Nanoscale mapping of heterogeneity of the polarization reversal in lead-free relaxor-ferroelectric ceramic composites.

Relaxor/ferroelectric ceramic/ceramic composites have shown to be promising in generating large electromechanical strain at moderate electric fields. Nonetheless, the mechanisms of polarization and strain coupling between grains of different nature in the composites remain unclear. To rationalize the coupling mechanisms we performed advanced piezoresponse force microscopy (PFM) studies of 0.92BNT-0.06BT-0.02KNN/0.93BNT-0.07BT (ergodic/non-ergodic relaxor) composites. PFM is able to distinguish grains of different phases by characteristic domain patterns. Polarization switching has been probed locally, on a sub-grain scale. k-Means clustering analysis applied to arrays of local hysteresis loops reveals variations of polarization switching characteristics between the ergodic and non-ergodic relaxor grains. We report a different set of switching parameters for grains in the composites as opposed to the pure phase samples. Our results confirm ceramic/ceramic composites to be a viable approach to tailor the piezoelectric properties and optimize the macroscopic electromechanical characteristics.

Imaging and dosimetric errors in 4D PET/CT-guided radiotherapy from patient-specific respiratory patterns: a dynamic motion phantom end-to-end study.

Effective positron emission tomography / computed tomography (PET/CT) guidance in radiotherapy of lung cancer requires estimation and mitigation of errors due to respiratory motion. An end-to-end workflow was developed to measure patient-specific motion-induced uncertainties in imaging, treatment planning, and radiation delivery with respiratory motion phantoms and dosimeters. A custom torso phantom with inserts mimicking normal lung tissue and lung lesion was filled with [(18)F]FDG. The lung lesion insert was driven by six different patient-specific respiratory patterns or kept stationary. PET/CT images were acquired under motionless ground truth, tidal breathing motion-averaged (3D), and respiratory phase-correlated (4D) conditions. Target volumes were estimated by standardized uptake value (SUV) thresholds that accurately defined the ground-truth lesion volume. Non-uniform dose-painting plans using volumetrically modulated arc therapy were optimized for fixed normal lung and spinal cord objectives and variable PET-based target objectives. Resulting plans were delivered to a cylindrical diode array at rest, in motion on a platform driven by the same respiratory patterns (3D), or motion-compensated by a robotic couch with an infrared camera tracking system (4D). Errors were estimated relative to the static ground truth condition for mean target-to-background (T/Bmean) ratios, target volumes, planned equivalent uniform target doses, and 2%-2 mm gamma delivery passing rates. Relative to motionless ground truth conditions, PET/CT imaging errors were on the order of 10-20%, treatment planning errors were 5-10%, and treatment delivery errors were 5-30% without motion compensation. Errors from residual motion following compensation methods were reduced to 5-10% in PET/CT imaging, <5% in treatment planning, and <2% in treatment delivery. We have demonstrated that estimation of respiratory motion uncertainty and its propagation from PET/CT imaging to RT planning, and RT delivery under a dose painting paradigm is feasible within an integrated respiratory motion phantom workflow. For a limited set of cases, the magnitude of errors was comparable during PET/CT imaging and treatment delivery without motion compensation. Errors were moderately mitigated during PET/CT imaging and significantly mitigated during RT delivery with motion compensation. This dynamic motion phantom end-to-end workflow provides a method for quality assurance of 4D PET/CT-guided radiotherapy, including evaluation of respiratory motion compensation methods during imaging and treatment delivery.

Mathematical and computational models of drug transport in tumours.

The ability to predict how far a drug will penetrate into the tumour microenvironment within its pharmacokinetic (PK) lifespan would provide valuable information about therapeutic response. As the PK profile is directly related to the route and schedule of drug administration, an in silico tool that can predict the drug administration schedule that results in optimal drug delivery to tumours would streamline clinical trial design. This paper investigates the application of mathematical and computational modelling techniques to help improve our understanding of the fundamental mechanisms underlying drug delivery, and compares the performance of a simple model with more complex approaches. Three models of drug transport are developed, all based on the same drug binding model and parametrized by bespoke in vitro experiments. Their predictions, compared for a 'tumour cord' geometry, are qualitatively and quantitatively similar. We assess the effect of varying the PK profile of the supplied drug, and the binding affinity of the drug to tumour cells, on the concentration of drug reaching cells and the accumulated exposure of cells to drug at arbitrary distances from a supplying blood vessel. This is a contribution towards developing a useful drug transport modelling tool for informing strategies for the treatment of tumour cells which are 'pharmacokinetically resistant' to chemotherapeutic strategies.

Are there gender-specific aspects of gastric banding? Data analysis from the quality assurance study of the surgical treatment of obesity in Germany.

BACKGROUND: Since 1 January 2005, the situation of bariatric surgery has been examined in Germany. All data are registered prospectively in cooperation with the Institute of Quality Assurance in Surgery at the Otto-von-Guericke University Magdeburg. METHODS: Data collection on the results of gastric banding procedures was started in 2005, and the data are registered in an online database. Follow-up data were collected once a year. Participation in the quality assurance study is voluntary. RESULTS: Since 2005, 3,453 gastric banding procedures have been performed at 88 hospitals. The mean age of patients was 40.7 years, and the mean body mass index (BMI) was 45.2 kg/m2. BMI and comorbidities are significantly higher in male patients. Regarding gender-specific aspects, there are no significant differences in the perioperative complication rates. The amelioration rate of comorbidities in male patients is lower than in female patients. CONCLUSION: Gastric banding in Germany is generally performed in patients with a BMI below 45 kg/m2. The perioperative complication rate is low. Data from the nationwide survey of the German Bariatric Surgery Registry show significant differences in preoperative comorbidities and their amelioration between male and female patients. There is a need for further evaluation of gender-specific aspects of gastric banding procedures to optimize patient selection, reduce specific postoperative complications, and achieve long-term effects on weight loss and remission of comorbidities.

Ripple formation in weakly turbulent flow.

The formation of granular ripples under liquid shear flow in an annular channel is studied experimentally. The erodible granular bed is subject to weakly turbulent flows without a defined sharp boundary layer close to the granular bed. The flow field and the degree of turbulence is characterized quantitatively by using a particle image velocimeter and a laser-Doppler velocimeter, respectively. A new range of particle Reynolds numbers at the lower limit of the Shields diagram were explored. Quantitative measurements of the granular flow on the surface reveal that the threshold for particle motion coincides within the order of one percent with the threshold for ripple formation. In fully developed ripples it was found that on the leeward side of the ripples regions of low-velocity gradients exist where granular motion is scarce, indicating that the coupling between the ripples is mainly caused by the flow field of the liquid.

Stress induced phase transformation of a cesium stabilized leucite porcelain and associated properties.

OBJECTIVES: The addition of CS2O to dental porcelains might provide a means for controlling the thermal expansion and toughness of feldspathic porcelains. The purpose of this investigation was to determine for a leucite porcelain the effect of CS2O content upon its coefficient of thermal expansion (alpha), toughness, hardness, and content of low (tetragonal) leucite and high (cubic) leucite. METHODS: In order to determine the amount of low leucite in the specimens, an x-ray calibration curve for low leucite and an internal standard of copper was obtained using quantitative x-ray diffraction techniques. Utilizing a stress induced phase transformation between low and high leucite, an x-ray intensity conversion ratio (r) was determined for high leucite so that the calibration curve for low leucite could be used to determine the amount of high leucite present in the experimental porcelains. Specimens were prepared with various amounts of CS2O (0.0, 0.5, 1.0, 1.5, 2.0 mol%) so that, except for the as-received porcelain (A), all had the same thermal history. Specimens were tested for content of low and high leucite, hardness (Vickers), toughness (indentation-strength method), and coefficient of thermal expansion (alpha) over two temperature ranges (30-500 degrees C and 30-640 degrees C). Fractured surfaces were examined with a scanning electron microscope (SEM). For each property, specimen groups were compared for statistical differences. These comparisons were statistically analyzed using analysis of variance (ANOVA) and Fisher's protected least significant differences (PLSD). RESULTS: Quantitative x-ray examination of abraded and heat-treated specimens demonstrated that a stress induced phase transformation occurred which could be reversed by heat treatment. The conversion ratio was determined as r = 1.93 +/- 0.29. The addition of CS2O lowered the wt% of low leucite from 63 +/- 6% to 0% and increased the amount of high leucite from 0% to 62 +/- 5%. ANOVA showed that the addition of CS2O had a significant effect on alpha (p < 0.0001), hardness (p < 0.005), and toughness (p < 0.0001). CS2O significantly (PLSD) lowered the alpha (p < 0.0001), hardness (p < 0.01), and toughness (p < 0.0001) of a high-content leucite porcelain. SIGNIFICANCE: A stress induced phase transformation of high leucite to low leucite was demonstrated and, as a consequence, suggested the potential for phase transformation toughening. The alpha of a leucite porcelain could be controlled by stabilizing high (cubic) leucite to room temperature with the fraction of high leucite dependent upon the amount of CS2O added. A method was developed to determine the amount of high leucite present in a porcelain.

Cerium oxide as a silver decolorizer in dental porcelains.

OBJECTIVES: Silver-base alloys are known to produce an esthetically unpleasant yellow-green tint in the dental porcelain when making PFM restorations. Cerium oxide is used in dental porcelains to simulate the natural fluorescence found in human dental enamel, and has also been used in the glass industry as a decolorizer. The purpose of this study was to determine the effect of CeO2 additions on the resistance of dental porcelain to staining from silver contamination. METHODS: Five batches of porcelain were prepared according to Weinstein et al. (1962) with 0.00, 0.05, 0.10, 0.15 and 0.20 wt% additions of CeO2. To determine the resistance of these porcelains to silver staining, 0.10 wt% additions of the silver oxides were triturated into the prepared CeO2 porcelains prior to sample fabrication. This procedure provided a more quantitative method of staining than firing directly on silver alloys. Silver oxide was added in two valence states as Ag2O and AgO to test for any possible effects on staining. Samples were pressed into a 17 mm diameter mold, and fired to 960 degrees C under vacuum. Three additional samples were prepared from the non-cerium porcelain frit to produce a non-stained control group. Color measurements were made with a spectrophotometer on the ten experimental groups and the control group. The CIE L*a*b* color difference, delta E*, was calculated between the control and the experimental groups. RESULTS: There was a significant decrease in the silver staining of dental porcelains when CeO2 additions of 0.10 wt% or greater were used. SIGNIFICANCE: Cerium oxide additions in the range of 0.10 to 0.20 wt% caused a three-fold reduction in the staining of dental porcelain samples which had been doped with 0.10 wt% of AgO or Ag2O.

Color distribution of three regions of extracted human teeth.

OBJECTIVES: Knowledge of human tooth color and its distribution are critical to the understanding of shade matching in esthetic dentistry. The color of human teeth shows a gradation from the gingival to the incisal region. There have been many reports in the literature on the distribution of color in teeth, but not in the CIE 1976 L*a*b* system. This study was conducted to determine the color distribution in three regions in a sample of human teeth and express the results in Munsell notation, CIE 1976 L*a*b* and CIE delta E* color differences. The hypothesis of this research was that it is possible to detect significant differences in the color parameters of the three distinct regions in teeth. METHODS: All of the teeth used in this study were extracted, cleaned and stored in artificial saliva. Prior to measurement, the teeth were removed from the solution and mounted in a holder to ensure consistent measurements. Spectral data were collected using a GE recording spectrophotometer, CIE chromaticity coordinates calculated using CIE illuminant C and 1931 observer data, and conversions made to L*, a*, b* and Munsell notation. The results were analyzed by ANOVA and Scheffé's multiple comparisons test. RESULTS: The mean L*, a*, b*s were 72.6, 1.5, 18.4 for gingival, 72.4, 1.2, 16.2 for middle, and 71.4, 0.9, 12.8 for incisal. Average Munsell parameters were 1.2 Y 7.1/2.7 for gingival, 1.3 Y 7.1/2.4 for middle, and 1.4 Y 7.0/1.9 for incisal. The mean CIE delta E* between the gingival and incisal regions of the 95 teeth showed a clinically significant difference of 8.2. SIGNIFICANCE: The distribution of color was identified for three regions of the tooth. A statistical analysis determined that there are statistically significant color differences between the regions, and these differences are also clinically significant. This information is beneficial when esthetic restorations are required.

Prognosis of childhood epilepsy in newly referred patients.

The aim of this study was to investigate the prognosis of childhood epilepsy and to analyze prognostic factors in addition to remission rate in a follow-up of newly referred patients. Two hundred eighty-one patients were followed for a mean period of 5.3 years. Overall, 253 patients (90%) achieved 1-year remission. The beginning of a 1-year seizure-free period was achieved in 77.9% by 1 year, in 84% by 2 years and in 88.6% by 3 years after onset of treatment. Early onset of seizures, symptomatic etiology, and neurologic handicap predicted a worse prognosis. In 44 of 253 children with complete suppression of seizures for 1 year, relapses occurred within the follow-up period. In one child with a relapse, remission could not be achieved in the 2nd year thereafter. In conclusion, our study shows a good prognosis for most children with epilepsy, especially in patients with idiopathic epilepsy and late onset of seizures and without neurologic dysfunction. Moreover, our data strongly suggest that the long-term pattern of seizure control is largely established during the first 2 years of treatment.

Evaluation of some properties of an opaque porcelain fired simultaneously with the body porcelain.

Recently, a porcelain-fused-to-metal opaque porcelain was introduced that does not require a separate firing before application of the body porcelain. The objective of this study was to determine the properties of this new opaque porcelain and its ability to bond to metal. The properties studied included flexural strength, linear firing shrinkage, coefficient of thermal expansion, powder particle size, and ability to bond to body porcelain and dental alloys. Sintering of this opaque porcelain was complete when fired at 1760 degrees F (960 degrees C) with a linear firing shrinkage of 13.1% +/- 0.2%. No boundary between the opaque and body porcelains could be found with a scanning electron microscope after firing at 1760 degrees F (960 degrees C). The mean flexural strengths were 99 +/- 7 and 101 +/- 8 MPa respectively, for this opaque porcelain and a conventional opaque porcelain, and were not significantly different as assessed with Student's t-test (p = 0.548). The coefficients of thermal expansion for this opaque porcelain was 13.3 +/- 0.2 x 10(-6)/degrees C. Particle size analysis showed a 63% increase in the particles below 5 microns for this opaque porcelain and bonding to two alloys was adequate as indicated by its cohesive failure. Simultaneous firing of this special opaque porcelain and body porcelain produced satisfactory sintering, strength, and bonding to metal.

Leucite content of selected dental porcelains.

Leucite is a major crystalline component of dental porcelains. The presence of tetragonal leucite in dental porcelains increases their coefficients of thermal expansion due to its high coefficient of thermal expansion (20-25 x 10(-6)/degrees C). This is particularly useful for those porcelains designed for bonding to precious metals and nickel alloys. The purpose of this study was to determine the leucite content of selected commercial dental porcelains in relation to their coefficient of thermal expansion values. The weight fraction of leucite was determined with quantitative x-ray diffraction using copper as an internal standard. Coefficient of thermal expansion values were determined using a thermal dilatometric analyzer. Five commercial body porcelains were studied. Leucite was not detected in samples of Vitadur N and Duceram LFC. An ANOVA showed that there was a significant difference in the weight fraction of leucite for Silhouette, Ceramco II, and Optec HSP porcelains. Linear regression revealed a correlation (R = 0.91) between weight fraction of leucite and the coefficient of thermal expansion for those samples containing leucite. Duceram LFC, which is recommended by the manufacturer for use with metals and leucite-containing porcelains, had no detectable leucite although the coefficient of thermal expansion was found to be 13.2 +/- 0.4 x 10(-6)/degrees C at 25-472 degrees C. A low glass transition temperature contributed to the high average coefficient of thermal expansion value.

Color differences coefficients of body-opaque double layers.

Porcelain restorations have double-layer color effects resulting from the presence of body and opaque layers. The purpose of this study was to quantify the color differences resulting when a defined thickness of body porcelain is fired on an opaque porcelain of the same shade designation and from the same porcelain brand. A color difference coefficient was defined as the color change resulting from a 1-mm-thick layer of body porcelain on an opaque porcelain of the same shade and brand. Six shades and four porcelain brands were evaluated in this study. The range of color difference coefficients for all shades and brands was 6.76 to 14.32. There was no significant difference between shades or between brands. The use of color difference coefficients is a practical method of evaluating porcelain shades and brands and should provide guidance in the choice of porcelains and the fabrication of porcelain restorations to better achieve the desired esthetics.

The strengthening mechanism of a magnesia core ceramic.

A high-expansion core material containing magnesia and forsterite may be used to make all-ceramic dental crowns with porcelain-fused-to-metal body porcelains. The purpose of this study was to investigate the strengthening mechanism for the magnesia core material. Six batches of the magnesia core material were made by reacting magnesia with a silica glass with holding times ranging from 17 to 120 min. The flexural strength was measured using three-point loading according to the ISO specification for dental ceramics. The forsterite content was measured using quantitative x-ray diffraction. A statistically significant correlation was found between the forsterite content and flexural strength. The proposed mechanism for strengthening is the precipitation of fine forsterite crystals in the glass matrix surrounding unreacted magnesia. Longer reaction times produced more dissolution of magnesia and subsequent precipitation of forsterite. This method results in a new strengthening mechanism for dental ceramics which have previously relied on the incorporation of alumina, leucite or ceramic whiskers.

Differences in color between fired porcelain and shade guides.

The inaccuracy of premixed porcelain shades may cause errors when color matching porcelain crowns. Most brands of porcelain are labeled to match shades of the Vita shade guide, but produce slightly different colors from this guide upon firing. The purpose of this study was to quantify in CIE delta E* units the color differences between the Vita shade guide colors and four commercial porcelains for metal ceramic crowns. Two operators prepared shade-guide teeth from six shades of four brands of porcelain. Opaque, body, and incisal layers were fired in the form of shade-guide teeth on Vita ceramic carriers used for making custom shade-guide teeth. The colors of these teeth were measured with a Beckman spectrophotometer with an integrating sphere. The average delta E* values for the differences between the colors of the Vita shade guide and the fired porcelains for each of the brands were 3.1, 2.9, 4.1, and 2.0, respectively, for the first operator and 4.1, 2.6, 2.8, and 1.6, respectively, for the second operator. The color difference between the custom shade-guide teeth and the Vita master shade guide were significantly affected by both brands and shades. The overall average error resulting from the differences in colors between the Vita shade guide and fired porcelains was 3.0 for the first operator and 2.8 for the second operator. The mean delta E* between the teeth prepared by the two operators was 3.6. The color difference between the teeth made by the two operators was not significantly affected by brands or shades.

[Improved properties of systems for computer-assisted motility analysis]. / Verbesserung der Eigenschaften von Systemen der computerunterstützten Motilitätsanalyse.

For a number of years, computer-assisted methods have been employed for the motility analysis of spermatozoa. In addition to a number of advantages, such as short processing time and good reproducibility, they have certain shortcomings in the recognition and tracking of spermatozoa at high densities. For example, sperm cells and contaminating particles of the same size cannot be distinguished. The tracking of crossing sperm cell trajectories is also a problem. For this reason, procedures that are free from such shortcomings have been introduced. Their application leads to an improvement in the performance of computer-assisted semen analysis methods.

Sources of color variation on firing porcelain.

The final color matching of porcelain crowns depends upon the accuracy of the original shade matching by the dentist and variables introduced during processing. Possible sources of processing variables include thickness and color of the opaque, thickness, color, and translucency of the body and enamel layers, firing temperature, and number of firings (Miller, 1987). These processing variables can lead to an error in shade match. The purpose of this study was to quantify, in CIE delta E units: (1) the shade variations when the same batches are fired, (2) the shade variations between different batches, and (3) the differences in color produced by the multiple firing. Three lots of six shades of four commercial brands were included in this study. The color variation of the opaque samples (mean delta E was 0.46) was generally lower than that of the body/opaque samples (mean delta E was 0.86). The average color variation for three different batches of the body/opaque samples was 1.44. The average color difference produced as a result of multiple firings was 1.00 after six firings, compared with the color after three firings.

Coverage errors of two shade guides.

Dental shade guides contain a limited selection of colors compared to those found in human teeth. An error in shade selection is thus introduced, since many tooth colors must be defined by approximation to the nearest shade of the guide. The Bioform and Vita Lumin guides, and a combination of the two, were spectrophotometrically compared to the published colors of 335 human teeth. The minimum CIE L*a*b* color difference was calculated for each tooth using each shade guide. The average of these color differences was defined as the coverage error. The Bioform and Vita shade guide coverage errors were not significantly different, but the coverage error was significantly lower when the combination was used. The use of both guides in shade selection is recommended to reduce the coverage error.

A new, small-color-difference equation for dental shades.

Traditionally, dental-shade-guide standards are designated in terms of Munsell hue (H), value (V), and chroma (C). However, delta E color differences proposed as ADA tolerances for shade guides are in the CIE L*a*b* system. The purpose of this study was to evaluate a new color-difference equation, delta EM = C delta H/5 + 7 delta V + 4 delta C for estimation of small color differences by Munsell parameters. The published values of the Bioform shade-guide tooth colors determined with a Beckman spectrophotometer were used. Color differences among 276 combinations of the 24 Bioform shade-guide colors were calculated with Eq. 1, with use of the Munsell notation, and also with the CIE L*a*b* equation for delta E. An estimate of the accuracy of Eq. 1 was 0.41 delta E units when delta E CIE was below 4.0. The Vita shade-guide colors were determined with a Beckman spectrophotometer. This data set contained 16 samples, and 120 combinations were used for calculation of color difference. An estimate of the accuracy for this set of data was 0.35 delta E units when delta E CIE was less than 4.0. The new color-difference equation provides a means for estimation of delta E CIE L*a*b* color difference between dental shades with Munsell notation. This equation will be useful for estimation of small delta E CIE L*a*b* values for shade-guide teeth that are designated in terms of Munsell notation.

[Function and structure of families with an epileptic child]. / Funktion und Struktur von Familien mit einem epilepsiekranken Kind.

Although the impact of psycho-social factors on the individual patient with epilepsy has been widely investigated, the influence of the illness on the family as a whole is still underestimated. By means of the Family Assessment Measure (FAM III), a well-validated instrument, we investigated which measurable influence the epilepsy of one child had on the functioning of the families. Data from a group of 72 families with a child suffering from epilepsy (EG), but without any other handicap were analysed and compared with those of 75 families with a child with severe mental retardation (SMG) and 76 control families (CG). Data were gathered through home visits. Only complete families were studied. Results showed that the EG was similar to the SMG in all 3 scales of FAM III, but differed significantly from the CG. In 26% of the families in EG and in 19% of the SMG clear signs of family malfunctioning were found, as compared with 6.5% of the CG. Family disfunctioning in EG was of a greater variety that in SMG. We found that within the EG the type of seizures (41 patients with generalized tonic clonic fits, 10 with complex partial seizures and 21 with absences) did not have any impact on the results. In addition, neither the duration of the illness nor the absolute length of seizure-free periods seemed to matter. Only families who had the subjective feeling that their children were still suffering from epilepsy showed significantly higher rates of family malfunctioning. Summarizing, we found that epilepsy in a child can have a severe impact, not only on his individual life and on the mother-child relationship, but on the functioning of his family as the whole. This fact should be taken into account in the treatment of these children and should influence family counselling, as well.

[Computerized tomography in epilepsy in children]. / Computertomographie bei Epilepsien im Kindesalter.

We present a retrospective study of 160 children attending our epilepsy out-patient department. Computed tomography (CT) was performed on 123 (77%) patients, namely all children with the exception of those with febrile seizures, typical absence seizures, and benign Rolandic epilepsy. Incidence of CT abnormalities and their correlation with clinical features were evaluated. The CT scan was normal in 84 and abnormal in 39 patients. Although in general, the detection of abnormality on CT will not alter the management of the child, in a small percentage (2%) of our cases a lesion treatable by surgery was discovered. The indications for CT are summarized.