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Biomedical subjects

A Johansen

Publications and source records attributed to A Johansen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Effects of interactions between powder particle size and binder viscosity on agglomerate growth mechanisms in a high shear mixer.

A study was performed in order to elucidate the effects of the interactions between powder particle size and binder viscosity on the mechanisms involved in agglomerate formation and growth. Calcium carbonates having mean particle sizes in the range of 5-214 microm and polyethylene glycols having viscosities in the range of approximately 50-100000 mPas were melt agglomerated in a high shear mixer. Agglomerate growth by nucleation and coalescence was found to dominate when agglomerating small powder particles and binders with a low viscosity. Increasing the binder viscosity increased the formation of agglomerates by immersion of powder particles in the surface of the binder droplets. With a larger powder particle size, an increasing binder viscosity was necessary in order to obtain an agglomerate strength being sufficient to avoid breakage. Due to a low agglomerate strength, a satisfying agglomeration of very large particles (214 microm) could not be obtained, even with very viscous binders. The study demonstrated that the optimum agglomerate growth occurred when the agglomerates were of an intermediate strength causing an intermediate deformability of the agglomerates. In order to produce spherical agglomerates (pellets), a low viscosity binder has to be chosen when agglomerating a powder with a small particle size, and a high viscosity binder must be applied in agglomeration of powders with large particles.

Adhesiveness↗
PubMed2001

Effects of physical properties of powder particles on binder liquid requirement and agglomerate growth mechanisms in a high shear mixer.

A study was performed in order to elucidate the effects of the physical properties of small powder particles on binder liquid requirement and agglomerate growth mechanisms. Three grades of calcium carbonate having different particle size distribution, surface area, and particle shape but approximately the same median particle size (4-5 microm), were melt agglomerated with polyethylene glycol (PEG) 3000 or 20,000 in an 8-l high shear mixer at three impeller speeds. The binder liquid requirement was found to be very dependent on the packing properties of the powder, a denser packing resulting in a lower binder liquid requirement. The densification of the agglomerates in the high shear mixer could be approximately predicted by compressing a powder sample in a compaction simulator. With the PEG having the highest viscosity (PEG 20,000), the agglomerate formation and growth occurred primarily by the immersion mechanism, whereas PEG 3000 gave rise to agglomerate growth by coalescence. Powder particles with a rounded shape and a narrow size distribution resulted in breakage of agglomerates with PEG 3000, whereas no breakage was seen with PEG 20,000. Powder particles having an irregular shape and surface structure could be agglomerated with PEG 20,000, whereas agglomerate growth became uncontrollable with PEG 3000. When PEG 20,000 was added as a powder instead of flakes, the resultant agglomerates became rounder and the size distribution narrower.

Calcium Carbonate↗
PubMed2001

Interpretive intra- and interobserver reproducibility of rest/stress 99Tcm-sestamibi myocardial perfusion SPECT in a consecutive group of male patients with stable angina pectoris before and after percutaneous transluminal angioplasty.

BACKGROUND: Observer variability of 99Tcm-sestamibi myocardial perfusion imaging (MPI) has rarely been investigated. The aim of our study was to evaluate the interpretive reproducibility with this technique. PATIENTS: We report on 108 consecutive male patients with stable angina pectoris, investigated before and after percutaneous transluminal angioplasty (PTCA). METHODS: A 2-day rest/stress 99Tcm-sestamibi gated single photon emission computed tomography (SPECT) protocol was used. MPI was interpreted by two independent observers without knowledge of clinical data, using a 20-segment scoring model. RESULTS: Intra- and interobserver agreement was found to be good to excellent (kappa = 0.71-0.85) with regard to the overall diagnosis as well as the individual vessel diagnosis (kappa = 0.60-0.87). However, agreement was higher for left anterior descending coronary artery (LAD) and left circumflex coronary artery (LCX) vascular territories than for the right coronary artery (RCA) territory. Moderate to good intraobserver agreement (kappa = 00.54-0.68) and slightly lower interobserver agreement (kappa = 0.52-0.56) was found for segmental score interpretation. When comparing the interpretive reproducibility before and after PTCA intra- and interobserver agreement was better after PTCA, probably reflecting the increase in normal scans after revascularization. CONCLUSIONS: In a group of consecutive male patients with stable angina pectoris interpretive reproducibility (overall and individual vessel diagnosis) was good to excellent. However, segmental scoring reproducibility was moderate to good.

Adult↗
PubMed2000

Cost effectiveness analysis of BMD referral for DXA using ultrasound as a selective pre-screen in a group of women with low trauma Colles' fractures.

Measurements of bone density (BMD) are central to the World Health Organisation (WHO) approach to the definition of osteoporosis. Dual energy X- ray absorptiometry (DXA) remains the gold standard technique for measuring the bone mineral density (BMD) but Quantitative Ultrasound (QUS) is an attractive alternative method of bone assessment because it is easy to use and relatively inexpensive. It has been suggested that QUS could be used as a selective population pre-screen, to maximise the cost effectiveness of referral for DXA assessment of BMD. We set out to examine how such an approach might perform in the assessment of women with low trauma Colles' fracture. In 46 women aged 50-80 (mean 67) years we used DXA to measure BMD at lumbar spine and hip, and heel bone ultrasound to measure Broad Band Attenuation (BUA) and Velocity of Sound (VOS). We calculated local costs of pounds sterling 45 for DXA and pounds sterling 15 for QUS. We identified a BUA threshold of 60 dB/MHz as most cost effective as pre-screen, and calculated a sensitivity of 93% and specificity of 84% in identifying those subjects who were subsequently identified as having osteoporosis by DXA. DXA assessment of all patients had a cost of pounds sterling 77 per osteoporotic subject identified. We examined the cost-effectiveness of using QUS as a pre-screen, only referring subjects for more expensive DXA assessment if BUA was less than 60 dB/MHz. However this approach had no advantage, still costing pounds sterling 78 per osteoporotic subject identified. QUS assessment does not appear cost-effective as a pre-screen for DXA, even in this high risk group of women with low trauma Colles' fracture. A QUS pre-screen would only be cost-effective if the scan could be performed at a substantially lower cost.

Absorptiometry, Photon↗
PubMed1999

Evaluation of melt agglomeration properties of polyethylene glycols using a mixer torque rheometer.

Lactose was melt agglomerated in a mixer torque rheometer with polyethylene glycol (PEG) 2000, 3000, 6000, 8000, 10 000, or 20 000 as meltable binder. A longer massing time caused an increase in mean torque until a maximum value after which the torque decreased. A smaller particle size of the PEG gave rise to a faster initial rise in mean torque. The higher viscosity of the PEG 20 000 resulted in a higher mean torque, whereas no clear difference in mean torque was obtained with the other PEGs. The binder concentration could be varied within a rather wide range without causing overwetting, the range being wider with PEG 3000 than with PEG 20 000. The mean torque values obtained were found to be related to the liquid saturation of the agglomerates. The reproducibility of the experiments was found to be very dependent on the experimental conditions, the highest binder viscosities and binder concentrations giving rise to a poor reproducibility. The results were compared with a few melt agglomeration experiments with PEG 3000 in a high shear mixer. The mixer torque rheometer was found not to be suitable for predicting melt agglomeration properties in the high shear mixer because of a marked difference in the shear forces in the two mixers.

Agglutination↗
PubMed1998

[Prevention of thrombosis in medical patients--documentation is missing].

A questionnaire regarding current routines for thromboprophylaxis was distributed to all 63 medical departments in Norwegian hospitals; 58 (92%) responded. All departments declared that they practiced prophylaxis against venous thromboembolism, and in most departments the decision (as to whether to practice prophylaxis) was left to the physicians. Written guidelines were used in only 12 departments, 21% of those who responded. The indications listed were those associated with a particular risk of thrombosis. Previous thrombosis and malignancy were listed less frequently than expected. There is a need for specific evidence regarding the efficacy and safety of thromboprophylaxis in medical patients. In our opinion this requires that further placebo-controlled studies be carried out.

Documentation↗
PubMed1998

Cutis/subcutis thickness at insulin injection sites and localization of simulated insulin boluses in children with type 1 diabetes mellitus: need for individualization of injection technique?

The study aimed to describe the variations of cutis/subcutis thickness at insulin injection sites in children with Type 1 diabetes mellitus and to localize the tissue position of a simulated insulin bolus in order to evaluate the need for individualization of injection technique in children. Cutis/subcutis thickness was measured by ultrasound in 47 children (25 girls and 22 boys) without compression (CSCUT) and with compression (CSCT) of the skin at 11 insulin injection sites. Tissue deposition of insulin was measured by ultrasound of a simulated insulin bolus of 200 microl of sterile air injected by the patients using their usual technique and site. On the thigh, 44% of girls and 95% of boys had a CSCT of less than 8 mm at one of the measured sites, while 16% of girls and 50% of boys had a CSCT of less than 6 mm at one injection site on the thigh and buttock. Significant differences in cutis/subcutis thickness in the same anatomical region were shown. CSCT was up to 35% less than CSCUT. The air bolus injection was placed inappropriately by 19% of children (using 8 mm needles). Unawareness of the skin thickness at the injection sites may contribute to inappropriate deposition. We propose that regular ultrasound measurements of subcutis depth at insulin injection sites be taken. This will allow the injection technique to be individualized (vertical or at an angle of 45 degrees). More children would be able to use the simpler vertical technique if 6 mm needles were used where available, or if even shorter (4 mm) needles were produced.

Adolescent↗
PubMed1998

Trauma admissions in the elderly: how does a patient's age affect the likelihood of their being admitted to hospital after a fracture?

In two projects we have studied patients presenting to Accident and Emergency (A&E) departments with a fracture, to examine how their age influences their likelihood of admission. Over 1 year from April 1994 we collected data on all 6467 Cardiff residents who presented to the city's A&E department with a fracture. In total 1226 (19%) were admitted. Overall, only 12% of those under 65, but 47% of older patients required admission. This was largely a reflection of the age-distribution of hip fracture, an injury for which admission is inevitable. In a subsequent study of eight A&E departments in South Wales we therefore considered the proportion of patients admitted following fractures at specific anatomical sites. In people over the age of 55 we identified 6889 fractures, 2115 (31%) of which led to admission. After standardisation to control for the age-distribution of incidence for different fracture sites, we found that the likelihood of admission was 22% greater for people aged over 65 years. Elderly people very often require hospital admission after a fracture, primarily as a consequence of the types of fractures that they tend to sustain. Admissions directly attributable to the effects of age and age-related medical, psychiatric and social comorbidity appear of more limited significance.

Adolescent↗
PubMed1998

Effect of leflunomide and cyclosporine on graft survival and changes in lymphocyte phenotypes in a rat heart allotransplantation model.

Cyclosporine-A (CSA) and leflunomide (LF) can delay or prevent organ graft rejection. We investigated the combination of LF, CSA and splenectomy on graft survival and changes in lymphocyte phenotypes (LP) in a rat allotransplantation model. In the study 19 Lewis rats were splenectomized prior to heterotopic heart transplantation. SPRD rats served as donors. The recipients were divided into three groups: A--five animals received CSA and LF for two weeks, B--five received intermittent CSA and LF for the whole investigation period and C--nine received no drug therapy. LP was quantified relatively by flow cytometric analysis. We found that graft survival was longer in group A (median 155 days, range 52-348) and B (341, range 338-342), compared to group C (8, range 7-13). The histological examination, however, revealed signs of rejection in all allografts. In group A all except one animal and in group C the morphological changes were characterized by severe acute rejection. In contrast, one animal in group A and all the animals in group B revealed signs of moderate acute rejection and in most animals signs of chronic rejection were also found. The reduction of Pan-T and CD4+ cells in group B compared to the control group was associated with no clinical rejection, while the increase of CD8+ cells in group C and partly in group A (except for animal 3) was associated with clinical rejection. No difference in LP was detected between groups A and B in the study period. We concluded that a combination of CSA, LF and splenectomy was efficient in preventing clinical rejection, however, there were signs of rejection morphologically even in animals without clinical rejection. The changes in LP over time could not predict the clinical outcome. However, increase in CD8+ cells was highly associated to clinical rejection among nonimmunosuppresed animals.

Animals↗
PubMed1997

The effect of ankle oedema on bone ultrasound assessment at the heel.

Relatively inexpensive, portable bone ultrasound systems are of particular relevance to disabled or elderly subjects, who may have problems with access to other forms of densitometry. The effects of local soft tissues on ultrasound measurements are poorly understood and, as ankle oedema is common in such subjects, we examined its consequences for bone ultrasound readings at the heel. Eleven elderly subjects (mean age 81 years) with below-knee pitting oedema were assessed using a direct-contact bone ultrasound system (CUBA Clinical). We made a total of 16 series of readings, 6 unilateral and 5 bilateral. In each series an initial reading was followed by repeated pressure over the measurement site to disperse oedema; subsequent readings were thus subject to a progressively lessening degree of local oedema, until a steady state was eventually reached in which no further oedema could be displaced. Heel width fell by a mean of 6.3 mm between initial and steady-state readings; consistent with the clinical appearance of moderate oedema, pitting to a mean depth of only 3.15 mm. Measurements in the presence of oedema were compared with those after its elimination, and oedema was shown to cause a mean reduction of 23.9 m/s in velocity of sound (VOS) and of 5.5 dB/MHz in broadband ultrasound attenuation (BUA). Both changes were equivalent to a fall by a quarter of one standard deviation of the reference range, and were significant at p < 0.05 on paired t-test. As the severity of oedema will vary through the day, and from day to day, measurement protocols for bone ultrasound should pay attention to the confounding effects of oedema.

Aged↗
PubMed1997

Chitooligosaccharides stimulate Atlantic salmon, Salmo salar L., head kidney leukocytes to enhanced superoxide anion production in vitro.

Chitosans and chitooligosaccharides stimulated Atlantic salmon, Salmo salar L., head kidney leukocytes in vitro to produce elevated levels of superoxide anion. Both soluble and insoluble chitooligosaccharides were stimulatory 2 and 7 days after addition. Protein-chitooligosaccharide conjugates were also stimulatory in vitro both at 2 and 7 days after addition. Deacetylation seemed to be of little importance for the stimulatory capacity. High concentrations of the 80% deacetylated chitosan/chitooligosaccharides were toxic to the leukocytes as judged by reduced reduction of nitroblue tetrazolium and morphology.

Acetylation↗
PubMed1997

Reliability of parathyroid hormone measurements in the period immediately following hip fracture.

AIM: As it is unclear whether parathyroid hormone (PTH) measurements performed immediately after hip fracture are reliable indicators of pre-fracture metabolic status, we set out to define how PTH levels are affected by hip fracture and its surgical repair. METHOD: In two longitudinal projects, we studied 12 patients presenting with hip fracture and eight patients undergoing elective hip replacement. PTH, calcium and 25-hydroxyvitamin D (25OHD) levels were measured on admission, 2 days and 1 week later and after recovery at least 2 months after initial admission. FINDINGS: In the subjects presenting with hip fracture, PTH levels during inpatient care were no different from those subsequently measured during the recovery period. In subjects undergoing elective hip surgery, PTH levels did not change following surgery and again remained unchanged into the recovery period. CONCLUSIONS: Measurements of PTH performed during inpatient care of those with hip fracture appear sufficiently reliable for use in assessment of metabolic status.

Aged↗
PubMed1997

Using audit to improve senior house officer training.

The British Geriatrics Society has described 16 training objectives for senior house officers (SHOs) in geriatric medicine. We have developed these into an audit standard, and in a controlled trial we consider the effectiveness of audit as a means of monitoring and improving SHO training. SHOs from three hospitals were sent a questionnaire asking about the adequacy of formal and informal training for each objective; there was a response rate of 87%. Results were presented at an audit meeting in one hospital, inadequacies of training identified and the hospital's programme of teaching modified appropriately. Two control hospitals remained unaware of the audit findings and were therefore unable to modify their training programmes. Re-audit at six months completed the audit cycle; the control hospitals showing no change between the two audits. In the intervention hospital the adequacy of training over the 16 objectives improved from 59% at first audit to 73% at re-audit. The initial audit had highlighted three target objectives as needing special attention; here the improvement from 38% to 69% was even more impressive, and statistically significant at p < 0.05 on chi 2 test. Thus, although a questionnaire approach is inevitably subjective and affected by SHO satisfaction, the discipline of audit appeared effective in identifying and correcting deficiencies in an SHO training programme.

Education, Medical, Graduate↗
PubMed1996

A simple model of recurrent epidemics.

A cellular automaton conceived as a simple model of disease spreading is investigated. We show that the steady-state of the model is described by a spatial organization of the infectious individuals on fronts and undamped temporal oscillations in the number of infectious individuals. This behaviour is observed both for a deterministic and a stochastic input of susceptible individuals, hence showing that recurrent epidemic behaviour can be persistent without any external forcing. The simplicity of the model suggests that such spatio--temporal behaviour can be obtained from nothing, but a direct transmission mechanism between nearest neighbors provided some mechanism for the introduction of new susceptible individuals, e.g., loss of immunity is present.

Computer Simulation↗