An in situ thermo-mechanical rig for lattice strain measurement during creep using neutron diffraction

A long-term high-temperature testing stress rig has been designed and fabricated for performing in situ neutron diffraction tests at the ENGIN-X beamline, ISIS facility in the UK. It is capable of subjecting metals to high temperatures up to 800 °C and uniaxial loading under different boundary conditions including constant load, constant strain, and elastic follow-up, each with minimum of external control. Samples are held horizontally between grips and connected to a rigid rig frame, a soft aluminium bar, and a stepper motor with forces up to 20 kN. A new three zone split electrical resistance furnace which generates a stable and uniform heat atmosphere over 200 mm length was used to heat the samples. An 8 mm diameter port at 45° to the centre of the furnace was made in order to allow the neutron beam through the furnace to illuminate the sample. The entire instrument is mounted on the positioner at ENGIN-X and has the potential ability to operate continuously while being moved in and out of the neutron diffraction beam. The performance of the rig has been demonstrated by tracking the evolution of lattice strains in type 316H stainless steel under elastic follow-up control at 550 °C.

Effect of boundary conditions on the evolution of lattice strains in a polycrystalline austenitic stainless steel

The effect of boundary conditions (constant load, constant strain and elastic follow-up) on lattice strain evolution during creep in a polycrystalline austenitic stainless steel was studied using in situ neutron diffraction at 550 °C. The lattice strains were found to remain constant under constant load control. However, under constant strain and elastic follow-up control, the lattice strains relaxed the most in the elastically softest lattice plane {200} and the least in the elastically stiffest lattice plane {111}. The intergranular stresses created between different grain families were constant during creep tests irrespective of the boundary conditions with the initial applied stresses of 250 MPa.

Sample environment for neutron scattering measurements of internal stresses in engineering materials in the temperature range of 6 K to 300 K

Internal stresses in materials have a considerable effect on material properties including strength, fracture toughness, and fatigue resistance. The ENGIN-X beamline is an engineering science facility at ISIS optimized for the measurement of strain and stress using the atomic lattice planes as a strain gauge. Nowadays, the rapidly rising interest in the mechanical properties of engineering materials at low temperatures has been stimulated by the dynamic development of the cryogenic industry and the advanced applications of the superconductor technology. Here we present the design and discuss the test results of a new cryogenic sample environment system for neutron scattering measurements of internal stresses in engineering materials under a load of up to 100 kN and in the temperature range of 6 K to 300 K. Complete cooling of the system starting from the room temperature down to the base temperature takes around 90 min. Understanding of internal stresses in engineering materials at cryogenic temperatures is vital for the modelling and designing of cutting-edge superconducting magnets and other superconductor based applications.

A fatal pulmonary infection by Nocardia brasiliensis

The reported case is of primary pulmonary nocardiosis, caused by Nocardia brasiliensis, in a immunocompromised patient, which ended fatally despite appropriate treatment. The partially acid fast filamentous bacterium was predominant on direct examination of the sputum. It was cultured on blood agar, MacConkey agar and by paraffin baiting technique. The bacterium was resistant to cotrimoxazole, the drug of choice for nocardiosis.

Outbreak of Acinetobacter spp septicemia in a neonatal ICU

An outbreak of Acinetobacter spp infection in the neonatal unit at Lok Nayak Hospital, New Delhi, India, is described. During a 6-month period, 68 strains of Acinetobacter baumannii were isolated from the blood and CSF of 47 neonates admitted to the intensive care unit. Diagnosis of clinically significant bacteremia was made in 36 patients. On environmental/personnel sampling, Acinetobacter spp isolates with similar antibiogram were recovered from intravenous catheter and washbasin. Control of the outbreak was possible only after strict infection control practices in the unit. It was concluded that any clinical multidrug resistant A. baumannii isolate can be a potential nosocomial outbreak strain.

Salmonella senftenberg: a new pathogen in the burns ward

This is the first report of Salmonella senftenberg serovar outbreak in a burns unit. This unit admits about 2000 patients with major burn injuries annually. Routine sampling from wound swabs in December 1995 revealed S. senftenberg in a few samples following which a study was instituted from January to March 1996. Of 446 burn admissions during this period 80 patients were culture positive for S. senftenberg in wound swabs. The protocol for investigation included wound swabs on admission and then at biweekly interval, blood culture studies on clinically toxic patients, anti-microbial sensitivity studies, environmental sampling and hand swabs and stool cultures from about 50 staff members of the burns ward. No wound swab at the time of admission was positive for S. senftenberg. Environmental study and the study of staff members did not reveal any obvious source of the infection. S. senftenberg strains were sensitive to more than seven of the 11 anti-microbials tested at the beginning of the study but later 96.3% of the strains showed multidrug (more than three drugs) resistance. By April 1996 the isolates became negligible and later disappeared completely. The organism resurfaced again in March 1997 and the same study was instituted again on 413 admissions between March and May 1997. Fifty patients were culture positive for S. senftenberg. This time stool sample from one burn dresser tested positive for S. senftenberg. Interestingly, again at the beginning of the second outbreak the Salmonella strains were sensitive to 9 out of 11 anti-microbials tested, but later 96.11% strains became multidrug resistant. S. senftenberg strains showed maximum resistance to amoxycillin (97.5%) and minimum to chloramphenicol, tetracycline and cotrimoxazole (12%). It was noticed that Salmonella strains surfaced in wound swabs after 3-4 weeks of hospital stay. Forty-five out of 130 patients studied, in both the episodes, died due to septicemia. The majority of the patients who died had sustained > 60% TBSA burns. Blood cultures were done in 34/130 patients and eight yielded growth (2 S. senftenberg, 4 Klebsiella spp., and two Pseudomonas spp.)

Pleuro pulmonary infection with Salmonella group E

A patient was admitted with a history of cough, shortness of breath and fever. After investigations, he was found to have a left-sided pneumonia with pleural effusion. Culture of the patient's sputum, pleural fluid and blood revealed Salmonella senftenberg. The patient was started on antibiotics according to the sensitivity report and responded to therapy. The past history revealed attempt at suicide by the intake of corrosive acid, which caused an esophageal stricture. The leak of gastric contents into the mediastinum lead to the infection of the pleural cavity and pneumonia.

Serum concentrations of rifampicin and isoniazid in tuberculosis

Ninety-four patients, 1-13 years of age suffering from different types of tuberculosis were investigated for serum rifampicin (RIF) and isoniazid (INH) concentrations using microbiological and fluorimetric methods, respectively. Of these, 64 (68.1%) had pulmonary primary complex (PPC); 20 (21.3%) progressive primary disease (PPD) and 10 (10.6%) tuberculous meningitis (TBM). Patients with PPC, PPD and TBM were given two-drug (6HR), three drug (2HRZ, 4HR) and four drug (2SHRZ, 4HRE, 3HE) regimens, respectively. RIF and INH were administered in a dose of 12 and 10 mg/kg/day, respectively. After 10-12 days of continuous therapy, their serum concentrations were estimated at 0, 2, 4, 6, 8 hours for RIF and 0, 1, 3, 5, 7 hours for INH. For RIF, the time to achieve maximum concentrations (Tmax) was 2 hours, range of mean of maximum concentration (Cmax) 3.38 to 3.88 micrograms/ml, terminal half life elimination (T1/2) 3.03 to 3.81 hours and area under serum concentration curve (AUC) 0-8 hours 24.7 to 28.3 micrograms/ml hours in different forms of tuberculosis. INH had a Tmax of 1 h, Cmax 4.38 to 8.17 micrograms/ml, T1/2 4.0 to 4.98 hours and AUC 0-7 hours 34.1 to 57.5 micrograms/ml hours. The concentrations achieved at 7-8 hours with these dosages were much above those required for therapeutic efficacy (minimum inhibitory concentration), being 50 to 250 times for RIF and 35-60 times for INH. We recommend pharmacokinetic studies with lower doses of RIF and INH for less toxic, equally effective and cheaper antitubercular chemotherapy.