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Biomedical subjects

L Bellaiche

Publications and source records attributed to L Bellaiche.

35 records · Page 2Linked to original sources
PubMed2000

Finite-temperature properties of Pb(Zr1-xTi(x))O3 alloys from first principles

A first-principles-derived approach is developed to study finite-temperature properties of Pb(Zr1-xTix)O3 (PZT) solid solutions near the morphotropic phase boundary (MPB). Structural and piezoelectric predictions are in excellent agreement with experimental data and direct first-principles results. A low-temperature monoclinic phase is confirmed to exist, and is demonstrated to act as a bridge between the well-known tetragonal and rhombohedral phases delimiting the MPB. A successful explanation for the large piezoelectricity found in PZT ceramics is also provided.

Journal Article↗
PubMed2000

Microscopic view of a two-dimensional lattice-Gas ising system within the grand canonical ensemble

A reversible 2D critical transition is observed on the GaAs(001) surface and modeled as a lattice-gas Ising system. Without depositing any material, 2D GaAs islands spontaneously form. The order parameter, four critical exponents, and coupling energies are measured from scanning tunneling microscope images of the microscopic domain structure and correlation functions as a function of temperature and pressure. Unprecedented insight into the domain structure of a 2D Ising system through the critical point and a complete Hamiltonian for modeling the GaAs(001) surface are presented.

Journal Article↗
PubMed1997

Clinical evaluation of Duraflo II heparin treated extracorporeal circulation circuits (2nd version). The European Working Group on heparin coated extracorporeal circulation circuits.

OBJECTIVES: To evaluate whether the application of heparin treated circuits for elective coronary artery surgery improves postoperative recovery, a European multicenter randomised clinical trial was carried out. METHODS: In 11 European heart centers, 805 low-risk patients underwent cardiopulmonary bypass (CPB) with either an untreated circuit (n = 407) or an identical but heparin treated circuit (n = 398, Duraflo II). RESULTS: Significant differences were found among participating centers with respect to patient characteristics, blood handling procedures and postoperative care. The use of heparin treated circuits revealed no overall changes in blood loss, blood use, time on ventilator, occurrence of adverse events, morbidity, mortality, and intensive care stay. These results did not change after adjustment for centers and (other) prognostic factors as analysed with logistic regression. In both groups no clinical or technical (patient or device related) side effects were reported. Because female gender and aortic cross clamp time appeared as prognostic factors in the logistic regression analysis, a subgroup analysis with these variables was performed. In a subpopulation of females (n = 99), those receiving heparin treated circuits needed less blood products, had a lower incidence of rhythm disturbances and were extubated earlier than controls. In another subgroup of patients with aortic cross clamp time exceeding 60 min (n = 197), the amount of patients requiring prolonged intensive care treatment (> 24 h) was significantly lower when they received heparin treated circuits versus controls. CONCLUSION: These findings suggest that improved recovery can be expected with heparin treated circuits in specific higher risk patient populations (e.g. females) and when prolonged aortic cross clamp time is anticipated. Further investigations are recommended to analyses the clinical benefit of heparin treated circuits in studies with patients in different well defined risk categories and under better standardised circumstances.

Adult↗
PubMed1997

-Arthrography of the hip-.

Painful hip with normal X-rays (including false-lateral view of both hips) is the main indication for hip arthrography, searching for focal chondropathy. In the presence of moderate hip degenerative arthritis contrasting with increasing disability, a labrum lesion must be investigated. Such lesions are of two kinds, mainly degenerative (of the superior labrum) or post-traumatic (of the posterior labrum). Arthrography allows the diagnosis of cystic changes located in the acetabulum. It also allows the diagnosis and evaluation of the extent of synovial osteochondromatosis or villonodular synovitis. In three indications, computed tomographies must be added to plain arthrography: posterior labrum lesions, osteochondromatosis (looking for foreign bodies in the acetabular fossa) and cystic changes in the acetabulum (with density measurements). In all cases, a complete conventional radiological assessment must be available. Strict asepsis must be ensured. When osteochondromatosis is suspected, evaluation of articular capacity must be systematic.

Acetabulum↗
PubMed1997

[Useful imaging data before intervention for an unstable shoulder].

Recurrent instability of the shoulder may sometimes be a difficult diagnostic challenge. Bernageau's standard X-rays set, which includes 3 antero-posterior X-rays with medial rotation and 2 glenoid views, is able to confirm the existence of anterior instability events. However, it gives no information on the glenoid labrum and the glenohumeral ligaments. As surgical techniques are more sophisticated, more precise imaging techniques are needed in order to adapt the surgical technique to the anatomical lesions. Although CT arthrography is today the best imaging technique to choose a surgical technique, it will probably be replaced by MR arthrography in the near future. Pros and cons of each imaging techniques are described, together with their implications for the choice of treatment.

Arthrography↗
PubMed1996

Monitoring thrombin generation with prothrombin fragment 1.2 assay during cardiopulmonary bypass surgery.

UNLABELLED: Despite high plasma levels of heparin during cardiopulmonary bypass surgery, activation of the coagulation system has been reported. We hypothesize that the coagulation system activity most appropriately could be assessed by molecular markers of thrombin generation. The aim of the present study was to describe the changes in thrombin generation during CPB, using prothrombin fragment F1 + 2 (F1.2) as an indicator and evaluate different blood sampling regimens for interpretation of the F1.2 measurements. Twenty patients, operated under extracorporeal circulation with coronary artery bypass grafting (CABG), comprised the study material. The heparin levels were maintained above 2.5 IU/ml throughout the bypass procedure and the functional AT-III level was kept above 0.5 U/ml. Despite of this anticipated inactivation of the coagulation system, the concentrations of F1.2 and FpA increased throughout CPB, particularly after release of the aortic crossclamp. F1.2 and FpA correlated significantly (R = 0.69). No statistically significant correlation was found between F1.2 formation rate and age, bodyweight, baseline ACT, ACT after 200 IU heparin/kg, average heparin concentration during CPB or average AT-III level during CPB. CONCLUSIONS: Thrombin formation seems to be a continuous process during CPB despite adequate heparinization. The pattern of thrombin generation can be assessed most appropriately in terms of F1.2 generation rate. Extraordinary high levels of F1.2 were seen after release of the aortic crossclamp, indicating that the periods before and after aortic crossclamping should be evaluated separately.

Adult↗
PubMed1996

Magnetic resonance imaging of the spine in plasma cell dyscrasias. A review.

This review of recent data on the techniques and results of spinal magnetic resonance imaging in plasma cell dyscrasias provides a basis for selecting those patients who are most likely to benefit from this investigation. Sagittal images should be obtained using T1-weighted spin-echo and T2-weighted gradient-echo sequences. Epiduritis is best detected on sagittal or axial images acquired after gadolinium injection using T1-weighted spin-echo or phase-opposed gradient-echo sequences. Among patients with symptomatic multiple myeloma, 80% have abnormal magnetic resonance images of the lower spine due to plasma cell infiltration and this proportion increases with the stage in the Durie and Salmon staging system. Bone marrow signal abnormalities can be focal, diffuse and homogeneous, or diffuse and variegated. Vertebral fractures due to spinal infiltration or osteoporosis are seen in 48% of cases and spinal canal narrowing with impingement of bone tumors or epiduritis on nervous structures in 20%. The response to chemotherapy as evaluated based on conventional criteria is fairly well correlated with changes in magnetic resonance imaging findings. Among asymptomatic multiple myeloma patients with normal roentgenograms, 50% have tumor-related abnormalities on magnetic resonance images of the lower spine, which are associated with an increased likelihood of rapid progression to symptomatic disease. Similarly, one third of patients with an apparently solitary plasmacytoma of bone have evidence of other plasma cell tumors on magnetic resonance images of the lower spine, and this finding is associated with persistence of monoclonal component production after irradiation therapy, which may be of adverse prognostic significance. Patients with monoclonal gammopathies of uncertain significance have no evidence of tumorous lesions on magnetic resonance images of the lower spine.

Bone Marrow↗
PubMed1994

Current status of musculoskeletal interventional radiology.

This article details many of the latest developments in the field of musculoskeletal interventional radiology. Some of the topics included in this discussion are percutaneous biopsy of musculoskeletal lesions, automated percutaneous discectomy, facet joint arthrography, percutaneous vertebroplasty, and percutaneous drainage of abscesses.

Biopsy, Needle↗
PubMed1993

[The role of MRI of the knee].

Imaging of the knee is one of the main indications of MRI in musculo-skeletal diseases. Some of the most recent papers dealing with MR imaging of the knee are discussed in this review article. Abnormal conditions reviewed are meniscal injuries including those occurring in previously operated menisci, osteochondral fractures, osteochondritis dissecans and rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1993

[Topography of tumoral and pseudotumoral lesions of the proximal femur].

This study of the topographic distribution of tumoral and pseudotumoral lesions of the proximal femur shows that certain lesions have a preferential site, for example osteoid osteoma affects the internal cortex of the neck and diaphysis or the intertrochanteric zone; chondroblastoma occurs in zones of epiphyseal ossification of the head; fibrous dysplasia affects the femoral neck, while sparing the epiphyseal femoral head and trochanters. The island of osteosclerosis is situated, at least partially, in the support fan; so-called physiological cysts are situated on or above the midline of the neck and below the basicapital line. Osteolytic or mixed metastases preferentially involve Ward's triangle in the femoral neck and the intertrochanteric region. The sites of these lesions therefore appears to depend on the bony architecture which, in turn, is dependent on mechanical stresses. However, this purely morphological study fails to demonstrate whether mechanical stresses influence the development of these lesions.

Bone Cysts↗
PubMed1993

[Radiological anatomy of the hip in adults].

The authors review the embryology of the hip joint with its pathological implications. The radioanatomy is presented in an elementary fashion, with the appearance of each component as seen on the various imaging techniques (conventional X-rays, CT scan, MRI). The authors also describe the views used in conventional radiology and the invasive techniques of arthrography and arthroscanning.

Acetabulum↗