The Influence of Hydroxyapatite Crystals on the Viscoelastic Behavior of Poly(vinyl alcohol) Braid Systems.

Composites of poly(vinyl alcohol) (PVA) in the shape of braids, in combination with crystals of hydroxyapatite (HAp), were analyzed to perceive the influence of this bioceramic on both the quasi-static and viscoelastic behavior under tensile loading. Analyses involving energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) allowed us to conclude that the production of a homogeneous layer of HAp on the braiding surface and the calcium/phosphate atomic ratio were comparable to those of natural bone. The maximum degradation temperature established by thermogravimetric analysis (TGA) showed a modest decrease with the addition of HAp. By adding HAp to PVA braids, an increase in the glass transition temperature (Tg) is noticed, as demonstrated by dynamic mechanical analysis (DMA) and differential thermal analysis (DTA). The PVA/HAp composite braids' peaks were validated by Fourier transform infrared (FTIR) spectroscopy to be in good agreement with common PVA and HAp patterns. PVA/HAp braids, a solution often used in the textile industry, showed superior overall mechanical characteristics in monotonic tensile tests. Creep and relaxation testing showed that adding HAp to the eight and six-braided yarn architectures was beneficial. By exhibiting good mechanical performance and most likely increased biological qualities that accompany conventional care for bone applications in the fracture healing field, particularly multifragmentary ones, these arrangements can be applied as a fibrous fixation system.

Edgewise Compression and Three-Point Bending Analyses of Repaired Composite Sandwich Panels.

In this work, the fracture behaviour of repaired honeycomb/carbon-epoxy sandwich panels under edgewise compression and three-point bending loading was analysed. Assuming the occurrence of damage resulting from a complete perforation leading to an open hole, the followed repair strategy consists of plug filling the core hole and considering two scarf patches with an angle of 10° in order to repair the damaged skins. Experimental tests were performed on undamaged and repaired situations in order to address the alteration in the failure modes and assess the repair efficiency. It was observed that repair recovers a large part of the mechanical properties of the corresponding undamaged case. Additionally, a three-dimensional finite element analysis incorporating a mixed-mode I + II + III cohesive zone model was performed for the repaired cases. Cohesive elements were considered in the several critical regions prone to damage development. The failure modes and the resultant load-displacement curves obtained numerically were compared with the experimental ones. It was concluded that the numerical model is suitable for estimating the fracture behaviour of sandwich panel repairs.

Osteosynthesis Metal Plate System for Bone Fixation Using Bicortical Screws: Numerical-Experimental Characterization.

This study reports the numerical and experimental characterization of a standard immobilization system currently being used to treat simple oblique bone fractures of femoral diaphyses. The procedure focuses on the assessment of the mechanical behavior of a bone stabilized with a dynamic compression plate (DCP) in a neutralization function, associated to a lag screw, fastened with surgical screws. The non-linear behavior of cortical bone tissue was revealed through four-point bending tests, from which damage initiation and propagation occurred. Since screw loosening was visible during the loading process, damage parameters were measured experimentally in independent pull-out tests. A realistic numerical model of the DCP-femur setup was constructed, combining the evaluated damage parameters and contact pairs. A mixed-mode (I+II) trapezoidal damage law was employed to mimic the mechanical behavior of both the screw-bone interface and bone fractures. The numerical model replicated the global behavior observed experimentally, which was visible by the initial stiffness and the ability to preview the first loading peak, and bone crack satisfactorily.

Thermal, Mechanical and Chemical Analysis of Poly(vinyl alcohol) Multifilament and Braided Yarns.

Poly(vinyl alcohol) (PVA) in multifilament and braided yarns (BY) forms presents great potential for the design of numerous applications. However, such solutions fail to accomplish their requirements if the chemical and thermomechanical behaviour is not sufficiently known. Hence, a comprehensive characterisation of PVA multifilament and three BY architectures (6, 8, and 10 yarns) was performed involving the application of several techniques to evaluate the morphological, chemical, thermal, and mechanical features of those structures. Scanning electron microscopy (SEM) was used to reveal structural and morphological information. Differential thermal analysis (DTA) pointed out the glass transition temperature of PVA at 76 °C and the corresponding crystalline melting point at 210 °C. PVA BY exhibited higher tensile strength under monotonic quasi-static loading in comparison to their multifilament forms. Creep tests demonstrated that 6BY structures present the most deformable behaviour, while 8BY structures are the least deformable. Relaxation tests showed that 8BY architecture presents a more expressive variation of tensile stress, while 10BY offered the least. Dynamic mechanical analysis (DMA) revealed storage and loss moduli curves with similar transition peaks for the tested structures, except for the 10BY. Storage modulus is always four to six times higher than the loss modulus.

Direct Evaluation of Mixed Mode I+II Cohesive Laws of Wood by Coupling MMB Test with DIC.

Governing cohesive laws in mixed mode I+II loading of Pinus pinaster Ait. are directly identified by coupling the mixed mode bending test with full-field displacements measured at the crack tip by Digital Image Correlation (DIC). A sequence of mixed mode ratios is studied. The proposed data reduction relies on: (i) the compliance-based beam method for evaluating strain energy release rate; (ii) the local measurement of displacements to compute the crack tip opening displacement; and (iii) an uncoupled approach for the reconstruction of the cohesive laws and its mode I and mode II components. Quantitative parameters are extracted from the set of cohesive laws components in function of the global phase angle. Linear functions were adjusted to reflect the observed trends and the pure modes (I and II) fracture parameters were estimated by extrapolation. Results show that the obtained assessments agree with previous experimental measurements addressing pure modes (I and II) loadings on this wood species, which reveals the appropriateness of the proposed methodology to evaluate the cohesive law under mixed mode loading and its components.

Thermoplastic Composites and Their Promising Applications in Joining and Repair Composites Structures: A Review.

Thermoset fiber reinforced composites, widely used in current structural applications, have complex repair procedures and generates significant amounts of scrap due to its recycling difficulties, which does not comply with the most recent environmental restrictions. These disadvantages may be overcome by using a thermoplastic matrix phase, which is very suitable to be joined and repaired by local melting, making the composite material fully recyclable. This work presents a literature review on the joining methods applicable to thermoplastic based composites and their potential applications to be used as repair procedures in structural elements. The effectiveness of selected adhesive and fusion bonding techniques for several thermoplastic composite systems is evaluated by a comparative study based on the joints' strength and toughness results available in the literature. This work focuses on the three most promising fusion bonding techniques: Resistance welding, induction welding, and ultrasonic welding. The advantages and drawbacks for each one of these processes are discussed, as well as their suitability for several specific structural applications. In addition, several discordant aspects for each welding technique are identified and the corresponding recommendations are discussed. A compilation of analytical models for the mechanisms of heat generation and transient heat transfer modelling is also presented for each fusion bonding process in order to promote their application in numerical modelling.

Experimental Investigation of Delamination in Composite Continuous Fiber-Reinforced Plastic Laminates with Elastic Couplings.

This paper presents an experimental evaluation of influence of the elastic couplings on the fracture toughness as well as on delamination initiation and propagation in carbon/epoxy composite laminates. For this purpose the mode I double cantilever beam (DCB) tests according to the American Society for Testing and Materials (ASTM) D5528 Standard were performed on specimens with different delamination interfaces and specific lay-ups composition exhibiting the bending-twisting (BT) and the bending-extension (BE) couplings. The critical strain energy release rates (mode I c-SERR, GIC) were calculated by using the classical methods, namely: the modified beam theory (MBT), the compliance calibration (CCM) and the modified compliance calibration (MCC). In order to evaluate an accuracy of the different methods, the values of c-SERR obtained by using standardized data reduction schemes were compared with values calculated by using the compliance based beam method (CBBM). All the methods give rise to comparable values of the GIC, which makes the CBBM an appealing choice, since it does not depend on crack length monitoring during the test. Initiation and propagation of delamination were investigated by using the acoustic emission (AE) technique. Moreover, the scanning electron microscope (SEM) analysis were performed after the experimental tests in order to investigate a fracture surface at delamination plane.

Protocolo de tratamiento de heridas con apósito de hidrofibra reforzada, con plata iónica al 1,2%, potenciado con EDTA y cloruro de bencetonio para evitar la recurrencia de biopelícula.

OBJECTIVE: Present a treatment protocol to avoid biofilm reformation in hard-to-heal wounds, using a hydrofiber dressing with 1.2% ionic silver, ethylenediaminetetraacetic acid and benzethonium chloride. METHOD: A retrospective, descriptive and analytic study on the use of a treatment protocol, including three case studies. Patient records for hard-to-heal wounds were analysed according to an algorithm for biofilm detection and best-practice recommendations for wound hygiene. RESULTS: The adopted protocol was based on three pillars: identifying clinical signs suggesting biofilm, performing wound hygiene, and applying an antibiofilm dressing. CONCLUSION: Wound healing rates can improve after protocol implementation. Adequate control of local signs of infection and exudate, as well as visual and indirect signs of biofilm, were achieved. All patients progressed well towards wound-size reduction and closure using the hydrofiber dressing.

OBJETIVO: Presentar un protocolo para evitar la reformación de biopelícula en heridas de difícil cicatrización con apósito de hidrofibra reforzada, con plata iónica al 1,2%, potenciado con ácido etilendiaminotetraacético (EDTA) y cloruro de bencetonio. MÉTODO: Estudio retrospectivo, descriptivo y analítico de aplicación de un protocolo de tratamiento, con tres casos de estudio de pacientes tratados en un centro de referencia internacional. Los registros de pacientes con úlceras complejas se analizaron y evaluaron de acuerdo con la inserción en el algoritmo de identificación clínica de biopelículas, y en base a las recomendaciones prácticas para la higiene de heridas. RESULTADOS: El protocolo adoptado se basó en tres pilares: identificación de signos clínicos de sugerencia para la presencia de biopelícula, prácticas de higiene en las heridas, y aplicación de la cobertura de antibiopelícula. CONCLUSIÓN: La capacidad de cicatrización de heridas con este protocolo puede considerarse alta. Los pacientes obtuvieron un adecuado control de todos los signos locales de infección y de exceso de exudado, y la desaparición de los signos visuales e indirectos de biopelícula. Todos presentaron una adecuada progresión, disminución de la superficie de la herida, y cicatrización tras el uso del apósito.

Protocolo de tratamiento de heridas con apósito de hidrofibra reforzada, con plata iónica al 1,2%, potenciado con EDTA y cloruro de bencetonio para evitar la recurrencia de biopelícula.

OBJECTIVE: Present a treatment protocol to avoid biofilm reformation in hard-to-heal wounds, using a hydrofiber dressing with 1.2% ionic silver, ethylenediaminetetraacetic acid and benzethonium chloride. METHOD: A retrospective, descriptive and analytic study on the use of a treatment protocol, including three case studies. Patient records for hard-to-heal wounds were analysed according to an algorithm for biofilm detection and best-practice recommendations for wound hygiene. RESULTS: The adopted protocol was based on three pillars: identifying clinical signs suggesting biofilm, performing wound hygiene, and applying an antibiofilm dressing. CONCLUSION: Wound healing rates can improve after protocol implementation. Adequate control of local signs of infection and exudate, as well as visual and indirect signs of biofilm, were achieved. All patients progressed well towards wound-size reduction and closure using the hydrofiber dressing.

OBJETIVO: Presentar un protocolo para evitar la reformación de biopelícula en heridas de difícil cicatrización con apósito de hidrofibra reforzada, con plata iónica al 1,2%, potenciado con ácido etilendiaminotetraacético (EDTA) y cloruro de bencetonio. MÉTODO: Estudio retrospectivo, descriptivo y analítico de aplicación de un protocolo de tratamiento, con tres casos de estudio de pacientes tratados en un centro de referencia internacional. Los registros de pacientes con úlceras complejas se analizaron y evaluaron de acuerdo con la inserción en el algoritmo de identificación clínica de biopelículas, y en base a las recomendaciones prácticas para la higiene de heridas. RESULTADOS: El protocolo adoptado se basó en tres pilares: identificación de signos clínicos de sugerencia para la presencia de biopelícula, prácticas de higiene en las heridas, y aplicación de la cobertura de antibiopelícula. CONCLUSIÓN: La capacidad de cicatrización de heridas con este protocolo puede considerarse alta. Los pacientes obtuvieron un adecuado control de todos los signos locales de infección y de exceso de exudado, y la desaparición de los signos visuales e indirectos de biopelícula. Todos presentaron una adecuada progresión, disminución de la superficie de la herida, y cicatrización tras el uso del apósito.

Sequential sampling plans and economic injury levels for Empoasca kraemeri on common bean crops at different technological levels.

BACKGROUND: Empoasca kraemeri is an important pest on common bean crops at different technological levels. However, for this pest on this crop, economic injury levels have not yet been determined and plan for sequential sampling plans has not yet been developed. Thus, the objectives of this research were to develop E. kraemeri sequential sampling plans and to determine economic injury levels in the common bean at different crop technological levels. RESULTS: Common bean plants tolerate low attack intensities of this pest (up to 1 adult plant-1 ). However, with an increase in attacks, there is a reduction in grain production by the plants. The economic injury levels were 0.48, 0.39 and 0.35 adults sample-1 (leaf beating on a tray) for crops with low (1200 kg ha-1 ), medium (1800 kg ha-1 ) and high (2400 kg ha-1 ) technological levels, respectively. Sequential sampling plans and the standardized plan produced similar decisions. However, in these decisions there was a time saving of more than 60% compared with the standardized plan. CONCLUSION: All three economic injury levels determined and the sequential sampling plans developed in this study are suitable for incorporation into integrated management programs for common bean pests because they can be used by farmers operating at various technological levels to make adequate and rapid decisions. © 2017 Society of Chemical Industry.

Fracture Characterization of Human Cortical Bone Under Mode I Loading.

A miniaturized version of the double cantilever beam (DCB) test is used to determine the fracture energy in human cortical bone under pure mode I loading. An equivalent crack length based data-reduction scheme is used with remarkable advantages relative to classical methods. Digital image correlation (DIC) technique is employed to determine crack opening displacement at the crack tip being correlated with the evolution of fracture energy. A method is presented to obtain the cohesive law (trapezoidal bilinear softening) mimicking the mechanical behavior observed in bone. Cohesive zone modeling (CZM) (finite-element method) was performed to validate the procedure showing excellent agreement.

Analysis of the properties of dental cements after exposure to incubation media containing Streptococcus mutans.

AIM: Indirect restorations are increasingly used in dentistry, and the cementation interface is possibly the most critical region of the work. The objective of the present work was to evaluate the influence of exposure to a culture medium containing S. mutans on the hardness and solubility of four different cementing agents (zinc phosphate, glass ionomer, glass ionomer modified with resin and resin cement). MATERIALS AND METHODS: Test specimens composed of these cements were exposed for 30 days in a culture medium containing S. mutans. After leaching, the test materials were assessed in terms of their solubility (loss of mass) and Knoop (KHN) microhardness. Changes in surface morphology were identified using scanning electron microscopy (SEM). RESULTS: The resin cement showed no significant solubility and its hardness increased following exposure and leaching, while the zinc phosphate cement was the most soluble and its hardness decreased after exposure to the culture medium. SEM analyses identified morphological alterations on the surfaces of the test materials that were compatible with the solubility results. CONCLUSION: It is concluded that resinous cements perform better than water-based cements when exposed to acidic conditions. CLINICAL SIGNIFICANCE: The effects of acids from Streptococcus mutans can interfere with the efficiency and properties of some cements used for fixation of indirect restorations, exposed to the buccal environment.

Incidence of lower limbs deep vein thrombosis after open and laparoscopic gastric bypass: a prospective study.

BACKGROUND: Lower limbs deep vein thrombosis (DVT) and pulmonary embolism (PE) are major causes of morbidity and mortality and are even higher in bariatric patients. The longer operative time and higher immobility in these patients increase the DVT risk. Although deaths after bariatric surgery have been reported, there is no consensus regarding the prophylaxis of DVT. This study's objective is to determine the incidence of lower limbs DVT in patients submitted to Roux-en-Y-gastric bypass (RYGBP) under prophylaxis by enoxaparin. METHODS: Patients with body mass index (BMI) equal to or higher than 35 kg/m(2) who submitted to RYGBP by laparotomy or laparoscopy using 40 mg/day of enoxaparin for 15 days were recruited between October 2004 and August 2005. Individuals with previous DVT and heparin allergy were excluded. Patients were tested for DVT using color Doppler ultrasound performed before surgery and on the second and fifth weeks after surgery. RESULTS: The study population included 136 patients, with 126 concluding the protocol. There were 79% (100/126) of female patients aged 19 to 65 years old, with mean of 40 years SD = 10 and BMI between 35 and 61 kg/m(2), mean of 43 kg/m(2) (SD = 5). All patients who submitted to RYGBP were divided as 55% (69/126) by laparoscopy and 45% (57/126) by laparotomy. The incidence rate of lower limbs DVT was 0.79% (1/126). CONCLUSION: The low incidence rate of DVT found in our study suggests that obesity might not be a major risk factor for venous thromboembolism in patients submitted to RYGBP.

Ten years experience of thoracic and thoracoabdominal aortic aneurysm surgical repair: lessons learned.

In the last few years, advances in surgical techniques and in organ protection adjuncts have improved outcomes in thoracic (TAA) and thoracoabdominal aortic aneurysm (TAAA) surgical repair, although mortality and morbidity are still noteworthy. The aim of the current retrospective study is to determine whether the use of adjuncts influenced mortality and morbidity rates. From 1993 to 2003 we performed 353 procedures for TAA (175 cases) and TAAA (178 cases). This series has been divided into two consecutive groups: in group I (from 1993 to 1997), distal aortic perfusion with left atriofemoral bypass and cerebrospinal fluid drainage were used selectively, and in group II (from 1998 to 2003), the adjuncts were used routinely (together with surgical techniques of less invasive approach in selected cases). Total in-hospital mortality rates were significantly different ( p < 0.05): 15.9% in group I and 8.6% in group II. The overall incidence of paraplegia or paraparesis in group I was 8.3% and in Group II it was 5.1%. Renal failure occurred in 9.6% of group I and in 4.1% of group II. The incidence of respiratory failure in group I was 28%, and was 17.9% in group II. Respiratory failure was significantly lower ( p < 0.05) in group II. The reduction in the incidence of renal failure and paraplegia in the two groups was nonsignificant. In conclusion, the use of adjuncts and our improved experience allowed us to achieve a significant improvement in mortality and major morbidity rates in the group of patients operated on after 1998.