In this study, two novel bioactive bone-bonding cements based on the crystalline phase Ca2KNa(PO4)(2) were studied in vivo in order to characterize their bone regenerative capacities as well as their biodegradability. The implantation site was located underneath the patellar sliding plane of the distal femur of rabbits in an area which is almost free of bony trabeculae. Highly porous beta-TCP granules and empty defects served as controls. In order to obtain information especially regarding the remodeling properties time periods of up to 48 weeks were chosen. When used as bulk material, both cements showed bone formation rates which were comparable to those of the TCP granules in combination with a favorable biodegradability, which however was lower than that of TCP granules due to the considerably lower porosity. Taken together, a guided bone regeneration in conjunction with biomaterials degradation was observed with all three materials. The empty defects (negative control) did not show comparable bone formation rates. Based on this study, both cements can be considered as valuable materials for percutaneous treatment of bone defects in traumatology, for example.

Introduction Bioactive calcium phosphate ceramics have been widely used for bone regeneration.However, depending on the clinical application, these materials need to exhi bit varying degrees of biodegradability. For example,inclinical applications inwhi chimplants are tobe insertedintothe regeneratedsite,rapidbiodegradability is more important comp aredtoapplications inwhichthis is not the case.Therefore, there have been numerous efforts todev elop novel materials witha higher solubilitycomparedtotricalcium phosphate(TCP).Amongthevariouscalc ium phosphatematerials whichare currently clinically available,TCP possesses the highest solubility andbiodegradability. The most reliable methodfor evaluatinga bone substitute mat erial’s capability to degrade and promote bone formation and osseous regeneration is by performing hist omorphometric measurements onex vivospecimens from animal experiments.Anim al studies,however,are very cost-intensive.Furthermore,due toanincreasing focus onanimal ethic s,there has beenanongoingsearchfor alternative in vitromethods whichcancontribute toreduc ing the number of animal experiments.Consequently,this study compares aninvitromethodfor evaluating the biodegradability of novel calcium-alkali-orthophosphate ceramic particulates - by using solubility measurements - tohistomorphometric evaluationof the biodegradability of these materials by determining the decrease of particle size inhistological sections whichwer e obtainedsubsequent toimplantationinvivousingasheepmodel. Material and Methods Three novel calcium-alkali-orthophosphate ceramic bone substitute materials were studied. These materials are glassy-crystalline materials witha higher solubility thanβ-tricalcium phosphate [1-3].The compositionof these materials is rather similar, since their maincrystalline phase is the new phase Ca

This article presents a novel approach to evaluate two-dimensional histomorphometric studies of biodegradable ceramic particles by means of element-sensitive, three-dimensional and non-destructive synchrotron-microtomography (SCT). An in vivo study was performed in which bone substitute materials (Cerasorb) were implanted in the mandible to support the bone regeneration. After 6 months of implantation samples were prepared and investigated using SCT and subsequent 3D image analysis as well as histological evaluation. A comparison of corresponding tomographical and histological slices delivers information about the newly formed bone and its stage of development. Additionally SCT gives insights into the structural changes of the bony tissue in a given defect and the local biodegradation of the bone substitute material in a three-dimensional manner. This emphasizes the fact that the completion of investigations by 2D histological images with 3D tomographical images is required in order to be able to draw conclusions concerning the influence of different bioceramics on the bone regeneration.

In a small river catchment, microbiological quality of different sewage treatment plants under regular conditions and in case of heavy rainfall, when combined sewage overflow basins (CSOs) are activated, was examined regarding microbial indicators and pathogens. In the watercourse, no self-cleaning effects could be observed. Small compact treatment plants discharge treated wastewater with a poor microbiological quality compared to river water quality and the quality of treated wastewater of larger plants. During storm water events, concentrations of microorganisms downstream of sewer overflows were approximately two logs higher than during dry weather conditions. Concentrations of parasites decreased slowly during the overflow, in parallel to filterable matter and particle-bound substances. The annual load of microorganisms originating from CSOs significantly exceeds the load from treated effluent of the sewage plants. Thus, an improved hygienic quality of the water course could be achieved by preventing overflows and by enhancing sewage treatment plants.

Non-ideal hydrophone frequency responses may impede correct acoustic output measurements on medical ultrasound equipment, in particular when high frequency or nonlinearly distorted waveforms have to be detected. It is shown that correct pressure waveforms p(t) and the associated standard pulse parameters such as positive peak pressure p+ and rarefactional peak pressure p- can be obtained by impulse deconvolution if the non-ideal frequency response of the hydrophone M(f) is provided with high frequency resolution both in amplitude and phase in a broad frequency range. The complex-valued calibration data required can be obtained by a secondary hydrophone calibration technique which was recently developed and uses broadband, nonlinearly distorted, focused ultrasound pulses and an optical multilayer hydrophone as reference. The results obtained for a membrane and a needle-type hydrophone are applied to improve exposure measurements on a commercial diagnostic ultrasound machine. This is shown for different operation modes and parameter settings of the diagnostic machine by comparison of the pressure pulse waveforms and pulse parameters obtained by the commonly applied evaluation method using the voltage-to-pressure transfer factor at the acoustic working frequency M(fawf) with those obtained by pulse deconvolution using the complete broadband complex-valued transfer function M(f).

A substitution calibration technique for piezoelectric ultrasonic hydrophones is presented that uses an optical multilayer hydrophone as the reference receiver. Broadband nonlinearly distorted focused pulses are first measured with the reference hydrophone and then with the hydrophone to be calibrated. By Fourier transformation of the time wave forms and division of the frequency spectra, the complex-valued frequency response of the hydrophone under test is obtained in a broad frequency range in a very fast and efficient way and with high frequency resolution. The results obtained for a membrane hydrophone and a needle-type hydrophone are compared with those obtained by independent calibration techniques such as primary calibration using optical interferometry and secondary calibration using time-delay spectrometry, and good agreement is found. The calibration data obtained are apt to improve the results of ultrasound exposure measurements using broadband voltage-to-pressure conversion. This is demonstrated for standard pulse parameter determination from exemplar exposure measurements on a commercial diagnostic ultrasound machine. For the membrane hydrophone, the evaluation method commonly used leads to an overestimation of the positive peak pressure by up to 50%, an underestimation of the rarefactional peak pressure by up to 11%, and an overestimation of the pulse intensity integral by up to 28%.

Two hydrophone calibration techniques are presented which provide amplitude and phase of hydrophone sensitivity. Heterodyne time-delay spectrometry can be applied in the frequency range from 0.5 to 50 MHz to all common hydrophones but needs a standard to obtain absolute values. A pulse technique between 1 and 70 MHz allows exploiting of an optical multilayer hydrophone as a phase standard. In combination with HTDS, a calibration service is established that covers the complete spectrum of common piezoelectric and optical hydrophones for absolute amplitude and phase calibration. The measured complex frequency responses form the basis of deconvolution procedures suitable for the correction of measurements of, for example, the output of ultrasound diagnostic machines.

A fiber-optic instrument for temperature measurement is presented. The sensing element consists of an optical dielectric multilayer system acting as a micro-interferometer which is deposited on a single-mode fiber tip. The sensitivity of the implemented system is theoretically derived and experimentally determined by a calibration measurement. The small size of the probe makes the system well-suited, for instance, for endoscopic in vitro and in vivo measurements in medical applications, especially in small samples. The sensor is used for the investigation of the transient thermal behavior of vitreous during Er:YAG laser irradiation in order to study the local thermal effects that are important to minimize the potential for unintentional injury in laser vitrectomy and laser vitreoretinal surgery.

A fibre-optic hydrophone with a dielectric coating is presented that can be used for the characterization of both high energy acoustical pulses, such as shock waves, and low-intensity ultrasonic fields. The principle of operation is discussed, and a first experimental test described in which the simplest version of a coated fibre-optic hydrophone was used to measure lithotripter shock waves.

An optical multilayer detection array for ultrasonic measurements is presented. The probe comprises a dielectric interference filter structure that is evaporated onto a glass plate. An incident acoustic pressure signal deforms the layer system, and the induced modulation of the optical reflectance is determined by a simple optical detection scheme. The principle of measurement is demonstrated by a line scan through the focus of a broadband transducer and can be applied to rapid two-dimensional characterization of ultrasonic fields. The high temporal and spatial resolution of the measurements is combined with high sensitivity and durability of the probe, and, in contrast with fiber-tip multilayer hydrophones, the multilayer detection array provides signals that are not influenced by acoustic resonances and diffraction phenomena.

Emission of hydrogen ions has been used to investigate the charging of the nuclear track being produced by fission fragments in organic solids. The question of interest is, if in insulating material the lifetime of ionisation along the nuclear track is sufficiently long to allow atomic motion driven by Coulomb repulsion of neighbouring ionized atoms. It is shown in this article that the hydrogen ions experience the potential produced by the ionized track core, but weaker than Auger electrons (see Schiwietz et al., Phys. Rev. Lett. 69 (1992) 628). In order to determine the mean initial energy of emission, we measured the time-of-flight distributions of secondary ions by means of a linear TOF instrument being equipped with 2 acceleration grids and converted them into axial energy distributions. Monte Carlo simulations were used to simulate the time distributions and to estimate the mean charge along the nuclear track causing the observed line shifts.

After deposition of cattle manure for 308 days neither the total nitrogen nor the nitrate but only the ammonia content in the soil (0-70 cm) was significantly increased. During a 258 days period from autumn to spring the observed microbial oxidation of penetrated ammonia to nitrate was tardy and by no means quantitative. So leaching of nitrate was hardly to be detected during the whole period. In the soil layer 40-70 cm a maximum of 1.6 g NO3--N/M2 was measured, which was in an equivalent range with the amounts detected by large scale investigations in agricultural soils at the same season. Therefore the manure heaps in question did not lead to an uncommon increase of nitrate in soil. The protection of the heaps against precipitation simply brought about small and only a few times significant reductions in soil N(min) content.

We have demonstrated four-wave mixing in multiple-quantum-well (MQW) GaAlAs-laser diodes (LD) by injecting two narrow-band signals from optically/electronically stabilized LDs into a mixer LD. S/N-ratios of the heterodyne-detected mixing signals were measured for frequency differences (delta) (nu) between the pump-lasers up to the THz-range being sufficient for phase-coherent optical frequency synthesis. The measured dependence of the mixing signal S/N ratio on (delta) (nu) indicates a intraband population relaxation time T1 <EQ 200 fs. Schemes for dividing an optical frequency interval into two or three equal parts are discussed. Furthermore, all-optical frequency interval bisection is demonstrated for the first time.