X-radiography front tracking gradient furnace for directional solidification of bulk Al-alloys.

A unique gradient furnace for directional solidification experiments with bulk Al-alloy samples developed at German Aerospace Center is presented. It allows for in situ process control in solidifying samples by using x-radiography, and further insight into the solidification process is gained in combination with x-ray computational tomography on the solidified samples. Tracking of interfaces during directional solidification of bulk samples via in situ x-radiography (TIREX) enables the investigation of the melting process and observation of the movement of the entire mushy zone through the sample, tracing the solid-liquid interface during directional solidification and correlating the observations with the microstructure of the samples. Monitoring the temperature profile inside the sample by in situ observation of the length of the mushy zone is particularly important because the temperature gradient G and the rate of interfacial growth v determine the microstructure of solidification. The x-radiography setup offers temporal and spatial resolutions of 0.5 s and 70 µm, respectively, with a field of view of 10 × 50 mm2. Constant solidification velocities of up to 0.15 mm s-1 at a temperature gradient of up to 8 K mm-1 can be achieved in a temperature range of 537-1373 K. A flat solid-liquid interface inside a rod-like sample with 5 mm diameter is achieved by surrounding the sample by thermal isolating graphite foam. Performance tests with hypoeutectic Al-10 wt. % Cu alloy samples show the functionality of the furnace facility.

Ni-base superalloy single crystal (SX) mosaicity characterized by the Rotation Vector Base Line Electron Back Scatter Diffraction (RVB-EBSD) method.

In the present work we present the Rotation Vector Base Line Electron Back Scatter Diffraction (RVB-EBSD) method, a new correlative orientation imaging method for scanning electron microscopy (OIM/SEM). The RVB-EBSD method was developed to study crystal mosaicity in as-cast Ni-base superalloy single crystals (SX). The technique allows to quantify small crystallographic deviation angles between individual dendrites and to interpret associated accommodation processes in terms of geometrically necessary dislocations (GNDs). The RVB-EBSD method was inspired by previous seminal approaches which use cross correlation EBSD procedures. It applies Gaussian band pass filtering to improve the quality of more than 500 000 experimental patterns. A rotation vector approximation and a correction procedure, which relies on a base line function, are used. The method moreover features a novel way of intuitive color coding which allows to easily appreciate essential features of crystal mosaicity. The present work describes the key elements of the method and shows examples which demonstrate its potential.

Bioactivity and electrochemical behavior of hydroxyapatite-silicon-multi walled carbon nano-tubes composite coatings synthesized by EPD on NiTi alloys in simulated body fluid.

In order to improve the surface bioactivity of NiTi bone implant and corrosion resistance, hydroxyapatite coating with addition of 20wt% silicon, 1wt% multi walled carbon nano-tubes and both of them were deposited on a NiTi substrate using a cathodic electrophoretic method. The apatite formation ability was estimated using immersion test in the simulated body fluid for 10days. The SEM images of the surface of coatings after immersion in simulated body fluid show that the presence of silicon in the hydroxyapatite coatings accelerates in vitro growth of apatite layer on the coatings. The Open-circuit potential and electrochemical impedance spectroscopy were measured to evaluate the electrochemical behavior of the coatings in the simulated body fluid at 37°C. The results indicate that the compact structure of hydroxyapatite-20wt% silicon and hydroxyapatite-20wt% silicon-1wt% multi walled carbon nano-tubes coatings could efficiently increase the corrosion resistance of NiTi substrate.

Polyethylene wear particles induce TLR 2 upregulation in the synovial layer of mice.

A cellular and receptor mediated response to ultra-high-molecular-weight-polyethylene (UHMWPE) wear particles results in a release of proinflammatory cytokines and induces an inflammatory reaction causing osteolysis in total joint replacement. This investigation offers insight into the toll-like receptor (TLR) mediated activation by polyethylene wear particles in the synovial layer of mice. We hypothesized that, similar to recent in vitro results, UHMWPE particles lead to an upregulation of TLR 1 and 2 and TLR 4 in vivo in the synovial tissue of mice as well. Therefore, UHMWPE particles were generated in a common knee simulator according to the ISO standard, separated by acid digestion and determined by scanning electron microscopy. Endotoxin was removed using a method based on ultracentrifugation. A particle suspension (50 µl; 0.1 vol./vol.%) was injected into the left knee joint of female Balb/c mice (n = 8). In a control group, phosphate-buffered saline was injected into the left knee of Balb/c mice (n = 8). The mice were sacrificed after 7 days. Immunohistochemical staining was performed with TLR 1, 2 and 4 polyclonal antibodies for Balb/c mice and evaluated by light microscopy. The particle-stimulated group showed a thickened synovial layer, an increased cellular infiltration and a TLR 2-upregulation in the synovial layer compared to the control group. An increased expression of TLR 1 and TLR 4 could not be demonstrated. These results indicate a mainly TLR 2-induced inflammation to polyethylene wear debris in the synovial layer of mice.

[Postoperative pain management after minimally invasive hysterectomy: thoracic epidural analgesia versus intravenous patient-controlled analgesia]. / Postoperative Schmerztherapie nach minimalinvasiver Hysterektomie : Thorakale Periduralanalgesie vs. intravenöse patientenkontrollierte Analgesie.

BACKGROUND: In view of the development of innovative and non-traumatic surgical techniques, postoperative pain management should be carried out depending on the invasiveness of the intervention. In the present study two analgesic strategies were compared in patients undergoing minimally invasive hysterectomy: epidural analgesia (EDA) and intravenous patient-controlled analgesia (iv-PCA). MATERIAL AND METHODS: For this prospective case controlled study 60 women with benign uterine diseases undergoing vaginal hysterectomy (VH) or laparoscopically assisted vaginal hysterectomy (LAVH) were enrolled. Patients were divided for analysis into two groups (n=30 each) according to the postoperative analgesic strategy (EDA group versus iv-PCA group). A matched-pair analysis was applied (matching criteria: risk assessment, surgeon and age of patient) to minimize the differences between both groups. Patients were evaluated with respect to the extent of pain determined by a numeric rating scale (NRS 0-10 scale), analgesic consumption, rate of postoperative nausea and vomiting (PONV), mobilization from bed, oral intake of nutrition, complications, duration of stay in the recovery room as well as hospital stay and health-related quality of life (SF-36 Health Survey; collected before and 6 weeks after surgery). RESULTS: Laparoscopically assisted removal of the uterus was carried out in 22 women and by vaginal hysterectomy in 38 women. No significant differences between the study groups were seen in the duration of surgery (iv-PCA 58 ± 25 min versus EDA 60 ± 26 min). Demographic data of both groups as well as intraoperative hemodynamic and respiratory parameters were comparable to a great extent. Compared to the iv-PCA group, women in the EDA group showed lower NRS values (p<0.01): recovery room admission 4.7 ± 2.5 iv-PCA vs. 0.9 ± 1.3 EDA, recovery room discharge 3.8 ± 1.8 iv-PCA vs. 1.0 ± 1.2 EDA, day of surgery at 8 p.m. 5.0 ± 2.1 iv-PCA vs. 1.8 ± 2.3 EDA and first postoperative day at 8 a.m. 3.5 ± 1.7 iv-PCA vs. 1.9 ± 2.2 EDA. In addition, less PONV (iv-PCA 9/30 vs. EDA 1/30, p<0.01), less shivering (iv-PCA 8/30 vs. EDA 2/30, p<0.05), reduced fatigue (iv-PCA 26/30 vs. EDA 9/30, p<0.05) and a lower consumption of analgesics were found. Average postoperative requirement for piritramide in the iv-PCA group was 7 mg (range 0-24 mg) on the day of surgery and 5 mg (0-39 mg) on the first postoperative day. In the EDA group no opiate medication was given postoperatively (p<0.01). Duration of stay in the recovery room was shorter in the EDA group (71 ± 32 min vs. 50 ± 13 min, p<0.05). Hospital stay was 5 days on average in both groups. There were no surgical complications or epidural catheter-related complications. Because of urinary retention catheterization of the bladder had to be made in 3 patients of the iv-PCA group and 13 patients of the EDA group (p<0.05). Furthermore, the possibility to take a shower postoperatively was restricted in the EDA group because the epidural catheter was in place and thereby hygiene concerns. Regarding the early oral nutritional intake as well as postoperative mobilization, no significant differences between groups were found. In comparison with the preoperative status, the results regarding health-related quality of life were significantly better for both groups after a follow-up of 6 weeks (p<0.01); however, this effect was especially pronounced in the EDA group (p<0.05). CONCLUSIONS: To reduce the number of patients suffering from postoperative pain a procedure-specific pain management should be developed. The results of this study have shown that even in minimally invasive surgery, such as vaginal hysterectomy and laparoscopically assisted vaginal hysterectomy there are some advantages for epidural analgesia compared to intravenous patient-controlled analgesia. In particular reduced pain intensity, lower need for analgesics and reduced occurrence of PONV can lead to excellent patient comfort, fast recovery as well as positive effects on health-related quality of life. However, there are also some disadvantages such as an increased rate of urinary retention and restriction of mobility.

The biocompatibility of dense and porous Nickel-Titanium produced by selective laser melting.

Nickel-Titanium shape memory alloys (NiTi-SMA) are of biomedical interest due to their unusual range of pure elastic deformability and their elastic modulus, which is closer to that of bone than any other metallic or ceramic material. Newly developed porous NiTi, produced by Selective Laser Melting (SLM), is currently under investigation as a potential carrier material for human mesenchymal stem cells (hMSC). SLM enables the production of highly complex and tailor-made implants for patients on the basis of CT data. Such implants could be used for the reconstruction of the skull, face, or pelvis. hMSC are a promising cell type for regenerative medicine and tissue engineering due to their ability to support the regeneration of critical size bone defects. Loading porous SLM-NiTi implants with autologous hMSC may enhance bone growth and healing for critical bone defects. The purpose of this study was to assess whether porous SLM-NiTi is a suitable carrier for hMSC. Specimens of varying porosity and surface structure were fabricated via SLM. hMSC were cultured for 8 days on NiTi specimens, and cell viability was analyzed using two-color fluorescence staining. Viable cells were detected on all specimens after 8 days of cell culture. Cell morphology and surface topography were analyzed by scanning electron microscopy (SEM). Cell morphology and surface topology were dependent on the orientation of the specimens during SLM production. The Nickel ion release can be reduced significantly by aligned laser processing conditions. The presented results clearly attest that both dense SLM-NiTi and porous SLM-NiTi are suitable carriers for hMSC. Nevertheless, before carrying out in vivo studies, some work on optimization of the manufacturing process and post-processing is required.

Do cement nanotubes exist?

Using atomistic simulations, this work indicates that cement nanotubes can exist. The chemically compatible nanotubes are constructed from the two main minerals in ordinary Portland cement pastes, namely calcium hydroxide and a calcium silicate hydrate called tobermorite. These results show that such nanotubes are stable and have outstanding mechanical properties, unique characteristics that make them ideally suitable for nanoscale reinforcements of cements.

Functional interactions within the newborn brain investigated by adaptive coherence analysis of EEG.

To assess functional cortical organization in newborns during quiet sleep we investigated instantaneous interhemispheric coherences in six healthy full-term subjects using linked ear reference and average reference. Tracé alternant was the most frequent EEG pattern during quiet sleep of these newborns and consists of burst and interburst periods. The calculation of coherence was performed by means of time-variant autoregressive models on the basis of Kalman filtering. Coherence changes simultaneously with the appearance of these burst and interburst periods. The highest level of coherence was observed during burst periods in comparison with interburst periods. The lowest level of coherence was observed just before the burst started. During burst, maximal coherence was reached at different moments--late in the low frequency band (0.5-1.5 Hz; about 3 s after the burst started) and earlier in higher frequency bands (> 2 Hz, about 2 s). Interhemispheric coherence depended on the region being investigated. A significant level of coherence could be observed over frontal, temporal and occipital regions. Our data demonstrate significant modification of interhemispheric coherence during quiet sleep of full-term newborns and, irrespective of the immaturity of the brain, these coherences differ significantly between cortical regions.

Spectral analysis of electroencephalogram during sleep-related apneas in pre-term and term born infants in the first weeks of life.

OBJECTIVES: A correlation between sudden infant death syndrome (SIDS) and apnea has been discussed in a variety of studies. We analyzed polysomnographic data in 51 infants and investigated correlations between the manifestation of apneas and changes in EEG pattern. METHODS: Measurements were performed by means of the commercial polysomnographic device 'ALICE III'. Spectral analysis of certain parts of the registered EEG was performed. RESULTS: During apnea a reduction of the EEG amplitude was seen. The extent of the decrease differed slightly between the frequency bands. CONCLUSIONS: According to the widespread agreement that a lower voltage of electrical brain activity is a fundamental sign of waking up, we hypothesize that the observed change might be an immature type of arousal reaction.

Brain dysmaturity index for automatic detection of high-risk infants.

The definition of an electroencephalographic (EEG)-based brain dysmaturity index that could allow automatic detection of neonates who deviate from expected ontogenetic patterns is proposed. The investigation was performed in a group of 94 term and preterm infants (28-112 weeks postconceptional age). For each neonate, one continuous two-channel EEG of 1-6 hours was recorded. The cluster analysis of different age groups was performed with a self-referential neural network. The network performed a nonlinear discriminant analysis; the synaptic strength of input nodes indicates the relevance of an individual EEG feature. The most relevant EEG features are given by the average amplitude in the delta and theta bands and by the relative amplitudes of beta-1/theta and beta-1/delta, respectively. The correlation between the frequency shifts and the postconceptional age agreed with measures of brain dysmaturity in healthy preterm neonates. Thus the presented trend in early EEG development demonstrates that it is possible to establish clinically relevant age dysmaturity scores.

Application of ion-chromatography for the determination of the organic-group parameters AOCl, AOBr and AOI in water.

A method of differential AOX-analysis, i.e. the simultaneous determination of AOCl, AOBr and AOI is described. Individual steps of the method including enrichment at activated carbon, combustion in an oxygen stream and ion-chromatographic detection were optimized. In most cases quantitative recoveries of various organic Cl, Br and I containing substances of different polarity and structure were obtained. The method was applied to the determination of AOX-fractions in municipal and hospital wastewater. A good agreement between conventional coulometric and the described ion-chromatographic determination was found. High concentrations up to 130 microg/L I of organic iodine compounds were measured in the influent and effluent of a municipal treatment plant in Berlin and up to 10 mg/L I in a hospital waste-water.

[Doppler ultrasound monitoring of cerebral circulation during neonatal intensive care with special reference to artificial respiration]. / Untersuchungen zur dopplersonographischen Uberwachung der zerebralen Zirkulation während der neonatalen Intensivpflege unter besonderer Berücksichtigung der künstlichen Beatmung.

BACKGROUND: Doppler sonographic data from routine cerebral ultrasonic examination of mechanically ventilated premature neonates were analyzed in order to find out which intensive care influence factors take effect on the cerebral circulation. It was to be demonstrated if Doppler sonographic results are changed by current intensive medical influences especially mechanically ventilation. PATIENTS AND METHODS: In 24 premature neonates (mean gestational age 29.6 +/- 4 weeks, mean birth weight 1367 +/- 660 g) treated with mechanical ventilation for IRDS cerebral blood flow parameters were assessed by pulsed Doppler sonography. A single Doppler sonographic investigation was performed during the first week of life (median: day 5). Doppler flow velocity waveforms were obtained, and resistance index (RI) and pulsatility index (PI) values were calculated from the anterior cerebral arteries (ACA) as well as from the internal carotid artery (ACI). Oscillometrically measured blood pressure, pH, pCO2, and parameters of mechanical ventilation were registered. RESULTS: Besides the well established influence of pCO2 and blood pressure parameters of mechanical ventilation PEEP and time of inspiration have an influence on cerebral blood flow. CONCLUSIONS: Our results demonstrate the impact of mechanical ventilation on cerebral blood flow and therefore indicate the necessity of Doppler sonographic monitoring during mechanical ventilation. To our knowledge this is the first report about the influence of mechanical ventilation on cerebral blood flow in neonates.

Clinical relevance of age-dependent EEG signatures in the detection of neonates at high risk for apnea.

Age dependent EEG signatures were detected in the EEG of 71 neonates of 28-100 weeks of conceptional age (CA). Using the new method presented, neonates were automatically classified in three age groups (28-35 weeks CA), (36-40 weeks CA) and (41-100 weeks CA). Analysis was performed employing relative distance functions for the complete frequency spectra of the EEG registered by electrodes in C3 and C4 positions. The analysis was successful in automatic identification of individuals showing EEG anomalies. Polysomnographic analysis demonstrated these to be apnea risk patients. Accordingly, a purely EEG based detection of neonates that are medically at risk becomes feasible.

[Monitoring kidney function during neonatal intensive care: comparison between Doppler ultrasound findings and renal function parameters]. / Uberwachung der Nierenfunktion während der neonatalen Intensivtherapie: Vergleich zwischen dopplersonografischen Befunden und renalen Funktionsparametern.

33 neonates between 4th and 7th day of life were enrolled in the study. The data of renal Doppler sonography were compared to renal excretion parameters. In infants with respiratory distress a decrease of creatinine clearance as well as an increase of fractional sodium excretion were associated with reduced peak systolic flow velocity in the A. renalis. The results suggest the importance of the Doppler sonography in the monitoring of the renal function in the newborn intensive care.

Fructose 2,6-bisphosphate induces irreversible transitions in cell-free extracts of rat liver.

The effect of fructose 2,6-bisphosphate on the dynamics of the 6-phosphofructo-1-kinase/fructose-1,6-bisphosphatase cycle is investigated in a cell-free extract of rat liver under steady-state conditions. Bistability emerges on the basis of the reciprocal allosteric modulation of 6-phosphofructo-1-kinase and fructose-1,6-bisphosphatase. Under conditions of bistability fructose 2,6-bisphosphate may cause transitions between alternative steady states. However, in contrast to what is frequently observed in bistable systems, within a broad range of experimental conditions these transitions proceed irreversibly from states with high ATP to states characterized by low ATP.

Bistability and damped oscillations in the fructose 6-phosphate/fructose 1,6-bisphosphate cycle in cell-free extracts from rat liver.

The dynamics of the fructose 6-phosphate/fructose 1,6-bisphosphate substrate cycle was investigated in cell-free extracts from rat liver. Under conditions of continuous substrate supply different types of stationary states and damped oscillations were observed experimentally and found to be in qualitative agreement with theoretical predictions. Changing the adenylate energy charge of the substrate supply, bistability was shown to be related to irreversible transitions between functionally different branches of stable stationary states.

Penile sympathic skin response in erectile dysfunction.

Penile sympathic skin response (PSSR) was measured in 20 normal patients and in 46 patients with erectile dysfunction (ED). PSSR could be registered in 80% of normal patients. The latencies were 1,100-1,600 ms. In patients with ED, latencies were 1,240-3,640 ms. A reproducible normal latency of PSSR (< 1,600 ms) indicates a normal sympathic innervation of the penis. Long latencies (> 1,800 ms) indicate neuropathy of unmyelinated nerval fibers. The loss of a reproducible answer however allows no exact diagnostic information. PSSR is a useful diagnostic test for detecting neuropathy of unmyelinated nerval fibers as a possible cause of ED.

[School performance of former premature infants in the first four years of school]. / Schulleistungen ehemaliger Frühgeborener in den ersten vier Schuljahren.

School achievement during the first four grades was analysed by means of subject marks in 203 prematurely born and in 140 maturely born children. In subjects referring to behaviour in the classroom, no statistically significant differences in average marks could be found between prematurely born children and the control group. The average marks in performance subjects were slightly higher in the subgroup of very prematurely born children. However, statistically significant lower marks were observed in the subject of sports only, and for formerly immature children also in the subject of manual training. The higher the educational level of the mothers, the better the average marks without sports. No relationships between school performance and manifestation of postnatal risk factor like Apgar score, blood gas values and duration of oxygen dependency could be seen. These results demonstrate that school performance of former premature infants lies within the normal variance of their grade.

[The renal effects of dopamine therapy in premature infants in the first week of life]. / Untersuchungen zu renalen Auswirkungen der Dopamintherapie bei Frühgeborenen in der ersten Lebenswoche.

It is known that Dopamine therapy induces loss of water and sodium on the first or second days of life. On the other hand, no studies have been published on renal function under long-term therapy. In our study we could prove an altered excretion of water and sodium as well as fractional sodium excretion in preterm infants who received dopamine for at least the first week of life. Conclusions for clinical practice are drawn.

[Diagnostic possibilities and limits of 4-electrode rheoencephalography in premature infants with risk of brain damage]. / Diagnostische Möglichkeiten und Grenzen der 4-Elektroden-Rheoenzephalografie bei Frühgeborenen mit drohender Hirnschädigung.

Diagnostic value of cerebral electrical impedance for recognizing the risk of cerebral damage was analysed in 63 premature infants with postnatal respiratory disturbance during the first 4 weeks of life. Relationship between clinical risk factors like gestational age, Apgar scores, blood gas values on the one hand and impedance parameter of pulse volume, flow velocity and periphereal vascular resistance on the other were studied by means of correlation as well as variance analysis. Decrease of gestational age, Apgar score and increasing severity of respiratory disturbance cause statistically significant lowering of impedance parameters indicating reduction of volume, flow velocity and periphereal resistance in cerebral circulation by extreme immaturity, serious asphyxia as well as idiopathic respiratory distress syndrome. On contrast no statistically significant difference could be found between infants with and without intraventricular haemorrhages. However, significant differences were seen between group of patients only. Because of intercorrelation of risk factors and distinct variance no critical level of impedance parameters could be defined for the individual patient.