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Biomedical subjects

A Axelsson

Publications and source records attributed to A Axelsson.

At least 19 recordsLinked to original sources
PubMed2001

Superdeformation in the doubly magic nucleus (40)(20)Ca(20).

A rotational band with seven gamma-ray transitions between states with spin 2 Planck's constant and 16 Planck's constant has been observed in the doubly magic, self-conjugate nucleus (40)(20)Ca(20). The measured transition quadrupole moment of 1.80(+0.39)(-0.29)eb indicates a superdeformed shape with a deformation beta(2) = 0.59(+0.11)(-0.07). The features of this band are explained by cranked relativistic mean field calculations to arise from an 8-particle 8-hole excitation.

Journal Article↗
PubMed2001

Theories of chromatographic efficiency applied to expanded beds.

Various quantities such as plate height (HETP), number of plates (N), axial dispersion coefficient (Dax) and Bodenstein number (Bo) are used to describe the efficiency of, and dispersion in chromatographic columns. Different quantities highlight different aspects of the performance. Due to the expansion of expanded-bed columns, the information contained in some of these quantities is not the same for expanded beds as for packed beds. In this article the mentioned quantities are described and discussed both theoretically and related to experimental data. It is concluded that they are often used in a confusing way. Quantities modified to be more informative when comparing beds of different expansions are developed (N(EB) = N/expansion2 and HETP(EB) = HETP x bed expansion) and recommendations of which quantity to use in what situation are given.

Chromatography↗
PubMed2001

Hearing development in classical orchestral musicians. A follow-up study.

Using pure tone audiometry in 1995, a hearing reassessment was made in 56 classical musicians who participated in Axelsson & Lindgren's study 16 years earlier, in 1979. This study focuses on hearing development in these classical orchestra musicians, active in Göteborg, Sweden. The aim of the study is to evaluate the risk of progressive hearing loss during work in a classical orchestra. Another aim is to study possible hearing differences in females and males and to compare the high frequency pure-tone average values found in the study with two normal materials. The main findings were that the male, compared to the female musicians, showed a tendency toward a more pronounced, although not significant, hearing reduction in the high frequency region and higher threshold distribution within the 90th percentile than the females. This was found most often in the left ear. The median audiogram for all females showed a notch configuration at 6 kHz, compared to the males who had a high-tone sloping configuration. When comparing high frequency pure-tone average (HFPTA) values with ISO 7029, the females are distributed around the ISO 7029 median and well within the 90th percentile. The average among the males was equal with the median. Comparison with Davis normal population "all the sample, overall occupational group" showed a more even distribution of the HFPTA values around the median for both females and males on both occasions. This follow-up study showed no extended negative progress of the pure-tone hearing threshold values in spite of an additional 16 years of musical noise exposure.

Adult↗
PubMed2001

Hearing assessment of classical orchestral musicians.

Pure-tone audiometry was performed on 140 classical orchestral musicians employed at the Gothenburg Symphony Orchestra and the Gothenburg Opera in Sweden. This report is based on the results from hearing threshold measurements, presented as median audiograms according to gender, age group and instrument group. The results did not show severe hearing losses that could be attributed to exposure to musical noise. However, the study reflects the subjects' present hearing ability status and does not give an answer to the question of future hearing dysfunction. Female musicians were shown to have significantly better hearing thresholds in the high-frequency area than did male musicians. Furthermore, the median pure-tone hearing thresholds for the male musicians displayed a notch configuration at 6 kHz in the left ear, similar that of to noise-induced hearing loss. A small, but in general not significant, difference was detected when comparing the median hearing thresholds between each instrument group. Percussion and woodwind players displayed slightly worse hearing thresholds than did other musicians. Players of large string instruments had the best hearing threshold values. When comparing age groups and gender it was noted that the median hearing thresholds were stable and within 20 dB HL up to the age group of 40-49 years for both females and males.

Adult↗
PubMed2001

Bystander cardiopulmonary resuscitation: would they do it again?

During the last three decades, community education programs have been initiated with the purpose of teaching community citizens cardiopulmonary resuscitation (CPR). Millions of people have learned the technique. However, the frequency of bystander initiated CPR prior to emergency medicine service (EMS) arrival is still very low. This can lead one to ask if CPR training is optimal. Perhaps motivational aspects and psychological inhibitors to starting CPR should be included in CPR training. So far, CPR training has been skills oriented and has assumed that a bystander competent in CPR will intervene when required. However, this does not seem to be the case, as there are indications in recent research, for example, that the will to help and the courage to intervene are also needed. Bystanders who intervene in a cardiac arrest event improve the victim's chance of survival. However, there is little knowledge regarding the rescuers' reactions concerning their performance and whether they will overcome the trauma of the event and be prepared to do it again.

Altruism↗
PubMed2001

Measurement of skills in cardiopulmonary resuscitation--do professionals follow given guidelines?

Since it is suggested that only effective cardiopulmonary resuscitation (CPR) improves survival rates, quality control of training outcomes is important and comparisons between different training methods are desirable. The aim of this study was to test a model of quality assurance, consisting of a computer program combined with the Brennan et al. checklist, for evaluation of CPR performance. A small group of trained medical professionals (cardiac care unit nurses) (n = 10) was used in this pilot study. The result points out several points of concern: half of the participants did not open the airway prior to breathing control. Over 90% of all inflations were 'too fast' and 71% were 'too much'. Only 6.5% of the inflations were correct. On average, the participants made 5.4 inflations per minute. Concerning chest compressions, 40% were 'too deep' while only 4% were 'too shallow'. In spite of the fact that the participants had an average rate at 95 compressions per minute the number of compressions varied between 32 and 51 during 1 minute. When new guidelines are discussed, it would be beneficial if they were tested by a number of people to investigate if following the guidelines is at all possible.

Adult↗
PubMed2000

Use of holographic laser interferometry to study the diffusion of polymers in gels.

The aim of this study was to demonstrate the potential for holographic interferometry to be used for diffusion studies of large molecules in gels. The diffusion and partitioning of BSA (67,000 g/mol) and pullulans (5,900-112,000 g/mol) in agarose gel were investigated. The gel diffusion coefficients obtained for BSA were higher when distilled water was used as a solvent compared to those obtained with 0.1 M NaCl as the solvent. Furthermore, the gel diffusion coefficient increased with increasing BSA concentration. The same trend was found for liquid BSA diffusion coefficients obtained by DLS. BSA partition coefficients obtained at different agarose gel concentrations (2-6%, w/w) decreased slightly with increasing gel concentration. However, all BSA gel diffusion coefficients measured were significantly lower than those in pure solvent and they decreased with increasing agarose concentration. The gel diffusion coefficients obtained for pullulans decreased with increasing pullulan molecular weight. The same effect from increased molecular weight was seen in the liquid diffusion coefficients measured by DLS. The pullulan partition coefficients obtained decreased with increasing molecular weight. However, pullulans with a larger Stokes' radius than BSA had partition coefficients that were higher or approximately the same as BSA. This implied that the pullulan molecules were more flexible than the BSA molecules. The results obtained for BSA in this study agreed well with other experimental studies. In addition, the magnitude of the relative standard deviation was acceptable and in the same range as for many other methods. The results thereby obtained showed that holographic interferometry is a suitable method for studying diffusion of macromolecules in gels.

Diffusion↗
PubMed2000

Diffusion of lysozyme in gels and liquids. A general approach for the determination of diffusion coefficients using holographic laser interferometry.

A study on diffusion measurements of the protein lysozyme in liquids and agarose gels, at different pH and ionic strengths, has been performed using holographic laser interferometry. The measurements showed that the diffusive flux was very dependent on pH and ionic strength when the protein was not at its isoelectric point or when the charge of the lysozyme molecules was not screened by ions in the solution. Evaluation of the experimental data with Fick's law, resulted in diffusion coefficients for lysozyme that are strongly dependent on pH and ionic strength. Evaluation of the experimental data using a more general transport model, based on chemical potential gradients instead of concentration gradients resulted in lysozyme diffusion coefficients that are independent of pH and ionic strength. The chemical potential was estimated by using the Poisson-Boltzmann equation.

Diffusion↗
PubMed2000

How bystanders perceive their cardiopulmonary resuscitation intervention; a qualitative study.

The importance of bystander cardiopulmonary resuscitation (CPR) prior to arrival of the emergency medical service is well documented. In Sweden, CPR is initiated prior to emergency medical services (EMS) arrival in about 30% of cardiac arrests out-of-hospital, a figure which should be improved urgently. To do so, it is of interest to know more about the bystanders' perceptions of their intervention. A qualitative method inspired by the phenomenographic approach was applied to 19 bystanders who had performed CPR. In the analysis, five main categories and 14 subcategories emerged. The main categories were: to have a sense of humanity, to have competence, to feel an obligation, to have courage and to feel exposed. Interviews described how humanity and concern for another human being were the foundation of their intervention. CPR training offers the possibility to give appropriate help in this emergency. If the aim of CPR training was extended beyond teaching the skill of CPR to include preparation of the rescuer for the intervention and his/her reactions, this might increase the number of people able to take action in the cardiac arrest situation.

Cardiopulmonary Resuscitation↗
PubMed2000

Attitudes of trained Swedish lay rescuers toward CPR performance in an emergency. A survey of 1012 recently trained CPR rescuers.

59 years old. Only 1% had attended the course because of their own or a relative's cardiac disease. Ninety-four per cent believed there was a minor to major risk of serious disease transmission while performing CPR. When predicting their willingness to perform CPR in six scenarios, 17% would not start CPR on a young drug addict, 7% would not perform CPR on an unkempt man, while 97% were sure about starting CPR on a relative and 91% on a known person. In four of six scenarios, respondents from rural areas were significantly more positive than respondents from metropolitan areas about starting CPR. In conclusion, readiness to perform CPR on a known person is high among trained CPR rescuers, while hesitation about performing CPR on a stranger is evident. Respondents from rural areas are more frequently positive about starting CPR than those from metropolitan areas.

Adult↗
PubMed1999

Superporous agarose beads as a hydrophobic interaction chromatography support.

Superporous agarose beads were used as a support for hydrophobic interaction chromatography. These beads have large connecting flow pores in addition to their normal diffusion pores. The flow pores, which are approximately one fifth of the overall diameter of the superporous agarose beads, were earlier shown to give the beads improved mass transfer properties relative to homogeneous agarose beads (Gustavsson and Larsson, J. Chromatogr. A, 734 (1996) 231-240). Superporous agarose beads and homogeneous agarose beads of the same particle size range (106-180 microns) were derivatized with phenyl groups. The properties of the superporous beads were then compared with the homogeneous beads in the separation of a mixture of three model proteins (ribonuclease A, lysozyme and bovine serum albumin) at various superficial flow velocities from 30 to 600 cm/h. The superporous beads gave satisfactory separation at flow velocities five times higher than was possible for homogeneous beads. The performance of the two types of beads was also compared in the purification of lactate dehydrogenase from a beef heart extract at a superficial flow velocity of 150 cm/h. The superporous beads performed considerably better, leading to twice the purification factor and twice the concentration of the desired product. The results were interpreted using the theoretical treatment given by Carta and Rodrigues (Carta and Rodrigues, Chem. Eng. Sci., 48 (1993) 3927).

Adsorption↗
PubMed1999

Hypersensitivity to sound--questionnaire data, audiometry and classification.

This study included consecutive case histories and audiometry of 100 patients with hypersensitivity to sounds. There are several different conditions with the symptom of hypersensitivity to sounds. Hyperacusis is one of those and is seldom described in the literature. The term hyperacusis is often used synonymously with hypersensitivity to sound. We propose that there is a specific condition that could be termed hyperacusis. Hyperacusis is often elicited by loud sounds or by a number of other traumata or diseases. It is not typical of occupational noise exposure (with the exception of exposure to music). The typical patient is relatively young, the mean age being approximately 10 years less than for a population of patients with tinnitus or noise-induced hearing loss. In addition to hypersensitivity to sound, the patients often suffer from tinnitus (86%). Sounds are frequently painful and exposure to loud sounds worsens the condition for some time. The patients often have headaches. Pure tone audiograms show normal hearing or a slight high tone loss. The uncomfortable loudness level is markedly decreased, mostly less than 90 dB HL. Patients with hyperacusis may also be divided into those hypersensitive to the loudness of sounds with a decreased pure tone uncomfortable loudness level and those hypersensitive to certain specific sounds irrespective of loudness showing relatively high pure tone uncomfortable loudness levels and decreased uncomfortable loudness levels to specific sounds. With a careful history other conditions with the symptom of hypersensitivity to sound can be excluded.

Adolescent↗
PubMed1998

Direct measurements of convective fluid velocities in superporous agarose beads.

Superporous agarose beads contain two sets of pores, diffusion pores and so-called superpores or flow pores, in which the chromatographic flow can transport substances to the interior of each individual bead [Gustavsson and Larsson, J. Chromatogr. A 734 (1996) 231]. The existence of pore flow may be proven indirectly by the chromatographic performance of beads but it has never been directly demonstrated in a chromatographic bed. In this report, pore flow was directly measured by following the movement of micro-particles (dyed yeast cells) in a packed bed. The passage of the micro-particles through the superpores and through the interstitial pores was followed by a microscope/video camera focused on beads which were situated four layers from the glass wall. The video recordings were subsequently used to determine the convective fluid velocities in both the superpores and the interstitial pores. Experiments were carried out with three different bead size ranges, all of which contained superporous beads having an average superpore diameter of 30 microns. The superpore fluid velocity as % of interstitial fluid velocity was determined to be 2-5% for columns packed with 300-500-micron beads (3% average value), 6-12% for columns packed with 180-300-micron beads (7% average value) and 11-24% for columns packed with 106-180-micron beads (17% average value). These data were compared to and found to agree with theoretically calculated values based on the Kozeny-Carman equation. In order to observe and accurately measure fluid velocities within a chromatographic bed, special techniques were adopted. Also, precautions were made to ensure that the experimental conditions used were representative of normal chromatography runs.

Chromatography, Liquid↗
PubMed1998

Swelling kinetics of poly(N-isopropylacrylamide) gel.

In many gel applications the swelling and shrinking kinetics are very important, e.g. in controlled/slow release, where the kinetics determined the rate of out-diffusion of the active component, and in gel extraction where the gel is swollen and shrunk several times. In this study swelling kinetics of poly(N-isopropylacrylamide) gel (NiPAAm gel) was determined by monitoring the swelling process using a stereo microscope and a video camera. The swelling of spherical gel bodies could conveniently be studied after a temperature change. The results obtained were treated according to the approach of Tanaka and Fillmore, in which the swelling and shrinking of a gel is described as a motion of the gel network according to the diffusion equation. This was shown to be valid when the temperature changes are kept below the critical point of the gel. However, the model fails to describe the shrinking process when passing from below to above the critical temperature. The collective diffusion coefficient (D), defined as the osmotic bulk modulus divided by the friction factor, was determined by fitting to the experimental data. D was found to increase with temperature according to the Wilke-Chang relation D = 2.0.10(-11) + 7.6.10(-17).T/mu. The results were used to simulate the swelling/shrinking process. The simulations show the importance of having sufficiently small gel bodies to achieve a short swelling time.

Acrylic Resins↗
PubMed1998

Direct measurement of intraparticle fluid velocity in superporous agarose beads.

Superporous agarose beads contain both normal diffusion pores and special, very wide superpores through which part of the chromatographic flow is transported, a situation that may greatly improve the chromatographic performance. For the first time such pore flow was measured directly by following the movement of microparticles (dyed yeast cells) through superporous beads packed in a chromatographic bed. The passage of the microparticles through the superpores and through the interstitial pores was recorded by a microscope/video camera. The video recordings were subsequently used to determine flow paths as well as the convective fluid velocities in both the superpores and the interstitial pores. The superpore fluid velocity was found to be proportional to the ratio between the squares of the respective pore diameters, which is in agreement with the Kozeny-Carman equation. Values for two-dimensional and three-dimensional tortuosity of the flow paths were measured and calculated respectively.

Chromatography, Agarose↗
PubMed1998

Factors surrounding cardiopulmonary resuscitation influencing bystanders' psychological reactions.

The incidence of Sweden's out-of-hospital cardiac arrests averages 10000 annually. Each year bystanders initiate cardiopulmonary resuscitation (CPR) approximately 2000 times prior to arrival of emergency medical service (EMS). The aim of this study was to identify factors influencing the bystanders psychological reactions to performing CPR. We mailed a questionnaire to all bystanders who reported performing CPR to the CPR Centre of Sweden from autumn 1992 to 1995. The study included 544 bystander reports. Nine factors were found to be associated with bystanders experience in a univariate analysis. Among these were victim outcome (p < 0.0001), CPR duration (p = 0.0009) and their experience of the attitude of the EMS personnel (p = 0.004). In a multivariate logistic regression model, lack of debriefing following the intervention (p = 0.0001) and fatal victim outcome (p = 0.03) were independent predictors of a negative bystander psychological reaction. The importance of having someone to talk to following an intervention and the EMS personnel concern for the rescuer should be emphasised. The goal should be that critical incident debriefing is available to every bystander following his or her CPR attempt.

Attitude of Health Personnel↗
PubMed1998

Experience with the use of automated external defibrillators in out of hospital cardiac arrest.

AIM: To describe the sequences of arrhythmias, number of shocks delivered and the number of failures in a consecutive series of patients with out-of-hospital cardiac arrest attended by our emergency medical service (EMS) and in whom cardio-pulmonary resuscitation (CPR) was initiated and in whom automated external defibrillators (AEDs) were used. PATIENTS: All patients with out-of-hospital cardiac arrest attended by the EMS and in whom AEDs were used. Time for inclusion in the study: January 1st, 1987 to December 31st, 1992. RESULTS: In all there were 1781 out of hospital cardiac arrests during the study period. Among them AEDs were used in 383 cases (22%). The total number of interpreted rhythms delivered in these patients was 2719. Among all rhythm sequences coarse ventricular fibrillation (VF) was found on 375 occasions (14%); fine VF on 107 occasions (4%) and ventricular tachycardia (VT) on 12 occasions (0.4%). In ten cases with coarse VF (nine patients) the AED did not advise a shock (2.7%). In five of those nine patients a human error was interpreted as the explanation and in four there was a possible technical error. In these four patients defibrillation was delayed by 33-43 s, respectively. Among the 2225 rhythm sequences not judged as VF/VT the AED advised a shock on one occasion (0.04%). CONCLUSION: Among patients with coarse VF AED gave inaccurate instructions in 2.7%. However, the majority of the failures were judged to be caused by human errors.

Aged↗