High-Frequency Sound in a Unitary Fermi Gas.

We present an experimental and theoretical study of the phonon mode in a unitary Fermi gas. Using two-photon Bragg spectroscopy, we measure excitation spectra at a momentum of approximately half the Fermi momentum, both above and below the superfluid critical temperature T_{c}. Below T_{c}, the dominant excitation is the Bogoliubov-Anderson (BA) phonon mode, driven by gradients in the phase of the superfluid order parameter. The temperature dependence of the BA phonon is consistent with a theoretical model based on the quasiparticle random phase approximation in which the dominant damping mechanism is via collisions with thermally excited quasiparticles. As the temperature is increased above T_{c}, the phonon evolves into a strongly damped collisional mode, accompanied by an abrupt increase in spectral width. Our study reveals strong similarities between sound propagation in the unitary Fermi gas and bosonic liquid helium.

Energy and contact of the one-dimensional Fermi polaron at zero and finite temperature.

We use the T-matrix approach for studying highly polarized homogeneous Fermi gases in one dimension with repulsive or attractive contact interactions. Using this approach, we compute ground state energies and values for the contact parameter that show excellent agreement with exact and other numerical methods at zero temperature, even in the strongly interacting regime. Furthermore, we derive an exact expression for the value of the contact parameter in one dimension at zero temperature. The model is then extended and used for studying the temperature dependence of ground state energies and the contact parameter.

Exotic superfluid states of lattice fermions in elongated traps.

We present real-space dynamical mean-field theory calculations for attractively interacting fermions in three-dimensional lattices with elongated traps. The critical polarization is found to be 0.8, regardless of the trap elongation. Below the critical polarization, we find unconventional superfluid structures where the polarized superfluid and Fulde-Ferrell-Larkin-Ovchinnikov-type states emerge across the entire core region.

Induced interactions and the superfluid transition temperature in a three-component Fermi gas.

We study many-body contributions to the effective interaction between fermions in a three-component Fermi mixture. We find that effective interactions induced by the third component can lead to a phase diagram different from that predicted if interactions with the third component are neglected. As a result, in a confining potential a superfluid shell structure can arise even for equal populations of the components. We also find a critical temperature for the BCS transition in a 6Li mixture which can deviate strongly from the one in a weakly interacting two-component system.

Strongly interacting Fermi gases with density imbalance.

We consider density-imbalanced Fermi gases of atoms in the strongly interacting, i.e., unitarity, regime. The Bogoliubov-de Gennes equations for a trapped superfluid are solved. They take into account the finite size of the system, as well as give rise to both phase separation and Fulde-Ferrel-Larkin-Ovchinnikov-type oscillations in the order parameter. We show how radio-frequency spectroscopy reflects the phase separation, and can provide direct evidence of the FFLO-type oscillations via observing the nodes of the order parameter.

Beyond linear response spectroscopy of ultracold fermi gases.

We study rf spectroscopy of ultracold Fermi gas by going beyond the linear response in the field-matter interaction. Higher order perturbation theory allows virtual processes and energy conservation beyond the single-particle level. We formulate an effective higher order theory, which agrees quantitatively with experiments on the pairing gap and is consistent with the absence of the mean-field shift in the spin-flip experiment.

Signatures of superfluidity for Feshbach-resonant Fermi gases.

We consider atomic Fermi gases where Feshbach resonances can be used to study the whole BCS-Bose-Einstein condensate crossover. We show how a probing field transferring atoms out of the superfluid can be used to detect the onset of the superfluid transition in the high-T(c) and BCS regimes. The number of transferred atoms, as a function of the energy given by the probing field, peaks at the gap energy. The shape of the peak is asymmetric due to the single particle excitation gap. Since the excitation gap also includes a pseudogap contribution, the asymmetry alone is not a signature of superfluidity. The incoherent nature of the noncondensed pairs leads to broadening of the peak. The broadening decays below the critical temperature, causing a drastic increase in the asymmetry. This provides a signature of the transition.

Pairing gap and in-gap excitations in trapped fermionic superfluids.

We consider trapped atomic Fermi gases with Feshbach-resonance enhanced interactions in pseudogap and superfluid temperatures. We calculate the spectrum of radio-frequency (or laser) excitations for transitions that transfer atoms out of the superfluid state. The spectrum displays the pairing gap and also the contribution of unpaired atoms, that is, in-gap excitations. The results support the conclusion that a superfluid, in which pairing is a manybody effect, was observed in recent experiments on radio-frequency spectroscopy of the pairing gap.

Biodegradation and strength retention of poly-L-lactide screws in vivo. An experimental long-term study in sheep.

BACKGROUND AND AIMS: Poly-L-lactide implants have gained popularity in the fixation of fractures and osteotomies in the past decade. The aim of the present experimental long-term study was to examine the degradation and strength retention of self-reinforced poly-L-lactide (SR-PLLA) lag-screws and the bone tissue response. MATERIAL AND METHODS: A total of 27 young adult sheep were used. Self-reinforced poly-L-lactide (SR-PLLA) lag-screws of 6.3 mm were implanted in the left proximal femur of nine sheep. At two, three and five years three of the sheep were sacrificed and the degradation was studied radiologically, microradiographically and histologically. For the strength retention measurements five SR-PLLA lag-screws of 6.3 mm and five lag-screws of 4.5 mm were implanted in the subcutaneous tissue of the five sheep and lag-screws of 6.3 mm for the pull-out test in the left proximal femur of 20 sheep. At 0, 12, 18, 24, 32, and 36 weeks bending and shear strength, molecular weight and pull-out measurements were performed. RESULTS: At five years no SR-PLLA material could be seen. The implant area was surrounded by high density bone with bone ingrowth in the screw area. At 36 weeks the bending strength of the 6.3 mm screws had decreased from 257.9 MPa to 36.4 MPa and the shear strength from 131.8 MPa to 19.8 MPa. The pull-out strength of the lag-screws of 6.3 mm in diameter decreased from 1507 N to 331 N in 24 weeks. CONCLUSIONS: SR-PLLA lag-screws showed high initial values, a controlled strength retention and gradual degradation process making the use of them safe also in demanding fixations.

Comparison of absorbable poly-L-lactide and metallic intramedullary rods in the fixation of femoral shaft osteotomies: an experimental study in rabbits.

An osteotomy of the distal femoral diaphysis was fixed with an intramedullary self-reinforced poly-L-lactide (SR-PLLA) rod in 22 and with a metallic rod in 38 skeletally mature rabbits. Histomorphometric and quantitative computed tomography (QCT) were performed to assess time-related changes in the consolidation process of the osteotomy of cortical bone and development of the external callus. The follow-up times were 8, 16, 24, and 48 weeks for radiologic and 16, 24, and 48 weeks for histologic studies; 19/22 of the SR-PLLA and 34/38 of the metallic fixed osteotomies healed during the observation periods. On microscopic evaluation, no difference was found in histologic parameters such as external callus area and fraction, and endosteal callus area and fraction between SR-PLLA and metallic fixed osteotomies. The total external callus area increased up to 16 weeks and subsequently decreased linearly over time in both experimental groups. However, the mean endosteal bone area and fraction decreased after 16 weeks in metallic fixated femora, while in the SR-PLLA fixated femora, both these values increased, being greater in the SR-PLLA group. The mean external callus QCT density decreased after 8 weeks in both experimental groups, the decrease being greater in the SR-PLLA group. Nevertheless, no significant difference was detected between SR-PLLA and metallic fixed femora in any of the follow-ups. These results suggest that both SR-PLLA and metallic rods are suitable in the fixation of femoral shaft osteotomies in rabbits. Furthermore, SR-PLLA rod fixation seems to have a minor stress-shielding effect.

PACS in Töölö hospital.

A 3-year PACS project was started in 1997 and completed in 1999 with filmless radiology and surgery. An efficient network for transferring images provides the infrastructure for integration of different distributed imaging systems and enables efficient handling of all patient-related information on one display station. Because of the need for high-speed communications and the massive amount of image data transferred in radiology, ATM (25, 155 Mbit/s) was chosen to be the main technology used. Both hardware and software redundancy of the system have been carefully planned. The size of the Dicom image library utilizing MO discs is currently 1.2 TB with 300 GB RAID capacity. For the increasing amount of teleradiologic consultations, a special Dicom gateway is planned. It allows a centralized and resilient handling and routing of received images around the hospital. Hospital-wide PACS has already improved the speed and quality of patient care by providing instant access to diagnostic information at multiple locations simultaneously. The benefits of PACS are considered from the viewpoint of the entire hospital: PACS offers a method for efficiently transporting patient-related images and reports to the referring physicians.

Key elements of the implementation of a quality system in three Finnish clinical laboratories.

The aim of the study was to discover how an implemented quality system succeeded in fulfilling the personnel and management expectations and to identify the factors that facilitate or hinder quality management implementation in clinical laboratories. The concepts assessed include leadership (commitment and change management), clear and common goals, human recourses focus, client focus, management by fact and process improvement. The quality process in the laboratories had not, even after 3-4 years, reached a level of acceptance allowing its use as a daily development tool. The factors that predict a success of the quality system include willingness to improve the laboratory services and to keep the process going and good atmosphere at work. However, the study showed that the senior managers of the laboratory should take a more visible role in leading the change, and emphasize more explicitly the long-term goals. The middle managers (physicians, biochemists and head technologists) should arrange opportunities for the staff to participate in the system and disseminate the information on, and practical applications of, the quality principles and tools. The staff should be more active in finding new information and in participating in the system.

Factors affecting neurosensory disturbance after mandibular bilateral sagittal split osteotomy.

PURPOSE: The current study evaluated the incidence of subjective neurosensory disturbances after bilateral sagittal split osteotomy (BSSO) in relation to gender, age, indication for osteotomy, magnitude of mandibular movement, degree of manipulation of the inferior alveolar nerve at operation, side of the mandible operated, and complications during and after surgery. PATIENTS AND METHODS: Thirty patients (60 sides) who had undergone a BSSO were followed up for 1 year after operation. The patients were classified into different groups according to gender, age, indication for osteotomy, magnitude of mandibular movement, degree of manipulation of the nerve, and complications during or after surgery. A self-administered questionnaire was used at every follow-up to evaluate the sensations in the mental region. RESULTS: A statistically significant positive correlation was found between subjective neurosensory loss and the patient's age (P = .039), magnitude of mandibular movement (P = .044), and degree of manipulation of the nerve (P = .0007). However, no significant correlation was found between disturbances of sensation and gender, indication for osteotomy, side of the operated mandible, or intraoperative and postoperative complications. Even if all patients evaluated their sensation as "normal" 1 year postoperatively, 31% of them reported slightly altered sensation in the mental region. CONCLUSIONS: After BSSO, a prolonged neurosensory deficit is strongly related to age, the intraoperative magnitude of mandibular movement, and the degree of manipulation of the inferior alveolar nerve. However, a long-term sensory loss is very rare, and patients seem to adapt to a mild neurosensory deficit and report sensory function as "normal" despite slightly altered sensation.

Monitoring, modelling and environmental exposure assessment of industrial chemicals in the aquatic environment.

Monitoring and laboratory data play integral roles alongside fate and exposure models in comprehensive risk assessments. The principle in the European Union Technical Guidance Documents for risk assessment is that measured data may take precedence over model results but only after they are judged to be of adequate reliability and to be representative of the particular environmental compartments to which they are applied. In practice, laboratory and field data are used to provide parameters for the models, while monitoring data are used to validate the models' predictions. Thus, comprehensive risk assessments require the integration of laboratory and monitoring data with the model predictions. However, this interplay is often overlooked. Discrepancies between the results of models and monitoring should be investigated in terms of the representativeness of both. Certainly, in the context of the EU risk assessment of existing chemicals, the specific requirements for monitoring data have not been adequately addressed. The resources required for environmental monitoring, both in terms of manpower and equipment, can be very significant. The design of monitoring programmes to optimise the use of resources and the use of models as a cost-effective alternative are increasing in importance. Generic considerations and criteria for the design of new monitoring programmes to generate representative quality data for the aquatic compartment are outlined and the criteria for the use of existing data are discussed. In particular, there is a need to improve the accessibility to data sets, to standardise the data sets, to promote communication and harmonisation of programmes and to incorporate the flexibility to change monitoring protocols to amend the chemicals under investigation in line with changing needs and priorities.

Prediction of recovery from neurosensory deficit after bilateral sagittal split osteotomy.

OBJECTIVE: To observe the suitability of different combinations of readily available tests to predict recovery from a neurosensory deficit after bilateral sagittal split osteotomy (BSSO). STUDY DESIGN: Thirty patients scheduled for BSSO were examined before surgery and 4 days, 3 weeks, 3 months, 6 months, and 1 year after surgery. At each follow-up, the patients self-evaluated the subjective neurosensory deficit of the lower lip and chin of both sides. Neurosensory function was also measured by tests consisting of light touch, 2-point discrimination, pin tactile discrimination, thermal discrimination, and sensibility testing of the mandibular molars. The positive predictive values (PPV) of each test for recovery from the neurosensory deficit were calculated. Furthermore, different tests were combined, and the PPVs for recovery from the neurosensory deficit of these combinations were analyzed. RESULTS: A positive response to sensibility testing of the mandibular first and second molars 4 days and 3 weeks after surgery was related to a PPV of 100% and 87%, respectively, for full recovery from sensation loss at 1 year. However, none of the tests alone could reliably predict recovery from the neurosensory deficit after BSSO. When 3 different tests were combined, the best results were achieved by the combinations of a light test or a 2-point discrimination test and a pin tactile test with the sensibility testing of mandibular molars. CONCLUSIONS: Sensibility testing of mandibular molars can be used to predict recovery from the neurosensory deficit after BSSO. The best positive predictive ability can be achieved by combining a mechanoceptive test, a nociceptive test, and sensibility testing of mandibular molars.

Psychiatric admissions at different levels of the national health care services and male criminality: the Northern Finland 1966 Birth Cohort study.

BACKGROUND: It has earlier been suggested that one-third of violent offenders are recorded in psychiatric case registers. Our aim was to study whether violent and non-violent offenders differ with respect to admissions to any health care inpatient service due to psychiatric disorders. METHODS: We used a genetically homogeneous, general population database from the Northern Finland 1966 Birth Cohort, together with the Finnish Hospital Discharge Register and national crime registers. RESULTS: We found that one-third of violent and one-fourth of non-violent male offenders had at least one hospital admission due to a psychiatric disorder before the age of 32. Sixty-five violent criminals - 1.2% of all cohort males (n = 5636) - accounted for 14.4% of all psychiatric treatment days. The admission rates among both violent and non-violent male offenders were significantly higher when compared with males with no criminal history. Among violent males, only half (55.5%) of the inpatient hospital days due to psychiatric disorders occurred in psychiatric hospitals. The corresponding percentages for non-violent criminals and non-criminals were 64.9% and 74.1%, respectively. Among the violent offenders, one-third of hospital inpatient days occurred in university hospitals or central hospitals, and only 1.9% of them occurred in a comprehensive community care system. CONCLUSIONS: Violent offenders' admission rates due to a psychiatric diagnosis are high, and they are frequently treated at an inappropriate health care level.

Prioritization attitudes among doctors and nurses examined by a scenario method.

OBJECTIVES: To investigate doctors' and nurses' attitudes toward 14 potential prioritization criteria. METHODS: This study was performed by using the random paired scenario method. The respondents received a questionnaire with 12 pairs of scenarios, imaginary patient cases, each of which contained two to three different prioritization criteria (e.g., child, old patient, poor patient). Respondents were asked which one of each scenario pair they would choose if only one patient could be treated. The scenarios were randomly put into 30 different questionnaire sets. There was a random selection of 241 doctors and 151 nurses in Finland, with response rates of 60.3% and 50.3%, respectively. RESULTS: Doctors prioritized young patients, severe disease, expensive treatments and posteriorized (negatively prioritized) demented or institutionalized patients, and patients having a self-caused disease. Children were strongly prioritized, even over serious diseases. Expensive treatments appeared to be favored by doctors, and this result cannot be explained by severity of disease. Nurses' attitudes were similar to those of doctors. CONCLUSIONS: Children were strongly prioritized. Elderly persons were posteriorized if they had dementia or were living in institutions. Patients having a self-caused disease are posteriorized, more often by nurses than by doctors.

Natural coral as bone-defect-filling material.

Natural coral (NC) has been studied experimentally and clinically as a bone substitute, but its resorption rate and possible replacement by bone still need to be defined in humans. In this study bicortical bone was harvested from the iliac crest of 10 patients. The defect was filled with a NC block, and changes were monitored by X-rays and quantitative CT scans for a mean of 2.1 years. A biopsy was taken at 1 year. The purpose of the study was to investigate the resorption rate and pattern of NC (Porites) implants and the replacement, if any, of the implant by new bone. The blocks underwent centripetal resorption, but all the blocks still could be detected by X-rays and CT scans at the end of the follow-up period. The density of the remaining block did not change. Seven of the 10 implants were smaller than 50% of their original size at the end of the study. Bone ingrowth could be observed only in two of seven biopsies. One implant had to be removed after 1.7 years due to infection. The study shows that resorption of natural coral proceeds centripetally and apparently more rapidly when accompanied by tissue ingrowth. None of the blocks resorbed completely, and the defect at the iliac crest had not been restored by the end of the study.

Chondrosarcoma in a family with multiple hereditary exostoses.

Multiple hereditary exostoses is an autosomal dominant skeletal disorder in which there are numerous cartilage-capped excrescences in areas of actively growing bone. The condition is genetically heterogeneous, and at least three genes, ext1, ext2 and ext3 are involved. The reported risk for malignant transformation to chondrosarcoma has been from 0.6% to 2.8%. We have reviewed six generations of a family with 114 living adult members, 46 of them with multiple exostoses. Four have had operations for chondrosarcoma, giving the risk for malignant transformation as 8.3% in this family. Clinical and radiological examination revealed two additional patients with a suspicion of malignancy, but in whom the histological findings were benign. Reported elsewhere in detail, genetic linkage analysis mapped the causative gene to chromosome 11 and molecular studies revealed a guanine-to-thymine transversion in the ext2 gene. Patients with multiple hereditary exostoses carry a relatively high risk of malignant transformation. They should be informed of this possibility and regularly reviewed.

Reference values for radiological evaluation of cervical vertebral body shape and spinal canal.

BACKGROUND: Defining normal values is essential for reliable evaluation of growth disturbances. Previous studies of the cervical spine have mainly focused on the sagittal canal diameter and interpedicular distances. Values for vertebral body height and depth have been published only in adult men and cadavers. OBJECTIVES: To define normal values for vertebral body height (H)/vertebral body depth (D) ratio (H/D ratio) and sagittal canal diameter (S)/ vertebral body depth ratio (S/D ratio) in C2-7. MATERIALS AND METHODS: Lateral cervical spine radiographs were available from 441 children and 192 adults. Subjects' ages varied from newborn to 39 years. Vertebral body height and depth and sagittal canal diameter were measured and ratios were calculated. This was a cross-sectional and retrospective study. RESULTS: Vertebral bodies grow relatively more in height than in depth, most actively at puberty. At all levels, the H/D ratio remains below 1, indicating that vertebral body depth is greater than height. The SD ratio is quite stable until 7-8 years of age and then it starts to decline slowly. CONCLUSIONS: When estimating platyspondyly, the age of the patient must be taken into consideration because vertebral body height is lower in children. Growth of the spinal canal declines after 7-8 years of age.