Biomedical subjects

Albert H Titus

Publications and source records attributed to Albert H Titus.

4 recordsLinked to original sources

PubMed2006

Tailored xerogel-based sensor arrays and artificial neural networks yield improved O2 detection accuracy and precision.

The objective of this research is to develop arrays of tuned chemical sensors wherein each sensor element responds to a particular target analyte in a unique manner. By creating sol-gel-derived xerogels that are co-doped with two luminophores at a range of molar ratios, we can form suites of sensor elements that can exhibit a continuum of response profiles. We trained an artificial neural network (ANN) to "learn" to identify the optical outputs from these xerogel-based sensor arrays. By using the ANN in concert with our tailored sensor arrays we obtained a 5-10 fold improvement in accuracy and precision for quantifying O2 in unknown samples. We also explored the response characteristics of these types of sensor elements after they had been contacted with rat plasma/blood. Contact with plasma/blood caused approximately 15% of the luminophore molecules within the xerogels to become non-responsive to O2. This behavior is consistent with rat albumin blocking certain pore sub-populations within the mesoporous xerogel matrix thereby limiting O2 access to the luminophores.

Journal Article↗

PubMed2006

An analog VLSI chip emulating polarization vision of Octopus retina.

Biological systems provide a wealth of information which form the basis for human-made artificial systems. In this work, the visual system of Octopus is investigated and its polarization sensitivity mimicked. While in actual Octopus retina, polarization vision is mainly based on the orthogonal arrangement of its photoreceptors, our implementation uses a birefringent micropolarizer made of YVO4 and mounted on a CMOS chip with neuromorphic circuitry to process linearly polarized light. Arranged in an 8 x 5 array with two photodiodes per pixel, each consuming typically 10 microW, this circuitry mimics both the functionality of individual Octopus retina cells by computing the state of polarization and the interconnection of these cells through a bias-controllable resistive network.

Algorithms↗

PubMed2006

O(2)-responsive chemical sensors based on hybrid xerogels that contain fluorinated precursors.

We report the development and analytical figures of merit associated with several new O(2)-responsive sensor materials. These new sensing materials are formed by sequestering the luminophore tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ([Ru(dpp)(3)](2+)) within hybrid xerogels that are composed of two of the following methoxysilanes: tetramethoxysilane, n-propyl-trimethoxysilane, 3,3,3-trifluoropropyl-trimethoxysilane, phenethyl-trimethoxysilane, and pentafluorophenylpropyl-trimethoxysilane. Steady-state and time-resolved luminescence measurements are used to investigate these hybrid xerogel-based sensor materials and elucidate the underlying reasons for the observed performance. The results show that many of the [Ru(dpp)(3)](2+)-doped composites form visually uniform, crack-free xerogel films that can be used to construct O(2) sensors that have linear calibration curves and excellent long-term stability. To the best of our knowledge, the [Ru(dpp)(3)](2+)-doped fluorinated hybrid xerogels also exhibit the highest O(2) sensitivity of any reported [Ru(dpp)(3)](2+)-based sensor platform.

Biosensing Techniques↗

PubMed2004

Multilevel category structure in the ART-2 network.

Multilevel categorization is investigated within the context of analog activity patterns on the output layer of an ART 2 network. The ART 2 network parameters are analyzed in terms of stable category formation and in terms of the number of nodes in the output layer that can become most active. The resulting activity patterns on the output layer demonstrate a multilevel category structure based on the relative differences between patterns that exist for many different values of the vigilance parameter. We have shown that the information contained in the output analog patterns can be interpreted in several different ways, which is not possible when the category is represented by a single winning node. Also, favorable comparisons are also demonstrated between the category structure emerging from the set of category patterns and principles of categorization in psychology and neurobiology.

Neural Networks, Computer↗