EBSD characterization of carbide–carbide boundaries in WC–Co composites

A sample of WC‐6wt%Co was investigated for grain boundary character distribution and occurrence of coincidence site lattice (CSL) boundaries on a statistical basis. For this purpose orientation measurements of the grains were carried out using electron back‐scattered diffraction (EBSD). The dominant misorientation relationships were determined by complementary EBSD data representation tools such as orientation maps, misorientation angle distribution histograms and the sectioned three‐dimensional misorientation space. It was found that the grain boundary character distribution of the material is nearly random and the CSL boundaries are not present in statistically significant amounts. It was also found that the amount of binder phase does not play a role in the formation of special boundaries. The paper focuses on the methodology of characterizing grain boundaries in a hexagonal material using EBSD.     

DIC image reconstruction on large cell scans

The width of the emission spectrum of a common fluorophore allows only for a limited number of spectral distinct fluorescent markers in the visible spectrum, which is also the regime where CCD-cameras are used in microscopy. For imaging of cells or tissues, it is required to obtain an image from which the morphology of the whole cell can be extracted. This is usually achieved by differential interference contrast (DIC) microscopy. These images have a pseudo-3D appearance, easily interpreted by the human brain. In the age of high throughput and high content screening, manual image processing is not an option. Conventional algorithms for image processing often use threshold-based criteria to identify objects of interest. These algorithms fail for DIC images as they have a range from dim to bright with an intermediate intensity equal to the background, so as to produce no clear object boundary. In this article we compare different reconstruction methods for up to 100 MB-large DIC images and implement a new iterative reconstruction method based on the Hilbert Transform that enables identification of cell boundaries with standard threshold algorithms.     

Comparison of the microstructures in continuous-cooled and quench-tempered pre-hardened mould steels

The increased demand for plastic mould steels in pre-hardened condition has drawn the attention to this specific type of steel. As a result, more investigations are performed to understand microstructure and properties. In this work, the microstructures of two pre-hardened plastic mould steels, one quench-tempered (Uddeholm Impax HH) and the other continuously cooled (Uddeholm Nimax), are studied in delivery condition by means of different microscopy techniques and are linked to their production procedure. The results show that the quench-tempered material contains large amounts of M₃C carbides formed within the martensite plates as well as at the lath- and prior austenite grain boundaries. A few coarser Cr-rich M₇C₃ carbides have also been found. In comparison, the microstructure of the continuously cooled material consists of mainly bainite with much lower density and finer cementite particles. The hardness is with ∼40 HRC more or less constant over the cross section of both materials.     

A new method for in vivo evaluation of biofilms on surface-modified silicone rubber voice prostheses

A new method is presented that permits a rapid and accurate in vivo evaluation of biofilm formation on surface-modified silicone rubber voice prostheses. The method is based on partial modification of a Groningen button voice prosthesis by exposing half of the prosthesis to an argon plasma. This results in one side of the prosthesis becoming hydrophilic while leaving the unmodified side hydrophobic as a control. Modified prostheses were placed in patients for an evaluation period of approximately 4 weeks. Despite making the silicone rubber surface hydrophilic, biofilm formation was stimulated when compared to unmodified, hydrophobic silicone rubber. Findings show that biofilm formation on voice prostheses is influenced by hydrophobicity of a silicone rubber surface. The method of partial surface modification used was seen to be suitable for demonstrating such influences regardless of nutrition and other variations in the patient's lifestyle. Microbiological analysis of the biofilms on both sides of the prosthesis valve did not show any changes in microbial composition, with Candida albicans, streptococci and staphylococci being the most commonly isolated strains.     

Stenosis of the tubular neck: a possible mechanism for progressive renal failure

OBJECTIVE: To study the influence of continuous administration of heparin on platelet function in intensive care patients. DESIGN: Prospective, serial investigation. SETTING: Clinical investigation on a surgical and neurosurgical intensive care unit in a university hospital. PATIENTS: The study included 45 patients: 15 postoperative with patients sepsis (Acute Physiology and Chronic Health Evaluation II score between 15 and 25), 15 trauma patients (Injury Severity Score 15 to 25), and 15 neurosurgical patients. INTERVENTIONS: Management of the patients was carried out according to the guidelines for modern intensive care therapy. Sepsis and trauma patients received standard (unfractionated) heparin continuously [aim: an activated partial thromboplastin time (aPTT) approximately 2.0 times normal value; sepsis-heparin and trauma-heparin patients], whereas neurosurgical patients received no heparin (neurosurgical patients). MEASUREMENTS AND RESULTS: From arterial blood samples, platelet aggregation was measured by the turbidimetric method. Platelet aggregation was induced by adenosine diphosphate (ADP; 2.0 mumol/l), collagen (10 micrograms/ml), and epinephrine (25 mumol/l). Measurements were carried out on the day of diagnosis of sepsis or 12 h after hemodynamic stabilization (trauma and neurosurgery patients) (baseline) and during the next 5 days at 12.00 noon. Standard coagulation parameters [platelet count and fibrinogen and antithrombin III (AT III) plasma concentrations] were also monitored. Heparin 4-10 U/kg per h (mean dose: approximately 500 U/h) was necessary to reach an aPTT of about 2.0 times normal. Platelet count was highest in the neurosurgical patients, but it did not decrease after heparin administration to the trauma and sepsis patients. AT III and fibrinogen plasma levels were similar in the three groups of patients. In the sepsis group, platelet aggregation variables decreased significantly (e.g., epinephrine-induced maximum platelet aggregation:-45 relative % from baseline value). Platelet function recovered during the study and even exceeded baseline values (e.g., ADP-induced maximum platelet aggregation: +42.5 relative % from baseline value). Continuous heparinization did not blunt this increase of platelet aggregation variables. In the heparinized trauma patients, platelet aggregation variables remained almost stable and were no different to platelet aggregation data in the untreated neurosurgical patients. CONCLUSIONS: Continuous administration of heparin with an average dose of approximately 500 U/h did not negatively influence platelet function in the trauma patients. Recovery from reduced platelet function in the sepsis group was not affected by continuous heparinization. Thus, continuous heparinization with this dose appears to be safe with regard to platelet function in the intensive care patient.