MIMO Transmission through Reconfigurable Intelligent Surface: System Design, Analysis, and Implementation

Reconfigurable intelligent surface (RIS) is a new paradigm that has great potential to achieve cost-effective, energy-efficient information modulation for wireless transmission, by the ability to change the reflection coefficients of the unit cells of a programmable metasurface. Nevertheless, the electromagnetic responses of the RISs are usually only phase-adjustable, which considerably limits the achievable rate of RIS-based transmitters. In this paper, we propose an RIS architecture to achieve amplitude-and-phase-varying modulation, which facilitates the design of multiple-input multiple-output (MIMO) quadrature amplitude modulation (QAM) transmission. The hardware constraints of the RIS and their impacts on the system design are discussed and analyzed. Furthermore, the proposed approach is evaluated using our prototype which implements the RIS-based MIMO-QAM transmission over the air in real time.Comment: This paper aims to investigate the feasibility of using RIS for MIMO wireless transmission for higher-order modulation by presenting an analytical modeling of the RIS-based system and providing experimental results from a prototype which has been buil

Hong Kong Renal Registry Report 2012

SummaryThis report examined the characteristics and trends of dialysis and renal transplant patients among the resident population of Hong Kong who were managed by hospitals or dialysis centers of the Hospital Authority, and accounted for approximately 95% of all patients receiving renal replacement therapies (RRTs) in the territory. Patients receiving RRTs solely in the private sector were not included in this report. Data trends from 1996 to 2011 are presented. In 2011, 1115 new patients were accepted into RRT programs, and the incident rate was 157 patients per million populations (pmp). An increasing trend was noted. The incident rate was 95.1 pmp at the commencement of the annual report in 1996. The point prevalence on December 31, 2012 was 8197 with a prevalence rate of 1152.5 pmp. Overall, there were 3573 patients (43.6%) on peritoneal dialysis (PD) and 1246 patients (15.2%) on hemodialysis (HD), and 3378 patients (41.2%) were living with a functioning renal transplant. The PD/HD ratio was 74.2:25.8. The “PD First” policy was continued. The overall mortality rate among RRT patients was 9.95 patients per 100 patient-years exposed. There was a decreasing trend in mortality among PD patients. Infection and cardiovascular complications were the most common causes of death. Renal transplant was the modality with the best survival rates. The 5 years cumulative patient survival rate for patients on transplant treatment was 89.6%, whereas the corresponding patient survival rates for PD and HD patients were 50.7% and 55.7%, respectively. More than 70% of RRT patients with reports on rehabilitation were active and had normal daily activities

The Enhanced metastatic potential of hepatocellular carcinoma (HCC) cells with sorafenib resistance

Acquired resistance towards sorafenib treatment was found in HCC patients, which results in poor prognosis. To investigate the enhanced metastatic potential of sorafenib resistance cells, sorafenib-resistant (SorR) cell lines were established by long-term exposure of the HCC cells to the maximum tolerated dose of sorafenib. Cell proliferation assay and qPCR of ABC transporter genes (ABCC1-3) were first performed to confirm the resistance of cells. Migration and invasion assays, and immunoblotting analysis on the expression of epithelial to mesenchymal transition (EMT) regulatory proteins were performed to study the metastatic potential of SorR cells. The expression of CD44 and CD133 were studied by flow cytometry and the gene expressions of pluripotency factors were studied by qPCR to demonstrate the enrichment of cancer stem cells (CSCs) in SorR cells. Control (CTL) and SorR cells were also injected orthotopically to the livers of NOD-SCID mice to investigate the development of lung metastasis. Increased expressions of ABCC1-3 were found in SorR cells. Enhanced migratory and invasive abilities of SorR cells were observed. The changes in expression of EMT regulatory proteins demonstrated an activation of the EMT process in SorR cells. Enriched proportion of CD44+ and CD44+CD133 + cells were also observed in SorR cells. All (8/8) mice injected with SorR cells demonstrated lung metastasis whereas only 1/8 mouse injected with CTL cells showed lung metastasis. HCC cells with sorafenib resistance demonstrated a higher metastatic potential, which may be due to the activated EMT process. Enriched CSCs were also demonstrated in the sorafenib resistant cells. This study suggests that advanced HCC patients with acquired sorafenib resistance may have enhanced tumor growth or distant metastasis, which raises the concern of long-term sorafenib treatment in advanced HCC patients who have developed resistance of sorafenib. © 2013 Chow et al.published_or_final_versio

Carboxyl-terminal truncated HBx regulates a distinct microRNA transcription program in Hepatocellular carcinoma development

Background: The biological pathways and functional properties by which misexpressed microRNAs (miRNAs) contribute to liver carcinogenesis have been intensively investigated. However, little is known about the upstream mechanisms that deregulate miRNA expressions in this process. In hepatocellular carcinoma (HCC), hepatitis B virus (HBV) X protein (HBx), a transcriptional trans-activator, is frequently expressed in truncated form without carboxyl-terminus but its role in miRNA expression and HCC development is unclear. Methods: Human non-tumorigenic hepatocytes were infected with lentivirus-expressing full-length and carboxyl-terminal truncated HBx (Ct-HBx) for cell growth assay and miRNA profiling. Chromatin immunoprecipitation microarray was performed to identify the miRNA promoters directly associated with HBx. Direct transcriptional control was verified by luciferase reporter assay. The differential miRNA expressions were further validated in a cohort of HBV-associated HCC tissues using real-time PCR. Results: Hepatocytes expressing Ct-HBx grew significantly faster than the full-length HBx counterparts. Ct-HBx decreased while full-length HBx increased the expression of a set of miRNAs with growth-suppressive functions. Interestingly, Ct-HBx bound to and inhibited the transcriptional activity of some of these miRNA promoters. Notably, some of the examined repressed-miRNAs (miR-26a, -29c, -146a and -190) were also significantly down-regulated in a subset of HCC tissues with carboxyl-terminal HBx truncation compared to their matching non-tumor tissues, highlighting the clinical relevance of our data. Conclusion: Our results suggest that Ct-HBx directly regulates miRNA transcription and in turn promotes hepatocellular proliferation, thus revealing a viral contribution of miRNA deregulation during hepatocarcinogenesis. © 2011 Yip et al.published_or_final_versio

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Surface composition analysis of ultra-shallow surface regions in complex multilayers and multicomponent alloys by ion scattering and photoelectron spectroscopy

Quantitative compositional analysis at ultra-shallow depth scales is important for the understanding and optimization of processes that involves modification of the topmost layers of surfaces to subsurfaces using plasmas and ion beams. A thorough and precise understanding of the behavior of the surface under exposure to plasmas and ion beams is important in applications such as the mirror optics facing the tin plasma in an extreme ultra-violet lithography (EUVL) tool. Moreover, such understanding is also essential in developing a predictive model for the self-organization behavior of nanoscale structures on surfaces upon low energy ion irradiation, a phenomenon that is both very intriguing from a physics point of view and promising for controllable, one-step, bottom-up fabrication of nanostructures. For low energy ions, the modification is confined within ~10 nm below the surface. Therefore, probing the plasma- and ion-induced changes requires extremely surface-sensitive characterization techniques. In this dissertation, x-ray photoelectron spectroscopy (XPS) and low energy ion scattering spectroscopy (LEISS) have been utilized for the compositional analysis and depth profiling of complex multicomponent materials. XPS is the most widely used technique in obtaining chemical state information at the top <10 nm of the surface, and LEISS is the most surface-sensitive technique capable of probing the composition of the topmost monolayer. Combining XPS and LEISS analysis, researchers are then able to compare and contrast the compositional and chemical state information at different depth scales within the first 10 nm of the surface. Two applications involving complex and technologically important materials have been chosen as demonstrations of combining XPS and LEISS in surface compositional analysis. The first application involves utilizing LEISS analysis combined with carefully tuned sputter depth profiling to map the depth distribution of tin (Sn) particles in ZrO2-capped Mo/Si ultra-thin multilayer mirrors (MLMs) exposed to tin ions from a Sn plasma, which is the source of extreme ultra-violet (EUV) light in EUV lithography, the only lithography technique that can produce next generation sub-10 nm node semiconductor chips in high volumes. The results have shown that LEISS depth profiling, when optimized, was able to produce compositional depth profiles that agreed well with simulations, and more accurate than conventional XPS depth profiling due to its extreme surface sensitivity. The measured Sn concentration and distribution were also consistent with XPS analysis, demonstrating the reliability of LEISS. Elemental detection sensitivity with LEISS is also satisfactory and comparable with XPS, being able to detect a Sn concentration as low as 0.08 ± 0.05 at-%. In addition, by complementing with XPS analysis and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) it allows characterization of structural defects and chemical changes due to Sn ion exposure as well. The second application involves utilizing a combination of XPS and LEISS analysis to characterize the compositional changes of Zr52.5Cu17.9Ni14.5Al10.0Ti5.0 (Vit 105) bulk metallic glass (BMG), a glassy alloy that exhibits superior mechanical properties compared to typical metal alloy, upon low energy Kr+ ion beam irradiation and correlate the changes to highly-ordered nanopattern formation on the surface. Utilizing in-situ XPS and LEISS analysis, this work has found that highly-ordered patterns can be induced on Vit 105 only if the amount of W impurities has exceeded a certain threshold. This information is essential in formulating a theoretical description for pattern formation, which is intrinsically extremely complicated involving many synergistic physical and chemical mechanisms. In addition, XPS and LEISS analysis have revealed a very different composition and amount of W impurities at the subsurface and at the top surface respectively. This indicates the existence of a heterogeneous composition at the surface. These results have emphasized the importance of utilizing a multitude of surface characterization techniques to extract information from different depth scales and provide a more complete picture of the ion-induced changes at the surface.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

A systematic study of ion-induced nanopatterning on photonic crystal-based label-free optical biosensor

Photonic crystal (PC)-based biosensors are promising candidates for label-based fluorescence and label-free optical biosensors. This is due to the presence of PC, a periodically-structured dielectric material with diffraction gratings engineered on the surface that can control light propagation through its depth. PC enables resonance of a certain wavelength of light, leading to a significant increase in the intensity of light reflected off the surface, and hence the optical and fluorescent signal output from target analytes. In addition to the use of PC, sensor surfaces can be modified to become more biocompatible and sensitive to changes in target analyte concentrations. It is known that surface topography and chemistry are two main factors affecting protein affinity and conformation on biointerfaces, and the topography and chemistry can be tailored to improve their affinity and adhesion to the surface. It is also known that the presence of nanostructures can increase sensor sensitivity by providing a larger surface area for target adsorption. For example, a sensor surface coated with nanorods has been shown to increase the amount of proteins adsorbed by up to 4x. The tailoring of topography and chemistry can be achieved by the use of ion-beam nanopatterning, in which a beam of energetic ions is incident onto the surface with a tunable energy, incident angle and fluence, in order to disturb the equilibrium of the surface and induce redistribution of surface atoms, and hence changes in surface topography and chemistry. There has already been extensive research in ion-beam nanopatterning in numerous applications, implying its potential in surface modification. However, in these research either a bulk crystal or a thin film with a flat surface is used. When nanopatterning involves thin film with a non-flat surface due to the presence of larger pre-existing structures, such as the diffraction gratings on a PC surface, these pre-existing structures may have a shadowing effect, causing non-uniform sputtering of the surface, and resulting in variations of surface topography on different areas of the pre-existing structures, as well as affecting the PC’s ability to resonate and reflect light due to possible changes in the shape of these structures. Moreover, nanostructures on biosensors are often grown using conventional self-assembled deposition processes such as glancing angle deposition (GLAD), which has a low controllability on the size and shape of structures. To increase the variety of the size, shape and spacing of nanostructures, it is necessary to overcome the thermodynamic constraints by inducing a self-organization process on the surface, which can be initiated by ion-beam nanopatterning. Therefore, to address these two concerns, a systematic study on ion-beam nanopatterning on non-flat surfaces is needed. A systematic study of ion-beam irradiation on titanium dioxide (TiO2) thin film of ~ 100 nm thick coated on a non-flat polymer-based photonic crystal biosensor with one-dimensional rectangular diffraction gratings was carried out. Five parameters, i.e. ion species, ion energy, incident angle, beam orientation relative to the diffraction grating wave vector, and ion fluence, was varied in order to study their effect on the surface topography, chemistry and optical transmission property. It was found that ion-beam irradiation was able to induce topographical changes and growth of nanostructured ripples while keeping the surface chemistry unchanged. The topographical changes depended on the irradiation conditions as well as the position on the surface. Despite the topographical changes, either the surface chemistry remained unchanged, as in the case of O2+ irradiation, or the oxidation state of TiO2 was temporarily reduced, and then reverted back to the original state upon exposure to the atmosphere for a sufficient amount of time, as in the case of Ar+ irradiation. In addition, it was found that irradiation caused a blue-shift in optical resonant peak wavelength, probably due to a decrease in film thickness by sputtering. Nevertheless, the peaks remained sharp and intense enough to be distinguishable from the background signal in most cases, implying the sensor’s ability to detect peak wavelength changes, and thus act as a label-free biosensor to detect changes in target molecule adsorption based on the peak wavelength changes, is not affected. It was further found that an additional resonant peak was present when irradiation was carried out at an oblique angle of 30o relative to the edges of the diffraction gratings. This result is surprising, and the reason for this phenomenon was unclear. It might be related to the surface of the gratings being slanted towards one direction after irradiation. Further experiments in varying the beam orientation at a finer scale will be needed to examine the relationship between the topography and the appearance of extra resonant peaks. The goal of this study was to induce nanostructures of varying shapes and sizes, and hence increase the surface area which in turn improve the biosensor sensitivity up to the magnitude achieved by GLAD deposition of nanorods observed in a previous research conducted by Cunningham et al. (~4x increase in the amount of proteins adsorbed onto the sensor). However, it was found that the changes in topography due to irradiation were able to increase the surface area by only a few percent, much less than that achieved by GLAD (~4x). In addition, the study to relate the presence of nanostructures to sensitivity of the biosensor, i.e. to relate the increase in surface area due to nanostructures to the amount of proteins adsorbed onto the surface, was inconclusive. Proteins of different sizes and different adsorption mechanisms were used, but there was no clear trends of the amount of proteins adsorbed on surfaces as functions of separation of nanostructures and increase in surface area due to these structures. Moreover, the trends shown from XPS and optical transmission results, two techniques to determine the amount of target proteins present on the surface, did not match with each other. These experiments need to be repeated in the future to average out the data and hopefully observe more insightful trends. More samples with different ripple periodicity and surface area will also be needed