Martensitic Transformation in Fe_{x}Mn_{80-x}Co_{10}Cr_{10} High-Entropy Alloy.

High-entropy alloys and even medium-entropy alloys are an intriguing class of materials in that structure and property relations can be controlled via alloying and chemical disorder over wide ranges in the composition space. Employing density-functional theory combined with the coherent-potential approximation to average over all chemical configurations, we tune free energies between face-centered-cubic and hexagonal-close-packed phases in Fe_{x}Mn_{80-x}Co_{10}Cr_{10} systems. Within Fe-Mn-based alloys, we show that the martensitic transformation and chemical short-range order directly correlate with the face-centered-cubic and hexagonal-close-packed energy difference and stacking-fault energies, which are in quantitative agreement with recent observation of two phase region (face-centered cubic and hexagonal closed pack) in a polycrystalline high-entropy alloy sample at x=40 at.%. Our predictions are further confirmed by single-crystal measurements on a x=40 at.% using transmission-electron microscopy, selective-area diffraction, and electron-backscattered-diffraction mapping. The results herein offer an understanding of transformation-induced or twinning-induced plasticity in this class of high-entropy alloys and a design guide for controlling the physics at the electronic level.

Half metallicity in Cr substituted Fe2TiSn.

Band structure tailoring has been a great avenue to achieve the half-metallic electronic ground state in materials. Applying this approach to the full Heusler alloy Fe2TiSn, Cr is introduced systematically at Ti site that conforms to the chemical formula [Formula: see text]Sn. Compositions so obtained have been investigated for its electronic, magnetic, and electrical transport properties with an aim to observe the half-metallic ferromagnetic ground state, anticipated theoretically for Fe2CrSn. Our experimental study using synchrotron X-ray diffraction reveals that only compositions with [Formula: see text] 0.25 yield phase pure L2[Formula: see text] cubic structures. The non-magnetic ground state of Fe2TiSn gets dramatically affected upon inclusion of Cr giving rise to a localized magnetic moment in the background of Ruderman-Kittel-Kasuya-Yosida (RKKY) correlations. The ferromagnetic interactions begin to dominate for x = 0.25 composition. Results of its resistivity and magnetoresistance (MR) measurement point towards a half-metallic ground state. The calculation of exchange coupling parameter, [Formula: see text], and orbital projected density of states that indicate a change in hybridization between 3d and 5p orbital, support the observations made from the study of local crystal structure made using the extended X-ray absorption fine structure spectroscopy. Our findings here highlight an interesting prospect of finding half-metallicity via band structure tailoring for wide application in spintronics devices.

The effects of severe plastic deformation on the mechanical and corrosion characteristics of a bioresorbable Mg-ZKQX6000 alloy.

In this work, a bioresorbable Mg-ZKQX6000 (Mg-6Zn-0.6Zr-0.4Ag-0.2Ca (wt%)) alloy was severely plastically deformed via equal channel angular pressing (ECAP) according to three unique hybrid routes at low temperatures (200 °C to 125 °C). The roles of ECAP processing on microstructure, and ensuing mechanical properties and corrosion rates, are assessed. Microstructurally, ECAP induces a complex plethora of features, especially variations in grain sizes and precipitates' sizes, distributions, and morphologies for individual cases. Mechanically, ECAP generally refined grain size, resulting in ultra-high strength levels of about 400 MPa in ultimate tensile strength for several cases; however, deformation via ECAP of precipitates induced embrittlement and low elongation to failure levels. Corrosion testing, conducted in simulated bodily fluid at bodily pH levels to mimic conditions in the human body, revealed consistent corrosion rates across several techniques (mass loss, hydrogen evolution, and electrochemical impedance spectroscopy (EIS)), showing that severe plastic deformation deteriorates corrosion resistance for this material. In-situ corrosion monitoring explained that corrosion accelerated after ECAP due to the creation of heterogeneous, anodic shear zones, which exhibited dense regions of refined grains and fine precipitates. Suggestions for future design and thermomechanical processing of Mg alloys for bioresorbable orthopedic implants are provided.

Glassy Phonon Heralds a Strain Glass State in a Shape Memory Alloy.

Shape memory strain glasses are frustrated ferroelastic materials with glasslike slow relaxation and nanodomains. It is possible to change a NiCoMnIn Heusler alloy from a martensitically transforming alloy to a nontransforming strain glass by annealing, but minimal differences are evident in the short- or long-range order above the transition temperature-although there is a structural relaxation and a 0.18% lattice expansion in the annealed sample. Using neutron scattering we find glasslike phonon damping in the strain glass but not the transforming alloy at temperatures well above the transition. Damping occurs in the mode with displacements matching the martensitic transformation. With support from first-principles calculations, we argue that the strain glass originates not with transformation strain pinning but with a disruption of the underlying electronic instability when disorder resonance states cross the Fermi level.

A Sensory Material Approach for Reducing Variability in Additively Manufactured Metal Parts.

Despite the recent growth in interest for metal additive manufacturing (AM) in the biomedical and aerospace industries, variability in the performance, composition, and microstructure of AM parts remains a major impediment to its widespread adoption. The underlying physical mechanisms, which cause variability, as well as the scale and nature of variability are not well understood, and current methods are ineffective at capturing these details. Here, a Nickel-Titanium alloy is used as a sensory material in order to quantitatively, and rather rapidly, observe compositional and/or microstructural variability in selective laser melting manufactured parts; thereby providing a means to evaluate the role of process parameters on the variability. We perform detailed microstructural investigations using transmission electron microscopy at various locations to reveal the origins of microstructural variability in this sensory material. This approach helped reveal how reducing the distance between adjacent laser scans below a critical value greatly reduces both the in-sample and sample-to-sample variability. Microstructural investigations revealed that when the laser scan distance is wide, there is an inhomogeneity in subgrain size, precipitate distribution, and dislocation density in the microstructure, responsible for the observed variability. These results provide an important first step towards understanding the nature of variability in additively manufactured parts.

Reversible Martensitic Transformation under Low Magnetic Fields in Magnetic Shape Memory Alloys.

Magnetic field-induced, reversible martensitic transformations in NiCoMnIn meta-magnetic shape memory alloys were studied under constant and varying mechanical loads to understand the role of coupled magneto-mechanical loading on the transformation characteristics and the magnetic field levels required for reversible phase transformations. The samples with two distinct microstructures were tested along the [001] austenite crystallographic direction using a custom designed magneto-thermo-mechanical characterization device while carefully controlling their thermodynamic states through isothermal constant stress and stress-varying magnetic field ramping. Measurements revealed that these meta-magnetic shape memory alloys were capable of generating entropy changes of 14 J kg-1 K-1 or 22 J kg -1 K-1, and corresponding magnetocaloric cooling with reversible shape changes as high as 5.6% under only 1.3 T, or 3 T applied magnetic fields, respectively. Thus, we demonstrate that this alloy is suitable as an active component in near room temperature devices, such as magnetocaloric regenerators, and that the field levels generated by permanent magnets can be sufficient to completely transform the alloy between its martensitic and austenitic states if the loading sequence developed, herein, is employed.

Effect of grain constraint on the field requirements for magnetocaloric effect in Ni45Co5Mn40Sn10 melt-spun ribbons.

The influence of grain constraint on the magnetic field levels required to complete the isothermal martensitic transformation in magnetic shape memory alloys has been demonstrated for a NiCoMnSn alloy, and the magnetocaloric performance of an optimally heat treated alloy was quantified. Ni45CoxMn45-xSn10 melt spun ribbons with x = 2, 4, 5, and 6 were characterized. The x = 5 sample was determined to exhibit the lowest transformation thermal hysteresis (7 K) and transformation temperature range during transformation from paramagnetic austenite to nonmagnetic martensite, as well as a large latent heat of transformation (45 J kg-1 K-1). For this composition, it was found that increasing the grain size to thickness ratio of the ribbons from 0.2 to 1.2, through select heat treatments, resulted in a decrease in the magnetic field required to induce the martensitic transformation by about 3 T due to the corresponding reduction in the martensitic transformation temperature range. This decrease in the field requirement ultimately led to a larger magnetocaloric entropy change achieved under relatively smaller magnetic field levels. The giant inverse magnetocaloric effect of the optimized alloy was measured and showed that up to 25 J kg-1 K-1 was generated by driving the martensitic transition with magnetic fields up to 7 T.

Long-term sustainability of zero central-line associated bloodstream infections is possible with high compliance with care bundle elements.

Central-line-associated bloodstream infection (CLABSI) is one of the most important problems in intensive care units (ICUs) worldwide. A bundle of CLABSI care measures was introduced at a 13-bed medical/surgical ICU in Kocaeli, Turkey in January 2010. Compliance rates with the bundle were measured at the beginning of the third quarter of 2010 until June 2013 and compared with CLABSI rates. During the post-intervention period, of 2196 ICU patients, 732 lines placed for 4366 line-days were monitored. Feedback to staff reinforced a culture of patient safety in the ICU. Infection rates remained zero for 38 months after the implementation. There was a strong negative correlation between bundle compliance rate and CLABSI rates. With the implementation of the central-line bundle of care, together with emphasis on high compliance with all its components and a culture of patient safety, it was possible to achieve and maintain a zero rate of CLABSI in this ICU.

Biomechanical properties of Achilles tendon in diabetic vs. non-diabetic patients.

BACKGROUND/OBJECTIVES: Structural and functional impairments of the Achilles tendon in diabetic patients has the potential to contribute to ulcer formation through altered foot mechanics. This study aimed to examine the biomechanical and histopathological alterations in Achilles tendon specimens from diabetic vs. non-diabetic individuals. MATERIALS AND METHODS: 42 Achilles tendon samples obtained from patients treated with below-knee or above-knee amputation for chronic diabetic foot ulcers (n=21) or for non-diabetic conditions (n=21) were included. A tensile test was performed for each tendon and a stress vs. strain graft was obtained to calculate following biomechanical parameters: elasticity (Young modulus), load, stiffness, toughness, energy, strain, elongation and tenacity. Groups were also compared with regard to histopathological findings (inflammatory cell infiltration, collagen organization, and degeneration). RESULTS: Non-diabetic tendons exhibited a superior biomechanical profile over diabetic tendons with regard to the following biochemical parameters: elasticity, maximum load, stiffness, toughness, load, energy, strain and elongation at break point, tenacity, and strain at automatic load drop (p<0.05 for all comparisons). Diabetic tendons had mild impairment of collagen organization and focal collagen degeneration, whereas neither diabetic nor non-diabetic tendons had inflammatory cell infiltration. CONCLUSION: The structural and functional alterations associated with diabetes adversely affect the biomechanical properties of the Achilles tendon, potentially acting together with neuropathy and ischemia in the development of diabetic foot ulcers.

Long-term sustainability of zero central-line associated bloodstream infections is possible with high compliance with care bundle elements

Central-line-associated bloodstream infection (CLABSI) is one of the most important problems in intensive care units (ICUs) worldwide. A bundle of CLABSI care measures was introduced at a 13-bed medical/surgical ICU in Kocaeli, Turkey in January 2010. Compliance rates with the bundle were measured at the beginningof the third quarter of 2010 until June 2013 and compared with CLABSI rates. During the post-intervention period, of 2196 ICU patients, 732 lines placed for 4366 line-days were monitored. Feedback to staff reinforced a culture of patient safety in the ICU. Infection rates remained zero for 38 months after the implementation. There was a strong negative correlation between bundle compliance rate and CLABSI rates. With the implementation of the central-line bundle of care, together with emphasis on high compliance with all its components and a culture of patient safety, it was possible to achieve and maintain a zero rate of CLABSI in this ICU.

Les infections sur cathéter central sont l'un des problèmes les plus importants dans les unités de soins intensifs au niveau mondial. Un ensemble de soins dispensés en cas d'infections sur cathéter central a été introduit dans une unité de soins intensifs médicaux et chirurgicaux de 13 lits à Kocaeli (Turquie) en janvier 2010. Le degré d'application de l'ensemble de soins a été évalué du début du troisième trimestre 2010 jusqu'à juin 2013 et comparé aux taux d'infections sur cathéter central. Au cours de la période suivant l'intervention, parmi les 2196 patients ayant séjourné dans l'Unité des soins intensifs, 732 cathéters centraux posés pendant 4366 jours cumulés ont été soumis à observation. Le retour d'information fourni au personnel a permis de renforcer la culture de la sécurité du patient en unité de soins intensifs.Les taux d'infections sont restés nuls pendant les 38 mois ayant suivi la mise en oeuvre. Il existait une forte corrélation négative entre le degré d'application de l'ensemble de soins et les taux d'infections sur cathéter central. La mise en oeuvrede cet ensemble de soins concernant les cathéters centraux, associée à l’accent mis sur le degré d'application de toutes ses composantes et une culture de la sécurité du patient, a permis d'atteindre et de maintenir un taux zéro d'infection sur cathéter central dans cette unité de soins intensifs.

Corrosion fatigue behavior of a biocompatible ultrafine-grained niobium alloy in simulated body fluid.

The present study reports on the corrosion fatigue behavior of ultrafine-grained (UFG) Niobium 2 wt-% Zirconium (NbZr) alloy in simulated body fluid (SBF). The alloy was processed using multipass equal channel angular processing at room temperature, resulting in a favorable combination of high strength and ductility along with superior biocompatibility and excellent corrosion resistance. Electrochemical measurements revealed stable passive behavior in SBF saline solutions, similar to conventional Ti-6Al-4V alloy. High-cycle fatigue tests showed no alteration in the crack initiation behavior due to the SBF environment, and an absence of pitting and corrosion products. More severe test conditions were obtained in the fatigue crack growth experiments in saline environments. Crack growth rates in UFG NbZr were marginally increased in SBF as compared to laboratory air at a constant test frequency of 20 Hz. Upon a 100 fold decrease in the test frequency, slightly higher crack growth rates were observed only in the near-threshold region. Such excellent corrosion and corrosion fatigue properties of UFG NbZr recommend it as an attractive new material for biomedical implants.

The transscrotal approach for recurrent and iatrogenic undescended testes.

PURPOSE: Aim of the study was to evaluate the efficacy of the transscrotal approach in redo orchiopexy. MATERIAL AND METHODS: Redo orchiopexy using the transscrotal approach was used to treat 16 testes during a 4-year period from 2005 to 2009. Five of these cases occurred following inguinal hernia repair and 11 after previous orchiopexy. Only testes located distal to the external ring that could be moved to the upper part of the scrotum were included in the study. The vas deferens and testicular vessels were dissected free from the surrounding tissue using a scrotal approach and the testis placed into a dartos pouch. RESULTS: All testes except one could be placed into the scrotum with the transscrotal approach. The mean duration of surgery was 33+/-13 min. No patient suffered from atrophy or reascending testes. CONCLUSION: The transscrotal approach is a fast, simple and reliable method for redo procedures for undescended testes.

Does gum chewing reduce postoperative ileus after intestinal resection in children? A prospective randomized controlled trial.

INTRODUCTION: The aim of this study was to determine whether the addition of gum chewing to standardized postoperative care is associated with a significantly earlier return of bowel function compared to simple postoperative management in children with intestinal anastomosis. MATERIALS AND METHODS: We performed a prospective, randomized, controlled trial. All patients who underwent laparotomy with either colon or small bowel resection between June 2006 and March 2008 were randomized to one of two groups. Group one consisted of patients receiving standardized postoperative care plus gum chewing (gum-chewing group) (n=15); Group two consisted of patients receiving only standardized postoperative care (control group) (n=15). The patients in the gum-chewing group chewed one stick of sugarless gum three times per day, for an hour, each day. RESULTS: The groups were statistically similar. The time to first flatus was 35.73+/-14.67 h in the gum-chewing group and 42.00+/-20.77 h in the control group (p=0.347). The time to first bowel movement was 56.27+/-22.14 h in the gum-chewing group and 63.00+/-26.34 in the control group (p=0.444). The length of hospital stay was 5.80+/-0.68 days for the gum-chewing group and 6.67+/-0.98 days for the control group (p=0.005). The hospital charges were 2451+/-806 YTL for the gum-chewing group and 2102+/-678 YTL for the control group (p=0.206). CONCLUSIONS: The addition of gum chewing to the standardized postoperative care of children with intestinal anastomosis was not associated with a significantly earlier return of bowel function compared to simple postoperative management, but it was associated with an earlier discharge from hospital, although this earlier discharge had only minor clinical significance and no difference was found in hospital charges.

Design and application of a mechanical load frame for in situ investigation of ferromagnetic shape memory alloys by magnetic force microscopy.

An in situ mechanical load frame has been developed for a commercially available atomic force microscope. This frame allows examining changes in topography and magnetic domain configuration under a given constant load or strain. First results obtained on Ni-Mn-Ga ferromagnetic shape memory alloy single crystals are presented. The magnetic force microscopy (MFM) measurements under different strain levels confirm the one-to-one correspondence, i.e., the magnetomicrostructural coupling between the martensite twins and the magnetic domains. Additionally, the growth of the twin variant with favorable orientation to the compression axis during martensite detwinning was observed. It will be shown that this load frame can be used for the investigation of the relationship between the microstructure and the magnetic domain structure in ferromagnetic shape memory alloys by MFM.

External cystic rectal duplication: an unusual presentation of rectal duplication cyst.

Duplications of gastrointestinal tract are rare anomalies, and rectal duplications account for five percent of the alimentary tract duplications. We present an unusual case of rectal duplication, which was located externally in a newborn female, and discuss the types of distal hindgut duplications.

Our experience with transanal endorectal pull-through in Hirschsprung's disease.

AIM: The aim of the study was to evaluate the functional results, complications, the problems caused, and the outcomes of the transanal endorectal pull-through (TEPT) operation in Hirschsprung's disease. PATIENTS AND METHODS: The 22 patients who were operated for Hirschsprung's disease with TEPT between November 2003 and September 2006 were reviewed retrospectively. The patients were evaluated for age, gender, operational findings, duration of hospitalization and functional outcomes after the operation. RESULTS: A total of 22 patients, sixteen males (72.7 %) and 6 females (27.3 %) aged 23 days to 11 years (mean 19.3 +/- 6.9 months), were operated using TEPT over a 34-month period. The mean length of the resected aganglionic segment was 23 +/- 2.4 cm; the shortest segment was 7 cm and the longest 40 cm. The postoperative hospital stay was 3 - 10 days, oral feeding was started at 1 - 4 days, the first bowel movement was at 1 - 7 days and the number of daily movements for patients in whom the colostomy was closed was 2 - 5. The mean postoperative follow-up period was 18 +/- 2.4 months (1 - 33 months). Two patients (9 %) were hospitalized once for enterocolitis. One patient had a constipation problem that resolved with medical treatment. One patient needed colostomy for anastomosis leakage on the 5th postoperative day, followed by a redo pull-through using a posterior sagittal approach. None of the patients had a continence problem. No urethral damage was observed and there were no abscesses at the muscular cuff. We observed that mucosal dissection was more difficult in the rectal biopsy area. CONCLUSIONS: Although only recently accepted, TEPT has quickly found a place in clinical practice as it is based on an operational technique whose results are well identified and accepted and with which there is extensive experience. It seems that TEPT has the advantages of having no additional problems compared to the classical techniques with respect to complications and functional outcomes while providing better patient comfort and cosmetic outcomes. We conclude that TEPT may be preferred in appropriate cases and will evolve to become a more practical and effective technique.

Is endothelial function impaired in erectile dysfunction patients?

Erectile dysfunction (ED) and vascular disease are thought to be linked at the level of the endothelium. Endothelial dysfunction, resulting in the inability of the smooth muscle cells lining the arterioles to relax, prevents vasodilatation. Likewise, penile erection depends on the relaxation of smooth muscle in the corpus cavernosum and the wall of small arteries. The aim was to assess the systemic vascular function in patients with ED. In all, 32 ED patients diagnosed with Doppler Ultrasound and the International Index of Erectile Function-5-item questionnaire and 25 healthy men as a control group enrolled to the study. They all underwent the tests including serum glucose and lipid levels. Echocardiography and exercise stress test was performed routinely. Baseline demographics (body mass index, heart rate and blood pressures), fasting glucose and lipid levels were not significantly different between ED and control groups. Endothelial-dependent brachial artery flow-mediated vasodilatation and brachial artery response to 0.4 mg nitroglycerine (NTG) were measured. Participants were negative on exercise stress test, and echocardiographic parameters including ejection fraction were similar. Endothelial-dependent brachial artery percent diameter change with flow-mediated dilatation (6.01+/-2.9 vs 12.3+/-3.5) and brachial artery response to NTG (12.8+/-4.2 vs 17.8+/-5.2) were significantly different between groups (P<0.001). We found that endothelial function was impaired in ED patients with no apparent cardiovascular disease and diabetes mellitus. This impaired function might be explained by the abnormality in systemic nitric oxide-cyclic guanosine monophosphate vasodilator system and suggest that ED and vascular disease may be linked at the level of the endothelium.

Outcome of primary peritoneal drainage for perforated necrotizing enterocolitis: comparison between laparotomy and drainage.

Perforation of the gastrointestinal tract in neonates is still associated with high mortality rates. Laparotomy is usually required to treat gastrointestinal perforation, however peritoneal drainage under local anesthesia has been also described as an alternative mode of treatment. In our institute, laparotomy was the first choice for the management of gastrointestinal perforation in neonates until 1999. Because of the high mortality rates in this group of patients, our policy has since changed to the use of primary peritoneal drainage instead. The aim of this study is to compare the effectiveness of primary peritoneal drainage (PPD) and primary laparotomy (PL) procedures in the management of gastrointestinal perforation due to necrotizing enterocolitis in neonates. Between 1994 - 1998, ten babies with intestinal perforation underwent PL, whereas fifteen newborns with similar findings were treated with PPD between 1999 and 2003. Eight (80 %) of the patients died in the PL group prior to 1999. In the PPD group 8 (53.3 %) of babies required no further treatment and were discharged without any complications. Four (26.7 %) patients in this group needed laparotomy later, and three (75 %) of them survived. In conclusion, we believe that PPD is more effective than PL for the management of perforated necrotizing enterocolitis in neonates. Laparotomy can be used in particularly unresponsive cases after primary peritoneal drainage.

Comparison of closed-tube thoracostomy and open thoracotomy procedures in the management of thoracic empyema in childhood.

PURPOSE: There is still an argument concerning the correct management of pleural empyema. The aim of this study is to compare the effectiveness of closed-tube thoracostomy and open thoracotomy procedures in the management of empyema in children. METHODS: This is a prospective study of 30 patients with parapneumonic empyema who were managed randomly either by closed-tube thoracostomy or open thoracotomy procedures. The two procedures were compared based on the respective times to achieving normal body temperature and breath rates, duration of tube drainage, length of hospitalization, and complication rates. Both groups were also assessed by comparing tube drainage duration, pleural fluid pH, agent pathogen and glucose level. RESULTS: Average tube duration was 7.5 +/- 1.1 days and average hospital stay was 9.5 +/- 1.5 days in the open thoracotomy group. In the closed tube thoracostomy group tube, duration was 13.8 +/- 2.3 days and average hospital stay 15.4 +/- 2.3 days. In the open thoracotomy group 73.3% of the patients had achieved normal body temperature and 66.7 % had a normal breath rate within the first 48 hours. In the closed tube thoracostomy group these rates were 40% and 20%, respectively. In both groups, tube drainage duration was found to be longer in patients whose pleural fluid pH was < 7.2. CONCLUSION: The authors conclude that open thoracotomy is a safe, efficient, and easy method of treatment for pleural empyema in children. It was also observed that pleural fluid pH level is the most important prognostic criteria in pleural empyema.