Edge Detection by Cost Minimization

Edge detection is cast as a problem in cost minimization. This is achieved by the formulation of two cost functions which evaluate the quality of edge configurations. The first is a comparative cost function (CCF), which is a linear sum of weighted cost factors. It is heuristic in nature and can be applied only to pairs of similar edge configurations. It measures the relative quality between the configurations. The detection of edges is accomplished by a heuristic iterative search algorithm which uses the CCF to evaluate edge quality. The second cost function is the absolute cost function (ACF), which is also a linear sum of weighted cost factors. The cost factors capture desirable characteristics of edges such as accuracy in localization, thinness, and continuity. Edges are detected by finding the edge configurations that minimize the ACF. We have analyzed the function in terms of the characteristics of the edges in minimum cost configurations. These characteristics are directly dependent of the associated weight of each cost factor. Through the analysis of the ACF, we provide guidelines on the choice of weights to achieve certain characteristics of the detected edges. Minimizing the ACF is accomplished by the use of Simulated Annealing. We have developed a set of strategies for generating next states for the annealing process. The method of generating next states allows the annealing process to be executed largely in parallel. Experimental results are shown which verify the usefulness of the CCF and ACF techniques for edge detection. In comparison, the ACF technique produces better edges than the CCF or other current detection techniques

Terahertz Detection and Mixing Using Two-Dimensional Materials

The discovery of graphene in 2004 and the rise of the two-dimensional materials provide an excellent platform for developing optoelectronics for terahertz (THz) detection and mixing. For graphene and black phosphorus, their high carrier mobility, attractive electrical and thermal properties show promises for tunable terahertz technology. In the first part of the thesis, we discuss the THz photoresponse of black phosphorus (BP). The rediscovery of BP as a two-dimensional material in 2014 has drawn attention to its near and mid-infrared application. Here, we present an ultrafast THz detector based on black phosphorus with high efficiency at room temperature. The detector has a noise equivalent power of 130 µW/√ Hz at 2.5 THz, and an ultrafast photoresponse of about 20 ps was observed. Two detection mechanisms were observed: a strong photothermoelectric effect and a weak bolometric effect. The high carrier mobility allows BP to absorb THz radiation through free-carrier absorption, even thought the photon energy (10 meV) is far below the band gap (300 meV) of the material. The intrinsic responsivity of BP is also estimated via a Joule-heating experiment and using a free-carrier model. In the second part of the thesis, we discuss down frequency mixing and the fabrication process of a graphene FET mixer. Graphene exhibits a significant change in conductivity when the Fermi energy is altered by applying a gate voltage. Near the Dirac point, graphene field effect transistors (FETs) show a strongly nonlinear response (i.e. a nonlinear change in resistivity with applied gate voltage) that can be exploited to provide efficient rectification and mixing of THz signals. Although rectification in graphene field-effect transistors has been demonstrated, heterodyne mixing in the THz band has not been explored. We examine a THz graphene mixer using an antenna-coupled graphene FET configuration. We will discuss the antenna and graphene device design optimized for heterodyne mixing at 0.35 THz. In addition, fabrication and preliminary measurements of a microwave frequency prototype will be presented to demonstrate the principle of the operation

Modulation of Natural Killer Cell Cytotoxicity in Human Cytomegalovirus Infection: The Role of Endogenous Class I Major Histocompatibility Complex and a Viral Class I Homolog

Natural killer (NK) cells have been implicated in early immune responses against certain viruses, including cytomegalovirus (CMV). CMV causes downregulation of class I major histocompatibility complex (MHC) expression in infected cells; however, it has been proposed that a class I MHC homolog encoded by CMV, UL18, may act as a surrogate ligand to prevent NK cell lysis of CMV-infected cells. In this study, we examined the role of UL18 in NK cell recognition and lysis using fibroblasts infected with either wild-type or UL18 knockout CMV virus, and by using cell lines transfected with the UL18 gene. In both systems, the expression of UL18 resulted in the enhanced killing of target cells. We also show that the enhanced killing is due to both UL18-dependent and -independent mechanisms, and that the killer cell inhibitory receptors (KIRs) and CD94/NKG2A inhibitory receptors for MHC class I do not play a role in affecting susceptibility of CMV-infected fibroblasts to NK cell–mediated cytotoxicity

Digital Platform-Enabled Community Development: A Case Study of a Private-Public Partnership Sustainability Initiative

The significant human impact on the environment has prompted many governments to invest in sustainability initiatives across cities and communities. Moreover, although it has been suggested that information technology can aid in the development of these sustainability initiatives, there is a dearth of empirical field studies in this area. In this research-in-progress paper, we present preliminary findings from a case study of a private-public partnership (PPP) community-based sustainability initiative that is enabled by a digital platform. Preliminary analysis sheds light on the mechanisms underlying the formation of the PPP, the development of the PPP’s business model, the development of the digital platform, and ultimately the emergence of a community for sustainability. A framework for digital platform-enabled community development is posited based on the case analysis. Implications to both research and practice, as well as future research work are then discussed in concluding this paper

3D Super-Resolution Optical Profiling Using Microsphere Enhanced Mirau Interferometry

We present quantitative three dimensional images of grooves on a writable Blu-ray Disc based on a single objective Mirau type interferometric microscope, enhanced with a microsphere which is considered as a photonic nanojet source. Along the optical axis the resolution of this microsphere assisted interferometry system is a few nanometers while the lateral resolution is around 112 nm. To understand the physical phenomena involved in this kind of imaging we have modelled the interaction between the photonic jet and the complex disc surface. Agreement between simulation and experimental results is demonstrated. We underline that although the ability of the microsphere to generate a photonic nanojet does not alone explain the resolution of the interferometer, the nanojet can be used to try to understand the imaging process. To partly explain the lateral super-resolution, the potential role of coherence is illustrated. The presented modality may have a large impact on many fields from bio-medicine to nanotechnology.Peer reviewe

Assessing the ecological Inputs in selected forestry related Environmental Impact Assessment (EIA) reports in Sabah, Malaysia

Logging activity is one of the prescribed activities for Environment Impact Assessment (EIA) reporting in Sabah. Ecology is a component of EIA and studies on ecological input in EIAs have identified a number of shortcomings. As there has been no review of the EIA in logging activity, this study sets to investigate the ecological input in the forestry related EIA reports. By knowing this, there is an opportunity to advance the current ecological component inclusion in EIA reports related to forestry projects for future improvements. Four main review areas were assessed in this study: (1) description of the development, the local environment and thebaseline conditions (2) identification and evaluation of key ecological impacts (3) alternatives and mitigation and (4) communication of results. Results showed that the quality of the ecological components for three out of four main review areas generally met the satisfactory level of ecological components in EIA report. Review area 3 showed the highest level of poor ecological component quality compared to other scores, solely due to the reports lacking feasible alternatives to the proposed forestry project. However, this aspect is not required as compliance with the local EIA guidelines by the Sabah Environmental Protection Department (EPD). Nonetheless, it is still a good practice to include all mitigations and alternatives of project operations related to ecological components in the EIA report

Draft Genome Sequences of Listeria monocytogenes Serotype 4b Strains 944 and 2993 and Serotype 1/2c Strains 198 and 2932

Listeria monocytogenes is a foodborne pathogen and the causative agent of listeriosis among humans and animals. The draft genome sequences of L. monocytogenes serotype 4b strains 944 and 2993 and serotype 1/2c strains 198 and 2932 are reported here

Recombinant Listeria promotes tumor rejection by CD8+ T cell-dependent remodeling of the tumor microenvironment.

Agents that remodel the tumor microenvironment (TME), prime functional tumor-specific T cells, and block inhibitory signaling pathways are essential components of effective immunotherapy. We are evaluating live-attenuated, double-deleted Listeria monocytogenes expressing tumor antigens (LADD-Ag) in the clinic. Here we show in numerous mouse models that while treatment with nonrecombinant LADD induced some changes in the TME, no antitumor efficacy was observed, even when combined with immune checkpoint blockade. In contrast, LADD-Ag promoted tumor rejection by priming tumor-specific KLRG1+PD1loCD62L- CD8+ T cells. These IFNγ-producing effector CD8+ T cells infiltrated the tumor and converted the tumor from an immunosuppressive to an inflamed microenvironment that was characterized by a decrease in regulatory T cells (Treg) levels, a proinflammatory cytokine milieu, and the shift of M2 macrophages to an inducible nitric oxide synthase (iNOS)+CD206- M1 phenotype. Remarkably, these LADD-Ag-induced tumor-specific T cells persisted for more than 2 months after primary tumor challenge and rapidly controlled secondary tumor challenge. Our results indicate that the striking antitumor efficacy observed in mice with LADD-based immunotherapy stems from TME remodeling which is a direct consequence of eliciting potent, systemic tumor-specific CD8+ T cells