105 research outputs found
Experimentelle Verformung von natürlichen Quarzeinkristallen : Einfluss der Wasserneuverteilung auf die Deformation und mikrostrukturelle Untersuchungen
No full textQuartz is one of the common minerals present in the Earth’s crust that controls its rheology and has a simple chemical composition. There is a lot of data available for quartz, which makes it one of the best studied minerals in nature as well as in experiments. Griggs and Blacic (1965) first described the phenomenon of “hydrolytic weakening” in experimentally deformed natural quartz. They found that “dry” natural quartz deformed at much lower flow stresses in a water containing environment compared to “dry” quartz without added water.
The aim of this study is to investigate the effect of temperature, confining pressure and water on the deformation of natural quartz single crystal. For this purpose, axial compression experiments were performed in a modified solid medium (NaCl) Griggs apparatus at different temperatures (700 –1000°C) and different confining pressures (700 MPa, 1000 MPa and 1500 MPa) with constant strain rates of ~10^-6s^-1. Samples, 6.5 mm in diameter and 10 mm to 13.5 mm in length, were cored from a narrow zone of a constant fluid inclusion density in a large single crystal in two different orientations: 1) normal to one of the prism planes (⊥m) and 2) 45° to and 45° to [c] (O+). These orientation were use to achieve the highest resolved shear stress to activate 1) prism slip and 2) basal slip and prism [c] slip.
The strengths of the samples of both orientations at 900°C are between 150 MPa and 250 MPa. At lower temperatures the strength is accordingly higher (800°C – ~800 MPa ⊥m or 550 MPa O+, 700°C - ~1600 MPa ⊥m or 1400 MPa O+). Changes in confining pressure show only very small variations in strength. In deformed samples and both orientations microstructures like undulatory extinction, deformation lamellae and deformation bands can be observed. Recrystallized quartz grains are extremely rare and isolated. The microstructures as well as the sample shape and the strength are typical for crystal plastic deformation by dislocation glide. Sample shape, orientation of microstructures, EBSD measurements and [c]-axis rotation (by CIP) are used to define the active slip systems. In ⊥m samples the dominant slip system is prism slip, but [c]-axis misorientations indicate the activity of a secondary slip system. Basal slip is the active slip system in O+ samples.
The observation of fluid inclusions and the measurements of water content by FTIR, point out that the fluid inclusions of the starting material are very heterogeneous. The quartz starting material, away from fluid inclusions is characterized by flat FTIR-absorption and the water content calculated from these spectra yields low values (~50 H/10^6 Si). Therefore it can be described as a “two phase” material of dry quartz and water rich fluid inclusions. During pressurization and deformation the fluid inclusions of the starting material change shape and size dramatically (several 100 µm down to nm scale). Especially pressurization leads to the decrepitation of fluid inclusions and the formation of microcracks, which are the pathways for water. Fast crack healing due to high temperatures facilitates the local wetting of quartz. Pressurized samples show broad absorption band, typical for molecular water. The water content varies between several thousands H/10^6 Si and very low water contents of only tens of H/10^6 Si. These variations are probably caused by the redistribution of fluid inclusions that cannot be avoided during the FTIR measurements. After deformation a broad absorption band is still present but differs from pressurized samples, in that it is more pointed. Additionally a sharp absorption band at 3585 cm^-1 appears. This band is only present in deformed regions.
Due to the redistribution of fluid inclusions and therefore water a “one phase” material develops which behaves like “wet” quartz (mechanically weak). High temperatures, fluid inclusions decrepitation and the fast crack healing are the precursor for plastic deformation by dislocation glide in quartz single crystals in our experiments
Modelling and Observing the Effects of Long Distance bus Market Liberalization in Germany
No full textAbstractSince January 2013 the long-distance passenger market is open to bus operators. This paper is about the efforts of the German railway company in market research and model building to predict the effect of bus market liberalisation in advance. Methods, forecast and the real development of the bus market will be shown. The major focus is the design of the situational stated preference conjoint and the parameter estimation of the mode choice model
Glioma imaging in Europe: A survey of 220 centres and recommendations for best clinical practice
No full textObjectives At a European Society of Neuroradiology (ESNR) Annual Meeting 2015 workshop, commonalities in practice, current controversies and technical hurdles in glioma MRI were discussed. We aimed to formulate guidance on MRI of glioma and determine its feasibility, by seeking information on glioma imaging practices from the European Neuroradiology community. Methods Invitations to a structured survey were emailed to ESNR members (n=1,662) and associates (n=6,400), European national radiologists’ societies and distributed via social media.
Results Responses were received from 220 institutions (59% academic). Conventional imaging protocols generally include T2w, T2-FLAIR, DWI, and pre- and post-contrast T1w. Perfusion MRI is used widely (85.5%), while spectroscopy seems reserved for specific indications. Reasons for omitting advanced imaging modalities include lack of facility/software, time constraints and no requests. Early postoperative MRI is routinely carried out by 74% within 24–72 h, but only 17% report a percent measure of resection. For follow-up, most sites (60%) issue qualitative reports, while 27% report an assessment according to the RANO criteria. A minority of sites use a reporting template (23%).
Conclusion Clinical best practice recommendations for glioma imaging assessment are proposed and the current role of advanced MRI modalities in routine use is addressed.
Key Points
• We recommend the EORTC-NBTS protocol as the clinical standard glioma protocol.
• Perfusion MRI is recommended for diagnosis and follow-up of glioma.
• Use of advanced imaging could be promoted with increased education activities. • Most response assessment is currently performed qualitatively.
• Reporting templates are not widely used, and could facilitate standardisation.EORTC Brain Tumour GroupDepto. de Radiología, Rehabilitación y FisioterapiaFac. de MedicinaTRUEpu
Die DNS-Synthese am Ende der S-Phase und das G-Banding in neoplastischen Zellen der Ratte
No full textAcoustic testing of a 1.5 pressure ratio low tip speed fan with a serrated rotor (QEP fan B scale model)
No full textA scale model of the bypass flow region of a 1.5 pressure ratio, single stage, low tip speed fan was tested with a serrated rotor leading edge to determine its effects on noise generation. The serrated rotor was produced by cutting teeth into the leading edge of the nominal rotor blades. The effects of speed and exhaust nozzle area on the scale models noise characteristics were investigated with both the nominal rotor and serrated rotor. Acoustic results indicate the serrations reduced front quadrant PNL's at takeoff power. In particular, the 200 foot (61.0 m) sideline noise was reduced from 3 to 4 PNdb at 40 deg for nominal and large nozzle operation. However, the rear quadrant maximum sideline PNL's were increased 1.5 to 3 PNdb at approach thust and up to 2 PNdb at takeoff thust with these serrated rotor blades. The configuration with the serrated rotor produced the lowest maximum 200 foot (61.0 m) sideline PNL for any given thust when the large nozzle (116% of design area) was employed
Glioblastoma:New Molecular Concepts Pave the Way for Advances in Diagnosis and Treatment
No full textGlioblastoma (also known as glioblastoma multiforme), a type ofglioma, is a high-grade brain tumor that develops from the glial cellssurrounding neurons. It is the most common aggressive intrinsic braintumor in adults, with the potential to spread rapidly within the brain.Patients with glioblastoma face a poor prognosis, with median overallsurvival of approximately 15 months. However, our growingunderstanding of the molecular biology of gliomas means that thisoutlook may be improving.The identification of clinically relevant subgroups defined byspecific genetic mutations is challenging the traditional delineationbetween low- and high-grade gliomas that has been based onhistological appearance and imaging. Indeed, it is becoming clear that,as a molecular entity, a glioblastoma, which by traditionalclassification is a grade IV glioma, may present with a lower gradeinitially and then become more aggressive – an important addition tothe established concept.The care of a patient with a glioblastoma requires a coordinatedapproach delivered by a multidisciplinary team, with the aim ofmaintaining quality of life for as long as possible. Here, we provide aconcise overview of the diagnosis and management of glioblastoma, aswell as discussion of our emerging understanding of the moleculardrivers that are helping us to delineate different patient subgroups.These subgroups will, hopefully, allow more targeted treatments inthe future.This resource will be of interest to all those involved in caring forpatients with this aggressive brain tumor, including neurologists,neurosurgeons, neuro-oncologists, radiation oncologists, palliativecare specialists, specialist nurses and medical students.<br/
Glioblastoma:New Molecular Concepts Pave the Way for Advances in Diagnosis and Treatment
No full textGlioblastoma (also known as glioblastoma multiforme), a type ofglioma, is a high-grade brain tumor that develops from the glial cellssurrounding neurons. It is the most common aggressive intrinsic braintumor in adults, with the potential to spread rapidly within the brain.Patients with glioblastoma face a poor prognosis, with median overallsurvival of approximately 15 months. However, our growingunderstanding of the molecular biology of gliomas means that thisoutlook may be improving.The identification of clinically relevant subgroups defined byspecific genetic mutations is challenging the traditional delineationbetween low- and high-grade gliomas that has been based onhistological appearance and imaging. Indeed, it is becoming clear that,as a molecular entity, a glioblastoma, which by traditionalclassification is a grade IV glioma, may present with a lower gradeinitially and then become more aggressive – an important addition tothe established concept.The care of a patient with a glioblastoma requires a coordinatedapproach delivered by a multidisciplinary team, with the aim ofmaintaining quality of life for as long as possible. Here, we provide aconcise overview of the diagnosis and management of glioblastoma, aswell as discussion of our emerging understanding of the moleculardrivers that are helping us to delineate different patient subgroups.These subgroups will, hopefully, allow more targeted treatments inthe future.This resource will be of interest to all those involved in caring forpatients with this aggressive brain tumor, including neurologists,neurosurgeons, neuro-oncologists, radiation oncologists, palliativecare specialists, specialist nurses and medical students.<br/
Surface-mountable LTCC-SiP module approach for reliable RF and millimetre-wave packaging
No full textAbstractThe rapid growth in the wireless communications markets together with the emerging need for high-bit-rate (≫ 100 Mb/s) multimedia/data services are pushing the usage of radio spectrum resources below 10 GHz to the uttermost limit. The lack of bandwidth has led to an extensive development of mobile/fixed BWA systems for the higher microwave and millimetre-wave regions up to the V-band frequencies (50–75 GHz). In order for these systems to have mass deployment and to meet cost-sensitive consumer markets’ requirements, their cost and size must be reduced from current levels. One of the most viable packaging approaches to satisfy these demands is the low-temperature co-fired ceramic (LTCC) based system-in-package (SiP) module technology combined with fully automated surface-mount assembly techniques. However, one of the main challenges of this approach has been previously associated with the broadband radio frequency (RF) and reliability performance constraints of the board-level solder joints in LTCC/PCB assemblies. In this thesis the primary focus is to tackle these limitations and significantly extend the feasibility of the LTCC module technology to various wireless/mixed-signal packaging applications. The thesis is divided into three main parts. In the first part, design, modelling and implementation of vertical package transitions (BGA, flip-chip, substrate via) over a very wide frequency range are presented. In the second part, the emphasis is on the improvement of the thermal fatigue endurance of the board-level solder joints in the LTCC/PCB assemblies. In the last part, the results are merged to realize a high-performance LTCC module platform for use in a wide variety of SiP products in the telecommunication sector. The flip-chip, substrate-via and BGA transition structures exhibited excellent signal transmission properties up to the V-band frequencies. The developed equivalent circuit models of the transitions matched well with the measurements. Cascading the transitions together allows the building of different combinations of vertical interconnection paths in SiP modules. To demonstrate this, a surface-mountable LTCC filter package for K-band radio link frequencies was implemented. The developed composite BGA solder joint structure with plastic-core solder balls significantly enhanced the thermal fatigue life in LTCC/PCB assemblies in different thermal cycling conditions, indicating adequate board-level reliability for many practical LTCC-BGA packaging applications. Moreover, electromagnetic analysis showed that the use of the plastic-core solder ball has no detrimental impact on the RF performance of the solder joint. Finally, based on the obtained results a reliable lead-free LTCC-BGA module platform was developed for broadband packaging applications. The BGA module platform with a size of 15 mm × 15 mm included 38 low-frequency and two wideband RF input/output connections up to the K-band frequencies. The module structure also allowed plenty of space to mount discrete SMD/bare-die components on the surface and/or to embed passive components in the 1.2 mm thick substrate. Preliminary thermal cycling results of the soldered LTCC/PCB assemblies demonstrated sufficient reliability for telecommunication applications. Therefore, the presented module platform can serve as a physical building block for various wireless/mixed-signal SiP products, and hence significantly reduce their development time and associated costs. Academic dissertation to be presented, with the assent of the Faculty of Technology of University of Oulu, for public defence in Kajaaninsali (Auditorium L6), Linnanmaa, on November 21st, 2008, at 12 noonAbstract
The rapid growth in the wireless communications markets together with the emerging need for high-bit-rate (≫ 100 Mb/s) multimedia/data services are pushing the usage of radio spectrum resources below 10 GHz to the uttermost limit. The lack of bandwidth has led to an extensive development of mobile/fixed BWA systems for the higher microwave and millimetre-wave regions up to the V-band frequencies (50–75 GHz). In order for these systems to have mass deployment and to meet cost-sensitive consumer markets’ requirements, their cost and size must be reduced from current levels. One of the most viable packaging approaches to satisfy these demands is the low-temperature co-fired ceramic (LTCC) based system-in-package (SiP) module technology combined with fully automated surface-mount assembly techniques. However, one of the main challenges of this approach has been previously associated with the broadband radio frequency (RF) and reliability performance constraints of the board-level solder joints in LTCC/PCB assemblies. In this thesis the primary focus is to tackle these limitations and significantly extend the feasibility of the LTCC module technology to various wireless/mixed-signal packaging applications.
The thesis is divided into three main parts. In the first part, design, modelling and implementation of vertical package transitions (BGA, flip-chip, substrate via) over a very wide frequency range are presented. In the second part, the emphasis is on the improvement of the thermal fatigue endurance of the board-level solder joints in the LTCC/PCB assemblies. In the last part, the results are merged to realize a high-performance LTCC module platform for use in a wide variety of SiP products in the telecommunication sector.
The flip-chip, substrate-via and BGA transition structures exhibited excellent signal transmission properties up to the V-band frequencies. The developed equivalent circuit models of the transitions matched well with the measurements. Cascading the transitions together allows the building of different combinations of vertical interconnection paths in SiP modules. To demonstrate this, a surface-mountable LTCC filter package for K-band radio link frequencies was implemented.
The developed composite BGA solder joint structure with plastic-core solder balls significantly enhanced the thermal fatigue life in LTCC/PCB assemblies in different thermal cycling conditions, indicating adequate board-level reliability for many practical LTCC-BGA packaging applications. Moreover, electromagnetic analysis showed that the use of the plastic-core solder ball has no detrimental impact on the RF performance of the solder joint.
Finally, based on the obtained results a reliable lead-free LTCC-BGA module platform was developed for broadband packaging applications. The BGA module platform with a size of 15 mm × 15 mm included 38 low-frequency and two wideband RF input/output connections up to the K-band frequencies. The module structure also allowed plenty of space to mount discrete SMD/bare-die components on the surface and/or to embed passive components in the 1.2 mm thick substrate. Preliminary thermal cycling results of the soldered LTCC/PCB assemblies demonstrated sufficient reliability for telecommunication applications. Therefore, the presented module platform can serve as a physical building block for various wireless/mixed-signal SiP products, and hence significantly reduce their development time and associated costs
Determination of the permittivity of some dielectrics in the microwave and millimetre wave region
No full textAbstractIn the first part of this study, determination of the dielectric properties of the low loss microwave ceramic material, barium nonatitanate (Ba2Ti9O20), around 1 GHz is discussed. The structures under test were coaxial resonators, the cores of which were made of barium nonatitanate and the metallization was realised by thick film silver. The measured value of the real part of the relative dielectric constant was εr = 37 and that of the loss tangent was tan σ = 0.00014. The change of the resonance frequency of the coaxial resonators with temperature, in the range -20 … +80 C, was 4 ppm/ C. In addition, realisation of compact interdigital and comb-line bandpass filters was demonstrated for the 900 MHz mobile phone band. Besides Ba2Ti9O20, Ba(Sm,Nd)2Ti5O14 ceramic material with a dielectric constant of εr = 78 was also employed in order to improve the miniaturisation. The volume of the smallest filter was 2 cm3 and the weight was 9 g.In the second part of this study, various measurement methods have been demonstrated to determine the real part of the relative permittivity of FR4 fibreglass circuit board. Test structures were straight asymmetric open-circuited strip lines. It was found that the real part of the relative permittivity decreased slightly with frequency. At 0.72 GHz and 4.5 GHz, εr values of 4.3 and 4.1, respectively, were measured. All the characterisation methods used gave consistent values for εr, and electromagnetic simulators were used to verify the results.In the third part of this study, the structures under test were microstrip or strip line transmission lines, the S parameters of which were measured by using on-wafer measurement techniques. It was found that the insertion loss of the 10 mm long etched Cu microstrip was slightly less than that of the Ag microstrips which were manufactured by etching and gravure offset printing techniques, respectively. The performance of the Ag microstrips was, however, similar. In addition, a theoretical basis was established for the determination of εr of the dielectric substrate and the attenuation coefficient of the transmission lines under test. The calculations were based on signal flow diagrams. The method was applied to determine the dielectric and loss properties of a commercial, Kyocera, Japan, LTCC (Low Temperature Cofired Ceramic) material up to 50 GHz. The measured value of the real part of the relative permittivity was εr = 5.7, and the loss tangent was approximately tan σ = 0.003.The essential idea behind the studies reported in this thesis was twofold. First, the studies aimed at characterising dielectric media which find usage in the realisation of UHF, microwave or millimetre wave circuits. Second, the studies aimed to obtain data of immediate value in practical design work. For this reason, the structures under test were transmission lines having extensive usage in practical high frequency circuit design. Academic Dissertation to be presented with the assent of the Faculty of Technology, University of Oulu, for public discussion in Kajaaninsali (Auditorium L 6), Linnanmaa, on April 16th, 1999, at 12 noon.Abstract
In the first part of this study, determination of the dielectric properties of the low loss microwave ceramic material, barium nonatitanate (Ba2Ti9O20), around 1 GHz is discussed. The structures under test were coaxial resonators, the cores of which were made of barium nonatitanate and the metallization was realised by thick film silver. The measured value of the real part of the relative dielectric constant was εr = 37 and that of the loss tangent was tan σ = 0.00014. The change of the resonance frequency of the coaxial resonators with temperature, in the range -20 … +80 C, was 4 ppm/ C. In addition, realisation of compact interdigital and comb-line bandpass filters was demonstrated for the 900 MHz mobile phone band. Besides Ba2Ti9O20, Ba(Sm,Nd)2Ti5O14 ceramic material with a dielectric constant of εr = 78 was also employed in order to improve the miniaturisation. The volume of the smallest filter was 2 cm3 and the weight was 9 g.
In the second part of this study, various measurement methods have been demonstrated to determine the real part of the relative permittivity of FR4 fibreglass circuit board. Test structures were straight asymmetric open-circuited strip lines. It was found that the real part of the relative permittivity decreased slightly with frequency. At 0.72 GHz and 4.5 GHz, εr values of 4.3 and 4.1, respectively, were measured. All the characterisation methods used gave consistent values for εr, and electromagnetic simulators were used to verify the results.
In the third part of this study, the structures under test were microstrip or strip line transmission lines, the S parameters of which were measured by using on-wafer measurement techniques. It was found that the insertion loss of the 10 mm long etched Cu microstrip was slightly less than that of the Ag microstrips which were manufactured by etching and gravure offset printing techniques, respectively. The performance of the Ag microstrips was, however, similar. In addition, a theoretical basis was established for the determination of εr of the dielectric substrate and the attenuation coefficient of the transmission lines under test. The calculations were based on signal flow diagrams. The method was applied to determine the dielectric and loss properties of a commercial, Kyocera, Japan, LTCC (Low Temperature Cofired Ceramic) material up to 50 GHz. The measured value of the real part of the relative permittivity was εr = 5.7, and the loss tangent was approximately tan σ = 0.003.
The essential idea behind the studies reported in this thesis was twofold. First, the studies aimed at characterising dielectric media which find usage in the realisation of UHF, microwave or millimetre wave circuits. Second, the studies aimed to obtain data of immediate value in practical design work. For this reason, the structures under test were transmission lines having extensive usage in practical high frequency circuit design
Response to the comment by C. Kisielowsky, H.A. Calderon, F.R. Chen, S. Helveg, J.R. Jinschek, P. Specht, D. van Dyck on the article "On the influence of the electron dose-rate on the HRTEM Image contrast" by J. Barthel, M. Lentzen, A. Thust
No full textIn a recent article [1] we examined the influence of the applied electron dose rate on the magnitude of the image contrast in high-resolution transmission electron microscopy (HRTEM). We concluded that the magnitude of the image contrast is not substantially affected by the applied electron dose rate. This result is in obvious contradiction to numerous earlier publications by Kisielowski and coworkers [2–7], who commented our recent article due to this contradiction. The present short communication is a response to the comment of Kisielowski and coworkers on our recent article, where we provide additional arguments supporting our initial findings and conclusions on the magnitude of the image contrast in HRTEM
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