. In this way, the joint space can be increased and an organized blood thrombus be created, where an autologous or synthetic tendinous interposition graft may be attached. Stage III can also be treated by means of a classical open-wedge resection arthroplasty, an arthrodesis or prosthetic implantation, depending on the surgeon's preferences.

The aim of this study was to analyze the effects of 3 different low/moderate load strength training methods (full-back squat [SQ], resisted sprint with sled towing [RS], and plyometric and specific drills training [PLYO]) on sprinting, jumping, and change of direction (COD) abilities in soccer players. Thirty-two young elite male Spanish soccer players participated in the study. Subjects performed 2 specific strength training sessions per week, in addition to their normal training sessions for 8 weeks. The full-back squat protocol consisted of 2–3 sets 3 4–8 repetitions at 40–60% 1 repetition maximum (;1.28–0.98 m$s21). The resisted sprint training was compounded by 6–10 sets 3 20-m loaded sprints (12.6% of body mass). The plyometric and specific drills training was based on 1–3 sets 3 2–3 repetitions of 8 plyometric and speed/agility exercises. Testing sessions included a countermovement jump (CMJ), a 20-m sprint (10-m split time), a 50-m (30-m split time) sprint, and COD test (i.e., Zig-Zag test). Substantial improve ments (likely to almost certainly) in CMJ (effect size [ES]: 0.50– 0.57) and 30–50 m (ES: 0.45–0.84) were found in every group in comparison to pretest results. Moreover, players in PLYO and SQ groups also showed substantial enhancements (likely to very likely) in 0–50 m (ES: 0.46–0.60). In addition, 10–20 m was also improved (very likely) in the SQ group (ES: 0.61). Between-group analyses showed that improvements in 10–20 m (ES: 0.57) and 30–50 m (ES: 0.40) were likely greater in the SQ group than in the RS group. Also, 10–20 m (ES: 0.49) was substantially better in the SQ group than in the PLYO group. In conclusion, the present strength training methods used in this study seem to be effective to improve jumping and sprinting abilities, but COD might need other stimulus to achieve positive effects.

Spider major ampullate gland silks (MAS) vary greatly in material properties among species but, this variation is shown here to be confined to evolutionary shifts along a single universal performance trajectory. This reveals an underlying design principle that is maintained across large changes in both spider ecology and silk chemistry. Persistence of this design principle becomes apparent after the material properties are defined relative to the true alignment parameter, which describes the orientation and stretching of the protein chains in the silk fiber. Our results show that the mechanical behavior of all Entelegynae major ampullate silk fibers, under any conditions, are described by this single parameter that connects the sequential action of three deformation micromechanisms during stretching: stressing of protein-protein hydrogen bonds, rotation of the β-nanocrystals and growth of the ordered fraction. Conservation of these traits for over 230 million years is an indication of the optimal design of the material and gives valuable clues for the production of biomimetic counterparts based on major ampullate spider silk.

We report a study about the structural properties of polycrystalline samples of nominal composition Gd 5 Ge 2 (Si 1− x Sn x ) 2 ( x =0.23, 0.40) that closely influence their physical behavior particularly related to electric resistivity and magnetocaloric (MCE) effect. The samples were characterized by X-ray diffraction (XRD) using the Rietveld refinement method, metallographic analyses, 119 Sn Mossbauer spectroscopy, DC magnetization and electrical transport measurements. It was identified a Gd 5 Si 2 Ge 2 -monoclinic phase for x =0.23 and a Sm 5 Sn 4 -orthorhombic phase (type II) for x =0.40, both with two non-equivalent crystallographic sites for the Sn ions. We were able to infer on the role of tin on the magnetic and transport properties in these compounds.

The characterization of silkworm and spider silk from nanometer to micrometer scale by atomic force microscopy reveals similar design principles despite the distance of their spinning organisms in evolutionary terms. Nanoglobules are the basic microstructural blocks in both materials, but this common microstructural design is tuned to fulfill the biological function of each silk. Spider silk nanoglobules are isotropic, and its size varies during stretching. Silkworm silk nanoglobules are anisotropic and loosely aligned with the fiber axis. The combination of our results with previous data on the structure of silks at a molecular level allows a model of the supramolecular organization of both silkworm and spider silk to be proposed. The detailed characterization of the microstructure of natural silks should contribute to the development and production of a new family of bioinspired fibers.

A study of the influence of UV radiation on the tensile properties of spider silk has shown that the shape of the stress-strain curves is not affected by 254-nm irradiation, except for a significant decrease in the tensile strength and strain at breaking. This decrease has been found in both forcibly silked and maximum-supercontracted fibers, despite the different initial alignments of the protein chains. Local damage is also induced by UV radiation. With this procedure, it is possible to recover and analyze fracture surfaces. These show different granular microstructures that are characteristic of fibers spun from a solution.

The tensile properties and fracture surfaces of N-methylmorpholine-N-oxide (NMMO) regenerated silk fibroin fibers produced with a range of draw ratios has been characterized and related to their microstructure with data obtained from Raman spectroscopy and birefringence measurements. The spinning process allows control of two different draw ratios, coagulation, and postspinning, and it has been found that the microstructure and the properties of the fibers can be modified by the proper combination of both draw ratios. NMMO regenerated silk fibroin fibers subjected to postspinning drawing yield tensile properties comparable to other regenerated fibers and strain at breaking comparable to natural Bombyx mori silk fibers. Tensile strength; however, is still significantly lower than that of natural fibers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2568–2579, 2007

The extraordinary mechanical performance of spider dragline silk is explained by its highly ordered microstructure and results from the sequences of its constituent proteins. This optimized microstructural organization simultaneously achieves high tensile strength and strain at breaking by taking advantage of weak molecular interactions. However, elucidating how the original design evolved over the 400 million year history of spider silk and identifying the basic relationships between microstructural details and performance have proven difficult tasks. Here we show that the analysis of maximum supercontracted single spider silk fibers using X ray diffraction shows a complex picture of silk evolution where some key microstructural features are conserved phylogenetically while others show substantial variation even among closely related species. This new understanding helps elucidate which microstructural features need to be copied in order to produce the next generation of biomimetic silk fibers.

Spider silk fibers were obtained by the monitored forced silking method. This procedure allows measurement of the silking force during the process and retrieving the fibers so their tensile behavior can be characterized. Silking conditions, including the reeling speed and the use of an anaesthetising gas, were varied to ascertain their influence on the tensile properties of the silk. In all cases, it was found that the tensile properties are determined by the silking stress, obtained by dividing the silking force by the diameter of the fiber. This suggests that the sophisticated spinning system of the spider can be characterized essentially by a single parameter, which controls the properties of spider silk almost independently of the reeling conditions.

The characterization of silk properties requires a reliable measurement of stress-strain curves from tensile tests, which calls for a detailed analysis of what is considered the cross section of the sample and how it varies during the experiments. Here, spider silk fibers from the major ampullate gland (MAS) of Argiope trifasciata spiders are tensile tested, and the cross-sectional area is measured under different strained configurations. It has been found that the fiber volume remains practically constant during stretching, and deformation proceeds homogeneously in all the fibers. The conservation of volume is validated independently of the type of fiber and the strain level. This result, applied to compute true stress-strain curves for different MAS fibers, shows that the description of their properties depends noticeably on which set of tensile parameters is chosen (true or engineering), and that engineering values could lead to misinterpretation of experiments that combine results from different strain ranges.

Psoas abscess (PA) is an uncommon disease and its diagnosis is difficult. It can be primary or secondary. Primary abscesses are of unknown origin and are presumably caused by haematogenous or lymphatic spread from a distant infectious focus. Secondary PA is caused by spreading from a contiguous infected structure, such as vertebrae (espondilodiscitis) or mesenteric abscesses (Crohn's disease). PA infrequently has been associated with an infection of total hip arthroplasty (ITHA). The correct diagnosis in these cases is difficult due to the clinical similarities between PA and ITHA. Since connection between PA and ITHA is established through the acetabulum, we consider that computed tomography (CT) is the most accurate radiological test because of its efficacy in evaluating the bone structure, and the optimum therapeutic strategy is two-stage replacement surgery. We report one case of PA associated with ITHA and a review of the previous literature.

SUMMARY The spinning of spider silk requires a combination of aqueous environment and stretching, and the aim of this work was to explore the role of stretching silk fibers in an aqueous environment and its effect on the tensile properties of spider silk. In particular, the sensitivity of the spider silk tensile behaviour to wet-stretching could be relevant in the search for a relationship between processing and the variability of the tensile properties. Based on this idea and working with MAS silk from Argiope trifasciata orb-web building spiders, we developed a novel procedure that permits modification of the tensile properties of spider silk: silk fibers were allowed to supercontract and subsequently stretched in water. The ratio between the length after stretching and the initial supercontracted length was used to control the process. Tensile tests performed in air, after drying,demonstrated that this simple procedure allows to predictable reproduction of the stress-strain curves of either naturally spun or forcibly silked fibers. These results suggest that the supercontracted state has a critical biological function during the spinning process of spider silk.

Spider dragline silk has a unique combination of desirable mechanical properties—low density, high tensile strength and large elongation until breaking—that makes it attractive from an engineering perspective [Nature 410 (2001) 541]. Nevertheless, this outstanding performance is threatened by the way mechanical properties are affected by a wet environment, particularly if the stress of these fibers can relax when exposed to moisture. Tests on spider dragline silk ( Argiope trifasciata ) performed by the authors have shown that when the fiber is clamped and exposed to a wet enough environment non-vanishing supercontraction forces develop. When the moisture is removed the residual stresses increase, and this effect has proven long lasting, as the fiber remains stressed for hours. In addition, the tensile properties of the fiber remain unaffected by the residual stresses build up after removing the moisture or after a wetting and drying cycle. These tests give support to the thesis that supercontraction helps to keep the spider webs tight and opens new applications for synthetic analogs.

We present a study of magnetization and magnetocaloric effect for the SmMnO3 compound. This compound was synthesized by combustion reaction and its magnetic and structural properties studied by X-ray powder diffraction (XRD) and magnetization (M) measurements as a function of temperature and under magnetic fields. The XRD pattern at room temperature confirmed the presence of a single phase with orthorhombic structure. From magnetization versus temperature, we observe two magnetic orderings, the first one at 6 K due to Sm3+, and the other one at T N =57(2) K is the anti-ferromagnetic long-range ordering. The magnetic entropy change, ΔS M , was obtained from magnetization isotherms close to T N where it reaches a maximum value of about 8.0 J/kg K for an applied field of 7 T.

The mechanical behavior of living murine T-lymphocytes was assessed by atomic force microscopy (AFM). A robust experimental procedure was developed to overcome some features of lymphocytes, in particular their spherical shape and non-adherent character. The procedure included the immobilization of the lymphocytes on amine-functionalized substrates, the use of hydrodynamic effects on the deflection of the AFM cantilever to monitor the approaching, and the use of the jumping mode for obtaining the images. Indentation curves were analyzed according to Hertz's model for contact mechanics. The calculated values of the elastic modulus are consistent both when considering the results obtained from a single lymphocyte and when comparing the curves recorded from cells of different specimens.

The structure and properties of silk fibers are at the root of their performance and applicability in scaffolds for tissue engineering. This chapter briefly reviews the composition and structure, the production and the mechanical behavior of silk fibers either natural or artificial. The main properties and structural characteristic of silks produced by silkworms or spiders, and also the behavior of synthetic silk fibers obtained from regenerated silkworm silk or recombinant artificial spider silk are considered, with special attention to the mechanical response under the influence of water and temperature. The chapter also presents some models intending to describe the relationship between the structure and the mechanical properties of silk fibers.

Spider silk fibers were produced through an alternative processing route that differs widely from natural spinning. The process follows a procedure traditionally used to obtain fibers directly from the glands of silkworms and requires exposure to an acid environment and subsequent stretching. The microstructure and mechanical behavior of the so-called spider silk gut fibers can be tailored to concur with those observed in naturally spun spider silk, except for effects related with the much larger cross-sectional area of the former. In particular spider silk gut has a proper ground state to which the material can revert independently from its previous loading history by supercontraction. A larger cross-sectional area implies that spider silk gut outperforms the natural material in terms of the loads that the fiber can sustain. This property suggests that it could substitute conventional spider silk fibers in some intended uses, such as sutures and scaffolds in tissue engineering.

The Boscán field is a giant heavy oil reservoir (10° API) located in western Venezuela. The field is operated by the Empresa Mixta PetroBoscán. OOIP is estimated as high as 35 billion barrels. For over 60 years of production history, only ~5% of the OOIP has been recovered thereby considerable development opportunities remain at Boscán to increase recovery. Drilling highly deviated completions has proven to be a successful strategy to maximize oil recovery and mitigate ever increasing water production. The southern part of the reservoir is in contact with an active aquifer where a high contrast in fluid viscosity is present between formation water and heavy oil (0.7 vs. 350 cP) generating large differences in the mobility ratio. This causes premature water breakthrough and sharp increases in water cuts over short periods of time. Water production during the last 10 years has exceeded the handling, separation and injection capabilities at Boscán leading to a significant number of wells being prematurely shut-in. In the past, in order to control water production, shorter vertical wells were drilled and bottom water shut-off jobs were performed. However, these strategies have proven unattractive since overall net pay was reduced and coning tendencies were high. A new strategy was introduced of drilling highly deviated wells to maximize the reservoir exposed and mitigate water production by reducing pressure drawdown in the near wellbore region. Recently, a ~5.5 million upscaled grid-block reservoir simulation model was developed and is being utilized to understand the aquifer impact and for optimal field development. Initial simulation results confirmed that highly deviated wells perform better and delay water conning. This paper focuses on a deviated well strategy to increase recovery per well from a heavy oil reservoir with a strong aquifer influx. It shows how multi-disciplinary teamwork is being utilized to develop and execute the strategy and how Boscán may be used as an analogy for other fields having similar reservoir conditions.

Prealloyed iron-based powders with different Mo–Cu–Ni–C contents were uniaxially compacted at 700 MPa and sintered at 1120°C in a nitrogen–hydrogen atmosphere. After sintering, all the materials were thermochemically treated by carburizing (endogas atmosphere) and carbonitriding. Treatment conditions for the carburizing process were heating at 875°C during 100 min with two different potentials of carbon: 0.88 and 0.55% for the two cycles. The carbonitriding process took place at 820°C with two cycles: carbonitriding-40 during 90 min and carbonitriding-20 during 45 min. Materials were evaluated through the study of radial crushing strength and the complete microstructural study was carried out using optical microscopy and SEM. Finally, the fracture surface was analysed through SEM. Other properties like friction coefficient, density and microhardness were evaluated. Crushing strength test results show that, in all cases, treated materials present higher strength than sintered base materials. Carburizing is also more positive than carbonitriding, reaching the maximum properties always for the first cycle (low carbon content) of carburizing. A maximum crushing strength of 1290 MPa was obtained when using Fe–1.5% Mo as base material.

Prealloyed steel powders with different amount of Mo-Cu-Ni-C were compacted at 700 MPa and sintered at 1120 °C in 95 % N2-5 % H2. After sinterizing, these materials were treated by carburizing. For materials characterization radial crushing strength were preformed, density was calculated and a complete study of fracture surfaces was carried out using scanning electron microscopy. The results of radial crushing strength show that resistance after carburizing is higher than in sintered materials. The fracture surfaces give an idea of materials briteless and the treatment depth. In sintered materials, a dúctil surface was observed, with the characteristic dimples. The fracture surfaces after different treatments show britelessnes in the outer zone, while inside appears a mix of dúctil and briteles fracture.Polvos prealeados de aceros con diferentes contenidos de Mo-Cu-Ni -C se compactaron a 700 MPa y se sinterizaron a 1.120 °C en atmósfera de 95 % N2-5 % H2. Después de la sinterización, los materiales se trataron termoquímicamente para su cementación (proceso endogas). Para la caracterización de todos los materiales se realizaron ensayos de compresión del tipo radial crushing strength, se calculó la densidad y se hizo un completo estudio de las superficies de fracturas a través de microscopía electrónica de barrido. Los resultados de resistencia a compresión muestran, después de la cementación, valores superiores a los encontrados en el estado sintetizado. La superficie de fractura da idea de la fragilidad del material y de la profundidad del tratamiento. En estado sintetizado, se observa una superficie de fractura totalmente dúctil, donde aparecen las características cavidades. Las superficies de fractura, tras distintos tipos de cementación, reflejan un comportamiento frágil en el exterior, mientras que el interior aparece una mezcla de fractura dúctil con frágil.

Supercontraction is commonly considered as a functional adaptation of major ampullate gland (MA) silk to its role as the main structural material in orb-webs. However, the observation of supercontraction in the dragline silk of a lynx spider species, as it is shown in this work, offers a strong support to the hypothesis that the appearance of supercontraction preceded the advent of capture webs. Moreover, the absence of proline in the sequence of dragline silk spidroin in Oxyopidae and related spiders indicates that the presence of this amino acid may not be required for the existence of supercontraction. In this regard, the presence of particular subrepeats – in orb-web and non-orb-web building spiders – adds new clues for the understanding of supercontraction and associated effects.

The structure and properties of silk fibers are at the root of their performance and applicability in scaffolds for tissue engineering. This chapter briefly reviews the composition and structure, the production and the mechanical behavior of silk fibers either natural or artificial. The main properties and structural characteristic of silks produced by silkworms or spiders, and also the behavior of synthetic silk fibers obtained from regenerated silkworm silk or recombinant artificial spider silk are considered, with special attention to the mechanical response under the influence of water and temperature. The chapter also presents some models intending to describe the relationship between the structure and the mechanical properties of silk fibers.

Regenerated silk fibroin solutions from Bombyx mori were tested for electrospinning. Simple and reproducible tensile tests were performed on threads of aligned fibers to obtain information about their mechanical performance at the fiber level. The binary solvent formic acid/chloroform (10:1, v/v) rendered unbeaded thinner fibers with increased extensibility before failure when compared with pure formic acid. A remarkable improvement in strength was induced by immersing length-restricted fibers into ethanol for 5 min. Conformational changes of the protein chains were studied by solid-state NMR.

Factors that affect to the proposed mechanisms that produce the double yield phenomenon in semicrystalline polymeric materials were studied. The systems under study were ternary blends of low-density polyethylene (LDPE), linear LDPE (LLDPE) and ethylene propylene diene (EPDM). The influence on the yield mechanisms of the following different factors were analysed: processing conditions, composition, stretching rate, cooling conditions and different types of elastomers. The behaviour of these blends in the region where the double-yield points occur was found to be different for those LDPE-rich blends from those LLDPE-rich ones. These differences are explained in terms of the two mechanisms in the double yield phenomenon; that is, the slip of the crystalline blocks and the shear on the crystalline blocks. The stretching-rate effect is explained in terms of the stress relaxation time. The effects of EPDM content, cooling conditions and type of EPDM are found to be equivalent to a smaller stretching rate.

An automatic segmentation method is presented for PET images based on an iterative approximation by threshold value that includes the influence of both lesion size and background present during the acquisition.Optimal threshold values that represent a correct segmentation of volumes were determined based on a PET phantom study that contained different sizes spheres and different known radiation environments. These optimal values were normalized to background and adjusted by regression techniques to a two-variable function: lesion volume and signal-to-background ratio (SBR). This adjustment function was used to build an iterative segmentation method and then, based in this mention, a procedure of automatic delineation was proposed. This procedure was validated on phantom images and its viability was confirmed by retrospectively applying it on two oncology patients.The resulting adjustment function obtained had a linear dependence with the SBR and was inversely proportional and negative with the volume. During the validation of the proposed method, it was found that the volume deviations respect to its real value and CT volume were below 10% and 9%, respectively, except for lesions with a volume below 0.6 ml.The automatic segmentation method proposed can be applied in clinical practice to tumor radiotherapy treatment planning in a simple and reliable way with a precision close to the resolution of PET images.

International audience; Spider silks combine a significant number of desirable characteristics in one material, including large tensile strength and strain at breaking, biocompatibility, and the possibility of tailoring their properties. Major ampullate gland silk (MAS) is the most studied silk and their properties are explained by a double lattice of hydrogen bonds and elastomeric protein chains linked to polyalanine beta-nanocrystals. However, many basic details regarding the relationship between composition, microstructure and properties in silks are still lacking. Here we show that this relationship can be traced in flagelliform silk (Flag) spun by Argiope trifasciata spiders after identifying a phase consisting of polyglycine II nanocrystals. The presence of this phase is consistent with the dominant presence of the -GGX- and -GPG- motifs in its sequence. In contrast to the passive role assigned to polyalanine nanocrystals in MAS, polyglycine II nanocrystals can undergo growing/collapse processes that contribute to increase toughness and justify the ability of Flag to supercontract

Summary True stress-true strain curves of naturally spun viscid line fibers retrieved directly from the spiral of orb-webs built by Argiope trifasciata spiders were measured using a novel methodology. This new procedure combines a method for removing the aqueous coating of the fibers and a technique that allows the accurate measurement of their cross sectional area. Comparison of the tensile behaviour of different samples indicates that naturally spun viscid lines show a large variability, comparable to that of other silks, such as major ampullate gland silk and silkworm silk. Nevertheless, application of a statistical analysis allowed identifying two independent parameters that underlie the variability and characterize the observed range of true stress-true strain curves. Combination of this result with previous mechanical and microstructural data suggested the assignment of these two independent effects to the degree of alignment of the protein chains and to the local relative humidity which, in turn, depends on the composition of the viscous coating and on the external environmental conditions.

The treatment of intertrochanteric fractures using a minimally invasive dynamic hip screw (MIDHS) technique has been reported to provide better results than the conventional technique (CDHS). The present study aims to determine whether there are any differences in terms of transfusion needs, morbidity, length of hospital stay, and economical costs, based on a study of two retrospective cohorts.Cohorts study of 80 patients with intertrochanteric femoral fractures (31-A1 and 31-A2.1) who underwent DHS procedure from July 2005 to September 2007; 40 of them were treated using the traditional technique (CDHS), and the other 40 using the minimally invasive technique (MIDHS).No differences were found in terms of blood loss, transfusion requirements or morbidity. Mean hospital stay for MIDHS group was 1.3 days lower, reducing the costs regarding the CDHS group by €306.3, but this difference was not statistically significant (P=.3). The time required to perform the surgery was shorter for the MIDHS group: 49.3 versus 78.8minutes (p=0.0001).Contrary to previous studies published, the present study did not show any advantage for the MIDHS technique, except for a shorter surgical time to perform the procedure. We consider that the MIDHS could help in improving operating room productivity and efficiency.

The contraction of the actomyosin cytoskeleton, which is produced by the sliding of myosin II along actin filaments, drives important cellular activities such as cytokinesis and cell migration. To explain the contraction velocities observed in such physiological processes, we have studied the contraction of intact cytoskeletons of Dictyostelium discoideum cells after removing the plasma membrane using Triton X-100. The technique developed in this work allows for the quantitative measurement of contraction rates of individual cytoskeletons. The relationship of the contraction rates with forces was analyzed using three different myosins with different in vitro sliding velocities. The cytoskeletons containing these myosins were always contractile and the contraction rate was correlated with the sliding velocity of the myosins. However, the values of the contraction rate were two to three orders of magnitude slower than expected from the in vitro sliding velocities of the myosins, presumably due to internal and external resistive forces. The contraction process also depended on actin cross-linking proteins. The lack of α-actinin increased the contraction rate 2-fold and reduced the capacity of the cytoskeleton to retain internal materials, while the lack of filamin resulted in the ATP-dependent disruption of the cytoskeleton. Interestingly, the myosin-dependent contraction rate of intact contractile rings is also reportedly much slower than the in vitro sliding velocity of myosin, and is similar to the contraction rates of cytoskeletons (different by only 2–3 fold), suggesting that the contraction of intact cells and cytoskeletons is limited by common mechanisms.

The germinative behavior of nine plant species of the Iberian Peninsula, four of them catalogued as vulnerable or endangered by the International Union for the Conservation of Nature, was studied under controlled laboratory conditions. Most of the species studied germinated better at relatively low temperatures (15 °C and 20 °C) and, in general, high germination rates were also obtained at alternating temperatures (25/15 °C). Coronopus navasii germinated over 60% at 25 °C, the highest temperature used in this study. Lavatera oblongifolia did not surpass 20% germination under any of the conditions assayed. Seed coat scarification increased germination in Helianthemum squamatum, while seed pretreatments with hot water or sulfuric acid were effective in H. polygonoides. Less favorable results were obtained in Lavatera oblongifolia, whereas scarification was completely ineffective in Onobrychis peduncularis ssp. matritensis.

Major ampullate (MA) dragline silk supports spider orb webs, combining strength and extensibility in the toughest biomaterial. MA silk evolved ~376 MYA and identifying how evolutionary changes in proteins influenced silk mechanics is crucial for biomimetics, but is hindered by high spinning plasticity. We use supercontraction to remove that variation and characterize MA silk across the spider phylogeny. We show that mechanical performance is conserved within, but divergent among, major lineages, evolving in correlation with discrete changes in proteins. Early MA silk tensile strength improved rapidly with the origin of GGX amino acid motifs and increased repetitiveness. Tensile strength then maximized in basal entelegyne spiders, ~230 MYA. Toughness subsequently improved through increased extensibility within orb spiders, coupled with the origin of a novel protein (MaSp2). Key changes in MA silk proteins therefore correlate with the sequential evolution high performance orb spider silk and could aid design of biomimetic fibers.

The mechanical behavior and microstructure of minor ampullate gland silk (miS) of two orb-web spinning species, Argiope trifasciata and Nephila inaurata, were extensively characterized, enabling detailed comparison with other silks. The similarities and differences exhibited by miS when compared with the intensively studied major ampullate gland silk (MAS) and silkworm (Bombyx mori) silk offer a genuine opportunity for testing some of the hypotheses proposed to correlate microstructure and tensile properties in silk. In this work, we show that miSs of different species show similar properties, even when fibers spun by spiders that diverged over 100 million years are compared. The tensile properties of miS are comparable to those of MAS when tested in air, significantly in terms of work to fracture, but differ considerably when tested in water. In particular, miS does not show a supercontraction effect and an associated ground state. In this regard, the behavior of miS in water is similar to that of B. mori silk, and it is shown that the initial elastic modulus of both fibers can be explained using a common model. Intriguingly, the microstructural parameters measured in miS are comparable to those of MAS and considerably different from those found in B. mori. This fact suggests that some critical microstructural information is still missing in our description of silks, and our results suggest that the hydrophilicity of the lateral groups or the large scale organization of the sequences might be routes worth exploring.

The mechanical behavior and microstructure of bioinspired fibers spun from solutions of recombinant spidroin-like proteins were extensively characterized, and compared with those of natural spider silk fibers. It is confirmed that high performance bioinspired fibers indistinguishable from natural spider silk up to large strains can be produced through genetic engineering and conventional spinning technologies. It is also found that fibers spun from spidroin-like proteins that contain different motifs of sequence exhibit variations in their microstructure in terms of crystallinity and chain alignment, but these differences are not reflected in distinct tensile properties. This similarity in terms of their mechanical behavior indicates that bioinspired fibers are largely independent of their exact sequence of recombinant proteins and, in particular, of their proline content. Finally, it is shown that the largest differences between natural and bioinspired fibers are found at very large deformations, marking the ultimate challenge in the synthesis of silk-like fibers.

Making artificial fibers inspired in spider silks is considered as one of the milestones in the field of biomimetics. The interest is usually justified by the outstanding tensile properties of natural fibers, but it is usually overlooked that spider silk is endowed with a number of related properties – supercontraction, recovery and the existence of a ground state – that impart the material with additional desirable features, such as the possibility of tuning its mechanical behaviour. In this work we present a review on the experimental analysis and significance of these properties, stressing the contributions of our research group to the field. It is also demonstrated how the knowledge gained in the basic study of the natural material has been essential for the improvement of the properties exhibited by artificially processed bio-inspired silk fibers.

The remarkable properties of spider silks have stimulated an increasing interest in understanding the roles of their composition and processing, as well as in the mass-production of these fibers. Previously, the variability in the mechanical properties of natural silk fibers was a major drawback in the elucidation of their behavior, but the authors have found that supercontraction of these fibers allows one to characterize and reproduce the whole range of tensile properties in a consistent way. The purpose of this review is to summarize these findings. After a review of the pertinent mechanical properties, the role of supercontraction in recovering and tailoring the tensile properties is explained, together with an alignment parameter to characterize silk fibers. The concept of the existence of a mechanical ground state is also mentioned. These behaviors can be modeled, and two such models-at the molecular and macroscopic levels-are briefly outlined. Finally, the assessment of the existence of supercontraction in bio-inspired fibers is considered, as this property may have significant consequences in the design and production of artificial fibers.