Evaluation of the Fatigue Behaviour and Failure Mechanisms of 52100 Steel Coated with WIP-C1 (Ni/CrC) by Cold Spray

Cold spray technique has been major improved in the last decades, for studying new properties for metals and alloys of aluminum, copper, nickel, and titanium, as well as steels, stainless steel and other types of alloys. Cold sprayed Ni/CrC coatings have the potential to provide a barrier as well as improved protection to steels. Fatigue characteristics of 52100 steel coated with Ni/Chrome-Carbide (Ni/CrC) powder mixture by using cold gas dynamic spray are investigated. Fatigue samples were subjected to symmetrically alternating, axially applied cyclic fatigue loading until failure. The test was stopped if a sample survived more than 5 × 10⁶ cycles at the applied stress. Fracture surfaces for each sample were examined to investigate the behaviour of the coating both at high stress levels and at a high number of stress cycles. Scanning electron microscopy was used to assess the damage in the interface of the two materials. Good fatigue behaviour of the coating material was observed, especially at low stresses and a high number of cycles. Details of the crack initiation region, the stable crack propagation region and the sudden crack expansion region are identified for each sample. In most of the samples, the initiation of the crack occurred on the surface of the base material and propagated into the coating material. The possible effects of coatings on the initial deterioration of the base material and the reduction of the lifespan of the coated system were also investigated. The aim of the paper was to study the interface between the base material and the coating material at the fatigue analysis for different stresses, highlighting the appearance of cracks and the number of breaking cycles required for each sample.     

Microcoil embolisation for ablation of septal hypertrophy in hypertrophic obstructive cardiomyopathy

BACKGROUND AND AIM: Percutaneous transcatheter occlusion with ethanol injection of septal arteries is an efficient treatment procedure of hypertrophic obstructive cardiomyopathy (HOCM). The aim of our study was to evaluate the feasibility and efficiency of septal artery embolisation with microcoils. METHODS: Microcoils were delivered through the guide-wire lumen of a 2mm-diameter coaxial balloon positioned inside the target vessel as distally as possible. One or more 0.018"-straight microcoils (Hilal straight coils, Cook, USA) were used for each target vessel until complete flow obstruction was achieved. The intraventricular pressure gradient was measured before, during and after the procedure. Septal branch occlusion was finally documented by coronary angiography. RESULTS: We treated 7 patients (5 males; mean age: 48 +/- 10 years). All patients were symptomatic (NYHA class III or IV). The target vessels were successfully occluded in all patients without complications. Moderate pain was recorded during and after the procedure and the CK level increased five- to ten-fold. The pressure gradient diminished during the procedure from 72 +/- 21 mmHg to 30 +/- 15 mmHg. The number of coils delivered ranged from 3 to 7 per patient. The embolised septal branches included 1 vessel in 5 patients, 2 vessels in 1 patient and 3 vessels in 1 case. After the procedure, the pressure gradient, evaluated by transthoracic echocardiography, was 34 +/- 16 mmHg and 42 +/- 12 mmH at 3 month-follow-up. Clinical improvement was recorded in all patients after the procedure (NYHA class I or II). Temporary pacing was necessary in 3 patients during and immediately after the procedure but no patient needed permanent pacing. CONCLUSIONS: Microcoil embolisation is an efficient and safe approach for transcatheter ablation of septal hypertrophy in HOCM. This technique induced myocardial necrosis without the toxic effects of alcohol, reducing the risk of complications such as permanent pacemaker implantation or ethanol flow to other myocardial regions.     

Simultaneous adsorption of SO2 and CO2 in an Ni(bdc)(ted)0.5 metal–organic framework

The metal–organic framework Ni(bdc)(ted)_0.5 is a promising material for simultaneous capture of harmful gases such as SO₂ and CO₂. We found that SO₂ performs much better than CO₂ during adsorption, and the lack of physical insight was clarified through detailed analyses of the electronic structures obtained from density functional theory calculations. Our results showed that strong interactions of the d band of Ni atoms with the valence states (2n, 3n, and 4n) of SO₂ but almost not with those of CO₂ are the main reasons. Our finding is useful for the rational design of new metal–organic frameworks with suitable interactions for the simultaneous capture of not only SO₂ and CO₂ but also other gases.

SO₂ performs much better than CO₂ during co-adsorption due to the d-band of Ni atoms.     

Algorithm for mapping cutaneous tissue oxygen concentration using hyperspectral imaging

The measurement of tissue oxygenation plays an important role in the diagnosis and therapeutic assessment of a large variety of diseases. Many different methods have been developed and are currently applied in clinical practice for the measurement of tissue oxygenation. Unfortunately, each of these methods has its own limitations. In this paper we proposed the use of hyperspectral imaging as new method for the assessment of the tissue oxygenation level. To extract this information from hyperspectral images a new algorithm for mapping cutaneous tissue oxygen concentration was developed. This algorithm takes into account and solves some problems related to setting and calculation of some parameters derived from hyperspectral images. The algorithm was tested with good results on synthetic images and then validated on the fingers of a hand with different blood irrigation states. The results obtained have proved the ability of hyperspectral imaging together with the developed algorithm to map the oxy- and deoxyhemoglobin distribution on the analyzed fingers. These are only preliminary results and other studies should be done before this approach to be used in the clinical setting for the diagnosis and monitoring of various diseases.OCIS codes: (000.2170) Equipment and techniques, (110.4234) Multispectral and hyperspectral imaging, (170.6935) Tissue characterization, (300.6550) Spectroscopy, visible     

Anterior resection of the rectum for rectal cancer--options, limits, immediate complications

A number of factors have recently led to a more conservative approach for middle or low rectal cancers, making possible sphincter preservation and reducing the number of abdomino perineal excisions of the rectum. We have performed a retrospective analysis on 510 patients operated on in our unit between 1994 and 2003 for rectal cancer. There were a number of 118 anterior resection of rectum; in 20 cases the TME has been performed and in 6 cases a very low anterior resection of rectum was done. The overall operative morbidity rate was 16.10% in direct relation with the distal limit of resection. We note urinary dysfunctions, anastomotic leakage, recto-vaginal fistulas as immediate postoperative complications. With the practice of total mesorectal excision, the use of abdomino perineal excision of the rectum is decreasing. The use of preoperative radiotherapy can increase the rate of operative morbidity but despite of these, its long-term benefit, is important.     

Cyst duplication of the colon in an adult. Case report

The cystic type of the enteric duplication has the same histological structure as the digestive tract and the same mucosal lining as the segment to which is attached. These are rare pathological conditions especially in an adult as they usually are diagnosed and treated in childhood. A 39 year-old women has been elective admitted in our unit complaining of upper abdominal pain and a palpable abdominal mass in epigastrium and left upper quadrant. The imagistic findings (abdominal ultrasound and CT scan) raise the suspicion of a pancreatic cystic lesion. Intraoperative we found a large cystic lesion localized in the transverse mezocolon close to the transverse colon. The resected specimen was examined histopatologically and found to be a cystic duplication of the colon. The patient made an uneventful postoperative recovery.     

Tumors of the kidneys: new entities

Since 1998 new entities have surfaced in renal tumor classification and have been included in the WHO 2004 classification. In this article, we will discuss the following entities: multilocular clear cell renal carcinoma, Xp11 translocation carcinoma, low grade mucinous tubular carcinoma, epithelioid angiomyolipoma, benign mixed epithelial and stromal tumor. We will investigate new concepts of hybrid oncocytoma and chromophobe renal cell carcinoma and the syndrome of Birt-Hogg-Dube which is associated to kidney tumors. At least, we will touch on new elements in the Bellini carcinoma definition.     

Tribological Behavior and Microstructural Analysis of Atmospheric Plasma Spray Deposited Thin Coatings on Cardan Cross Spindles

Cardan joints are used in transmissions between misaligned shafts, as in all-wheel-drive (AWD) cars and railway applications. Their functioning is accompanied by heavy cyclical loads, with the cardan cross spindles subjected to intensive abrasive wear and pitting. In this paper, a solution to the mentioned issue is proposed, thin anti-wear coatings of Metco 32 and Metco 72 metallic powders deposited by atmospheric plasma spray (APS) on cylindrical samples cut from spindles of two cardan crosses made of 40Cr10 and RUL2 steel. The morphological analysis of the coated surfaces was realized by scanning electron microscopy (SEM), and the elemental composition of the tested samples was elaborated by energy-dispersive X-ray spectroscopy (EDS). To investigate the wear resistance of the coated samples in dry and grease-lubricated conditions, tests at constant load and constant speed were carried out using an AMSLER tribometer. The results of greased tests proved that the expulsion of the lubricant from the tribological contact occurred no matter the combination of coated or uncoated samples. During grease-lubricated tests of ten minutes, the least coefficient of friction was measured for uncoated specimens with better surface finishing; but in dry friction tests, the lowest values of the mean friction coefficients were obtained for the Metco 72 coatings. The porous coatings may act as lubricant reservoirs in long-lasting tests, providing a solution to the expulsion phenomenon of the lubricant to the boundary outside the area of the larger-diameter roller.