High resolution readout of metal oxide gas sensors using time-to-digital conversion

Time-to-digital conversion is investigated as a new method to record highly sensitive responses of semiconductor gas sensors. The method is evaluated by exposing metal oxide gas sensors to very low carbon monoxide (CO) concentrations. The noise equivalent detection limit is about 0.5 ppb CO     

Genomic Instability Is an Early Event in Aluminium-Induced Tumorigenesis

Genomic instability is generally considered as a hallmark of tumorigenesis and a prerequisite condition for malignant transformation. Aluminium salts are suspected environmental carcinogens that transform mammary epithelial cells in vitro through unknown mechanisms. We report here that long-term culture in the presence of aluminium chloride (AlCl₃) enables HC11 normal mouse mammary epithelial cells to form tumours and metastases when injected into the syngeneic and immunocompetent BALB/cByJ strain. We demonstrate that AlCl₃ rapidly increases chromosomal structural abnormalities in mammary epithelial cells, while we failed to detect direct modulation of specific mRNA pathways. Our observations provide evidence that clastogenic activity—a well-recognized inducer of genomic instability—might account in part for the transforming abilities of aluminium in mammary epithelial cells.     

Hydroxyapatite scaffolds for bone tissue engineering made by 3D printing

Nowadays, there is a significant need for synthetic bone replacement materials used in bone tissue engineering (BTE). Rapid prototyping and especially 3D printing is a suitable technique to create custom implants based on medical data sets. 3D printing allows to fabricate scaffolds based on Hydroxyapatite with complex internal structures and high resolution. To determine the in vitro behaviour of cells cultivated on the scaffolds, we designed a special test-part. MC3T3-E1 cells were seeded on the scaffolds and cultivated under static and dynamic setups. Histological evaluation was carried out to characterise the cell ingrowth. In summary, the dynamic cultivation method lead to a stronger population compared to the static cultivation method. The cells proliferated deep into the structure forming close contact to Hydroxyapatite granules.     

A 0.7-V MOSFET-only switched-opamp /spl Sigma//spl Delta/ modulator in standard digital CMOS technology

A 0.7-V MOSFET-only /spl Sigma//spl Delta/ modulator for voice band applications is presented. The second-order modulator is realized using a switched-opamp technique. All capacitors are realized using compensated MOS devices operated in the depletion region. A combination of parallel and series compensated depletion-mode MOSCAPs is used to obtain high area efficiency. The circuit is fabricated in a 0.18-/spl mu/m CMOS process. The only components used are standard n-MOS and p-MOS transistors with threshold voltages of approximately 400 mV. All transistors are operated within the supply voltage window of 0.7 V; voltage boosting techniques are not used. The active area is 0.082 mm/sup 2/. The modulator achieves 67-dB signal-to-noise-and-distortion ratio, 70-dB signal-to-noise ratio, and 75-dB dynamic range at 8-kHz signal bandwidth and consumes 80 /spl mu/W of power.     

Biocompatibility of ceramic scaffolds for bone replacement made by 3D printing

Bone replacement materials used in tissue engineering require a high degree of safety and biological compatibility. For these reasons synthetic bone replacement materials based on calcium‐phosphates are being used more widely. To mimic natural bone, rapid prototyping processes and especially 3D printing are favourable. Using 3D printing, complex 3 dimensional structures can be made easily. In this study we successfully performed biocompatibility tests with a Hydroxyapatite test structure (HA‐S) made by 3D printing. Cytotoxicity tests were carried out according to DIN ISO 10993‐5 in static and dynamic cultivation setups. To estimate cell proliferation and analyze morphology, histological evaluation was done. In summary, good cell viability as well as good proliferation behaviour were found. Moreover, these results show that the 3D printing process in combination with the suitable material presented in this study is well suited for fabricating scaffolds for TE in the required accuracy and biological compatibility.     

Design of low-voltage MOSFET-only /spl Sigma//spl Delta/ modulators in standard digital CMOS technology

A design strategy of low-voltage high-linearity MOSFET-only /spl Sigma//spl Delta/ modulators in standard digital CMOS technology is presented. The modulators use substrate-biased MOSFETs in the depletion region as capacitors, linearized by different compensation techniques. This work shows the design, simulation and measured results of a number of MOSFET-only /spl Sigma//spl Delta/ modulators using different implementations of so called compensated depletion-mode MOS capacitors. The modulators are designed for the demands of speech band applications. The performance of the modulators proves the capability of compensated depletion-mode MOS capacitors to fulfill analog circuit requirements at low supply voltages with reduced processing efforts.     

A 1.8-V MOSFET-only ΣΔ modulator using substrate biaseddepletion-mode MOS capacitors in series compensation

A low-voltage high-linearity MOSFET-only ΣΔ modulator for speech band applications is presented. The modulator uses substrate biased MOSFETs in the depletion region as capacitors, linearized by a series compensation technique. A second-order fully differential single-loop architecture has been realized in a conventional 0.25-μm digital n-well CMOS process without extra layers for capacitors. An SNDR of 72 dB and an SNR of 77 dB is obtained with 8-kHz signal bandwidth at an oversampling ratio of 64. The circuit consumes about 1 mW from a single 1.8-V power supply and occupies a core area of 0.08 mm²     

Characterisation of photovoltaic generators

Reliable knowledge on the performance of different photovoltaic generators (as single cells, modules, laminates, shingles, car roofs, etc.) under actual operating conditions is essential for correct product selection and accurate prediction of their electricity production. For this purpose, an outdoor test facility was erected at the Paul Scherrer Institute, PSI. It consists of a sun-tracked sample holder, electronic loads and a PC-based measuring system. Insolation is measured with pyranometers, pyrheliometers and reference cells. Characterisation of a generator under given test conditions means the precise acquisition of its electrical behaviour under varying load. The generator's efficiency and all the relevant electrical parameters are derived on-line from a series of measured current/voltage (I/V) values. I/V-scans at constant insolation and at different generator temperatures enable the temperature coefficients of the efficiency and the electrical parameters to be determined. Thereafter I/V-scans at different insolations (10–1200 W/m²) and air masses (1.1–5) yield (via temperature correction) the insolation dependence of the efficiency at constant temperature. A complete scan takes about 5–15 s. Samples of size varying from 1 by 1 mm up to 1.5 by 1 m can be tested at currents up to 32 A and at voltages up to 120 V. For modelling purposes, the results are represented in the form of correlations, e.g. the efficiency as a function of the operating parameters temperature, insolation and air mass. Results obtained in PSI's test facility were confirmed by the Fraunhofer-Insitut für Solare Energiesysteme, D-79100 Freiburg, Germany. Measurements are presented from some modules and single cells as well as some efficiency correlations. Results are also presented on lamination losses, on PSI's high efficiency cell, on Grätzel cells and watch modules as well as on shading effects and of a small thermophotovoltaic generator.