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Macroporous silicon has been etched from n-type Si, using a vertical etching cell where no rear side contact on the silicon wafer is necessary. The resulting macropores have been characterised by means of Scanning Electron Microscopy (SEM). After etching, SiO₂ was thermally grown on the top of the porous silicon as an insulating layer and Si₃N₄ was deposited by means of Low Pressure Chemical Vapour Deposition (LPCVD) as transducer material to fabricate a capacitive pH sensor. In order to prepare porous biosensors, the enzyme penicillinase has been additionally immobilised inside the porous structure. Electrochemical measurements of the pH sensor and the biosensor with an Electrolyte/Insulator/Semiconductor (EIS) structure have been performed in the Capacitance/Voltage (C/V) and Constant capacitance (ConCap) mode.
In-beam study of ¹⁴³ Eu
(1988)
Yrast states up to spin 18 have been identified in ¹³²Ce. The energies and spins of the levels suggest the existence of two fairly well-behaved collective bands. The results are compared with those obtained in the rare-earth deformed region.
Side-bands in ¹⁸⁰ Os
(1981)
High spin states in ¹⁸⁸ Au
(1982)
High-spin states in ¹⁸⁰ Os
(1979)
Band structure in ¹⁹⁴ Au
(1979)
Isomeric state in ¹³⁴ La
(1981)
Isomeric state in ¹³⁶ La
(1981)
High-spin states in ¹³³ La
(1980)
High-spin states in ¹³³ La
(1982)
Isomeric states in ¹³⁴ Ba
(1980)
Isomeric states in ¹³⁴ Ba
(1980)
In-beam study of ¹⁴⁴ Gd
(1978)
In-beam study of ¹⁴⁴ Gd
(1977)
In-beam study of ¹⁴⁴ Gd
(1978)
High spin states in ¹³⁶ Ce
(1975)
High spin states in ¹³⁶ Ce
(1975)
This work describes a procedure to yield attenuation maps from MR images which are used for the absorption correction (AC) of brain PET data. Such an approach could be mandatory for future combined PET and MRI scanners, which probably do not include a transmission facility. T1-weighted MR images were segmented into brain tissue, bone, soft tissue, and sinus; attenuation coefficients corresponding to elemental composition and density as well as to 511 keV photon energy were respectively assigned. Attenuation maps containing up to four compartments were created and forward projected into sinograms with attenuation factors which then were used for AC during reconstruction of FDG-PET data. The commonly used AC based on a radioactive (68Ge) transmission scan served as reference. The reconstructed radioactivity values obtained with the MRI-based AC were about 20% lower than those obtained with PET-based AC if the skull was not taken into account. Considering the skull the difference was still about 10%. Our investigations demonstrate the feasibility of a MRI-based AC, but revealed also the necessity of a satisfying delineation of bone thickness which tends to be underestimated in our first approach of T1-weighted MR image segmentation.
Side bands in ¹⁷² Hf
(1978)
New isomeric state in ¹⁴⁵ Eu
(1979)
In-beam study of ¹⁴⁵ Gd
(1979)
New isomeric state in ¹⁴⁴ Eu
(1980)
High spin states in ¹⁹¹ Au
(1975)
High spin states in ¹⁹¹ Au
(1975)