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AbstractAbstract
[en] An improvement in the theoretical treatment of the reduced magneto-thermal conductivity of a boron-doped silicon sample having shallow acceptors with p=9.0x1016cm-3 is presented. It is shown that this impurity concentration lies in the intermediate region and use is made of Mikoshiba's inhomogeneity model to include in the calculation both the relaxation rates for bound hole-phonon and free hole-phonon scatterings. The results cover a range of temperature from 1-5 deg. K and magnetic fields up to 55 KG. Good agreement is found up to about 25 KG. For higher fields the agreement is poor emphasising the necessity of including more details of the scattering mechanism in the calculations. The overall agreement is improved when compared to previous works. (author)
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Jul 1984; 11 p
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Report
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AbstractAbstract
No abstract available
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Journal Article
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Physical Review. D, Particles Fields; v. 6(6); p. 1648-1654
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AbstractAbstract
[en] A small addition of tungsten (0.5 at. percent) was shown to have an effect similar to that of molybdenum on the phase transformation characteristics of alloy Ta7Cr (with a nominal composition of 1 at. percent Ta, 7 at. percent Cr, balance Fe). The existence of time-temperature dependent transformation behavior in alloy Ta7Cr0.5W was confirmed. The effect of spheroidization time and temperature on creep strength was determined. In addition, effect of mechanical processing prior to aging, on creep strength was also determined. It was also shown that by suitable modifications of composition, the grain boundary film can be broken during the aging treatment without the use of spheroidization treatment. Microhardness, tensile and creep properties have been determined. Optical metallography and scanning electron microscopy have been used to follow the microstructural changes and mode of fracture. The creep rupture strength of alloy Ta7CrW alloy was found to be superior to many of the best commercially available ferritic alloys at 12000F. (21 fig., 8 tables)
Original Title
1 at. percent Ta, 7 at. percent Cr, 0.5 at. percent W; 1 at. percent Ta, 7 at. percent Cr, 0.25 at. percent W; 0.25 at. percent Mo
Primary Subject
Source
Dec 1975; 57 p; Available from NTIS; Thesis. Available from NTIS. $4.50.
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Report
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AbstractAbstract
[en] Surgical resection, chemotherapy, radiotherapy, and combinations thereof are a plethora of possible treatment modalities of head and neck malignancies. Treatment regimens including radiotherapy however put jaws at risk of subsequent osteoradionecrosis. Besides cancer cells, irradiation impacts on all tissue-inherent cells, including mesenchymal stem cells (MSCs). Since it is the bone and bone marrow MSC, which contributes to bone regeneration through proliferation and osteogenic differentiation of its progeny, the influence of irradiation on MSC viability and the respective differentiation capacity appears to be critical. However to date, only a few reports picked MSCs role out as a pivotal topic. As a first attempt, we irradiated human bone derived MSC in vitro. With increasing doses the cells self-renewal capabilities were greatly reduced. Notably however, the mitotically stalled cells were still capable of differentiating into osteoblasts and preadipocytes. Next, the mandibles of Sus scrofa domestica were irradiated with a total dose of 18 Gy. At different time points post radiatio, MSCs were isolated from bone autopsies. In comparison between irradiated and non- irradiated samples, no significant differences regarding the proliferation and osteogenic differentiation potential of tissue specific MSC became apparent Therefore, pig mandibles were irradiated with doses of 9 and 18 Gy, and MSCs were isolated immediately afterwards. No significant differences between the untreated and bone irradiated with 9 Gy with respect of proliferation and osteogenic differentiation were observed. Cells isolated from 18 Gy irradiated specimens exhibited a greatly reduced osteogenic differentiation capacity, and during the first two weeks proliferation rates of explanted cells were greatly diminished. Thereafter, cells recovered and showed proliferation behaviour comparable to control samples. These results imply that MSCs can cope with irradiation up to relatively high doses. Whether MSCs are protected by the local surrounding tissues, their niche, or are capable of migrating into the affected area has to be defined in future experiments. (author)
[de]
Im Rahmen der Behandlung maligner Kopf- und Halstumoren erfolgt meistens in Kombination oder auch alleine eine chirurgische Intervention, eine Chemotherapie, oder eine Radiotherapie. Infolge der Radiotherapie kann Osteoradionekrose im Bereich der Kiefer auftreten. Neben malignen Zellen werden auch andere gewebsstaendige Zellen wie z.b.: Mesenchymale Stammzellen (MSCs) von ionisierender Strahlung getroffen. Bekanntermassen erfolgt die Regeneration von Knochen und Knochenmark durch die Proliferation und kontrollierte Differenzierung von MSCs. Der Einfluss ionisierender Strahlen auf die Vitalitaet und Differenzierungsfaehigkeit von MSCs wurde bislang nicht ausreichend untersucht. Daher wurden aus humanen Knochen isolierte MSCs in vitro bestrahlt. Waehrend mit steigender Dosis die Proliferationsfaehigkeit abnahm, war die osteo- und adipogene Differenzierungskapazitaet in allen Dosisbereichen weitgehend unbeeintraechtigt. Anschliessend wurden im Rahmen eines in vivo Versuches unterkiefer von Sus scrofa domestica mit einer Dosis von 18 Gy bestrahlt. Spaeter wurden zu verschiedenen Zeitpunkten Biopsien aus der bestrahlten Mandibula entnommen und MSCs isoliert. Im Gegensatz zum in vitro Versuch war kein signifikanter unterschied bezueglich Proliferationsraten und Differentationsqualitaet der aus bestrahlter und unbestrahlter Mandibula entnommenen MSC feststellbar. Aus diesem Grund wurden die unterkiefer von Schweinen einmal mit 9 Gy und einmal mit 18 Gy bestrahlt. Sofort nach der Bestrahlung wurden MSCs isoliert. Es war kein signifikanter unterschied bezueglich Proliferationsraten und Differentationsqualitaet zwischen unbestrahlten und mit 9 Gy bestrahlten Knochenproben feststellbar. Allerdings zeigten die mit 18 Gy bestrahlten Proben eine deutlich herabgesetzte osteogene Differentationsqualitaet und waehrend der ersten zwei Wochen war die Proliferationsrate deutlich herabgesetzt. Nach diesen 2 Wochen zeigten sie ein aehnliches Proliferationsmuster wie die unbestrahlte Kontrollgruppe. Diese Resultate implizieren, dass MSCs relativ hohe Strahlendosen verkraften. Ob MSCs durch das umgebende Gewebe oder in ihrer Nische vor einwirkender Strahlung geschuetzt sind, oder ob sie faehig in das beschaedigte Gewebe einzuwandern muss in weiteren Experimenten untersucht werden. (author)Primary Subject
Source
2009; 131 p; Available from Library of the University of Innsbruck, Innrain 50, 6020 Innsbruck (AT); Thesis (Ph.D.)
Record Type
Miscellaneous
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Thesis/Dissertation
Country of publication
ANIMAL CELLS, ANIMAL TISSUES, ANIMALS, BIOLOGICAL EFFECTS, BIOLOGICAL RADIATION EFFECTS, BODY, DISEASES, DOMESTIC ANIMALS, HEMATOPOIETIC SYSTEM, INJURIES, LOCAL RADIATION EFFECTS, MAMMALS, MEDICINE, NECROSIS, NUCLEAR MEDICINE, ORGANS, PATHOLOGICAL CHANGES, POPULATIONS, RADIATION EFFECTS, RADIATION INJURIES, RADIOLOGY, SKELETAL DISEASES, SKELETON, SKULL, SOMATIC CELLS, THERAPY, VERTEBRATES
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AbstractAbstract
[en] In order to guarantee the reproducibility of welded joints of even quality (above all in the metal working industry), it is proposed that before starting resistance point welding, a preheating current should be allowed to flow at the site of the weld. A given reduction of the total resistance at the site of the weld should effect the time when the preheating current is switched over to welding current. This value is always predetermined empirically. Further possibilities of controlling the welding process are described, where the measurement of thermal expansion of the parts is used. A standard welding time is given. The rated course of electrode movement during the process can be predicted and a running comparison of nominal and actual values can be carried out. (RW)
[de]
Um die Reproduzierbarkeit von Schweissverbindungen gleichmaessiger Qualitaet - vor allem in der blechverarbeitenden Industrie - zu gewaehrleisten, wird vorgeschlagen, vor Beginn einer Widerstandspunktschweissung einen Vorwaermstrom ueber die Schweisstelle fliessen zu lassen. Dabei soll eine vorgegebene zeitliche Abnahme des Gesamtwiderstandes an der Schweisstelle den Zeitpunkt der Umschaltung vom Vorwaermstrom auf Schweisstrom bewirken. Dieser Wert wird jeweils vorher empirisch festgelegt. Weitere Moeglichkeiten der Steuerung des Schweissprozesses werden beschrieben, wobei einmal die Messung der Waermeausdehnung der Fuegeteile benutzt wird, eine 'Normal'-schweisszeit vorgegeben wird. Auch kann der Sollverlauf der Elektrodenbewegung waehrend des Prozesses vorgegeben und ein laufender Vergleich von Soll- und Ist-Werten vorgenommen werden. (RW)Original Title
Verfahren zur Qualitaetssicherung der Schweissverbindungen beim elektrischen Widerstandspunktschweissen
Primary Subject
Source
23 Jun 1977; 11 p; DE PATENT DOCUMENT 2555792/A/; Also available from Dt. Patentamt, Muenchen (FRG)
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Patent
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AbstractAbstract
[en] All implantable devices must be sterile. However, autoclaves produce poor surface properties that jeopardize the integration process. The application of a modified ultraviolet light source has proven to enhance bioreactivity by controlling surface properties, but it lacks validation of its sterilization capabilities. Forty-eight titanium implants were contaminated with spores of the biological indicator Bacillus stearothermophilus and subjected to dynamic sterilization by ultraviolet light. Forty-seven of the implants were successfully sterilized, as indicated by not producing turbidity in a suitable growth medium. This sterilization technique only requires a 20-second exposure to achieve sterility
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Journal Article
Journal
International Journal of Oral and Maxillofacial Implants; ISSN 0882-2786; 
; CODEN IJOIE; v. 4(2); p. 139-146
; CODEN IJOIE; v. 4(2); p. 139-146
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Singh, S.; Christendat, D.
Brookhaven National Laboratory BNL National Synchrotron Light Source NSLS (United States). Funding organisation: DS (US)2006
Brookhaven National Laboratory BNL National Synchrotron Light Source NSLS (United States). Funding organisation: DS (US)2006
AbstractAbstract
[en] The bifunctional enzyme dehydroquinate dehydratase-shikimate dehydrogenase (DHQ-SDH) catalyzes the dehydration of dehydroquinate to dehydroshikimate and the reduction of dehydroshikimate to shikimate in the shikimate pathway. We report the first crystal structure of Arabidopsis DHQ-SDH with shikimate bound at the SDH site and tartrate at the DHQ site. The interactions observed in the DHQ-tartrate complex reveal a conserved mode for substrate binding between the plant and microbial DHQ dehydratase family of enzymes. The SDH-shikimate complex provides the first direct evidence of the role of active site residues in the catalytic mechanism. Site-directed mutagenesis and mechanistic analysis revealed that Asp 423 and Lys 385 are key catalytic groups and Ser 336 is a key binding group. The arrangement of the two functional domains reveals that the control of metabolic flux through the shikimate pathway is achieved by increasing the effective concentration of dehydroshikimate through the proximity of the two sites
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Source
BNL--78646-2007-JA; AC02-98CH10886
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Journal Article
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AbstractAbstract
[en] The authors have developed a fast spatial presaturation technique for outer volume suppression that uses a series of short small-tip selective radio frequency (RF) excitations during one-half cycle of a rotating gradient. In their technique, each individual RF pulse excites everything outside the projection of the region of interest (ROI) at the angle defined by the rotating gradient at that instant. Multiple excitation of the outer region during one-half cycle of the rotating gradient leads to spatial presaturation, whereas the magnetization within the ROI remains unaffected. An RF pulse then interrogates the preserved magnetization in the ROI to acquire data from the three-dimensional localized volume. The technique can be extended to isolate multiple ROIs of arbitrary shape during a single presaturation cycle. The advantage of this technique for selecting ROIs of various shapes is demonstrated in this paper
Primary Subject
Source
Anon; 395 p; 1988; p. 390; Radiological Society of North America Inc; Oak Brook, IL (USA); 74. scientific assembly and annual meeting of the Radiological Society of North America (RSNA); Chicago, IL (USA); 27 Nov - 2 Dec 1988; CONF-8811134--
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Book
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Conference
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AbstractAbstract
No abstract available
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Journal Article
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Nuclear Engineering and Design; v. 21(1); p. 126-136
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AbstractAbstract
No abstract available
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Journal Article
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Progress Report
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J. Amer. Ceram. Soc; v. 53 p. 169
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