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Biomedical subjects

J Lahtinen

Publications and source records attributed to J Lahtinen.

At least 19 recordsLinked to original sources
PubMed2006

Adhesion as an interplay between particle size and surface roughness.

Surface roughness plays an important role in the adhesion of small particles. In this paper we have investigated adhesion as a geometrical effect taking into account both the particle size and the size of the surface features. Adhesion is studied using blunt model particles on surfaces up to 10 nm root-mean-square (RMS) roughness. Measurements with particles both smaller and larger than surface features are presented. Results indicate different behavior in these areas. Adhesion of particles smaller than or similar in size to the asperities depend mainly on the size and shape of the asperities and only weakly on the size of the particle. For large particles also the particle size has a significant effect on the adhesion. A new model, which takes the relative size of particles and asperities into account, is also derived and compared to the experimental data. The proposed model predicts adhesion well over a wide range of particle/asperity length scales.

Journal Article↗
PubMed2004

Radiation monitoring strategy: factors to be considered.

In a nuclear or radiological emergency radiation measurements provide indispensable data needed in the management of the situation at hand. In order to assess the possible consequences correctly and to carry out proper countermeasures on time, the authorities must have a pre-prepared monitoring strategy at their disposal. There are, however, many different factors that affect a strategy. Thus, drawing up a comprehensive yet realistic emergency monitoring strategy is far from being an easy task. Some of the key factors related to strategies are reviewed and a simple way of producing a strategy plan is presented.

Decision Support Systems, Management↗
PubMed2001

Microbiological quality and shelf-life of vacuum-packaged 'gravad' rainbow trout stored at 3 and 8 degrees C.

Microbiological and sensory changes of vacuum-packaged 'gravad' rainbow trout slices were studied during storage at 3 and 8 degrees C. At the time of spoilage, after 27 and 20 days of storage at 3 and 8 degrees C, respectively, both mesophilic viable counts (MVC) and psychrotrophic viable counts (PVC) reached 10(6)-10(7) cfu/g at 3 degrees C and 10(7)-10(5) cfu/g at 8 degrees C. H2S-producing bacteria constituted a high proportion of the PVCs and lactic acid bacteria (LAB) counts were lower than the other determined bacterial counts. Sensory scores decreased with increasing MVC and PVC. The judges considered samples unfit for human consumption at MVC and PVC levels exceeding 10(6) and 10(7) cfu/g for samples stored at 3 and 8 degrees C, respectively. At respective levels of 10(7) and 10(8) cfu/g, most of the samples were deemed unfit. The main reasons for sensory rejection at both storage temperatures were the lack of the typical product odour or an ammonia off-odour and colour change to dark violet. The shelf-lives of the rainbow trout slices based on microbiological and sensory analyses were 20 days and 18 days at 3 and 8 degrees C, respectively.

Animals↗
PubMed2001

Scaling of random spreading in small world networks.

In this study we have carried out computer simulations of random walks on Watts-Strogatz-type small world networks and measured the mean number of visited sites and the return probabilities. These quantities were found to obey scaling behavior with intuitively reasoned exponents as long as the probability p of having a long range bond was sufficiently low.

Journal Article↗
PubMed1998

Neuromuscular functioning of athletes and non-athletes in the drop jump.

In many sports vertical jumping is important. This study compared neuromuscular functioning of the lower extremity muscles together with some kinetic and kinematic parameters before and during ground contact in drop jumps from two heights [0.4 m (DJ40) and 0.8 m (DJ80)] in 7 highly trained triple-jumpers and 11 physically active controls. The triple-jumpers jumped 32% higher in DJ40 and 34% higher in DJ80, had shorter braking and total contact times, and greater average and peak vertical ground reaction forces than the controls. In both drop jumps in the electromyogram pre-activity of the vastus lateralis and gastrocnemius muscles started earlier in the jumpers than in the controls. For the control group the increase in dropping height was associated with a decrease in the propulsion force, and resulted in more extended knee and ankle angles at touch down and more flexed angles at the deepest position than for the jumpers. All angular displacements for DJ80 were larger than for DJ40 in the control group. The triple jumpers and control subjects differed with respect to their neuromuscular functioning in the drop jump exercise and they responded in a different way to the increase in dropping height.

Adult↗
PubMed1998

Computed tomographic evaluation of retrosternal adhesions after pericardial substitution.

BACKGROUND: Reoperative median sternotomy can result in cardiac injury and serious bleeding, with the rate ranging from 2% to 6%. Closure of the native pericardium can maintain a preventing plane of cleavage. In patients in whom primary pericardial closure is not possible, several substitutes have been tried with variable results. We conducted a prospective study to evaluate the clinical feasibility of polytetrafluoroethylene and polyglycolic acid patches as pericardial substitutes, using computed tomography for imaging the postoperative state of the retrosternal space. METHODS: The basic population comprised 540 patients who were scheduled for coronary artery bypass grafting, and 52 of them who met the research criteria were chosen for computed tomographic evaluation after 5 years after the primary operation. RESULTS: As a substitute, polytetrafluoroethylene seemed to be less adhesive to the posterior surface of the sternum. Total adhesion scores were also statistically significant (p < 0.001) to the advantage of polytetrafluoroethylene over polyglycolic acid as a pericardial substitute. CONCLUSIONS: Polytetrafluoroethylene membrane seems to be capable of minimizing retrosternal adhesion formation and thus it may protect the heart during subsequent reoperative sternotomy.

Coronary Artery Bypass↗
PubMed1998

Options for the management of poststernotomy mediastinitis.

The management of 27 consecutive deep sternotomy wound infections is reviewed. In 22 cases the initial treatment was debridement, sternal refixation and dilute antibiotic irrigation via multiple irrigation-suction catheters. In the nine cases (41%) in which these measures failed, more extensive sternal and costal cartilage debridement and closure with a muscle flap were performed. Five cases were initially managed with major reconstructive surgery. For reconstruction, a bilateral pectoralis major myocutaneous flap was used alone in eight cases, while in six the flap was insufficient to obliterate the whole poststernectomy space, and was supplemented with rectus abdominis muscle. Early mediastinitis can be effectively treated with thorough wound debridement and mediastinal irrigation, but if there is a two-week delay from the initial sternotomy to manifestation of infection, radical debridement with muscle flap closure should be seriously considered.

Aged↗
PubMed1998

Pericardial closure with polytetrafluoroethylene surgical membrane or biodegradable polyglycolic acid mesh after coronary artery bypass surgery--a baseline report.

BACKGROUND AND AIMS: Complete and tight closure of the native pericardium may kink or even occlude bypass grafts after coronary artery bypass grafting (CABG) and therefore the feasibility of tight closure has been debated. The growing number of reoperations has raised the question how to reduce the risk of damage of the right ventricle and patent grafts. We are performing a prospective randomized trial aiming to evaluate the feasibility of polytetrafluoroethylene (PTFE) surgical membrane and biodegradable polygycolic acid (PGA) mesh as pericardial substitutes for closure purposes in patients undergoing primary isolated CABG surgery. MATERIAL AND METHODS: The series comprises 540 patients who underwent a primary isolated CABG procedure at the Oulu University Hospital from October 1989 to May 1994. RESULTS AND CONCLUSIONS: The baseline results suggest that the PTFE and PGA materials seem to be similar despite the subtle early expression of tamponade related to the PTFE membrane after postoperative bleeding.

Adult↗
PubMed1997

Surgical and long-term outcome of graft replacement of aneurysms of the descending thoracic aorta. Analysis of 28 consecutive cases.

A consecutive series of 28 patients operated on at the Oulu University Hospital during the years 1974-1994 for aneurysms of the descending thoracic aorta is presented. Twenty-five cases were elective and three were operated on as emergencies. Their mean age was 58 years. During the aortic cross-clamp, circulatory support of the lower body, was used in 27 cases as follows: a direct aorto-femoral shunt without a pump (12/28), left-heart bypass (11/28) or femoro-femoral perfusion (4/28). Hospital mortality was 14% (4/28). One patient with a ruptured aneurysm died of renal failure, but there were no other renal complications. None had paraplegia postoperatively. Three had symptoms of paraparesis, but only one of them had a slight permanent discomfort while walking. The mean follow-up time was 100 months, range 2-242 months. Late actuarial survival including hospital mortality, was 65% at 5 years and 41% at 10 years, reflecting the generalized aortic disease with a high risk of very late rupture (4) and other manifestations of atherosclerosis with myocardial infarction (6) or cerebral atherosclerosis (1), the remaining late deaths being unrelated. The efficacy of lower body circulatory support in avoiding peroperative renal and spinal cord ischaemic complications is demonstrated.

Adult↗
PubMed1996

Acute abdominal pain in adults.

The purpose of this prospective study was to elucidate the characteristics of adult patients with acute abdomen admitted to a Finnish university hospital. A total of 639 patients entered the study. The most common cause of acute abdomen was non-specific abdominal pain (NSAP) (33.0%) followed by acute appendicitis (23.3%) and acute biliary disease (8.8%). The male:female ratio was 47:53 in the whole study population, but there were differences in the age and sex distributions when studied by diagnosis. NSAP was mainly presented in young women, but also in patients over 75 years of age. Acute appendicitis was most frequently found in young men, and biliary disease was most common in elderly women. A male predominance was noted in cases of alcoholic pancreatitis and gastritis, renal stones and peptic ulcer. Young women and elderly patients were slightly over-represented in the study population when compared with the whole population residing within the study area. 43% of the patients were operated on, and surgery was most common in patients aged 55-64 years and 15-24 years. Altogether 15% of the patients were discharged without hospitalisation. Twelve patients (1.9%) died of various causes, the most common of which was malignancy (four patients). In conclusion, a considerably large proportion (one third) of cases with acute abdomen remained without any specific explanation. Further, age and gender seem to be important factors when the most probable cause of acute abdomen is to be considered. Operative treatment is necessary in almost half of cases, and mortality for acute abdomen is low.

Abdomen, Acute↗
PubMed1996

The outcome of elderly patients after operation for acute abdomen.

A retrospective analysis of 224 patients was carried out to evaluate the outcome of elderly patients after operation for acute abdominal pain. The mean (+/- SD) age of the patients was 74.6 (+/- 6.4) years (range 65-96) and the male/female ratio was 104/120. The most common causes for an emergency operation were acute biliary disease (26%), acute appendicitis (18%), gastrointestinal cancer (11%) and incarcerated hernia (10%). Twenty-nine patients (13%) died during the one-month postoperative period. The most common causes of death were gastrointestinal cancer (24%), ischaemic heart disease (14%) and complicated peptic ulcer disease (14%). Ninety-two (41%) patients had non-lethal postoperative complications, the commonest of which were wound infection or dehiscence (28%), urinary tract infection (17%), and paralytic ileus (8%). Ten patients were reoperated on for postoperative complications. The mean hospitalization time was 12.5 days (range 1-99). The results in the analysis of the long-term outcome (mean follow-up time 21 months) revealed that 17% of the primarily survived patients had died. Living patients were satisfied with the treatment and only a few patients were institutionalised after surgery. We conclude that both the short-term and long-term outcome of elderly patients after an emergency abdominal operation is good in benign diseases, and active surgery is justified.

Abdomen, Acute↗
PubMed1995

The long-term outcome after negative appendix operation.

We evaluated the long-term outcome of "negative appendix" (NA) by analysing the follow-up results of 76 patients identified from a group of 670 appendectomized patients. Randomly selected and histologically proven cases of true acute appendicitis (TA) matched for age and sex were identified to construct case control pairs. Special interest was focused on gender and age, by analysing the results separately in men and women in two age groups (15-39 years and > or = 40 years). The results showed that NA was most common in women aged 15-39 years (21% of appendectomized cases in this age group). At follow-up examination after a mean follow-up of 2.9 years two-thirds of patients were symptomfree. Women aged 15-39 years had significantly more complaints (P < 0.05) and findings (P < 0.05) than patients with TA. In women aged > or = 40 years no significant differences were detected, nor in either age groups in men. Lactose intolerance was the most common finding in symptomatic patients. In conclusion, patients with NA were mostly young women. At long-term follow-up the great majority of patients were symptomfree and appeared not to have developed any serious disease. Routine follow-up for patients with NA does not thus seem necessary.

Adolescent↗
PubMed1993

Biomechanical effects of fatigue during continuous hurdle jumping.

Jumping drills that include several successive take-offs are popular in many sports events. An understanding of the effects of fatigue on biomechanical parameters during continuous jumping drills is important when selecting drills and their durations for sports training. In the present study, effects of continuous hurdle jumping on myoelectrical (EMG) activity, ground reaction forces, vertical movements of the body's centre of mass and knee joint angle kinematics were studied among eight male volleyball players (age 20-26 years). The subjects jumped hurdles (height 0.65 m) continuously for 45 s with bilateral foot contacts. All of the take-offs were performed from force-platforms which registered the three components of ground reaction force. The two middle take-offs in both directions were used for further analysis. Knee angular data were recorded by an electrical goniometer for determination of angular displacement and velocity. The jumping was videotaped sagittally to determine the location of the centre of mass at different phases of contact and flight, as well as to calculate the movement amplitude for the centre of mass. The EMG activity was monitored using surface electrodes, full-wave rectified and averaged for a pre-contact period of 55 ms as well as for the eccentric and concentric phases of contact for the M. rectus femoris, vastus lateralis and vastus medialis. The ground reaction forces and knee angular data were used to determine the eccentric and concentric phases of contact. The average EMG activity of the knee extensor muscles during the eccentric and concentric phases of contact increased during the jumping drill.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

A nuclear incident at a power plant in Sosnovyy Bor, Russia.

Several radionuclides were identified in the surface air in Finland following a nuclear incident in Sosnovyy Bor on 24 March 1992. In addition to gases, the release contained small uranium fuel particles. The radionuclide concentrations were of the same order of magnitude as the concentrations detected in Northern Finland in 1987 after the nuclear explosion in Novaya Zemlya (1 mBq m-3) but five orders of magnitude smaller than the concentrations during the Chernobyl accident in 1986. The radiological consequences in Finland were insignificant. However, studies show that even a minor release, across the sea and more than 100 km away, can be detected and important information, including the time of the incident and the composition of the release and the burn-up of the damaged fuel, can be revealed by the most accurate radioactivity measurements.

Accidents↗
PubMed1992

Results of 500 general surgery patients operated on in the ambulatory surgery unit.

This study examined the outcome of 597 general surgery operations performed on 500 patients in the ambulatory surgery unit of the University Hospital of Kuopio between November 1989 and May 1990. Endoscopies were excluded from the study. Spinal (41.0%) and local infiltration (31.2%) were the most often used forms of anaesthesia. During anaesthesia 15.8% of patients required treatment for hypotension, and 13.6% for bradycardia. Of the 351 (70.2%) patients, who returned the one month follow-up questionnaire, 41 (11.7%) had visited a doctor postoperatively. The main reasons for this visit were pain in 41 (100%), minor bleeding in 24 (58.5%) and inflammation in 16 (39.0%) patients. No deaths or other major complications were observed. 92% of the patients were satisfied with the treatment and anaesthesia.

Adolescent↗