Structure of ice Ih and ice Ic as described in the language of Delaunay simplices.

Classification of the Delaunay simplex forms is carried out for the ideal structures of ice Ih and ice Ic. Classification according to the number of edges of different length reveals six types of simplices, while classification according to the number and mutual positions of edges of the unit length (equal to the length of the hydrogen bond) reveals five types of indices. Ice Ic is composed of simplices of three types (one of which has the form of a perfect tetrahedron), ice Ih from six simplices. Degeneracy is removed in computer models of slightly distorted ice by means of insignificant shifting of water molecules from their ideal positions. This makes it possible to provide the unambiguous partition of the crystal structure into Delaunay simplices. It is found that degeneracy removal results in the appearance of Delaunay simplices of specific forms with a very small volume (Kije simplices). The shape characteristics of simplices of different types and their percentage are calculated in the large computer models of ice. In particular, the fraction of the Kije simplices is found to be about 7.5% in ice Ih.

[Endoscopic total hip replacement in conditions of acetabulum bone structures deficiency].

76 patients with acetabulum defects of posttraumatic, oncologic, displastic or systemic character, as wall as due to complications after previous hip replacement, were operated on. The author's non-tensioned acetabular component installation technique worked out for the endoscopic total hip replacement was used. Long-term follow-up results were considered to be successful in 88.6% of cases. Maximal follow-up period is 10 years.

An algorithm for three-dimensional Voronoi S-network.

The paper presents an algorithm for calculating the three-dimensional Voronoi-Delaunay tessellation for an ensemble of spheres of different radii (additively-weighted Voronoi diagram). Data structure and output of the algorithm is oriented toward the exploration of the voids between the spheres. The main geometric construct that we develop is the Voronoi S-network (the network of vertices and edges of the Voronoi regions determined in relation to the surfaces of the spheres). General scheme of the algorithm and the key points of its realization are discussed. The principle of the algorithm is that for each determined site of the network we find its neighbor sites. Thus, starting from a known site of the network, we sequentially find the whole network. The starting site of the network is easily determined based on certain considerations. Geometric properties of ensembles of spheres of different radii are discussed, the conditions of applicability and limitations of the algorithm are indicated. The algorithm is capable of working with a wide variety of physical models, which may be represented as sets of spheres, including computer models of complex molecular systems. Emphasis was placed on the issue of increasing the efficiency of algorithm to work with large models (tens of thousands of atoms). It was demonstrated that the experimental CPU time increases linearly with the number of atoms in the system, O(n).

Total hip replacement for proximal femoral tumours: our midterm results.

Data from 44 patients (23 males, 21 females) with a median age of 39 (range 13-80) years who underwent total hip arthroplasty for proximal femoral tumours (1994-2004) were analysed. The histological diagnoses included 14 metastases, six osteosarcomas, six chondrosarcomas, four Ewing's sarcomas, four giant cell tumours, three malignant fibrous histiocytomas, two parosteal and two periosteal osteosarcomas, and one each primary neuroectodermal tumour, myeloid disease, and aneurysmal bone cyst. Twenty-one patients (48%) had pathological fractures. The cause of the pathological fracture was metastasis in 12 patients (57%). Twenty-eight patients (64%) had soft tissue invasion. Complications observed in 17 patients (37%) were local recurrence in two, postoperative haematoma in two, dislocation of prosthesis in five, deep infection in six, and one patient died of myocardial infarction in the early postoperative period. During our midterm survival analysis, functional results were excellent in 25% of patients, good in 57%, fair in 12%, and poor in 6%.

[Surgical treatment of chronic purulent diseases of extremities' bones and great joints].

Results of treatment of chronic purulent diseases of extremities' bones (n=414) and great joints (n=136) were analyzed. Combined treatment included surgical sanation of the inflammatory focus, autospongioplasty of residual cavities and defects after sequesterectomy (87 cases), extrafocal osteosynthesis, aspiration- flushing drainage. In 46 cases of severe suppuration in the zone of hip joint's endoprosthesis the resection arthroplasty was performed, in 43 cases of severe consequences of ankle-joint's fracture-dislocations -- compression talo-tibial and calcaneo-tibial arthrodesis. The follow-up was 15 years. Positive results were seen in 93.6% patients.

[Ways of surgical technique optimization and prevention of hip endoprosthesis dislocation following total hip arthroplasty].

The article presents experience concerning intraoperative prevention of hip endoprosthesis dislocation, gained in the orthopedic surgical clinic of Moscow Regional Research Clinical Institute. The results of 1208 total articular replacements allowed the development of intraoperative dislocation-preventive measures, taking into account the approach to the hip joint, necessary mobilization of articular ends, the relative position of total endoprosthesis components. The cases of hip endoprosthesis dislocation were analyzed. The offered preventive measure system allowes reduction in total endoprosthesis dislocation rate down to 1.5%.

Computer simulation study of intermolecular voids in unsaturated phosphatidylcholine lipid bilayers.

Computer simulation of the liquid crystalline phase of five different hydrated unsaturated phosphadidylcholine (PC) lipid bilayers, i.e., membranes built up by 18:0/18:1omega9cis PC, 18:0/18:2omega6cis PC, 18:0/18:3omega3cis PC, 18:0/20:4omega6cis PC, and 18:0/22:6omega3cis PC molecules have been performed on the isothermal-isobaric ensemble at 1 atm and 303 K. (The notation n:domegapcis specifies the lipid tails: n refers to the total number of carbon atoms in the chain, d is the number of the methylene-interrupted double bonds, p denotes the number of carbons between the chain terminal CH(3) group and the nearest double bond, and cis refers to the conformation around the double bonds.) The characteristics of the free volume in these systems have been analyzed by means of a generalized version of the Voronoi-Delaunay method [M. G. Alinchenko et al., J. Phys. Chem. B 108, 19056 (2004)]. As a reference system, the hydrated bilayer of the saturated 14:014:0 PC molecules (dimyristoylphosphatidylcholine) has also been analyzed. It has been found that the profiles of the fraction of the free volume across the membrane exhibit a rather complex pattern. This fine structure of the free volume fraction profiles can be interpreted by dividing the membrane into three separate major zones (i.e., zones of the aqueous, polar, and apolar parts of the membrane) and defining five subzones within these zones according to the average position of various atomic groups in the membrane. The fraction of the free volume in the middle of the membrane is found to increase with increasing unsaturation of the sn-2 chain of the lipid molecule. This is due to the fact that with increasing number of methylene-interrupted double bonds the lipid tails become more flexible, and hence they do not extend to the middle of the membrane. It is found that there are no broad enough preformed channels in the bilayers through which small penetrants, such as water molecules, can readily go through; however, the existing channels can largely facilitate the permeation of these molecules.

[Endoprosthesis of great joints of extremities in difficult anatomic conditions]. / Endoprotezirovanie krupnykh sustavov konechnostei v slozhnykh anatomicheskikh usloviiakh.

Experience in endoprosthesis of great joints in 408 patients in difficult clinical cases associated with defects and deformations of bones of posttraumatic, oncological, dysplastic and systemic character, and also in the cases of complications after primary endoprosthesis is analyzed. Special constructions of implants, instruments, surgical technique were used depending on anatomic and functional changes. Results of endoprosthesis of great joints were accessed as successful in 95% patients in maximal period of follow-up during 13 years.

[Surgical treatment of chronic post-traumatic osteomyelitis of the femur in pseudarthrosis, ununited fractures and defects]. / Khirurgicheskoe lechenie khronicheskogo posttravmaticheskogo osteomielita bedrennoi kosti pri lozhnykh sustavakh, nesrosshikhsia perelomakh i defektakh.

The authors have analyzed the results of treatment for chronic posttraumatic osteomyelitis of the femoral bone in 69 cases of ununited fractures, false joints ad femoral bone defects. The treatment included surgical sanation of the osteomyelitic nidus together with aspiration lavage drainage and extranidal osteosynthesis by external fixation as well as local and general antibacterial therapy. In 13 cases free bone autoplasty of the osteomyelitic cavities or defects was used together with spongious structures of iliac bone (crest and wing), in 2 of these patients it was applied for replacement of the large defects of the diaphysis of the femoral bone (8 and 12 cm). In 57 patients surgical treatment was carried out in one stage, a major requisite for this was the opportunity for joining bone fragments inside the open wound after sequestrectomy as well as stable external fixation by the apparatus. This treatment gave successful results in 97% of patients.

[Change in concentration of cholesterol and lipoprotein fractions of rabbit blood serum in the dynamics of hypercholesterolemia]. / Osoblyvosty zmin kontsentratsiï kholesterynu ta fraktsii lipoproteïniv syrovatky krovy kroliv u dynamitsi hiperkholesterynemiï.

Three quantitatively different periods have been detected as a result of 21-week monitoring of blood serum total cholesterol at hypercholesterolemia in rabbits. The first of them (4th week) ends by a relative decrease of cholesterol concentration: the second one (4th-13th weeks) is characterized by its sharp increase; in the third period (13th-21st weeks) the sterol accumulation slows down. Concentration variations of all main lipoprotein fractions are observed in each of the above periods. Their specific features enable us to suppose that in the first period the cholesterol transport system is activated which, probably, reflects the development of adaptation mechanisms of hypocholesterolemia. The second period can be considered as a transition stage from norm to pathology and is most likely, connected with atherogenesis induction. In the third period, in spite of relative stabilization of total cholesterol level clear signs of hyperbeta and hypoalpha dyslipoproteinemias are observed.

[Surgical correction of deformities of the knee joint]. / Operativnaia korrektsiia deformatsii v oblasti kolennogo sustava.

Fifty-nine knee joint deformities were corrected by supracondylar (24 surgeries) and subcondylar (35 cases) osteotomies. Stable fixation with massive submerged implants and Ilizarov's devices promoted a functional management during the postoperative period. Osteotomies are advisable before degenerative dystrophic changes develop in the joint. It should be borne in mind that arthrosis severity and advanced age of the patients are not contraindications against corrective osteotomies if the knee joint mobility is intact. The clinical result depends on the adequacy of the deformation hypercorrection. Despite the absence of an essential regression of degenerative changes in the joint, 35 of the 38 patients evidenced neither pain nor pain alleviation, and improvement of the motor activity in a year after surgery.