735 research outputs found
Energy localization in pumped systems
No full textConsidering a local nonlinear oscillator interacting with a chain of coupled Linear oscillators, we demonstrate that the dynamics of the local oscillator is characterized by a frequency-dependent damping constant, related to the frequency-dependent density of states of the linear modes. Further, we demonstrate how this intrinsic damping provides possibilities for multiple steady states of the nonlinear oscillator, and how these steady states may create local potentials for electrons that are adiabatically coupled with the linear modes. Finally, the implications on coarse-grained mode-ling of hard, softy and biological matter are discussed
Towards the tumble resistant microlight
No full textThe tumble mode is a pitching departure from controlled flight which leads to a pitch autorotation that is generally unrecoverable – resulting in vertical ground impact, usually preceded by in-flight breakup (the mechanism for which, surprisingly, can sometimes prevent loss of life). This was identified in work led by the British Microlight Aircraft Association beginning in 1997 as a response to a number of fatal accidents in Rogallo winged microlight aeroplanes, although the tumble is also known to occur to hang-gliders. This paper explains how this class of aeroplane is controlled, and how it has been found that they can enter the tumble mode. The mechanism by which the tumble can be entered is described. This has led to work showing how flight testing can be used to establish and demonstrate resistance to tumble entry – particularly important with increasing number of very high performance flexwings. These flight tests will be explained, together with the significance of the results. Recent accident investigation work has also shown a new mechanism of tumble entry, through partial failure of the A-frame structure and the pitch-trimmer mechanism. Also described is a possible relevance to well known historical accidents to flying wing aeroplanes– specifically the YB-49 and dH-108, and discovered data on the characteristics of the BKB-1flying wing glider; are also described
Calculation of surface tension using CALPHAD software as a Zero Phase Fraction line of ""surface"" phase
No full textA new approach for calculation of surface tension of solutions is presented. Based on the proposal of Butler (Proc. R. Soc. Lond. A: Math. Phys. Eng. Sci. 135 (1932) 348 [3]), a surface phase was assumed to be in equilibrium with a corresponding bulk phase. Following the proposal of Pajarre et al. (Calphad 30 (2006) 196 [71), a surface area element (X) was introduced, only in the surface phase. The surface tension can be obtained by Constrained Gibbs Energy Minimization (CGEM) under a constraint of constant surface. The equilibrium chemical potential of the surface element, X, was interpreted to be proportional to the surface tension. According to the present author (Calphad 50 (2015) 23 [9]), the surface tension calculation by the CGEM can be interpreted as if the bulk phase and the surface phase are in equilibrium with each other, and the chemical potential of the area element is obtained as a result of the equilibrium. It was shown that a geometrical relationship among the molar Gibbs energies of the bulk phase and the surface phase, the surface tension, and the surface concentration is found. In the present study, further improvement was made in such a way that the chemical potential of the area element can be simply obtained by combining the CGEM with Zero Phase Fraction (ZPF) line in Type II phase diagram, where the chemical potential of the area element is used as an axis variable. Such phase diagram can be easily calculated using conventional CALPHAD softwares. The proposed approach was validated for a number of binary and ternary systems. (C) 2015 Elsevier Ltd. All rights reserved.1122sciescopu
Near-IR Luminescent Yb-III Coordination Polymers Composed of Pyrene Derivatives for Thermostable Oxygen Sensors
No full textThis work synthesized oxygen sensitive and near infrared (NIR) luminescent Yb(III) coordination polymers incorporating ligands based on pyrene derivatives: Yb(III)-TBAPy and Yb(III)-TIAPy (TBAPy: 1,3,6,8-tetrskis(p-benzoate)pyrene, TIAPy: 1,3,6,8-tetrakis(3,5-isophtalic acid)pyrene). The coordination structures of these materials were characterized using electrospray ionization mass spectrometry, X-ray diffraction and thermogravimetric analysis, while the porous structure of the Yb(III)-TIAPy was evaluated based on its adsorption isotherm. The NIR luminescence properties of the Yb(III)-TBAPy and Yb(III)-TIAPy were examined by acquiring emission spectra and determining emission lifetimes under air, argon and vacuum. The Yb(III)-TIAPy exhibited high thermal stability (with a decomposition temperature of 400 °C), intense luminescence (with an emission quantum yield under argon of 6.6%) and effective oxygen-sensing characteristics. These results suggest that NIR luminescent Yb(III) coordination polymers made using pyrene derivatives could have applications in novel thermo-stable oxygen sensors
Achieving aerospace standard porosity levels when welding thin and thick-section aluminium using fibre-delivered lasers : executive summary
No full textEnvironmental and commercial pressures have forced the aerospace industry to look at
alternatives to riveting for the manufacture of aluminium aircraft structures. This resulted, at
the end of last century, in an extensive study by Airbus into the possiblities of using CO2
lasers, which led to the process being implemented for a (small) number of stringer-to-skin
fuselage panels in the newer Airbus models. Since this initial commercial success, new laser
sources have become available that are more suitable for the welding of aluminium than CO2
lasers, in the form of Nd: YAG and Yb-fibre lasers. Both produce a wavelength that is
absorbed more efficiently by aluminium alloys than the CO2 laser wavelength, resulting in an
improved keyhole stability, as demonstrated in the late nineties for Nd: YAG lasers. In addition,
Yb-fibre lasers have become available at output powers higher than available for Nd: YAG
lasers, allowing thicker sections of aluminium to be welded in a single pass. However, despite
their claimed advantages, no efforts were made to demonstrate the potential of these lasers
for (aluminium) aircraft manufacture. For this reason, the author initiated a series of studies in
2001, with the overall aim to develop procedures to laser weld both thin (3.2mm) and thicksection
(12.7mm) aerospace aluminium alloys using these fibre-delivered lasers to a weld
quality, in particular related to weld metal porosity, suitable for aerospace service. The focus
in this research was on weld metal porosity, because this is a particular problem when laser
welding aluminium, either in the form of fine (hydrogen) porosity or larger porosity associated
with an unstable keyhole behaviour. The benchmark weld metal porosity for this study was
obtained from the stringent weld quality classes defined in BS EN 13919-2 and AWS D17.1.
The approach to this research was in three parts, with work in the first aimed at demonstrating
that a 3kW Nd: YAG laser was capable of producing low-porosity welds in 3.2mm thickness
2024 aluminium alloy, and thus can be considered for replacing the CO2 laser currently used
for the stringer-to-skin fuselage application. Prior to the final part of the research, in which a
7kW Yb-fibre laser was used to demonstrate that these benchmark porosity levels could also
be achieved in thicker section (aerospace-grade) aluminium, a comparison study was carried
out to quantify the difference in welding performance between the Nd: YAG and the Yb-fibre
laser. At an output power of 4kW focused in a 0.4mm diameter spot, the Yb-fibre laser was
capable of a 30% higher welding speeds in 4mm (5083) aluminium alloy, or a 20% increase in
depth of penetration for welding speeds between 1 and 15m/min, compared with the Nd: YAG
laser. This improvement in welding performance, together with an output power of 7W,
produced full penetration in 12.7mm thickness (aerospace-grade) AI-Zn-Mg-Cu aluminium
alloy using the Yb-fibre laser autogenously, or in a hybrid configuration with a MIG arc. Both
the autogenous laser and hybrid laser-MIG process were capable of producing welds with a
weld metal porosity in line with the BS EN 13919-2 and AWS D17.1 benchmark conditions, at
welding speeds of 0.55 and 0.75m/min, respectively. At these production rates, the 248
metres of stringer incorporated in a typical aluminium wing structure can be welded in 7.5 and
5.5 hours, in case of autogenous laser and hybrid laser-MIG, respectively, compared with
37.6 hours currently needed for the riveting process
Isolation, characterization, and expression of the rat liver glutathione s-transferase yb-, subunit gene, 1989
No full textIn situ hybridization using a cDNA probe complementary to glutathione S-transferase Yb-j mRNA was utilized to isolate a glutathione S-transferase Yb-| gene from a rat liver genomic library. DNA sequence analysis incorporating "gene walking" strategies revealed that the Yb-j gene spans approximately 5.5 Kb, is comprised of eight exons separated by seven introns and is 99% homologous to the Ybi cDNA clone pGTA/C44. The transcription start site, which maps 29 bp downstream of the TATA element, was determined by primer extension analysis. Gene fragments containing the Yb-| promoter (and various deletions of the promoter region) were inserted upstream of the structural gene encoding chloramphenicol acetyl transferase (CAT). When these chimeric genes were transfected into mammalian cells, CAT assays revealed that the Yb^ minimal promoter is contained within an 80 bp DNA fragment which contains a TATA element, a transcription initiation site and 50 bp of sequence upstream of the TATA element. Contrary to in vivo studies which have shown that Yb-| gene activity is induced in response to phenobarbital and 3-methylcholanthrene administration, no elevation in activity was observed when mammalian hepatoma cells which had been transfected with the chimeric genes were treated with these xenobiotics. These data suggests that the regulatory element which confers xenobiotic inducibility is absent from the first 1700 bp of the Yb-j gene
Synthesis and Reactions of [Cp*Yb-2](2)(mu-Me) and [Cp*Yb-2](2)(mu-Me)(Me) and Related Yb-2(II, III) and Yb-2(III, III) Compounds
No full textbibtex: ISI:000418109700009 bibtex\location:'1155 16TH ST, NW, WASHINGTON, DC 20036 USA',publisher:'AMER CHEMICAL SOC',type:'Article',affiliation:'Andersen, RA (Reprint Author), Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Dept Chem, Berkeley, CA 94720 USA. Andersen, RA (Reprint Author), Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA. Walter, Marc D.; Matsunaga, Philip T.; Burns, Carol J.; Andersen, Richard A., Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Dept Chem, Berkeley, CA 94720 USA. Walter, Marc D.; Matsunaga, Philip T.; Burns, Carol J.; Andersen, Richard A., Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA. Walter, Marc D., Tech Univ Carolo Wilhelmina Braunschweig, Inst Anorgan & Analyt Chem, Hagenring 30, D-38106 Braunschweig, Germany. Maron, Laurent, Univ Toulouse, INSA UPS LPCNO, 135 Ave Rangueil, F-31077 Toulouse, France. Maron, Laurent, Univ Toulouse, CNRS LPCNO, 135 Ave Rangueil, F-31077 Toulouse, France.','author-email':'[email protected]',da:'2018-12-05','doc-delivery-number':'FQ1IG',eissn:'1520-6041','funding-acknowledgement':'Office of Science, Office of Basic Energy Sciences (OBES), of the U.S. Department of Energy [DE-AC020-5CH11231]; Fannie and John Hertz Foundation; Alexander von Humboldt Foundation; CalMip','funding-text':'This work was supported by the Director, Office of Science, Office of Basic Energy Sciences (OBES), of the U.S. Department of Energy under Contract No. DE-AC020-5CH11231. We thank Fred Hollander (at CHEXRAY, the UC Berkeley X-ray diffraction facility) for assistance with the crystallography. C.J.B. thanks the Fannie and John Hertz Foundation for a fellowship. R.A.A. acknowledges the Alexander von Humboldt Foundation for a reinvitation grant within the Humboldt Senior Research Award program. L.M. is grateful to the Alexander von Humboldt Foundation for a grant of experienced researcher and the Chinese Academy of Science. CalMip is acknowledged for a generous computational grant.','journal-iso':'Organometallics','keywords-plus':'C-H ACTIVATION; CRYSTAL-STRUCTURE; HYDRIDE COMPLEXES; DECAMETHYLYTTERBOCENE COMPLEXES; INTERMEDIATE-VALENCE; LANTHANIDE COMPLEXES; INCLUSION-COMPOUNDS; METHANE METATHESIS; METHYL COMPLEXES; LUTETIUM METHYL','number-of-cited-references':'83','research-areas':'Chemistry','researcherid-numbers':'Walter, Marc/E-4479-2012','times-cited':'3','unique-id':'ISI:000418109700009','usage-count-last-180-days':'4','usage-count-since-2013':'11','web-of-science-categories':'Chemistry, Inorganic & Nuclear; Chemistry, Organic'\International audienceA new type of synthesis, referred to as oxidative methylation, is developed for [Cp*Yb-2](2)(mu-X) and [Cp*Yb-2](2)(mu-X)(X), where X = Me, using MeCu or Cp*2VMe as the methyl transfer reagent and Cp*Yb-2. The synthetic methodology is extended to other X derivatives such as the halides and BH4. Reaction of [Cp*Yb-2](2)(mu-Me)(Me) and H-2 yields the mixed-valent hydride [Cp*Yb-2](2)(mu-H), which eliminates H-2 on gentle heating, forming Cp*Yb-2. When Cp*2VX is replaced by Cp*2TiX, 1:1 adducts based upon Ti(III,d(1)) are isolated. The X-ray crystal structure of [Cp*Yb-2](mu-Me)[TiCp*(2)] shows that the methyl group bridges the two different decamethylmetallocene fragments in a near-linear fashion, a geometry that is likely to resemble the transition state of the single-electron-transfer precursor complex. A CASSCF computational study on the mixed-valent hydride [Cp*Yb-2](2)(mu-H) shows that the ground state is a spin doublet in which the hydride forms a symmetric bridge to both Yb atoms. The three spins forming the ground-state doublet are aligned as Yb(f(13)(alpha),(d(z2))(0))center dot center dot center dot H center dot center dot center dot Yb(f(13)(alpha),(d(z2))(1)(beta)), and the unpaired d electron is delocalized between the d(z2) orbitals of the two Yb centers via the hydride bridge using the sigma* orbital of the Yb(d(z2))-H bond. The first excited state lies 0.09 eV (725 cm(-1)) higher in energy and is a spin quartet in which the three spins are aligned as Yb(f(13)(alpha),(d(z2))(0))center dot center dot center dot H center dot center dot center dot Yb(f(13)(alpha),(d(z2))(1)(alpha)), also giving rise to delocalization of the d electron between the d(z2) orbitals of the two Yb centers. The second spin doublet resembles the Lewis structure with an asymmetric mu-H bridge in which the Yb(II) metallocene has a closed-shell electronic configuration and is approximately 0.15 eV (1210 cm(-1)) higher in energy than the ground-state delocalized open-shell doublet. The electronic structure of the mixed-valent methyl is closely related to that of the hydride, but the methyl group is localized on the Cp*Yb-2(III) fragment. Electronic energies (Delta E) computed at the DFT (B3PW91) level of theory provide insights into the thermochemistry of the formation and decomposition of [Cp*Yb-2](2)(mu-H). The BDE for Yb-H is ca. 15 kcal/mol stronger than that for the corresponding Yb-Me in the monomeric metallocenes. In contrast, formation of [Cp*Yb-2](2)(mu-CH3) is ca. 60 kcal/mol more exothermic than the formation of [Cp*Yb-2](2)(mu-H). This difference is ascribed to enhanced intramolecular steric repulsion between the Cp*Yb-2 moieties in the linear Yb-H-Yb unit
Synthesis and Reactions of [Cp*Yb-2](2)(mu-Me) and [Cp*Yb-2](2)(mu-Me)(Me) and Related Yb-2(II, III) and Yb-2(III, III) Compounds
No full textbibtex: ISI:000418109700009 bibtex\location:'1155 16TH ST, NW, WASHINGTON, DC 20036 USA',publisher:'AMER CHEMICAL SOC',type:'Article',affiliation:'Andersen, RA (Reprint Author), Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Dept Chem, Berkeley, CA 94720 USA. Andersen, RA (Reprint Author), Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA. Walter, Marc D.; Matsunaga, Philip T.; Burns, Carol J.; Andersen, Richard A., Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Dept Chem, Berkeley, CA 94720 USA. Walter, Marc D.; Matsunaga, Philip T.; Burns, Carol J.; Andersen, Richard A., Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA. Walter, Marc D., Tech Univ Carolo Wilhelmina Braunschweig, Inst Anorgan & Analyt Chem, Hagenring 30, D-38106 Braunschweig, Germany. Maron, Laurent, Univ Toulouse, INSA UPS LPCNO, 135 Ave Rangueil, F-31077 Toulouse, France. Maron, Laurent, Univ Toulouse, CNRS LPCNO, 135 Ave Rangueil, F-31077 Toulouse, France.','author-email':'[email protected]',da:'2018-12-05','doc-delivery-number':'FQ1IG',eissn:'1520-6041','funding-acknowledgement':'Office of Science, Office of Basic Energy Sciences (OBES), of the U.S. Department of Energy [DE-AC020-5CH11231]; Fannie and John Hertz Foundation; Alexander von Humboldt Foundation; CalMip','funding-text':'This work was supported by the Director, Office of Science, Office of Basic Energy Sciences (OBES), of the U.S. Department of Energy under Contract No. DE-AC020-5CH11231. We thank Fred Hollander (at CHEXRAY, the UC Berkeley X-ray diffraction facility) for assistance with the crystallography. C.J.B. thanks the Fannie and John Hertz Foundation for a fellowship. R.A.A. acknowledges the Alexander von Humboldt Foundation for a reinvitation grant within the Humboldt Senior Research Award program. L.M. is grateful to the Alexander von Humboldt Foundation for a grant of experienced researcher and the Chinese Academy of Science. CalMip is acknowledged for a generous computational grant.','journal-iso':'Organometallics','keywords-plus':'C-H ACTIVATION; CRYSTAL-STRUCTURE; HYDRIDE COMPLEXES; DECAMETHYLYTTERBOCENE COMPLEXES; INTERMEDIATE-VALENCE; LANTHANIDE COMPLEXES; INCLUSION-COMPOUNDS; METHANE METATHESIS; METHYL COMPLEXES; LUTETIUM METHYL','number-of-cited-references':'83','research-areas':'Chemistry','researcherid-numbers':'Walter, Marc/E-4479-2012','times-cited':'3','unique-id':'ISI:000418109700009','usage-count-last-180-days':'4','usage-count-since-2013':'11','web-of-science-categories':'Chemistry, Inorganic & Nuclear; Chemistry, Organic'\International audienceA new type of synthesis, referred to as oxidative methylation, is developed for [Cp*Yb-2](2)(mu-X) and [Cp*Yb-2](2)(mu-X)(X), where X = Me, using MeCu or Cp*2VMe as the methyl transfer reagent and Cp*Yb-2. The synthetic methodology is extended to other X derivatives such as the halides and BH4. Reaction of [Cp*Yb-2](2)(mu-Me)(Me) and H-2 yields the mixed-valent hydride [Cp*Yb-2](2)(mu-H), which eliminates H-2 on gentle heating, forming Cp*Yb-2. When Cp*2VX is replaced by Cp*2TiX, 1:1 adducts based upon Ti(III,d(1)) are isolated. The X-ray crystal structure of [Cp*Yb-2](mu-Me)[TiCp*(2)] shows that the methyl group bridges the two different decamethylmetallocene fragments in a near-linear fashion, a geometry that is likely to resemble the transition state of the single-electron-transfer precursor complex. A CASSCF computational study on the mixed-valent hydride [Cp*Yb-2](2)(mu-H) shows that the ground state is a spin doublet in which the hydride forms a symmetric bridge to both Yb atoms. The three spins forming the ground-state doublet are aligned as Yb(f(13)(alpha),(d(z2))(0))center dot center dot center dot H center dot center dot center dot Yb(f(13)(alpha),(d(z2))(1)(beta)), and the unpaired d electron is delocalized between the d(z2) orbitals of the two Yb centers via the hydride bridge using the sigma* orbital of the Yb(d(z2))-H bond. The first excited state lies 0.09 eV (725 cm(-1)) higher in energy and is a spin quartet in which the three spins are aligned as Yb(f(13)(alpha),(d(z2))(0))center dot center dot center dot H center dot center dot center dot Yb(f(13)(alpha),(d(z2))(1)(alpha)), also giving rise to delocalization of the d electron between the d(z2) orbitals of the two Yb centers. The second spin doublet resembles the Lewis structure with an asymmetric mu-H bridge in which the Yb(II) metallocene has a closed-shell electronic configuration and is approximately 0.15 eV (1210 cm(-1)) higher in energy than the ground-state delocalized open-shell doublet. The electronic structure of the mixed-valent methyl is closely related to that of the hydride, but the methyl group is localized on the Cp*Yb-2(III) fragment. Electronic energies (Delta E) computed at the DFT (B3PW91) level of theory provide insights into the thermochemistry of the formation and decomposition of [Cp*Yb-2](2)(mu-H). The BDE for Yb-H is ca. 15 kcal/mol stronger than that for the corresponding Yb-Me in the monomeric metallocenes. In contrast, formation of [Cp*Yb-2](2)(mu-CH3) is ca. 60 kcal/mol more exothermic than the formation of [Cp*Yb-2](2)(mu-H). This difference is ascribed to enhanced intramolecular steric repulsion between the Cp*Yb-2 moieties in the linear Yb-H-Yb unit
Studies of cerebrospinal fluid dynamics withintrathecally administered (169)Yb-DTPA. Ⅰ. Usefulness of (169)Yb-DTPA as a radiopharmaceutical for cisternography
No full textRecently, radioisotope cisternography has become a widely used method for the morphological assessment of cerebrospinal fluid (CSF) dynamics by means of radioactive materials introduced into the subarachnoid space. This technique provides useful information regarding the intracranical subarachnoid CSF dynamics. A wide variety of radioactive agents have been used with varying success to make the CSF space visible. In particular, in respect to stability, molecular weight and half-life, (169)Yb-DTPA has been found to be one of the best radio-pharmaceuticals for cisternography. The purpose of this paper is to discuss the characteristics of (169)Yb-DTPA compared with (131)I-HSA in cisternography, based on the author's experimental data and clinical experience. Experimental studies: (1) After injecting (131)I-HSA, (169)Yb-DTPA and (99m)Tc-pertechnetate respectively into the lumbar subarachnoid space of three groups of dogs, the author investigated serially the movement of these tracers with a scintillation camera and the transport of these isotopes from CSF space to blood by counting the radiosctivity of the blood samples with a well-type scintillation counter. The author observed that there is a good possibility that (169)Yb-DTPA will show the dynamics of CSF absorption in both spinal and intracranial subarachnoid spaces. (2) Ten ml of autologous whole blood was injected into the cisterna magna of dogs, and the injection was repeated 2-3 times at weekly intervals. Three to five weeks after the last injection, chronic subarachnoid hemorrhage was achieved. In both chronic subarachnoid hemorrhage dogs and control dogs, laminectomy was performed at C(2) level and silicon tube was cannulated into the intrathecal or intracranial subarachnoid space, and then, the intrathecal subarachnoid space was completely divided from intracranial subarachnoid space by extradural ligation. After 100
μCi of (169)Yb-DTPA was injected into the intrathecal or intracranial subarachnoid space, 1.0ml
of physiological saline solution was injected into the same place from the tube. Then, CSF pressure changes were recorded continuously by the pressure transducer and blood samples were taken at regular time intervals from the veins in order to determine the amount of activity of (169)Yb-DTPA transported into the blood from the subarachnoid space. In control cases, the elevated pressure immediately after injection of saline solution decreased to the level of 100-150 mmH(2)O for the period of approximately 10 minutes. According to these pressure changes, large amount of (169)Yb-DTPA were transported into the blood from the subarachnoid space, but in chronic subarachnoid hemorrhage cases, prolonged elevation of CSF pressure was seen and little (169)Yb-DTPA was transported into the blood. These results suggest that the transportation of (169)Yb-DTPA into the blood from the subarachnoid space is closely related to the absorption dynamics of CSF in the intrathecal and intracranial subarachnoid space. Clinical studies: In clinical cases, the author tried to determine how clearly one can see CSF dynamics, particularly in the intrathecal subarachnoid space by (169)Yb-DTPA cisternography combined with the (169)Yb-DTPA transfer test. With the patient in a lateral position, a spinal puncture was performed at L(4)-5 interspace. After measuring CSF uressure, the author injected
500 μCi of (169)Yb-DTPA into the lumbar subarachnoid space. Then scintigrams of the head and lumbar regions were taken 1, 2, 6, 24 and 48 hours after the injection. In addition, at varying time intervals up to 6 hours, blood samples were taken from the veins in order to determine the amount of activity of (169)Yb-DTPA transported to the blood from the subarachnoid space. Here, the author considered the (169)Yb-DTPA concentration curve in the blood from a time immediately after the injection up to 1 hour thereafter (when (169)Yb-DTPA was still located only in the intrathecal space), reflects the absorption dynamics of CSF in the intrathecal subarachnoid space. In normal cases, the concentration curve of (169)Yb-DTPA in the blood showed two peaks around 1-2 and 4-5 hours after injection. This finding agree with the canine experimental data. First of all, the author studied the correlation between the changes in the (169)Yb-DTPA concentration curve in the blood and CSF pressure. When CSF pressure was under 100 mmH(2)O, the concentration curve in the blood was plotted in the lower levels at about 1/5 of the height of normal CSF pressure cases. On the other hand, when the movement of (169)Yb-DTPA into the blood was rapid and little (169)Yb-DTPA went up into intracranial space, the CSF pressure was inclined to be somewhat higher. This means that (169)Yb-DTPA was rapidly transported to the blood from the subarachnoid space in the cases with high CSF pressure like a brain tumor case. There are some occasions to use (131)I-HSA instead of (169)Yb-DTPA in such cases. The molecular weight of (131)I-HSA is 100 times greater than that of (169)Yb-DTPA, and from this reason (131)I-HSA is less likely to be absorbed from the intrathecal subarachnoid space. In addition, the author may note that there was no close relation between the amount of CSF protein or CSF osmotic pressure and the pattern of concentration curve in the blood. In the next place, the cases which had subarachnoid hemorrhage following the ruptured aneurysm, showed various abnormal CSF dynamics, such as low absorption from the intrathecal space and from the parasagittal arachnoid villi and reflux of (169)Yb-DTPA into the venricular system. In some of these cases, when ventricular dilatation is strong and ventricular stasis of (169)Yb-DTPA is observed over a 24 hour period the (169)Yb-DTPA concentration curve came to show high levels when a great deal of (169)Yb-DTPA appeared in the ventricles. This may mean that CSF is absorbed from the ventricular system in pathological condition. Lastly, when performing (169)Yb-DTPA cisternography, it is very important to know whether (169)Yb-DTPA was injected correctly into the lumbar subarbchnoid space. To determine this, it is useful to monitor the (169)Yb-DTPA concentration curve in the blood for several minutes, in addition to taking scintigram of the lumbar region, because when (169)Yb-DTPA is injected extradurally, the (169)Yb-DTPA concentration curve in the blood shows the same form as that in the blood after the direct intravenous injection. As mentioned above, the author consider that (169)Yb-DTPA is an unique and useful radio-pharmaceutical for cisternography, particularly when it is necessary to study the absorption dynamics of CSF not only from intracranial, but also from intrathecal subarachnoid space
Fiber design for high-power low-cost Yb:Al-doped fiber laser operating at 980nm
No full textWe investigated an Yb:Al-doped depressed-clad hollow optical fiber (DCHOF) for cladding-pumped 980nm laser operation. With a careful design, the nonzero fundamental-mode cutoff characteristics of a DCHOF allows the competing 1030-1060nm emission to be filtered out, despite being quite close to 980nm. The laser yielded over 3W of output power in a diffraction limited beam (M -parameter degrades to 2.7, as a result of increased cladding-mode lasing, as the cladding thickness is reduced
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