Mechanism for the Retardation of the Acid Dissolution Rate of Hydroxyapatite by Strontium

Dissolution rates and apparent solubilities for synthetic hydroxyapatite in acetate buffers containing phosphate and strontium ions in the range of 10-3 to 10-2 M were determined under various pH and buffer conditions. Critical examination of the role of strontium with a physical model suggests that a calcium-strontium apatite surface complex may govern the driving force of the dissolution reaction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67293/2/10.1177_00220345730520051901.pd

Interfacial Reactions of Ozone with Surfactant Protein B in a Model Lung Surfactant System

Oxidative stresses from irritants such as hydrogen peroxide and ozone (O_3) can cause dysfunction of the pulmonary surfactant (PS) layer in the human lung, resulting in chronic diseases of the respiratory tract. For identification of structural changes of pulmonary surfactant protein B (SP-B) due to the heterogeneous reaction with O_3, field-induced droplet ionization (FIDI) mass spectrometry has been utilized. FIDI is a soft ionization method in which ions are extracted from the surface of microliter-volume droplets. We report structurally specific oxidative changes of SP-B_(1−25) (a shortened version of human SP-B) at the air−liquid interface. We also present studies of the interfacial oxidation of SP-B_(1−25) in a nonionizable 1-palmitoyl-2-oleoyl-sn-glycerol (POG) surfactant layer as a model PS system, where competitive oxidation of the two components is observed. Our results indicate that the heterogeneous reaction of SP-B_(1−25) at the interface is quite different from that in the solution phase. In comparison with the nearly complete homogeneous oxidation of SP-B_(1−25), only a subset of the amino acids known to react with ozone are oxidized by direct ozonolysis in the hydrophobic interfacial environment, both with and without the lipid surfactant layer. Combining these experimental observations with the results of molecular dynamics simulations provides an improved understanding of the interfacial structure and chemistry of a model lung surfactant system subjected to oxidative stress

Metaphyseal sclerosis in patients with chronic renal failure

We reviewed radiographs of the hands and wrists of 33 patients with immature skeletons and chronic renal disease. Various radiographic manifestations of renal osteodystrophy were seen, including osteopenia in 23 patients (70%), subperiosteal resorption in 20 (61%), distal tuft resorption in 14 (42%), sclerosis of vertebral bodies in 2 (6%), and soft-tissue calcification in 1 (3%). We also noted that 13 patients (39%) exhibited metaphyseal sclerosis adjacent to the growth plates. Five of these 13 showed persistent sclerosis years after the growth plates had fused. None of the patients showed other radiographic changes of rickets, and there was no correlation between the serum calcium, phosphorus, or aluminum levels and the presence of metaphyseal sclerosis. Neither was there any association with the underlying cause of renal failure, method of treatment, presence of a transplant, or type of dialysis. We view this finding as another manifestation of renal osteodystrophy. The importance of distinguishing it from other sclerotic lesions is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46802/1/256_2004_Article_BF00241668.pd

From limit cycles to strange attractors

We define a quantitative notion of shear for limit cycles of flows. We prove that strange attractors and SRB measures emerge when systems exhibiting limit cycles with sufficient shear are subjected to periodic pulsatile drives. The strange attractors possess a number of precisely-defined dynamical properties that together imply chaos that is both sustained in time and physically observable.Comment: 27 page

Synchrotron X-Ray Studies of Surface Disordering

Contains an introduction and reports on three research projects.Joint Services Electronics Program Contract DAAL03-92-C-000

Physical Model for Plaque Action in the Tooth-Plaque-Saliva System

A physical model describing the interrelationships of demineralization, remineralization, plaque thickness, glucose levels, and plaque enzymatic activity was presented. Selection of constants and variations of the parameters were kept in the range of possible in vivo situations. The results of calculations were discussed and correlated with the results of in vivo studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66483/2/10.1177_00220345700490013001.pd

Формування законодавчої і нормативної бази архівної справи в республіці Казахстан

Аналізується законодавство Республіки Казахстан, спрямоване на забезпечення збереження документальної спадщини, регулювання діяльності архівної системи в умовах державного суверенітету. Визначаються особливості архівного законодавства кінця 1990-х рр., прослідковуються його зміни та напрями удосконалення в 2000-х рр., процеси формування нормативної бази архівної справи.Анализируется законодательство Республики Казахстан, направленное на обеспечение сохранности документального наследия, регулирование деятельности архивной системы в условиях государственного суверенитета. Определяются особенности архивного законодательства конца 1990-х гг., прослеживаются его изменения и направления усовершенствования в 2000- х гг., процессы формирования нормативной базы архивного дела.The legislation of Republic of Kazakhstan, directed on providing of safety of documentary legacy, adjusting of activity of the archival system in the conditions of the state sovereignty is analysed in the article. The features of the archival legislation the end of 1990-th are determined, its changes and directions of improvement in the 2000-th, the processes of forming of normative base of the archival affairs are traced

Kinetics and Mechanism of Hydroxyapatite Crystal Dissolution in Weak Acid Buffers Using the Rotating Disk Method

The dissolution rates of synthetic hydroxyapatite pellets under sink conditions were measured using the rotating disk method. The experimental data were analyzed by means of a physical model that yielded an ionic activity product of KHAP = a10Ca2+ a6 PO4 3- a2OH- = 1 × 10-124.5±1.0 that was found to govern the dissolution reaction. Also, a surface resistance factor of k' equal to about 174 sec/cm was deduced from the data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67157/2/10.1177_00220345760550033201.pd

X-Ray Diffuse Scattering

Contains introduction and reports on three research projects.Joint Services Electronics Program DAAL03-89-C-000