Bacterial adhesion to bisphosphonate coated hydroxyapatite

Staphylococcus aureus (S. aureus) is commonly associated with microbial infection of orthopaedic implants. Such infections often lead to osteomyelitis, which may result in failure of the implant due to localised bone destruction. Bacterial adhesion and subsequent colonisation of the device may occur as a consequence of contamination during surgery, or by seeding from a distant site through the blood circulation. Coating of the hydroxyapatite (HA) ceramic component of artificial hip joints with the bisphosphonates clodronate (C) and pamidronate (P) has been proposed as a means to minimise osteolysis and thereby prevent loosening of the implant. However, the effect of the bisphosphonate coating on bacterial adhesion to the HA materials must be determined before this approach can be implemented. In this study coated HA materials were incubated with the S. aureus and the number of adherent bacteria determined using the Modified Vortex Device (MVD) method. The number of bacteria adherent to the P coated HA material was significantly greater than that adherent to uncoated HA (60-fold increase) or to the C coated HA (90-fold increase). Therefore, even though earlier studies suggested that P bound to HA may improve osseointegration, the results presented would suggest that the use of this coating may be limited by the potential increased susceptibility of the coated device to infection.     

Bioceramics composition modulate resorption of human osteoclasts

Biomaterials used in bone regeneration are designed to be gradually resorbed by the osteoclast and replaced by new bone formed through osteoblastic activity. The aim of the present study is to analyze the role of osteoclasts in the resorption process. The attachment of human osteoclasts and the appearance of their resorption lacunae, when cultured on either the resorbable crystalline, calcium orthophosphate materials or on the long-term stable bioceramic material was investigated. The resorbable materials contain Ca₁₀[K,Na](PO₄)₇ (AW-Si) and Ca₂KNa(PO₄)₂ (GB14, GB9 & D9/25) as their main crystal phases, however they differ in their total solubility. These differences result from small variations in the composition. The long-term stable material consist of about 30% fluorapatite beside calcium zirconium phosphate (Ca₅(PO₄)3F + CaZr₄(PO₄)₆) and shows a very small solubility. AW-Si has an alkali containing crystalline phase, Ca₁₀[K,Na](PO₄). While GB14, GB9 and D9/25 contain the crystalline phase Ca₂KNa(PO₄)₂ with small additions of crystalline and amorphous diphosphates and/or magnesium potassium phosphate (GB14). D9/25 and AW-Si is less soluble compared to GB14, and GB9 among the resorbable materials. Resorbable and long-term stable materials vary in their chemical compositions, solubility, and surface morphology. Osteoclasts modified the surface in their attempts to resorb the materials irrespective of the differences in their physical and chemical properties. The depth and morphology of the resorption imprints were different depending on the type of material. These changes in the surface structure created by osteoclasts are likely to affect the way osteoblasts interact with the materials and how bone is subsequently formed.     

Zur Anwendbarkeit des zur Bestimmung von Alkohol- und Extraktgehalt in Weinen entwickelten Verfahrens

Zusammenfassung Verff. überprüften das zur Bestimmung des Alkohol- und Extraktgehaltes ausgearbeitete neue Verfahren, welches auf der Messung des spezifischen Gewichtes und Refraktionswertes ohne Destillation — unmittelbar aus dem Wein — beruht. Die mit dem konventionellen und neuen Verfahren in verschiedenen Instituten erhaltenen Ergebnisse wurden verglichen und die Fehler beider Methoden mit Hilfe der Regressionsanalyse bestimmt.

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On the application of a new method for the determination of alcohol and extract in wine

Summary The new method worked out for alcohol and extract determination in wine, based on the measurement of specific density and refractive index by omitting distillation, was controlled. The results obtained for the alcohol and extract content as established at various institutes with the traditional and the new method, were compared and the error of both methods was calculated by means of regression analysis.

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Bei den technischen Arbeiten waren I. Szárföldi-Szalma, T. Kutz-Szorokin und K. Kardos behilflich.     

Resource allocation in computer networks by a regional accessibility model

The problem of resource allocation in computer networks is modeled as a regional accessibility model. These models, which have been used in urban and regional planning, provide a means for planning and evaluating computer networks. We present a straightforward solution procedure which allows for the efficient solution of large models and is well suited to studying the sensitivity of the model to various parameter changes. The model and solution technique are used to study a computer network for the Finnish universities.     

Das Verhalten linearer Induktionsmaschinen bei Überlichtgeschwindigkeit ihrer Wanderwellen

Übersicht Die Arbeit behandelt die Eigenschaften linearer Induktionsmaschinen unter der hier erstmalig gemachten Annahme, daß die Phasengeschwindigkeit der ständererregten Wanderwellen die Lichtgeschwindigkeit übertrifft. Der Untersuchung wird ein rotationssymmetrisches Zylindermodell der Maschine zugrunde gelegt. Sein elektromagnetisches Feld wird aus der achsialen Komponente eines Fitzgeraldschen Vektors hergeleitet, der radiale Zylinderwellen enthält. Zufolge von Resonanz der aufgedrückten Frequenz mit einer elektromagnetischen Eigenschwingung des von Ständer und Läufer eingeschlossenen Spaltgebietes vermag der Imaginärteil des komplexen Eingangsleitwertes positive und negative Werte anzunehmen, während sein Realteil stets positiv bleibt. Die Maschine arbeitet daher als Motor oder als Bremse, nicht jedoch als Generator.

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Contents This paper deals with the properties of a linear induction machine under the assumption, made here for the first time, that the phase velocity of the stator-excited travelling waves surpasses light velocity. A cylindric, rotationally-symmetric model of the machine is used whose electromagnet field is deduced but from the axial component of Fitzgerald's vector. The solution of its partial differential equation shows the appearing of radially propagating waves. In accordance with the resonance of the imposed frequency to one of the electromagnetic eigenvibrations of the space separating the stator from the rotor the input admittance can change the sign of its imaginary component whereas its real component remains positive. Therefore the machine is able to performe the work of a motor or of a brake but not of a generator.