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Biomedical subjects

K H Andersen

Publications and source records attributed to K H Andersen.

At least 19 recordsLinked to original sources
PubMed2002

Pattern dynamics of vortex ripples in sand: nonlinear modeling and experimental validation.

Vortex ripples in sand are studied experimentally in a one-dimensional setup with periodic boundary conditions. The nonlinear evolution, far from the onset of instability, is analyzed in the framework of a simple model developed for homogeneous patterns. The interaction function describing the mass transport between neighboring ripples is extracted from experimental runs using a recently proposed method for data analysis, and the predictions of the model are compared to the experiment. An analytic explanation of the wavelength selection mechanism in the model is provided, and the width of the stable band of ripples is measured.

Journal Article↗
PubMed2001

Stability balloon for two-dimensional vortex ripple patterns.

Patterns of vortex ripples form when a sand bed is subjected to an oscillatory fluid flow. Here we describe experiments on the response of regular vortex ripple patterns to sudden changes of the driving amplitude a or frequency f. A sufficient decrease of f leads to a "freezing" of the pattern, while a sufficient increase of f leads to a supercritical secondary "pearling" instability. Sufficient changes in the amplitude a lead to subcritical secondary "doubling" and "bulging" instabilities. Our findings are summarized in a "stability balloon" for vortex ripple pattern formation.

Journal Article↗
PubMed2001

Dynamical models for sand ripples beneath surface waves.

We introduce order parameter models for describing the dynamics of sand ripple patterns under oscillatory flow. A crucial ingredient of these models is the mass transport between adjacent ripples, which we obtain from detailed numerical simulations for a range of ripple sizes. Using this mass transport function, our models predict the existence of a stable band of wave numbers limited by secondary instabilities. Small ripples coarsen in our models and this process leads to a sharply selected final wave number, in agreement with experimental observations.

Journal Article↗
PubMed1999

[Bowing fracture of the ulna with concomitant dislocation of the distal radioulnar joint].

This work presents the first case of bowing fracture of the ulna associated with dislocation of the distal radioulnar joint. Etiology, radiographs and treatment are described and discussed. Bowing fractures are frequently missed on primary examination, mainly due to their rarity and the fact that the primary examination in the accident and emergency department is undertaken by junior doctors. We find that careful clinical examination combined with good radiographs should reveal the diagnosis. As closed reduction of bowing fractures may be very difficult to carry out, open reduction may frequently be preferable.

Adolescent↗
PubMed1999

Shell model for time-correlated random advection of passive scalars.

We study a minimal shell model for the advection of a passive scalar by a Gaussian time-correlated velocity field. The anomalous scaling properties of the white noise limit are studied analytically. The effect of the time correlations are investigated using perturbation theory around the white noise limit and nonperturbatively by numerical integration. The time correlation of the velocity field is seen to enhance the intermittency of the passive scalar.

Journal Article↗
PubMed1998

[Heat of polymerization of bone cement can induce cardiac arrest].

Total hip arthroplasty is associated with cardiopulmonary complications including cardiac arrest. We present one of four cases of cardiac arrest, two of the cases were fatal. The pathogenesis suggested to explain these complications is venous air embolism, generated by the methylmethacrylate bone cement polymerization causing thermal blood damage. To prevent this happening cortical bone allotransplantation around the prosthesis and bone cement with a low temperature of polymerization may be used.

Aged↗
PubMed1998

[Ségond fracture in acute knee injuries].

Two patients with a lateral tibia avulsion fracture (Ségond fracture) are presented. The correlation between the Ségond racture and rupture of the anterior cruciate ligament is pointed out, as well as the fact that patients with Ségond fracture and rupture of the anterior cruciate ligament often have other injuries such as meniscus lesions and lesion of the medial collateral ligament.

Adult↗
PubMed1994

Alcohol-induced brain growth restrictions (microencephaly) were not affected by concurrent exposure to cocaine during the brain growth spurt.

The prevalence of concomitant use of alcohol and cocaine among drug abusers has raised concern about the possible increased risk of fetal damage. The aim of this study was to assess the interactive effects of alcohol and cocaine on lethality, somatic growth, and brain growth using an animal model system. Sprague-Dawley rat pups were used as subjects. They were randomly assigned to 1 of the 9 artificially reared groups which varied with respect to the combination treatments of cocaine (0, 40, or 60 mg/kg) and alcohol (0, 3.3, or 4.5 g/kg). All artificially reared pups were given daily cocaine and alcohol treatments during a major part of the brain growth spurt period (postnatal days 4-9). An additional group of suckled control animals raised by their natural dams was included to control for artificial rearing. The results are summarized as follows: 1) Drug-induced lethality was higher in cocaine-treated groups when compared with non-cocaine-treated groups, and the concurrent administration of high doses of alcohol and cocaine significantly increased the mortality rate. 2) Somatic growth, in terms of body weight, was not affected by alcohol, cocaine, or the combination of both drugs using the artificial rearing technique. 3) Alcohol exposure during this brain growth spurt period significantly reduced whole brain weight, as well as forebrain, cerebellum, and brain stem weights. 4) In contrast to alcohol, cocaine failed to exert a detrimental effect on brain weight measures during this early postnatal period.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Oesophageal intubation can be undetected by auscultation of the chest.

Prompt detection of oesophageal intubation is a primary concern in anaesthetic practice. This blind, randomised study evaluates three widely used tests of intubation. Forty patients had both their trachea and oesophagus intubated, each patient was studied twice. Auscultation of the epigastrium, right and left axilla is more reliable than auscultation of the chest, and the anaesthetist's feeling when he squeezes the bag. P = 0.001 and P = 0.048, respectively. The tests were carried out after gastric distension with gas had occurred. We conclude that auscultation of epigastrium, right and left axilla, are recommended.

Abdomen↗
PubMed1992

[Intraoperative complications during cementation of hip arthroplasty. Avoiding air embolization during cementation].

Circulatory collapse is known to occur during cementation of hip arthroplasty. The pathogenesis is multifarious, but the most important cause is believed to be formation of air embolism during insertion and cementation of the femoral component followed by air embolism in the heart. Inserting the cement retrogradely with a cement gun following distal plugging of the femoral cavity with spongiosa and using a plastic catheter for suction drainage reduces the air embolisation. Cement producing as little heat as possible during the setting should be used. Maintaining anaesthesia with N2O air embolism and should be avoided during and after cementation. Pre- and intraoperative care of the patient's circulation and oxygenation is essential. The use of pulse oximetry, capnography and precordially recorded Doppler ultrasound are recommended for monitoring air embolism.

Anesthesia, Inhalation↗
PubMed1991

[Methods for ensuring correct tracheal intubation. A review].

To confirm correct intubation of the trachea, the literature mentions the following methods: Auscultation of thorax, the sensation of normal ventilation, gastric and thorax movement, condensation of water vapor in the tube lumen, external palpation on the patient's neck of the tube and the cuff, tactile palpation through the patient's mouth of the tube, x-ray of thorax and detection of hemoglobin oxysaturation with pulse oximetry. These methods can be used, but cannot be recommended, because they are not reliable. The following methods are recommended in the literature as reliable: Repeated laryngoscopy when there are direct visualization of the vocal cords, fiberoptic bronchoscopy, suction on the tube with a 60-ml syringe, auscultation of the upper abdomen and lungs and end-tidal carbon dioxide measurement. For the daily routine, control, of the endotracheal tube placement, by auscultation over the epigastrium, then in the right and left axilla, and continuous measurement of carbon dioxide in the expired air are recommended.

Auscultation↗
PubMed1990

Illicit anabolic steroid use: a controlled personality study.

The illicit use of anabolic steroids for strength and cosmetic reasons appears to be an increasing problem. Although alcohol and drug abuse have been associated with increased risk for personality psychopathology, the personality correlates of illicit anabolic steroid abuse are unknown. To determine whether personality psychopathology is common among anabolic steroid users, we evaluated a series of illicit anabolic steroid users and compared them with a group of age-matched alcoholics and 2 control groups. Anabolic steroid users were found to have increased risk for personality psychopathology compared with community controls. The risk appeared to be partially explained by a group membership effect. Additionally, similar to the alcoholic group, illicit anabolic steroid users also demonstrated significant antisocial traits.

Adolescent↗
PubMed1989

[Complications following preventive treatment of thromboembolism with Dihydergot-heparin].

The observation of two cases of ergotism after administration of dihydroergotamine (Dihydergot-heparin (DHEH], led to review of the literature concerning documentation of the use of this drug in postoperative thromboembolism prophylaxis and the incidence of complications to this treatment. DHE is supposed to exert a selective constrictive effect on veins. There are now, however, numerous reports of ergotism because of arterial spasm. Some authors find better thromboembolic prophylactic effect, when DHE is used in combination with low-dose heparin (LDH) while others cannot show any advantages of using this drug. Several trials show that the best method for thromboembolic prophylaxis consists of graduated supportive stockings (TED) combined with LDH. The use of DHE in postoperative thromboembolism prophylaxis cannot be recommended. TED combined with LDH should be preferred.

Dihydroergotamine↗
PubMed1989

Behavioral performance and seizure activity of lithium-intoxicated Sprague-Dawley rats treated with theophylline.

Male Sprague-Dawley rats were divided into four groups that were treated with various combinations of lithium, saline, and theophylline, i.e., saline/saline, saline/theophylline, lithium/theophylline, and lithium/saline. Neurobehavioral testing of cerebellar and neuromuscular functioning, and determination of the effect of the drug combinations on the animals' seizure threshold concluded that while theophylline increases lithium clearance, it does not exacerbate lithium neurotoxicity.

3-Mercaptopropionic Acid↗