External physical stimuli

Although the construction of sensors for external physical stimuli, such as light, heat or pressure, is relatively simple, it becomes more complicated when the target stimuli come from atoms or molecules. These types of sensors are often referred to as chemical sensors or chemosensors and biochemical sensors or biosensors (see below in Sects. 1.2 and 1.3). For the latter types, a sensing material should be used that can respond to the presence of the target analyte. This response may or may not be obviously true with vague information. Hence, chemo- and biosensors should be... 

The classical mechanical device used for information processing is the abacus. Even today human operators perform arithmetical calculations at speed with these beads-on-wires . Molecular emulation of the form and function of the abacus could allow rapid switching speeds and calculation rates, with bead position and position read-out being performed by external physical stimuli rather than human manipulation and observation. Approaches to the type of materials suitable for use as thread and beads and to the manipulation and determination of bead position have been made via self-assembling rotaxanes [72]. 

Dynamic materials are being developed that can undergo constituent exchange, reorganization, and selection in response to external physical stimuli. In a DCL where the distribution changes upon variation of external conditions, amplification of a particular species within the library is indicative of its greater stability, relative to the other hbrary members, when acted upon by an external physical stimulus. 

A gel is a structure in which a liquid (in a broad sense, a gas is included) coexists with a solid that acts as a 3D matrix. The solute dissolved in the liquid can interact with the solid at the liquid/solid matrix interface. This interaction is determined by the type and properties of the solute, material and structure of the gel matrix, and the composition of the liquid. Hence, multiple solute components can be separated using differences in interaction. The separation can also be accelerated using external physical stimuli, such as the electric field, magnetic field, and pressure. 

Cortical tissue is the dense part of bone. As a living entity, this material is able to maintain and adapt its stracture to external physical stimuli [1], The seat of bone remodeling mechanisms corresponds to cyhndrical stractuial elements called osteons. Each osteon is surrounded by a thin layer (cement line) and is centered on Haversian canal which runs primarily in the bone longitudinal axis. The Haversian canals contain the vasculature, the nerves and interstitial fluid. There are also Volkmann canals which are similar to Haversian canals except that they run along the transverse direction of the bone. At a smaller scale, other extravascular pores exist in the solid matrix of the bone forming the la-cuno-canalicular system. This porous network irrigates the mechano-sensitive osteocytes which are believed to play an important role in bone adaptation as stated in recent experimental studies [2,3,4]. 

The occurrence of two different structures that can be interconverted through the agency of an external light stimulus can be the basis of a molecular switch. Moreover, when photochromic molecules are incorporated into polymeric compounds, their photoisomerization can affect the structure and the physical properties of the attached macromolecules. Therefore, photochromic polymers may be highly promising materials for application in optical technologies, as well as in the design of photoswitchable devices. 

Psychologists distinguish between illusions and hallucinations. An illusion is a distorted perception of a real physical stimulus in your environment. A hallucination is a total creation of a perception when nothing is really present. If you walk into a dimly lit room and temporarily mistake a coat on a coat rack for a man lurking in the dark, that s an illusion. If the same nonexistent (as far as the rest of us are concerned) man walks out into the well-lit and empty hall with you, that s a hallucination. We can view illusions and hallucinations as extreme points on the continuum of simulation of the world. In illusion the simulation begins with sensory stimulation, but the simulation is a very poor representation. At the other extreme of hallucination, the simulation process produces a perception, an internal simulation, with no external stimulation involved. 

Figure 7 Schematic diagram illustrating the central role of the keratinocyte in skin inflammation. In response to an external noxious stimulus (e.g., chemical, physical, or mechanical), the keratinocyte produces a vast array of chemical mediators, including the proinflammatory cytokines. These mediators initiate a cascade of cellular events in their target cells. More details on cytokine function can be found in Table 11. (After Ref. 190 with permission.)...

The conjugation of proteins to stimuli responsive polymers are used in the field of protein isolation and separation [29,30]. The ability of some polymers to undergo a reversible change in response to an external physical, chemical, or biochemical stimulus gave them the name smart polymers [31]. Different stimuli have been utilized, such as temperature, light, ionic strength, or electric field for physical factors, or pH and specific ions for chemical triggers or metabolites for biochemical reactions [32, 33]. 

A highly desirable property in information storage systems based on molecular switches is gated response.1491 Gated photochemical reactivity implies that no change occurs upon irradiation unless another external stimulus, either physical or chemical, is applied to the system. Scheme 18 shows a typical write-lock-unlock-erase cycle involving photoisomerization and protonation. 

There is no term in equation (21.3) for air flow. External air flow around organisms is sufficiently slow (subsonic) that it may usually be treated as incompressible (Vogel, 1994). This incompressibility means that the concentration of chemical stimulus molecules (n) will not be increased noticeably by the pressures that, develop adjacent to insect sensory hairs or antennae due to moving air (or moving antennae). The replacement of any captured molecules by the arrival of fresh odorant-laden air is the primary reason why air flow has such a dramatic effect on interception rate. One way of considering the influence of air flow is that at best the air flow could bring the interception rate closer to the limit predicted by equation (21.3). In order to discuss approaches more complex than that provided by equation (21.3), we have to consider the physical bases for molecular movements diffusion and convection. 

These concepts were first developed and described by Lehn [67] and Giuseppone [11]. The constitutional recomposition of a dynamic library of imines can display complex behavior under the effect of two external parameters a physical (T) stimulus and a chemical effector ([H+]) [67]. These results illustrate the possibility of modulating an optical by constitutional recomposition induced by a specific trigger. Such features have been used for the development of stimuli-responsive, functional dynamic materials. 

Controlled-release technology based on the external temperature-activated release can find application in diverse industrial fields. In the pharmaceutical area, for example, the deviation of the body temperature from the normal temperature (37°C) in the physiological presence of the pathogens or pyrogens can be utilized as a useful stimulus that induces the release of the therapeutic agents from a thermosensitive controlled-release system. Physically controlled temperature using a heat source such as the microwaves from outside the body can also be used for temperature-activated antitumor drug release combined with the local hyperthermic treatment of cancer. 

Manipulation, detection, measurement, and analysis of single cell make it possible to observe inhomogeneous cellular response to an external stimulus, which have been averaged and completely neglected in the study with large amount of cells. The optoelectrofluidics can provide an efficient way to handle individual particles at the single cell level. Especially, interactive and parallel manipulation of individual cells based on the light-driven electrokinetics can be applied in a number of applications in life and physical sciences. 

In principle, the choice of materials used to develop both the electrodes and the insulator of an OFET-based sensor should be basically the same as for OFETs developed for other applications. Similarly, the design of the device should follow the same rules. However, there are some unique aspects that are intrinsic to sensors and deserve special attention. For instance, the sensing area of the device this is the area where the external stimulus (chemical or physical) must be applied to the device without affecting its integrity and/or robustness. The first example of an ISOFET reported in the literature [13] was fabricated on silicon and the only organic component of it was the semiconductor employed as the active layer. In order to develop this structure, it is necessary to etch the highly doped silicon from the back side of the device... 

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