Current landmine detection methodologies are not much different in principle from those employed 75 years ago, in that they require actual presence in the minefield, with obvious risks to personnel and equipment. Other limitations include an extremely large ratio of false positives, as well as a very limited ability to detect non-metallic landmines. In this lecture a microbial-based solution for the remote detection of buried landmines described. The small size requirements, rapid responses and sensing versatility of bacterial bioreporters allow their integration into diverse types of devices, for laboratory as well as field applications. The relative ease by which molecular sensing and reporting elements can be fused together to generate dose-dependent quantifiable physical (luminescent, fluorescent, colorimetric, electrochemical) responses to pre-determined conditions allows the construction of diverse classes of sensors. Over the last two decades we and others have employed this principle to design and construct microbial bioreporter strains for the sensitive detection of (a) specific chemicals of environmental concern (heavy metals, halogenated organics etc.) or (b) their deleterious biological effects on living systems (such as toxicity or genotoxicity). In many of these cases, additional molecular manipulations beyond the initial sensor-reporter fusion may be highly beneficial for enhancing the performance of the engineered sensor systems. This presentation highlights several of the approaches we have adopted over the years to achieve this aim, while focusing on the application of live cell microbeads for the remote detection of buried landmines and other explosive devices.
Recent studies of the minute morphology of the skin by optical coherence tomography showed that the sweat ducts
in human skin become helically shaped tubes in the Epidermis and are filled with an aqueous solution. When
considered as entities embedded in a dielectric media, they resemble helical antennas. The spectral response
obtained by our computer simulations coincides with the analytical prediction of antenna theory and support this
hypothesis, if a fast enough current mechanism exists in the duct. In particular the strongest spectral response of the
simulation was noted around the predicted frequencies (240 GHz and 380 GHz) for the respective normal and axial
modes of the helical structure. Furthermore, circular dichroism of the reflected electromagnetic field is a
characteristic property of such helical antennas and it was shown that it is indeed a characteristic of the simulation
model. Fast proton hopping is posited as the current mechanism.
Consequently experimental evidence is presented that the spectral response of the skin in the sub-Terahertz region is
governed by the level of activity of the perspiration system. This in turn is moderated by the Sympathetic Nerve
Response and is demonstrated by the correlation to physiological stress as manifested by the pulse rate and the
systolic blood pressure. These physical relaxations are tonic in nature (lasting more than a minute). Could the phasic
characteristic of emotional excitation also be evident in the reflection coefficient? By applying techniques borrowed
from psychiatric science we hope to answer this point in our paper.
In this paper we describe recent progress in the study of scale-free optical propagation in super-cooled nonergodic
ferroelectrics. Our experimental and theoretical findings indicate that a regime can be found in which
diffusion-driven photorefractive effects can fully annul the diffraction of focused laser beams. This demonstrates
that diffraction can be systematically eliminated from an optical system and not simply compensated, with
fundamental implications for optical imaging and microscopy. The effect transfers directly from the paraxial
regime into the non-paraxial regime described by the Helmholtz Equation, and suggests a means to achieve the
propagation of super-resolved optical images. The result is a nonlinear-based metamaterial, even though the
underlying nano-structuring of the ferroelectric is random and the effect is both non-absorptive and wavelengthindependent
for a wide spectrum.
Refractive index engineering (RI_Eng) by ion implantations is a generic methodology for constructing multi-component
integrated circuits of electrooptic and nanophotonic devices with sub-wavelength features operating in the visible - near
IR wavelengths. The essence of the method is to perform spatially selective implantations for sculpting complex 3D pre-designed
amorphized patterns with sub-wavelength features and reduced refractive index within the volume of the
substrate. A number of devices that were constructed in a substrate of potassium lithium tantalate niobate are described,
including a submerged slab waveguide, an optical wire and a channel waveguide array.
We present a new technology for uncooled focal plane arrays, which is based on optical readout. An electrooptic crystal, operated in the paraelectric phase, is used as the temperature sensitive element. A lateral readout configuration is utilized, and an entire row of pixels is read simultaneously through electrical triggering. The optical readout diminishes the electronic noise mechanisms resulting in a predicted NETD of 5-7mk. This low NETD of the device is determined by the temperature fluctuations noise, thus approaching the theoretical limit for uncooled FPAs.
Hologram writing and fixing mechanisms are examined in disordered conjugated polymer/glass composites. The conjugated polymers used were alkoxy substituted poly(phenylenevinylne) analogs and the glass matrices were zirconia-organosilica xerogels. Hologram formation mechanism is shown to be a photochromic process consisting of light induced photo- oxidation (bleaching) of the embedded conjugated polymer resulting in the formation of an absorption grating and a phase grating. IR and Raman spectroscopy show that the chemical transformations upon photo-bleaching involve chain scission and oxidation of the polymer at the vinylic position of the conjugated polymer. Oxygen removal increases hologram formation time by more than an order of magnitude and halves the total hologram efficiency. The oxygen dependence was also highly correlated with photo-bleaching of the samples and beam interaction of the writing beams. Light sensitivity was compared for several polymer/glass composites showing that the new composites and film preparation techniques are promising for blue and ultraviolet sensitive holographic materials. A hologram fixing method based on a PMMA coating, applied on the film after hologram formation is demonstrated and shown to increase hologram erasure times by four. These important findings show that conjugated polymer/glass composites based storage media can be manufactured and fixed efficiently for a long term based on this method.