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Liposomes are promising drug delivery vesicles due to their biodegradibility, large volume and biocompatibility towards both hydrophilic and hydrophobic drugs. They suffer, however, from poor stability which limits their use in controlled delivery applications. Herein, a novel method was devised for modification of liposomes with small molecules, polymers or nanoparticles to afford stimuli responsive systems that release on demand and stay relatively stable in the absence of the trigger.. This dissertation discusses thermosensitive, pH sensitive, light sensitive and magnetically triggered liposomes that have been prepared for controlled drug delivery application. RAFT polymerization was utilized for the preparation of thermosensitive liposomes (Cholesterol-PNIPAm) and acid-labile liposomes (DOPE-PAA). With low Mw Cholesterol-PNIPAm, the thermosensitive liposomes proved to be effective for controlled release and decreased the cytotoxicity of PNIPAm by eliciting the polymer doses. By crosslinking the DOPE-PAA on liposome surface with acid-labile diamine linkers, DOPE-PAA liposomes were verified to be sensitive at low pH. The effects of polymer structures (linear or hyperbranched) have also been studied for the stability and release properties of liposomes. Finally, a dual-responsive Au@SPIO embedded liposome hybrid (ALHs) was prepared with light-induced “on-and-off” function by photo-thermal process (visible light) and instant release properties triggered by alternating magnetic field, respectively. The ALH system would be further applied into the cellular imaging field as MRI contrast agent.

A computerized program was designed to test whether arranging a common element in two, otherwise independent, 2-term correlations (stimulus-stimulus and response-stimulus) would result in emergent simple discriminative-stimulus properties for the antecedent stimulus relative to an arrangement with no common elements programmed. Data from 8 adult participants in this experiment indicate that common element arrangements led to relatively high rates of responding in the presence of the putative discriminative stimulus and relatively low rates or no responding in the presence of the putative s-delta during testing in extinction. Conversely, the uncommon element arrangements produced no clear discriminative control. The current data reflect a comparison of arrangements across subjects. These data support Sidman's (2000) suggestion that common elements among contingencies are sufficient to produce stimulus classes and cause class mergers. The data also have implications for thinking about the mechanism by which and the conditions under which discriminative control develops. Finally, these data have the potential to inform the programming and implementation of reinforcement contingencies in applied settings.

This study investigated the stimulus-reinforcer relations possible in matching-to-sample, and determined the extent that each relation contributed in the transfer to subsequent matching-to-sample. Fifty three homing pigeons were autoshaped on a single key, with two stimuli, red and green. Forty eight subjects were then divided equally in 12 groups receiving the experimental treatments, and five subjects served as no-treatment controls. Group assignments were first based on autoshaping to either an identity, non-identity, or identity and non-identity stimulus relation. Each stimulus relation consisted of a center stimulus followed by an outer key stimulus. For identity, the center and outer stimuli were the same. For non-identity the center and outer stimuli were different, The second aspect determining group divisions was the correlation of reinforcement to the stimulus relation; explicitly paired, explicitly unpaired, truly random, or omission (identity only). The subjects received 10 sessions of autoshaping where each session consisted of 50 exposures to the stimulus sequence correlated with the reinforcement. Subjects were then transferred to an operant task--two color zero-delay matching-to-sample. In matching-to-sample training, the 6-second sample was followed by the presentation of 2 outer key comparison stimuli. The comparisons remained illuminated for 6 seconds or until a response occurred. A response to the matching comparison was reinforced and a response to the non-matching comparison resulted in the inter-trial interval. Sessions consisted of 50 trials. The results from the single stimulus autoshaping sessions revealed that all subjects acquired reliable autoshaping within 150 stimulus-food pairings. The results from the autoshaping sessions revealed that stimulus sequences explicitly paired with food produced reliable responding to both the center and outer stimuli.. No significant differences were observed between center and outer key responding for subjects trained with an explicitly paired food arrangement. Subjects receiving identity stimuli explicitly paired with food and non-identity stimuli explicitly unpaired with food responded differentially to the outer key stimuli, showing control by the identity and non-identity stimulus relations. The truly random, explicitly paired/omission, or explicitly unpaired conditions resulted in center and outer key responses decreasing across sessions. The results from the matching sessions revealed that only autoshaping discrimination training (identity explicitly paired and non-identity explicitly unpaired with food) facilitated transfer to the operant task. Autoshaping training on a single stimulus relation in matching-to-sample (identity or non-identity) did not facilitate matching transfer. The results from the omission training suggest that the key pecking was very susceptible to operant controls. These data were taken to indicate that exposure to and differential responding in the presence of the conditional discriminative stimuli in matching-to-sample may be necessary for matching performance. Exposure and behaving in the presence of components of matching did not produce matching. Therefore any explanation of matching in terms of learning a single stimulus relation rule may be questioned.

Light as a catalyst of undefined perceptual opportunitiesA light stimuli research will try to deepen into the relation between perceived spaceand daylight, understanding the importance of daylight compositions and the way that stimulates people. A research on how perception plays an important role in energizing spaces.Experiencing atmospheres (light+space+material) is vital to understand light in the space. Previous researches have put the main focus on the perceived spaciality and enclosure in relation to the distribution of light and to show how can space be shaped. However, daylight changes, together with architecture, are capable of modifying perceptively movement in the interior space, turning the static into dynamic.The study will relate perceptual theory with experiential studies, investigating the possibilities light has when experiencing a transitional space and establishing the common points that induces the user to movement. Will focus on the intangible from a qualitative and personal point of view, presenting the light effects that instinctively stimulate a change of position in space.

The purpose of this research was to study children's ability to recognize partially occluded images. Tasks were constructed which consisted of occluded images from video games, trademarks, and household objects. The tasks were administered to third and sixth grade students at two elementary schools in Arlington, Texas. The researcher discovered no significant differences between the scores of males and females except for the males' higher score on the video game task .

Thesis / Doctor of Philosophy (PhD)

<p> Several experimental situations were designed to show that when all visual, tactile and chemical stimuli are eliminated, fish are still capable of attracting one another and orienting to one another. Attempts to ascertain the nature of this unknown sensory basis of schooling were unsuccessful.</p> / Thesis / Master of Arts (MA)

Bone growth and remodeling are complex phenomena that are influenced by a variety of factors including mechanical stimuli. However, it is still unclear how to identify and quantitatively characterize the mechanical stimuli responsible for bone cell growth. The objective of this study is to design and simulate an experimental apparatus to cyclically apply pressure and shear stresses to bone cells and observe their growth (or lack thereof) as a function of the applied loads.